Influence of chamber pressure on heat transfer characteristics of a closed loop R134-a spray cooling

A closed loop R134-a spray cooling system was designed using a commercial full-cone nozzle to generate the spray for the cooling of an upward plain copper surface. Given the flow rate, the spray cooling characteristics such as heat flux, critical heat flux (CHF) and spray efficiency were obtained under different spray chamber pressures. The results show the CHF and spray efficiency were enhanced with the increase of the chamber pressure. Due to the dependence of the saturation temperature on the vapor pressure, the cooling temperature of the target surface was directly proportional to the chamber pressure. Moreover, an improved empirical correlation was proposed for the non-dimensional heat flux as a function of the Jacob number, the Weber number, the dimensionless mass flow rate, the dimensionless pressure and the dimensionless bubble departure radius.