Sensitivity study on factors affecting air volume of vehicle air conditioning

Abstract

The vehicle air conditioning (AC) flow rate directly impacts the cabin comfort level and energy efficiency. Analyzing and validating the effects of factors such as vehicle speed, blower speed, air mixing mode, pressure relief valve, air discharge path, and cabin leakage on the vehicle’s ventilation performance helps to identify the influence patterns for each factor. Through full-scale wind tunnel airflow measurement experiments and CFD simulations (using a k-omega turbulence model with near-wall grids at y+<1), the research quantitatively evaluates the influence of these factors on HVAC airflow rate. By comparing CFD results with experimental data, the study ensures an airflow deviation of <5% and a temperature error of <2°C. The analysis further evaluates the sensitivity of each factors, while taking into account the interactions among factors at the same time, providing critical insights to optimize HVAC system design and enhance energy efficiency and passenger comfort. For instance, specify the requirement of the minimum ventilation rate for each occupant in the passenger compartment to be greater than 30 m³/h, and for the comfort need, specify the requirement of surface air velocity on each human body: 0.2–0.5 m/s in summer, and 0.1–0.2 m/s in winter. These targets are established to ensure adequate air circulation and comfort for vehicle occupants.