Моделювання теплоперенесення в стікаючій плівці рідини, що випаровується в перехресний потік нейтрального газу

Abstract

Наведені результати дослідження закономірностей теплоперенесення в стікаючій з нагрітої вертикальної поверхні плівки рідини в умовах випаровування в перехресний потік нейтрального (інертного) газу. Ці дослідження здійснювали на математичній моделі заснованій на запропонованих фізичних уявленнях про даний процес, що дозволило отримати диференційні рівняння теплоперенесення в рідкій плівці і газовій фазі.

The article presents the results of investigation concerning the heat transfer in a liquid film flowing down from a heated vertical surface and evaporating into a cross stream of a neutral (inert) gas. The cross interaction of fluid and gas flows is of interest from the point of view of increasing the intensity of the evaporation process by removing vapor from the surface of the liquid. The presence of a neutral gas above the film allows reducing the vapor pressure of the vaporized liquid in the vapor-gas mixture and, accordingly, gaining the effect concerned at lower temperatures. The investigation was performed using a mathematical model based on physical concepts, which include assumptions about a constant surface temperature and the absence of friction between the film and gas. When developing the model, it was assumed that the motion of the film and the gas stream as well as the heat transfer in them, is an established processes. The heat transfer between the film and gas stream occurs due to both the heat flow transferred by the steam and the heat exchange flow resulted from the contact of the phases. These ideas allowed obtaining differential equations of the heat transfer in a liquid film and a gas phase. By means of the numerical solution of these equations and using the equations that were previously derived by solving the hydrodynamic problem, the equations were obtained, which describe the changes in the temperatures of the film and gas flow along the height of the heated surface and in the temperatures of the gas along the width of the surface. It is shown that the film temperature reaches an equilibrium value when moving away from its initial section. With a further increase in the distance from the section, the liquid can completely evaporate. The developed calculation algorithm allows determining these distances for various initial parameters of the heat transfer process. The results can be used to develop film heat and mass transfer apparatus with cross-interaction of liquid and gas flows.