Performance degradation of helium refrigerator for cryogenic hydrogen system at J-PARC

J-PARC低温水素システム用ヘリウム冷凍機の性能低下

麻生 智一 ; 勅使河原 誠   ; 長谷川 勝一   ; 武藤 秀生*; 青柳 克弘*; 高田 弘   

Aso, Tomokazu; Teshigawara, Makoto; Hasegawa, Shoichi; Muto, Hideki*; Aoyagi, Katsuhiro*; Takada, Hiroshi

Since January 2015, a pressure drop gradually increased between heat exchangers and an adsorber (ADS) in the helium refrigerator of the cryogenic hydrogen system every operation. To investigate the cause of the performance degradation, impurities accumulated in helium gas was measured. However, no significant amount of impurities was observed. By cleaning inside of the heat exchangers and replacing ADS with new one, the refrigerator performance could be restored. As a result of dismantling the replaced ADS, we found that oil was locally accumulated in membranous form onto the felt at the helium entrance side. This might cause the pressure drop because the frozen oil during cooling down obstructed helium flow. There are still some doubtful relation between the pressure drop and the performance degradation at the heat exchanger. We are still making effort to investigate the cause.