Heat transfer to liquid and supercritical helium in superconducting rotors

Cooling designs of superconducting generator rotors are important for maintaining a stable superconducting state of field windings, and it is essential to comprehend the heat transfer characteristics of helium in rotating fields. Experiments were carried out using a large-scale rotating cryostat with a cold rotor diameter of approximately 800 mm. Clear differences among the steady-state heat transfer characteristics of helium were confirmed between low centrifugal acceleration fields and high centrifugal acceleration fields, resulting in the collection of heat transfer data under the supercritical state necessary for cooling designs. The heat transfer characteristics of liquid and supercritical helium under conditions of gravitational and centrifugal acceleration fields are discussed