A high capacity GM cryocooler working at liquid helium temperatures for horizontal operation

With the advantages of high efficiency and high reliability, GM cryocoolers have been widely used in the fields of superconducting magnet cooling, scientific instruments and semiconductor manufacturing. For some special applications, GM cryocoolers must operate horizontally. However, the performance of high-capacity GM cryocoolers working at liquid helium temperatures significantly degrades when operated horizontally compared to operated vertically. This severely impacts the application of high-capacity GM cryocoolers. In this paper, a GM cryocooler was designed and optimized based on the commercial GM cryocooler KDE420 to meet the requirement of high capacity GM cryocooler working at liquid helium temperatures operating horizontally. The cooling capacity of the cyocooler in the vertical direction was first improved by optimizing the second-stage regenerator and displacer stroke length. By using a spring support structure and optimizing the second-stage regenerator length, the performance degradation in horizontal operation was reduced. The optimized cryocooler achieved a capacity of 2.60 W vertically and 2.30 W horizontally at 4.20 K, with a reduced performance degradation from 0.85 W in KDE420 to 0.28 W. A long-term operation test for 570 h has been conducted and the test results showed that the cooling performance of the optimized cryocooler is stable, with a cooling capacity of 45.0 W@38.0 K and 2.20 W@4.20 K. The FOM of the optimized GM cryocooler in horizontal operation is 3.28 %. The experimental optimization method in this paper is useful in guiding the design and optimization of the horizontal operation of high capacity GM cryocooler working at liquid helium temperatures.