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Introduction
Fire Behaviour
Norminal Fires
Time Equivalence
Parametric Fires
Localised Fires
External Window Fires
Zone Models
CFD

Fire Modelling

Fire model
Norminal fires
Time equivalences
Compartment fires
Zone Models
CFD / field models
Parametric
Localised
One-zone
Two-zone
Complexity
Simple
Intermediate
Advanced
Fire Behaviour
Post-flashover fires
Pre-flashover fires
Post-flashover fires
Pre-flashover / localised fires
Complete temperature-time relationships
Temperature distribution
Uniform in whole compartment
Non-uniform along plume
Uniform
Uniform in each layer
Time and space dependent
Input parameters
Fire type
No physical parameters
Fire load
Ventilation conditions
Thermal properties of boundary
Compartment size
Fire load & size
Height of ceiling
Fire load
Ventilation conditions
Thermal properties of boundary
Compartment size
Detailed input for heat & mass balance of the system
Detailed input for solving the fundamental equations of the fluid flow
Design tools
BSEN1991-1-2
COMPF2
OZone
SFIRE-4
CCFM
CFAST
OZone
FDS
SMARTFIRE
SOFIE
PD7974-1
PD7974-1
Simple equations for hand calculations
Spreadsheet
Simple equations
Computer models


Figure 1 Options for fire modelling in compartments

Generally, the factors influencing the severity of a compartment fire can be summarised as follows:

  • Fire load type, density and distribution
  • Combustion behaviour of fire load
  • Compartment size and geometry
  • Ventilation conditions of compartment
  • Thermal properties of compartment boundary

The occurrence of flashover in a compartment fire imposes a transition to the fire development. Therefore, many fire models are classified under pre- or post-flashover, except for the computational fluid dynamic (CFD) models, which cover both phases.

There are a number of options available to calculate the fire severity as follows:

The level of complexity increases from simple fire models to field models as shown in Figure 1. Basically, the first four fire models can be considered as simple models, whereas the zone and CFD models are advanced models. The input parameters for each of these models are quite different with the advanced models requiring very detailed input data and simple models requiring little input.

In the simple fire models, the gas temperature of a compartment is taken as uniform and represented by a temperature-time relationship. The smoke movement and fire spread cannot be considered. They are more suitable for modelling post-flashover fires.

The advanced fire models are normally theoretical computer models that simulate the heat and mass transfer process associated with a compartment fire. They can predict compartment gas temperatures in much more detail. The smoke movement and fire spread may be taken into account. As reflected in their names, a zone model may present the gas temperature into single or different zones, whereas a CFD model provides a space/field dependent gas temperatures distribution.

Each of the fire models will be discussed in the section.

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