Effect of chimney design on flow induced by a heat source in a room

Fire induced airflow in a compartment is numerically investigated. The fire is modeled by a volumetric heat source centrally located in the fire room. Natural ventilation is provided by a door that plays the role of fresh air entrance and hot gas exhaust. Numerical simulations are carried out using the standard k–e turbulence model coupled with a near wall boundary approach namely the “enhanced wall treatment”. The first part of this study discusses the validity of the Boussinesq approximations to deal with high density variations effects. Results obtained by this assumption together with those found with the ideal gas theory were compared with available experimental data. A better agreement in the temperature prediction was perceived with the second approach (ideal gas) especially in the regions presenting high temperature gradient as the heat source areas. This assumption is therefore adopted in the second part of this work which includes an analysis of the ventilation parameters effects on the airflow pattern inside the fire room. Different geometric parameters as the height, the cross section, the shape and the location of a chimney were investigated. Results of this parametric study have enabled to determine the optimum chimney characteristics ensuring the best ventilation of the fire room studied.