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

Abstract

As a common building appendage, balconies can significantly alter the flow pattern near the building façade, thus greatly affecting the convective heat transfer coefficient (CHTC) of façades. In the present study, computational fluid dynamics (CFD) simulations are performed with the 3D steady Reynolds-averaged Navier-Stokes (RANS) SST k-ω model to evaluate the convective heat transfer at the building façade with balconies. This model is systematically validated by a reduced-scale wind tunnel experiment and then utilized to conduct simulations with high-resolution grids. The effects of the balcony height (height of balcony parapet walls), depth, and length on the forced convective heat exchange at the façade 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 façade. 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 façade 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.