Outlets airflow velocity enhancement of an automotive hvac duct

Heating, ventilation, air-conditioning (HVAC) duct system for an automotive has a complex geometry due to space constraints in the engine compartment. This could reduce air pressure inside the duct, decreasing the airflow velocity at the HVAC outlets, and correspond to the intended value prescribed by design. Higher air velocity at the ventilation outlets is desirable to promote thermal comfort in the passenger cabin. This study aims to enhance the airflow velocity and uniformity at each duct outlet by varying outlet geometry and duct elbow angles using the computational fluid dynamics (CFD) method. A typical HVAC duct of a C-segment car has been chosen as the case study. Steady-state parametric flow analyses were conducted to determine the duct geometry that would significantly improve the airflow uniformity and velocity at the duct outlets. It was found that a combination of circular outlets with a 65° elbow angle results in the best improvement in the airflow velocity distribution inside the duct. It was also found that the airflow velocity at the outlets increases between 4% to 9% compared to the baseline design. The air velocity difference between all outlets is around 1.3%, which can be considered negligibly small.