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

Cryogenic Engineering Conference 2015

材料科学;物理学

Iwakuma, M.^1 ; Adachi, K.^1 ; Yun, K.^1 ; Yoshida, K.^1 ; Sato, S.^1 ; Suzuki, Y.^2 ; Umeno, T.^2 ; Konno, M.^3 ; Hayashi, H.^4 ; Eguchi, T.^4 ; Izumi, T.^5 ; Shiohara, Y.^5

Research Institute of Superconductors Science and Systems, Kyushu University, Fukuoka

819-0395, Japan^1

Taiyo Nippon Sanso Co., Tokyo

142-8558, Japan^2

Fuji Electric Co. Ltd., Kawasaki

210-9530, Japan^3

Kyushu Electric Power Co. Inc., Fukuoka

815-8250, Japan^4

ISTEC, Kawasaki

213-0012, Japan^5

关键词: Boundary planes;    Coated conductors;    Expansion turbines;    Finned tube heat exchangers;    Maintenance intervals;    Natural convection flow;    Sub-cooled liquid nitrogen;    Superconducting transformer;   

Others  :  https://iopscience.iop.org/article/10.1088/1757-899X/101/1/012026/pdf
DOI  :  10.1088/1757-899X/101/1/012026

学科分类：材料科学（综合）

来源: IOP

【 摘 要 】

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 LN2in 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 LN2in the cryostat was one atmosphere. Just under the LN2 surface, a stationary layer of LN2was 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 LN2was formed and temperature was almost uniform over 1 m depth. The boundary plane between the stationary layer and the natural convection region was visible.