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Description
Bulk insulation materials such as expanded perlite are widely used in double-walled cryogenic insulation systems and well known to the industry. However, expanded perlite is also known to be very fragile. Mechanical stress e.g. due to thermal cycling or vibrations can result in material degradation over time and limit its application.
In contrast, hollow glass microspheres which are engineered and well-defined bulk insulation materials are reported to not only exceed the thermal insulation performance of perlite but also stand out with their higher robustness. In the field application of a spherical liquid hydrogen tank 3M’s K1 Glass Bubbles have been shown to reduce LH2 boil-off by 46% versus perlite with no decline of the insulation performance over three full thermal cycles within six years.
Emerging applications for storage and transport of liquid hydrogen and other cryogenic liquids require more and more strong and robust insulation materials.
This paper presents a lab study on the uniaxial compression behavior of hollow glass microspheres (3M Glass Bubbles) comparing it to commercial cryo-insulation grade expanded perlite.
Stress-compression data of bulk hollow glass microspheres was generated in a proprietary test setup and correlated with true density measured in a gas pycnometer. Consequently, the macroscopic uniaxial compression data can be interpreted with respect to mechanical damage of the Glass Bubbles on the microscopic scale. This allows engineers to assess if the respective insulation material meets their requirements. The paper presents the stress-compression behavior of various commercial grades highlighting the potential to also serve demanding applications.
A cyclic testing mode was implemented allowing the simulation of application conditions such as thermal cycling. Data shows that the Glass Bubbles remain undamaged even after undergoing a 1000x cycle test if the maximum stress is appropriately chosen. This information can help to select suitable Glass Bubbles grades based on anticipated stresses or dimensional changes.
To put the data on hollow glass microspheres into perspective, commercially available cryo-insulation grade perlite was analyzed in the same setup for comparison.
| Submitters Country | Germany |
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