Integrated modeling of pedestrian energy exchange and thermal comfort in urban street canyons

Abstract

An open-air scale model is used to quantify pedestrian radiative and convective energy exchanges in street canyons of varying geometry, as well as surface-atmosphere energy exchanges above the urban canopy. A semi-empirical model based on measured data in summer is developed to link between the two levels, for the prediction of pedestrian energy exchange within a given street canyon based on climatic conditions above the street array. The relationships identified in the semi-empirical model are then tested with an independent data set from the winter season, demonstrating that the semi-empirical model may be used to predict the effect of street geometry on pedestrian comfort under varying seasonal conditions. Finally, the estimation of pedestrian energy exchange by street geometry is refined to include the effects of humidity and evaporative heat loss along with radiation and convection, and results are used to correlate between physiological energy exchange and thermal sensation, which is a more direct measure of human thermal comfort. The results reinforce previous findings, which indicate that in a hot-arid climate, compact street canyons can substantially reduce overall pedestrian thermal discomfort if their axis orientation is approximately north–south, while in east–west oriented canyons the effect of street proportions is much less pronounced.