A Performance-driven Numerical Approach for Optimizing the Plenum Opening Area of Cowl Box

There is a scarcity of research in literature regarding the determination of Plenum Opening Area of cowl box. The area of the plenum opening in the cowl box significantly affects the airflow rate in fresh airflow modes, such as face and defrost modes, as well as issues related to water ingress. Primarily, the size of the plenum opening is determined by the necessary HVAC airflow rate. This study aims to investigate how the plenum opening area impacts both airflow discharge and the water ingress issue in the HVAC module. A novel approach is introduced in this research to determine the optimal plenum opening area of the cowl box, taking into account both airflow rate and water ingress concerns. The ANSYS FLUENT software is utilized to analyze airflow discharge in both face and defrost modes, while the SPH (Smooth Particle Hydrodynamics) based Preonlab tool is employed for water ingress analysis. Airflow discharge is evaluated for various plenum opening sizes in both modes, and the area that maximizes flow rate is further examined for water ingress. The study also investigates the velocity reduction in the IP duct between fresh air and recirculation modes through CFD analysis, comparing the results with experimental data. A strong correlation was found between the experimental and simulation results in the water ingress analysis. This research offers significant insights for designers who are evaluating airflow discharge in both fresh air and recirculation modes. Balancing airflow between these modes also enhances the design of the cowl box by optimizing the plenum opening area while addressing water ingress issues.