Experimental and Numerical Simulation Study on Multilayer Cable Trays Fire Under Mechanically Ventilated Conditions

The performance-based standard for fire protection was first proposed for light water reactor electric generating plants in NFPA-805. The zone model is considered as a main option for fire safety analysis in nuclear power plant. Cable fire is one of the most common hazards in nuclear power plant. The structure of multilayer cable trays fire is a challenge for simulation by zone model. At the same time, the mechanical ventilation has significant effects on the fire process. Therefore, the focus of this paper is to investigate the reliability of zone model software simulating the multilayer cable trays fire under mechanical ventilation. Fire experiments of four-layer cable trays were conducted in a confined room with mechanical ventilation. The mass loss rate of cable trays, the ceiling jet temperature, and the vertical temperature distribution in the room were recorded during the cable burning. According to the measured vertical temperature profile under mechanical ventilation, it is found that the fire room can be divided into upper hot layer and lower cool layer, which is conformed to the basic assumption for two-zone model. Therefore, the zone fire model CFAST (Consolidated Model of Fire Growth and Smoke Transport), was used to simulate the multilayer cable trays fire under mechanical ventilation. Comparing the predicted ceiling jet and upper layer temperatures with experimental data, it is shown that CFAST has good prediction on multilayer cable trays fire under mechanical ventilation. By setting each layer of cable tray as one fire source, CFAST can catch the burning characteristics of multiple-layer cable tray fire.