HEAT-TRANSFER THROUGH A HIGH-TEMPERATURE SUPERCONDUCTING CURRENT LEADAT CRYOGENIC TEMPERATURES

A study of heat transfer through a high temperature superconducting (H TSC) current lead in both, resistive and superconducting mode, has bee n performed. The set of dimensionless governing parameters was defined , and the physical meaning of different parameters elaborated. An opti mal selection of thermal design parameters was suggested. The selectio n of parameters has been based on : (i) the numerical solution of a se t of nonlinear governing differential equations; and (ii) an estimatio n of the irreversibility induced by heat transfer and Joule heating ph enomena. The results were discussed for a YBa2Cu3O7-delta (YBCO) compo und system. The case study has been based on a cryogenic current lead model that includes the nonlinearities as follows: (i) variable therma l conductivity; (ii) variable electrical resistivity (in resistive mod e); and (iii) Variable heat transfer coefficient. The results obtained correspond to the temperature range between 4.2 and 77 K. It was show n that a local variation in heat transfer coefficient does not influen ce the selection of optimal design parameters. (C) 1997 Elsevier Scien ce Ltd.