Research Information Center

National bureau of Standards

Gaithersburg, Maryland 20399

NBSIR 87-3633 nov 2 1987

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g* I M 0 f U D

Test Results and Predictions for the

Response of Near-Ceiling Sprinkler

Links in a Full-Scale Compartment

Fire

Leonard Y. Cooper and David W. Stroup

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

September 1987

Sponsored in Part: U.S. Fire Administration

Emmitsburg, MD 21717

NBSIR 87-3633

TEST RESULTS AND PREDICTIONS FOR THE

RESPONSE OF NEAR-CEILING SPRINKLER

LINKS IN A FULL-SCALE COMPARTMENT

FIRE

Leonard Y. Cooper and David W, Stroup

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Gaithersburg, MD 20899

September 1987

Sponsored in Part: U.S. Fire Administration

Emmitsburg, MD 21717

U.S. DEPARTMENT OF COMMERCE, Clarence J. Brown, Acting Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director

TABLE OF CONTENTS

Page

ABSTRACT 1

1. BACKGROUND 2

2. THE NEAR-CEILING FIRE -GENERATED ENVIRONMENT AND RESPONSE OF

SPRINKLER LINKS - EXPERIMENT MOTIVATION 3

2.1 The Fire-Driven Ceiling Jet 3

2.2 The Distribution of Velocity and Temperature Within the

Ceiling Jet 4

2 . 3 Effect of the Upper Hot Gas Layer 5

3. THE EXPERIMENTS 7

3 . 1 General Remarks 7 3.2 The Experimental Setup 7

4. ANALYSIS AND DISCUSSION OF THE EXPERIMENTAL RESULTS 10

4.1 Temperatures in the Burn Room and Thickness of the Ceiling

Layer 10

4.2 Heat Release as a Function of Time 14

4.3 Response of the Simulated Links 14

4.4 Predicting the Response of the Links With a Revised Fire

Growth History 22

5. SUMMARY OF CONCLUSIONS AND RECOMENDATIONS FOR FURTHER RESEARCH 25

6. ACKNOWLEDGMENTS 35

7. REFERENCES 36

iii
LIST OF FIGURES

Page

Figure 1. Sketch of test enclosure 8 Figure 2. Measured gas temperatures at specified times 11

Figure 3. Normalized gas temperatures at specified times 12

Figure 4. Measured gas temperatures in the upper layer at different

distances below the ceiling and the average (solid curve)

upper layer gas temperature 13

Figure 5 . Heat release rate 15

Figure 6. Measured simulated link temperatures at different distances

below the ceiling, the calculated temperature of a nearceiling link (solid curve) , and a plot of the predicted,

normalized ceiling jet velocity profile: Center of the

Room 16

Figure 7. Measured simulated link temperatures at different distances

below the ceiling, the calculated temperature of a nearceiling link (solid curve) , and a plot of the predicted,

normalized ceiling jet velocity profile: Near the

Doorway 17

Figure 8. Calculated link temperature with (solid curve) and without

(dotted curve) upper layer: Center of the Room 20

Figure 9. Calculated link temperature with (solid curve) and without

(dotted curve) upper layer: Near the Doorway 21

Figure 10. Heat Release Rate (Revision 1) 23

Figure 11. Measured simulated link temperatures at different distances

below the ceiling and the calculated temperature of a nearceiling link using the Figure 10 Heat Release Rate (solid

curve) : Center of the Room 24

Figure 12. Measured simulated link temperatures at different distances

below the ceiling and the calculated temperature of a nearceiling link using the Figure 10 Heat Release Rate (solid

curve) : Near the Doorway 26

Figure 13. Calculated link temperature with (solid curve) and without

(dotted curve) upper layer using the Figure 10 Heat Release

Rate: Center of the Room 27

iv
LIST OF FIGURES (Cont.)

Page

Figure 14. Calculated link temperature with (solid curve) and without

(dotted curve) upper layer using the Figure 10 Heat Release

Rate: Near the Doorway 28

Figure 15. Heat Release Rate (Revision 2) 29

Figure 16. Measured simulated link temperature at different distances

below the ceiling and the calculated temperature of a nearceiling link using the Figure 15 Heat Release Rate (solid

curve) : Center of the Room 30

Figure 17. Measured simulated link temperature at different distances

below the ceiling and the calculated temperature of a nearceiling link using the Figure 15 Heat Release Rate (solid

curve) : Near the Doorway 31

Figure 18. Calculated link temperature with (solid curve) and without

(dotted curve) upper layer using the Figure 15 Heat Release

Rate: Center of the Room 32

Figure 19. Calculated link temperature with (solid curve) and without

(dotted curve) upper layer using the Figure 15 Heat Release

Rate: Near the Doorway 33

v

TEST RESULTS AND PREDICTIONS FOR THE RESPONSE OF NEAR- CEILING

SPRINKLER LINKS IN A FULL-SCALE COMPARTMENT FIRE

By

Leonard Y. Cooper and David W. Stroup

Abstract

This paper presents and analyzes a portion of the data acquired during a test

program which involved full-scale, sprinklered, compartment fires. The work

here focuses attention specifically on key features of the typical sprinkler

link deployment/response problem. It is found that the elevated temperature,

upper smoke layer which develops inevitably in compartment fires can have a major impact on the thermal response of sprinkler links. It is shown that

traditionally accepted methods of predicting sprinkler link response which do

not account for this upper layer can be totally inadequate. Link response

predictions used here involve a new method of calculation which does take

account of the smoke layer environment. Favorable comparisons between

predictions and experiment are obtained and experiments for further validation

of this method are recommended. Finally, it is found that sprinkler link- to

ceiling spacing can have a significant effect on the thermal response of links

and it is recommended that a method which accounts for this effect be

developed and validated.

Key words: Automatic sprinklers, ceiling jets, compartment fires,

fire -generated flows, fusing, heat transfer, link- to-ceiling

spacing, link- to -fire spacing, smoke layer, sprinkler links,

thermal response, unconfined ceilings, validation.

1
1 . BACKGROUND

A series of full-scale, sprinklered, compartment fire tests were carried out

[1] . One purpose of the test series was to study the response of sprinkler

links and resulting sprinkler actuation during realistic compartment fire

scenarios. This report presents and analyzes a portion of the data acquired

during the test program. It focuses attention specifically on key features of

the typical sprinkler link deployment/response problem which are of such

critical importance to fire safe design.

For any fire which develops in a given compartment configuration, the response

of a sprinkler link is a function of 1) location and design of the link, and

2) time from fire initiation. Here, the location of the link is defined by

the distance between the fire plume -ceiling impingement point (the point on

the ceiling directly above the effective center of the fire) and the point on

the ceiling directly above the effective center of the link, and by the

distance of the link from the ceiling. The design of the link is

characterized by the RTI (response time index) . The RTI of a particular link

is a measure of its rate -of- temperature change when immersed in a relatively

uniform- velocity , uniform- temperature stream [1,2],

The effects of the link location parameters were of particular interest here.

Also of key interest was the effect on link response of a changing, high

temperature, upper- layer fire -generated environment which typically develops

prior to link actuation in compartment fire scenarios. These effects, some of

which are ignored in currently accepted sprinkler deployment technology [3-7]

,

2
are studied here within the context of a growing fire in an office module -type

scenario

.

2. THE NEAR- CEILING FIRE -GENERATED ENVIRONMENT AND RESPONSE OF SPRINKLER

LINKS - EXPERIMENT MOTIVATION

2.1 The Fire-Driven Ceiling Jet

As a fire grows, it releases energy and other products of combustion, both

gaseous and solid. Because of their elevated temperature, the products of

combustion, typically referred to as smoke, are driven upwards by buoyancy

forces. These products generate a turbulent plume of upward moving, elevated

temperature gases. All along the axis of the plume, relatively quiescent

ambient air is entrained into and mixed with the plume gases as they continue

their ascent to the ceiling. As a result of the entrainment, the total upward

mass flux in the plume continuously increases and the average temperature in

the plume continuously decreases with increasing height. When the upward

movement of the plume gases is blocked by the compartment ceiling, they spread

radially outward forming a relatively thin, high- temperature , high-velocity

turbulent ceiling jet. Unlike the location of the unwanted fire and its plume

which is not known a priori, the near-ceiling region is one zone in a compartment of fire origin where one is insured of a relatively intense fire

environment. For this reason the near-ceiling region, i.e., the location of

the ceiling jet, is a prime zone for the deployment of sprinklers and their

heat sensitive actuating links. Effective and reliable selection and

3
deployment of sprinkler links must be based on an understanding of the flow

conditions in this zone, local to the link, which provide the driving

mechanism for its response and actuation.

2.2 The Distribution of Velocity and Temperature Within the Ceiling Jet

As the gases of the ceiling jet flow radially outward under the ceiling

surface from the region of fire plume-ceiling impingement, they entrain and

mix with relatively cool gases from below. With increasing radius, this leads

to a continuous increase in thickness and decrease in the peak temperature and

velocity of the ceiling jet gases.

At any given radial position, the velocity and temperature of the ceiling jet

varies significantly throughout its thickness. The velocity is always zero at

the ceiling surface. Below the ceiling the velocity rises rapidly to its peak

value. The velocity then decreases continuously with further increases in

distance from the ceiling, until, at the local thickness of the ceiling jet,

it approaches the negligible velocity of the lower, near- quiescent

environment. Velocity distributions in ceiling jets have been measured [e.g.,

8,9] and a general equation which predicts the velocity and correlates well

these data has been developed [10]. The equation predicts the ceiling jet

velocity distribution as a function of fire energy release rate, fire- toceiling spacing, distance from the fire plume -ceiling impingement point, and

distance below the ceiling.

4
The situation for the temperature distribution thoughout the thickness of the

ceiling jet is somewhat different than that of the velocity. Immediately

adjacent to the ceiling itself, the temperature of the ceiling jet is

identical to that of the ceiling surface. However, at any given radius, this

surface temperature is itself changing rapidly from its initial, cool, ambient

temperature state. Below the ceiling surface the temperature typically rises

rapidly to its peak value and then, with increasing distance from the ceiling,

the temperature continously decreases. Further below the ceiling and near the

edge of the ceiling jet, its temperature approaches the temperature of the

lower quiescent environment. Significant progress has been made in the

development of means to predict the radial- and time -dependent temperature of

ceiling surfaces [11-13]. Also, temperature distributions of ceiling surfaces

[14-16] and throughout ceiling jets [e.g., 15-19] have been measured in ,a

variety of test configurations. However, as compared to the ceiling jet

velocity distribution, a complete methodology for predicting the time- and

space -dependent temperature distribution in the ceiling jet has not yet been

assembled. Such a methodology could be used to enhance significantly the

effectiveness and reliability of sprinkler link design and deployment.

2.3 Effect of the Upper Hot Gas Layer

Existing accepted design methods for predicting sprinkler link response are based on characteristics of fire plume-driven ceiling jets flowing beneath

what are referred to as unconfined ceilings, i.e., ceilings without any

confining walls. The unconfined ceiling configuration is associated with an

5
idealized fire scenario. In actuality, real compartment fires involve

structural walls that capture and contain fire-generated plume and ceiling jet

gases. Throughout the early stages of a fire, these gases fill the space with

an upper layer of smoke which grows continuously in thickness and in

temperature. In many real fires it is typical for the growing smoke layer to

engulf the ceiling jet rapidly, i.,e., in time intervals which are comparable

to the expected time of sprinkler actuation. Also, prior to sprinkler

actuation the fire plume gases which drive the ceiling jet would have to

travel a large part of their total fire- to-ceiling ascent through the elevated

temperature upper smoke layer. As a result of all this, the characteristics

of real fire plumes in the region of ceiling impingement and the

characteristics of resulting plume-driven ceiling jets can differ

significantly from those of idealized, unconfined ceiling, "design" fire

scenarios. These upper layer effects have been modeled analytically

[11,20,21] and they have been observed experimentally [16,18,22]. Depending

on the fire growth history and on the dimensions of the compartment, the

effect of the upper layer and the ceiling structure can lead to link

temperatures which are higher, and possibly even lower than corresponding link

temperatures that would be measured in a comparable unconfined ceiling fire

scenario

.

6
3 . THE EXPERIMENTS

3 . 1 General Remarks

The purpose of this paper is to discuss those aspects of the experiments which

bring into play and measure some of the above-mentioned effects of real

compartment fires and corresponding sprinkler link response. Only those

features of the experiments which were essential to this objective will be

included here. For a comprehensive description of the overall test program

the reader is referred to [1].

3.2 The Experimental Setup

One test scenario is considered. It involves a wastepaper-basket fire

initiation of an office -module compartment fire. The office furniture

includes a desk, chair and bookcase, all heavily loaded with a paper/book- type

fuel load. Referring to Figure 1, the combustibles are assembled and the fire

is initiated in the inside corner of a 2 .44 m x 3 . 66 m room of 2.44 m height.

There is an open doorway to the room, 0.76 m wide x 2.03 m high, and this is

located in the far 2.44 m wall. Smoke flowing out of the doorway is collected

in a large hood/ventilated duct flow-through system equipped with oxygendepletion-measurement capabilities. Data from this lead to an estimate of the

time -dependent total energy release rate of the fire. The realistic, but

relatively modest size of the test space, the general magnitude of the energy

release rate of the fire and the size of the doorway are such as to lead to an

7
8

Figure

1.

Sketch

of

Test

Enclosure
upper layer in the burn room which would achieve very rapidly (compared to the

response of sprinkler links) a deep, and relatively constant thickness.

Toward the center of the burn room is a "tree" of 20 mil diameter

chromel- alumel , bare -wire thermocouples located at the ceiling and between the

ceiling and floor at 0.152 m (6.0 in) intervals. These are used to obtain the

temperature in the burn room, away from the combustion zone and plume, as a function of time and elevation.

There is one active sprinkler and quick response link with RTI of 46 (ms) 1/2 .

It is deployed in the center of the room, approximately 2 . 20 m from the room

corner and from the fire plume -ceiling impingement point. The link is

approximately 0.10 m (4. in) below the ceiling surface. Also near the center

of the room is a near- ceiling, vertical "tree" of five simulated sprinkler

link disks each having an RTI of 46 (ms) 1/2 . The disks are 0.0095 m ( 0.375

in) in diameter and 0.00079 m (0.03125 in) thick and they are aligned with

their axes parallel to the ceiling and in a near -optimum- streamline

orientation in relation to a radial velocity ceiling jet. The ceiling- tosimulated- link separation distances were indicated in Figure 1. There is a

second, near-ceiling tree of simulated links located near the middle of the

doorway. It is identical to the first tree except for the ceiling-disk

separation distances whose values are also identified in Figure 1. All

simulated links are instrumented with thermocouples so that their temperature

time response could be monitored during the tests. Since the simulated links

have the same RTI as the active link, their temperature response during a test

would provide a direct indication of the effect of link- to-ceiling spacing

9
(i.e., the effect of the anticipated spatial distribution of ceiling jet

velocity and temperature) on the response of an active link.

4. ANALYSIS AND DISCUSSION OF THE EXPERIMENTAL RESULTS

4.1 Temperatures in the Bum Room and Thickness of the Ceiling Layer

Plots of temperature as a function of distance from the ceiling as measured by

the floor- to-ceiling thermocouple tree are presented in Figure 2 for different

times following initiation of the fire, but prior to the activation of the

sprinkler which occured at approximately 175 s subsequent to ignition. These

temperature distributions are normalized by the temperature measured at the

uppermost, gas - submerged thermocouple (0.152 m below the ceiling) and the

normalized results are replotted in Figure 3. It can be noted from these

latter plots that 1) an upper, elevated- temperature gas layer grows rapidly to

a relatively uniform thickness; 2) there is an interface that separates these

upper layer gases from a relatively low- temperature and spatially-uniform

lower layer; and 3) the interface is at a near-constant elevation of 0.99 m

below the ceiling (1.45 m above the floor), corresponding to an elevation of

0.58 m below the top of the doorway.

Based on the above observations, the above -interface temperature measurements

for each time of the Figure 2 and 3 plots were averaged spatially. The

result, the average upper- layer temperature as a function of time, is plotted

in Figure 4 and used below in the analysis of link response. Also included in

Figure 4 are the actual temperature- time measurements of the individual

10
(O) 3HfUVU3dW31

w

©e

•H

JJ •o

©u

3

bO

11

DISTANCE

BELOW

CEILING

(cm)
o

LO

C\J

3dn±Vd3dlAI31 Q3ZnVIAI«ON

cn0) e

•r-l U

m

®u

3

QO

•iH u*

12

DISTANCE

BELOW

CEILING

(cm)
13

Figure

4.

Measured

gas

temperatures

in

the

upper

layer

at

different

distances

below

the

ceiling

and

the

average

(solid

curve)

upper

layer

gas

temperature
upper -layer -submerged thermocouples. Activation of the active sprinkler head

is seen clearly to occur at approximately 175 s.

4 . 2 Heat Release as a Function of Time

The total heat release of the combustibles as a function of time was deduced

from the oxygen depletion calorimetry measurements acquired in the hood/duct

of the smoke collection/exhaust system. This is presented in Figure 5. As

can be seen, the activation of the sprinkler at approximately 175 s reduces

abruptly the strength of the fire. The Figure 5 result will be used in the

next paragraph to predict the thermal response of the simulated sprinkler

links and to compare these predictions to measured time- temperature data.

Although the general peak levels of the energy release rate curve of Figure 5

and their timing are consistent with the visually observed fire growth, the

very low early levels and the indicated sharp increase at 100 - 125 s are not.

Predicted sprinkler link response to a Figure 5 -type energy release rate, but

with a more realistic early growth rate, will be presented below in the last

paragraph of this section.

4.3 Response of the Simulated Links

The measured temperature responses of the two trees of simulated links are

plotted in Figures 6 and 7 for the room- center tree and the near- doorway tree

locations, respectively. Also included in these figures are plots of

theoretical estimates for the normalized velocity of the elevated- temperature

14
CO

LU

I15

Figure

5.

Heat

Release

Rate
(0) 3UniVH3dlN31

16

TIME

(s)

Figure

6.

Measured

dummy

link

temperatures

at

different

distances

below

the

celling,

the

calculated

temperature

of

a

near-celling

link

(solid

curve)

,

and

a

plot

of

the

predicted,

normalized

celling

Jet

velocity

profile

(insert)

:

Center

of

the

Room
V *o

-hO

> M

O

41 X 4

x> e •’->

o o

«>u&

(O) 3UniVH3dV\l31

17
smoke as If Mows past; each link of the two simulated link trees. These

velocity estimates were obtained from Eq . (1) of [10].

The thermal response of sprinkler links are determined by and depend on the

local " f ree-f leld" gas temperature and velocity. As seen f rom the plots of

predicted smoke velocity, a significant variation in link response as a function of celling elevation is to be expected and was measured. For

example, for the link tree at the center of the room, near the deployed active

sprinkler, If Is seen in Figure 6 that at the time of sprinkler actuation the

coolest of the links was the one 0.01 m below and closest to the ceiling. At

this time that Link was L4°C less than the hottest of the center-of - the-room

links which reached approximately 64°C above ambient (i.e., 88°C) and was

located 0.0b m below the celling. Similarly, for the near-doorway tree, it is

••eri In Figure / that at the time of sprinkler actuation the coolest of the

links was, again, the one 0.01 m below and closest to the celling. At this

time that link was 10°C less than the hottest of the near-doorway links which

reached approximately b3°C above ambient (i.e., 77°C) and was located 0.07 m

be I ow the celli rig

If Is particularly noteworthy that all existing accepted and recently proposed

methods of estimating sprinkler link response [3,b -7] are based on estimates

of peal' velocity and temperature. These depend only on radial distance from

the fire and not on distance from the ceiling. Provided a link is located

within /i relatively wide range of elevations, below the celling, but not too

close or too far, the relatively broad velocity distributions and measured

I Ink temperatures of Figures 6 arid / are conslstant with the fact that the

18
traditional approach is a reasonable one. However, for more reliable and

versatile design, especially for links very close to ceilings, it is evident

that predictions of the response of a link must be determined as a function of

the vertically-varying , local, free- field gas environment.

The accepted approach to sprinkler link deployment design is based on

calculation procedures of link response which are strictly valid only for

links deployed below unconfined ceilings, i.e., where there is no growth of an upper smoke layer. To the extent that they generate reliable results in such

configurations they can also provide reasonable engineering estimates of link

response relatively early in time for confined ceilings. However, for most of

the time interval between fire initiation and sprinkler actuation, ceiling

jets and sprinkler links are typically submerged in a hot upper smoke layer.

For this reason, such calculation procedures do not have general

applicability. This is illustrated graphically in the dashed plots of Figures

8 and 9 which are the result of an unconfined ceiling calculation for the link

temperature response in the present experiment for the center-room and neardoor deployed links, respectively. The calculation used the DETACT-QS

computer program [6], the previously described room geometry characteristics,

the energy release rate history of Figure 5, and a 46 (ms) 1/z RTI . The

predicted link thermal responses are far lower than would be required to

predict the observed, 175 s sprinkler actuation. It is clear that a design

procedure which uses predictions of unconfined ceiling link response is not

adequate in the present type of typical fire scenario.

19
(0) aonivaadwai mn aoiosisa

20

Figure

8.

Calculated

link

temperature

with

(solid

curve)

and

without

(dotted

curve)

upper

layer:

Center

of

the

Room
(0) aynivd3di^i3i mnh uoioaiaa

21

Figure

9.

Calculated

link

temperature

with

(solid

curve)

and

without

(dotted

curve)

upper

layer:

Near

the

Doorway
As mentioned in an earlier section, calculation procedures which take account

of the effect of the upper layer on link reponse (but not yet the link- to -

ceiling distance) have been developed [11,20,21]. These have been advanced

further and applied in the present fire scenario. The result of applying

these calculation procedures are presented in the solid line plots of Figures

8 and 9 for a center-room and near-door link, respectively. The Figure 8

result predicts that a 46 (ms) 1/2 RTI , 74° C fuse- temperature link would fuse

at approximately the same time, 175 s, that the experimental link and

sprinkler were actuated.

The calculated two -layer link responses of Figures 8 and 9 are replotted in

Figures 6 and 7, respectively. As can be seen in the latter figures, the

comparisons between the experimental data and the predictions are quite good

at times of the experiment close to the time of sprinkler actuation. However,

there is a significant qualitative and quantitative difference between

predicted and measured results at intermediate times. It is believed that the

major reason for this discrepency is related to the above-mentioned

inaccuracies in the data for the fire's early energy release rate history as plotted in Figure 5 and as used in the predictions of link response.

4.4 Predicting the Response of the Links With a Revised Fire Growth History

The two -layer link response calculations were carried out a second and third

time using two different revised- Figure 5 fire growth histories. These two

fire growths, plotted in Figures 10 and 11, involve early- time fire energy

release rates which grow linearly with time and which intercept the Figure 5

22
oo

C\J

LO

N-O

in

in

CMoo

in

h*o

in

in

CVJ o

LU

I23

Figure

10.

Heat

Release

Rate

(Revision

1)
0.05

(0) 3UniVU3dV\l3±

24

TIME

(s)

Figure

11.

Measured

dummy

link

temperatures

at

different

dfstances

below

the

celling

and

the

calculated

temperature

of

a

near-ceiling

link

using

the

Figure

10

Heat

Release

Rate

(solid

curve):

Center

of

the
growth rates at each of two different times close to its 100 - 125 s peak. It

is believed that these revised fire growth histories represent experimentally

the observed fire growth more accurately than the fire growth of Figure 5.

The results of the analysis of link response to the Figure 10 fire growth rate

are plotted in Figures 12 - 15 in a manner which is analogous to the plots of

Figures 6-9. Results of a similar analysis, but using the Figure 11 fire

growth rate, are presented in Figures 16 - 19. As can be seen from these

figures, there is a significant improvement in the comparison between the

measured and newly predicted results for link response. For example, as can

be seen in Figure 16 (to be compared to the previous results of Figure 6) , for

a link deployed at the center of the room both the qualitative and

quantitative aspects of the predicted link response is remarkably close to

measured values . These favorable results provide very encouraging support for

the overall link response prediction methodology which has, heretofore, never

been evaluated experimentally.

5. SUMMARY OF CONCLUSIONS AND RECOMENDATIONS FOR FURTHER RESEARCH

This report presented and analyzed a portion of the data acquired during a

test program which involved full-scale, sprinklered, compartment fires. The

work here focused attention specifically on key features of the typical

sprinkler link deployment/response problem. The following is a summary of

conclusions and recommendations for futher research:

25
(0) aamvaadwai

26

TIME

(s)

Figure

12.

Measured

dummy

link

temperatures

at

dlfXerent

distances

below

the

ceiling

and

the

calculated

temperature

of

a

near-ceiling

link

using

the

Figure

10

Heat

Release

Rate

(solid

curve):

Near

the
o

o> 00

ooo

N- CD

ooo in^tCOCMooo

T“

(0) 3uruvyadiAi3i mn uoioaiaa

27

TIME

(s)

Figure

13.

Calculated

link

temperature

with

(solid

curve)

and

without

(dotted

curve)

upper

layer

using

the

Figure

10

Heat

Release

Rate:

Center

of

the

Room
(0) aanivaadwai mn aoioaiaa

28

TIME

(s)

Figure

14.

Calculated

link

temperature

with

(solid

curve)

and

without

(dotted

curve)

upper

layer

using

the

Figure

10

Heat;

Release

Rare:

Hear

the
(M>i) 3iva Bsvaiaa 1V3H

29

Figure

15.

Heat

Release

Rate

(Revision

2)
(0) 3UfUVU3dl/\l3±

30

TIME

(s)

Figure

16.

Measured

dummy

link

temperatures

at

different

distances

belov

the

ceiling

and

the

calculated

temperature

of

a

near-ceiling

link

using

the

Figure

15

Heat

Release

Rate

(solid

curve):

Center

of

the
(0) 3yniVU3dlN31

31

TIME

(s)

Figure

17.

Measured

dummy

link

temperatures

at

different

distances

below

the

ceiling

and

the

calculated

temperature

ofa

near-ceiling

link

using

the

Figure

15

Heat

Release

Rate

(solid

curve):

Near

the

Doorway
(0) aamvuadwai mn aoioaiaa

32

TIME

(s)

Figure

18.

Calculated

link

temperature

with

(solid

curve)

and

without

(dctteo

curve)

upper

layer

using

the

Figure

15

Heat

Release

Rate:

Center
(O) 3HfUVU3dlN31 *NH 00103130

33

Figure

19.

Calculated

link

temperature

with

(solid

curve)

and

without

(dotted

curve)

upper

layer

using

the

Figure

15

Heat

Release

Rate.

Near

the

Doorway.
The elevated temperature, upper smoke layer which develops inevitably in

compartment fires can have a major impact on the thermal response of sprinkler

links. As was the case in the experiment discussed here, traditionally

accepted methods of predicting sprinkler link response can be totally

inadequate. This is because of the fact that such methods are based on

idealized, unconfined ceiling fire scenarios, and they do not account for the

effects of the smoke layer on the flow dynamics of the upper fire plume and on

the ceiling jet, the latter of which engulfs and drives the thermal response

of the sprinkler link.

The link response predictions of this work used a new method of calculation

which does take account of the smoke layer environment. Favorable comparisons

between predictions and experiment were obtained. While this was very

encouraging, before this new method can be recommended for general use it

should be validated over a range of experimental conditions. Toward this end

it is recommended that an experimental program be carried out which measures

link responses under confined ceiling conditions involving a range of: link

RTI , link-to-fire spacing, link- to-ceiling spacing, fire- to-ceiling spacing,

fire growth rate, and ceiling material. It is noteworthy that no such

validation exists for the sprinkler link response calculation procedure which

was used, for example, to develop the Standard of [5],

Sprinkler link- to-ceiling spacing can have a significant effect on the thermal

response of links. For example, in the present experiment, at the time of

fusing of the active link (designed to occur at 74° C) the temperatures of

nearby, like-RTI, simulated links at 0.01 m and 0.05 m below the ceiling

34
varied by approximately 14° C, with the link closer to the ceiling being the

cooler of the two. This can be of critical importance, especially in the

reliable use of certain modern sprinkler- link systems which are often deployed

very close to, and even embedded into ceiling surfaces. Although a method is

at hand to include the effect of link- to-ceiling spacing in link response

predictions, such a method does not yet exist. It is recommended that such a method be developed and validated with the data base which will be generated

by the above -recommended test program.

6 . ACKNOWLEDGMENTS

This work was supported by the U.S. Fire Administration. The authors would

like to express their appreciation to Edward Wall and Tom Smith for their

continued interest in this area of study.

35
7 . REFERENCES

1. Walton, W.D. and Budnick, E.K., Quick Response Sprinklers in Office

Configurations: Fire Test Results, to appear as a NBSIR, US National

Bureau of Standards, Gaithersburg, MD.

2. Heskastad, G., The Response Time Index (RTI) , Paper RC 81-tp-3

presented at the Technical Conference on Residential Sprinkler Systems,

Factory Mutual Research Corporation, Norwood, MA, April 28-29, 1981.'

3. Evans, D.D., Thermal Actuation of Extinguishing Systems, Combustion

Science and Technology, Vol. 40, pp79-92, 1984.

4. Alpert, R.L.

,

Calculation of the Response Time of Ceiling-Mounted Fire

Detectors, Fire Technology, Vol. 8, ppl81-195, 1972.

5. Standard on Automatic Fire Detectors, NFPA 72E - 1984, Appendix C,

National Fire Protection Association, Batterymarch Park, Quincy, MA.

6. Evans, D.D. and Stroup, D.W., Methods to Calculate the Response Time of

Heat and Smoke Detectors Installed Below Large Unobstructed Ceilings,

Fire Technology, Vol. 22, pp54-65, 1986.

7. Stroup, D.W., Evans, D.D., and Martin, P., Evaluating Thermal Detection

Systems, NBS Special Publications 712 (English Units) and 713 (SI

Units), US National Bureau of Standards, Gaithersburg, MD, 1986.

36
8. Alpert, R.I., Turbulent Ceiling-Jet Induced by Large-Scale Fires,

Combustion Science and Technology,. Vol. 11, ppl97-213, 1975.

9. Motevalli, V. , et al , Measurements of the Transient Temperature and

Velocity Profiles in Ceiling Jets, Proceedings of the Fall Technical

Meeting of the Eastern Section of the Combustion Institute, Dec. 15-17,

1986.

10. Cooper, L.Y.

,

Ceiling Jet-Driven Wall Flows in Compartment Fires,

NBSIR 87-3535, US National Bureau of Standards, Gaithersburg, MD.

11. Cooper, L.Y.

,

Heat Transfer to Ceilings Above Enclosure Fires, 19th

Symposium (International) on Combustion, the Combustion Institute,

Pittsburgh, PA, pp933-939, 1982.

12. Cooper, L.Y. and Woodhouse, A., The Buoyant Plume-Driven Adiabatic

Ceiling Temperature Revisited, Journal of Heat Transfer, pp822-826, 1986.

13. Cooper, L.Y. and Stroup, D.W.

,

Thermal Response of Unconfined Ceilings

Above Growing Fires and the Importance of Convective Heat Transfer,

Journal of Heat Transfer, Vol. 109, ppl72-178, 1987.

14. Woodhouse, A., Marks, C.H., and Cooper, L.Y.

,

An Experimental Study of

the Transient Thermal Response of Unconfined Ceilings Above Fire Plumes,

Proceedings of the 1987 ASME-JSME Thermal Engineering Conference, Vol.l,

pp387-394, American Society of Mechanical Engineers, New York, NY, 1987.

37
15. Veldman, C.C., Kubota, T., and Zukoski, E.E., An Experimental

Investigation of the Heat Transfer from a Buoyant Gas Plume to a Horizontal Ceiling - Part 1. Unobstructed Ceiling, NBS -GCR- 77 - 97

,

prepared by the California Institute of Technology for the National

Bureau of Standards, Gaithersburg, MD, 1975.

16. Zukoski, E.E. and Kubota, T., An Experimental Investigation of the Heat

Transfer from a Buoyant Gas Plume to a Horizontal Ceiling - Part 2.

Effects of Ceiling Layer, NBS-GCR-77-98 , prepared by the California

Institute of Technology for the National Bureau of Standards,

Gaithersburg, MD, 1975.

17. You, H.-Z. and Faeth, G.M., An Investigation of Fire Impingement on a Horizontal Ceiling, prepared by the Pennsylvania State University for

the National Bureau of Standards, Gaithersburg, MD, 1979.

18. Stroup, D.W., Development of an Automated Probe Positioner for

Measurements in Fire-Generated Plumes and Ceiling Jets, NBSIR 86-3379,

National Bureau of Standards, Gaithersburg, MD, 1986.

19. Heskastad, G. and Hamada, T. , Ceiling Flows of Strong Fire Plumes, FMRC

Report J.I. 0K0E1.RU 070(A), Factory Mutual Research Corporation,

Norwood, MA, 1984.

38
20. Cooper, L.Y. , A Buoyant Source in the Lower of Two, Homogeneous, Stably

Stratified Layers, 20th Symposium (International) on Combustion, the

Combustion Insitute, Pittsburgh, PA, ppl567-1573, 1984.

21. Evans, D.D. , Calculating Fire Plume Characteristics in a Two-Layer

Environment, Fire Technology, Vol. 20, pp39-63, 1984.

22. Evans, D.D. and Morehart, J., Investigation of the Effects of a Stratified Two Layer Environment on Fire Plume Temperatures, Proceedings

of the 1987 ASME-JSME Thermal Engineering Conference, Vol.l, pp381-386,

American Society of Mechanical Engineers, New York, NY, 1987.

39
U i. pePT, OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See Instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR -87/3633

2. Performing Organ. Report No. 3. Publication Date

September 1987

4. TI TLE AND SUBTITLE

TEST RESULTS AND PREDICTIONS FOR THE RESPONSE OF NEAR-CEILING SPRINKLER

LINKS IN A FULL-SCALE COMPARTMENT FIRE

5. AUTHOR(S)

Leonard Y. Cooper and David W. Stroup

6. PERFORMING ORGANIZATION (If Joint or other than NBS, see Instructions)

NATIONAL BUREAU OF STANDARDS

U.S. DEPARTMENT OF COMMERCE

GAITHERSBURG, MD 20899

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State. ZIP)

7. Contract/Grant No.

I. Type of Report & Period Covered

U.S. Fire Administration

Emmitsburg, MD 21727

10. SUPPLEMENTARY NOTES

] Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11. ABSTRACT (A 200-word or less factual summary of most significant Information. If document Includes a significant

bi bl iography or literature survey, mention It here)

This paper presents and analyzes a portion of the data acquired during a test program

which involved full-scale, sprinklered, compartment fires. The work here focuses

attention specifically on key features of the typical sprinkler link deployment/

response problem. It is found that the elevated temperature, upper smoke layer which

develops inevitably in compartment fires can have a major impact on the thermal

response of sprinkler links. It is shown that traditionally accepted methods of

predicting sprinkler link response which do not account for this upper layer can be

totally inadequate. Link response predictions used here involve a new method of

calculation which does take account of the smoke layer environment. Favorable

comparisons between predictions and experiment are obtained and experiments for

further validation of this method are recommended. Finally, it is found that

sprinkler link- to-ceiling spacing can have a significant effect on the thermal

response of links and it is recommended that a method which accounts for this

effect be developed and validated.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) automatic sprinklers; ceiling jets; compartment fires; fire-generated flows; fusing;

heat transfer; link-to-ceiling spacing; link-to-f ire spacing; smoke layer; sprinkler

links; thermal response; unconfined ceilings; validation

13. AVAILABILITY

[X] Unlimited

[ | For Official Distribution. Do Not Release to NTIS

f | Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

45

15. Price

$11.95

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