A11107 3TD147

NBS

PUBLICATIONS

NBSIR 83-2708

Development of A Calorimeter for

Simultaneously Measuring Heat

Release and Mass Loss Rates

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Washington, DC 20234

June 1983

100

, U56

33-2708

1933

C.2

S. DEPARTMENT OF COMMERCE

VTIONAL BUREAU OF STANDARDS

NATIONAL BUB'-AU OF STANDARDS

LIB BABY JUN 2 7 (SO* CXtC.'

NBSIR 83-2708

... . DEVELOPMENT OF A CALORIMETER FOR

SIMULTANEOUSLY MEASURING HEAT

RELEASE AND MASS LOSS RATES

John Tordella and William H. Twilley

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Fire Research

Washington, DC 20234

June 1983

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS. Ernest Ambler, Director

1983

0

(Jv

TABLE OF CONTENTS

LIST OF FIGURES

Page

lv

LIST OF TABLES lv

Abstract 1

1

.

INTRODUCTION 1

2. DESIGN...' 2

2.1 Specifications 2 2.2 Choices 2 2.2.1 Specimen Size 2 2.2.2 Radiant Panel Type 2 2.2.3 Panel Configuration 3 2.2.4 Measurement of Heat Release Rate 3 2.2.3 Substitution Burner 4

2.2.

b Pilot Ignition of Specimens 4 2.2.7 Specimen Carrier - Calibration Burner 4

2.2.

B Measurement of Flow Rates 5 2.2.9 Dilution Air-Cooling Towers 3 2.2.10 Specimen holders and Load Cell 3 2.2.11 Safety Interlocks 3

3. CONSTRUCTION 6

3.1 Mechanical Details 6 3.2 Gas and Low Pressure Air Distribution 6 3.3 High Pressure Air and Water Distribution 6 3.4 Electrical 6

3.3

Instrumentation 7

4. OPERATING PROBLEMS 7 4.1 Start-Up Problem 7 4.2 The Stack Problem 7

3. OPERATION b

3.1 Flux Range b 3.2 Start-Up Procedure 3 3.3 Operating Procedures 10

5.4 Calibration Procedure 12

6. ILLUSTRATIVE DATA 14

7. PROGRAM 14

b. ACKNOWLEDGMENTS 13

9. REFERENCES 15
LIST OF FIGURES

Page

Figure 1. View Factors, Vertical Specimen

Figure 2. View Factors, Horizontal Specimen , 17

Figure 3* Response Time of NBS I Calorimeter to two square wave methane calibration 1°

Figure 4. Artist's Rendition, NBS II Calorimeter 19

Figure 5- Dimensioned View of Calorimeter 20

Figure 6. Sectional View of Calorimeter 21

Figure 7» Operation of Carriage-Elevator 22

Figure 8. Combustion Gas and Low Pressure Air Schematic 23

Figure 9. High Pressure Air and Water Schematic 24

Figure 10. Legend for Figures 8 and 9 25

Figure 11. Heat Release Rate and Remaining Mass Curves for Polystyrene 26

Figure 12. Heat Release Rate of Black Polymethylemathacrylate 27

Figure 13- Heat Release Rate of Ceiling Tile 28

LIST OF TABLES

Page

Table 1. Specification for New NBS Heat Release Rate Calorimeter 29

Table 2. Engineering Drawing Schedule for Calorimeter 30

iv
DEVELOPMENT OP A CALORIMETER FOR SIMULTANEOUSLY

MEASURING HEAT RELEASE AND MASS LOSS RATES

John Tordella*

Society of the Plastics Industry

and

William H. Twilley

Center for Fire Research

Abstract

A heat release rate calorimeter (deslgnatea as NBS II) was designed,

built, and put into operation. Specimens may be burned vertically or horizontally without the use of reflectors to provide a uniform external

radiant flux field. The flux range is 2b to BO kW/m^. heat release rate, mass loss rate, smoke, and heat of combustion of the unburned gaseous

decomposition products are measured. The heat release rate measurement

involves the use of a substitution burner technique which provides fast

response. The ratio of the heat release to mass loss rates, the apparent

heat of combustion, is provided as a function of time. The calorimeter may

also be operated in other modes, e.g., stack temperature increase and oxygen

depletion, to obtain the heat release rate.

Representative data are reported for wood and a number of synthetic

P polymers burned horizontally at a flux of 50 kW/m . These specimens

generate considerable heat and a significant amount of uncombusted fuel.

A program involving thorough characterization of the instrument,

obtaining reference heat release data for numerous materials, and conducting

research in heat release rate ana other flammability characteristics is

recommended.

Key words: calorimeter; fire test; heat of combustion; heat release

rate; mass loss rate.

1 . INTRODUCTION

The rate of heat release by materials as they burn is recognized as an important factor

governing the rate of fire growth in real world situations involving these materials. A number

of devices have been used over the past 10 to 15 years to measure heat release rate [l] 1

. Notwithstanding, there was need for an instrument which would:

(1) accept sufficiently large specimens;

(2) operate equally well with either vertical or horizontal specimen orientation;

* This work was conducted while Dr. Tordella was a Research Associate at the National Bureau of

Standards

.

1 Numbers in brackets refer to literature references listed at the end of this report.

1
(3) provide rate of maaa loss ae well aa rate of heat release; and

(4) provide reliable aata in a reaaonable time.

Existing instruments were deficient in one or more of the above requirements. The Factory

Mutual calorimeter developed by Tewarson et al . L 2 j employs rather small specimens oriented

horizontally. The Ohio State University (OSU) calorimeter L3] does not measure mass loss, has

slow response, and uses small specimens. The OSU use of a reflector for horizontal specimen

exposure with its corresponding shortcomings of smoke dulling and strong reradlative effects

introduce several errors. The existing National Bureau of Standaras Instrument, NBS I L^O,

employs a relatively small specimen, does not provide for specimen mass loss, and has a poor

geometry for horizontal specimens.

A new instrument was designed and built to overcome these deficiencies and satisfy the

objectives set forth above. This task was begun in February 1976. Details of the design,

construction, and operation are given herein, as are illustrative heat release data ana a recommendea program for future research.

2. DESIGN

2.1 Specifications

The design specifications for the new National Bureau of Standards heat release rate

calorimeter, NBS II, are given in Table 1. These specifications were set by consensus of those

at the Bureau who worked or had been involved in heat release rate calorimetry. The design

specifications are those for a "state-of-the-art" heat release rate calorimeter.

2.2

Choices

2.2.1 Specimen Size

Specimen sizes of 300 x 300 mm (1 x 1 ft) for vertical specimens and 150 x 300 mm

(1/2 x 1 ft) for horizontal specimens were chosen. These sizes were expected to be sufficiently large that the data would be largely Independent of specimen size. Specimen area to thickness ratios were anticipated to be large enough that errors due to "edge effects" would be

relatively small.

2.2.2

Radiant Panel Type

Gas-heated radiant panels were chosen to provide the desired do kk/m^ flux. Electric,

nlchrome resistance heaters do not proviae sufficiently high flux for reasonable rates of

electrical power consumption, high color temperature, short wavelength radiation electric

heaters were avoided because light and dark specimens have different absorbency at these wavelengths. Gas heated radiant panels with their longer wavelength radiation avoid problems of

differential absorption and more nearly represent real world fire exposures. Reflectors,

usually used with high color temperature sources, are also a problem. Loss of reflectivity due

to coating by smoke particles may reduce the energy reflected to the specimen during a test.

Silicon carbide rod heaters, which are now used in the OSU calorimeter, were not considered.

These heaters are limited area sources. Decisions between the desirability of these relative

to gas panels may be best arrived at through experience.

2
Kadiant panels manufactured by Eclipse Combustion Engineering, Inc. 2 were chosen over the

often used British-made ones. The American panels had the advantages of mounting and general

consulting services available for associated equipment supplied by the manufacturer

.

2.2.3 Panel Configuration

To provide sufficiently uniform flux for horizontal specimens, the radiant panel heaters

were arranged to form the four sides of a box. The horizontal specimen is located at the

bottom of this box geometry. For testing vertical specimens, a holder is placed upright at the

center of the heated area with the specimen "looking into" the radiant panels.

The arrangement of the radiant panels is shown schematically in figures 1 and 2 for

vertical and horizontal specimens. The view factor is the fraction of the solia angle subtended by the radiant panels at the specimen face. View factors were calculated Lb] for the

two orientations with the panels nearly touching along the edges in each of the four sides and

a separation of 13, 2b, and 3d mm at the corners. The 36-mm opening was chosen for the actual

design because the full specimens could be viewed through these openings and because the flux

range across the specimen faces did not exceed 10 percent. Various positions on the specimen

are indicated as I, II, III, etc. These correspond to center, corner, or edge, as indicated.

The size of the array of radiant panels is 600 x 600 mm (2 x 2 ft) and 300 x 600 mm (1x2 ft). For the specimen sizes chosen, this size array of panels is adequate because the

specimens are outside the zone of convective heating by the panels.

2.2.4 Measurement of Heat Release Rate

Several modes of measurement of the heat release rate were available. Temperature rise of

stack gases due to sample combustion was the earliest method, which is still used in the OSU

calorimeter L3]. This constitutes, effectively, a sensible enthalpy measurement. The long

response time of such an instrument was much reduced by use of a "substitution" burner. This

scheme was to maintain a constant stack gas temperature by reducing the fuel to the substitution burner as combustion of the specimen added heat. Stack temperature is held constant by a temperature controller acting on the fuel flow to the substitution burner. The measurement of

the decrease in substitution burner fuel feed directly represents the specimen heat release.

Response using both types of readouts in the first Bureau heat release rate calorimeter, MBS I, to two square wave methane calibrations is shown in figure 3. With the isothermal substitution

burner technique, full response to a step change was realized in less than 5 seconds. When the

instrument was operated in the sensible enthalpy measurement mode, full response took much

longer than 1 minute.

Recently, the lag inherent in the sensible enthalpy technique was reduced by the use of a "thermal inertia compensator" with the OSU calorimeter; this is being evaluated by an ASTM task

group. A numerical compensation scheme also has been presented by Evans and Breden [6].

Another mode of measurement of the heat release rate is by oxygen consumption. A significant number of materials liberate a nearly constant amount of heat for a given amount of oxygen

consumed. While there is no inherent time lag associated with oxygen consumption, there is a lag associated with measurement of oxygen concentration.

2 Certain commercial equipment. Instruments, or materials are identified in this report in

order to adequately specify the experimental procedure. In no case does such identification

imply recommendation or endorsement by the National Bureau of Standards, nor does it imply

that the material or equipment identified is necessarily the best available for the purpose.

3
The operating choice between the Isothermal method and the oxygen consumption method now appears to be a matter of preference. When the NBS II calorimeter was designed, the Isothermal

method was obviously the best choice. NBS II can be operated In any of the three modes.

Experience and the specific task at hand will probably aetermlne the more desirable mode.

2.2.5

Substitution Burner

A blast burner, forced air and gas, was chosen for a substitution burner. This design

permits the burner to be placed In the wall of the calorimeter, out of the stream of combustion

products without introduction of burner thermal mass into the stream. The burner chosen was an Eclipse 40 AH2 burner designed for heating air. It has Infinite turndown, i.e., the ability to combust the fuel gas at rates from maximum to zero. This is a desirable characteristic since

the entire capacity of the burner Is then available for the measurement of heat release rate.

p Control for the substitution burner was provided by a Leeds and Northrup Electromax III 41 temperature controller with proportional band, reset, approach, and lag controls. The

controller operates Into a Kepco P114783 2 power supply which drives the control valve. This

control valve Is a fast response, solenoid modulating valve of small size: Brooks Instrument

Control Valve, b94bB037BMA2. The small size of this valve necessitated use of high pressure

gas, 100 kPa (15 psi), to get sufficient gas through it to accommodate a 500 kW/m2 heat release

rate for 300 x 300 mm specimens.

2.2.6

Pilot Ignition of Specimens

Two types of specimen ignition are provided. Electric spark ignition pilots are used at

the top of vertical specimens and over the edge of horizontal specimens. Electric spark ignition pilots avoid the difficulty of gas pilots which can be blown out or snuffed out by speci- men decomposition products.

A curtain pilot also was provided as an option to engulf the face of vertical specimens.

This pilot is stationary within the calorimeter; the specimen is elevated into position beside

it. A bottom point pilot, such as that used with the OSU calorimeter, can be operated from the same source. Spark ignition of the pilot flames is provided.

2.2.7

Specimen Carrier - Calibration Burner

Since radiant panels surround the specimens on four sides, specimens had to be introduced

from below. A rolling carriage-elevator arrangement was devised for the purpose. In the

forward elevated position, the specimen holder is accessible at the front of the calorimeter.

This is where the specimen is loaded on a holder, attached to the load cell. The elevator is

lowered with a pneumatic cylinder, the carriage pushed back, and the elevator raised to bring

the specimen within view of the radiant panels. Figure 7 shows this operation pictorially

.

The elevator was made with two sides. The second side is used to carry a diffusion flame

pipe burner, which provides a convenient mode for calibration. Were calibration sufficiently

Infrequent, the line pilot could be used for this purpose and the second position could be used

to mount a second specimen holder. If both vertical and horizontal specimen holders were mounted, tedious exchange of holders could be avoided. However, this would require an additional load cell arrangement for measuring the mass loss.

4
2.2.8

Measurement of Plow Rates

Orifice gauges were used to measure the flow rate of dilution air, air to the substitution

burner, air to the radiant panels, and gas to the radiant panels. Mass flow meters were provided to measure gas to the substitution and calibration burners. A variable area flow meter

was provided to check the accuracy of the mass flow meter on the calibration burner. 2.2.9

Dilution Air-Cooling Towers

Dilution Air, additional air beyond that required for combustion either of the specimens

or of gas from the various burners, is introduced for several reasons. In the event that

energy balance is to be calculated, sufficient dilution air will permit use of thermal data for

air rather than having to use data for the individual combustion products. Another reason is

that dilution air lowers the temperature of the instrument significantly.

The possibility of ignition of the premixed gas and air within the radiant panels was thought to be a problem. Irradiation of one panel by another in the box configuration could

raise the temperature of the metal parts of the burner sufficiently that the premix would

ignite and destroy the procelain burner panels. To avoid this possibility, dilution air was introduced through an air manifold at the base of the calorimeter and directed up vertical

pipes, called cooling towers to the back of each radiant panel. One cooling tower was located

behind each vertical burner array. Parts in each tower directed air at the bolts holding each

burner onto its manifold. The air was to cool the back of the burners.

The cooling of the burner backs themselves described above was found to be unnecessary.

Operation at maximum flux with no dilution air flow produced a temperature of only about 400°C

at the back of the porcelain panel plaques. The ignition temperature for natural gas-air

mixtures is about 500°C. Even though the cooling of the burner backs was found to be unnecessary, their use was found to be desirable for keeping the sheetmetal shrouds cooler. Cool

shrouds help keep the room housing the calorimeter more comfortable to work in and reduce the

possibility of personnel getting burned.

2.2.10

Specimen Holders and Load Cell

Vertical and horizontal specimen holders were designed with water-cooling elements between

the holder and load cell. The whole frame for the vertical holders was water-cooled. Connection for the cooling water was done through pliant coils of copper tubing which did not rub or touch anything. Friction from touching would result in "backlash" and step-like weight versus

time curves. The load cell was mounted in a five-sided stainless steel box, each side of which

is water-cooled.

2.2.11

Safety Interlocks

There are explosion hazards associated with the use of gaseous fuels. Safety interlock

devices and conservative design were employed to reduce the hazard. The calorimeter has the

following features designed for safe operation. The flue gases from the calorimeter go

directly through the building roof by way of the instrument's own stack; bypassing the

building's central hood and duct exhaust system. This stack assures that uncombusted natural

gas does not enter the building's exhaust ducts and create an explosion hazard. There is a pressure interlock switch on the dilution air to the instrument downstream of the butterfly

throttling valve. If the dilution air is not flowing to the Instrument, the Interlock switch

5
causes the main gas valve to close. This avoids accumulating explosive concentrations of gas

within the Instrument. The Instrument stack and dilution air pressure switch constitute the

main safety features. An additional safety device consists of a "flame rod". This Is a device

which senses whether there Is a flame on the surface of the radiant panel and causes the main

gas valve to shut down If the flame goes out. This device Is Installed on the radiant panels

that are operated for both vertical and horizontal specimens. The hazard that this device

protects against is the gas going off, then coming back on again and not being Ignited. With

the flame rod, the main gas valve will close when the flame goes out and will not reopen If the

gas comes on later.

A hood over the specimen loading and unloading station protects the operator against fumes

from the specimen residues. Curtains can be installed If greater air velocity past the

operator Is needed.

3. CONSTRUCTION

3.1

Mechanical Details

Mechanical details of the calorimeter are described In the group of engineering drawings

listed In table 2. An artist's rendition of the Instrument, figure 4, illustrates the main

features. A dimensioned view of the calorimeter Is shown In figure 5. The calibration burner

is shown within the array of radiant panels, in the sectional view of figure 6. The cooling

towers carrying dilution air are also shown. The main base of the instrument Is a rectangular

frame of 130 x 300 mm rectangular tubing about 1 x 1-1/2 m (3-1/2 x 4 ft) overall. This frame

also serves as the dilution air manifold. An angle iron frame on the main instrument frame

supports the shrouds which have windows for viewing the burning specimens. The shrouos constitute a box about 1-1/3 m In length, width, and height. A transition to a rectangular stack

sits atop the shroud support frame. The thermocouples which monitor flue gas temperature are about 1-1/3 m above the top of the transition. The whole instrument is supported by rigid

angle iron legs weloed to the dilution air manifold. The sample carriage-elevator arrangement

rolls between the legs on aluminum support rails hung from the dilution air manifold. Figure 7 shows the operation of the carriage-elevator moving the vertical sample holder from outside the

calorimeter, where samples are loaded and unloaded, to the inside of the calorimeter exposing

them to the radiant panels.

3.2

Gas and Low Pressure Air Distribution

Gas and low pressure air piping to the calorimeter are shown In figure b. The air

pressure is applied by the blower at 5.2 kPa (12 oz/in^).

3.3

high Pressure Air and Water Distribution

A schematic drawing of high pressure air and cooling water to the calorimeter is given in

figure y. The legend for figures b and y is found in figure 10.

3.4

Electrical

Electrical power for the calorimeter is supplied by a single 120 volt 60-cycle 20 amp

circuit. A single switch on the control panel deactivates the calorimeter, electrical, air

blower, water, and instrumentation. Compressed air to hold the sample elevator up remains

always on.

6
3.5 Instrumentation

Plow rate of gas to the substitution burner Is measured by a Datametrlcs 800 LM 2 mass flow

meter of 0-2.36 L/s (0-5 ftVmln), 0-10 V output. The output signal goes to a signal conditioner which inverts it and provides a continuously adjustable gain. This adjustable gain

p allows the output to be rationalized so that a recorder may read directly in kto/mc heat release

for a given specimen size.

Plow rate to the calibration burner of the specimen pilots is read on a second identical

mass flow meter without a signal conditioner. A variable area flow meter is used optionally in

series with the mass flow meter to check the calibration.

p Specimen weight is measured with an Automatic Timing Control series 60050* weigh cell and

demodulator model &101-F2

. The weigh cell range is 0-2 kg (0-4 lb) with 12 kg (2b lb) tare

weight adjustment.

The smoke meter was designed by J.S. Steel. It consists of a laser light source, Metrologic ME-620 2

, 0.8 mW, and a 1P39 phototube receiver with a logarithmic amplifier. The output

is 0-5 volts, which corresponds to 0-5 optical density units.

The combustion meter is a Leeds and Northrup total combustible gas analyzer,

#7867-4-3-l-005-0-2-l-00-0 2

. The output is 0-10 V for 0-5 percent combustibles.

A Gardon flux gage, 0-100 kW/m2

, is used to monitor the flux incident on the specimen,

p either vertical or horizontal. The output is about 0.0125 mV/kW/m flux.

p A six point, console Rlkadenko recorder is used adjacent to the calorimeter. The data

can also be taken digitally, stored on discs, and later reduced on a minicomputer in another

building.

4 . OPERATING PROBLEMS

4.1 Start-Up Problem

Completion of the instrument took many months. The large parts were completed by the main

shop in July 1977. Sheet metal, plumbing, and electrical work were done in mid November 1977;

instrument-type plumbing, electrical, and mechanical work went on until June 1978.

Once the basic assembly work was completed and start up testing begun many new problems

appeared. Even with the commercially purchased ignition system, reliable panel ignition took

much trial and error fitting the sample load cell and carriage-elevator worked well when the

calorimeter was cold but became erratic or jammed when the calorimeter was at normal operating

temperatures. These problems were ultimately overcome by reinforcing the calorimeters base and

judicious use of water cooled shielding.

4.2 The Stack Problem

The single most serious problem in operation has been that of fluctuations in rate of flow

of gas to the substitution burner, under steady operating conditions. These fluctuations were ultimately found to be the result of variable wind velocity at the top of the stack, resulting

in a pressure differential as large as 50 to 75 Pa (0.2 to 0.3 in H2 0).

7
The best baseline uniformity, l.e., the gas flow rate at steady conditions with no specimen in the calorimeter, corresponded to +_ 2 to 3 kW/m2 on 300 x 300-mm specimen basis. During

gusty winas preceding a rain squall, the baseline varied randomly over a range of 100 to

150 kW/m2. On a gusty winter day, baseline variation was often 50 to 100 kW/m2

. The tolerable

maximum is about 10 to 20 kW/m2.

The first approach to solving the stack problem was to Install (a) a venturi type cap on

the stack to prevent "downdrafting" and (b) a barometric damper in the stack. The rationale

was that the venturi cap would assure a negative stack pressure and the damper would modulate

the negative pressure to a constant value. This approach did not solve the problem. The stack

pressure was not sufficiently negative for the barometric damper to function.

Two other approaches were tried unsuccessfully:

1. Air flow through the instrument was increased to a maximum so that the stack

pressure change due to the wind would be a smaller part of the total

pressure drop. The fuel flow variation was reduced, but large positive

pressure in the calorimeter, about 25 Pa (0.1 in H2 O), was objectionable.

Combustion products leaked out into the room causing eye and throat discomfort, and possible toxicity problems.

2. Air flow was minimized and the substitution burner was operated at capacity.

The objective was to maximize the draft in order to cause the barometric

damper to function. The draft produced at 430 C was inadequate, about

12.5 Pa (0.05 in H2 0), to operate the damper. (Insulating the stack would

also increase the draft. Calculations indicated only about a 10 percent

increase in draft could be obtained, which was considered to be inadequate. )

Increased stack height to get above eddies caused by the building did not appear to be a viable solution. Significant pressure variations occurred even in the main stack, which is

about 7.6 m (25 ft) taller than the calorimeter stack. Architectural practices at the Bureau

militate against a stack taller than the main building stack.

The variable stack pressure problem possibly could be solved by installing a draft

inducing blower and an adjustable damper in series in the stack. The objective is to create a large pressure change going up the stack such that the pressure variation due to eddies is

relatively small. A pressure of 1.25 kPa (5 in H2 0) appears to be a good goal. The capacity

of the blower must be adequate to handle the volume of the calorimeter stack gases. Pressure

in the calorimeter itself should be neutral. Calorimeter pressure can be adjusted by varying

the damper opening. The barometric damper should be removed to reduce the effect of pressure

changes due to opening and closing building doors on calorimeter operation. This design change

might improve the stability of the baseline but at present it has not been tried, limiting

optimum calorimeter operation to relatively calm days.

5 . OPERATION

5.1 Flux Range

The radiant panels operate over a pressure range of about 100 Pa (0.4 in H2 0) to a design

maximum of 870 Pa (3.5 in H2 0). The associated flux range is about 25 to bo kW/m2

.

8
5.2 Start-Up Procedure

Check main panel to be sure all switches are OFF.

Turn main power switch on panel to ON (level handle). This will activate the following

functions:

• main panel power on,

• opens cooling water solenoid valves,

• energizes both duplex receptlcles on power panel,

• energizes control system,

• energizes data system,

• energizes air pump and combustion analyzer, and

• energizes laser on smoke meter.

Turn air blower on by pushing green START button.

This will turn on the air blower in the equipment room — wait for yellow light — and

will close the air pressure safety switch to supply power to main gas valve.

If yellow light does not come on within 2 minutes, increase the air flow by opening valve

35.

Open gas valve 8 for samples being tested in the vertical sample holder or valves 7 and 8 for samples being tested in the horizontal sample holder.

Open gate valve 32 for vertical samples or valves 32 and 33 for horizontal samples to 250 Pa (1 in H2O) or more of premixed gas and air.

Turn radiant panel switch on main panel from OFF to IGN and hold on IGN until red light

comes on.

This will activate the following:

• spark igniters on face of radiant panels will ignite panels, and

• main gas valve will be held open by flame rod relay when flame is established and pilot light comes on.

Turn substitution burner switch from OFF to IGN to ignite pilot flame for substitution

burner.

The following controls are located on the control panel. Turn the substitution burner

controller toggle switch from MANUAL to AUTO.

Turn voltage control knob to the maximum setting that does not open substitution burner

valve, about "11 o'clock".

Turn temperature controller knob to 220 C or greater.

Turn toggle switch to signal conditioner to ON.

9
Turn toggle switch for power to controller ON to activate the substitution burner.

Turn combustion analyzer toggle switch to ON.

Turn smoke meter analyzer toggle switch ON.

Turn toggle switch on outlet box on main panel ON to activate laser, smoke pump, ana smoke

anlayzer.

Turn analog to digital converter toggle switch ON.

Turn both modems table units ON by operating rocker switches on back of units.

Turn on strip chart recorder by switching ON main power switch on front of recorder.

Turn on all rocker switches for each individual pen, on top of recorder.

Set chart speed as desired.

This concludes the start-up procedure.

5.3 Operating Procedures

Once the calorimeter is started, it is necessary to set several variables to the desired

levels. First, it is necessary to establish the orientation of the sample, either horizontally

or vertically. Second, the size of sample to be tested must be established. The standard

maximum size for horizontal samples is 150 x 300 mm (1/2 x 1 ft) and for vertical samples is

300 x 300 njn (1 x 1 ft); smaller sizes may be used. The thickness of the sample is limited

primarily by the sample holder being used. Third, the type of sample ignition must be established — either gas flame, electric spark, or no igniter. Once these variables have been

established, NBS II must be adjusted to meet them. Horizontal samples require a pan or tray

approximately the same size as the sample to be tested to rest on the insulation above the load

cell.

Vertical samples require Installation of a special f ramie to be mounted on the load cell.

This can be accomplished by moving the carriage elevator so the load cell is outside the calorimeter. This is the normal position of the carriage-elevator when loading and unloading

samples. The vertical sample holder is then bolted to the load cell, and the cooling water

connections are made. The flux meter should be attached to the side of the sample holder ana

the water and electric lines for it connected. The water lines must be pliant and must not

touch each other or any part of the frame or the load cell output will be erratic. Once the

vertical sample holder is in place, samples are Inserted into the holder backed up with ceramic

insulation board and secured with spring clamps.

With the sample holder positioned, it is necessary to install the sample igniter system,

if one is going to be used. The spark Igniter on the horizontal sample holder involves the use

of a spark plug with a long tip and ground electrode. This spark plug is held on a metal strap

which can position the electrodes over or near the sample. Voltage for the spark is picked up

by way of an 18 cm (7 in) long wire which engages a high voltage wire frame inside the stationary part of the calorimeter. This igniter can be attached and adjusted while the calorimeter

is in operation.

10
The spark igniter for the vertical sample holder attaches to the top of the sample holder,

and employs a similar type of spark plug as the one used on the horizontal sample holder. This

spark plug also engages a high voltage wire frame inside the calorimeter. It can be attached

and adjusted while the calorimeter is in operation.

The gas igniter for both the horizontal and vertical sample holders uses a stainless steel

tube with holes in the end to generate an igniter flame. The pilot flame for the horizontal

sample holder may be positioned above or alongside the sample simply by bending the tubing

slightly. -The igniter flame for the vertical sample is placed in front of and below the sample

holder. In this position, either a small igniter flame or a sheet igniter flame may be used.

The sample igniter is supplied by way of a solenoid controlled gas valve. To install the gas

igniters for either the horizontal or vertical holder, the calorimeter is turned off and

allowed to cool. The back panel is removed by taking out fourteen 10-32 hex head screws and

lifting it off. This will give access to the fittings on the solenoid controlled gas line.

The appropriate igniter is connected to the gas line using the compression fittings supplied.

The back cover is replaced and the calorimeter started up.

It is now necessary to set the flux levels. With the calorimeter operating, the appropriate sample holder is inserted into the calorimeter so that the flux meter is facing the

radiant panels. Note that when using the vertical sample holder, only those radiant panels

facing the sample will be used. The other half of the radiant panels will be turned off.

Adjust the gate valves 7 and 8, or valve 8 only for vertical samples, to obtain the desired

flux. An hour warm-up is required to assure that a steady state has been reached.

The substitution burner is set to about 1.9 L/s (4 SCFM) on natural gas, as read on the mass flow meter*. This will yield near maximum turn down measuring capacity without seriously

affecting the elevator operating transient. Settings of below 1.9 L/s (4 SCFM) or above

2.1 L/s (4.5 SCFM) tend to give an excessively slow recovery time when the elevator is

operated. Some samples may cause the substitution burner to shut down completely; hence, peak

heat release rate from a sample will not be ascertained. If this occurs, the sample size must

be reduced so that peak heat release will be within the range of response of the substitution

burner.

In setting the dilution air, it is desirable to control the dilution air going into the

calorimeter to provide a neutral pressure condition near the specimen height level in the

calorimeter. To accomplish this, adjust dilution air valve 35 until the manometer reading air

pressure in the calorimeter is about zero. Take note that closing valve 35 too far may cause

the pressure safety switch to trip out and shut down the calorimeter. If this occurs, open

valve 35 back up and restart the calorimeter. It Is advisable to strive for a neutral or balanced air pressure, as a strong positive pressure will cause much loss of heated air when

the elevator is operated. This heat loss will exaggerate the recovery time for the substitution burner. Likewise, an excessive negative pressure inside the calorimeter will draw in cold

air when the elevator is operated, also resulting in a worsening of the recovery time for the

substitution burner.

Once the dilution air has been set, it may be necessary to reset the substitution burner

gas flow rate back to 1.9 L/s (4 CFM). With the dilution air, substitution burner, and flux

set, the calibration procedure should be carried out before testing any samples. Once this

calibration procedure is completed, the operation of the calorimeter in testing a sample

* This adjustment is made by setting an appropriate value for the stack thermocouple grid

temperature, typically about 220°C.

11
involves simply inserting, the sample in the appropriate sample holaer, operating, the elevator

to bring, the sample inside the calorimeter, ana operating, the switch "Ignition specimen pilot"

if a spark igniter is to be used. With the gas flame igniter, the "Ignition specimen pilot"

switch need not be operated as the flame size has been set ana is left burning all the time.

Once the test is completed, remove the old sample and replace with a new sample and proceed as above.

5.4 Calibration Proceaure

Certain elements of the calorimeter should be checked before each day's run. These items

include the mass flow meters, strip chart recorder, flow to calibration burner, substitution

burner turn down, and the weigh cell. All calibration tests should be performed after the

calorimeter has had a warm-up period of at least one hour.

Calibrate the mass flow meters first. To do this, proceed as follows:

1. Turn mass flow meters OFF; set the mechanical zero on the meter face.

Needle should reaa exactly zero with the unit off. If not, adjust the

mechanical zero with a small screwdriver.

2. Turn the mass flow meter ON, with calorimeter at operating temperature;

proceed to aajust the meter.

3. Adjust zero flow readings.

(a) Shut off gas valves 14 and 20 completely, stopping flow to meter

sensors.

(b) Set function switch to clean and hold for 5 seconds.

(c) Set function switch to CALIBRATE and the three-position toggle switch

to BAL; the needle should read exactly "0" on the top scale. If not,

adjust the BAL screwdriver potentiometer until the reading is zero.

(d) Set the three-position toggle switch to its downward position FS. The

meter should read full-scale within +_1.2 cm (+ 1/2 in) Adjust the FS

screwdriver potentiometer until the reading is full-scale.

(e) Return the three-position toggle switch to its center position, ZERO.

The meter should read zero within 1.6 min (1/16 in). Adjust the ZERO

screwdriver potentiometer until the reading is zero.

(f) Reopen valves 14 and 20 and let the substitution burner equilibrate.

This completes the electronic calibration of the mass flow meters. The mass flow meters

must also be calibrated against the variable area flow meter. This test Insures that the mass

flow meters have not lost their calibration. It also assures that the composition of the

natural gas being supplied to the calorimeter has not changed. To perform this cross check

test, turn substitution burner control to MANUAL, open valves 25, 51, 54, and 21; close valves

20, 22, and 53. The gas is now set to flow through the variable area flow meter and the

sensing unit, numbers 16 and 24 of the mass flow meters. Make certain that the calibration

12
burner Is properly positioned Inside the calorimeter. Open modulating solenoid valve 15 and

set control valve voltage knob to approximately "12 o'clock". Open gas cock number 14 and

ignite the gas flowing to the calibration burner. Both mass flow meters should read 0.5 L/s

(1.0 SCFM). If not, adjust the control valve voltage knob until both meters read exactly

0.5 L/s (1.0 SCFM). Check the variable area flow meter; it should read 0.36 L/s (46 SCFH). If

variable area flow meter reads +_1.0 L/min (+.2 SCFH) different from 0.36 L/s (46 SCFH), recalibrate the mass flow meters. If variable area flow meter reads +_ 1.0 L/mln (+_ 2 SCFH) of

0.36 L/s (46 SCFH) (but not exactly), record this difference, as it will be used as a calibration correction. With this completed, reset all appropriate valves to their normal operating

position. This completes meter calibration. Just before running any series of heat release

experiments, it is necessary to make one final calibration. With all the above meter checks

completed and the calorimeter operating, place the calibration burner into the calorimeter,

open valves 20, 21, and 25, and adjust the natural gas flow on the variable area flow meter to

0.36 L/s (46 SCFH) using valve 54. Ignite the gas and note the response the substitution

burner gives on the strip chart. From this calibration, all subsequent heat release calculations can be made.

The strip chart recorder must be calibrated, as the output from this recorder will be used

to set other parameters. First, set the zero set point for all the pens. With all pens

operating and the chart running, turn all six attenuator knobs to off (short). All the pens

will give a straight line trace at some point on the chart. These pens may be moved to any

convenient point on the chart by use of the zero adjuster knobs. With the zero set point

established start turning the attenuator on; first pen numbers 1 and 2, the substitution

burner, and substitution burner with signal averager to the 10-volt mark (full-scale). These

pens should be in the left quarter of the chart when the substitution burner is consuming

approximately 2.0 L/s (4.0 CFM) of natural gas. These pens should move toward the right side

of the chart as the substitution burner gas flow is reduced. A quick check on this is to

simply switch the power toggle switch to the substitution burner controller off and determine

if the pens stay within the chart boundaries.

The flux pen (number 3) is turned from zero (short) to 10 millivolts (full-scale). This

pen moves from left to right as flux increases. For every 1 millivolt Increase in output, the

p actual flux increases approximately 12.5 kW/rn . To check the actual flux, insert the appropriate sample holder (horizontal or vertical) and flux gage and read the output in millivolts

from the zero (short) point. Multiply the millivolt output by 1.26, the constant for the flux

gages; this will yield the actual flux falling on the flux meter. To increase or decrease

flux, use valves 7 and b.

The optical density smoke meter (pen 4) is turned from the zero (short) set point to the

5-volt full-scale position. This pen moves from left to right and, for every volt increase in

output, the observation is Increased 10-fold. There is no calibration check for the optical

density output.

The combustion meter (pen 5) is turned from the zero (short) set point to the 1-volt fullscale position; the pen will move off the zero point and establish a new equilibrium point.

This pens moves from left to right. To calibrate the combustion meter, insert the calibration

burner into the calorimeter, and open the solenoid gas valve to the calibration burner by

turning the switch "Calibration Burner" to ON. Set the variable area flow meter to 0.36 L/s

(46 SCFH). Do not ignite the gas. The pen will move to the right to about 0.65 volts. The

pen should register a 0.0712-volt change for every 5.0 L/mln (10-SCFM) change in the rotometer.

If this ratio changes, investigate the moisture trap and paper filter on the combustion meter

sampling line for possible obstruction.

13
The weigh cell (pen 6) Is turned from the zero (short) set position to the 1-volt level

full-scale for samples weighing up to 500 grams. Heavier samples may be weighed by turning the

demodulator range switch from zero to 100; at this setting, samples of 1000 grams may now be

used. The weigh cell Is calibrated by simply placing a known weight on the sample holder and

noting the response pen 6 yields. It Is often quite helpful to start by placing 50 grams on

the sample holder and working up to a total of 500 grams. The output of pen 6 should be In step fashion corresponding to the added weights applied. Prom this calibration, a gram/

division ratio may be developed.

6 . ILLUSTRATIVE DATA

The first test in the NBS II calorimeter was on a 75 x 30 x 13 mm (3 x 1 x 1/2 in) polystyrene specimen In the horizontal orientation using the Isothermal mode of measurement. A tracing of the original heat release rate and mass remaining curves are shown in figure 11.

Heat release rate measurements were made by Babrauskas [7] on black polymethylmethacryate

using the oxygen consumption technique. The samples were 100 x 100 x 13 mm (k x 4 x 1/2 In)

and were mounted horizontally. The mean values for six sets of measurements together with the

standard deviation Is plotted In figure 12. An extensive series of heat release rate tests were run on wood products by Chamberlain [8j. A tracing of an original data curve for a vertical specimen of ceiling tile, 300 x 300 x 13 mm (12 x 12 x 1/2 In), exposed at 5Q kW/m^ and

measured in the Isothermal mode Is seen in figure 13.

7 . PROGRAM

The new heat release rate calorimeter, MBS II, appears to be a good quality instrument

with broad potential for fire research.

The following research program is suggested for Its use:

a. measure for representative materials:

heat release rate mass loss rate vs. smoke

uncombusted fuel

specimen size

specimen orientation

air velocity

type of piloting

b. compare the heat release rate measured directly by oxygen consumption in the

MBS II;

c. compare the data obtained with NBS II with the data from NBS I, 0SU, and

instruments based on oxygen consumption;

d. recommend conditions of measurement for heat release rate on the basis of

the experience and understanding gained above;

e. publish heat release aata for an extended group of materials measured In the

recommended way (these data could constitute the beginning of a handbook of

data describing combustibility of materials ) ; and.

14
f. determine the effect of material composition (carbon, hydrogen, halogens,

oxygen) on heat release rate — compare the heat release rates of celluloslc

and synthetic polymers.

B. ACKNOWLEDGMENTS

The development of the new calorimeter was supported In large part by the Society of the

Plastics Industry who sponsored Dr. Tordella as a Research Associate at the Bureau from

February 1, 1976 through July 31, 1978.

Many people helped in this period, and special thanks are extended to them. A partial

list is W.J. Parker, supervisor; M.M. Brown and J.M. Loewe, secretaries; J.S. Steel, physicist;

W.H. Bailey, supervisor of Building 205; J.G. LaRock, designer draftsman; and H.E. Brown,

welding shop supervisor.

9 . REFERENCES

LI j Chamberlain, D.L., "Rate of Heat Release — Tool for the Evaluation of the Fire

Performance of Materials", presented at the Joint Meeting of the Central and Western

States Section of the Combustion Institute on Flammability and Burning Characteristics of

Materials and Fuels, San Antonio, Texas, April 1975.

L 2 j Tewarson, A., Tamanlni, F., "Research and Development for a Laboratory-Scale Flammability

Test Method for Cellular Plastics, Final Report FMRC Serial No. 22524, Grant No.

RP-75-1-33A, Factory Mutual Engineering, August 1976.

L 3 ] Smith, E.E., ASTM STP 502, American Society for Testing Materials, Philadelphia,

Pennsylvania (1972), pp. 119-134.

[4] Parker, W.J. and Long, M.E., ibid, pp. 135-151.

L5 j Hamilton, D.C. and Morgan, W.R., NACA Tech. Note 2836, 1952.

L 6 j Evans, D.D. and Breden, L.H., Fire Technology, Vol. 14, No. 2, pp. 85-96, May 1978.

L 7 II Babrauskas, V., "Performance of the OSU Rate of Heat Release Apparatus Using PMMA and

Gaseous Fuels", Fire Safety Journal, _5_, 9-20 (1983).

L8] Chamberlain, D.L., "Heat Release Rate Properties of Wood-Based Materials", NBSIR (to be

published)

.

15
Radiant

panels EEo

(0a

</>

k_

0)ctm. oo

CD <0 00 04 o

CO

Na o.a r«.a

VO o (0 (0

CM 00

Na

Na

Na

CO * o 0> (O

00a 00a

a

Na

04 in in o O 0) 00 00 00

C0o

CL 9CaM

k.ecoo

16

Figure

1.

View

Factors,

Vertical

Specimen
Radiant

panels

E

E.

o>

Ic

o

(0

a

c/>

k.c

k.

o

o

GO

CO

in

CM

CO

00 o 0) CD N 00 <0

in CO 00

00 00

CD CM

00 O) 00

N in o

00 O) 00 00 01

c

17

Figure

2.

View

Factors,

Horizontal

Specime
RESPONSE TIME

Figure 3. Response Time, NBS I Calorimeter
19
VENTURI

CAP

20

ALL

DIMENSIONS

IN

METERS

OSua OS j Ed o H X EdZ

Ed

M

•J OS CU o X _} < <

co

u

-J Ed < a u M M CO H z

OS U4

Ed> VH

Ed > 1<U a 00 <

Ed Ed

H

OS

O

M < h

Q Hf CO Ed OS O

OS OS Ed < 3 u o O

•J Ed c Q o

OS

M <H o 4 4J H CO 0 < M > O «

Ed

H

a 4 o

Id

cuM9

ao

EdQ

l-T

C/3 Z

Ed

osw os z w

OS

H

X Ed « XM Z 03 o o M J H < < U

OSCQM

_)

<!

cj

22
RADIANT

PANELS

COOLING

TOWERS

SUBST.

CALIB.

SPECIMEN iiiiiiii

i~i I—

II—

II—

II—

II—I

BURNER

BURNER

PILOTS I

23

Figure
REGULATOR

AND

OILER

24

WATER

FLOW

SCHEMATIC
1 1" gas cock

2 1" motorized gas valve, Eclipse 304-MV-IS-3

3 1 1/2" pressure reducer, Eclipse RV-81

4 Orifice meter, Eclipse 1" pipe size

5 Zero reducer, Eclipse 306 ZG

6 Zero reducer, Eclipse 306 ZG

7 1" gas cock, Eclipse

8 1" gas cock. Eclipse

9 Variset mixer, Eclipse 646

10 Variset mixer, Eclipse 646

11 Manometer, Dwyer 422-5

12 Manometer, Dwyer 422-5

13 Solenoid valve

14 1/2" gas cock

15 Modulating solenoid valve. Brooks 948037 BMA

16 Datametrics mass flow meter 80 LM

17 Air heat burner. Eclipse 40 RAH

18 Solenoid valve

19 1/4" gas cock

20 1/2" gas cock

21 1/2" gas cock

22 1/2" gas cock

23 Variable area flow meter, Dwyer RM2-102-88V

24 Datametrics mass flow meter 800 LM

25 Solenoid valve

26 Calibration burner

27 1/2" gas cock

28 Solenoid valve

29 Air blower. Eclipse SM- 881 7 - 7- 1 / 2-E

30 Orifice meter, Eclipse 3" size

31 Low gas pressure switch. Eclipse C437-H

32 1 1/2" gate valve

33 1 1/2" gate valve

34 Orifice meter, Eclipse 6" pipe

35 Butterfly valve. Eclipse 24 BV

36 Orifice meter. Eclipse 3" size

37 Butterfly valve, Eclipse 112 BV

38 1" gate valve

39 Air gun valve

40 Air pressure regulator and oiler

41 Solenoid spool valve

42 Solenoid valve

43 1/4" needle valve

44 1/4" needle valve

45 Solenoid valve

46 1/2" ball valve

47 1/4" needle valve

48 1/4" needle valve

49 1/8" needle valve

50 3/8" ball valve

51 1/2" gas cock

52 1/2" gas cock

53 1/2" gas cock

54 1/2" gas cock

Figure 10. Legend for Figures 8 and 9

25
(s-jU/nw) 31VU 3SV333U 1V3H

(jUJ/mh) 3iVd 3SV313U 1V3H

26

Figure

11.

Heat

Release

Rate

and

Remaining

Mass

Curve

for

Polystyrene

at

50

kw/m^

Exposure
(s-jW/ma) 31VH 3SV313H 1V3H

(jUi/MH) 31VU 3SV313U 1V3H

Figure

12.

Heat

Release.

Rate

of

"Black

Polymethylmethacrylate
[s-ju/niai am asvaiaa ivaH

Ijui/mh) 3ivu asvaiaa ivaH

28

Figure

13.

Heat

Release

Rate

of

Wood

Fiber

Ceiling

Tile.

50

kw/m^

Exposure
Table 1. Specification for New NBS Heat Release Rate Calorimeter

1. SPECIMEN:

-external heat flux uniform over specimen surface to 10 percent

orientation and size

vertical -- 300 x 300 mm horizontal -- 150 x 300 mm view -- full, continuous

ignition pilots -- upper, lower, and curtain

2. CAPACITY:

flux 25 to 80 kW/m^

maximum heat release rate capability

500 to 1000 kW/m^ -- vertical

1000 to 2000 kW/m -- horizontal

3. PERFORMANCE:

warm-up — 2 hours

stability -- long term

convenient operation

easy specimen placement

flux meter built in

calibration burner built in

low maintenance

accuracy — + 10 percent

precision -- + 5 percent

2 sensitivity -- 5 kW/m

response speed — <5 sec to step change

all flows measurable

4. DATA:

(a) sample heat release and weight loss rates

(b) stack gas/smoke density and heat of combustion

5. RECORDING:

chart recorder and computer terminal

6. MECHANICALLY AND STRUCTURALLY SOUND; SAFE

29
Table 2. Engineering Drawing Schedule for Calorimeter*

Air Manifold (101087)

Air Tower (101067)

Air Transition (101093)

Baffle Support Bar (101046)

Base Cover (101077)

Bearing Carrier (101038)

Bearing Retainer (101037)

Burner Bracket (101049)

Calibration Burner (101073)

Curtain Pilot (101086)

Cylinder Top Br'k't (101050)

Detector Holder (101059)

Detent Block (101063)

Elevator Cable Bracket (101045)

Elevator Guide Plate (101065)

Elevator Lift Bar (101054)

Elevator Plate (101082)

Elevator Shroud (101066)

Fluxmeter Bracket (101044)

Frame (101092)

Gas/Air Manifold (101091)

Guide Rails (101083)

Heater Banks (101090)

Heat Chamber Frame (101068)

Holder Backing (101079)

Holder Slide (101080)

Horizontal Specimen Holder (101085)

Insert, Weigh Cell Insulator (101047)

Insulator, Weigh Cell (101048)

Large Side Panel (101071)

Laser Insulator (101057)

Laser Mount (101061)

Laser Plate (101060)

Latch Pin Holder (101062)

Lift Plate (101055)

Lower Cylinder Br'k't (101053)

Lower End Frame (101034)

Lower Slide Frame (101036)

Mixer Coupling (101042)

Pilot Bracket (101064)

Pipe Adapter (101056)

S.D. Mount Plate (101058)

Short End - Frame (101041)

Shroud Cover (101084)

Side Frame (101040)

Small Side Panel (101072)

Smoke Detector Box (101080)

Thermocouple Carrier (101074)

Mixer Coupling (101042)

Pilot Bracket (101064)

Pipe Adapter (101056)

S.D. Mount Plate (101058)

Short End - Frame (101084)

Side Frame (101040)

Small Side Panel (101072)

Smoke Detector Box (101081)

Thermocouple Carrier (101074)

Thermocouple Carrier Front (101076)

Thermocouple Chamber (101075)

Tie Block (101052)

Transition - Large Side (101069)

Transition - Short Side (101070)

Vertical Carrier Guide (101035)

Vertical Sample Frame, Water-Cooled (101088)

Weigh Cell Shroud (101089)

Weigh Cell Shroud Car (101078)

Weigh Cell Stand-Off (101051)

* Copies of the engineering drawings for the calorimeter may be obtained from

the Engineering Design Office of the National Bureau of Standards.

30
NBS-114A (REV. 2 -80 ) 3. Publication Date

June 1983

U.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 83-2708

2. Performing Organ. Report No.

4. TITLE AND SUBTITLE

Development of a Calorimeter for Simultaneously Measuring Heat Release and Mass

Loss Rates

5. AUTHOR(S)

John Tordella and William H. Twilley

6. PERFORMING ORGANIZATION (If joint or other than NBS. see instructions)

national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No.

8 . Type of Report & Period Covered

9.

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

10.

SUPPLEMENTARY NOTES

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

11.

ABSTRACT (A 200-word or less factual summary of most significant information. If document includes a significant

bi bliography or literature survey, mention it here)

A heat release rate calorimeter (designated as NBS II) was designed, built, and put

into operation. Specimens may be burned vertically or horizontally without the use

of ref lectors^to provide a uniform external radiant flux field. The flux range is

25 to 80 kW/m . Heat release rate, mass loss rate, smoke, and heat of combustion of

the unburned gaseous decomposition products are measured. The heat release rate

measurement involves the use of a substitution burner technique which provides fast

response. The ratio of the heat release to mass loss rates, the apparent heat of

combustion, is provided as a function of time. The calorimeter may also be operated

in other modes, e.g., stack temperature increase and oxygen depletion, to obtain the

heat release rate.

Representative data are reported £or wood and a number of synthetic polymers burned

horizontally at a flux of 50 kW/m . These specimens generate considerable heat and

a significant amount of uncombusted fuel.

A program involving thorough characterization of the instrument, obtaining reference

heat release data for numerous materials, and conducting research in heat release

rate and other flammability characteristics is recommended.

12.

KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolons)

calorimeter; fire test; heat of combustion; heat release rate; mass loss rate.

13.

AVAILABILITY

[_Xj Unlimited

| | For Official Distribution. Do Not Release to NTIS

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

20402.

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

14. NO. OF

PRINTED PAGES

34

15. Price

$8.50

USCOMM-DC 6043-P80

i1