Thermal performance study of a liquid-cooled porous thermosyphon system

Abstract

With the ever rapid advances in silicon chip technology, heat fluxes from high speed electronic devices are increasing at an alarming rate and have now, reached levels where single phase cooling such as air cooled can adequately remove the heat. The use of two-phase cooling in thermosyphons has proven to be the potential alternative in managing high heat loads. A thermosyphon system comprises a condenser, an evaporator base simulating a heat dissipating silicon chip and a coolant chamber. The aim of this project is to investigate the effects of inclination angle and graphite foam geometry modifications on the heat transfer performance of a thermosyphon.

A dielectric fluid, namely FC-72, was used and experiments performed . Experimental results showed that inclination have minor effect on the performance of the thermosyphon. However, the trend observed from inclining the thermosyphon showed decreased performance of heat transfer. Next, three different modified graphite foams were prepared and its performance were investigated. All foams performed relatively the same, except at low heat fluxes with cross cut and slant cut foam achieve lower wall temperature as compared to a straight cut and block foam. High speed image capturing of the boiling processes was also carried out to study the differences in bubble dynamics for different inclination angles and geometrical structures. In general, it is evident that bubble nucleation departure diameter and frequency play important roles in heat transfer performance of this two-phase system.