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

• The closed loop spray cooling systems for R134-a and R22 were designed.
• Found the replacement point that R134-a could replace R22 in spray cooling system.
• The heat transfer behavior of R134-a and R22 were analyzed.
• The critical heat flux and superheat degree with R134-a and R22 were compared.

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.