An improved thermal analysis method for vapor-cooled current leads considering convective heat transfer efficiency

Abstract

As an important part of superconducting devices, the heat leakage of current leads directly affects the overall heat load of the cryogenic system. Therefore, the design of low heat leakage current leads is one of the most important issues in system design of superconducting devices. Vapor-cooled current leads (VCCL) are widely used in various superconducting devices because they have lower heat leakage compared with conduction-cooled current leads, and smaller consumption of cooling gas and higher economy compared with gas-cooled current leads. In this paper, an improved thermal analysis method for solving the heat leakage, temperature distribution and heat transfer efficiency of VCCL is proposed, which has a great advantage in terms of time-consumption and convergence while guaranteeing accuracy in comparison to conventional finite element method. Firstly, based on the heat balance equation of VCCL, the relationship of the heat transfer efficiency and convective heat transfer coefficient between VCCL and cooling gas is clarified. Subsequently, the formula to calculate the heat transfer efficiency of VCCL is derived according to heat transfer and fluid dynamics. Then, a thermal analysis method for VCCL based on iterative algorithm is put forward. Finally, the feasibility of the thermal analysis method is verified by finite element model based on COMSOL, which has been proved to be correct by experimental results in existing literature. The results indicate that for several VCCLs with typical structures, the calculation differences of heat leakage between the thermal analysis method proposed in this paper and COMSOL are all within 5 % and the calculation differences of temperature distribution are all within 10 K. However, in terms of time-consumption and convergence, the thermal analysis method proposed in this paper has a significant advantage, especially for VCCLs with complex structures.