CFD simulation analysis and visualization experimental study of gas contamination condensation distribution in coaxial pulse tube cryocooler.

Condensable gas contamination is one of important factors limiting the longevity of pulse tube coolers. To further understand the way in which contamination affect the performance of pulse tube cooler, the behavioral characteristics of the contamination inside the pulse tube cooler were investigated. In this study, a 2-D simulation model of the regenerator was developed, and the diffusion and phase change distribution characteristics of the contamination at the cold end were investigated by CFD method. The transition of gas flow and pressure loss caused by the contamination were analyzed. The results show that condensation occurs first in the pulse tube and distribute mainly in the pulse tube and the regenerator eventually. The transition of the gas flow state due to the accumulation of contamination is likely to be an important cause of degradation in the performance of pulse tube
cooler. And contamination will accumulate in the flow straightener when the cooling temperature closer to the saturation temperature, which can further affect the state of gas flow in the pulse tube, resulting in higher pressure losses. In addition, based on the technology of neutron radiography, a visualization experiment on the accumulation of contamination in pulse tube cooler was completed, and the experimental results were compared with the simulation results.