PUMPED TWO-PHASE FUEL CELL COOLING

A cooling system for a fuel-cell system onboard a vehicle such as an aircraft in one embodiment employs the latent heat of evaporation of a two-phase coolant to reduce mass and parasitic power requirements of the cooling system. In another embodiment the cooling system has a primary ambient air heat exchanger coolant loop for cooling the fuelcell system, and a secondary coolant loop comprising a fluid circuit configured to circulate a coolant in thermal contact with a phase-change material (PCM) in thermal contact with the fuel-cell to absorb heat from the fuel-cell. The secondary coolant loop includes a heat pump for cooling the PCM.