Speaker
Description
The knowledge of forced flow heat transfer characteristics of liquid hydrogen (LH2) is important and necessary for design and cooling analysis of high critical temperature superconducting devices. However, there is few test facility of LH2 forced flow cooling for superconductors. We have already developed such a test system that it can make a LH2 forced flow (~10 m/s) of short period (less than 100 s). The test system was composed of two LH2 tanks connected by a transfer line with a controllable valve, where the forced flow rate and its period were limited by the storage capacity of tanks. In this paper, we describe a liquid hydrogen recirculation system which was designed and fabricated in order to study characteristics of superconducting cables in a stable forced flow of liquid hydrogen for a long period. This LH2 loop system consists of a centrifugal pump with dynamic gas bearings, a heat exchanger which is immersed in a liquid hydrogen tank, and a buffer tank where a test section (superconducting wires or cables) is set. The buffer tank has LHe cooled superconducting magnet which can produce an external magnetic field (up to 7T) at the test section. A performance test was conducted. The maximum flow rate was 43.7 g/s. The lowest temperature was 22.5 K. It was confirmed that the liquid hydrogen can stably circulate for 7 hours.
