Ambient air insulation systems for low-temperature (sub-ambient) applications are difficult to achieve because of moisture ingress and environmental degradation, as well as thermal stress-cracking. Most currently accepted methods for externally applied outdoor environments are fraught with problems centered around moisture and sealing.
The novel thermal insulation system described here is based on a layered composite approach following, in part, prior development of the layered composite insulation (LCI) system for high vacuum or soft vacuum applications and other materials research and development of the last 10 years.
The key distinguishing feature for the new LCI system for extreme outdoor environments (LCI-EX) is the ambient air exposure and lack of requirement for a sealed outer envelope (i.e., no vacuum jacket is required). This configuration difference makes the LCI-EX technology novel and unique, although related in principle to the prior LCI technology. The system can be adapted to a wide range of needs. The common elements are a primary insulation layer, a radiant barrier layer, and an overwrap layer. The materials should be hydrophobic in nature. The overwrap is optional, depending on system longevity requirements, and/or appearances and protection from UV radiation degradation.
The system works using two basic components: a primary insulation blanket and a compression blanket. The primary blanket is preferably hydrophobic, such as an aerogel composite blanket, but can be any suitable flexible insulation material, such as polymeric foam. The primary blanket goes onto the cold inner surface of the tank or piping, or other cold process object. One or more layers can be applied to comprise the first insulation stack as per the heat leak design requirements. The compression blanket then goes onto the primary blanket and so forth to create a blanket stack. The compression layer is also an insulating layer, but primarily selected to offer the mechanical compliance, compressibility, and placement to enable a good fit of the primary insulation layers with optimal closure of seams and gaps. This layer is preferably a polymeric air-sealed material. The compression layers also include the radiant barrier facings (aluminized plastic film or aluminum foil) in a combined and integrated layer. The outermost compression layer can incorporate an aluminum foil layer for further utilization to conform to complex shapes or to close out the blanket stack around a flange, port, or other component. The LCI-EX system can be field applied or pre-fabricated per specifications for piping, tanks, or flat panels.
This work was done by James Fesmire of the John F. Kennedy Space Center. For more information, contact the Kennedy Space Center Technology Transfer Office at 321-867-5033. KSC-13777