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HEAT AND MASS TRANSFER IN SYSTEMS

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A unique complex of large-scaled setups has been developed at the Institute for the study of heat and mass transfer in two-phase systems. The IR thermography, electric-chemical, and capacity methods, speed photography, and video shooting are being used to measure the local characteristics of two-phase multicomponent systems.
    A film condensation of vapor, under various geometry and regime parameters, was studied including porous and grained media. It was determined during vapor condensation on tube bundles, that vapor condensates on overcooled drops and jets in the intra tube space.
    Crisis and transition phenomena were studied during boiling under the conditions of free and forced convection in cryogenic liquids, freons, and other liquids. The instability of the bubble structure of evaporation was determined. When liquid is being heated above the threshold values, evaporation fronts are formed on the surface of the vapor bubble. These fronts propagate in a metastable liquid with a constant velocity, which by order, exceeds the velocity of a bubble growth.

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The investigation circuit for hydrodynamics and heat transfer during the forced two-phase flow of cryogenic liquids.

The thermogram of liquid film flowing down a vertical plane with a local heat source of 6.5+13 mm.

The study condensation of vapor film.

The crisis and dynamics of the changing boiling regimes were studied using different heat release laws. Description models for the development of a nonstationary crisis were proposed. The effect of the law and temp of the heat load's increase was studied together with the heater's time lag, and pressure reduced by a value of the critical heat flux. The stability and development of one and two-dimensional sites of film boiling are being investigated. Criteria which characterize the boundary conditions at the front of changing boiling regimes are determined depending on the thermophysical and geometrical parameters of the heat-liberating surface.
    The studying of heat transfer and hydrodynamics during heating, evaporation, boiling, and the heat transfer crisis in flowing liquid films is in progress. Thermocapillary convection, underheating, and the heaters' sizes are being investigated. Experiments are being carried out using a wide range of fluids such as water, ethanol, freons, nitrogen, carbon perfluorates, and their mixtures. A phenomenon of horizontal standing wave was determined during the evaporation of a downward liquid film flow underheated lower than the saturation temperature. Calculation dependencies for the critical heat flux in flowing films of saturated liquid arebeing obtained for different ranges of the changing Weber number.
    The modeling of interconnected heat and substance transfers in two-phase multicomponent systems is one of the investigation directions. The main peculiarity of these systems is mass transfer from one phase to another, accompanied by the great release or absorption of heat. Precise analytical solutions are being obtained in the framework of the developed models for one of the above processes of vapor or gas absorption by liquids. These solutions are used for the calculation of efficient absorption apparatus including heat pumps and refrigerators.

Авксентюк Б.П., Овчинников В.В. Исследование динамики парообразования при давлениях больших атмосферного, ЖПМТФ, 1996, т. 37, № 6, С. 91-98.

Накоряков В.Е., Григорьева Н.И., Потатуркина Л.В. Анализ точных решений задач тепломассопереноса при абсорбции на пленках и струях, ТОХТ, 1997, т. 31, № 2, С. 141-148.

Шемагин И.А., Будов В.Я., Дорохов А.Р., Гогонин И.И. Теплообмен при пленочной конденсации в пленочном кипении в энергооборудовании АЭС, Москва: Энергоатомиздат, 1993, 208 с.

Gogonin I.I. and Kabov O.A., An experimental study of R-11 and R-12 film condensation on horizontal integral-fin tubes, J. Enhanced Heat Transfer, 1996, vol. 3, no.1, p. 43-53.

Kutateladze S.S., Gogonin I.I., Sosunov V.I. The influence of condensate flow rate on heat transfer in film condensation of stationary vapour on horizontal tube banks // Intern.J.Heat Mass Transfer. 1985.V.28, no.5.P.1011-1018.

Pavlenkо A.N., Chekhovich V.Yu. Heat transfer crisis at transient heat release, Russ. J. of Eng. Thermophys., 1991, vol. 1, p. 73-92.

   
 

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