Abstract:
This study presents a numerical simulation, using FLUENT ver. 6.3, for a point supply ventilation system (PSVS) of full-scale road tunnel. The conducted simulations are used to evaluate the effectiveness of the ventilation system by analyzing the numerical predictions of temperature, visibility and CO concentration fields for different sizes of tunnel fire namely; 5, 10, 20 and 40 MW. Numerical simulations predicted the overall flow field and gave valuable estimates of the temperatures, visibility and CO distribution throughout the tunnel. The hazard areas are determined according to environmental limitations established by National Fire Protection Association (NFPA) of United States. A comparison of PSVS and point exhaust ventilation system (PEVS) is also carried out to predict the hazard areas in the tunnel for both systems. The PEVS accomplishes NFPA limitations almost for all fire sizes. While, PSVS fails to do at fire sizes higher than 5 MW. These conclusions are true for the range of fire sizes and tunnel configuration considered in this study. The results of the study suggest the use of multiple openings at different locations on the tunnel ceiling and according to the fire location; one or more opening (the closest to the fire location) can be chosen to operate.