利用流量法测量微型金属杜瓦瓶热负载及其计算方法

Heat load measurement of the micro metal dewar with mass flow method and its calculation

详细讨论了微型金属杜瓦瓶热负载的测量原理和方法,提出了一种新的流量法测量微型金属杜瓦瓶热负载的数据处理方法。流量法通过流量计检测单位时间内的液氮蒸发量,利用相变在相同温度和压力下两相间的比焓差计算热负载,标准工况和测量工况下的计算因子分别为4.151和5.212。这种新方法通过检测微型金属杜瓦瓶内管冷端最低温度下的质量流量或者此时刻前1 min内汽化液氮的质量来计算热负载,可以统一称量法和流量法测量热负载的检测时刻和测量区间,有利于减少称量法中结霜的影响。

The measuring principle and method of heat load of micro metal dewar was discussed in detail. A new data process method was proposed based on heat load measurement of micro metal dewar with mass flow method. The measurement principle of mass flow method was introduced, with which heat load was tested by measuring the evaporating mass of liquid nitrogen in unit time. In calculating heat load by latent heat of vaporization, the calculation factor was 4.151 and 5.212 for both standard condition and practical measurement condition respectively. With this new data process method, heat load was calculated by measuring mass flow of the cold end of inner tube of micro metal dewar under the lower temperature with mass flow method or measuring the evaporating mass of liquid nitrogen 1 min before the lowest temperature of dewar cold end with weighing method. This method can achieve unify of measurement region and measurement moment in two measuring method, and can also reduce influence of frost with weighing method.