The research testing and demonstration of new bulk-fill materials for cryogenic thermal insulation systems was performed by the Cryogenics Test Laboratory at NASA Kennedy Space Center. Thermal conductivity testing under actual-use cryogenic conditions is a key to understanding the total system performance encompassing engineering, economics, and materials factors. A number of bulk fill insulation materials, including aerogel beads, glass bubbles, and perlite powder, were tested using a new cylindrical cryostat. Boundary temperatures for the liquid nitrogen boil-off method were 293 K and 78 K. Tests were performed as a function of cold vacuum pressure from high vacuum to no vacuum conditions. Results are compared with other complementary test methods in the range of 300 K to 20 K. Various testing techniques are shown to be required to obtain a complete understanding of the operating performance of a material and to provide data for answers to design engineering questions

Augustynowicz, S. D.

Fesmire, J. E.

Heckle, K. W.

Sass, J. P.

Scholtens, B. E.

NASA Technical Reports Server

General Disclaimer 
One or more of the Following Statements may affect this Document 
 
 This document has been reproduced from the best copy furnished by the 
organizational source. It is being released in the interest of making available as 
much information as possible. 
 
 This document may contain data, which exceeds the sheet parameters. It was 
furnished in this condition by the organizational source and is the best copy 
available. 
 
 This document may contain tone-on-tone or color graphs, charts and/or pictures, 
which have been reproduced in black and white. 
 
 This document is paginated as submitted by the original source. 
 
 Portions of this document are not fully legible due to the historical nature of some 
of the material. However, it is the best reproduction available from the original 
submission. 
 
 
 
 
 
 
 
Produced by the NASA Center for Aerospace Information (CASI) 
https://ntrs.nasa.gov/search.jsp?R=20130012853 2019-08-31T01:04:18+00:00Z
CRYOGENIC THERMAL PERFORMANCE TESTING 
OF BULK-FILL AND AEROGEL INSULATION MATERIALS 
B. E. Scholtens', J.E. Fesmire 1 , J. P. Sass', S.D. Augustynowicz 2 , and K. W. 
Heckle2 
'NASA Kennedy Space Center, KT-E 
Kennedy Space Center, FL, 32899, USA 
2 Sierra Lobo, Inc., SLI-2 
Kennedy Space Center, FL, 32899, USA 
ABSTRACT 
The research testing and demonstration of new bulk-fill materials for cryogenic thermal 
insulation systems was performed by the Cryogenics Test Laboratory at NASA Kennedy Space 
Center. Thermal conductivity testing under actual-use cryogenic conditions is a key to 
understanding the total system performance encompassing engineering, economics, and 
materials factors. A number of bulk fill insulation materials, including aerogel beads, glass 
bubbles, and perlite powder, were tested using a new cylindrical cryostat. Boundary temperatures 
for the liquid nitrogen boil-off method were 293 K and 78 K. Tests were performed as a 
function of cold vacuum pressure from high vacuum to no vacuum conditions. Results are 
compared with other complementary test methods in the range of 300 K to 20 K. Various testing 
techniques are shown to be required to obtain a complete understanding of the operating 
performance of a material and to provide data for answers to design engineering questions. 
KEYWORDS: Cryogenic tanks, thermal insulation, granular materials, aerogel, thermal 
conductivity, liquid nitrogen boil-off 
PACS: 65.60.+a, Thermal properties of amorphous solids and glasses
INTRODUCTION 
Thermal performance of bulk-fill insulation materials under actual-use cryogenic 
conditions is important for understanding current systems and for developing new systems. 
Example systems include double-wall tanks, double-wall piping, cold boxes, and cavities. 
Difficult to insulate cavities are prevalent on launch vehicles and cryogenic propellant loading 
systems in areas such as umbilicals, quick-disconnects, pipe bellows, tank flanges, 
instrumentation feedthroughs, and numerous other critical components. Testing must be 
performed to meet requirements for both engineering and economics factors. The first step is to 
completely characterize the insulation materials in configurations and environments as they will 
be used in the field. The Cryogenics Test Laboratory at Kennedy Space Center has developed a 
family of test cryostats and standardized test methods according to this purpose. Several bulk-
fill insulation materials, including aerogels, have been tested using the latest test apparatus, 
Cryostat-100. These comprehensive new sets of thermal performance data are being used for 
engineering design, thermo-economic analysis, and as the basis for new materials development. 
Development of new insulation materials requires complete understanding of the contributions of 
the different modes of heat transfer and how they vary with vacuum level. The results have 
already been applied to successful demonstrations of insulation solutions for the Space Shuttle 
External Tank, liquid hydrogen storage tanks, and other industrial applications. 
CRYOSTAT-100 TEST APPARATUS AND METHOD 
The Cryostat-100 test apparatus, shown in Figure 1, is the replacement for Cryostat-1 [1, 
2, 3]. The similar Cryostat-1 was used in earlier studies of bulk-fill materials [4, 5]. The system 
is a liquid nitrogen boil-off (evaporation) calorimeter which provides absolute data for the 
apparent thermal conductivity (k-value) of materials or systems. Mass flow of nitrogen gas 
under steady-state, energy-rate balanced conditions is the primary measurement. This new 
apparatus is capable of extremely stable boil-off rates over a very wide range of heat flux. 
The cold mass cylindrical configuration is 167-mm by 1026-mm, including guarded ends. 
The standard thickness for test specimens is 25-mm. Bulk-fill materials are kept in place using a 
thin black sleeve. Test temperatures are as follows: cold-boundary temperature (CBT) 78 K, 
warm-boundary temperature (WBT) 293 K, temperature difference (AT) 216 K, and mean 
temperature 186K. Multiple temperature sensors are included for boundary and thickness layer 
temperatures as shown in Figure 2. 
The test specimens are evacuated and heated to achieve a high vacuum level within the 
material prior to beginning a series of tests. After a suitable warm vacuum pressure (WVP) is 
obtained, typically below 1 millitorr, tests are conducted over the full range of cold vacuum 
pressures (CVP). Most engineering applications fall into one of three levels of thermal 
performance as designated by the following CVP: high vacuum (HV), below 1XI04 ton; soft 
vacuum (SV), -1 ton; and no vacuum (NV), 760 ton. A typical test series consists of a 
minimum of eight CVP starting at HV and increasing decade by decade to NV. Nitrogen is the 
residual gas for all tests reported here. Liquid nitrogen is supplied to the three chambers 
independently. The boil-off mass flow rates from all three chambers, after system cool down 
and thermal stabilization is complete, are continuously measured. The boil-off flow from the test
Map 
chamber is averaged over the peiod of time when the test chamber is between 92 and 88% full of 
liquid nitrogen, and used to calculate the k-value. 
FIGURE 1. Overall view of the Cryostat-100 test apparatus and system for determining the absolute k-value for a 
cryogenic thermal insulation system.
Sow LoGim 
flI.IU.113 
T1.1536 kM 
1111 c 1	 ,a1)
*fUIinwLvn 
fl	 iliii
I in 
(d 
OwNk
in 
C 
C 
FIGURE 2. Schematic of Cryostat-100 showing cold mass chambers, insulation material, black sleeve, and location 
of temperature sensors.
BULK-FILL INSULATION TEST MATERIALS 
Three different bulk-fill insulation materials—perlite powder, glass bubbles, and aerogel 
beads—were tested in the Cryostat-100 test apparatus. The perlite powder was an evacuated 
cryogenic grade perlite processed by Silbrico Corp. under the trade name Ryolex grade no. 39. 
The glass bubbles material is manufactured by 3M under the name 3M Scotchlite Type KI Glass 
Bubbles. The aerogel beads are commercially available from Cabot Corporation under the trade 
name Nanogel. All three materials 
appear to be a similar white powder TABLE 1. Microscope comparison of the three white bulk-fill 
to the naked	 eye.	 However,	 insulations. Note: Glass Bubbles are shown at 300x. 
noticeable differences at a 
microscopic level are shown in Table 
1. The combination of morphology, 
microstructure, and submicroscopic 
features of a given material 
determine how the heat energy will 
be transmitted through the bulk of  
the material at a particular vacuum 
level. Further details have been 
reported [4-6]. 
Each material was carefully 
measured and poured cup by cup into 
the black sleeve around the cold 
mass. Thickness and density details 
are shown in Table 2. Each material 
was heated above 340K and 
evacuated to approximately 1 
millitorr or lower WVP. 
TABLE 2. Installed densities for insulation test materials. 
Ref. No. Material Thickness	 Mass Tap Volume Tap Density 
mm	
3 
cm g/cc 
A102 Glass Bubbles 25.4	 885.6	 11073 0.080 
A 10 Perlite 25.4	 1875	 11268 0.166 
A108 Aerogel Beads 1	 25.4	 967	 11268 0.086 
TEST RESULTS 
A total of 83 tests of 3 material systems are reported here. An additional test series of 15 
tests were run without any insulation material inside the black sleeve. The corresponding steady-
state run time on Cryostat-100 was over 500 hours. Variation of absolute k-value with CVP is 
presented in Figure 4. The variation of heat flux with CVP is given in Figure 5. The k-values 
rose sharply in the soft-vacuum range as gas conduction began to dominate the heat transfer. The 
glass bubbles had much better thermal performance than perlite for all vacuum levels. The glass 
bubbles were also better than aerogel beads at high vacuum up to soft vacuum. Above 1000 
microns the aerogel beads perform significantly better than glass bubbles and perlite. The 
lOx	 1 0o 
Glass
 
Bubbles 
--65tm 
Perlite - 
Powder
'^ A^.^j 
Aerogel . 
Beads 
-2000 tm
A
---
10 
E 
0
vacuum only test is included to illustrate the reduction in heat flux through the system by using 
an insulation material. This data provides a basis for the heat transfer analysis of the materials. 
An example test (aerogel beads at 1 millitorr) is presented in Figures 6. The final k-value 
and heat flux are taken from the averaged test chamber boil-off flow rate when the liquid 
nitrogen level is between 88% to 92% full (or between about 17 and 21 hours in the example 
case). The standard requirement is to achieve a fine thermal equilibrium that is coincident with a 
liquid level of about 90%. As Figure 6 shows, one or two refills are sometimes required beyond 
the initial cooldown phase. 
100
-+-- A 102 3M Glass Bubbles 
- — --A103 Perlite Powder 
-- —e— A 108 Aerogel Beads 
-- Al 14 Vacuum Only
0.1'	 i	 i	 i	 i	 I 
0.001	 0.01	 0.1	 1	 10	 100	 1000	 10000 100000 1000000 
CVP (millitorr) 
FIGURE 4. Variation of apparent thermal conductivity (absolute k-value) with cold vacuum pressure for bulk-fill 
cryogenic insulation materials. The boundary temperatures are approximately 78 K and 293 K. The residual gas is 
nitrogen.
2000 
1500 
E 
-100 
500
5.0 
4.0
E 
E 
3.0 
2.0
n. 
1.0 
1000 
100 
10 
I	 I	 I 
0.001	 0.01	 0.1	 I	 10	 100	 1000	 10000	 100000	 1000000
CVP (mliuitorr) 
FIGURE 5. Variation of heat flux with cold vacuum pressure for bulk-fill cryogenic insulation materials. The 
boundary temperatures are approximately 78 K and 290 K. The residual gas is nitrogen. 
0	 I	 1	 i0.0 
0	 2	 4	 6	 8	 JO	 12	 14	 16	 18	 20	 22	 24	 26
Time (hours) 
FIGURE 6. Nitrogen boil-off flow rate and the calculated k-value show stabilization in the 92-88% full range.
ANALYSIS AND DISCUSSION 
Complementary test methods are necessary for establishing a complete understanding of 
the heat transfer properties for a given material system and to establish credibility of the heat 
measurement results. This fact is 
illustrated in Table 3 by TABLE 3. Comparison of Cryostat-100 and other test methods at high 
vacuum. Notes: * 1oafi value. **average 
comparing the Cryostat- 100 
results for perlite and aerogel 
beads at high vacuum to the 
results of the in-house CESAT 
project [6], Fulk [7], and our  
research partners at the  
FSU/NHMFL [8]. Extrapolating  
the data to the Cryostat-100 
average temperature gives a good 
irresnnndente if the results 
The vacuum test series and the literature were used to determine the effect of the three 
bulk-fill insulation materials on the different modes of heat transfer. The total thermal 
conductivity is the sum of the thermal conductivity of each mode of heat transfer 
( k T = k,,+ kgc + k + kr where k,c is the solid conduction thermal conductivity, kgc is the gas 
conduction thermal conductivity, kc
 is the convection thermal conductivity, and k r is radiation 
thermal conductivity). At high vacuum, gas conduction and convection are neglected, while it is 
assumed that solid thermal conduction and radiation are constant at all vacuum levels. Figure 7 
illustrates the thermal conductivity of gas conduction and convection for the three bulk-fill 
materials calculated by using the data from Cryostat-100 and extrapolating data in the literature 
[8, 9, 10]. Although adding a bulk-fill insulation material to a vacuum system introduces solid 
conduction, the materials improve thermal performance by reducing heat transfer by radiation, 
convection, and gas conduction. 
CONCLUSIONS 
Thermal performance testing of perlite powder, glass bubbles, and aerogel beads was 
successfully completed at the Cryogenics Test Laboratory using Cryostat-100. However, a 
number of tests under different conditions are needed to completely understand and characterize 
insulation materials for the full vacuum pressure range. These results will be applied to a number 
of different projects in the area of energy-efficient cryogenics for space vehicles, space launch, 
and industry. 
Aerogel granules by Cabot and aerogel composite beads and blankets by Aspen Aerogels 
are some of the newer materials currently being studied for cryogenic applications. Current 
experimental work also includes evacuation and vacuum retention rates, flammability and fire 
compatibility, and the effects of different residual gases. Current work also includes a focus on 
non-vacuum cryogenic insulation systems. A new test apparatus using industry piping 
equipment will provide for laboratory scale field demonstrations and allow practical insulation 
solutions to old problems using new materials. 
Material Test WBT K
CBT 
K
Average T 
K
k-value 
mW/rn-K 
Perlite
A103 293 78 186 0.94 
CESAT 296 20 158 1.03* 
Fulk 304 1	 20 162 0.65 
Fulk 76 4 40 0.08 
Aerogel
A108 293 78 186 1.71 
Fulk 304 76 190 2.10 
Fulk 
IFSU/NHMFL
76 - 20 48 0.20 
29 0 .16 **
4 
2
Im 
loo 
	
0.01 1	 If	 I	 I	 I	 I 
	
01	 0.1	 I	 10	 leO	 1000	 10000	 100000	 1000000 
Figure 7. Calculated gas conduction and convection thermal conductivities for each material as a function of CVP. 
The boundary temperatures are approximately 78 K and 293 K. The residual gas is nitrogen. 
REFERENCES 
1. Fesmire, J.E. and Augustynowicz, "Methods of Testing Thermal Insulation and Associated Test Apparatus," 
US Patent 6,742,926 June 1, 2004. 
2. Fesmire, J.E., Scholtens, B.E., and Augustynowicz, S.D., "Thermal performance testing of cryogenic insulation 
systems," International Thermal Conductivity Conference 29, Birmingham, AL, USA, June 2007. 
3. Fesmire, J.E., Augustynowicz, S.D., Heckle, K.W., and Scholtens, B.E., "Equipment and methods for 
cryogenic thermal insulation testing," in Advances in Cryogenic Engineering, 49, American Institute of 
Physics, New York, pp. 579-586, (2004). 
4. Fesmire, i.E., and Augustynowicz, S.D, "Thermal performance testing of glass microspheres under cryogenic-
vacuum conditions," in Advances in Cryogenic Engineering, 49, American Institute of Physics, New York, pp. 
612-618, (2004). 
5. Fesmire, J.E., Augustynowicz, S.D., and Rouanet, S., "Aerogel beads as cryogenic thermal insulation system," 
in Advances in Cryogenic Engineering, 47, American Institute of Physics, New York, pp. 1541-1548, (2002). 
6. Sass, J.P., Fesmire, J.E., Morris, D.L., Nagy, Z.F., Augustynowicz, S.D., Sojourner, S.J., "Thermal 
performance comparison of glass microsphere and perlite insulation systems for liquid hydrogen storage 
tanks," Cryogenics Engineering Conference, Chattanooga, TN, July 2007. 
7. Fulk, M.M., "Evacuated powder insulation for low temperatures," in Progress in Cryogenics, 1, 1959, pp. 65-
84. 
8. Barrios, M.N., Choi, Y.S., and Van Sciver, S.W., "Thermal conductivity of powder insulations below 180K," 
Cryogenic Engineering Conference, Chattanooga, TN, July 2007. 
9. Cunnington, G.R., and Tien, C.L., "Apparent thermal conductivity of uncoated microsphere cryogenic 
insulation," in Advances in Cryogenic Engineering, 22, American Institute of Physics. New York. pp. 263-?, 
(1977). 
10. Kropschot, R.H. and Burgess, R.W., "Perlite for cryogenic insulation," in Advances in Cryogenic Engineering 
8, Plenum, New York, 1963, pp. 425-436. 
11. Rettelbach, Th, Sauberlich, J., Korder, S., and Fricke, J., "Thermal conductivity of IR-opacified silica aerogel 
powders between 10K and 275K" in


Cryogenic Thermal Performance Testing of Bulk-Fill and Aerogel Insulation Materials

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server