Thermohydraulic analysis of cold dielectric high temperature superconducting cable with counter-flow cooling

Abstract

High temperature superconducting (HTS) cables cooled with liquid nitrogen (LN2) have been found to be most promising alternative to conventional cables for meeting the ever-rising energy demand across the world. The heat accommodated by the LN2 flowing in HTS cable has various major sources such as AC loss in the superconductor, dielectric loss in dielectric material, and heat influx through the cryogenic enclosure wall from ambient temperature. Thus, in order to operate long length HTS cables, the thermal and hydraulic analysis of LN2 flowing in the HTS cable is essential. However, the LN2 flow is more complex when flowing through stainless steel corrugated pipes with counter-flow cooling arrangement. In the present work, counter-flow cooling system is considered for the analysis to reduce the highest temperature attained in the HTS cable. Moreover, the influence of various heat fluxes and heat generations on the pressure drop and heat transfer is carried out using computational fluid dynamics (CFD) approach. The two-equation turbulence model k-epsilon (k-ϵ) is used to analyze the thermohydraulic behavior of LN2, where the thermophysical properties of LN2 are considered to be temperature dependent. The obtained pressure drop is compared with the experimental data of a parallel flow HTS system, fabricated in NEDO project. Consequently, the friction factor for counter flow HTS system is found to be quite larger than the parallel flow HTS system.