Experimental Study Of Evaporators With Novel Enhancement Structure In Advanced Thermosyphon System

There is a great challenge for electronic industry to deal with thermal management as electronic components are developed to smaller sizes and higher processing speed. In order to meet the needs of operating temperature, secure the reliability and save the lifetime of the components, different novel cooling methods have been developed, such as heat pipes and thermosyphon cooling. Thermosyphon is also called gravity-assisted heat pipe. For thermosyphon of single pipe system and heat pipe, the counter-current vapor/liquid flow may happen at high heat fluxes, which unavoidably leads to a limitation for the heat transfer capacity of the system. The thermosyphon loops with evaporator of enhanced boiling Nano-Porous surface has the potential to perform significantly better than the heat pipes.This paper conducts detailed experimental study on closed advanced two-phase thermosyphon loop system with evaporators of smooth and enhanced boiling Nano-Porous surfaces with working fluid R134a, respectively. Firstly, experiment is performed to investigate the effect of channel dimensions of smooth evaporators on the heat transfer performance of thermosyphon loop system. The results show that the channel dimensions influence significantly the heat transfer performance of the closed advanced two-phase thermosyphon loop system at a certain amount of R134a and at a certain reduced pressure (p_r=0.16). Secondly, experiment is performed to study the influence of a novel nano- and micro-porous structure in the evaporator on the heat transfer performance and to compare these results with the smooth surface evaporator with same dimensions and conditions. Thirdly, the heat transfer performances are compared with different levels of working fluids and with different diameters of the riser. Visualization experiments are performed with a high speed digital video camera to analyze the boiling two-phase flow patterns in evaporator with smooth and enhanced nano-porous surfaces, respectively. The obtained experimental results of the heat transfer performance are compared with the correlations of Rahmatollah Khodabandeh. At last, conclusions are presented along with some improvements of the thermosyphon system.