Comparison of FPETool:

FIRE SIMULATOR With Data

From Full Scale Experiments

Robert L. Vettori

Daniel Madrzykowski

Prepared for:

U. S. General Services Administration

Public Buildings Service

NISTIR 6470
NISTIR 6470

Comparison of FPETool:

FIRE SIMULATOR With Data

From Full Scale Experiments

Robert L. Vettori

Daniel Madrzykowski

Building and Fire Research Laboratory

National Institute of Standards and Technology

Gaithersburg, MD 20899-8641

February 2000

U.S. Department of Commerce

William M. Daley, Secretary

Technology Administration

Dr. Cheryl L. Shavers, Under Secretary of

Commerce for Technology

National Institute of Standards and Technology

Raymond G. Kammer, Director

Prepared for:

U.S. General Services Administration

David J. Barram, Administrator

Public Buildings Service

Robert A. Peck, Commissioner
iii

Table of Contents

LIST OF TABLES ........................................................ iv

LIST OF FIGURES ......................................................... v

ABSTRACT ............................................................... 1

1.0 INTRODUCTION ....................................................... 2

1.1 Fire Plume Algorithm .............................................. 2

1.2 Ceiling Jet Algorithm ............................................... 4

1.3 Heat Release Rate ................................................. 7

1.4 Sprinkler Activation Algorithm ....................................... 7

1.5 Internal Energy Loss ............................................... 8

2.0 CHEMICAL LABORATORY EXPERIMENTS ............................... 9

2.1 Comparisons - Sprinkler Activation Times ............................. 10

2.2 Comparisons - Upper Layer Temperature and Upper Layer Depth ......... 11

2.3 Comparisons - Heat Release Rate at Sprinkler Activation ................ 12

2.4 Discussions and Conclusions ........................................ 12

3.0 AIRCRAFT HANGER EXPERIMENTS .................................... 13

3.1 Comparisons - Ceiling Jet and Disk Temperatures ...................... 14

3.2 Comparisons - Upper Layer Depth ................................... 14

3.3 Discussions and Conclusions ........................................ 15

4.0 RESIDENTIAL SPRINKLER EXPERIMENTS .............................. 15

4.1 Location of Fire .................................................. 17

4.2 Comparisons - Sprinkler Activation Times ............................. 19

4.3 Comparisons - Upper Layer Temperature and Upper Layer Depth ......... 20

4.4 Comparisons - Ceiling Jet Velocities and Temperatures .................. 20

4.5 Comparisons - Heat Release Rate at Sprinkler Activation ................ 21

4.6 Discussion and Conclusions ......................................... 21

5.0 CONCLUSIONS ....................................................... 23

6.0 REFERENCES ........................................................ 24
iv

LIST OF TABLES

Table 1 - Input for FPETool simulations - chemical laboratory experiments ............... 27

Table 2 - Heat release rate input - chemical laboratory simulations ..................... 28

Table 3 - Activation time summary for simulation 1 - chemical laboratory experiments ...... 29

Table 4 - Activation time summary for simulations 2 and 3 - chemical laboratory experiments

.................................................................. 29

Table 5 - Activation time summary for simulation 4 - chemical laboratory experiments ...... 29

Table 6 - Heat release rate at time of sprinkler activation ............................. 30

Table 7 - Input for FPETool simulations - aircraft hanger experiments .................. 30

Table 8 - Heat release rate input - aircraft hanger simulations ......................... 31

Table 9 - Excess ceiling jet temperature comparisons - hanger experiments ............... 31

Table 10 - Input for FPETool simulations - residential sprinkler experiments .............. 32

Table 11 - Heat release rate input - fast fire - residential sprinkler simulations ............. 32

Table 12 - Heat release rate input - medium fire - residential sprinkler simulations .......... 33

Table 13 - Heat release rate input - slow fire - residential sprinkler simulations ............ 34

Table 14 - Activation time summary - burner detached - vent open - residential sprinkler .... 35

Table 15 - Activation time summary - burner detached - vent closed - residential sprinkler ... 35

Table 16 - Activation time summary - burner against wall - vent open - residential sprinkler. . . 35

Table 17 - Activation time summary - burner in corner - vent open - residential sprinkler. .... 35

Table 18 - Heat release rate at time of sprinkler activation. Burner detached - vent open - residential

sprinkler ............................................................ 36

Table 19 - Heat release rate at time of sprinkler activation. Burner detached - vent closed -

residential sprinkler. ................................................... 36

Table 20 - Heat release rate at time of sprinkler activation. Burner against wall - vent open -

residential sprinkler. Assuming heat release rate input for FPETool is doubled due to effect

of wall on plume entrainment. ........................................... 36

Table 21 - Heat release rate at time of sprinkler activation. Burner against wall - vent open -

residential sprinkler. Assuming heat release rate input for FPETool is multiplied by 1.5 due

to effect of wall on plume entrainment. ..................................... 37

Table 22 - Heat release rate at time of sprinkler activation. Burner in corner - vent open - residential

sprinkler. Assuming heat release rate input for FPETool is quadrupled due to effect of corner

walls on plume entrainment ............................................. 37

Table 23 - Heat release rate at time of sprinkler activation. Burner in corner - vent open - residential

sprinkler. Assuming heat release rate input for FPETool is multiplied by 2.2 due to effect of

corner walls on plume entrainment ........................................ 37
v

LIST OF FIGURES

Figure 1 - Plan view for a typical chemical laboratory ............................... 38

Figure 2 - Heat release rate for chemical laboratory experiments ....................... 38

Figure 3 - Approximate sprinkler location for experiments 1, 2, and 3 ................... 39

Figure 4 - Approximate sprinkler location for experiment number 4 .................... 39

Figure 5 - Upper layer temperature - chemical laboratory experiments .................. 40

Figure 6 - Upper layer depth development - chemical laboratory experiments ............. 40

Figure 7 - Measured and predicted temperature increase for plume and detector link at 0.0 m -

aircraft hanger experiments ............................................. 41

Figure 8 - Measured and predicted temperature increase for ceiling jet at 2.7 m - aircraft hanger

experiments. Detector link not shown due to instrument malfunction .............. 41

Figure 9 - Measured and predicted temperature increase for ceiling jet and detector link at 5.5 m -

aircraft hanger experiments ............................................. 42

Figure 10 - Measured and predicted temperature increase for ceiling jet and detector link at 8.2 m -

aircraft hanger experiments ............................................. 42

Figure 11 - Measured and predicted temperature increase for ceiling jet and detector link at 11.0 m -

aircraft hanger experiments ............................................. 43

Figure 12 - Plan view - burner locations - residential sprinkler experiments ............... 43

Figure 13 - Instrumentation set up for arrays 1 and 2 ............................... 44

Figure 14 - Heat release rates for fast, medium, and slow fires. NFPA 72, 1993 edition ..... 44

Figure 15 - Upper layer temperature increase - slow fire - detached burner - vent open ...... 45

Figure 16 - Upper layer temperature increase - slow fire - detached burner - vent closed .... 45

Figure 17 - Upper layer temperature increase - medium fire - detached burner - vent open ... 46

Figure 18 - Upper layer temperature increase - medium fire - detached burner - vent closed . . 46

Figure 19 - Upper layer temperature increase - fast fire - detached burner - vent open ....... 47

Figure 20 - Upper layer temperature increase - fast fire - detached burner - vent closed ...... 47

Figure 21 - Upper layer temperature increase - slow fire - burner against wall - vent open .... 48

Figure 22 - Upper layer temperature increase - medium fire - burner against wall - vent open

.................................................................. 48

Figure 23 - Upper layer temperature increase - fast fire - burner against wall - vent open ..... 49

Figure 24 - Upper layer temperature increase - slow fire - burner in corner - vent open ...... 49

Figure 25 - Upper layer temperature increase - medium fire - burner in corner - vent open ... 50

Figure 26 - Upper layer temperature increase - fast fire - burner in corner - vent open ....... 50

Figure 27 - Upper layer development - slow fire - detached burner - vent open ............ 51

Figure 28 - Upper layer development - slow fire - detached burner - vent closed ........... 51

Figure 29 - Upper layer development - medium fire - detached burner - vent open ......... 52

Figure 30 - Upper layer development - medium fire - burner detached - vent closed ........ 52

Figure 31 - Upper layer development - fast fire - burner detached - vent open ............. 53

Figure 32 - Upper layer development - fast fire - burner detached - vent closed ............ 53

Figure 33 - Upper layer development - slow fire - burner against wall - vent open .......... 54

Figure 34 - Upper layer development - medium fire - burner against wall - vent open ....... 54

Figure 35 - Upper layer development - fast fire - burner against wall - vent open ........... 55

Figure 36 - Upper layer development - slow fire - burner in corner - vent open ............ 55

Figure 37 - Upper layer development - medium fire - burner in corner - vent open ......... 56
vi

Figure 38 - Upper layer development - fast fire - burner in corner - vent open ............. 56

Figure 39 - Velocity measurements - slow fire - detached burner - vent open ............. 57

Figure 40 - Velocity measurements - slow fire - detached burner - vent closed ............ 57

Figure 41 - Velocity measurements - medium fire - detached burner - vent open ........... 58

Figure 42 - Velocity measurements - medium fire - detached burner - vent closed .......... 58

Figure 43 - Velocity measurements - fast fire - detached burner - vent open .............. 59

Figure 44 - Velocity measurements - fast fire - detached burner - vent closed ............. 59

Figure 45 - Velocity measurements - slow fire - burner against wall - vent open ........... 60

Figure 46 - Velocity measurements - medium fire - burner against wall - vent open ......... 60

Figure 47 - Velocity measurements - fast fire - burner against wall - vent open ............ 61

Figure 48 - Velocity measurements - slow fire - burner in corner - vent open ............. 61

Figure 49 - Velocity measurements - medium fire - burner in corner - vent open ........... 62

Figure 50 - Velocity measurements - fast fire - burner in corner - vent open .............. 62

Figure 51 - Ceiling jet temperature increase - slow fire - detached burner - vent open ....... 63

Figure 52 - Ceiling jet temperature increase - slow fire - detached burner - vent closed ...... 63

Figure 53 - Ceiling jet temperature increase - medium fire - detached burner - vent open ..... 64

Figure 54 - Ceiling jet temperature increase - medium fire - detached burner - vent closed ... 64

Figure 55 - Ceiling jet temperature increase - fast fire - detached burner - vent open ........ 65

Figure 56 - Ceiling jet temperature increase - fast fire - detached burner - vent closed ....... 65

Figure 57 - Ceiling jet temperature increase - slow fire - burner against wall - vent open ..... 66

Figure 58 - Ceiling jet temperature increase - medium fire - burner against wall - vent open . . 66

Figure 59 - Ceiling jet temperature increase - fast fire - burner against wall - vent open ...... 67

Figure 60 - Ceiling jet temperature increase - slow fire - burner in corner - vent open ....... 67

Figure 61 - Ceiling jet temperature increase - medium fire - burner in corner - vent open ..... 68

Figure 62 - Ceiling jet temperature increase - fast fire - burner in corner - vent open ........ 68
1

Comparison of FPETool: FIRE SIMULATOR With Data From Full Scale Experiments

Robert L. Vettori

Daniel Madrzykowski

ABSTRACT

A comparison of the compartment zone fire model FPETool: FIRE SIMULATOR is made with data

from three different full scale experimental compartment fire studies. These three studies represent

a variation of room geometry, ventilation factors, thermal physical properties, fuels, fire geometry and

fire growth. Depending on the experimental data presented, comparisons were made for the

following parameters, ceiling jet velocity, ceiling jet temperature, upper layer temperature, upper layer

depth, detector link temperature, time to sprinkler activation, and heat release rate at time of sprinkler

activation. Results for predicted sprinkler activation times ranged from 74% to 159% of measured

times depending on the RTI chosen for the sprinkler, characteristics of the fire, and fire growth rate.

All predicted ceiling jet velocities differed by approximately a factor of two from measured values.

Generally, upper layer depth predictions were good only for situations where there was not a large

vent from the room. For the full scale experiment conducted in a large room with a high ceiling,

predicted link and ceiling jet temperatures had better agreement with measured values if consideration

was given to the time required for the transport of the products of combustion from the fire to the

link. For experiments which had varying fire growth rates predictions for upper layer temperature

increase were better for experiments with the slower fire growth rates.

Key Words: ceiling jets; computer models; fire growth; layer heights; quick response sprinklers;

residential sprinkler; sprinklers; sprinkler response; wall fires; zone models;
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l

' z

o

% 0.166Q0

2/5

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Zl

)T

Number in brackets indicate literature references at the end of the paper. 1

2

(1)

1.0 INTRODUCTION

Zone fire models are being used to assist in both the design of fire protection systems and in the

reconstruction of fires [1-5]. The capability to predict the effects of a fire on the environment within 1

a compartment is an important element for fire protection system and life safety analyses. In addition,

the ability to predict the activation times of smoke detectors, sprinklers, or other thermal detectors

is important since these devices are used to warn occupants of a potential fire, initiate suppression,

and summon outside help. For the accident investigator, this capability could assist in the

understanding of factors that produce hazardous conditions and to devise ways to mitigate their

effects in the future. This paper discusses the performance of the compartment zone fire model

FPETool: FIRE SIMULATOR version 3.2 [6,7], henceforth referred to in this paper as FPETool,

against experimental data obtained from three different full scale compartment fire test series.

FPETool is a single room, two zone model simulating the effects of pre and post flashover fires within

the fire compartment and characterizes the effluent (energy, gases, and fuel ) that leave the fire

compartment. FPETool is based on the compartment filling model developed by Zukoski [8].

Zukoski developed an analytical model to determine the time required to fill a room with products

of combustion from a small fire. The room is assumed to be closed except for small openings at

either the floor or ceiling level. The leaks through these openings are assumed to be just large enough

so that any pressure change within the room can be neglected. The products of combustion are

assumed to occupy an upper layer next to the ceiling and Zukoski’s model also predicts the growth

or thickness of this upper layer as a function of time.

1.1 Fire Plume Algorithm

FPETool assumes an axisymmetrical or unconfined plume. The plume is considered a point source

and is able to entrain air along its entire perimeter. There is no effect on this free entrainment of air

by walls or other objects. The relationships for air entrainment into the fire plume used by FPETool

were developed by Heskestad [11]. Heskestad’s relationships deal with axisymmetric, turbulent fire

plumes in which the environment is uncontaminated by fire products and is uniform in temperature.

The upward buoyant gas stream of the plume is considered turbulent, except when the source is very

small and smoldering. Once an upper layer has formed within the compartment, Heskestad’s

relationships cease to be valid beyond the elevation where the plume enters this upper layer.

Two predictive relations are used by FPETool for plume entrainment. The first considers an area

extending above a limiting elevation within the plume, the second, the area within the plume that is

below this limiting elevation. This limiting elevation , is defined as the elevation within the plume

where the mean center line temperature increase = 500 EC (900 EF). For normal atmospheric

conditions, the limiting elevation can be expressed as [11]:
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o

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2/5

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f

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))

f B

)

1/2

m0 ' 0.071Q0

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c

(z&z

o

)

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[1%0.026Q0

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(z&z

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z

o

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c

z

o

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Q0

D

m0

f

m0

))

f

z

l

z

l

m0

Q0

c

z

3

(2)

(3)

(4)

where: = height above the top of combustible where = 500 EC

= height of virtual origin above or below the top of combustible (m)

= convective heat release rate into the plume (kW)

The virtual origin, in the above equation, is a computational tool rather than a physical one.

Since the derivations for the plume relationships assume that the plume is rising from a point source,

a correction needs to be made to the real source of the plume. This is done by identifying a virtual

origin for the plume. The location of this virtual origin is such that a plume originating from this

point source will have identical entrainment characteristics as the real source. The virtual origin can

be located above or below the actual surface of the fire. For normal atmospheric conditions and fire

sources that do not have substantial in-depth combustion, the prediction for the virtual origin of a fire

plume is [12]:

where: = effective diameter of the fire source (m)

= total heat release rate of the fire source (kW)

FPETool uses the following method to calculate the effective diameter of the fire source.

where: = the effective diameter of the fire source (m)

= mass burning rate (kg/s)

= mass burning rate per unit area (kg/s m ). FPETool has set this as a default 2

rate based on the mass burning rate of wood needed to produce 1135 kW/m .

2

The limiting elevation , in Eq. 1, closely corresponds to the median visible flame height of the fire.

The median flame height is the location above the fire source where the flame is present 50 % of the

time. Therefore, it can be seen that the two entrainment relationships used are divided into elevations

above the flaming region of the plume and elevations within the flaming region of the plume.

For elevations within the plume that are greater than or equal to or elevations of the plume above

the flaming region, the prediction for mass flow rate in the plume is:

where: = mass of air entrained (kg/s)

= convective heat release rate into the plume (kW)

= distance from the top of combustible to bottom of smoke layer (m)
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c

z

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= height of virtual origin above or below the top of combustible (m)

For elevations within the plume less than or what would be considered the flaming region, the

mass flow rate in the plume is:

Equation 5 is limited to pool fires or horizontal surface fires. The relationship becomes inaccurate

for fire sources with substantial in-depth combustion such as well ventilated wood crib and wood

pallet fires, fires involving high storage, and vertical wall or corner fires [11]. A fire with substantial

in-depth combustion may have a large portion, greater than 33%, of the volatiles undergoing

combustion within or internally of the fuel array by air entering the array [13]. Equation 4 is not

limited with respect to the fire source. However, predicting the location of the virtual origin used

in Eq. 4, is itself limited to fire sources that do not have substantial in-depth combustion.

1.2 Ceiling Jet Algorithm

The time to sprinkler activation algorithm used in FPETool is based on the sprinkler activation model

DETACT-QS developed by Evans and Stroup [14]. DETACT-QS calculates the thermal response

of a thermal element located at the ceiling in which the ceiling area is large enough to neglect the

effects of smoke layer development. Therefore any heating of the thermal element will be based only

on the temperature and velocity of the ceiling jet. No account is made for the effects of a warm gas

layer. This methodology may be applied to large spaces such as industrial buildings or for short times

after fire ignition when enclosure effects are negligible. The correlations used by DETACT-QS for

ceiling jet temperatures and velocities were developed by Alpert [15]. Alpert’s correlations assume

that the fire is under a smooth, horizontal, unconfined ceiling, and that the fire plume entrains air

which is at ambient temperature. The correlations for the maximum temperature of the ceiling jet are

divided into two regions.

where: = maximum gas temperature in the ceiling jet EC

= initial gas temperature EC

= total heat release rate of the fire source (kW)

= distance from the top of the combustible to the ceiling (m)
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Q0

H

)

1/3

for r

H

# 0.15

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1/3

H

1/2

r

5/6

for r

H

> 0.15

0.12 (H)

r

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= radial distance of the thermal element from the vertical axis of the fire (m)

The correlations for maximum velocity of the ceiling jet are also divided into two regions.

Where: = maximum gas velocity in the ceiling jet (m/s)

Equations 7 and 9 are independent of radius and are axial plume flow temperatures and velocities

calculated at the ceiling height above the fire source. Equations 8 and 10 apply to the region outside

of the plume as the flow moves away from the impingement area.

Alpert found that for smooth horizontal ceilings when there is only negligible accumulation of

stagnant hot gases underneath, that the maximum gas temperature within the ceiling jet occurs a

distance below the ceiling of no more than 1 percent of the distance between the uppermost burning

fuel surface and the ceiling. [15] The temperature of the ceiling jet approaches room temperature at

5.5 to 12.5 percent of the fire to ceiling height. The maximum ceiling jet velocity is also found quite

close to the ceiling, and the ceiling jet velocity approaches zero at approximately the same distance

below the ceiling where the gas temperature approaches room temperature. [15]

In compartment sizes characteristic of office and living spaces, a warm upper layer of gas may

accumulate rapidly after ignition. As a warm upper layer develops the fire plume no longer entrains

air only from the cool lower layer, but includes warm upper layer entrained gases. In FPETool the

sprinkler activation algorithm includes what the effect of entraining these warm upper layer gases has

on the ceiling jet temperatures and velocities. The implementation of this warm upper layer gas

entrainment algorithm begins when the thickness of the warm upper layer exceeds that of the ceiling

jet. Using the correlations that Alpert developed, the thickness of the fully developed ceiling jet

considered in FPETool is [16]:

where: = distance from the top of the combustible to the ceiling (m)

In a room fire in which a warm upper gas layer has accumulated above the lower ambient gas forming

a two layer environment, the weakly buoyant point source plume flow calculations are just as

applicable in the lower layer containing the fire as in a totally uniform ambient environment.

However, adjustments are needed to describe the plume flow after penetration into the upper layer.

A method developed by Evans [17] is used in FPETool to take into account the effects of entrainment
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of the warm upper layer gases. This plume continuation method relates plume flow in a two layer

environment to an equivalent flow in a single layer environment at the temperature of the warm upper

layer. The adjustments made consist of changing the fire source heat release rate and location of the

fire source a distance below the ceiling. The substitute source location and heat release rate are

calculated by preserving across the interface between the cool lower and warm upper layers the

maximum temperature in the plume and the excess enthalpy flux. Preserving velocity and closely

associated plume mass and momentum fluxes are not considered as important as preserving excess

temperature and excess energy flux in calculating sprinkler activation times, because thermal detectors

primarily respond to temperature rise and not gas velocity [18]. In the equations presented below,

the subscripts 1 and 2 will be used to indicate quantities related to the original source and the second

or pseudo source respectively. The dimensionless heat release rate of the fire source is evaluated at

the interface between the upper and lower layer:

where: = convective heat release rate of the fire (kW)

= density of air at ambient temperature (kg/m )

3

= specific heat of air at ambient temperature (kJ/kgEK)

= ambient temperature of 293 EK

= gravitational acceleration (m/s )

2

= height of the layer interface from the top of combustible (m)

The dimensionless heat release rate for the second or pseudo source is:

where: = 9.115 [19]

= ratio of the upper layer temperature to lower layer temperature

The position of the second or pseudo fire source relative to the interface is:

where: = 0.913 [20]

The dimensional heat release rate is
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where: = convective heat release rate of the pseudo fire source (kW)

= density of the warm upper layer gas (kg/m )

3

= temperature of warm upper layer gas (EK)

and the position relative to the ceiling is

where: = height above the pseudo source to the ceiling

= height above the original source to the ceiling

The values and replace and in Alpert’s algorithm. The result of adding this

warm air entrainment algorithm is the prediction of higher ceiling jet temperatures and faster ceiling

jet velocities.

FPETool assumes that the detector, smoke or thermal, is located such that it is exposed to both the

maximum ceiling jet temperature and ceiling jet velocity.

1.3 Heat Release Rate

For all three experimental series, the heat release rate of the fuel packages was determined by using

the principle of oxygen consumption calorimetry [21,22]. The oxygen consumption technique for

measuring the rate of heat release is predicated upon the capture of all the combustion gases through

a duct where the mass flow rate and oxygen concentration are measured as a function of time. From

these measurements, the rate at which oxygen is consumed by the fire in the combustion process can

be determined. For most common fuels, the rate of heat release per unit mass of oxygen is

approximately (13.1 ± 0.66) MJ/kg of oxygen consumed [23]. In addition to the uncertainty inherent

to this method, uncertainties in instrument measurements and fluctuations in the volume of exhaust

gases through the duct need to be taken into account to determine the heat release rate measurement.

Yeager [31] reports uncertainties from 5% to 60% depending of the flow rate of exhaust gases

through the duct. However, he was able to establish an optimal uncertainty of ± 6% for fires with

heat release rates as low as 71 kW when the mass flow through the duct was controlled at 2 m /s. 3

1.4 Sprinkler Activation Algorithm

An input required for the sprinkler activation algorithm in FPETool is the Response Time Index (RTI)

of the sprinkler [24,25]. The RTI is a characterization of the detector’s thermal inertia, a measure

of how quickly the thermal element reaches its activation temperature. The smaller the RTI value the

more thermally responsive the element is to changes in gas temperature. The model used to calculate

the heating of a sprinkler bulb or link is based on several assumptions. First, the sprinkler element

is heated purely by forced convection. Second, there are no conduction losses from the sprinkler

element to the supporting structure. Finally, the sprinkler element heats uniformly. With these

approximations, the heat balance on the sensing element is:
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hcAL

hc% u

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1/2 ' constant

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)T

g

J

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c

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hc

AL

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(18)

(19)

(20)

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where: = the excess temperature of the link above its initial temperature (EC)

= the excess temperature of the gas above the initial link temperature (EC)

and is a time constant related to the properties of the sensing element and the convective heating

of the gas flow to which it is exposed according to:

where: = the mass of the sensing element (kg)

= the specific heat of the sensing element (kJ/kgEK)

= the convective heat transfer coefficient over the sensing element (kW/m EK) 2

= the area of the sensing element (m )

2

For a given sensing element, the time constant depends only on the convective heat transfer

coefficient. Data on convective heating and cooling of objects similar to typical sensing elements

show that for conditions expected in the fire environment that [24]

where: = velocity of gas flow (m/s)

Consequently the time constant of a given sensing element is proportional to or equivalently:

This constant is the RTI of the sprinkler and has units (m-s) or (ft-s) . The RTI parameter is nearly 1⁄2 1⁄2

constant for a given sprinkler, and together with the sprinkler’s operating temperature, is sufficient

for predicting sprinkler response for known gas temperatures and gas velocities near the sprinkler as

long as conduction losses to the supporting structure are small compared with the convective heating

rate.

1.5 Internal Energy Loss

The internal energy loss is a measure of the combined instantaneous fraction of the total heat

release rate lost by the combustion zone, the plume gases, and the hot upper layer gases to the

bounding surfaces of the room and its contents. [28] The total rate of energy loss which is

characterized by occurs as a result of a variety of different convective and radiative heat transfer
8c

8c

8c

8c

9

exchanges between the room’s gases and the above mentioned surfaces. Although is taken as

a constant, it is in fact, a time varying parameter. However, in the early stages of a fire in a single

room, the value of is relatively constant and in the range of 0.6 to 0.9. The lower value of 0.6

would relate to high aspect ratio spaces (ratio of ceiling span to room height) with smooth ceilings

and with fires positioned far away from the walls. The 0.9 value for would relate to low aspect

ratio spaces, and fire scenarios where the fire position is within a room height from the walls. For

the simulations conducted in this paper a value of 0.9 was chosen for .

2.0 CHEMICAL LABORATORY EXPERIMENTS

The first experimental series modeled was conducted in chemical laboratories [26]. Four experiments

were conducted to evaluate the performance of an automatic sprinkler system against a flammable

liquid spill fire. A fifth experiment without sprinklers was also conducted. This series was modeled

to compare predicted sprinkler activation times, upper layer depth, upper layer temperatures, and

ceiling jet temperatures with measurements.

Each experiment was conducted in a different laboratory and the configuration of each laboratory was

slightly different. All laboratories were constructed with concrete floors and ceilings with tile block

walls. Each had a single open doorway, 2.1 m high x 0.91 m wide (6.9 ft x 3.0 ft) connecting the

laboratory to the building corridor and a closed wooden double hung window connecting the

laboratory to the outside. All laboratories were approximately 5.48 m (18 ft) deep, 3.2 m (10.5 ft)

high, and varied in width between 3.2 m and 3.7 m (10.5 ft and 12 ft). A typical plan view of one of

the chemical laboratories is shown in figure 1. The FPETool inputs for each of the five simulations

is shown in table 1.

The fuel package consisted of a 134.3 kg (296 lb) steel laboratory bench with a stone laboratory

bench top. Above the bench was a 24.0 kg (53 lb) open wooden shelving unit. On top of the

laboratory bench and in the shelving unit were 50.8 kg (112 lb) of paper, files and other miscellaneous

supplies. Four liters of acetone were used as the initial fuel ignited. Three liters were placed in a 0.76

m x 1.23 m (30 in x 48 in) steel pan on the floor and one liter in a 0.46 m x 0.61 m (18 in x 24 in)

steel pan on the bench top. The heat release rate inputs for this fuel package are listed in table 2. A

graph of this heat release curve is shown in figure 2.

Temperature measurements were taken with 0.05 mm (0.02 in) diameter chromel-alumel

thermocouples. While the absolute uncertainty in thermocouple measurements as reported by the

manufacturer is ± 2.2 EC (± 4.0 EF), at the start of an experiment, the thermocouples used in the

analysis registered ambient temperature to within ± 3.0 EC (± 5.4 EF). The method used to determine

either the start time of the experiment or the sprinkler actuation time were not mentioned. These

timing uncertainties may be on the order of ± 1 s each.

Of the four experiments which utilized sprinklers, one utilized a standard upright sprinkler, two

utilized quick response pendent sprinklers and one utilized a quick response sidewall sprinkler. In

the original report for this experimental series, no RTI values were reported, only the sprinkler

activation temperatures. For a standard fusible link sprinkler, the typical RTI values range from 193

(m-s) to 331 (m-s) (350 (ft-s) to 600 (ft-s) ), while for quick response sprinklers RTI values range 1⁄2 1⁄2 1⁄2 1⁄2
PR

r/H

10

from 25 (m-s) to 55 (m-s) (45 (ft-s) to 100 (ft-s) ). For this analysis several values of RTIs’ were 1⁄2 1⁄2 1⁄2 1⁄2

used for each experiment to determine the sensitivity of the simulation to this parameter.

Since the radiative fraction of acetone is 28% and that of some natural materials such as wood

and paper in the range of 38% to 41% [27] the radiative fraction was approximated to be 35%.

2.1 Comparisons - Sprinkler Activation Times

The first experiment, table 3, utilized the standard upright sprinkler with an activation temperature

of 74 EC (165 EF) located 0.61 m (1.5 ft) radially from the center of the floor pan, figure 3.

The value is 0.19 which places the sprinkler at the edge of the plume. The sprinkler deflectors

were located 0.24 m (9.5 in) below the ceiling. A value of 250 (m-s) (452 (ft-s) ) was originally 1⁄2 1⁄2

chosen for the RTI of the sprinkler. The time to activation predicted by FPETool of 34 s is a

difference of 5 s from the measured time of 39 s. Two additional simulations were performed one

with a high and one with a low value for the RTI. This was done in order to bracket the response of

the sprinkler to this environment as a function of the sprinkler RTI. By changing the RTI value to

300 (m-s) (544 (ft-s) ), and leaving all other inputs the same, FPETool predicted an activation time 1⁄2 1⁄2

of 37 s. For the low value, the RTI was chosen as 200 (m-s) (362 (ft-s) ) and the predicted

1⁄2 1⁄2

activation time was 32 s.

For both experiment 2 and experiment 3, table 4, a 71 EC (160 EF) quick response pendent sprinkler

was utilized. In both experiments the sprinklers were located 0.61 m (1.5 ft) radially from the center

of the floor pan, figure 3. As in the previous experiment this places them at the edge of the plume.

In experiment 2 the sprinkler deflectors were located 0.28 m (11 in) below the ceiling, and in

experiment 3 the sprinkler deflectors were located 0.33 m (13 in) below the ceiling. With the value

of 40 (m-s) (75 (ft-s) ) originally chosen for the RTI, FPETool predicted an activation time of 17 1⁄2 1⁄2

s. The reported times for experiments 2 and 3 were 16 s and 18 s respectively. Again, in order to

bracket the response of the sprinkler to this environment as a function of the sprinkler RTI, a value

of 25 (m-s) (45 (ft-s) ) was used for the low RTI and a value of 55 (m-s) (100 (ft-s) ) was used 1⁄2 1⁄2 1⁄2 1⁄2

for the high RTI. The results were predicted activation times of 15 s and 19 s for experiment 2 and

14 s and 19 s for experiment 3.

Experiment 4, table 5, utilized a 71 EC (160 EF) quick response sidewall sprinkler located 3.66 m (12

ft) radially from the center of the floor pan, figure 4. The sprinkler deflectors was located 0.20 m (8

in) below the ceiling. Since the sprinkler algorithm used in FPETool assumes the sprinkler is

positioned on a flat horizontal unobstructed ceiling, the effects of placing the sprinkler in a sidewall

position is considered by assuming a reduction in the ceiling jet velocity. FPETool calculates what

the ceiling jet velocity would be at the location of the sprinkler, as if it were placed on the ceiling, and

then reduces it by a velocity reduction factor. The default value for FPETool is a 50% reduction in

the ceiling jet velocity. There were no referenced papers in the FPETool technical reference manual

indicating how the value of 50% was derived. Additionally, there were no papers found in the

literature describing a method for the prediction of the activation time of a side wall sprinkler in the

context of a zone model. No effect on the ceiling jet temperature is considered in the model. For the

original RTI value of 40 (m-s) (72 (ft-s) ) and a velocity reduction factor of 50%, FPETool

1⁄2 1⁄2
)Tref (t) ' max [T(z

top, t)] & Tamb (ztop )

T(z

i

, t) & Tamb(z

i

) '

N )Tref (t)

100

)Tref (t)

T(z

top, t)

z

top

Tamb (z

top)

T(z

i

, t)

Tamb(z

i

)

)T

11

(29)

(30)

predicted a sprinkler activation time of 31 s compared to a measured time of 26 s. With a ceiling

height of 3.2 m (10.5 ft), the thickness of the ceiling jet is approximately 0.38 m (15 in). Since the

sprinkler is 0.20 m (8 in) below the ceiling it is still considered within the ceiling jet. By allowing the

velocity reduction factor to be 0, which gives the same results as placing the sprinkler on the ceiling

i.e., not in a sidewall position, the predicted activation time by FPETool is 27 s. By varying the RTI

of the sprinkler along with the velocity reduction factor the predictions by FPETool can be bracketed

for this environment as a function of both the RTI and velocity reduction factor.

2.2 Comparisons - Upper Layer Temperature and Upper Layer Depth

Data from experiment 5 was used to compare predicted with measured results for upper layer

temperature and upper layer depth development. This experiment did not have sprinklers and the

room was allowed to burn until manually extinguished. In the experimental set up a thermocouple

array was placed in the corner of each burn room with thermocouples placed (48, 109, 170, 231, 292)

cm ((19, 43, 67, 91,115) in) below the ceiling. In order to determine the depth of the layer based on

the reported temperature data a method developed by Cooper et al [29] named the N Percent Rule

is used. To use the N Percent Rule, at a specified time in the experiment, compute a reference upper

layer temperature based on the maximum temperature change of the thermocouple at the highest

elevation.

where: = referenced upper layer temperature at time t (EC )

= temperature at top most thermocouple at time t (EC )

= the elevation of the top most thermocouple (m)

= ambient temperature at top most thermocouple at time 0 (EC )

Then by the N Percent rule, the interface is defined as passing the elevation zi(t) at that time t when

z first satisfies i

where: = temperature of thermocouple at elevation z at time t (EC) i

= ambient temperature of thermocouple at elevation z (EC) i

Cooper concluded that allowing N = 10 would provide a reasonable basis for an experimentally

determined interface elevation history.

Temperatures for each thermocouple were obtained from the data files. A vertically averaged

temperature increase is estimated from
)T(t) '

1

H m

H

0

[T(z,t)&Tamb(z)] dz

)T(t) .

1

H j

x

n'1

[T(z

n

, t)&Tamb(z

n

)] )z

n

)T(t)

H

T(z

n

,t)

Tamb(z

n

)

)z

n

12

(31)

(32)

where: = vertically averaged temperature increase at time t (EC)

= floor to ceiling height of the compartment (m)

= temperature of the n thermocouple in the array (EC) th

= ambient temperature of the n thermocouple in the array (EC) th

= the vertical zone of influence associated with this thermocouple (m)

By using the N Percent Rule, a determination was made as to which thermocouples were to be

considered in the upper layer. Then each one was assigned a zone of influence depending on its

vertical distance from the thermocouple above and below it. Comparisons of measured versus

predicted upper layer temperature are presented in figure 5, and comparisons of measured versus

predicted upper layer depth are presented in figure 6.

2.3 Comparisons - Heat Release Rate at Sprinkler Activation

Another comparison that can be made, and possibly more important since it may give a more detailed

picture of the impact of the fire on the environment, is to compare the heat release rate of the fire at

measured sprinkler activation to the heat release rate at predicted sprinkler activation. For rapidly

growing fires such as these a relatively short time interval can translate into a significant increase of

the heat release rate of the fire. Table 6 gives this comparison. Column two of table 6 is the

measured heat release rate of the fire at sprinkler activation. Column three is the predicted range of

heat release rates based on the RTI of the sprinkler used on the model.

2.4 Discussions and Conclusions

Predictions by FPETool for experiment number 1 of the chemical laboratories series showed faster

activation times than actually measured. In order for FPETool to predict an activation time of 39

s, a RTI of 339 (m-s) (615 (ft-s) ) has to be used. This assumes all other inputs remain constant. 1⁄2 1⁄2

A value of 339 (m-s) (615 (ft-s) ) is only slightly higher than the range of values recommended by 1⁄2 1⁄2

FPETool for this type of sprinkler.

For experiments 2 and 3 of the chemical laboratories series the predicted activation times are in

excellent agreement with the measured values. The choice of RTI in this case is not as critical since

the range of suggested values is rather narrow when compared to the range offered for the standard

sprinkler.
13

For these first 3 experiments, it must be noted that none of the sprinklers were within 1% of the

distance from the top of the combustible to the ceiling. The distance that FPETool assumes. For this

series the height was taken as the distance from the floor to ceiling since the initial fire was a

flammable liquid on the floor of the laboratory. However all three were within 12% of this value

which places them within the confines of the ceiling jet. For these experiments 12% of the floor to

ceiling height is 0.38 m (15 in). Additionally, and more likely the case, the proximity to the center

of the fire places the sprinklers close to the edge of the plume. Alpert gives a range of the ceiling jet

thickness of 5% to 12%. The value of 5% is more appropriate near the plume.

For experiment number 4 of the chemical laboratory series, the sidewall sprinkler experiment, there

is a wide range of predicted times depending on which scenario is used. As in the previous three

experiments, FPETool was exercised using 3 different RTI values. Using the default value for

velocity reduction of 50% adds 3 to 4 s onto the activation times.

A possible explanation for the relatively good agreement between the measured and predicted values

of the sprinkler activation times is that the fire growth was at such a rapid rate. Figure 2 shows the

heat release rate curve of the fuel package used in the chemical laboratory experiments. As can be

seen the fire has an output of 1 MW at approximately 30 s. This provides an environment for the

sprinkler similar to that found in the plunge test.

The upper layer temperature increase and upper layer depth development both follow that predicted

by FPETool, figures 5 and 6. There is only a small period of time, approximately 150 s into the

experiment, that the measured upper layer depth drops to a level 2.92 m from the ceiling. It should

be remembered that these two graphs were developed from data obtained from one thermocouple

array placed in the corner of the room, figure 1.

The heat release rate at the measured time of sprinkler activation for the standard sprinkler,

experiment 1, is double that of the quick response sprinklers, experiments 2 and 3. The quick

response side wall sprinkler which was located 3.66 m from the fire activated faster than the standard

sprinkler located 0.61 m from the fire. The difference in heat release rate at time of sprinkler

activation for these two experiments is approximately 400 kW. Heat release rate is not predicted by

FPETool, it is an input supplied by the user. Column 3 of table 6 gives the range of heat release rates

at predicted sprinkler activation times. Depending on the RTI used and in the case of the sidewall

sprinkler, the value of the velocity reduction factor, a wide range of predicted sprinkler activation

times is obtained. This translates into a range of heat release rates for these predicted activation

times. For experiment 1, the range of heat release rates is approximately 150 kW, for experiments

2 and 3, 180 kW and 230 kW respectively. For experiment 4, which had the greatest range of

predicted sprinkler activation times, the range of heat release rates is approximately 390 kW.

3.0 AIRCRAFT HANGER EXPERIMENTS

The second experimental series modeled was conducted in an aircraft hanger [30]. The experiments

were conducted as part of the acceptance of the fire detection system within the hanger. This series

was modeled to compare ceiling jet temperatures, detector link temperatures at various radial

distances from the fire, and upper layer depth.
14

Two experiments were conducted in a hanger which measured 37.2 m x 40.2 m (122 ft x 132 ft) with

a ceiling height of 14 m (46 ft). Since the results of these two experiments were similar only data

from one of the experiments was reported. The hanger had concrete block walls to a height of 11.0

m (36.5 ft) with the remaining upper walls of steel panel construction. The flat ceiling was composed

of corrugated steel panels supported on 254 mm (10 in) deep steel I beams installed on 2.0 m (6.6

ft) trusses. The fuel package for this experimental series was industrial grade isopropyl alcohol placed

in steel pans that formed a square measuring 1.8 m x 1.8 m (6 ft x 6 ft). The pans were supported

on bricks approximately 125 mm (5 in) above the floor. Enough alcohol was placed in the pans to

allow the experiment to run for 60 s, at which time the fire was extinguished. The FPETool inputs

are listed in table 7. The heat release rate input for this fuel package is given in table 8.

There were no sprinklers used in this experimental series. Instead, thermocouples attached to 9.75

mm (0.384 in) diameter x 2.3 mm (0.092 in) thick brass disks simulated the heat responsive element

of a sprinkler. The RTI measured for the brass disks was 57.7 (m-s) (101 (ft-s) ). Since there is 1⁄2 1⁄2

no activation temperature for a brass disk, a device activation temperature of 999EC was used in the

FPETool inputs. Brass disks were located a distance of 380 mm (15 in) below the ceiling at radial

distances of (0, 2.7, 5.5, 8.2, 11.0) m ((0, 9, 18, 27, 36) ft) from the center of the fire. Comparisons

are made of the measured thermal device temperature with that predicted by the model. The only

difference between the computer model simulations is the radial distance from the center of the fire

source the simulated sprinkler link is located. In addition, 0.05 mm (0.02 in) diameter chromelalumel thermocouples were located next to each brass disk to measure the temperature of the ceiling

jet at that location. Temperatures obtained from the thermocouples were used to measure the ceiling

jet temperatures and temperatures obtained from the brass disks to simulate temperatures of sprinkler

links.

3.1 Comparisons - Ceiling Jet and Disk Temperatures

Comparisons of the measured versus predicted temperatures for the brass disks and ceiling jet are

presented in figures 7 through 11 for the five radial distances. Table 9 shows the average measured

excess ceiling jet temperature, the standard deviation of these measured temperatures, and the

average excess ceiling jet temperature predicted by FPETool. The average measured excess ceiling

jet temperature applies to the portion of the experiment where the ceiling jet temperature has become

steady state. The standard deviation was obtained from this portion of the data. The average excess

ceiling jet temperature predicted by FPETool is taken from the portion after steady state, but before

the initiation of the warm air entrainment model. Before the initiation of the warm air entrainment

model FPETool over predicts the excess ceiling jet temperature from between one and three standard

deviations. At the 2.7 m (9 ft) location the difference is over 4 standard deviations. Once the warm

air entrainment model is initiated the over prediction by FPETool is greater.

3.2 Comparisons - Upper Layer Depth

The depth of the upper layer is based on the response of two thermocouples located 11 m (36 ft) from

the fire. The first was positioned 1.8 m (6 ft) below the ceiling, the second 3.4 m (11 ft) below the

ceiling. The thermocouple located 1.8 m (6 ft) started to respond to an increase in temperature at

approximately 36 s into the experiment, FPETool predicted that the layer would not reach this level

until 46 s. The second thermocouple located 3.4 m (11 ft) did not respond to an increase in
r/H

15

temperature during the experiment and FPETool also predicted that the upper layer would not reach

this level within the 60 s experiment time.

3.3 Discussions and Conclusions

For these hanger experiments the degree to which the predicted values by FPETool agree with those

measured also depends on how far out radially the measurement is taken. The measured gas and disk

temperatures shown in figures 7 through 11 show an increasing time offset with increasing radial

distance from the centerline of the fire. Thermocouples at 0.0 m and 2.7 m (9 ft) initially respond

at the same time. This is due to the plume expanding to a radius that includes the 2.7 m thermocouple

before striking the ceiling. The value at the 2.7 m position is 0.19 which places the

thermocouple at the edge of the plume. The offset time for the (5.5, 8.2, 11.0) m ((18, 27, 36) ft)

thermocouples is approximately 8 s, 12 s, and 18 s respectively.

A reason for this discrepancy between measured and predicted values is FPETool, like many zone

models does not take into account transport time for the products of combustion to travel to a

specified location. Any change in the heat release of the fire immediately effects the upper layer and

does so throughout the upper layer. This can be seen graphically in figures 7 and 11 where FPETool

predicts that the thermocouples and disks respond instantaneously. The transport time usually does

not have a significant effect on the predictive outcome from FPETool when used in rooms that are

typical of residential or office spaces. However, as can be seen here when the distances become great

the transport time for the products of combustion need to be taken into consideration.

At 42 s into the simulations, FPETool predicts that the layer has dropped down 12 percent of the

distance from the top of the combustible to the ceiling. At this point FPETool uses Evans’

correlation to take into account what the effect of entraining these additional warm gases has on the

ceiling jet temperatures. This can be seen in the sudden increase in the excess temperatures in figures

8 through 11. In figure 7 there is a decrease, albeit small, in the plume temperature at 42 s.

For these simulations, FPETool predicted that the upper layer would descend 2.4 m (94 in) below

the ceiling. This is between two thermocouples, one at 1.8 m (6 ft) below the ceiling and the second

3.4 m (11 ft) below the ceiling. The distance between these two thermocouples is 1.6 m (5 ft). This

distance represents 11% of the floor to ceiling height. Since the first thermocouple responded and

the second did not, all that can be said is that the upper layer descended between 1.8 m (6 ft) and 3.4

m (11 ft) below the ceiling. It would seem reasonable, for this configuration, that FPETool predicted

the upper layer depth within 11% of the floor to ceiling height.

4.0 RESIDENTIAL SPRINKLER EXPERIMENTS

The third experimental series modeled [32] was conducted in a room 9.2 m x 5.6 m (30 ft x 18 ft)

with a ceiling height of 2.4 m (8 ft), figure 12. The walls and ceiling were constructed of a wood

frame covered with 12.7 mm (0.5 in) gypsum board. The floor was concrete. A hollow steel door

measuring 2.1 m high x 0.91 m wide (6.9 ft x 3.0 ft) opened to the outside. The air gap under the

door measured 25 mm (1 in). This door was closed for all experiments. The only vent consisted of

a stairway which measured 2.7 m x 0.9 m (8.9 ft x 3 ft) leading to an upper floor that had the same

dimensions as the fire compartment. There was no vent from this upper floor. Since FPETool does
Q0 ' "t

2

Q0

16

(34)

not allow vents to be located on the ceiling, this vent was modeled as having a height of 2.4 m (8 ft)

which places the top of the vent at the ceiling, a width of 2.7 m (8.9 ft) which is the length of the

original opening to the upper floor, and a sill height of 1.5 m (5 ft), which makes the opening height

of this vent 0.9 m (3 ft).

Four instrumentation arrays were located within the room as shown in figure 12. Each of the

instrumentation arrays had 0.51 mm (0.02 in) nominal diameter type K thermocouples located (0, 25,

50, 75, 100, 125, 150, 250, 350, 450, 550, 900) mm ((0, 1.0, 2.0, 3.0, 3.9, 4.9, 5.9, 9.8, 13.8, 17.7,

21.7, 35.4) in) below the ceiling, figure 13. Additionally, gas velocity measurements were recorded

at instrumentation arrays one and two using bi directional probes [33]. The bi-directional probes

were located (25, 75, 125, 250) mm ((1, 3, 4.9, 9.8) in) below the ceiling, figure 13. The standard

uncertainty for the velocity measurements is ± 0.1 m/s (± 0.3 ft/s) based on the manufacturer’s data

for the differential pressure transducers. At the start of each test the readings from the velocity

probes were assumed to be zero. There were no gas velocity measurements taken at sprinklers three

and four.

At each of the four instrumentation locations a quick response residential pendent sprinkler was

installed on the ceiling in accordance with the 1993 edition of the National Fire Protection

Association (NFPA) 13D, Sprinkler Systems in One and Two Family Dwellings and Manufactured

Homes [34]. The sprinklers used throughout these experiments were commercially available quick

response residential pendent sprinklers. The sprinklers had glass bulb elements with an activation

temperature of 68 ± 2.4 EC (154 ± 5.4 EF). The response time index (RTI) for the sprinklers was

55.8 (m-s) (100 (ft-s) ), as determined by an independent testing laboratory [35]. When mounted 1⁄2 1⁄2

the sprinklers were fully exposed and the center of the glass bulb element was 25 mm (1 in) below

the gypsum ceiling. The sprinkler system was pressurized with air to approximately 100 kPa (15 psi).

Each sprinkler was connected to a pressure switch that was electronically connected to a timer. The

pressure switches were set at 5 kPa (1 psi) so that upon sprinkler activation the drop in pressure

would automatically stop the corresponding timer. This provided an activation time accurate to ±

0.1 s.

The FPETool inputs for this experimental series are listed in table 10.

The fire source in this experimental series consisted of a rectangular methane gas burner with a

piloted ignition. The burner had dimensions of 0.7 m x 1.0 m (28 in x 40 in) and was 0.31 m (1 ft)

high. A technical grade of methane was used, which was certified by the supplier to contain at least

98% methane. The flow of methane to the burner was controlled by a computer. The computer was

programmed to monitor the flow of methane through four mass flow controllers arranged in parallel.

With this configuration the heat release rate curve produced by the burner is one that follows the fire

growth rates used in the 1993 edition of the NFPA 72 National Fire Alarm Code Appendix B [36].

The fast, medium and slow fires described by this NFPA standard are based on a wide variety of fires

that grow with the square of time and are sometimes referred to as t-squared (t ) fires. A

2

mathematical representation for these curves is as follows:

where: = heat release rate (kW)
m0

plume % Q0

1/3

C

"

t

8c

m0

plume

Q0

C

17

(36)

= coefficient (kW/s )

2

= time (s)

Figure 14 demonstrates the repeatability obtained with the burner during calibration tests. The three

theoretical fire growth curves used in this experimental series are overlaid with data obtained from

the respective burner calibration tests. For each fire growth rate, two calibration tests were

performed. The heat release inputs used for the fast fire growth are listed in table 11. For the

medium and slow fire growths the heat release rate inputs are listed in tables 12 and 13 respectively.

A value of 14% was used to model the radiative fraction for methane gas [27]. Internal heat

loss was set at 0.9.

4.1 Location of Fire

In addition to varying the heat release rate of the fire, the burner was placed in three different

locations within the room. These locations were as follows; in the open or away from any wall

(detached experiment), against a wall (wall experiment), and in a corner (corner experiment). The

effect of placing the burner against a wall or in a corner of the room is to restrict the entrainment of

air into the plume [20,37]. When the burner is placed away from a wall or what would be considered

in the open, cool room air is entrained into the plume from all directions. By placing the burner

adjacent to one or more walls, the area over which this cool room air can be entrained into the plume

is reduced. One result of this reduction in entrainment is higher flame heights. Since the fuel requires

the same amount of air to complete the oxidation process a greater distance is now needed for the

fuel vapors to mix with the smaller quantity of air that is entering the plume. With the higher flame

height there is also less distance from the tip of the flame to the bottom of the warm upper layer for

the plume to entrain cool air than in the case for the burner placed in the open. The higher plume

temperatures that result from the reduced cool air entrainment cause similar increases in the upper

layer temperatures.

Zukoski [20] placed a vertical wall across the diameter of a circular burner which caused it to be

reduced to a semi-circular geometry figure. The effect of placing the wall over a diameter of the

burner, blocking off half of the burner, was to reduce entrainment to 0.57 of the original value

obtained when the burner was placed in the center of the room, a reduction of 43%. The rate of

entrainment for a fire is related to the heat release rate as:

where = mass entrainment into the plume (kg/s)

= convective heat release rate of fire (kW)

By placing the fire against a wall, the entrainment is now limited to one half the perimeter of the fire.

For a wall fire, a pseudo heat release rate of two times the actual heat release is used to represent the
m0

plume % (2Q0C

)

1/3

m0

plume % 0.5(2Q0C

)

1/3 ' 0.63Q0

1/3

C

m0

plume % 0.25(4Q0C

)

1/3 ' 0.40Q0

1/3

C

TMTplume %

Q0

C

m0

plume

m0

plumecenter

m0

plumewall

'

1

0.63

' 1.6

m0

plumecenter

m0

plumecorner

'

1

0.4

' 2.5

Q0

c

18

(37)

(38)

(39)

(40)

(41)

(42)

effect of the wall on entrainment. The entrainment would be expected to increase by a factor of (2)1/3

or:

Since the entrainment only occurs over half the perimeter of the pseudo fire the actual entrainment

rate would be:

This value is close to the measured value of 0.57 reported by Zukoski.

By applying the same argument to a fire in the corner in which the entrainment will occur over one

fourth of the perimeter, this corner geometry fire entrainment rate compared to a center geometry fire

would be:

Additionally the temperature difference within a plume is related to the entrainment rate as follows:

For a given heat release rate , the change in temperature over ambient in the plume varies

inversely with the entrainment of air into the plume. For a wall fire:

which suggests that the average plume temperature rise within the plume will increase by a factor of

1.6 over that of a plume in the open at the same height.

For the corner case:
)T % Q0

2/3

)Twall

)Tcenter

'

Q0

2/3

wall

Q0

2/3

center

Q0

wall ' 1.3

3/2 Q0

center ' 1.5 Q0center

PR

PR

19

(43)

(44)

(45)

which suggests that the average plume temperature rise within the plume will increase by a factor of

2.5 over that of a plume in the open at the same height. To account for this effect on entrainment

and the subsequent rise in plume temperatures, Alpert [37] suggests doubling the heat release rate

for a wall fire geometry and quadrupling the heat release rate for a corner fire geometry when

calculating the rise in plume temperature.

Another effect that reduced entrainment rates have on corner and wall fire geometries is the warm

upper layer is moved upward in the room. This in turn allows the entrainment of lower layer air,

albeit at a reduced rate, to occur over a greater distance. Therefore, the excess temperature of the

plume as it enters the warm upper layer should be less than the factors calculated in Eqs. 37 and 38.

Mowrer [38] calculated a mass balance between the plume and the doorway mass fluxes which

permits the layer height, and consequently the compartment mass fluxes to be determined. By

plotting this mass balance between the plume and doorway mass fluxes it was found that the layer

height interface moves up for the wall and corner geometries as compared with the center fire

geometry. From this Mowrer suggests that the temperature increase in the plume be multiplied by

a factor of 1.3 for fires placed along walls and 1.7 for fires placed in corners. Since plume theory

relates the temperature rise above the fire source as:

 then

The ratio of temperatures differences between the center fire and the wall fire is 1.3. Thus

Therefore a fire along the wall is equivalent with respect to temperature difference to a fire about 1.5

times as large in the center of the room. By using the value of 1.7 for the ratio of temperature

difference a fire placed in a corner is equivalent with respect to temperature difference to a fire about

2.2 times as large in the center of the room.

4.2 Comparisons - Sprinkler Activation Times

Tables 14 and 15 give sprinkler activation times with the burner detached or placed away from any

wall and the vent to the upper floor opened and closed respectively For each heat release rate slow,

medium, and fast, three experiments were performed. The activation time for each experiment is

shown. Next to the activation times is a simple average of the three experiments. Two FPETool

simulations were performed, one with the default value for the fraction of radiative heat loss or =

0.35 and one with = 0.14. The predicted activation times are listed along with the percent

difference from the average of the three experiments.
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Tables 16 and 17 give sprinkler activation times for the burner placed against a wall and in the corner

respectively. In all cases the vent to the upper floor was open. For each heat release rate slow,

medium, and fast, three experiments were performed. The activation time for each experiment is

shown. Next to the activation times is a simple average of the three experiments. Two FPETool

simulations were performed for each scenario. For the wall scenario, one in which the heat release

rate was multiplied by a factor of 2 and one in which the heat release rate was multiplied by a factor

of 1.5. For the corner scenario, one in which the heat release rate was multiplied by a factor of 4 and

one in which the heat release rate was multiplied by a factor of 2.2. For both scenarios, the value for

the fraction of radiative heat loss or was set at 0.14. The predicted activation times are listed

along with the percent difference from the average of the three experiments. No experiments were

conducted with the burner placed against a wall or in the corner and the vent to the upper floor

closed.

4.3 Comparisons - Upper Layer Temperature and Upper Layer Depth

Using the N Percent Rule, the upper layer temperatures and upper layer depths were calculated.

Results for upper layer temperatures are presented in figures 15 through 20 for the detached burner

scenarios. Plotted along with the measured values are two predicted values from FPETool. The first

utilized a radiative heat loss fraction or of 0.35, the default value, and the second a radiative heat

loss fraction or of 0.14. For the experiments where the burner was placed against a wall the

measured values are compared with the heat release rate multiplied by a factor of 2 and 1.5. In this

case the radiative heat loss fraction or was 0.14. The wall scenario are presented in figures 21

through 23. For the experiments where the burner was placed in a corner of the room, the measured

values are compared with the heat release rate multiplied by a factor of 4 and 2.2. In this case the

radiative heat loss fraction or was 0.14. The corner scenario are presented in figures 24 through

26.

The upper layer development are presented in figures 27 through 32 for the detached burner

scenarios. Two measured depths were obtained for the upper layer, the first using N = 10 and the

second using N = 20. Plotted along with these two measured values are two predicted values from

FPETool. The first utilized a radiative heat loss fraction or of 0.35, the default value, and the

second a radiative heat loss fraction or of 0.14. For the experiments where the burner was

placed against a wall the two measured depths are compared with both the center heat release rate

multiplied by a factor of 2 and 1.5. In both cases the radiative heat loss fraction was 0.14. The

wall scenario are presented in figures 33 through 35. For the experiments where the burner was

placed in the corner of the room the two measured depths are compared with the heat release rate

multiplied by a factor of 4 and 2.2. In both case the radiative heat loss fraction was 0.14. The

corner scenario are presented in figures 36 through 38.

4.4 Comparisons - Ceiling Jet Velocities and Temperatures

Results for ceiling jet velocities are presented in figures 39 through 44 for the detached burner

scenarios. Plotted along with the measured values are two predicted values from FPETool. The first

utilized a radiative heat loss fraction of 0.35, the default value, and the second a radiative heat

loss fraction of 0.14. For the experiments where the burner was placed against a wall the

measured values are compared with the heat release rate multiplied by a factor of 2 and 1.5. In both
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cases the radiative heat loss fraction was 0.14. The wall scenario are presented in figures 45

through 47. For the experiments where the burner was placed in the corner of the room, the

measured values are compared with the heat release rate multiplied by a factor of 4 and 2.2. In both

cases the radiative heat loss fraction was 0.14. The corner scenario are presented in figures 48

through 50.

Results for the ceiling jet temperatures are presented in figures 51 through 56 for the detached burner

scenario. Plotted along with the measured values are two predicted values from FPETool. The first

utilized a radiative heat loss fraction of 0.35, the default value, and the second a radiative heat

loss fraction of 0.14. For the experiments where the burner was placed against a wall the

measured values are compared with the heat release rate multiplied by a factor of 2 and 1.5. In both

cases the radiative heat loss fraction was 0.14. The wall scenario are presented in figures 57

through 59. For the experiments where the burner was placed in the corner of the room, the

measured values are compared with the heat release rate multiplied by a factor of 4 and 2.2. In both

cases the radiative heat loss fraction was 0.14. The corner scenario are presented in figures 60

through 62.

4.5 Comparisons - Heat Release Rate at Sprinkler Activation

As in the chemical laboratory experiments a comparison is made of the heat release rate of the fire

at measured sprinkler activation to the heat release rate at predicted sprinkler activation. Tables 18

and 19 provide this for the detached burner scenario with the vent opened and closed respectively.

The format for these tables follows closely the one used to compare sprinkler activation. The

measured heat release rate at sprinkler activation is shown for each experiment. Next to the heat

release rates is a simple average of the three experiments. The heat release rate at the time of

predicted sprinkler activation is listed along with the percent difference from the average of the three

experiments.

For the scenario where the burner is placed against the wall, table 20 shows the results when the input

heat release rate for FPETool is doubled in order to take into account the effect of the wall on

entrainment. The measured heat release rate at sprinkler activation is shown for each experiment.

Next to the heat release rates is a simple average of the three experiments. The heat release rate at

the time of predicted activation is listed along with the percent difference from the average of the

three experiments. Table 21 shows the results when the input heat release rate for FPETool is

multiplied by 1.5 in order to take into account the effect of the wall on entrainment.

For the scenario where the burner is placed in the corner, table 22 shows the results when the input

heat release rate for FPETool is quadrupled in order to take into account the effect of the corner

geometry on entrainment. The measured heat release rate at sprinkler activation is shown for each

experiment. Next to the heat release rates is a simple average of the three experiments. The heat

release rate at the time of predicted activation is listed along with the percent difference from the

average of the three experiments. Table 22 shows the results when the input heat release rate for

FPETool is multiplied by 2.2 in order to take into account the effect of the corner geometry on

entrainment.

4.6 Discussion and Conclusions
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For the detached burner experiments the use of a of 0.14 as the fraction of radiative heat loss

provided better agreement with experimental results. By using a of 0.35 for the fraction of

radiative heat loss, FPETool over predicted activation times by 28% to 59%. By using a of 0.14

the model still over predicted activation times, but by a range of 10% to 39%. In this configuration

the effect of the vent or stairs to the upper floor being opened or closed was examined and it was

found not to have an appreciable effect on the measured or predicted activation times of the sprinkler.

Placing the burner against the wall had no appreciable effect on measured activation times. Therefore

in this situation, multiplying the heat release rate by any factor in an attempt to take into account any

increase in ceiling jet temperatures gave, as expected, faster predicted activation times. When the

burner against the wall, a short side of the burner was placed against the wall figure 12. The original

perimeter of the burner was 3.4 m (11 ft). By placing the short side of the burner against the wall the

perimeter is only reduced by 0.7 m (28 in), a reduction of only 21%. In this configuration, air was

being entrained over 79% of the burner perimeter.

Placing the burner in the corner did have an effect on the measured activation times. In this

configuration, the perimeter over which air can be entrained was reduced by 50%. The method of

quadrupling the heat release rate in order to take into account wall effects under predicted activation

times for all fire growth rates by a range of 9% to 26%. By using Mowrer’s correlation the model

over predicted activation times by a range of 3% to 24%.

For upper layer temperature increase with the burner in the detached position, the use of of

either 0.14 or 0.35 lie within the data scatter, figures 15 through 20. As with sprinkler activation

times, placing the burner against a wall did not have an appreciable effect on the upper layer

temperature increase, figures 21 through 23.

The upper layer development for the detached burner experiments, figures 27 through 32, was also

insensitive to the value of chosen. For the three scenarios in which the vent was open, FPETool

predicted a layer that asymptotically approached 1.8 m, while the measured values showed that the

layer continued toward the floor. For the three scenarios in which the vent was closed, FPETool did

predict that the layer in the room continued toward the floor as was measured. Upper layer

development was also insensitive to which method was used to take into account the effect of walls

when the burner was placed against a wall or in a corner, figures 33 through 38. Mowrer’s and

Alpert’s correlations gave similar predictions.

Gas velocity predictions for the detached burner experiments, figures 39 through 44, were also

insensitive to the value of chosen. Gas velocity predictions were also insensitive as to which

method was used to take into account the effect of walls when the burner was placed against a wall

or in a corner, figures 45 through 50. Mowrer’s and Alpert’s correlations gave similar predictions.

For all 6 scenarios, the measured gas velocity was consistently higher than that predicted by a factor

of 2.

Ceiling jet temperature increase predictions for the detached burner experiments, figures 51 through

55 had better agreement when using = 0.14 instead of 0.35 for the slow and medium fires.

However, both under predicted the increase in ceiling jet temperature. For the fast fire growth
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scenario the use of of 0.14 or 0.35 produced similar results, as both were within the data scatter.

Placing the burner against a wall did not have an appreciable effect on the measured ceiling jet

temperature. Multiplying the heat release rate by a factor in an attempt to take into account any

increase in ceiling jet temperature simply brought the predictions more in line with the measured

values.

The heat release rate at sprinkler activation again shows the importance of fire growth rate. Take for

example the scenario in which the burner is detached from any walls and the vent to the upper floor

is open. This is depicted in tables 14 and 18. For the slow fire growth rate the difference in predicted

sprinkler activation times is 23 s depending on which is chosen, table 14. However, the

difference in the heat release rate at predicted sprinkler activation is only 25 kW. Compare this when

the fast fire growth rate is used. Here the difference in predicted sprinkler activation times is 7 s and

the difference in heat release rate is 80 kW.

5.0 CONCLUSIONS

The applicability of FPETool to these three building spaces and fire geometries has been examined.

FPETool can provide useful predictions of fire generated environments in a single room such as those

described in this paper. Predictive capabilities of FPETool were compared against equivalent or

nearly equivalent measurements from the three experimental series. For the variables deemed of

interest, FPETool provides predictions which range in quality from within a few percent to double

the measured values. Presentation of the differences between FPETool predictions and the

experimental data are intentionally simple. Experimental uncertainties in full scale fire experiments

are difficult to determine since individual tests do not allow for the assessment of reproducibility of

the experimental results. Of these three experimental series, only the one dealing with residential

sprinklers had repeat tests.

The fires in these experiments can be characterized from those that grow with the square of time, tsquared fires, to those that reach steady state in a matter of seconds. Heat release rates from these

fires varied significantly. From 100 to 200 kW for the residential sprinkler experiments to 2 MW for

the chemical laboratory experiments and up to 3.6 MW for the hanger experiment fire. Compartment

geometries and ventilation factors also varied.

It must be noted that the physical make up of the compartment being modeled does not always agree

with the assumptions in FPETool. For example only the sprinklers in the residential sprinkler

experiments meet the criteria of being under a smooth unobstructed ceiling and within 1% of the fire

to ceiling height. In this set of experiments only when the burner was in the detached position does

it meet the requirement by FPETool that the fire be away from a wall. When the burner is placed

against a wall or in a corner adjustments where made in the heat release rate to take into account the

effect walls have on entrainment. This is not part of FPETool, but is an assumption that the modeler

makes.

Additionally, it was shown that when using FPETool to model a large space such has the hanger

experiment, that consideration needs to be taken for the time required for the products of combustion
24

to leave the combustion zone, travel to the ceiling and then out radially to the sensor. This is shown

clearly in figures 7 through 11 where the predicted temperatures of the link and ceiling jet agree well

with measured values. Only the time to reach these temperatures is significantly different. An

exception to this is figure 8 where the predicted temperatures is significantly greater than measured.

This may have been due to the proximity of the sensor to the plume. The ceiling jet is thinnest where

it strikes the ceiling and gradually thickens as it expands radially. FPETool assumes that the ceiling

jet is a constant thickness. This sensor may have been just below the ceiling jet.

Fire models such as FPETool estimate major fire generated effects. Due to the complex nature of

fire, mathematical prediction models, which FPETool is, are often simplified and based on a number

of assumptions. Knowledge is necessary of the limitations, approximations, and possible errors

associated with the assumptions and equations used in any computer model. The engineer has an

obligation to use this knowledge. This evaluation report is intended to be used in conjunction with

the models’ user manual and/or technical reference guide.

6.0 REFERENCES

1. Stroup, D. W., Analyzing Fire Safety Through Computer Modeling and Product Testing.

General Services Administration, Washington DC, Interscience Communications Limited.

Fires and Materials. 2nd International Conference, September 23-24, 1993 Arlington Virginia

pp 7-12.

2. Bonisch, W. D., Computer Fire Modeling Analysis of Smoke Control System Performance

in an Arena. Society of Fire Protection Engineers, Proceedings of Performance Based Fire

Safety Engineers, November 15-17, 1993, Phoenix, AZ pp 75-83.

3. Custer, R. L. P., Computer Modeling in Fire Reconstruction and Failure Analysis. Custer

Powell, Inc., Wrentham, MA, Society of Fire Protection Engineers and Worcester Polytechnic

Institute. Computer Applications in Fire Protection. Proceedings. June 28-29, 1993,

Worcester, MA, pp 69-74.

4. Bukowski, R.W., Analysis of the Happyland Social Club Fire with Hazard I. Journal

of Fire Protection Engineering, Vol. 4, No. 4, 117-131, 1992.

5. Bukowski, R.W., Modeling a Backdraft: The Fire at 62 Watts Street. NFPA Journal, Vol.

89, No. 6, 85-89, 1995.

6. Nelson, H. E., FPETool: Fire Protection Engineering Tools for Hazard Estimation. NISTIR

Report 4380, National Institute of Standards and Technology; October 1990.

7. Deal, S., Technical Reference Guide for FPETool Version 3.2. NISTIR 5486,

National Institute of Standards and Technology; August 1994.

8. Zukoski, E. E., Development of a Stratified Ceiling Layer in the Early Stages of a ClosedRoom Fire, Fire and Materials, Vol. 2, No., 2 1978.

11. Heskestad, Gunnar, Engineering Relations for Fire Plumes, Fire Safety Journal, Vol. 7, 1984,

p 25-32.

12. Heskestad, Gunnar, Virtual Origins of Fire Plumes, Fire Safety Journal, Vol 5, 1983, p 109-

114.

13. Heskestad, G., Fire Plumes, Section 2 Chapter 2 Society of Fire Protection Engineers

Handbook of Fire Protection Engineering, Second Edition, Boston MA., National Fire

Protection Association.
25

14 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,

No. 1, 54-65, February 1986.

15. Alpert, R. L., Calculation of Response Time of Ceiling-Mounted Fire Detectors. Fire

Technology, Vol. 8, No. 3, 181-195, August 1972.

16 Madrzykowski, D., The Effect of Recessed Sprinkler Installation on Sprinkler Activation

Time and Prediction. Master’s Thesis, University of Maryland, Department of Fire Protection

Engineering, College Park, Maryland, November 1993

17. Evans, D. D., Calculating Sprinkler Actuation Time in Compartments. Fire Safety Journal,

Vol. 9, No. 2, 147-155 1985.

18. Evans, D. D., Thermal Actuation of Extinguishing Systems NBSIR 83-2807. National

Institute of Standards and Technology, March 1984, Gaithersburg, Maryland, 20899.

19 Yokoi, S., The Use of Models in Fire Research, Publication No. 786, National Academy of

Sciences, National Research Council: Washington D.C., 1961, p 186-206.

20 Zukoski, E. E., Kubota, T., and Cetegen, B., Entrainment in Fire Plumes. Fire Safety Journal,

Vol. 3, 107-121 1980.

21. Parker, W. J., Calculations of the Heat Release Rate by Oxygen consumption For Various

Applications. Journal of Fire Sciences, Vol. 2, No, 2, 380-395, September/October 1994.

22. Janssens, M. L., Measuring Rate of Heat Release by Oxygen Consumption. Fire Technology,

Vol. 27, No. 3, 234-249, August 1991.

23. Huggett, C., Estimation of Rate of Heat Release by Means of Oxygen Consumption

Measurements. Fire and Materials, Vol. 4, No. 2, 1980.

24. Heskestad, G., and Smith, H. F., Investigation of a New Sprinkler Sensitivity Approval Test:

The Plunge Test. Technical Report, Factory Mutual Research Corporation, FMRC Serial

22485, RC76-T-50, December 1976.

25. Heskestad, G., and Bill, R. G., Quantification of Thermal Responsiveness of Automatic

Sprinklers Including Conduction Effects. Fire Safety Journal, Vol. 14, No. 1 and 2, 113-125,

July 1, 1988.

26. Walton, W. D., Quick Response Sprinkler in Chemical Laboratories: Fire Test Results.

NISTIR 89-4200, National Institute of Standards and Technology, December 1989.

27. Tewarson, A., Generation of Heat and Chemical Compounds in Fires. Society of Fire

Protection Engineers Handbook, 2nd Edition.

28. Cooper, L. Y., Estimating Safe Available Egress Times From Fires, NBSIR 80-2172.

National Institute of Standards and Technology (formerly National Bureau of Standards),

1982.

29. Cooper, L. Y., Harkleroad, M., Quintiere, J. Q., Rinkinen, W., An Experimental Study of

Upper Hot Layer Stratification in Full Scale Multi Room Fire Scenarios. Journal of Heat

Transfer, November 1982, Vol. 104, p 741-749.

30. Walton, W. D., and Notarianni, K. A., Comparison of Ceiling Jet Temperatures Measured in

an Aircraft Hanger Test Fire With Temperatures Predicted by the DETACT-QS and

LAVENT Computer Models. NISTIR 4947, National Institute of Standards and Technology,

January 1993.

31. Yeager, R. W., Uncertainty Analysis of Energy Release Rate Measurement for Room Fires.

Journal of Fire Sciences, Vol. 4, No. 4, July August 1986.
26

32. Vettori, R. L., Effect of an Obstructed Ceiling on the Activation Time of a Residential

Sprinkler. NISTIR 6253, November 1998, National Institute of Standards and Technology,

Gaithersburg, MD 20899.

33. McCaffery, B.J., Heskestad, G., A Robust Bidirectional Low-Velocity Probe For Flame And

Fire Application. Combustion and Flame, Vol. 26, No. 1, 127-127, February 1976.

34. National Fire Protection Association, National Fire Protection Association 13D Sprinkler

Systems in One and Two Family Dwellings and Manufactured Homes 1993 Edition, National

Fire Protection Association, Quincy, MA 02269.

35. Underwriters Laboratory Inc., Determination of the Response Time Index (RTI) and

Conductivity © Factor. Project Number 96NK9527 April 1996.

36. National Fire Protection Association, “National Fire Protection Association 72 Standard

National Fire Alarm Code Appendix B 1993 Edition, National Fire Protection Association,

Quincy, MA 02269.

37. Alpert, R. L., and Ward, E. G., Evaluating Unsprinklered Fire Hazards. Factory Mutual

Research Corporation, Norwood, MA, SFPE TR 83-02, FMRC J. I. 01836.20, August 1982.

38. Mowrer, F. A., Williamson, R. B., Estimating Room Temperatures From Fires Along Walls

and in Corners. Fire Technology, Vol. 23, No. 2, 133-145, May 1987.
27

Table 1 - Input for FPETool simulations - chemical laboratory experiments

INPUT PARAMETER Simulation 1 Simulation 2 Simulation 3 Simulation 4 Simulation 5

Minimum oxygen level 21 (EC) 10.0 10.0 10.0 10.0 10.0

600 (EC) 2.0 2.0 2.0 2.0 2.0

Heat transfer factor radiant fraction 0.35 0.35 0.35 0.35 0.35

max energy loss internal 0.90 0.90 0.90 0.90 0.90

Sprinkler

distance from center of fire (m) 0.61 0.61 0.61 3.66 n/a

RTI (m-sec) 250 40 40 40 n/a -5

activation temperature (EC) 74 71 71 71 999

sidewall velocity reduction factor (%) n/a n/a n/a 50 n/a

Door opening

height (m) 2.11 2.11 2.11 2.11 2.11

width (m) 0.91 0.91 0.91 0.91 0.91

height above sill (m) 0.0 0.0 0.0 0.0 0.0

Fire height (m) 0 0 0 0 0

Room dimensions

ceiling height (m) 3.20 3.20 3.20 3.20 3.20

length (m) 5.48 5.48 5.48 5.48 5.48

width (m) 3.66 3.66 3.27 3.20 3.66

Ceiling material concrete concrete concrete concrete concrete

thickness (mm) 100 100 100 100 100

thermal conductivity (kW/m-K) 0.0016 0.0016 0.0016 0.0016 0.0016

density (kg/m ) 2400 2400 2400 2400 2400 3

specific heat (kJ/kg-K) 0.75 0.75 0.75 0.75 0.75

kDc 2.88 2.88 2.88 2.88 2.88

Wall materials concrete concrete concrete concrete concrete

thickness (mm) 100 100 100 100 100

thermal conductivity (kW/m-K) 0.0016 0.0016 0.0016 0.0016 0.0016

density (kg/m ) 2400 2400 2400 2400 2400 3

specific heat (kJ/kg-K) 0.75 0.75 0.75 0.75 0.75

kDc 2.88 2.88 2.88 2.88 2.88
28

Table 2 - Heat release rate input - chemical laboratory simulations

Time Heat Release Rate

(s) (kW)

0 0

10 234

20 698

30 1039

40 1334

50 1553

60 1834

70 2002

80 1117

90 992

100 985

110 1067

120 949

130 915

140 907

150 876

160 792

170 769

180 718

190 610

200 554

210 506

220 485

230 431

240 709

250 630

260 508

270 500

280 442

290 395

300 319
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Table 3 - Activation time summary for simulation 1 - chemical laboratory experiments

Type and activation Measured Predicted activation time (s)

temperature of activation

sprinkler used in time (s)

experiment

RTI=200(m-s) RTI=250(m-s) RTI=300(m-s) 1⁄2 1⁄2 1⁄2

Standard Upright 39 32 34 37

74EC

Table 4 - Activation time summary for simulations 2 and 3 - chemical laboratory experiments

Type and activation Measured Predicted activation time (s)

temperature of activation

sprinkler used in time (s)

experiment

RTI=25(m-s) RTI=40(m-s) RTI=55(m-s) 1⁄2 1⁄2 1⁄2

Quick Response Exp 2 = 18 15 17 19

71 EC Exp 3 = 16 14 17 19

Table 5 - Activation time summary for simulation 4 - chemical laboratory experiments

Quick Response Side Wall Sprinkler - Activation Temperature of 71EC

Measured activation time 26 s

Response Time Index Velocity Reduction Factor Time to Sprinkler Activation

(m-s) (%) FPETool (s) 1⁄2

25 0 23

25 50 26

40 0 27

40 50 31

55 0 31

55 50 35
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Table 6 - Heat release rate at time of sprinkler activation

Experiment Number Heat release rate at time of Heat release rate for range of

measured sprinkler activation predicted sprinkler activation

(kW) times.

(kW)

1 1300 1100 to 1250

2 600 470 to 650

3 510 420 to 650

4 900 800 to 1190

Table 7 - Input for FPETool simulations - aircraft hanger experiments

INPUT PARAMETERS Simulation 1 Simulation 2 Simulation 3 Simulation 4 Simulation 5

Minimum oxygen level 21 (EC) 10.0 10.0 10.0 10.0 10.0

600 (EC 2.0 2.0 2.0 2.0 2.0

Heat transfer factor radiant fraction 0.30 0.30 0.30 0.30 0.30

max energy loss internal 0.90 0.90 0.90 0.90 0.90

Sprinkler

distance from center of fire (m) 0.0 2.7 5.5 8.2 11.0

RTI (m-sec) 57.7 57.7 57.7 57.7 57.7 -5

activation temperature (EC) 999 999 999 999 999

Door opening na na na na na

height (m)

width (m)

height above sill (m)

Fire height (m) 0.125 0.125 0.125 0.125 0.125

Room dimensions

ceiling height (m) 14.0 14.0 14.0 14.0 14.0

length (m) 40.2 40.2 40.2 40.2 40.2

width (m) 37.2 37.2 37.2 37.2 37.2

Ceiling material steel steel steel steel steel

thickness (mm) 100 100 100 100 100

thermal conductivity (kW/m-K) 0.458 0.458 0.458 0.458 0.458

density (kg/m ) 7850 7850 7850 7850 7850 3

specific heat (kJ/kg-K) 0.473 0.473 0.473 0.473 0.473

kDc 170.05 170.05 170.05 170.05 170.05

materials steel steel steel steel steel

thickness (mm) 25 25 25 25 25

thermal conductivity (kW/m-K) 0.458 0.458 Wall 0.458 0.458 0.458

density (kg/m ) 7850 7850 7850 7850 7850 3

specific heat (kJ/kg-K) 0.473 0.473 0.473 0.473 0.473

kDc 170.05 170.05 170.05 170.05 170.05
31

Table 8 - Heat release rate input - aircraft hanger simulations

Time Heat Release Rate

(s) (kW)

0 0

5 385

10 1750

15 3650

60 3650

Table 9 - Excess ceiling jet temperature comparisons - hanger experiments

Radial distance Average measured Standard deviation of Average excess

(m) excess ceiling jet measured excess ceiling jet

temperature ceiling jet temperature FPETool

(EC) temperature (EC)

0.0 44 6 51

2.7 31 4 48

5.5 28 2 30

8.2 20 1 23

11.0 16 1 19
32

Table 10 - Input for FPETool simulations - residential sprinkler experiments

INPUT PARAMETERS DETACHED WALL CORNER DETACHED

VENT OPEN VENT OPEN VENT OPEN VENT CLOSED

Minimum Oxygen level 21 (EC) 10.0 10.0 10.0 10.0

600 (EC) 2.0 2.0 2.0 2.0

Heat transfer factor radiant fraction 0.14 0.14 0.14 0.14

max energy loss internal 0.90 0.90 0.90 0.90

Sprinkler

distance from center of fire (m) 2.2 2.4 2.1 2.2

RTI (m-sec) 55.8 55.8 55.8 55.8 -5

activation temperature (EC) 68 68 68 68

Door opening na

height (m) 2.4 2.4 2.4

width (m) 2.7 2.7 2.7

height above sill (m) 1.5 1.5 1.5

Fire height (m) 0.3 0.3 0.3 0.3

Room dimensions

ceiling height (m) 2.4 2.4 2.4 2.4

length (m) 9.2 9.2 9.2 9.2

width (m) 5.6 5.6 5.6 5.6

Ceiling material gypsum board gypsum board gypsum board gypsum board

thickness (mm) 12.7 12.7 12.7 12.7

thermal conductivity (kW/m-K) 0.0017 0.0017 0.0017 0.0017

density (kg/m ) 960 960 960 960 3

specific heat (kJ/kg-K) 1.1 1.1 1.1 1.1

kDc 0.18 0.18 0.18 0.18

Wall materials gypsum board gypsum board gypsum board gypsum board

thickness (mm) 12.7 12.7 12.7 12.7

thermal conductivity (kW/m-K) 0.0017 0.0017 0.0017 0.0017

density (kg/m ) 960 960 960 960 3

specific heat (kJ/kg-K) 1.1 1.1 1.1 1.1

kDc 0.18 0.18 0.18 0.18

Table 11 - Heat release rate input - fast fire - residential sprinkler simulations

Time Heat Release Rate

(s) (kW)

0 0

5 58

10 75

15 110

20 127

25 163

30 173

35 192

40 196

45 216

50 271

55 309
Time Heat Release Rate

(s) (kW)

33

60 379

Table 12 - Heat release rate input - medium fire - residential sprinkler simulations

Time Heat Release Rate Time Heat Release Rate

(s) (kW) (s) (kW)

0 0 65 117

5 10 70 124

10 20 75 134

15 25 80 143

20 34 85 153

25 42 90 162

30 51 95 170

35 59 100 174

40 66 105 181

45 77 110 192

50 83 115 210

55 94 120 239

60 104
34

Table 13 - Heat release rate input - slow fire - residential sprinkler simulations

Time Heat Release Rate Time Heat Release Rate

(s) (kW) (s) (kW)

0 0 95 75

5 6 100 78

10 9 105 80

15 13 110 85

20 16 115 87

25 20 120 94

30 23 125 97

35 26 130 100

40 30 135 105

45 33 140 109

50 35 145 112

55 41 150 115

60 42 155 121

65 50 160 124

70 52 165 130

75 56 170 137

80 62 175 143

85 65 180 148

90 69
35

Table 14 - Activation time summary - burner detached - vent open - residential sprinkler

Fire growth Time to sprinkler activation (s)

rate

Exp # Exp # Exp # Average FPETool prediction

1 2 3

P = 35 % diff P = % diff R R

Slow 100 117 116 111 177 59 154 39

Medium 88 67 78 78 111 42 97 24

Fast 46 43 41 43 59 37 52 21

Table 15 - Activation time summary - burner detached - vent closed - residential sprinkler.

Fire growth Time to sprinkler activation (s)

rate

Exp # Exp # Exp # Average FPETool prediction

1 2 3

P = 35 % diff P = % diff R R

Slow 134 127 127 129 165 28 142 10

Medium 74 75 74 74 106 43 92 24

Fast 39 44 40 41 57 39 50 22

Table 16 - Activation time summary - burner against wall - vent open - residential sprinkler.

Fire growth Time to sprinkler activation (s)

rate

Exp # Exp # Exp # Average FPETool prediction

1 2 3

HRR x 2 % diff HRR x 1.5 % diff

Slow 129 116 124 123 108 12 126 2

Medium 70 71 68 70 70 0 81 16

Fast 42 40 39 40 36 11 43 8

Table 17 - Activation time summary - burner in corner - vent open - residential sprinkler.

Fire growth Time to sprinkler activation (s)

rate

Exp # Exp # Exp # Average FPETool prediction

1 2 3

HRR x 4 % diff HRR x 2.2 % diff

Slow 99 84 84 89 72 19 98 10

Medium 54 47 54 52 47 10 64 23

Fast 35 29 29 31 23 26 32 3
36

Table 18 - Heat release rate at time of sprinkler activation. Burner detached - vent open -

residential sprinkler.

Fire growth Heat release rate at sprinkler activation (kW)

rate

Exp # Exp # Exp # Average FPETool

1 2 3

P = 35 % diff P = % diff R R

Slow 80 90 90 85 145 70 120 41

Medium 160 120 140 140 195 39 175 25

Fast 225 210 200 215 365 70 285 33

Table 19 - Heat release rate at time of sprinkler activation. Burner detached - vent closed -

residential sprinkler.

Fire growth Heat release rate at sprinkler activation (kW)

rate

Exp # Exp # Exp # Average FPETool

1 2 3

P = 35 % diff P = % diff R R

Slow 105 100 100 100 130 30 110 10

Medium 130 135 130 130 185 42 165 27

Fast 195 210 195 200 335 68 270 35

Table 20 - Heat release rate at time of sprinkler activation. Burner against wall - vent open -

residential sprinkler. Assuming heat release rate input for FPETool is doubled due to effect of

wall on plume entrainment.

Fire growth Heat release rate at sprinkler activation (kW)

rate

Exp # Exp # Exp # Average FPETool

1 2 3

HRR X 2 % difference

Slow 100 90 95 95 85 11

Medium 125 125 120 125 125 0

Fast 205 195 195 200 195 3
37

Table 21 - Heat release rate at time of sprinkler activation. Burner against wall - vent open -

residential sprinkler. Assuming heat release rate input for FPETool is multiplied by 1.5 due to

effect of wall on plume entrainment.

Fire growth Heat release rate at sprinkler activation (kW)

rate

Exp # Exp # Exp # Average FPETool

1 2 3

HRR x 1.5 % difference

Slow 100 90 95 95 100 5

Medium 125 125 120 125 145 16

Fast 205 195 195 200 210 5

Table 22 - Heat release rate at time of sprinkler activation. Burner in corner - vent open -

residential sprinkler. Assuming heat release rate input for FPETool is quadrupled due to effect of

corner walls on plume entrainment

Fire growth Heat release rate at sprinkler activation (kW)

rate

Exp # Exp # Exp # Average FPETool

1 2 3

HRR x 4 % difference

Slow 80 65 65 70 55 21

Medium 90 80 90 85 80 6

Fast 190 170 170 175 150 14

Table 23 - Heat release rate at time of sprinkler activation. Burner in corner - vent open -

residential sprinkler. Assuming heat release rate input for FPETool is multiplied by 2.2 due to

effect of corner walls on plume entrainment

Fire growth Heat release rate at sprinkler activation (kW)

rate

Exp # Exp # Exp # Average FPETool

1 2 3

HRR x 2.2 % difference

Slow 80 65 65 70 75 7

Medium 90 80 90 85 115 35

Fast 190 170 170 175 180 3
38

Figure 1 - Plan view for a typical chemical laboratory

Figure 2 - Heat release rate for chemical laboratory experiments
39

Figure 3 - Approximate sprinkler location for experiments 1, 2, and 3

Figure 4 - Approximate sprinkler location for experiment number 4
40

Figure 5 - Upper layer temperature - chemical laboratory experiments

Figure 6 - Upper layer depth development - chemical laboratory experiments
41

Figure 7 - Measured and predicted temperature increase for plume and

detector link at 0.0 m - aircraft hanger experiments

Figure 8 - Measured and predicted temperature increase for ceiling jet at 2.7

m - aircraft hanger experiments. Detector link not shown due to instrument

malfunction
42

Figure 9 - Measured and predicted temperature increase for ceiling jet and

detector link at 5.5 m - aircraft hanger experiments

Figure 10 - Measured and predicted temperature increase for ceiling jet and

detector link at 8.2 m - aircraft hanger experiments
43

Figure 11 - Measured and predicted temperature increase for ceiling jet and

detector link at 11.0 m - aircraft hanger experiments

Figure 12 - Plan view - burner locations - residential sprinkler experiments
44

Figure 13 - Instrumentation set up for arrays 1 and 2

Figure 14 - Heat release rates for fast, medium, and slow fires. NFPA 72,

1993 edition
45

Figure 15 - Upper layer temperature increase - slow fire - detached burner -

vent open

Figure 16 - Upper layer temperature increase - slow fire - detached burner -

vent closed
46

Figure 17 - Upper layer temperature increase - medium fire - detached burner

- vent open

Figure 18 - Upper layer temperature increase - medium fire - detached burner -

vent closed
47

Figure 19 - Upper layer temperature increase - fast fire - detached burner - vent

open

Figure 20 - Upper layer temperature increase - fast fire - detached burner - vent

closed
48

Figure 21 - Upper layer temperature increase - slow fire - burner against wall -

vent open

Figure 22 - Upper layer temperature increase - medium fire - burner against

wall - vent open
49

Figure 23 - Upper layer temperature increase - fast fire - burner against wall -

vent open

Figure 24 - Upper layer temperature increase - slow fire - burner in corner -

vent open
50

Figure 25 - Upper layer temperature increase - medium fire - burner in corner -

vent open

Figure 26 - Upper layer temperature increase - fast fire - burner in corner - vent

open
51

Figure 27 - Upper layer development - slow fire - detached burner - vent open

Figure 28 - Upper layer development - slow fire - detached burner - vent

closed
52

Figure 29 - Upper layer development - medium fire - detached burner - vent

open

Figure 30 - Upper layer development - medium fire - burner detached - vent

closed
53

Figure 31 - Upper layer development - fast fire - burner detached - vent open

Figure 32 - Upper layer development - fast fire - burner detached - vent closed
54

Figure 33 - Upper layer development - slow fire - burner against wall - vent

open

Figure 34 - Upper layer development - medium fire - burner against wall - vent

open
55

Figure 35 - Upper layer development - fast fire - burner against wall - vent

open

Figure 36 - Upper layer development - slow fire - burner in corner - vent open
56

Figure 37 - Upper layer development - medium fire - burner in corner - vent

open

Figure 38 - Upper layer development - fast fire - burner in corner - vent open
57

Figure 39 - Velocity measurements - slow fire - detached burner - vent open

Figure 40 - Velocity measurements - slow fire - detached burner - vent closed
58

Figure 41 - Velocity measurements - medium fire - detached burner - vent open

Figure 42 - Velocity measurements - medium fire - detached burner - vent

closed
59

Figure 43 - Velocity measurements - fast fire - detached burner - vent open

Figure 44 - Velocity measurements - fast fire - detached burner - vent closed
60

Figure 45 - Velocity measurements - slow fire - burner against wall - vent open

Figure 46 - Velocity measurements - medium fire - burner against wall - vent

open
61

Figure 47 - Velocity measurements - fast fire - burner against wall - vent open

Figure 48 - Velocity measurements - slow fire - burner in corner - vent open
62

Figure 49 - Velocity measurements - medium fire - burner in corner - vent open

Figure 50 - Velocity measurements - fast fire - burner in corner - vent open
63

Figure 51 - Ceiling jet temperature increase - slow fire - detached burner - vent

open

Figure 52 - Ceiling jet temperature increase - slow fire - detached burner - vent

closed
64

Figure 53 - Ceiling jet temperature increase - medium fire - detached burner -

vent open

Figure 54 - Ceiling jet temperature increase - medium fire - detached burner -

vent closed
65

Figure 55 - Ceiling jet temperature increase - fast fire - detached burner - vent

open

Figure 56 - Ceiling jet temperature increase - fast fire - detached burner - vent

closed
66

Figure 57 - Ceiling jet temperature increase - slow fire - burner against wall -

vent open

Figure 58 - Ceiling jet temperature increase - medium fire - burner against wall

- vent open
67

Figure 59 - Ceiling jet temperature increase - fast fire - burner against wall -

vent open

Figure 60 - Ceiling jet temperature increase - slow fire - burner in corner -

vent open
68

Figure 61 - Ceiling jet temperature increase - medium fire - burner in corner -

vent open

Figure 62 - Ceiling jet temperature increase - fast fire - burner in corner - vent

open