Role of Supercritical Nitrogen (SCN) on the hydraulic and thermal characteristics of futuristic High Temperature Superconducting (HTS) cables

Abstract

Cryogenic fluids such as Liquid Helium (LHe), Liquid Nitrogen (LN2), Liquid Oxygen (LOX) and Liquid Hydrogen (LH2) played a vital role in cooling various superconducting devices. The boiling temperatures of cryogenic fluids being lower than the critical temperature of the superconductors have enabled such an advantage. Moreover, supercritical fluids such as Supercritical Helium (SHe) and Supercritical Nitrogen (SCN) are also found to be replacing the liquid coolants thereby eliminating the possibility of reduction in heat transfer due to multiphase flow of working fluid. Hence, it is essential to investigate the role of such supercritical fluids in cooling the superconducting cables. Hence, in the present work, Super Critical Nitrogen (SCN) is proposed as a coolant for cooling of High Temperature Superconducting (HTS) cables. As the thermophysical properties are strongly affected by the temperature, analytical functions of thermophysical properties of SCN such as viscosity, density, specific heat and thermal conductivity are developed and implemented in the Thermohydraulic analysis of 1 m HTS cable. A 3-Dimensional computational model of HTS cable is modeled and developed in commercial software ANSYS-FLUENT for solving governing equations of mass, momentum and energy simultaneously. Different mass flow rates ranging from 16 L/min to 20 L/min and heat loads ranging from 1 W/m to 3 W/m are considered in estimating the thermohydraulic performance of HTS Cable. Friction factor, pressure drop, pumping power and heat transfer rate are estimated and compared with the results of experiments available in the literature. It can be concluded that SCN may be used as coolant to cool the HTS cables having higher critical temperature.