In order to investigate the influences of subcooling degree

mass flow rate and heat flux on the performance of the spray cooling system

a closed spray cooling system with R134a was built. The subcooling degree was adjusted by the subcooled section located before the nozzle inlet

the mass flow rate was controlled by the variable gear pump

and the heat flux was dominated by changing the voltage and current of the heating power. The experimental results indicated that

the variation of subcooling degree did not have significantly influence on the heat surface temperature and heat transfer coefficient as the heat flux and the mass flow rate were fixed. When the heat flux and the subcooling degree were constant

there existed a critical value of the mass flow rate

as the mass flow rate was smaller than the critical value the heat surface temperature decreased with the mass flow rate increasing

on the contrary

the heat surface temperature would increase with the mass flow rate increasing when the mass flow rate exceeded the critical value. When the mass flow rate and the subcooled temperature kept constant

there also existed a heat flux value which made the evaporation capacity equal to the supplement of droplets

therefore the heat transfer coefficient could reach the maximum value.