Determining heat and mass exchange kinetic in a column heat exchanger with direct phases contact

Abstract

The object of this study was the processes of heat and mass transfer in a column heat exchanger with direct phases contact. The investigated problem is related to the need to determine the estimates of the kinetic characteristics of heat exchange during the concentration of solutions in a contact heat exchanger equipped with dual-flow trays. In particular, it was assumed that the determination of the influence of the gas velocity in the apparatus and the density of liquid irrigation of the plates, as well as the geometry of the plates, on the kinetic coefficients would make it possible to reveal the patterns of heat and mass exchange between the liquid and the air in contact with it in the column apparatus. It was determined that to increase the intensity of mass transfer in the gas and heat transfer in the liquid, it is necessary to increase the gas velocity and irrigation density. Then the gas velocity and irrigation density have approximately the same effect on the intensity of mass transfer in the gas and heat transfer in the liquid. When studying the effect of the geometry of the plate on the kinetic coefficients of heat transfer in the liquid and mass transfer in the gas, it was established that the value of the portion of the free cross section of the plate has a decisive influence on the value of the considered kinetic coefficients. A generalized equation was built, which makes it possible not only to calculate the enthalpy transfer coefficient during the interaction of sodium chloride solution with air but also to determine the limiting stage of this process. The results could be used to design a unit for concentrating a hot solution of sodium chloride by evaporating water during blowing with air in a contact heat exchanger. This would make it possible to obtain crystalline sodium chloride using secondary energy resources and other non-traditional sources of thermal energy