Development of heat dissipation system for electronic devices using flow boiling heat transfer

2006 Fiscal Year Final Research Report Summary

• Project/Area Number: 17560167
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Thermal engineering
• Research Institution: Ibaraki University
• Principal Investigator: KAMINAGA Fumito Ibaraki University, College of Engineering, Professor, 工学部, 教授 (80114015)
• Co-Investigator(Kenkyū-buntansha): MATSUMURA Kunihito Ibaraki University, College of Engineering, Lecturer, 工学部, 講師 (00291287)
• Project Period (FY): 2005 – 2006
• Keywords: Boiling / Electronic device / heat dissipation / Heat transfer / Enhancement / Narrow channel

Research Abstract

The purpose of this study is to obtain fundamental knowledge how to make use of flow boiling heat transfer to develop innovated heat dissipation system for high heat loaded electronic devices. This study was performed under conditions of narrow working flow path and low flow rate which are encountered in practical cases and used water as a working fluid to meet requirements of high source power and environmental issues. In the study pressure drop, heat transfer coefficient, and maximum heat flux which are important design factors are experimentally examined.
Two types of studies were performed. One was to propose correlations for pressure drop and heat transfer coefficient in terms of experimental data in a fine circular tube previously obtained in our laboratory. The other was an experimental investigation about heat transfer and pressure drop in narrow rectangular channels, 1.0 and 1.5 mm gap and 20 mm width and 80 mm length (40 mm heated length).
From the first study, the pressure dro p and boiling heat transfer coefficient in a fine circular tube could be predicted by correlations developed in a normal size tube by taking additional account of large effect of vapor flow. In the second study, experiments were performed to measure pressure drop, heat transfer coefficient, and maximum heat flux at mass flux of 16 to 76 kg/m^2s. The major findings of the experiments are as follows. Smaller gap size, than 1.0 mm was suggested since the maximum pressure drop as much as 500 Pa and then the pressure drop is much lower than the circular tube. However, the fluctuation of the pressure drop is much larger than that in the tube. The heat transfer coefficients are similar between the tube and the channel in the relationship between heat flux and wall superheat, but the relationship in the rectangular channel between the coefficient and local quality is different form that in the circular tube. The correlation developed for circular tubes highly overpredicted the maximum heat flux and the correlation developed by using data of rectangular channels give much better prediction. The liquid phase distribution in the cross section of the channel significantly affects the heat transfer coefficient and maximum heat flux.