Airflow management represents a critical and multidisciplinary aspect of modern automotive engineering, influencingpassengerthermal comfort, system efficiency, aerodynamic drag, and electric vehicle driving range. Asthe global automotive industry continuesitstransitiontoward electrification and sustainability, optimizing both internal heating, ventilation, and air-conditioning (HVAC) airflowsystemsandexternalaerodynamic characteristics has become increasingly essential. Thisresearch presents a comprehensive Computational FluidDynamics(CFD)-based investigation integrating internal duct flow optimization and external aerodynamic drag reduction through S-duct implementation.Reynolds-Averaged Navier–Stokes (RANS) simulations were employed to analyze airflow behavior under steady-state conditions. InternalHVAC duct modifications, including outlet geometry transformation and elbow angle optimization, resulted in airflowvelocityimprovementsranging from 4% to 9% while maintaining outlet velocity uniformity within 1.3%. External aerodynamic optimizationusinganS-ductconfiguration demonstrated a measurable reduction in drag coefficient, corresponding to an estimated 48 kmimprovement inelectricvehicledriving range under highway conditions. The results highlight the importance of adopting a holistic airflow optimization strategythat integratesinternalthermalmanagementandexternalaerodynamicperformancetoimprove comfort, efficiency, and sustainability simultaneously. Keywords: CFD Tool, AC Duct