Modeling of positive pressure ventilation to prevent smoke spreading in sprinklered high-rise buildings

Abstract

This paper analyzes the positive pressure ventilation to prevent the smoke from entering the stairwell using Large Eddy Simulation in a sprinklered high-rise building with the heat release rate of 1.5 MW. Two methods are compared to get a more effective way: (1) the pressurization air flow into the stairwell from the group of multiple air supply outlets, and (2) the group of 2 air supply outlets next to the fire floor. The results have shown that to prevent the smoke from entering the stairwell, the minimum pressurization air supply volume flow rates are less in the group of 2 air supply outlets than those in the group of multiple air supply outlets. When the pressurization fan is located on the top of the stairwell, based on the mass and energy conservation, a simple method is developed to predict the airflow mass flow rates at the outlets. Further, the correlation of the average pressure in the stairwell on the fire floor and the pressurization air supply volume flow rate is developed. The minimum pressurization air supply volume flow rate to obtain smoke free zone and maximum one to avoid the door being too heavy to open during evacuation can be estimated.