Heat and mass transfer in a solar regenerator

Abstract

Chemical dehumidification of air in an important industrial process. Solar energy can be used effectively in such processes for regenerating the absorbent solution. An analytical study of a gas-phase controlled solar regenerator in which the absorbent solution flows as a thin film and air flows cocurrent to it has been made. The governing equations which admit similar solutions for air streams have been solved, the independent parameter being the ratio of liquid to air velocities. The profiles of velocity, temperature and concentration, as well as their gradients, are presented. The normal convective velocity of water evaporating from the moving absorbent liquid surface is always present and has been taken into consideration in the present analysis. As the solution velocity increases, the mass transfer coefficient increases for a given air velocity. The results have been compared with those already reported for cases in which the resistance to mass transfer stems from the liquid phase as well. The analysis also includes the effect of free convection, an effect which is present in solar devices which use relatively low stream velocities, such as those encountered in practical solar regenerators.