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ScienceDirect Publication: International Journal of Heat and Mass Transfer

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Permalink for 'Erratum to “A statistical model for predicting the fluid displaced/added mass and displaced heat capacity effects on transport and heat transfer of arbitrary density particles in turbulent flows” [Int J Heat Mass Transfer 54 (2011) 4247–4265]'

Erratum to “A statistical model for predicting the fluid displaced/added mass and displaced heat capacity effects on transport and heat transfer of arbitrary density particles in turbulent flows” [Int J Heat Mass Transfer 54 (2011) 4247–4265]

Posted: February 11th, 2012, 4:29pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 10 February 2012

Leonid I. Zaichik, Vladimir M. Alipchenkov

First law analysis for viscous dissipation in liquid flows in micro-channels

Posted: February 11th, 2012, 4:29pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 10 February 2012

Daisuke Kawashima, Yutaka Asako

This paper focuses on temperature rise due to the viscous dissipation in liquids flowing through micro-channels. In the past, equations for the prediction of the temperature rise have been obtained as a function of the friction factor, Reynolds number and Eckert number or a similar form, starting from Navier–Stokes equation and energy equation under the assumption of fully developed laminar flow by researchers. The temperature rises calculated from the equations have been compared with experimental data and the equations have been validated. However, in this paper, a new equation for the prediction of the temperature rise is simply obtained from the first law of thermodynamics without restriction of fully developed laminar flow.

Nonlocal heat transport with phonons and electrons: Application to metallic nanowires

Posted: February 9th, 2012, 6:32pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 9 February 2012

D. Jou, V.A. Cimmelli, A. Sellitto

In the framework of Extended Irreversible Thermodynamics we develop a model for coupled heat conduction by phonons and electrons. Particular emphasis is given to nonlocal effects, which may arise when the mean-free paths of phonons and/or electrons are comparable to the size of the system. As particular cases, we recover two parabolic equations of the Guyer–Krumhansl type which model the concurrent presence of the diffusion of heat superposed to the propagation of heat waves, and two hyperbolic equations of the Maxwell–Cattaneo type. In the latter case, the phase speed of temperature waves is calculated. The size dependence of the Wiedemann–Franz law is briefly analyzed for metallic nanowires.

Constructal design of distributed energy systems: Solar power and water desalination

Posted: February 9th, 2012, 6:32pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 8 February 2012

S. Lorente, A. Bejan, K. Al-Hinai, A.Z. Sahin, B.S. Yilbas

Here we show the fundamental tradeoffs that underpin the design of a distributed energy system with two objectives: the production and distribution of electric power driven by solar heating, and desalinated water produced by consuming solar power. We show analytically that larger solar power plants and desalination plants are more efficient than smaller plants. This phenomenon of economies of scale is countered by the greater losses associated with larger distribution networks. From this conflict emerges the proper allocation of nodes of production of power and water on a territory. We show that as the individual needs of power and water increase in time, the sizes of solar plants and desalination plants increase, and so does the size of the territory served by each power plant. At the same time, the territory served by each desalination plant decreases, and this means that the number of desalination plants allocated to one power plant increases.

Fully developed flow and heat transfer characteristics in a wavy passage: Effect of amplitude of waviness and Reynolds number

Posted: February 9th, 2012, 6:32pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 7 February 2012

Abhishek G. Ramgadia, Arun K. Saha

The present study deals with numerical simulation of fully developed flow and heat transfer through a wavy surface described by the functiony = 2a sin(πx/L). Finite volume method on collocated grid is used to solve incompressible, time-dependent Navier–Stokes and energy equation in primitive variable form. Effect of geometry, generated by varyingHmin/Hmaxratio from 0.1 to 0.5 and keepingL/aratio fixed to 8, on fluid flow and heat transfer characteristics has been elaborated at a Reynolds number of 600. The critical Reynolds number of unsteadiness is found to depend on the geometrical parameters. At Re = 600, one model shows the flow with multiple frequencies while the others reveal single frequency. It is established that geometry withHmin/Hmaxratio 0.2 produces the highest Nusselt number and spawns the best thermal performance factor (TPF). With increase in Reynolds number, the steady flow shows a decrease inTPFwhile an increase inTPFis noticed when the flow is unsteady.

Temperature distribution and local heat flux in the unidirectional freezing of antifreeze-protein solution

Posted: February 9th, 2012, 6:32pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 7 February 2012

Yoshimichi Hagiwara, Daichi Yamamoto

Experiments have been conducted on the unidirectional freezing of dilute aqueous solutions of winter flounder antifreeze protein, which are 0.02 mm thick, between two cover glasses on the stage of a microscope. The instantaneous temperature field has been obtained by measuring the intensity of near-infrared light with a near-infrared camera. In addition, the local protein concentration has been measured separately using the brightness of fluorescence emitted from molecules tagged to the protein. It is found that the temperature distribution in the ice region near the ice/water interface is similar to that predicted from the modified Neumann solution. Furthermore, the temperature measurement made using the near-infrared light with a specific wavelength is verified. In addition to this, in the case of antifreeze protein solutions, serrated interfaces are observed. The sum of the conduction heat flux of a protein solution near the front edge of the serrated interface and the heat flux for solidification is lower than the conduction heat flux of ice. On the other hand, the sum of the conduction heat flux of protein solution near the bottom edge of the serrated interface and the heat flux for solidification is higher than the conduction heat flux of ice. The balance of heat flux is obtained by taking account of heat convection due to high-concentration regions of protein. These regions move to the deepest parts of the interface and form narrow liquid regions inside the ice. The convection is maintained by the heat conduction in a direction perpendicular to the direction of ice growth. Not only protein adsorption to the interface but also the heat conduction/convection contributes to the modification of ice growth in the non-equilibrium state.

Pressure corrections for the potential flow analysis of Kelvin–Helmholtz instability with heat and mass transfer

Posted: February 9th, 2012, 6:32pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 7 February 2012

Mukesh Kumar Awasthi, Rishi Asthana, G.S. Agrawal

Pressure corrections for the viscous potential flow analysis of Kelvin–Helmholtz instability at the interface of two viscous fluids have been carried out when there is heat and mass transfer across the interface. Both fluids are taken as incompressible and viscous with different kinematic viscosities. In viscous potential flow theory, viscosity enters through normal stress balance and effect of shearing stresses is completely neglected. We include the viscous pressure in the normal stress balance along with irrotational pressure and it is assumed that this viscous pressure will resolve the discontinuity of the tangential stresses at the interface for two fluids. It has been observed that heat and mass transfer has destabilizing effect on the stability of the system. A comparison between viscous potential flow (VPF) solution and viscous contribution to the pressure for potential flow (VCVPF) solution has been made and it is found that the effect of irrotational shearing stresses stabilizes the system.

The condition requiring conjugate numerical method in study of heat transfer characteristics of tube bank fin heat exchanger

Posted: February 9th, 2012, 6:32pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 7 February 2012

Ye Wang, Liang-Chen Wang, Zhi-Min Lin, Yu-Huan Yao, Liang-Bi Wang

The overall heat transfer performance of a tube bank fin heat exchanger is very important for engineering applications. Developing a fin pattern with good heat transfer performance for tube bank fin heat exchanger needs more our intensive effort. There are two methods to obtain the heat transfer performances of a fin pattern, i.e., one is experimental method, and the other is numerical method. If numerical method is used, the thermal boundary condition on the fin surfaces is necessary. Generally, there are two ways to treat the thermal boundary, i.e., one is to treat fin surface with uniform temperature, and the other is to use a conjugate numerical method. The former is very easy to be applied in numerical method, but the latter needs more numerical effort. This paper reports the condition under which whether a conjugate numerical method or a numerical method just specifying uniform temperature thermal boundary condition should be used. It is found that such condition is the fin efficiency. When the fin efficiency is less than 0.8, a conjugate numerical method must be used. Otherwise, the numerical results obtained by applying an uniform temperature thermal boundary condition on the fin surfaces has only slightly differences with the results obtained by a conjugate numerical method. The reported results will provide a criterion for the researchers to choose a suitable numerical method in finding a fin pattern more efficiently and reliably.

Conduction based calibration of handmade platinum thin film heat transfer gauges for transient measurements

Posted: February 6th, 2012, 6:12pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 6 February 2012

Rakesh Kumar, Niranjan Sahoo, Vinayak Kulkarni

Heat transfer measurement using thin film gauges (TFG) is the most prevalently used technique for determination of surface heat flux. They are best suited for short duration transient surface temperature measurements and typically used in the applications where convection is a dominant mode of heat transfer such as gas turbine engines, high speed flights etc. However, in few interdisciplinary research areas, there are practical issues and difficulties in exposing the gauges for convection based measurements. These present investigations are aimed at exploring the possibility of using thin film gauges for short duration conduction based transient measurements with pure conduction mode of heat transfer. A simple calibration set-up has been used to supply known heat flux of different magnitudes to the thin film gauges that are fabricated in-house with platinum as sensing element and pyrex as an insulating substrate. Experimentally recorded temperature signals from the gauges are compared with simulated temperature histories obtained through finite element analysis. Convoluted integral of one-dimensional heat conduction equation is used to predict the surface heat flux and compared with input heat loads. The presently developed calibration setup is seen to be very useful for conduction based measurements of thin film gauges.

Permalink for 'Examination of minimum-heat-flux-point condition for film boiling on a sphere in terms of the limiting liquid superheat and the critical vapor film thickness'

Examination of minimum-heat-flux-point condition for film boiling on a sphere in terms of the limiting liquid superheat and the critical vapor film thickness

Posted: February 6th, 2012, 6:12pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 6 February 2012

Osamu Makishi, Hiroshi Honda

Previously proposed theories of the minimum-heat-flux-point (MHF-point) condition were examined using available experimental data obtained from the immersion cooling of spheres in water. The sphere diameter ranged from 9.5 to 30 mm and the liquid subcooling from 0 to 85 K. The limiting liquid superheat predicted by the Lienhard equation was compared with the liquid–solid interface superheat at the instant of liquid–solid contact at the MHF-point. The results showed that the liquid–solid interface superheat was not limited by the limiting liquid superheat and its value was connected with the collapse mode of vapor film. The collapse mode was a coherent collapse at a low interface superheat and the mode changed to a propagative collapse as the interface superheat increased. The critical vapor film thickness obtained from the linear stability analysis of vapor film was compared with the calculated value of average vapor film thickness at the MHF-point. For all data, the ratio of the average vapor film thickness to the critical vapor film thickness was correlated well as a function of liquid subcooling. The ratio decreased with increasing liquid subcooling and tended to about 0.8 to 1 depending on the experiments. This indicated that the MHF-point at a high liquid subcooling was determined by the critical vapor film thickness. A physical consideration was given to the effect of liquid–solid contact that occurred in the film boiling region on the calculated value of the vapor film thickness and the stability of vapor film.

Coupling a two-temperature model and a one-temperature model at a fluid-porous interface

Posted: February 6th, 2012, 6:12pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 6 February 2012

A. d’Hueppe, M. Chandesris, D. Jamet, B. Goyeau

We study a convective heat transfer problem in a fluid-porous domain in the case of the local thermal non-equilibrium assumption (LTNE). The issue of this study is to determine appropriate boundary conditions to model heat transfer, while using models with a different number of equations: a two-temperature model in the homogeneous porous region versus a one-temperature model in the free region. To proceed, a two-step up-scaling approach is used, which has the particularity to provide closed jump relations depending on intrinsic characteristic of the interface. Thus, the use of jump or continuity conditions depend only on the interface location inside the fluid-porous transition region. The pertinence of the approach is illustrated on a 2D convective heat transfer problem considering a solid heat source in the porous medium.

Permalink for 'Polydisperse aerosol condensation with heat and mass conservation: I. Model description with applications to homogeneous systems'

Polydisperse aerosol condensation with heat and mass conservation: I. Model description with applications to homogeneous systems

Posted: February 3rd, 2012, 5:21pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 3 February 2012

Jun Geng, Chu Nie, William H. Marlow

A computational solution of the coupled heat and mass transport equations for aerosols, which may be either single component or multicomponent, in a finite volume is developed under nonsteady state and nonisothermal conditions. It is capable of computing the temperature and vapor density profile around the droplets. Both mass and heat are conserved effectively in the volume, which enables this computational model to describe time-dependent, competitive, aerosol condensation and evaporation. Calculations for pure water particles and sodium nitrate particles in the presence of water vapor are performed. By comparing the particle growth for different number densities at various initial supersaturation conditions, both the initial saturations and particle number concentrations are shown to have great impact on the aerosol condensational growth. Detailed discussions on the change of bulk temperature, bulk relative humidity (RH), total surface area and volume are given.

Double diffusion in rotating porous media under general boundary conditions

Posted: February 3rd, 2012, 5:21pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 2 February 2012

Paolo Falsaperla, Andrea Giacobbe, Giuseppe Mulone

In this article we study a binary fluid saturating a rotating porous medium; the fluid is modeled according to Darcy–Brinkman law and the boundary conditions are rigid or stress-free on the velocity field and of Robin type on temperature and solute concentration.We determine the threshold of linear instability and its dependence on Taylor and Darcy numbers. Using a Lyapunov function we prove analytically, under certain assumptions, the coincidence of linear and nonlinear thresholds. A second Lyapunov function allows us to prove numerically the coincidence of the two thresholds with weaker assumptions on the parameters.We show that in the particular limit case of fixed heat and solute fluxes this system has a remarkable feature: the wave number of critical cells goes to zero when the Taylor number is below a threshold. Above such threshold, the wave number is non-zero when the Darcy number belongs to a finite interval. These phenomena could perhaps be tested experimentally.

Permalink for 'Corrigendum to “History recovery and source identification of multiple gaseous contaminants releasing with thermal effects in an indoor environment” [Int. J. Heat Mass Transfer 55 (2012) 422–435]'

Corrigendum to “History recovery and source identification of multiple gaseous contaminants releasing with thermal effects in an indoor environment” [Int. J. Heat Mass Transfer 55 (2012) 422–435]

Posted: February 3rd, 2012, 5:21pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 1 February 2012

Di Liu, Fu-Yun Zhao, Han-Qing Wang

The near wall physics and wall functions for turbulent natural convection

Posted: February 3rd, 2012, 5:21pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 1 February 2012

P. Kiš, H. Herwig

Highly accurate results of direct numerical simulations (DNS) for Grashof numbers up to 4.0 × 10in a differentially heated infinite vertical channel are used to deduce wall functions for turbulent natural convection. These functions represent the unique time-averaged behaviour of velocity, temperature, and shear stress in the vicinity of the wall for the Grashof number range under consideration. There is a good indication that these wall function are valid as the Grashof number tends to infinity. Previous attempts to find such wall functions relied on the blending of at least two functions which are valid in adjacent regions of the flow field. In conformity with the time-averaged momentum and thermal energy equation, this study introduces a continuous description of the near wall region up to the velocity maximum.

Dual solutions in a double-diffusive convection near stagnation point region over a stretching vertical surface

Posted: February 3rd, 2012, 5:21pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 1 February 2012

S.V. Subhashini, R. Sumathi, I. Pop

The development of double-diffusive convection near stagnation point region over a stretching vertical surface with constant wall temperature has been investigated. The external flow and the stretching velocities are assumed to vary withwherexis the distance from the slot where the stretching surface is issued. Using the local similarity method, it has been shown that a set of suitable similarity transformations reduces the non-linear coupled partial differential equations governing the flow, thermal and concentration fields into a set of non-linear coupled ordinary differential equations. The non-linear self-similar equations along with the boundary conditions form a two point boundary value problem and are solved using Shooting method, by converting into an initial value problem. In this method, the system of equations is converted into the set of first order system which is solved by fourth-order Runge–Kutta method. Flows with both assisting and opposing buoyancy forces are considered in the present investigation. The study reveals that the dual solutions of velocity, temperature and concentration exist for certain values of suction/injection and buoyancy parameters. Prandtl and Schmidt numbers strongly affect the thermal and concentration boundary layer thicknesses, respectively. The effects of various parameters on the velocity, temperature and concentration profiles are also presented here.

High heat flux point source sensitivity and localization analysis for an ultrasonic sensor array

Posted: February 3rd, 2012, 5:21pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 1 February 2012

M.R. Myers, A.B. Jorge, M.J. Mutton, D.G. Walker

State estimation procedures using the extended Kalman filter are investigated for a transient heat transfer problem in which a high heat flux point source is applied on one side of a thin plate and ultrasonic pulse time of flight is measured between spatially separated transducers on the opposite side of the plate. This work is an integral part of an effort to develop a system capable of locating the boundary layer transition region on a hypersonic vehicle aeroshell. Results from thermal conduction experiments involving one-way ultrasonic pulse time of flight measurements are presented. Uncertainties in the experiments and sensitivity to heating source location are discussed. One key finding is that sensitivity to heating source location is greater in the direction normal to the ultrasonic pulse propagation path. Scaled sensitivities to boundary conditions and thermal conductivity are presented and analyzed for all possible source locations using a square sensor grid. While sensitivity to the primary heat flux was determined to be the highest, sensitivity to the other parameters is either on the same order of magnitude or one order of magnitude less. Two different measurement models are compared for heating source localization: (1) directly using the one-way ultrasonic pulse time of flight as the measurement vector and (2) indirectly obtaining distance from the one-way ultrasonic pulse time of flight and then using these obtained distances as the measurement vector in the extended Kalman filter. Heating source localization results and convergence behavior are compared for the two measurement models. Two areas of sensitivity analyses are presented: (1) heat source location relative to sensor array position, and (2) sensor noise. The direct measurement model produced the best results when considering accuracy of converged solution, ability to converge to the correct solution given different initial guesses, and smoothness of convergence behavior.

Permalink for 'Erratum to “Three-dimensional modelling of fluid flow and heat transfer in micro-channels with synthetic jet” [Int J Heat Mass Transfer 55 (2012) 198–213]'

Erratum to “Three-dimensional modelling of fluid flow and heat transfer in micro-channels with synthetic jet” [Int J Heat Mass Transfer 55 (2012) 198–213]

Posted: February 3rd, 2012, 5:21pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 1 February 2012

A. Lee, V. Timchenko, G.H. Yeoh, J.A. Reizes

Brownian dynamics study of particles in chemical vapor deposition of aluminum nitride

Posted: February 3rd, 2012, 5:21pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 1 February 2012

Derek Endres, Sandip Mazumder

Aluminum nitride (AlN) films are commercially grown by chemical vapor deposition. In this process, it has been experimentally observed that AlN nanoparticles are formed in the gas-phase. Although these particles are formed in the vicinity of the hot substrate, they tend to stay away from the hot substrate and are observed to deposit on the cold walls of the reactor. In this study, the trajectories of the AlN particles are simulated with the goal to understand the mechanisms responsible for their motion. A three-dimensional (3D) Lagrangian Brownian dynamics simulator based on the Langevin equation is developed, and coupled with a 3D computational fluid dynamics (CFD) solver. The model is validated, and then explored for the problem at hand. It is found that thermophoretic forces are primarily responsible for driving the particles away from the hot substrate and depositing them on the cold reactor walls.

Permalink for 'Scaling for the Prandtl number of the natural convection boundary layer of an inclined flat plate under uniform surface heat flux'

Scaling for the Prandtl number of the natural convection boundary layer of an inclined flat plate under uniform surface heat flux

Posted: January 31st, 2012, 8:49pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 31 January 2012

Suvash C. Saha, Richard J. Brown, Y.T. Gu

An improved scaling analysis and direct numerical simulations are performed for the unsteady natural convection boundary layer adjacent to a downward facing inclined plate with uniform heat flux. The development of the thermal or viscous boundary layers may be classified into three distinct stages: a start-up stage, a transitional stage and a steady stage, which can be clearly identified in the analytical as well as the numerical results. Previous scaling shows that the existing scaling laws of the boundary layer thickness, velocity and steady state time scale for the natural convection flow on a heated plate of uniform heat flux provide a very poor prediction of the Prandtl number dependency of the flow. However, those scalings perform very well with Rayleigh number and aspect ratio dependency. In this study, a modified Prandtl number scaling is developed using a triple-layer integral approach forPr > 1. It is seen that in comparison to the direct numerical simulations, the modified scaling performs considerably better than the previous scaling.

Optical probing of anisotropic heat transport in the quantum spin ladder Ca9La5Cu24O41

Posted: January 31st, 2012, 8:49pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 31 January 2012

M. Otter, G. Athanasopoulos, N. Hlubek, M. Montagnese, M. Labois, ...

A transient thermal imaging technique is used to monitor heat diffusion at the surface of the antiferromagnetic spin ladder material Ca9La5Cu24O41. This material shows highly anisotropic thermal conductivity due to a large uni-directional magnetic heat transport along the ladders. The thermal conductivity is measured using optical heating as well as electrical heating, yielding 37 ± 3 W m Kfor the fast (ladder) direction and 2.5 ± 0.5 W m Kfor the slow direction, respectively. The fast direction result is in agreement with the thermal conductivity measured using other dynamic methods, but about 60% lower than the thermal conductivity measured using steady state methods.

Numerical analysis of convective drying of gypsum boards

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Thijs Defraeye, Geert Houvenaghel, Jan Carmeliet, Dominique Derome

Convective drying of gypsum boards is investigated by numerical modelling, within the context of gypsum board manufacturing where enhancing processing efficiency, reducing energy usage and optimising product quality are essential. The aim of this parametric study is to provide a first step towards modelling of the drying process in an industrial drier by investigating the main factors impacting the drying process, such as the influence of air speed, turbulence intensity, approach flow temperature and heterogeneous drying conditions but also the influence of the paper liner on the drying process. Therefore, this study is performed for a simple configuration and at ambient air temperatures. In terms of air flow modelling, CFD simulations are performed in addition to the use of standard convective transfer coefficients. The sensitivity of the drying process to the air flow conditions is found to be limited for a gypsum board with a paper liner due to the high resistance of the paper liner to vapour transport, compared to the boundary layer resistance. Thus, guidelines for modelling drying of gypsum boards under representative manufacturing conditions conclude that detailed flow modelling is less critical to assess this specific drying problem. Instead, characterisation of the material transport properties at high temperatures is more relevant, particularly for the paper liner.

Permalink for 'Reduction of angle splitting and computational time for the finite volume method in radiative transfer analysis via phase function normalization'

Reduction of angle splitting and computational time for the finite volume method in radiative transfer analysis via phase function normalization

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Brian Hunter, Zhixiong Guo

The commonly implemented splitting of solid angles to ensure scattered energy conservation in the finite volume method does not exactly conserve phase function asymmetry factor after directional discretization, leading to significant changes in scattering effect for radiative transfer analysis in highly anisotropic scattering media. In addition, use of a large number of split sub-angles results in drastic increases in computational CPU time and computer memory. The phase function normalization approach considered in this study is found to guarantee accurate conservation of both scattered energy and asymmetry factor simultaneously after directional discretization as well as depress solid angle splitting, vastly reducing the computational convergence time with improved accuracy. As a test, radial and axial radiative heat flux profiles in a scattering cylinder generated both with and without the phase function normalization are compared among different levels of angle discretization and splitting as well as with the discrete-ordinates method. The effects of changes in optical thickness, angular resolution, scattering albedo, and phase function approximation are examined.

Permalink for 'Impacts of the mixed wettability on liquid water and reactant gas transport through the gas diffusion layer of proton exchange membrane fuel cells'

Impacts of the mixed wettability on liquid water and reactant gas transport through the gas diffusion layer of proton exchange membrane fuel cells

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Rui Wu, Qiang Liao, Xun Zhu, Hong Wang

In this paper, we develop a pore network model for liquid water and reactant gas transport through the porous gas diffusion layer (GDL) of mixed wettability. We first consider the case of uniform distribution of hydrophilic fraction along the GDL thickness. It is revealed that the addition of hydrophilic pores has a negligible impact on liquid saturation profile when the hydrophilic fraction is low (⩽0.2), whereas in the case of higher hydrophilic fraction (⩾0.4), a flat shape of liquid saturation profile is observed along the GDL thickness. The total liquid saturation in the GDL is found to first decrease and then increase with the increase of hydrophilic pores; and an optimum hydrophilic fraction exists leading to the maximum limiting current density. Also, we investigate the transport process in the GDL of non-uniform wettability (i.e., the hydrophilic fraction is 0.4 near the network inlet, while at the downstream region it is 0.3). As compared to the uniform case, the liquid saturation level at the downstream region is drastically decreased in the non-uniform system, thereby leading to a higher limiting current density. These findings suggest that the fuel cell performance can be improved by designing the GDL with appropriate wettability distribution.

An implicit lattice Boltzmann model for heat conduction with phase change

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Mohsen Eshraghi, Sergio D. Felicelli

In this work, a new variation of the lattice Boltzmann method (LBM) was developed to solve the heat conduction problem with phase change. In contrast to previous explicit algorithms, the latent heat source term was treated implicitly in the energy equation, avoiding iteration steps and improving the formulation stability and efficiency. The Bhatnagar–Gross–Krook (BGK) approximation with a D2Q9 lattice was applied and different boundary conditions including Dirichlet and Neumann boundary conditions were considered. The developed model was tested by solving a one-dimensional melting problem for a pure metal, and one and two-dimensional solidification problems for a binary alloy. The results of the LBM solution were compared with analytical and finite element solutions and a good consistency was observed. Considering the special capabilities that LBM offers, like local characteristic, and inherent parallel structure, the developed model is an interesting alternative to traditional continuum models.

Multifunctional heat exchangers derived from three-dimensional micro-lattice structures

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Kevin J. Maloney, Kathryn D. Fink, Tobias A. Schaedler, Joanna A. Kolodziejska, Alan J. Jacobsen, ...

A micro-scale cross-flow heat exchanger is constructed from a hollow nickel micro-lattice structure, which is fabricated by conformally electroplating nickel onto a sacrificial polymer micro-lattice formed from self-propagating photopolymer waveguides. The periodic unit cell of the hollow nickel micro-lattice structure tested here includes lattice members with a diameter <1 mm and a nominal pore size <9 mm. The heat transfer performance of the micro-lattice-based heat exchanger is analyzed in terms of thermal conductance per unit volume, which is equal to the value of overall heat transfer coefficient multiplied by surface area to volume ratio. Calculated values range from 0.84 to 1.58 W/cmK for Reynolds number ranges of between 3400 ± 200 and 6500 ± 500 for hot water flow inside the hollow lattice members and 85 ± 6 and 240 ± 20 for cold water flow around the lattice members. Based on a developed correlation, the experimental heat transfer data is used to predict the thermal performance of larger and smaller micro-lattice-based heat exchangers, as well as various micro-lattice feature dimensions that are tunable with the fabrication process (node-to-node spacing, inner diameter, etc.). The micro-lattice heat exchanger was tested under quasi-static compression and the results illustrate the multifunctional capability for load bearing and energy absorption applications. This work demonstrates a multifunctional heat exchanger with a fully-scalable fabrication process which is useful for size and weight constrained heat transfer applications, including those in the automotive and aerospace industries.

Fluid flow and heat mass transfer in membrane parallel-plates channels used for liquid desiccant air dehumidification

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Si-Min Huang, Li-Zhi Zhang, Kai Tang, Li-Xia Pei

Fluid flow and convective heat mass transfer in membrane-formed parallel-plates channels are investigated. The membrane-formed channels are used for liquid desiccant air dehumidification. The liquid desiccant and the air stream are separated by the semi-permeable membrane to prevent liquid droplets from crossing over. The two streams, in a cross-flow arrangement, exchange heat and moisture through the membrane, which only selectively permits the transport of water vapor and heat. The two flows are assumed hydrodynamically fully developed while developing thermally and in concentration. Different from traditional method of assuming a uniform temperature (concentration) or a uniform heat flux (mass flux) boundary condition, the real boundary conditions on membrane surfaces are numerically obtained by simultaneous solution of momentum, energy and concentration equations for the two fluids. Equations are then coupled on membrane surfaces. The naturally formed boundary conditions are then used to calculate the local and mean Nusselt and Sherwood numbers along the channels. Experimental work is performed to validate the results. The different features of the channels in comparison to traditional metal-formed parallel-plates channels are disclosed.

On the thermal conductivity of sintered metallic fibre structures

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

C. Veyhl, T. Fiedler, O. Andersen, J. Meinert, T. Bernthaler, ...

The present paper investigates the anisotropic thermal conductivity of a novel sintered metallic fibre structure with different porosities (i.e. 51.9%, 74.9%, 81.4%). Different methodologies are applied: numerical calculations (i.e. Finite Element and Lattice Monte Carlo methods) based on micro-computed tomography images, experimental tests (i.e. steady-state plate method) and analytical modelling. Good agreement between the numerical methods and experimental measurements is obtained for high porosity models (i.e. porosity > 72.5%). Furthermore, the thermal conductivity decreases with increasing porosity. A distinct thermal anisotropy is found where maximum values are in the parallel direction and minimum values in the transverse direction to the fibres.

Thermal analysis of a low flow piezoelectric air pump

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Andrew Eastman, Mark Kimber, Atsuhiko Hirata, Gaku Kamitani

With the propagation of ever faster and more powerful electronics, the need for active, low power cooling is becoming apparent. In particular, applications which have traditionally relied only on natural convection will soon require an active cooling solution due to continually rising heat loads. A promising solution lies in utilizing piezoelectric materials via fans or pumps. Examples of such devices include synthetic jets and piezoelectric pumps, both of which rely on an oscillating diaphragm to induce flow. The device under investigation in this paper is able to generate flow rates up to 1 L/min and overcome pressures of over 2 kPa. The focus is to experimentally characterize the cooling potential of a piezoelectric-based air pump oriented normal to the heated element, an environment similar to jet impingement. Experimental characterizations were made through the use of a thin film heater which provided a constant heat flux while an infrared camera was used to capture the resulting temperature field of the heated surface. Full-field data of the convection coefficient was analyzed as a function of vibration amplitude of the piezoelectric diaphragm and distance from the nozzle to the heated target. The maximum heat transfer coefficient was found to always be at the stagnation point regardless of vibration amplitude or distance to the target. Correlations have been developed which account for both variables considered and can be used to predict the performance of future designs which rely on the same physical characteristics.

Permalink for 'Heat transfer and pressure drop during flow boiling of pure refrigerants and refrigerant/oil mixtures in tube with porous coating'

Heat transfer and pressure drop during flow boiling of pure refrigerants and refrigerant/oil mixtures in tube with porous coating

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Bartosz Dawidowicz, Janusz T. Cieśliński

The experimental stand and procedure for flow boiling investigations are described. Experimental data for pure R22, R134a, R407C and their mixtures with polyester oil FUCHS Reniso/Triton SEZ 32 in a tube with porous coating and smooth, stainless steel reference tube are presented. Mass fraction of oil was equal to 1% or 5%. During the tests inlet vapour quality was set at 0 and outlet quality at 0.7. Mass velocity varied from about 250 to 500 kg/ms. The experiments have been conducted for average saturation temperature 0 °C. In the case of flow boiling of pure refrigerants, the application of a porous coating on inner surface of a tube results in higher average heat transfer coefficient and simultaneously in lower pressure drop in comparison with the flow boiling in a smooth tube for the same mass velocity. Correlation equation for heat transfer coefficient calculation during the flow boiling of pure refrigerants inside a tube with porous coating has been proposed.

Heat transfer enhancement in microchannel heat sinks using nanofluids

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Tu-Chieh Hung, Wei-Mon Yan, Xiao-Dong Wang, Chun-Yen Chang

Heat transfer enhancement in a 3-D microchannel heat sink (MCHS) using nanofluids is investigated by a numerical study. The addition of nanoparticles to the coolant fluid changes its thermophysical properties in ways that are closely related to the type of nanoparticle, base fluid, particle volume fraction, particle size, and pumping power. The calculations in this work suggest that the best heat transfer enhancement can be obtained by using a system with an Al2O3–water nanofluid-cooled MCHS. Moreover, using base fluids with lower dynamic viscosity (such as water) and substrate materials with high thermal conductivity enhance the thermal performance of the MCHS. The results also show that as the particle volume fraction of the nanofluid increases, the thermal resistance first decreases and then increases. The lowest thermal resistance can be obtained by properly adjusting the volume fraction and pumping power under given geometric conditions. For a moderate range of particle sizes, the MCHS yields better performance when nanofluids with smaller nanoparticles are used. Furthermore, the overall thermal resistance of the MCHS is reduced significantly by increasing the pumping power. The heat transfer performance of Al2O3–water and diamond–water nanofluids was 21.6% better than that of pure water. The results reported here may facilitate improvements in the thermal performance of MCHSs.

Radiation effects on mixed turbulent natural and forced convection in a horizontal channel using direct numerical simulation

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

Atsushi Sakurai, Koji Matsubara, Kenji Takakuwa, Ryo Kanbayashi

The purpose of this study is to clarify the radiation effects on mixed turbulent convection in a horizontal channel. The present study provides turbulence statistics using direct numerical simulation (DNS) in an optically thin medium. When the radiation effect is considered, the flow structure and the temperature distribution in the channel change with an increase in the optical thickness of the fluid. The radiation effect changes the distributions of the temperature fluctuation intensity and the turbulent heat flux. These radiation effects on mixed convection can be clearly explained by the turbulence statistics obtained from the DNS results.

Mathematical optimisation of laminar forced convection heat transfer through a vascularised solid with square channels

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 28 January 2012

O.T. Olakoyejo, T. Bello-Ochende, J.P. Meyer

This paper presents a three-dimensional geometric optimisation of cooling channels in forced convection of a vascularised material with the localised self-cooling property subjected to a heat flux. A square configuration was studied with different porosities. Analytical and numerical solutions were provided. The geometrical configuration was optimised in such a way that the peak temperature was minimised at every point in the solid body. The optimisation was subject to the constraint of a fixed global volume of solid material, but the elemental volume was allowed to morph. The solid material was subject to a heat flux on one side and the cooling fluid was forced through the channels from the opposite direction with a specified pressure difference. The structure had three degrees of freedom as design variables: the elemental volume, channel hydraulic diameter and channel-to-channel spacing. A gradient-based optimisation algorithm was used to determine the optimal geometry that gave the lowest thermal resistance. This optimiser adequately handled the numerical objective function obtained from numerical simulations of the fluid flow and heat transfer. The numerical results obtained were in agreement with a theoretical formulation using scale analysis and the method of intersection of asymptotes. The results obtained show that as the pressure difference increases, the minimised thermal resistance decreases. The results also show the behaviour of the applied pressure difference on the optimised geometry. The use of the optimiser made the numerical results to be more robust with respect to the optimum internal configurations of the flow systems and the dimensionless pressure difference.

Numerical modeling of tunable optofluidics lens based on combined effect of hydrodynamics and electroosmosis

Posted: January 28th, 2012, 8:06pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 27 January 2012

Haiwang Li, Teck Neng Wong, Nam-Trung Nguyen, John C. Chai

A numerical model of liquid-core liquid-cladding optofluidics lens under the combined effect of hydrodynamics and electroosmosis are presented in this paper. In the numerical simulation, a combined formulation using only one set of conservation equations to treat both fluids are employed. The coupled electric potential equation and Navier–Stokes equation are solved using the finite volume method. The level-set method is used to capture the interface between the fluids. To overcome a weakness in the level-set method, the localized mass correction scheme is applied to ensure mass conservation. The validity of the numerical scheme is evaluated by comparing with the experimental results; numerical results highlight the electroosmotic effect; the combined effect of pressure driven and electroosmosis can form optically smooth interfaces with arc-shape between the cladding fluids and the core fluid. Under fixed cladding flow rates, the same electric field forms symmetric biconvex lens only. Different electric fields can form biconvex lens, plane-convex lens, and meniscus lens. The results also present the velocity profiles and flow fields of micro lens. There is a good agreement between numerical and experimental results.

EDITORIAL BOARD

Posted: January 27th, 2012, 4:08pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Volume 55, Issues 7–8, March 2012, Pages IFC

[No author name available]

Boiling time effect on CHF enhancement in pool boiling of nanofluids

Posted: January 27th, 2012, 4:08pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 27 January 2012

Tomio Okawa, Masahiro Takamura, Takahito Kamiya

Using TiO2–water nanofluids as the test liquid, pool boiling experiments were carried out to investigate the dependence of the nucleate boiling heat transfer, surface wettability and critical heat flux (CHF) on the boiling time in nanofluids. In the experiments performed at sufficiently high nanoparticle concentrations, the boiling heat transfer first degraded, then improved, and finally reached an equilibrium state. It was hence supposed that the present nanofluids had competing effects to deteriorate and enhance the nucleate boiling heat transfer. As for the surface wettability and CHF, the static contact angle asymptotically decreased whilst the CHF asymptotically increased with an increase in the boiling time. The maximum CHF enhancement measured in the present experiments was 91%, and strong correlation was found between the contact angle and the CHF. Although the boiling time needed to achieve the maximum CHF enhancement was less than a minute at high particle concentrations, a longer time of the order of 1 h was necessary at the lowest particle concentration tested in this work. This experimental result indicated that sufficient attention should be paid to the boiling time effect particularly in industrial applications of nanofluids to emergency cooling.

Thermal and flow characteristics of the condensation of R404A refrigerant in pipe minichannels

Posted: January 20th, 2012, 5:38pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 18 January 2012

Henryk Charun

This article presents the results of experimental investigations of heat exchange and pressure drop during the condensation of R404A refrigerant in stainless steel pipe minichannels with internal diameters of 1.4–3.30 mm. A review is provided of the present state of knowledge concerning the condensation of this refrigerant in conventional channels and in small-diameter channels. It is emphasized that there are few prior publications concerning this issue. The test setup is described as well as the results of the experimental tests. We discuss the dependence of the heat transfer coefficient and the pressure drop of the R404A refrigerant on both minichannel diameter and process parameters. The pressure drop during the condensation of this refrigerant is satisfactorily described by the Friedel and Garimella correlations. Based on the experimental tests, we propose a new correlation for the calculation of the local heat transfer coefficient. The values calculated from this correlation were in agreement with the experimental results to within ±20%.

A two-step discrete method for reconstruction of temperature distribution in a three-dimensional participating medium

Posted: January 20th, 2012, 5:38pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 18 January 2012

Qun-xing Huang, Fei Wang, Jian-hua Yan, Yong Chi

A new two-step discrete method is proposed in this paper for reconstruction of three-dimensional temperature distribution in an absorbing, emitting and isotropically scattering medium. With this new method, the temperature of the wall is also considered. The local radiative source term is reconstructed in the first step through the discrete transfer method from the directional, exit radiation intensities measured by CCD cameras. Then, the temperature of each discrete element is calculated in the second step by subtracting the scattering contribution from the retrieved radiative source term through the discrete ordinate method. The least squares minimum residual algorithm is employed to solve the ill-posed reconstruction equations and the calculation is improved to reduce the computational cost. The performance of the proposed method is examined by numerical test problems with unimodal and bimodal temperature distributions. The ill-conditioning of the reconstruction problem is checked by the Picard condition. The effects of the measurement noise and the radiative properties on the reconstruction accuracy are discussed. The results show that the method proposed in this paper is capable of reconstructing the temperature distribution accurately in large, confined, participating media, even with noisy input data. The computation time reduction of this new method is significant when compared with other methods.

Permalink for 'Total dietary fat and fatty acid content modifies plasma phospholipid fatty acids, desaturase activity indices, and urinary prostaglandin E in women'

Total dietary fat and fatty acid content modifies plasma phospholipid fatty acids, desaturase activity indices, and urinary prostaglandin E in women

Posted: January 17th, 2012, 7:10pm MST

Publication year: 2012
Source: Nutrition Research, Volume 32, Issue 1, January 2012, Pages 1-7

Susan K. Raatz, Lindsay R. Young, Matthew J. Picklo, Edward R. Sauter, Wenyi Qin, ...

Compared with diets high in fat, low-fat diets are associated with reduced risk of cardiovascular disease. We hypothesized that a low-fat (LF) (20% fat) and an LF high–omega-3 (n-3) fatty acid diet (LFn3) (23% fat with 3% asα-linolenic acid, eicosapentaenoic acid, and docosahexaenoic acid [DHA]) would enhance n-3 composition of plasma phospholipid fatty acid and reduce urinary prostaglandin E2(PGE2) relative to a high-fat diet (HF) (40% fat) and that these changes would be associated with alterations inδ5 desaturase (D5D) andδ6 desaturase (D6D) activity. Phospholipid fatty acids and urinary PGE2were measured, and D5D and D6D activity indices calculated in a crossover trial in 17 postmenopausal women fed each of 3 test diets (HF, LF, and LFn3) for 8-week feeding periods. Desaturase activity indices were calculated as D5D, 20:4n-6/20:3n-6, and D6D, 20:3n-6/18:2n-6. Plasma phospholipid fatty acid,α-linolenic acid, eicosapentaenoic acid, docosapentaenoic acid (DPA), DHA, and total n-3 fatty acids increased, whereas linoleic acid and arachidonic acid decreased with consumption of LFn3. The LF resulted in enhanced arachidonic acid and DHA. High fat reduced D6D, whereas both HF and LF increased D5D. Urinary PGE2was reduced in response to both the LF and LFn3 diets. Low-fat diets, with or without long-chain n-3 fatty acids, promote positive health effects due in part to favorable alteration of plasma phospholipid fatty acid profiles and modification in desaturase activity indices, suggesting that the type and amount of fat consumed are modifiable risk factors for the prevention of cardiovascular disease.

Permalink for 'Supplementation of Korean fermented soy pastedoenjangreduces visceral fat in overweight subjects with mutant uncoupling protein-1 allele'

Supplementation of Korean fermented soy pastedoenjangreduces visceral fat in overweight subjects with mutant uncoupling protein-1 allele

Posted: January 17th, 2012, 7:10pm MST

Publication year: 2012
Source: Nutrition Research, Volume 32, Issue 1, January 2012, Pages 8-14

Myoungsook Lee, Soowan Chae, Yoonsoo Cha, Yongsoon Park

The purpose of this study was to examine the hypothesis that the antiobesity effect ofdoenjang, a Korean fermented soy paste is different between the mutant and the wild-type alleles of a polymorphism upstream of theuncoupling protein-1 (UCP-1)gene in overweight subjects. In our randomized, double-blind, placebo-controlled trial, a total of 51 subjects with a body mass index of 23 kg/mor greater and a waist-to-hip ratio of 0.90 or greater for men or 0.85 or greater for women were randomly assigned to take 9.9 g/d of either a placebo ordoenjangfor 12 weeks. The relative frequency of the mutant G allele of theUCP-1polymorphism was 0.60 in the placebo group and 0.62 in thedoenjanggroup. Supplementation ofdoenjanghad no significant effect on the visceral fat area compared with that of the placebo group, but there was a significantly reduced amount of visceral fat in subjects with the G allele ofUCP-1polymorphism.Doenjangsupplementation was found to significantly increase the free fatty acid concentration in subjects with both the A allele and the G allele. There was a significant association between visceral fat and age in study subjects with both the wild-type and mutant alleles of theUCP-1gene.Doenjangsupplementation significantly reduced visceral fat and increased the free fatty acid concentrations in subjects with the G allele of theUCP-1polymorphism, which suggests thatdoenjangmay be related to increased free fatty acid levels caused by elevated lipolysis in these subjects.

Permalink for 'Low-dose fish oil supplementation increases serum adiponectin without affecting inflammatory markers in overweight subjects'

Low-dose fish oil supplementation increases serum adiponectin without affecting inflammatory markers in overweight subjects

Posted: January 17th, 2012, 7:10pm MST

Publication year: 2012
Source: Nutrition Research, Volume 32, Issue 1, January 2012, Pages 15-23

Anders Gammelmark, Trine Madsen, Kim Varming, Søren Lundbye-Christensen, Erik B. Schmidt

Obesity is associated with an increased risk of cardiovascular disease, whereas long-chain n-3 polyunsaturated fatty acids (PUFAs) from fish may have cardioprotective and anti-inflammatory effects. This study aimed to investigate the hypothesis that acute and short-term supplementation with a low dose of marine n-3 PUFA exerts an anti-inflammatory effect in overweight subjects. In a double-blind, placebo-controlled trial with 2 parallel groups, 50 overweight subjects were randomized to receive daily supplementation with 2 capsules containing either 2 g of fish oil (1.1 g marine n-3 PUFA) or 2 g of olive oil. Blood samples and adipose tissue biopsies were collected at baseline, after 1 day (acute effect), and after 6 weeks (short-term effect) of supplementation. No significant effects were seen after supplementation for 1 day, but after 6 weeks, subjects receiving fish oil had a significant increase in the n-3 PUFA content of granulocytes and adipose tissue (P< .01). Serum adiponectin levels were increased by 0.55μg/mL (95% confidence interval, 0.02-1.08) in the fish oil group compared with the control group (P= .04) after 6 weeks of supplementation. Levels of interleukin 6 were inversely correlated to the marine n-3 PUFA content of granulocytes and adipose tissue at baseline (excludingα-linolenic acid). In conclusion, daily supplementation with 1.1 g of marine n-3 PUFA significantly increased serum adiponectin, but the effect was small, and no overall anti-inflammatory effect of the supplement could be demonstrated.

Permalink for 'The association of alcohol consumption with metabolic syndrome and its individual components: the Taichung community health study'

The association of alcohol consumption with metabolic syndrome and its individual components: the Taichung community health study

Posted: January 17th, 2012, 7:10pm MST

Publication year: 2012
Source: Nutrition Research, Volume 32, Issue 1, January 2012, Pages 24-29

Ching-Chu Chen, Wen-Yuan Lin, Chia-Ing Li, Chiu-Shong Liu, Tsai-Chung Li, ...

Alcohol has both adverse and protective effects on the individual components of metabolic syndrome (MS). We hypothesize that alcohol consumption increases the risk of developing MS and that the consumption of different types of alcoholic beverages has different effects on the development of MS and its individual components. We enrolled 2358 men for this cross-sectional study. The data were collected from self-reported nutrition and lifestyle questionnaires. Individuals who drank at least once per week for 6 consecutive months were classified as current drinkers. Current drinkers were at a higher risk of developing MS, abdominal obesity, and high triglyceride levels, but they were at a lower risk of developing low levels of high-density lipoprotein cholesterol (HDL-C). The increased risk of developing MS, high triglyceride, and high fasting glucose levels was dose dependent, whereas low HDL-C levels demonstrated a reverse relationship. The dose needed to reduce the risk of having low HDL-C levels was ≧50 g/d. This dose, however, resulted in an increased risk of developing high fasting glucose and high triglyceride levels. Consuming mixed types of alcohol increased the risk of developing MS and abdominal obesity. Meanwhile, those who drank liquor or wine had a greater risk of developing high triglyceride or high fasting glucose levels, respectively. In conclusion, alcohol consumption dose-dependently increased the risk of developing MS and some of its individual components while dose-dependently decreasing the risk of developing low HDL-C levels. The type of alcoholic beverage had different effects on the development of the individual components of MS.

Amino acid mixture acutely improves the glucose tolerance of healthy overweight adults

Posted: January 17th, 2012, 7:10pm MST

Publication year: 2012
Source: Nutrition Research, Volume 32, Issue 1, January 2012, Pages 30-38

Bei Wang, Lynne M. Kammer, Zhenping Ding, David G. Lassiter, Jungyun Hwang, ...

Certain amino acids have been reported to influence carbohydrate metabolism and blood glucose clearance, as well as improve the glucose tolerance in animal models. We hypothesized that an amino acid mixture consisting of isoleucine and 4 additional amino acids would improve the glucose response of healthy overweight men and women to an oral glucose tolerance test (OGTT). Twenty-two overweight healthy subjects completed 2 OGTTs after consuming 2 different test beverages. The amino acid mixture beverage (CHO/AA) consisted of 0.088 g cystine 2HCl, 0.043 g methionine, 0.086 g valine, 12.094 g isoleucine, 0.084 g leucine, and 100 g dextrose. The control beverage (CHO) consisted of 100 g dextrose only. Venous blood samples were drawn 10 minutes before the start of ingesting the drinks and 15, 30, 60, 120, and 180 minutes after the completion of the drinks. During the OGTT, the plasma glucose response for the CHO/AA treatment was significantly lower than that of the CHO treatment (P< .01), as was the plasma glucose area under the curve (CHO/AA 806 ± 31 mmol/L·3 hours vs CHO 942 ± 40 mmol/L·3 hours). Differences in plasma glucose between treatments occurred at 30, 60, 120, and 180 minutes after supplement ingestion. Plasma glucagon during the CHO/AA treatment was significantly higher than during the CHO treatment. However, there were no significant differences in plasma insulin or C-peptide responses between treatments. These results suggest that the amino acid mixture lowers the glucose response to an OGTT in healthy overweight subjects in an insulin-independent manner.

Mulberry leaf extract increases adiponectin in murine 3T3-L1 adipocytes

Posted: January 17th, 2012, 7:10pm MST

Publication year: 2012
Source: Nutrition Research, Volume 32, Issue 1, January 2012, Pages 39-44

Jarinyaporn Naowaboot, Choon Hee Chung, Patchareewan Pannangpetch, Ran Choi, Bo Hwan Kim, ...

We have previously shown that mulberry leaf extract (MA) causes blood glucose levels to decrease in rats with streptozotocin-induced diabetes while enhancing glucose uptake by isolated fat cells. We hypothesized that the antidiabetic activity of MA is mediated via enhancement of adiponectin secretion and adipogenesis, which consequently decreases blood glucose. In the present study, we aimed to elucidate the molecular basis for the observed antidiabetic activity using murine 3T3-L1 preadipocyte cultures. We found that treatment of differentiating 3T3-L1 cells with MA at concentrations of 5, 15, and 45μg/mL increased expression of adiponectin messenger RNA from 1.4-fold (control) to 1.5-, 1.95-, and 2.2-fold above basal values, respectively, while causing adiponectin secretion to increase from 70 ± 7.4 ng/mL to 100 ± 1.4, 138 ± 2.0, and 176 ± 21.4 ng/mL, respectively. Furthermore, we observed an increase in both lipid accumulation and messenger RNA expression of transcription factors, such as CCAAT/enhancer-binding proteinαand peroxisome proliferator-activated receptorγ; and of the fatty acid–binding protein aP2 in differentiated 3T3-L1 cells pretreated with MA. Our findings indicate that the stimulatory effects of mulberry leaf extract on adipocyte proliferation and differentiation likely occur through up-regulation of adipogenic transcription factors and downstream gene expression. Such effects of mulberry leaf extract on adiponectin secretion and adipocyte activity may account for, at least in part, the antidiabetic effects of consumption of beverages containing mulberry leaves.

Permalink for 'Ascorbate and dehydroascorbic acid as biomarkers of oxidative stress: validity of clinical data depends on vacutainer system used'

Ascorbate and dehydroascorbic acid as biomarkers of oxidative stress: validity of clinical data depends on vacutainer system used

Posted: January 17th, 2012, 7:10pm MST

Publication year: 2012
Source: Nutrition Research, Volume 32, Issue 1, January 2012, Pages 66-69

Jens Lykkesfeldt

Ascorbate and dehydroascorbic acid are frequently used as biomarkers of oxidative stress, but their lack of stability ex vivo and rapid postsampling interconversion continue to result in erroneous reference values. One problem is the large variety of vacutainer devices used for blood sampling purposes and the basic question of plasma vs serum as matrix. This study acquired blood samples by using 9 different and commonly used vacutainer systems followed by acidic stabilization and analysis by a well-validated method with the purpose of identifying acceptable means of collecting samples for proper ascorbate/dehydroascorbic acid analysis. In comparison, K3-EDTA vacutainers were superior in maintaining low ex vivo oxidation of vitamin C.

Contact line behavior for a highly wetting fluid under superheated conditions

Posted: January 17th, 2012, 6:30pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 17 January 2012

R. Raj, C. Kunkelmann, P. Stephan, J. Plawsky, J. Kim

The contact line behavior of a highly wetting, dielectric liquid (FC-72) droplet under superheated conditions is investigated. Relatively large macroscopic contact angles atypical of FC-72 droplets were observed under superheated conditions. The addition of a non-condensable dissolved gases in the system increased the contact angle at a given superheat. Numerical simulations of the transport phenomena near the microscopic three phase contact line were performed that show how the macroscopic contact angle is related to the superheat and thickness of the adsorbed film ahead of the contact line. The use of a macroscopic contact angle that is a function of superheat in established models for bubble departure diameter and the onset of nucleate boiling enhanced the ability of those models to describe the behavior of highly wetting fluids.

Parameter estimation of in-situ thermal response tests for borehole ground heat exchangers

Posted: January 17th, 2012, 6:30pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 17 January 2012

Min Li, Alvin C.K. Lai

This paper discusses some aspects of parameters estimation used in in-situ thermal response tests of ground heat exchangers, including sensitivity analysis and comparison of iterative minimization algorithms. First, several sensitivity coefficients of parameters and uncertainties occurring in in-situ tests are examined in depth. Starting from an analytical heat transfer model of borehole ground heat exchangers, sensitivity coefficients for single U-tube ground heat exchangers are of analytical forms. The sensitivity analysis provides some general and new guidelines for mitigating the influence of testing uncertainties. Next, Monte Carlo simulation is performed to evaluate reliability of two powerful minimization algorithms, the Levenberg–Marquardt method and a trust region method subject to bounds. The Monte Carlo simulation shows that if thermal diffusivity of soil is an estimated parameter, the Levenberg–Marquardt method may result in unreliable results, and its performance depends strongly on the quality of the initial guessed values. In contrast, the interior trust region method considered in this paper can produce more reliable results, and its performance depends on the range of input parameters bounds. Finally, feasibility of the highlighted methodology is illustrated by applying it to two real in-situ thermal response tests.

Approximation accuracy of the two-point third moments of the velocity field in the homogeneous turbulence

Posted: January 17th, 2012, 6:30pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 16 January 2012

V.A. Babenko, V.A. Frost

Different approximations for two-point third moments of velocity field appearing in the Karman–Howart equation are compared. For this purpose, the known experimental results of Townsend and Stewart and the model form of turbulence energy spectrum, which enables approximating the experimentally determined second moments of velocity field, are used. The latter are applied for evaluation of the two-point third moments by the procedures proposed by various authors. Calculation results are compared to experimental data, which allows obtaining quantitative assessments of approximation accuracy. For a number of models, the second-order structural function is found from the Kolmogorov equation for inertial subrange. Thus, in the Hasselman and Lytkin models for the structural functionDLLthe power law expected in the inertial subrangeDLL(r) ∼ ris obtained.

Coupled thermocapillary convection on Marangoni convection in liquid layers with curved free surface

Posted: January 17th, 2012, 6:30pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 16 January 2012

K. Li, Z.M. Tang, W.R. Hu

This paper numerically studied the coupled Marangoni convection and thermocapillary convection in a finite liquid layer (Pr = 11.6) in the microgravity conditions. The multi-cellular flow structure and the marginal instability boundary of the coupled convection are predicted. Oscillatory coupled convection is also reported in concave liquid layers of volume ratio between 0.80 and 0.85.

Experimental study on the pool boiling CHF enhancement using magnetite-water nanofluids

Posted: January 17th, 2012, 6:30pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 16 January 2012

Jong Hyuk Lee, Taeseung Lee, Yong Hoon Jeong

This paper described the effects of a magnetite-water nanofluid (MWNF) on the critical heat flux (CHF) enhancement using an Ni–Cr wire in pool boiling. All experiments were performed at a saturated condition under atmospheric pressure. The CHF values between the MWNF and the other nanofluids with several volume concentrations were compared to evaluate the effect of the MWNF on the CHF enhancement. The CHF values of the MWNF were enhanced from approximately 170% to 240% of pure water as the nanoparticle concentration increased. In addition, the CHF for the MWNF showed the highest value among the evaluated nanofluids. In this paper, three methods were introduced to elucidate the mechanism underlying CHF enhancement. First, scanning electron microscope (SEM) images were obtained to explain the CHF enhancement mechanism due to the deposited nanoparticles, which is related to the surface wettability of the heating surface during the pool boiling. Second, bubble formation in pool boiling was analyzed using image processing to demonstrate the relationship between bubble dynamics and CHF enhancement. Finally, the magnetic field was analytically calculated using the Biot–Savart law to evaluate the effects of the magnetic field on the CHF.

Mixed convection flow and heat transfer across a square cylinder under the influence of aiding buoyancy at low Reynolds numbers

Posted: January 14th, 2012, 8:51pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 14 January 2012

Neha Sharma, Amit K. Dhiman, Surendra Kumar

In this paper, mixed convection flow and heat transfer around a long cylinder of square cross-section under the influence of aiding buoyancy are investigated in the vertical unconfined configuration (Reynolds number,Re = 1–40 and Richardson number,Ri = 0–1). The semi-explicit finite volume method implemented on the collocated grid arrangement is used to solve the governing equations along with the appropriate boundary conditions. The onset of flow separation occurs betweenRe = 1–2, betweenRe = 2–3 and betweenRe = 3–4 forRi = 0, 0.5 and 1, respectively. The flow is found to be steady for the range of conditions studied here. The friction, pressure and total drag coefficients are found to increase with Richardson number, i.e., as the influence of aiding buoyancy increases drag coefficients increase at the constant value of the Reynolds number. The temperature field around the obstacle is presented by isotherm contours at the Prandtl number of 0.7 (air). The local and average Nusselt numbers are calculated to give a detailed study of heat transfer over each surface of the square cylinder and an overall heat transfer rate and it is found that heat transfer increases with increase in Reynolds number and/or Richardson number. The simple expressions for the wake length and average cylinder Nusselt number are obtained for the range of conditions covered in this work.

Permalink for 'Erratum to “Laminar flow of non-linear viscoelastic fluids in straight tubes of arbitrary contour” [Int. J. Heat Mass Transfer 54 (2011) 2188–2202]'

Erratum to “Laminar flow of non-linear viscoelastic fluids in straight tubes of arbitrary contour” [Int. J. Heat Mass Transfer 54 (2011) 2188–2202]

Posted: January 14th, 2012, 8:51pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 14 January 2012

[No author name available]

Permalink for 'Experimental thermal–hydraulic evaluation of CuO nanofluids in microchannels at various concentrations with and without suspension enhancers'

Experimental thermal–hydraulic evaluation of CuO nanofluids in microchannels at various concentrations with and without suspension enhancers

Posted: January 13th, 2012, 8:05pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 13 January 2012

Matthew D. Byrne, Robert A. Hart, Alexandre K. da Silva

This experimental study focuses on the effect of two important factors on the heat transfer and flow properties of copper oxide (CuO)/water nanofluids in a parallel microchannel flow configuration. The first factor considered is the solid media (CuO) concentration. In this investigation, concentration values of 0.005%, 0.01%, and 0.1% by volume were tested. The second factor is the use of a surfactant, cetyltrimethylammonium bromide (CTAB), as a suspension enhancer. All together, these two factors led to a total of six types of nanofluids, which were tested in addition to pure water, the reference fluid. The experimental setup allowed for the determination of the hydrodynamic and thermal performance of each nanofluid. In addition, a selection of the nanofluids were characterized by the use of scanning transmission electron microscopy (STEM) and Dynamic Light Scattering (DLS) techniques. The DLS transient settling measurements showed that for a nanofluid with a concentration of 0.1% by volume, the nanoparticle dispersion and suspension is negatively affected unless a surfactant is used. Hydrodynamic losses, which were evaluated by comparing the effect of the imposed pressure drop on the mass flow rate, were not meaningfully affected by the composition of the nanofluids tested. The measurements also showed that nanofluids containing a surfactant generally provided a modest increase in heat transfer rate when compared with tests performed using pure water. The largest increase was about 17% for a fluid with a concentration of 0.01% by volume. Consequently, the gains in heat transfer do not appear to be accompanied by a significant pumping power penalty. The results of this study suggest that the use of a surfactant is essential in maintaining a proper suspension of nanoparticles in the fluid, especially at higher concentrations.

Investigation on heat and mass transfer in 3D woven fibrous material [Int. J. Heat Mass Transfer 54 (2011) 3575–3586]

Posted: January 13th, 2012, 8:05pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 12 January 2012

X.J. Ran, Q.Y. Zhu, Y. Li

Permalink for 'Crystalline structure and mechanical property of poly(lactic acid) nanocomposite probed by near-infrared (NIR) hyperspectral imaging'

Crystalline structure and mechanical property of poly(lactic acid) nanocomposite probed by near-infrared (NIR) hyperspectral imaging

Posted: January 12th, 2012, 5:28pm MST

Publication year: 2012
Source: Vibrational Spectroscopy, Available online 12 January 2012

Hideyuki Shinzawa, Masakazu Nishida, Toshiyuki Tanaka, Wataru Kanematsu

The crystalline structure of a poly(lactic acid) (PLA) nanocomposite is probed by near-infrared (NIR) hyperspectral imaging to derive penetrating insight into its improved mechanical properties by inclusion of organoclay particles. A set of PLA nanocomposite samples are prepared under varying levels of clay content. The variation of the crystalline structure of PLA and corresponding mechanical strength are examined by NIR hyperspectral imaging and thermomechanical analysis (TMA), respectively. By carrying out the detailed analysis of the NIR hyperspectral image, it effectively provided a more detailed picture of the nanocomposite system. Namely, the addition of the clay substantially increases the frequency of the spontaneous nucleation of the PLA crystals. Corresponding decrease of the amorphous portion, in turn, restricts mechanical deformation of the samples under a certain level of load. Consequently, by carrying out detailed band position shift analysis of the NIR image spectra, the chemically meaningful information concerning the nanocomposite system can be effectively extracted.

Structural and vibrational study of 3- or 5-methyl substituted 2-N-ethylamino-4-nitropyridine N-oxides

Posted: January 12th, 2012, 5:28pm MST

Publication year: 2012
Source: Vibrational Spectroscopy, Available online 12 January 2012

J. Lorenc, J. Hanuza, J. Janczak

X-ray crystal structures of two isomers C8H11N3O3,i.e.2-N-ethylamino-5-methyl-4-nitropyridine N-oxide (EN5MPO) and 2-N-ethylamino-3-methyl-4-nitropyridine N-oxide (EN3MPO) have been determined. The different substitutions of the–CH3groups lead to change of the unit-cell structure, molecular and intermolecular arrangement. Both structures are monoclinic, space group P21/c and P21/n with a parallel and antiparallel orientation along thea-axis, respectively. In each of the two subunits, the methyl carbons and N-atoms of the nitro group are almost coplanar with the pyridine ring, but the N-oxide bonds are inclined from this plane. The crystal structures are stabilized by a set of the weak inter- and intramolecular hydrogen bonds of the N − H···O type. The structures of both isomers have been confirmed by the results of IR and Raman spectra measurements, quantum chemical calculations and potential energy distribution (PED). The role of methyl group introduced in 3 or 5 position of 2-N-ethylamino-4-nitropyridine N-oxide has been analyzed.

Cross-linking of linear vinylpolysiloxanes by hydrosilylation - FTIR spectroscopic studies

Posted: January 12th, 2012, 5:28pm MST

Publication year: 2012
Source: Vibrational Spectroscopy, Available online 12 January 2012

Anna Nyczyk, Czeslawa Paluszkiewicz, Magdalena Hasik, Marek Cypryk, Piotr Pospiech

Linear polysiloxanes with regular vinyl group distribution along the chains, obtained by ring-opening polymerizations of 1,3,3,5,5-pentamethyl-1-vinylcyclotrisiloxane (D2V) and 1,3,5-trimethyl-1,3,5-trivinylcyclotrisiloxane (V3) have been cross-linked with hydrogensiloxanes of various functionalities and molecular structures. The reactions have been performed in the presence of Karstedt's catalysts at equimolar ratios of reactive groups and followed by ATR-FTIR spectroscopy. It has been found that in none of the systems the cross-linking process proceeds completely. The highest amount of unreacted Si-H groups has remained when tetrafunctional 2,4,6,8-tetramethylcyclotetrasiloxane (D4) has been used in the process, lower in the case of the reactions with tetrafunctional branched tetrakis(dimethylsiloxy)silane (Q(M)4) and the lowest for linear difunctional 1,1,3,3-tetramethyldisiloxane (MM). The differences have been explained by differences in functionality and molecular structure of hydrogensiloxanes applied as cross-linking agents. Lower concentration of vinyl groups in D2V polymer than in V3polymer has facilitated its reaction with tetrafunctional hydrogensiloxanes as compared to the most reactive difunctionalMM. Results of the studies may be helpful when planning application of polysiloxanes cross-linked by hydrosilylation as preceramic materials.

Quantification of the mineralogical composition of clays using FTIR spectroscopy

Posted: January 12th, 2012, 5:28pm MST

Publication year: 2012
Source: Vibrational Spectroscopy, Available online 12 January 2012

S. Kaufhold, M. Hein, R. Dohrmann, K. Ufer

The qualitative and quantitative determination of the mineral composition of clays still is a challenge. Commonly XRD methods–either pattern addition, single line or Rietveld methods–and chemical methods are used for the determination of the quantitative mineralogical composition. Infrared spectroscopy, on the other hand, is mostly used as complementary tool for clay mineral identification but can also provide quantitative information. In the present study a quantitative IR method is presented which is based on the quantitative comparison of the measured spectrum of the clay with spectra of 57 different reference standards. The results obtained for 38 bentonites, 10 Westerwald clays (ceramic clays), 3 Opalinusclays (marine consolidated clays), and the 3 “Reynoldscup 5” samples are discussed.As expected, the quantitative IR method revealed mineral specific possibilities and limitations, i.e. different minerals can be quantified with different accuracy and precision. The key issues for a successful quantification are i) qualitative mineral analysis (application of additional methods is required), ii) availability of suitable reference spectra, and iii) particle size, which is known to be of particular importance in the case of quartz. The IR method using KBr pellets as presented in the present study is not suitable to substitute XRD characterization and XRD quantification but proved to be useful as complementary quantitative method.

A new method for the quantification of mineral mixtures (rocks) based on IR spectroscopy was established which is based on manual pattern addition. The graph shows the measured and modelled spectrum of the second Reynoldscup V sample.

Permalink for 'Quantum chemical computations including intermolecular interactions, natural bond orbital analysis and scaled quantum mechanical force field calculations on bezafibrate–a cholesterol drug for HIV infected'

Quantum chemical computations including intermolecular interactions, natural bond orbital analysis and scaled quantum mechanical force field calculations on bezafibrate–a cholesterol drug for HIV infected

Posted: January 12th, 2012, 5:28pm MST

Publication year: 2012
Source: Vibrational Spectroscopy, Available online 11 January 2012

N.K. Chithra, C. James

The solid phase FTIR and FT-Raman spectra of biologically active drug (2-{p-[2-(p-chlorobenzamide)ethyl]phenoxy}-2-methyl-propanoic acid) have been recorded in the regions 4000–500 and 4000-100 cm, respectively. The equilibrium geometry, vibrational frequencies, band intensities have been calculated by density functional B3LYP method with the 6-31G* basis set. Two molecules of the compound were modeled, incorporating the strong O-H…O intermolecular interaction (O-H of carboxylic acid with C = O of secondary amide group). The current study provides complete vibrational assignments for all the vibrational modes, which is supported by normal coordinate analysis, force constants and potential energy distributions. In the scaled quantum mechanical (SQM) approach the systematic errors of the computed harmonic force field have been corrected by multiple scale factors and the theoretical spectrogram for the infrared and Raman spectra of the title molecule have been constructed. Natural bond orbital analysis has been carried out to understand the nature of different interactions responsible for the electron delocalization and the intramolecular charge transfer between the orbitals (n→π*, n→σ*, π→π*).Differences in the geometries of the molecule due to the substitution of highly electronegative Cl atom and the conjugation, resonance effect due to the secondary amide group were analyzed. The presence of strong O-H···O and O···H—N intermolecular hydrogen bonding was evidently exposed from the IR spectrum. Secondary amide increases the stability of this protein molecule, which is well established. Steric and conjugation effects due to the vibrations of phenyl rings were well established from the spectra. The biological activity of the compound increases due to the π*→π* interactions that leads to a very high stabilization energy, up to 1023.093 kJ mol

Editorial Board

Posted: January 12th, 2012, 5:28pm MST

Publication year: 2012
Source: Vibrational Spectroscopy, Volume 58, January 2012, Pages CO2

[No author name available]

Laminar flow of non-linear viscoelastic fluids in straight tubes of arbitrary contour

Posted: January 12th, 2012, 4:56pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 11 January 2012

Dennis A. Siginer, Mario F. Letelier

The fully developed steady velocity field in pressure gradient driven laminar flow of non-linear viscoelastic fluids with instantaneous elasticity constitutively represented by a class of single mode, non-affine quasilinear constitutive equations is investigated in straight pipes of arbitrary contour∂D. A continuous one-to-one mapping is used to obtain arbitrary tube contours from a base tube contour∂D0. The analytical method presented is capable of predicting the velocity field in tubes with arbitrary cross-section. The base flow is the Newtonian field and is obtained atO(1). Field variables are expanded in asymptotic series in terms of the Weissenberg numberWi. The analysis does not place any restrictions on the smallness of the driving pressure gradients which can be large and applies to dilute and weakly elastic non-linear viscoelastic fluids. The velocity field is investigated up to and including the third order inWi. The Newtonian field in general arbitrary contours is obtained and longitudinal velocity field components due to shear-thinning and to non-linear viscoelastic effects are identified. Third order analysis shows a further contribution to the longitudinal field driven by first normal stress differences. Secondary flows driven by unbalanced second normal stresses in the cross-section manifest themselves as well at this order. Longitudinal equal velocity contours, the secondary flow field structure, the first and the second normal stress differences as well as wall shear stress variations are discussed for several non-circular contours some for the first time.

Water droplet evaporation on Cu-based hydrophobic surfaces with nano- and micro-structures

Posted: January 12th, 2012, 4:56pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 11 January 2012

Chi Young Lee, Bong June Zhang, Jiyeon Park, Kwang J. Kim

The characteristics of water droplet evaporation on three different hydrophobic surfaces, PCu (Plain Copper,θ = 115°), MSCu (Micro-Structured Copper,θ = 126°) and NSCuO (Nano-Structured Copper Oxide,θ = 159°) with coating of the same SAM (Self-Assembled Monolayer) material, were experimentally investigated. For industrial heat transfer applications, copper material was used as the substrate, and the simple and cost-effective fabrication technique to prepare the superhydrophobic surface, NSCuO, was introduced. Based on the observations, the behavior of droplet evaporation was divided into three stages: Stage I (constant contact area stage), Stage II (constant contact angle stage) and Stage III (mixed stage). When studying the PCu surface, the Stages I, II, and III were observed, consistent with previous reports. For the MSCu surface, Stages I and III appeared without Stage II, and the pinning period of contact line was the longest among the test samples due to the formation of Wenzel state droplet. In the case of the superhydrophobic NSCuO surface, only Stage III occurred, and the contact line moved freely during the entire evaporation time because of the formation of Cassie state droplet. The total evaporation time of the NSCuO was the longest out of all the samples tested. At the last stage of evaporation, the edge of the droplet shrank at a much faster rate in all surfaces. On the other hand, the shrinking velocity of the droplet height drastically increased only on the NSCuO, which was considered as the unique behavior of superhydrophobic surface. In this experiment, it was found that the surface structure determines the motion of the contact line on the surface, which, in turn, strongly influences the characteristics of the droplet evaporation.

Investigation of heat transfer in square porous-annulus

Posted: January 10th, 2012, 8:45pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 10 January 2012

Irfan Anjum Badruddin, Abdullah A.A.A. Al-Rashed, N.J. Salman Ahmed, Sarfaraz Kamangar

The current study is focused to analyze the heat transfer characteristics in a porous duct. The mathematical model of heat transfer in a porous duct was solved by converting the governing partial differential equations into a set of algebraic equations with the help of finite element method. A simple three noded triangular element is used to mesh the duct domain. The current problem consists of a square duct with outer walls being exposed to hot temperatureTh, and inner walls subjected to cool temperatureTc. Emphasis is given to investigate the effect of width ratio of cavity on heat and fluid flow characteristics inside the porous medium. The results are reported for various duct width ratios, Rayleigh number etc. It is found that the Nusselt number increases with increase in height of cavity along the vertical walls of duct; however the Nusselt number for certain values of duct ratio oscillates along the width of the porous medium at bottom wall of the cavity.

Experimental investigation of thermal model of parallel flow microchannel heat exchangers subjected to external heat flux

Posted: January 9th, 2012, 6:44pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 7 January 2012

B. Mathew, H. Hegab

This communication documents the experimental investigation of the theoretical model for predicting the thermal performance of parallel flow microchannel heat exchangers subjected to external heat flux. The thermal model investigated in this communication is that previously developed by the authors of this communication; Mathew and Hegab [B. Mathew, H. Hegab, Application of effectiveness-NTU relationship to parallel flowmicrochannel heat exchangers subjected to external heat transfer, International Journal of Thermal Sciences 31 (2010) 76–85]. The validity of the theoretical model with respect to microchannel profile, hydraulic diameter, heat capacity ratio and degree of external heat transfer is checked. The microchannel profiles investigated are trapezoidal and triangular with hydraulic diameter of 278.5 and 279.5 μm, respectively. The influence of hydraulic diameter is analyzed using trapezoidal microchannels with hydraulic diameters of 231 and 278.5 μm. Experiments are conducted for heat capacity ratios of unity and 0.5 using the heat exchanger employing the trapezoidal microchannel with hydraulic diameter of 278.5 μm for purposes of validating the model. Experiments are done for all heat exchangers for two different levels of external heat transfer; 15% and 30% of the maximum possible heat transfer. Irrespective of the parameter that is investigated the experimental data are found to perfectly match with the theoretical predictions thereby validating the thermal model investigated in this communication.

New solutions to the species diffusion equation inside droplets in the presence of the moving boundary

Posted: January 9th, 2012, 6:44pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 7 January 2012

I.G. Gusev, P.A. Krutitskii, S.S. Sazhin, A.E. Elwardany

Two new solutions to the equation, describing the diffusion of species during multi-component droplet evaporation, are suggested. The first solution is the explicit analytical solution to this equation, while the second one reduces the solution of the differential transient species equation to the solution of the Volterra integral equation of the second kind. Both solutions take into account the effect of the reduction of the droplet radius due to evaporation, assuming that this radius is a linear function of time. The analytical solution has been incorporated into a zero dimensional CFD code and applied to the analysis of a bi-component droplet evaporation. The case of an initial 50% ethanol–50% acetone mixture and droplets with initial diameter equal to 142.7 μm moving in air at atmospheric pressure has been considered. To separate the effect of the moving boundary on the species diffusion equation from a similar effect on the heat conduction equation inside droplets, described earlier, a rather artificial assumption that the droplet temperature is homogeneous and fixed has been made. It has been pointed out that the effect of the moving boundary slows down the increase in the mass fraction of ethanol (the less volatile substance in the mixture) and leads to the acceleration of droplet evaporation.

Permalink for 'Generalized model of thermal boundary conductance between SWNT and surrounding supercritical Lennard-Jones fluid – derivation from molecular dynamics simulations'

Generalized model of thermal boundary conductance between SWNT and surrounding supercritical Lennard-Jones fluid – derivation from molecular dynamics simulations

Posted: January 6th, 2012, 7:50pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 5 January 2012

JinHyeok Cha, Shohei Chiashi, Junichiro Shiomi, Shigeo Maruyama

Using classical molecular dynamics simulations, we have studied thermal boundary conductance (TBC) between a single-walled carbon nanotube (SWNT) and surrounding Lennard-Jones (LJ) fluids. With an aim to identify a general model that expresses the TBC for various surrounding materials, TBC was calculated for three different surrounding LJ fluids, hydrogen, nitrogen, and argon in supercritical phase. The results show that the TBC between an SWNT and surrounding LJ fluid is approximately proportional to local density (ρL) formed on the outer surface of SWNT and energy parameter (ε) of LJ potential, and inverse proportional to mass (m) of surrounding LJ fluid. In addition, the influence of the molecular mass of fluid on TBC is far more than other inter-molecular potential parameters in realistic range of molecular parameters. Through these parametric studies, we obtained a phenomenological model of the TBC between an SWNT and surrounding LJ fluid.

$Permalink for 'An inverse problem to estimate relaxation parameter and order of fractionality in fractional single-phase-lag heat equation'$

An inverse problem to estimate relaxation parameter and order of fractionality in fractional single-phase-lag heat equation

Posted: January 6th, 2012, 7:50pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 5 January 2012

Hamid R. Ghazizadeh, A. Azimi, M. Maerefat

In this paper, an inverse analysis is performed for simultaneous estimation of relaxation time and order of fractionality in fractional single-phase-lag heat equation. This fractional heat conduction equation is applied on two physical problems. In inverse procedure, solutions of a previously validated linear dual-phase-lag model on the physical problems under study have been used as the measured temperatures. The inverse fractional single-phase-lag heat conduction problem is solved using the nonlinear parameter estimation technique based on the Levenberg–Marquardt method. The results of the present study show that the Levenberg–Marquardt method can be successfully applied on the inverse fractional heat transfer problem. The solution procedures employed in the present study for direct and inverse problems have greatly increased the reliability and success of parameter estimation problem. In the present study, for the first time, relaxation time and fractionality of a non-homogeneous medium (i.e. processed meat) have been determined. Also, the results of this study show that the fractional single-phase-lag model can predict the same temperature distribution as the linear dual-phase-lag model for the problem under study. This latter result enables us to consider further generalization of the dual-phase-lag model to fractional dual-phase-lag models.

Permalink for 'Heat and mass transfer of thermophoretic MHD flow over an inclined radiate isothermal permeable surface in the presence of heat source/sink'

Heat and mass transfer of thermophoretic MHD flow over an inclined radiate isothermal permeable surface in the presence of heat source/sink

Posted: January 6th, 2012, 7:50pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 5 January 2012

N.F.M. Noor, S. Abbasbandy, I. Hashim

In this paper, a free convection thermophoretic hydromagnetic flow over a radiate isothermal inclined plate with heat source/sink effect is considered. The shooting method is employed to yield the numerical solutions for the model. The effects of thermophoretic parameter and internal heat generation/absorption for both suction and injection cases are discussed and presented graphically. The values of skin friction, wall heat flux and wall deposition flux are also tabulated with the variation of thermophoresis, heat source/sink and suction/injection parameters.

The Infrared and Raman spectra of solid tridehydropeptides: Influence of ΔAla and ΔPhe on the Spectral Profile

Posted: January 4th, 2012, 8:52pm MST

Publication year: 2012
Source: Vibrational Spectroscopy, Available online 3 January 2012

Kamilla Malek, Maciej Makowski

A series of solid tripeptides Boc-Gly-X-Gly-OMe (X = dehydroalanine (ΔAla), dehydrophenylalanine (ΔPhe)) was investigated by Raman scattering and Fourier transform infrared spectra to examine the conformational marker bands of the unsaturated residue. The observed fundamental modes gave us the opportunity to analyse structural features that change due to the substitution of Ala by ΔAla and due to the different spatial arrangement of ΔPhe (ZandEisomers). In addition, we showed the alteration of the spectral profile when the large size residue (Phe) is introduced into the backbone of the peptide with ΔPhe (in Boc-Gly-ΔPhe-Phe-OMe). The frequency ranges of interest included the NH stretching, carbonyl stretching and amide deformation modes as well as vibrations of the investigated dehydroresidues. The observed differences of positions and intensities of IR and Raman bands provided an insight into the structural and spectroscopic properties of the selected dehydropeptides.

Heat transfer to a sphere in tube flow of power-law liquids

Posted: January 4th, 2012, 8:31pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 4 January 2012

Daoyun Song, Rakesh K. Gupta, R.P. Chhabra

Extensive new results on forced convection heat transfer from an isothermal heated sphere exposed to the fully developed laminar velocity profile of power-law fluids in a tube are reported herein. In particular, these results endeavor to elucidate the influence of the pertinent dimensionless governing parameters, namely, Reynolds number (5 ⩽ Re ⩽ 100), Prandtl number (1 ⩽ Pr ⩽ 100), power-law index (0.2 ⩽ n ⩽ 1) and sphere-to-tube diameter ratio (0.05 ⩽ ⩽ 0.5). The heat transfer characteristics are analyzed in terms of the local as well as surface averaged values of the Nusselt number. Broadly, all else being equal, shear-thinning behavior promotes heat transfer, though confinement limits such an increase in shear-thinning fluids depending upon the value of the power-law index. Similarly, all else being equal, confining walls also enhance the rate of heat transfer which is, however, maximum in the case of Newtonian fluids. Possible reasons for such counter-intuitive trends are advanced. The present numerical results have been approximated by simple expressions thereby enabling their interpolation for the intermediate values of the governing parameters like Reynolds number, Prandtl number, diameter ratio and power-law index.

Heat and mass diffusion fluxes on a permeable wall with foreign-gas blowing

Posted: January 3rd, 2012, 7:15pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 3 January 2012

E.P. Volchkov, M.S. Makarov, S.N. Makarova

In the present paper, we consider the variation of heat and mass diffusion fluxes on a permeable plate with blowing of a foreign gas into the boundary layer, the fluxes being considered as functions of the permeability parameter, varied through variation of blowing intensity, free-stream velocity, or longitudinal coordinate. It is shown that at a fixed distance from the leading edge of the plate one can, varying the value of blowing intensity while preserving the uniformity of the blowing over the plate length, obtain a non-monotonic variation of the wall heat and mass diffusion fluxes. In contrast to the heat and mass diffusion fluxes, the shear stress always monotonically decreases with increasing the blowing intensity. Similar to the shear stress, on increase of permeability parameter achieved through changing either the free-stream velocity or the longitudinal coordinate the heat flux and the mass diffusion flux both show a monotonic reduction. Using the integral relations of boundary-layer theory, we have derived simple analytical expressions allowing determination of the maximum values of the heat and mass diffusion fluxes in laminar and turbulent flow regimes. The obtained analytical relations were verified by performed numerical simulations.

Fully-developed thermal transport in combined electroosmotic and pressure driven flow of power-law fluids in microchannels

Posted: January 3rd, 2012, 7:15pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 3 January 2012

Chien-Hsin Chen

Thermally fully-developed heat transfer has been analyzed for combined electroosmotic and pressure driven flow of power-law fluid in a microchannel. Analytical expressions for transport parameters are presented in terms of the flow behavior index, the length scale ratio (ratio of Debye length to half channel height), dimensionless pressure gradient, and Joule heating parameter (ratio of Joule heating to surface heat flux). Closed form solutions are obtained for some specific values of the flow behavior index, while numerical solutions are presented for general cases. The results show that the temperature variation across the channel increases with increasing the pressure gradient. To reduce the length scale ratio is found to decrease the temperature variation, particularly for shear-thinning fluids. To increase the Joule heating parameter is to enlarge the temperature variation in the channel, especially for shear-thickening fluids. The Nusselt number can be increased by decreasing the length scale ratio due to the electroosmotic effect. Also, the Nusselt number increases with decreasing the values of flow behavior index and dimensionless pressure gradient.

Permalink for 'Vibrational spectroscopic, optical and thermal properties of a deuterated ferroic crystal, [(CH2OD)3CND3]2SiF6–an experimental and theoretical study'

Vibrational spectroscopic, optical and thermal properties of a deuterated ferroic crystal, [(CH2OD)3CND3]2SiF6–an experimental and theoretical study

Posted: January 2nd, 2012, 6:34pm MST

Publication year: 2012
Source: Vibrational Spectroscopy, Available online 2 January 2012

D. Podsiadła, O. Czupiński, M. Rospenk, B. Kosturek

[(CH2OD)3CND3]2SiF6ferroic crystal, abbreviated as D-(TRIS)2SiF6crystal was investigated. Optical (linear birefringence) and thermal (differential scanning calorimetry, DSC) measurements indicated a solid-solid phase transition (PT) of the first order at 185 K. The vibrational infrared spectra of powdered D-(TRIS)2SiF6crystal in Nujol and Fluorolube mulls were studied in the wide range of temperature, from 308 K to 133 K. The temperature changes of wavenumber, width, centre of gravity position and intensity of the bands were analyzed to clarify the molecular mechanism of the phase transition and the contribution of SiF6and -CH2OD groups to the PT. A wide range (4000-400 cm) of internal vibrations of the DTRISand SiF6ions was investigated and the assignment of the observed infrared absorption bands was discussed. Raman spectra of the crystal at room temperature (RT) were recorded and discussed in relation to the structure of isostructural (TRIS)2SiF6crystal in the range (4000-400 cm). Theoretical calculations were made based on density functional theory (DFT). The calculated normal vibrational modes of the molecules, their intensities and frequencies were compared with those obtained from experimental data.

Thermophoresis particle deposition in natural convection over inclined surfaces in porous media

Posted: January 2nd, 2012, 6:13pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 2 January 2012

Adrian Postelnicu

The present paper is focused on the analysis of heat and mass transfer in boundary-layer free convection over an inclined flat plate embedded in a fluid saturated porous medium in the presence of thermophoresis. The governing equations are transformed into a set of coupled differential equations, which are solved numerically using the local non-similarity method. A comparison between the results given by this method and the local similarity method is also presented. For various values of the problem parameters, graphs of thermophoretic wall velocity, Nusselt number and concentration profiles in the boundary layer are presented. Variation of the dimensional thermophoretic wall velocity along the plate for different angles of inclination are presented in a physical relevant case.

An experimental study of boiling in dilute emulsions, part A: Heat transfer

Posted: January 2nd, 2012, 6:13pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 2 January 2012

M.L. Roesle, F.A. Kulacki

Results are reported of an experimental study of heat transfer in pool boiling of dilute emulsions of pentane in water and FC-72 in water. Heat transfer coefficients for single phase convection, boiling of the dispersed component, and enhanced boiling of the continuous component are reported. Results show that the boiling heat transfer coefficient is a function primarily of superheat of both the dispersed component and continuous component, sub-cooling of the bulk of the emulsion, and volume fraction of the dispersed component up to ∼1%. Other properties of the dispersed component are relatively unimportant, as are the geometry of the heated surface and droplet size of the emulsion. Droplets of the dispersed component can accumulate on the heated surface, but this accumulation affects heat transfer only in single phase convection.

An experimental study of boiling in dilute emulsions, part B: Visualization

Posted: January 2nd, 2012, 6:13pm MST

Publication year: 2012
Source: International Journal of Heat and Mass Transfer, Available online 2 January 2012

M.L. Roesle, F.A. Kulacki

Results are reported of an experimental study of heat transfer in pool boiling of dilute emulsions of pentane in water and FC-72 in water. Heat transfer data for single phase convection, boiling of the dispersed component, and enhanced boiling of the continuous component are correlated with images of the emulsion near the heated surface. Large bubbles are observed to form on the heated surface and remain attached to the surface. There is evidence of boiling of individual droplets that do not contact the heated surface under some circumstances. For very dilute emulsions and at moderate heat flux the attached bubbles are the dominant boiling mode.

Permalink for 'Synthesis and vibrational properties of trifluoromethyl trifluoromethantiolsuphonate and comparison with covalent sulfonates'

Synthesis and vibrational properties of trifluoromethyl trifluoromethantiolsuphonate and comparison with covalent sulfonates

Posted: December 31st, 2011, 4:16pm MST

Publication year: 2011
Source: Vibrational Spectroscopy, Available online 30 December 2011

M.E. Defonsi Lestard, L.A. Ramos, M.E. Tuttolomondo, S.E. Ulic, A. Ben Altabef

Trifluoromethyl trifluoromethanethiosuphonate, CF3SO2SCF3was characterized byC- NMR,F-, NMR, and vibrational spectroscopy. Infrared spectra of CF3SO2SCF3were obtained for the gaseous and liquid phases, while the Raman spectrum was recorded for the liquid phase. The experimental data were complemented with quantum chemical calculations. Both experimental and theoretical data indicate that only one conformer,gauche,is possible by rotating around the S–S bond. This conformational preference was studied using the total energy scheme and natural bond orbital partition scheme. These results evidence that electron delocalization and especially LP Y(Y= S, O) → σ* S(6) = O(4,5) and LP O(4,5) → σ* S(6)-Y interactions play an interesting role in the reactivity of oxoesters and thioesters.

Soret and Dufour effects for three-dimensional flow in a viscoelastic fluid over a stretching surface

Posted: December 31st, 2011, 3:55pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 31 December 2011

T. Hayat, Ambreen Safdar, M. Awais, S. Mesloub

This article deals with the Soret and Dufour effects on three-dimensional boundary layer flow of viscoelastic fluid over a stretching surface. The governing partial differential equations are transformed into a dimensionless coupled system of non-linear ordinary differential equations and then solved analytically by the homotopy analysis method (HAM). Graphs are plotted to analyze the variation of different parameters of interest on the velocity, concentration and temperature fields.

Experimental study on diffusive solid combustion behavior during transition from normal- to reduced-gravity

Posted: December 31st, 2011, 3:55pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 30 December 2011

L.H. Hu, M.A. Delichatsios, J. Li, X.L. Zhang, S.F. Wang, ...

Experiments are carried out in a simplified drop system, which can provide a 2.3 s 10 g reduced gravity period, to investigate the transition of solid material combustion behavior from normal- to reduced-gravity. A CCD camera records the diffusion flames produced by a solid fuel, Methenamine (C6H12N4), which easily sublimes and decomposes to flammable CH4and H2. The temperature distribution within the flame is analyzed by a monochromatic line of sight CCD measurement calibrated by a thermocouple measurement. It is revealed that during the transition period from normal- to reduced-gravity, the change of the flame shape, from tall and thin (pear like) to spherical, is faster than that of the luminance which represents the radiation intensity, indicating a relatively shorter adjustment time scale of dynamical gas flow buoyancy than that of the heat transfer when subjected to such a sudden change of gravity condition. It is also found that owing to the change of the flow affecting the oxygen and heat supply, the luminance of the flame as well as the burning rate, which was deduced based on projected area of the solid fuel according to d-law, first decreases followed by an increment near the end of the drop where the gravity level slightly increases. The flame temperature gradually decreases, as the flame suddenly goes into reduced-gravity. Interpretation based on analysis of heat transfer balance and pyrolysis rate as well as the experimental results both indicate that the transitional effect is less pronounced for a smaller fuel particle than for a larger one, where buoyancy is stronger under normal-gravity whereas the flame has a larger standoff distance with increasing importance of the radiation losses from the fuel particle surface under reduced-gravity. The present work is relevant in assessing fire hazards of solid material during space travel as gravity levels change.

Dyslipidemia is not associated with cardiovascular disease risk in an animal model of mild chronic suboptimal nutrition

Posted: December 29th, 2011, 9:12pm MST

Publication year: 2011
Source: Nutrition Research, Available online 29 December 2011

Fima Lifshitz, Patricia M. Pintos, Christian E. Lezón, Elisa V. Macri, Silvia M. Friedman, ...

Previous studies performed in an experimental model of nutritional growth retardation (NGR) have observed metabolic adaptation. We hypothesized that changes in lipid-lipoprotein profile, glucose, and insulin levels occur, whereas overall body growth is reduced.The aim of this study was to assess serum lipid-lipoprotein profile, hepatogram, insulinemia and glycemia, and CVD risk markers in rats fed a suboptimal diet. Weanling male rats were assigned either to control (C) or NGR group. In this 4-week study, C rats were fed ad libitum a standard diet, and NGR rats received 80% of the amount of food consumed by C. Zoometric parameters, body fat content, serum lipid-lipoprotein profile, hepatogram, insulinemia, and glycemia were determined, and the cardiovascular disease (CVD) risk markers homeostasis model assessment–insulin resistance and homeostasis model assessment andβ-cell function were calculated. Suboptimal food intake induced a significant decrease in body weight and length, which were accompanied by a reduction of 50% in body fat mass. Serum lipoproteins were significantly higher in NGR rats, with the exception of high-density lipoprotein cholesterol, which remained unchanged. Nutritional growth retardation rats had decreased triglycerides compared with C rats. No significant differences were detected in liver function parameters. The CVD risk markers homeostasis model assessment (HOMA)–insulin resistance and homeostasis model assessment andβ-cell function were significantly lower in NGR rats. Mild chronic suboptimal nutrition in weanling male rats led to growth retardation and changes in the lipid-lipoprotein profile, glucose, and insulin levels while preserving the integrity of liver function. These data suggest a metabolic adaptation during suboptimal food intake, which ensures substrates flux to tissues that require constant energy—in detriment to body growth. The CVD risk markers suggested that mild chronic food restriction of approximately 20% could provide protection against this degenerative disease.

Magnesium absorption from mineral water decreases with increasing quantities of magnesium per serving in rats

Posted: December 29th, 2011, 9:12pm MST

Publication year: 2011
Source: Nutrition Research, Available online 29 December 2011

Eri Nakamura, Hideyuki Tai, Yoshinobu Uozumi, Koji Nakagawa, Tohru Matsui

It is hypothesized that magnesium (Mg) absorption from mineral water is affected by the concentration of Mg in the water, the consumption pattern, and the volume consumed per serving. The present study examined the effect of serving volume and consumption pattern of artificial mineral water (AMW) and Mg concentration on Mg absorption in rats. Magnesium in AMW was labeled with magnesium-25 as a tracer. Each group consisted of 6 or 7 rats. In experiment 1, the rats received 1 mL of AMW containing 200 mg Mg/L at 4 times, 400 mg Mg/L twice, or 800 mg Mg/L at 1 time. In experiment 2, the rats received 1 mL of AMW containing 200 mg Mg/L or 0.25 mL of AMW containing 800 mg Mg/L at 4 times or 1 mL of AMW containing 800 mg Mg/L at 1 time. The absorption of Mg decreased with increasing Mg concentrations in the same serving volume of AMW with different serving frequencies. When the AMW containing 800 mg Mg/L was portioned into 4 servings, Mg absorption increased to the level of absorption in the group exposed to AMW containing 200 mg Mg/L served at the same frequency. These results suggest that the Mg concentration and the volume of AMW do not affect Mg absorption per se, but Mg absorption from AMW decreases when the amount of Mg in each serving is increased. Thus, frequent consumption is preferable for mineral water rich in Mg when the total consumption of mineral water is the same.

Permalink for 'Bimodal action of miroestrol and deoxymiroestrol, phytoestrogens fromPueraria candolleivar.mirifica,on hepatic CYP2B9 and CYP1A2 expressions and antilipid peroxidation in mice'

Bimodal action of miroestrol and deoxymiroestrol, phytoestrogens fromPueraria candolleivar.mirifica,on hepatic CYP2B9 and CYP1A2 expressions and antilipid peroxidation in mice

Posted: December 29th, 2011, 9:12pm MST

Publication year: 2011
Source: Nutrition Research, Available online 29 December 2011

Latiporn Udomsuk, Thaweesak Juengwatanatrakul, Waraporn Putalun, Kanokwan Jarukamjorn

Miroestrol and deoxymiroestrol are phytoestrogens isolated fromPueraria candolleivar.mirifica.The influence of miroestrol and dexoymirosestrol on hepatic cytochrome P450 (P450) enzymes and antioxidative activity in brain was examined in C57BL/6 mice compared with that of a synthetic female sex hormone estradiol. We hypothesized that miroestrol and deoxymiroestrol would induce CYP2B9 expression, whereas CYP1A2 expression would be suppressed compared with estradiol. Miroestrol and deoxymiroestrol treatment significantly increased uterus weight and volume. In addition, both of these phytoestrogens induced the expression of CYP2B9 and suppressed the expression of CYP1A2, as expected. Hepatic P450 activities correspondingly showed that both compounds increased benzyloxyresorufinO-dealkylase activity, whereas methoxyresorufinO-dealkylase activity was reduced. These observations suggested that miroestrol and deoxymiroestrol might affect hepatic P450 enzymes, including the CYP2B9 and CYP1A2 P450 isoforms. Assessment of lipid peroxidation demonstrated that miroestrol and deoxymiroestrol markedly decreased levels of malondialdehyde formation in the mouse brain. This is the first report suggesting miroestrol and deoxymiroestrol as potential alternative medicines to estradiol because of their distinctive ability to regulate mouse hepatic P450 expression and their beneficial antioxidative activities.

Conduction through a damaged honeycomb lattice

Posted: December 29th, 2011, 8:38pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 29 December 2011

C. Pozrikidis, A.I. Hill

The temperature distribution and rate of heat transfer across an infinite periodic strip of a honeycomb lattice consisting of conductive segments or links joined at nodes or junctions is discussed. A pristine honeycomb behaves like an isotropic medium whose effective conductivity is independent of the orientation of an applied macroscopic temperature gradient. Monte Carlo simulations are performed to determine the effect of link damage or disruption and lattice deformation due to junction displacement. In the simulations, a specified percentage of randomly distributed links are assigned a conductivity that is lower than that of the undamaged links. The balance equations governing the nodal temperatures at the junctions are solved by iteration subject to a periodicity condition along the strip and the Dirichlet condition along the two infinite edges of the strip. The results illustrate the effect of imperfections on the temperature distribution over the network and document the dependence of the effective conductivity on the percentage and conductivity of the defective links. In the case of nonconductive damaged links, the effective conductivity becomes nearly zero when a critical percentage of links are clipped, in agreement with bond percolation theory. However, the functional form of the number density of possible pathways connecting the lower to the upper edge of the strip predicted by percolation theory differs from that of the effective conductivity. Lattice deformation due to random node displacement has a small effect on the effective conductivity of the network.

Heat transfer enhancement by recirculating flow within liquid plugs in microchannels

Posted: December 29th, 2011, 8:38pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 29 December 2011

Zhizhao Che, Teck Neng Wong, Nam-Trung Nguyen

Plug flow can significantly enhance heat transfer in microchannels as compared to single phase flow. Using an analytical model of flow field, heat transfer in plug flow is investigated. The constant-surface-temperature boundary condition is considered. Three stages of the heat transfer in plugs are identified: (i) development of thermal boundary layer; (ii) advection of heated/fresh fluid in the plug; and (iii) thermally fully developed flow. Due to the transport of heated fluid and fresh fluid within the plug by the recirculating flow, oscillations of the Nusselt number at high Peclet numbers are observed and explained. The effects of the Peclet number and the plug length on the heat transfer process are evaluated. The results show that short plugs are preferable to long plugs since short plugs result in high Nusselt numbers and high heat transfer indices.

Distribution of tellurite polymorphs in the xM2O-(1-x)TeO2(M = Li, Na, K, Cs, and Rb) binary glasses using Raman spectroscopy

Posted: December 28th, 2011, 7:37pm MST

Publication year: 2011
Source: Vibrational Spectroscopy, Available online 28 December 2011

Angelos G. Kalampounias, Soghomon Boghosian

Raman spectra of xM2O-(1-x)TeO2(M = alkali metal atom) binary glass-forming oxide systems were measured over a wide composition range and for all alkali-types in an effort to extend the structural aspects of previous works on this field and reveal the composition-and modifier type-induced structural changes in a quantitative manner for the first time. Analysis of the Raman spectroscopic data after a reduction procedure and focusing on spectral effects caused by structural changes allowed the “quantitative” monitoring of the well-known transformation of the TeO4(predominating in the low modifier content glass) into TeO3trigonal pyramids at increased alkali content. The main finding pertains to the estimation of the relative populations of the basic building blocks for a wide compositional range and for different alkali-types directly from the Raman spectroscopic data, thereby permitting the calculation of the average number around Te atoms versus modifier content and alkali-type. The variation of the coordination number implies that the structure of all M2O-TeO2tellurite glasses with the same composition is comparable and almost independent of alkali-type.Spectroscopic evidence suggests that the presence of neutral trigonal pyramid TeO2/2(=O) units is questionable, while the increase of M2O content leads to a gradual transformation of TeO4/2initially to TeO3/2Oand then to TeO1/2O(=O) trigonal pyramid units depending on the modifier content. The structural model based on Raman spectroscopic results is in agreement with the findings of NMR work on binary alkali-tellurite glasses.

Unsteady boundary-layer flow and heat transfer of a nanofluid over a permeable stretching/shrinking sheet

Posted: December 28th, 2011, 7:15pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 28 December 2011

Norfifah Bachok, Anuar Ishak, Ioan Pop

The unsteady boundary layer flow of a nanofluid over a permeable stretching/shrinking sheet is theoretically studied. The governing partial differential equations are transformed into ordinary ones using a similarity transformation, before being solved numerically. The results are obtained for the skin friction coefficient, the local Nusselt number and the local Sherwood number as well as the velocity, temperature and the nanoparticle fraction profiles for some values of the governing parameters, namely, the unsteadiness parameter, the mass suction parameter, the Brownian motion parameter, the thermophoresis parameter, Prandtl number, Lewis number and the stretching/shrinking parameter. It is found that dual solutions exist for both stretching and shrinking cases. The results also indicate that both unsteadiness and mass suction widen the range of the stretching/shrinking parameter for which the solution exists.

Determination of hematocrit using on-line conductance cell

Posted: December 28th, 2011, 7:15pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 28 December 2011

Jin M. Jung, Dong H. Lee, Ki-Tae Kim, Young I. Cho

Hematocrit has been considered as an important marker of oxygen carrying capacity of the blood associated with whole blood viscosity to assess the mortality risk of both cardiovascular, cerebral, and kidney diseases. The present study developed a new on-line conductivity cell to measure the hematocrit of whole blood using a bipolar square-wave voltage signal at a frequency of 5 kHz. By applying such a voltage signal to a blood flowing in a range of 1.2–3.0 mL/min, the electrolyte effect of blood plasma, the conductive and capacitive effects of blood cells, and the sedimentation effect of erythrocytes on the conductivity of whole blood could be minimized for an accurate hematocrit measurement. The coefficient of correlation between the present method and conventional microcentrifuge method showed an excellent linear relationship. A new equation between the specific conductance andHctof whole blood was obtained:C = 12.561 − 0.1527Hct(P < 0.001).

Permalink for 'Identification of spacewise and time dependent source terms in 1Dheat conduction equation from temperature measurement at a final time'

Identification of spacewise and time dependent source terms in 1Dheat conduction equation from temperature measurement at a final time

Posted: December 28th, 2011, 7:15pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 28 December 2011

Alemdar Hasanov

Inverse problems of identifying the unknown spacewise and time dependent heat sourcesF(x) andH(t) of the variable coefficient heat conduction equationut = (k(x)ux)x + F(x)H(t) from supplementary temperature measurement (uT(x)≔u(x, Tf)) at a given single instant of timeTf > 0, are investigated. For both inverse source problems, defined to be as ISPF and ISPH respectively, explicit formulas for the Fréchet gradients of corresponding cost functionals are derived. Fourier analysis of these problems shows that although ISPF has a unique solution, ISPH may not have a unique solution. The conjugate gradient method (CGM) with the explicit gradient formula for the cost functionalJ1(F) is then applied for numerical solution of ISPF. New collocation algorithm, based on the piecewise linear approximation of the unknown sourceH(t), is proposed for the numerical solution of the integral equation corresponding to ISPH. The proposed two numerical algorithms are examined through numerical examples for reconstruction of continuous and discontinuous heat sourcesF(x) andH(t). Computational results, with noise free and noisy data, show efficiency and high accuracy of the proposed algorithms.

The effect of Weber number on the central binary collision outcome between unequal-sized droplets

Posted: December 28th, 2011, 7:15pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 28 December 2011

N. Nikolopoulos, G. Strotos, K.S. Nikas, G. Bergeles

The central binary collision of two unequal sized droplets is numerically investigated using the volume of fluid (V.O.F.) methodology. The numerical method based on the solution of the continuity and momentum equations in axi-symmetric formulation is coupled with a recently developed adaptive local grid refinement technique, thus allowing an accurate representation of the interface between the liquid and gas phase. Mass transfer mechanisms are reproduced by solving a transport equation for a colour function representing the mass of one of the colliding droplets before and after collision and mixing. The investigation is performed assuming either constant relative velocity of the colliding droplets or constant total energy of the system, thus creating a combination of the standard non-dimensional parameters affecting the collision process, i.e. Weber (We) and Ohnesorge (Oh) numbers as also droplet diameter ratio (Δ). The reliability of the procedure is first established by comparing predictions with available experimental data. The effect of the above mentioned parameters on ligament’s formation, maximum deformation of the two droplets, the penetration of one droplet into the other and satellite droplet formation is quantified.

Joule heating induced heat transfer for electroosmotic flow of power-law fluids in a microcapillary

Posted: December 27th, 2011, 6:00pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 27 December 2011

Cunlu Zhao, Chun Yang

Capillary electrophoresis systems mainly used for chemical analyses and biomedical diagnoses usually involve biofluids in electrolyte buffers which cannot be treated as Newtonian fluids. In addition, the presence of Joule heating can limit the performance of capillary electrophoresis systems. This study presents a detailed analysis of Joule heating induced heat transfer for electroosmotic flow (EOF) of power-law fluids in a microcapillary. The steady, fully developed EOF field of power-law fluids governed by the Cauchy momentum equation is solved analytically by using two approximate schemes for modified Bessel functions,I0(x) andI1(x). Subsequently, under the widely accepted assumption of thin electric double layer (EDL) in microfluidics, an exact solution for temperature field induced by Joule heating is analytically solved from the energy equation subject to a mixed thermal boundary condition outside the capillary. Closed form expressions are obtained for the two-dimensional temperature field, the average fluid temperature and the local Nusselt number in both thermally developing and thermally developed regions. It is found that the rheological properties of power-law fluids affect the heat transfer characteristics mainly through the thermal Peclet number.

Operational characteristics of two biporous wicks used in loop heat pipe with flat evaporator

Posted: December 27th, 2011, 6:00pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 27 December 2011

B.B. Chen, Z.C. Liu, W. Liu, J.G. Yang, H. Li, ...

Two special biporous wicks are adopted in stainless-steel–ammonia loop heat pipes (LHPs) with flat evaporator to enhance their heat transfer performances. The experimental results demonstrate that thermal and hydraulic characteristics of the wick with porosity of 69% (in LHP 2) are better than that of the wick with porosity of 65% (in LHP 1). The maximum heat loads of LHP 1 and LHP 2 could, respectively, reach 120 W (heat flux 11.8 W/cm) and 130 W (12.8 W/cm) at the allowable evaporator temperature below 60 °C. Meanwhile, they can start up at heat load as low as 2.5 W. The LHPs show very fast and smooth response to heat load and operate stably without obvious temperature oscillation. The total thermal resistances of the LHPs vary between 1.47 and 0.33 °C/W at heat load ranging from 10 to 130 W.

Experimental analysis of the solidification of Sn–3 wt.%Pb alloy under natural convection

Posted: December 27th, 2011, 6:00pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 27 December 2011

Lakhdar Hachani, Bachir Saadi, Xiao Dong Wang, Abdallah Nouri, Kader Zaidat, ...

A quasi-two-dimensional solidification benchmark experiment with controlled thermal boundary conditions is proposed. The experiment consists in solidifying a rectangular ingot of Sn–3 wt.%Pb alloy using two lateral heat exchangers to extract the heat flux from one or two sides of the sample. The temperature difference between the two sides of the heat exchangers may vary from 0 to 40 K and the cooling rate from 0.02 to 0.04 K/s. This slow-cooling condition has been used to promote segregation formation. An array of fifty thermocouples placed on the corresponding sample walls is used to determine the instantaneous temperature distribution. During the solidification process, the temperature field is recorded versus time and analyzed. This makes it possible to estimate the change in temperature due to natural convection, the velocity field and the solidification macrostructure and segregation behavior. After each experiment, the segregation patterns are obtained by X-ray analysis and confirmed by eutectic fraction measurements. The local solute distribution is determined by means of induction coupled plasma analysis.

Modelling of impingement phenomena for molten metallic droplets with low to high velocities

Posted: December 26th, 2011, 5:29pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 26 December 2011

H. Tabbara, S. Gu

Thermal spray coatings are formed by accelerating a stream of powder particles towards a targeted substrate surface where they impact, deform, and adhere. A fundamental understanding of the splat formation can pave the way for future developments in thermal spray technology through better understanding. Numerical modelling is applied in this investigation which simulates the detailed transient flow of a molten metal droplet impacting, deforming, and solidifying on a flat, solid substrate. The computations are carried out on a fixed Eularian structured mesh using a volume of fluid method to simulate the boundary between the metallic and atmospheric-gas phases. The results shed light on the break-up phenomena on impact and describe in detail how the solidification process varies with an increasing impact velocity.

Phonon and magnetic properties of nanocrystalline MnWO4prepared by hydrothermal method

Posted: December 24th, 2011, 4:12pm MST

Publication year: 2011
Source: Vibrational Spectroscopy, Available online 24 December 2011

Mirosław Mączka, Maciej Ptak, Adam Pikul, Leszek Kępiński, Paweł E. Tomaszewski, ...

Well-crystallized MnWO4nanoparticles with 20-100 nm sizes were synthesized by a mild hydrothermal crystallization process. X-ray diffraction and TEM results show that particles have tendency to grow in a shape of nanorods elongated in thecdirection. They also show that the particles synthesized from MnCl2have smaller concentration of defects than those synthesized from MnSO4•H2O. Raman spectra revealed weak changes with decreasing particle size due to phonon confinement effect and defects. In contrast to this behavior, IR spectra showed much more pronounced changes. Origin of this behavior is discussed. Raman and IR spectra showed also presence of additional bands at 923 and 914 cm, respectively. These bands have been attributed to presence of terminal W = O bonds at the surface of MnWO4nanocrystallites. Specific heat and magnetization studies revealed broad anomalies at 11.0-11.4 K, which correspond to the two magnetic transitions found for bulk MnWO4at 12.5 and 13.5 K.

Highlights► Nanoparticles of MnWO4were synthesised with size 20-100 nm ► Particles synthesized from MnCl2have smaller concentration of defects than those synthesized from MnSO4•H2O ► IR spectra of MnWO4nanoparticles differ significantly from IR spectrum of bulk due to polar character of the observed modes ► Nanoparticles exhibit clear magnetic phase transition at 11.0-11.4 K.

Permalink for 'Quantitative comparison of reversibility in thermal-induced hydration of poly(N-isopropylacrylamide) and poly(N-isopropylmethacrylamide) in aqueous solutions by “concatenated” 2D correlation analysis'

Quantitative comparison of reversibility in thermal-induced hydration of poly(N-isopropylacrylamide) and poly(N-isopropylmethacrylamide) in aqueous solutions by “concatenated” 2D correlation analysis

Posted: December 24th, 2011, 4:12pm MST

Publication year: 2011
Source: Vibrational Spectroscopy, Available online 23 December 2011

Li Ping Zhang, Isao Noda, Yuqing Wu

“Concatenated” two-dimensional (2D) correlation analysis is a newly proposed method. By extracting more detailed information, such as the comparison of effects of two different perturbations or different systems, it helps one to clearly reveal the subtle difference between two dynamic changes resembling to each other. We demonstrate the new applications of “concatenated” 2D correlation analysis in quantitative comparison of the reversibility in the thermally induced hydration and conformational changes of poly(N-isopropylacrylamide) (PNiPA) and poly(N-isopropylmethacrylamide) (PNiPMA) in aqueous solution. The reversibility of the two polymers will be compared both by hydrophilic amide group and hydrophobic CH group in different temperature ranges. By the pretreatment of an intensity normalization on the original spectra, the intensities of cross-peaks in the asynchronous spectrum calculated from the roundtrip data matrix are quantitatively compared. The contribution of different factors to the 2D asynchronous spectrum can be separated by selecting different spectral section for concatenation. The irreversibility of the thermally induced hydration in PNiPA is not constant during the entire round trip process: it is most obvious in the narrow temperature interval of phase separation process, while in the temperature ranges far away from the interval it is negligible. The irreversibility of the behavior of CH groups in both PNIPA and PNIPMA is not as strong as that of amide group during the round trip. It further supports the conclusion that the hydration of hydrophilic amide group has the dominant effect in the temperature-induced phase separation of the polymer in aqueous solution.

Solidification of PCM around a curved tube

Posted: December 24th, 2011, 3:52pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 24 December 2011

Kamal Abdel Radi Ismail, Lourival Matos de Sousa Filho, Fátima Aparecida Morais Lino

This paper presents the results of an experimental and numerical investigation on the solidification of PCM around a curved cold tube to determine the effects of the Dean number, cooling fluid flow rate and its temperature on the interface velocity, the time for complete solidification and the solidified mass. To formulate the solidification process around a curved tube a conduction model was used together with the immobilization technique and the Landau transform. The energy equation and the associated boundary conditions were discretized by the finite control volumes method. The computational program was optimized by numerical experiments and the optimized form was used to validate the model. Comparisons of the numerical predictions and experiments to investigate the effects the Dean number on the solidified mass showed agreement within 1% while the interface velocity and the time for complete solidification showed agreements of about 8% and less than 6%, respectively. The effects of the flow rate of the working fluid could be predicted within less than 8% for the solidified mass and to less than 4% for both the interface velocity and the time for complete solidification. The effects of the temperature of the working fluid are predictable to within less than 8% for the time for complete solidification and the interface velocity.

Permalink for 'In-situ measurements of concentration and temperature during transient solidification of aqueous solution of ammonium chloride using laser interferometry'

In-situ measurements of concentration and temperature during transient solidification of aqueous solution of ammonium chloride using laser interferometry

Posted: December 22nd, 2011, 8:49pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 22 December 2011

D. Vikas, S. Basu, P. Dutta

The variation in temperature and concentration plays a crucial role in predicting the final microstructure during solidification of a binary alloy. Most of the experimental techniques used to measure concentration and temperature are intrusive in nature and affect the flow field. In this paper, the main focus is laid on in-situ, non-intrusive, transient measurement of concentration and temperature during the solidification of a binary mixture of aqueous ammonium chloride solution (a metal-analog system) in a top cooled cavity using laser based Mach–Zehnder Interferometric technique. It was found from the interferogram, that the angular deviation of fringe pattern and the total number of fringes exhibit significant sensitivity to refractive index and hence are functions of the local temperature and concentration of the NH4Cl solution inside the cavity. Using the fringe characteristics, calibration curves were established for the range of temperature and concentration levels expected during the solidification process. In the actual solidification experiment, two hypoeutectic solutions (5% and 15% NH4Cl) were chosen. The calibration curves were used to determine the temperature and concentration of the solution inside the cavity during solidification of 5% and 15% NH4Cl solution at different instants of time. The measurement was carried out at a fixed point in the cavity, and the concentration variation with time was recorded as the solid–liquid interface approached the measurement point. The measurement exhibited distinct zones of concentration distribution caused by solute rejection and Rayleigh Benard convection. Further studies involving flow visualization with laser scattering confirmed the Rayleigh Benard convection. Computational modeling was also performed, which corroborated the experimental findings.

Influence of chitosan and porosity on heat and mass transfer in chitosan-treated porous fibrous material

Posted: December 21st, 2011, 8:17pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 21 December 2011

Q.Y. Zhu, M.H. Xie, J. Yang, Y.Q. Chen, K. Liao

This paper focuses on a theoretical investigation of the coupling mechanism of heat transfer and liquid moisture diffusion in chitosan-treated porous fibrous material. The porous fibrous materials made of cotton with different porosities are modified by chitosan solution with different concentrations. The moisture regain of the chitosan-treated porous fibrous material increases and the contact angle of the chitosan-treated fiber decreases significantly after modification. For comparison, the simultaneous heat and liquid moisture transfer in porous fibrous materials with different porosities modified by chitosan solution with different concentration are discussed. With specification of initial and boundary conditions, the distributions of the water vapor concentration in the void spaces, the volume fraction of the liquid water in the void spaces, the distribution of the water content in fibers and the temperature changes in chitosan-treated porous fibrous material are obtained numerically. The comparison with the experimental measurements shows the superiority of the numerical model in resolving the coupled heat and mass transfer in chitosan-treated porous fibrous material. Analysis of the computational and experimental results illustrates that the heat and mass transfer in chitosan-treated porous fibrous material is influenced by chitosan concentration and fabric porosity significantly.

Numerical simulation of the onset characteristics in a standing wave thermoacoustic engine based on thermodynamic analysis

Posted: December 21st, 2011, 8:17pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 21 December 2011

L.M. Qiu, B.H. Lai, Y.F. Li, D.M. Sun

In this paper, a simplified physical model of standing wave thermoacoustic engines (SWTE) is developed based on thermodynamic analysis. Transient pressure drop and heat transfer data are first calculated based on linear thermoacoustic theory. The effects of stack spacing, charge pressure, and resonator length on onset temperature were investigated and compared with experimental results. The calculations agree well with the experimental results, which validates the model for calculating the onset conditions.

Particle Swarm Optimization-based algorithms for solving inverse heat conduction problems of estimating surface heat flux

Posted: December 21st, 2011, 8:17pm MST

Publication year: 2011
Source: International Journal of Heat and Mass Transfer, Available online 21 December 2011

Fung-Bao Liu

An inverse analysis of estimating a time-dependent surface heat flux for a three-dimensional heat conduction problem is presented. A global optimization method known as Particle Swarm Optimization (PSO) is employed to estimate the unknown heat flux at the inner surface of a crystal tube from the knowledge of temperature measurements obtained at the external surface. Three modifications of the PSO-based algorithm, PSO with constriction factor, PSO with time-varying acceleration of the cognitive and social coefficients, and PSO with mutation are carried out to implement the optimization process of the inverse analysis. The results show that the PSO with mutation algorithm is significantly better than other PSO-based algorithms because it can overcome the drawback of trapping in the local optimum points and obtain better inverse solutions. The effects of measurement errors, number of dimensionalities, and number of generations on the inverse solutions are also investigated.

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ScienceDirect Publication: International Journal of Heat and Mass Transfer

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Posted: January 17th, 2012, 7:10pm MST

Posted: January 17th, 2012, 7:10pm MST

Posted: January 17th, 2012, 7:10pm MST

Posted: January 17th, 2012, 7:10pm MST

Posted: January 17th, 2012, 7:10pm MST

Posted: January 17th, 2012, 7:10pm MST

Posted: January 17th, 2012, 7:10pm MST

Posted: January 17th, 2012, 6:30pm MST

Posted: January 17th, 2012, 6:30pm MST

Posted: January 17th, 2012, 6:30pm MST

Posted: January 17th, 2012, 6:30pm MST

Posted: January 17th, 2012, 6:30pm MST

Posted: January 14th, 2012, 8:51pm MST

Posted: January 14th, 2012, 8:51pm MST

Posted: January 13th, 2012, 8:05pm MST

Posted: January 13th, 2012, 8:05pm MST

Posted: January 12th, 2012, 5:28pm MST

Posted: January 12th, 2012, 5:28pm MST

Posted: January 12th, 2012, 5:28pm MST

Posted: January 12th, 2012, 5:28pm MST

Posted: January 12th, 2012, 5:28pm MST

Posted: January 12th, 2012, 5:28pm MST

Posted: January 12th, 2012, 4:56pm MST

Posted: January 12th, 2012, 4:56pm MST

Posted: January 10th, 2012, 8:45pm MST

Posted: January 9th, 2012, 6:44pm MST

Posted: January 9th, 2012, 6:44pm MST

Posted: January 6th, 2012, 7:50pm MST

Posted: January 6th, 2012, 7:50pm MST

Posted: January 6th, 2012, 7:50pm MST

Posted: January 4th, 2012, 8:52pm MST

Posted: January 4th, 2012, 8:31pm MST

Posted: January 3rd, 2012, 7:15pm MST

Posted: January 3rd, 2012, 7:15pm MST

Posted: January 2nd, 2012, 6:34pm MST