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Liquid hydrogen (LH2) can serve simultaneously as a fuel and a low-temperature heat sink for high-temperature superconducting devices. However, repeated testing of an LH2-cooled system is difficult because of the safety and facility requirements associated with hydrogen. This study presents a thermal-hydraulic similarity procedure for designing a liquid-nitrogen-based surrogate experiment for an LH2-cooled gaseous-helium circulation system. The similarity conditions were derived from the dimensionless momentum and energy equations. For a geometrically identical helium loop, the principal similarity parameters for forced convective heat transfer are the Reynolds and Prandtl numbers. An evaluation of helium properties showed that the Prandtl number varies only moderately between the LH2 and LN2 temperature ranges. Consequently, the surrogate mass flow rate can be determined primarily by matching the Reynolds number using the ratio of helium dynamic viscosities at the target and surrogate conditions. The procedure was applied to a closed helium circulation loop consisting of a cryogenic heat exchanger, circulator, vacuum-insulated piping, and simulated heat-load section. The analysis also showed that Reynolds–Prandtl similarity does not preserve the heat-exchanger number of transfer units, pressure drop, or transient thermal response because of differences in fluid properties, mass flow rate, and structural heat capacity. The proposed procedure provides a rational basis for selecting surrogate operating conditions and clarifies which experimental results may be transferred to an LH2-cooled helium circulation system.
*Acknowledgement : This research was supported by the National Research Foundation of Korea (NRF) through the National R&D Program funded by the Ministry of Science and ICT (RS-2026-25542124) and the Basic Science Research Program funded by the Ministry of Education (RS-2025-25396743).
| Submitters Country | Republic of Korea |
|---|---|
| Are you a student? | No |
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