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As a strategy of natural ventilation, the standard type of general gravity ventilator can be installed on the roof of an industrial building. The modified shape of ventilator with different width and/or height ratio was often used for improving ventilation efficiency and assuring structural safety concem. Although the ventilation rates could ve affected by different ventilator width and/ of height, the design data of appropriate ventilation rate have not been established yet. In this study, the ventilation rates of both standard and modified gravity ventilator were thus estimated for the purpose ofcomparison of ventilation dfficiencies. For the standard gravity ventilator, the factorial combinations of 4 parameters( 3 wind directions, 6 wind speeds, 5temperature differences and 3 ventilator neck widths) which consist of 270 cases. were simulated. Additionally, for the modified gravity ventilator, the factorial combinations of 5 parameters (3 wimd directions, 5wind speeds, 9 temperature differences, 3 ventilaor neck widths and 2 modified ventilator heights) which result in 270 caces, were simulated. A commercially available CFD code, FLUENT(Ver. 6. 0) package, was used to estimate the ventilation rates numerically. it was found from the thorough analyses that the ventilation performance were enhanced as ① wind direction is close to the latitudinal direction of industrial building, ② wind speed increases. ③ the temperature difference between the exterior and interior of a building increases and ④ ventilator neck is wider. The flow rate of low height ventilator is lower than that of standard height ventilator while the flow rate of taller ventilator was not increased proportionally. Therefore, standard ventilator is more suitable than modified ventilator for effective and safe ventilation.
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