Wind tunnel study on convective heat transfer performance of vegetation canopies with different structures

Abstract

Turbulent airflow around urban vegetation significantly affects transpiration cooling, pollutant dispersion, insect habitat, outdoor thermal environment, and building energy consumption. A major challenge is investigating the effect of different vegetation canopies on turbulent transfer and improving the calculation of the canopy convective heat transfer coefficients ( h c ) using canopy structural parameters. To address this challenge, we conducted 744 experiments using an adjustable artificial vegetation canopy and assessed different canopy structures and wind speeds and the presence/absence of obstacles. The results showed that the h c was not significantly affected by the relative angle between the leaves at a constant leaf windward angle. The largest h c occurred at a leaf windward angle ( θ ) of 24° and a windward leaf area index ( L A I w ) of 1.1. The proposed semi-mechanical and empirical models showed good prediction accuracy ( R a d 2 = 0.93). Moreover, the predictability of canopy turbulent transfer, vegetation energy budgets, and thermal comfort was enhanced by incorporating the h c model into urban microclimatic models (UMMs). Future applications and development of this model will facilitate wind-sensitive urban planning and help provide guidelines for landscape management to mitigate insect problems and improve building ventilation. • The h c was not significantly affected by the relative angle between leaves. • The maximum h c at a leaf windward angle of 24° and an LAI of 1.1. • A wind tunnel experiment method for the h c is proposed. • Plant selection and pruning strategies are provided.