N I STIR 89-3908

INTERLABORATORY COMPARISON

OF TWO TYPES OF LINE-SOURCE

THERMAL-CONDUCTIVITY

APPARATUS MEASURING FIVE

INSULATING MATERIALS

Jerome G. Hust

David R. Smith

National Institute of Standards and Technology

(formerly National Bureau of Standards)

U.S. Department of Commerce

Boulder, Colorado 80303-3328

January 1989

NISTIR 89-3908

INTERLABORATORY COMPARISON

OF TWO TYPES OF LINE-SOURCE

TH ERMAL-CON DUCTIVITY

APPARATUS MEASURING FIVE

INSULATING MATERIALS

Jerome G. Hust

David R. Smith

Chemical Engineering Science Division

Center for Chemical Engineering

National Engineering Laboratory

National Institute of Standards and Technology

Boulder, Colorado 80303-3328

January 1989

Sponsored, in part, by

U.S. Department of Energy

Oak Ridge National Laboratory

Oak Ridge, Tennessee 37830

U.S. DEPARTMENT OF COMMERCE, C. William Verity, Secretary

Ernest Ambler, Acting Under Secretary for Technology

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, Raymond G. Kammer, Acting Director

CONTENTS

Page

LIST OF TABLES iv

LIST OF FIGURES v

ABSTRACT 1

1. Introduction 2

2 . Scope 2

3. Experimental Data 3

4. Data Analysis 3

5. Summary and Conclusions 4

6. References 4
LIST OF TABLES Page

Table 1. Dimensions and Densities of Specimens Used in the

Interlaboratory Comparison 5

Table 2. Laboratory Codes and Features of Apparatus 5

Table 3. Thermal Conductivity of the Fibrous Glass Specimens.. 6

Table 4. Thermal Conductivity of the Expanded Polystyrene

Specimens 7

Table 5. Thermal Conductivity of the Extruded Polystyrene

Specimens 8

Table 6. Thermal Conductivity of the Ottawa Silica Sand

Specimens 9

Table 7. Thermal Conductivity for the Paraffin Wax Specimens.. 10

Table 8. Mean Thermal Conductivity and Percent Standard

Deviation from the Mean for Each Type of Apparatus

and Each Material 11

IV
Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6.

Figure 7

LIST OF FIGURES

Interlaboratory comparison of thermal conductivity

of fibrous glass insulation with a density of 45

kg/m3 . The solid line indicates the trend of

data from the literature on similar material....

Interlaboratory comparison of thermal conductivity

of expanded polystyrene insulation with a density of 21 kg/m3 . The solid line indicates the

trend of data from the literature on similar

material

Interlaboratory comparison of thermal conductivity

of extruded polystyrene insulation with a density of 32 kg/m3 . The solid line indicates the

trend of data from the literature on similar

material

Interlaboratory comparison of thermal conductivity

of paraffin wax with a density of 850 kg/m3 . The

solid line indicates the trend of data from the

literature on similar material

Interlaboratory comparison of thermal conductivity

of Ottawa silica sand with a density of 1640

kg/m3 . Downward-pointing triangles represent

data for sand containing 3.5 percent by weight

of moisture; all other symbols are for dry

sand

Interlaboratory comparison of thermal conductivity

of dry Ottawa silica sand with a density of

1640 kg/m3 . The solid line indicates the trend

of data from the literature on similar

material

Interlaboratory comparison of thermal conductivity

of Ottawa silica sand with a density of 1640

kg/m3 and containing 3.5 percent by weight of

moisture

Page

12

13

14

15

16

17

18

v

Interlaboratory Comparison of Two Types of Line-Source ThermalConductivity Apparatus Measuring Five Insulating Materials

Jerome G. Hust

David R. Smith

Center for Chemical Engineering

National Engineering Laboratory

National Institute of Standards and Technology

Boulder, CO 80303-3328

We compare measurements of apparent thermal conductivity performed

by five different laboratories. Subcommittee C-16.30 (Thermal

Measurements) of the American Society for Testing and Materials

(ASTM) sponsored this interlaboratory comparison. Two different

types of line-source apparatus were used: the needle and the hot

wire. The five laboratories measured thermal conductivity of

Ottawa silica sand, paraffin wax, and three insulating materials

(fibrous glass, expanded polystyrene, and extruded polystyrene )

.

Comparison of the test results illustrates the interlaboratory

reproducibility. The standard deviation of the thermal conductivity results for the needle apparatus is 26 percent, whereas the

standard deviation of the results for the hot-wire apparatus is 17

percent. For the insulating materials the mean values of the test

results from the needle apparatus lie about 35 percent below those

for the hot-wire apparatus. For the more dense materials, Ottawa

sand and paraffin wax, the difference is about 15 percent. We do

not at present know which apparatus is the more accurate. Further

work needs to be done to establish and/or improve the reliability

of each of these methods for use in a laboratory environment such

as for quality control or research.

Key words: ambient temperature; apparent thermal conductivity;

expanded polystyrene; extruded polystyrene; fibrous glass; hot

wire; interlaboratory comparison; line-source apparatus; needle

probe; Ottawa silica sand; paraffin wax; thermal insulation.

This work was funded, in part, by DOE/ORNL under contract ORNL/IA21428.

1
1 . Introduction

During the last two decades equipment and techniques for measuring

thermal resistance of thermal insulations have been appreciably

improved, particularly for measurements at ambient temperature.

There is considerable interest in using apparatus that measure

thermal conductivity more rapidly than can steady-state apparatus

such as the guarded hot plate and heat flow meter. Rapid measurements are especially important for production-line analysis.

Transient measurement techniques, such as the needle probe and the

hot wire, are attractive from the standpoint of speed.

However, little is known about the precision and bias of these

transient methods. As a consequence, a committee was formed under

the auspices of Subcommittee C-16.30 of the American Society of

Testing and Materials to perform an interlaboratory comparison

(ILC) using line-source apparatus at ambient temperatures. The

ILC was initiated in 1985 under the direction of Mark Bomberg of

the National Research Council (NRC) of Canada. He prepared most

of the specimens for distribution to the participants. However,

due to a change in his duties, the direction of the task was

transferred to the first author, at the Boulder, Colorado Laboratory of the National Institute of Standards and Technology (NIST),

formerly the National Bureau of Standards (NBS). The available

specimens were transferred from NRC to NIST-Boulder , which

characterized and distributed them to the participants.

2 . Scope

This report presents and analyzes thermal conductivity data obtained in the ILC for five different materials. Prior to shipping

the specimens to the participants, the densities were measured at

NIST-B. The specimens are characterised in table 1. The densities of the specimens of paraffin wax and Ottawa silica sand could

not be determined at NIST because these specimens were prepared in

place by the participants. In addition, only two specimens of

sand, and four of paraffin wax, were distributed. These specimens

were sent from one participant to another for testing.

The names of the six testing laboratories participating in the ILC

are given here to identify the sources of the data presented.

Listing the names of the five commercial firms does not in any way

imply endorsement of the companies or of their products by the

National Institute of Standards and Technology or by the U.S.

government. The participants were:

Dynatech R/D Company (now Holometrix, Inc.), Cambridge, Mass.

Geotherm Inc. , Newmarket, Ontario, CANADA

Manville Corporation, Denver, Colo.

National Refractories and Minerals, Pleasanton, Cal.

2
Ontario Hydro, Toronto, Ontario, CANADA

U.S. National Institute of Standards and Technology (NIST),

(formerly National Bureau of Standards), Boulder, Colo.

Random numbers and symbols were assigned to the data sets from

these laboratories for use throughout this report. These laboratory codes are given in table 2. Also given in table 2 are some

of the salient features, where known, of the apparatus used by

each participant. Some laboratories did not report the lengths or

diameters of their hot wires or needle probes.

3 . Experimental Data

We compiled the experimental data for thermal conductivity of the

different materials into tabular files for analysis by computer.

Tables 3 through 7 contain the raw data as supplied by the five

participants in the ILC and converted by the authors to SI units.

4. Data Analysis

Thermal conductivity test results for each of the five materials

are shown in figures 1 through 7. Due to the large scatter in the

data, no functional dependence of thermal conductivity on temperature is deducible. Table 8 lists the mean value of thermal conductivity and the standard deviation from the mean, for each

material and for both types of apparatus.

Thermal conductivity test results on the insulating materials

(fibrous glass; expanded and extruded polystyrene) all exhibit the

same trend (figs. 1-3). For these materials the mean values from

the needle apparatus all lie about 35% below those of the hot-wire

apparatus. For the paraffin wax and Ottawa sand the results for

the needle device are also appreciably different from those of the

hot-wire apparatus (figs. 4-6).

Each solid line in figures 1-4 and figure 6 is an estimate of the

thermal conductivity of the corresponding material, obtained from

a limited examination of literature data for similar materials.

Uncertainties in moisture content and density for the literature

material, and for each material as measured by the participants,

preclude matching literature data exactly with the data for the

particular specimens used here. However, the slopes of the solid

lines suggest trends of thermal conductivity with temperature that

are helpful in comparing the results. Different mean values of

conductivity for each laboratory may be due to uncorrected biases,

but if the biases are insensitive to temperature over the range

studied, correct slopes might still be obtained. Even these

slopes cannot be deduced here due to the scatter in the data

collection taken as a whole. The slope of conductivity with temperature for some individual laboratories is consistent with that

suggested by the solid line.

3
Figure 4 shows the results for paraffin wax. Again there is a

clear difference between the results from the needle probe and

those from the hot-wire apparatus, with data from the needle probe

generally lying 7 percent higher than those from the hot wire

(Table 8) . Figure 5 shows the results for Ottawa silica sand. This composite

plot contains data for both dry sand and sand containing 3.5 percent by weight of moisture (downward-pointing triangles). Figures

6 and 7 show these data separately. The moist sand shows a significantly greater apparent thermal conductivity. This is not

surprising, for moisture, as a condensed phase, would be expected

to contribute its thermal conductivity to that of the sand grains.

Moisture would bridge across between sharp points and edges of

adjoining grains, greatly reducing the inter-grain contact resistance. For a transient measurement method, represented here by

both the needle and the hot wire, moisture migration would

contribute heat transfer along with the mass transfer. The mean

values of the test results from the needle apparatus are 14

percent lower than values obtained with the hot-wire apparatus.

5. Summary and Conclusions

With the exception of the results for paraffin wax, thermal

conductivity test results measured in this ILC with the needle

probe lie 14 to 35 percent lower than the results with the hot

wire. This large difference in results from the two apparatus

casts doubt on the accuracy ol measurements performed on either

apparatus. At present there are no measurements that would permit

the establishment of the accuracy of either apparatus by direct

comparison with results from guarded hot plates or from heat-flow

meters. Furthermore, these results are considerably more scattered than those obtained from steady-state methods as recently

reported [1]. Thus it is debatable whether either apparatus is

suitable even for use in comparative measurements, such as might

be used in quality control. It is not now clear what the principal source of the scatter is. Further work needs to be done to

establish and/or improve the reliability of each of these methods

for use in a laboratory environment such as quality control or

research

.

6. References

1. Hust, J.G. and Pelanne, C.M., "Round robins on the apparent

thermal conductivity of low-density glass fiber insulations using

guarded hot plate and heat flow meter apparatus", NBSIR 85-3026,

U.S. National Institute of Standards and Technology, 1985.

4
Table 1. Dimensions and Densities of Specimens Used in the Interlaboratory Comparison.

Mat * 1 Specimen Length Thickness Width Mass Density

(cm) (cm) (cm) (g) ( kg/m3

) Fibrous Fib ( 1

)

61.00 12.70 11.73 402.90 44.34

glass

Fib ( 4

)

61.00 12.67 11.81 424.00 46.45

Fib( 5

)

60.90 12.67 11.76 425.40 46.88

Fib ( 6

)

60.70 12.50 11.66 405. 10 45.79

Fib( 7

)

60.70 12.45 11.68 422.90 47.91

Expanded Exp( 1

)

59.90 9.47 17.68 216. 10 21 . 55

Poly- Exp( 4

)

59.60 9.40 17.73 200.30 20.16

styrene

Exp( 5

)

59.80 9.40 17.73 206.00 20.67

Exp( 6

)

59.80 9.40 17.70 209.60 21.07

Exp( 7

)

59.70 9.37 17.73 208.30 21.00

Extruded Ext ( 1

)

60.90 10.11 17.75 346.70 31.72

Poly- Ext ( 4

)

61.00 9.98 17.70 360. 70 33.47

styrene: Ext ( 5

)

60.90 10.01 17.78 361.30 33.33

Ext (6) 61.20 10.03 17.68 360.50 33.22

Ext ( 7

)

60.90 10.11 17.75 360.50 32.99

ParaffinPWX(l) 830, 890

PWX ( 3

)

900.

PWX ( 4

)

Ottawa OSS ( 1

)

1640.

silica OSS ( 2

)

1640.

sand

Table 2. Laboratory Codes and Features of Apparatus.

Lab

.

No.

Apparatus

Type

Active

Length

(cm)

Diameter

(mm

)

Symbols used

in Figures

1 Needle 10 3.2 O

2 Wire 15 0.37 A

3 Wire 20 NR* O

4 Needle 15 3 V

5 Wire NR NR o

*NR = Not Reported

5
Table 3. Thermal Conductivity of the Fibrous Glass Specimens

Lab

Code

Specimen

Ident i f i er Test

Durat i on

(»)

Temp.

Ri se

(K)

Mean

Temp.

(K)

Thermo 1 Conduct ivi ty

mW/(m.K)

1 FIB(5) 600 6.00 295.00 24.00

1 FIB(5) 600 3.00 295.00 24.00

1 FIB(5) 600 2.2© 296.50 22.00

1 FIB(5) 600 i. 50 295.00 22.00

2 FIB(1) 564 1.55 298.06 36.40

2 FIB(1) 564 4.66 301.12 37.00

2 F1B(1) 564 10.16 306 . 45 37.40

3 FIB(7) NR 20.00 305.15 33.80

3 FIB(7) NR 20.00 307.15 35.00

3 FIB(7) NR 20.00 307.15 34.30

3 FIB(7) NR 20.00 308.15 34.80

3 F I B ( 7) NR 20.00 307.15 34.70

3 FIB(7) NR 20.00 308.15 35.50

3 FIB(7) NR 20.00 308.15 34.30

3 F1B(7) NR 20.00 308.15 33.30

3 FIB(7) NR 20.00 308.15 34.00

3 FIB(7) NR 20.00 308.15 34.90

3 F 1 B( 7

)

NR 39.00 317.15 37.00

3 F1B(7) NR 39.00 317.15 36.80

4 FIB(6) 600 2.27 300 . 54 23.00

4 FIB(6) 600 2.37 300 . 20 21 .00

4 FIB(6) 600 4.89 301.58 18.00

4 FIB(6) 1200 -3.34 300.01 21 .00

4 FIB(6) 1200 -3.42 299.67 21 .00

4 FIB(6) 1200 6.22 300.91 28.00

5 FIB(4) NR NR 295.95 35.00

5 FIB(4) NR NR 295.95 36.20

5 F1B(4) NR NR 297.35 37.00

NR « Not Reported

6
Table 4. Thermal Conductivity of the Expanded Polystyrene Specimens.

Lab

Code

Specimen

Ident i f ier

Test

Durat i on

(8)

Temp.

Rise

(K)

Mean

Temp.

(K)

Thermo 1 Conduct ivi ty

mW/(m.K)

1 EXP (5) 600 7.00 295.00 21 .00

1 EXP(5) 600 3.00 295.00 20.00

1 EXP(5) 600 2.30 296.50 22.00

1 EXP(5) 600 8.70 295.00 22.00

2 EXP ( 1

)

564 1 .48 296.93 32.40

2 EXP ( 1

)

564 5.02 299.86 33.00

2 EXP(1) 564 10.82 305.17 33.40

3 EXP(7) NR 20.00 307.15 31 .00

3 EXP(7) NR 20.00 307.15 29.70

3 EXP(7) NR 20.00 308.15 30.50

3 EXP (7) NR 20.00 309.15 30.90

3 EXP(7) NR 20.00 308.15 30.80

3 EXP(7) NR 20.00 306.15 29.70

3 EXP(7) NR 20.00 308.15 30.10

3 EXP(7) NR 20.00 308.15 29.30

3 EXP(7) NR 20.00 308.15 29.10

3 EXP ( 7

)

NR 20.00 308.15 29.10

3 EXP(7) NR 20.00 308.15 29.40

3 EXP (7) NR 20.00 309.15 29.50

3 EXP (7) NR 20.00 308.15 29.70

3 EXP(7) NR 38.00 317.15 31.10

3 EXP(7) NR 38.00 319.15 31 .50

4 EXP(6) 600 5.91 301 .45 15.00

4 EXP(6) 600 2.46 300 . 67 21 .00

4 EXP(6) 1200 -6.66 301.07 17.00

4 EXP(6) 1200 -3.77 300 . 02 28.75

5 EXP(4) NR NR 296.05 33.58

5 EXP (4) NR NR 295.85 31 .56

5 EXP(4) NR NR 295.75 32.42

NR « Not Reported

7
Table 5. Thermal Conductivity of the Extruded Polystyrene Specimens.

Lab

Code

Specimen

Ident i f ier

Test

Durat i on

<•>

Temp.

R i se

(K)

Mean

Temp.

(K)

Therma

1

Conduct i v i ty

mW/(m.K)

1 EXT(5) 6®0 7.00 295.00 19.00

1 EXT(5) 600 4.00 295.00 18.00

1 EXT (5) 600 2.30 296.50 20.00

1 EXT(5) 600 8.90 295.00 21 .00

2 EXT ( 1

)

564 1 .58 297 5© 29.7®

2 EXT(1) 564 5.43 300 . 82 28.60

2 EXT(1) 564 11.41 306 . 07 29.0®

3 EXT(7) NR 20.00 306.15 28.40

3 EXT (7) NR 20.00 307.15 29.2®

3 EXT (7) NR 20.00 308.15 29.50

3 EXT(7) NR 20.00 308.15 28.1©

3 EXT (7) NR 20.00 306.15 28.00

3 EXT(7) NR 20.00 308.15 29.70

3 EXT (7) NR 20.00 308.15 28.6©

3 EXT(7) NR 20.00 308.15 27.5®

3 EXT(7) NR 20.00 308.15 30.10

3 EXT (7) NR 20.00 308.15 29.30

3 EXT (7) NR 20.00 308.15 28.00

3 EXT(7) NR 37.50 317.15 29.90

3 EXT(7) NR 37.50 318.15 29.90

A EXT(6) 600 5.64 303.26 17.00

A EXT (6) 600 2.70 300 . 72 19.00

4 EXT (6) 1200 -7.34 302.41 16.00

4 EXT (6) 1200 -3.74 300 . 20 18.00

5 EXT(4) NR NR 295.75 26.08

5 EXT (4) NR NR 295.65 27.38

5 EXT(4) NR NR 296.25 26.80

NR * Not Reported

8
Table 6. Thermal Conductivity of the Ottawa Silica Sand Specimens.

Lab

Code

Specimen

Ident i f ier

Test

Durat i on

(8)

Temp.

Rise

(K)

Mean

Temp.

(K)

Thermo 1 Conduct i vi ty

mW/(m.K)

1 0SS(1) 600 7.00 295.00 287.00

1 OSS(1) 600 4.00 295.00 288.00

1 OSS(1) 600 2.50 295.00 266.00

1 0SS(1) 600 7.30 295.00 289.00

2 0SS(2) 564 0.61 300.14 365.80

2 0SS(2) 564 5.91 305 . 62 371 .00

2 OSS (2) 564 16.84 316.15 349.40

3 0SS(2) NR 20.00 309.15 269.00

3 OSS(2) NR 20.00 308.15 288.00

3 OSS (2) NR 20.00 308.15 293.00

3 OSS(2) NR 20.00 309.15 300 . 00

3 OSS (2) NR 20.00 310.15 288.00

3 OSS (2) NR 20.00 312.15 291 .00

3 0SS(2) NR 20.00 310.15 278 . 00

4 oss(i-e) 600 0.40 298.22 291 .00

4 OSS (1-0) 600 6.51 314.23 294.00

4 oss(i-e) 600 4.09 308 . 04 287.00

4 OSS(1-0) 1200 -1 .08 297.88 232.00

4 oss(i-e) 1200 -18.20 308 . 38 216.00

4 oss(i-e) 1200 -11.46 304.35 216.00

4 OSS (1-3. 5) 600 0.08 298.08 1194.00

4 OSS(1-3.5) 600 0.44 299.40 1819.00

4 OSS(1-3.5) 600 2.30 31 1.54 848 . 00

4 OSS(1-3.5) 1200 -0.42 297.91 1084.00

4 OSS (1-3. 5) 1200 -2.42 298.41 1299.00

4 OSS(1-3.5) 1200 -15.43 304.97 1220.00

NR * Not Reported

9
Toble 7. Thermal Conduct iv i-ty for the Parof f i

n

Wax Specimens

Lob Specimen Test Temp. Mean Thermal

Code Ident I f ier Durat i on Rise Temp. Conduct ivi ty

(») (K) (K) mW/(m.K)

1 PWX(1) 600 7.50 295.00 245.00

1 PWX(1) 600 4.50 295.00 242.00

1 PWX(1) 600 2.70 295.00 239 . 00

1 PWX(1) 600 7.80 295.00 251 .00

2 PWX(3) 564 1 .00 298.39 201 .00

2 PWX(3) 564 3.43 299.94 194.00

2 PWX(3) 564 6.69 302.77 190.00

3 PWX(4) NR 15.00 305.15 276.00

3 PWX(4) NR 15.00 306.15 291 .00

3 PWX(4) NR 15.00 305.15 300.00

3 PWX(4) NR 15.00 305.15 281 .00

3 PWX(4) NR 15.00 306.15 280 . 00

3 PWX(4) NR 15.00 307.15 292.00

3 PWX(4) NR 15.00 307.15 255.00

3 PWX(4) NR 15.00 307.15 264.00

4 PWX(1) 600 4.56 310.14 296.00

4 PWX(1) 600 4.56 309.80 292.00

4 PWX(1) 600 0.60 299.35 242.00

4 PWX(1) 600 4.90 310.50 261 .00

4 PWX(l) 600 0.50 300.20 214.00

4 PWX(l) 600 0.40 299.75 336.00

4 PWX(1) 600 3.90 309.40 373.00

4 PWX(1) 600 6.40 313.65 300 . 00

4 PWX( 1) 1200 -8.80 305 . 65 324.00

4 PWX(1) 1200 -8.40 305.55 335.00

4 PWX(1) 1200 -1 .00 298.95 223.00

4 PWX(l) 1200 -9.90 305 . 50 263.00

4 PWX(1) 1200 -1 .30 299 . 60 152.00

4 PWX(1) 1200 -0.91 299.30 239 . 00

4 PWX(1) 1200 -8.00 304.85 340.00

4 PWX(1

)

1200 -14.00 309 . 85 286 . 00

5 PWX(3) NR NR 296.05 244.25

5 PWX(3) NR NR 295.25 247.71

5 PWX(3) NR NR 294.95 242 . 23

NR « Not Reported

10
Table 8. Mean Thermal Conductivity k and Percent Standard Deviation from the Mean for £ach Type of Apparatus and Each

Material

.

Needle

Apparatus

Hot Wire

Apparatus

Material Mean k

mW/(m. K)

Percent

Std . Dev.

Mean k

mW/(m.K)

Percent

Std . Dev.

Fibrous glass 22.4 11.7 35.4 3.6

Polystyrene: extruded 18.5 8.9 28.6 4. 1

Polystyrene: expanded 20.8 20.2 30.8 4.6

Paraffin wax 273. 23.8 254. 16.8

Ottawa silica sand: dry 267. 13.7 309. 11 . 5

Ottawa silica sand: moist

(3.5% moisture by weight)

1244. 26.0 — — —

11
Thermal

Conduct

l

vlty

,

mW/m.

Temperature, K

Figure 1. Interlaboratory comparison of thermal conductivity of

fibrous glass insulation with a density of 45 kg/m3

.

The solid line indicates the trend of data from the

literature on similar material.

12
Thermal

Conductivity,

mW/m.

290 295 300 305 310 315 320 325

Temperature, K

Figure 2. Interlaboratory comparison of thermal conductivity of

expanded polystyrene insulation with a density of

21 kg/m3 . The solid line indicates the trend of data

from the literature on similar material.

13
Thermal

Conductl

vli

y,

mN/m.

Temperature, K

Figure 3. Interlaboi^tory comparison of thermal conductivity of

extruded polystyrene insulation with a density of

32 kg/m3 . The solid line indicates the trend of data

from the literature on similar material.

14
Temperature, K

Figure 4. Interlaboratory comparison of thermal conductivity of

paraffin wax with a density of 850 kg/m3 . The solid

line indicates the trend of data from the literature

on similar material.

15
Temperature, K

Figure 5. Interlaboratory comparison of thermal conductivity of

Ottawa silica* s: nd with a density of 1640 kg/m3 . Downward-pointing triangles represent data for sand

containing 3.5 percent by weight of moisture; all

other symbols are for dry sand.

16
Temperature, K

Figure 6. Interlaboratory comparison of thermal conductivity of

dry Ottawa silica sand with a density of 1640 kg/m3 . The solid line indicates the trend of data from the

literature on similar material.

17
Thermal

Conductl

vl

ty

,

mW/m.

1900

1800

1700

1600

1500

1400 -

1300

3200

1100

1000

900

800 I .... I I .... I 1 a 1 292.5 295 297.5 300 302.5 305 307.5 310 312.5 315

Temperature, K

Figure 7. Interlaboratory comparison of thermal conductivity of

Ottawa silica sand with a density of 1640 kg/m3 and

containing 3.5 percent by weight of moisture.

18
U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication D ate BIBLIOGRAPHIC DATA

SHEET (See instructions)

REPORT NO.

NISTIR 89-3908 January 1989

4. TITLE AND SUBTITLE

Interlaboratory Comparison of Two Types of Line-Source Thermal-Conductivity

Apparatus Measuring Five Insulating Materials

5. AUTHOR(S)

Jerome G. Hust and David R. Smith

6. PERFORMING ORGANIZATION (If joint or other than N BS, see in struction s) 7. Contract/Grant No.

National Institute of Standards and Technology

DEPARTMENT OF COMMERCE 8. Type of Report & Period Covered

WASHINGTON, D.C. 20234

9.

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

II. S. Department of Energy

Oak Ridge National Laboratory

Oak Ridge, Tennessee 37830

10.

SUPPLEMENTARY NOTES

3 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

bl iography or literature survey, mention it here)

We compare measurements of apparent thermal conductivity performed

by five different laboratories. Subcommittee C-16.30 (Thermal

Measurements) of the American Society for Testing and Materials

(ASTM) sponsored this interlaboratory comparison. Two different

types of line-source apparatus were used: the needle and the hot

wire. The five laboratories measured thermal conductivity of

Ottawa silica sand, paraffin wax, and three insulating materials

(fibrous glass, expanded polystyrene, and extruded polystyrene )

.

Comparison of the test results illustrates the interlaboratory

reproducibility. The standard deviation of the thermal conductivity results for the needle apparatus is 26 percent, whereas the

standard deviation of the results for the hot-wire apparatus is 17

percent. For the insulating materials the mean values of the test

results from the needle apparatus lie about 35 percent below those

for the hot-wire apparatus. For the more dense materials, Ottawa

sand and paraffin wax, the difference is about 15 percent. We do

not at present know which apparatus is the more accurate. Further

work needs to be done to establish and/or improve the reliability

of each of these methods for use in a laboratory environment such

as for quality control or research.

12.

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

ambient temperature; apparent thermal conductivity; expanded polystyrene; extruded

polystyrene; fibrous glass; hot wire; interlaboratorv comparison: line-source

apparatus; needle probe; Ottawa silica sand: paraffin wax; thermal insulation

13.

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