Variable density multilayer insulation for cryogenic storage

Abstract

Two analytical models for a foam/Variable Density Multi-Layer Insulation (VD-MLI) system performance are discussed.

Cryogenic hydrogen fuel tanks for large hypersonic cruise vehicles

“…Recently, the concept of variable density MLI (VD-MLI), where two distinct layers of MLI with a different layer density are combined, has been introduced [52,53,61e63] and it has been shown that the lowest possible foil spacing at the hottest boundary results in the best design [62,63]. Compared to the classical single density MLI configuration, VD-MLI can lead to a boil-off reduction of 58%, or a weight saving of 41% for the same boil-off amount [52,53]. To minimize the heat leakage into the tank, another insulation technique has been used by combining MLI and a vapor-cooled shield (VCS) [64,65].…”

“…However, for a given installation method, the choice of radiative blanket and spacer material also has a considerable influence on the thermal performance of the MLI. The thin radiation shields are usually made of plastic film (Mylar or Kapton) coated on one or both sides with a thin layer of high reflectance metal, such as aluminium or gold (thickness of about 500 Å [50,52,53]), while polyester, glass fiber paper, nylon netting or silk tissue is often used for the spacer material [50,53e55]. The combination of spacers and screens minimizes the main modes of heat transfer, i.e.…”

Heat radiation reduction in cryostats with multilayer insulation technique

“…Furthermore, a large number of radiation shield means increase of material and assembly costs in the experiment. It follows that the layer density must be optimized [18,32]. This optimization can be performed by varying the distance between layers and adjusting the number of layers within a fixed thickness of the insulation blanket.…”

Improving MRI magnet thermal performance using variable density multilayer insulation

“…Such MLI systems are used in storage of high value cryogens and thus tend to be custom made in small quantities without concern for repeatability and mass production in an industrial environment. Nevertheless, the studies show significant benefit of using variable density insulation [2,3,7].…”

“…The amount of literature available on variable density MLI is limited [1,4,6], however there is increasing interest in using it in space vehicle support systems [2,3,7]. Such MLI systems are used in storage of high value cryogens and thus tend to be custom made in small quantities without concern for repeatability and mass production in an industrial environment.…”