Design of an experimental setup for heat transfer coefficient measurements of supercritical helium for hydrogen aviation applications

Helium is widely employed as a coolant in engineering applications. In its supercritical state, it eliminates liquid–vapor phase separation and enables stable forced-flow cooling, making it attractive for superconducting devices, fusion reactors, and particle accelerators. In our recent studies on liquid-hydrogen-powered aircraft for Integrated Zero Emission Aviation (IZEA), supercritical helium was identified as the preferred coolant for superconducting generators, motors, power converters, and high-current cables, with operation required in the 30–70 K range at 15–20 bar. Accurate knowledge of its forced-convective heat transfer coefficient under these conditions is essential for designing compact and efficient heat exchangers, yet existing data span only limited pressure, temperature, and Reynolds number ranges. To address this gap, we present the design of an experimental facility for precise measurements of supercritical helium heat transfer coefficient under controlled flow and heating conditions. The system was optimized to balance loop diameter, cryofan performance, cryocooler capacity, sensor resolution, and heating requirements. The final setup circulates helium through a 0.5-inch test section at Reynolds numbers up to 10⁶, while sustaining pressures up to 20 bar and temperatures down to 4 K. By directly probing this unexplored parameter space, the platform will generate critical data to reduce uncertainties in correlation-based models and advance cryogenic heat exchanger design for IZEA and various applications beyond it. The measurement approach and instrumentation have been designed to ensure high reliability and repeatability of the collected data. The first experimental dataset generated using this platform will be reported in a subsequent publication.