Cooling structure surface-treated and cooling method of cryogenic system using the same

Abstract

The present invention provides a pattern layer in which at least two materials with different thermal conductivity are alternately arranged on the inner surface of a fluid receiving portion to form a pattern. When a liquid low-temperature or cryogenic fluid is injected into the fluid receiving portion for pre-cooling, the fluid undergoes a phase change to a gaseous state on the inner surface of the fluid receiving portion that has high thermal conductivity, while the fluid remains in a liquid state on the inner surface that has relatively low thermal conductivity. This induces contact of the liquid with the surface during the pre-cooling process, thereby enabling a faster transition from gas film boiling to transition boiling, and thus the cooling efficiency can be further improved. Additionally, by forming a pattern layer by coating the inner surface of a fluid receiving portion formed of metal with Teflon, which has lower thermal conductivity than metal, the structure is simple and easy to manufacture, while effectively improving cooling efficiency.

Description

Technology Field

[0001] The present invention relates to a cooling structure with a surface-treated inner surface and a cooling method for a cryogenic system utilizing the same, wherein a portion of the inner surface of a fluid receiving portion is formed as a pattern layer made of a low thermal conductivity material, thereby further improving cooling efficiency during pre-cooling of the fluid receiving portion, and a cooling method for a cryogenic system utilizing the same. Background Technology

[0002] Recently, the use of cryogenic fluids has been increasing in various fields; specifically, the use of liquid oxygen as an oxidizer is increasing in the aerospace sector, and the use of hydrogen energy as a new energy source is increasing in the energy sector. Since cryogenic fluids must be stored and transported while maintaining a liquid state to reduce volume per unit mass, a cryogenic system is required for this purpose.

[0003] A cryogenic system is a general term for a system designed to generate, maintain, and control cryogenic conditions. Its interior is constructed with metal walls of sufficient strength to withstand extreme temperature changes and pressures. During normal operation, a cryogenic system requires a pre-cooling process. This pre-cooling process involves injecting a cryogenic fluid into a tank at ambient temperature and cooling it sufficiently to ensure the fluid remains in a liquid state. During this pre-cooling process, the cryogenic fluid passes through the vapor film boiling, transition boiling, and nucleation boiling regions. Specifically, when a liquid cryogenic fluid is injected into a tank at ambient temperature, a phase change occurs instantaneously, causing the internal surface to be covered by a vapor film; this is referred to as the vapor film boiling region. In this region, heat transfer efficiency is low because a gas with low thermal conductivity is in contact with the surface, which prevents the metal surface from cooling rapidly. When the internal surface temperature in the aforementioned gas film boiling region is sufficiently lowered, the process transitions to a transition boiling region, where both gas and liquid films coexist on the surface and exhibit higher cooling efficiency. In this transition boiling region, direct contact occurs between the liquid, which has high heat transfer efficiency, and the metal surface, thereby cooling the surface and resulting in heat transfer with higher efficiency than in the gas film boiling region. Subsequently, the process transitions to the nucleation boiling region.

[0004] Conventional cryogenic systems suffer from the problem of prolonged total cooling time and very low cooling efficiency because they remain in the gas film boiling region, where cooling efficiency is very low, for most of the initial cooling period. Therefore, a technology is required to shorten the cooling time by rapidly transitioning from the gas film boiling region to the transition boiling region during the initial cooling phase. Prior art literature

[0005] Republic of Korea Registered Patent No. 10-2430334 The problem to be solved

[0006] The objective of the present invention is to provide a cooling structure with a surface-treated inner surface capable of further improving cooling efficiency during pre-cooling of a fluid receiving portion, and a cooling method for a cryogenic system utilizing the same. means of solving the problem

[0007] A cooling structure surface-treated with a low thermal conductivity material according to the present invention comprises: a fluid receiving portion in which an inner surface contacts a liquid low-temperature or cryogenic fluid in which boiling heat transfer occurs; and a pattern layer provided on at least a portion of the inner surface of the fluid receiving portion and formed in a pattern in which materials having different thermal conductivity are alternately arranged on the inner surface.

[0008] The pattern layer comprises: a first pattern layer formed by a first material having a first thermal conductivity, wherein the first material is spaced apart by a preset spacing distance (d) on the inner surface of the fluid receiving portion to form a first pattern; and a second pattern layer wherein a second material having a second thermal conductivity lower than the first thermal conductivity is laminated on the remaining portion of the inner surface excluding the first pattern, thereby forming a second pattern disposed between the first patterns on the inner surface of the fluid receiving portion.

[0009] The first pattern layer is formed integrally with the fluid receiving portion.

[0010] The above separation distance (d) is set as half the distance (λ) between two points where bubbles are generated because the thickness of the gas film is formed thicker than the surroundings in Zuber’s minimum film boiling model defined by the following mathematical formula, and the distance (λ) between the two points is set to satisfy the following mathematical formula.

[0011] <Mathematical Formula>

[0012]

[0013] Here, σ represents the surface tension of the cryogenic fluid, ρ represents the density of the cryogenic fluid, and g represents the acceleration due to gravity.

[0014] The first material is a metal, and the second material is a low-thermal-conductivity material with a thermal conductivity of 1 / 10 or less of the thermal conductivity of the first material.

[0015] The above pattern layer forms a mosaic pattern in which a first material and a second material having different thermal conductivity are alternately and repeatedly arranged in a square shape.

[0016] The pattern layer is formed such that a second material having a lower thermal conductivity than the first material is stacked on the surface of the first material at a predetermined spacing distance, and the surface of the first material forms a grid pattern in the portion where the second material is not stacked, so that the first material and the second material are alternately exposed to a fluid.

[0017] The above pattern layer forms a concentric pattern in which a first material and a second material having different thermal conductivity are alternately arranged and have different diameters and form a concentric arrangement.

[0018] A cooling structure surface-treated with a low thermal conductivity material according to another aspect of the present invention comprises: a fluid receiving portion in which an inner surface comes into contact with a liquid low-temperature or cryogenic fluid in which boiling heat transfer occurs; The above-mentioned fluid receiving portion includes a pattern layer formed in a mosaic pattern in which materials having different thermal conductivity are alternately arranged on at least a portion of the inner surface of the above-mentioned fluid receiving portion, wherein the pattern layer is formed such that a second material having a lower thermal conductivity than the first material is stacked on the surface of the first material at a predetermined spacing distance (d), and the surface of the first material forms a grid pattern in the portion where the second material is not stacked, so that the first material and the second material are alternately exposed to the fluid, wherein the first material is a metal and the second material includes Teflon, and the spacing distance (d) is set to half the distance (λ) between two points where bubbles are generated because the thickness of the gas film is formed thicker than the surroundings in Zuber's minimum film boiling model defined by the following mathematical formula, and the distance (λ) between the two points is set to satisfy the following mathematical formula.

[0019] <Mathematical Formula>

[0020]

[0021] Here, σ represents the surface tension of the cryogenic fluid, ρ represents the density of the cryogenic fluid, and g represents the acceleration due to gravity.

[0022] A cooling method for a cryogenic system utilizing a cooling structure surface-treated with a low thermal conductivity material according to the present invention comprises the steps of: forming a pattern layer by arranging a material having a thermal conductivity lower than that of the solid surface in a spaced-apart pattern on at least a portion of the solid surface of a cooling object; and cooling the cooling object by bringing a liquid low-temperature or cryogenic fluid into contact with the cooling object, wherein the fluid in contact with the solid surface vaporizes to cover the solid surface with a gas film, and the fluid is continuously supplied in a liquid state to the pattern layer to enable continuous phase change heat transfer.

[0023] A cooling structure surface-treated with a low thermal conductivity material according to another aspect of the present invention comprises a cooling target formed of a metal; and a pattern layer formed by arranging a material having lower thermal conductivity than the cooling target in a spaced-apart pattern on at least a portion of the surface of the cooling target.

[0024] A cooling structure surface-treated with a low thermal conductivity material according to another aspect of the present invention comprises: a cooling target having a solid surface in contact with a liquid low-temperature or cryogenic fluid; and a pattern layer formed of a material having lower thermal conductivity than the solid surface, which is arranged in a spaced-apart pattern on the solid surface and in contact with the fluid, wherein the fluid vaporizes through heat transfer with the cooling target to cool the cooling target, and the fluid in contact with the solid surface vaporizes to cover the solid surface with a gas film, and the fluid is continuously supplied in a liquid state to the pattern layer to enable continuous phase change heat transfer to cool the cooling. Effects of the invention

[0025] The present invention provides a pattern layer in which at least two materials with different thermal conductivity are alternately arranged on the inner surface of a fluid receiving portion to form a pattern. When a liquid low-temperature or cryogenic fluid is injected into the fluid receiving portion for pre-cooling, the fluid undergoes a phase change to a gaseous state on the inner surface of the fluid receiving portion that has high thermal conductivity, and the fluid remains in a liquid state on the inner surface that has relatively low thermal conductivity. This induces contact of the liquid on the surface during the pre-cooling process, thereby enabling a faster transition from gas film boiling to transition boiling, and thus the cooling efficiency can be further improved.

[0026] In addition, by forming a pattern layer by coating the inner surface of a fluid receiving portion formed of metal with Teflon, which has lower thermal conductivity than metal, the structure can be simple and easy to manufacture, while effectively improving cooling efficiency. Brief explanation of the drawing

[0027] FIG. 1 is a schematic cross-sectional view of a cryogenic system utilizing a cooling structure surface-treated with a low thermal conductivity material according to one embodiment of the present invention. FIG. 2 is a plan view showing a pattern layer according to one embodiment of the present invention. Figure 3 is a cross-sectional view taken in the direction of line AA of Figure 2. Figure 4 is a schematic diagram showing Zuber's Minimum Film Boiling (MFB) model. FIG. 5 is a plan view showing a pattern layer according to another embodiment of the present invention. Figure 6 is a cross-sectional view taken in the direction of line BB of Figure 5. Figure 7 is a graph comparing the improved cooling efficiency of a cryogenic system utilizing a cooling structure surface-treated with a low thermal conductivity material according to the present invention. Specific details for implementing the invention

[0028] Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.

[0029] FIG. 1 is a schematic cross-sectional view of a cryogenic system utilizing a cooling structure surface-treated with a low thermal conductivity material according to one embodiment of the present invention.

[0030] Referring to FIG. 1, a cryogenic system according to one embodiment of the present invention is a system to which a cooling structure utilizing boiling is applied.

[0031] The above cryogenic system includes a cooling target having a solid surface that comes into contact with a liquid low-temperature or cryogenic fluid (hereinafter referred to as cryogenic fluid) in which boiling heat transfer occurs, and a pattern layer (20) formed of a material having lower thermal conductivity than the solid surface, which is arranged in a spaced-apart pattern on the solid surface of the cooling target and comes into contact with the fluid.

[0032] The above-mentioned cooling object is described as a fluid receiving part that receives a cryogenic fluid, and below, the fluid receiving part is described as a cryogenic fluid tank (10).

[0033] However, the above fluid receiving portion is not limited thereto and can be modified and applied in various ways as long as it comes into contact with the cryogenic fluid, such as a transfer pipe for transporting cryogenic fluid.

[0034] The above cryogenic fluids include liquid nitrogen (LN2), liquid oxygen (LO2), liquid hydrogen (LH2), liquefied natural gas (LNG), etc.

[0035] The above cryogenic fluid tank (10) includes a chamber (11) for receiving cryogenic fluid and an insulating material (12) surrounding the outside of the chamber (11).

[0036] The above chamber (11) is a container made of metal. In this embodiment, the metal is described as stainless steel (SUS) as an example.

[0037] FIG. 2 is a plan view showing a pattern layer according to one embodiment of the present invention. FIG. 3 is a cross-sectional view seen in the direction of line AA of FIG. 2.

[0038] Referring to FIGS. 2 and FIGS. 3, the pattern layer (20) is provided on at least a portion of the inner surface of the chamber (11).

[0039] In this embodiment, the pattern layer (20) is described as being provided on the bottom surface of the inner surface of the chamber (11) as an example, but is not limited thereto and may also be provided on the inner side.

[0040] The above pattern layer (20) is formed in a pattern in which materials having different thermal conductivity are alternately arranged on the inner bottom surface of the chamber (11). In this embodiment, it is described as having a heterogeneous surface in a pattern in which two first and second materials are alternately arranged.

[0041] The above pattern layer (20) includes a first pattern layer (21) and a second pattern layer (22).

[0042] The first pattern layer (21) is formed by a first material having a first thermal conductivity. The first material is a metal and is described as stainless steel.

[0043] In this embodiment, the chamber (11) is described as being formed of the same metal as the first material. Therefore, the first pattern layer (21) is formed integrally with the chamber (11) to form the inner surface of the chamber (11), but is not covered by the second pattern layer (22) and is exposed to the surface to form the first pattern described later. However, this is not limited thereto, and it is also possible for the first pattern layer (21) to be formed separately on the inner surface of the chamber (11) if it is made of a different material from the chamber (11).

[0044] The first pattern layer (21) is formed such that the first material is exposed at a predetermined spacing distance (d) from the inner bottom surface of the chamber (11) to form a first pattern.

[0045] The first pattern above is explained as an example in which the first material is exposed in a square shape with a spacing (d) from each other to form a mosaic pattern.

[0046] The second pattern layer (22) is formed by a second material having a second thermal conductivity. The second thermal conductivity must be lower than the first thermal conductivity.

[0047] The thermal conductivity of the second material is described by example as using a low thermal conductivity material that is about 1 / 10 or less of the thermal conductivity of the first material. However, it is not limited thereto, and if the thermal conductivity of the first material and the second material have a predetermined difference, it can have an effect of improving cooling efficiency.

[0048] In this embodiment, the second material is described as being Teflon, but it is not limited thereto and can be varied and applied as long as it is a low thermal conductivity material with lower thermal conductivity than the first material.

[0049] In a temperature range of about 77 to 300K, the thermal conductivity of the stainless steel used as the first material is about 8 to 15 W / m·K, and the thermal conductivity of the Teflon used as the second material is about 0.3 W / m·K or less.

[0050] The second pattern layer (22) is formed by laminating it on the first pattern layer (21). The second pattern layer (22) is a Teflon film layer formed by coating the second material into the second pattern on the portion of the inner surface of the chamber (11) excluding the first pattern. Accordingly, the second pattern is placed between the first patterns.

[0051] In this embodiment, the chamber (11) and the first pattern layer (21) are described as being integrally formed by being made of the same metal. Therefore, the second pattern layer (22) is a Teflon film layer formed by applying the second material onto the surface of the chamber (11) to form the second pattern. That is, the first pattern layer (21) is a portion exposed on the inner surface of the chamber (11), and the second pattern layer (21) is a separate layer laminated on the inner surface of the chamber (11) other than the first pattern layer (21).

[0052] However, not limited thereto, if the first pattern layer (21) is separately laminated and formed on the surface of the chamber (11), it is also possible to form the first pattern layer (21) and the second pattern layer (22) so as to be located on the same plane.

[0053] The above second pattern is described as a mosaic pattern in which the second material is arranged spaced apart from each other in a square shape.

[0054] Accordingly, the pattern layer (20) is formed as a mosaic pattern in which a first material and a second material having different thermal conductivity are alternately and repeatedly arranged in a square shape, as shown in FIG. 2.

[0055] The distance between surfaces with high thermal conductivity in the pattern layer (20), that is, the spacing distance (d) between first materials adjacent to each other in the first pattern layer (21), is set through Zuber’s Minimum Film Boiling (MFB) model defined by the following mathematical formula.

[0056] Figure 4 is a schematic diagram showing Zuber's Minimum Film Boiling (MFB) model.

[0057] Referring to Fig. 4, it can be seen that in Zuber’s minimum film boiling model, the vapor film formed on the surface during the phase change of a cryogenic fluid is formed in the shape of a curve with a predetermined period (λ).

[0058] It can be seen that bubbles are generated at the first and second points (P1) and (P2), where the thickness of the gas film is thickest, and that there is a part between the first point (P1) and the second point (P2) where the thickness of the gas film is relatively very thin.

[0059] Mathematical formula 1 represents the distance (λ) between the parts where the thickness of the gas film is thickest, that is, between the first point (P1) and the second point (P2) where bubbles are generated.

[0060]

[0061] Here, σ represents the surface tension of the cryogenic fluid, ρ represents the density of the cryogenic fluid, and g represents the acceleration due to gravity.

[0062] In the present invention, the pattern layer (20) was formed by referring to the Zuber minimum film boiling model and mathematical formula as described above.

[0063] Referring to Fig. 4 and Equation 1, the first material is placed in the area where bubbles are generated because the thickness of the gas film is relatively thicker than the surrounding area, thereby forming a surface with high thermal conductivity so that bubbles are generated in the first pattern layer (21).

[0064] In addition, the second material is placed in the region where the thickness of the gas film is relatively thinner than the surrounding area to form a surface with low thermal conductivity, thereby inducing the liquid state of the cryogenic fluid to remain in the second pattern layer (22).

[0065] Accordingly, the separation distance (d) of the first materials adjacent to each other in the first pattern layer (21) was set to half the distance (λ) between the parts where the thickness of the gas film is thicker than the surroundings, according to Zuber's minimum film boiling model.

[0066] That is, the spacing distance (d) of the first materials of the first pattern layer (21), which has high thermal conductivity in the pattern layer (20), is set to half the spacing (λ) between the points where bubbles are generated in the mathematical formula, and the second material is patterned and applied between the first materials to form the second pattern.

[0067] Accordingly, the spacing distance (d) of the first materials adjacent to each other in the first pattern layer (21) is equal to the size of the second materials in the second pattern layer (22).

[0068] By using the Zuber minimum film boiling model above to calculate the spacing distance (d) of the first materials in the first pattern layer (21) and setting the position and size of the second materials in the second pattern layer (22), the cryogenic fluid in a liquid state is induced to remain on the second material, which has a lower thermal conductivity than the surroundings during the phase change of the cryogenic fluid, thereby allowing the liquid cryogenic fluid, which has a higher heat transfer efficiency than gas, to come into contact with the surface and cool the surface of the cryogenic fluid tank (10) more quickly.

[0069] In this embodiment, the spacing distance (d) of the first materials of the first pattern layer (21) is explained as being set to half the spacing (λ) between the points where bubbles are generated in the mathematical formula.

[0070] However, it is not limited to this, and the above separation distance (d) can be varied within an error range for half of the above spacing (λ), but the highest cooling efficiency can be achieved when arranged with the above separation distance (d).

[0071] In addition, it is possible to laminate the second material over the entire surface of the first material, and the cooling efficiency can be improved compared to the case where the second material is not present.

[0072] Figure 7 is a graph comparing the cooling efficiency in the case of a conventional bare metal surface and a multi-level surface including a pattern layer in the present invention.

[0073] Referring to Fig. 7, it can be seen that the heat flux is higher than in the conventional case in the case of the double surface of the present invention.

[0075] A cooling method for a cryogenic system utilizing a cooling structure surface-treated with a low thermal conductivity material according to one embodiment of the present invention configured as described above is as follows.

[0076] The pre-cooling process of the cryogenic fluid tank (10) is a process for cooling the interior of the cryogenic fluid tank (10) by injecting a liquid cryogenic fluid into the cryogenic fluid tank (10) at room temperature. The pre-cooling process includes a gas film boiling region, a transition boiling region, and a nucleation boiling region according to the phase change process of the cryogenic fluid.

[0077] In the present invention, since the inner surface of the cryogenic fluid tank (10) is formed by alternately arranging first and second materials having different thermal conductivity to form the first and second patterns, when the cryogenic fluid is injected, the heat transfer rate differs depending on which position of the first and second patterns the cryogenic fluid comes into contact with on the inner surface of the cryogenic fluid tank (10).

[0078] When the cryogenic fluid is injected into the cryogenic fluid tank (10), boiling heat transfer occurs. At least a portion of the cryogenic fluid comes into contact with the first pattern layer (21), and the remainder comes into contact with the second pattern layer (22).

[0079] The fluid in contact with the first pattern layer (21) undergoes a rapid phase change and vaporizes, cooling the surface through heat transfer with the first pattern layer (21). Since the first pattern layer (21) has a relatively higher thermal conductivity than other parts among the internal surfaces of the cryogenic fluid tank (10), the surface of the first pattern layer (21) becomes covered with a gas film, resulting in reduced cooling efficiency.

[0080] The fluid in contact with the second pattern layer (22) cools the surface through heat transfer with the second pattern layer (22). Since the second pattern layer (22) is a region within the inner surface of the cryogenic fluid tank (10) that has a relatively lower thermal conductivity than the first pattern layer (21), the fluid in contact with the surface of the second pattern layer (22) is induced to remain in a partially liquid state. Therefore, continuous phase change heat transfer is possible on the surface of the second pattern layer (22), resulting in high cooling efficiency.

[0081] Since the second pattern layer (22) is formed by applying Teflon, which has a much lower thermal conductivity than metal, it is possible to prevent the second pattern layer (22) from being 100% covered by a gas film.

[0082] As described above, the cryogenic fluid in contact with the surface of the first pattern layer (21) vaporizes due to boiling heat transfer on the surface of the first pattern layer (21), thereby forming a vapor film on the surface of the first pattern layer (21).

[0083] Meanwhile, on the surface of the second pattern layer (22), the gaseous fluid formed by the vaporization of the cryogenic fluid is not formed to form a gas film covering the entire area, and is instead induced to remain in a partial liquid state.

[0084] That is, the area covered by gas on the surface of the first pattern layer (21) is larger than the area covered by gas on the surface of the second pattern layer (22).

[0085] As described above, when a liquid low-temperature or cryogenic fluid is brought into contact with the surface of the cryogenic fluid tank (10), boiling heat transfer occurs. The fluid in contact with the surface of the first pattern layer (21) is covered with a gas film due to rapid phase change heat transfer, thereby reducing cooling efficiency, whereas the fluid in contact with the surface of the second pattern layer (22) can remain in a partially liquid state, allowing for continuous phase change heat transfer. That is, a liquid cryogenic fluid, which has a higher heat transfer efficiency than a gaseous state, is continuously supplied to the surface of the second pattern layer (22), thereby enabling continuous phase change heat transfer, so the surface of the cryogenic fluid tank (10) can be cooled more quickly.

[0086] Accordingly, as both a gas film and a liquid film coexist on the inner surface of the cryogenic fluid tank (10) in the gas film boiling region, which is the initial stage of the pre-cooling process of the cryogenic fluid, the transition from the gas film boiling region to the transition boiling region can be made more quickly. Since the transition boiling region has a much higher cooling efficiency than the gas film boiling region, the inner surface can be cooled more rapidly. Since the time required for the gas film boiling region is drastically shortened and the transition can be made quickly to the transition boiling region, the cooling efficiency of the pre-cooling process can be greatly improved.

[0088] Meanwhile, FIG. 5 is a plan view showing a pattern layer according to another embodiment of the present invention. FIG. 6 is a cross-sectional view seen in the direction of line BB of FIG. 5.

[0089] A cryogenic system surface-treated with a low thermal conductivity material according to another embodiment of the present invention differs from the first embodiment in that the pattern layer (30) formed on the inner surface of the chamber (11) of the cryogenic fluid tank (10) is formed such that a grid pattern in which horizontal and vertical patterns intersect is exposed on the surface of the first material having a higher thermal conductivity than the second material among the first material and the second material having different thermal conductivity, and the second material is positioned between the grid patterns. Since the remaining configuration and operation are similar to the first embodiment, a detailed description of similar content is omitted below, and the description focuses on the differences.

[0090] The above chamber (11) is formed from the above first material.

[0091] The pattern layer (30) comprises a first pattern layer (31) formed from the first material and a second pattern layer (32) in which the second material is spaced apart from the surface of the first material by a predetermined spacing distance.

[0092] In this embodiment, the first pattern layer (31) is formed integrally with the chamber (11) to form the inner surface of the chamber (11), and is described as an example in which it is exposed to the surface and forms a pattern without being covered by the second pattern layer (32). However, this is not limited thereto, and it is also possible for the first pattern layer (31) to be formed separately on the inner surface of the chamber (11) if it is made of a different material from the chamber (11).

[0093] That is, the first pattern layer (31) is a layer exposed to fluid in which the portion of the surface of the first material where the second material is not laminated forms a grid pattern in which horizontal and vertical patterns intersect.

[0094] The second pattern layer (32) forms a pattern in which the second material is alternately and repeatedly arranged in a square shape between the grid patterns and is exposed to a fluid.

[0095] Accordingly, the inner surface of the chamber (11) is alternately arranged with the first material and the second material, so that the first material and the second material are alternately exposed to the fluid.

[0096] In this embodiment, the second material is coated and formed on at least a portion of the surface of the first material, so that at least a portion of the surface of the first material is covered by the second material, and the remaining portion is exposed as a grid pattern between the square-shaped second pattern layers (32).

[0097] The spacing distance (d) of the first material that is exposed without being covered by the second material in the pattern layer (30) is set by the mathematical formula 1.

[0098] The first material above uses a metal with high thermal conductivity, and in this embodiment, it is described as stainless steel.

[0099] The second material is described as Teflon. The second material is coated onto the first material in the grid pattern.

[0100] Meanwhile, the pattern layer (30) is not limited to the above embodiments and can be applied by changing it to a pattern other than the grid pattern. That is, the pattern layer can be applied by changing it to various patterns as long as the first material and the second material are arranged alternately so that the inner surface of the chamber (11) has a surface having different thermal conductivity. For example, it is also possible for the pattern layer (30) to form a concentric pattern in which the first material and the second material are arranged alternately to have different diameters and form a concentric arrangement.

[0102] The present invention has been described with reference to the embodiments illustrated in the drawings, but this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Accordingly, the true technical scope of protection of the present invention should be determined by the technical spirit of the appended claims. Explanation of the symbols

[0103] 10: Cryogenic fluid tank 11: Chamber 12: Insulation material 20,30: Pattern layer 21,31: 1st pattern layer 22,32: 2nd pattern layer

Claims

Claim 1 A cooling structure having a surface-treated inner surface, comprising: a fluid receiving portion in which the inner surface contacts a liquid low-temperature or cryogenic fluid in which boiling heat transfer occurs; and a pattern layer formed in a pattern in which materials having different thermal conductivity are alternately arranged on at least a portion of the inner surface of the fluid receiving portion. Claim 2 A cooling structure having a surface-treated inner surface according to claim 1, wherein the pattern layer comprises: a first pattern layer formed by a first material having a first thermal conductivity and forming a first pattern in which the first material is spaced apart by a preset spacing distance (d) on the inner surface of the fluid receiving portion; and a second pattern layer formed by a second material having a second thermal conductivity lower than the first thermal conductivity on the remaining portion of the inner surface excluding the first pattern layer, wherein the second material is alternately arranged with the first material on the inner surface of the fluid receiving portion. Claim 3 A cooling structure having a surface-treated inner surface, comprising: a fluid receiving portion in which an inner surface contacts a liquid low-temperature or cryogenic fluid in which boiling heat transfer occurs; and a second pattern layer formed on the inner surface of the fluid receiving portion to form a second pattern in which a second material having a lower thermal conductivity than a first material forming the inner surface is spaced apart, wherein the portion of the inner surface where the second pattern layer is not formed and is exposed forms a first pattern in which a spaced-apart distance (d) is spaced apart. Claim 4 A cooling structure having a surface-treated inner surface according to claim 2 or claim 3, wherein the separation distance (d) is set to half the distance (λ) between two points where bubbles are generated by forming a gas film thicker than the surroundings in Zuber’s minimum film boiling model defined by the following mathematical formula, and the distance (λ) between the two points is set to satisfy the following mathematical formula. Here, σ represents the surface tension of the cryogenic fluid, ρ represents the density of the cryogenic fluid, and g represents the acceleration due to gravity. Claim 5 A cooling structure having a surface-treated inner surface, wherein the first material is a metal and the second material has a low thermal conductivity material having a thermal conductivity of 1 / 10 or less of the thermal conductivity of the first material. Claim 6 A cooling structure having a surface-treated inner surface, wherein, in claim 2 or claim 3, the first pattern and the second pattern are alternately and repeatedly arranged in a square shape to form a mosaic pattern. Claim 7 The cooling structure according to claim 2 or claim 3, wherein the first pattern is formed as a grid pattern, and the inner surface is surface-treated. Claim 8 A cooling structure having a surface-treated inner surface, wherein the second pattern is formed as a concentric pattern having different diameters and forming a concentric arrangement. Claim 9 A fluid receiving portion in which an inner surface contacts a liquid low-temperature or cryogenic fluid in which boiling heat transfer occurs; and a pattern layer provided on at least a portion of the inner surface of the fluid receiving portion, wherein materials having different thermal conductivity are alternately arranged on the inner surface, wherein the pattern layer is formed such that a second material having a lower thermal conductivity than the first material is stacked on the surface of the first material at a predetermined spacing distance (d), and the surface of the first material forms a grid pattern in the portion where the second material is not stacked, so that the first material and the second material are alternately exposed to the fluid, wherein the first material is a metal and the second material includes Teflon, wherein the spacing distance (d) is set to half the distance (λ) between two points where bubbles are generated because the thickness of the gas film is formed thicker than the surroundings in Zuber's minimum film boiling model defined by the following mathematical formula, and the distance (λ) between the two points satisfies the following mathematical formula A cooling structure with a surface-treated inner surface that is set.<Mathematical Formula> Here, σ represents the surface tension of the cryogenic fluid, ρ represents the density of the cryogenic fluid, and g represents the acceleration due to gravity. Claim 10 A cooling method for a cryogenic system utilizing a cooling structure with an internal surface treated with a surface treatment, comprising: a step of forming a pattern layer on a solid surface of a cooling object to be cooled, wherein a material having a lower thermal conductivity than the solid surface is spaced apart from each other to form a pattern; and a step of cooling by bringing a liquid low-temperature or cryogenic fluid into contact with the cooling object, wherein the fluid in contact with the solid surface vaporizes to cover the solid surface with a gas film, and the fluid is continuously supplied in a liquid state to the pattern layer to enable continuous phase change heat transfer. Claim 11 A cooling structure having an internal surface that is surface-treated, comprising: a cooling object formed of metal; and a pattern layer formed by arranging a material having a lower thermal conductivity than the cooling object in a spaced-apart pattern on the surface of the cooling object. Claim 12 A cooling structure having a surface-treated inner surface, comprising: a cooling object having a solid surface in contact with a liquid low-temperature or cryogenic fluid; and a pattern layer formed of a material having lower thermal conductivity than the solid surface, which is arranged in a spaced-apart pattern on the solid surface and in contact with the fluid, wherein the fluid vaporizes through heat transfer with the cooling object to cool the cooling object, the fluid in contact with the solid surface vaporizes to cover the solid surface with a gas film, and the fluid is continuously supplied in a liquid state to the pattern layer to enable continuous phase change heat transfer to cool the object.

Images