A Two-zone fire growth and smoke movement model for multi-compartment buildings

A fire growth and smoke movement model for a multi-compartment building has been developed at the National Research Council of Canada. This development is primarily intended to help evaluate the risk from fires in buildings. This paper presents the related physical models, numerical methods, and some verification examples. The 2-zone ordinary differential equations (ODEs) are derived for the compartments with fire or smoke. The four independent variables for one compartment are selected as pressure, enthalpy of upper layer, and mass of upper and lower layers. The implemented fire sub-models are introduced, including combustion, fluid flow and heat transfer models. For each compartment without smoke or fire, a non-linear algebraic equation based on mass conservation is used instead of the ODEs. The numerical solution of the governing equations is obtained using a room by room iteration method. In this algorithm, an existing ODE solver, LSODA, has been modified and used to solve the stiff ODEs, and the Steffensen Acceleration Method is used to solve the algebraic equations. Experimental data for single and two-compartment fire tests are compared to the predictions of the model. The comparison shows favourable results, especially for the upper layer gas temperature, interface height, and vent flow rate. NOMENCLATURE A Area (m 2) CV A Area of the ceiling vent (m 2) A DV Area of part of a door/window type vent (m 2) A int Area of interface (m 2) A w Surface area of a wall, ceiling or floor (m 2) C Specific heat (J/kgK) CV C Coefficient of ceiling vent flow DV C Coefficient of door/window type vent flow C LOL Lower oxygen limiting coefficient C P , C V Specific heat at constant pressure or volume (J/kgK) C soot Volume fraction of soot in smoke layer E Internal energy (J) F kj Configuration factor from surface k to surface j for radiation FO S Stoichiometric fuel to oxygen ratio 1 FO P Fuel to oxygen ratio in fire plume H Enthalpy (J) si H Rate of net enthalpy gain of layer i by mass flow across its boundary (W) h Convection heat transfer coefficient (W/m 2 K) h IC , h OC Convection heat transfer coefficients of the inside and outside surface of a wall, ceiling or floor (W/m 2 K) (∆H) F Heat of combustion per unit kilogram fuel (J/kg) (∆H) O Heat of combustion per unit kilogram oxygen (J/kg) K Conductivity (W/mK) …