A rooftop wind driven turbine ventilator provides effective and environmental friendly natural ventilation in buildings and is commonly found in most countries of the world. The experimental and numerical studies of the complex flow field emanating from the wake shed by the ventilator and its interaction with the boundary layer of the inclined roof forms the basis of this thesis.During the experimental phase, the multi hole pressure probe technique of velocity and pressure measurement was successfully extended and adapted to obtain skin friction measurement on the roof which is a major contribution of this study. The numerical study also demonstrates that performance study of the operation of a turbine ventilator on an inclined rooftop is possible using commercial CFO package such as FLUENT opening up that possibility of greater use of numerical tools by ventilator designers working in industry.The present study identifies some important parameters that affect the performance of a ventilator. A given mass flow extraction rate, for example, can be achieved by varying the blade geometry of a ventilator particularly its height. In addition, the ventilator rotation and the force acting on the ventilator are found to increase linearly with free stream velocity thereby increasing the flow extraction rate of the ventilator. The presence of inclined roof also reduces the total force acting on the ventilator providing a new concept to extend the margin of safety during its operation at higher wind speed. In non-dimensional form, the force coefficient IS found to be independent of Reynolds number above a rotational speed suggesting that rooftop inclination has minimal effect III extracting air from a building at low wind speed. However, if higher mass flow extraction rate is desired at no or below a certain wind speed, ventilation in buildings may be boosted by a hybrid system incorporating other power sources such as solar power.The present study provides a greater understanding of complex flow field generated inside and around a ventilator during its operation and aid in the design of more cost effective ventilation system in buildings with lower carbon footprint to improve human comfort and air quality.
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