Nozzle spray-cooling coupled PEMFC stack radiator: Thermal-hydraulic performance and integrated correlations

As the automotive industry shifts towards electrification to combat climate change, proton-exchange membrane fuel cell (PEMFC) stacks present a viable solution for heavy-duty trucks with extended ranges. This paper addresses the challenge of PEMFC cooling using the evaporative effect of exhaust water injected into a stack radiator via a nozzle. An experimental optimization of the thermal-hydraulic characteristics of a nozzle spray cooling-integrated stack radiator under diverse operating conditions was performed. The effect of the nozzle orientation and the impact of air velocity/temperature, coolant flowrate/temperature, and spray flowrate/temperature were investigated. The findings revealed that the effect of nozzle orientation on the performance decreased as the air velocity increased. Furthermore, the spray cooling performance was highly sensitive to changes in the air velocity and spray flow rate, whereas the coolant-side variables had a relatively low impact. The optimal thermal performance was obtained when the spray flowrate was set to 0.30 LPM, and the nozzle was oriented at 60°. Compared with the air-cooled radiator, the heat rejection improved by 167.7 %, whereas the air pressure drop increased by 124.1 % when applying the spray. Two novel empirical correlations were established to accurately predict the heat transfer enhancement and spray cooling efficiency with mean absolute errors of 5.3 % and 2.87 %, respectively. These results highlight the promising application of spray cooling in stack radiators for fuel-cell vehicles, and the correlations provide crucial guidance for the design of spray-cooled radiators for future electric vehicles.