Abstract: A 17- story numerical high- rise building model was built by the FDS. Considering the small opening flow of slit, coupled with HVAC model based on open flow theory, the process of smoke spreading through elevator shaft in high- rise building was researched and the rule of fire smoke spread induced by chimney effect in high- rise building was obtained. The results indicated that the fire at lower floors would heat the air significantly in the building which leads to chimney effect,and a neutral plane exists at certain height of the building.By comparing the results between simulation and the oretical calculation,the simulated mass flow rate is about 1.5 times of the calculation.This is because the HVAC model doesn't count the effect of vent flow loss. By further modification,better simulation results can be obtained by taking the opening loss coefficient K as 3.56.

Key words: high rise building, fire, slit flow, chimney effect, elevator shaft