Experimental data of a Joule-Thomson cryocooler driven by a floating scroll-type compressor

Data presented here shows experimental data of a Joule-Thomson cryocooler (JT) driven by a floating scroll-type compressor working at liquid helium temperature. Figure 3 shows cool down process of the JT unit. After about 9 hours, Td consistent with Tb and Tc, achieved and kept stable at 4.5 K. Figure 4 shows the pressure regulation process. In order to increase pressure ratio, additional Helium-4 gas was charged into the JT cryocooler several times. When pd approached nearly 1.00 MPa and kept stable, as shown in the region “JT valve opening reduced” of Figure 4, by reducing the JT valve opening, the desired pressure ratio could be obtained. Figure 5 shows temperature behavior with heat load of 33.1 mW. When the heat load was increased to 33.1 mW, both pd and ps increased at first because of additional Helium-4 evaporation. To control variables (pd and ps), a part of Helium-4 gas was vented outside the JT cryocooler several times by pre-installed discharge valve. Tb, Tc and Td can keep stable at 4.5 K by repetitive gas venting in the beginning. Finally, Tb rises away unlimited which means that the JT cryocooler is overloaded. Figure 6 shows temperature stability over 1 hour when pb = 0.85 MPa. It can be found that the cooling temperature, Td, can keep stable at 4.4 K which is consistent with the temperature at the inlet of the CHX, Tc. Table 1 shows cooling capacity measurement at steady conditions. It is found that pd can remain stable at about 1.00 MPa with a mass flow rate above 11 mg/s during the adjusting process. When pb decreases from 1.01 MPa to 0.85 MPa, ηex increases from 7.61 % to 8.65 % with an efficiency increment about 13.67%. The ηex=8.65% with an uncertainty of 0.13% is close to the efficiency of two-stage linear compressors (8.06%) applied in the Planck satellite . When pb decreases from 0.85 MPa to 0.80 MPa, the ηex decreases from 8.65% to 7.63%. It is indicated that there exists an optimal pb to maximize the ηex of the floating scroll-type compressor which is worth further study.

本数据集呈现了一台由浮动滑片式压缩机驱动的焦耳-汤姆逊制冷机（JT）在液氦温度下的实验数据。图3展示了JT单元的降温过程。经过大约9小时，Td与Tb和Tc达到一致并稳定在4.5 K。图4展示了压力调节过程。为了增加压力比，多次向JT制冷机中充入额外的氦-4气体。当pd接近1.00 MPa并保持稳定时，如图4中“JT阀开度减小”所示，通过减小JT阀的开度，可以获得所需的压力比。图5展示了在33.1 mW热负载下的温度行为。当热负载增加到33.1 mW时，由于额外的氦-4蒸发，pd和ps首先增加。为了控制变量（pd和ps），通过预先安装的排放阀多次将一部分氦-4气体排放至JT制冷机外部。通过初始阶段的重复排放气体，Tb、Tc和Td可以稳定在4.5 K。最终，Tb无限上升，意味着JT制冷机过载。图6展示了在pb = 0.85 MPa时超过1小时的温度稳定性。可以发现，冷却温度Td可以稳定在4.4 K，这与CHX进口处的温度Tc一致。表1展示了在稳态条件下的冷却能力测量结果。在调整过程中，pd可以保持在约1.00 MPa，同时质量流量超过11 mg/s。当pb从1.01 MPa降至0.85 MPa时，ηex从7.61%增加到8.65%，效率增量约为13.67%。ηex=8.65%，不确定性为0.13%，接近于在Planck卫星中应用的二级线性压缩机（8.06%）的效率。当pb从0.85 MPa降至0.80 MPa时，ηex从8.65%降至7.63%。这表明存在一个最佳pb值，可以最大化浮动滑片式压缩机的ηex，值得进一步研究。