Experimental study on spray cooling heat transfer performance of R245fa/R142b mixture in boiling regime

Abstract

In this paper, the combination of spray cooling technology and non-azeotropic mixture was proposed to achieve the precise temperature control of heated surface. Experiments were performed with R245fa/R142b as the working fluid to study the spray cooling heat transfer of non-azeotropic mixture in boiling region. With the phase Doppler anemometer (PDA), the spray characteristics of working fluid at different height and mixing ratio were studied. The results showed that the non-azeotropic mixture existed a mixing ratio, at which the smallest droplet Sauter mean diameter (SMD) and the largest droplet density were obtained. This is beneficial to spray cooling heat transfer, and the mixing ratio is defined as the optimal mixing ratio. Heat transfer experiments proved that the surface uniformity of spray cooling is the best under the mixing ratio corresponding to the optimal spray characteristics. Further studies found that, at low heat flow in the two-phase region, the spray heat transfer performance of the non-azeotropic mixture was significantly weakened compared with that of any single component. With the increase of heat flux, the heat transfer performance of the non-azeotropic mixture gradually exceeds that of the single component R142b, which is related to the effect of additional mass transfer resistance in different stages.