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
