HYDROGEN LIQUEFACTION DEVICE AND HYDROGEN LIQUEFACTION METHOD

Abstract

The present disclosure relates to a hydrogen liquefaction device capable of liquefying gaseous hydrogen into a liquid state through multi-stage cooling by heat exchange between a heat pipe in which a refrigerant cooled by a cryocooler flows and hydrogen flowing through a micro-channel. The device may comprise a hydrogen pipe for connecting a hydrogen supply unit in which gaseous hydrogen is stored and a storage container in which liquid hydrogen liquefied in a liquid state is stored; and a heat exchange unit that cools hydrogen by at least one or more heat exchangers installed on the hydrogen pipe so that hydrogen being introduced from the hydrogen supply unit and flowing through the hydrogen pipe toward the storage container can be cooled and liquefied in a process of passing through the hydrogen pipe and be discharged to the storage container as liquid hydrogen.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and priority to U.S. Provisional Application Ser. No. 63/452,754, filed on Mar. 17, 2023, the entire contents of which is incorporated herein by reference.

BACKGROUND

1. Field of the Invention

The present disclosure relates to a hydrogen liquefaction device and a hydrogen liquefaction method, and more specifically, to a hydrogen liquefaction device and a hydrogen liquefaction method capable of liquefying gaseous hydrogen into a liquid state through multi-stage cooling by heat exchange between a cryocooler and hydrogen flowing through a micro-channel.

2. Description of the Related Art

Demand for replacing gaseous hydrogen with liquid hydrogen as a fuel in conventional hydrogen transportation vehicles is increasing due to its higher storage density compared to high-pressure hydrogen. In particular, liquid hydrogen is widely used in the aerospace industry as a propellant for rockets, and is expected to be widely used in trucks, buses, ships, and aircraft in the future. Such liquid hydrogen is produced in large-scale plants and can only be sold to users with a long-term supply, so even as liquid hydrogen use is expected to grow, there is limited supply for small-scale users.

To solve this problem, a method of producing small quantities of liquid hydrogen using a cryocooler is being used in places where small quantities of liquid hydrogen are used. However, a hydrogen liquefaction device and hydrogen liquefaction method based on the small-scale production method using a conventional cryocooler had a problem of being difficult to use in areas where liquid nitrogen is difficult to procure due to that precooling using liquid nitrogen has been required.

For example, the conventional hydrogen liquefaction device and hydrogen liquefaction method using a cryocooler had a problem of having to periodically replenish liquid nitrogen because, in a process of precooling, such device or method uses liquid nitrogen by using latent heat resulting from evaporating at atmospheric pressure. Although liquid nitrogen is known to be a very inexpensive refrigerant, it is not only not available cheaply everywhere, but it may not even be available at all since there are areas where it is difficult to smoothly procure liquid nitrogen.

In addition, the conventional hydrogen liquefaction devices and hydrogen liquefaction methods that relied on conventional cryocoolers used one-stage cryocoolers connected either in series or in parallel, operating only at temperatures of 80K or lower, pre-cooled with liquid nitrogen. This posed an issue as it did not fully utilize cooling capacity of the cryocooler.

Refrigeration capacity of a cryocooler can vary depending on temperature. For example, the cryocooler may have a small refrigeration capacity at low temperatures and a large refrigeration capacity as temperature increases. Generally, as the cryocooler used to liquefy hydrogen operates near 20K, which is the hydrogen liquefaction temperature, and uses the refrigeration capacity at 20K to liquefy hydrogen, the cryocooler must cool and liquefy hydrogen from the temperature of hydrogen being introduced into the cryocooler to liquefaction temperature. In this case, the lower the inflow temperature of hydrogen, the lower the refrigeration load of the cryocooler, and for this purpose, hydrogen at room temperature was lowered to the temperature of liquid nitrogen by using the liquid nitrogen and introduced into the cryocooler to reduce the cryocooler's load and increase the amount of liquefaction. However, this method had a problem of installing a liquid nitrogen container and a heat exchanger to use liquid nitrogen and periodically having to inject liquid nitrogen.

SUMMARY

The present disclosure is intended to solve various problems including the above problems, and is to provide a hydrogen liquefaction device and a hydrogen liquefaction method that can maximize a heat exchange effect by applying multi-stage cooling that can efficiently use refrigeration capacity of a cryocooler, and by installing a mixed refrigerant heat pipe or a metal heat conductor in a heat exchanger that can exchange heat between a cryocooler and hydrogen gas to enable precooling at various temperatures through multi-stage cooling. However, these objectives are exemplary, and the scope of the present disclosure is not limited thereto.

According to an aspect of the present disclosure, a hydrogen liquefaction device is provided. The hydrogen liquefaction device may comprise a hydrogen pipe for connecting a hydrogen supply unit in which gaseous hydrogen is stored and a storage container in which liquid hydrogen liquified in a liquid state is stored; and a heat exchange unit that cools hydrogen by at least one or more heat exchangers installed on the hydrogen pipe so that hydrogen being introduced from the hydrogen supply unit and flowing through the hydrogen pipe toward the storage container can be cooled and liquefied in a process of passing through the hydrogen pipe and be discharged to the storage container as liquid hydrogen; wherein the heat exchanger includes a cryocooler; a heat transfer unit configured to be in thermal contact with the cryocooler; and a heat exchange unit configured to be in thermal contact with the heat transfer unit and including a micro-channel formed therein through which hydrogen can flow to perform heat exchange between the cryocooler and hydrogen through the heat transfer unit.

According to an embodiment of the present disclosure, the heat transfer unit may be formed in a pipe shape elongated in a vertical direction so that one end thereof can be in thermal contact with the cryocooler, and include a heat pipe filled with a refrigerant therein; wherein the heat exchange unit may be formed to surround the heat pipe, which is formed in a pipe shape, in an annular shape, and may be formed with a micro-channel such that heat exchange between the cryocooler and hydrogen can be performed by heat convection of the refrigerant.

According to an embodiment of the present disclosure, a top portion in the pipe shape of the heat pipe may be configured to be in contact with a cold head of the cryocooler such that the refrigerant vaporized into a gaseous state at a bottom in the pipe shape and raised to the top portion is liquefied again into a liquid state to flow back down along an inner wall by gravity.

According to an embodiment of the present disclosure, the heat exchanger may further include a refrigerant supply unit capable of supplying or retrieving at least any one of methane, argon, nitrogen, neon, hydrogen, and helium into the heat pipe as the refrigerant.

According to an embodiment of the present disclosure, the refrigerant supply unit may fill a single refrigerant made of any one of methane, argon, nitrogen, neon, hydrogen, and helium, or a mixed refrigerant made of mixed materials including at least two materials of methane, argon, nitrogen, neon, hydrogen, and helium at a predetermined ratio and pressure so as to fill the heat pipe with the refrigerant suitable for a predetermined temperature range in which heat exchange is performed in the heat exchanger.

According to an embodiment of the present disclosure, the heat pipe may be configured to be filled with a single refrigerant made of any one of methane, argon, nitrogen, neon, hydrogen, and helium, or a mixed refrigerant made of mixed materials including at least two materials of methane, argon, nitrogen, neon, hydrogen, and helium therein at a predetermined ratio and pressure and to be sealed from outside so as to be suitable for a predetermined temperature range in which heat exchange is performed in the heat exchanger.

According to an embodiment of the present disclosure, the heat exchange unit may be configured to be filled with a porous material therein or to be installed with at least one of a perforated thin plate and a protruding disk so as to form the micro-channel.

According to an embodiment of the present disclosure, the heat transfer unit may include a heat conductor formed in a pillar shape elongated in a vertical direction so that one end thereof can be in thermal contact with the cryocooler; wherein the heat exchange unit may be formed as the micro-channel, which is formed to penetrate a surface of the heat conductor or an inside of the heat conductor so as to expand a heat transfer area of the heat conductor, such that heat exchange between the cryocooler and hydrogen can be performed by heat conduction of the heat conductor.

According to an embodiment of the present disclosure, the heat exchange unit may include a plurality of heat exchangers installed on the hydrogen pipe at predetermined intervals and having lower cooling temperatures from front to rear based on a flow direction of hydrogen so that hydrogen can be cooled in multiple stages from room temperature to liquefaction temperature in a process of passing through the hydrogen pipe.

According to an embodiment of the present disclosure, the heat exchange unit may include a first heat exchanger installed on the hydrogen pipe to cool hydrogen to a first cooling temperature; and a second heat exchanger installed at a rear of the first heat exchanger based on a flow direction of hydrogen on the hydrogen pipe to cool hydrogen to a second cooling temperature lower than the first cooling temperature.

According to an embodiment of the present disclosure, the hydrogen pipe may include a connecting pipe configured to connect a bottom of the first heat exchanger and a top portion of the second heat exchanger to flow hydrogen discharged from the first heat exchanger to the second heat exchanger.

According to an embodiment of the present disclosure, the connecting pipe may be installed with a Joule-Thomson (JT) valve to decrease the temperature of hydrogen by expanding hydrogen that passes through the connecting pipe.

According to an embodiment of the present disclosure, the heat exchange unit may further include an n-th heat exchanger installed at a rear of an n−1st heat exchanger based on a flow direction of hydrogen on the hydrogen pipe to cool hydrogen to the n-th cooling temperature lower than the n−1th cooling temperature.

According to an embodiment of the present disclosure, the cryocooler may be configured so that a cold head formed to be in thermal contact with the heat transfer unit to cool the heat transfer unit by conductive cooling is installed in a vacuum container.

According to other aspect of the present disclosure, a hydrogen liquefaction device is provided. The hydrogen liquefaction device may comprise a hydrogen pipe for connecting a hydrogen supply unit in which gaseous hydrogen is stored and a storage container in which liquid hydrogen liquified in a liquid state is stored; and a heat exchange unit that cools hydrogen by a plurality of heat exchangers installed on the hydrogen pipe at predetermined intervals and having lower cooling temperatures from front to rear based on a flow direction of hydrogen so that hydrogen being introduced from the hydrogen supply unit and flowing through the hydrogen pipe toward the storage container can be cooled and liquefied in multiple stages in a process of passing through the hydrogen pipe and be discharged to the storage container as liquid hydrogen; wherein the heat exchanger may include a cryocooler; a heat transfer unit configured to be in thermal contact with the cryocooler; and a heat exchange unit configured to be in thermal contact with the heat transfer unit and including a micro-channel formed therein through which hydrogen can flow to perform heat exchange between the cryocooler and hydrogen through the heat transfer unit; wherein the heat transfer unit may include one of a heat pipe formed in a pipe shape elongated in a vertical direction so that one end thereof can be in thermal contact with the cryocooler, and a heat conductor formed in a pillar shape elongated in a vertical direction so that one end thereof can be in thermal contact with the cryocooler; wherein the heat exchange unit may be formed to surround the heat pipe, which is formed in a pipe shape, in an annular shape, and may be formed with a micro-channel through which hydrogen can flow such that heat exchange between the cryocooler and hydrogen can be performed by heat convection of the refrigerant, or may be formed as the micro-channel, which is formed to penetrate a surface of the heat conductor or an inside of the heat conductor so as to expand a heat transfer area of the heat conductor, such that heat exchange between the cryocooler and hydrogen can be performed by heat conduction of the heat conductor.

According to another aspect of the present disclosure, a hydrogen liquefaction method is provided. The liquefaction method may comprise: (a) introducing hydrogen into a hydrogen pipe in a gaseous state from a hydrogen supply unit at room temperature in which hydrogen is stored; (b) cooling and liquefying hydrogen in a process of passing through the hydrogen pipe by at least one or more heat exchangers installed on the hydrogen pipe; and (c) discharging liquid hydrogen liquefied in a liquid state from the hydrogen pipe and storing it in a storage container; wherein (b) may include (b-1) cooling the heat transfer unit by a cryocooler that is formed to be in thermal contact with the heat transfer unit of the heat exchanger; (b-2) cooling hydrogen by heat exchange between the cryocooler and the heat exchange unit of the heat exchanger, which is configured to be in thermal contact with the heat transfer unit and includes a micro-channel formed therein through which hydrogen flows, via an intermediary of the heat transfer unit.

According to another embodiment of the present disclosure, (b) may be performed multiple times by a plurality of heat exchangers installed on the hydrogen pipe at predetermined intervals and having lower cooling temperatures from front to rear based on a flow direction of hydrogen so that hydrogen can be cooled in multiple stages from room temperature to liquefaction temperature in a process of passing through the hydrogen pipe.

According to another embodiment of the present disclosure, in (b), when hydrogen cooled in any of the heat exchangers flows through a connecting pipe to another heat exchanger for multi-stage cooling, a volume thereof may expand and the temperature may decrease in a process of passing through a JT valve installed in the connecting pipe.

According to another embodiment of the present disclosure, in (b-1), a refrigerant filled inside a heat pipe formed in a pipe shape of the heat transfer unit may be liquefied by being cooled by the cryocooler that is in thermal contact with the heat pipe, and in (b-2), hydrogen may be cooled by heat exchange performed between the cryocooler and hydrogen that flows through the micro-channel inside the heat exchange unit which is formed to surround the heat pipe in an annular shape, by heat convection of the refrigerant vaporized inside the heat pipe.

According to another embodiment of the present disclosure, in (b-1), the heat conductor formed in a pillar shape of the heat transfer unit may be cooled by the cryocooler which is in thermal contact with the heat conductor, and in (b-2), hydrogen can be cooled by heat exchange performed between the cryocooler and hydrogen that flows through the micro-channel of the heat exchange unit which is formed to penetrate a surface of the heat conductor or an inside of the heat conductor, by heat conduction of the heat conductor.

According to an embodiment of the present disclosure configured as described above, multi-stage cooling is applied by arranging heat exchangers capable of exchanging heat between the cryocooler and hydrogen gas in multiple stages along the flow direction of hydrogen gas flowing along the hydrogen pipe, thereby efficiently using refrigeration capacity of the cryocooler.

In addition, in case of using liquid nitrogen using latent heat evaporating at atmospheric pressure, the precooling temperature may be 77K, which is the atmospheric pressure saturation temperature of nitrogen, and thus the precooling may be very limited. However, according to an embodiment of the present disclosure, the heat exchanger uses a heat pipe or a metal heat conductor to which various refrigerants are applied such as a single refrigerant, e.g., methane, argon, nitrogen, neon, hydrogen, and helium, as well as mixed refrigerants such as methane/argon, nitrogen/argon, nitrogen/neon and the like, so as to perform precooling at various temperatures during the multi-stage cooling process of hydrogen gas, thereby performing multi-stage cooling in a wider temperature range to gradually lower temperatures so as to maximize precooling effect.

As such, since liquid nitrogen or liquefied natural gas, which has been used in conventional hydrogen liquefaction devices, is not used for precooling, there is no need to transport a separate device or a separate refrigerant for precooling, thereby removing a restriction on location of hydrogen liquefaction. In addition, multi-stage cooling using a heat exchanger installed with a cryocooler and a heat pipe or a metal heat conductor to which a single refrigerant or a mixed refrigerant is applied can maximize the precooling effect to increase hydrogen liquefaction efficiency, and it is possible to implement a hydrogen liquefaction device and a hydrogen liquefaction method capable of performing a hydrogen liquefaction process that is convenient to operate and maintain. Of course, the scope of the present disclosure is not limited by these effects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view schematically showing a hydrogen liquefaction device according to an embodiment of the present disclosure.

FIG. 2 is a cross-sectional view schematically showing an embodiment of a heat exchanger included in a heat exchange unit installed in the hydrogen liquefaction device of FIG. 1.

FIG. 3 is a cross-sectional view schematically showing another embodiment of the heat exchanger included in the heat exchange unit installed in the hydrogen liquefaction device of FIG. 1.

FIG. 4 is a table showing embodiments of a configuration of a single refrigerant and a mixed refrigerant that may be used as a refrigerant in a heat exchanger according to a temperature range for multi-stage cooling of hydrogen.

FIG. 5 is a cross-sectional view schematically showing another embodiment of the heat exchanger included in the heat exchange unit installed in the hydrogen liquefaction device of FIG. 1.

FIG. 6 is a cross-sectional view schematically showing yet another embodiment of the heat exchanger included in the heat exchange unit installed in the hydrogen liquefaction device of FIG. 1.

FIG. 7 is a flowchart sequentially showing a hydrogen liquefaction method according to another embodiment of the present disclosure.

DETAILED DESCRIPTION

Hereinafter, various preferred embodiments of the present disclosure will be described in detail with reference to the appended drawings.

The embodiments of the present disclosure are provided to more completely explain the present disclosure to those skilled in the art, and the following embodiments can be modified into various other forms, and the scope of the present disclosure is not limited to the following embodiments. Rather, these embodiments are provided to make the present disclosure more faithful and complete and to fully convey the spirit of the present disclosure to those skilled in the art. Additionally, the thickness and size of each layer in the drawings are exaggerated for convenience and clarity of explanation.

Hereinafter, embodiments of the present disclosure will now be described with reference to drawings that schematically show ideal embodiments of the present disclosure. In the drawings, variations of a depicted shape may be expected, for example, depending on manufacturing technology and/or tolerances. Accordingly, embodiments of the present disclosure should not be construed as being limited to the specific shape of an area shown in this specification, but should include, for example, changes in shape resulting from manufacturing.

FIG. 1 is a conceptual view schematically showing a hydrogen liquefaction device 1000 according to an embodiment of the present disclosure.

As shown in FIG. 1, the hydrogen liquefaction device 1000 according to an embodiment of the present disclosure may, primarily, include a heat exchange unit 100 and a hydrogen pipe 200.

As shown in FIG. 1, the hydrogen pipe 200 is a type of pipe for connecting a hydrogen supply unit 1, where gaseous hydrogen is stored, and a storage container 2, where liquid hydrogen liquefied in a liquid state is stored. This hydrogen pipe 200 allows gaseous hydrogen to be cooled in multiple stages by the heat exchange unit 100, to be described later, in a process of flowing through the hydrogen pipe 200 and finally being liquefied into liquid hydrogen.

The hydrogen supply unit 1 connected to one end of the hydrogen pipe 200 is a room temperature environment and may store hydrogen therein in a gaseous state. In addition, the storage container 2 connected to the other end of the hydrogen pipe 200 is a container for storing liquid hydrogen in a process of flowing through the hydrogen pipe 200. Although not shown, the storage container 2 may have a storage space insulated from external environment by having an insulating wall to prevent generation of evaporative gas from liquid hydrogen stored therein, and may include a re-cooling system for maintaining liquefaction temperature of liquid hydrogen.

As shown in FIG. 1, the heat exchange unit 100 may cool hydrogen by at least one or more heat exchangers 10 installed on the hydrogen pipe 200 so that hydrogen being introduced from the hydrogen supply unit 1 and flowing through the hydrogen pipe 200 toward the storage container 2 can be cooled and liquefied in a process of passing through the hydrogen pipe 200 and be discharged to the storage container 2 as liquid hydrogen.

More specifically, the heat exchange unit 100 may include a plurality of heat exchangers 10-1, 10-2, 10-3, . . . , 10-n installed on the hydrogen pipe 200 at predetermined intervals and having lower cooling temperatures from front to rear, based on a flow direction of hydrogen, so that hydrogen can be cooled in multiple stages from room temperature to liquefaction temperature in a process of passing through the hydrogen pipe 200.

For example, the heat exchange unit 100 may include a first heat exchanger 10-1 installed on the hydrogen pipe 200 to cool hydrogen to a first cooling temperature, a second heat exchanger 10-2 installed at the rear of the first heat exchanger 10-1 based on the flow direction of hydrogen on the hydrogen pipe 200 to cool hydrogen to a second cooling temperature lower than the first cooling temperature, a third heat exchanger 10-3 installed at the rear of the second heat exchanger 10-2 based on the flow direction of hydrogen on the hydrogen pipe 200 to cool hydrogen to a third cooling temperature lower than the second cooling temperature, and an n-th heat exchanger 10-n installed at the rear of the third heat exchanger 10-3 based on the flow direction of hydrogen on the hydrogen pipe 200 to cool hydrogen to the n-th cooling temperature lower than the third cooling temperature.

From the first cooling temperature of the first heat exchanger 10-1 cooling hydrogen to the n-th cooling temperature of the n-th heat exchanger 10-n, cooling temperature may be lowered in multiple stages so that it becomes closer to hydrogen liquefaction temperature from room temperature. For example, hydrogen cooled to the first cooling temperature may be cooled to 120K in a process of passing through the first heat exchanger 10-1, hydrogen cooled to the second cooling temperature may be cooled to 80K in a process of passing through the second heat exchanger 10-2, hydrogen cooled to the third cooling temperature may be cooled to 50K in a process of passing through the third heat exchanger 10-3, and finally, hydrogen cooled to the n-th cooling temperature may be cooled to a liquefaction temperature of 20K in a process of passing through the n-th heat exchanger 10-n and be discharged as liquid hydrogen. Here, the above-described multi-stage cooling temperatures are an embodiment, and are not limited thereto, and may be set to a wide variety of cooling temperatures as necessary.

As such, each of the heat exchangers 10-1, 10-2, 10-3, . . . , 10-n may use a single refrigerant or mixed refrigerant having a different configuration to cool hydrogen in multiple stages with different cooling temperatures. A detailed configuration thereof will be described in more detail in a description of a heat pipe 121 of the heat exchanger 10 to be described later.

In addition, in this embodiment, the heat exchange unit 100 is exemplified as including four heat exchangers 10-1, 10-2, 10-3, . . . , 10-n, but is not necessarily limited to FIG. 1, and may be installed with a wide variety of numbers of heat exchangers, and may also be installed with a single heat exchanger 10 rather than multi-stage heat exchangers considering refrigeration capacity of the cryocooler 110 of the heat exchanger 10, temperature of hydrogen initially supplied from the hydrogen supply unit 1 depending on installation environment, and production volume of liquid hydrogen required at an installation site and the like.

Hereinafter, a configuration of the heat exchanger 10 included in the above-described heat exchange unit 100 of multiple stages will be described in detail.

FIG. 2 is a cross-sectional view schematically showing an embodiment of a heat exchanger 10 included in a heat exchange unit 100 installed in the hydrogen liquefaction device 1000 of FIG. 1; FIG. 3 is a cross-sectional view schematically showing another embodiment of the heat exchanger 10 included in the heat exchange unit 100 installed in the hydrogen liquefaction device 1000 of FIG. 1; and FIG. 4 is a table showing embodiments of a configuration of a single refrigerant and a mixed refrigerant that may be used as a refrigerant in the heat exchanger 10 according to a temperature range for multi-stage cooling of hydrogen. FIG. 5 is a cross-sectional view schematically showing another embodiment of the heat exchanger 10 included in the heat exchange unit 100 installed in the hydrogen liquefaction device 1000 of FIG. 1; and FIG. 6 is a cross-sectional view schematically showing yet another embodiment of the heat exchanger 10 included in the heat exchange unit 100 installed in the hydrogen liquefaction device 1000 of FIG. 1.

Here, the heat exchanger 10 constituting the heat exchange unit 100 in FIG. 2 and FIG. 3 is briefly shown only with a first heat exchanger 10-1 and an n-th heat exchanger 10-n for convenience to help to understand the invention, but the number of installations of the heat exchanger 10 constituting the heat exchange unit 100 is not necessarily limited to FIG. 2 and FIG. 3.

As shown in FIG. 2, the heat exchanger 10 may, primarily, include a cryocooler 110, a heat transfer unit 120, and a heat exchange unit 130.

As shown in FIG. 2, the cryocooler 110 may include a cold head 111 formed to be in thermal contact with the heat pipe 121 of the heat transfer unit 120 or a heat conductor 122 (See FIG. 5), to be described later, to cool refrigerant filled in the heat pipe 121 or the heat conductor 122 itself by conductive cooling; and a compressor 112 connected to the cold head 111 through a He injection pipe (See “Hel”) and a He discharge pipe (See “He T”) to supply compressed helium (He) to the cold head 111 so that the cold head 111 can be cooled to cryogenic temperature.

For example, the cold head 111 may be installed in a vacuum container 3 isolated from external environment to effectively maintain cryogenic temperature and increase the efficiency of conductive cooling to the heat pipe 121 or the heat conductor 122, and may be formed in a circular or polygonal block shape, and in case of being formed in plural numbers, the cold head 111 may be arranged in an annular or straight shape at a bottom, top, or side of the vacuum container 3. In this case, the compressor 112 may be located outside the vacuum container 3 separately from the cold head 111.

In addition, although not shown, at least a portion of the cold head 111 may be formed to protrude inwardly of the heat pipe 121 through which the refrigerant flows to further increase efficiency of conductive cooling to the heat pipe 121.

As shown in FIG. 2, the heat transfer unit 120 may be configured to be in thermal contact with the cryocooler 110 and may include the heat pipe 121 filled with refrigerant therein.

The heat pipe 121 is a pipe shape capable of withstanding high pressure, and may be formed in a pipe shape elongated in a vertical direction so that one end thereof is in thermal contact with the cryocooler 110.

More specifically, the heat pipe 121 may be formed such that an upper part in a pipe shape contacts the cold head 111 of the cryogenic refrigerator 110, allowing refrigerant vaporized into a gaseous state from a lower part of a tubular shape elongated in a vertical direction and raised to the upper part to be liquefied again and circulated inside the heat pipe 121 while flowing down an inner wall again by gravity.

Accordingly, in the heat pipe 121, the top portion in the pipe shape in contact with the cold head 111 may be configured to be a low-temperature portion where the refrigerant is cooled, and the bottom may be configured to be a high-temperature portion for cooling the cooling object (hydrogen), which may take away ambient latent heat and rise to the top portion during a process of vaporizing of the refrigerant. The heat pipe 121 is in contact with the cold head 111 of the cryocooler 110 at the top portion, and thus the high-temperature portion is not limited to the bottom and can be uniformly distributed throughout the heat pipe 121 except for a portion of the top portion that is in contact with the cold head 111.

In conventional heat pipes in the prior art, an inner pipe is formed inside through which a cooled refrigerant descends by gravity, and the refrigerant evaporated at a high-temperature portion is retrieved to a low-temperature portion through an internal space between an exterior of the inner pipe and an outer pipe. However, the heat pipe 121 of the present disclosure is characterized in that a separate inner pipe is not formed, and it is possible to cool the cooling object (i.e., hydrogen) through a surface of an outer pipe.

At this time, the heat exchanger 10 may include a refrigerant supply unit 140 that can supply or retrieve at least any one of methane, argon, nitrogen, neon, hydrogen, and helium into the heat pipe 121 as a refrigerant, and may fill a single refrigerant or mixed refrigerant, which is suitable for a range in which heat exchange with hydrogen, i.e., a cooling object, is performed, at a predetermined pressure through a connecting tube 141 connected to the internal space of the heat pipe 121.

For example, as shown in FIG. 4, the refrigerant supply unit 140 may fill a single refrigerant (100% ratio) made of any one of methane, argon, nitrogen, neon, hydrogen, and helium, or a mixed refrigerant made of mixed materials including at least two materials of methane, argon, nitrogen, neon, hydrogen, and helium at a predetermined ratio (e.g., 50:50) and pressure (e.g., 30 bar) so as to fill the heat pipe 121 with a refrigerant suitable for a predetermined temperature range (123K, 100K, 93K, 85K, 77K, 55K, 30K) in which heat exchange is performed in the heat exchanger 10.

At this time, as shown in FIG. 2, the connecting tube 141, which supplies the single refrigerant or the mixed refrigerant from the refrigerant supply unit 140 to an inner space of the heat pipe 121, is installed with a Joule-Thomson (JT) valve or a JT nozzle, thereby having an effect of lowering temperature of the single refrigerant or the mixed refrigerant by allowing volume thereof to expand in a process of passing through the connecting tube 141.

In addition, as in the heat exchanger 10 according to another embodiment of the present disclosure shown in FIG. 3, without including a separate refrigerant supply unit 140, the heat pipe 121 may be used in a state of being filled in advance with a single refrigerant made of any one of methane, argon, nitrogen, neon, hydrogen, and helium, or a mixed refrigerant made of mixed materials including at least two materials of methane, argon, nitrogen, neon, hydrogen, and helium therein at a predetermined ratio and pressure, and being sealed from outside so as to be suitable for a predetermined temperature range in which heat exchange is performed in the heat exchanger 10.

As shown in FIG. 2 and FIG. 3, a heat exchange unit 130 may be configured to be in thermal contact with the heat transfer unit 120 and include a micro-channel 131 therein through which hydrogen can flow, thereby enabling heat exchange between the cryocooler 110 and hydrogen to be performed through the heat transfer unit 120.

For example, the heat exchange unit 130 is formed to be in thermal contact with the heat pipe 121, which is the heat transfer unit 120, and a micro-channel 131 through which hydrogen can flow is formed within the heat exchange unit 130, so that heat exchange between the cryocooler 110 and hydrogen can be performed by heat convection of the refrigerant.

More specifically, the heat exchange unit 130 may be formed to surround the heat pipe 121, which is formed in a pipe shape, in an annular shape, and be filled with a porous material therein or be installed with at least one of a perforated thin plate and a protruding disk so as to form the micro-channel 131 therein. In addition to this, the heat exchange unit 130 may be installed with all shapes of structures capable of forming the micro-channel 131 therein.

In this way, the heat exchange unit 130 having an annular cross-section, in which the micro-channel 131 is formed, is configured along a surface of an outer pipe of the heat pipe 121 capable of cooling the cooling object (i.e., hydrogen) through the surface of the outer pipe, and thus gaseous hydrogen flowing along the hydrogen pipe 200 can be cooled by heat exchange with the heat pipe 121 in a process of passing through the micro-channel 131.

Such micro-channel 131 formed inside the heat exchange unit 130 stagnates a flow of hydrogen passing through the inside and simultaneously maximizes heat exchange area, thereby having an effect of maximizing efficiency of heat exchange with the heat pipe 121.

In addition, since hydrogen cooled by heat exchange with the heat pipe 121 inside the heat exchange unit 130 may have a property of sinking downward due to gravity resulting from an increase in specific weight in a process of being cooled to a low temperature, as shown in FIG. 2 and FIG. 3, it may be desirable that, in the hydrogen pipe 200, a connecting pipe 210 configured to connect one heat exchanger (e.g., the first heat exchanger, 10-1) and a next heat exchanger (e.g., the n-th heat exchanger, 10-n) is configured to connect a bottom of the first heat exchanger 10-1 and a top portion of the n-th heat exchanger 10-n to flow hydrogen discharged from the bottom of the first heat exchanger 10-1 to the top portion of the n-th heat exchanger 10-n.

According to the above-described configuration of the connecting pipe 210, hydrogen is introduced from the heat exchanger 10 to a top portion of the heat exchange unit 130, and heat exchange with the heat pipe 121 occurs continuously in a process of flowing from the top portion to the bottom of the heat exchange unit 130 through the micro-channel 131, thereby increasing heat exchange time and area with the heat pipe 121, utilizing refrigeration capacity of the cryocooler 110 maximally, and having an effect of increasing efficiency of heat exchange with the heat pipe 121.

In addition, the connecting pipe 210 is installed with a JT valve or a JT nozzle, thereby having an effect of lowering temperature of hydrogen by allowing volume thereof to expand in a process of passing through the connecting pipe 210.

Furthermore, although not shown, in the connecting pipe 210, a temperature sensor and a pressure sensor are installed at a portion connected to an inlet side of the heat exchange unit 130 of the heat exchanger 10 and a portion connected to an outlet side of the heat exchange unit 130, thereby measuring temperature and pressure of hydrogen at an inlet and an outlet of the heat exchanger 10 through which hydrogen is introduced and discharged.

This configuration of the heat transfer unit 120 is not necessarily limited to the aforementioned heat pipe 121, and can be applied to any type of medium which can act as an intermediary for heat exchange with hydrogen that flows through the cryocooler 110 and the micro-channel 131 of the heat exchange unit 130.

For example, as shown in FIG. 5, the heat transfer unit 120 may include a heat conductor 122 formed in a circular pillar shape or a polygonal pillar shape elongated in a vertical direction, so that one end thereof can be in thermal contact with a cold head 111 of the cryocooler 110.

The heat conductor 122 may be made of metal material so that conductive cooling can be made through an upper part of the pillar shape that contacts the cold head 111. The heat conductor 122 may selectively use various types of metal materials with heat conduction properties, such as aluminum or copper, to suit a predetermined temperature range where heat exchange is performed in the heat exchanger 10.

As stated above, in case that the heat transfer unit 120 is configured as the heat conductor 122, the heat transfer unit 130 may, as shown in FIG. 5, be formed as the micro-channel 131, which is formed to penetrate a surface of the heat conductor 122 or an inside of the heat conductor so as to expand a heat transfer area of the heat conductor 122, such that heat exchange between the cryocooler 110 and hydrogen can be performed by heat conduction of the heat conductor 122.

More specifically, as shown in FIG. 5 and FIG. 6, the heat exchange unit 130 may be formed as various types of micro-channels 131 so as to penetrate a surface of the heat conductor 122 or an inside of the heat conductor 122, which is formed in a pillar shape.

Accordingly, by the heat exchange unit 130 formed in the heat conductor 122 in a micro-channel 131 shape so as to expand a heat transfer area with the heat conductor 122, hydrogen in a gaseous state that flows along the hydrogen pipe 200 can be cooled during a process of passing through the micro-channel 131 by heat exchange with the cryocooler 110 through the heat conductor 122.

This heat exchange unit 130 formed in the heat conductor 122 in a micro-channel 131 shape stagnates the flow of hydrogen that passes through the heat exchange unit 130 as well as maximally expands a heat transfer area, thereby maximizing efficiency of heat exchange with the heat conductor 122.

As such, hydrogen, which has passed through a plurality of heat exchangers (10-1, 10-2, 10-3, . . . , 10-n) while repeating the above-mentioned heat exchange process through the heat transfer unit 120, is cooled below liquefaction temperature in a process of finally passing through the n-th heat exchanger 10-n by multi-stage cooling, thereby being discharged as liquid hydrogen in a liquid state through a bottom of the n-th heat exchanger 10-n, and can be stored in the storage container 2 through an end portion of the hydrogen pipe 200.

At this time, a JT valve or JT nozzle is also installed at the end portion of the hydrogen pipe 200 through which liquid hydrogen passes, thereby having an effect of lowering temperature of liquid hydrogen by allowing a volume thereof to expand in a process of passing through the end portion of the hydrogen pipe 210. In addition, a level meter is installed in the storage container 2 where liquid hydrogen is stored to check the amount of liquid hydrogen stored in the storage container 2, thereby monitoring production amount of liquid hydrogen in real time.

Hereinafter, a hydrogen liquefaction method using the above-described hydrogen liquefaction device 1000 will be described in detail.

FIG. 7 is a flowchart sequentially showing a hydrogen liquefaction method according to another embodiment of the present disclosure.

As shown in FIG. 7, the liquefaction method may comprise: (a) introducing hydrogen into a hydrogen pipe 200 in a gaseous state from a hydrogen supply unit 1 at room temperature in which hydrogen is stored; (b) cooling and liquefying hydrogen in a process of passing through the hydrogen pipe 200 by at least one or more heat exchangers 10 installed on the hydrogen pipe 200; and (c) discharging liquid hydrogen liquefied in a liquid state from the hydrogen pipe 200 and storing it in a storage container 2.

Here, (b) may include (b-1) cooling the heat transfer unit 120 by a cryocooler 110 that is formed to be in thermal contact with the heat transfer unit 120; and (b-2) cooling hydrogen by heat exchange between the cryocooler 110 and the heat exchange unit 130 of the heat exchanger 10, which is configured to be in thermal contact with the heat transfer unit 120 and includes a micro-channel 131 formed therein through which hydrogen flows, via an intermediary of the heat transfer unit 120.

For example, in (b-1), the refrigerant filled inside a heat pipe 121 formed in a pipe shape of the heat transfer unit 120 may be liquefied by being cooled by the cryocooler 110 that is in thermal contact with the heat pipe 121.

Subsequently, in (b-2), hydrogen may be cooled by heat exchange performed between the cryocooler 110 and hydrogen that flows through the micro-channel 131 inside the heat exchange unit 130 which is formed to surround the heat pipe 121 in an annular shape, by heat convection of the refrigerant vaporized inside the heat pipe 121.

At this time, the heat pipe 121 in (b-1) may be configured to be filled with a single refrigerant made of any one of methane, argon, nitrogen, neon, hydrogen, and helium, or a mixed refrigerant made of mixed materials including at least two materials of methane, argon, nitrogen, neon, hydrogen, and helium therein at a predetermined ratio and pressure so as to be suitable for a predetermined temperature range in which heat exchange is performed in the heat exchanger 10, and the heat exchange unit 130 in (b-2) may be configured to be filled with a porous material therein or to be installed with at least one of a perforated thin plate and a protruding disk so as to form the micro-channel 131.

In addition to this, in (b-1), the heat conductor 122 formed in a pillar shape of the heat transfer unit 120 may be cooled by the cryocooler 110 that is in thermal contact with the heat conductor 122.

In this case, in (b-2), hydrogen can be cooled by heat exchange performed between the cryocooler 110 and hydrogen that flows through the micro-channel 131 of the heat exchange unit 130 which is formed to penetrate a surface of the heat conductor 122 or an inside of the heat conductor 122, by heat conduction of the heat conductor 122.

At this time, (b) including (b-1) and (b-2) may be performed multiple times by a plurality of heat exchangers 10-1, 10-2, 10-3, . . . , 10-n installed on the hydrogen pipe 200 at predetermined intervals and having lower cooling temperatures from front to rear based on a flow direction of hydrogen, so that hydrogen can be cooled in multiple stages from room temperature to liquefaction temperature in a process of passing through the hydrogen pipe 200. As such, in a process where (b) is performed multiple times, when hydrogen cooled in one heat exchanger flows to another heat exchanger through a connecting pipe 210 for multi-stage cooling, a volume thereof may expand and temperature may thus decrease in a process of passing through a JT valve or JT nozzle installed in the connecting pipe 210.

Therefore, according to the hydrogen liquefaction device 1000 and the hydrogen liquefaction method according to various embodiments of the present disclosure, multi-stage cooling is applied by arranging heat exchangers 10 capable of exchanging heat between the cryocooler 110 and hydrogen gas in multiple stages along a flow direction of hydrogen gas flowing along the hydrogen pipe 200, thereby efficiently using refrigeration capacity of the cryocooler 110.

In addition, the heat exchanger 10 selectively uses the heat pipe 121 or the heat conductor 122 of a metal material to which various refrigerants are applied such as a single refrigerant, e.g., methane, argon, nitrogen, neon, hydrogen, and helium, as well as mixed refrigerants such as methane/argon, nitrogen/argon, nitrogen/neon and the like so as to perform precooling at various temperatures during the multi-stage cooling process of hydrogen gas, thereby performing multi-stage cooling in a wider temperature range to gradually lower temperature to maximize an precooling effect.

Accordingly, since liquid nitrogen or liquefied natural gas used for precooling, which has been used in conventional hydrogen liquefaction devices, is no longer used, there is no need to transport a separate device or a separate refrigerant for precooling, thereby removing restriction on a location of hydrogen liquefaction. In addition, multi-stage cooling using a heat exchanger 10 installed with a cryocooler 110 and a heat pipe 121 or a heat conductor 122 of a metal material to which a single refrigerant or mixed refrigerant is applied can maximize the precooling effect to increase hydrogen liquefaction efficiency, and it becomes possible to implement a hydrogen liquefaction process that is convenient to operate and maintain.

Although the above has shown and described various embodiments of the present disclosure, the present disclosure is not limited to the specific embodiments described above. The above-described embodiments can be variously modified and implemented by those skilled in the art to which the present invention pertains without departing from the gist of the present disclosure claimed in the appended claims, and these modified embodiments should not be understood separately from the technical spirit or scope of the present disclosure. Therefore, the technical scope of the present disclosure should be defined only by the appended claims.

In the embodiments disclosed herein, arrangement of illustrated components may vary depending on requirements or environment in which the invention is implemented. For example, some components may be omitted or some components may be integrated and implemented as one.

Claims

1. A hydrogen liquefaction device, comprising: wherein the heat exchanger includes:

a hydrogen pipe for connecting a hydrogen supply unit in which gaseous hydrogen is stored and a storage container in which liquid hydrogen liquefied in a liquid state is stored; and

a heat exchange unit that cools hydrogen by at least one or more heat exchangers installed on the hydrogen pipe so that hydrogen being introduced from the hydrogen supply unit and flowing through the hydrogen pipe toward the storage container can be cooled and liquefied in a process of passing through the hydrogen pipe and be discharged to the storage container as liquid hydrogen;

a cryocooler;

a heat transfer unit configured to be in thermal contact with the cryocooler; and

a heat exchange unit configured to be in thermal contact with the heat transfer unit and including a micro-channel formed therein through which hydrogen can flow to perform heat exchange between the cryocooler and hydrogen through the heat transfer unit.

2. The hydrogen liquefaction device according to claim 1,

wherein the heat transfer unit is formed in a pipe shape elongated in a vertical direction so that one end thereof can be in thermal contact with the cryocooler, and includes a heat pipe filled with a refrigerant therein;

wherein the heat exchange unit is formed to surround the heat pipe, which is formed in a pipe shape, in an annular shape, and is formed with a micro-channel such that the heat exchange between the cryocooler and hydrogen can be performed by heat convection of the refrigerant.

3. The hydrogen liquefaction device according to claim 2,

wherein a top portion in the pipe shape of the heat pipe is configured to be in contact with a cold head of the cryocooler such that the refrigerant vaporized into a gaseous state at a bottom in the pipe shape and raised to the top portion is liquefied again into a liquid state to flow back down along an inner wall by gravity.

4. The hydrogen liquefaction device according to claim 2, a refrigerant supply unit capable of supplying or retrieving at least any one of methane, argon, nitrogen, neon, hydrogen, and helium into the heat pipe as the refrigerant.

wherein the heat exchanger further includes:

5. The hydrogen liquefaction device according to claim 4,

wherein the refrigerant supply unit is configured to fill a single refrigerant made of any one of methane, argon, nitrogen, neon, hydrogen, and helium, or a mixed refrigerant made of mixed materials including at least two materials of methane, argon, nitrogen, neon, hydrogen, and helium at a predetermined ratio and pressure so as to fill the heat pipe with the refrigerant suitable for a predetermined temperature range in which heat exchange is performed in the heat exchanger.

6. The hydrogen liquefaction device according to claim 2,

wherein the heat pipe is configured to be filled with a single refrigerant made of any one of methane, argon, nitrogen, neon, hydrogen, and helium, or a mixed refrigerant made of mixed materials including at least two materials of methane, argon, nitrogen, neon, hydrogen, and helium therein at a predetermined ratio and pressure and to be sealed from outside so as to be suitable for a predetermined temperature range in which heat exchange is performed in the heat exchanger.

7. The hydrogen liquefaction device according to claim 2,

wherein the heat exchange unit configured to be filled with a porous material therein or to be installed with at least one of a perforated thin plate and a protruding disk so as to form the micro-channel.

8. The hydrogen liquefaction device according to claim 1,

wherein the heat transfer unit includes a heat conductor formed in a pillar shape elongated in a vertical direction so that one end thereof can be in thermal contact with the cryocooler, and

the heat exchange unit is formed as the micro-channel, which is formed to penetrate a surface of the heat conductor or an inside of the heat conductor so as to expand a heat transfer area of the heat conductor, such that heat exchange between the cryocooler and hydrogen can be performed by heat conduction of the heat conductor.

9. The hydrogen liquefaction device according to claim 1,

wherein the heat exchange unit includes:

a plurality of heat exchangers installed on the hydrogen pipe at predetermined intervals and having lower cooling temperatures from front to rear based on a flow direction of hydrogen so that hydrogen can be cooled in multiple stages from room temperature to liquefaction temperature in a process of passing through the hydrogen pipe.

10. The hydrogen liquefaction device according to claim 9,

wherein the heat exchange unit includes:

a first heat exchanger installed on the hydrogen pipe to cool hydrogen to a first cooling temperature; and

a second heat exchanger installed at a rear of the first heat exchanger based on the flow direction of hydrogen on the hydrogen pipe to cool hydrogen to a second cooling temperature lower than the first cooling temperature.

11. The hydrogen liquefaction device according to claim 10,

wherein the hydrogen pipe includes:

a connecting pipe configured to connect a bottom of the first heat exchanger and a top portion of the second heat exchanger to flow hydrogen discharged from the first heat exchanger to the second heat exchanger.

12. The hydrogen liquefaction device according to claim 11,

wherein the connecting pipe is installed with a Joule-Thomson (JT) valve to decrease temperature of hydrogen by expanding hydrogen that passes through the connecting pipe.

13. The hydrogen liquefaction device according to claim 10,

wherein the heat exchange unit further includes:

an n-th heat exchanger installed at a rear of an n−1th heat exchanger based on a flow direction of hydrogen on the hydrogen pipe to cool hydrogen to an n-th cooling temperature lower than an n−1th cooling temperature.

14. The hydrogen liquefaction device according to claim 1,

wherein the cryocooler is configured so that a cold head formed to be in thermal contact with the heat transfer unit to cool the heat transfer unit by conductive cooling is installed in a vacuum container.

15. A hydrogen liquefaction device, comprising:

a hydrogen pipe for connecting a hydrogen supply unit in which gaseous hydrogen is stored and a storage container in which liquid hydrogen liquefied in a liquid state is stored; and

a heat exchange unit that cools hydrogen by a plurality of heat exchangers installed on the hydrogen pipe at predetermined intervals and having lower cooling temperatures from front to rear based on a flow direction of hydrogen so that hydrogen being introduced from the hydrogen supply unit and flowing through the hydrogen pipe toward the storage container can be cooled and liquefied in multiple stages in a process of passing through the hydrogen pipe and be discharged to the storage container as liquid hydrogen;

wherein the heat exchanger includes:

a cryocooler;

a heat transfer unit configured to be in thermal contact with the cryocooler; and

a heat exchange unit configured to be in thermal contact with the heat transfer unit and including a micro-channel formed therein through which hydrogen can flow to perform heat exchange between the cryocooler and hydrogen through the heat transfer unit;

wherein the heat transfer unit includes one of a heat pipe formed in a pipe shape elongated in a vertical direction so that one end thereof can be in thermal contact with the cryocooler; and

a heat conductor formed in a pillar shape elongated in a vertical direction so that one end thereof can be in thermal contact with the cryocooler,

wherein the heat exchange unit is formed to surround the heat pipe, which is formed in a pipe shape, in an annular shape, and is formed with a micro-channel through which hydrogen can flow such that heat exchange between the cryocooler and hydrogen can be performed by heat convection of the refrigerant, or is formed as the micro-channel, which is formed to penetrate a surface of the heat conductor or an inside of the heat conductor so as to expand a heat transfer area of the heat conductor, such that heat exchange between the cryocooler and hydrogen can be performed by heat conduction of the heat conductor.

16. A hydrogen liquefaction method, comprising: wherein (b) includes:

(a) introducing hydrogen into a hydrogen pipe in a gaseous state from a hydrogen supply unit at room temperature in which hydrogen is stored;

(b) cooling and liquefying hydrogen in a process of passing through the hydrogen pipe by at least one or more heat exchangers installed on the hydrogen pipe; and

(c) discharging liquid hydrogen liquefied in a liquid state from the hydrogen pipe and storing it in a storage container;

(b-1) cooling the heat transfer unit by a cryocooler that is formed to be in thermal contact with the heat transfer unit of the heat exchanger;

(b-2) cooling hydrogen by heat exchange between the cryocooler and the heat exchange unit of the heat exchanger, which is configured to be in thermal contact with the heat transfer unit and includes a micro-channel formed therein through which hydrogen flows, via an intermediary of the heat transfer unit.

17. The hydrogen liquefaction method according to claim 16,

wherein (b) is performed multiple times by a plurality of heat exchangers installed on the hydrogen pipe at predetermined intervals and having lower cooling temperatures from front to rear based on a flow direction of hydrogen so that hydrogen can be cooled in multiple stages from room temperature to liquefaction temperature in a process of passing through the hydrogen pipe.

18. The hydrogen liquefaction method according to claim 17,

wherein, in (b),

when hydrogen cooled in any of the heat exchangers flows through a connecting pipe to another heat exchanger for multi-stage cooling, a volume thereof expands and temperature decreases in a process of passing through a JT valve installed in the connecting pipe.

19. The hydrogen liquefaction method according to claim 16,

wherein, in (b-1),

a refrigerant filled inside a heat pipe formed in a pipe shape of the heat transfer unit is liquefied by being cooled by the cryocooler that is in thermal contact with the heat pipe, and

in (b-2),

hydrogen is cooled by heat exchange performed between the cryocooler and hydrogen that flows through the micro-channel inside the heat exchange unit which is formed to surround the heat pipe in an annular shape, by heat convection of the refrigerant vaporized inside the heat pipe.

20. The hydrogen liquefaction method according to claim 16,

wherein, in (b-1),

the heat conductor formed in a pillar shape of the heat transfer unit is cooled by the cryocooler which is in thermal contact with the heat conductor, and

in (b-2),

hydrogen is cooled by heat exchange performed between the cryocooler and hydrogen that flows through the micro-channel of the heat exchange unit which is formed to penetrate a surface of the heat conductor or an inside of the heat conductor, by heat conduction of the heat conductor.