Paper Conference

Proceedings of ASim Conference 2014: 2nd Asia conference of IBPSA-China, Japan, Korea


A basic study on numerical simulation methods for sensible heat flux from building external surfaces to the atmosphere

Kan CHEN, Takashi ASAWA

Abstract: Sensible heat flux from building external surfaces is one of the essential factors warming the atmosphere around buildings and causing urban heat island effects. In order to predict it accurately, this study uses a numerical method which applies the 3D CAD-based heat balance simulation developed by the authors’ group and can calculate the detailed surface temperature distribution taking into account the building geometry, and couples it with Low Reynolds number k-ε model (the Low-Re model) CFD simulation. Previous studies didn’t realize it. By using the Low-Re model, we can simulate air temperature and wind speed distribution inside the wall boundary layers. This study is implemented to figure out the appropriate prediction formula for CHTC (Convective heat transfer coefficient) that can be used for the prediction of heat fluxes by high Reynolds number k-ε model (the High-Re model), in order to apply this method to the analysis of urban block scales. Firstly, we used the High-Re model and the Low-Re model to predict CHTC and compared these results with the result of a wind tunnel experiment. Then we used coupled analysis of the heat balance simulation and CFD using the Low-Re model to predict the sensible heat flux from the building external surfaces of a house complex located in Tokyo. Finally we obtained the experimental approximation formula between CHTC and the effective wind speed near the building surface in forced convection dominant cases.
Keywords: Sensible heat flux, CHTC, the Low-Re model, the High-Re model, Heat island effects
Pages: 228 - 234