Effects of Parameters Affecting Ventilation Performance of a Vertical Shaft

It is frequently reported that kitchen exhaust hoods do not function properly in high-rise apartment buildings. The uneven pressure distributions in a vertical shaft can cause hood fans to extract insufficient airflows depending on the floor level. It is important to investigate the pressure and airflow characteristics in a vertical shaft in order to understand overall building ventilation performance. There are various system parameters affecting the pressure distributions in a shaft, such as building height, shaft size, fan characteristics, concurrent hood fan usage, shaft bottom inlet condition, outdoor temperature, and etc. It is the objective of the present study to investigate the effects of these parameters on pressure distributions and overall ventilation performance of a building. A computer program has been developed by implementing the principles of fluid dynamics in a vertical air column with horizontal branches. Simulation results have been obtained in a 25-story apartment building according to the method of experimental design for various parameter combinations. Analysis of variance has been conducted to investigate correlations between parameters. The results show that the pressure deviation based on -4mmAq has a strong correlation with the maximum pressure in the shaft. It indicates the possibility of using the pressure deviation as a single objective parameter which represents both the maximum value and the standard deviation of the pressure distribution in the shaft. The roof fan rpm and the inlet damper opening can be used as operation parameters, and the pressure at the top-most level and the outside temperature can be used as sensing parameters.