Cryogenics Test Laboratory, Thermal Insulation

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area of the Cryogenics Test Laboratory at the NASA. Kennedy ... efficient storage, transfer, and use of cryogens on. Earth and .... Free flowing, fills small cavities.
NanogelTM Advanced Thermal Insulation

CryogenicsTestbed John F. Kennedy Space Center

Cryogenics Test Laboratory, Thermal Insulation Systems Ø Thermal Insulation Systems is a technology focus area of the Cryogenics Test Laboratory at the NASA Kennedy Space Center. Ø Our objective is to develop the materials, the testing technologies, and the engineering for the efficient storage, transfer, and use of cryogens on Earth and in space. Ø Some applications include: Ø Low-Cost High-Efficiency Pipelines for Long Distance Transfer of Cryogens Ø Long-Term Storage of Cryogens on Mars Using Soft Vacuum Insulation System Ø Long Flexible Cryo Pipelines for High-Temperature Superconducting Cables July 2001

CEC/ICMC Madison

energy efficient cryogenics

NanogelTM CryogenicsTestbed

Advanced Thermal Insulation

John F. Kennedy Space Center

Insulation Testing Technologies Ø  Cryostats which use the liquid nitrogen boil-off method are used to measure thermal performance. Ø  Cryostat-1 is a calorimeter apparatus for direct measurement of the apparent thermal conductivity (k-value) of a material system at a fixed vacuum level. The configuration includes a 1 m long cylindrical cold mass with liquid nitrogen guard chambers. The steady-state measurement of the apparent k-value is made when the vacuum level, all temperatures, and the boiloff flow are stable. Ø  Cryostat-2 is a calorimeter apparatus for calibrated measurement of the k-value. The configuration is ½ m long cylindrical with aerogel disks for thermal guards. This apparatus with its removable cold mass allows a quicker testing of different specimens, is convenient for materials screening, and can also be configured for flat plate geometries.

July 2001

CEC/ICMC Madison

NanogelTM CryogenicsTestbed

Advanced Thermal Insulation

John F. Kennedy Space Center

Basic Test Parameters Ø Boundary temperatures: approximately 77 K and 293 K Ø Nominal thickness: 25 mm Ø Cold vacuum pressure (CVP): from 1x10-5 torr to 760 torr Ø Residual gas: nitrogen Ø Materials (thicknesses and densities are as-installed): Ø Aerogel beads 25.4 mm, 81.0 kg/m3. Ø Opacified aerogel beads 25.4 mm, 94.1 kg/m3 (carbon black R300) Ø Perlite powder 25.4 mm, 115 kg/m3 (50 x 50 mesh) Ø Multilayer insulation (MLI) 21.3 mm, 92.0 kg/m3 (foil and paper, 60 layers)

July 2001

CEC/ICMC Madison

NanogelTM Advanced Thermal Insulation

CryogenicsTestbed John F. Kennedy Space Center

Aerogel Beads Production Ø Economical precursor: sodium silicate Ø Bead formation using high throughput spray nozzle Ø High product consistency Ø Narrow bead size distribution Ø Aerogel produced by low cost process Ø Surface sylation of hydrogel Ø Ambient pressure drying

Waterglass July 2001

Sol

Hydrogel

Silation CEC/ICMC Madison

Aerogel

Hydrogel Bead Spraying System Picture Courtesy of Axiva GmbH, Frankfurt Am Main, Germany

NanogelTM Advanced Thermal Insulation

CryogenicsTestbed John F. Kennedy Space Center

Properties of Aerogel Beads 100

Nominal Diameter 1 mm Bead Density 140 kg/m3 Bulk Density 80 kg/m3 Surface Area 650 m2/g Pore Volume 3.17 cm3/g Outgassing (TML) < 1% Flammability non-combustible Minimum ignition temperature 400 oC (hydrophilic available for LOX service)

90 80

mass fraction [ % ]

70

50 40 30 20 10 0 0.1

1 Diameter [ mm ]

0.07

Aerogel bead particle Size distribution Courtesy of Axiva GmbH, Frankfurt Am Main, Germany

0.06 Po re Vo lu me dV /dr (cc /gA)

60

8 % 1 mm beads 0.05 0.04 0.03 0.02 0.01 0 10

100

1000

Place holder plastic bag Beads

Pore Radius (A)

Aerogel bead Pore Size Distribution Courtesy of William Ackerman, Cabot Corp. July 2001

CEC/ICMC Madison

10

NanogelTM Advanced Thermal Insulation

CryogenicsTestbed John F. Kennedy Space Center

Test Results

Aerogel   B eads   as   C ryogenic   T hermal   I nsulation C ryostat   T est   S ummary V ariation   of   A pparent   T hermal   C onductivity   with   C V P

Summary:

Apparent Thermal Conductivity (mW/m-K)

100.0

Ø Aerogel beads gave superior performance for all CVP above 0.1 torr: Ø For example 7.6 mW/m-K at 10 torr versus 27 mW/m-K for perlite Ø The opacifier improved the performance of the aerogel beads for CVP below 10 torr. For example, high vacuum (1x10-4 torr) performance: Ø Aerogel beads, 0.5 mW/m-K. Ø Opacified beads, 0.3 mW/m-K (40 percent better than plain beads)

10.0

1.0

Aerogel Beads Opacified Beads Perlite Powder MLI (60 layers)

0.1 0.0001

0.001

0.01

0.1

1

Cold Vacuum Pressure (torr)

July 2001

10

100

1000

Advantages of Aerogel Beads: Ø Free flowing, fills small cavities Ø Minimal dusting. Ø Non-settling, does not compact Ø No pre-conditioning needed Ø Can be molded or formed using binders CEC/ICMC Madison