Effective thermal conductivity in HTS coils

We present a numerical model to determine the effective thermal conductivit y in high-T-c superconducting (HTS) coils. The model, based on the heat con duction equation solved with the finite element method, will help us to com pute the temperature dependence of the effective thermal conductivity in co ils with varying proportions of epoxy in the total winding volume. The cond uctor parameters in the coils correspond to those in a real Bi-2223/Ag mult ifilamentary composite tape, where the anisotropy of the Bi-2223 material h as been taken into account. We will furthermore discuss about the effects o f geometry of the composite structure on effective thermal conductivity. Ou r result shows that in epoxy impregnated HTS coils at temperatures below 60 K, the effective thermal conductivity is over two orders of magnitude high er in the parallel direction with the conductor axis compared to the perpen dicular direction. (C) 2000 Elsevier Science Ltd. All rights reserved.