Thermal Insulation Test of new Designed Cryogenic Pipes for the Superconducting DC Power Transmission System in Ishikari, Japan

Abstract

New cryogenic pipes were designed for the superconducting DC power transmission systems constructed in the Ishikari area in Japan. In the designs two inner pipes, for the cable and for the return of liquid nitrogen, are installed in a single outer pipe for the circulation of liquid nitrogen. In contrast to the cryogenic pipes commonly used for the superconducting power transmission, in which corrugated pipes are used, straight pipes are adopted to reduce pressure loss of the circulation of the liquid nitrogen. A radiation shield to reduce heat leak to the inner pipe for the cable is adopted in one of the designs.Two types of test pipes with and without the radiation shield were constructed and heat leak of these pipes was measured to evaluate the effciency of the test pipes. The lowest heat leak of 0.73W/m was measured for the test pipe with the radiation shield.