Estimation of the Air Quality of a Vehicle Interior: The Effect of the Ratio of Fresh Air to Recirculated Air From a Heating, Ventilation and Air-Conditioning System

The air quality inside the cabin of an automobile is closely related to the health of those who spend much time in their vehicles. The automotive indoor-air quality can be improved in several ways, the most common and effective of which involves diluting the polluted air with fresh air through the vehicle's heating, ventilation and air-conditioning system. In this study, we switched between the outside-air mode and the recirculation mode of the automotive heating, ventilation and air-conditioning system to assess how the switch affected the concentration of pollution within the vehicle. The flow rates in the possible door angles between the outside-air mode and the recirculation mode of the vehicle's heating, ventilation and air-conditioning system obtained from experiments were applied to the computational fluid dynamics analysis. Furthermore, actual vehicles were infused with gas over time and concentrations were measured to validate the numerical results. In the computational fluid dynamics analysis, a user-defined function was applied to a commercial code to find the ratio of fresh air to recirculated air in heating, ventilation and air-conditioning systems. The obtained numerical data were analyzed under a variety of conditions such as the flow rate and the ratio of fresh air to recirculated air to identify the change in the indoor-air quality source concentrations.