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Improvement on Superconducting Magnet Performance using Fountain Effect of Superfluid Helium

利用超流氦喷泉效应改进超导磁体性能

基本信息

批准号：
12650193
负责人：
OKAMURA Tetsuji
金额：
$ 2.3万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

项目摘要

Heat transport characteristics of superfluid helium (He n) in channel segmented by different types of spacer having several holes have been investigated on the basis of both experiment and numerical analysis. The heat transport performance has been examined for the following spacers : (a) FRP spacer without any hole, (b) FRP spacer with several holes of 2 or 4 mm diameter, (c) porous spacer made of fine powder of sintered Al_2O_3, (d) porous spacer made of high density polyethylene (HDPE) which is more flexible than Al_2O_3. The average diameter of the porous is about 1μm. It is expected that helium flow is induced in the channel because of a fountain effect when the porous spacer is applied.The λ-transition heat flux when we use the spacers having holes of diameter 2 mm and 4 mm is almost the same. This value is about 1.5 times larger than that in the case of using spacer without any hole. The λ-transition heat flux depends on the porosity of the spacer. A relatively high cooling performance can be realized when the porosity is only about 5%. These results lead to the understanding that the introduction of some holes in the spacer is a very effective way to suppress local temperature rise in the He II channel.The λ-transition heat flux increases remarkably when the porous spacer is used instead of the FRP spacer with holes of 2 or 4 mm in diameter, because Hen flow is induced in the heated channel by a fountain effect. It is also found that the use of porous spacers between Hell channels is effective to suppress a steep temperature rise in the heated channel not only when the channel is filled with He II entirely but also when normal helium (He I ) is generated in the channel.

通过实验和数值分析，研究了超流氦（He n）在不同类型多孔隔板分隔通道中的传热特性。本文研究了以下几种垫片的传热性能：（a）无孔玻璃钢垫片，（B）有几个直径为2或4 mm的孔的玻璃钢垫片，（c）由烧结Al_2O_3细粉制成的多孔垫片，（d）由比Al_2O_3更柔软的高密度聚乙烯（HDPE）制成的多孔垫片。多孔体的平均直径约为1μm。实验结果表明，当采用多孔隔板时，由于喷泉效应，可以在通道中诱导氦气流动，而当采用孔径为2 mm和4 mm的隔板时，λ-转换热通量几乎相同。该值比使用没有任何孔的间隔件的情况大约1.5倍。λ转变热通量取决于间隔件的孔隙率。当孔隙率仅为约5%时，可以实现相对高的冷却性能。结果表明，在隔板上开孔是抑制He II通道局部温升的有效方法，当用多孔隔板代替直径为2或4 mm的FRP隔板时，由于喷泉效应在加热通道中诱导了Hen流动，λ-转变热流密度显著增加。它还发现，使用的多孔间隔之间的地狱通道是有效的，以抑制急剧的温度上升，在加热的通道，不仅当通道完全充满了他II，但也正常的氦（他I）时，在通道中产生。