Optimal design of thermostat for proton exchange membrane fuel cell cooling system

Highlights: • The confluence and divergence modes of paraffin thermostats are designed. • Predict the influence of the thermostat on the system under different ambient temperatures. • Using the splitting scheme to optimize the temperature of the hydrothermal system. • Electronic thermostat to improve the sensitivity of the stack. The temperature conversion and control of hydrothermal system is crucial for the performance and durability of fuel cell engines. We firstly built the simulation and experiment platform for the cooling system, include confluence mode and split mode for the thermostat. Through the model calculation, in the split mode, the error of the stack outlet is about 0.8%, and the temperature shock time error is about 5%, the maximum temperature error when switching between large and small cycles is about 0.7%, and the temperature fluctuation is small in the confluence mode. The calculated results are in good agreement with the experimental results, which proved the rationality of the model. Secondly, the influence of the temperature fluctuation caused by the cycle switching of the system size on the catalyst activity and the electrochemical reaction rate is researched, by studying the different position settings of the thermostat in the system. It is found that the thermostat confluence mode increases the response speed and a wider temperature control area. Finally, based on the hysteresis characteristics of the temperature melting of the paraffin-type thermostat, the system uses an electronic thermostat to replace the thermostat. Through the optimized control strategy, temperature fluctuations are basically eliminated, and the temperature management of the cooling system is optimized.