Modular Cryogenic Insulation

"Modular cryogenic insulation" denotes a chaff for installation in the partially evacuated annular spaces between the inner and outer walls of tanks used to store and transport liquid nitrogen and other cryogenic liquids. The insulating chaff was developed to replace low-density powders (e.g., perlite, silica aerogel, carbon black, or diatomaceous earth) that have been used to insulate cryogenic tanks. Thermal cycling of a tank causes some of the powder to fall to the bottom of the annular space; over time, the powder accumulates in the bottom and becomes compacted there, with consequent loss of thermal-insulation performance. In addition, the compaction generates stresses that can damage the tank. The chaff was selected from among several candidate materials that were investigated to find one that would not settle with thermal cycling, would be readily manufacturable, would offer the requisite thermal-insulation performance, would thermally expand and contract along with the tank walls, and could be installed easily.