获得1.2K低温的实验研究

本文从低温传热的观点出发,通过对减压过程的传热分析和温度分布的测量,提出建立该类低温装置应遵循的基本原则;发现低温实验装置中,主颈管的导热漏热占主导地位,减压过程中冷气流大小对温度分布的影响很敏感,改变了颈口热辐射决定的轴向距离、77K辐射屏位置及屏间距.实验对减压降温过程进行了动态测量,并提出液氦玻璃杜瓦的非正常输入的概念。

Experimental Investigation on Achieving a Temperature of 1.2K

An experimental investigation for obtaining a temperature of 1.2 K is reported. By heat transfer analysis of the pressure reducing process and the temperature distribution measured, the basic principle to be obeyed for such a device is that the heat leaks to the system from the outside should be minimum and the transfer of heat within the system should be efficient. It is found that the heat leak via the main neck tube is dominant (28%). The strength of the cold gas flow affects sensitively the temperature profile during the pressure reducing process. Compared with the case where the pressure is not reduced, the experimental dewar should be mounted higher than ordinary cryostat. The distance between radiation shields should be reduced. The dynamic process where the temperature is decreased with the pressure reduced has been measured. The concept of abnormal influx of glass dewar flasks for liquid is proposed after the experiment. The experimental device is capable of storing 3.5 litres of liquid helium. The evaporation rate of liquid helium is lower than 50 ml/hr. The device is found to have the required characteristic and feature of a cryostat to obtain a temperature of 1K and below.