NBS A111D2 flSM31b

PUBLICATIONS

NBSIR 88-3094

FIBROUS ALUMINA-SILICA

INSULATION BOARD

AS A CANDIDATE

STANDARD REFERENCE MATERIAL

OF THERMAL RESISTANCE

Jerome G. Must

David R. Smith

National Bureau of Standards

U.S. Department of Commerce

Boulder, Colorado 80303-3328

June 1988

100

.056

#88-3094

1988

C.2

Stimulating America's Progress

1913-1988

Jteeearcli Infonuatian GenteflP iNatioBal Bureau of Standards

Gaithersburg, Maryland 20899

NBSIR 88-3094 AJfeSC,

FIBROUS ALUMINA-SILICA

INSULATION BOARD

A^ A PANDIDATE

STANDARD REFERENCE MATERIAL

OF THERMAL RESISTANCE

Jerome G. Must

David R. Smith

Chemical Engineering Science Division

Center for Chemical Engineering

National Bureau of Standards

U.S. Department of Commerce

Boulder, Colorado 80303-3328

June 1988

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

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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CONTENTS

Page

List of Tables iv

List of Figures v

ABSTRACT 1

1. INTRODUCTION 2

2. MATERIAL CHARACTERIZATION 2

3. MEASUREMENTS 2

4. DATA ANALYSIS 3

A. Conductivity as a Function of Temperature 4

B. Conductivity as a Function of Density 5

C. Conductivity as a Function of Pressure 6

D. Conductivity as a Function of Environmental Gas 7

5. COMPARISONS 8

6. RECOMMENDATIONS 8

7. REFERENCES 9
LIST OF TABLES

Page

Table 1. Thermal conductivity of one pair of fibrous aluminasilica insulation board with a density of 259 kg/m3

at mean temperatures of 93 to 311 K. Measurements

were performed in dry nitrogen gas at a pressure of

83 kPa (623 Torr) using the NBS low-temperature

guarded hot plate 10

Table 2. Thermal conductivity of eight specimens of fibrous

alumina-silica insulation board with densities of

236 to 249 kg/m3 , at mean temperatures of 313 to

746 K. Measurements were performed in air at 83

kPa (623 Torr), using the NBS high-temperature

guarded hot plate 10

Table 3. Thermal conductivity of a selected pair of fibrous

alumina-silica insulation boards with densities of

236 to 249 kg/m^ , at mean temperatures of 313 and

693 K. Measurements were performed in air at pressures from 84 to 0.0047 kPa, using the NBS hightemperature guarded hot plate 12

Table 4. Thermal conductivity of the selected pair of fibrous

alumina-silica insulation board with a density of

247 kg/m^ , at mean temperatures of 313 to 692 K.

Measurements were performed in helium gas at pressures from 84 to 87 kPa (630 to 650 Torr), using the

NBS high-temperature guarded hot plate 13

Table 5a. Thermal conductivity of eight different specimens

of fibrous alumina-silica insulation board with

densities of 236 to 249 kg/m^ , at a mean temperature of 313 K. Measurements were performed in

air at 84 kPa using the NBS high-temperature

guarded hot plate 14

Table 5b. Thermal conductivity of fibrous alumina-silica

insulation board (round-robin material) with densities of 207 to 308 kg/m3 , at a mean temperature of

313 K. Measurements were performed in air at 84 kPa

using the NBS high-temperature guarded hot plate... 14
LIST OF FIGURES

Fi^re 1

Fi^re 2

Figure 3

Figure 4

Figure 5.

Figure 6

Figure 7

Figure 8

Page

Thermal conductivity of a pair of fibrous aluminasilica insulation boards as measured by NBS/B, at

mean temperatures of 93 to 311 K and at ambient

atmospheric pressure of 83 kPa . Boards have a density of 259 kg/m3 . The solid line was calculated from eq(l) 15

Deviations of the NBS low-temperature thermal conductivity data from eq(l) 16

Thermal conductivity of a pair of fibrous aluminasilica insulation boards as measured by NBS/B,

at mean temperatures of 313 to 746 K and at ambient

atmospheric pressure of 83 kPa . Boards have a density of 247 kg/m3 . The solid line was calculated

from eq ( 2 ) 17

Deviations of the NBS high-temperature thermal conductivity data from eq(2) 18

Thermal conductivity of fibrous alumina-silica

insulation boards as measured by NBS/B, at a mean

temperature of 333 K and at ambient atmospheric

pressure of 84 kPa . The solid line was calculated

from eq ( 3 ) 19

Deviations of the NBS thermal conductivity data

from eq ( 3 ) 20

Thermal conductivity of fibrous alumina-silica

insulation boards as measured by NBS/B, at a mean

temperature of 313 K. The boards have a density

of 247 kg/m3 . The solid line was calculated from

eq(4) with ko = 5.75, A = 778, Po 0.054 kPa

and n = 0.5 21

Deviations of the NBS thermal conductivity data

from eq ( 4 ) 22

V
Figure 9. Thermal conductivity of fibrous alumina-silica

insulation boards as measured by NBS/B, in an

environment of ure helium gas. The board density

is 247 kg/m3 . The solid line was calculated from

eq(5) 23

Figure 10. Round-robin measurements, by seven participating

labs including NBS/B, of thermal conductivity

of fibrous alumina-silica insulation boards, at

the local ambient atmospheric pressure of each

part icipating laboratory. The board density is

238 kg/m3 . The solid line is calculated from

eq ( 1 ) 24

Figure 11. Thermal conductivity of fibrous alumina-silica

insulation boards, as measured by the producer

(solid line) at a pressure of 84 kPa , for a board with a density of 244 kg/m3 . The solid

line is given by eq(6). Data points shown are

NBS data for a different specimen with a density

of 247 kg/m3 25

Figure 12. Deviations of the NBS/B thermal conductivity data

from the producer’s data, eq (6) 26

VI
Fibrous Alumina-Silica Insulation Board

as a Candidate Standard Reference Material

of Thermal Resistance

Jerome G. Hust

and

David R. Smith

Center for Chemical Engineering

National Engineering LaboratoryNational Bureau of Standards

Boulder, CO 80303-3328

Measurements of apparent thermal conductivity are reported in

order to provide the basis for certifying fibrous alumina-silica

insulation board as a Standard Reference Material (SRM) of thermal

resistance. These data encompass ranges of temperature from 93 to

746 K, densities from 207 to 308 kg/m^ , and fill-gas pressures

from roughing-pump vacuum to atmospheric pressure, in environments

of both air and helium. Detailed analyses and intercomparisons of

previously published data are given.

Key words: alumina-silica board; apparent thermal conductivity:

density: pressure; Standard Reference Material; temperature:

thermal insulation; thermal resistance.

This work was funded in part by DOE/ORNL under contract ORNL-iA

21428.

1
1. INTRODUCTION

The

National

Materials

physical

Office of Standard

Bureau of Standards

( SRMs ) needed to

properties. The

Center for Chemical Engineer!

about 25 years in the effort

over a broad range of conduct

of this work has been summari

Reference Materials ( OSRM ) of the U.S.

( NBS ) establishes Standard Reference

improve reliability in measurement of

Properties of Solids Group within the

ng (CCE) has actively participated for

to establish SRMs of thermal resistance

ivities and temperatures . The status

zed by Bust [ 1]

During the mid-1970’s, Committee C-16 of the American Society

for Testing and Materials recognized the great need for SRMs of

thermal insulation. As a consequence, a task-group was established

under the auspices of ASTM Subcommittee C16.30 on thermal measurements. Recommendations for establishing thermal insulation SRMs

were published in 1978 [2].

Clay-bonded fibrous alumina-silica insulation is being investigated for possible use as a high-temperature SRM of thermal resistance. We report measurements of the apparent thermal conductivity

of several specimens of this material using two different guardedhot-plate apparatus (GHP). The low-temperature GHP obtained data

over a range of mean specimen temperature from 93 to 311 K; the

high-temperature GHP covered the range of mean temperatures from 313

to 746 K. At the present time no SRM of thermal resistance for

temperatures above 330 K is available from OSRM, in spite of the

strong need for such SRMs.

2. MATERIAL CHARACTERIZATION

The material studied is produced as rigid boards from claybonded fibers of alumina-silica. The specimens obtained from the

producer are nominally 2.5 cm (1 in) thick and about 30 cm (If)

square. The alumina-silica fibers are oriented approximately parallel to the faces of the boards. The bulk densities of the specimens

ranged from 207 to 308 kg/m^

This material was investigated because of the recommendations

of the ASTM C16.30 task-group. The producer of this material had

decided to establish it as an in-house standard and to cooperate

with us by providing carefully selected specimens for determining

the suitability of the material as an SRM.

2
3. MEASUREMENTS

For brevity we shall use the term "thermal conductivity" to

denote "apparent thermal conductivity" in the following text. Analysis of our data in the following section suggests that radiative

and convective heat transfer in this fibrous alumina-silica board

contribute only a small amount in comparison to conductive heat

transfer. "Thermal conductivity" seems to be a valid descriptor of

the heat-transfer behavior of this material.

Thermal conductivity data reported here were obtained with the

high-temperature GHP, described by Hust, Filla, Hurley, and Smith

[3,4], and with the low-temperature GHP, described by Smith, Hust,

and Van Poolen [5]. The diameters of the circular stack and metered

main heater areas are respectively 20 and 10 cm for the low-temperature GHP, and are 25 and 12.5 cm for the high-temperature GHP.

Thermal conductivity at low temperatures was measured in dry

nitrogen gas at atmospheric pressure (83 kPa ; 623 Torr), for a single pair of specimens whose mean bulk density was 259 kg/m^ . Table

1 lists the thermal conductivity measurements on this pair under the

two-sided mode of operation of the low-temperature GHP, at mean

temperatures ranging from 93 to 311 K (-180 to +38°C).

Measurements of thermal conductivity at high temperatures were

performed initially on an additional set of eight carefully selected

specimens in an atmosphere of air at ambient pressure, 83 kPa . Each

specimen was individually measured in the single-sided mode of

operation of the high-temperature GHP to determine the variability

of thermal conductivity within the set. The first block of data in

table 2 lists thermal conductivity data for a mean temperature of

313 K. Because multiple measurements were made on some of the

specimens there are more than eight data points in this first block.

From the set of eight specimens we selected two, matched in

density; this matched pair was then measured in air at 83 kPa , at

mean temperatures ranging from 313 to 746 K (second block of table

2). In addition, the thermal conductivity of this pair was measured

at various air pressures from ambient to low vacuum. Table 3 gives

the data at mean temperatures of 313 and 693 K and for various

pressures ranging from 83.6 to 0.0047 kPa (0.035 Torr).

Thermal conductivity of this matched pair was also measured in

an environment of helium gas at 84 to 87 kPa at five different mean

temperatures from 313 to 692 K (table 4). The variation in pressure

was due to the rise in temperature of the sealed system.

Because the bulk densities of the group of eight specimens covered only a very small range (see table 5a), four additional specimens were obtained with appreciably different bulk densities. These

specimens were individually measured in the single-sided mode to

determine how the thermal conductivity depends on density. Finally,

measurements were included from a study of thirteen more specimens

3
which were used in a high-temperature interlaboratory comparison

[6]. The results of single-sided thermal conductivity measurements

on all the additional seventeen specimens, at mean temperatures of

333 K, are also presented here (table 5b) to aid in assessing

specimen variability and dependence on density. All these measurements were conducted in air at 84 kPa . Multiple measurements performed on some of the specimens are responsible for the presence of

more data points in tables 5a and 5b than the number of specimens.

4. DATA ANALYSIS

The data were analyzed to determine the dependence of thermal

conductivity on temperature, density, and environmental gas pressure

and species.

A. Conductivity as a Function of Temperature.

The first matched pair of specimens, measured in dry nitrogen

gas at 83 kPa (623 Torr) in the low-temperature apparatus, had a mean density of 259 kg/m3 . The temperature dependence of thermal

conductivity for temperatures from 93 to 311 K was represented by

k(T) = 6.932 + 0.1769-T - 0 . 3070x10- 6 . T3 , (1)

where k is in mW/(m- K) and T is in K. This correlation was obtained

using the thermal conductivity integral method [7] and a weighted

least-squares fit, as were all the correlations obtained in the

following analysis. The weighting gives approximately equal percentage deviations, to reflect the usual experimental practice of

holding the relative error of the measurements constant. The data

used to determine this correlation, along with values calculated

from it, are listed in table 1 and illusti-ated in figure 1.

Deviations of the data from eq(l) are shown in figure 2.

The dependence of thermal conductivity on temperature for a different matched pair of specimens, each having a density of about

247 kg/m3 , and measured in air at atmospheric pressure in the hightemperature apparatus, was represented by

k(T) = 15.12 + 0.09489-T + 2 . 888x10- 8 . T3 , (2)

where k is in mW/(m- K) and T is in K. This correlation is valid for

mean temperatures from 313 to 746 K and for specimens in air at 83

kPa. The data used to determine this relation are listed in table 2

and illustrated in figure 3. The deviations of the data from eq(2)

are illustrated in figure 4.

4
The very small positive value of the coefficient of the T3 term

in eq ( 2 ) correlates with the slight upward curvature evident in

figure 3. At T 310 K the term contributes 0.86 mW/(m- K) to the

total thermal conductivity value of 45.4 mW/(m-K), or only 2%. At

the upper temperature limit of this study, 750 K, the term

represents 12% of the total thermal conductivity. On theoretical

grounds the physical origin of this relatively small T3 term in the

k(T) function is probably radiative heat transfer. The material is

dense enough that convective heat transfer is negligible at room

temperature. Thus conductive heat transfer through the solid fibers

and through the environmental gas (air) between the fibers is the

major contributor to the total heat transfer.

At a typical temperature of 312 K, eq(l) yields a thermal conductivity of 52.8 mW/(m- K) for one pair, while eq(2) yields 45.6

mW/(m- K) for the other pair, a difference of 14%. The low-temperature and the high-temperature apparatus each have an estimated accuracy of 2% at 312 K, and the experimental repeatability for removal

and re-installation of specimens is about 0.5% for each apparatus.

The dependence of the thermal conductivity on density is not known

very precisely, as will be discussed in the next two paragraphs. It

is quite possible that differences in density between the two pairs

are responsible for the lack of agreement in the values of k at the

same temperature. The second pair was manufactured several years

after the first pair, and was measured 6 years later.

B. Conductivity as a Function of Density

The data used to determine the dependence of thermal conductivity on density are illustrated in figure 5 and listed in table 5b.

The dependence of thermal conductivity on density for specimens at a temperature of 333 K and in air at 83 kPa was represented by

k(D) = 42. + 0 . 033- D, (3)

where k(D) is in mW/(m- K) and D is in kg/m^ . This correlation is

valid for a range of densities from 207 to 308 kg/m^

The large scatter of data in this figure (.+ 8% at the low end

of the curve) shows that unknown factors are present. Some of these

specimens, used in the round-robin study, were not as carefully selected as the specimens selected as candidates for SRM certification

The imprecision caused by the measurement process is thought to be

less than 1%. As a consequence of the large scatter, the correla

tion with density is highly uncertain. The deviations of the data

from eq(3) are illustrated in figure 6. The relatively large

deviations, and concomitant large uncertainty in the k(D) correla

tion, are attributed to specimen variations of unknown origin.

5
C. Conductivity as a Function of Pressure

The dependence of thermal conductivity on pressure for specimens at a temperature of 313 K and having a density of 247 kg/m^ was

represented by

A - P

k(P) = ko +

(1 + [P/Po]n)l/n

(4)

where k and ko are in mW/(m- K), and P is in kPa; ko and A are

constants. Po is a pressure parameter which determines the location

of the transition region where k rises rapidly with increasing P.

The parameter ko models the constant value approached by k at very

low values of P (P<<Po). Thus the value of ko represents conduction

by the solid fiber matrix. This contribution is independent of gas

pressure and is what remains at zero pressure. To match the observed behavior k also approaches a different constant, ko + A- Po , at

high values of P (P>>Po). At P = Po, k(Po) = ko + A-Po/2(i/n).

Values of ko and A were obtained by an unweighted least squares

fit with n and Po chosen by trial and error to yield the minimum

standard deviation of the fit. In performing this fit it was found

that, for the somewhat limited range of pressure for which we obtained data, the minimum standard deviation of the fit (1.26) is

relatively insensitive to the values of n and Po . Thus for simplicity we forced n = 0.5 (1/n = 2) and then found ko = 5.75 mW/(m- K)

A = 778, and Po = 0.054 kPa (0.40 Torr), with a resulting standard

deviation of 1.34, very close to the global minimum.

The data used to determine this dependence on air pressure,

along with the smooth curve calculated from eq(4), are listed in

table 3 and shown in figure 7. Deviations of the data from eq(4)

are illustrated in figure 8. The relatively large variations exhibited at low pressures are attributed to large relative uncertainties

in the measurement and control of the air pressure.

This pressure dependence of k indicates a reduction of -0.9% in

thermal conductivity in the value at the 1650 m (5400 ft) elevation

of our laboratory at Boulder, Colorado, in comparison to the value

at sea level.

Using kinetic theory we can also estimate, from the value of Po

obtained above, the effective size of the pores in the material.

The transition region, passing from the upper constant value to the

lower constant value in the k(P) correlation as the air pressure is

reduced, should be found where the mean free path (mfp) of the air

molecules becomes about equal to the pore size. In this region, the

probability of a collision with another air molecule becomes approximately equal to the probability of a collision with a fiber of

insulation material. Reference [ 8 ] derives a relation showing the

6
mfp to be inversely proportional to pressure, and estimates the mfp

of oxygen molecules to be about 8 x 10' 8 m at standard conditions

(101.3 kPa and 273 K). At 313 K and 0.054 kPa (0.4 Torr) the mfp of

oxygen molecules is estimated to be 0.15 mm. The atmosphere is

composed of 20% O2 and 79% N2 ; nitrogen has a molecular mass only

12% less than that of oxygen, so for our purposes the estimated mfp

of air should be about the same as the estimate for oxygen. Thus

the estimated pore size in the material is also about 0.15 mm. We

can see no pores larger than an upper limit of about 0.2 mm.

D. Conductivity as a Function of Environmental Gas

The temperature dependence of thermal conductivity for the match

ed pair in an atmosphere of pure helium gas was represented by a relation similar in form to that used for the conductivity in air:

kHe = 86.166 + 0.2940- T - 0 . 13783x10- v . T3 . (5)

The data used to determine this correlation are listed in table 4

and plotted in figure 9. The standard deviation of the data from

the solid curve is only 0.03%.

At 293 K (20oC) pure helium gas at atmospheric pressure has a thermal conductivity of 147.1 mW/(m-K). For the fibrous aluminasilica insulation in pure helium gas at the same temperature and

pressure, eq(5) gives a thermal conductivity value of 172.0 mW/(m- K)

The pressure dependence of conductivity at low pressure suggested

that ko = 5.75 mW/(m-K) is the contribution to the thermal conductivity by the solid fiber matrix alone. The conductivity of the fiber

matrix in helium is greater than that for pure helium alone by a difference of 24.9 mW/(m- K), which is significantly greater than ko

A similar comparison is possible using the corresponding data

for air. For specimens in air at 293 K and atmospheric pressure, we

used eq(2) as the correlation (by extrapolation) because this relation was obtained for data from the same high-temperature GHP used

to obtain the helium correlation, eq(5). Eq(2) gives a value of

43.7 mW/(m- K) for the thermal conductivity. At the same temperature

and pressure pure air has a conductivity of 25.1 mW/(m- K). The conductivity of the fiber matrix in air is greater than the conductivi

ty of pure air alone by a difference of 18.6 mW/(m-K), which again

exceeds the conductivity of the fiber matrix alone, and by approx

mately the same magnitude as the difference found for helium gas.

This increase in conductivity between a pure gas and the same gas in

the solid fiber matrix should depend on the density of the solid

fibers, the porosity of the fiber matrix, and on the conduct ivi t

of the solid fibers and of the environmental gas. Analysis of the

interaction between the environmental gas and solid fiber matrix

will be left as the subject of a separate paper.

7
5. COMPARISONS

The high-temperature results obtained by this investigation can

be compared to two other sources of thermal conductivity data: (a)

the results [6] of a recently completed round robin sponsored by

ASTM Committee C 16.30, and, (b) data published [9] by the producer

of this material. The round-robin data, for a set of specimens

having a mean density of 238 kg/m^ , are compared to eq(l) in figure

10. The results reported here lie within the band of measurements

reported by the round robin participants. The effect of variation

in density for the round-robin specimens is known [6] to be negligible here.

The high-temperature measurements reported by the producer,

using five different apparatus, are compared in figure 11. The

spread of the results from these five apparatus was reported to be

10%. A least-squares fit to the producer’s data gave the relation

k(T) = 14.2 + 0.0916 T + 2.776 x 10-8 T3 (6)

which is plotted as the solid line in figure 11. The standard

deviation of eq(5) from the NBS data (circles in figure 12) for the

SRM candidate material is -4.4%, well within the 10% spread of the

results found by the producer. Visually the line appears to be

parallel to the data points, showing the deviation to be systematic.

6. RECOMMENDATIONS

Measurements of the thermal conductivity of the eight specimens

carefully selected for possible use as an SRM reveal a low variability for this material. This suggests that this material can be

supplied with a sufficiently small variability to serve as an

excellent SRM. However, the specimens used in the round robin study

exhibited a much larger variability. If a large lot of this

material (100 to 200 specimens) can be obtained with a variability

similar to that of the originally supplied ten specimens, this

material would be recommended for use as an SRM. If on the other

hand the larger variability is more typical of this material, each

specimen would need to be individually measured by NBS to be useful,

and would then be certified individually as calibrated transfer

specimens

8
7. REFERENCES

[1] Bust, J.G. "Status of Thermal Conductivity Standard Reference

Materials at the National Bureau of Standards", Thermal Conductivity

1

. Proceedings of the 18th International Conference on Thermal

Conductivity; Ashworth, T., and Smith, David R. , Eds.; pp. 327-338

(Plenum, New York, 1985).

[2] ASTM Subcommittee C16.30, "Reference Materials for Insulation

Measurement Comparisons", Thermal Transmission Measurements of Insulati on , ASTM STP 660, Tye , R.P., Ed., pp. 7-29 (ASTM, Philadelphia,

1978) .

[3] Bust, J.G., Filla, B.J., Burley, J.A. and Smith, David R. , "An

Automated Bigh Temperature Guarded-Bot-Plate Apparatus for Measuring

Thermal Conductivity", NBSIR 87-3089, (U.S. National Bureau of

Standards, May 1988).

[4] Bust, J.G., Filla, B.J., Burley, J.A. and Smith, David R. , "An

Automated Bigh Temperature Guarded-Bot-Plate Apparatus for Measuring

Thermal Conductivity of Insulations Between 300 and 750 K", to be

published in Proceedings of ASTM "Symposium on Thermal Insulation,

Materials and Systems", STP 922 (1988).

[5] Smith, David R. , Bust, J.G.

and Van Poolen, L. J. "A GuardedBot-Plate Apparatus for Measuring Effective Thermal Conductivity of

Insulations Between 80 K and 360 K" , NBSIR 81-1657, (U.S. National

Bureau of Standards, 1982).

[6] Bust, J.G. and Smith, David R. , "Round-Robin Measurements of

the Apparent Thermal Conductivity of Two Refractory Insulation Materials, Using Bigh-Temperature Guarded-Bot-Plate Apparatus", NBSIR

88-3087, (U.S. National Bureau of Standards, April 1988).

[7] Bust, J.G. and Lankford, A.B., "Comments on the Measurement of

Thermal Conductivity and Presentation of a Thermal Conductivity

Integral Method", Int. J. of Thermophysics 3/1 , 67-77, (Oct. 1982).

[8] Sears, Francis W. , Thermodynamics . 2nd Ed. ( Addison-Wesley

Reading, Mass. 1959), p. 257.

[9] Mitchell, B., "The Development of a Refractory Fiber Insulation for Use as a Bigh Temperature Thermal Transmission Calibration

Sample", Thermal Conductivity 19, Proceedings of the 19th

International Thermal Conductivity Conference; Yarbrough, D. , ed

(Plenum, New York, 1988).

9
Table 1. Thermal conductivity of one pair of fibrous o I urn i no-s i I i ca insulation board with a density of 259 kg/m^, at mean temperatures of 93 to 311 K. Meosurements were performed in dry

n i t rogen gas at a pressure of 83 kPa (623 Torr) using the

NBS 1 ow- tempe rature guarded hot plate.

Thi TIo Tmean Kdat AREA DELX DENSITY PRESSURE

(K) (K) (K) mW/ (m . K) (cm^) (cm) (kg/m^) (kPa)

147.292 121 .818 134.555 30.43 83.1 2.531 259.60 . 826E+02

159.939 134.593 147.266 32.19 83.2 2.531 259.50 .826E+02

172.069 146.907 159.488 34.02 83.2 2.531 259 . 50 . 826E+02

185.024 159.714 172.369 35.88 83.3 2.532 259.50 . 826E+02

106.266 80.793 93.530 22.75 83.0 2.529 259 . 70 .826E+02

121 .561 96.019 108.790 25.77 83.1 2.530 259.70 .826E+02

134.154 108.346 121 .250 28.13 83.1 2.530 259 . 60 . 826E+02

197.521 172.114 184.818 37.81 83.3 2.532 259.40 .826E+02

210.219 184.973 197.596 39.44 83.3 2.533 259 . 40 . 826E+02

222.916 197.561 210.239 41 .20 83.4 2.533 259.30 .826E+02

235.513 210.235 222.874 42.49 83.4 2.533 259.30 .826E+02

247.982 222.836 235 . 409 44.09 83.5 2.534 259.20 . 826E+02

247.966 222.829 235.398 44.85 83.5 2.534 259.20 .826E+02

260.591 235.438 248.015 46.04 83.5 2.534 259.20 . 826E+02

273.216 247.996 260.606 47.70 83.6 2.535 259.20 .826E+02

285.723 260.569 273.146 49.01 83.6 2.535 259.10 . 826E+02

298.308 273.177 285.743 49.89 83.7 2.536 259.10 .813E+02

310.859 285.696 298.278 51 .65 83.7 2.536 259.00 . 826E+02

323.394 298.310 310.852 53.15 83.8 2.537 259.00 . 826E+02

able 2. Thermal conductivity of eight specimens of f i b rous a 1 urn i no— silica i nsu lotion board with dens i t i es of 236 to 249 kg/m^

at mean temperatures of 313 to 746 K. Meosurements were

pe r f 0 rmed in air at 83 kPa (623 Torr), using the NBS hightemperature gua rded hot plate.

Thi TIo Tmean Kdat AREA DELX DENSITY PRESSURE

(K) (K) (K) mW/(m . K) (cm^) (cm) (kg/m^) (kPa)

323.042 303.114 313.078 45.44 128.4 2.537 242.70 . 836E+02

323.050 303.127 313.089 45.63 128.4 2.537 249.40 .836E+02

323.050 303.049 313.050 45.56 128.4 2.537 244.70 .836E+02

323.024 303.095 313.060 45.29 128.4 2.537 236.40 . 836E+02

323.069 303 . 1 29 313.099 45.94 128.4 2.537 242.70 .836E+02

323.066 303.077 313.072 45.81 128.4 2.537 247.00 . 836E+02

323.080 303.061 313.071 45.89 128.4 2.537 245 . 40 . 836E+02

323.041 303.063 313.052 45.02 128.4 2.537 244.70 . 836E+02

323.068 303.036 313.052 45.85 128.4 2.537 247.80 . 836E+02

323.055 303.134 313.095 45.77 128.4 2.537 247.00 . 836E+02

323.027 303.137 313.082 45.51 128.4 2.537 247.00 .836E+02

323.036 303.147 313.092 45.47 128.4 2.537 247.00 .836E+02

323.034 303.146 313.090 45.51 128.4 2.537 247.00 . 836E+02

323.073 303.146 313.110 45.79 128.4 2.537 247.00 . 836E+02

323.055 303.120 313.088 45.66 128.4 2.537 247.00 .836E+02

323.008 303.099 313.054 46.18 128.4 2.537 247.40 . 836E+02

323.090 303.131 313.111 45.81 128.4 2.537 247.40 . 836E+02

323.167 303.125 313.146 45.68 128.4 2.537 247.40 . 833E+02

10
Tob 1 e 2

Thi

(K)

(cont .

TIo

(K)

Tmean Kdat

(K) mW/(m.K)

AREA

(cm ) DELX

(cm)

DENSITY

(kg/m ) PRESSURE(kPa)

343.207 323. 167 333.187 47.97 128.4 2.539 247.40 . 833E+02

392.895 373. 102 382.999 53.20 128.5 2.541 247.20 . 833E+02

393. 149 373. 124 383.137 53.18 128.5 2.541 247.20 . 833E+02

483.262 463. 197 473.230 63.71 128.7 2.544 246.80 . 833E+02

591 .999 553. 118 572.559 75.03 128.9 2.549 246.40 . 833E+02

622.470 523.118 572.794 74.55 129.0 2.549 246.40 . 833E+02

671 .898 493.743 582.821 75.56 129.1 2.549 246.30 . 833E+02

612.959 573.066 593.013 77.69 128.9 2.550 246.30 . 833E+02

633.178 593. 161 613.170 80.13 129.0 2.551 246.20 . 833E+02

653.224 613.126 633.175 82.73 129.0 2.552 246.10 . 833E+02

673.212 633.088 653.150 85.26 129.1 2.553 246.00 . 833E+02

692.745 653. 134 672.940 87.86 129.1 2.554 245.90 . 833E+02

712.137 672.899 692.518 91 .82 129.1 2.555 245.80 . 833E+02

713.045 673.111 693.078 91 .94 129.1 2.555 245.80 . 833E+02

763.373 728.645 746.009 96.89 129.2 2.557 245.60 . 833E+02

712.512 673.096 692.804 89.75 129.1 2.555 245.80 .833E+02

343.187 323. Ill 333.149 47.77 128.4 2.538 247.30 . 833E+02

363.220 343.159 353.190 49.84 128.5 2.539 247.30 .833E+02

383.227 363.068 373.148 51 .94 128.5 2.540 247.20 . 833E+02

403.241 383.245 393.243 54.34 128.5 2.541 247.10 .833E+02

423.173 383.018 403.096 55.15 128.6 2.541 247.10 . 833E+02

443. 123 383.149 413.136 56.16 128.6 2.541 247.00 .833E+02

463. 157 383.201 423.179 57.25 128.7 2.542 247.00 .833E+02

482.963 383.211 433.087 58.29 128.7 2.542 246.90 . 833E+02

502.896 383.163 443.030 59.40 128.7 2.543 246.90 .833E+02

522.995 383.157 453.076 60.52 128.8 2.543 246.90 .833E+02

542.784 383.222 463.003 61 .66 128.8 2.543 246.80 . 833E+02

562.750 383.205 472.978 62.79 128.8 2.544 246.80 . 833E+02

582.598 383.137 482.868 63.98 128.9 2.544 246.70 .833E+02

622.635 403.204 512.920 67.38 129.0 2.546 246.60 .833E+02

662.267 402.976 532.622 69.62 129.0 2.547 246.50 . 833E+02

403.221 383.096 393.159 54.44 128.5 2.540 247.10 . 833E+02

423.294 403.295 413.295 56.74 128.6 2.541 247.00 . 833E+02

443.185 403.088 423.137 57.53 128.6 2.542 247.00 . 833E+02

483.279 443.028 463.154 62.03 128.7 2.543 246.80 . 833E+02

523.221 481 .285 502.253 66.51 128.8 2.545 246.70 .833E+02

323.101 303.125 313.113 45.97 128.4 2.537 247.40 .833E+02

523.295 483.055 503.175 66.44 128.8 2.545 246.60 . 833E+02

563.183 522.134 542.659 70.91 128.8 2.547 246.50 .833E+02

603.096 562.959 583.028 75.94 128.9 2.549 246.30 •833E+02

642.828 602.915 622.872 80.46 129.0 2.551 246.20 .833E+02

682.820 642.974 662.897 85.13 129.1 2.553 246.00 .833E+02

323.121 303.098 313.110 46.00 128.4 2.538 247.50 .833E+02

323.140 303.157 313.149 46.25 128.4 2.538 247.50 . 833E+02

323.637 303.184 313.411 46.45 128.4 2.538 247.50 .833E+02

583.149 563.174 573.162 75.53 128.9 2.549 246.40 . 833E+02

583.174 563.105 573.140 75.55 128.9 2.549 246.40 .833E+02

332.357 312.336 322.347 46.98 128.4 2.538 247.40 . 833E+02

333.150 313.150 323.150 46.98 128.4 2.538 247.40 .833E-(-02

583.140 563.083 573.112 75.87 128.9 2.549 246.40 •833E+02

588.178 568.141 578.160 76.45 128.9 2.549 246.40 . 833E+02

583.168 563.151 573.160 75.86 128.9 2.549 246.40 .833E+02

11
Table 3. Thermal conductivity of o selected pair of fibrous alumina

silica insulotion boards with densities of 236 to 249 kg/m^

ot mean temperatures of 313 ond 693 K. Measurements were per formed in air at pressures from 84 to 0.0047 kPo , using th NBS h i gh-t empe ro t u re guarded hot plate.

Thigh T 1 ow Tmean Kdat Pressure Percen

(K) (K) (K) mW/(m.K) (kPa) Dev i at

323.042 303.114 313.078 45.44 .836E+02 -.70

323.050 303.127 313.089 45.63 .836E+02 -.29

323.050 303.049 313.050 45.56 .836E+02 -.45

323.024 303.095 313.060 45.29 .836E+02 -1 .04

323.069 303.129 313.099 45.93 .836E+02 .38

323.066 303.077 313.072 45.81 .836E+02 . 1

323.080 303.061 313.071 45.89 .836E+02 .28 323.041 303.063 313.052 45.02 .836E+02 -1 .63

323.068 303.036 313.052 45.85 .836E+02 .19 323.055 303. 134 313.095 45.77 .836E+02 .02 323.027 303. 137 313.082 45.51 .836E+02 -.55

323.036 303.147 313.092 45.47 .836E+02 -.64

323.034 303. 146 313.090 45.51 .836E+02 -.55

323.073 303.146 313.110 45.79 .836E+02 .05 323.055 303. 120 313.088 45.66 .836E+02 -.22

323.008 303.099 313.054 46.18 .836E+02 .92 323.090 303.131 313.111 45.81 .836E+02 .10

323.063 303.066 313.065 45.54 .667E+02 .13

323.087 303.151 313.119 45.00 .400E+02 .55 323.119 303.148 313.134 43.03 . 133E+02 1 .05 323.131 303.100 313.116 39.33 .400E+01 .77 323.121 303.175 313.148 35.20 . 133E+01 2.15

323.122 303.145 313.134 27.92 . 400E+00 -.63

323.150 303.146 313.148 22.38 . 133E+00 3.37

323.137 303.033 313.085 14.04 .400E-01 -7.00

323.089 303.117 313.103 8.04 .467E-02 3.22

323.097 303.018 313.058 7.84 .467E-02 .74

323.167 303.125 313. 146 45.67 .833E+02 -.18

323.101 303. 125 313.113 45.97 .833E+02 .47 323.121 303.098 313.110 46.00 .833E+02 .53

tandard Devii at i on = 1 .69

712.512 673.096 692.804 89.75 .833E+02

712.522 673.042 692.782 89.52 . 666E+02

712.483 671 .335 691 .909 80.08 .400E+01

713.057 673.109 693.083 56.10 . 173E+00

12
Table 4. Thermal conductivity of the selected pair of fibrous aluminasilica insulation board with a density of 247 kg/m^ , at mean temperatures of 313 to 692 K. Measurements were performed in helium gas at pressures of 84 to 87 kPa (630 to 650 Torr)

using the NBS high-temperature guarded hot plote.

Thi

(K)

TIo

(K)

Tmean

(K)

Kdat

mW/(m.K)

AREA

(cm*)

DELX

(cm)

DENSITY

(kg/m^)

PRESSURE

(kPa)

323.066 303.152 313.109 177.74 128.4 2.537 247.40 .840E+02

343.066 323.134 333.100 183.71 128.4 2.538 247.30 . 840E+02

363. 100 343.154 353.127 189.34 128.5 2.539 247 . 30 .840E+02

383.119 363.154 373.137 195.14 128.5 2.540 247.20 . 840E+02

711.169 673.166 692.168 285.10 129.1 2.555 245.80 .866E+02

13
Table 5a. Thermal conductivity of eight different specimens of fibrous

alumina-silica insulation board with densities of 236 to 249

kg/m^ , at a mean temperature of 313 K. Measurements were performed in air at 84 kPo using the NBS high-temperature

guarded hot plate.

Thi

(K)

TIo

(K)

Tmean

(K)

Kdat

mW/(m.K)

AREA

(cm^)

DELX

(cm)

DENSITY

(kg/m’)

PRESSURE

(kPa)

323.042 303.114 313.078 45.44 128.4 2.537 242.70 .836E+02

323.050 303.127 313.089 45.63 128.4 2.537 249 . 40 .836E+02

323.050 303.049 313.050 45.56 128.4 2.537 244.70 .836E+02

323.024 303.095 313.060 45.29 128.4 2.537 236.40 .836E+02

323.069 303.129 313.099 45.94 128.4 2.537 242 . 70 .836E+02

323.066 303.077 313.072 45.81 128.4 2.537 247 . 00 .836E+02

323.080 303.061 313.071 45.89 128.4 2.537 245.40 .836E+02

323.041 303.063 313.052 45.02 128.4 2.537 244 . 70 .836E+02

323.068 303.036 313.052 45.85 128.4 2.537 247.80 . 836E+02

323.055 303 . 1 34 313.095 45.77 128.4 2.537 247 . 00 .836E+02

323.027 303.137 313.082 45.51 128.4 2.537 247.00 .836E+02

323.036 303 . 1 47 313.092 45.47 128.4 2.537 247 . 00 .836E+02

323.034 303.146 313.090 45.51 128.4 2.537 247 . 00 .836E+02

323.073 303.146 313.110 45.79 128.4 2.537 247.00 .836E+02

323.055 303.120 313.088 45.66 128.4 2.537 247 . 00 . 836E+02

323.008 303.099 313.054 46.18 128.4 2.537 247 . 40 .836E+02

323.090 303.131 313.111 45.81 128.4 2.537 247 . 40 .836E+02

Table 5b

Thi

(K)

The rma 1 conduct i v

board (round-robin

kg/m’ , at a mean performed in air at guarded hot plate.

TIo Tmean

(K) (K)

ty of fibrous alumina—

materiel) with densit

temperature of 313 K. 84 kPa using the NBS

Kdat AREA DELX

mW/(m.K) (cm*) (cm)

silica i nsu 1 at i on

ies of 207 to 308

Measurements were high— temperature

DENSITY PRESSURE

(kg/m’) (kPa)

343.187 323.111 333.149 47.77 128.4 2.538 247.30 .833E+02

343.207 323.167 333.187 47.97 128.4 2.539 247 . 40 .833E+02

343.197 323.181 333.189 53.02 128.4 2.525 295.10 .853E+02

343.108 323.179 333.144 53.22 128.4 2.512 295.80 .853E+02

343.314 323.067 333.191 50.74 128.4 2.712 306.50 .833E+02

343.376 323.117 333.247 50.62 128.4 2.662 307 . 70 . 833E+02

343.294 323.089 333.192 52.77 128.4 2.600 237.00 . 833E+02

343.399 323.157 333.278 50.94 128.4 2.628 221.40 .829E+02

343.316 323.063 333.190 49.26 128.4 2.557 236.40 .826E+02

343.232 323.107 333.170 54.39 128.4 2.628 225.70 .834E+02

343.468 323.028 333.248 52.77 128.4 2.611 223 . 40 .832E+02

343 . 440 323.069 333.255 53.65 128.4 2.634 225.00 .842E+02

343 . 1 69 323.126 333.148 53.36 128.4 2.611 220.50 .841E+02

343.154 323.113 333.134 46.84 128.4 2.600 220.10 .837E+02

343.341 323.160 333.251 47.23 128.4 2.635 217.40 . 833E+02

343.179 323.082 333.131 46.46 128.4 2.649 207.20 .830E+02

343.224 323.076 333.150 46.18 128.4 2.628 207.90 . 833E+02

343.506 323.168 333 . 337 48.03 128.4 2.651 214.20 . 830E+02

343.309 323.003 333.156 46.14 128.4 2.610 215.30 .829E+02

343 . 438 323.185 333.312 46.32 128.4 2.626 209 . 00 .842E+02

343.273 323.239 333.256 54.65 128.4 2.627 225.80 .840E+02

343.112 323.192 333.152 54.31 128.4 2.627 225.80 .840E+02

343.370 323.184 333.277 53.19 128.4 2.645 222.60 .840E+02

343.190 323.143 333.167 53.03 128.4 2.645 222.60 .840E+02

14
Temperature^ K

Figure 1. Thermal conductivity of a pair of fibrous alumina-silica

insulation boards as measured by NBS/B, at mean temperatures of 93 to 311 K and at ambient atmospheric pressure

of 83 kPa. Boards have a density of 259 kg/m3 . The solid

line was calculated from eq(l).

15
^coLc^^^coLc

1.5

0.5

0.5

-1

-1.5

-2

-2.5

' ' '

' I

' ’ '

' I

' '

' I

' ' '

' I

' ' ' ‘

I

' ' '

'

I

o

o

o

o o

o

O o

o

o O

o o

I . . . . I , . . 75 100 125 150 175 200 225 250 275 30CT 325

Temperature, K

Figure 2. Deviations of the NBS low-temperature thermal conductivity

data from eq ( 1 )

16
Temperature, K

Figure 3. Thermal conductivity of a pair of fibrous alumina-silica

insulation boards as measured by NBS/B, at mean temperatures of 313 to 746 K and at ambient atmospheric pressure

of 83 kPa. Boards have a density of 247 kg/m^ . The solid

line was calculated from eq(2).

17
Figure 4. Deviations of the NBS high-temperature thermal conductivity

data from eq ( 2 )

18
DENSlTY,kg/m^

Figure 5. Thermal conductivity of fibrous alumina-silica insulation

boards as measured by NBS/B, at a mean temperature of 333 K

and at ambient atmospheric pressure of 84 kPa . The solid

line was calculated from eq(3).

19
100(x

10

7.5 -

5

-

2.5 -

tn JJ° 0

-2.5 -

o

O

o

o

7.5

o

5 h O o

o

o

' ' I ' I I

o

o

o

o

''''''''''''' I . . , .

o

o

‘ 200 210 220 230 240 250 260 270 280 290 300 310

DENS I TY ^kg/

Figure 6. Deviations of the NBS thermal conductivity data from eq(3).

20
APPARENT

THERMAL

CONDUCTIVITY

0.03 0.1 0.3 13 10 30

PRESSURE^ kPa

Figure 7. Thermal conductivity of fibrous alumina-silica insulation boards as measured by NBS/B, at a mean temperature of

313 K. The boards have a density of 247 kg/m3 . The solid

line was calculated from eq(4) with ko = 5.75, A = 778,

Po = 0.054 kPa and n = 0.5.

21
Figure 8. Deviations of the NBS thermal conductivity data from eq(4).

22
RPPRRENT

THERMAL

CONDUCTIVITY

Temperature^ K

Figure 9. Thermal conductivity of fibrous alumina-silica insulation

boards as measured by NBS/B, in an environment of pure

helium gas. The board density is 247 kg/m^ . The solid

line was calculated from eq(5).

23
Thermal

Conduct

lvl

mN/(m.K)

Temperature

Figure 10. Round-robin measurements, by seven participating labs

including NBS/B, of thermal conductivity of fibrous

alumina-silica insulation boards, at the local ambient

atmospheric pressure of each participating laboratory.

The board density is 238 kg/m3 . The solid line is calculated from eq (1).

24
APPARENT

THERNAL

CONDUCTIVITY

Figure 11. Thermal conductivity of fibrous alumina-silica insulation boards, as measured by the producer (solid line)

at a pressure of 84 kPa , for a board with a density

of 244 kg/m3 . The solid line is given by eq(6). Data

points shown are NBS data for a different specimen with

a density of 247 kg/m^

25
^coLc ^

'^^coLc

300 350 400 450 500 550 600 650 700 750

Temperot ure ^ K

Figure 12. Deviations of the NBS/B thermal conductivity data from

the producer's data, eq (6).

25
NBS-H4A REV. 2-aCi

u.S. DEPT. OF COMM.

BIBLIOGRAPHIC DATA

SHEET (See instructions)

1. PUBLICATION OR

REPORT NO.

NBSIR 88-3094

2. Performing Organ. Report No. 3. PubI ication Date June 1988

4 . TITLE and subtitle

Fibrous Alumina-Silica Insulation Board as a Candidate Standard Reference Material

of Thermal Resistance

5. AUTHOR(S)

Must, Jerome G. and Smith, David R.

6. PERFORMING ORGANIZATION (If joint or other than NBS, see in struction s)

national bureau of standards

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

7. Contract/Grant No. ORNL/IA-21428

8. Type of Report & Period Covered

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

Dept, of Energy

P.O. Box X Oak Ridge National Laboratory

Oak Ridge, TN 37830

10. SUPPLEMENTARY NOTES

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

11. ABSTRACT (A 200-word or less factual summary of most significant information. I f document Includes a significant

bi bliography or literature survey, mention it here)

Measurements of apparent thermal conductivity are reported in

order to provide the basis for certifying fibrous alumina-silica

insulation board as a Standard Reference Material (SFiM) of thermal

resistance. These data encompass ranges of temperature from 93 to

746 K, densities from 207 to 308 kg/m^ , and fill-gas pressures

from roughing-pump vacuum to atmospheric pressure, in environments

of both air and helium. Detailed analyses and intercomparisons of

previously published data are given.

12. KEY WORDS (Six to twelve entries; alphabetical order; capitalize only proper names; and separate key words by er’ -co alumina-silica board; apparent thermal conductivity; density; pressure;

Standard Reference Material; temperature; thermal insulation; thermal resistance,

13. AVAILABILITY

[2] Uni imited

I I For Official Distribution. Do Not Release to NTIS

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

20402.

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

14. NO. Of

PRINTED PAG!

36

15. P'