Experimental determination of cooling performance on heat sinks with cone-jet electrospray mode

Abstract

In this study, electrospray cooling characteristics for smooth surface heat sink and finned surface heat sink were investigated. An experimental study was carried out using ethanol for 7 different heat fluxes in the cone-jet mode, in which a stable and continuous droplet diameter is produced. In the experiments, 7 kV voltage, 20 mm nozzle-to-substrate distance, a stainless steel nozzle with 0.61 mm inner diameter (di) and 0.45–0.60 ml/min flow rates were used. Due to that the two flow rate values are very close to each other, no difference in the formation of electrospray was observed, but since the amount of fluid sent to the heat sink is higher, at 0.60 ml/min flow rate, 15–44% better a cooling was achieved under different heat fluxes compared to 0.45 ml/min flow rate. In addition, finned heat sink applied for the first time in electrospray cooling provided approximately 1.3–1.6 times better cooling than smooth surface heat sink. The effect of electrospray dripping on cooling in a finned heat sink is expressed by enhancement ratio (ER). Additionally, the change in fin enhancement ratio (FER), which denotes the enhancement of cooling in finned heat sink in comparison to that in finless heat sink, was scrutinized at different surface temperatures. As a result, as a distinction from the studies on improving heat transfer with electrospray cooling, it was suggested that finned surface heat sinks, which were not used before, can be used as an effective parameter to further enhance the heat transfer.