平衡氢三相点(13.8033K)是ITS-90规定的最低温度固定点,常用于标准套管铂电阻温度计的检定或校准。改进后的国家温度基准使用基于闭循环制冷机的低温恒温器提供准绝热环境,采用量热法进行密封式平衡氢三相点的复现实验。由平衡氢转化催化剂引起的三相点容器的预熔化现象以及实验组装的差异均会导致组件热容或系统热阻的变化,从而影响复现水平。建立了系统的传热模型,通过2次绝热条件不同的复现实验,测量了低温恒温器三相点组件的热容、绝热屏与三相点组件的热阻等参数,分析了低温恒温器绝热性能对平衡氢三相点复现的影响规律。结果显示,在复现开始前通过测量热阻并确认系统绝热性能良好,复现4个平衡氢三相点温坪的标准偏差优于0.1mK。
Abstract
The triple point of equilibrium hydrogen (13.8033K) is one of the cryogenic fixed points with the lowest temperature specified in ITS-90 and is commonly used for the calibration of capsule standard platinum resistance thermometers(CSPRTs). A cryogen-free cryostat has been used to improve the national primary temperature standard, which can provide an ideal adiabatic environment for the realization of equilibrium hydrogen of sealed triple point, and to perform experiments of realization using calorimetry. Pre-melting of the triple point vessel due to spin-conversion catalysts of equilibrium hydrogen and differences between experimental assembling can lead to variety in the heat capacity of the vessel or the thermal resistance of the system, which can affect the realization. A heat transfer model of the system was developed and experiments were carried out under two different adiabatic conditions. The heat capacity of the assembly and the thermal resistance of the adiabatic shield and assembly were measured and the influence of the adiabatic properties of the cryostat on the realization of triple point of equilibrium hydrogen was analyzed. The results show that by measuring the thermal resistance before the start of the realization and confirming that the system has good adiabatic properties, the standard deviation of four plateau of triple point of equilibrium hydrogen is less than 0.1mK.
关键词
计量学 /
低温恒温器 /
平衡氢三相点 /
固定点复现 /
准绝热
Key words
metrology;cryostat /
triple point of equilibrium hydrogen /
realization of fixed point /
quasi-adiabatic
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参考文献
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基金
国家重点研发计划(2021YFF0603703)
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