Effects of geometry and multisource heat input on flow and heat transfer in single closed-loop pulsating heat pipe

Abstract

To study the effect of geometry and multisource heat input on the thermal performance and flow pattern, a single closed-loop pulsating heat pipe (CLPHP) with two ends in different shapes, round or right angled in shape, is studied numerically. The volume of fluid (VOF) model is applied for tracking the interface between two phases. Our results show that the proposed CLPHP with right angled elbow at evaporator end starts more quickly than that with round evaporator end, and it is found that the proposed CLPHP has the mean heat transfer coefficient of 1477 W/(m2·K), which is higher than the PHP with round evaporator end. The fast Fourier transform (FFT) technique is used to analyze the heat fluxes oscillation. For all of these geometries, the CLPHP shares the same peak frequency of 0.381 Hz in the evaporation end. For the condensation end, however, the characteristic frequency is changeable due to different flow patterns caused by the heat pipe bending mode. Due to the multisource input of heat, the ‘local flow direction switch flow’ and ‘stop-over’ would rarely be seen inside CLPHPs with round or right angled elbow at evaporation section, implicating that the heat transfer becomes stable and the fluctuation of CLPHP weakens.