Transcript Q Wang (Presentation)
CFD Applications of PHOENICS on Building Environment and Fire Safety Design
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Qian Wang, PhD, CFD Specialist Kenneth Ma, Senior Associate Micael Lundqvist, Senior Fire Engineer Ove Arup Pty Ltd Level 10, 201 Kent Street, Sydney NSW 2000, Australia
Abstract ARUP has been using PHOENICS for many years to deal with various CFD modellings in
building thermal comfort design
,
indoor environment
,
fire safety control
, etc. and has gained good results recognised by the clients. This paper summarises some selected CFD studies of normal & emergency ventilation controls.
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Software PHEONICS PC version 3.3 & 3.4 Computers
COMPAQ
WorkStation Pentium 3/800MHz & Pentium 4/1.6GHz
INTRRODUCTION
Project Type Urban underground railway station with connecting tunnel to the ground level, heavily occupied with diesel trains CFD Objectives 1. Platform: thermal comfort & air quality .
2. Tunnel: smoke ventilation control during emergency fire in the connecting tunnel.
Description of Project
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Diagram
Description of Project
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CFD Tasks & Outcomes
•
To provide all detailed information to support the final design of mechanical ventilation system.
•
Temperature, air velocity, concentration of pollutant gases (CO, CO 2 , NO, etc) in winter & summer seasons.
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Station Normal Ventilation
CFD Domain Station Normal Ventilation
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CFD Input Conditions
Main Settings
Total cells Turbulance model Differencing scheme Global convergence criterion
Descriptions
X=73, Y=138, Z=36 Standard
K-e
(KEMODL) HYBRID 0.01% Reference temperature Boundary effect on turbulence Coefficient for auto wall functions Total number of iteration Domain material
density viscosity specific heat
15 o C in winter, 27 o C in summer Off LOG-LAW 2000 40 dummy fluid (self-edited) 1.18
1.83E-05 1005
conductivity
0.026
Station Normal Ventilation
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Velocity Vector
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Station Normal Ventilation - winter
Station Normal Ventilation - winter
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Velocity Vectors
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Station Normal Ventilation - summer
Velocity Vectors
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Station Normal Ventilation - summer
Summary
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Winter Allowable concentration of CO (25ppm) is acceptable. Gas fume is accumulating near ceiling.
• • • •
Summer Well mixed fluid domain.
Containment materials may be driven towards the platforms .
Hot layer within T > 30 °C is broader and thicker, may result in discomfort to the passengers. The 0.082% CO level (25ppm) is quite close to the platforms – greater ventilation capacity is required.
Station Normal Ventilation
CFD Tasks & Outcomes
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To evaluate the smoke control policy during emergency fires in the sloped tunnel (450m x 8.9m x 6m) .
•
Transient air velocities, temperatures and smoke concentrations.
•
Behaviours of backlayering of smoke towards station platform.
Tunnel Fire Smoke Control
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Tunnel Fire Smoke Control
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Train Fire in Entry Tunnel
8.9m
Ventilation Shaft Jet Fan
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Entrance of Ground Level Ventilation Shaft Fire Source Train Fire Connection to Station Tunnel Fire Smoke Control
Fire Safety Design Criteria
•
T < 200
°
C if hot layer is above 1.5m from floor level.
•
T < 60
°
C less than if hot layer is below 1.5m and/or the visibility not be 6m (ie the optical density should not exceed 0.14m
-1 ).
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Fire Scenario 1 Carriage Fire 2 Suppressed Diesel Fire Description 'worst credible' fire breaking out inside a train that is stopping in the tunnel between the two vent shafts.
Assumed to be an exponentially ‘fast’ growing fire with the maximum fire size 15 MW, as a fully developed carriage fire.
'worst credible‘ scenario for a fire outside a stopped train between the two vent shafts and is leaking diesel. The fire is assumed to be a ‘fast’ (0.047kW/s²) growing fire, which is suppressed upon activation of the foam suppression system at track level.
3 This fire scenario is a sensitivity analysis of the diesel fire outside the carriage (Scenario 2) in the event of failure of the foam suppression system. The fire Unsuppres therefore continuos to grow to its maximum size 40 MW, involving both the diesel sed Diesel and a carriage.
Fire Tunnel Fire Smoke Control
40 Q [MW] 20 Fire starts
Q
7 .
81 10 7
t
2
All jet fans stop
Scenario 1- Scenario 2- Scenario 3--
abc abe abcd F1 operates: 180m 3 /s c d
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4.22
0 a b e Tunnel Fire Smoke Control
t
[min] 15.5
Temperature Concentration
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Tunnel Fire Smoke Control Scenario 1
Temperature Concentration
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Backlayering Distance
90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 6 7 8 9 10
Time after fire ignation [min]
11 12 13 14 15
Tunnel Fire Smoke Control Scenario 3
Tunnel Fire Smoke Control
Double click the image to play !
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Summary
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It is proved that the design smoke control/ventilation system during different fires will be able to provide a reasonable fire safety condition according to the calculated internal temperature, CO concentration levels.
Conclusions of PHOENICS PHOENICS applications on building internal air quality control and emergency fire smoke control strategy have been carried out. Very detailed thermal and fluid behaviours of internal air have been analysed, which either identified the efficiency of the ventilation systems or provided the optimisation to the design features. All these results prove that PHOENICS can deal with very broad fluid dynamic modelling, and is the most cost effective tool in professional engineering consultant services.
Tunnel Fire Smoke Control