Heterogeneous heat-mass transfer and effective thermal conductivity of pores in ceramic materials at arbitrary knudsen numbers

1981 ◽  
Vol 41 (2) ◽  
pp. 876-879
Author(s):  
E. Ya. Litovskii ◽  
F. S. Kaplan ◽  
A. V. Klimovich
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Effective Thermal Conductivity ◽  
Heat Mass Transfer ◽  
Ceramic Materials ◽  
Knudsen Numbers

scholarly journals Numerical Simulation of Heat Mass Transfer Effects on MHD Flow of Williamson Nanofluid by a Stretching Surface with Thermal Conductivity and Variable Thickness

Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 684
Author(s):  
Saeed Islam ◽  
Haroon Ur Rasheed ◽  
Kottakkaran Sooppy Nisar ◽  
Nawal A. Alshehri ◽  
Mohammed Zakarya
Keyword(s):  
Thermal Conductivity ◽  
Boundary Layer ◽  
Mass Transfer ◽  
Differential Equations ◽  
Variable Thickness ◽  
Heat Mass Transfer ◽  
Mathematical Formulation ◽  
Stretching Surface ◽  
Nanofluid Flow ◽  
The Impact

The current analysis deals with radiative aspects of magnetohydrodynamic boundary layer flow with heat mass transfer features on electrically conductive Williamson nanofluid by a stretching surface. The impact of variable thickness and thermal conductivity characteristics in view of melting heat flow are examined. The mathematical formulation of Williamson nanofluid flow is based on boundary layer theory pioneered by Prandtl. The boundary layer nanofluid flow idea yields a constitutive flow laws of partial differential equations (PDEs) are made dimensionless and then reduce to ordinary nonlinear differential equations (ODEs) versus transformation technique. A built-in numerical algorithm bvp4c in Mathematica software is employed for nonlinear systems computation. Considerable features of dimensionless parameters are reviewed via graphical description. A comparison with another homotopic approach (HAM) as a limiting case and an excellent agreement perceived.

Numerical Simulation of Heat and Mass Transfer in Metal Hydride Hydrogen Accumulators of Different Complex Designs

2010 ◽  
Author(s):  
Dmitriy Lazarev ◽  
Valeriy Artemov ◽  
Georgiy Yankov ◽  
Konstantin Minko
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Effective Thermal Conductivity ◽  
Heat And Mass Transfer ◽  
Metal Hydride ◽  
Solid Phase ◽  
Three Dimensional ◽  
Calculated Data ◽  
Sorption Rate ◽  
Gas Admixtures

A three-dimensional mathematical model of unsteady heat and mass transfer in porous hydrogen-absorbing media, accounting for presence of “passive” gas admixtures, is developed. New technique for evaluation of effective thermal conductivity of porous medium, which consists of microparticles, is suggested. Effect of “passive” gas admixtures on heat and mass transfer and sorption rate in metal hydride reactor is analyzed. It is shown that decrease of effective thermal conductivity and partial hydrogen pressure under decrease of hydrogen concentration effect on the hydrogen sorption rate considerably. It is disclosed that an intensive 3D natural convection takes place in a gas volume of reactor under certain conditions. Numerical analysis of heat and mass transfer in metal-hydride reactor of hydrogen accumulation systems was done. Sorption of hydrogen in cylindrical reactors with external cooling and central supply of hydrogen are analyzed including reactors with finned active volume and tube-shell reactor with external and internal cooling cartridge matrix. Unsteady three dimensional temperature and concentration fields in solid phase are presented. Integral curves representing the dynamic of sorption and desorption are calculated. Data on efficiency of considered reactors are presented and compared.

scholarly journals A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in dry snow

2015 ◽  
Vol 9 (5) ◽  
pp. 1857-1878 ◽  
Author(s):  
A. C. Hansen ◽  
W. E. Foslien
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Diffusion Coefficient ◽  
Effective Thermal Conductivity ◽  
Heat And Mass Transfer ◽  
Effective Diffusion ◽  
Mixture Theory ◽  
Temperature Gradients ◽  
Snow Metamorphism ◽  
Sublimation Rates

Abstract. The microstructure of a dry alpine snowpack is a dynamic environment where microstructural evolution is driven by seasonal density profiles and weather conditions. Notably, temperature gradients on the order of 10–20 K m−1, or larger, are known to produce a faceted snow microstructure exhibiting little strength. However, while strong temperature gradients are widely accepted as the primary driver for kinetic growth, they do not fully account for the range of experimental observations. An additional factor influencing snow metamorphism is believed to be the rate of mass transfer at the macroscale. We develop a mixture theory capable of predicting macroscale deposition and/or sublimation in a snow cover under temperature gradient conditions. Temperature gradients and mass exchange are tracked over periods ranging from 1 to 10 days. Interesting heat and mass transfer behavior is observed near the ground, near the surface, as well as immediately above and below dense ice crusts. Information about deposition (condensation) and sublimation rates may help explain snow metamorphism phenomena that cannot be accounted for by temperature gradients alone. The macroscale heat and mass transfer analysis requires accurate representations of the effective thermal conductivity and the effective mass diffusion coefficient for snow. We develop analytical models for these parameters based on first principles at the microscale. The expressions derived contain no empirical adjustments, and further, provide self consistent values for effective thermal conductivity and the effective diffusion coefficient for the limiting cases of air and solid ice. The predicted values for these macroscale material parameters are also in excellent agreement with numerical results based on microscale finite element analyses of representative volume elements generated from X-ray tomography.

Heat and Mass Transfer in Wet Fibroporous Material Considering Moisture Evaporation

2015 ◽  
Vol 1097 ◽  
pp. 51-55
Author(s):  
V.Yu. Polovnikov ◽  
E.V. Gubina
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Mass Transfer ◽  
Heat Flux ◽  
Effective Thermal Conductivity ◽  
Heat And Mass Transfer ◽  
Total Heat Flux ◽  
Moisture Evaporation ◽  
Volume Fractions ◽  
Mass Fluxes

Results of numerical simulation of heat and mass transfer in a wet fibroporous material in conditions of evaporation and steam diffusion were completed. Values of heat and mass fluxes were established. The contribution of evaporation effect to total heat flux and need to consider volume fractions of water and steam into the structure of fibroporous material in calculation of effective thermal conductivity were shown. Nonstationarity of heat and mass transfer in conditions of considered problem can be ignored.

scholarly journals Kinetic approach to solution of evaporation-condensation problems taking into account multi-particle interactions in liquid

2021 ◽  
Vol 2088 (1) ◽  
pp. 012044
Author(s):  
I N Shishkova ◽  
A P Kryukov
Keyword(s):  
Thermal Conductivity ◽  
Mass Transfer ◽  
Kinetic Equation ◽  
Condensed Phase ◽  
Heat Mass Transfer ◽  
Numerical Procedure ◽  
Liquid Argon ◽  
Kinetic Approach ◽  
Particle Interactions

Abstract The presented work is devoted to the study of heat-mass transfer in vapor and liquid, taking into account multi-particle interactions in the condensed phase. An appropriate numerical procedure is proposed to solve the kinetic equation, both in the vapor and in the liquid. Using this approach, the problems of thermal conductivity in liquid argon, as well as the problem of evaporation-condensation, are solved.

Sign in / Sign up

Export Citation Format

Share Document