Influence of fire power and window position on smoke movement mechanisms and temperature distribution in an emergency staircase

• Smoke movement experiments were conducted in a scaled emergency staircase.
• Stack effect and turbulent mixing act at different stages.
• Smoke movement mechanism effects vertical temperature distribution in staircases.

A set of experiments was conducted to study the mechanisms of smoke movement in emergency staircase by varying the height of opened window in a scaled building model with 12 floors. Stack effect and turbulent mixing are found to be primarily responsible for the vertical movement of hot smoke in the emergency staircase. It is found that the velocity of hot smoke movement has two quasi-steady state stages. The turbulent mixing plays a significant role in smoke movement at the first stage while the stack effect becomes dominant at the second stage. The mechanisms of smoke movement have great effects on the vertical temperature distribution in the staircase. Temperature attenuation coefficient β in the turbulent mixing stage is greater than that in the stack effect stage. Moreover, heat release rate of fire source and height of opened window significantly affect the duration of stage and temperature attenuation coefficient β. The results could be beneficial for engineers to design the smoke control system in the emergency staircase in high-rise buildings.