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.     

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.     

Use of equations for transfer of particle pulsation characteristics for calculating two-phase flows in the stabilized section of a tube

A stationary isothermal system of equations defining the behavior of a two-phase rising flow in the region of steady motion of a gas suspension in an axially symmetric channel has been developed. The equation of motion of the carrying medium is closed using a one-parameter model of turbulence, and the equation of momentum transfer in the dispersed phase is closed with the use of the equations for the second, third, and fourth moments of the pulsation velocities of the particles. The main mechanisms of two-phase turbulent flows were numerically investigated. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 4, pp. 99–109, July–August, 2007.     

Some features of the heat and mass transfer in a fire within an atrium

A field method of calculating the heat and mass transfer in a fire within an atrium is proposed. Results of numerical simulation of the three-dimensional temperature, velocity, smoke optical-density, and visibility fields in the gas medium in a fire within an atrium with the use of the mathematical model developed are presented. It is shown that the mechanisms of heat and mass transfer determined by the method proposed substantially change the modern views on the dynamics of the dangerous factors of a fire within an atrium and that the pattern of thermodynamics of the gas in a fire obtained with the indicated model cannot be obtained with integral and zonal models. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 5, pp. 135–146, September–October, 2006.     

Temperature shock waves in a moving medium with allowance for the relaxation of the heat flux

The solution of the gasdynamic equation with allowance for the heat transfer in the relaxation of the heat flux is analyzed. The relations expressing the laws of conservation on the front of strong discontinuity of the quantities sought, including the discontinuity of the temperature and the heat-flux density, are discussed. The possibility of existence of two shock waves with fixed initial data is shown using the self-similar solution of the problem on gas motion ahead of the piston. The occurrence of two strong discontinuities is due to the presence of different velocities of propagation of gasdynamic and thermal disturbances — the velocity of sound and the finite rate of heat transfer at a nonzero time of relaxation of the heat flux. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 57–68, July–August, 2006.     

Solutions of the type of traveling waves including hyperbolic heat transfer

Solutions of the type of traveling waves defining heat transfer and gas motion with account for the relaxation of the heat flow have been obtained and investigated. A comparative analysis of solutions of both types has been carried out. It is shown that, in the case where the relaxation of the heat flow is taken into account, solutions of the type of traveling waves can exist for any relation between the velocity of the traveling wave and the velocity of sound. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 2, pp. 290–302, March–April, 2008.     

Features of the Heat and Mass Transfer in a Fire Within a Building of Complex Geometry

A method of calculating the heat and mass transfer in a fire within a building of complex geometry is proposed. The results of calculation of the three-dimensional temperature, velocity, and visible-range fields in the gas medium of a fire simulated in the atrium, corridors, and floors of a building with the use of the mathematical model developed are presented. The method proposed allowed us to reveal regularities of the heat and mass transfer in a fire within the building considered that substantially differ from the existing views of the dynamics of the hazardous factors of a fire in such buildings. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 3, pp. 22–29, May–June, 2005.     

Nonstationary radiation-gasdynamic model of a laser-plasma accelerator

Based on the system of two-dimensional axisymmetrical continuity equations, Navier-Stokes and energy equations, and the equations of selective heat radiation transfer, a computational model is constructed and conditions of unsteady subsonic flows in a cylindrical channel of a power unit of the laser-plasma accelerator type are investigated. The governing parameters of the model are calculated, at which numerical solutions can be obtained to describe steady laminar gas flow in the neighborhood of the region of heat release, nonstationary oscillatory motions, and nonstationary vortex motion. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 1, pp. 174–179, January–February, 2000.     

Investigation of Heat Transfer in the Case of Upward and Downward Turbulent Flow of a Mixture of Gas and Solid Particles in a Pipe

The continual model developed by us is used to investigate the effect of the force of gravity on a nonisothermal turbulent flow of a gas suspension in a vertical pipe for upward and downward motion. The reasons behind the intensification of heat transfer in the case of a downward locally nonequilibrium motion of gas suspension are found.     

Investigation of heat and mass transfer in a rarefied gas using high-frequency measurement techniques

Devices based on a high-frequency generator for investigating heat and mass transfer in a rarefied gas — solid system are described. Their fundamental characteristics are given and procedures and results of tests are presented. __________ Translated from Izmeteritel’naya Tekhnika, No. 3, pp. 49–54, March, 2006.     

Determination of the local parameters of heat- and mass transfer in deep cooling in a tube bundle of fuel combustion products of thermal power plants

The specific features of heat and mass transfer of flue gases deeply cooled below the dew point of the steam contained in them have been analyzed. A method of determining the local parameters of heat and mass transfer in surface condensation heat utilization units is suggested. An analysis of the local characteristics of cooled and condensing combustion products allows one to study the relationship between the heat and mass transfer parameters and justify the optimum geometric characteristics of condensation heat utilization units. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 82, No. 2, pp. 289–295, March–April, 2009.     

Numerical Investigation on Turbulence and Bubbles Distribution in Bubbly Flow Under Normal Gravity and Microgravity Conditions

Two-phase flows of gas and liquid are increasingly paid much attention to space application due to excellent properties of heat and mass transfer, so it is very meaningful to develop studies on them in microgravity. In this paper, gas-phase distribution and turbulence characteristics of bubbly flow in normal gravity and microgravity were investigated in detail by using Euler–Lagrange two-way model. The liquid-phase velocity field was solved by using direct numerical simulations (DNS) in Euler frame of reference, and the bubble motion was tracked by using Newtonian motion equations that took into account interphase interaction forces including drag force, shear lift force, wall lift force, virtual mass force and inertia force, etc. in Lagrange frame of reference. The coupling between gas–liquid phases was made with regarding interphase forces as a momentum source term in the momentum equation of the liquid phase. Under the normal gravity condition, a great number of bubbles accumulate near the walls under the influence of the shear lift force, and addition of bubbles reduces turbulence of the liquid phase. Different from the normal gravity condition, in microgravity, an overwhelming majority of bubbles migrate towards the centre of the channel driven by the pressure gradient force, and bubbles have little effect on the turbulence of the liquid phase.     

High-speed imaging and CFD simulations of a deforming liquid metal droplet in an electromagnetic levitation experiment

Electromagnetic levitation of a liquid metal droplet is of great interest to study gas–liquid metal reactions. An important prerequisite for the evaluation of the overall mass transfer between the gas and metal is to characterize the geometry of the deforming molten droplet, which determines the interfacial reaction area. In this article, the free surface shape and dynamics of a molten 80%Ni–20%Cr droplet is investigated both experimentally and numerically. The frequencies associated to the oscillatory translational motions of the drop and to the vibrations of its free surface are measured using high-speed video image analysis. A 2D transient model is then presented, in which three interacting phenomena are considered: electromagnetic phenomena, the turbulent flow of liquid metal in the drop and the change in the drop shape. The numerical results presented demonstrate the capabilities of the model.     

Inherent frame dependence of thermodynamic fields in a gas

Summary Grad's 13-moment theory – appropriate for rarefied gases – implies that a gas cannot perform a rigid rotation, if it conducts heat. Indeed, stationary heat conduction in a gas between co-axial cylinders at rest in a non-inertial frame exhibits azimuthal components of velocity and heat flux. The fields of velocity and heat flux are calculated. The effects are due to Coriolis terms in all transfer equations that result from the Boltzmann equation.     

Possible intensification of interphase heat and mass transfer in a gas suspension with pulsating resonance flow

Calculated motions and heat transfer of particles suspended in a gas stream pulsating at large amplitude (resonance) show that the heat transfer and the amount of heat transferred to a particle increases, while the mean flow velocity required to transport particles decreases in comparision with the corresponding values in flow without pulsation. The use of resonance oscillations is claimed to intensify interphase heat and mass transfer in a gas suspension.     

Heat transfer in a circulating fluidized bed

On the basis of similarity theory a relationship is established for calculating the conductive-convective component of the coefficient of heat transfer in a circulating bed. Recommendations on the calculation of the total coefficient of heat transfer in a high-temperature bed are given. The gas gap between the heat-transfer surface and the first row of particles is evaluated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 3, pp. 447–453, May–June, 1998.     

Structure of pulse dispersed jet upon change in its frequency characteristics

Intensities of heat and mass transfer for continuous and pulse spray in interaction with the vertical surface of a heat exchanger differ considerably from one another when the time-averaged spraying rate [1–6] is kept constant. This difference is determined by characteristic properties of gas-drop flows of continuous and pulse sprays and their interaction with the heat-exchanging surface. Results of experimental studies of basic hydrodynamic parameters of pulse drop flow are presented: velocity and drop size dispersions, spectral characteristics of the kinetic energy of the spray at various distances from the source, and influence of the gas concurrent flow on these parameters. A difference in the heat transfer is shown upon variation of the pulse drop flow parameters from the heat transfer at the stationary supply of spray.     

Special features of propagation of hydrogen in a building

A three-dimensional mathematical model for calculating heat and mass transfer in propagation of hydrogen in a building that allows for gas exchange with the environment through an opening has been proposed. Based on numerical calculations performed by the proposed model, the author revealed certain features of the concentration fields of hydrogen in the case of its inflow at the floor level. It is shown that the dimensions and location of the explosion- and fire-hazardous zones change considerably during the process. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 73, No. 4, pp. 739–743, July–August, 2000.     

Modeling of radiative heat transfer and mass transfer processes in drop-flow-based heat exchangers for spacecraft

Modeling of radiative heat transfer and mass transfer in drop-flow-based heat exchangers for spacecraft is considered. A Monte Carlo-based numerical model is presented. Results obtained with the aid of the model are analyzed and compared with existing data. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 71, No. 1, pp. 92–96, January–February, 1998.