Influences of spherical tree canopy on thermal radiation disturbance to exterior wall under the condition of no shade cast on the wall

Research on the influence of thermal radiation of tree canopies to adjacent exterior walls has relevance to the selection of tree species and the spatial arrangement of trees for urban planning. In the last decade, there have been many studies on the influence of tree shadows on the thermal environment and energy consumption of buildings. However, there is a lack of research on how trees affect the thermal radiation of adjacent buildings, when they do not cast direct shadows on the walls. In view of this, a combination of experiment and simulation was used to explore the influence of spherical canopy on the intensity changes of net long-wave thermal radiation (TRDL) and net short-wave thermal radiation (TRDS) absorbed by the adjacent wall. Both measured and simulated results show that the tree canopy has a TRD (the sum of TRDL and TRDS) effect on the south wall of adjacent buildings in summer. The peak of TRD from the tree to the adjacent wall was obtained by ENVI-met under 27 scenarios. A functional relationship was further given between the peak TRD and the canopy diameter (DC), the minimum distance between wall and tree canopy (DW-T). Moreover, the influence of DC, DW-T and leaf area density (LAD) on TRD was discussed by simulation. Additionally, the TRD of canopy decays exponentially in the horizontal direction and linearly in the vertical direction of the wall. The above methods and results can guide the selection of tree species, green space design around buildings and the evaluation of the influence of trees on indoor cooling energy consumption in summer.