On heat and mass transfer in the unsteady squeezing flow between parallel plates

This paper reports the heat and mass transfer characteristics in a viscous fluid which is squeezed between parallel plates. The governing partial differential equations for unsteady two-dimensional flow with heat and mass transfer of a viscous fluid are reduced to ordinary differential equations by similarity transformations. Homotopy analysis method (HAM) is employed to construct the series solution of the problem. Physical interpretation to various embedding parameters is assigned through graphs for temperature and concentration profiles and tables for skin friction coefficient, local Nusselt number and local Sherwood number.     

The thermodynamic design of heat and mass transfer processes and devices

This review article places in perspective the new work devoted both to the analysis of the thermodynamic irreversibility of heat and mass transfer components and systems and to the design of these devices on the basis of entropy generation minimization. The review focuses on the fundamental mechanisms responsible for the generation of entropy in heat and fluid flow and on the design tradeoff of balancing the heat transfer irreversibility against the fluid flow irreversibility. Applications are selected from the fields of heat exchanger design, thermal energy storage, and mass exchanger design. This article provides a comprehensive, up-to-date review of second-daw analyses published in the heat and mass transfer literature during the last decade.     

Convection and heat/mass transfer processes under space flight conditions

A simulation of 3D convective flows and heat/mass transfer processes under space flight conditions on the basis of hydrodynamic models and a numerical analysis of these models is discussed. The significance of the methods of mechanics in microgravity sciences and the role of the journal “Fluid Dynamics” in the development of this branch of science is examined. The results of recent investigations of certain problems are presented.     

Conjugated heat and mass transfer between a reactive solid and a gas in the presence of nonequilibrium chemical reactions

An investigation of a multicomponent boundary layer taking account of nonequilibrium chemical reactions has been made in a number of publications [1–3]; here, the temperature of the solid was assumed to be known or was determined from the condition of the conservation of energy at the interface between the gas and the solid, taking account of the solution of the equation of thermal conductivity in the solid phase. At the same time, heating of the material of a coating is an unavoidable step in any mechanism of thermokinetic decomposition and, in view of this, it is necessary to take account of the lag of the heat-transfer process inside the solid. Therefore, it is necessary to solve the equation of the energy balance in the solid phase simultaneously with the system of the equations of the boundary layer, i.e., the conjugate problem. The present article discusses the problem of flow around a solid in the vicinity of a frontal critical point, taking account of the dependence of the processes taking place in the solid body on the time, in the presence of two heterogeneous and one homogeneous reactions. The distributions of the velocity, the temperature, and the concentrations in the boundary layer are obtained, as well as the mass rate of entrainment of the material at different moments of time. The time of the change between kinetic and diffusion conditions of the course of the heterogeneous chemical reactions (the ignition time) is determined. It is established that, in the presence of a homogeneous chemical reaction, the mass rate of entrainment is less than with a frozen flow.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 121–128, March–April, 1974.     

A mixture theory for evaluating heat and mass transport processes in nonhomogeneous snow

A multiphase mixture theory is developed and then utilized to study heat and mass transport processes in layered snow cover. The material is represented as a granular ice phase and a vapor phase which occupies the pore space. The theory is then implemented to study the process of temperature gradient metamorphism in dry seasonal snow cover and the effect of density layering on metamorphism of snow. Calculated results were found to be consistent with field observations of temperature gradient and density layering effects. The theory demonstrates that sharp variations in density induce a migration of vapor from the lower density snow toward the more dense layer, resulting in a gradual erosion of density of layers adjacent to dense snow. It is also shown that alteration in vapor density and temperature near the layer interface result.     

Quasi-linear heat and mass transfer

Flow, Turbulence and Combustion - From the assumption that the heat flux (mass flux with respect to the mass-average velocity) vector is an isotropic function of the temperature (mass-fraction)...     

On the application of an approximate kinetic equation of heat and mass transfer processes: the effect of body shape

An approximate kinetic equation of heat and mass transfer has been presented. It is an ordinary differential equation which is easy to integrate. The derivation of this approximation was based on an analysis of the available analytical solution of the problem. The proposed equation can be applied to bodies (pellets) in the shape of an infinite slab, infinite cylinder and sphere. A generalization of this equation to cases where the transfer resistance occurs both in the body and in the surrounding fluid has been proposed. The equation has been tested in various conditions both for thermal and diffusive processes. Radiative cooling of bodies has been considered as a thermal process and adsorption in a single pellet—as a diffusive process. All tests showed high accuracy of the approximate equation; in many cases the results were indistinguishable from the results of the exact model. A special feature of the proposed equation is its high accuracy for short times of the process, what significantly differentiates it from the classical approximate kinetic equation Linear Driving Force.     

Investigation of hydrodynamic and heat and mass transfer processes for crystal growing by the Czochralski method

A mathematical model and numerical method are developed and used to investigate nonstationary flow and heat and mass transfer regimes in a melt appropriate to the conditions of Czochralski crystal growth. A study is made of the separate and combined influence of rotation and thermal, concentration, and thermocapillary convection on the distribution of the temperature and the dopant in the range of regime parameters corresponding to large charging masses of the melt with small value of the kinematic viscosity. Large-scale fluctuations are found to occur when rotation and thermal convection interact. Thermocapillary convection is shown to have an important influence on the resulting motion when it interacts with the thermal and concentration forms of convection. A comparison is made with the results of experimental and theoretical investigations of other authors.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 1, pp. 55–65, January–February, 1981.     

On the torsion of chiral bars in gradient elasticity

This paper contains a study of the problem of torsion of chiral bars with arbitrary cross-sections in the context of the linear theory of gradient elasticity. The solution is expressed in terms of solutions of four auxiliary plane problems characterized by loads which depend only on the constitutive coefficients. It is shown that, in general, the torsion produces extension (or contraction) and bending effects. The results are used to investigate the torsion of a homogeneous circular bar. In contrast with the case of achiral circular cylinders, the torsion and extension cannot be treated independently of each other.     

多孔介质在压力梯度作用下的热质耦合数值模拟

多孔介质干燥导致热质耦合传输过程。本文基于连续介质力学的宏观尺度,对多孔介质的热、湿和气三者耦合迁移进行数值模拟,研究压力梯度对热质传输的影响。多孔介质传质机理主要为水汽和空气的对流和扩散传输、吸附水在含湿量梯度作用下的自由扩散和其在温度梯度即Soret效应驱动下的流动。采用Galerkin加权余量的有限元方法,提出了...     

Combined heat and mass transfer in natural convection between vertical parallel plates

This study purposes to examine the effects of latent heat transfer associated with the liquid films vaporization on the heat transfer in the natural convection flows driven by the simultaneous presence of combined buoyancy forces of thermal and mass diffusion. Results are especially presented for an air-water system under various conditions. The influence of channel length and system temperatures on the momentum, heat and mass transfer in the flow are investigated in great detail. The important role of transport of latent heat of vaporization under the situations of buoyancy-aiding and opposing flows is clearly demonstrated.     

Effects of chemical reaction, heat and mass transfer on laminar flow along a semi infinite horizontal plate

An approximate solution for the steady laminar flow along a semi infinite horizontal plate in the presence of species concentration and chemical reaction has been obtained using Numerical Technique. It has been observed that in the presence of chemical reaction, (i) the velocity and concentration increase with decrease of Schmidt number Sc. (ii) Skin friction and rate of concentration decrease with the increase of chemical reaction parameter. Received on 12 January 1999     

On energy transfer between vibrating systems under linear and nonlinear interactions

The present study deals with energy transfer in a dissipative mechanical system. Numerical results are given by considering two different potentials and periodical excitation. Specifically, we show energy transfer from linear oscillator to another one, depending on initial conditions. Also, energy transfer from linear to nonlinear (energy pumping), as well as from nonlinear to linear, oscillator is analyzed, under linear and nonlinear interactions.     

Convection heat and mass transfer from a disk

The aim of the present study is to investigate the coupling influence of the disk rotating speed and air velocity from laboratory room on the local heat and mass characteristics from a disk in wind tunnel with the naphthalene sublimation technique. The experiments are performed at four different free stream flow velocities. From the experimental results, the correlation of Sherwood number with the coupling Reynolds number and of Nusselt number with the coupling Reynolds number are both proposed in the present work.     

Three-dimensional numerical analysis of heat and mass transfer in heat pipes

A three-dimensional finite-element numerical model is presented for simulation of the steady-state performance characteristics of heat pipes. The mass, momentum and energy conservation equations are solved for the liquid and vapor flow in the entire heat pipe domain. The calculated outer wall temperature profiles are in good agreement with the experimental data. The estimations of the liquid and vapor pressure distributions and velocity profiles are also presented and discussed. It is shown that the vapor flow field remains nearly symmetrical about the heat pipe centerline, even under a non-uniform heat load. The analytical method used to predict the heat pipe capillary limit is found to be conservative.     

Modeling of simultaneous heat and mass transfer processes in ammonia–water absorption systems from general correlations

This paper presents a general differential mathematical model to analyze the simultaneous heat and mass transfer processes that occur in different components of an ammonia–water absorption system: absorber, desorber, rectifier, distillation column, condenser and evaporator. Heat and mass transfer equations are considered, taking into account the heat and mass transfer resistances in the liquid and vapour phases. The model considers the different regions: vapour phase, liquid phase and an external heating or cooling medium. A finite difference numerical method has been considered to solve the resulting set of nonlinear differential equations and an iterative algorithm is proposed for its solution. A map of possible solutions of the mass transferred composition z is presented when varying the interface temperature, which enables to establish a robust implementation code. The analysis is focused on the processes presented in ammonia–water absorption systems. The model is applied to analyze the ammonia purification process in an adiabatic packed rectification column and the numerical results show good agreement with experimental data.