Basic Research on Boiling-Evaporative cooling system for the Ultra High Heat Generation Density Electronic Devices

随着电子技术的显著进步，半导体芯片的发热密度迅速增加。电子设备的液体冷却系统必然是传统空气冷却系统的替代技术。特别是开发具有相变现象(沸腾或蒸发)的液体冷却系统。本文首先对沸腾气泡作用下的薄液膜进行了基础研究。(1)研制了具有背部加热器和温度传感器的高性能透明受热面。为气泡下薄液膜的详细观察和高精度的传热测量提供了可能。(Ii)在窄间隙过冷沸腾条件下，对气泡与受热面的接触面积进行了光学测量。实验数据表明，加热速度越高，气泡接触面积越小。(3)提出了基于水平集方法的数值计算方法。通过对剪切流动中气泡生长和脱离的模拟，证实了该方法适用于汽液两相系统。其次，进行了实际应用的研究和开发。(4)开发了具有凹槽受热面的闭道式冷却系统。沸腾通道间隙减小到2 mm时，没有发现换热恶化。(5)在热管中使用自润湿流体，与传统的水热管相比，最大导热能力提高了40%，热阻降低。

Heat generation density of semiconductor chip is increasing rapidly with remarkable progress of electronic technology. Liquid cooling system for electronic devices must be an alternative technology of conventional air cooling system. Especially, the liquid cooling system with phase change phenomena(boiling or evaporation) should be developed.In this work, at first, basic research for the thin liquid film under boiling bubbles were conducted. (i)High performance transparent heating surface with backside heaters and temperature sensors was developed. The detailed observation of thin liquid film under bubbles and high accurate heat transfer measurements were made possible. (ii)Bubble contact area with heating surface was optically measured in subcooled boiling at narrow gaps. The experimental data showed that bubble contact area is smaller, as the heating speed is higher, (iii)Numerical method based on the "level set method" was developed. It was confirmed that this method was applicable to the liquid-vapor two phase system through the simulation of bubble growth and detachment in a shear flow.Secondary, the research and development for practical application had been conducted. (iv)The closed-channel type cooling system, which has a grooved heating surface, was developed. No heat transfer deterioration was recognized by the reduction of boiling channel gap to 2mm. (v)By the use of self-wetting fluid to heat pipes, maximum heat transportation capacity is increased by 40% and thermal resistance is decreased compared with the conventional water heat pipes.