Effects of primary flow temperature on phase change characteristics in hydrogen recirculation ejector for PEM fuel cell system

The hydrogen recirculation ejector, known for its low cost and simple structure, has garnered widespread attention in PEM fuel cell applications. As a fluid-driven passive component, the fluid dynamics inside the ejector play a pivotal role in determining its entrainment performance. This study explores the impact of the primary flow temperature on phase change characteristics based on the Euler-Lagrange model. Results indicate that at a primary flow temperature of -40 degrees C, the mass flow rate of droplets at the outlet reaches 285.2 mg/s, representing a condensation efficiency of 24.1%. Concurrently, condensation elevates the outlet temperature by 31.2 degrees C, resulting in an 8.8% reduction in the entrainment ratio. The mass flow rate of droplets decreases significantly as the primary flow temperature increases. As the temperature rises to 60 degrees C, homogeneous droplets vanish entirely. Simultaneously, foreign heterogeneous droplets evaporate by 42.0%, attributed to the negative subcooling degree at the diffuser and outlet pipe. This study emphasizes the significance of controlling the primary flow temperature for the hydrogen recirculation ejector.