An Innovative Falling Film Evaporative Cooling With Recirculation Driven by Low-Grade Heat

Abstract

A falling film evaporator integrated with a recirculation tube driven by low-grade heat has been proposed to achieve a more compact and reliable system, which can be easily integrated into small-scale systems. An experimental study of the evaporative cooling of such an innovative falling film evaporator is presented. Water was used as the working fluid. The results are compared with published data for systems using mechanical pumps to circulate the fluid. Experimental investigation showed that the evaporative heat transfer coefficient of 6770–6870 W/m2 K can be achieved when the inlet temperature of the falling fluid is 29°C and the hot water entry temperature is 70°C. Detailed investigation on the effects of the driving heat source temperature and the inlet temperature of the hot water on the liquid film cooling mechanism was investigated. The results showed that for such a system, the effect of the falling film inlet temperature is more pronounced as compared with the other two parameters. Comparisons with traditional falling film evaporator with a mechanical pump indicated that the proposed integrated evaporator is more compact, reliable, and cost effective without impairing the heat transfer performance.