Numerical study on air extraction performance of rooftop ventilators

[[abstract]]This research numerically studied the air extraction performance of rooftop natural ventilators, including the conventional and a newly developed ventilators. This newly developed ventilator has combined features of static and turbine ventilators. It is modified from the conventional ventilator, where its top cover is removed and replaced by a low-pressure ventilation device. A Computational Fluid Dynamics (CFD) analysis is performed to explore the flow fields around and inside the rotating and non-rotating ventilators, and the air extraction performance. The air extraction rate is obtained from the mean velocity at the inlet of an open channel, connected to a ventilation tube. Results show that the modified ventilator exhibits better ventilation effects than the conventional one at all of the investigated wind speeds, especially at low speeds. When the ventilator is not rotating, the modified ventilator is still able to extract air out of the ventilator, while the conventional ventilator has negative air extraction rate.[[notice]]補正完