Heat exchanger for reliquefaction for liquid hydrogen storage tank and liquid hydrogen storage and reliquefaction system including the same

Abstract

According to one embodiment of the technical concept of the present invention, a heat exchanger for re-liquefaction for a liquid hydrogen storage tank and a liquid hydrogen storage and re-liquefaction system including the same relates to a heat exchanger for re-liquefaction applying a fractal structure and a liquid hydrogen storage and re-liquefaction system including the same, comprising: a first branch pipe group including first branch pipes extending from an inlet pipe and branching into a fractal structure having a predetermined branch angle; a second branch pipe group including second branch pipes extending from a discharge pipe and branching into a fractal structure having a predetermined branch angle, and positioned at a predetermined distance from the first branch pipe group; and a connecting pipe group including connecting pipes connecting the ends of the first branch pipes of the first branch pipe group and the ends of the second branch pipes of the second branch pipe group, wherein a refrigerant introduced into the inlet pipe can be discharged through the first branch pipes of the first branch pipe group, the connecting pipes of the connecting pipe group, and the second branch pipes of the second branch pipe group.

Description

Technology Field

[0001] The present invention relates to a heat exchanger for reliquefaction for a liquid hydrogen storage tank and a liquid hydrogen storage and reliquefaction system including the same, and more specifically, to a heat exchanger for reliquefaction applying a fractal structure and a liquid hydrogen storage and reliquefaction system including the same. Background Technology

[0002] Liquid hydrogen storage tanks are essential devices for long-term storage or transportation of produced liquid hydrogen. However, liquid hydrogen is stored at cryogenic temperatures (-253°C, 20K), and a problem arises where some of it evaporates and converts into a gaseous state due to heat entering from the outside of the tank.

[0003] To solve this problem, a reliquefaction device is required to re-liquefy gaseous hydrogen evaporated inside the storage tank. Conventional reliquefaction devices are primarily configured to cool and re-liquefy gaseous hydrogen through a heat exchanger using cryogenic gaseous helium.

[0004] However, parallel heat exchangers used as conventional reliquefaction devices have problems such as difficulty in securing an optimal heat exchange area within the same volume, high pressure loss in fluid flow, non-uniform refrigerant flow, localized cooling concentration in specific areas, and inconsistent heat transfer performance.

[0005] Many inventors have been conducting research to solve these problems, but satisfactory results have not yet been obtained. The problem to be solved

[0006] The technical problem to be solved by the re-liquefaction heat exchanger for a liquid hydrogen storage tank and the liquid hydrogen storage and re-liquefaction system including the same, according to the technical concept of the present invention, is to provide a re-liquefaction heat exchanger for a liquid hydrogen storage tank and a liquid hydrogen storage and re-liquefaction system including the same, which can minimize power consumption by maximizing the heat exchange area, minimizing pressure drop, and maintaining uniform flow distribution through a re-liquefaction heat exchanger applying a fractal structure.

[0007] The technical problems to be solved by the heat exchanger for reliquefaction of a liquid hydrogen storage tank and the liquid hydrogen storage and reliquefaction system including the same, according to the technical concept of the present invention, are not limited to those mentioned above, and other unmentioned problems will be clearly understood by a person skilled in the art from the description below. means of solving the problem

[0008] According to one embodiment of the technical concept of the present invention, a heat exchanger for re-liquefaction for a liquid hydrogen storage tank comprises: a first branch pipe group including first branch pipes extending from an inlet pipe and branching into a fractal structure having a predetermined branch angle; a second branch pipe group including second branch pipes extending from an outlet pipe and branching into a fractal structure having a predetermined branch angle, and positioned at a predetermined distance from the first branch pipe group; and a connecting pipe group including connecting pipes connecting the ends of the first branch pipes of the first branch pipe group and the ends of the second branch pipes of the second branch pipe group, wherein a refrigerant introduced into the inlet pipe can be discharged through the first branch pipes of the first branch pipe group, the connecting pipes of the connecting pipe group, and the second branch pipes of the second branch pipe group.

[0009] The first branch piping group and the second branch piping group can be branches on a branch plane parallel to each other.

[0010] In the first branch pipe group and the second branch pipe group, the first branch pipes and the second branch pipes can have their diameters and lengths determined by Equation (1) and Equation (2).

[0011] (D k+1 / D k )=2 -1 / 3 Equation (1)

[0012] (L k+1 / L k )=2 -1 / 2 (2)

[0013] Here, k is a branching step and is an integer greater than or equal to 0, and D k is the diameter of the k-th branched branch, and L k is the length of the k-th branched duct.

[0014] The branching angle can be 30 degrees or 180 degrees.

[0015] The first branch piping group, the connecting piping group, and the second branch piping group can be formed by 3D metal printing technology.

[0016] According to another embodiment of the technical concept of the present invention, a heat exchanger for re-liquefaction for a liquid hydrogen storage tank comprises: a first branch pipe group including first branch pipes extending from an inlet pipe and branching into a fractal structure having a predetermined branch angle; and a second branch pipe group including second branch pipes extending from a discharge pipe spaced coaxially with the inlet pipe of the first branch pipe group and branching into a fractal structure having a predetermined branch angle toward the first branch pipe group, wherein the first branch pipe group and the second branch pipe group branch on a branching plane that rotates by a predetermined rotation angle around an axis connecting the inlet pipe and the discharge pipe at each branching stage, and the ends of the first branch pipes of the first branch pipe group and the ends of the second branch pipes of the second branch pipe group are connected to each other, and a refrigerant introduced into the inlet pipe can be discharged through the first branch pipes of the first branch pipe group and the second branch pipes of the second branch pipe group to the discharge pipe.

[0017] The branching angle and the rotation angle can each be 90 degrees.

[0018] The first quarter piping group and the second quarter piping group can be formed by 3D metal printing technology.

[0019] A liquid hydrogen storage and re-liquefaction system according to another embodiment based on the technical concept of the present invention comprises: a vertical storage tank in which liquid hydrogen is stored, wherein an inlet pipe for introducing a refrigerant from the outside and an outlet pipe for discharging a refrigerant from the inside penetrate one side; a first branch pipe group including first branch pipes extending from the inlet pipe on a horizontal branching plane and branching into a fractal structure having a predetermined branching angle; and a second branch pipe group including second branch pipes extending from the outlet pipe on a horizontal branching plane and branching into a fractal structure having a predetermined branching angle, and positioned vertically spaced apart from the first branch pipe group by a predetermined distance. The system includes a connecting pipe group comprising connecting pipes that connect the ends of the first branch pipes of the first branch pipe group and the ends of the second branch pipes of the second branch pipe group, wherein the first branch pipe group, the connecting pipe group, and the second branch pipe group are located inside a vertical storage tank, and the refrigerant introduced through the inlet pipe can be discharged through the first branch pipes of the first branch pipe group, the connecting pipes of the connecting pipe group, and the second branch pipes of the second branch pipe group to the outlet pipe.

[0020] In the first branch pipe group and the second branch pipe group, the first branch pipes and the second branch pipes can have their diameters and lengths determined by Equation (1) and Equation (2).

[0021] The branching angle can be 30 degrees or 180 degrees.

[0022] The first branch piping group, the connecting piping group, and the second branch piping group can be formed by 3D metal printing technology.

[0023] A liquid hydrogen storage and re-liquefaction system according to another embodiment of the technical concept of the present invention comprises: a vertical storage tank in which liquid hydrogen is stored, wherein an inlet pipe for introducing a refrigerant from the outside and an outlet pipe for discharging a refrigerant from the inside vertically penetrate one side; and a first branch pipe group including first branch pipes extending from the inlet pipe and branching into a fractal structure having a predetermined branching angle; The first branch piping group includes a second branch pipe group comprising second branch pipes extending from the end of a discharge pipe positioned vertically spaced at a predetermined distance from the end of an inlet pipe of the first branch piping group and branching toward the first branch piping group in a fractal structure having a predetermined branch angle, wherein the first branch piping group and the second branch piping group are located inside a vertical storage tank, and the first branch piping group and the second branch piping group are branched on a branching plane that rotates by a predetermined rotation angle around a vertical axis connecting the inlet pipe and the discharge pipe at each branching stage, and the ends of the first branch pipes of the first branch piping group and the ends of the second branch pipes of the second branch piping group are connected to each other, and the refrigerant introduced into the inlet pipe can be discharged through the first branch pipes of the first branch piping group and the second branch pipes of the second branch piping group to the discharge pipe.

[0024] The branching angle and the rotation angle can each be 90 degrees.

[0025] The first quarter piping group and the second quarter piping group can be formed by 3D metal printing technology.

[0026] A liquid hydrogen storage and re-liquefaction system according to another embodiment of the technical concept of the present invention comprises: a horizontal storage tank in which liquid hydrogen is stored, wherein an inlet pipe for introducing a refrigerant from the outside and an outlet pipe for discharging a refrigerant from the inside vertically penetrate one side; and one or more re-liquefaction heat exchangers located within the horizontal storage tank and connected to the inlet pipe and the outlet pipe, wherein the re-liquefaction heat exchangers include: a first branch pipe group comprising first branch pipes extending from the inlet pipe on a horizontal branching plane and branching into a fractal structure having a predetermined branching angle; and a second branch pipe group comprising second branch pipes extending from the outlet pipe on a horizontal branching plane and branching into a fractal structure having a predetermined branching angle, and positioned vertically spaced apart from the first branch pipe group by a predetermined distance. and a connecting pipe group including connecting pipes connecting the ends of the first branch pipes of the first branch pipe group and the ends of the second branch pipes of the second branch pipe group, wherein the refrigerant introduced into the inlet pipe can be discharged through the first branch pipes of the first branch pipe group, the connecting pipes of the connecting pipe group, and the second branch pipes of the second branch pipe group to the discharge pipe.

[0027] In the first branch pipe group and the second branch pipe group, the first branch pipes and the second branch pipes can have their diameters and lengths determined by Equation (1) and Equation (2).

[0028] The branching angle can be 30 degrees or 180 degrees.

[0029] The first branch piping group, the connecting piping group, and the second branch piping group can be formed by 3D metal printing technology.

[0030] A liquid hydrogen storage and re-liquefaction system according to another embodiment of the technical concept of the present invention comprises: a horizontal storage tank in which liquid hydrogen is stored, wherein an inlet pipe for introducing a refrigerant from the outside and an outlet pipe for discharging a refrigerant from the inside vertically penetrate one side; and one or more re-liquefaction heat exchangers located within the horizontal storage tank and connected to the inlet pipe and the outlet pipe, wherein the re-liquefaction heat exchangers comprise a first branch pipe group including first branch pipes extending from the inlet pipe and branching into a fractal structure having a predetermined branching angle; The second branch piping group includes second branch pipes extending from the end of a discharge pipe positioned vertically spaced at a predetermined distance from the end of an inlet pipe of the first branch piping group and branching toward the first branch piping group in a fractal structure having a predetermined branch angle, wherein the first branch piping group and the second branch piping group branch on a branching plane that rotates by a predetermined rotation angle around a vertical axis connecting the inlet pipe and the discharge pipe at each branching stage, and the ends of the first branch pipes of the first branch piping group and the ends of the second branch pipes of the second branch piping group are connected to each other, and the refrigerant introduced into the inlet pipe can be discharged through the first branch pipes of the first branch piping group and the second branch pipes of the second branch piping group to the discharge pipe.

[0031] The branching angle and the rotation angle can each be 90 degrees.

[0032] The first quarter piping group and the second quarter piping group can be formed by 3D metal printing technology. Effects of the invention

[0033] According to embodiments of the technical concept of the present invention, a heat exchanger for re-liquefaction for a liquid hydrogen storage tank and a liquid hydrogen storage and re-liquefaction system including the same can minimize power consumption by maximizing the heat exchange area, minimizing pressure drop, and maintaining uniform flow distribution through a heat exchanger for re-liquefaction with a fractal structure.

[0034] According to embodiments of the technical concept of the present invention, a heat exchanger for re-liquefaction for a liquid hydrogen storage tank and a liquid hydrogen storage and re-liquefaction system including the same can improve heat exchange performance by increasing the heat transfer coefficient of the fluid flowing inside the heat exchanger for re-liquefaction and reducing the pressure drop, and local re-liquefaction can be prevented by ensuring that the distribution of the fluid is more uniform than in the past.

[0035] However, the effects that can be achieved by the heat exchanger for reliquefaction for a liquid hydrogen storage tank and the liquid hydrogen storage and reliquefaction system including the same, according to embodiments of the technical concept of the present invention, are not limited to those mentioned above, and other unmentioned effects will be clearly understood by a person skilled in the art from the description below. Brief explanation of the drawing

[0036] A brief description of each drawing is provided to help to better understand the drawings cited in this specification. FIG. 1 illustrates a liquid hydrogen storage and reliquefaction system including a first reliquefaction heat exchanger according to one embodiment of the technical concept of the present invention, and shows a schematic perspective view and a plan view when the branching angle of the first reliquefaction heat exchanger is 30 degrees. FIG. 2 schematically illustrates the fractal structure of a first heat exchanger for re-liquefaction according to one embodiment of the technical concept of the present invention. FIG. 3 illustrates a schematic perspective view and a plan view of a first heat exchanger for re-liquefaction according to one embodiment of the technical concept of the present invention when the branching angle is 180 degrees. FIG. 4 schematically illustrates a liquid hydrogen storage and reliquefaction system including a second reliquefaction heat exchanger according to another embodiment of the technical concept of the present invention. FIG. 5 illustrates a schematic perspective view and plan view of a horizontal storage tank in which a heat exchanger for re-liquefaction is located according to embodiments of the technical concept of the present invention. Figure 6 is a diagram comparing the internal heat transfer coefficient and pressure drop between the re-liquefaction heat exchanger of the present invention and a re-liquefaction heat exchanger of the prior art with a simple parallel shape. Specific details for implementing the invention

[0037] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that the present invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0038] In describing the present invention, if it is determined that a detailed description of related prior art may unnecessarily obscure the essence of the present invention, such detailed description is omitted. Additionally, numbers used in the description of this specification (e.g., 1st, 2nd, etc.) are merely identification symbols to distinguish one component from another.

[0039] In addition, when a component is described in this specification as being "connected" or "combined" with another component, it should be understood that the component may be directly connected or directly combined with the other component, but unless otherwise specifically stated, it may also be connected or combined through another component in between.

[0040] In addition, components expressed as '~part' in this specification may consist of two or more components combined into a single component, or a single component may be divided into two or more components according to more detailed functions. Furthermore, each component described below may additionally perform some or all of the functions performed by other components in addition to the primary function it is responsible for, and it goes without saying that some of the primary functions performed by each component may be exclusively performed by other components.

[0041] Hereinafter, embodiments based on the technical concept of the present invention will be described in detail in turn.

[0042] FIG. 1 illustrates a liquid hydrogen storage and reliquefaction system including a first reliquefaction heat exchanger according to one embodiment of the technical concept of the present invention, and shows a schematic perspective view and a plan view when the branching angle of the first reliquefaction heat exchanger is 30 degrees.

[0043] A first re-liquefaction heat exchanger (100) according to one embodiment of the technical concept of the present invention may be located inside a liquid hydrogen storage tank and may include a first branch pipe group (110), a second branch pipe group (120), and a connecting pipe group (130). FIG. 1 illustrates a vertical storage tank (10) as an example of a liquid hydrogen storage tank.

[0044] Liquid hydrogen is stored in a vertical storage tank (10), and an inlet pipe (111) for introducing refrigerant from outside the vertical storage tank (10) and an outlet pipe (121) for discharging refrigerant from inside the vertical storage tank (10) can pass through one side of the vertical storage tank (10). In FIG. 1, both the inlet pipe (111) and the outlet pipe (121) are shown as being positioned to pass through the upper surface of the vertical storage tank (10), but the inlet pipe (111) may pass through the vertical storage tank (10) through the lower part of the vertical storage tank (10), and the outlet pipe (121) may pass through the vertical storage tank (10) through the upper part of the vertical storage tank (10).

[0045] The refrigerant may be a cryogenic refrigerant, and various cryogenic refrigerants including gaseous helium may be used. The refrigerant introduced into the inlet pipe (111) may be discharged through the discharge pipe (121) by passing through the first branch pipes (112) of the first branch pipe group (110), the connecting pipe (132) of the connecting pipe group (130), and the second branch pipes (122) of the second branch pipe group (120) in sequence. During this process, the refrigerant re-liquefies the gaseous hydrogen through heat exchange with the gaseous hydrogen evaporated inside the vertical storage tank (10).

[0046] The first re-liquefaction heat exchanger (100) may be positioned in the gaseous region within the vertical storage tank (10), and may also be positioned in both the gaseous region and the liquid region within the vertical storage tank (10).

[0047] The first branch pipe group (110) may include first branch pipes (112) connected to an inlet pipe (111). The first branch pipes (112) may branch out from the inlet pipe (111) in a fractal structure having a predetermined branching angle on a horizontal branching plane and may extend radially. In FIG. 1, the case where the branching angle of the first branch pipes (112) is 30° is illustrated as an example.

[0048] Here, fractal structures are commonly found in the natural world and possess a bifurcation structure, similar to tree branches or bronchial structures. More specifically, fractal structures are geometric structures exhibiting self-similarity, characterized by maintaining a form similar to the original structure even when a part of the whole is magnified. Fractal structures feature the repetition of identical patterns across multiple scales, allowing for the efficient use of internal space while maximizing surface area.

[0049] The second branch pipe group (120) may be positioned above the first branch pipe group (110) at a predetermined distance and may include second branch pipes (122) connected to the discharge pipe (121). The second branch pipes (122) may branch out from the discharge pipe (121) in a fractal structure having a predetermined branching angle on a horizontal branching plane and may extend radially. The second branch pipes (122) may branch out on a branching plane parallel to the branching plane on which the first branch pipes (112) branch out. FIG. 1 illustrates an example where the branching angle of the second branch pipes (122) is 30°.

[0050] The connecting pipe group (130) may include vertically extended connecting pipes (132), and the connecting pipes (132) may connect the ends of the first branch pipes (112) of the first branch pipe group (110) and the ends of the second branch pipes (122) of the second branch pipe group (120).

[0051] FIG. 2 schematically illustrates the fractal structure of a first heat exchanger for re-liquefaction according to one embodiment of the technical concept of the present invention.

[0052] The fractal structure of the first branch pipes (112) branching at a branching angle (θ) from the first branch pipe group (110) and the second branch pipes (122) branching at a branching angle (θ) from the second branch pipe group (120) can have their diameter and length determined by Equation (1) and Equation (2).

[0054] (D k+1 / D k )=2 -1 / 3 Equation (1)

[0055] (L k+1 / L k )=2 -1 / 2 (2)

[0056] Here, k is a branching step and is an integer greater than or equal to 0 (in FIG. 2, k has values ​​from 0 to 4), and D k is the diameter of the k-th branched branch, and L k is the length of the k-th branched duct.

[0057] FIG. 3 illustrates a schematic perspective view and plan view of a first re-liquefaction heat exchanger according to an embodiment of the technical concept of the present invention when the branching angle is 180 degrees. Although the vertical storage tank (10) is omitted in FIG. 3, the first re-liquefaction heat exchanger (100) may be positioned inside the vertical storage tank (10) in the manner described in FIG. 1.

[0058] A first heat exchanger for re-liquefaction according to one embodiment of the technical concept of the present invention can be formed by 3D metal printing technology. 3D metal printing is a method of manufacturing a desired shape by stacking metal materials layer by layer using additive manufacturing (AM) technology. Unlike conventional cutting (CNC) or casting methods, this technology has the advantage of being able to manufacture parts with complex shapes in a single step, so multi-stage branching piping such as fractal structures can be manufactured in a single process.

[0059] The metal material to be used for 3D metal printing may be an alloy that maintains durability even in a cryogenic environment, and stainless steel (316L), Inconel, aluminum alloy, titanium alloy, etc. may be used.

[0060] FIG. 4 schematically illustrates a liquid hydrogen storage and reliquefaction system including a second reliquefaction heat exchanger according to another embodiment of the technical concept of the present invention.

[0061] A second heat exchanger (200) for re-liquefaction according to another embodiment of the technical concept of the present invention may be located inside a liquid hydrogen storage tank and may include a first branch piping group (210) and a second branch piping group (220). FIG. 4 illustrates a vertical storage tank (10) as an example of a liquid hydrogen storage tank.

[0062] Liquid hydrogen is stored in a vertical storage tank (10), and an inlet pipe (211) for introducing refrigerant from outside the vertical storage tank (10) and an outlet pipe (221) for discharging refrigerant from inside the vertical storage tank (10) can pass through one side of the vertical storage tank (10). Although FIG. 4 shows that both the inlet pipe (211) and the outlet pipe (221) are positioned to pass through the upper surface of the vertical storage tank (10), the inlet pipe (211) may pass through the vertical storage tank (10) through the lower part of the vertical storage tank (10), and the outlet pipe (221) may pass through the vertical storage tank (10) through the upper part of the vertical storage tank (10).

[0063] The refrigerant may be a cryogenic refrigerant, and various cryogenic refrigerants including gaseous helium may be used. The refrigerant introduced into the inlet pipe (211) may be discharged through the discharge pipe (221) by passing through the first branch pipes (212) of the first branch pipe group (210) and the second branch pipes (222) of the second branch pipe group (220) in sequence. During this process, the refrigerant re-liquefies the gaseous hydrogen through heat exchange with the gaseous hydrogen evaporated inside the liquid hydrogen storage tank.

[0064] The second re-liquefaction heat exchanger (200) may be positioned in the gaseous region within the vertical storage tank (10), and may also be positioned in both the gaseous region and the liquid region within the vertical storage tank (10).

[0065] The first branch pipe group (210) may include first branch pipes (212) connected to the inlet pipe (211). The first branch pipes (212) may extend from the inlet pipe (211) and branch out in a fractal structure having a predetermined branching angle toward the second branch pipe group (220).

[0066] The second branch pipe group (220) may include second branch pipes (222) connected to a discharge pipe (221) that is spaced apart from the inlet pipe (211) of the first branch pipe group (210) by a predetermined distance on the same axis. The second branch pipes (222) may extend from the discharge pipe (221) and branch out in a fractal structure having a predetermined branching angle toward the first branch pipe group (210).

[0067] The branching angles of the first branch pipe group (210) and the second branch pipe group (220) may be the same, and the first branch pipe group (210) and the second branch pipe group (220) may be 3D fractal structures, and branching may occur on a branching plane that rotates by a predetermined rotation angle around the vertical axis (Z) connecting the inlet pipe (211) and the outlet pipe (221) at each branching stage. The second re-liquefaction heat exchanger (200) of FIG. 4 illustrates the case where the branching angle and rotation angle of the first branch pipe group (210) and the second branch pipe group (220) are each 90°.

[0068] The ends of the first branch pipes (212) of the first branch pipe group (210) and the ends of the second branch pipes (222) of the second branch pipe group (220) can be connected to each other.

[0069] The first branch piping group (210) and the second branch piping group (220) can be formed by 3D metal printing technology.

[0070] FIG. 5 illustrates a schematic perspective view and plan view of a horizontal storage tank in which a heat exchanger for re-liquefaction is located according to embodiments of the technical concept of the present invention.

[0071] A liquid hydrogen storage and re-liquefaction system according to another embodiment of the technical concept of the present invention may include a horizontal storage tank (20) and one or more first re-liquefaction heat exchangers (100).

[0072] Liquid hydrogen is stored in the horizontal storage tank (20), and an inlet pipe (111) for introducing refrigerant from outside the horizontal storage tank (20) and an outlet pipe (121) for discharging refrigerant from inside the horizontal storage tank (20) can pass through one side of the horizontal storage tank (20). Although FIG. 5 shows that both the inlet pipe (111) and the outlet pipe (121) are positioned to pass through the upper surface of the horizontal storage tank (20), the inlet pipe (111) may pass through the horizontal storage tank (20) through the lower part of the horizontal storage tank (20), and the outlet pipe (121) may pass through the horizontal storage tank (20) through the upper part of the horizontal storage tank (20). Inside the horizontal storage tank (20), the inlet pipe (111) and the outlet pipe (121) can be branched and connected to each first re-liquefaction heat exchanger (100).

[0073] The refrigerant introduced into the horizontal storage tank (20) through the inlet pipe (111) can be discharged to the outside of the horizontal storage tank (20) through the discharge pipe (121) by passing through the first branch pipes (112) of the first branch pipe group (110), the connecting pipe (132) of the connecting pipe group (130), and the second branch pipes (122) of the second branch pipe group (120) in sequence. In this process, the refrigerant re-liquefies the gaseous hydrogen through heat exchange with the gaseous hydrogen evaporated inside the horizontal storage tank (20).

[0074] The first re-liquefaction heat exchanger (100) may be positioned in the gaseous region within the horizontal storage tank (20), or may be positioned in both the gaseous region and the liquid region within the horizontal storage tank (20). Since the configuration of the first branch piping group (110), the connecting piping group (130), and the second branch piping group (120) is the same as the configuration described above, a repetitive description is omitted.

[0075] A liquid hydrogen storage and re-liquefaction system according to another embodiment of the technical concept of the present invention may include a horizontal storage tank (20) and one or more second re-liquefaction heat exchangers (200).

[0076] Liquid hydrogen is stored in the horizontal storage tank (20), and an inlet pipe (211) for introducing refrigerant from outside the horizontal storage tank (20) and an outlet pipe (221) for discharging refrigerant from inside the horizontal storage tank (20) can pass through one side of the horizontal storage tank (20). Although FIG. 5 shows that both the inlet pipe (211) and the outlet pipe (221) are positioned to pass through the upper surface of the horizontal storage tank (20), the inlet pipe (211) may pass through the horizontal storage tank (20) through the lower part of the horizontal storage tank (20), and the outlet pipe (221) may pass through the horizontal storage tank (20) through the upper part of the horizontal storage tank (20). Inside the horizontal storage tank (20), the inlet pipe (211) and the outlet pipe (221) can be branched and connected to each second re-liquefaction heat exchanger (200).

[0077] The refrigerant introduced into the horizontal storage tank (20) through the inlet pipe (211) can be discharged to the outside of the horizontal storage tank (20) through the discharge pipe (221) by passing through the first branch pipes (212) of the first branch pipe group (210) and the second branch pipes (222) of the second branch pipe group (220) in sequence. In this process, the refrigerant re-liquefies the gaseous hydrogen through heat exchange with the gaseous hydrogen evaporated inside the horizontal storage tank (20).

[0078] The second re-liquefaction heat exchanger (200) may be positioned in the gaseous region within the horizontal storage tank (20), or may be positioned in both the gaseous region and the liquid region within the horizontal storage tank (20). Since the configuration of the first branch piping group (210) and the second branch piping group (220) is the same as the configuration described above, a repetitive description is omitted.

[0079] FIG. 6 is a diagram comparing the internal heat transfer coefficient and pressure drop between the reliquefaction heat exchanger of the present invention and a reliquefaction heat exchanger of the prior art with a simple parallel configuration. As can be seen in FIG. 6, it can be confirmed that the reliquefaction heat exchanger of the present invention (first reliquefaction heat exchanger) ("fractal") exhibits superior heat transfer and hydrodynamic performance compared to the prior art ("parallel"), and the reliquefaction heat exchanger of the present invention can exhibit higher flow uniformity compared to the prior art.

[0080] Accordingly, although the present invention has been described in detail with reference to the examples above, those skilled in the art may make modifications, changes, and variations to these examples without departing from the scope of the invention. Explanation of the symbols

[0081] 10: Vertical storage tank 20: Horizontal storage tank 100: First reliquefaction heat exchanger 110: 1st Quarter Piping Group 120: 2nd Quarter Piping Group 130: Connection Piping Group 200: Second heat exchanger for reliquefaction 210: 1st Quarter Piping Group 220: 2nd Quarter Piping Group

Claims

Claim 1 A heat exchanger for re-liquefaction for a liquid hydrogen storage tank, comprising: a first branch pipe group including first branch pipes branching from an inlet pipe in a fractal structure having a predetermined branch angle; a second branch pipe group including second branch pipes branching from an outlet pipe in a fractal structure having a predetermined branch angle; and a connecting pipe group including connecting pipes connecting the first branch pipes and the second branch pipes, wherein a refrigerant introduced into the inlet pipe is discharged through the first branch pipes, the connecting pipes, and the second branch pipes to the outlet pipe. Claim 2 A heat exchanger for reliquefaction according to claim 1, characterized in that the first branch piping group and the second branch piping group branch on a branch plane parallel to each other. Claim 3 A heat exchanger for reliquefaction according to claim 1, characterized in that the diameter and length of the first branch pipes and the second branch pipes in the first branch pipe group and the second branch pipe group are determined by Equation (1) and Equation (2). (D k+1 / D k )=2 -1 / 3 Equation (1)(L k+1 / L k )=2 -1 / 2 Equation (2) Here, k is a branching step and is an integer greater than or equal to 0, and D k is the diameter of the k-th branched branch, and L k is the length of the k-th branch. Claim 4 A heat exchanger for re-liquefaction according to claim 1, characterized in that the branching angle is 30 degrees or 180 degrees. Claim 5 A heat exchanger for reliquefaction according to claim 1, characterized in that the first branch piping group, the connecting piping group, and the second branch piping group are formed by 3D metal printing technology. Claim 6 A heat exchanger for re-liquefaction for a liquid hydrogen storage tank, comprising: a first branch pipe group including first branch pipes branching from an inlet pipe in a fractal structure having a predetermined branch angle; and a second branch pipe group including second branch pipes branching from an outlet pipe toward the first branch pipe group in a fractal structure having a predetermined branch angle and connected to the first branch pipes, wherein the first branch pipe group and the second branch pipe group branch on a branching plane that rotates by a predetermined rotation angle around an axis connecting the inlet pipe and the outlet pipe at each branching stage, and a refrigerant introduced into the inlet pipe is discharged through the first branch pipes and the second branch pipes to the outlet pipe. Claim 7 A heat exchanger for re-liquefaction according to claim 6, characterized in that the branch angle and the rotation angle are each 90 degrees. Claim 8 A heat exchanger for reliquefaction according to claim 6, characterized in that the first branch piping group and the second branch piping group are formed by 3D metal printing technology. Claim 9 A liquid hydrogen storage and re-liquefaction system comprising: a vertical storage tank through which liquid hydrogen is stored and through which an inlet pipe for introducing refrigerant and an outlet pipe for discharging refrigerant are penetrated; a first branch pipe group comprising first branch pipes branching from the inlet pipe in a fractal structure having a predetermined branching angle on a horizontal branching plane; a second branch pipe group comprising second branch pipes branching from the outlet pipe in a fractal structure having a predetermined branching angle on a horizontal branching plane; and a connecting pipe group comprising connecting pipes connecting the first branch pipes and the second branch pipes, wherein the refrigerant introduced through the inlet pipe is discharged through the first branch pipes, the connecting pipes, and the second branch pipes to the outlet pipe. Claim 10 A liquid hydrogen storage and reliquefaction system according to claim 9, characterized in that the diameter and length of the first branch pipes and the second branch pipes in the first branch pipe group and the second branch pipe group are determined by Equation (1) and Equation (2). (D k+1 / D k )=2 -1 / 3 Equation (1)(L k+1 / L k )=2 -1 / 2 Equation (2) Here, k is a branching step and is an integer greater than or equal to 0, and D k is the diameter of the k-th branched branch, and L k is the length of the k-th branch. Claim 11 A liquid hydrogen storage and reliquefaction system according to claim 9, characterized in that the branching angle is 30 degrees or 180 degrees. Claim 12 A liquid hydrogen storage and reliquefaction system according to claim 9, characterized in that the first branch piping group, the connecting piping group, and the second branch piping group are formed by 3D metal printing technology. Claim 13 A liquid hydrogen storage and re-liquefaction system comprising: a vertical storage tank through which liquid hydrogen is stored and through which an inlet pipe for refrigerant is introduced and an outlet pipe for refrigerant is discharged; a first branch pipe group including first branch pipes branching from the inlet pipe in a fractal structure having a predetermined branching angle; and a second branch pipe group including second branch pipes branching from the end of the outlet pipe toward the first branch pipe group in a fractal structure having a predetermined branching angle and connected to the first branch pipes, wherein the first branch pipe group and the second branch pipe group branch on a branching plane that rotates by a predetermined rotation angle around a vertical axis connecting the inlet pipe and the outlet pipe at each branching stage, and the refrigerant introduced into the inlet pipe is discharged through the first branch pipes and the second branch pipes to the outlet pipe. Claim 14 A liquid hydrogen storage and reliquefaction system according to claim 13, characterized in that the branching angle and the rotation angle are each 90 degrees. Claim 15 A liquid hydrogen storage and reliquefaction system according to claim 13, characterized in that the first branch piping group and the second branch piping group are formed by 3D metal printing technology. Claim 16 A liquid hydrogen storage and re-liquefaction system comprising: a horizontal storage tank through which liquid hydrogen is stored and through which an inlet pipe for introducing refrigerant and an outlet pipe for discharging refrigerant are penetrated; one or more re-liquefaction heat exchangers located within the horizontal storage tank and connected to the inlet pipe and the outlet pipe, wherein the re-liquefaction heat exchangers comprise: a first branch pipe group including first branch pipes branching from the inlet pipe in a fractal structure having a predetermined branching angle on a horizontal branching plane; a second branch pipe group including second branch pipes branching from the outlet pipe in a fractal structure having a predetermined branching angle on a horizontal branching plane; and a connecting pipe group including connecting pipes connecting the first branch pipes and the second branch pipes, wherein the refrigerant introduced through the inlet pipe is discharged through the first branch pipes, the connecting pipe, and the second branch pipes. Claim 17 A liquid hydrogen storage and reliquefaction system according to claim 16, characterized in that the diameter and length of the first branch pipes and the second branch pipes in the first branch pipe group and the second branch pipe group are determined by Equation (1) and Equation (2). (D k+1 / D k )=2 -1 / 3 Equation (1)(L k+1 / L k )=2 -1 / 2 Equation (2) Here, k is a branching step and is an integer greater than or equal to 0, and D k is the diameter of the k-th branched branch, and L k is the length of the k-th branch. Claim 18 A liquid hydrogen storage and reliquefaction system according to claim 16, characterized in that the branching angle is 30 degrees or 180 degrees. Claim 19 A liquid hydrogen storage and reliquefaction system according to claim 16, characterized in that the first branch piping group, the connecting piping group, and the second branch piping group are formed by 3D metal printing technology. Claim 20 A liquid hydrogen storage and re-liquefaction system comprising: a horizontal storage tank through which liquid hydrogen is stored and through which an inlet pipe for introducing refrigerant and an outlet pipe for discharging refrigerant pass; one or more heat exchangers for re-liquefaction located within the horizontal storage tank and connected to the inlet pipe and the outlet pipe, wherein the heat exchangers for re-liquefaction comprise: a first branch pipe group including first branch pipes branching from the inlet pipe in a fractal structure having a predetermined branching angle; and a second branch pipe group including second branch pipes branching from the end of the outlet pipe toward the first branch pipe group in a fractal structure having a predetermined branching angle and connected to the first branch pipes, wherein the first branch pipe group and the second branch pipe group branch on a branching plane that rotates by a predetermined rotation angle around a vertical axis connecting the inlet pipe and the outlet pipe at each branching stage, and the refrigerant introduced into the inlet pipe is discharged through the first branch pipes and the second branch pipes to the outlet pipe. Claim 21 A liquid hydrogen storage and reliquefaction system according to claim 20, characterized in that the branching angle and the rotation angle are each 90 degrees. Claim 22 A liquid hydrogen storage and reliquefaction system according to claim 21, characterized in that the first branch piping group and the second branch piping group are formed by 3D metal printing technology.

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