Sprinkler Protection for Cloud Ceilings – Phase 2:
Small Area Clouds
Final Report
Prepared by:
Dr. Jason Floyd
Steve Strege
Matt Benfer
Hughes Associates, Inc.
Baltimore, MD
© August 2014 Fire Protection Research Foundation
THE FIRE PROTECTION RESEARCH FOUNDATION
ONE BATTERYMARCH PARK
QUINCY, MASSACHUSETTS, U.S.A. 02169-7471
E-MAIL: [email protected]
WEB: www.nfpa.org/Foundation
—— Page ii —— FOREWORD
Cloud ceilings are ceiling panels that sit beneath the structural ceiling of a room or space and are
seen increasingly in commercial and industrial buildings. “Cloud” panels range in area from
discrete ceiling panels with large spaces in between, to close-to-full-room-area contiguous
coverage with small gaps at the perimeter wall location. NFPA 13, Standard for the Installation of
Sprinkler Systems, does not have definitive guidance on automatic sprinkler installation
requirements for these ceilings and in some conditions requires sprinklers at both the structural
ceiling and cloud ceiling panel elevations. Recent NFPA 13 change proposals were rejected based
on a lack of validation of modeling results.
The Fire Protection Research Foundation initiated this project to obtain an understanding of how
cloud ceiling panels impact sprinkler actuation thresholds with an overall goal to provide the
technical basis for sprinkler installation requirements. A Phase 1 study investigated the
effectiveness of sprinklers on large area clouds. Phase 2 of this work, which is covered in this
report, focused on developing guidance for sprinkler installation requirements for small area
clouds by determining the maximum gap size between the wall and cloud edge at which ceiling
sprinklers are not effective.
The Research Foundation expresses gratitude to the report authors Dr. Jason Floyd, Steve Strege,
and Matt Benfer, who are with Hughes Associates, Inc. located in Baltimore, MD. The Research
Foundation appreciates the guidance provided by the Project Technical Panelists, the funding
provided by the project sponsors, and all others that contributed to this research effort.
The content, opinions and conclusions contained in this report are solely those of the authors.
About the Fire Protection Research Foundation
The Fire Protection Research Foundation plans, manages, and communicates research on a broad
range of fire safety issues in collaboration with scientists and laboratories around the world. The
Foundation is an affiliate of NFPA.
About the National Fire Protection Association (NFPA)
NFPA is a worldwide leader in fire, electrical, building, and life safety. The mission of the
international nonprofit organization founded in 1896 is to reduce the worldwide burden of fire and
other hazards on the quality of life by providing and advocating consensus codes and standards,
research, training, and education. NFPA develops more than 300 codes and standards to minimize
the possibility and effects of fire and other hazards. All NFPA codes and standards can be viewed
at no cost at www.nfpa.org/freeaccess.
Keywords: automatic sprinkler systems, cloud ceilings, automatic sprinkler installation
—— Page iii —— —— Page iv —— PROJECT TECHNICAL PANEL
Jarrod Alston, Arup
Melissa Avila, Tyco Fire Protection Products
Bob Caputo, Fire and Life Safety America
Dave Fuller, FM Global
Dave Lowrey, City of Boulder Fire Rescue
Jamie Lord, ATF Fire Research Laboratory
Steven Scandaliato, SDG LLC
Karl Wiegand, Global Fire Sprinkler Corporation
Matt Klaus, NFPA Staff Liaison
PROJECT SPONSORS
American Fire Sprinkler Association
National Fire Sprinkler Association
The Reliable Automatic Sprinkler Company
Viking Corporation
—— Page v —— —— Page vi —— Sprinkler Protection for Cloud Ceilings, Part 2: Small Area Clouds
Prepared for
Amanda Kimball
National Fire Protection Research Foundation
1 Batterymarch Park
Quincy, MA 02169
Prepared by
Dr. Jason Floyd
Steve Strege
Matt Benfer
Hughes Associates, Inc.
3610 Commerce Dr., Suite 817
Baltimore, MD 21227
July 31, 2014
FIRE SCIENCE & ENGINEERING
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE ii
TABLE OF CONTENTS
BACKGROUND ............................................................................................................................. 1
TASK 1: EXPERIMENTAL PROGRAM AND RESULTS ............................................................... 2
2.1.
Experimental Setup ...................................................................................................... 2
2.1.1. Cloud Array ......................................................................................................... 2
2.1.2. Instrumentation ................................................................................................... 3
2.1.3. Test Matrix .......................................................................................................... 4
2.2.
Experimental Procedure............................................................................................... 4
2.3.
Experimental Results ................................................................................................... 5
2.4.
FDS Modeling of Experiments ..................................................................................... 7
2.4.1. Grid Study ........................................................................................................... 8
2.4.2. Results of Experimental Simulations ................................................................... 9
2.5.
Task 1 Summary ......................................................................................................... 11
3. TASK 2: NUMERICAL MODELING OF CLOUD CEILING CONFIGURATIONS.......................... 11
3.1.
Methodology ............................................................................................................... 11
3.1.1. FDS Model ........................................................................................................ 11
3.1.2. Performance Criteria ......................................................................................... 14
3.1.3. Analysis Approach ............................................................................................ 15
3.2.
Results and Analysis .................................................................................................. 18
3.2.1. First Pass Results ............................................................................................. 18
3.2.2. Second Pass Results ........................................................................................ 19
3.2.3. Third Pass Results ............................................................................................ 20
3.2.4. Fourth Pass Results .......................................................................................... 20
3.2.5. Summary of Simulations and Development of Installation Guidance ................. 20
4. SUMMARY ................................................................................................................................... 24
4.1.
Summary of Task 1 and Task 2.................................................................................. 24
4.2.
Limitations of Study ................................................................................................... 25
5. REFERENCES ............................................................................................................................. 25
APPENDIX A – Experimental Average Temperature Data ............................................................... 27
APPENDIX B – Operated Sprinkler Heads for FDS Simulations ..................................................... 39
B1 – Corner Fires ............................................................................................................................... 39
B1.1 8 ft Ceiling Height .......................................................................................................... 39
B1.2 14 ft Ceiling Height ........................................................................................................ 45
B1.3 20 ft Ceiling Height ........................................................................................................ 54
B2 – Cross Fires ................................................................................................................................ 59
B2.1 8 ft Ceiling Height .......................................................................................................... 59
B2.2 14 ft Ceiling Height ........................................................................................................ 60
1.
2.
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BACKGROUND
1.
Cloud ceilings are increasingly seen in commercial and industrial facilities. The ceilings consist of
ceiling panels separated by gaps that are suspended beneath the structural ceiling. Designs for cloud
ceilings can vary greatly in terms of the shape and size of the panels, the gaps between panels, and
the spacing between the panels and the structural ceiling. The use of cloud ceilings presents
challenges for sprinkler protection that are not definitively addressed in NFPA 13. These challenges
result from 1) heat from the fire plume entering the gaps between the panels and rising to the structural
ceiling which may prevent sprinklers below the clouds from activating and 2) that sprinklers above the
clouds may have their spray distribution blocked by the clouds. As a result, in some conditions the code
would require sprinklers both below the clouds and at the structural ceiling.
A prior study [1] investigated the effectiveness of sprinklers on large area clouds. A large area cloud
was defined as a cloud whose extents were large enough to require at least one sprinkler per cloud. A
combination of full scale testing and CFD fire modeling was used to examine the effectiveness of
sprinklers on large area clouds in order to determine conditions where only sprinklers on the undersides
of clouds would be required. The study concluded that where the clouds are level and co-planar,
sprinklers can be omitted on the structural ceiling if:
•
•
The gap between a wall and any cloud is less than or equal to 1 inch of gap per foot of
ceiling height, or
The gap between any two adjacent clouds is less than or equal to 1 ¼ inch of gap per foot of
ceiling height.
The study also made a number of recommendations including the following recommendation
•
If clouds are small enough (or have a large enough aspect ratio) that at least one sprinkler
per cloud is not required based upon the listed sprinkler spacing, then a ceiling jet might
encounter additional gaps between clouds. Depending upon the gap size and cloud size, the
ceiling jet may not have the strength (e.g. velocity) to jump the gap in order to reach a
sprinkler. Conditions under which only below cloud sprinklers would be allowed for small
area clouds are likely to be much more limited than for large area clouds. A study of similar
effort to this study is recommended.
This report documents efforts to address the above recommendation. Specifically this project has two
tasks:
1. Selected fire dynamics modeling of cloud ceiling configurations, exploring the impact of cloud
and ceiling height, plenum height, gap distances, fire growth rates, and fire locations on
sprinkler actuation time and temperatures at the cloud and structural ceiling levels.
Configurations of cloud ceilings will include multiple clouds with a range of gap distances
between clouds as well as between clouds and walls.
2. Recommendations for appropriate sprinkler installation criteria for cloud ceilings constructed
with smaller clouds based on these results.
To accomplish the tasks above a two task work plan was proposed for the project and accepted by the
technical panel. Task 1 of the plan is a short experimental program using the Hughes movable ceiling
apparatus. The primary goal of the experimental program is to collect data on fire plume interactions
with small clouds in order to develop appropriate CFD model inputs for Task 2. Task 2 of the plan is to
execute a matrix of simulations for the variables in Task 1 above and use those results to develop the
recommendations for Task 2 above.
The remainder of this report documents Task 1 and Task 2 of the work plan.
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2.
TASK 1: EXPERIMENTAL PROGRAM AND RESULTS
2.1.
Experimental Setup
PAGE 2
2.1.1. Cloud Array
A square array of nine 2 ft x 2 ft cloud panels was constructed with the panels arranged in a 3 x 3 grid.
The panels were 0.25 inch thick gypsum drywall and had a 4 in. separation between panels. The
panels were connected by a frame work of 2 by 4 and 2 by 2 dimensional lumber (i.e., studs). Pairs of 2
x 4 studs were placed on end approximately 16 inches apart; sets of three clouds were then centered
and screwed to the pair of studs. The three sets of three clouds were then connected by three 2 x 2
studs placed at the approximate centers of the panels, perpendicular to the 2 x 4 studs. The panels
were attached to the ceiling framework using four 2 x 2 studs placed near the corners of the array.
These studs provided a rigidity and stability for the cloud array. The cloud array was centered beneath
a 12 ft x 12 ft layer of 0.25 inch drywall that was attached to the existing structural ceiling. The bottom
surface of the clouds were 18 inches below the drywall attached to the structural ceiling. A photograph
of the cloud array is shown in Figure 1. There were no walls or baffles attached to the structural ceiling;
therefore, this setup is equivalent to an unconfined ceiling with no layer buildup.
Figure 1 – Cloud array mounted on movable ceiling
A 12 inch x 12 inch propane sand burner was used to provide the heat release rates desired for testing.
The flowrate to this sand burner was controlled using an Alicat mass flow controller. A shroud was
constructed for the burner to prevent ambient airflows from causing excessive lean of the fire plume.
The shroud consisted of a square built from four pieces of drywall measuring 2 ft x 4 ft and placed on
top of four standard bricks laid on end. The propane burner was placed on the ground and centered
within the shroud. A photograph of the shroud is shown in Figure 2.
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Figure 2 – Burner with shroud
2.1.2. Instrumentation
Eighteen thermocouples were mounted to the clouds and the moveable ceiling. The thermocouple (TC)
locations are shown in Figure 3. At the centers of each cloud, type K, 0.032 diameter TCs were
mounted with the beads 2 inches below both the cloud and the structural ceiling. Data was recorded at
a rate of 1Hz using National Instruments cDAQ hardware and LabView software. Figure 4 shows the
cloud numbers and fire locations (X’s) for referencing the data spreadsheets.
8 ft
2 ft
Structural Ceiling
Cloud
TC (2” below both clouds and structural ceiling)
Fire Location
Figure 3 – Plan view of ceiling plenum
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9
6
3
8
5
2
7
4
1
Figure 4 – Instrumentation numbering for data acquisition and fire locations (blue x)
2.1.3. Test Matrix
Twelve tests were run as part of this test series. Each test shown in the test matrix (Table 1) was run in
duplicate. Three fire locations, which are illustrated in Figure 3 and Figure 4, were used: centered
below a cloud (cloud center), centered between two clouds (cloud-cloud-slot), and centered between
four clouds (cloud-cloud-cross). The cloud ceiling was set to two different heights: 8 ft and 16 ft above
the floor. For each test, two different fire sizes were used sequentially (see Section 3.0).
Table 1 – Test Matrix
2.2.
Test
Configuration
1
2
3
4
5
6
Cloud Center
Cloud-Cloud-Cross
Cloud-Cloud-Slot
Cloud Center
Cloud-Cloud-Cross
Cloud-Cloud-Slot
Ceiling Height
(m [ft])
2.4 [8]
2.4 [8]
2.4 [8]
4.9 [16]
4.9 [16]
4.9 [16]
Fire Size
(kW)
50, 100
50, 100
50, 100
100, 200
100, 200
100, 200
Experimental Procedure
Prior to testing, the ceiling was raised to the appropriate height. The bottom of the cloud ceiling was set
to either 8 ft or 16 ft. The cloud ceiling was leveled using adjustment straps attached to the sides of the
structural ceiling. The propane burner was placed in the appropriate location for the specific test. All
ventilation and circulation fans in the lab were turned off to prevent air currents from causing excessive
flame lean. The DAQ system was turned on for a period of 1 minute or more to ensure the system was
operational and to capture background temperatures. The mass flow controller was set to a zero flow
and valves for the propane system were opened. A lit handheld propane torch was positioned near the
propane burner prior to ignition. The mass flow controller was set to the first output level and the burner
was ignited. The burner was allowed to burn at the first level for a minimum of 5 minutes. After 5
minutes, the mass flow controller was set to the second output level for a minimum of 5 minutes. The 5
minute period ensured that the temperatures reached steady-state levels. After the second 5 minute
burn, the mass flow controller was secured; data was secured after the temperatures reached near
ambient conditions. Overhead exhaust ventilation fans were operated until the space above the
structural ceiling was clear of combustion products.
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2.3.
1JEF00019.000
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Experimental Results
During some of the testing, the propane flame experienced some leaning as is illustrated in Figure 5.
This caused the plume to shift somewhat from the intended location; however, the leaning was
intermittent and varied from test to test.
Figure 5 – Photograph showing a typical plume lean
The ambient temperatures were between 19 and 25 ˚C at the beginning of the tests. Table 2 lists the
ambient temperatures for each test. These temperatures were average temperatures taken over all 18
thermocouples during the 60 second background data acquisition time.
Table 2 – Test Matrix
Test
Configuration
1A
1B
2A
2B
3A
3B
4A
4B
5A
5B
6A
6B
Cloud Center
Cloud Center
Cloud-Cloud-Cross
Cloud-Cloud-Cross
Cloud-Cloud-Slot
Cloud-Cloud-Slot
Cloud Center
Cloud Center
Cloud-Cloud-Cross
Cloud-Cloud-Cross
Cloud-Cloud-Slot
Cloud-Cloud-Slot
Ceiling
Height
(ft)
8
8
8
8
8
8
16
16
16
16
16
16
Ambient
Temperature
(˚C)
22
25
21
21
22
21
25
24
21
19
21
19
Steady-state average temperatures were calculated for each burner output level during each test. An
interval of 200 seconds was selected from each steady state period and the temperature values were
averaged across this period. An example of the steady state period selection is shown in Figure 6.
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Figure 6 – Example of Data Processing Methodology
Average steady state temperatures for Test 1A is shown in Figure 7. Appendix A contains all the
average test data. The fire location is marked with a blue “X” on each figure.
In general, the tests were very repeatable. Differences in average steady state temperatures for the
same cloud in the repeat tests were generally less than 5 ˚C for all clouds in tests 2, 4, 5, and 6. In test
3, the largest differences between average steady state temperatures were as high as 6 ˚C. For test 1,
at the 50 kW burner output, the differences in average steady state temperatures for the same cloud
were less than 5 ˚C, but the largest differences at the 100 kW burner output were up to 15 ˚C. The
largest difference of 15 ˚C was located below the cloud (#7) directly located above the propane burner.
The average temperatures at this location were the highest out of all of the tests at 131 ˚C (test 1A) and
156 ˚C (test 1B).
For all the tests, the figures show a temperature rise over all clouds for all fire locations. However, for
Tests 1 and 4 with the fire centered below a cloud, only a small rise in temperature is seen for the
opposite corner cloud especially as compared to the structural ceiling cloud. Taken together these
observations indicate that there is the potential to activate a sprinkler over multiple cloud gaps from the
fire location, but the permissible gap size and number of gaps is not likely to be large.
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50 kW Average, SS Temperatures
100 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
54
48
48
73
72
69
58
55
51
77
78
72
56
57
53
95
86
74
Below Cloud
Below Cloud
39
31
26
51
39
29
57
44
30
77
57
39
92
58
41
131
81
53
Figure 7 – Test 1A results (x is fire location)
2.4.
FDS Modeling of Experiments
FDS [2-6] was used to simulate each of the 6 tests after performing a grid study. FDS comparisons
were made to the average of each pair of identical tests. The procedure in the FDS Validation Guide [5]
was followed in making the comparisons to determine model error and bias. The experimental error
was taken by performing a propagation of error on the test data using the standard error of the two test
average, the estimated error in the thermocouple measurement (expanded error of 5 % [5]), and the
manufacturer reported error for the mass flow controller (50 kW – 2.3 %, 100 kW – 1.4 %, and 200 kW
– 0.9 %) adjusted to temperature [5]. Comparisons were made for each fire size separately for the
cloud ceiling and the moveable ceiling locations as well as for each fire size for all locations combined
for each test. Two sets of comparisons were made. The first set used the experimental data as
collected. The second set attempted to account for plume lean of the fire by averaging symmetric
locations. The symmetric locations are shown in Figure 8 below.
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Figure 8 – Symmetric locations for plume lean correction (like colors)
2.4.1. Grid Study
Test 1 was used for a grid study. Three meshing schemes were evaluated during the study. The first
scheme was a uniform 2 inch mesh. The second scheme was a uniform 1 inch mesh extending 1 ft to
the sides of the cloud array and 2/3 ft above and below the array with the remainder of the domain a
uniform 2 inch mesh. The third meshing scheme replaced the finer 1 inch mesh with an 0.5 in mesh.
The three meshing schemes respectively placed 2, 4, or 8 cells across the gap between clouds. Table
3 and Table 4 below shows the results of the grid study.
As can be seen in the tables, for all grid sizes the errors are 17 % or less. This is the same as the 16 %
error seen for ceiling jets in the FDS Validation Guide. When all the data for a test is grouped together,
little difference is seen between the three meshing strategies. However, when the data is spilt into
cloud and movable ceiling measurement locations, differences are apparent. Presented in this manner
the uniform mesh has a higher error than the other two meshes. The 1 inch vs 0.5 inch mesh around
the clouds show similar levels of error. From this it is concluded that a modeling goal should be to
target 4 cells across the gap.
An additional observation is that FDS is slightly under predicting the temperatures overall (the bias over
all data is less than 1). Much of this is likely the plume lean being towards the open edge of the cloud
array which can be seen in Test 2 and Test 5 where the outer edge clouds next to the fire have a higher
temperature than the inner clouds next to the fire. When data is separated based on location, the cloud
bias is less than 1 and the movable ceiling bias is greater than 1. This is a desirable outcome as under
predicting the cloud temperatures will result in conservative predictions of sprinkler operation for below
cloud sprinklers.
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Table 3 – Grid Study Results Unadjusted Data
Dataset
All 50 kW
data
All 100 kW
data
50 kW
Cloud
50 kW
Movable
100 kW
Cloud
100 kW
Movable
Uniform 2 inch
mesh
error
bias
1 inch mesh
around clouds
error
bias
0.5 in mesh
around clouds
error
bias
0.12
0.98
0.10
1.00
0.11
0.98
0.16
0.93
0.11
0.94
0.14
0.94
0.10
0.96
0.08
0.93
0.05
0.89
0.14
1.01
0.07
1.07
0.06
1.08
0.15
0.93
0.12
0.89
0.12
0.85
0.17
0.93
0.05
1.00
0.09
1.03
Table 4 – Grid Study Results Symmetrically Averaged Data
Dataset
All 50 kW
data
All 100 kW
data
50 kW
Cloud
50 kW
Movable
100 kW
Cloud
100 kW
Movable
Uniform 2 inch
mesh
error
bias
1 inch mesh
around clouds
error
bias
0.5 in mesh
around clouds
error
bias
0.13
0.91
0.12
0.92
0.13
0.91
0.16
0.88
0.12
0.89
0.16
0.89
0.12
0.88
0.10
0.85
0.07
0.81
0.15
0.06
0.06
1.00
0.06
1.01
0.16
0.83
0.16
0.87
0.14
0.80
0.17
0.89
0.06
0.95
0.09
0.99
2.4.2. Results of Experimental Simulations
Based on the grid study, the 1 inch mesh around the clouds with a 2 inch mesh for the remainder of the
domain was used as the meshing strategy in FDS to simulate all 6 tests. Figure 9 below shows
scatterplots for the measured vs. the predicted data where the diagonal line represents perfect
agreement. The plots show a good agreement between FDS and the measured data. The plots indicate
somewhat more scatter for the movable ceiling than the cloud ceiling. The negative bias observed in
the grid study for the cloud ceiling locations can also be seen in the plots (more data below the diagonal
line for the clouds than above it).
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160
PAGE 10
160
120
Cloud Data
All Data
140
Movable Ceiling Data
140
100
80
60
Predicted Temperature (°C)
Predicted Temperature (°C)
Predicted Temperature (°C)
100
120
120
100
80
60
80
60
40
40
40
20
20
20
40
60
80
100
120
Measured Temperature (°C)
140
160
20
20
40
60
80
100
120
Measured Temperature (°C)
140
160
20
40
60
80
100
Measured Temperature (°C)
120
Figure 9 – Scatterplots of predicted vs. measured data
Table 5 and Table 6 below show the results for all simulations for the unadjusted and averaged test
data. With the exception of the unadjusted data for Test 2 at 100 kW, all the predictions fall within the
ceiling jet error noted in the FDS Validation Guide. As with the grid study, a slight negative bias is seen
for the cloud predictions and slight positive bias is seen for the movable ceiling predictions. The
average biases are not large. The average cloud bias is 0.95 (under predict by 5 %), and the average
movable ceiling bias is 1.02 (over predict by 2 %).
Table 5 – All Test Simulation Results Unadjusted Data
Test
1
2
3
4
5
6
Fire Size
(kW)
50
100
50
100
50
100
100
200
100
200
100
200
All Data
error
bias
0.10
1.00
0.11
0.94
0.13
0.98
0.19
0.95
0.15
0.98
0.17
1.01
0.03
1.00
0.05
0.94
0.04
1.00
0.06
0.97
0.05
1.02
0.04
0.97
Cloud
error
bias
0.08
0.93
0.12
0.89
0.13
0.94
0.22
0.93
0.13
0.94
0.17
0.98
0.02
0.97
0.04
0.93
0.02
0.96
0.06
0.92
0.03
0.99
0.04
0.95
Movable
error
bias
0.07
1.07
0.05
1.00
0.13
1.02
0.17
0.97
0.16
1.03
0.18
1.04
0.01
1.02
0.05
0.96
0.04
1.04
0.02
1.01
0.04
1.05
0.04
0.99
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Table 6 – All Test Simulation Results Symmetrically Averaged Data
Test
1
2
3
4
5
6
2.5.
Fire Size
(kW)
50
100
50
100
50
100
100
200
100
200
100
200
All Data
error
bias
0.10
1.00
0.11
0.94
0.10
0.97
0.12
0.93
0.14
0.98
0.17
1.01
0.03
1.00
0.05
0.94
0.04
1.00
0.05
0.96
0.05
1.02
0.04
0.97
Cloud
error
bias
0.08
0.93
0.12
0.89
0.04
0.93
0.03
0.89
0.12
0.94
0.17
0.98
0.02
0.97
0.04
0.93
0.00
0.96
0.02
0.92
0.03
0.99
0.04
0.95
Movable
error
bias
0.05
1.06
0.06
1.00
0.12
1.02
0.16
0.97
0.16
10.3
0.18
1.04
0.01
1.02
0.05
0.96
0.04
1.04
0.01
1.01
0.04
1.05
0.04
0.99
Task 1 Summary
A set of six experiments using an array of nine small clouds was conducted to collect data for model
development and validation. The experiments varied fire size, fire location, and ceiling height. The
experimental results indicate that a portion of the energy from the fire can cross multiple cloud gaps.
FDS was used to simulate all six of the experiments in two parts. The first part used Test 1 and
performed a grid study. The grid study determined that four cells across the gaps results in a
reasonable predictive accuracy of the below cloud and above cloud conditions. The second part used
the grid determined in the first part to simulate the six tests. For all test variables it was determined that
selected meshing strategy resulted in FDS predictions as accurate as the ceiling jet results in the
validation guide. Additionally the bias in the predictions was appropriately conservative with the cloud
ceilings slight under predicted and the structural ceiling slightly over predicted.
3.
TASK 2: NUMERICAL MODELING OF CLOUD CEILING CONFIGURATIONS
The goal of Task 2 was to simulate a range of cloud ceiling configurations in order to develop
installation guidance and code recommendations. Simulations were performed using FDS 6.0.1.
3.1.
Methodology
3.1.1. FDS Model
3.1.1.1. Geometry
Modeling was based upon the geometry used in the first cloud ceiling study. This was a 30 ft by 30 ft
room with an open doorway along one wall. A fixed ceiling plenum height of 2 ft was used in this study.
The prior study varied plenum height; however, it determined that ceiling plenum height had little impact
on the permissible cloud spacing. Geometry variables in this study were cloud size, the gap between
clouds, and ceiling height. A schematic of the room geometry is shown in Figure 10.
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3.1.1.2. Fire
The first cloud study varied fire growth and used one of five fire locations. It determined that growth rate
was not a significant factor in the permissible cloud spacing; therefore, this study used a medium
growth rate. The first study also determined that the gap sizes were driven by two fire locations: fire in a
corner and fire directly below the intersection of four clouds. Based upon that observation, this study
only used the two limiting fires hereinafter referred to as corner-fire and cross-fire.
Each simulation used a medium growth fire with a 1500 kJ/m2 heat release rate based on a woodplastic mix representative of typical ordinary combustibles. This was represented as C2.13H8N4 with a
5 % soot yield and a 3.8 % CO yield that had a heat of combustion of 17 kJ/kg.
Prediction of sprinkler activation time is dependent upon reasonably predicting the fire plume
temperatures as a function of time. If the fire in FDS was defined as just a single burner, then until it
grows in size it would be a diffuse heat source over a large area with low plume temperatures. To
prevent this and keep the fire plume representative of a growing, flaming fire, the fire source in FDS
was implemented as a series of concentric rectangles, see Figure 11. The fire would grow by
increasing in size over one rectangle until it reached 1500 kJ/m2 and then having the next rectangle
start burning. In this manner medium growth t2 fire was created that grew in size over time.
Varies
Cloud Panel
Varies
Door
9.1 m (30 ft)
Figure 10 – Schematic of simulation geometry
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Corner-fire
Figure 11 – Fire source implementation in FDS
3.1.1.3. Sprinklers
Sprinkler activation was determined by FDS using its built-in sprinkler response model – the RTI
equation. All sprinklers were modeled as quick response (RTI = 50 (m·s)1/2) with an activation
temperature of 73.9 °C (165 °F). Sprinklers were positioned 5 cm (2 inches) below the clouds.
Sprinklers were located at cloud centers, centered in the gap at cloud corners, and centered in the gap
at the cloud edges as shown in Figure 12 (also shown for reference are the fire locations).
Structural Ceiling
Cloud
Sprinkler
Fire Location
Figure 12 – Modeled sprinkler locations plus fire locations for a 3x3 cloud array
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3.1.1.4. Material Properties
The walls, clouds, and structural ceiling were given the properties of 3/8” gypsum wallboard. In general
one would expect these surfaces to be some form of insulating (i.e. low thermal conductivity) material
and gypsum is a common interior finish. The floor of the room was given the properties of 15 cm (6 in)
of concrete. The floor plays little role in the overall heat balance of the room since a configuration would
be considered a failure if the hot layer reached the floor prior to sprinkler activation.
3.1.2. Performance Criteria
Sprinkler requirements for cloud ceilings are in NFPA 13 [7]. The purpose of NFPA 13 is “to provide to
provide a reasonable degree of protection for life and property from fire through standardization of
design, installation, and testing requirements for sprinkler systems, including private fire service mains,
based on sound engineering principles, test data, and field experience.”
The goal of this project was to determine configurations where the sprinklers would not be needed (or
effective) on the structural ceiling when a cloud ceiling is present. It is obvious, and borne out by prior
results, that a porous ceiling will result in increased time to sprinkler activation. Therefore, determining if
a cloud configuration would require sprinklers both above and below the clouds means determining at
what point the delay in activation prevents a reasonable degree of protection for life and property. Since
the listing standards (e.g. UL 199 [8]) for automatic sprinklers do not contain a pre-actuation
temperature requirement for the compartment gas or structure, a metric was needed to evaluate the
model results. This project decided to apply a similar metric as was done for the FPRF residential
sprinkler on sloped ceiling project [9]. The objective of the criteria was define a performance level that
should ensure that life and property would be protected in accordance with the purpose of NFPA 13.
The criteria were:
1. Below cloud sprinklers must activate due to the fire plume (e.g. ceiling jet) and not due to the
development of a hot layer [9].
2. The temperature at 1.6 m (63 in) above the floor cannot exceed 93 °C (200 °F) away from the fire
and cannot exceed 54 °C (130 °F) for over two minutes [8].
3. The temperature below either the structural ceiling or the drop ceiling cannot exceed 315 °C
(600 °F) at a distance of 50 % of a standard flat ceiling sprinkler spacing [8].
4. The backside temperature of the structural and cloud ceilings must remain below 200 °C (392 °F)
[8].
Simulations were performed until one of the above criteria was met. The extent of sprinkler operation
that had occurred prior to that time was then used in the development of spacing requirements.
The rationale for the criteria are discussed below.
3.1.2.1. Plume vs. Layer Sprinkler Operation
If the fire is able to grow large enough, at some point it will fill the plenum space above the clouds with
hot gases. At that point in time the layer will drop below the clouds. Since the layer will be relatively
uniform in temperature, this has the potential for near simultaneous operation of a large number of
sprinklers. This condition could lead to reduced effectiveness over the sprinkler coverage area. This
condition should be avoided. Rather it is desired that sprinkler operation result from the fire plume and
ceiling jet where a small number of sprinklers closest to the fire operate.
This is illustrated in Figure 13 below. These figures are for a simple 2x2 cloud array with a corner fire
(upper left corner) and show temperature just below the clouds at the time of the first sprinkler
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operation. On the left it is seen that the highest temperatures are on the cloud immediate over the fire.
In this case the first sprinkler operation is the sprinkler closest to the fire, a desired outcome. On the
right is the same fire with a larger gap between the clouds. At the time of the first sprinkler operation,
the highest below cloud temperatures are in the opposite corner from the fire and at all the gaps
between the clouds. In this case the first operation is away from the fire and results from the layer
banking down below the clouds. This is an undesirable outcome.
Figure 13 – Below cloud temperatures for plume (left) vs. layer activation (right), sprinkler
indicated by blue circles.
3.1.2.2. Head Height Temperatures
One of the goals of NFPA 13 is life safety. In the context of a fire that, in part, means ensuring
conditions remain tenable for occupants to safely egress. A primary hazard to persons egressing the
room with the fire is the thermal environment. In this case there is the risk of exterior burns and
pulmonary injury from the inhalation of hot gasses [10]. Sprinkler operation will result in the creation of
large amounts of water vapor which can condense in the lungs releasing the sensible enthalpy of the
water. Keeping any extended exposure below 60 °C will greatly avoid the risk. Keeping the
instantaneous exposure below 100 °C will avoid exterior skin injury.
3.1.2.3. Ceiling and Cloud Temperatures
The last two criteria address hazards to the structure and other combustible materials in the room.
Preventing a large area of a layer from exceeding 315 °C (600 °F), a radiative flux of < 7 kW/m2, would
be expected to prevent the radiative ignition of most combustibles remote from the fire location. If this
avoided, then there is a greatly reduced risk of flashover which would threaten both the structure and its
occupants.
Preventive high backside temperatures addresses the risk of fire spread and structural failure. Low
backside temperatures reduce the risk that combustibles in contact with the backside of the ceiling will
ignite. Low backside temperatures should also ensure that the structure and fasteners holding the
ceiling to the structure should remain intact.
3.1.3. Analysis Approach
Simulations were performed using the basic principles of spiral development. That is, an initial set of
simulations was performed in a first cut attempt to bound the end result. Those simulations were
analyzed, and the results used to inform the creation of the next set of simulations.
The prior study determined when there is one sprinkler per cloud that a cloud-to-cloud gap spacing of 1
inch or less per foot of ceiling height would result in adequate sprinkler performance. With smaller
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clouds, there is the potential for there to be clouds without sprinklers. Every gap that a ceiling jet has to
cross to reach a sprinkler will result in additional heat loss from the ceiling jet into the plenum space. It
was anticipated that the prior study results would not result in adequate performance. Therefore, the
first modeling pass consisted of cloud ceiling heights of 8 ft, 14 ft, and 20 ft; with 3x3, 6x6, and 9x9
cloud arrays; and gap sizes of 0.5 or 1 inch per foot of ceiling height.
For each simulation the time when the first criteria in Section 3.1.2 is exceeded is used to end the
simulation. The sprinkler operations at that time are used to determine a permissible sprinkler spacing.
The 3x3 cloud, for a 4 inch gap for an 8 foot ceiling is used below to demonstrate the analysis
approach. Figure 14 shows the evaluation of the four criteria at the point in time of the first failure. In the
upper left image is the backside temperature of the clouds (the fire is the white square in the upper left
of the image). As can be seen there are no temperature in excess of 200 °C over the cloud area. In the
upper right is the head level temperature. There are no temperatures that exceed 93 °C and while there
are temperatures that exceed 54 °C; they have not done so for over 2 minutes. The bottom right image
is the below cloud gas temperatures. From this it can be seen that there is no hazardous hot layer
forming and that the layer has not yet dropped below the clouds as the fire plume is clearly the source
of the highest temperatures. In the bottom left is the below ceiling gas temperatures. Here it can be
seen that the simulation is showing a large region which exceeds 315 °C. This violates the third criteria.
Figure 14 – Evaluation of Section 3.1.2 Criteria.
The sprinkler operations at 240 s were then evaluated. The heads that operated were examined and
the maximum and minimum radius of the region of operation was determined. The radius was
measured from the center of the fire. The average radius was taken as the permissible sprinkler
spacing. This is demonstrated in Figure 15 below. In the figure the average radius is 15 ft. This can be
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expressed as a uniform sprinkler spacing by assuming it represents the diagonal of a square. This
would yield a coverage area of 449 ft2, Figure 16. Note that this is larger than the maximum coverage
area of 225 ft2 allowed in NFPA 13 for standard sprinklers. Therefore, if standard sprinklers were being
used, the coverage area would have to be reduced to that given by the maximum sprinkler spacing as
specified by the manufacturer.
Corner Fire - 3x3 Cloud - 4 in. gap, 8 ft. ceiling
at 240 seconds
30
25
Criteria 1:
Criteria 2:
Criteria 3:
Criteria 4:
Closed Heads
Open Heads
R(min) = 14.2 ft
R(max)= 15.8 ft
15
R(max)
10
R(min)
5
0
0
5
10
15
20
25
30
Distance (feet)
Figure 15 – Evaluation of Sprinkler Spacing.
21.2 ft
15 ft
21.2 ft
Distance (feet)
20
288s
282s
240s
270s
449 ft2
Figure 16 – Evaluation of Sprinkler Coverage Area.
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Results and Analysis
3.2.1. First Pass Results
The first set of simulations was a pass through the permutations of 0.5 in. of gap/ft ceiling height and
1.0 in. of gap/ ft of ceiling height for 3x3, 6x6, and 9x9 clouds with ceiling heights of 8, 14, and 20 ft. All
permutations were run for the corner fire location while the cross-fire location was limited to 0.5 in. of
gap/ft ceiling height for the 8 ft and 14 ft ceiling heights. These are respectively shown in Table 7 and
Table 8 below. Note that plots of all operated heads for all scenarios are shown in Appendix A.
Table 7 – First Pass Results Corner Fire
Cloud
Array
3x3
6x6
9x9
Gap
(in.)
4
8
7
14
10
20
4
8
7
14
10
20
4
8
7
14
10
20
Ceiling
(ft)
8
14
20
8
14
20
8
14
20
Ratio
(in./ft)
0.5
1.0
0.5
1.0
0.5
1.0
0.5
1.0
0.5
1.0
0.5
1.0
0.5
1.0
0.5
1.0
0.5
1.0
Rmin
(ft)
14.2
7.2
11.4
7.6
11.4
7.8
10.4
3.9
10.5
6.2
8.2
6.4
7.2
4.1
8.7
4.4
5.6
4.5
Rmax
(ft)
15.8
7.2
14.3
7.6
14.3
11.7
10.7
3.9
10.8
6.2
10.9
7.8
8.6
4.1
9.6
5.3
9.8
5.6
Coverage
(ft2)
900
207
357
231
660
380
445
60.8
454
108
365
202
250
48
335
94.1
237
102
Table 8 – First Pass Results Cross Fire
Cloud
Array
3x3
6x6
9x9
Gap
(in.)
4
7
4
7
7
Ceiling
(ft)
8
14
8
14
14
Ratio
(in./ft)
0.5
0.5
0.5
0.5
0.5
Rmin
(ft)
7
7
7
7
7
Rmax
(ft)
11.1
15.5
10.5
14.9
14.1
Coverage
(ft2)
328
506
306
480
445
The following observations are noted:
•
The corner fire results are more limiting than the cross fire results. This echoes conclusions
from the first study.
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•
For all the cases, the 0.5 in. of gap/ft of ceiling height results in a sprinkler spacing that is larger
than the 225 ft2 allowed in the code for a standard sprinkler. This indicates that the permissible
gap size can be larger.
•
At 1.0 in. of gap/ft of ceiling height the coverage area drops significantly in most cases from
>225 ft2 to 60 to 100 ft2. This indicates that a larger gap should not be used.
•
The coverage area decreases as the cloud size decreases.
3.2.2. Second Pass Results
Since there was a significant drop in coverage area between gaps of 0.5 in./ft of ceiling height and 1.0
in./ft of ceiling height the second pass targeted gaps between those size. A gap ratio of 0.75 was used
for the 8 ft ceiling. To maintain the current FDS gridding for the 14 and 20 ft ceiling heights (where the
cloud grid was coarser than for the 8 ft ceiling heights) the gap ratios were 0.71 and 0.86. Results are
shown in Table 9 for corner fires and in Table 10 for cross fires.
Table 9 – Second Pass Results Corner Fire
Cloud
Array
3x3
6x6
9x9
Gap
(in.)
6
10
6
10
12
6
10
12
14
Ceiling
(ft)
8
14
8
14
8
14
20
Ratio
(in./ft)
0.75
0.71
0.75
0.71
0.86
0.75
0.71
0.86
0.71
Rmin
(ft)
7.3
7.5
5.8
7.5
6.1
5
5.2
4.9
4.4
Rmax
(ft)
11.3
11.4
5.8
8.2
7.5
5.5
5.7
5.3
6.6
Coverage
(ft2)
346
357
135
246
185
110
119
104
121
Table 10 – Second Pass Results Cross Fire
Cloud
Array
6x6
9x9
Gap
(in.)
10
12
10
12
Ceiling
(ft)
14
Ratio
(in./ft)
0.71
0.86
0.71
0.86
Rmin
(ft)
5.0
5.0
3.3
1.7
Rmax
(ft)
8.7
8.3
9.3
7.15
Coverage
(ft2)
396
365
346
204
The following observations are noted:
•
As previously seen, corner fire results are more limiting than the cross fire results.
•
There is an increasing drop in coverage area as the gap is increased from 0.5 in./ft of ceiling
height. Gaps on the order of 0.75 in./ft of ceiling height still provide coverage areas of 100 ft2 or
larger.
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3.2.3. Third Pass Results
For the third pass the cloud arrays were increased to 12x12 and 15x15 in order to evaluate the effects
of smaller clouds. Only corner fire cases were run for these simulations. Results are shown in Table 11.
Table 11 – Third Pass Results Corner Fire
Cloud
Array
12x12
15x15
Gap
(in.)
4
6
7
10
10
14
4
6
7
10
Ceiling
(ft)
8
14
20
8
14
Ratio
(in./ft)
0.50
0.75
0.50
0.71
0.50
0.70
0.50
0.75
0.50
0.71
Rmin
(ft)
5.7
4.2
5.9
4
5.5
4.2
4.6
4.4
5.3
3.3
Rmax
(ft)
7.7
5.6
7.5
4.4
8.4
5.1
6.2
4.5
6
4.1
Coverage
(ft2)
180
96.0
180
70.6
193
86.5
117
79.2
128
54.8
The following observations are made:
•
Coverage areas have decreased from the larger cloud sizes. No 225 ft2 or larger coverage
areas were seen for the 0.5 in./ft of ceiling height cloud spacing.
•
Coverage decreases with decreasing cloud size with the 15x15 clouds having a smaller
coverage area than the 12x12 clouds.
3.2.4. Fourth Pass Results
For the fourth pass two simulations were run with a 12x6 cloud array to examine the impact of having a
non-square cloud. Only corner fires were run. Results are shown in Table 12.
Table 12 – Fourth Pass Results Corner Fire
Cloud
Array
12x6
Gap
(in.)
7
10
Ceiling
(ft)
14
Ratio
(in./ft)
0.50
0.71
Rmin
(ft)
7.0
5.0
Rmax
(ft)
7.8
6.0
Coverage
(ft2)
219
121
It can be seen that the coverage areas for the 12x6 clouds are close to the coverage areas for the
equivalent 12x12 case. This indicates that when determining how to apply spacing rules, that the
smaller dimension of the cloud should be used.
3.2.5. Summary of Simulations and Development of Installation Guidance
Plots of coverage area vs. gap ratio for corner fires are shown by cloud size in Figure 17. Coverage
area is clearly seen to decrease with both decreasing cloud size and with increasing gap size. Figure
18 plots all ceiling heights on a single plot. In this plot there is a clear pattern that coverage area
decrease with the size of the cloud array. In other words, coverage area decreases with the fraction of
area that the ceiling is open.
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14 ft Ceiling
8 ft Ceiling
900
700
800
600
600
3x3
500
6x6
400
9x9
300
12x12
200
Coverage Area (ft2)
Coverage Area (ft2)
700
15x15
500
3x3
400
6x6
300
9x9
12x12
200
15x15
100
100
0
0
0.50
0.60
0.70
0.80
Gap to Ceiling Ratio (in/ft)
0.90
1.00
0.50
0.60
0.70
0.80
Gap to Ceiling Ratio (in/ft)
0.90
1.00
20 ft Ceiling
700
Coverage Area (ft2)
600
500
400
3x3
300
6x6
9x9
200
12x12
100
0
0.50
0.60
0.70
0.80
Gap to Ceiling Ratio (in/ft)
0.90
1.00
Figure 17 – Sprinkler Coverage Area by Height, Gap Ratio, and Cloud Array for Corner Fires.
400
900
350
800
700
250
3x3
6x6
200
9x9
150
12x12
100
15x15
50
Coverage Area (ft2)
Coverage Area (ft2)
300
600
3x3
500
6x6
400
9x9
300
12x12
200
15x15
100
0
0
0.50
0.60
0.70
0.80
Gap to Ceiling Ratio (in/ft)
0.90
1.00
0.50
0.60
0.70
0.80
Gap to Ceiling Ratio (in/ft)
0.90
1.00
Figure 18 – Sprinkler Coverage Area by Gap Ratio and Cloud Array for Corner Fires.
Figure 19 below presents the same data as the prior two figures in a slightly different manner. For each
cloud configuration the total area of the gaps was computed and then normalized by the total ceiling
area. This results in the open area fraction of the ceiling. While the data in this figure does not show a
clear pattern with the cloud array, it does indicate if the gap area fraction is less than 20 % that a 225 ft2
or larger coverage area can be used. However, immediately after crossing that threshold coverage
areas for some configurations drop to 50-60 ft2. Closer examination of the reveals that the points in the
lower left are primarily from the 8 ft ceiling height and that ceiling height increases towards the upper
right of the point in the plot.
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400
900
350
800
700
250
3x3
6x6
200
9x9
150
12x12
100
Coverage Area (ft2)
300
Coverage Area (ft2)
PAGE 22
15x15
50
600
3x3
500
6x6
400
9x9
300
12x12
200
15x15
100
0
0
0
0.2
0.4
0.6
Gap Area Fraction
0.8
1
0
0.2
0.4
0.6
Gap Area Fraction
0.8
1
Figure 19 – Sprinkler Coverage Area by Gap Fraction to Height Ratio and Cloud Array for Corner
Fires
Figure 20 and Figure 21 take the data from Figure 19 and normalizes the independent axis by the
ceiling height. Figure 20 shows this data by ceiling height and Figure 21 shows all the data on one plot.
For the 14 ft ceiling height, which has the most simulations, the data collapses to a clear trend. The
same basic trend is seen on the other two ceiling heights.
14 ft Ceiling
900
800
800
700
700
600
3x3
500
6x6
400
9x9
300
12x12
200
15x15
100
Coverage Area (ft2)
Coverage Area (ft2)
8 ft Ceiling
900
600
3x3
500
6x6
400
9x9
300
12x12
200
15x15
100
0
0
0
0.01
0.02
0.03
0.04
0.05
0.06
Gap Area Fraction to Ceiling Height (1/ft)
0.07
0
0.01
0.02
0.03
0.04
0.05
Gap Area Fraction to Ceiling Height (1/ft)
0.06
20 ft Ceiling
900
800
Coverage Area (ft2)
700
600
500
3x3
400
6x6
300
9x9
200
12x12
100
0
0
0.01
0.02
0.03
0.04
Gap Area Fraction to Ceiling Height (1/ft)
0.05
Figure 20 – Sprinkler Coverage Area by Gap Fraction to Height Ratio, Ceiling Height, and Cloud
Array for Corner Fires.
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900
800
Coverage Area (ft2)
700
600
3x3
500
6x6
400
9x9
300
12x12
200
15x15
100
0
0
0.01
0.02
0.03
0.04
0.05
0.06
Gap Area Fraction to Ceiling Height (1/ft)
0.07
Figure 21 – Sprinkler Coverage Area by Gap Fraction to Height Ratio and Cloud Array for Corner
Fires
When all the ceiling heights are plotted together, Figure 21, there appears to be a hyperbolic section
defined by the points. Figure 22 shows a best fit hyperbolic section through the data points. The
function is limited to a lower bound of 36 ft2 the minimum coverage area for a standard sprinkler per
NFPA 13.
900
800
Area = 0.076xRatio-2
Coverage Area (ft2)
700
600
3x3
500
6x6
400
9x9
300
12x12
200
15x15
100
0
0
0.01
0.02
0.03
0.04
0.05
0.06
Gap Area Fraction to Ceiling Height (1/ft)
0.07
Figure 22 – Figure 21 Fit with a Power Function to the Lower Edge of the Data
Based on the previous figure a simple rule can be given:
•
The coverage area, A, is defined by the gap area fraction to ceiling height ratio, RG, according
the following formula. The computed coverage area should be limited by any NFPA 13
restrictions (e.g. limited a maximum of 225 ft2 for a standard sprinkler or a manufacturer’s listed
spacing for an extended coverage sprinkler). A computed coverage area less than permitted by
NFPA 13 would indicate the need for sprinklers above the clouds
‫ = ܣ‬0.076 × ܴீ ଶ
For reasons of aesthetics, it may be desirable to have a uniform array of sprinklers to match the uniform
array of clouds. A sprinkler spacing rule which counts clouds may be useful. Figure 23 below plots the
coverage from Figure 21 in terms of the number of clouds that could be skipped when installing
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sprinklers. The figure is summarized as a tabular rule in Table 13. Note this table is applicable only far
gap to ceiling height ratios of 1 in./ft or less.
4
Cloud Skipping
3
3x3
6x6
2
9x9
12x12
1
15x15
0
0
0.01
0.02
0.03
0.04
0.05
0.06
Gap Area Fraction to Ceiling Height (1/ft)
0.07
Figure 23 – Cloud Skipping by Gap Fraction to Height Ratio and Cloud Array for Corner Fires
Table 13 – Sprinkler Spacing Rule Table for Cloud Skipping
Cloud Size1
(ft)
over 10 ft
5 ft to 10 ft
3 ft 4 in. to 5 ft
2 ft 6 in. to 3 ft 4 in.
under 2 ft 6 in.
Gap Area Fraction to Ceiling Height
(1/ft)
Every
Other
Every Third
Each Cloud2
Cloud
Cloud
Up to 1 inch/ft
>0.025
<0.025
>0.045
0.03≤gap≤0.045
<0.03
>0.05
0.035≤gap≤0.05
<0.035
>0.06
0.04≤gap≤0.06
<0.04
1. Dimension is gap center to gap center based on smaller cloud dimension
2. 1 inch of gap/ft of ceiling height was the limit established for large clouds in [1].
4.
SUMMARY
4.1.
Summary of Task 1 and Task 2
A two-part study was conducted to determine conditions under which sprinklers could be placed only
below clouds for ceilings where the cloud size is less than the listed sprinkler spacing. The first part of
the study was experimental, and the second part of the study was numerical.
The experimental study was conducted to develop and validate a modeling approach for cloud ceiling
sprinklers using FDS. Based upon the experimental results, it was determined that at least 4 grid cells
are required across a gap to resolve the appropriate partitioning of plume flow through a gap vs. plume
flow across the bottom of a cloud. Modeling of all experiments using the selected gridding approach
resulted in FDS predictions whose modeling uncertainty matched those for ceiling jets in the FDS
validation guide. Additionally, the modeling results showed a positive bias for the structural ceiling (over
predicted temperatures) and a negative bias for the cloud ceiling (under predicted temperature). This
was a conservative result for the purpose of this study as it decreased the chance of a below cloud
sprinkler operating.
The numerical study consisted of 44 simulations. The simulations varied ceiling height, cloud size, gap
size, and fire location. The simulations were done in a series of sets of simulations. The first set used
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the gap size recommendation from a previous study on large area clouds and one-half that gap size.
The second set refined the gap size to an intermediate value. The third set looked at smaller cloud
sizes. Finally, the fourth set examined the impact of non-square (rectangular) clouds.
The numerical study showed that there is a complicated relationship between cloud size, gap size, and
ceiling height. This relationship was best characterized by the ratio of the gap area fraction (area of
gaps over the entire area of the ceiling) to the height of the cloud ceiling. Two simple rule sets were
developed. The first simply looked at coverage area as a function of the gap area fraction to height
ratio. The second expressed coverage area in terms of the number of clouds that could be skipped
assuming a uniform array of sprinklers.
4.2.
Limitations of Study
The conclusions of this study are limited to following:
•
Uniform gap sizes. Note that extrapolation to large gap sizes should be possible if area fractions
are computed assuming all gaps are the largest size.
•
Uniform cloud arrays. Note that extrapolation to non-uniform arrays (tessellations of multiple
cloud sizes) should be possible if area fractions are computed assuming a uniform tessellation
of the smallest cloud.
•
Flat, level clouds all mounted at the same elevation.
•
Ceiling heights of 8 ft to 20 ft; however, simple scaling laws would suggest the conclusions
would be applicable to larger heights.
•
Cloud sizes greater than 1.1 ft (The smallest cloud tested was for a 15x15 array with 10 inch
gap and 20 ft cloud height).
5.
REFERENCES
1.
Floyd, J. and Dinaburg, J., “Sprinkler Protection for Cloud Ceilings”, Fire Protection Research
Foundation, Quincy, MA, 2013.
2.
McGrattan, K., Hostikka, S., McDermott, R., Floyd, J., Weinschenk, C., Overholt, K., "Fire
Dynamics Simulator User's Guide," NIST SP 1019, National Institute of Standards and
Technology, Gaithersburg, MD, 2013.
3.
McGrattan, K., Hostikka, S., McDermott, R., Floyd, J., Weinschenk, C., Overholt, K., "Fire
Dynamics Simulator Technical Reference Guide Volume 1: Mathematical Model," NIST SP
1018, National Institute of Standards and Technology, Gaithersburg, MD, 2013.
4.
McGrattan, K., Hostikka, S., McDermott, R., Floyd, J., Weinschenk, C., Overholt, K., "Fire
Dynamics Simulator Technical Reference Guide Volume 2: Verification," NIST SP 1018,
National Institute of Standards and Technology, Gaithersburg, MD, 2013.
5.
McGrattan, K., Hostikka, S., McDermott, R., Floyd, J., Weinschenk, C., Overholt, K., "Fire
Dynamics Simulator Technical Reference Guide Volume 3: Validation," NIST SP 1018, National
Institute of Standards and Technology, Gaithersburg, MD, 2013.
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6.
McGrattan, K., Hostikka, S., McDermott, R., Floyd, J., Weinschenk, C., Overholt, K., "Fire
Dynamics Simulator Technical Reference Guide Volume 4: Configuration Management Plan,"
NIST SP 1018, National Institute of Standards and Technology, Gaithersburg, MD, 2013.
7.
NFPA 13 (2013), Standard for the Installation of Sprinkler Systems, National Fire Protection
Association, Quincy, MA.
8.
Underwriters Laboratories Inc. (1997), “Standard for Automatic Sprinklers for Fire-Protection
Service,” UL-199, Northbrook, IL.
9.
Floyd, J., Budnick, E., Boosinger, M., Dinaburg, J., and Boehmer, H. (2010), “Analysis of the
Performance of Residential Sprinkler Systems with Sloped or Sloped and Beamed Ceilings,”
The Fire Protection Research Foundation, Quincy, MA.
10.
Purser, D. (2008), “Assessment of Hazards from Smoke, Toxic Gases, and Heat,” SPFE
Handbook of Fire Protection Engineering, Chapter 2-6, Society of Fire Protection Engineers,
Bethesda, MD.
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APPENDIX A – Experimental Average Temperature Data
50 kW Average, SS Temperatures
100 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
54
48
48
73
72
69
58
55
51
77
78
72
56
57
53
95
86
74
Below Cloud
Below Cloud
39
31
26
51
39
29
57
44
30
77
57
39
92
58
41
131
81
53
Figure 24 – Test 1A results (x is fire location)
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50 kW Average, SS Temperatures
100 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
57
50
50
80
73
72
62
58
53
85
86
79
60
57
55
91
96
87
Below Cloud
Below Cloud
43
33
28
56
40
33
60
45
33
86
63
42
98
62
44
156
89
59
Figure 25 – Test 1B results (x is fire location)
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50 kW Average, SS Temperatures
100 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
51
49
49
76
74
68
64
65
52
96
98
75
70
70
54
107
107
82
Below Cloud
Below Cloud
36
35
31
37
43
40
53
56
38
71
81
49
69
71
48
107
115
72
Figure 26 – Test 2A results (x is fire location)
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50 kW Average, SS Temperatures
100 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
50
49
49
74
75
66
63
65
51
90
93
76
67
68
52
103
103
79
Below Cloud
Below Cloud
36
35
31
40
43
40
54
56
37
69
79
52
66
69
46
103
115
74
Figure 27 – Test 2B results (x is fire location)
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50 kW Average, SS Temperatures
100 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
51
51
50
70
70
70
55
55
56
76
74
79
70
70
50
100
101
68
Below Cloud
Below Cloud
31
33
30
36
39
37
42
49
39
53
63
50
69
72
49
93
101
64
Figure 28 – Test 3A results (x is fire location)
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50 kW Average, SS Temperatures
100 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
49
49
49
68
71
73
53
53
56
73
73
80
68
69
50
98
102
69
Below Cloud
Below Cloud
31
31
30
31
36
36
41
46
38
47
60
50
65
71
47
92
101
64
Figure 29 – Test 3B results (x is fire location)
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100 kW Average, SS Temperatures
200 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
47
49
50
63
69
68
53
52
50
70
72
68
56
52
47
79
74
61
Below Cloud
Below Cloud
42
39
38
55
52
49
51
46
40
68
61
53
62
50
42
84
69
56
Figure 30 – Test 4A results (x is fire location)
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100 kW Average, SS Temperatures
200 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
44
44
43
63
62
60
49
49
44
67
68
62
48
49
43
68
69
60
Below Cloud
Below Cloud
40
39
36
53
52
47
49
47
38
65
64
53
53
50
40
75
73
58
Figure 31 – Test 4B results (x is fire location)
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100 kW Average, SS Temperatures
200 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
44
48
48
60
66
64
49
50
48
67
68
64
54
51
45
76
71
57
Below Cloud
Below Cloud
40
38
36
52
49
47
49
44
37
65
58
49
59
48
40
80
65
52
Figure 32 – Test 5A results (x is fire location)
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100 kW Average, SS Temperatures
200 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
44
44
43
64
62
60
50
50
44
69
69
62
50
50
44
69
70
60
Below Cloud
Below Cloud
39
39
35
53
52
48
49
49
39
66
64
53
51
50
40
76
73
57
Figure 33 – Test 5B results (x is fire location)
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100 kW Average, SS Temperatures
200 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
43
43
43
61
60
61
46
46
44
65
65
61
49
49
42
72
72
60
Below Cloud
Below Cloud
36
36
34
49
48
45
42
42
37
58
58
50
50
49
40
72
71
55
Figure 34 – Test results (x is fire location)
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100 kW Average, SS Temperatures
200 kW Average, SS Temperatures
Below Structural Ceiling
Below Structural Ceiling
43
43
43
59
58
59
46
46
43
63
63
59
48
49
42
69
69
57
Below Cloud
Below Cloud
35
36
33
48
47
45
42
42
37
57
57
50
50
50
40
69
69
53
Figure 35 – Test 6B results (x is fire location)
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APPENDIX B – Operated Sprinkler Heads for FDS Simulations
B1 – Corner Fires
B1.1 8 ft Ceiling Height
Corner Fire - 3x3 Cloud - 4 in. gap, 8 ft. ceiling
at 240 seconds
30
25
Distance (feet)
20
R(min) = 14.2 ft
R(max)= 15.8 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 36 – 3x3 cloud, 4 in. gap, 8 ft ceiling, corner fire
Corner Fire - 3x3 Cloud - 6 in. gap, 8 ft. ceiling
at 235 seconds
30
25
Distance (feet)
20
R(min) = 7.3 ft
R(max) = 11.3 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 37 – 3x3 cloud, 6 in. gap, 8 ft ceiling, corner fire
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Corner Fire - 3x3 Cloud - 8 in. gap, 8 ft. ceiling
at 231 seconds
30
25
Distance (feet)
20
R(min) = 7.4 ft
R(max) = 7.4 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 38 – 3x3 cloud, 8 in. gap, 8 ft ceiling, corner fire
Corner Fire - 6x6 Cloud - 4 in. gap, 8 ft. ceiling
at 223 seconds
30
25
Distance (feet)
20
R(min) = 10.4 ft
R(max) = 10.7 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 39 – 6x6 cloud, 4 in. gap, 8 ft ceiling, corner fire
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Corner Fire - 6x6 Cloud - 6 in. gap, 8 ft. ceiling
at 219 seconds
30
25
Distance (feet)
20
R(min) = 3.8 ft
R(max) = 5.8 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 40 – 6x6 cloud, 6 in. gap, 8 ft ceiling, corner fire
Corner Fire - 6x6 Cloud - 8 in. gap, 8 ft. ceiling
at 213 seconds
30
25
Distance (feet)
20
R(min) = 3.9 ft
R(max) = 3.9 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 41 – 6x6 cloud, 8 in. gap, 8 ft ceiling, corner fire
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Corner Fire - 9x9 Cloud - 4 in. gap, 8 ft. ceiling
at 215 seconds
30
25
Distance (feet)
20
R(min) = 7.2 ft
R(max) = 8.6 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 42 – 9x9 cloud, 4 in. gap, 8 ft ceiling, corner fire
Corner Fire - 9x9 Cloud - 6 in. gap, 8 ft. ceiling
at 221 seconds
30
25
Distance (feet)
20
R(min) = 5.0 ft
R(max) = 5.5 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 43 – 9x9 cloud, 6 in. gap, 8 ft ceiling, corner fire
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Corner Fire - 9x9 Cloud - 8 in. gap, 8 ft. ceiling
at 220 seconds
30
25
Distance (feet)
20
R(min) = 2.8 ft
R(max) = 4.1 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 44 – 9x9 cloud, 8 in. gap, 8 ft ceiling, corner fire
Corner Fire - 12x12 Cloud - 4 in. gap, 8 ft. ceiling
at 228 seconds
30
25
Distance (feet)
20
R(min) = 5.7 ft
R(max) = 7.7 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 45 – 12x12 cloud, 4 in. gap, 8 ft ceiling, corner fire
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Corner Fire - 12x12 Cloud - 6 in. gap, 8 ft. ceiling
at 220 seconds
30
25
Distance (feet)
20
R(min) = 5.7 ft
R(max) = 7.7 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 46 – 12x12 cloud, 6 in. gap, 8 ft ceiling, corner fire
Corner Fire - 15x15 Cloud - 4 in. gap, 8 ft. ceiling
at 220 seconds
30
25
Distance (feet)
20
R(min) = 4.6 ft
R(max) = 6.2 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 47 – 15x15 cloud, 4 in. gap, 8 ft ceiling, corner fire
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Corner Fire - 15x15 Cloud - 6 in. gap, 8 ft. ceiling
at 221 seconds
30
25
Distance (feet)
20
R(min) = 4.4 ft
R(max) = 4.5 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 48 – 15x15 cloud, 6 in. gap, 8 ft ceiling, corner fire
B1.2 14 ft Ceiling Height
Corner Fire - 3x3 Cloud - 7 in. gap, 14 ft. ceiling
at 253 seconds
30
25
Distance (feet)
20
R(min) = 11.4 ft
R(max) = 14.3 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 49 – 3x3 cloud, 7 in. gap, 14 ft ceiling, corner fire
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Corner Fire - 3x3 Cloud - 10 in. gap, 14 ft. ceiling
at 253 seconds
30
25
Distance (feet)
20
R(min) = 7.5 ft
R(max) = 7.5 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 50 – 3x3 cloud, 10 in. gap, 14 ft ceiling, corner fire
Corner Fire - 3x3 Cloud - 14 in. gap, 14 ft. ceiling
at 257 seconds
30
25
Distance (feet)
20
R(min) = 7.6 ft
R(max) = 7.6 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 51 – 3x3 cloud, 14 in. gap, 14 ft ceiling, corner fire
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Corner Fire - 6x6 Cloud - 7 in. gap, 14 ft. ceiling
at 249 seconds
30
25
Distance (feet)
20
R1 = 10.5 ft
R2 = 10.8 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 52 – 6x6 cloud, 7 in. gap, 14 ft ceiling, corner fire
Corner Fire - 6x6 Cloud - 10 in. gap, 14 ft. ceiling
at 254 seconds
30
25
Distance (feet)
20
R(min) = 7.5 ft
R(max) = 8.2 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 53 – 6x6 cloud, 10 in. gap, 14 ft ceiling, corner fire
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Corner Fire - 6x6 Cloud - 12 in. gap, 14 ft. ceiling
at 251 seconds
30
25
Distance (feet)
20
R(min) = 6.1 ft
R(max) = 7.5 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 54 – 6x6 cloud, 12 in. gap, 14 ft ceiling, corner fire
Corner Fire - 6x6 Cloud - 14 in. gap, 14 ft. ceiling
at 250 seconds
30
25
Distance (feet)
20
R(min) = 4.2 ft
R(max) = 5.6 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 55 – 6x6 cloud, 14 in. gap, 14 ft ceiling, corner fire
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Corner Fire - 9x9 Cloud - 7 in. gap, 14 ft. ceiling
at 251 seconds
30
25
Distance (feet)
20
R(min) = 8.7 ft
R(max) = 9.6 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 56 – 9x9 cloud, 7 in. gap, 14 ft ceiling, corner fire
Corner Fire - 9x9 Cloud - 10 in. gap, 14 ft. ceiling
at 246 seconds
30
25
Distance (feet)
20
R(min) = 5.2 ft
R(max) = 5.7 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 57 – 9x9 cloud, 10 in. gap, 14 ft ceiling, corner fire
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Corner Fire - 9x9 Cloud - 12 in. gap, 14 ft. ceiling
at 245 seconds
30
25
Distance (feet)
20
R(min) = 4.9 ft
R(max) = 5.3 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 58 – 9x9 cloud, 12 in. gap, 14 ft ceiling, corner fire
Corner Fire - 9x9 Cloud - 14 in. gap, 14 ft. ceiling
at 245 seconds
30
25
Distance (feet)
20
R(min) = 4.4 ft
R(max) = 5.3 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 59 – 9x9 cloud, 14 in. gap, 14 ft ceiling, corner fire
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Corner Fire - 12x12 Cloud - 7 in. gap, 14 ft. ceiling
at 245 seconds
30
25
Distance (feet)
20
R(min) = 5.9 ft
R(max) = 7.5 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 60 – 12x12 cloud, 7 in. gap, 14 ft ceiling, corner fire
Corner Fire - 12x12 Cloud - 10 in. gap, 14 ft. ceiling
at 238 seconds
30
25
Distance (feet)
20
R(min) = 4.0 ft
R(max) = 4.4 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 61 – 12x12 cloud, 10 in. gap, 14 ft ceiling, corner fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 52
Corner Fire - 15x15 Cloud - 7 in. gap, 14 ft. ceiling
at 238 seconds
30
25
Distance (feet)
20
R(min) = 5.3 ft
R(max) = 6.0 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 62 – 15x15 cloud, 7 in. gap, 14 ft ceiling, corner fire
Corner Fire - 15x15 Cloud - 10 in. gap, 14 ft. ceiling
at 234 seconds
30
25
Distance (feet)
20
R(min) = 3.3 ft
R(max) = 4.1 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 63 – 15x15 cloud, 10 in. gap, 14 ft ceiling, corner fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 53
Corner Fire - 12x6 Cloud - 7 in. gap, 14 ft. ceiling
at 248 seconds
30
25
Distance (feet)
20
R(min) = 7.0 ft
R(max) = 7.8 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 64 – 12x6 cloud, 7 in. gap, 14 ft ceiling, corner fire
Corner Fire - 12x6 Cloud - 10 in. gap, 14 ft. ceiling
at 240 seconds
30
25
Distance (feet)
20
R(min) = 5.0 ft
R(max) = 6.0 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 65 – 12x6 cloud, 10 in. gap, 14 ft ceiling, corner fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 54
B1.3 20 ft Ceiling Height
Corner Fire - 3x3 Cloud - 10 in. gap, 20 ft. ceiling
at 251 seconds
30
25
Distance (feet)
20
R(min) = 11.4 ft
R(max) = 14.3 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 66 – 3x3 cloud, 10 in. gap, 20 ft ceiling, corner fire
Corner Fire - 3x3 Cloud - 20 in. gap, 20 ft. ceiling
at 267 seconds
30
25
Distance (feet)
20
R(min) = 7.8 ft
R(max) = 11.7 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 67 – 3x3 cloud, 20 in. gap, 20 ft ceiling, corner fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 55
Corner Fire - 6x6 Cloud - 10 in. gap, 20 ft. ceiling
at 254 seconds
30
25
Distance (feet)
20
R(min) = 8.2 ft
R(max) = 10.9 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 68 – 6x6 cloud, 10 in. gap, 20 ft ceiling, corner fire
Corner Fire - 6x6 Cloud - 20 in. gap, 20 ft. ceiling
at 266 seconds
30
25
Distance (feet)
20
R(min) = 6.4 ft
R(max) = 7.8 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 69 – 6x6 cloud, 20 in. gap, 20 ft ceiling, corner fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 56
Corner Fire - 9x9 Cloud - 10 in. gap, 20 ft. ceiling
at 251 seconds
30
25
Distance (feet)
20
R(min) = 5.6 ft
R(max) = 9.8 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 70 – 9x9 cloud, 10 in. gap, 20 ft ceiling, corner fire
Corner Fire - 9x9 Cloud - 14 in. gap, 20 ft. ceiling
at 254 seconds
30
25
Distance (feet)
20
R(min) = 4.4 ft
R(max) = 6.6 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 71 – 9x9 cloud, 14 in. gap, 20 ft ceiling, corner fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 57
Corner Fire - 9x9 Cloud - 20 in. gap, 20 ft. ceiling
at 262 seconds
30
25
Distance (feet)
20
R(min) = 4.6 ft
R(max) = 5.6 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 72 – 9x9 cloud, 20 in. gap, 20 ft ceiling, corner fire
Corner Fire - 12x12 Cloud - 10 in. gap, 20 ft. ceiling
at 251 seconds
30
25
Distance (feet)
20
R(min) = 5.5 ft
R(max) = 8.4 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 73 – 12x12 cloud, 10 in. gap, 20 ft ceiling, corner fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 58
Corner Fire - 12x12 Cloud - 14 in. gap, 20 ft. ceiling
at 251 seconds
30
25
Distance (feet)
20
R(min) = 4.2 ft
R(max) = 5.1 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 74 – 12x12 cloud, 14 in. gap, 20 ft ceiling, corner fire
Corner Fire - 15x15 Cloud - 6 in. gap, 20 ft. ceiling
at 246 seconds
30
25
Distance (feet)
20
R(min) = 8.3 ft
R(max) = 8.7 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 75 – 15x15 cloud, 6 in. gap, 20 ft ceiling, corner fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 59
B2 – Cross Fires
B2.1 8 ft Ceiling Height
Cross Fire - 3x3 Cloud - 4 in. gap, 8 ft. ceiling
at 209 seconds
30
25
Distance (feet)
20
R(min) = 7.0 ft
R(max) = 11.1 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 76 – 3x3 cloud, 4 in. gap, 8 ft ceiling, cross fire
Cross Fire - 6x6 Cloud - 4 in. gap, 8 ft. ceiling
at 211 seconds
30
25
Distance (feet)
20
R(min) = 7.0 ft
R(max) = 10.5 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 77 – 6x6 cloud, 4 in. gap, 8 ft ceiling, cross fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 60
B2.2 14 ft Ceiling Height
Cross Fire - 3x3 Cloud - 7 in. gap, 14 ft. ceiling
at 245 seconds
30
25
Distance (feet)
20
R(min) = 7.0 ft
R(max) = 15.5 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 78 – 3x3 cloud, 7 in. gap, 14 ft ceiling, cross fire
Cross Fire - 6x6 Cloud - 7 in. gap, 14 ft. ceiling
at 246 seconds
30
25
Distance (feet)
20
R(min) = 7.0 ft
R(max) = 14.9 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 79 – 6x6 cloud, 7 in. gap, 14 ft ceiling, cross fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 61
Cross Fire - 6x6 Cloud - 10 in. gap, 14 ft. ceiling
at 247 seconds
30
25
Distance (feet)
20
R(min) = 5.0 ft
R(max) = 14.9 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 80 – 6x6 cloud, 10 in. gap, 14 ft ceiling, cross fire
Cross Fire - 6x6 Cloud - 12 in. gap, 14 ft. ceiling
at 252 seconds
30
25
Distance (feet)
20
R(min) = 5.0 ft
R(max) = 14.1 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 81 – 6x6 cloud, 12 in. gap, 14 ft ceiling, cross fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 62
Cross Fire - 9x9 Cloud - 7 in. gap, 14 ft. ceiling
at 225 seconds
30
25
Distance (feet)
20
R(min) = 7.0 ft
R(max) = 14.1 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 82 – 9x9 cloud, 7 in. gap, 14 ft ceiling, cross fire
Cross Fire - 9x9 Cloud - 10 in. gap, 14 ft. ceiling
at 246 seconds
30
25
Distance (feet)
20
R(min) = 3.3 ft
R(max) = 15.3 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 83 – 9x9 cloud, 10 in. gap, 14 ft ceiling, cross fire
HUGHES ASSOCIATES
Sprinkler Protection for Cloud Ceilings,
Part 2: Small Area Clouds
1JEF00019.000
PAGE 63
Cross Fire - 9x9 Cloud - 12 in. gap, 14 ft. ceiling
at 242 seconds
30
25
Distance (feet)
20
R(min) = 7.0 ft
R(max) = 14.1 ft
15
10
5
0
0
5
10
15
Distance (feet)
20
25
30
Figure 84 – 9x9 cloud, 12 in. gap, 14 ft ceiling, cross fire
HUGHES ASSOCIATES