Experimental study on a 20W/80K high frequency pulse tube cryocooler

The cryocoolers working around the liquid nitrogen temperature have important applications in high temperature superconducting, infrared detectors and gas liquefaction. A cryocooler sometimes needs to work in different temperatures. For the high-frequency pulse tube cryocooler operating around the liquid hydrogen temperature, due to the limitation of the length of the regenerator, it is often impossible to simultaneously have higher performance around the liquid nitrogen temperature. Therefore, this paper enhances its performance around the liquid nitrogen temperature based on a high-frequency pulse tube cryocooler working around the liquid hydrogen temperature, by changing the effective length of the regenerator with filling different lengths of copper mesh. Firstly, the effect of filling different lengths and meshes of copper mesh on its 80 K refrigeration performance is simulated. Finally, the experimental verification is also carried out. Moreover, by further optimizing the phase modulation mechanism and operating parameters including working frequency and charge pressure, the cryocooler can provide 20 W cooling capacity at 78 K under the input electric power of 420 W. The relative Carnot efficiency is increased from the initial 9.8 % to 13.56 %.