Daisaku Kasao

Stability analysis of a forced-flow cooled superconductor

Abstract A numerical analysis of the thermal stability of a superconductor composite cooled by forced-flow supercritical helium has been performed. The analytical model consists of simultaneous two-dimensional coolant flow equations and a one-dimensional superconductor equation. The equations of conservation of mass, momentum and energy for coolant flow and the Fourier heat conduction equation for the superconductor were solved numerically. Current-sharing mode, temperature-dependent properties of the conductor, and pressure- and temperature-dependent coolant properties were fully taken into account. The transient behaviour of the conductor, coolant flow, the effects of disturbance-heated length of the conductor, the initial pressure and initial velocity of coolant on the thermal stability of superconductors are discussed.

AN EXPERIMENTAL STUDY ON THE FORCED-CONVECTIVE HEAT TRANSFER TO SUPERCRITICAL HELIUM 4 FLOWING DOWNWARD IN A CIRCULAR TUBE

The forced-convective heat transfer to supercritical helium 4 has been investigated. The test section is a stainless steel tube with 1.25/1.62 mm in diameter and 285 mm long, held vertical in the cryostat and heated by passing DC current through it. The direction of flow was vertical downward, the inlet fluid temperature between 5 and 10 K, the system pressures 0.5 and 0.8 MPa and mass velocity 40 kg/(m2. s). The heat transfer characteristics measured compare rather well with the conventional correlation of heat transfer though the heat transfer coefficients seem a little higher than the values predicted by the conventional correlation.