Theory of Generalized Micropolar Thermoelastic Diffusion Under Lord–Shulman Model

The general equations of motion and constitutive equations, based on the theory of Lord–Shulman with one relaxation time, are derived for a general homogeneous anisotropic medium with a microstructure, taking into account the effects of heat and diffusion. A variational principle for the governing equations is obtained. Then we show that the variational principle can be used to obtain a uniqueness theorem under suitable conditions. A reciprocity theorem for these equations is given. The obtained results are valid for some special cases which can be deduced from our generalized model.     

On the Theory of Two-Temperature Thermoelasticity with Two Phase-Lags

The present paper is concerned with the theory of two temperature thermoelasticity with two phase-lags in which the theory of heat conduction in deformable bodies depends on two distinct temperatures – the conductive temperature and the thermodynamic temperature. A generalized heat conduction law with dual-phase-lag effects was proposed by Tzou (1995) for the purpose of considering the delayed response in times due to the microstructural interactions in the heat transport mechanism. Recently, Quintanilla (2008) has proposed to combine this constitutive equation with a two temperature heat conduction theory and has proved that a dual-phase-lag theory with two temperatures is a well-posed problem. In the present work we consider the basic equations concerning this dual-phase lag theory of two temperature thermoelasticity and make an attempt to establish some important theorems in this context. A uniqueness theorem has been established for a homogeneous and isotropic body. An alternative characterization of mixed boundary initial value problem is formulated and a variational principle as well as reciprocal principle have been established.     

喷管内传递特性对微尺度扩散火焰的影响

对均匀空气流中微尺度甲烷扩散燃烧进行了数值模拟,重点考察微喷管内的流动和传热传质对微尺度燃烧特性的影响.结果表明,在低流速下,内径为0.3 mm的微喷管内进气速度为1.0 m/s时燃料与空气的混合已经发生,混合气被管外的热量预热,同时火焰的热损失增加.在喷管直径一定时,减小燃料喷出速度,传热传质现象对微尺度甲烷扩散火焰特性的影响增强;当进气速度为0.5 m/s时,甲烷在微喷管内开始燃烧,放出热量.在进行微尺度解析计算时,必须包含一定的喷管区域.     

Heat and Mass Transfer with Condensation in Non-Saturated Porous Media

Heat and mass transfer with condensation in porous media was numerically studied coupling with distributions of temperature, vapor concentration, pressure and water saturation. The transport processes in porous media displayed two distinct stages, or early and late stages. Different characteristics during these stages were described with the consideration of physical nature. A systematical investigation was conducted to explore the influence of different parameters on the processes, including the temperature, the particle diameter, the porosity, and the thermal conductivity of the particle. A modeling experiment was conducted to partially validate the calculation.     

太阳能热水器传热传质和强化传热研究

在低温太阳能光热光伏联合应用试验台的基础上,结合GB/T 17049—2005,利用Gambit、Ansys Fluent和Tecplot软件,对全玻璃真空管太阳能热水器进行传热传质和强化传热分析。结果表明:所建立的二维数值计算模型,能准确反映同一条件下,全玻璃真空管太阳能热水器的变化趋势;在数值模拟基础上,确定了单面受热时的最佳安装角度为51°,加装反光板类似双面受热的最佳安装角度为38°;在粗略估算和细化分析的基础上,确定了不同真空管结构的最佳导流板长度及安装位置;通过实验和数值模拟,确定了58mm×1 800mm为优化的全玻璃真空管结构。     

气液降膜流动传热传质研究的综述

气液降膜是工业中常见的传热传质过程,在很多领域中有着广泛的应用,在湿空气透平（HAT）循环的主要部件饱和器中,也有着重要的意义。本文回顾了降膜分别在气体剪切力下以及由界面相变引起的热非平衡状态下的流动稳定性及传热传质的发展现状和研究进展,总结了气液降膜流动已有的理论和实验结果,并展望了气液降膜流动技术的发展前景。     

Fundamental Solution in the Theory of Micropolar Thermoelasticity for Materials with Voids

This paper concerns with the linear theory of micropolar thermoelasticity for materials with voids. We construct the fundamental solution of the system of differential equations in the case of steady oscillations in terms of elementary functions. Some basic properties of this solution are established.     

Efficiency and Optimization of a Straight Rectangular Fin with Combined Heat and Mass Transfer

An analysis was carried out to study the efficiency of a straight rectangular fin with a uniform cross-section area when subjected to simultaneous heat and mass transfer mechanisms. The temperature and humidity ratio differences are the driving forces for the heat and mass transfer, respectively. Numerical solutions are obtained for the temperature distribution over the fin surface when the fin surface is dry, fully wet, and partially wet. The psychrometric correlation of an air-water vapor mixture was used to simulate the relation between the temperature and humidity ratio instead of the linear approximate correlations used in the literature. The effect of atmospheric pressure on the fin efficiency was also studied, in addition to fin optimum thickness for specific operating conditions. The numerical solution was compared with those of previous studies in order to find if the linear model in the published analytical results are near to the real situation. It is found that the linear model for the relation between the humidity ratio and the temperature used by Wu and Bong is a reasonable engineering approximation for small values of the fin parameter and at low relative humidities.     

旋膜式除氧器传热传质特点及性能试验

介绍了旋膜式除氧器的主要结构和工作原理。对其主要除氧元件起膜管进行了冷态试验研究,根据试验情况分析了其传热传质特点。介绍了在某厂进行的旋膜式除氧器性能试验的主要数据,并据此评价了这种除氧器的实际除氧效果。     

丁苯橡胶深床干燥的传热传质模拟

本文通过实验,确定了丁苯橡胶的干燥常数,并建立了丁苯橡胶深床干燥的传热传质数学模型,利用有限差分法进行数值求解,计算得出不同深度处物料温度与含水率随时间的变化规律,以及在不同的干燥介质温度下物料含水率随时间的变化规律。     

Numerical Simulation of Heat and Mass Transfer during Absorption of Hydrogen in Metal Hydride Tank

The present study is concerned with cooling a metal hydride tank during the charging process by using a water jacket and fins. Results indicate that the effect of the water jacket becomes more significant over time. Variation of the Reynolds number has no influence on the charging time in the turbulent regime while changing the flow regime from laminar to turbulent improves the results slightly. Furthermore, adding fins on the cooling jacket enhances the heat transfer significantly through better removal of the heat from the central region of the metal bed. Hence, the charging time was significantly reduced.     

气化炉液池内单个高温气泡传热、传质的数值模拟

建立了气、液间传热传质数学模型,对单个热气泡在上升过程中与处于蒸发阶段的水之间的传热、传质规律进行了数值研究,获得了气泡半径、气泡温度、水蒸发速率以及蒸发量随时间的变化规律.研究表明:在水恒温蒸发阶段,由于传热传质的共同作用,气泡半径随着气泡的上升而变小,并逐渐趋于稳定;随着气、液间温度差的增大,气泡半径缩小得越快;在气泡与水开始接触时,水的蒸发速率及气泡内的水蒸汽增量最大;气泡温度在较短时间内急剧下降,并趋于稳定;随着气泡半径的缩小,气泡冷却速率提高;但随着接触时间的继续增加,对气体的冷却效果却无明显作用.     

Potential Method in the Linear Theory of Thermoelasticity with Microtemperatures

In the present paper the linear theory of thermoelasticity with microtemperatures is considered. The basic boundary value problems of steady vibrations are investigated using the potential method. Sommerfeld–Kupradze type radiation conditions and the basic properties of thermoelastopotentials are established. The uniqueness and existence theorems of classical solutions of the external (with respect to an unbounded domain) boundary value problems are proved.     

Three-Dimensional Mixed Convection Heat and Mass Transfer in a Rectangular Duct: Case of Longitudinal Rolls

This article presents numerical study of 3-D thermosolutale mixed convection (TSMC) in horizontal rectangular channels. The contribution of this work is to characterize the travelling wave's appearance and to generalize the behavior of Poiseuille-Rayleigh-Benard (PRB) systems for a broad range of dimensionless parameters, which control the double diffusive mixed convection. The numerical results consist of analyzing the flow regimes of the steady longitudinal thermoconvectives rolls for the case of purely thermal mixed convection (TMC) and for both thermal and mass transfer (TSMC). The transition from opposed volume forces to cooperating ones at fixed Rayleigh (Ra), Reynolds (Re), and Lewis (Le) numbers, considerably affects the birth and the development of the longitudinal rolls (noted R_//). The heat and mass transfers distribution, presented by the average Nusselt and Sherwood numbers, are also examined.     

Finite-Element Solution of Integral Equations Arising in Radiative Heat Transfer and Laminar Boundary-Layer Theory

Abstract

Finite-element solutions of a number of one-dimensional linear and nonlinear (nonsingular) integral equations arising in radiative heat transfer and boundarylayer theory are presented.     

Mathematical Modeling of Heat and Mass Transfer during Convective Dehydration of an Anisotropic Cylindrical Foodstuff

Two‐dimensional, unsteady‐state mass transfer was studied for air drying of an anisotropic finite cylindrical body. A mathematical model was developed for predicting the temperature of the drying sample at any time and moisture in any position in the drying sample at any time. The anisotropic nature of the drying material was considered in the mathematical model by taking into account the different moisture diffusivities in the axial and radial directions. A cut fresh green bean was used as an anisotropic material and a pilot‐scaled dryer was set up to investigate the drying behavior of this foodstuff. Several length‐to‐diameter ratios of fresh green beans were considered and the mathematical model was validated by comparison of the predicted values of average moisture content with the experimental data. The model was used to predict the moisture distributions inside the drying samples. Different moisture content distributions in the axial and radial directions during drying confirms the anisotropic nature of cut green bean samples. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21119     

Viscous Potential Flow Analysis of Kelvin–Helmholtz Instability of a Cylindrical Flow with Heat and Mass Transfer

A linear analysis of Kelvin–Helmholtz instability of a cylindrical interface has been carried out when there is heat and mass transfer across the interface, using viscous potential flow theory. Both fluids are considered as incompressible, viscous, and thermally conducting with different kinematic viscosities. Both axisymmetric as well as asymmetric disturbances are considered. Stability criterion is given by a critical value of relative velocity and stability is discussed theoretically as well as numerically. Various graphs with respect to physical parameters such as wave number, viscosity ratio, heat transfer coefficients, Reynolds number, etc., have been drawn and the effect of various parameters have been described. A comparison with the linear stability analysis of inviscid fluids (Lee [10]) has been made and it is observed that viscosity has a stabilizing effect on the stability of the system. © 2013 Wiley Periodicals, Inc. Heat Trans Asian Res, 43(6): 489–503, 2014; Published online 3 October 2013 in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21092