Natural neon-helium mixture as working fluid for 40-80 K cryogenic refrigerators.

A general quest in the design of cryogenic systems is to ensure high efficiency and low cost. Cryogenic refrigerators for HTS cables require 10-25 kW cooling capacity at a temperature below 77 K. The reversed Brayton cycle is recognized as the most promising process for this application. Prototype systems based mainly on neon as a refrigerant and oil-free turbo-compressors with magnetic bearings have been developed by some suppliers in the last decade. Unfortunately, there are no reports available about their operation and corresponding maintenance cost. However, the relatively high cost of pure neon as refrigerant can affect the economics of this application. An alternative working fluid for such systems, earlier proposed by the TU Dresden is Nelium – a mixture of neon and helium. In the context of the mixture composition optimisation, the neon production process was studied and is described in this paper. The “Natural Nelium” – a mixture containing helium, neon and hydrogen with a composition according to the relative proportion of these gases in air (patent is pending) – was found to be attractive as a potential refrigerant. The power demand, process parameters at each production stage and process design are discussed in the paper.

低温系统设计的核心目标之一是兼顾高效率与低成本。用于高温超导（HTS）电缆的低温制冷机，需在77 K以下的温度环境中提供10~25 kW的制冷量。反向布雷顿循环被公认为该应用场景中最具潜力的循环方案。近十年来，多家供应商已开发出以氖为核心制冷剂、搭载磁悬浮无油涡轮压缩机的原型系统。遗憾的是，目前尚无关于这类系统的运行工况及对应维护成本的公开报道。此外，纯氖制冷剂相对高昂的采购成本，可能对该应用的经济性产生不利影响。德累斯顿工业大学（Technische Universität Dresden，TU Dresden）早前曾提出一种替代工质方案：氖氦混合工质（Nelium），即氖与氦的混合气体。为开展该混合工质的成分优化研究，本文对氖的生产工艺展开了研究并进行详细阐述。本文还提出了一种"天然氖氦混合工质（Natural Nelium）"的新型工质：其组分为氦、氖与氢，各组分比例与空气中这些气体的相对占比一致（目前专利申请中），该工质作为潜在制冷剂极具应用吸引力。文中还讨论了该工艺的功耗需求、各生产阶段的工艺参数以及整体流程设计。