TABLE OF CONTENTS - The Professional Green Building Council

Theme B: Creating a livable, healthy and environmentally viable cities3.3 Velocity variation in cavityThe solar radiation provided source of heat with the cavity so that naturalventilation occurred due to the stack effect. The variation of air velocity in bothcavities is shown in Figure 9-Figure 10.Generally, the velocity at air inlet was the greatest. After the air was induced intothe bottom of cavity, its velocity was diminished due to the change of pathway ofair movement. The velocity increased as the air travelled near outlet at the top ofcavity due to the suction effect from the top of cavity which is exposed toatmosphere. However, its velocity was slower than that at the air inlet.The statistical summary of air velocity in both cavities is shown in Table 1. Itappears that the velocity in the cavity was influenced by solar radiation. Thevelocity in the west cavity had higher values when the sun was on the west sideafter it passed south.irradiance [W/m^2]5040302010InletCenterOutletOutdoor00:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00TimeFigure 5: Temperature Variation in eastern cavity (Oct.9. 2007)irradiance [W/m^2]5040302010InletCenterOutletOutdoor00:00 3:00 6:00 9:00 12:00 15:00 18:00 21:00Time544