Air quality and passenger comfort in an air-conditioned bus micro-environment

In this study, passenger comfort and the air pollution status of the micro-environmental conditions in an air-conditioned bus were investigated through questionnaires, field measurements, and a numerical simulation. As a subjective analysis, passengers' perceptions of indoor environmental quality and comfort levels were determined from questionnaires. As an objective analysis, a numerical simulation was conducted using a discrete phase model to determine the diffusion and distribution of pollutants, including particulate matter with a diameter < 10 μm (PM₁₀), which were verified by experimental results. The results revealed poor air quality and dissatisfactory thermal comfort conditions in Jinan's air-conditioned bus system. To solve these problems, three scenarios (schemes A, B, C) were designed to alter the ventilation parameters. According to the results of an improved simulation of these scenarios, reducing or adding air outputs would shorten the time taken to reach steady-state conditions and weaken the airflow or lower the temperature in the cabin. The airflow pathway was closely related to the layout of the air conditioning. Scheme B lowered the temperature by 0.4 K and reduced the airflow by 0.01 m/s, while scheme C reduced the volume concentration of PM₁₀ to 150 μg/m³. Changing the air supply angle could further improve the airflow and reduce the concentration of PM₁₀. With regard to the perception of airflow and thermal comfort, the scheme with an airflow provided by a 60° nozzle was considered better, and the concentration of PM₁₀ was reduced to 130 μg/m³.