Experiments on Air Extraction Performance of Rooftop Natural Ventilators

This research experimentally investigated the air extraction performance of rooftop conventional turbine ventilator and a modified ventilator. The modified ventilator has the combined features of static and turbine ventilators, modified from the conventional ventilator where its top cover is removed and replaced by a low-pressure ventilation device. An open wind tunnel system is used for this study, which simulates the condition where the wind blows over the rooftop ventilator. The air extraction rate is determined by the air mean velocity at the open slot of a ventilation pipe connected to the ventilator. The studies include ventilator rotation speeds and air extraction rates with and without ventilator's rotating, under different wind speeds and heights of the low-pressure ventilation device. Results show that the modified ventilators exhibit better air extraction rates than the conventional one does at all of the test wind speeds, especially at low wind speeds and as the ventilator not rotating. Also, the air extraction rate is generally proportional to the total height of the low-pressure ventilation device.