Thermosyphon cooling system for high heat flux electronic components

• Main Author: Koh, Zheng Jie.
• Other Authors: Leong Kai Choong
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Mechanical engineering::Energy conservation
• Online Access: http://hdl.handle.net/10356/40526
• Institution: Nanyang Technological University

Over the years, heat fluxes from high speed electronic devices are increasing at an alarming rate and have now, reached levels where air and liquid cooling can no longer handle. 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 electronic module and a coolant chamber. The aim of this project is to investigate the effects of working fluid, graphite foam and geometrical configuration on the heat transfer performance of a thermosyphon. Two dielectric fluids, namely FC-72 and HFE-7000, were used and experiments performed using the latter yielded lower wall temperatures due to its relatively lower boiling point. However, the overall heat transfer coefficients of systems using FC-72 were significantly larger. Next, four graphite foams licensed under trade names POCO and Koppers were used as heat sinks on the heated surface. Tests using the high density HTC POCO foam showed the best results in achieving the lowest wall temperatures and highest heat transfer coefficients at all heat fluxes. Kopper Foam Grade D1 performed the worst. Results showed that the block foam heat sink performance was significantly better than the finned foam. High speed image capturing of boiling processes was also carried out to study the differences in bubble dynamics in different coolants, foams 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.