Modern Problems of Intensification of Heat Exchange in Channels

The current achievements in the field of intensification of heat exchange in tube heatexchange apparatus are considered. Requirements for highefficiency heattransfer surfaces have been formulated. Problems of intensification of heat exchange in bundles of finned tubes and in heatexchange apparatus under conditions of condensation and boiling of heattransfer agents and under scaling conditions have been investigated. Highefficiency designs of heatexchange apparatus are presented.     

Numerical Analysis of the Jet‐Vortex Pattern of Flow in a Rectangular Trench

Numerical simulation of the vortex structure of threedimensional laminar flow in a rectangular trench of square cross section has been carried out on the basis of the finitevolume solution of steadystate Navier–Stokes equations.     

Surface Heat Treatment of Facing and Other Materials with Concentrated Solar Energy

Surface treatment of building materials, ornamental ceramics, covercoat enamels, blastfurnace and openhearth slags, and natural stones of the basalt type has been carried out with the use of solar furnaces and their simulators for the purpose of obtaining protectivedecorative vitreous and glazed coatings. The specific energy consumption and the optimum heat fluxes necessary to obtain highquality coatings have been determined. The results of searching investigations testify to the fact that renewable environmentally safe concentrated solar energy can be utilized in industry and the national economy for surface heat treatment of different materials by melting them in the air.     

One Method of Determination of the Effective Absorption Coefficient in Pulsed Laser Irradiation of Metals

An experimentaltheoretical method of determination of the absorption coefficients in laser treatment of metals has been proposed based on the solution of the boundaryvalue axisymmetric problem of heat conduction for a halfspace and metallographic measurements of the dimensions of the thermalhardening zone.     

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.     

Influence of Multiple‐Scattering Processes on the Laser Probing of Biological Tissues

Theoretical aspects of multiplescattering processes in laser probing of biological tissues have been considered. The method of digital dynamic specklephotography has been described. The results of experimental studies of the nearsurface blood flow and stressedstrained states in a pinstructure–toothroot model are presented.     

Solution of Mixed Contact Problems in the Theory of Nonstationary Heat Conduction by the Method of Summation‐Integral Equations

The laws governing the development of spatial nonstationary temperature fields in a bounded cylinder and a halfspace where one of the end surfaces of the cylinder touches the surface of the halfspace in a circular region are determined. A solution of a mixed axisymmetric nonstationary problem of heat conduction is obtained in the region of Laplace transforms. In solution of this problem, there appear summationintegral equations with the parameter of the integral Laplace transform (Lparameter) and the parameter of the finite integral Hankel transform (Hparameter).     

Investigation of the Strength and Elastic Properties of Glass‐Ceramic of a Lithium Alumosilicate Composition

This paper presents the results of investigations of the strength and elastic properties of the glassceramic obtained by novel technology with the use of the method of casting blanks from highdensity aqueous suspensions of lithium alumosilicate glass into porous moulds followed by their sintering and crystallization under combined conditions of thermal treatment. Comparison of the properties of the proposed glassceramic with the properties of the glassceramics obtained by conventional technology enabled us to gain a better insight into its potentialities and provide the necessary information for calculating the structural strength.     

Role of the Structural‐Rheological State of Poly(Meth)Acrylate Solutions in Their Soaking into Capillary‐Porous Bodies

We have investigated the influence of the structuralrheological state of solutions of poly(meth)acryl copolymers on the rate of their capillary rise and the uniformity of the polymer distribution in the bulk of porous bodies — models of monuments of art made of ceramics, terracotta, loessial and lime plaster, and concrete. It has been found that in the region of concentrations corresponding to the transition of poly(meth)acrylate solutions from the viscousNewtonian to the structuralviscous rheological state there is a sharp decrease in the rate of capillary rise of solutions into clay, chalk, and cementsand specimens. A worsening of the uniformity of the polymer distribution over the height of the porous specimens, a decrease in their surface wetting with copolymer solutions, and a decrease in the value of the polymer adsorption on the filler surface are also observed.     

Numerical Calculation of the Flow Regimes of a Fluid Partially Filling a Horizontal Rotating Heat‐Exchange Cylinder

Consideration is given to a numerical determination of a twodimensional unsteady viscous flow with the free surface in a stationarily rotating horizontal cylinder in which heatexchange processes are carried out. The markerandcell method in a polar coordinate system is used. The features of modeling of the walllayer regime and the circulating flow regime that occur in rapid and slow rotation of the cylinder, respectively, are discussed. Based on the given results of numerical calculations, the influence of the Reynolds number on the character of flow is analyzed.     

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.     

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.     

Heat Exchange and Hydrodynamics of Two‐Phase Media under Conditions of Forced Motion in Porous Structures

Experimental data on the heat transfer and resistance of twophase media in porous structures are given. Results of calculating the thermal state of a heat exchanger with a porous insert that is cooled by a twophase flow are presented.     

Study of the Temperature Fields in Oil and Gas Strata with Water Injection Based on the Perturbation Method

The problem of the thermal action on oil and gas strata by injection of a heating medium using expansion in a small parameter is reduced to an infinite sequence of boundaryvalue problems that are solved by the method of integral transforms. It is shown that, with an appropriate selection of the small parameter, the zerothorder approximation corresponds to a spaceaveraged (across the stratum thickness) solution of the main problem and leads to a concentratedcapacity scheme that is constructed assuming that the stratum temperature is independent of the vertical coordinate. The first approximation permitted marked refinement of calculations according to the concentratedcapacity scheme and an evaluation of its error. Spacetime temperature distributions are presented that have been calculated using the analytical solutions obtained.     

Investigation of Sonoluminescence Amplification under the Interaction of Ultrasonic Fields Widely Differing in Frequency

The laws of sonoluminescence generation under the interaction of ultrasonic fields widely differing in frequency have been investigated. It is shown that nonadditive amplification of the sonoluminescence is observed not only under the simultaneous action of the fields on a liquid, but also in a highfrequency field after preliminary insonification of the liquid by a lowfrequency field. The phenomenon of a longduration aftereffect of the lowfrequency field on the cavitation generated by the highfrequency field has been revealed. On the basis of the obtained results the conclusion has been drawn that the main mechanism of increasing the cavitation activity in the interacting fields is the generation of new cavitation nuclei as a result of the collapse of bubbles excited by the lowfrequency field.     

Investigation of the Processes in Torches for High‐Speed Gas‐Plasma Spraying of Powder Materials with the Use of the Flow‐Rate Method of Action on the Flow

The comparative characteristic of torches with geometric and flowrate methods of control of the characteristics of a twophase flow are given. Based on the mathematical model proposed, the advantage of the flowrate method is shown by calculation. By using particular examples, the estimates of the optimum values are given for the relation of the flow rates in feeding units and for the length of the heating portion for torches with a flowrate method of control of the twophase flow.     

On the Limiting Form of the Equation of Anisotropic Heat Conduction in a Rod

The paper considers the problem of the asymptotically substantiated reduction of the threedimensional, in coordinates, equation describing the process of heat propagation in an anisotropic material to a onedimensional equation. As a heattransfer region, a cylindrical rod of an arbitrary cross section was taken. It is assumed that the matrix of thermal diffusivity coefficients depends on the spatial coordinates. In the constructed equivalent heatconduction equation, a certain effective heattransfer coefficient is represented and formulas for its calculation have been obtained. Examples of the calculation have been considered.     

Influence of the Mass Transfer of Water in Cartilaginous Tissue on the Temperature Field Induced by Laser Radiation

A study is made of the influence of the mass transfer of water on the temperature field occurring in cartilaginous tissue under the action of laser pulses. Two different mechanism of mass transfer of water in cartilaginous tissue (moleculardiffusion mechanism and laminar flow) have been considered in solving heat and masstransfer equations. The calculations have shown that the maximum temperature is attained inside the sample because of the evaporation of water from the biologicaltissue surface. The influence of different parameters of laser radiation and mass transfer of water on the surface temperature, on the maximum value of the temperature, on the position of the temperature maximum, and on the characteristic time at which the diffusionlimited relaxation of stresses in the cartilaginous tissue occurs has been analyzed.     

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.     

Numerical Analysis of the Effect of Viscosity on the Vortex Dynamics in Laminar Separated Flow Past a Dimple on a Plane with Allowance for Its Asymmetry

Based on numerical solution of the Navier–Stokes threedimensional stationary equations by a factorized finitevolume method, the influence of physical viscosity on selforganizing jetvortex structures in a dimple on a plane immersed in a laminar flow is analyzed with allowance for the asymmetry of the dimple shape.