Hydraulic characteristics in superconducting power transmission cables

The hydraulic characteristics of sub-cooled nitrogen in superconducting pow er transmission line have been investigated to design the transmission line . To estimate the friction factor in corrugated pipes, the pressure drop wa s measured across a 10-m length corrugated pipe for various mass flow rates and compared with that in smooth pipes (Proc. 17th Cryo. Eng. Conf. (1998) 475). Another concern is the cooling method of the transmission line. A us ual counter-flow cooling method has been found to be very difficult at liqu id nitrogen temperature, because the thermal conductivity of the dielectric materials between the counter-flows at liquid nitrogen temperature are 10 times larger than that at liquid helium temperature. Instead, an externally cooling method was proposed (Proc. 17th Cryo. Eng. Conf. (1998) 475). As t he results, the friction factor of outer corrugated jacket within three cab les has become an important parameter to design the transmission lines. Thi s friction factor is measured and compared with various formulas in this pa per. (C) 2001 Elsevier Science B.V. All rights reserved.