Equation of DNB Heat Flux for Upward Forced Flow of Cryogenic Liquids

Superconductivity Centennial Conference, SCC 2011 ; 18 September 2011 through 23 September 2011Knowledge of departure from nucleate boiling (DNB) heat flux is important for design of superconducting systems cooled by cryogenic liquids. We have already presented the equation of DNB heat flux that can describe the experimental data of liquid hydrogen. To see the applicability of the equation to other cryogenic liquids, similar heat transfer tests in forced flow of liquid nitrogen are performed for wide ranges of conditions in this work. It was confirmed that the DNB heat flux equation derived by the authors can express not only the data for liquid hydrogen but also those for liquid nitrogen

Liquid Hydrogen Recirculation System for Forced Flow Cooling Test of Superconducting Conductors

Advances in Cryogenic Engineering: Proceedings of the Cryogenic Engineering Conference (CEC) 2017 (previous edition: CEC-2015). 9–13 July 2017, Madison, Wisconsin, USA.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 are few test facilities available for LH₂forced flow cooling for superconductors. A test system to provide a LH₂forced flow (∼10 m/s) of a short period (less than 100 s) has been developed. The test system was composed of two LH₂tanks connected by a transfer line with a controllable valve, in which the forced flow rate and its period were limited by the storage capacity of tanks. In this paper, 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 longer period, was described. This LH₂loop 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

Development of an experimental system for characterization of high-temperature superconductors cooled by liquid hydrogen under the external magnetic field

11th European Conference on Applied Superconductivity, EUCAS 2013 ; 15 September 2013 through 19 September 2013 ; GenoaAn experimental system has been developed to investigate electro-magnetic properties of high-Tc superconductors cooled by liquid hydrogen under the external magnetic field of up to 7 T. A LH2 cryostat is concentrically mounted on the inside of a LHe cryostat to cool a NbTi superconducting magnet. The experimental system is installed in an explosion-proof room. Explosion proof electrical devices are used and current leads are covered with an enclosure filled with nitrogen gas. A remote control system has been developed. Furthermore, the effects of stray magnetic field on the existing and the new devices are investigated and electro-magnetic shielding panels and enclosure made of iron were designed. It is confirmed through the cryogenic test that the experimental system meets the design requirements