Theoretical and Experimental Investigation on the Axial Temperature Mismatch and its Optimization for Coaxial Inertance Pulse Tube Cryocoolers

Abstract

In a coaxial pulse tube cryocooler, the radial thermal conduction between the pulse tube and the regenerator has a large influence on cryocooler performance. Caused by the temperature mismatch between the pulse tube and regenerator, this phenomenon needs to be carefully considered during the cryocooler design process. In this work, models with and without radial thermal conduction between the regenerator and its coaxial pulse tube have been constructed to analyze the mechanism and predict its effect on cryocooler performance. Experiments have been carried out to characterize the coaxial pulse tube axial temperature distribution under a variety of working conditions. A linear variable differential transformer (LVDT) has been used to analyze the pressure-flow phase angle in the test system. The results were then compared with the simulated results and were used to provide direction for further optimization. The simulation results show that a steady radial thermal conduction exists between the pulse tube and the regenerator, and this heat transfer can affect the fluid dynamics and thermodynamics in the system. Experiments show that the shape of the wall temperature distribution curve is a useful indicator of the cooler performance and the appropriateness of the arrangement of the pulse tube and the regenerator for achieving optimal working conditions. The simulation results are in good agreement with the experimental data, which verifies the numerical simulation modeling. To validate the theoretical and experimental studies, the configuration of a previous 2W at 60K experimental prototype PT was redesigned and optimized to get an optimal axial temperature match between the regenerator and pulse tube. The new experimental prototype achieved a COP of 2% at 60 K and 4.3% at 80 K with around 100 W of input electric power.