Encyclopaedia Index

TITLE : Thermal radiation in a compartment fire

BY : Dr S V Zhubrin, CHAM Ltd

DATE : November, 2000

FOR : Demonstration case for V3.3.3.


An IMMERSOL application is presented aimed at the demonstration of the method for the simulation of fire in a 3D enclosure when the convection, chemical reactions, thermal radiation and conjugate heat transfer in the internal structures have to be considered simultaneously.


The demonstration case considered consists of rectangular room with an internal wall of finite thickness and door opening at the front end of the room. The dimensions of the room are those of the Test Compartment used by Swedish National Testing Institute for calibration experiments.

It is supposed that a fuel (methane) leaks from the communication system and enters the room vertically upwards through an aperture located at the floor in the bottom of the rear wall. In the vicinity of fuel leak, there is a vent supplying the air for heating and ventilation purposes.

The fuel is ignited on entry and steady combustion is in progress producing the high temperarture combustion products. Their movement is greatly influenced by buoyancy with the salient features as follows

The task is to calculate the temperatures of the internal wall structure and combustion gases along with all related field distributions.


Conservation equations

The independent variables of the problem are the three components of cartesian coordinate system, namely X, Y and Z.

The main dependent (solved for) variables are:

Turbulence and combustion models

The K-epsilon model, KEMODL, closed by wall functions is used to calculate the distribution of turbulence energy and its dissipation rate from which the turbulence viscosity is deduced.

Combustion is treated as a single-step irreversible diffusion-controlled chemical reaction with a infinitely fast rate between fuel and oxygen. The gas composition and its enthalpy are related to the mixture fraction according to the Simple Chemical Reaction Scheme, SCRS, concept.

Model of radiative transfer

The IMMERSOL model is used to simulate the distribution of T3 within the space filled with combustion gases and solid blocks. From the temperature fields the radiant heat fluxes, QRX, QRY and QRZ, W/m^2, are calculated and used as the heat sources for H1 in iterative manner.

Properties and auxiliary relations

The gas density is computed from the local pressures, gas temperatures and local mixture molecular masses.

The specific enthalpies are related to gas temperatures, fuel mass fraction and the heat of combustion.


The plots show the distribution of temperatures, velocities and other related fields within the furnace and loads.

Pictures are as follows :


All model settings have been made in VR-Editor of PHOENICS 3.3.3.

The relevant Q1 file can be inspected by clicking here.