Experimental and theoretical studies on the heat extraction and smoke transportation via a board-coupled ceiling extraction system in tunnel fires

Understanding the interrelationship of heat and mass transfer during the extraction process is the key to developing better smoke extraction technologies in tunnel fires. The traditional method always tries to avoid the plug-holing phenomenon by limiting the exhaust rates of the vent, leading to the low performance of smoke control in tunnels. Previous research has validated that the plug-holing can be alleviated by installing a board beneath the vent. This study aims to explore the interrelationship of heat extraction and smoke transportation via a board-coupled ceiling extraction system (BCES) in tunnel fires. A total of 40 experiments were conducted in a 1/20 scale model tunnel, and the influence of the board location and the exhaust rate were investigated. Experimental results revealed that the BCES is efficient, achieving a maximum improvement of 48.2% in smoke heat extraction compared to the traditional ceiling extraction system. Besides that, the ceiling temperature attenuation was found to be related to the smoke extraction performance. Moreover, a model for predicting the smoke propagation length was proposed. These findings can provide positive insights into optimizing tunnel ventilation strategies and smoke control methods.