Optimization of the Adaptability of the Fuel Cell Vehicle Waste Heat Utilization Subsystem to Extreme Cold Environments

In extremely cold environments, the fuel cell vehicle (FCV) waste heat utilization subsystem can only exchange a small amount of proton exchange membrane fuel cell (PEMFC) waste heat into the warm air circuit for cab heating, which has poor adaptability to extremely cold environments. The first step in this study was to build a test bench for the waste heat utilization subsystem of fuel cell vehicles. Secondly, the PEMFC heating capacity and liquid–liquid exchanger heat transfer capacity were analyzed using experimental data to assess the ability of FCV waste heat utilization subsystems with different rated powers to adapt to extremely cold environments. Then, the optimization mathematical model of the liquid–liquid exchanger was established, and the heat transfer performance of the liquid–liquid exchanger was orthogonally optimized based on the Taguchi method. Finally, the optimized liquid–liquid exchanger was installed in the waste heat utilization subsystem for experimental tests. The results show that when the ambient temperature is −20 °C, −25 °C or −30 °C, in the optimized waste heat utilization subsystem, the inlet and outlet temperatures of the PEMFC are reduced, and the power consumption of the positive temperature coefficient (PTC) is reduced by 57.6% and 48% and 34.3%, respectively, improving the utilization rate of PEMFC waste heat, and thereby improving the adaptability of FCV in extremely cold environments.