fire scenario - hae.ithae.it/.../10/nigro-ferrari-filippo-boundary-conditions-sfpe2016.pdf ·...

FIRE SCENARIOInfluence of material of

boundary condition on results

Luciano Nigro – Andrea Ferrari – Elisabetta Filippo

Hughes Associates Europe srl – Jensen Hughes EU Alliance - [email protected]

HUGHES ASSOCIATES EUROPE, srl

FIRE SCIENCE & ENGINEERING

INDUSTRIAL LOSS CONTROL & eng Analisi e Controllo dei Rischi Industriali

& e.

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.

Fire Safety Engineering

Scenarios and boundary condition23-25 May 2016 – Warsaw, Poland 3

Developing of fire scenario

Events description represents the fire scenario. The events aredescribed with three main aspects:

1. Characterization of the fire – HRR curve, yield of soot or fireproducts;

2. Boundary condition of the internal or external ambient;

3. Characterization of occupant.



Developing of fire scenario 2The definition of boundary condition of the domain is the way thebuilding characteristics are an input for the model.

• In particular:i. Dimension/characteristic

ii. Natural/mechanical ventilation

iii. Thermodynamic characteristics of the enclosure

iv. Detection system

v. Alarm system

vi. Protection system



Developing of fire scenario 3

The focus of the study being presented today is:

Influence of physical characteristic of domain on results ofanalysis

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 thecharacteristics of materials that will be used toactually “make” the building are often not defined atthe time when the performance based analysis isconducted.

It is important to understandhow the boundary conditionsinfluence the results of thequantitative 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 modelReal 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 curveFour different typical fires in a hotel atrium:



• 0,5 MW • Laptop

• Christmas tree

• 1,0 MW • Sofa

• Metal office storage units clear aisle

• 2,0 MW • 12 chairs in 2 stacks

• 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]




• 1,0 MW • Sofa

• Metal office storage units clear aisle


T. Stainhaus, W. Jahn, Laboratory Experiments and their applicability,– The Dalmarnock Fire tests: Experiments and Modelling – University of Edinburgh 2007




• 2,0 MW • 12 chairs in 2 stacks

• Kiosk





• 9,0 MW • Flashover



The analysis is on steady state condition.

The HRR curve is constant over a period of simulation




Input parameters – Boundary Condition

The definition of material of ceiling is the characterization ofboundary condition.

Floor and external walls are in adiabatic condition.



Convective thermal exchange ispossible through the ceiling only.

Input parameters – Boundary ConditionCeiling boundary conditions are:



2. Glass

• density 3100 kg/m3

• specific heat 0,84 kJ/kg°K

• conductivity 0,064 W/m°K

• thickness 4 cm

3. Concrete

• density 2000 kg/m3

• specific heat 0,88 kJ/kg°K

• conductivity 2 W/m°K

• thickness 14 cm

Input parameters – Boundary ConditionTwo 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.


Scenarios and boundary condition2623-25 May 2016 – Warsaw, Poland

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.


Scenarios and boundary condition2623-25 May 2016 – Warsaw, Poland

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)

The first and most important parameter that was investigated with thisstudy is the temperature.

The variation of the gas temperature of the smoke layer is measured byusing two different detectors. Ceiling gas temperature is measured byusing detectors of temperature called thermocouples.

Another detector is used to calculate the gas temperature. The name ofthis detector is slice.



Investigated parameters 1/2

The second significant parameter, usually investigated when performingthis kind of studies, is the visibility, correlated to the soot produced by thefire.

It is possible to say that the variations in the visibility, as a consequenceof the variations of the boundary conditions, are negligible, whenchanging the different ceiling characteristics.

The visibility will not be further mentioned in the study.



Investigated parameters 2/2



Output

Table of scenario A – B – C – D





Results Scenario A – Fire 0,5 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 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

• The results show how the characterization of material finishing influence thegas temperature.

• The variation of gas temperature value is more significant when the heatrelease rate of the fire is greater.

• The adiabatic condition for the ceiling is conservative, but it is important todefine the boundary conditions, in particular the materials of which shell orouter walls are constituted, not to neglect the thermal exchange with theexternal environment.



Conclusion

• It is important to define the boundary conditions not to neglect thethermal exchange with the external environment.

• The detailed characterization of the material has little influence. Themain temperatures of the scenarios with glass ceiling are not sodifferent when compared to the main temperature of the scenarios withconcrete ceiling.



Conclusion

• It is very important to know if there are openings within the domain orduring the evolution of the fire scenario, because the temperature ofsmoke layer changes dramatically when the internal domain andexternal environment are connected.

• The typical example is the breaking of the glasses



Conclusion

• 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 FireDynamics 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 FireDynamics 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.



References

fire scenario - hae.ithae.it/.../10/nigro-ferrari-filippo-boundary-conditions-sfpe2016.pdf ·...

Documents