A study of intermittent liquid nitrogen sprays

Abstract

Cryogenic spray cooling using liquid nitrogen as coolant is an attractive option for open loop cooling applications involving sub-zero temperatures. But for applications which require higher operating temperature (−180 to 20 °C) an intermittent spray is required, where the spray is pulsed at a certain frequency and with a certain open period. This versatile spray process can be adjusted using the mass flow rate, frequency and duty cycle (percentage of open time in one cycle) to match the required cooling rate on the target. Liquid nitrogen sprays were studied by conducting steady state experiments and intermittent spray cooling for various temperature ranges covering all regimes. The intermittent spray experiments were conducted for various ranges of surface temperatures (−180 °C–20 °C), and the r6ange of heat flux removable at each of the regimes was identified along with quantification of surface temperature amplitude, duty cycle and frequency.