Thermodynamic characteristics and structural optimization of pure hydrogen vortex tubes: An experimental and numerical investigation

Efficient thermal management of high-pressure hydrogen (H 2 ) is a critical bottleneck in the global hydrogen energy infrastructure. The Ranque-Hilsch Vortex Tube (RHVT), possessing intrinsic safety with zero moving parts, presents an ideal cooling solution for explosive H 2 environments. This study provides systematic experimental and three-dimensional numerical investigation of temperature separation in a RHVT operated with hydrogen at ambient inlet temperature. A test facility was designed and operated to acquire H 2 thermodynamic data. Furthermore, novel aerodynamic configurations-an internal expansion annular trapezoidal structure (No02), a supersonic Laval nozzle (No03), and a combined structure (No04)-were proposed. For the conventional straight nozzle (No01) vortex tube, a maximum total temperature difference Δ T max of 46.75 K was recorded at a cold mass fraction μ c of 0.9. Besides, investigations reveal that conventional straight nozzles induce severe aerodynamic choking and irreversible entropy generation. By contrast, the optimized supersonic Laval nozzle (No03) governs a highly directional, isentropic pre-expansion. This structure boosts the mass throughput (+8.27%) and achieves a peak total temperature separation (Δ T max ≈ 49.25 K at μ c = 0.9), which improved by 5.33% compared to No01. Flow-field analyses confirm that this deep supersonic expansion significantly prolongs the reverse flow boundary and intensifies energy transfer and conversion process, while fundamentally suppressing entropy generation. This study not only provides experimental benchmarks for H 2 vortex dynamics but also establishes an optimization design paradigm for safe, high-efficiency hydrogen thermal systems.