Flow Visualization of Closed Loop Pulsating Heat Pipe-CFD Analysis

Abstract

A simulation model was developed to study the fluid flow distribution in the form of liquid slugs and vapour bubbles in CLPHP. The flow visualization during the experiments that have been carried out in  an 8 turn closed loop pulsating heat pipe with water as working fluid were considered for comparison .The setup consist of a copper capillary tube of 2mm and 3 mm inner and outer diameters respectively. The main intention is to investigate the flow patterns in the tubes due to the different working conditions. CLPHP has its own characteristic in fluid flow behaviour for a specific geometry and fill ratio. A glass tube made of borosilicate is placed between evaporator and condenser sections for visualisation of fluid flow patterns through camera. Thus the recorded images gives the understanding of fluid flow behaviour inside the tube as a response to the operating conditions such as heat input supplied, fill ratio and orientation etc. The fluid flow patterns also observed using CFD analysis for water at 50% fill ratio at different time intervals. The liquid slugs and vapour bubbles were observed during fluid flow in the evaporator, adiabatic and condenser sections of CLPHP.