Ventilation of Enclosed Car Parks Using Jetfan Systems
for pollution and smoke control
© Fläkt Woods
Why ventilate a car park?
• Pollution control (vehicle emissions)
• Smoke extract (in case of fire)
• Building regulations
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Ductwork system
Duct
work
Lighting
Grilles
Hi-level
(50%)
Grilles
Lo-level
(50%)
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Generally applied method ( Ducted System)
• 6 ACH - pollution
• 10 ACH - fire / smoke extract
• Extract ductwork system, high / low level grilles
(50%), changing to Jetfan systems
• Extract fans, 2 off 50% duty each
• HT operation 300°C / 60mins
• Supply air, via entrance, louvred inlet or fans
© Fläkt Woods
Limitations
• Ventilation rate not matched to demand (too high)• Limited monitoring of pollution (CO)
• System operating all the time• 50% of extract at low level (not effective)• 10 ACH rate arbitrary, no account of specific fire size• Ductwork / grilles add resistance• Increased fan speed, absorbed power, and noise levels• Reduction in rental space, obstruct view and appearance
© Fläkt Woods
Jetfan system
Car park
Jetfoil Fan
Lighting
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Jetfan system solution• Remove ductwork, retain high level extract points
• Main HT rated extract fans (identify supply)• Position Jetfoil fans throughout the car park • Analyse complex air flows using Computational Fluid Dynamics (CFD)• Easier installation of services• Reduce obstructions and improve appearance• Increase space for parking / rental• Reduction in system resistance• Reduction in fan speed and noise level• Reduction in absorbed power (running cost)
© Fläkt Woods
Main fans (Extract System)
Silencers
FAN:
100JM(HT)
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Jetfoil fans
CFD OF JET FAN SHOWING VELOCITY PROFILE
1.0/s
2.5m/s6.0m/s
2.5m/s
8.0m/s20.0m/s
1.0m/s
0.5m/s
0.5m/s
0.5m/s
0.5m/s
1.0m/s
10.0m/s
© Fläkt Woods
Standard car park Jetfan: -35JM.Jet/2/SP
455m
m
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Low Profile car park Jetfan: -31JM.Jet/2/LP
350m
m
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Installation - 35JM.Jet/2/SP
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Isometric plan view
3D model of car park
Extract grilles (2 off)
Jetfoil fans
Inlet
(via ramp)
Inlet
(via louvred inlets)
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Isometric plan view
3D model of car park
Extract grilles
Jetfoil fans
Supply
grilles
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3D model of car park
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Isometric plan view
Extract points
Entrance / exit
Park Street
Entrance / exit
Alison Street
3D model of car park
© Fläkt Woods
Isometric plan viewLow level Jetfans
Henibique beamsLarge arch
Small archEntrance
/ exit
Specific project requirements
• Operate ventilation system on demand (CO detection)
• Check extract rate vs. smoke production• Select ventilation based on “design fire” (MW)
• Possible to use model fire using CFD• Smoke / heat control (reduce spread temperature)
• Link fan operation with CFD / detection systems (mode table)
© Fläkt Woods
CFD Analysis to assist in elimination of ‘dead-spots’
AFTERBEFORE
= Primary ‘dead-spots’
Smoke production
Qρ = Convective Rate of Heat OutputQρ = KQ
where Q = Total Rate of Heat Outputand K = Radiation Factor ( ≅ 0.2 to 0.35)
Radiation Losses
Replacement AirReplacement Air
© Fläkt Woods
Large volume undivided buildings
M = Rate of production of hot gasses (kg/sec)M = 0.19PY1.5
where P = Perimeter of the fire in metresand Y = Height of smoke layer in metres© Fläkt Woods
AC rate vs. smoke production
C a r p a rkS iz e(m 2 )
E x tra c t b a s e d o n 1 0 A C H (m 3 /s ) H ig h /lo w H ig h le v e l le v e l o n ly
S m o k e ra tep ro d u c tio n
(m 3 /s )
1 0 0 02 0 0 03 0 0 04 0 0 08 0 0 0
6 .91 3 .92 0 .82 7 .85 5 .6
3 .57 .0
1 0 .41 3 .92 7 .8
1 0 .61 0 .61 0 .61 0 .61 0 .6
Notes:-- Effect height of car park = 2.5m- Clear Layer under smoke = 1.75m- Fire size = 3MW - Radiation loss = 25% - Fire perimeter = 12m
© Fläkt Woods
Temperature plot
Plan view© Fläkt Woods
Fire location
Barrier
Ducted system: -Extract grills every 10m, 100 off in total
Air speed Air quality
Extractgrilles
Inlet (Via ramp)
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Air speed Air quality
Jetfans
Inlet (Via ramp)
Extract fans
Jetfans
Jetfan system: -16 off Jetfoil fans, extract fans located in wall on the RHS
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Smoke Testing
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CFD ANIMATION
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CFD ANIMATION
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CFD ANIMATION
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