Integrated impacts of anthropogenic heat locations and building configurations on urban wind-thermal environments and pollutant exposure in two-dimensional street canyons

The anthropogenic heat (AH) from buildings significantly influences urban microclimate. While AH release from buildings with distinct functions originates from different locations (e.g., sidewalls and rooftops), the integrated effects of AH locations and urban morphologies remain underexplored. By computational fluid dynamics (CFD) simulations, as a novelty, this study numerically investigated the coupling impacts of AH emission locations (sidewall or rooftop) and building arrangements (uniform-height buildings, varied-height buildings, and elevated buildings) on urban airflows, air temperature, and pollutant dispersion in typical (H/W = 1) and deep (H/W = 5) street canyons.

Results indicate that rooftop AH produces a much weaker influence on urban microclimate than sidewall AH. It confirms urban airflows near and above the rooftop have much stronger dilution capacity and releasing AH at the rooftop can effectively reduce its negative impacts. For H/W = 1, sidewall AH reduces intra-canyon velocity by up to 10 % and significantly increases pollutant intake fraction (IF) and air temperature by ∼ 1 mg/m³ and 1 K. Conversely, for H/W = 5, sidewall AH enhances the near-ground velocity by around 100 times and reduces the pedestrian-level pollutant concentration by 10 to 100 times, but raises the intra-canyon air temperature by ∼ 2–10 K. The single-sidewall heat source only increases air temperature by 1–3 K, increases velocity from 10^-4 to 10^-2 m/s, and reduces pollutant concentration by 1–2 times. Elevated building designs mitigate AH impacts by improving ventilation. These findings underscore the importance of strategic heat source placement and urban morphology in balancing thermal comfort and pollution exposure.