A Loop Thermosyphon Type Cooling System for High Heat Flux

Jiwon Yeo¹, Seiya Yamashita¹, Mizuki Hayashida¹, Shigeru Koyama^2,3*

¹Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Fukuoka, Japan.
²Faculty of Engineering Sciences, Kyushu University, Fukuoka, Japan.
³International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University, Fukuoka, Japan.

DOI: 10.4236/jectc.2014.44014                

Abstract

With rapid development of the semiconductor technology, more efficient cooling systems for electronic devices are needed. In this situation, in the present study, a loop thermosyphon type cooling system, which is composed mainly of a heating block, an evaporator and an air-cooled condenser, is investigated experimentally in order to evaluate the cooling performance. At first, it is examined that the optimum volume filling rate of this cooling system is approximately 40%. Next, four kinds of working fluids, R1234ze(E), R1234ze(Z), R134a and ethanol, are tested using a blasted heat transfer surface of the evaporator. In cases of R1234ze(E), R1234ze(Z), R134a and ethanol, the effective heat flux, at which the heating block surface temperature reaches 70°C, is 116 W/cm², 106 W/cm², 104 W/cm² and 60 W/cm², respectively. This result indicates that R1234ze(E) is the most suitable for the present cooling system. The minimum boiling thermal resistance of R1234ze(E) is 0.05 (cm²·K)/W around the effective heat flux of 100 W/cm². Finally, four kinds of heat transfer surfaces of the evaporator, smooth, blasted, copper-plated and finned surfaces, are tested using R1234ze(E) as working fluid. The boiling thermal resistance of the blasted surface is the smallest among tested heat transfer surfaces up to 116 W/cm² in effective heat flux. However, it increases drastically due to the appearance of dry-patch if the effective heat flux exceeds 116 W/cm². On the other hand, in cases of copper-plated and finned surfaces, the dry-patch does not appear up to 150 W/cm² in effective heat flux, and the boiling thermal resistances of those surfaces keep 0.1 (cm²·K)/W.

Keywords

Cooling, Boiling, Loop Thermosyphon, Grobal Warming Potential, Thermal Resistance

Conflicts of Interest

The authors declare no conflicts of interest.

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