An IR thermography study of the influence of spray cooling parameters on heat transfer characteristics with a subcooled liquid

This study presents the results of an experimental investigation of heat transfer during spray cooling with subcooled distilled water using two types of nozzles. The influence of key operating parameters — the distance between the nozzle and the heater surface, liquid flow rate and initial liquid temperature — on heat transfer and temperature field distribution during spray cooling was studied. It is shown that the optimal distance at which maximum heat transfer and minimum surface temperature are achieved depends on the nozzle type and occurs at different ratios of diameter of impact area to heater size (D/a). Increasing the liquid flow rate and its initial temperature leads to an enhancement of heat transfer intensity during spray cooling. At the same time, as the flow rate increases, the rate of growth of the heat transfer coefficient with heat flux decreases, which is explained by the reduction of the relative contribution of phase transitions to the overall heat transfer balance. In contrast, a decrease in the degree of subcooling results in a higher rate of increase in the heat transfer coefficient, since the contribution of evaporation and boiling to the heat transfer process becomes more significant.