An experimental comparison of heat transfer characteristic between R134-a and R22 in spray cooling

Abstract

Spray cooling is one of the promising technologies in heat removing for high power density equipment, especially for the equipment with high heat flux surface. R134-a is one of the most prospective alternative refrigerants of R22 due to the zero ODP, low GWP, non-toxicity and non-inflammability, it is necessary to do comparative study on the heat transfer characteristics of R22 and R134-a in spray cooling. In this article, two closed loop spray cooling test rigs with the same spray nozzle are established to investigate the thermal performance of R22 spray cooling and R134-a spray cooling. The main parameters such as critical heat flux (CHF), heat transfer coefficient and target surface temperature are compared in the same thermal condition. The CHF of R134-a spray is lower due to the lower latent heat. The heat transfer coefficient of R22 spray is higher than that of R134-a spray with the same spray chamber pressure. However, R134-a spray cooling could replace R22 spray cooling in the phase change heat transfer region when the heat flux is less than 80 W cm−2.