Numerical study of mixed convective heat transfer coefficients for building cluster

The convective heat transfer coefficient (CHTC) of building surfaces is an important parameter to evaluate building thermal performance, and it also affects the calculation of sensible heat in urban canopy models. In this paper, The CHTCs at different building surfaces and ground for a building cluster at high Reynolds number is studied by Large Eddy Simulations (LES) with Smagorinsky subgrid-scale model and wall damping. The forced, natural and mixed convective heat transfer cases are simulated with 6×3 and 3×3 cubes used as the model buildings respectively. The Reynolds numbers are from 3.31×105 to 2.65×106 and the Grashof numbers are from 4.42×1011 to 3.54×1012. The results show that, the forced convection Nusselt number (NuF) is proportional to Re0.79, the natural convection Nusselt number (NuN) is proportional to Gr1/3 and the mixed convection Nusselt number can be calculated by (NuF)n+(NuN)nn with n varying from 1.9 to 3.8.