Comparative study of double-sided spray cooling system under atmospheric and sub-atmospheric ambient pressures

Spray cooling is a highly efficient cooling technique that is widely used on the ground, but is more challenging with regards to the thermal management of airborne microelectronics due to the sub-atmospheric ambient pressure. In this study, we conducted experimental analyses on a double-sided spray cooling system designed to cool both sides of a copper block under sub-atmospheric and atmospheric pressure, with variations in heat fluxes and spray flow rates. The results show that under sub-atmospheric ambient pressure, the cooling rate is higher, cooling surface temperature at steady state is lower, and the heat transfer coefficient is higher. The max heat transfer coefficients are achieved at intermediate flow rates. Taking into account of both heat transfer and power consumption, the coefficient of performance (COP) and power efficiency coefficient (PEC) exhibit a gradual decrease with increasing flow rates. In all the examined operating conditions, the spray system achieves max COP and PEC when the flow rate is low. Under sub-atmospheric pressure, the spray cooling performance shows an improvement of over 40% compared to that under atmospheric pressure.