Numerical Simulation and Experimental Study of DN1250 Cryopump under Different Thermal Conditions

摘要

A large-scale cryopump (DN1250) used in large vacuum leak detecting system was designed and itsperformance experimentally investigated by Beijing Institute of Spacecraft Environment Engineering. Thecryopump was cooled by four closed cycle helium refrigerators. Detailed numerical analysis of the heat transferin the first stage array was performed by using computational fluid dynamic method (CFD). Several designparameters were considered to find the effect on the temperature distribution and the cooldown time. Thevariation of thermal conductivity and heat capacity with temperature was taken into account. The thermalanalysis method based on numerical techniques was introduced in this study, the heat transfer in the first stagearray and the second stage cryopanels were carefully analysed to determine important considerations in thethermal design of the cryopump. A performance test system according to the RNEUROP standards was builtto test main performance of the cryopump. The experimental results showed that the structure of first stagearray which was optimized by the method could meet the requirement of the cryopump well. The temperatureof the cryopanels were down to 10 K within 300 min and the result of the experiment was accordant withtheoretical conclusion of the analysis. The test also showed that the pumping speed for N_2 of the pump was upto 5.8×10~4 L/s, and the crossover value was over than 3.0×10~5 Pa·L.