Optimising the design of ventilators for natural ventilation

The basic mechanism for natural ventilation in a building involves air flowing through purpose-made ventilator openings. These ventilators must be carefully designed as natural ventilation driving forces are weak compared to the dynamic forces created by mechanical systems. This paper describes a series of experimental parametric studies that investigated how components within a ventilator (in this case louvers and wire mesh screens) interacted. Airflow measurements through the individual louver and mesh components were compared to the airflow through mesh / louver combinations. Initial results indicated that the airflow through a louver-mesh combination was always significantly less than the flow through an individual mesh or individual louver. At low pressure differences a louver with a small diameter mesh (insect screen) was experiencing airflow reductions of the order of 50%. For a large diameter mesh (bird and animal screens) the reductions were approximately 20%.