Abstract:

In order to improve the performance of isothermal chamber, a convection heat transfer model of isothermal chamber  was studied during discharge. Four solenoid valves with known flow rate characteristics were used in four different isothermal chambers deflated experiments respectively, pressure curve during discharge was collected, and the temperature curve was collected by “stop method”. Based on the convection heat transfer model and combined with pressure curve and temperature curve during discharge, the convection heat transfer coefficient was determined. Finally, the convection heat transfer empirical formulae in sound velocity and subsonic speed phases were fitting by similarity principle respectively. The two empirical formulae include deflated speed and the copper wire filling density. That is to  say the deflated speed and porosity can influence the heat transfer. The air compression ratio was introduced in the empirical formula of sound velocity phase. It can explain the problem that the heat transfer is influenced by compressibility while the air in the conditions of high compression.

Key words: isothermal chamber, convection heat transfer coefficient, empirical formula, porous media, high compression

摘要：

为了提高等温容器的性能,对等温容器放气过程中的对流换热模型进行了研究。用4个已知流量特性的电磁阀分别对4种等温容器进行了放气实验,采集放气过程中的压力曲线,并采用“停止法”得到放气过程中的温度曲线。基于等温容器放气过程的热力学模型,结合放气过程中的压力曲线和温度曲线,确定了放气过程中的对流换热系数,最后利用相似原理拟合得到了放气过程中声速阶段和亚声速阶段的对流换热经验关系式。声速阶段和亚声速阶段的经验关系式不仅体现了放气速度对对流换热的影响,还反映了铜丝填充密度,也就是孔隙率对换热的影响;声速阶段的经验关系式中还引入了空气压缩比,体现了空气在高压缩状态下压缩性对对流换热的影响。

关键词: 等温容器, 对流换热系数, 经验关系式, 多孔介质, 高压缩