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

在高度亚冷的沸腾中，许多微泡是从加热表面上的聚泡发射出的，而热通量的增加高于过渡沸腾中普通的临界热通量。沸腾状态称为微泡发射沸腾，缩短了MEB。 MEB在亚冷水沸腾中非常明显发生，在水平矩形通道中，蒸馏水的最大热通量为10MW/m^2，高度为17mm，宽度为14mm，平方加热表面为10mm×10mm，位于通道底部的表面上。根据泡沫行为和压力波动，MEB分为两种类型，它们是暴力的MEB和无声的MEB。在剧烈的MEB中，压力波动升高，热通量随着加热表面的温度升高而增加。在剧烈的MEB中观察到了一种周期性的MEB。在周期性类型的MEB中，一系列气泡塌陷，液体供应，气泡产生和气泡生长是孔的……更定期地进行了定期，并且在通道中观察到了周期性的压力波。热通量与压力波动的频率成比例增加。压力频率被认为是液体供应到加热表面的频率。在MEB达到最大热通量点后，加热表面被薄蒸气膜覆盖，它像米勒表面一样变亮，然后表面温度迅速上升，热量提高了。这是MEB的最终阶段。水的末端阶段的表面温度约为200℃，与非MEB相比，它非常高。然后研究了沸腾的沸腾。Meb的水平圆形通道的直径为2.5mm，5mm，10mm和16mm。该通道是在由铜制成的圆形加热块中心制造的，直圆管与加热块相连。加热表面是通道的一部分，通道的长度为10mm。将30个墨盒加热器平行于加热块中的通道组装。 MEB发生在过渡沸腾中，热通量高于普通的临界热通量。 MEB中的热通量随着液体流速的增加而增加。例如，MEB中的最大热通量为5MW/m^2，为0.5m/s，6mW/m^2的最大热通量为1.0m/s，1.5m/s的最大热通量为1.5m/s，在1.5m/s和10mW/m^2的2.5m/m^2时，在30K的液体液体液体液体液体液体液体下冷却10mm Diameter的通道。液体速度是MEB的强大因素之一，与液体亚冷却一样。对于具有不同直径的各种通道，该通道中MEB的热通量增加，直径较大0.25m/s的低液体速度较大，但是，在1.0m/s的液体速度下，通道之间没有热通道的差异。在圆形通道中也发生了周期性的MEB，而不管液体冷却，液体速度和通道直径如何，热通量随压力频率的增加。较少的