Optimization of Layer Densities for Multilayered Insulation Systems

Abstract

Numerous tests of various multilayer insulation systems have indicated that there are optimal densities for these systems. However, the only method of calculating this optimal density was by a complex physics based algorithm developed by McIntosh. In the much data were collected on the performance of these insulation systems with many different variables analyzed. All formulas generated included number of layers and layer density as geometric variables in solving for the heat flux, none of them was in a differentiable form for a single geometric variable. It was recently discovered that by equations became functions of layer density, temperatures, and material properties only. The thickness and number of layers of the blanket were merged into a layer density. These equations were then differentiated with respect to layer density. By setting the first derivative equal to zero, and solving for the layer density, the critical layer density was determined. This method was checked and validated using test data from the Multipurpose

Evaluating cryostat performance for naval applications

“…This was unexpected when comparing to historical evidence [3]. However, this result could be explained by the data showing that the higher density system obtained a lower vacuum pressure and knowing that MLI system performance is highly sensitive to residual gas pressure.…”

“…FIGURE 2 shows a schematic cross-section of the end fitting. All weld joints were tested to ensure a helium leak rate of less than 1x10 -8 standard cm 3 /sec. The vacuum jackets were baked out at 373 K with intermittent heating and pumped to a warm vacuum pressure of less than 1 millitorr.…”

Heat radiation reduction in the cryostat with multilayer insulation technique

“…(3.2), the radiation heat load remains invariant for a constant value of N. It follows that there must be an equilibrium between the radiation and conduction heat loads. This equilibrium point would represent the optimal N where the total heat load is minimum for that material [2,18]. We have calculated the optimal N for the selected perforated DAM with Glass−tissue, perforated DAM with Dacron, as well as unperforated DAM with the Silk−net radiation shield and spacer materials for a reference N = 40.…”

“…These broad fields of applications reveal the enthusiasm of the scientists working in this field worldwide. There are ample cryogenic thermal research works being performed after the first experimental test on MLI by Sir James Dewar in 1900 when he tested with three layers of Aluminum foil (current form of MLI with layered radiation shield system was described firstly by William D. Cornell in the late 1940s) [18,19]. The design, analysis, and testing of a given MLI system depend on the nature and requirements of the specific application.…”

Improving MRI magnet thermal performance using variable density multilayer insulation

“…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.…”