Impact of wind on solar-induced natural ventilation through double-skin facade

Abstract

Although wind-buoyancy interactions have been widely explored, their mixing associated with semi-transparent facades are not yet clearly understood. This gap greatly restraints the implementation of naturally ventilated double-skin facades (NVDSFs). In this study, the impact of wind on the buoyancy flow in an NVDSF was investigated on a range of wind speeds, wind angles, and solar radiation intensities. The wind's realistic impinging associated with solar radiation's transportation between facades are revealed. Results present three aspects: the impact of wind on façade temperatures; the counteraction of wind on buoyant outflow; and defining and correlating the ‘critical wind velocity’ according to targeted natural ventilation rates. Results correlated the additional temperature drops on the outer glazing for wind speed 0.125–1.0 m/s, attack angles 5° ∼ 85° and solar radiation between 200–1000W/m2. The wind at 1 m/s and 5° can cause 10.5% reduction in façade temperature. By proposing a ‘wind inflow coefficient’, we established an empirical model to calculate the total ventilation rate under the mixed wind-buoyancy effect. Furthermore, an important concept – ‘critical wind velocity’, was introduced accordingly. It indicates the wind velocity under which the targeted natural ventilation can be met for an NVDSF for different solar conditions, e.g. the velocity at which the wind cancels out the buoyant outflow or below which the indoor ventilation can be satisfied. The novel correlations for the combination of mixed wind-buoyancy field with solar radiation and glazing materials can contribute significantly to NVDSFs under realistic environmental conditions.