Optimization of Intake and Exhaust Valves for 4 K Gifford-McMahon Cryocooler

Abstract

Intake and exhaust valves are key components of Gifford-McMahon (GM) cryocooler, and include several important factors, such as valve type, valve structure and valve timing. This chapter focuses on the influence of intake and exhaust valve timing on performance of 4 K GM cryocooler at various cooling temperatures in order to optimize the intake and exhaust valves. The 4 K GM cryocooler is a standard two-stage type one with a rotary valve for intake and exhaust. The second stage regenerator in the cryocooler has both lead spheres and spherical magnetic regenerator material with the latter arranged at the colder end. The cooling capacities of the first stage and the second stage are measured in wide temperature ranges. The results indicate that the optimum intake and exhaust valve timing is dependent on the cooling temperature and is possible to be different for each stage. The optimum intake and exhaust valve timing is dependent on the cooling temperature, and is possible to be different between the first stage and the second stage. In other words, the cooling temperature is important for the optimization of the intake and exhaust valves. The 4 K GM cryocooler delivers great cooling capacities not only at 4.2 K but also at much higher temperatures.