Numerical and experimental study on a Stirling/pulse tube hybrid refrigerator operating around 30 K
Abstract Stirling / pulse tube hybrid refrigerator (SPR) has attractive prospects due to its high reliability, high efficiency and compactness around 30K. As the typical characteristics of the SPR, the inter-stage cooling capacity allocation characteristics allows the refrigerator to shift cooling capacity of both stages by adjusting the movement of the displacer, which enables the SPR to meet the demand of time-varying heat loads at different cooling temperatures and makes it a competitive choice in complicated space applications. In this paper, a SPR designed by our lab is adopted to study the typical characteristics. A one-dimensional thermoacoustics-based numerical model is adopted to optimize the structure parameters and the operating parameters. The cooling capacities, relative Carnot efficiencies at different displacer phases are given. The axial distributions of gas temperature and wall temperature in SPR are drawn. In addition, axial distributions of pressure amplitude, phase difference between volume flow and pressure wave and acoustic power are presented and compared. Experimental results operating at different mean pressures and frequencies are given. Compared the experimental results with the corresponding simulation results, a good consistency is revealed. The experimental results show that the SPR can obtain cooling capacities of 8.8 W at 80K plus 0.81 W at 30K with an input electric power of 245W, which indicates an overall relative Carnot efficiency of 12.85%.