Smoke spread through the elevator shafts of high rise buildings has been numerically investigated using the Fire Dynamics Simulator (FDS), which is a computational fluid dynamics (CFD) program suitable for fire induced heat and mass transfer. A model of a high rise building was developed and a fire was set at the first level. The smoke spread process through the elevator shafts was evaluated. The process can be divided into two phases. In the first phase, the smoke gradually fills the shafts, and the gas temperature and pressure in the shafts are transient. After this phase, the smoke fully fills the shafts, the temperature and pressure in the shaft are almost steady, which suggests that the smoke inflow rate equals the outflow rate. Throughout the process, the spatial distributions of temperature and pressure in the elevator shaft under fire situations were reported. The hot fire product gases entering the shaft causes a stack effect, which transports smoke to the upper levels. A method of partially enclosing the elevator lobbies was also investigated by the CFD simulation. The results were compared with the unenclosed situation, and showed that enclosing lobbies not only increases the time needed for the smoke to fully fill the shafts, but also reduces the temperature and pressure differences in the shafts.

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