A Simplified Model to Predict Smoke Movement in Vertical Shafts During a High-Rise Structural Fire

Abstract

A simplified two-layered zonal model coupled with a network model is developed to predict the smoke movement in vertical shafts such as stairwells and elevator shafts during a high-rise fire. The main governing equations of smoke movement consist of conservation equations of mass and energy, convective heat transfer, radiative heat transfer and momentum transfer. It is essential to consider the temperature distribution in the vertical shaft, the buoyancy-induced flow and heat transfer results of strong upward forces known as “stack effect”. This model is aiming at predicting the smoke movement in order to develop a successful fire protection plan and improve the occupants’ safety in the event of fire. The model analysis yields three main measures to improve safety on the upper floors, including increasing the vent size on the top of the elevator shaft, pressurizing the floors except the fire floor and reducing the gaps around elevators. These measures can also raise the location of neutral pressure plane (NPP) which is critical for upper floor smoke controls. Ultimately, the location of NPP can be raised above the total height of structure, thus the smoke will be kept inside and exhausted out of the elevator shaft.

Keywords

• Smoke movement
• Stack effects
• Elevator shafts
• Neutral Pressure Plane
• Pressurizing floors
• High-rise fire