Performance Analysis of 2K Heat Exchanger for Superfluid Helium Cryogenic System at KEK

KUMAR Ashish （総研大）；仲井浩孝, 中西功太, 清水洋孝, 原和文, 小島裕二, 本間輝也（KEK）

Abstract:The recent operating temperature of the superconducting RF cavities is 2.0 K or below, because of the higher resonant frequency of the niobium cavities (1.3 GHz). The necessity of 2K heat exchangers arises due to the requirement for increment of the continuous production rate of superfluid helium, while maintaining the level of superfluid helium inside the helium tanks of the superconducting RF cavities during steady state operation. The temperature of liquid helium is reduced from 4.4 K to 2.0 K or lower by a heat exchanger in which the incoming liquid helium at 4.4 K is cooled down with cold gaseous helium at 2.0 K evaporated from the helium tanks. Lower inlet temperature of liquid helium at JT valve ensures higher production rate of superfluid helium at the outlet of the valve.
At KEK, we have two variants of laminated finned type 2K Heat exchanger: Type I (Older Version) designed to handle low heat loads up to 30W and Type II (New Version) for higher heat loads up to 100W. Numerical analysis of Type II heat exchanger with static heat load of 37 W gave the effectiveness approximately 72% and it reduces as the heat load increases. A 2K Heat exchanger test stand is employed at KEK to measure the performance of different kinds of 2K heat exchangers. Performance tests of these heat exchangers are in progress to verify the numerical results.