A Stirling type pulse tube cryocooler working at liquid hydrogen temperatures with a precooled transmission tube

•A Stirling pulse tube cryocooler (SPTC) with a precooled transmission tube is proposed and studied.•Geometry of the precooled transmission tube is designed considering the pV power loss and heat leak.•Results show that the SPTC with the precooled transmission tube has similar cooling performance to the original one.•A hot end heat exchanger of the precooled transmission tube is necessary for quickly stabilizing the cold end temperature. Stirling type pulse tube cryocoolers (SPTCs) usually require multi-stage configuration for working below liquid hydrogen temperatures but their cooling efficiency is still poor at present. One of the main reasons is that their high-temperature part regenerators consume large amount of input pV power as isothermal components with large temperature drop. Theoretically, when there is a surplus cold source such as LN2 or LNG for precooling, the high-temperature part regenerator can be replaced by an empty tube with little pV power drop, which will increase the efficiency of the SPTC while recovering cold energy. In this paper, the SPTC with a precooled transmission tube instead of high-temperature part regenerator is proposed and studied. The hot end of the transmission tube was linked to the room-temperature compressor at ~300 K, while its cold end was connecting to the low-temperature part regenerator precooled to ~ 80 K by LN2. The heat transfer and pV power losses in the precooled transmission tubes under different sizes were calculated and analyzed. Experiments were carried out to verify the feasibility of the precooled transmission tube in a SPTC. Results show that the SPTC can work well with the precooled transmission tube. A no-load refrigeration temperature of 17.7 K and cooling capacity of 1.74 W at 25 K are obtained with a total input pV power of about 52.9 W. The hot end heat exchanger of the precooled transmission tube is found to be necessary for quickly stabilizing the cold end cooling temperature.