Correlations of control parameters determining pressure distributions in a vertical exhaust shaft

摘要

The pressure distribution in a vertical exhaust shaft is important in determining the ventilation performances of local exhaust hoods in high-rise buildings. Uneven pressure distribution can cause insufficient exhaust airflows from hood fans, and can cause excessive exfiltration resulting in unwanted noise through any gap openings. There are various system parameters that affect the pressure distribution in a vertical shaft, such as building height, shaft size, roof fan characteristics, concurrent hood fan usage, and outdoor temperature. The objective of this study is to quantify and investigate the effects of these parameters numerically on the overall ventilation performance of a vertical shaft. In order to achieve this goal, specialized simulation software has been developed, which implements the principles of fluid dynamics in vertical air columns with horizontal branches. Simulation results have been obtained based on a model of a 25-story apartment building, according to the experimental design method. Analysis of the variance has been conducted to investigate any correlations between the parameters. The results show that the deviation of the pressure distribution based on a slight negative value (i.e. -30 Pa or -40 Pa) has a strong correlation with the maximum pressure in the shaft. This indicates the possibility of using the pressure deviation as a single objective parameter, which represents both the insufficiency and unevenness of the pressure distribution throughout the shaft. Roof fan rpm and inlet damper opening can be used as operational parameters, and the pressure and pressure gradient at the top-most level, and outside temperature can be used as sensing parameters for pressure control in a vertical shaft.