1045 McDaid - Pushing the Boundaries

8/9/2019 1045 McDaid - Pushing the Boundaries

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Introduction

Some building classifications in building codes are

more likely and sometimes certain to accommodate

occupants which may be described as “vulnerable”.

Codes attempt to assign stringent requirements forsuch occupancies.

Various other local fire regulations/guidelines may

specifically apply to occupancies housing vulnerable

occupants.


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Using CFD to Examine the Smoke Reservoir Size Limitations

and

Analyse

the Parameters Affecting These Limitations

Mark McDaid

Olsson Fire & Risk, State Manager NSW

MSc (Fire), BSc (Fire), PGDip (Fire), Dip (Fire & Const), Cert (Const)

Chartered Engineer (CEng, MIEI), MAAC(NSW), MSFS, RPEQ(QLD), C10 BPB (NSW)


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Overview of a Smoke Reservoir

History/Background of Smoke Reservoirs

Application of Smoke Reservoirs

Objectives of Smoke Reservoirs

Limitations of Smoke Reservoirs

International Guidelines

Previous Testing and Experimentation Use of Zone/Field Modelling for Smoke Control Designs

Overview of Simulations examined

Validation of CFD Modelling Tools

Sensitivity Studies

Simulation Results Conclusions


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Used to contain and control smokein pre-determined space/volume.

Restrict smoke spread beyondinitial fire affected area

Means of Escape and Fire FightingAccess

Property Damage Limitation


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Reports/Publications Parameters & Objectives

1963 Fire Research Technical Paper No. 7:“Investigations into the flow of hot gases in roofventing”

1964 Paper No. 10: “Design of roof-venting systemsfor single-storey buildings”

Industrial applications being adopted into towncentredevelopments and the studies in the 1970s

◦ Heselden and Hinkley, Smoke Travel in ShoppingMalls Experiments (with Glasgow Fire Brigade) FireResearch Note 832 BRE, 1970.

FPG 1 1972): Fire prevention in towncentreredevelopments, Fire Prevention Guide No. 1

BRE186 1990): Design principles for smokeventilation in enclosed shopping centres

BRE258 1993): Design approach for Smoke Controlin Atrium Buildings

CIBSE Guide E TM19 1995): Relationships for smokecontrol calculations

BRE368 1999): smoke and heat exhaust Design

methodologies for ventilation

Small-scale experiments

Single-storey buildings

Theoretical analysis ofsmoke movement

Examining the smokeflow created by buoyancypressure differences


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“Many regulations are unduly restrictive inthat they are of a type that impose “solutions”rather than “objectives” and are out of date inrelation to technological advances. There is a

danger that compliance takes precedenceover wider safety considerations …”

Cullen Report (Piper Alpha Disaster)


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“In the absence of experimental data, it issuggested that cooling effects should be allowedfor using computational fluid dynamics (CFD),where the area of the reservoir is greater than2000m 2 , and/or the average layer temperature isless than 10K above ambient when calculated by

neglecting cooling ”

“….these limits need not apply to all buildings,and detailed analysis may be undertaken todemonstrate the actual limits for smoke cooling”

CIBSE Guide E, TM19


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Applicable? Not Applicable?

Atria

Shopping Malls Large Warehouses

Large Industrial Buildings

Terminals

Large Retail

Ceiling Heights >5m

Sprinklers?

Offices

Carparks(?) Apartments Hotels Bars Restaurants Nightclubs

Ceiling Heights


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Industrial Buildings

Warehouses

Shopping Malls

Terminal Buildings

Atria


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Statistics on deaths by building category or usage.

A fire in a large building is more likely to be discovered andextinguished before involving the whole building, whencompared to a small (and predominantly cellularised) building.

The proportion of the building destroyed in a large buildingwould, therefore, be expected to be smaller than the proportion

destroyed in a small building.

In retail areas without sprinklers, approx. 60% of fires do notgrow beyond 1.0m2.

80% of reported fires confined to an area not exceeding 20m2 in

area. PD 7974-7


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Limitations Effects

Area◦

2000-2600m2

◦ 3000m2

Length◦ 60m

Temperature◦ 10-15deg C

Prevent excessive HeatLosses to surroundingwalls/ceiling

Psychological Effects onTravel below smoke layer

Prevent loss of buoyancy

Tenability Criteria


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200oC 2.5m 2.5kW/m2 2000-2600(3000) 60m 30m 10-15o

C


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NFPA92 -a clear layer height of at least 1.85m above the highest walkway open tothe atrium for a period of 1.5 times the calculated egress time, or 20 minuteswhichever is greater.

NFPA88A -no point in a basement carpark should be more than 61m (200 ft.)from a vent, i.e. separation distance of 122m apart.

The BCA – certain compartments exceeding 2000m2, automatic smoke exhaustsystems shall be employed.◦ Tenable conditions at least 2m above the floor level and smoke reservoirs be limited in size

to 2000m

2

and 60m in length (for walkways and malls).

The Singapore Fire Code -compartment exceeding 5000m2, with the samebuoyancy and “hot” layer tenability criteria.

TGD-B (Ireland) - “large undivided and windowless spaces” such as warehouses,industrial buildings, or shops, exceeding 4,000m2 or volume exceeds 20,000m3.

IBC - Where ESFR sprinklers are employed to a Frozen Food Storage Warehouse,there is no requirement for “Draft” curtains.


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Glasgow Fire Brigade Tunnel Tests

VESDA Systems

Atria in Spain, China, etc

CFD Studies in Australia, Hong Kong.

Hot Smoke Tests in Hong Kong, Brussels, Australia, China.

Hanger Studies in Hawaii & Keflavik

NIST, UL & FM Studies on Draft Curtains & Sprinklers


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+ 2 no. Validations Simulations+ 9 no. Sensitivity Studies


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Scope Graphical Results

Experimental Results

0.2m Grid Size Results

0.4m Grid Size Results

Positioning of devices

Grid size and devicelocation default

% Error including griddependant device locations


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Run 01, 4000m2, 10MW,32m x 32m x 5m

Run 13, 1000m2, 1MW,32m x 32m x 10m

Run 61, 1000m2, 2.5MW,

32m x 32m x 10m

> Effect of Grid Resolution

> Effect of Fire Size

> Size Geometry


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Smoke Detection◦ To activate vents

Slice Files◦ At 2.5m above floor◦ Under ceiling◦ at mid-point between fire and

boundary walls (long andshort)

Layer Height◦ Centreline of domain◦ Along outer perimeters

Long and short

Approx 0.5-1m from wall

Thermocouples◦ Sited along centreline◦ Spaced at 10m intervals◦ At 2.5m and under ceiling


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Numerical Input Graphical Results


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Temperatures at 2.5m level

Temperatures at under ceiling level

Average Temperatures between two points


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Aspect Ratios◦ 1:1, 1:2 and 1:4

Devices adjusted toaccommodate change indomain shape

Temperatures along eachthermocouple interval showsno appreciable effect withchange in aspect ratio


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Fire Size

Ceiling Height


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Wide Spill Plume at Opening

Ceiling Jet Formation

Descent at outermostboundary regions

Stabilisation of smoke layer

125m 15m32m


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Initial disturbance of air in front of ceiling jet by incoming mechanical inlet ventilation.

Ceiling jet eventually overcomes inlet flows and forces smoke across upper region of ceiling and

mechanical inlet air to flow in the lower regions. Fires examined were very large (20MW and 60MW

with fast and ultrafast fire growth rates)

This pushing of the upper layer and resulting lower inlet air causes a more defined interface of

upper and lower layers, which could assist the buoyancy of the smoke layer in a reservoir

Concern would arise in smaller compartments, especially those with smaller fires with a slow-

moderate fire growth rate.


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Tilt in smoke plume

Cooler temperaturesbelow vents

Hotter temperaturesbelow ceiling with no

vents

No appreciable effecton layer height

No appreciable effecton reservoir


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Normal SHEVs Calcs

Adjusted SHEVs Calcs◦ Heat Transfer Coefficients

Effect of Reservoir Area

(i.e. surface area incontact with smoke layer)

Only marginal differencein temperatures,

increasing slighting withreservoir size


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Majority of simulations resulted in smoke layer height lower thanSHEVs design

Effects of Aspect Ratio

Measurement of Smoke Layer Height in FDS


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Temperatures

◦


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Thermocouple readings

◦

At 2.5m and under ceiling◦ each 10m interval

15deg C above ambienttemperature of 15oC.◦ Does this actually mean

buoyancy?

Effect of Aspect Ratio

Effect of Fire Size

Impact of total SimulationTime (Steady Stateformation)


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Final Reservoir Size dependant on full designteam and stakeholder agreement on elements

such as:◦ Availability of Inlet Air;◦ Possible extended smoke damage to fabric;◦ Possible smoke/fire damage to property over

extended area;◦ Requirements during MOE Phase (ASET/RSET) ‘v’ FB

Access, Search & Rescue Phase (FBIM)◦ Type and Occupancy of Building◦ Actual Physical geometry (including possible

stagnant zones)


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“Notional” Reservoirs?◦ Jet Fan design technology◦ Similar to carpark zoned smoke clearance systems

◦ “The impulse fans are carefully positioned to direct the air flow towards themain extract fan intake points…providing smoke-free zones within the carpark….

◦ Large car parks are likely to be separated into zones (usually not morethan 2000 m 2 ), each fitted with at least two impulse fans. Activation of afire alarm within a specified zone will activate the fans, so that smoke is

directed in a controlled manner towards the extract point…should allowthe Fire Service access to a point within 10m of the fire base and keep allother zones clear of smoke .” CIBSE Guide E, BS 7346-7


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Parameters that DO affect the formation,development and stability of reservoir, or require

consideration in design of smoke control:◦ Fire Size

Growth Rate;

Perimeter;

Area;

◦ Area (dependant on fire size);◦ Height (dependant on fire size and presence of spill plume);◦ Aspect Ratio (slightly, but ASET/RSET considerations);◦ Clear Layer Height (ground or upper floors);◦ Fire Location;

◦ Wind??◦ Boundary Materials??


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Thank You, Questions…?

Master of Science Degree (Fire)

Bachelor of Science Degree (Fire)

Post Graduate Diploma (Fire)

Diploma (Fire & Construction)

Certificate (Construction)

MARK MCDAID | STATE MANAGER NSW

[email protected] | + 61 (0) 499 773 150 | www.olssonfire.com.au

Chartered Engineer (CEng)

Member Institute of Engineers Ireland

Member of Association of Accredited Certifiers (NSW)

Member of the Society of Fire Safety

Registered Professional Engineer of Queensland (QLD)

Building Professionals Board Accredited Fire Safety Engineer C10 (NSW)
mailto:[email protected]://www.olssonfire.com.au/http://www.olssonfire.com.au/mailto:[email protected]

1045 McDaid - Pushing the Boundaries

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