Thermal performance of a stack cooling radiator coupled with spray cooling for the future fuel cell electric vehicles

Abstract

Proton-exchange membrane fuel-cell electric vehicles require an appropriate stack cooling radiator (SCR) system to achieve optimal performance and safe operation. However, SCR cannot achieve high heat rejection under high power demands and hot ambient conditions. Hence, either the SCR needs to be enlarged to manage heat rejection or its ability to reject heat should be enhanced. In this study, a novel low pressure drizzling-aided spray cooling system (SCR-DS) is proposed for the first time. The thermal performance results were compared with those of a high-pressure nozzle-aided spray system (SCR-NS) and a conventional SCR system (SCR-CS). Based on the results, the coolant entry temperature to the stack reduced by up to 1.78 °C, and 2.75 °C when SCR-NS and SCR-DS configurations were active, respectively. Among the various operating factors, the spray cooling performance was significantly influenced by air velocity, spray temperature, and spray flow rate. Furthermore, the experienced mean increments in the heat rejection rate were up to 71.7 % and 123.5 % for the SCD-NS and SCR-DS, respectively, compared to SCR-CS. More importantly, these configurations aid in reducing the size of the SCR by 36.2 % and 45.9 %, respectively, under the same overall heat transfer coefficient conditions. Overall, the SCR-DS configuration was more beneficial than the SCR-NS configuration in terms of thermal performance owing to the slow and steady spray on the SCR surface along with more spray coverage, which aided in better liquid convection and film evaporation.