smoke management in a medium sized sprinklered car park · presentation outline •introduction...
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Friday, December 27, 2019
Smoke Management in a Medium Sized Sprinklered
Car Park
Dr. Dalia Essam Eldin Khalil ,and Prof.Dr. Essam E.Khalil,
Cairo University, Faculty of Engineering, Cairo, Egypt
1
Belgrade, December 2019
Friday, December 27, 2019
PRESENTATION OUTLINE
• Introduction
• Literature Review
• Methodology
• Case Study
• Results and Discussion
• Conclusions and Recommendations for Future Work
2
Friday, December 27, 2019
Why Sprinklers
Over the past few years, many national codes and standards
enforced the installation of sprinkler systems in enclosed
car parks.
للجراجاتالمصرىالكود•
ىتلقائرشاشاتنظامباستخدامحمايتهايتمالمغلقةالجراجاتحالةفى
الساللمفىرطبتلقائىنظامالىباالضافة
• NFPA 88A
6.4.3 Automatic sprinkler systems shall be installed in
enclosed parking structures located at or above grade, or
within or immediately below a building used for another
occupancy
3
Friday, December 27, 2019
Sprinklered Car Parks Statistics
A statistic on car park fires reported 3096 fires in car
parks in the UK between 1994 and 2005, only 162
incidents were in car parks provided by sprinklers,
➢16 (9.9%) operated and extinguished the fire,
➢84 (51.9%) operated and contained/controlled the fire,
➢1 (0.6%) operated but did not contain/control the fire
➢ 61 (37.6%) did not operate. (Noting that those that “did
not operate” are likely to be because the fire was too
small to activate the sprinklers)
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Friday, December 27, 2019
Unsprinklered Fire Disaster
A massive fire tore through up to 1,400 vehicles in a car
park in central Liverpool, stranding many people after their
New Year's Eve celebrations.
“One thing is for certain – had the building been
sprinklered there is every chance that they would have
suppressed the fire sufficiently then for us to be able to go in
and extinguish the fire without it spreading in the way that it
did” , said the chief fire officer
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Friday, December 27, 2019
Scope Of Work And Study Objectives
Scope Of Work
• Investigate the tenability criteria in an enclosed car
park provided with sprinklers and smoke
management system in case of ducted system and
impulse ventilation system.
• Study the interaction of water particles and their
downward movement with the smoke layer
• Study the effect of increasing the distance between
the sprinklers and smoke layer on the visibility
levels6
Friday, December 27, 2019
Scope Of Work And Study Objective
Scope Of Work
• Investigate the effect of increasing the
sprinkler operating pressure on the smoke
behaviour
• Calculating and implementing fire decay
equation after sprinkler activation.
• Parametric analysis for series Jet fan
configuration to study their effect on the smoke
layer disturbance
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Friday, December 27, 2019
Objectives
This investigation aims to :
• Demonstrate the physical effect of the sprinklers
water spray on the smoke behavior and propagation.
• Recommend a modelling approach to correctly
simulate the fire in a sprinklered car park.
• Propose solution to enhance the evacuation process
and tenability criteria of occupants in a sprinklered
car park.
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Friday, December 27, 2019
Literature Review Main Topics
Impulse ventilation system for smoke control in car parks
Sprinklers activation effect
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K.Y. Li, R. Huo, J. Ji, B.B. Ren (2009),
The discharge rate of a horizontal smoke vent adjacent to a sprinkler spray
is experimentally investigated.
Experimental results have shown that :
• The efficiency of smoke venting is controlled by a combination of
smoke buoyancy and drag force of sprinkler spray.
• The CO concentration was found to increase after sprinkler was
operated as the smoke is constrained in the spray region with horizontal
momentum decreased.
• Negative pressure difference is caused at the vent when there is smoke
venting logging, which might practically bring the exterior fresh air into
the fire building.
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Hugues Pretrel (2017)
This work deals with the interaction between water droplet flows and smoke in a
fire event in a confined and ventilated enclosure.
It was concluded that :
• The concentrations of species (oxygen and combustion products) are similar
near the ceiling and the ground. The water spray along with the smoke reach
the lower part of the room and thus reduces visibility and also the level of
oxygen near the seat of the fire.
• The energy released by the fire is mainly transferred to the walls and through
the ventilation network. If a water spray system is activated, a significant
share (up to 65%) of the energy is transferred to the droplet flow. The water
spray system is therefore a very efficient way to limit the spread of the fire
into the environment, the enclosure walls and the ventilation network.
Sketch of the facility with the location of the measurement
points and the fire room with the water spray system operating
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Assessment & Validation
A selected test from experiments carried out by
Gutierrez-Montes et al to predict the behavior of
smoke in an atria fire in Centro Technologic del
Metal, Spain was used in the validation process of
FDS (Version 6.5.3)
15
Test facility layout and main dimension
Friday, December 27, 2019
Assessment & Validation
16
Central section and top plane layout showing test apparatus used
(highlighted in red)
Heat release variation with time for each of
the three test cases as measured
Friday, December 27, 2019
Assessment & Validation
• Two parameters were examined, plume and
exhaust smoke temperature.
• The variations of plume and smoke
temperature were compared with the
experimental results carried out by
Gutierrez-Montes et al.
17
FDS geometry used for validation case
Friday, December 27, 2019
Assessment & Validation
18
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0 200 400 600 800 1000
Tem
per
ature
(C
)
time
Sensor 24
Temp (EXP)
Temp (FDS)
Plume and smoke
temperature measurements
Sensors 24,28 and 60 experimental and FDS temperature distribution
with time
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0 200 400 600 800 1000T
emp
erat
ure
(C
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time (s)
Sensor 28
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Temp(FDS)0
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0 200 400 600 800 1000
Tem
per
ature
(C
)
time (s)
Sensor 60
Temp(EXP)
Temp(FDS)
Friday, December 27, 2019
Base Case Study
• Geometry
• Boundary Conditions & Input Data
• Grid sensitivity study
• Simulated Base Cases
• Results
• Discussion & Recommendations
• Proposed Design Options
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Two car park outlets 8 m wide, 3 m
high on the south east side of the
building are available for cars exit.
One car park inlet 7 m wide, 3 m high
on the south west side of the building
is available for car entrance.
An enclosed car park 100 m long, 34 m wide, and 3 m high, is considered.
Geometry
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Friday, December 27, 2019
• The model applies 1,285,200 uniform cubic grid cells. The
overall volume of the simulated net car park is 10200 m3.
• The domain is divided into 16 meshes to save
computational time by performing FDS_MPI version.
• All walls, columns and jet fan shrouds are specified as
inert surfaces that are non-reacting solid boundary fixed at
40°C.
• The dimensions of the computational domain are chosen to
achieve the optimum solution as recommended by FDS 6
manual.
Mesh Mesh 01-16
X xY x Z 12.5m x 17m x 3 m
Uniform cubic cell size 0.2
Average Nx 63
Average Ny 85
Average Nz 15
Ntot 80325
Boundary Conditions & Input Data
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Supply Fresh Air
Fresh air is supplied in the car park by mechanical
supply system.
• The supply air/make-up air is introduced through
six supply fans at the right hand side of the car
park.
• The supply fans are simulated as three vent with
an area of 8 sq.m each (4 m wide and 2 m high)
and a flow rate of 6.14 m3/s each (65% of the total
exhaust air)
22
Friday, December 27, 2019 23
Exhaust System
Two systems are proposed for exhaust system namely:
• Impulse ventilation system: Five exhaust fans
located at the left side of the car park are used along
with eight jet fans. These exhaust fan stations are
simulated as vents with an area of as 3sqm. each (3 m
Wide and 1 m high) and 17 m3/s flow rate based on
assumption of 30 ach.
• Ducted system: 86 exhaust grill are located at ceiling
level extracting 86 m3/s based on 30 ACH
assumption. Each grill has a 0.16 m2 free area and
flow rate of 0.5 m3/s in case of normal mode and 1
m3/s in smoke mode
Friday, December 27, 2019
Jet Fans
• Eight jet fans are used with 50 N thrust force (2 m3/s volumetric flow).
• The upper shroud of each jet fan is located directly below the ceiling.
• Each fan is simulated with round cross section of 35 cm diameter and a
shroud length of 2.9 m.
• The flow rate is maintained for 180 s on the normal mode at 1 m3/s and
then the smoke mode 2m3/s is used till the end of the simulation time.
Car Fire
• The fire dimension is 4.4 m wide, 1.8 m long and 0.5 m high with a
heat release rate per unit area of 505 kw/m2.
• The car fire is simulated by flaming polyurethane as a burning fuel with
a soot yield of 0.1kg soot/kg fuel.
Parameter Value
Car fire heat release rate 4 MW
Fire type T-squared fire
Fire growthFast growing
fire
Car park size 100x34x3
Car park general
ventilation systemOn
Car park jet fans On
Ventilation rate 8 ach
Extraction rate 30 ach
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Sprinklers Parameters Value
Operating pressure 1 bar
Flow rate 80 l/min
K-factor 5.6
Orifice diameter 0.5 inch
Particles diameter 1 mm
Water particles
distribution
Rosin-Rammler
lognormal
Particles flux 10000 per second
Activation temperature 68 Deg.C
Sprinkler density 0.15 gpm/ft2
Sprinklers
• The investigated car park was covered with sprinklers
with 4 m distance between every two consecutive
sprinklers
• The firefighting system used is wet pipe system
• Sprinkler type is standard upright
• Sprinklers operate between 0.5-12 bar
25
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Grid Sensitivity Analysis
• Three different grid sizes were utilized to check the
results’grid independency and the effect of mesh
size on the CFD results with computational element
sizes of 0.1 m, 0.2 m and 0.4 m.
• Thermocouple temperature at point 1, 2, 3, 4 and 5
around car fire were investigated using the three
different mesh sizes.
• In each simulation the car fire heat release rate was
8 MW and the simulation time was 200 seconds.
26
Investigated car park and thermocouple locations
Friday, December 27, 2019
Grid Sensitivity Analysis
27
Simulation SIM.1 SIM.2 SIM.3
Cell volume, m3 0.001 0.008 0.064
Size of uniform Cubic Grid
Cell, m 0.1 0.2 0.4
Cells total number 11,870,208 1,483,776 185,472
Number of meshes 8 8 8
Computational mesh characteristics at different mesh sizes
Friday, December 27, 2019
Grid Sensitivity Analysis
28
0
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120
140
0 50 100 150 200 250
Temperature
Time
Temperature Profile for Thermocouple 1
SIM 1 SIM 2 SIM3
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Tem
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Time
Temperature Profile for Thermocouple 2
SIM 1 SIM 2 SIM 3
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Tem
per
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Time
Temperature Profile for Thermocouple 3
SIM 1 SIM 2 SIM 3
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0 50 100 150 200 250
Tem
per
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Temperature Profile for Thermocouple 4
SIM 1 SIM 2 SIM 3
Friday, December 27, 2019
Simulated Base Cases
The purpose of the following simulations is to find the suitable smoke management system
configuration to provide occupants’ safe egress at all times through the fire event as well as
clear access for fire brigades after 20min from fire ignition with different fire scenarios.
This can be achieved when:
• The egress route to the car park outlets with visibility of 10 m is maintained at all times
• A distance of 10-15 m downward the fire seat is maintained clear of smoke for fire
brigades to easily reach the fire
29
Friday, December 27, 2019 30
InputS1a S1b S2a S2b
Impulse ventilation system Ducted system
Fire load Constant at 4MW
Exhaust Air 30 ACH
Make-up air 65% of exhaust air
Jet fans quantity 8 jet fans -
Jet fan thrust and flow rate 50 N & 2m3/s -
Ducting system - 86 exhaust grills with 1 m3/s flow rate
Sprinklers Sprinklered
Sprinklers physical effect Not modelled Modelled Not modelled Modelled
Friday, December 27, 2019
Visibility Contours At 1.8 m above FFL For Case S1a
31
Visibility
Contours
180s 240s
300s 360s
480s 600s
Friday, December 27, 2019
Visibility Contours At 1.8 m above FFL For Case S1b
32
Visibility
Contours
180s 240s
300s 360s
480s 600s
Friday, December 27, 2019
Visibility Contours At 1.8 m above FFL For Case S2a
33
Visibility
Contours
180s 240s
300s 360s
480s 600s
Friday, December 27, 2019
Visibility Contours At 1.8 m above FFL For Case S2b
34
Visibility
Contours
180s 240s
300s 360s
480s 600s
Friday, December 27, 2019
Discussion & Recommendations
From the above figures it is observed that
• Upon sprinkler activation, smoke logging occurs where smoke is dragged to occupants
level due to sprinklers downward motion.
• Due to the assumed constant heat release rate, the smoke rate of production remains
constant throughout the simulation time.
The above will lead to:
• Lower visibility levels due to smoke logging after only 3 min from fire event threatening
the safe egress of occupants.
• Fire brigades will have more difficulty in locating the fire source and consequently
extinguish it.
35
Friday, December 27, 2019
Therefore three different design options were proposed in
order to achieve the smoke management system objectives
• The first design option is to increase the distance between the
sprinklers and the smoke layer to maintain the sprinklers spray region
below the smoke layer. This can only be achieved either by decreasing
the level of sprinkler installation or by increasing the height of the car
park at early project design stages.
36
Friday, December 27, 2019
• The second design option is to increase the minimum threshold of
the sprinklers operating pressure to 4-6 bar and consequently the
water flow rate to help trap the fire induced smoke below the water
spray and decrease its spread.
• The third design option is to change the common 4MW steady fire
curve and use a transient fire curve with unsteady HRR by
implementing the ASHRAE decay equation.
37
Friday, December 27, 2019
Design Option #1
38
• The common adopted sprinklers system is wet pipe system in
which the sprinklers are located near ceiling level within the
smoke region in order to operate when subjected to high
smoke temperature.
• To install the sprinklers outside of the smoke region, the
sprinklers level must be below the smoke layer that is
usually attached to car park ceiling
• Sprinklers’ activation must rely on another mean than the
usual temperature detection.
• For this to be achieved, the deluge system is proposed.
Installation of the Sprinklers below the Smoke Layer
Friday, December 27, 2019
Design Option #1
Deluge system that operates upon smoke detector signal
A Deluge System is a fixed fire protection system in which
the pipe system is empty until a deluge valve operates
upon smoke detector activation to distribute pressurized
water from sprinklers.
39
Friday, December 27, 2019 40
Six deluge networks are used as shown in the
figure, where each system relies on three smoke
detectors located above the parked cars for the
activating signal.
Once smoke is detected at one of the three
signals, all sprinklers on the deluge network are
activated.
It was found that deluge #3 operates after 100 s
where deluge #4 and #2 operate after 150 s.
Proposed Deluge System
Proposed Deluge System networks
Friday, December 27, 2019
Series Jet fan performance study
Investigation of the effect of the intermediate distance between the different jet fans on the predicted
visibility and local temperature. The following cases were investigated:
41
• Four jet fans were located 20 m away from each other
• Three jet fans were located 30 m away from each other
• Two jet fans were located 40 m away from each other
The fans were of similar capacity and were located 8 m away from the source of fire. The smoke behavior
was examined and the study was conducted at time interval of 90 s after the onset of fire event to ensure
that the smoke has propagated and moved from the fire source till the last jet fan.
Friday, December 27, 2019
Visibility Contours In A Vertical Y- Plane With No Jet Fans
42
Friday, December 27, 2019
Visibility Contours In A Vertical Y- Plane At 20 M Jet Fans Longitudinal Distance
43
Friday, December 27, 2019
Visibility Contours In A Vertical Y- Plane At 30 M Jet Fans Longitudinal Distance
44
Friday, December 27, 2019
Visibility Contours In A Vertical Y- Plane At 40 M Jet Fans Longitudinal Distance
45
Friday, December 27, 2019 46
From the above figures it can be concluded that:
• Jet fans operation causes smoke spreading down 2 m from ceiling level which will make the
installation of sprinklers at ceiling level within the smoke layer very challenging.
• At the same time sprinklers cannot be installed below 2.2m from floor level which is the
minimum allowable height for any mechanical system installation in a car park as per the
Egyptian code.
• Therefore, Three cases were modelled to investigate the visibility level at different ceiling height ;
• Car park with clear height of 3 m with sprinklers installed at 2.2 m
• Car park with clear height of 3.6 m with sprinklers installed at 2.2 m
• Car park with clear height of 4 m with sprinklers installed at 2.2 m
Friday, December 27, 2019
Visibility Contours At 1.8 m above FFL at 300s with
impulse ventilation system at different ceiling heights
47
Visibility
Contours
(m)
@ Ceiling height 3m
@ Ceiling height 3.6m
@ Ceiling height 4m
Friday, December 27, 2019 48
Ducted system study
• When ducted smoke extraction system is installed at ceiling level, it can be observed that the smoke layer
extends down to 1.4-1.5 m from ceiling level making it also difficult to install the sprinklers at a height of 2.2 m.
• Therefore, it is recommended to increase the car park clear height to avoid the sprinkler spray interaction with
smoke layer.
• Three cases were modelled to investigate the visibility level at different ceiling heights;
• Car park with full height of 3 m
• Car park with full height of 3.2 m
• Car park with full height of 3.4 m
Smoke layer depth with ducted exhaust without sprinkler activation
Friday, December 27, 2019
Visibility Contours At 1.8 m above FFL at 300s with
ducted system at different ceiling heights
49
Visibility
Contours
(m)
@ Ceiling height 3m
@ Ceiling height 3.2m
@ Ceiling height 3.4m
Friday, December 27, 2019
Design Option 1
Results & Discussion
50
For impulse ventilation system:
• Jet fan operation on ventilation mode leads to intense mixing between
the smoke layer and the surrounding air
• Increasing the number of consecutive jet fans in a row increases the
mixing of smoke layer with the air below
• Due to this mixing, the smoke layer height can reach up to 2 m below
the ceiling
• Car park height is recommended to be more than 3.5 m high in
order to efficiently install the sprinklers along with jet fans so
that the interaction between smoke and water spray can be
avoided
Friday, December 27, 2019 51
For ducted system:
• Ducted system at ceiling level allows for more uniform smoke layer
• Nevertheless, the smoke layer extends down to 1.2 m from ceiling
level
• Minimal turbulence and mixing can be observed throughout the car
park compared to impulse ventilation system
• Car park height is recommended to be more than 3.2 m high in
order to efficiently install the sprinklers along with jet fans so
that the interaction between smoke and water spray can be
avoided
Friday, December 27, 2019
Design Option #2
52
Three different sprinkler operating pressure will be
examined to study the effect of pressure and hence the
flow rate on the smoke behavior.
As per NFPA 13, the minimum pressure for a sprinkler
to effectively operate is 0.5 bar and the maximum
pressure a sprinkler can withstand is 12 bar. Therefore,
the sprinkler system network pressure must be
maintained within these limits.
TrialsSprinkler
pressure
Sprinkler
Flow rateSprinkler k-factor
Trial 1 1 bar 80 L/min 80 L/(min.atm^0.5)
Trial 2 4 bar 159 L/min 80 L/(min.atm^0.5)
Trial 3 6 bar 194 L/min 80 L/(min.atm^0.5)
Design option 2 trials
Increasing the Sprinklers Operating Pressure
Friday, December 27, 2019
Design Option #2
53
Sprinkler performance is described by the following equation:
Q = K √(P)
Where;
Q: Sprinkler flow rate (L/min)
K: Sprinkler discharge coefficient (L/min.bar^0.5)
P: Sprinkler operating pressure (bar)
A hydraulic calculation study is usually performed to ensure that the most remote twelve sprinklers can
achieve the required pressure and density.
Friday, December 27, 2019 54
Visibility contours at 1.8m for different
sprinklers operating pressure after 600 s
Friday, December 27, 2019 55
Temperatures contours at 1.8m for different
sprinklers operating pressure after 600 s
Friday, December 27, 2019 56
Design Option 2
Results & Discussion
• Sprinkler operating pressure can greatly enhance the tenability conditions in car park.
• The spread of smoke can be limited by the increased water flow rate and water pressure, as the
smoke is trapped beneath the sprinkler.
• The number of sprinklers activated decreases with the operating pressure increase where 32
sprinklers operated in case of 1 bar , 28 sprinklers in case of 4 bar and 22 sprinklers in case of 6 bar
were activated.
• The increased water flow rate will lead to a slight increase in fire pump capacity and consequently
fire tank size.
• To ensure that the most remote sprinklers operate at high pressure, a pump with higher head might
be needed.
• More balancing and accurate hydraulic calculations is required for the sprinklers network to
ensure that all sprinklers operate at high pressure.
Friday, December 27, 2019 57
Design Option #3
Over the last decade, many experimental tests were conducted to investigate the heat release rate of burning cars. The curves
obtained from these experiments differ depending on the experiment setup, source of ignition, car year of production,
location of ignition and many other factors.
The below figure illustrates different experimental curves done over the last 40 years
Using Transient Fire Curve instead of common Steady Fire Curve
HRR curves comparison from various car fire
experiments between the years 1994-2000HRR curves for experimental sedan passenger car fire in 2009
Friday, December 27, 2019
Change the common 4 MW steady fire curve used in case of sprinklered car park and apply the decay equation on the fire curve:
𝑸 = 𝑸𝒂𝒄𝒕 𝒆−(𝒕−𝒕𝒂𝒄𝒕)/𝝉
Where;
Q = post sprinkler actuation HRR, Btu/s (kW),
𝑸𝒂𝒄𝒕 = HRR at sprinkler actuation, Btu/s (kW),
t = time from ignition, s,
𝒕𝒂𝒄𝒕 = time of sprinkler actuation, s
𝝉 = time constant for fire decay, s.
Using a time constant correlation as found by Evans:
𝝉 =𝑪𝝉
𝝎𝟏.𝟖𝟓
Where;
𝜔 = spray density, gpm/ft2 (mm/s);
𝐶𝜏 = 6.15 (3.0 for SI).
58
Design Option #3
Friday, December 27, 2019
Sequence of operation
This part aims to demonstrate the sequence of sprinkler operation and its effect on the fire curve An 8 MW fast
growing car fire will be simulated to get sprinklers activation time. The whole car park is covered by sprinklers
as shown in figure below, the required sprinklers density for ordinary hazard spaces is 0.15 gpm/ft2 .
Sprinklers distribution within car park
59
Friday, December 27, 2019 60
First sprinkler operation @103 s Second sprinkler operation @105s
Third sprinkler operation @108s Fourth sprinkler operation @110s
Sprinklers operation @120s Start of the decaying fire @180s
Sequence of sprinkler operation
Friday, December 27, 2019 61
Friday, December 27, 2019
• From the simulation and as illustrated in figure above, it was
found that first sprinkler is activated after 105 sec from fire
ignition and the fourth sprinkler is activated at 110 sec from
fire ignition.
• The decay equation will be only implemented after 3 min
from the fire event to be more conservative.
• The fire load will be kept to increase according to the used t2
function until it reaches a peak of 1.52 MW at 180 s, then it
will decay as per ASHRAE handbook of smoke control
engineering decay equation.
Heat Release Rate Decay Due To Sprinkler Activation
62
0
200
400
600
800
1000
1200
1400
1600
0 200 400 600 800 1000 1200 1400
Friday, December 27, 2019
Heat Release Rate Change With Time
• The following data will be implemented in FDS to
accurately study the effect of different HRR on
smoke logging and hence the evacuation and
tenability criteria.
• The graph shows the decay in HRR as a result of
sprinkler activation, the maximum obtained HRR
is 1520 kW which is only 18.75 % from the 8
MW used in car park fires and 37.5 % from the
common 4 MW design fire used in sprinklered
car parks.
63
t Q t Q t Q t Q
0 0 230 1191.266 460 389.2007 690 127.1564
10 4.689 240 1134.712 470 370.7237 700 121.1198
20 18.756 250 1080.842 480 353.1239 710 115.3697
30 42.201 260 1029.53 490 336.3596 720 109.8926
40 75.024 270 980.654 500 320.3912 730 104.6756
50 117.225 280 934.0982 510 305.1808 740 99.70616
60 168.804 290 889.7526 520 290.6926 750 94.97268
70 229.761 300 847.5122 530 276.8922 760 90.46393
80 300.096 310 807.2772 540 263.7469 770 86.16922
90 379.809 320 768.9523 550 251.2258 780 82.0784
100 468.9 330 732.4469 560 239.299 790 78.18179
110 567.369 340 697.6746 570 227.9385 800 74.47017
120 675.216 350 664.553 580 217.1173 810 70.93476
130 792.441 360 633.0038 590 206.8098 820 67.56718
140 919.044 370 602.9525 600 196.9916 830 64.35948
150 1055.025 380 574.3277 610 187.6396 840 61.30406
160 1200.384 390 547.062 620 178.7316 850 58.3937
170 1355.121 400 521.0906 630 170.2464 860 55.6215
180 1519.236 410 496.3522 640 162.1641 870 52.98091
190 1447.111 420 472.7883 650 154.4655 880 50.46568
200 1378.411 430 450.343 660 147.1323 890 48.06986
210 1312.972 440 428.9633 670 140.1474 900 45.78778
220 1250.64 450 408.5986 680 133.494
Friday, December 27, 2019
Visibility Contours At 1.8 m above FFL For Design Option # 3 in case of ducted system
64
Visibility
Contours
(m)
180s 240s
300s 360s
480s 600s
Friday, December 27, 2019
Visibility Contours Across Fire For Design Option # 3 in case of Jet fans
65
Visibility
Contours
(m)
180s 240s
300s 360s
480s 600s
Friday, December 27, 2019 66
• It is noticeable that the sprinkler activation causes low visibility levels and high-water velocity only
downstream and in the vicinity of the fire thus keeping clear egress path upstream the fire throughout
the whole simulation.
• The bed of fire can be easily accessed by fire brigades and within only 10-15 min the whole car park is
clear of smoke due to decaying fire and hence decaying smoke production rate.
• In case of IVS, it can be clearly noticed that sprinkler skipping occurs; the sprinklers away from the
fire activate instead of the sprinklers right above the fire
• It can be concluded that if the sprinkler effect on fire curve is taken into consideration, then the results
will be improved drastically.
• The smoke production rate is low due to the decreasing heat release rate, consequently the visibility
across car park is within the tenable conditions at all times.
Design Option 3
Results & Discussion
Friday, December 27, 2019
• When modelling a sprinklered car park, the sprinklers and their physical effect has to be modelled
• Installing the sprinklers directly below the ceiling within the smoke layer leads to smoke logging where
high-pressure water particles drags the smoke along.
• Sprinkler system located exactly at ceiling level leads to lesser visibility at occupants level compared to
sprinklers installed further away from ceiling due to the interaction of the water spray with the smoke layer
creeping on the ceiling.
• To install the sprinkler beneath the smoke layer, a deluge system has to be used where the sprinklers
activation depends on smoke detectors signal rather than temperature signal
• The use of Jet fans led to intensified mixing and consequently lower visibility at occupants level compared to
the conventional ducted system
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Conclusions
Friday, December 27, 2019
• Ducted system has proven to be better in maintaining an undisturbed smoke layer compared to jet fan system
as demonstrated previously.
• For the IVS to work efficiently, a ceiling height of 3.5 m along with sprinklers installation level of 2.2 m is
recommended
• Sprinkler skipping occurs when IVS is used and this might lead to decreased sprinkler effectiveness
• For the ducted extraction system to work efficiently, a ceiling height of 3.2 m along with sprinklers
installation level of 2.2 m is recommended
• High sprinklers operating pressures trap the smoke underneath the activated sprinklers and limit its
horizontal spread
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Friday, December 27, 2019
• Therefore it is recommended to use sprinkler operating pressures higher than 4 bar in car park applications
• The use of steady fires leads to constant smoke production rate throughout the simulation and consequently
oversized smoke extract system as the smoke rate highly depends on the value of the heat release rate
• The use of decaying fire curves can significantly enhance the tenability criteria within car parks
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Friday, December 27, 2019
• Further investigations have to be made in order to reach the most feasible solution for eliminating
the smoke accumulation in the occupied zone in sprinklered car parks
• More experimental studies on the effect of sprinkler activation on fire curve and smoke
behavior in car parks have to be conducted
• Verify experimentally the possibility of increase the sprinkler network operating pressure to
a limit at which the smoke is trapped beneath the activated sprinklers and does not propagate into
the car park and hence affect the visibility.
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Recommendations For Future Work
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Friday, December 27, 2019
Questions
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