Effects of frontal area density on outdoor thermal comfort and air quality.

This paper systematically investigates the effects of the frontal area density of various three-dimensional (3D) array building models on the thermal comfort and air quality at the pedestrian level above four sidewalks (north, south, east and west). The buoyancy force for natural-convection flows and the realistic solar irradiance at local solar times (LSTs) from 0700 to 1700 are considered with five different frontal area densities (λ F = 0.0825–1.25). By a combination of the Rayman model and the ANSYS Fluent® software, the CO concentration and physiologically equivalent temperature (PET) are solved numerically. The simulated CO concentration and PET results are considered as outdoor parameters of the air quality and thermal comfort. A critical λ F is obtained for urban development by applying multivariable regression analysis to a group of dimensionless parameters. This analysis will facilitate the choice of building density and simultaneously enhance the air quality and thermal comfort. The results reveal that with an increase in λ F , the PET decreases above most of sidewalks during the daytime, while only is a steady reduction of air quality observed above west and east sidewalks of spanwise streets. According to the multivariable regression analysis for Hong Kong, the building density should have a λ F value between 0.82 and 0.84 to basically realize a PET <38 °C and CO concentration <30000 μg/m³ simultaneously in the daytime in June. • Effects of frontal area density on thermal comfort and air quality are investigated. • Outdoor thermal comfort is evaluated by PET considering realistic solar radiation. • Outdoor air quality is evaluated by CO concentration under realistic solar radiation. • A critical λ F is obtained for urban development by a regression analysis. [ABSTRACT FROM AUTHOR]