Phase change heat transfer enhancement with surface modification at atmospheric and sub-atmospheric pressures

Official URL: https://risc01.sabanciuniv.edu/record=b2766807_(Table of contents)

Surface modifications are one of the major techniques in enhancing boiling heat transfer, achievement of higher cooling performance, and energy efficiency. The surface modification can be performed with the external structures including micro pin fins or changes in surface wettability such as the use of biphilic surfaces. The aim of the first thesis 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 125 kg/m2s, 225 kg/m2s, and 325 kg/m2s within the heat flux range of 18 – 175 W/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.