3-D Numerical Analysis of the 68 kA Heat Exchanger of the ITER HTS Current Leads

High-temperature superconducting (HTS) current leads consist of a resistive and a superconducting part. The resistive part, which transfers the current from the room temperature termination to the top terminal of the HTS element, is a resistive heat exchanger cooled by cryogen gas and optimized for the specified operating conditions. This optimization requires complex analysis of multiple physical phenomena, such as Joule heating, fluid flow, and heat transfer by conduction and convection. The solution of such a problem requires a numerical approach. The paper reports on the 3-D numerical calculations made on the heat exchanger type adopted for the Large Hadron Collider HTS current leads. It consists of a central conductor with fins for increased heat transfer surface, and it is cooled by a forced flow of helium gas. The same type of heat exchanger has been adopted for the ITER HTS current leads operating at currents ranging from 10 to 68 kA. In this paper, the 3-D model of the ITER 68 kA heat exchanger is presented and discussed. In particular, the effect of the turbulence induced by the zig-zag flow of the gas between the fins is analyzed and quantified.