空间80K温区低温技术的实践证明，有运动部件的斯特林制冷技术可以实现长寿命和低振动，而无运动部件的脉管制冷技术存在膨胀功无法回收的本征低效率，能否结合两者的优点，避免两者的缺点，组合成更为高效更低温区的斯特林/脉管复合型液氦温区低温制冷技术？结合申请人近年来在高频液氦温区回热式制冷技术方面的研究基础和对相关关键科学问题的深入认识，以及国际上复合型回热式低温制冷技术的最新研究成果，本项目拟以斯特林/脉管复合型回热结构为载体，综合传热学、有限时间热力学和流体力学等相关理论，致力于解决液氦温区回热器在有限比热容有限时间条件下（高频）的高效换热、交变流动声功和压力的高效传输、小声功条件下高效调相等关键问题，最终实现在液氦温区下的高效高可靠长寿命回热式制冷方法。本项目的研究成果将为最终研制出满足空间应用特点的液氦温区回热式低温制冷技术奠定基础，以满足国家中长期空间探测计划的顺利实施。

The success applications of cooling technology at 80 K for space application indicate that Stirling coolers with moving parts at low temperature can be running for a long life as well as low vibration, while the advantage of no moving parts at low temperatures brings an intrinsic low efficiency as the expansion work is not recovered for pulse tube coolers. Can a high efficiency Stirling/pulse tube hybrid cooler combine the advantages of both of Stirling coolers and pulse tube coolers (PTCs) and avoid the disadvantages of them? Based on the research results of high frequency liquid helium temperature (4 K)pulse tube coolers in recent years of the applicant and a deep understanding of the key scientific problems that prevent high frequency PTCs working at 4 K efficiently and the latest research results of Stirling/pulse tube hybrid coolers, this proposal aims to investigate the following 3 key scientific problems by combining the theory of oscillating heat transfer, finite time thermodynamic and fluid mechanics and using Stirling/pulse tube hybrid cooler as a carrier. 1.Transient heat exchange characteristics of working fluid and matrixes at 4 K regenerators under finite heat transfer time and finite heat capacity of matrixes. Establishing real thermodynamic model of liquid helium temperature regenerator based on the finite time thermodynamic theory, and effects of finite heat exchange time and finite heat capacity on the performance of liquid helium temperature regenerator are investigated by introducing the time scale.Based on the energy equation of working gas and matrix, the effects of working frequency, heat capacity and temperature on the transient heat exchange characteristics of working fluid and matrixes in liquid helium temperature regenerators will be studied. 2.Pressure losses characteristics of oscillatory flow and high efficiency transmission of acoustic power in liquid helium temperature regenerators Based on the governing equations of oscillating gas, by applying the periodic boundary condition, the effect of mass flow rate, working frequency on the instantaneous and cycle-averaged friction coefficients will be investigated in theory. 3.High efficiency phase shifting method at low acoustic power condition. Effects of working parameters and geometry parameters on the phase shifting ability of inertance tube are calculated by theoretical analysis and experimental measurements. Comparisons and modifications of 3 inertance tube models will be carried out based on the experimental measurements. This research will get a better understanding of refrigeration mechanism of regenerative coolers at liquid helium temperature and lay a foundation for the manufacture of high efficiency and reliability long life hybrid regenerative cooler at liquid helium temperature, this kind of regenerative cooler would help to guarantee successful operation of national long term space exploration missions.