Development of cooling system for 66/6.9kV-20MVA REBCO superconducting transformers with Ne turbo-Brayton refrigerator and subcooled liquid nitrogen

M. Iwakuma, K. Adachi, K. Yun, K. Yoshida, S. Sato, Y. Suzuki, T. Umeno, M. Konno, H. Hayashi, T. Eguchi, T. Izumi, Y. Shiohara

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1 Citation (Scopus)

Abstract

We developed a turbo-Brayton refrigerator with Ne gas as a working fluid for a 3θ- 66/6.9kV-2MVA superconducting transformer with coated conductors which was bath-cooled with subcooled LN2. The two-stage compressor and expansion turbine had non-contact magnetic bearings for a long maintenance interval. In the future, we intend to directly install a heat exchanger into the Glass-Fiber-Reinforced-Plastics cryostat of a transformer and make a heat exchange between the working fluid gas and subcooled LN2. In this paper we investigate the behaviour of subcooled LN2 in a test cryostat, in which heater coils were arranged side by side with a flat plate finned-tube heat exchanger. Here a He turbo-Brayton refrigerator was used as a substitute for a Ne turbo-Brayton one. The pressure at the surface of LN2 in the cryostat was one atmosphere. Just under the LN2 surface, a stationary layer of LN2 was created over the depth of 20 cm and temperature dropped from 77 K to 65 K with depth while, in the lower level than that, a natural convection flow of LN2 was formed and temperature was almost uniform over 1 m depth. The boundary plane between the stationary layer and the natural convection region was visible.

Original languageEnglish
Article number012026
JournalIOP Conference Series: Materials Science and Engineering
Volume101
Issue number1
DOIs
Publication statusPublished - Dec 18 2015
Event2015 Joint Cryogenic Engineering and International Cryogenic Materials Conferences, CEC/ICMC 2015 - Tucson, United States
Duration: Jun 28 2015Jul 2 2015

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)

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