Heat Transfer in Straight Channels with Two‐Dimensional Cross‐Sectional Profiles under Conditions of Nonisothermal Stabilized Flow of a Fluid

Heat transfer in stabilized regimes of nonisothermal flows in a round tube and in channels with twodimensional convex cross sections is investigated with allowance for the velocity profile of a heating or cooling flow of a fluid. Mathematical models of unsteady processes of cooling by convection and radiation in pulling of rods and plane sheets at a constant velocity and of heat transfer (mass transfer) in a thin runningdown layer of a medium (fluid) are solved.     

Influence of a Long Stay of the Heat‐Release Surface in Kerosene on the Critical Heat Flux in Boiling in It under Steady‐State and Step Conditions of Heat Release

Results of experimental investigations of the influence of a long stay of the heatrelease surface in kerosene on the first critical density of the heat flux in boiling under the steadystate and step conditions of heat release are given.     

Complex Optimization of Processes of Heat Exchange in Gas‐Firing Installations with Utilization of Heat

Results of complex experimental investigations of the processes of combustion and combined heat exchange with separation of radiative and convective components of boilers with utilization of secondary energy resources are presented. The complex optimization is conducted by solving a system of partial differential equations on EC, CM, and IBM computers. For the purpose of controlling the combustion and heatexchange processes automatically, the calculated dependences are given and charts of regimes are composed.     

Determination of the Chemical Potential of Mass‐ and Heat‐Transfer Processes in Porous Bodies

The problem of determining the chemical potential of mass and heattransfer processes for porous bodies of a classical shape (an infinite plate, a sphere, etc.) is considered; the solution obtained is illustrated with examples of the nonisothermal extraction and nonisothermal adsorption purification of vegetable oils.     

Accommodation Two‐Moment Boundary Conditions in Problems of Thermal and Isothermal Slip

A new model of boundary conditions which generalizes the known Cercignani boundary condition is suggested. In this model, both the coefficient of accommodation of the tangential pulse of molecules and the coefficient of accommodation of the next moment of the distribution function are taken into account. The model is capable of approximating the mirrordiffuse boundary condition for the problems of slip with an accuracy of 1% and allows for the possibility of accommodation of different moments occurring differently on the surface. This possibility is absent in both the mirrordiffuse boundary condition and the Cercignani condition.     

Self‐Organization and Dynamic Chaos in Chemical‐Technology and Heat‐Exchange Devices: Problems and Tasks

Nonlinear phenomena in thermophysical and chemicaltechnology processes are considered in the context of nonlinearity, instability, nonuniqueness, nonstationarity, and irreversibility. The perturbation frequency (phase)toamplitude ratio is the governing parameter of the nonlinear interaction of perturbations that are described by the proposed general nonlinear parabolic equation. The nonlinearity of this ratio characterizes turbulence, while its linearity characterizes selforganization. It is shown that chaotic conditions can be selforganized under the action of white noise, which favors the system getting into the domain of attraction of a stable node. The mechanism of the occurrence of turbulence is substantiated.     

Thermal Processes in Capillary‐Porous Bodies with Internal and External Heat Sources

The problem of heating by internal energy sources a capillaryporous body in a medium with an elevated temperature is solved. The special features of the processes of heat and moisture transfer for different relations of the powers of the internal and external heating are analyzed. Simplified equations that describe the course of these processes are derived.     

Mathematical Model of Dynamic Heat‐ and Mass‐Exchange Processes in a Glassmaking Furnace

Theoretical foundations have been developed and a mathematical model of dynamic heat and massexchange processes in a glassmaking furnace has been constructed, which makes it possible to calculate and visualize nonstationary temperature fields in the furnace volume and nonstationary fields of velocities of convective glassmass flow in the molten bath. Test calculations for a specific structure of a glassmaking furnace which have shown the effectiveness of the model constructed have been performed.     

Investigation of the Performance of a Spiral‐Coil Finned Tube Heat Exchanger under Dehumidifying Conditions

In the present study, heattransfer characteristics of spiralcoil finned tube heat exchangers under dehumidifying conditions are investigated. A mathematical model of Ho et al. is modified by including fin efficiency. The derivation and solution methodologies are explained in detail. The effects of various inlet conditions of fluids flowing through the heat exchanger are discussed. The agreement of the model with the experimental data is satisfactory, with an average error of 1.2 and 4.0% for enthalpy and humidity effectivenesses, respectively.     

Identification of Heat‐Exchange Processes in a Supersonic Spatial Flow Past Aircraft

Direct and inverse problems of heat exchange in a supersonic spatial flow past the front part of an aircraft in the form of a spherically blunted nose cone have been solved numerically. The prospects of using highheatconductivity materials and the blowing of the gascoolant for lowering the temperature on the surface of an aerodynamic body have been shown. A comparison of the solutions of the direct and inverse problems in one, two, and threedimensional formulations for various materials of the sheath has been made. The error in recovering the heat flow by the thinwalled method has been estimated.     

Two‐Dimensional Calculation of the Parameters of a Steam‐Air Mixture in a Film‐Type Heat and Mass Exchanger

A mathematical model for twodimensional calculation of the temperature and density of the steam in a steamair mixture which rises between two water films flowing down adiabatic shields has been proposed. The parameters of the films have been calculated in a onedimensional approximation. The results of calculating the parameters of air according to the onedimensional and twodimensional models of the processes of heat and mass transfer have been compared. The range of applicability of the former to a filmtype heat and mass exchanger has been determined.     

Scattering and Heat Exchange of Disperse Impurity Particles in Turbulent Nonisothermal Gas and Low‐Temperature Plasma Jets

This paper considers issues connected with the simulation of the motion and heat exchange of disperse impurity particles in nonisothermal gas and lowtemperature plasma jets under the action of turbulent pulsations of the carrier flow. The influence of the outflow conditions, the initial parameters of the phases, and the conditions of particle injection into a jet flow on the laws of impurity scattering and heat exchange are investigated. The results of the numerical calculations are compared with the data obtained without taking into account the influence of turbulent pulsations on the particle motion.     

Process of Cooling of a High‐Temperature Two‐Phase Flow

A technique and a design of a transducer for measuring the enthalpy of twophase flows using the thinwall method have been developed. Working formulas for calculating the heat capacity and the enthalpy of a gas flow are substantiated. Results of a test of the transducer in hightemperature flows of powder gases, including those after the packing of a coolant, are presented. The results obtained show that cooling of powder gases due to an endothermic reaction makes it possible to decrease the enthalpy flux by a factor of 5 and the temperature by a factor of 2.     

Heat and Mass Transfer in a Two‐Component Developed Turbulent Gas‐Vapor‐Droplet Flow

A calculation model is developed and a numerical study is made of the heat and mass transfer characteristics in a turbulent gas–vapor–droplet flow moving in a round tube. The model takes into account the evaporation of droplets, the diffusion of vapor into air, and the acceleration of a carrier flow. Distributions of the parameters of the twophase flow are obtained with respect to the tube radius for different initial concentrations of the gas phase. Heat and masstransfer calculations are compared to the experimental and numerical works. On the whole, the evaporation of the droplets in the vaporgas flow leads to the intensification of heat transfer as compared to a onecomponent vapordroplet flow and singlephase flow of vapor.     

Mathematical Model of a Recuperative Heat Exchanger in a Two‐Dimensional Formulation

A twodimensional model of a recuperative heat exchanger which allows calculation of flows through a heattransfer wall and temperature at any point of it has been developed. The results of the calculations are in satisfactory agreement with experimental data.     

Heat Exchange with Horizontal Cylinders in a Centrifugal‐Bubbling Bed

The authors present results of an analysis of experimental data on heat exchange on horizontal cylinders in rotating gasliquid flow. The hydrodynamic parameters of a thin film in a centrifugalbubbling bed have been determined based on the mathematical modeling of a film flow in the case of a highvelocity gasliquid flow about it. Results of a generalization of the data on heat exchange are given, and the hydrodynamic stability criteria for the film flow on the cylinder surface are evaluated.     

Improvement of the Convergence of Fourier–Hankel Series in Solving Two‐Dimensional Heat‐Conduction Problems

In the present work, an analytical solution of a boundaryvalue problem of nonstationary heat conduction in a twodimensional solid (a prism, a cylinder) with improved convergence of Fourier–Hankel series is given. Using as an example a problem with cyclic inhomogeneous boundary conditions of the third kind, the author shows the uniformity of the convergence of the obtained solution on the boundaries of the solid and the matching of temperatures in passage from one period of the cycle to another.     

High‐Temperature Radiative‐Convective Heat Exchange on the Surface of Glass‐Reinforced Plastics

The results of experimental investigations of heat exchange on the surface of a thermalprotective material — glassreinforced plastic — in the flows of hightemperature gases have been presented. It has been established that the influence of injection on the value of the heat flux does not exceed 10% in the range of variation of gas temperatures 300–2000 K and Reynolds numbers 350–9800.     

Shrinkage and Strength of Capillary‐Porous Colloidal Materials

The processes of shrinking of capillaryporous colloidal bodies under the action of capillaryosmotic pressures have been investigated. The mechanisms of densification and strengthening of a material in the drying process have been considered. An equation relating the material's strength to its density, which agrees with experiment, is proposed.