A study of heat-transfer processes in a supersonic flow around a spherically blunted cone with allowance for injection of a gas-cooler

The heat- and mass-transfer processes of a spherically blunted cone and a supersonic air flow are identified by the methods of solving direct and inverse problems with allowance for the heat flow along the contour and the injection of a gas-cooler. The ranges of applicability of the standard one-dimensional approaches and the method of a thin wall for recovering heat fluxes directed toward the body in flow are shown in the entire time period considered. State University of Tomsk, Tomsk 634050. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 40, No. 5, pp. 123–132, September–October, 1999.     

Optimization of the earthreentry trajectory of a blunted body by the integral heat flux

The paper deals with optimization of the Earth reentry trajectory by the magnitude of the total convective heat flux at the stagnation point of a blunted body. The equations of a thin (hypersonic) viscous shock layer taking into account the nonequilibrium nature of chemical reactions and multicomponent diffusion are used as the initial mathematical model for heat flux calculations. The optimal solution is obtained by an effective robust method using the basic ideas of genetic algorithms. Institute of Applied Mathematics and Mechanics, Tomsk State University, Tomsk 634050. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 4, pp. 112–123, July–August, 2000.     

Numerical analysis of the effect of local energy supply on the aerodynamic drag and heat transfer of a spherically blunted body in a supersonic air flow

The effect of local source of energy in a supersonic flow on the aerodynamic drag and heat transfer of a spherically blunted body is studied numerically. Calculations are performed on the basis of the Navier-Stokes equations for a thermally equilibrium model of air. Data on the effect of the intensity and size of the energy source on the wave drag, friction, and heat transfer are obtained. Particular attention is given to studying the effect of drag reduction by means of a focused heat source. The gas-dynamic nature of this effect is studied. The limits of drag reduction are estimated, and optimal conditions of heat supply are determined. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 41, No. 5, pp. 171–179, September–October, 2000.     

Combined heat transfer in a boundary layer of a selectiviely absorbing medium on a permeable plate under the conditions of intense radiation heating

Results of a numerical study of unsteady radiative-convective heat transfer in a boundary layer on a thermally thin permeable plate in the presence of intense radiation heating from outside are reported. The conjugate formulation of the problem takes into account the thermal interaction between the plate and an external gas flow. We consider a turbulent flow of an emitting-absorbing medium with the selective character of absorption. Calculation results are analyzed with a view for clarifying the influence of the governing parameters, namely, the relative temperature of an external radiation source, the Stark number, and the injection parameter. The possibility of inversion of a convective heat flux on the plate under the conditions of high-level external radiation is found. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirisk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 5, pp. 126–133, September–October, 1998.     

Radiation effect on MHD mixed convection flow about a permeable vertical plate

This study investigates mixed convection heat transfer about a permeable vertical plate in the presence of magneto and thermal radiation effects. The effects of the mixed convection parameter, the radiation–conduction parameter, the surface temperature parameter, the magnetic parameter and the suction/injection parameter on the local skin friction and local heat transfer parameters are presented and analyzed.     

Mathematical simulation of conjugate mixed convection in a rectangular region with a heat source

Conjugate convective-conductive heat transfer in a rectangular region with forced flow and a heat source is simulated numerically. Distributions of the thermal and hydrodynamic characteristics of the flow regimes studied are obtained. The evolution of the process analyzed is shown. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 69–81, November–December, 2008     

Turbulent thermal in a stratified atmosphere

An approximate analytical model of a turbulent thermal in a stratified atmosphere is proposed. This model makes it possible to predict the dynamics of the ascent, suspension and oscillation processes of a buoyant cloud both within the troposphere and on entering the stratossphere. The values of the heat energy needed for the thermal to penetrate the tropopause in northern and southern latitudes are estimated. Estimates are obtained for the amount of material dumped into the stratosphere. A method of determining the thermal energy of volcanic eruptions of the explosive type is proposed. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 141–153, November–December, 1986.     

Effects of Viscous Dissipation on Unsteady Free Convection in a Fluid Past a Vertical Plate Immersed in a Porous Medium

The effects of viscous dissipation on unsteady free convection from an isothermal vertical flat plate in a fluid saturated porous medium are examined numerically. The Darcy–Brinkman–Forchheimer model is employed to describe the flow field. A new model of viscous dissipation is used for the Darcy–Brinkman–Forchheimer model of porous media. The simultaneous development of the momentum and thermal boundary layers are obtained by using a finite difference method. Boundary layer and Boussinesq approximation have been incorporated. Numerical calculations are carried out for various parameters entering into the problem. Velocity and temperature profiles as well as local friction factor and local Nusselt number are shown graphically. It is found that as time approaches infinity, the values of friction factor and heat transfer coefficient approach steady state.     

Effects of heat generation on g-Jitter induced natural convection flow in a channel with isothermal or isoflux walls

This paper discusses the behavior of g-jitter induced free convection in microgravity under the influence of a transverse magnetic field and in the presence of heat generation or absorption effects for a simple system consisting of two parallel impermeable infinite plates held at four different thermal boundary conditions. The governing equations for this problem are derived on the basis of the balance laws of mass, linear momentum, and energy modified to include the effects of thermal buoyancy, magnetic field and heat generation or absorption as well as Maxwell's equations. The fluid is assumed to be viscous, Newtonian and have constant properties except the density in the body force of the balance of linear momentum equation. The governing equations are solved analytically for the induced velocity and temperature distributions as well as for the electric field and total current for electrically-conducting and insulating walls. This is done for isothermal–isothermal, isoflux–isothermal, isothermal–isoflux and isoflux–isoflux thermal boundary conditions. Graphical results for the velocity amplitude and distribution are presented and discussed for various parametric physical conditions.     

Numerical Study of Heat Transfer in a Rectangular Channel with Porous Covering Obstacles

A numerical study is performed to analyze steady laminar forced convection in a channel in which discrete heat sources covered with porous material are placed on the bottom wall. Hydrodynamic and heat transfer results are reported. The flow in the porous medium is modeled using the Darcy–Brinkman–Forchheimer model. A computer program based on control volume method with appropriate averaging for diffusion coefficient is developed to solve the coupling between solid, fluid, and porous region. The effects of parameters such as Reynolds number, Prandtl number, inertia coefficient, and thermal conductivity ratio are considered. The results reveal that the porous cover with high thermal conductivity enhances the heat transfer from the solid blocks significantly and decreases the maximum temperature on the heated solid blocks. The mean Nusselt number increases with increase of Reynolds number and Prandtl number, and decrease of inertia coefficient. The pressure drop along the channel increases rapidly with the increase of Reynolds number.     

The effect of thermal dispersion on free convection film condensation on a vertical plate with a thin porous layer

An analytical solution to the problem of condensation by natural convection over a thin porous substrate attached to a cooled impermeable surface has been conducted to determine the velocity and temperature profiles within the porous layer, the dimensionless thickness film and the local Nusselt number. In the porous region, the Darcy–Brinkman–Forchheimer (DBF) model describes the flow and the thermal dispersion is taken into account in the energy equation. The classical boundary layer equations without inertia and enthalpyterms are used in the condensate region. It is found that due to the thermal dispersion effect, the increasing of heat transfer is significant. The comparison of the DBF model and the Darcy–Brinkman (DB) one is carried out.     

Dynamics of a vapor shell around a heated particle in a liquid

The dynamics and heat and mass exchange of a vapor bubble containing a heated particle is studied in relation to the problem of vapor explosions. It is shown that the process involves two stages: dynamic stage and thermal stage. The dynamic stage is characterized by pressure fluctuations and a rapid increase in the thickness of the vapor layer. It is shown that the simplifying assumptions of the constancy of assumptions of constant heat conductivity of the vapor and linear temperature profile in the vapor layer lead to qualitatively incorrect results. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 4, pp. 69–78, July–August, 2007     

Motion and heat and mass transfer in a disperse admixture in turbulent nonisothermal jets of a gas and a low-temperature plasma

The motion and heat and mass transfer of particles of a disperse admixture in nonisothermal jets of a gas and a low-temperature plasma are simulated with allowance for the migration mechanism of particle motion actuated by the turbophoresis force and the influence of turbulent fluctuations of the jet flow velocity on heat and mass transfer of the particle. The temperature distribution inside the particle at each time step is found by solving the equation of unsteady heat conduction. The laws of scattering of the admixture and the laws of melting and evaporation of an individual particle are studied, depending on the injection velocity and on the method of particle insertion into the jet flow. The calculated results are compared with data obtained with ignored influence of turbulent fluctuations on the motion and heat and mass transfer of the disperse phase. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 95–108, May–June, 2008.     

Modeling of heat transfer in a turbulent flow around a heat-conducting plate with local regions of heating

A solution of the coupled nonstationary boundary-value problem of turbulent flow around a flat heat-conducting plate of finite thickness having local regions with volume heat sources is given. For modeling the heat transfer in the boundary layer, thek-ε turbulence model is used. It is shown that the thermal conductivity of the plate material significantly affects the surface distributions of both temperature and local friction. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 79–86, November–December, 1998. The work received financial support from the International Scientific and Engineering Center (project No.199).     

Unsteady radiative-convective heat transfer in a high-temperature gas-particle flow past a semi-transparent plate

Numerical simulations of unsteady radiative-convective heat transfer in a turbulent flow of a mixture of gases and solid particles past a semi-transparent plate are performed. An ablation process is demonstrated to occur on the plate surface in the case of intense radiative heating of the plate by an external source with emission in a limited spectral range. Temperature fields and distributions of heat fluxes in the boundary layer and in the plate are calculated. Calculation results are presented, which allow determining the effect of ablation and reflecting properties of the plate surface on the thermal state of the medium in the system containing the boundary layer and the plate under conditions of plate heating by a high-temperature source of radiation. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 50, No. 3, pp. 140–146, May–June, 2009.     

Heat transfer in a wall jet propagating in a highly turbulent cocurrent flow

Heat transfer in a jet propagating in a cocurrent flow has been studied over wide ranges of the injection ratio (m=U_s/U₀<1 and m>1) and flow turbulence (Tu₀=0.2–25%). It is shown experimentally that for m<1, a 1% increase in turbulence leads to a 1% increase in heat transfer, and the wall adiabatic temperature and the relative heat-transfer function should be taken into account in heat-transfer calculations. For m>1, the flow turbulence does not affect the heat transfer and the heat production can be calculated using the laws typical of jet flows. Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 3, pp. 119–125, May–June, 1998.     

Analytical solution of conjugate heat transfer and optimum configurations of flat-plate heat exchangers with circular flow channels

An analytical solution is developed for conjugate heat transfer in a flat-plate heat exchanger with circular embedded channels. The analysis was carried out for fully-developed conditions in the circular tube and uniform heat flux at the plate boundary. The results are applicable to cooling channels that are 50 μm or more in diameter with a large length–diameter ratio. The thermal characteristics of the heat exchanger have been examined for a wide range of the relevant independent parameters and optimum designs for three different sets of constraints have been presented. It was found that the overall thermal resistance increases with the depth of the tube from the heated surface, as well as the spacing between the tubes. For a given combination of tubes’ depth and spacing, there is a certain tube diameter at which the thermal resistance attains a minimum value.     

Specific features of explosive boiling of liquids on a film microheater

Explosive boiling of liquids on film heaters under the action of pulsed heat fluxes q = 10⁸–10⁹ W/m ² is considered. A technique of stroboscopic visualization of boiling stages with a time resolution of 100 nsec is used. Numerous scenarios of evolution of explosive boiling are demonstrated. Conditions of the thermal effect (magnitude of the heat flux, duration and repetition frequency of heat pulses) are found, which ensure single and repeated boiling, intermittent boiling, and boiling with formation of complicated multi-bubble structures. It is noted that homogeneous nucleation is a dominating mechanism of incipience of examined liquids for q > 10⁸ W/m ². __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 81–89, March–April, 2007.     

Modeling the unsteady heat and mass transfer in the vapor outlet channel of a radiative-evaporative thermal protection system

The system of equations and boundary conditions for the problem of modeling the heat and mass transfer processes in the plane channel of a combined thermal protection system of the radiative-evaporative type is formulated for time-dependent external heat flux and pressure. The effect of the problem parameters on the basic characteristics of these processes is considered. The possibility of nonmonotonic behavior of the evaporation rate and evaporation surface temperature in the presence of a monotonically increasing heat flux is established. A physical explanation of these effects is given. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 5–12, January–February, 1994.     

Effect of local heat supply to a turbulent boundary layer on the friction

The results of calculating a supersonic turbulent boundary layer on a flat plate in the presence of thermal energy supply to the boundary layer are presented. Two methods of energy supply are considered: heating a local interval of the surface, which is otherwise thermally insulated and using a local volume heat source. It is shown that for the same amount of heat supplied to the gas volume heating leads, under certain conditions, to greater friction reduction than the surface heating. Localization of the energy supply zone leads to the intensification of the viscous drag reduction effect and to a greater decrease in the local friction coefficient, which extends a considerable distance downstream. Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 48–56, January–February, 1997. The work was carried out with financial support from the Russian Foundation for Fundamental Research (project No. 93-013-17600).