Experimental and numerical analysis of heat transfer and fluid flow characteristics inside pulsating heat pipe

Abstract

Heat pipes are a popular choice for many industries and research applications to extract heat effectively by maintaining desired device/location at almost isothermal conditions. Pulsating heat pipes, also known as wickless heat pipes, transfers the heat mainly by pumping phenomenon caused by the phase change which set the pulsating vapor-fluid motion. The evaluation of fluid flow and heat transfer characteristics inside the pulsating heat pipe is complex and challenging due to the oscillating two-phase flow between the heat source and heat sink sections. In this paper, a numerical investigation of the closed-loop pulsating heat pipe is performed to study the fluid flow dynamics and evaluate its thermal characteristics. The volume of fluid method is employed to numerically simulate the two-phase unsteady incompressible flow inside the pulsating heat pipe. The heat pipe tube has a 2 mm inside diameter filled with methanol as a working fluid at a preset pressure. The thermal performance of pulsating heat pipe is evaluated for various heat pipe filling ratios (50%, 65%, and 75%) where heat input loads of 5 ? 15 W are supplied at the evaporator end for each filling ratio case. The thermal characteristics of the pulsating heat pipe are presented in terms of the thermal resistance, heat transfer coefficient, and effective thermal conductivity, whereas fluid flow dynamics are presented as flow patterns produced inside pulsating heat pipe. The numerical simulations are compared and validated with experimental results. From the present numerical and experimental study, a filling ratio of 65% is an optimized charge quality for the current configuration of the pulsating heat pipe.