基于回热制冷系统的直流影响机理与有效利用研究

Regenerative cryogenic refrigerators are endowed with the potential of compactness, high efficiency, and high reliability, and are being applied in space and superconductor technology more and more widely. Although regenerative refrigerators are AC system, there exists DC (direct current) flow, and it influences the stability and COP of the refrigerators intensively. There are lots of problems related to the research. For example, insufficient factors to cover the influence mechanism theoretically, unable to measure and control the DC flow experimentally. Further investigations are required to solve these problems. This project focus on the object of solving the influence mechanism of DC flow and of utilizing the DC flow. Innovative methods of comprehensive theoretical investigations and experiments with small flow rate are proposed. The influence mechanism of DC flow on the refrigeration process will be investigated theoretically, factors of regenerator mechanism, precooling effect, loss mechanism of pulse tube, and real gas effect will be included, influence laws will be concluded; Micro flow measurement and control experiment system will be established, high accuracy of measurement and control will be achieved, so as to investigate the factors that influence on the refrigeration mechanism experimentally. The experiment test will verify and improve the theoretical model, achieving the goal of utilization of DC flow. Hopefully the refrigeration performance will be improved under some conditions. The meaning of the investigation of the DC flow in improving the mechanism investigation and the technology of regenerative refrigeration cannot be neglected.

回热式低温制冷机具有紧凑性好、效率高、可靠性高的突出优点，在空间探测和超导技术等重要领域应用越来越广泛。作为交变流动系统，回热式低温制冷机尤其是脉管制冷机中存在直流现象，对制冷机的温度稳定性、制冷效率产生重要影响。直流的影响机理与实验研究方法分别存在着研究不全面和直流难以测量控制等问题，急需深入研究。本课题以解决直流的影响理论并有效利用直流为目标，提出综合性理论研究方法与微质量流实验的创新方法。理论方面，系统研究直流通过回热机理、中部预冷效应、脉管损失机理和实际气体效应对制冷性能的影响机理，揭示这些因素的影响规律；实验方面，建立创新的微质量流量实验平台，实现直流流量的高精度测量与控制，实验研究直流的影响机理，验证并完善理论模型，最终实现对直流的有效利用，在一定工况下大幅提高制冷效率。该研究有望有力促进回热式制冷技术的机理研究与技术提升，具有重要意义。

回热式低温制冷机由于效率高、可靠性高的突出优点在空间探测和超导技术等重要领域的应用越来越广泛。直流问题对交变流动的回热式低温制冷机尤其是脉管制冷机的制冷效率、温度稳定性产生重要影响。但直流的影响机理与实验研究方法分别存在着研究不充分和直流难以测量与控制等突出问题。本项目在理论上深入开展了理想工况下液氦温区直流效应的研究，提出原创性理论，包括：研究了液氦温区的实际气体效应对于回热器的影响机理，首次完整给出了理想换热无流阻时实际气体效应影响下的回热器的理论制冷效率（COP）；提出以实际气体实现卡诺效率的原创性理论方法，即通过加减热法使得在近临界温区造成数倍于制冷量的损失予以回收，实现无损失的卡诺效率；进一步理论证明在液氦温区回热器的直流方法本质上降低了实际气体效应相关损失、提高制冷效率，并首次推导了与气体物性紧密相关的理论直流量大小，和相应的理论制冷效率；基于实际应用前景，发明了一种能实现可控稳定直流的装置，该专利为实现空间长寿命可控直流的应用打下了重要基础；合作研究了液氢温区可控直流机理，通过数值模拟详细分析了各能量项的分布。在实验中开展了可控直流实验并做了丰富的研究，包括：开展了首例液氮温区的高精度可控微质量直流实验，与以往研究不同，证明一定量的直流在液氮温区可以提升制冷性能，研究发现脉管具有一定的吸收焓流的能力；设计并建成预冷的斯特林型脉管制冷机实验平台，实现了3.6 K的无负荷制冷温度，处于国际先进水平；首次系统地实验研究了液氦温区回热器与脉管的独立的预冷效应，发现回热器、脉管、调相机构各自独特的性质，具有重要价值。