Temperature calculations in fire exposed structures with the
use of adiabatic surface temperatures

Abstract: Fire safety engineering is offering more and more advanced methods
including software for fire dynamic calculations. This thesis presents a
method for using the results obtained by fire modelling using the code FDS
(Fire Dynamic Simulator) as input to FEM calculations for predicting
temperature in fire exposed structures.

Prof. Wickström of SP - Swedish National Testing and Research Institute has
introduced the concept of adiabatic surface temperature (AST) for
calculating heat transfer to fire exposed structures. The AST is defined as
the temperature of a surface which cannot absorb any energy.

It may be calculated at any surface in the fire simulation software used in
this thesis. The aim in this work is to see if the AST at the surface of a
beam in one simulation gives satisfactory temperature result when used in a
temperature calculation of beams with different dimensions.

The work is divided into four parts. The first part is to validate the AST
as a means for calculations of temperature in fire exposed structures.
Using the AST in the calculations presented an almost perfect agreement
with the temperature obtained directly from the CFD code.

The second part is a comparison made to investigate whether AST calculated
by FDS could be used in a FEM simulation to predict heat transfer to a fire
exposed structure.

As the third part some different simulations are run to compare the FEM
temperature calculations of beams with AST from different simulations.

The result showed that AST obtained in one fire scenario can be used for
different beam sections. It is advised to use the technique with care since
certain circumstances such as choice of convection coefficients and flame
height can influence the results.

The final part is to make an experimentally verifiable set up. This is made
to be able to compare simulated results with tests to be made at SP and at
ULC (Underwriters’ Laboratories of Canada).