Ram-air cooling for fuel cell aircraft

Journal article, 2027

The ram-air cooling system for a fuel cell aircraft is conceptually designed. The ducted heat exchanger model captures internal and external flow effects, fan and pump operation and nozzle variability. Certain aerodynamic aspects are validated using RANS CFD. The complete system is optimized for minimal parasitic power draw. For an ATR 72-sized aircraft, an optimal design only capable of cruise requires approximately 4.3 % of the expected 1.2 MW fuel cell stack output. Enabling ISA +25 ^∘C hot-day take-off requires a larger system, increasing the power draw during cruise to 11.3 % of the stack output. The take-off requires 15.2 % of the expected 2 MW stack output. The results demonstrate that ram-air cooling remains feasible with low-temperature fuel cells, although take-off requirements impose a substantial cruise penalty. Three key enablers to low drag are identified: inlet oversizing, an application-suited heat exchanger design and an upstream-mounted fan.