Fuel Cell Membrane Humidifier

Abstract

A membrane humidifier for a fuel cell is disclosed that can prevent a decrease in efficiency caused by an increase in differential pressure in the membrane humidifier of a fuel cell, which occurs when the volume of the membrane humidifier of a fuel cell is reduced. The disclosed membrane humidifier of a fuel cell performs moisture exchange between a first fluid and a second fluid, and includes a mid-case, a second fluid inlet for allowing the second fluid to flow into the mid-case, a second fluid outlet for discharging the second fluid to the outside, a partition dividing the internal space of the mid-case into a first space and a second space, and an active bypass section for adjusting the flow rate of the second fluid flowing between the first space and the second space depending on the flow rate of the second fluid flowing in through the second fluid inlet.

Description

[Technical field]

[0001] The present invention relates to a membrane humidifier for a fuel cell, and more specifically, to a membrane humidifier for a fuel cell that can prevent a decrease in efficiency due to an increase in differential pressure within the membrane humidifier of a fuel cell caused by the miniaturization of the volume of the membrane humidifier of a fuel cell. [Background technology]

[0002] A fuel cell is a power generating battery that generates electricity by combining hydrogen and oxygen. Unlike general chemical batteries such as dry batteries and storage batteries, fuel cells can continuously generate electricity as long as hydrogen and oxygen are supplied, and have the advantages of no heat loss and being twice as efficient as an internal combustion engine. In addition, because the chemical energy produced by the combination of hydrogen and oxygen is directly converted into electrical energy, fuel cells emit less polluting substances. Therefore, fuel cells are not only environmentally friendly, but also have the advantage of reducing concerns about resource depletion due to increased energy consumption. Depending on the type of electrolyte used, such fuel cells can be broadly classified into polymer electrolyte membrane fuel cells (PEMFCs), phosphoric acid fuel cells (PAFCs), molten carbonate fuel cells (MCFCs), solid oxide fuel cells (SOFCs), alkaline fuel cells (AFCs), and the like. Although all of these fuel cells operate on the same fundamental principle, they differ in the type of fuel used, operating temperature, catalyst, electrolyte, etc. Among them, polymer electrolyte membrane fuel cells (PEMFCs) are known to be the most promising for use not only in small-scale stationary power generation equipment but also in transportation systems, as they operate at lower temperatures than other fuel cells, have high power density, and can be made compact. One of the most important factors in improving the performance of a polymer electrolyte fuel cell (PEMFC) is to maintain its function by supplying a certain amount of moisture to the polymer electrolyte membrane (PEM or proton exchange membrane) of the membrane electrode assembly (MEA). If the polymer electrolyte membrane dries out, the power generation efficiency drops sharply. There are three methods for humidifying a polymer electrolyte membrane: 1) a bubbler humidification method in which a pressure-resistant container is filled with water and the target gas is passed through a diffuser to supply moisture; 2) a direct injection method in which the amount of moisture required for the fuel cell reaction is calculated and moisture is supplied directly to the gas flow pipe via a solenoid valve; and 3) a humidification membrane method in which moisture is supplied to the gas flow bed using a polymer separation membrane.

[0003] Among these, the membrane humidification method, which utilizes a membrane that selectively allows only water vapor contained in exhaust gas to pass through and provides water vapor to air supplied to the polymer electrolyte membrane to humidify the polymer electrolyte membrane, is advantageous in that it allows the membrane humidifier to be made lighter and smaller. The selectively permeable membrane used in the membrane humidification method is preferably a hollow fiber membrane, which has a large permeation area per unit volume when forming a module. That is, when the hollow fiber membrane is used to manufacture a membrane humidifier, it is possible to highly integrate hollow fiber membranes with a large contact surface area, and it has the advantages that the fuel cell can be sufficiently humidified even with a small capacity, low-cost materials can be used, and the moisture and heat contained in the off-gas discharged at high temperature from the fuel cell can be recovered and reused through the membrane humidifier. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a membrane humidifier for a fuel cell that can prevent a decrease in efficiency caused by an increase in the pressure difference inside the membrane humidifier of a fuel cell, which occurs when the volume of the membrane humidifier of a fuel cell is reduced. [Means for solving the problem]

[0005] A membrane humidifier for a fuel cell according to an embodiment of the present invention performs moisture exchange between a first fluid and a second fluid and includes a midcase, a second fluid inlet for allowing the second fluid to flow into the midcase, a second fluid outlet for discharging the second fluid to the outside, a partition for dividing an internal space of the midcase into a first space and a second space, and an active bypass section for adjusting the flow rate of the second fluid flowing between the first space and the second space depending on the flow rate of the second fluid flowing in through the second fluid inlet. In the membrane humidifier of the fuel cell according to an embodiment of the present invention, the active bypass portion includes a bypass hole formed through the partition wall, and a bypass hole opening / closing means for opening and closing the bypass hole depending on the flow rate of the second fluid flowing in through the second fluid inlet. In the membrane humidifier for a fuel cell according to an embodiment of the present invention, the bypass hole opening and closing means is also a single valve membrane member formed in the partition wall and formed to cover the bypass hole. In the membrane humidifier for a fuel cell according to an embodiment of the present invention, the bypass hole opening and closing means is also a dual valve membrane member formed in the partition wall and covering both sides of the bypass hole. In the membrane humidifier of the fuel cell according to an embodiment of the present invention, the bypass hole opening and closing means is also a double valve membrane member formed in the partition wall to cover both sides of the bypass hole, but at least partially overlapping. In the membrane humidifier of the fuel cell according to an embodiment of the present invention, it is preferable that the bypass hole opening and closing means is made of a flexible material that is deformed when pressure increases and restored to its original shape when pressure is reduced. The membrane humidifier for a fuel cell according to an embodiment of the present invention also includes caps formed on both ends of the mid-case, and at least one cartridge disposed within the mid-case and housing a plurality of hollow fiber membranes. Further details of embodiments according to various aspects of the present invention are included in the following detailed description. Effect of the Invention

[0006] According to an embodiment of the present invention, a part of the second fluid flowing into the membrane humidifier of the fuel cell is discharged to the outside by bypassing the hollow fiber membrane depending on the flow rate of the second fluid, thereby eliminating the increase in the differential pressure. As a result, it is possible to prevent the increase in the differential pressure in the membrane humidifier of the fuel cell due to the reduction in the volume of the membrane humidifier of the fuel cell, and to improve the overall humidification efficiency. [Brief description of the drawings]

[0007] [Figure 1] 1 is a front view illustrating a membrane humidifier of a fuel cell according to an embodiment of the present invention; [Diagram 2] 1 is a plan view illustrating a membrane humidifier of a fuel cell according to an embodiment of the present invention; [Diagram 3] 3 is a cross-sectional view taken along line AA' in FIG. 2. [Figure 4] FIG. 2 is a cut-away side view of a humidification module with the cap removed of a membrane humidifier of a fuel cell according to one embodiment of the present invention. [Diagram 5] 2 is a perspective view illustrating a cartridge installed in a membrane humidifier of a fuel cell according to an embodiment of the present invention; FIG. [Figure 6] 2 is a cross-sectional view illustrating a cartridge installed in a membrane humidifier of a fuel cell according to an embodiment of the present invention; [Figure 7] 1A-1C are diagrams illustrating active bypass sections according to various embodiments. [Figure 8] 1A-1C are diagrams illustrating active bypass sections according to various embodiments. [Figure 9]1A-1C are diagrams illustrating active bypass sections according to various embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Although the present invention can be modified in various ways and can have various embodiments, specific embodiments are illustrated and described in detail by detailed description. However, it should be understood that the present invention is not limited to the specific embodiments, but includes all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention. The terms used in the present invention are merely used to describe a particular embodiment and are not intended to limit the present invention. A singular expression includes a plural expression unless the context clearly dictates otherwise. In the present invention, the terms "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, and should be understood not to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof. Hereinafter, a membrane humidifier for a fuel cell according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a front view of a membrane humidifier of a fuel cell according to one embodiment of the present invention, FIG. 2 is a plan view of a membrane humidifier of a fuel cell according to one embodiment of the present invention, FIG. 3 is a cross-sectional view cut along line A-A' of FIG. 2, and FIG. 4 is a side cut view of a humidification module with the cap removed of a membrane humidifier of a fuel cell according to one embodiment of the present invention.

[0009] As shown in FIGS. 1-4, a membrane humidifier for a fuel cell according to one embodiment of the present invention includes a humidification module 110, a cap 120, and an active bypass section . The humidification module 110 exchanges moisture between a first fluid supplied from the outside and a second fluid discharged from a fuel cell stack (not shown). The caps 120 are fastened to both ends of the humidification module 110. One of the caps 120 is formed with a first fluid inlet 121 for supplying the first fluid supplied from the outside to the humidification module 110, and the other is formed with a first fluid outlet 122 for supplying the first fluid humidified by the humidification module 110 to the fuel cell stack. The humidification module 110 includes a mid-case 111 having a second fluid inlet 112 and a second fluid outlet 113, and at least one cartridge 20 disposed in the mid-case 111. A second fluid discharged from a fuel cell stack (not shown) flows into the second fluid inlet 112, undergoes moisture exchange in the humidification module 110, and is then discharged to the second fluid outlet 113. In this specification, the fluid flowing in / discharging from the second fluid inlet 112 or the second fluid outlet 113 is not limited to the second fluid. Also, the fluid flowing in / discharging from the first fluid inlet 121 or the first fluid outlet 122 is not limited to the first fluid. Depending on the design, one of the caps 120 can supply the second fluid to the humidification module 110 and allow it to flow inside the hollow fiber membrane, and the other can discharge the second fluid after moisture exchange to the outside. In this case, the first fluid flows in through either the second fluid inlet 112 or the second fluid outlet 113, and the first fluid humidified by the humidification module 110 is supplied to the fuel cell stack through the remaining one. The flow directions of the first fluid and the second fluid can be the same or opposite to each other.

[0010] The mid case 111 and the cap 120 may be formed independently of each other from hard plastic or metal and may have a circular or polygonal widthwise cross section. The circle may include an ellipse, and the polygon may include a polygon with rounded corners. For example, the hard plastic may be polycarbonate, polyamide (PA), polyphthalamide (PPA), polypropylene (PP), etc. The internal space of the mid case 111 may be divided into a first space S1 and a second space S2 by a partition 114. The partition 114 may have an insertion opening H into which at least one cartridge 20 may be inserted. FIG. 5 is an oblique view illustrating a cartridge to be installed in a membrane humidifier of a fuel cell according to one embodiment of the present invention, and FIG. 6 is a cross-sectional view illustrating a cartridge to be installed in a membrane humidifier of a fuel cell according to one embodiment of the present invention. 5 and 6, the cartridge 20 includes a number of hollow fiber membranes 21, a potting portion 22, and an inner case . The hollow fiber membrane 21 also includes a polymer membrane formed from polysulfone resin, polyethersulfone resin, sulfonated polysulfone resin, polyvinylidene fluoride (PVDF) resin, polyacrylonitrile (PAN) resin, polyimide resin, polyamideimide resin, polyesterimide resin, or a mixture of at least two or more of them. The potting portion 22 fixes an end of the hollow fiber membrane 21. The potting portion 22 can be formed by hardening a liquid resin such as a liquid polyurethane resin through a casting method such as dip potting or centrifugal potting. The inner case 23 has openings at each end and houses a number of hollow fiber membranes 21 inside. The ends of the hollow fiber membranes 21 are potted in a potting section 22, which closes the openings of the inner case 23. The inner case 23 has a first mesh hole section MH1 arranged in a mesh pattern for fluid communication with the first space S1, and a second mesh hole section MH2 arranged in a mesh pattern for fluid communication with the second space S2. The second fluid that has flowed into the first space S1 of the mid case 111 through the second fluid inlet 112 flows into the inner case 23 through the first mesh hole portion MH1 and comes into contact with the outer surface of the hollow fiber membrane 21. Subsequently, the second fluid that has exchanged moisture with the first fluid flows through the second mesh hole portion MH2 into the second space S2, and is then discharged from the mid case 111 through the second fluid outlet 113.

[0011] When the flow direction of the second fluid is opposite to the flow direction of the first fluid flowing into the first fluid inlet 121, the second fluid flowing into the second space S2 of the mid case 111 through the second fluid outlet 113 flows into the inner case 23 through the second mesh hole portion MH2 and comes into contact with the outer surface of the hollow fiber membrane 21. Subsequently, the second fluid that has exchanged moisture with the first fluid exits into the first space S1 through the first mesh hole portion MH1, and is then discharged from the mid case 111 through the second fluid inlet 112. A gasket (not shown) may be provided between the mid-case 111 and the cartridge 20. The gasket mounts the cartridge 20 to the humidification module 110 through mechanical assembly. Therefore, if an abnormality occurs in a specific part of the humidification module 110 (e.g., the cartridge 20), the mid-case 111 and the gasket can be easily mechanically separated from the humidification module 110, and then only that part can be repaired or replaced. 7 to 9 are diagrams illustrating various embodiments of an active bypass unit. The active bypass unit 130 adjusts the flow rate of the second fluid flowing between the first space S1 and the second space S2 according to the flow rate of the second fluid flowing in through the second fluid inlet 112. The active bypass unit 130 includes a bypass hole 131 and a bypass hole opening / closing means 132. The bypass holes 131 are formed through the barrier ribs 114. The bypass holes 131 may be formed in various polygonal shapes, such as a triangle, a rectangle, a circle, or an ellipse, or in a circular shape. The bypass hole opening and closing means 132 is made of a flexible material that changes shape when pressure increases and returns to its original shape when pressure decreases. For example, the bypass hole opening and closing means 132 may be made of an elastic valve made of an elastic material (e.g., rubber).

[0012] The bypass hole opening / closing means 132 formed by an elastic valve membrane opens and closes the bypass hole 131 depending on the flow rate of the second fluid flowing in through the second fluid inlet 112 . If the flow rate of the second fluid increases, the pressure rises due to the increased flow rate, and the elastic valve membrane is deformed in the pressure direction to at least partially open the bypass hole 131. If the flow rate of the second fluid decreases, the pressure drops due to the reduced flow rate, and the elastic valve membrane is restored to its original direction to at least partially close the bypass hole 131. 7, the active bypass unit 130 includes a bypass hole 131 and a single valve member 132a formed in the bulkhead 114 to cover the bypass hole 131. The single valve member 132a only needs to be formed on one side of the bypass hole 131, which has the advantage of simplifying the manufacturing process. This can be said to be the most basic form of the active bypass unit 130. 8, the active bypass unit 130 also includes a bypass hole 131 and a dual valve membrane member 132b formed in the partition wall 114 to cover both sides of the bypass hole 131. The dual valve membrane member 132b is formed on both sides around the bypass hole 131, so that it can more sensitively respond to changes in the flow rate of the second fluid. This can be said to be an even more advantageous form when the volume of the membrane humidifier of the fuel cell is smaller than the basic form. 9, the active bypass section 130 also includes a bypass hole 131 and a double valve membrane member 132c formed in the partition wall 114, covering both sides of the bypass hole 131 but overlapping at least a portion of the double valve membrane member 132c. Since the double valve membrane member 132c overlaps at least a portion of the double valve membrane member 132c, it can respond more insensitively to changes in the flow rate of the second fluid. When the volume of the membrane humidifier of the fuel cell is larger than the basic form, it can be said to be an even more advantageous form.

[0013] A portion of the second fluid that has flowed into the second fluid inlet 112 flows from the first space S1 to the second space S2 through the active bypass section 130 depending on the flow rate of the second fluid, and is discharged to the second fluid outlet 113. The second fluid flowing through the active bypass section 130 does not come into contact with the first fluid, and therefore does not exchange moisture. A portion of the second fluid that has flowed into the second fluid inlet 112 flows from the first space S1 to the second space S2 through the active bypass section 130 depending on the flow rate of the second fluid, and is discharged to the second fluid outlet 113. The second fluid flowing through the active bypass section 130 does not come into contact with the first fluid, and therefore does not exchange moisture. In addition, if the volume of the membrane humidifier of the fuel cell is reduced, the pressure difference in the membrane humidifier of the fuel cell increases due to the second fluid flowing in from the fuel cell stack. Since such an increased pressure difference has a negative effect on the efficiency of the membrane humidifier of the fuel cell, it is necessary to eliminate the pressure difference. The active bypass unit 130 allows a portion of the second fluid flowing in to bypass the hollow fiber membrane and be discharged to the outside depending on the flow rate of the second fluid, thereby eliminating the increase in pressure difference. Therefore, the membrane humidifier for a fuel cell having the active bypass unit 130 according to the embodiment of the present invention has an advantage in that it is more advantageous in terms of miniaturization.

[0014] Although one embodiment of the present invention has been described above, a person having ordinary knowledge in the art may modify and change the present invention in various ways by adding, changing, deleting or adding components within the scope of the concept of the present invention described in the claims, and such modifications and changes are also within the scope of the rights of the present invention.

Claims

1. Moisture exchange is performed between the first fluid and the second fluid; Mid case and At least one cartridge disposed within the midcase and configured to house a plurality of hollow fiber membranes; A second fluid inlet that allows the second fluid to flow into the midcase; a second fluid outlet for discharging the second fluid to the outside; a partition wall that divides an internal space of the mid case into a first space and a second space; an active bypass portion that adjusts a flow rate of the second fluid flowing between the first space and the second space according to a flow rate of the second fluid flowing in through the second fluid inlet, the active bypass portion has a bypass hole formed through the partition wall, the second fluid that has flowed into the first space from the second fluid inlet flows into the cartridge and exchanges moisture with the first fluid, the second fluid that has exchanged moisture with the first fluid exits the cartridge into the second space and is discharged from the second fluid outlet, Here, a part of the second fluid that has flowed into the first space through the second fluid inlet passes through the bypass hole, bypasses the hollow fiber membrane, flows into the second space, and is discharged through the second fluid outlet. A membrane humidifier for a fuel cell comprising:

2. The active bypass unit is 2. The membrane humidifier of claim 1, further comprising: a bypass hole opening / closing means for opening and closing the bypass hole according to a flow rate of the second fluid flowing in through the second fluid inlet.

3. The bypass hole opening and closing means is 3. The membrane humidifier of claim 2, wherein the membrane humidifier is a single valve membrane member formed in the partition wall and covering the bypass hole.

4. The bypass hole opening and closing means is 3. The membrane humidifier of claim 2, further comprising a dual valve membrane member formed in the partition wall so as to cover both sides of the bypass hole.

5. The bypass hole opening and closing means is 3. The membrane humidifier of claim 2, wherein the partition is a double-valve membrane member that covers the bypass hole from both sides and is formed so as to overlap at least a portion of the double-valve membrane member.

6. 6. The membrane humidifier of claim 2, wherein the bypass hole opening and closing means is made of a flexible material that is deformed when pressure increases and returns to its original shape when pressure decreases.

7. The fuel cell membrane humidifier of claim 1 , further comprising caps formed on both ends of the midcase.

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