Development of the double two-phase thermosyphon loops used in low temperature Stirling refrigerator

Abstract

With the growing of demand for the low temperature pharmaceutical cold chain, the Stirling cooler has been attractive for years. However, the heat transfer inside the refrigerator could be ineffective by natural convection due to the small area of the plug-in Stirling cold finger. In this paper, the double two-phase thermosyphon loops (DTPTLs) used for low temperature Stirling refrigerator is developed. The characterization of heat transfer and pressure drop in the DTPTLs is investigated by theoretical calculation for various working refrigerants. Then the basic structure of the DTPTLs is modified and improved for dragging and moving convenience. Moreover, the comparison of the temperature distribution inside the refrigerator container between the DTPTLs and the plug-in cold finger methods is demonstrated by numerical simulation. The simulation result indicates that a well temperature distribution inside the container can be obtained by using DTPTLs. In the end, an experimental test is conducted at room temperature. It's shown that the no-load cooling temperature could reach −80 °C in a few minutes. Over steady-state operation, the maximum temperature difference all inside the container is less than 5 °C, which proved the positive heat transfer effect of the DTPTLs on the cooling performance of the low temperature Stirling refrigerator system.