A NEW MODEL FOR ESTIMATING NEUTRAL PLANE IN FIRE SITUATION

摘要

A new model is proposed for predicting the location of neutral plane in fire situation. The shaft space is divided into two-zones (fire zone and inner space of shaft) in the model. In each zone, the temperature is assumed uniform. For validating the proposed two-zone model, a computational fluid dynamics (CFD) code, which is named FDS based on large eddy simulation (LES) developed by the Building and Fire Research Laboratory,National Institute of Standards and Technology, USA, is applied. It is shown that the location of neutral plane is above the mid-height of building, and the simulation results are uniform with the two-zone model approximately.Under fuel-control condition, the value of neutral plane height as a percentage of ceiling height is independent of the building height, the HRR of fire, the dimension of ventilation, the dimension of fire zone, and the mode of ventilation. Its value is found between 0.5 and 0.6.