Multi-layer insulation system with dimpled spacer layer

Abstract

A multi-layer insulation (MLI) that provides improved loft and has lower layer density compared to conventional MLIs. The MLI includes a metallized layer and a spacer layer. The spacer layer comprises a plurality of dimples formed therein. By forming the spacer layer with dimples, the MLI is provided with a higher loft and a lower layer density.

Description

MULTI-LAYER INSULATION SYSTEM WITH DIMPLED SPACER LAYERRelated Application

[0001] This application claims priority to U.S. Provisional Application No. 63 / 573756, filed April 3, 2024, the disclosure of which is incorporated herein by reference.Field

[0002] This technical disclosure relates to a multi-layer insulation (MLI).Summary

[0003] A MLI is described that provides improved loft and has lower layer density compared to conventional MLIs. The MLIs described herein include at least one metallized layer and a spacer layer, and preferably a plurality of metallized layers and a plurality of spacer layers. Each spacer layer comprises a plurality of dimples formed therein. Applicant has discovered that by forming the spacer layer with dimples the MLI is provided with a higher loft and a lower layer density compared to a standard MLI.

[0004] In one embodiment, an MLI spacer layer that is used in combination with a metallized layer comprises a plurality of dimples formed therein. In another embodiment, an MLI is described that has at least one metallized layer and a spacer layer is disposed facing a first surface of the metallized layer, and the spacer layer comprises a plurality of dimples formed therein.

[0005] In another embodiment, an MLI includes a plurality of metallized layers arranged into a stack with a plurality of spacer layers. Each spacer layer includes a plurality of dimples formed therein, and the layers are arranged whereby one of the metallized layers forms an outermost layer of the stack and one of the spacer layers forms an innermost layer of the stack.

[0006] The MLIs described herein can be used to insulate any product or equipment in a vacuum, whether in outer space or a man made vacuum device, needing insulation. In one application, the MLIs described herein can be used with a cryogenic tank, for example in an evacuated space of the cryogenic tank that is formed between an inner wall and an outer wall. In another embodiment, the MLIs described herein can be wrapped around a first pipeconveying a fluid to insulate the first pipe, with the wrapped first pipe surrounded by a second pipe with a vacuum between the first pipe and the second pipe.Drawings

[0007] Figure 1 illustrates an example MLI with a plurality of layers arranged into a stack.

[0008] Figure 2 illustrates another example of an MLI having a single pair of layers.

[0009] Figure 3 illustrates an example of a cryogenic tank that uses the MLI of Figure 1.

[0010] Figure 4 illustrates an example of a pipe that can use the MLI of Figure 1 or Figure 2.Detailed Description

[0011] Referring to Figure 1, a first embodiment of an MLI 10 is depicted. The MLI 10 is formed by a plurality of metallized layers 14 alternating with a plurality of spacer layers 16. The layers 14, 16 are arranged into a stack as depicted in Figure 1. Preferably, the stack consists of, or consists essentially of, the metallized layers 14 and the spacer layers 16. However, in another embodiment, the stack can include one or more additional layers and / or include material, such as filler material that fills gaps between the metallized layers 14 and the spacer layers 16. The thicknesses of the layers 14, 16, the relative thicknesses of the layers 14, 16 to one another, are exaggerated in order to better illustrate the concepts herein.

[0012] In MLI, when referring to MLI layers, the convention is that this is in reference to the metallized layers only. So as used herein, an MLI layer refers to the metallized layer, and a plurality of MLI layers refers to a plurality of the metallized layers. Also, a layer pair, a pair of layers, or an MLI pair refers to the metallized layer 14 and the spacer layer 16. An MLI as described herein includes at least one layer pair, and in the embodiment illustrated in Figure 1 includes ten layer pairs.

[0013] The illustrated example depicts a total of ten of the metallized layers 14 and ten of the spacer layers 16. However, a smaller or larger number of the metallized layers 14 and of the spacer layers 16 can be provided. For example, referring to Figure 2, an example of an MLI(or MLI pair) 12 is depicted that has a single one of the metallized layers 14 and a single spacer layer 16.

[0014] Returning to Figure 1, each one of the metallized layers 14 comprises a film that is configured to reflect energy. In one embodiment, each metallized layer 14 can comprise a metallized film. Each metallized layer 14 typically has a thickness of about 0.25 to about 0.5 mil. The metallized layers 14 can be formed of any type of material used for forming metallized layers in an MLI including, but not limited to, polyethylene terephthalate (PET) or polyimide (PI). However, other metallized layers 14 are possible. Each metallized layer 14 can be generally flat and planar.

[0015] Each spacer layer 16 is formed with a plurality of dimples or embossments 20 which help to create insulation gaps between each metallized layer 14. The dimples 20 also act like resilient springs to help return the MLI 10 to an original shape if the MLI 10 is deformed or bent. Each spacer layer 16 can be formed from a material that is suitable for performing the function(s) of the spacer layer 16 described herein. For example, in one embodiment, each spacer layer can be formed from polyester spunbonded nonwoven fabric. In an embodiment, the spacer layers 16 can have a fabric weight of about 0.3 to about 0.6 oz / yd2. In one embodiment, the dimples 20 can be formed in the spacer layers 16 using a dimple pattern that forms dimples with a density of 1024 dimples / ft2with a profile height of about 1.5 mm up to about 3.0 mm. The dimples 20 give the spacer layer(s) 16 a generally sinusoidal appearance when viewed from the side like shown in Figures 1 and 2, with a plurality of peaks 24 and valleys 26. In an embodiment, the dimples 20 extend over the entire surface area of the spacer layer 16. However, the dimples 20 can be located at select locations on the spacer layer 16 (i.e. the dimples can occupy less than the entire surface area of the spacer layer 16). In the MLI 10, the layer pairs are arranged whereby one of the metallized layers 14 forms an outermost layer of the stack and one of the spacer layers 16 forms an innermost layer of the stack.

[0016] In an embodiment, the metallized layer 14 and the spacer layer 16 are not adhered or fused to one another. In addition, each pair of the layers 14, 16 is not adhered or fused to an adjacent pair of the layers 14, 16. However, the stack formed by the layers 14, 16 can be held together using one or more mechanical fasteners 22 (depicted in broken lines in Figure 1). The mechanical fastener(s) 22 can have any configuration that is suitable for holding the layers 14,16 together. For example, the fastener(s) 22 can comprise one or more t-tags. Similar mechanical fasteners 22 can be used in the MLI of Figure 2 to secure the layers 14, 16 to one another. In another embodiment, the metallized layer 14 and the spacer layer 16 in each pair may be adhered or fused to one another, for example at the peaks of the dimples 20.

[0017] The resulting MLI 10 (and the MLI 12) is flexible allowing it to conform to a structure during use. In addition, the MLI 10 has a higher loft and a lower layer density compared to conventional MLIs. For example, in one embodiment, the MLI 10 has a total loft of about 1.1 cm or more, or a loft of about 0.11 cm per layer pair (i.e. per pair of the metallized layer 14 and the spacer layer 16) and a layer density of about 9 layers / cm or less.

[0018] Figure 3 illustrates an example application of the MLI 10 of Figure 1 wrapped around a pipe or tank with ends of the MLI butted to each other at a seam 28. The resulting seam 28 between the butted ends can be closed using methods standard to MLI fabrication. Other applications are possible. In this example, the MLI 10 is used in a cryogenic application to insulate a cryogenic tank 30 in order to minimize heat transfer. The cryogenic tank 30 includes an inner tank 32 and an outer tank 34 defining a space 36 therebetween. The inner tank 32 can be made of metal, such as stainless steel, and the outer tank 34 can also be made of metal, such as carbon steel. The tank 30, including the inner tank 32 and the outer tank 34, can have any shape that is suitable for containing a liquid cryogen such as spherical, cylindrical, and the like.

[0019] The inner tank 32 defines an interior space 38 that contains a liquid cryogen, such as liquid oxygen, liquid nitrogen, liquid helium, liquid hydrogen, and the like. The tank 30 will include an inlet (not shown) for introducing the cryogen into the interior space 38, and an outlet (not shown) for discharging the cryogen from the interior space 38.

[0020] The space 36 is evacuated so that the space 36 is at vacuum pressure. The MLI 10 is disposed in the space 36 surrounding the inner tank 32 and substantially or entirely fills the space 36. In another embodiment, the MLI 10 only partially fills the space 36. The inner tank 32 is formed by a wall that has an exterior facing surface, and the MLI 10 is disposed so that the innermost spacer layer 16 is disposed between the innermost metallized layer 14 and the exterior facing surface. In particular, the MLI 10 is arranged so that the innermost spacer layer 16 of the stack faces the exterior facing surface, and the outermost metallized layer 14 of thestack faces an interior facing surface of the wall of the outer tank 34. The mechanical fasteners 22 described above in Figure 1 may or may not be present when the MLI 10 is in use in the cryogenic tank 30.

[0021] In another embodiment, the interior space 38 may contain a fluid, such as a gas or a liquid, at a high temperature, and the MLI 10 in the space 36, which is at vacuum pressure, insulates the tank 30 in order to minimize loss of heat from the fluid in the interior space 38.

[0022] Figure 4 illustrates an example application of the MLI 12 of Figure 2 spiral wrapped around an inner wall of a pipe or tank. In this example, the MLI 12 is used in a space at vacuum pressure between an inner pipe 40 and an outer pipe 44 surrounding the inner pipe 40 as an insulation wrap around the pipe 40 to minimize heat transfer from the pipe 40. The pipe 40 defines an interior space 42 in which a gas or a liquid may be disposed. The gas or liquid may be refrigerated, such as a cryogen, or a heated fluid at an elevated temperature. For example, in one embodiment, the pipe 40 may carry a superconducting cable in the interior space 42 and a cryogen in the interior space 42 is used to keep the superconducting cable as cold as possible.

[0023] The MLI 12 is disposed in the space between the inner pipe 40 and the outer pipe 44 around the exterior facing surface of the wall of the pipe 40 so that the spacer layer 16 is disposed between the metallized layer 14 and the exterior facing surface. The metallized layer 14 is close to and / or in contact with the inner facing surface of the outer pipe 44. The mechanical fasteners 22 described above in Figure 1 may or may not be present when the MLI 12 is in use. The example application in Figure 4 depicts the MLI 12 as being spiral wrapped five times around the pipe 40. However, a larger or small number of spiral wraps can be used. In addition, the MLI 12 can have multiple pairs of the layers 14, 16 like the MLI 10 in Figure 1.

[0024] The examples disclosed in this application are to be considered in all respects as illustrative and not limitative. The scope of the invention is indicated by the appended claims rather than by the foregoing description; and all changes which come within the meaning and range of equivalency of the claims are intended to be embraced therein.

Claims

CLAIMS1. A multi-layer insulation comprising: at least one metallized layer having a first surface and a second surface, and a spacer layer; the spacer layer is disposed facing the first surface of the metallized layer, and the spacer layer comprises a plurality of dimples formed therein.

2. The multi-layer insulation of claim 1, comprising a plurality of pairs of the metallized layer and the spacer layer.

3. The multi-layer insulation of claim 1, comprising ten pairs of the metallized layer and the spacer layer.

4. The multi-layer insulation of claim 1, wherein the metallized layer and the spacer layer are not fused or adhered to one another.

5. The multi-layer insulation of claim 2, comprising at least one mechanical fastener that holds the plurality of pairs of the metallized layer and the spacer layer together.

6. The multi-layer insulation of claim 1, wherein the spacer sub-layer comprises a polyester spunbonded nonwoven fabric.

7. The multi-layer insulation of claim 2, wherein the multi-layer insulation has a loft of at least 1.1 cm.

8. The multi-layer insulation of claim 2, wherein the multi-layer insulation has a layer density that is 9 layers / cm or less.

9. A product having a first wall that defines an interior space, the first wall having an exterior facing surface; a second wall spaced from the first wall to define a space therebetween, the space is at vacuum pressure; and the multi-layer insulation of claim 1 disposed in the space.

10. The product of claim 9, wherein the interior space contains a cryogen.

11. The product of claim 9, wherein the product comprises a pipe or a cryogenic tank.

12. A multi-layer insulation comprising: a plurality of layer pairs arranged into a stack, each layer pair consisting of a metallized layer and a spacer layer, each spacer layer includes a plurality of dimples formed therein, and the layer pairs are arranged whereby one of the metallized layers forms an outermost layer of the stack and one of the spacer layers forms an innermost layer of the stack.

13. The multi-layer insulation of claim 12, wherein the stack comprises ten of the layer pairs.

14. The multi-layer insulation of claim 12, wherein in each layer pair, the metallized layer and the spacer layer are not fused or adhered to one another.

15. The multi-layer insulation of claim 12, comprising at least one mechanical fastener that holds the plurality of layer pairs together.

16. The multi-layer insulation of claim 12, wherein each spacer layer comprises polyester spunbonded nonwoven fabric.

17. The multi-layer insulation of claim 12, wherein the multi-layer insulation has a loft of at least 0.11 cm per layer pair.

18. The multi-layer insulation of claim 12, wherein the multi-layer insulation has a layer density that is 9 layers / cm or less.

19. A product having a first wall that defines an interior space, the first wall having an exterior facing surface; a second wall spaced from the first wall to define a space therebetween, the space is at vacuum pressure; and the stack of claim 12 disposed in the space.

20. The product of claim 19, wherein the interior space contains a cryogen.

21. The product of claim 19, wherein the product comprises a pipe or a cryogenic tank.

Images