A numerical investigation into the effect of Windvent louvre external angle on passive stack ventilation performance

The Windvent is a commercially available passive ventilation device. The device is constructed from sheet metal and works on the principle of pressure differential. Whereby warm air rises, creating a low pressure in the receiving room, which then draws in the fresh air. This paper investigates the effect of altering the external angle of the Windvent louvres against the internal pressure and velocity within the device and the microclimate velocity. Numerical analysis is carried out using a commercial Computational Fluid Dynamics (CFD) code, to investigate the effect of various louvre angles (range 10–45°) on pressure and velocity to optimise the device performance. The results show that the louvre performance mimics that of thin airfoil from aerodynamic theory. The relationship between trailing-edge stall and delivery velocity is established. The optimum louvre angle with a prevailing wind velocity of 4.5 m/s is shown to be 35° with a stall angle of 40° illustrated. The external, performance enhancing louvre angle, determined through this investigation is subject to UK patent number 0809311.4.