航天器对流换热地面降压模拟的临界压力准则

航天器密封舱在地面模拟试验中常通过降压法抑制自然对流的影响,但降压比的选择往往缺乏定量准则,这使得自然对流的抑制效果得不到保证.使用数值模拟方法确定临界压力比,以几种典型航天器密封舱内的流动换热情况为例,分析了不同Gr/Re~2数和压力比下密封舱内的流动换热情况.得到了舱内气体温度分布和对流换热系数.通过比较空间情况和地面情况的计算结果,分析了自然对流给流动换热带来的影响,给出了判断临界压力的准则式,并给出了临界Gr/Re~2数.结果表明:临界压力的准则关系和密封舱的形状和内部结构无关.

Study on Criterion of Critical Pressure in Spacecrafts Using Lowering Pressure Method

To study the convection heat transfer in spacecraft cabins, the lowering pressure method is usually used to suppress the effect of natural convection in terrestrial experiments. Traditionally, the pressure in the spacecraft cabin was determined qualitatively, so that the effect of lowering pressure method cannot be assured. In the present work, the convection heat transfer in different spacecraft cabins was studied numerically under various Gr/Re~2 and various pressures, both in space condition and terrestrial conditions. The heat transfer coefficient and temperature distribution were obtained. Results were compared between in space condition and in terrestrial condition. The effect of pressure on suppressing the natural convection was analyzed quantitatively. The criterion formula was obtained for calculating the critical pressure in the lowering pressure method. The criterion formula for calculating the critical Gr/Re~2 was also obtained.