presentation

Fire Scenario
Influence of Material of
Boundary Condition on
Results
HUGHES ASSOCIATES EUROPE, srl
FIRE SCIENCE & ENGINEERING
Luciano Nigro – Andrea Ferrari – Elisabetta Filippo
Hughes Associates Europe srl – Jensen Hughes EU Alliance - [email protected]
Performance-Based Design Process
SFPE Engineering Guide to Performance-Based Fire Protection
defines the main steps of design process:
1. Defining project scope: identifying goals.
2. Developing fire scenarios: with determinist and statistic
analysis
3. Developing trial designs: quantifying design fire curves,
evaluating trial designs.
Developing of Fire Scenario
Events description represents the fire scenario. The events are
described with three main aspects:
1. Characterization of the fire – HRR curve, yield of soot or fire
products;
2. Boundary condition of the internal or external ambient;
3. Characterization of occupant.
Developing of Fire Scenario 2
The definition of boundary condition of the domain is the way the
building characteristics are an input for the model.
• In particular:
i.
ii.
iii.
iv.
v.
vi.
Dimension/characteristic
Natural/mechanical ventilation
Thermodynamic characteristics of the enclosure
Detection system
Alarm system
Protection system
Developing of Fire Scenario 3
The focus of the study being presented today is:
 Influence of physical characteristic of domain on results of
analysis
Namely:
Influence of thermal conductivity
Influence of density and transmittance
Why the Boundary Conditions Are a Problem
Main steps for
characterization of fire in a
fire model are:
• Chemical composition of
material;
• Heat release rate curve;
• Yield of soot or fire
products;
• Area of fire.
In a new building project, the type and/or the
characteristics of materials that will be used to
actually “make” the building are often not defined at
the time when the performance based analysis is
conducted.
It is important to understand
how the boundary conditions
influence the results of the
quantitative analysis.
Object of the Study
• To measure the effect of different boundary conditions on the
results that can be achieved by the model when applied to a
simple case study
• Elisabetta will show the case study and the results that were
obtained.
The Model
Real geometry of hotel
atrium
• Rectangular plane 13,2 x
18,8 m
• Prismatic roof: maximum
high 6,4m
• Open door 1,2 x 2,2 m
The Model
Input Parameters – HRR Curve
Four different typical fires in a hotel atrium:
• Laptop
• 0,5 MW
• Christmas tree
• Sofa
• 1,0 MW
• Metal office storage units clear aisle
• 12 chairs in 2 stacks
• 2,0 MW
• Kiosk
• 9,0 MW
• Flashover
Input Parameters – HRR Curve
• 0,5 MW
• Laptop
• Christmas tree
[Rif: Morgan J. Hurley, The SFPE
Handbook of Fire Protection
Engineering, Fifth Edition, 2015]
Input Parameters – HRR Curve
• 1,0 MW
• Sofa
• Metal office storage units clear aisle
[Rif: Morgan J. Hurley, The SFPE
Handbook of Fire Protection
Engineering, Fifth Edition, 2015]
T. Stainhaus, W. Jahn, Laboratory Experiments and their applicability,– The
Dalmarnock Fire tests: Experiments and Modelling – University of Edinburgh 2007
Input Parameters – HRR Curve
• 2,0 MW
• 12 chairs in 2 stacks
• Kiosk
[Rif: Morgan J. Hurley, The SFPE Handbook of Fire
Protection Engineering, Fifth Edition, 2015]
Input Parameters – HRR Curve
• 9,0 MW
• Flashover
[Rif: Morgan J. Hurley, The SFPE
Handbook of Fire Protection
Engineering, Fifth Edition, 2015]
Input Parameters – HRR Curve
The analysis is on steady state condition.
The HRR curve is constant over a period of simulation
[Rif: Morgan J.
Hurley, The SFPE
Handbook of Fire
Protection
Engineering, Fifth
Edition, 2015]
Input Parameters – Boundary Condition
The definition of material of ceiling is the characterization of
boundary condition.
Floor and external walls are in adiabatic condition.
Convective thermal exchange
possible through the ceiling only.
is
Input Parameters – Boundary Condition
Ceiling boundary conditions are:
2. Glass
•
•
•
•
density
specific heat
conductivity
thickness
3100 kg/m3
0,84 kJ/kg°K
0,064 W/m°K
4 cm
3. Concrete
•
•
•
•
density
specific heat
conductivity
thickness
2000 kg/m3
0,88 kJ/kg°K
2 W/m°K
14 cm
Input Parameters – Boundary Condition
Two basic cases are considered in order to have a comparison with
conditions that are generally accepted for the boundary conditions:
Case 1:
• adiabatic boundary condition:
• Ideal condition, not real. All materials of the boundary are adiabatic.
The whole heat is kept inside the domain because there is no heat
transfer with the external ambient.
Input Parameters – Boundary Condition
Second case:
• adiabatic boundary condition with opening on ceiling:
• All materials of boundary are adiabatic but there are openings
on the ceiling, which may be: the permanent openings,
occasionally open windows, natural smoke and heat exhaust
ventilators, or even a glass window that has crashed after a few
minutes because of the high temperature.
Basic Case 1 – Adiabatic Boundary Condition
Adiabatic external
walls: no heat
transfer
internal/external
ambient.
Basic Case 2 – Adiabatic Boundary Condition
with Opening on Ceiling
Openings
2% of total area
(4,4 m2)
Investigated Parameters 1/2
The first and most important parameter that was investigated with this
study is the temperature.
The variation of the gas temperature of the smoke layer is measured by
using two different detectors. Ceiling gas temperature is measured by
using detectors of temperature called thermocouples.
Another detector is used to calculate the gas temperature. The name of
this detector is slice.
Investigated Parameters 2/2
The second significant parameter, usually investigated when performing
this kind of studies, is the visibility, correlated to the soot produced by the
fire.
It is possible to say that the variations in the visibility, as a consequence
of the variations of the boundary conditions, are negligible, when
changing the different ceiling characteristics.
The visibility will not be further mentioned in the study.
Output
Output
Table of Scenario A – B – C – D
Results Scenario A – Fire 0,5 MW – Changing
Boundary Condition – Time 500 Seconds
Results Scenario A – Fire 0,5 MW – Changing
Boundary Condition – Time 500 Seconds
Fire Safety Engineering
Scenarios and boundary condition
Results Scenario B – Fire 1,0 MW – Changing
Boundary Condition – Time 500 Seconds
Results Scenario B – Fire 1,0 MW – Changing
Boundary Condition – Time 500 Seconds
Results Scenario C – Fire 2,0 MW – Changing
Boundary Condition – Time 500 Seconds
Results Scenario C – Fire 2,0 MW – Changing
Boundary Condition – Time 500 Seconds
Fire Safety Engineering
Scenarios and boundary condition
Results Scenario D – Fire 9,0 MW – Changing
Boundary Condition – Time 500 Seconds
Results Scenario D – Fire 9,0 MW – Changing
Boundary Condition – Time 500 Seconds
Table of Scenario Concrete
Results Scenario Concrete – Fire 2,0 MW – Changing
Boundary Condition – Time 500 Seconds
Results Scenario Concrete – Fire 2,0 MW – Changing
Boundary Condition – Time 500 Seconds
Conclusion
• The results show how the characterization of material finishing influence the
gas temperature.
• The variation of gas temperature value is more significant when the heat
release rate of the fire is greater.
• The adiabatic condition for the ceiling is conservative, but it is important to
define the boundary conditions, in particular the materials of which shell or
outer walls are constituted, not to neglect the thermal exchange with the
external environment.
Conclusion
• It is important to define the boundary conditions not to neglect the
thermal exchange with the external environment.
• The detailed characterization of the material has little influence. The
main temperatures of the scenarios with glass ceiling are not so
different when compared to the main temperature of the scenarios with
concrete ceiling.
Conclusion
• It is very important to know if there are openings within the domain or
during the evolution of the fire scenario, because the temperature of
smoke layer changes dramatically when the internal domain and
external environment are connected.
• The typical example is the breaking of the glasses
References
•
SFPE Engineering Guide to Performance-Based Fire Protection, National Fire Protection Association, Quincy, MA (2006);
•
B. McCaffrey, “Flame Height,” The SFPE Handbook of Fire Protection Engineering, 2nd ed., Society of Fire Protection Engineers and National Fire Protection
Association, Quincy, MA, pp. 2-1–28 (1995);
•
P.H. Thomas, “The Size of Flames from Natural Fires,” Ninth Symposium on Combustion, Combustion Institute, Pittsburgh, PA, pp. 844–859 (1963);
•
Morgan J. Hurley, The SFPE Handbook of Fire Protection Engineering, Fifth Edition, 2015;
•
McGrattan K., Klein B., Hostikka S., Floyd J., NIST Special Publication 1019-5, Fire Dynamics Simulator (Version 6) User’s Guide, NIST, Nov. 2013;
•
McGrattan K., Hostikka S., Floyd J., NIST Special Publication 1018-5, Fire Dynamics Simulator (Version 5) Technical Reference Guide, Volume 1: Mathematical Model,
NIST, Oct. 2008;
•
Kevin McGrattan, Simo Hostikka, Randall McDermott, Jason Floyd, Craig Weinschenk, Kristopher Overholt. NIST Special Publication 1018-2 Sixth Edition Fire
Dynamics Simulator Technical Reference Guide Volume 2: Verification, November 2015;
•
Kevin McGrattan, Simo Hostikka, Randall McDermott, Jason Floyd, Craig Weinschenk, Kristopher Overholt. NIST Special Publication 1018-2 Sixth Edition Fire
Dynamics Simulator Technical Reference Guide Volume 2: Validation, November 2015;
•
Antonio La Malfa, Prevenzione incendi Approccio ingegneristico alla sicurezza antincendio 5a Edizione, Settembre 2007;
•
Kai Kang, Assessment of a model development for window glass breakage due to fire exposure in a filed model, Fire Safety Journal, October 2008;
•
U. Wickstrom, D. Duthinh, K. McGrattan, Adiabatic surface temperature for calculating heat transfer to fire exposed structures;
•
EUROCODE 1 – Actions on structures - Part 1-1: General actions - Densities, self-weight, imposed loads for buildings, 2004 – Incorporating corrigendum March 2013.