Analysis of the Performance Difference Between4He and 3He in Space JT Cryocoolers

Joule-Thomson (JT) cryocoolers play an essential role in space exploration missions. The JT cryocoolers with different working fluids have different operating temperatures. 4He and 3He are used in JT coolers to obtain temperatures below 4 K. Due to the different physical properties of 4He and 3He, 4He is widely used to get the temperature above 2 K, while 3He is used to obtain the temperature below 2 K. In this paper, a finite-element model (FEM) of the counter-flow tube-in-tube heat exchangers (CFHX) is established. According to the Laval nozzle model, the mass flow rate and the cooling capacity of the JT process are analyzed. Finally, this paper combines these models and uses MATLAB for programming. The influence mechanism of the CFHX length and the JT orifice diameter on the 4He and 3He JT effects are obtained.