The heat and mass transfer process of the counter-flow dew point evaporative cooler

Abstract

The dew point evaporative cooling technology is a potential substitute for the conventional vapor compression chillers in the air conditioning systems. Most of the existing studies focus on the thermodynamic analysis of the dew point evaporative cooler under various conditions. As the dominant physical mechanism, the in-depth heat and mass transfer phenomena have yet been studied. In this paper, we propose a detailed investigation on the heat and mass transfer process of the counter-flow dew point evaporative cooler. An experimental setup was established to measure the temperature or humidity distributions of the supply air, working air and water film. The heat and mass transfer coefficients were calculated via the temperature and humidity distributions. Concurrently, a 2-D mathematical model was developed to predict the experimental results of the cooler based on the momentum, continuity, energy and species balance equations. Key results that emerged from this study include: (1) the governing dimensionless numbers/groups in the cooling process are determined; (2) the Nusselt number and Sherwood number, which reveal the intensity of the convective heat and mass transfer, are studied with reference to those dimensionless groups.