Heat Transfer Characterization of a Single Source Ultra-Low Flow Rate Electrospray

Abstract

The development and optimization of two phase electrospray cooling is currently restricted,in part due to the insufficient knowledge of how the various parameters that define an electrospray interact and their subsequent effect on the heat transfer coefficients and profiles.This research aims to characterise the heat transfer to impinging electrosprays for different nozzle sizes, separation heights and flow rates.The results show that electrospray coolingis dependent on separation height and cooling fluid flow rate,and partially on nozzle size. At lower separation heights and greater flow rates a saturation point was observed where a subsequent increase in the flow rate yields no increase in the peak heat transfer coefficient. In the case of greater separation heights and lower flow rates a dispersion threshold was noted where the working fluid becomes too dispersed causing reduced heat transfer coefficients. The radial enhancement region was shown to be slightly sensitive to varying flow rate and separation height though independent of nozzle size. Nozzle size was found to be important for moderate separation heights and high flow rates. Importantly, the results show that very high peak heat transfer enhancement over natural convection can be achieved with electrosprays with exceptionally low flow rates.