Experimental Characterization and Model-Based Altitude-Adaptive Liquid–Air Coupled Thermal Management of a High-Power PEMFC System in Plateau Environments

Proton exchange membrane fuel-cell (PEMFC) systems in plateau regions face reduced electrochemical performance because of lower oxygen partial pressure, while radiator heat rejection can be weakened by lower air density. This study compares an 80 kW class liquid-cooled PEMFC system in Wuhan (~0 m, 101.3 kPa) and Kunming (nominal 2000 m test condition, 80.1 kPa), using GB/T 24554-2022 as the test-method reference, and develops a model-based altitude-adaptive liquid–air-cooling strategy. At the end point of the steady-state current sweep, the highest recorded stack power decreases from 93.98 to 84.0 kW (−10.6%), maximum net power in rated-power tests decreases from 82 to 72 kW (−12.2%), load-up time increases by 33%, and unloading time decreases by 20%; in the Kunming load sweep, the parasitic share rises from 9.2% to 18.2% as net demand increases from 10 to 80 kW. A thermal sweep in which the recorded excess-air ratio falls from 5.63 at 10 kW to 2.18 at 80 kW reaches 80 kW net while maintaining the coolant outlet temperature at 78–86 °C. Under idealized International Standard Atmosphere (ISA) conditions, the modeled radiator air-side coefficient falls to 85.4% and 72.5% of its sea-level value at 2000 and 4000 m, respectively; inverse-density fan scaling restores the modeled coefficient at a fan-power cost proportional to 1/K(z)2. Unlike previous altitude studies focused on stack electrochemistry, the results indicate coupled air-supply constraints and modeled air-side heat-rejection sensitivity. These results support altitude-adaptive thermal management of high-power PEMFC systems. No 4000 m stack-power projection is reported: the apparent pressure ratio that would be required at that altitude to reproduce the cathode-inlet pressure recorded at the 80 kW point of Campaign B (3.23) is beyond the 2.48 reached in the tests, so the 4000 m analysis is restricted to that pressure-ratio requirement and to the idealized air-side coefficient of the radiator.