Investigation of convective heat transfer at the facade with balconies for a multi-story building

As a common building appendage, balconies can significantly alter the flow pattern near the building facade, thus greatly affecting the convective heat transfer coefficient (CHTC) of facades. In the present study, computational fluid dynamics (CFD) simulations are performed with the 3D steady Reynolds-averaged Navier-Stokes (RANS) SST k-omega model to evaluate the convective heat transfer at the building facade with balconies. This model is systematically validated by a reduced-scale wind tunnel experiment and then utilized to conduct simulations with highresolution grids. The effects of the balcony height (height of balcony parapet walls), depth, and length on the forced convective heat exchange at the facade and balcony surfaces are analyzed in detail. The results show that with the presence of balconies, the surface-averaged CHTC (CHTCavg) is reduced by about 17.5% at the windward facade, while it is reduced by 35.2% at the leeward facade. Furthermore, when the height of the balcony (Hp) varies from 0.5 to 1.5 m, CHTCavg decreases by up to 39%, 48.8%, and 50% on the leeward facade, the inner surfaces of windward and leeward balconies, respectively. However, balcony depth and length have relatively non-significant effects on the CHTCavg of building facades and balconies' surfaces. Finally, new correlations are established to describe the average CHTC along the facade and balconies' surfaces. The difference in CHTCavg obtained from the correlations and the simulations is less than 6%. The findings of the present study would facilitate the calculation of the cooling and heating loads of buildings with balconies.