In the petrochemical plant, the flammable materials are processed so that there exists risk of fire and/or explosion accidents. They come from the leakage of raw materials or petrochemical products from tubes or tanks. If the leakage occurs inside a reacting furnace with high temperature and pressure, it should lead to serious casualty. To prevent accidents or minimize the damage from these accidents, one should understand the behaviour of flame from a ruptured pipe inside the furnace. In the

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... esent study, a large eddy simulation was conducted to investigate flame propagation characteristics from ruptured reactor tube in a naphtha cracking furnace to understand flame propagation pattern and heat and mass transfer inside the furnace to generate secondary accident. Fire Dynamics Simulator (FDS) was used for the simulation and the number of grid points were around 700,000. The cracking furnace has burners at the bottom part to heat the reactor tubes and combustion gas flows out at the exit located on top of the furnace. Ruptured part was made on the reactor tube with the dimension of 10% of tube diameter and placed near the burner. Leakage flame starts from the ruptured part and evolved to be merged with the fire from burners and generate separated flamelets. Temperature inside the furnace rises higher than the safe temperature of the pipe material, which raises the possibility of successive rupture of neighbour tubes. Unburned hydrocarbons flow out of the vent, which could lead to secondary accidents.