HEAT TRANSFER STUDIES IN A CLOSED LOOP PULSATING HEAT PIPE

Abstract

Thermal resistance as a function of heat load and startup temperature with respect to time have been investigated for a pulsating heat pipe(PHP) at different inclination angle using different working fluids. PHP was made of 1.45 mm inner diameter copper tubes having 6 turns. The performance of de-ionized water and methanol as working fluid has been compared in terms of startup conditions, thermal resistance and performance at different orientation. The optimum filling ratio for water was 50% and for methanol 40%. Nanoparticle can further enhance the heat transfer characteristics of the working fluid; hence Al2O3 nanoparticle suspension in DI water with varying concentration was also used as the working fluid. The optimum concentration in vertical mode and at 45° inclinations was 1% by wt. while for horizontal orientation was 0.5% by wt. Further a correlation has been proposed to validate the experimental data.