Research on exergy transfer characteristics of mixing process inside hydrogen recirculation ejectors

Understanding the exergy transfer characteristics during the mixing process of hydrogen recirculation ejectors is essential for improving entrainment performance and advancing fuel cell technology. An exergy analysis method combined with an ejector model with species transport is proposed to addressing critical knowledge gaps in assessing two multi-component fluids interactions and operational condition effects on exergy distribution evolution and flow irreversibility. The evolution of mixing layer growth and exergy transfer under different operating conditions is systematically discussed, and the fundamental link between exergy transfer and entrainment performance is revealed. Key findings demonstrate that mechanical exergy dominates over 98 % of the entrainment process, with crucial interflow exergy transfer concentrated in the dynamically evolving mixing layer. At high primary pressure, the location of maximum secondary exergy gain moves downstream of the mixing chamber and the percentage of exergy loss in the diffuser increases to 45.96 %. The increase in nitrogen fraction will promote the growth of the mixing layer, while reducing net exergy transfer from primary flow to secondary flow. Under critical conditions, the secondary exergy gain is significant and the loss remains minimal in mixing process, while there are high exergy losses in the diffuser. Adding a bypass inlet in the diffuser can effectively improve the exergy utilization, when the current density is greater than 0.7 A/cm². Hydrogen circulation ratio is significantly increased by 22.17 % and the exergy loss is reduced by 36.4 W at 1.8 A/cm².