GM制冷与磁制冷复合式液氦温区制冷机机理的诠释

Liquid helium temperature range refrigeration has a significant role in superconducting magnet, low temperature electronic technology and low temperature physics, etc. In the liquid helium temperature region, new efficient refrigerator is an emphasis in the research of low temperature field. As the representative technologies in the field of cryogenic, GM refrigeration and magnetic refrigeration are combined to research the composite refrigeration in the two-fields. The contents from the project includes: 1) the theory is built in hybrid refrigeration cycle and the organizational structure and operation parameters is optimized by adopting near balance theory of irreversible process to analyse coupling relation from magnetic-hot field; 2) the strong coupling model and the weak coupling model are introduced to clearly study working mechanism and analyze the cycle and structure parameters on the performance; 3) the comparison is considered to obtain the most optimal operation from cycle, practical performance, reliability and economy. The project has innovations: 1) the coupling model from magnetic-hot field is constructed by near balance theory of irreversible process to analyze coupling relation under multi-field and interdisciplie; 2) the new multistage AMR is introduced into the strong coupling model to fully allow magnetocaloric materials’ play to strengthen refrigeration cycle performance; 3) the new weak coupling model of GM/magnetic refrigerator is proposed to learn by combining GM refrigeration and adiabatic demagnetization refrigeration. Revealed through the above research, this project intends to express work mechanism of the hybrid GM/magnetic refrigerator and obtain a new efficient refrigeration technology in temperature range of liquid helium.

液氦温区制冷对超导磁体、低温电子技术和低温物理学等有重要意义，新型液氦温区高效制冷机是低温领域的研究重点。本项目拟复合GM制冷与磁制冷，开展双势场耦合研究，内容包括：1）采用近平衡不可逆理论进行磁热双势场耦合分析，构建GM与磁制冷复合循环理论，优化复合式制冷循环的结构和参数；2）诠释强耦合型和弱耦合型复合制冷工作机理，考察循环和结构对其性能的影响；3）从循环构型、实际性能、可靠性以及经济性等方面进行对比，获得GM/磁制冷的最佳耦合。项目创新点：1）首次采用近平衡态不可逆理论分析方法，构建磁-热物理场双向耦合理论与数值模型；2）针对强耦合型GM磁制冷，引入新型多层AMR技术，充分发挥材料的磁热性能，以提高制冷循环性能；3）探索新型复合方式，结合绝热去磁和GM制冷提出了弱耦合型GM磁制冷。拟通过上述研究，本项目揭示复合磁制冷循环的工作机理，获得一种新型高效的液氦温制冷机。

液氦温区制冷是支撑现代科技最关键的技术之一，对超导磁体、低温电子技术和低温物理学等有重要意义。当前，液氦温区传统制冷机面临着氦气膨胀吸热制冷效应趋近于零与固体比热无法满足回热需求等瓶颈，新型液氦温区高效制冷机成为了该低温领域的研究重点。本项目基于磁制冷与气体膨胀制冷相互耦合的新思路，从主动式磁制冷和气体回热式制冷的循环机理和特征出发，采用近平衡不可逆理论开展了GM制冷与磁制冷相互耦合的复合制冷技术研究，主要研究进展如下：1）循环机理方面：基于气体回热式制冷与主动式磁制冷有相似的循环过程，构建了GM制冷与磁制冷耦合的低温复合制冷循环，主要揭示了强耦合型模型中较高的比热容和磁热效应的磁性材料有望克服气体制冷机中回热材料的热饱和现象；2）数值仿真与优化方面：构建了GM制冷与磁制冷耦合的二维复合制冷模型，主要对材料比热容、填充长度、耦合时序等进行了数值优化，其中时序模拟结果显示最优相位角的范围在60°~120°之间，制冷温度为4K时，复合磁制冷机制冷量和效率分别为0.18W和5.64%，是GM制冷机的1.34和1.38倍；3）整机研制及实验研究：开展了磁制冷与GM制冷复合制冷实验平台的研制等工作，对气体制冷与磁制冷耦合过程中的涡流与相位匹配精度等进行优化改进，并采用新研制的磁热材料（如TmCuAl基与EuTiO3基）组建多层AMR开展了实验研究，频率为0.5Hz时复合磁制冷机获得了3.5K无负荷温度，比纯气体制冷降低了0.7K。本项目的研究有效地拓展磁制冷低温区应用，揭示复合磁制冷循环的工作机理，为液氦温区高效制冷提供了一种新的途径。