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

A numerical investigation into the effect of windvent dampers on operating conditions

The United Kingdom has made a commitment to reduce buildings carbon emissions, placing a greater onus on sustainable energy sources. Therefore, an anticipated increase of usage of zero carbon technologies in new and existing building has led to the emergence of passive ventilation devices as an alternative to mechanical ventilation and air conditioning. 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 air rises, creating a low pressure in the receiving room, which then draws in the fresh air. The ensuing air delivery velocity is controlled by the dampers, installed at the room entry interface. The dampers are actuator operated, and form the basis of the control system for the device. The purpose of this paper is to investigate the control mechanism for the device and ascertain an optimum operating range. Numerical analysis is carried out using a commercial computational fluid dynamics (CFD) code, to investigate the effect of various damper angles (range 0–90°). The results show that optimum operating occurs at a damper angle range of 45–55°, at the UK average 4.5 m/s external wind speed. The operating range when considered in tandem with macro climatic influences is central to determining the overall control strategy for the fresh air supply. The results provide useful information for both engineers and architects when examining ways to reduce new and existing buildings running costs, and conform to new legislation

Investigation of a windvent passive ventilation device against current fresh air supply recommendations

Recent ecological and political developments have created an increased focus on sustainable energy sources. The purpose of this paper is to examine a passive ventilation device, the windvent, and evaluate its potential against current British Standards BS5952:1991 [British Standards, Ventilation principles and designing for natural ventilation, BS5925:1991 (1991)] recommended fresh air delivery rates. The results provide useful information for both engineers and architects when examining ways to reduce new and existing buildings running costs, and conform to new legislation. Numerical analysis is carried out using a commercial Computational Fluid Dynamics (CFD) code, to investigate the effect of various external wind velocities (1–5 m/s) and directions (concurrent and counter current) on the device performance. The results show that the windvent is capable of providing recommended rates of fresh air supply even at relatively low incident wind velocities. The performance indications show that the device warrants further analysis and provides a sustainable alternative ventilation system