Analysis of behaviour of HTS tapes cooled by liquid nitrogen under currents more than the critical current

Abstract

For proper HTS device protection knowledge is necessary about the behaviour of HTS tapes cooled by liquid nitrogen at current pulses more than critical current. In our previous works, we performed measurements of HTS tapes at the currents more than critical currents and found the peculiarities on voltage – current characteristics of HTS tapes. Later, the coupled thermal and electric numerical model was developed to analyse the behaviour of the HTS tape in these conditions. The numerical model helped us to understand qualitatively the heat transfer from the HTS tapes to liquid nitrogen. The peculiarities found were connected not only with the nonlinearity of electrical conductivity of the superconductors but with boiling hysteresis phenomenon in the liquid nitrogen as well. In the present paper we made additional suggestions about peculiarities in the nuclear boiling heat transfer. We also described the way to find out the real heat transfer coefficients during convection and nucleate boiling in liquid nitrogen by using data from measurements of voltage – time characteristics of the HTS tape cooled by liquid nitrogen at current pulses more than critical current.