小高宽比矩形通道中低温氮气的流动换热特性

Convective Heat Transfer of Low Temperature Nitrogen Gas in Rectangular Duct with Small Aspect Ratio

针对１００Ｋ以上的高温交流超导磁体的冷却问题，对９０－１６０Ｋ的氮气在五种小高宽比（Ａ＝０．０１３－０．０４７５）矩形通道中的对流换热进行了实验研究和机理分析。实验结果表明，矩形通道高度对传热与流动特性影响显著。随着通道高度的增加，通道进出口压差减小，层流向湍流转变的临界Ｒｅ数增大，层流区Ｎｕ数随通道高度增加而增大，湍流区Ｎｕ数随通道高度变化存在最佳值问题，０．５１ｍｍ为最佳高度。

Convective heat transfer was experimentally investigated for the flow of low temperature nitrogen gas in rectangular duct with small aspect ratio (A=0.013-0.0475) for the potential application of cooling of high TC superconductors. The results indicated that the height of the duct exerted a rather marked influence on the characteristics of heat transport and pressure drop in the duct. With the increment of duct height, pressure drop in the duct decreased while the transition Reynolds number increased. In the region of laminar flow, Nusselt number increased with the increase of duct height. In the region of turbulent flow, there existed an optimal height of the duct with the value of 0.51mm, which made the largest Nusselt number.