CRYOGENIC ENGINEERING OF HIGH-TEMPERATURE SUPERCONDUCTORS BELOW 77 K

The j-H characteristics of presently available high temperature superc onductors show a significant improvement with decreasing temperature. While the mast attractive refrigerant would be liquid nitrogen at 77 K under 1 bar, with the superconductor operating at a somewhat higher t emperature, say 80 K, for heat transfer purposes, this paper examines the possible and practical use of temperatures below 77 K for power en gineering applications. The types of refrigeration to be employed, whe ther using wet cooling, gas cooling or dry cooling via thermal contact , are also examined.