Smoke control research

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https://doi.org/10.4224/20373747

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Smoke control research

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Smoke

Control Research

Gary Lougheed

Fire Research Program

National Research Council

Short Course Smoke Control and Smoke Management May 26 ‐ 28, 2010 Carleton University, Ottawa, Ontario

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Outline

• Sprinklers and smoke control.

– Office buildings. – Mercantile.

• Atrium smoke management.

– Exhaust effectiveness – plugholing. – Balcony spill plumes.

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Outline

• Other smoke control research.

– Duct detection. – Cables in plenums. – Smoke movement algorithm. – Secondary suites.

• Future research.

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Sprinklers and Smoke Control

• Smoke control.

– An engineered system that includes all methods that can be used singly or in combination to modify smoke movement.

• Reduce production of smoke

– Automatic sprinklers, non‐combustible construction materials.

• Mechanical systems.

– Produce pressure differences, exhaust smoke,

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Sprinklers and Smoke Control

• NFPA 13 expected performance.

– Automatic sprinkler system will control the fire.

• Research projects.

– Sprinklers effective in extinguishing fire if water spray reaches seat of fire. – Shielded fires.

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Sprinklers and Smoke Control

• Initial project completed in 1994.

– Wood crib fires shielded by plywood. – Tests in large compartment and ten story tower. – Heat release rate reduced by > 50%. – Burned for up to 1 h. – Reduced temperatures and buoyancy forces. – High volumes of smoke produced.

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Sprinklers and Smoke Control

• Initial project.

– Assumed high fire load. – Did such scenarios exist in office buildings?

• Second project completed in 1997.

– Determine typical shielded scenarios in office buildings. – Open Plan Offices. – Simulate scenarios in full‐scale tests.

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Sprinklers and Smoke Control

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Sprinklers and Smoke Control

• Addressed by fire codes,

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Sprinklers

and Smoke Control

• Measurements.

– Heat release rate. – Temperatures. – CO and CO₂ production. – Smoke obscuration.

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Sprinklers and Smoke Control

t re le a se ra te (kW)

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Sprinklers and Smoke Control

Hea t re le a se ra te (kW)

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Sprinklers and Smoke Control

• Buoyant Smoke Flow (2001).

– To investigate smoke movement in atria for sprinklered mercantile fires in communicating spaces. – To provide a basis for a hazard analysis and an evaluation of current design approaches for smoke management.

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Sprinklers

and Smoke Control

• Test facility.

– Room adjacent to atrium. – 5 m x 9.2 m x 6.4 m high. – Four sprinklers ordinary hazard. – Application density 4.1, 6.1 and 8.1 mm/min. – Smoke exhaust.

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Sprinklers and Smoke Control

• Test facility.

– Application density 4.1, 6.1 and 8.1 mm/min. – Steady and t‐squared propane burner fires.

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Sprinklers and Smoke Control

• Low Heat Release

Rate

‐ non‐buoyant

smoke.

• Heat release rate >

250 ‐1000 kW –

buoyant

smoke

flow.

• Temperatures >

100°C ‐ additional

sprinklers activates.

Figure 6. Temperatures in compartment opening.

0 1000 2000 3000 4000 5000 -20 0 20 40 60 80 100 120 140 2.98 m 2.53 m 2.08 m 1.63 m 1.18 m 0.73 m

Heat Release Rate (kW)

0 1000 2000 3000 4000 5000 Temperatu re ( ºC) -20 0 20 40 60 80 100 120 140 2.98 m 2.53 m 2.08 m 1.63 m 1.18 m 0.73 m t-squared Steady

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Sprinklers and Smoke Control

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Sprinklers and Smoke Control

Hea t re le a se ra te (kW) Time (s) Hea t re le a se ra te (kW) Time (s)

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Atrium

Smoke Management

• Maintain smoke layer above design height for design time.

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Atrium

Smoke Management

• Plugholing. – Air from below smoke layer exhausted along with smoke. – Decrease system effectiveness.

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Atrium

Smoke Management

• Medium scale physical model. – Varied fire size (15 – 800 kW), height of inlet, number of inlets (1 – 32). – Simulate situations with cold air mixing with smoke exhaust. – Able to simulate with CFD

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Atrium

Smoke Management

• Large scale tests.

– Multiple inlets – 16. – Single inlet.

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Atrium

Smoke Management

• Large scale tests. – Propane burner. – Fire sizes 250 kW to 5 MW. – Fire area varied to maintain approximately 500 kW/m2_.

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Atrium

Smoke Management

• Smoke exhaust efficiency. – Dependent on smoke depth and smoke temperature. – For thin smoke layers, improve efficiency by using multiple inlets. – Locate inlets away from walls • High exhaust flow rates will not produce thin smoke layer.

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• NFPA 92B Requirements

– Choose minimum number of inlets such that maximum volumetric flow rate for each inlet not exceeded. – Maximum flow rate (m3_/s); – d = smoke layer depth, (m); – T_s = smoke layer temperature (K); – T_o = ambient temperature (K);

Atrium Smoke Management

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Atrium

Smoke Management

• Balcony Spill Plumes.

– Equation in early editions of NFPA 92B. – Initially was not used for sprinklered buildings. – With development of sprinklered design fires found to be dominant scenario for high atrium.

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Atrium Smoke Management

• m = mass flow rate in plume (kg/s); • Q = total heat release rate of the fire (kW); • W = width of the plume as it spills under the balcony (m); • z_b = height above the underside of the balcony to the smoke layer interface (m); • H = height of balcony above base of fire • Several algebraic equations developed for balcony spill plumes. • Based on 1:10 scale physical model experiments at BRE. • Equation used in NFPA 92B developed by Law.

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Atrium

Smoke Management

• Research. – Full‐scale model tests. – CFD modeling. • Smoke flow in balcony area. • Extend results to high atria. – Law’s correlation valid for low smoke layer interface heights (< 15 m above balcony). – New correlations developed for higher smoke layer interface heights.

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Atrium Smoke Management

• m = mass flow rate in plume (kg/s); • Q_c = convective heat release rate of the fire (kW); • W = width of the plume as it spills under the balcony (m); • z_b = height above the underside of the balcony to the smoke layer interface (m); • H = height of balcony above base of fire • Smoke layer interface height > 15 m. • Width of plume at balcony edge < 10 m. • CFD modeling indicated that line plumes such as those formed by balcony spill plumes transition to

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Atrium Smoke Management

• m = mass flow rate in plume (kg/s); • Q_c = convective heat release rate of the fire (kW); • W = width of the plume as it spills under the balcony (m); • z_b = height above the underside of the balcony to the smoke layer interface (m); • H = height of balcony above base of fire (m). • W=w + b if draft curtains not used to channel flow where w = width of opening (m) and b = depth of balcony (m). • Smoke layer interface height > 15 m. • Width of plume at balcony edge >10 m. • Balcony plume remains a line plume at higher heights.

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Atrium Smoke Management

• Make‐up air

– Current design requirements set a maximum make‐up air velocity of 1 m/s at the plume. – Based on research into effect of wind on flames. – Flame tilt with airflow velocity > 1 m/s increases smoke production. – Higher velocities can cause disruption of the

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Atrium Smoke Management

• Issue for designers

– To maintain a 40‐m clear height in a 50‐m tall atrium, with a fire size of 1 MW, the mass flow rate of the smoke exhaust should be 288.91 kg/s. – With a make‐up air velocity of 1 m/s, the area of the opening providing this air should be 347 m2. – If this opening is put at ground level with a height of 3 m, the length of the opening would be 115 m. – This may not be possible for many cases.

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Atrium Smoke Management

• Research project

– To use a Computational Fluid Dynamics (CFD) model to investigate the impact of make‐up air velocity on smoke exhaust effectiveness; and – To determine whether the 1 m/s make‐up air criterion is too severe.

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Atrium

Smoke Management

• FDS Simulations.

– Opening one wall. – Smoke exhausted from whole ceiling. – Flow rate calculated using NFPA 92B to give smoke layer interface height of 80% ceiling height. – Fire located different distances from opening.

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Atrium Smoke Management

Name Atrium 10 Atrium 20 Atrium 30 Atrium 50 Atrium 60

Dimensions 10x10x10 15x15x20 20x20x30 30x30x50 40x40x60 Distance from

opening, (m) 2.5 3.75 5.0 and 2.5 5.0 and 2.5 5.0 and 2.5 Height of smoke

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Atrium Smoke Management

• 50 m high atrium.

• 1 MW fire 5 m from

opening.

• Make‐up air

velocity.

– 0.5 m/s – 1 m/s – 1.25 m/s – 1.5 m/s

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Atrium Smoke Management

• 50 m high atrium.

• 2.5 MW fire 5 m from

opening.

• Make‐up air

velocity.

– 0.5 m/s – 1 m/s

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Atrium Smoke Management

• 50 m high atrium.

• 5.0 MW fire 5 m from

opening.

• Make‐up air

velocity.

– 0.5 m/s – 1 m/s – 1.25 m/s – 1.5 m/s

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Atrium Smoke Management

50‐m atrium 2.5 m 50‐m atrium 5 m

0 0.2 0.4 0.6 0.8 1 1.2 0 0.5 1 1.5 2 N o rmalized I n te rf ace H e ight 1 MW 2.5 MW 5 MW 0 0.2 0.4 0.6 0.8 1 1.2 0 0.5 1 1.5 2 N o rmalized I n te rf ace H e ight 1 MW 2.5 MW 5 MW

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Atrium Smoke Management

• For all cases studied, increased make‐up air

velocity lowers the interface height in the atrium.

• The 1.0 m/s requirement is not conservative as it

causes plume disturbance and lower interface

heights.

• Effect of make‐up air similar at 1.25 m/s and in

some

cases 1.5 m/s to that at 1.0 m/s.

• More impact for atrium < 20 m in height.

• More research required to validate results and

develop design tools for addressing effects of

make‐up air velocities.

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Other Smoke Control Research

• Duct Smoke Detection.

– Shutdown HVAC system earliest form of smoke control. – Required by Codes. • Limit re‐circulation of smoke through building by HVAC system. • Does not limit smoke movement through shafts and ducts used for air management.

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Other Smoke Control Research

• Duct Smoke Detection.

– Fire Detection Institute project. – Joint University of Maryland and NRC. – Issues. • Comparative driving forces. • Smoke aging and agglomeration. • Dilution. • Effect of filters. • Smoke stratification. • Efficacy of sampling system.

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Other Smoke Control Research

• Full‐scale tests investigated each of the issues. • Detection dependent on smoke concentration. • Should shutdown

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Other Smoke Control Research

• Communication Cable in Ceiling Void.

• Build up of cables. • Return Air Plenum.

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Other Smoke Control Research

• Canada . – FT4 CSA Test Method. – FT6 CAN/ULC S102.4. • US – CMP rating using tunnel test. • Limit fire spread and smoke production. JACKET – PVC INSULATION • POLYOLEFIN • PVC

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Other Smoke Control Research

• Plenum cable fire research.

– Cone calorimeter tests. • To assess flammability of used and new cables. • Production of smoke and irritant gases – HCl and HF. – Medium scale tests. • assess effect of hot air on cables. • Cables can produce additional smoke at temperatures >400⁰C.

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Other Smoke Control Research

• Plenum cable fire research.

– Full‐scale tests. • Assess effect of fully‐developed fire in room below plenum and potential fire spread. • Limited flame spread along cables. • Increase smoke production which can affect visibility. • Increased CO production which can increase risk of

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Other Smoke Control Research

• Network models.

– Since the 1970s, network models developed for use in design of smoke control systems. – CONTAM developed in 1990s. – Do not include energy equation and temperature assumed constant for all nodes of network. – Good for smoke control applications but cannot model fire induced smoke movement.

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Other Smoke Control Research

• Network models.

– Combination of zone models and network models. • Zone model determines smoke movement between compartments near fire. • Data used as input into network model to calculate smoke movement remote from fire. – New algorithm. • Combination zone and network model.

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Other Smoke Control Research

• Secondary suites.

– 3 bedroom house. – Constructed area as secondary suite in basement. – Investigate smoke movement between suites by HVAC system. – Proposed code requirements for secondary suites.

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Other Smoke Control Research

• Secondary suites.

– Polyurethane foam as fuel. – Ignited with propane burner. – Short duration fire with peak.

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Other Smoke Control Research

• Detection times

– < 20 s in fire compartment. – 78 – 120 s if located in separate room in basement. – 156 – 306 s in the first storey depending on the setup of the HVAC system.

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Other Smoke Control Research

• Smoke measurements

– Fire compartment, main floor (corridor and bedroom), main entryway. – Smoke accumulation on main floor dependent on setup of HVAC system. • HVAC system did affect smoke movement with earlier detection and more smoke measured on main floor in tests with system operating.

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Other Smoke Control Research

• Smoke measurements.

– Smoke levels in fire compartment indicated visibility could be affected in < 100 s. – Fire very under ventilated. • High CO (> 1%) and low oxygen (<6%) levels measured. • Indicates incapacitation times <20 s if exit through fire compartment.

• Second exit required.

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Future Research

• Pressurized stair shafts with open doors.

– Modeling study indicated that as long as the doorway on the fire floor is closed minimum pressure difference required to protect stairwell for sprinklered fires. – Does one need to use pressure compensation systems? – Need experiments to confirm.

• Atrium make‐up air

– Initial study indicated make‐up air velocities of 1 m/s

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Future Research

• Long atria (malls, airport terminals, etc).

– Know smoke will become non‐buoyant with extended horizontal propagation. How far? When are smoke curtains required?

• Large atria.

– Is there a limit to the design equations? Height? Area? – Very limited data.