Influence of internal response on the critical conditions of heat and mass transfer of carbon particles

Critical conditions of heterogeneous ignition and extinction of solid and porous carbon particles are determined in a gaseous oxidizer with allowance for concurrent chemical reactions and heat losses due to radiation in relation to inside diffusion of the oxidizer. The influence of the internal response on high- and low-temperature heat and mass transfer processes and the conditions of their implementation is investigated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 5, pp. 880–886, September–October, 1998.     

Inverse thermal effect of displaced liquid in a porous medium

The inverse thermal effect of the liquid displaced in a porous medium is investigated, with the effect occurring because of the fact that, with the thermal conductivity being neglected, temperature jumps move with the speed of convective heat transfer. In piston displacement, the front moves with a true velocity which several times exceeds those of filtration and of convective heat transfer. Due to the faster advance of the displacement front, a special zone is formed, in which the process of inverse thermal effect of the displaced liquid on the displacing one is observed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 139–145, July–August, 2006.     

Wave motion of porous particles in a pulsating gas flow in the presence of heat and mass transfer with deepening of the evaporation zone

Based on numerical solution of the dynamics equations of a monodisperse gas suspension with allowance for the interphase forces of aerodynamic drag, virtual masses, and the forces caused by nonstationary effects around particles, the influence of different forms of low-frequency harmonic and anharmonic oscillations of the gas on the motion of porous particles in the presence of heat and mass transfer accompanied by deepening of the evaporation zone has been investigated. The dependences of the solid-phase motion, kinetics of evaporation-zone deepening, and heat and mass transfer on the parameters of gas oscillations have been established. It is shown that on removal of free moisture, oscillations at certain parameters lead to enhancement of interphase heat and mass transfer. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 5, pp. 11–19, September–October 2006.     

The similarity regime for natural convection in a vertical cylindrical well filled with an anisotropic porous medium

An integral method based on Lighthill’s analysis (Q J Mech Appl Math 6 (1953) 398–439) is carried out to study the similarity regime for penetration of convective heat transfer in a vertical cylindrical well filled with an anisotropic porous medium. The porous medium is anisotropic in permeability with its principal axes oriented in a direction that is oblique to the gravity vector. In the limit of the slenderness of the porous matrix, the penetration length of the convective flow and the heat-transfer rate are expressed in terms of the anisotropic properties of the porous medium, the modified Darcy–Rayleigh number and the aspect ratio of the geometrical configuration. A scale analysis is applied to predict the order of magnitudes involved in the similarity regime of the phenomenon. The conditions of existence of the similarity pattern is found to be dependent on the anisotropic parameters. It is demonstrated that both the anisotropic permeability ratio and the orientation angle of the principal axes have a strong influence on the heat-transfer rate and on the vertical penetration length into the well.     

Non-Darcian convection flow in a circular duct partially filled with porous medium

The flow and heat transfer in a circular duct bounded by a porous bed is considered. The entire flow region is divided into two zones. The clean fluid region is described by the Navier–Stokes equations, while the Brinkman-extended Darcy model is used in the flow through a porous bed. In either zone the momentum and temperature equations are coupled. In order to obtain a better insight into this complex problem, the Galerkin finite element analysis with quadratic polynomial approximations is applied. The behavior of the velocity and temperature is analyzed. The shear stress and the rate of heat transfer are also obtained for various governing parameters.     

The propagation of linear waves in humid,gas-saturated media

The process of propagation of acoustic waves in humid, gas-saturated porous media is investigated in a two-velocity approximation. A dispersion relation is derived, which includes interphase interaction forces and heat transfer between the skeleton of porous medium, liquid, and gas. The effect of heat transfer between the phases on the propagation of the “fast” and “slow” waves is included by means of heat equation     

Development of a theory and methods for calculating the heat and mass transfer in drying a porous body with multicomponent vapor and liquid phases

Theoretical fundamentals and a numerical method for calculating the heat and mass transfer and phase transformations in drying porous bodies with multicomponent vapor and liquid phases have been developed. We have obtained expressions for the evaporation intensity and the phase transition heat of liquid mixture components and a formula for the equilibrium partial pressure of vapor phase components, from which, as limiting cases, empirical Raoult and Henry laws follow. The results of comparison between the calculated and experimental data are presented. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 6, pp. 1111–1124, November–December, 2008.     

Effect of the transparency of the skeleton on parameters of an axisymmetric cylindrical filtration combustion heater

Numerical simulation with a differential approximation of radiation transfer was carried out to study the effect of the partial transparency of the porous skeleton on the radiant efficiency, the maximum temperature, and the localization of the combustion front in an cylindrical axisymmetric filtration combustion heater. It is shown that the partial transparency of amorphous quartz grains for radiation provides a 2–5% increase in the radiant efficiency in comparison with nontransparent materials under the simulated conditions. It is shown that use of transparent fillings can both decrease and increase the skeleton temperature, depending on the size of the system and other parameters. Optical characteristics of porous fillings and models of radiation transfer in isotropic porous media are discussed. Translated from Inzhenerno-Fizcheskii Zhurnal, Vol. 71, No. 1, pp. 62–69, January–February, 1998.     

Theoretical principles of design of multilayer swelling heat protection with assigned properties

Theoretical principles of computer design of multilayer heat-protective coatings made of swelling materials, thermophysical and kinetic characteristics of which are found from the solution of a complex of inverse problems of heat and mass transfer and ignition, are considered. Various classes of swelling materials (including highly porous ones) and their mathematical models of thermodestruction, swelling, and breakdown are analyzed. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 52–60, January–February, 2000.     

Optimum control of porous body heating by a flow of incompressible liquid (gas)

Optimum control of the process of heating of a porous body by a flow of an incompressible liquid or gas is considered. The amount of heat energy accumulated in the porous body is selected as an optimization criterion. This amount must be maximized provided there are a prescribed amount of heat that can be transferred to the flow filtering through the porous body and prescribed duration of the process. The control is considered to be exercised by means of the temperature of the liquid (gas) flow on entry into the porous body. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 380–385, May–June, 1997.     

Use of integral boundary-layer theory for solving conjugate problems of heat transfer in channels of high-power plants

The solution of the conjugate problem of convective-conductive heat transfer in the channels of power plants is presented. The problem of convective heat transfer in the gas phase is solved by the integral theory of heat transfer. A one-dimensional problem of conductive heat transfer in the material of the wall is solved by the finite-difference method. Relative laws of heat and mass transfer and friction are obtained by numerical integration with respect to the boundary-layer thickness. The effect of the material and geometry of the wall on the level of problem “conjugation” is studied. Translated from Inzhenemo-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 131–137, January–February, 2000.     

Some energy characteristics of the process of heating of a porous layer by an incompressible liquid or gas flow

The process of heating of a porous body that is initially at a low temperature by an incompressible liquid or gas flow is considered. The amount of heat energy that cannot be transferred to the porous layer because of the temperature difference between the liquid (or gas) and solid phases, respectively, is calculated. This energy may be considered “excess” energy. Its quantity is calculated analytically for the case of heating of a semi-infinite porous body. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 2, pp. 195–199, March–April, 1997.     

Transfer processes in porous catalysts in a microwave-radiation field

The influence of microwave (superhigh-frequency) radiation on transfer processes in a porous catalyst is investigated theoretically with allowance for a heterogeneous chemical reaction. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 4, pp. 688–694, July–August, 2000.     

Gas Pressure Dependence of the Heat Transport in Porous Solids with Pores Smaller than 10 μm

To elucidate the gaseous heat transfer in open porous materials with pore sizes below 10 μm, an experimental setup for hot-wire measurements at high gas pressures was designed and tested. The samples investigated were organic, resorcinol–formaldehyde-based aerogels with average pore sizes of about 600 nm and 7μm. The range in gas pressure covered was 10 Pa to 10 MPa. To avoid effects due to mass transport along the inner surface of the porous backbone of the samples, He and Ar, i.e., gases with very low interaction with the sample surface at ambient temperature, were chosen. The study reveals a significant contribution of coupling effects to the thermal transport in nanoporous media. A model has been developed that qualitatively describes the observed gas pressure dependence of the heat transport.     

Natural convection heat transfer of a viscous fluid in a vertical porous channel

Approximate analytic solutions to second-order nonlinear systems arising in natural convection flow and heat transfer in vertical porous channels are obtained via the Galerkin–Legendre Spectral Method. Furthermore, existence, uniqueness, and concavity results are established using Green’s functions and degree theory. We find that an increase in either the Darcy number or the quadratic density temperature variation results in an increase in the velocity and the temperature of a Newtonian fluid. Finally, parametric zones for the occurrence of reverse flow are considered, and the resulting influences on the obtained approximate solutions are analyzed.     

Unsteady wave flows of a gas suspension with account for phase changes

A system of equations of unsteady motion of a gas suspension with account for heat and mass transfer is presented. As a result of the computational experiment, the effect of the gas vibrations at the channel inlet on the motion of the gas suspension and the rate of heat and mass transfer is studied. Specifically, it is shown that, in the considered parametric region, the gas vibrations enhance the interphase heat and mass transfer. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 3, pp. 487–492, May–June, 2000.     

Calculation of the effect of evaporating drops on the relative law of heat exchange with a disperse mist flow

On the basis of a two-layer scheme of wall turbulence, a relative law of heat exchange with a disperse mist flow is calculated. It is shown that the influence of drops on heat exchange leads to a finite “stepwise” increase in heat transfer compared to the case of a single-phase vapor flow. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 510–513, May–June, 1997.     

Numerical simulation of heat transfer in multilayer structures with generalized nonideal contact

A procedure is proposed for calculation of a class of problems on heat transfer in multilayer structures with generalized nonideal contact. The procedure is illustrated by calculating the heat transfer in a stack of plates with liquids moving in gaps between the plates. Institute of Technical Mechanics, National Academy of Sciences of Ukraine, Dnepropetrovsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 69, No. 5, pp. 773–778, September–October, 1996.     

Numerical simulation of high-temperature thermal processes in cylindrical furnaces

A mathematical model of the high-temperature process of heat transfer in a cylindrical furnace has been constructed. Based on this model, investigations and assessment of the contribution made by longitudinal radiation to the process of radiant heat transfer in the cylindrical furnace were carried out. It has been established that the assumption on the exclusively radial propagation of a radiant flux may lead to considerable errors. It is shown that the zone method in conjunction with the method of Monte Carlo statistical tests is efficient for solving the problem of radiative heat transfer. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 3, pp. 548–558, May–June, 2008.     

Analytical methods of investigation of the thermal state of a region with a moving boundary under the conditions of nonstationary heat transfer to the external medium

An analytical method of solution of combined problems of nonstationary heat conduction for a region with a boundary moving according to a known law and with a time-variable coefficient of heat transfer is developed. The idea of splitting the kernel of the obtained generalization of a singular integral Fourier transform with respect to a space variable provides a basis for the method. Theoretical results are used in mathematical simulation of heat transfer processes in the region with a moving boundary under the conditions of nonstationary heat transfer to the external medium. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 125–130, January–February, 2000.