Performance Analysis and Optimization of a Drizzling-Based Evaporative Cooling for Enhanced Thermal Management of FCEV Fuel Cell Stack

In response to increasingly stringent emissions regulations such as Euro 7, Fuel Cell Electric Vehicles (FCEVs) are emerging as a promising solution for commercial applications due to their high energy density, rapid hydrogen refueling, extended driving range, and minimal payload limitations. However, insufficient thermal management of the fuel cell stack can lead to power loss and reduced durability, underscoring the need for advanced cooling technologies. This study proposes a novel evaporative cooling approach that utilizes fuel cell discharge water sprayed onto the stack cooling radiator through a gravity-driven, low-pressure drizzling system to harness latent heat of evaporation. To validate the concept, component-level experiments were conducted using a full-scale radiator identical to that of an actual vehicle and a 40 kW electric fan. A total of 57 tests were performed under conditions of 45 °C ambient temperature and 70 °C coolant inlet temperature, while varying key parameters such as water flow rate (1.0 – 2.8 LPM), spraying distance (20 – 40mm), fan speed (1200 – 1700 RPM), and radiator coolant flow rate (190 – 310 LPM). The result demonstrated that the drizzling-based evaporative cooling system achieved up to 24.6 % improvement in cooling performance compared to a conventional water-cooling system by effectively utilizing latent heat. Furthermore, a performance prediction model based on Random Forest Regression was developed, achieving a high accuracy of R² = 0.989. The model identified optimal operating conditions that reduced fan power consumption by approximately 6.7 kW and improved vehicle energy efficiency by about 2.4 %. This study quantitatively demonstrates that a drizzling-based evaporative cooling system can significantly enhance both fuel cell stack thermal management and vehicle energy efficiency without requiring complex structures or additional pumps. The findings provide valuable insights for optimal design and control strategies toward real-world implementation in heavy-duty hydrogen fuel cell vehicles.