Ventilated solar façades in multi-storey buildings: natural ventilation with flow confluences

Effectively utilising solar facades combined with natural ventilation is vital for future zero-carbon buildings. However, the thermal-flow coupling and natural convection mechanisms in multi-inlet vertical airflow networks remain unclear, obstructing ventilation designs and energy consumption evaluations. To address this gap, we investigated the inter-storey flow interference within multi-storey solar facades. A numerical model validated using existing results and Particle Image Velocimetry (PIV) experiments analyses the vertical cavity flow field. The result illustrates a non-linear impact of the flow confluence on the ventilation performance at different floors, with a flow area contraction of 41%, 58%, 66% and 74% on the 2nd to 5th floor, respectively. A mathematical model was hence developed to estimate the dynamic discharge coefficient ( C d _ m ) of multi-storey NVDSF. Based on the derived coefficients for multi-storey buildings, we proposed to establish a ventilation satisfaction rate based on the air change rate (ACH). Through the analysis of annual climate data from two cities,we obtained ventilation satisfaction that is jointly influencedby floor-wise confluence coefficients and outdoor solar radiation intensities, thereby providing a more accurate analytical basis for assessing the natural ventilation potential and energy saving rates for multi-storey buildings.