Experimental study on the operating characteristics of a miniature pulse tube cryocooler less than 1 kg

Abstract

Miniature pulse tube cryocoolers are widely used in space science missions and military detection. But miniature pulse tube cryocoolers less than 1 kg generally exhibit low cooling power and have a small cooling power per unit mass. There is still a large gap compared with commercial miniature Stirling cryocoolers. Research on the operating characteristics of miniature pulse tube cryocoolers is scarce, and the operating mechanism needs to be further revealed. Therefore, a miniature pulse tube cryocooler weighing 0.91 kg is developed in this study. Experimental investigations are conducted on the influence of the input electric power, charging pressure, and refrigeration temperature on the operating frequency, and on the influence of the operating frequency on the cooling rate. The results show that when the refrigeration temperature is 80 K, under different input powers, the refrigeration performance maintains basically constant within 111 Hz to 116 Hz, with the efficiency change within 5 %. The higher the input power, the more significant the stable trend. Under different charging pressures, the cryocooler still remains stable within this range, indicating that this cryocooler has stable refrigeration performance over a wide frequency range. Additionally, the influence of frequency on the cooling rate is related to the refrigeration temperature. During the cooling process from room temperature to 120 K, the variation of the cooling rate within 104 Hz to 118 Hz is only 2 s. When further cooling to 80 K, operating at the optimum frequency can reduce the cooling time by 15 s. Finally, at a charging pressure of 4 MPa and an input electric power of 72 W, the cryocooler achieves a cooling power of 2.26 W at 80 K with a relative Carnot efficiency of 8.45 %. The cooling power per unit mass reaches 2.48 W/kg, demonstrating remarkable compactness among similar cryocoolers.