On the effect of elliptical pin Fins, distribution pin Fins, and tip clearance on the performance of heat sinks in flow boiling

Flow boiling in heat sinks has been rigorously exploited in the heat transfer community to achieve high heat removal rates for a variety of applications. In this regard, a higher cooling performance could be possible with surface modifications including the use of micro pin fins and tip clearance. The aim of this study is to reveal the effects of pin fins and tip clearance as well as distribution pin fins, which served for more uniform flow distribution, on flow boiling. For this, experiments were conducted on five different heat sinks including a reference configuration (plain channel) and different elliptical pin fin and tip clearance configurations at mass fluxes of 125kg/m2s, 225kg/m2s, and 325kg/m2s within the heat flux range of 18 - 175W/cm2 using de-ionized water as the working fluid. Experimental flow boiling heat transfer results and performances of each heat sink were presented with the help of flow visualization. Accordingly, the maximum heat transfer performance was achieved with a pin fin heat sink with distribution pin fins and no tip clearance on the heating area. It was also proven that streamlined pin fin configurations with uniform flow distribution are helpful in enhancing the heat transfer performance in flow boiling.