Natural ventilation is the process of supplying and removing air through an indoor space by natural means. There are two types of natural ventilation occurring in buildings: winddriven ventilation and buoyancy driven ventilation, or stack ventilation. The most efficient design for natural ventilation in buildings should implement both types of natural ventilation. Stack ventilation which is temperature induced is driven by buoyancy making it less dependent on wind and its direction. Heat emitted causes a temperature difference between two adjoining volumes of air, the warmer air will have lower density and be more buoyant thus will rise above the cold air creating an upward air stream. Combining the winddriven and the buoyancy driven ventilation will be investigated in this study through the use of a windcatcher natural ventilation system. Stack driven air rises as it leaves the windcatcher and it is replaced with fresh air from outside as it enters through the positively pressured windward side. To achieve this, CFD (computational fluid dynamics) tool is used to simulate the air flow in a two dimensional room fitted with a windcatcher based on the winddriven ventilation alone and on the combined buoyancy and winddriven ventilation.
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