Enhancing heat transfer in fuel cell stack radiators: A spray cooling approach with a reticulated foam surface

Proton exchange membrane fuel cell (PEMFC) stacks generate substantial operational heat, requiring effective cooling to maintain their performance and durability, especially in heavy-duty vehicles. Spray cooling is a promising solution that, uses fine droplets of by-product water for rapid evaporative heat removal; however, its effectiveness declines at high spray flow rates and, air velocities, and during spray-off periods. Integrating reticulated foam with the radiator surface addresses these issues by retaining droplets, ensuring uniform film distribution, and sustaining evaporation during off-cycles, significantly improving cooling stability and system efficiency. A comprehensive experimental investigation was conducted to explore the effects of spray cooling with and without reticulated foam on the thermal hydraulic performance of a PEMFC stack radiator. Experimentation was conducted under two spray modes, (continuous and pulsated). Optimal performance was achieved using a single front-side foam layer, a 0.45 LPM spray flow rate, and a 3 m/s air velocity. This configuration improved heat rejection by 122.95 % with a 68.5 % increase in air pressure drop compared to air cooling. Relative to the bare sprayed radiator, it achieved a 28 % heat rejection improvement with only a 9 % rise in air pressure drop. Foam integration significantly enhanced performance during intermittent spraying, especially for spray intervals of up to 60 s. Two empirical correlations were developed to predict the thermal and spray cooling efficiencies in foam-assisted radiators, with mean absolute errors of 8.36 % and 3.2 %, respectively. These results offer valuable design guidance for overcoming spray cooling limitations and advancing compact, energy-efficient PEMFC thermal management systems.