Performance evaluation of indigenously developed helium liquefier in mix mode operation

An indigenously developed helium liquefier of 50 L/h liquefaction capacity has been designed, fabricated and commissioned at RRCAT All the components of this system were either manufactured in-house or built through local manufacturers as per our design specifications. In order to improve the performance, the system was experimentally tested in mix modes of operation. System has been subjected to heat input through an electrical heater installed at the bottom of liquid helium collection container inside the cold-box to evaluate its performance as refrigerator. With reciprocating expansion engines and plate fin heat exchangers, the measured refrigeration power is 40 W at 4.2K without nitrogen precooling. There is also provision for liquid nitrogen precooling to further increase the refrigeration capacity. The maximum compressor power input for the system is 110 kW that can also be varied with variable frequency drive. In this paper, experimental results obtained from the system are presented and simultaneously validated with developed numerical model for the same conditions.