Thermophysical properties of porous ceramic material - thermal conductivity, specific heat, density, and porosity measurement

Dustin, P. C.

Hoagland, L. C.

Wentworth, R. L.

English

NASA Technical Reports Server

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ff 653 July 65 
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https://ntrs.nasa.gov/search.jsp?R=19660006098 2020-03-16T21:44:40+00:00Z
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c 37 D Y N A T E C i l  
SOXE THER?(i10PHYSIC14L PROPERTY MEASUREMENTS 
OF 
POROUS CERAMIC ftGWSSROCK" 
Submitted to: 
Xational Aeronautics and Space Administration 
Langley Research Center 
Langley Station 
Hampton, Virginia 
Prcparcd by: 
L. c .  Hoaglmd 
R. L. Weiitrvorth 
P. c. Dustin 
Dynatcch Report So .  558 
Dynatech Project KO. NAS-12 
May 13, 1965 
DYNATECH CORPORATION 
17 Tudor Street 
Cambridge, Massachusetts 02139 
Section 
1 INTRODUC TI ON 
2 THERMAL C0,NDI;CTMTY MEASUREXENTS 
2: 1 Test Prooed1_?rP, 
2 .2  Data Reduction 
2 . 3  Sample Calculation 
2 . 4  Test Results 
2 .5  Disclission of Results 
3 SPECIFIC HEAT "IiISUREMEhTS 
3 . 1  Test Procedure 
3 . 2  Data Reduction Method 
3 . 3  Sample Calculation 
3 . 4  Test I?esults 
3.5 Discussion of Results 
4 DENSITY AND POROSITY MEASUREMENTS 
4.1 Sumnary 
4.3 Porosity 
4.4 Coefficient of Thelma1 Expansion 
4 . 5  Discussion 
A 3 n n n c i t x r  
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P r o g r e s s  throicgh Research. " . 
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Fi,o;ure 
1 TCFC-R8 Series 
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3 Test Stack Arrangement 
Test Stack Assembly TCFC-R8 Series 
s - - .  4 Graph of Thermal Conductivity vs. Temperature 
r 5 QTA N-7-ER 
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7 Specific Heat vs. Temperature 
Sample and Guard Arrangement, Adiabatic Calorimeter 
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Section I 
INTRODUCTION 
I This report describes the measurements performed on a sxaple  of a porous ceramic described as ''Glassrock". These tests were coaducted by Dynatech Corpora- tion for  the NASA, Langley Research Center under Contract No. NAS 1-4758. 
means of a comparative test. mer the same temperahre range 'irie variation of 
specific heat with tem;jerature was measured. 
using techniques which rely upon measuring  he cubical expansion of the material. 
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The thermal conductivity was measured from room temperature to 700°F by 
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A determination of the variation of density with temperature ms performed 
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The 
procedures 
following sections of t i s  report present the methods of testing and the 
followed in this test program. 
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Sectim 2 
THERMAL COhiUC?TI?TY &li3I1SLZ3EblEN’rS 
2 . 1  Test Trocedure 
The thermal conductivity was determimd by the Comparative Xle~iod in which 
the Lhermai conauctiviv of Ehe mareriai is determixd by comparing i t  io Giai 01 a 
hewn standard. referred to as a he2: meter, This is accomplished by sandwich- 
ing tne test sLmple lxtween two identical heat meters and passing a midirectional 
heat flow through tke stack. Data w2s taken for  eight points between room tempera- 
ture aid 700°F. 
rool= temperature. 
The temperaare  points were rii in the sequence starting from 
The test stack configuration is shown m figure three. The sample was pro- 
vided with tiiermocoEgle grooves machined kit0 the faces and was instrumented 
wifn chrome1 Alumel thermocouples. The heat nietcrs were imtrumented in a 
similar manner also with chroniel alumel thermocouples. 
The sample w3s sandwiched bexveen two identical Pyroceram #9GOG heat 
meters and a heat f l - u  was directed through the stack by a heater placed at the top 
of the assembly. The temperature level of tile stack was maintained by an auxiliary 
heater placed between the bottom heat meter and a cooled heat sink. Water was 
used as the coolait in the sink for all points except for the room temperature point 
where liquid nitrogen was uscd. Insdating paper was placed between the auxiliary 
heater and tile heat sink in order to allow easy  control of the auxiliary heater 
temperature. Aluminum plates, l/& inch thick, were inserted between the heater 
and the hear. meters so a s  to provide an evenly distributed heat flux across the 
entire contact surface. To preclude side heat losses, the stack was surrounded by 
a cylindrical guard heater, the temperature of which was  maintained close to the 
average sample temperature, and the stack assembly was covered with a low con- 
duc tivity powder ed ins dation, 
Figure 1 shows the conductivity instrument used for this test. Figure 2 shows 
a typical test stack being assembled; the outer guard heater appears to the left o€ 
the stack. 
To mininiize thermal contact resistances, all surfaces were coated with a 
thin layer of silicone grease. A l o x i  of approximately 3 pounds was applied to the 
top of the test stack to further ensure good thermal contact. 
The tests were performed by heating the test stack to the requircd temperature 
level and allowing tile stack to reach -a equilibrium or  steady state condition. 
test was concluded when it was established that this condition had been maintained 
for  a minimum period of one hour. 
Each 
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DYNATECH 
COMPARATIVE THERMAL CONDUCTMTY APPARATUS 
TCFC-R8 SERIES 
DYNATECH CORPORATION 
17 TUDOR STREET 
CAMBRIDGE 39, MASSACHUSETTS 
Telephone : 617 - 868-8050 
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Test Stack Assembly 
TCFC-R8 Series 
Comparative Thermal Conductivity Apparatus 
DYNATECH CORPORATION 
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Figure 3. Test Stack A4r,-mgement 
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The rr,easuremznts were rmde mcier a bell jar which was evacuated by 
means of a rnechanicd vacuum pdmp. For all tests tila vacuun was maintained 
in the range of 30 to  100 microns. 
A separate determination w2s made at one temperature (approximately 125" F. ) 
of the variation of thermal conductivity with absolute pressure, Three measure- 
ments were taken. 
2.2 Data Reduction 
By assaaing a unidirectional heat flow under steady smte conditions, the heat 
flux through both heat me'ers a d  the sample is eqyai, i. e. 
or 
7 I 
where 
AX 7 thickness 
4T = tempcramre difference 
k = therinal conductivity 
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2 . 3  Saninle Cdcu I -+  'LLLGn 
A sample cdculatioa is ilow presented to illustrate the data reduction pro- 
c edur e. 
Test Data 
Heat meter material: Pyl-ocezarn +%OG 
= 0.38 Btu/hr-ft- F 
0.38; .313 - 
2 
L- 
= 0.313 Btu/hr-ft- "F 
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( ~ t u / i r r - i t - ~ ~ )  
Mean Sample 
Temp e r atur e 
0 .  
0.3Gd 
0.4c2 
0.437 
0.536 
0.561 
0.620 
0. ssc 
Upon <ampletion ol this ;>:;LSSO of thc progrsm the variatio:i of therlnal con- 
ductivity with absolute press ~rc :  was mesureo lor  o : ~  tenqci-ature point. 
Temperzture (hiean smple )  : 130 O F  
Pressure (Torr) 
760 mm 
380 
190 
li: Btu/lrr-ft- OF 
0, 505 
0.495 
0.495 
2 .  5 Discussion of X c s d t s  
With i;iie exception of the 400 OF t es tyok t  all G: t3e dam lie on a smooth curve. 
This p o k t  is appro.*xitcly 9 1/2 T.ie CSCL,! xcuracy  for this type of 
test is betmeen 2 5 and i - 10% It is felt t:.;t these results sre within tlie 10% 
allowance. 
iiigk. 
The tabulated difference of thermal conductivity with ahsokite pressure for 
a constant temperzture of 130 F shows little chmge. It seems also that w i + ~ n  the 
same experimental e r ror  the conductivity is independent of vacuum. 
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3 .  1 Test Procedure 
The specific heat was deterrib-eci as ;? >c:ctioLi ~i teniperature oyer tile range 
h t3is insti-uamt uAe spccisc h e t t  of the sxnplo is detemiiied 
-75 I: to i 700 O F i:~ tile D-ykatech ?Joi?el QT-'--57 c,rrm:itative zdiabatic cjlori- 
m&er (Figure 2 ) .  
by rlieasuririg >\e texpera'cure respor-sc of ;I--2 sainpk IO a h o ~ ~  lieat iiiput. '&e 
sample is iriserxd b x o  a ssmpk hz,ter assc-ably wixich is hstrisnentcd with 
th emio c oupf es fo 1- i er-ipe r stur z i ~ z  ;LS cl-cnic;--: a d  s us? ended ins idc a1 d i 3 b  atic 
jacket. (See Figure 6). The adiabatic jaclie: is ccnstantly m&daiiied at the same 
icnipcraLure as the szi%>le asscrAn;-; by MCXS of L? :cr!it.t 01- 3 3 r d  heater coupled 
to ;ill antoma:ic coritrol systeia. Thus, t k r e  is vel-:: Ilitle h a t  transfer between 
 he sanple assembly a d  its e;:viroxx?nt. Yo :xiuce fur ther  tiie heat transfer 
be'miecn the sxrns and its enviTaimxAilt, 8 iaecl- .~iic=~l pr.;np vacuum (1 to LOO microns) 
is provided betu7ee11 ihe sample t ssc~:?~ly  slld i!io &itj,atic jacket to eliminate con- 
vection and all surfaces are hidilly collshed lo reduce radiation. 
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The  mode of operation u e d  :'or Lhe xesLs descr5ed here consisted of operat- 
ing the sample heater at a constan; pon.er i n p ~ ~  tlxocghout the test and recording 
the sample teniperature versuv time responsa to th is  heat input over the temperature 
range of interest. 
contirmous record of suinaia specific  ai v a x i s  temperature is obtxined 
by operating dic instrument witi; :L colitiii~or.;. constmt power ixput to the sample 
assembly a:rd recording the smiplc' wxperartir3 as a function of time throughout 
the temperature range of ixlerest-. T;:e tmipcranrre response (and iieiice the 
M Cp product) of the sttmple container is first deterwied by opxating tiie instxu-. 
meix over the full temperature rang without a samqle. A sample of unlrnotvn . 
specific lieat is then kser ted lntothe saniple contaher and-the unit is again operated 
over the desired temperature range. The specific heat of the sample is then cal- 
culated from the equation: 
where 
q = heat input to sample container 
X Cp = 
T = temperature , 
t = time 
mass-specific heat product 
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DYNATE CH 
QUANTITAT N E  A DUBATI C CALORIMETER INSTRUMENT 
QTA-N7-ER SERIES 
DYNATECH CORPORATION 
17 TUDOR STREET 
CAMBRIDGE, MASSACHUSETTS 02139 
Telephone : 61 7-868 -8050 
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Solving for tlw sar~ipia specific heat: 
Cp = Btu/lb-"F; 
d (ern3 I_ d (emf) - -  
d T  
d T  - 
d t  d t  
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* Reference Table for Thermocouples. Circular 561, Xational Bureau of Standards. 
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Test Run of: April 19, 1965 
Saniple Ti'eighz: 46.948 grams 
Theimocou~les : Copper consxantm 
(m weight loss dux:g testj 
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Some thermophysical property measurements of porous ceramic ''Glassrock''

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