A porous building approach for modelling flow and heat transfer around and inside an isolated building on night ventilation and thermal mass

Recently, more and more attention is paid on passive energy saving technologies in buildings, including night ventilation and thermal mass. In the paper, a porous building model is proposed to investigate wind and thermal environment around and inside an isolated building on different amounts of night ventilation and amounts of thermal mass. Inside the building, the Brinkman-Forchheimer extended Darcy model (BFED model) and the local thermal non-equilibrium model (LTNE model) are first adopted, to represent flow and heat transfer between airflow and thermal mass. The reliability of the model is validated with published wind tunnel experimental data. After that, local wind and thermal characteristics, cooling effects of night ventilation are obtained. The effects of three key parameters: airflow velocity, airflow temperature and equivalent porosity of the building are investigated in detail. The results indicate that, the outdoor air temperature has a larger influence on the effects of night ventilation than airflow velocity. And the proposed porous building model shows great advantages in modelling heat transfer between airflow and thermal mass. The investigation provides thoughts for dealing with urban wind environment, outdoor thermal environment and wind environment of building arrays.