超流氦制冷系统2K冷却级热力分析

通过对节流阀阀前J-T换热器的效率以及2 K冷却级的制冷量等参量与节流阀前温度、压力以及J-T换热器冷、热端温差等关系的分析表明,考虑比热变化时J-T换热器的效率均低于不考虑比热变化时的J-T换热器的效率,且发现在降低换热器入口温度来提高单位质量氦气的2 K制冷量时,J-T换热器的热效率将降低。分析结果表明为避免系统变工况运行时换热器运行出现负温差,建议J-T换热器应该以限定冷端温差进行设计。

Thermal analyses on the 2K cooling stage for superfluid helium refrigerator system

In this paper,the relations cooling capacity at 2K and J-T heat exchanger efficiency with the temperature and pressure before the J-T valve and the temperature difference at the hot and cold ends of J-T heat exchanger have analyzed.The efficiency of the J-T heat exchanger considering variable specific heat of helium is lower than that at constant heat specific,and it decreases with decreasing of the inlet temperature of the J-T heat exchanger.In order to avoid the negative temperature difference in the J-T heat exchanger at various opening conditions,the paper suggests the design of heat exchanger may be developed at limited temperature difference at the cold end.