Ultra-low temperature composite insulation structure

Abstract

The application discloses a kind of ultra-low temperature composite heat insulation structure. The existing structure uses single metal as reflecting layer, and the heat leakage rate is relatively high, and the leakage is large. The present application includes pearl sand heat insulation layer near the cold end and multilayer heat insulation material structure near the hot end. The multilayer heat insulation material structure is divided into equal-density multilayer low-temperature, medium-low-temperature, medium-temperature, medium-high-temperature and high-temperature multilayer heat insulation material structure according to different temperature zones. The single-layer structure includes spacer layer, heat insulation layer and reflecting layer. The reflecting layers of the three temperature zones are aluminum 1100 metal foil, aluminum 3003 metal foil, aluminum 6061 metal foil and aluminum 5083 metal foil. The present application uses multiple metal foils as reflecting layer in multilayer heat insulation material structure according to the emissivity of different metals, realizes the characteristics that the emissivity of metal foil reflecting layer is very low between 300K and 20K, and further reduces the radiation heat loss, to obtain the effect of lower heat leakage of tank and long-term preservation of low-temperature working medium.

Description

[0001] This application is a divisional application of the invention patent application with application number 202110909233.3, application date August 9, 2021, and invention title "An Ultra-Low Temperature Composite Insulation Structure". Technical Field

[0002] This invention belongs to the field of cryogenic insulation technology, specifically relating to an ultra-low temperature composite insulation structure. Background Technology

[0003] Currently, various industries have an increasing demand for cryogenic liquid gases such as liquid hydrogen (boiling point 20K), liquid nitrogen (boiling point 77K), liquid oxygen (boiling point 90K), and liquefied natural gas (boiling point 110K). Cryogenic liquid gas storage utilizes a multi-layer insulation (MLI) structure within the vacuum insulation structure of cryogenic tank containers. The inner liner of these containers typically stores large quantities of cryogenic liquid hydrogen as a working fluid; a 10-degree gap is usually maintained between the inner and outer liner. -3 The vacuum level is below Pa, while the outer liner of the tank is exposed to room temperature (300K). The inner and outer liners of the tank are insulated using a high-vacuum insulation structure and a multi-layer metal foil insulation film.

[0004] Patent application number 201310185685.7 discloses a multilayer low-temperature insulation structure with variable density configuration. It employs multiple reflective layers divided into three parts along the thickness direction, with the density increasing sequentially from the cold boundary to the hot boundary. Different numbers of spacer materials are filled between adjacent reflective layers in each part. The reflective layers are made of double-layer aluminum-coated polyurethane film, and the spacer materials are P-type paper.

[0005] Patent No. 201811409473.1 discloses a low-temperature, lightweight, low-thermal-conductivity composite insulation structure, comprising a variable-density multilayer insulation component and a foam insulation component bonded together. The variable-density multilayer insulation component, located at the cold end, is used to reduce radiative heat leakage of the composite insulation structure in a vacuum environment. It consists of a low-thermal-conductivity lightweight spacer and a double-sided aluminized polyester film, with the density of the double-sided aluminized polyester film gradually increasing from the cold end to the hot end. The foam insulation component is used to reduce thermal conductivity and heat leakage of the composite insulation structure in an atmospheric pressure environment. The foam insulation component uses polyurethane foam material with hollow glass microspheres doped in the middle.

[0006] Patent application number 201911410741.6 discloses a composite insulation layer comprising a hollow microsphere layer and a multilayer insulation layer. The hollow microsphere layer is located near the cryogenic liquid, while the multilayer insulation layer is located near the external environment. The hollow microsphere layer includes a support and hollow microsphere powder, with the powder filling the interior of the support. The multilayer insulation layer uses a uniform-density multilayer insulation material layer or a variable-density multilayer insulation material layer. The multilayer insulation material layer includes alternating reflective layers and spacer layers. The reflective layer is made of aluminum foil or aluminized polyester film, and the spacer layers are made of polyester mesh, nylon mesh, or glass fiber paper.

[0007] It can be seen that multi-layer cryogenic insulation structures generally employ alternating layers of reflective and spacer layers. The reflective layers are typically made of aluminum foil or aluminized polyester film. This is because multi-layer cryogenic insulation structures must not only meet insulation requirements but also weight requirements in certain applications, such as aerospace. In tanks storing cryogenic liquids (typically 20K-120K), due to the significant temperature difference between the outer tank (300K) and the inner tank (20K), conventional insulation methods use only one type of insulation material to fill the vacuum cavity, resulting in substantial heat leakage and making them unsuitable for long-term storage of cryogenic liquids. Existing multi-layer cryogenic insulation structures often lead to significant leaks during 120-200 days of storage, causing substantial losses. Summary of the Invention

[0008] The purpose of this invention is to provide an ultra-low temperature composite insulation structure, which is composed of various insulation materials of different metal foils arranged in different temperature zones, and can be used for cryogenic liquid insulation storage in ultra-low temperature zones such as liquid hydrogen and liquid helium.

[0009] The present invention includes a pearlescent sand insulation layer near the cold end and a multi-layer insulation material structure near the hot end. The pearlescent sand insulation layer encloses a tank containing a low-temperature liquid working fluid, and the multi-layer insulation material structure encloses the pearlescent sand insulation layer.

[0010] The multilayer thermal insulation material structure, from the cold end to the hot end, includes, in sequence, a low-temperature multilayer thermal insulation material structure, a medium-low temperature multilayer thermal insulation material structure, a medium-temperature multilayer thermal insulation material structure, a medium-high temperature multilayer thermal insulation material structure, and a high-temperature multilayer thermal insulation material structure; the low-temperature multilayer thermal insulation material structure, the medium-low temperature multilayer thermal insulation material structure, the medium-temperature multilayer thermal insulation material structure, the medium-high temperature multilayer thermal insulation material structure, and the high-temperature multilayer thermal insulation material structure are all equal-density multilayer structures.

[0011] The single-layer structure in the aforementioned equal-density multilayer structure includes a spacer layer, a heat insulation layer, and a reflective layer, with the heat insulation layer located between the spacer layer and the reflective layer. The reflective layer of the low-temperature multilayer heat insulation material structure is aluminum 1100 metal foil, the reflective layer of the medium-low temperature multilayer heat insulation material structure is aluminum 3003 metal foil, the reflective layer of the medium-temperature multilayer heat insulation material structure is aluminum 6061 metal foil, the reflective layer of the medium-high temperature multilayer heat insulation material structure is aluminum 5083 metal foil, and the reflective layer of the high-temperature multilayer heat insulation material structure is copper foil.

[0012] The total thickness of the low-temperature multilayer insulation material structure is greater than that of the medium-temperature multilayer insulation material structure, and the layer density of the low-temperature multilayer insulation material structure is less than that of the medium-temperature multilayer insulation material structure. The total thickness of the medium-temperature multilayer insulation material structure is greater than that of the high-temperature multilayer insulation material structure, and the layer density of the medium-temperature multilayer insulation material structure is less than that of the high-temperature multilayer insulation material structure. The layer density of the medium-low temperature multilayer insulation material structure is greater than or equal to that of the low-temperature multilayer insulation material structure, and less than or equal to that of the medium-temperature multilayer insulation material structure. The layer density of the medium-high temperature multilayer insulation material structure is greater than or equal to that of the medium-temperature multilayer insulation material structure, and less than or equal to that of the high-temperature multilayer insulation material structure. Specifically:

[0013] The total thickness of the low-temperature multilayer thermal insulation material structure is 10–25 mm, and the layer density is 0.8–1.0 layers / mm.

[0014] The total thickness of the medium- and low-temperature multilayer thermal insulation material structure is 5–10 mm, and the layer density is 0.9–1.2 layers / mm.

[0015] The total thickness of the medium-temperature multilayer insulation material structure is 5–16 mm, and the layer density is 1.0–1.2 layers / mm.

[0016] The total thickness of the medium- and high-temperature multilayer thermal insulation material structure is 4–10 mm, and the layer density is 1.2–1.5 layers / mm.

[0017] The total thickness of the high-temperature multilayer thermal insulation material structure is 2-10 mm, and the layer density is 1.3-1.5 layers / mm.

[0018] Furthermore, the vacuum level of the vacuum chamber to which the multi-layer thermal insulation material structure belongs is less than or equal to 10. -3 Pa.

[0019] Furthermore, the thickness of the pearlescent sand insulation layer is 20-50 mm.

[0020] Furthermore, the heat insulation layer is P-type paper, N-type paper, or polyester film.

[0021] Furthermore, the spacer layer is a hollow glass microsphere layer. Even further, the layer density of the low-temperature multilayer insulation material structure, the medium-low temperature multilayer insulation material structure, the medium-temperature multilayer insulation material structure, the medium-high temperature multilayer insulation material structure, and the high-temperature multilayer insulation material structure is adjusted by the diameter of the glass microspheres in the hollow glass microsphere layer.

[0022] The core of this invention is based on the emissivity of different metals. The multi-layer thermal insulation material structure uses various metal foils as reflective layers, meaning it employs extremely low emissivity in high-temperature regions. The metal foil reflective layer uses low emissivity in the medium temperature range. The metal foil reflective layer uses a lower emissivity in the low-temperature range. The metal foil reflective layer achieves an emissivity ranging from 300K to 20K. These characteristics result in very low radiative heat loss between 300K and 20K, making them suitable for vacuum super insulation applications. This allows for lower heat loss from the container and long-term preservation of the cryogenic working fluid.

[0023] The present invention proposes various metal foil films with extremely low emissivity The MLI (Multi-Layer Insulation) wrapping method, employing different MLI multi-layer structures in different temperature zones, aims to enhance scientific rigor and practical value based on theoretical and experimental measurements demonstrating the relationship between material emissivity and temperature. Furthermore, given the limitations on heat leakage and weight in spacecraft cryogenic fuel storage tanks, the structure proposed in this patent, using different MLI multi-layer insulation materials in different temperature zones, is more effective in reducing heat leakage from the cryogenic tank while simultaneously saving on overall tank weight. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] Figure 2 for Figure 1 Single-layer thermal insulation material structure;

[0026] Figure 3 Emissivity curves for different metallic materials used as reflective layers in the range of 20-300K;

[0027] Figure 4 Schematic diagram of emissivity at different temperatures in the five-temperature zone embodiment;

[0028] Figure 5 A schematic diagram showing the temperature variation with the number of layers in MLI-encapsulated structures with different metal foils and films;

[0029] Figure 6A schematic diagram showing the variation of emissivity of the intermediate layer in different metal foil / film MLI-encapsulated structures with the number of layers. Detailed Implementation

[0030] like Figure 1 As shown, an ultra-low temperature composite insulation structure includes a pearlescent sand insulation layer I near the cold end and a multi-layer insulation material structure II near the hot end. During use, the cold end temperature is 20K and the hot end temperature is 300K. The pearlescent sand insulation layer I encloses a tank III containing a cryogenic liquid working fluid, and the multi-layer insulation material structure II encloses the pearlescent sand insulation layer I. The thickness of the pearlescent sand insulation layer I is 20–50 mm.

[0031] The multi-layer insulation material structure II includes, in sequence from the cold end to the hot end, low-temperature multi-layer insulation material structure 1, medium-low temperature multi-layer insulation material structure 2, medium-temperature multi-layer insulation material structure 3, medium-high temperature multi-layer insulation material structure 4, and high-temperature multi-layer insulation material structure 5.

[0032] Multi-layer insulation material structures 1, 2, 3, 4, and 5 are all equal-density multi-layer structures. (Examples given: 1) Medium-low temperature multi-layer insulation material structure; 2) Medium temperature multi-layer insulation material structure; 3) Medium-high temperature multi-layer insulation material structure; 4) High temperature multi-layer insulation material structure; 5) are all equal-density multi-layer structures. Figure 2 As shown, its single-layer structure consists of a spacer layer 11, a heat insulation layer 12, and a reflective layer 13, with the heat insulation layer 12 located between the spacer layer 11 and the reflective layer 13.

[0033] Each multilayer insulation material structure has an insulation layer 12 made of P-type paper, N-type paper, or polyester film, and a spacer layer 11 made of hollow glass microspheres. The layer density of each multilayer insulation material structure is adjusted by the diameter of the glass microspheres in the hollow glass microspheres. The reflective layer of the low-temperature multilayer insulation material structure 1 is aluminum 1100 metal foil, the reflective layer of the medium-low temperature multilayer insulation material structure 2 is aluminum 3003 metal foil, the reflective layer of the medium-temperature multilayer insulation material structure 3 is aluminum 6061 metal foil, the reflective layer of the medium-high temperature multilayer insulation material structure 4 is aluminum 5083 metal foil, and the reflective layer of the high-temperature multilayer insulation material structure 5 is copper foil.

[0034] The total thickness of the low-temperature multilayer thermal insulation material structure 1 is 10-25 mm, and the layer density is 0.8-1.0 layers / mm;

[0035] The total thickness of the medium- and low-temperature multilayer thermal insulation material structure 2 is 5–10 mm, and the layer density is 0.9–1.2 layers / mm.

[0036] The total thickness of the medium-temperature multilayer thermal insulation material structure 3 is 5-16 mm, and the layer density is 1.0-1.2 layers / mm.

[0037] The total thickness of the medium- and high-temperature multilayer thermal insulation material structure 4 is 4 to 10 mm, and the layer density is 1.2 to 1.5 layers / mm.

[0038] The total thickness of the high-temperature multilayer thermal insulation material structure 5 is 2-10 mm, and the layer density is 1.3-1.5 layers / mm.

[0039] Different emissivity is used in the vacuum insulation layer inside the cryogenic tank. The calculation method for the interlayer radiative heat transfer of multi-layer insulation materials in a multi-material thermal insulation structure with a metal reflective layer is as follows: In the formula, The Stephan-Boltsman constant is 5.67 × 10⁻⁶. -8 ; For the first Layer and first The average area of ​​radiative heat transfer in the layer, in units of ; and For the first Layer and first The temperature of the layer, in units of ; and For the first Layer and first The emissivity of the layer; Indicates the first A reflective layer of thermal insulation material. A value of 0 indicates the outer wall of the inner cylinder of the cryogenic container. for Indicates the inner wall surface of the outer cylinder of the cryogenic container.

[0040] The emissivity of the metal on the radiation screen is temperature-dependent. To obtain the emissivity of a multilayer thermal insulation radiation screen, the Hagen-Rubens approximation (typically used for radiation wavelengths greater than 5 micrometers) is applied in the 20-300K temperature range. The calculation method is as follows: In the formula, , , It is a temperature-dependent resistivity, and the resistivity of different materials can be obtained by looking up a table.

[0041] Figure 3 The emissivity values ​​for five metallic materials used as reflective layers in the 20-300K range are given. As shown in the figure, to reduce the emissivity of the multilayer insulation material and thus reduce heat loss, a copper foil multilayer insulation structure is used near the 300K temperature range, where the emissivity is... It is 0.001; in the vicinity of 200K temperature range, using a multi-layer insulation material structure with aluminum 5083 metal foil, the emissivity is... The emissivity ε is 0.01. In the 170K temperature range, using a multi-layer insulation material structure with aluminum foil film of material 6061, the emissivity ε is 0.02; in the 140K temperature range, using a multi-layer insulation material structure with aluminum foil film of material 3003, the emissivity ε is 0.022; and in the 28K temperature range, using a multi-layer insulation material structure with aluminum foil film of material 1100, the emissivity ε is 0.04. By using this arrangement of multi-layer insulation materials with different metal foil films in different temperature ranges, the emissivity value of the multi-layer insulation material can be effectively reduced. According to Formula 1, this reduces heat leakage loss from the multi-layer insulation material, allowing for longer storage time in the cryogenic working fluid tank and achieving better economic results.

[0042] The following are specific examples using different multilayer insulation material structures, as well as different thicknesses and layer densities.

[0043] Example 1.

[0044] A 20mm pearlescent sand insulation layer is used. In the multi-layer insulation material structure, the low-temperature multi-layer insulation material structure uses a 20-layer structure (total thickness 25.0mm, layer density 0.8 layers / mm, reflective layer is aluminum 1100 metal foil, total weight 9.86kg), the medium-low temperature multi-layer insulation material structure uses a 9-layer structure (total thickness 10.0mm, layer density 0.9 layers / mm, reflective layer is aluminum 3003 metal foil, total weight 4.37kg), and the medium-temperature multi-layer insulation material structure uses a 16-layer structure (total thickness 16...). The first type of insulation material has a thickness of 0.0 mm, a layer density of 1.0 layers / mm, and an aluminum 6061 foil reflective layer, with a total mass of 7.68 kg. The second type of insulation material has a 12-layer structure (total thickness 10.0 mm, layer density of 1.2 layers / mm, and an aluminum 5083 foil reflective layer, with a total mass of 4.83 kg). The third type of insulation material has a 13-layer structure (total thickness 10 mm, layer density of 1.3 layers / mm, and a copper foil reflective layer, with a total mass of 17.55 kg). The total mass of the reflective layer is 44.29 kg, and the measured total heat loss is 0.37 W.

[0045] Example 2.

[0046] A 20mm pearlescent sand insulation layer is used. In the multi-layer insulation material structure, the low-temperature multi-layer insulation material structure uses an 18-layer structure (total thickness 20.0mm, layer density 0.9 layers / mm, reflective layer is aluminum 1100 metal foil, total weight 8.87kg), the medium-low temperature multi-layer insulation material structure uses a 9-layer structure (total thickness 10.0mm, layer density 0.9 layers / mm, reflective layer is aluminum 3003 metal foil, total weight 4.37kg), and the medium-temperature multi-layer insulation material structure uses an 11-layer structure (total thickness 1... The first type of insulation material has a thickness of 0.0 mm, a layer density of 1.1 layers / mm, and an aluminum 6061 foil reflective layer, with a total mass of 5.28 kg. The second type of insulation material has a 12-layer structure (total thickness 10.0 mm, layer density of 1.2 layers / mm, and an aluminum 5083 foil reflective layer, with a total mass of 4.83 kg). The third type of insulation material has a 7-layer structure (total thickness 5 mm, layer density of 1.4 layers / mm, and a copper foil reflective layer, with a total mass of 9.45 kg). The total mass of the reflective layer is 32.80 kg, and the measured total heat loss is 2.51 W.

[0047] Example 3.

[0048] A 25mm pearlescent sand insulation layer is used. In the multi-layer insulation material structure, the low-temperature multi-layer insulation material structure uses an 18-layer structure (total thickness 20.0mm, layer density 0.9 layers / mm, reflective layer is aluminum 1100 metal foil, total weight 8.87kg), the medium-low temperature multi-layer insulation material structure uses a 7-layer structure (total thickness 7.0mm, layer density 1.0 layer / mm, reflective layer is aluminum 3003 metal foil, total weight 3.40kg), and the medium-temperature multi-layer insulation material structure uses an 11-layer structure (total thickness...). The first type of insulation material has a thickness of 10.0 mm, a layer density of 1.1 layers / mm, and an aluminum 6061 foil reflective layer, with a total mass of 5.28 kg. The second type of insulation material has a thickness of 5 mm, a layer density of 1.4 layers / mm, and an aluminum 5083 foil reflective layer, with a total mass of 3.38 kg. The third type of insulation material has a thickness of 5 mm, a layer density of 1.4 layers / mm, and a copper foil reflective layer, with a total mass of 9.45 kg. The total mass of the reflective layer is 30.38 kg, and the measured total heat loss is 2.96 W.

[0049] Example 4.

[0050] A 25mm pearlescent sand insulation layer is used. In the multi-layer insulation material structure, the low-temperature multi-layer insulation material structure adopts a 10-layer structure (total thickness of 10.0 mm, layer density of 1.0 layer / mm, reflective layer of aluminum 1100 metal foil, total mass of 4.93 kg), the medium-low temperature multi-layer insulation material structure adopts a 7-layer structure (total thickness of 7.0 mm, layer density of 1.0 layer / mm, reflective layer of aluminum 3003 metal foil, total mass of 3.40 kg), the medium-temperature multi-layer insulation material structure adopts a 6-layer structure (total thickness of 5.0 mm, layer density of 1.2 layer / mm, reflective layer of aluminum 6061 metal foil, total mass of 2.88 kg), the medium-high temperature multi-layer insulation material structure adopts a 7-layer structure (total thickness of 5.0 mm, layer density of 1.4 layer / mm, reflective layer of aluminum 5083 metal foil, total mass of 3.38 kg), and the high-temperature multi-layer insulation material structure adopts a 3-layer structure (total thickness of 2 mm, layer density of 1.5 layer / mm, reflective layer of copper foil, total mass of 4.05 kg). The total mass of the reflective layer is 18.64 kg, and the measured total heat loss is 7.59 W.

[0051] Example 5.

[0052] A 35mm pearlescent sand insulation layer is used. In the multi-layer insulation material structure, the low-temperature multi-layer insulation material structure adopts a 10-layer structure (total thickness of 10.0 mm, layer density of 1.0 layers / mm, reflective layer of aluminum 1100 metal foil, total mass of 4.93 kg), the medium-low temperature multi-layer insulation material structure adopts a 6-layer structure (total thickness of 5.0 mm, layer density of 1.2 layers / mm, reflective layer of aluminum 3003 metal foil, total mass of 2.92 kg), the medium-temperature multi-layer insulation material structure adopts a 6-layer structure (total thickness of 5.0 mm, layer density of 1.2 layers / mm, reflective layer of aluminum 6061 metal foil, total mass of 2.88 kg), the medium-high temperature multi-layer insulation material structure adopts a 6-layer structure (total thickness of 4.0 mm, layer density of 1.5 layers / mm, reflective layer of aluminum 5083 metal foil, total mass of 2.90 kg), and the high-temperature multi-layer insulation material structure adopts a 3-layer structure (total thickness of 2 mm, layer density of 1.5 layers / mm, reflective layer of copper foil, total mass of 4.05 kg). The total mass of the reflective layer is 17.68 kg, and the measured total heat loss is 8.11 W.

[0053] like Figure 4 As shown, the emissivity values ​​of five layers of metal foil films made of different materials (aluminum 1100, aluminum 3003, aluminum 6061, aluminum 5093, and copper) at different temperatures are illustrated in Example 5. Figure 4The data shows that the emissivity of aluminum 1100 remains between 0.03 and 0.04 in the low-temperature range; the emissivity of aluminum 3003 remains around 0.02 in the medium-low temperature range; the emissivity of aluminum 6061 also remains around 0.02 in the medium-temperature range; the emissivity of aluminum 5083 remains around 0.015 in the medium-high temperature range; and the emissivity of the copper foil coating remains around 0.002 in the high-temperature range. This rational arrangement minimizes the emissivity of the MLI multilayer insulation material, thereby reducing overall radiative heat loss, while ensuring that the overall weight of the insulation material meets practical application requirements.

[0054] Figure 5 This figure shows the temperature variation with the number of layers in different metal foil film MLI wrapping structures. The solid line represents temperatures from 77K to 300K, with all layers wrapped in aluminum 1100 metal foil film MLI. The dashed line represents temperatures between 77K and 180K, with aluminum 1100 MLI wrapping, and between 180K and 300K, with aluminum 6061 MLI wrapping. The dotted line represents temperatures between 77K and 120K, with aluminum 1100 MLI wrapping, between 120K and 160K, with aluminum 6061 MLI wrapping, and between 160K and 300K, with copper MLI wrapping. Calculations show that the heat loss of the structure using aluminum 1100 + aluminum 6061 + copper is 1.836W; the heat loss of the structure using only aluminum 1100 and aluminum 6061 is 5.45W; and the heat loss of the multilayer insulation material structure using aluminum 1100 metal foil as the reflective layer is 11.16W. It is evident that, at the same thickness, the heat leakage of the MLI structure using aluminum 1100 + aluminum 6061 + copper is only 16.5% of that of the MLI structure consisting entirely of aluminum 1100. Therefore, this structure represents an improvement over MLI multilayer insulation material technology.

[0055] Figure 6The figure shows the emissivity of the intermediate layer in different metal foil film MLI wrapping structures as a function of the number of layers. As can be seen from the figure, the solid line represents the temperature range from 77K to 300K. When all layers are wrapped with aluminum 1100 metal foil film MLI, the emissivity increases across the entire temperature range from 0.018 at 77K to 0.032 at 300K, an increase of 77%. The dashed line represents the temperature range of 77K-200K when aluminum 1100 MLI is wrapped, where the emissivity increases from 0.018 at 77K to 0.024; subsequently, when aluminum 6061 MLI is wrapped between 200K and 300K, the emissivity decreases from 0.024 to 0.012, a decrease of 100%. The dotted lines represent the following: Between 77K and 140K, the emissivity increases from 0.018 at 77K to 0.022 when encased in an aluminum 1100MLI structure; between 140K and 170K, the emissivity decreases from 0.022 to 0.01, a reduction of 110%; and between 140K and 300K, the emissivity decreases from 0.01 to 0.001, a reduction of 1000%. This is the fundamental reason for the significant changes in heat leakage across these three different structures.

Claims

1. A cryogenic composite insulation structure, comprising a perlite insulation layer near the cold end and a multi-layer insulation material structure near the hot end, wherein the perlite insulation layer encloses a tank containing a cryogenic liquid working fluid, and the multi-layer insulation material structure encloses the perlite insulation layer, characterized in that: The multilayer thermal insulation material structure, from the cold end to the hot end, sequentially includes a low-temperature multilayer thermal insulation material structure, a medium-low temperature multilayer thermal insulation material structure, a medium-temperature multilayer thermal insulation material structure, a medium-high temperature multilayer thermal insulation material structure, and a high-temperature multilayer thermal insulation material structure; the low-temperature multilayer thermal insulation material structure, the medium-low temperature multilayer thermal insulation material structure, the medium-temperature multilayer thermal insulation material structure, the medium-high temperature multilayer thermal insulation material structure, and the high-temperature multilayer thermal insulation material structure are all equal-density multilayer structures; The single-layer structure in the aforementioned equal-density multilayer structure includes a spacer layer, a heat insulation layer, and a reflective layer, with the heat insulation layer located between the spacer layer and the reflective layer; the reflective layer of the low-temperature multilayer heat insulation material structure is aluminum 1100 metal foil, the reflective layer of the medium-low temperature multilayer heat insulation material structure is aluminum 3003 metal foil, the reflective layer of the medium-temperature multilayer heat insulation material structure is aluminum 6061 metal foil, the reflective layer of the medium-high temperature multilayer heat insulation material structure is aluminum 5083 metal foil, and the reflective layer of the high-temperature multilayer heat insulation material structure is copper foil. The total thickness of the low-temperature multilayer insulation material structure is greater than that of the medium-temperature multilayer insulation material structure, and the layer density of the low-temperature multilayer insulation material structure is less than that of the medium-temperature multilayer insulation material structure; the total thickness of the medium-temperature multilayer insulation material structure is greater than that of the high-temperature multilayer insulation material structure, and the layer density of the medium-temperature multilayer insulation material structure is less than that of the high-temperature multilayer insulation material structure; the layer density of the medium-low temperature multilayer insulation material structure is greater than or equal to that of the low-temperature multilayer insulation material structure, and less than or equal to that of the medium-temperature multilayer insulation material structure; the layer density of the medium-high temperature multilayer insulation material structure is greater than or equal to that of the medium-temperature multilayer insulation material structure, and less than or equal to that of the high-temperature multilayer insulation material structure; specifically: The total thickness of the low-temperature multilayer thermal insulation material structure is 10–25 mm, and the layer density is 0.8–1.0 layers / mm. The total thickness of the medium- and low-temperature multilayer thermal insulation material structure is 5–10 mm, and the layer density is 0.9–1.2 layers / mm. The total thickness of the medium-temperature multilayer insulation material structure is 5–16 mm, and the layer density is 1.0–1.2 layers / mm. The total thickness of the medium- and high-temperature multilayer thermal insulation material structure is 4–10 mm, and the layer density is 1.2–1.5 layers / mm. The total thickness of the high-temperature multilayer thermal insulation material structure is 2-10 mm, and the layer density is 1.3-1.5 layers / mm.

2. An ultra-low temperature multilayer insulation structure according to claim 1, wherein: The vacuum degree of the vacuum cover to which the multi-layer thermal insulation material structure belongs is less than or equal to 10 -3 Pa.

3. An ultra-low temperature multilayer insulation structure according to claim 1, wherein: The thickness of the pearlescent sand insulation layer is 20-50 mm.

4. An ultra-low temperature multilayer insulation structure according to claim 1, wherein: The heat insulation layer is P-type paper, N-type paper, or polyester film.

5. An ultra-low temperature multilayer insulation structure as in claim 1, wherein: The spacer layer is a hollow glass microsphere layer.

6. An ultra-low temperature multilayer insulation structure according to claim 5, wherein: The layer density of the low-temperature multilayer insulation material structure, the medium-low temperature multilayer insulation material structure, the medium-temperature multilayer insulation material structure, the medium-high temperature multilayer insulation material structure, and the high-temperature multilayer insulation material structure can be adjusted by the diameter of the glass microspheres in the hollow glass microsphere layer.

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