AN INVESTIGATION OF MICROBUBBLE EMISSION BOILING AND APPLICATION TO ULTRA-HIGH HEAT FLUX COOLING TECHNOLOGY FOR HIGH POWERED ELECTRONIC DEVICES

微气泡发射沸腾及其在大功率电子器件超高热流冷却技术中的应用

基本信息

批准号：
14550200
负责人：
SUZUKI Koichi
金额：
$ 2.18万
依托单位：
Tokyo University of Science
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

项目摘要

In highly subcooled boiling, many microbubbles are emitted from coalesced bubbles on the heating surface and the heat flux increases higher than the ordinary critical heat flux in transition boiling. The boiling regime has been called Microbubble Emission Boiling, shortened MEB. MEB occurred remarkably in subcooled flow boiling and the maximum heat flux obtained was 10MW/m^2 for distilled water in the horizontal rectangular channel of 17mm height and 14mm width with square heating surface of 10mm×10mm placed on the bottom surface of the channel. According to the bubble behaviors and the pressure fluctuations, MEB was categorized into two type, they were violent MEB and silent MEB. In the violent MEB, the pressure fluctuations rose high and the heat flux increased steeply with the temperature rise of heating surface. A periodic type of MEB was observed in the violent MEB.In the periodic type of MEB, a series of bubble collapse, liquid supply, bubble generation and bubble growth was cond … More ucted periodically and the periodic pressure waves were observed in the channel. The heat flux increased proportionally to the frequency of pressure fluctuations. The pressure frequency is considered to be the frequency of liquid supply into the heating surface.After MEB reached the maximum heat flux point, the heating surface was covered with a thin vapor film and it brightened like a miller surface, then the surface temperature rose rapidly and the heat flux decreased. This is a terminal stage of MEB. The surface temperature at terminal stage was about 200℃ for water and it was very high compared with the case of non MEB. Then the boiling turned rapidly to film boiling.MEB was investigated for horizontal circular channels of 2.5mm, 5mm, 10mm and 16mm in diameter. The channel was manufactured in the center of circular heating block made of copper and straight circular tubes were connected with the heating block. The heating surface was a part of the channel and the length was 10mm for the channels. Thirty cartridge heaters were assembled parallel to the channel in the heating block. MEB occurred in transition boiling and the heat flux was higher than the ordinary critical heat flux. The heat fluxes in MEB increased with increasing liquid flow velocity. For example, the maximum heat fluxes in MEB were 5MW/m^2 at 0.5m/s, 6MW/m^2 at 1.0m/s, 9MW/m^2 at 1.5m/s and 10MW/m^2 at 2.5m/s at 30K of liquid subcooling in the channel of 10mm diameter. The liquid velocity is one of the strong factors in MEB as same as liquid subcooling. For the various channels with different diameters, the heat flux in MEB increased for the channel with the larger diameter 0.25m/s of low liquid velocity, however, no differences of heat fluxes between the channels were observed at 1.0m/s of liquid velocity. A periodic MEB also occurred in the circular channels and the heat flux increases with the pressure frequency regardless of liquid subcooling, liquid velocity and channel diameter.The experimental results obtained in the present study will be developed to an ultra-high heat flux cooling technology for high powered electronic devices. Less

在高度过冷沸腾中，加热表面上的聚结气泡释放出许多微气泡，并且热通量增加到高于过渡沸腾中的普通临界热通量，这种沸腾状态被称为微泡发射沸腾，MEB在过冷中发生显着缩短。流动沸腾，蒸馏水在17mm高、14mm宽的水平矩形通道内方形加热时获得的最大热通量为10MW/m^2 10mm×10mm的表面放置在通道的底面上，根据气泡行为和压力波动，MEB分为两种类型，即剧烈MEB和沉默MEB。在剧烈的MEB中，热通量随着受热面温度的升高而急剧增加。在周期性MEB中，发生了一系列的气泡破裂、供液、气泡生成和气泡生长。通道内观察到更多的周期性压力波，热通量与压力波动的频率成比例地增加。压力频率被认为是液体供应到加热表面的频率。MEB达到最大热通量后。此时，加热表面覆盖一层薄薄的蒸汽膜，呈米勒表面状发亮，随后表面温度迅速上升，热通量下降，这是MEB的末期，末期表面温度约为200℃。对于水来说，这是非常与非MEB的情况相比，沸腾迅速转变为薄膜沸腾。对直径为2.5mm、5mm、10mm和16mm的水平圆形通道进行了研究。该通道是在圆形加热块的中心制造的。加热块与铜管和圆形直管连接，加热面是通道的一部分，通道的长度为10mm，与加热块中的通道平行组装。 MEB中的热通量随着液体流速的增加而增加，例如在0.5m/s时，MEB中的最大热通量为5MW/m^2。液体过冷度为 30K 时，1.0m/s 时为 6MW/m^2，1.5m/s 时为 9MW/m^2，2.5m/s 时为 10MW/m^2在10mm直径的通道中，与液体过冷一样，液体速度是MEB中的重要因素之一。对于不同直径的通道，MEB中的热通量对于直径较大的通道增加0.25m/s。然而，在低液体速度下，在1.0m/s的液体速度下，没有观察到通道之间的热通量差异，在圆形通道中也出现周期性MEB，并且无论液体过冷度如何，热通量都随着压力频率而增加。液体速度和通道直径。本研究中获得的实验结果将开发用于高功率电子设备的超高热通量冷却技术。