SPRAY COOLING OF POWER ELECTRONICS AT CRYOGENIC TEMPERATURES

The operation of power electronics at liquid nitrogen temperature (LNT) is a very attractive possibility. However, a high heat flux (over 1.0 x 10(6) W/m(2)) cooling technique, like spray cooling, will have to be used to realize all the advantages of low-temperature operation. This study details the results from experiments conducted to study the heat transfer characteristics during spray cooling with liquid nitrogen. Four different nozzles at various pressures were used to study the variation in spray cooling heat transfer at LNT. The effect of nozzle and now rate on the critical heat flux and overall heat transfer characteristics are presented. Heat fluxes close to 1.7 x 10(6) W/m(2) were realized at temperatures below 100 K. The mass flow rate range was from 6.1 x 10(4) kg/h(.)m(2) to 3.2 x 10(5) kg/h(.)m(2).