Abstract
With the increased commercialization of high-temperature superconducting (HTS) power cables cooled using liquid nitrogen and the use of liquefied natural gas as fuel, the need for large-capacity reverse Brayton cryogenic systems is gradually increasing. In this paper, the thermodynamic design of a reverse Brayton cryogenic system with a cooling capacity of the 2 kW class at 77 K using neon as a refrigerant is described. Unlike conventional reverse Brayton systems, the proposed system uses a cryogenic turbo-expander, scroll compressor, and plate-type heat exchanger. The performance test conducted on the fabricated system is also described. The isentropic efficiency of the cryogenic turbo-expander was measured to be 86%, which is higher than the design specification. The effectiveness of the heat exchanger and the flow rate and operating pressure of the refrigerant were found to be lower than the design specifications. Consequently, the refrigeration capacity of the fabricated reverse Brayton cryogenic system was measured to be 1.23 kW at 77 K. In the future, we expect to achieve the targeted refrigeration capacity through further improvements. In addition, the faster commercialization of HTS power cables and more efficient storage of liquefied natural gas will be realized.
Highlights
With the increase in the demand for power, liquid nitrogen-cooled high-temperature superconducting (HTS) power cables (−196 ◦ C, 77 K) are being actively developed as an eco-friendly alternative to conventional power transmission cables; these cables offer almost no electrical resistance and can transfer five to six times more power than existing power cables [1,2]
We describe the thermodynamic design and fabrication of a reverse Brayton cryogenic system with a cooling capacity of a 2 kW class at 77 K
A fabricated reverse Brayton cryogenic system comprising a scroll compressor, plate-type heat exchanger equipment, and a cryogenic turbo-expander is described after the thermodynamic design
Summary
With the increase in the demand for power, liquid nitrogen-cooled high-temperature superconducting (HTS) power cables (−196 ◦ C, 77 K) are being actively developed as an eco-friendly alternative to conventional power transmission cables; these cables offer almost no electrical resistance and can transfer five to six times more power than existing power cables [1,2]. With tightening emission regulations around the globe, the importance of natural gas as an eco-friendly fuel is increasing. Liquid nitrogen is circulated inside HTS power cables to keep them at a temperature below 77 K (−196 ◦ C). The liquid nitrogen is heated due to the external atmosphere, as well as the heat load from the current-carrying HTS power cable.
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