With the rapid progress of the superconducting quantum computing technology, the cryogenic technology capable of providing appropriate cooling in the millikelvin temperature region is desirable. The cryogen-free dilution refrigerator featuring high reliability, long lifetime, and continuous cooling has become one of the most promising cryocooler candidates for this purpose. As one of the key components of the dilution refrigerator, the impedance component is used to control the flow and to liquefy He, which is crucial to achieving the millikelvin temperature. In this paper, a throttling model is proposed to analyze the dilution cycle and to eventually improve the refrigeration performance, which focuses on the influences of the complex physical properties of He and the dilution cycle from the subcooled state to saturation state. The effects of the inlet pressure and inlet temperature on the flow rate are studied, and the energy conversion on the throttling process is discussed. It indicates that the throttling model can reasonably predict the flow rate under different inlet pressure and inlet temperature and is helpful to the design and optimization of the millikelvin cryogen-free dilution refrigerator.

中文翻译：

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超导量子芯片冷却用稀释制冷机中 3He 节流过程研究

随着超导量子计算技术的快速进步，能够在毫开尔文温度范围内提供适当冷却的低温技术是人们所期望的。无制冷剂稀释制冷机具有高可靠性、长寿命和连续冷却的特点，已成为最有前途的制冷机候选之一。阻抗元件作为稀释制冷机的关键部件之一，用于控制流量和液化He，这对于实现毫开尔文温度至关重要。本文提出了一种节流模型来分析稀释循环并最终提高制冷性能，重点关注He复杂物理特性和从过冷状态到饱和状态的稀释循环的影响。研究了入口压力和入口温度对流量的影响，并讨论了节流过程中的能量转换。表明节流模型能够合理预测不同入口压力和入口温度下的流量，有助于毫开尔文无冷剂稀释制冷机的设计和优化。