A theoretical model of natural ventilation enhanced by solar thermal energy in double-skin façade

Compared to previous theoretical analysis of naturally ventilated double-skin façade (NVDSF), still in scarcity is a model that can reflect the coupling mechanism of radiation and natural convection, meanwhile being readily calculable to save from excessive numerical computing. Therefore, this study proposes a new theoretical model for an NVDSF that addresses its thermal and ventilation performance under varying environmental conditions. The theoretical analysis of energy balance and buoyancy flow is deepened by additional numerical modelling that reveals features of the coupled heat transfer and fluid flow. Key correlations between radiation and natural convection obtained from simulation data assisted in establishing an explicit solution of glazing temperatures, which are consequently used to moderate the fully mixed model for obtaining the natural ventilation rate. Eventually, the new theoretical model is featured with a more accurate evaluation of channel natural convection and straightforward calculation of temperature and flow rates in response to external conditions. In addition, an example performed over a daily condition demonstrates the capability of the theoretical model to replace time-consuming numerical simulations over transient changes. The in-depth understanding of the solar-assisted natural ventilation mechanisms revealed by this model can contribute mainly to facilitating similar passive energy-saving techniques that involve solar radiation absorption in glazing materials.