Dynamic Modelling and Simulation of a Spray Cooling System in Commercial Fuel Cell Vehicles

"Polymer electrolyte membrane fuel cells (FC) are an environmental friendly alternative to internal combustion engines (ICE) as a power source for commercial vehicles. A main chal-lenge for FC trucks is sufficient cooling under high load conditions at hot ambient tempera-tures. For the same propulsion power, the waste heat of a FC truck is about three times high-er than that of an ICE truck. Due to the low operating temperature of the FC (70 ?C) hardly any waste heat can be dissipated via the exhaust gas and must be almost completely dissi-pated by the cooling system. Due to the low coolant temperature, conventional liquid cooling systems in FC trucks have difficulties in reliably dissipating the waste heat. To overcome this cooling deficit, a spray cooling system for a heavy duty fuel cell truck was introduced in the technical SAE-Paper ?Design and analysis of a spray cooling system for a heavy duty fuel cell truck? (Manuscript Number 22NETP-0036 ? Status under Review). The Spray Cooling System recovers water from the FC exhaust gas and sprays it onto the truck's front-end heat exchanger to increase cooling capacity. In the paper, the new spray cooling system was identified as a very effective alternative to the conventional cooling system for FC trucks in terms of maintaining temperature limits and reducing energy consumption. In the present paper, the dynamic simulation model for the spray cooling system developed in Modelica is presented in detail. The simulation model is integrated into a co-simulation envi-ronment, which includes the fuel cells, the cooling circuit, the electrical truck powertrain and the vehicle ECU. Thus, we consider all relevant interactions between the subsystems. The entire vehicle simulation was validated with measurements on test benches. Various long-distance tracks are used to determine the benefits of a spray cooling system in a holistic manner. "