Fluorescent paint for determination on the effective thermal conductivity of YBCO coated conductor

Recently, YBa₂Cu₃O_7−x coated conductor (YBCO CC) has been developed intensively for different applications including power cables and high-filed magnets. Of all its physical properties, the thermal conductivity of the YBCO CC is considered as one of the most important parameters in guiding the temperature distribution, heat flux, and prediction of quench propagation. To accurately predict this property, a thermometry technique of high-speed fluorescent thermal imaging is introduced to monitor heat diffusion of commercial YBCO CCs in real time based on the Europium tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorate] (EuTFC) in this study. We propose a new imaging process to eliminate the influences of background intensity and non-uniform illumination on the calibration results accompanying with good accuracy of measurement. And the fluorescence performances are evaluated by static and dynamic calibration experiments. The experimental results show that the photoluminescence of EuTFC has excellent photostability and temperature dependence, and there is no hysteresis in the temperature response when comparing with the PT100 measurements. Subsequently, four kinds of commonly used theoretical models of thermal conductivity and the corresponding calculation curves of the YBCO CC are presented. Finally, the numerical simulation based on the theoretical models has been conducted to reproduce the transient heat conduction process. The simulation results show that the transient heat conduction predicted by the Maxwell's equivalent model show the best agreement compared with experimental results. (paper)