A STUDY OF INTERMITTENT SPRAY COOLING FOR THERMAL MANAGEMENT OF ELECTRONICS

Abstract

Spray cooling is one of the promising techniques available for thermal management of electronics. Most of the spray-cooled systems have more than the required coolant sprayed on the surface and this flooding mitigates phase change. An ideal system would match the rate of evaporation and boiling with the coolant inflow so that there is neither flooding nor dry out. Such a possibility exists with intermittent sprays where the coolant is sprayed intermittently at a particular frequency and for a particular percentage of time. In this study, closed loop feedback control based intermittent spray cooling of low flow water sprays on a thermal test chip for low heat fluxes, high flow water sprays on a copper block for high heat fluxes and liquid nitrogen sprays on a copper block were studied. The effects of heat flux and surface temperature on the surface temperature fluctuation, injection frequency and duty cycle were studied. The transient variation of heat transfer coefficient during spray-on time and spray-off time was also investigated by application of a sequential function specification method to solve the inverse heat conduction problem within the copper block. In addition the Nukiyama curve for liquid nitrogen sprays (for wall superheat temperature of up to 200K) were also obtained by solving the experimentally measured transient data using the sequential function specification method.