Thermal Modeling of Gaseous Helium as a Cryogen for High Temperature Superconducting Cable Components

A fluid mechanics and cryogenic thermal study of the termination system of a gaseous helium cooled second generation high temperature superconducting (HTS) cable is presented. This includes a discussion on the development of a 2-D turbulent model that uses finite element method within COMSOL to assess the temperature profiles in the terminations and the comparison of the model results with those obtained experimentally. Temperature gradients across the cable system were measured before an actual HTS cable was installed to ensure that they are within an acceptable range and to validate the cryogenic design of the cable terminations. The experiments were conducted at the gaseous helium cooled superconducting cable test facility at the Center for Advanced Power Systems (CAPS), Florida State University. The thermal model presented here confirms that temperature gradients across a 30-m-long HTS cable system operating at around 50 K can be maintained below 6 K with helium gas mass flow rates of <;10 g/s. The results of the thermal models agree with the experimental results. The modeling methods used and the resulting thermal model reported will be useful for future design studies in optimizing the cryogenic thermal and fluid flow designs of superconducting cables.