Fuel cell membrane humidifier

Abstract

The present invention relates to a fuel cell membrane humidifier that can prevent a decrease in humidification efficiency caused by a pressure difference between the inside and outside of the membrane humidifier, The fuel cell membrane humidifier according to one embodiment of the present invention comprises: The fuel cell comprises: a middle case having a module insertion section formed therein, the module insertion section having an outer partition wall spaced apart from the inner wall of the middle case; a cap case coupled to the middle case; a hollow fiber membrane module inserted into the module insertion section, the hollow fiber membrane module including at least one hollow fiber membrane bundle having a plurality of hollow fiber membranes integrated therein or at least one hollow fiber membrane cartridge containing a plurality of hollow fiber membranes; and an active pressure buffer section formed between the middle case and the module insertion section for preventing expansion of the module insertion section due to a pressure difference between the inside and outside of the middle case or for eliminating the pressure difference depending on the output status of the fuel cell.

Description

[Technical field]

[0001] The present invention relates to a fuel cell membrane humidifier, and more particularly to a fuel cell membrane humidifier capable of preventing a decrease in humidification efficiency caused by a pressure difference between the inside and outside of the membrane humidifier. [Background technology]

[0002] A fuel cell is a power generating battery that produces electricity by combining hydrogen and oxygen. Unlike ordinary chemical batteries such as dry batteries and storage batteries, fuel cells can continue to produce electricity as long as hydrogen and oxygen are supplied, and because there is no heat loss, they have the advantage of being about twice as efficient as internal combustion engines.

[0003] In addition, fuel cells emit less pollutants because they directly convert the chemical energy generated by the combination of hydrogen and oxygen into electrical energy, making them environmentally friendly and reducing concerns about resource depletion due to increased energy consumption.

[0004] 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), etc., depending on the type of electrolyte used.

[0005] Although all of these fuel cells operate on the same principle, they differ in the type of fuel used, operating temperature, catalyst, electrolyte, etc. Among them, polymer electrolyte fuel cells are known to be the most promising for use in small-scale stationary power generation equipment as well as transportation systems, as they operate at lower temperatures than other fuel cells, have a high power density, and can be made compact.

[0006] One of the most important factors in improving the performance of polymer electrolyte fuel cells is to maintain the moisture content by supplying a certain amount of moisture to the polymer electrolyte membrane (Polymer Electrolyte Membrane or Proton Exchange Membrane: PEM) of the membrane electrode assembly (Membrane Electrode Assembly: MEA). If the polymer electrolyte membrane dries out, the power generation efficiency drops sharply.

[0007] Methods for humidifying a polymer electrolyte membrane include 1) a bubbler humidification method in which an internal pressure vessel 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 layer using a polymer separation membrane.

[0008] Among these, the humidification membrane method, which utilizes a membrane that selectively allows only water vapor contained in the exhaust gas to pass through and provides water vapor to the gas supplied to the polymer electrolyte membrane to humidify the polymer electrolyte membrane, is advantageous in that it allows the humidifier to be made lighter and smaller.

[0009] The selectively permeable membrane used in the humidification membrane method is preferably a hollow fiber membrane with a large permeation area per unit volume when forming a module. That is, when a membrane humidifier is manufactured using a hollow fiber membrane, it is possible to highly integrate hollow fiber membranes with a large contact surface area, and it is possible to sufficiently humidify a fuel cell even with a small capacity, and it is possible to use low-cost materials. It is also possible to recover moisture and heat contained in unreacted gas discharged at high temperature from a fuel cell and reuse them through a humidifier.

[0010] On the other hand, when the membrane humidifier is in operation, a problem occurs in that the humidification efficiency decreases due to the pressure difference between the inside and outside of the membrane humidifier. This will be described with reference to Figs. 1 to 3. 1 to 3 are cross-sectional views of a conventional fuel cell membrane humidifier. For convenience of explanation, only the hollow fiber membrane in the potting part P is shown in the drawings, and the hollow fiber membrane in the remaining parts is omitted. In the conventional membrane humidifier, a hollow fiber membrane module 11 containing a plurality of hollow fiber membranes is housed inside a middle case 10. As shown in the drawings, the hollow fiber membrane module 11 may be formed in a cartridge shape. Inside the middle case 10, a module insertion part 12 is formed into which the cartridge-shaped hollow fiber membrane module 11 is inserted. The module insertion part 12 is formed of a plurality of partition walls 12a, 12b formed inside the middle case 10. Here, the partition wall 12b forming the outer periphery of the module insertion part 12 is substantially a part of the inner wall of the middle case 10.

[0011] As shown in Fig. 2, the hollow fiber membrane module 11 is inserted into the module insertion section 12 with both sides of the hollow fiber membrane module 11 sandwiched between partition walls 12a, 12b. At this time, the middle case 10 has a central recessed section 10a whose center is recessed, and the inner wall of the central recessed section 10a and the hollow fiber membrane module 11 are airtightly attached to each other. As a result, the two fluid flow spaces A and B formed by the unrecessed section 10b of the middle case 10 and the hollow fiber membrane module 11 are isolated. The partition walls 12b forming the outline of the central recessed section 10a and the module insertion section 12 are substantially identical.

[0012] Meanwhile, the second fluid discharged from the fuel cell stack (not shown) flows in through a fluid inlet (not shown) formed in the middle case 10 and exchanges moisture with the first fluid supplied from the blower and flowing inside the hollow fiber membrane while flowing through the hollow fiber membrane module 11. The cap case 20 is coupled to the middle case 10, and is formed with a fluid inlet 20a through which the first fluid flows in and out.

[0013] However, under high pressure operating conditions, i.e., when the second fluid flowing in from a fluid inlet (not shown) formed in the middle case 10 is a high pressure fluid with a higher pressure than the atmospheric pressure outside the membrane humidifier, a pressure difference occurs between the inside and outside of the membrane humidifier, and since the pressure of the second fluid flowing inside the membrane humidifier is higher than the atmospheric pressure outside, a pressure gradient is formed toward the outside of the membrane humidifier, and a part of the membrane humidifier (specifically, the recessed part of the middle case) is deformed toward the outside of the membrane humidifier as shown in Figure 3. On the other hand, since the pressure on both sides of the internal partition 12a is the same, no pressure gradient is formed and no deformation occurs.

[0014] The change in shape of the middle case 10 caused by the pressure gradient creates a gap between the hollow fiber membrane module 11 and the inner wall of the middle case 10, and the second fluid in the fluid flow space A flows through this gap into the fluid flow space B without flowing through the hollow fiber membrane module 11. The second fluid that does not flow through the hollow fiber membrane module 11 is a fluid that has not been humidified through the hollow fiber membranes, which results in a problem of reduced humidification efficiency.

[0015] FIG. 4 is a diagram showing another conventional fuel cell membrane humidifier (see Korean Patent Publication No. 2019-0138288) for solving the problems of the conventional fuel cell membrane humidifier shown in FIG. 1.

[0016] 4, a fuel cell membrane humidifier according to still another prior art has a module insertion section 12 and a pressure buffer section 22 formed inside a middle case 10. The pressure buffer section 22 includes a space created by separating the outer partition wall 12b and the middle case 10, and a connecting section 21 formed between the outer partition wall 12b and the middle case 10. The connecting section 21 separates the fluid flow space A from the fluid flow space B, and allows the fluid that has flowed in through the fluid inlet / outlet 20a to flow only through the hollow fiber membrane cartridge C.

[0017] The pressure buffer section 22 thus configured makes the pressures on both sides of the outer partition wall 12b substantially the same. Because the pressure buffer section 22 does not form a pressure gradient on both sides of the outer partition wall 12b, the outer partition wall 12b is not deformed. Therefore, unlike the fuel cell membrane humidifier shown in FIG. 1, no gap is generated between the hollow fiber membrane cartridge C and the outer partition wall 12b, and the fluid in the fluid flow space A is prevented from flowing into the fluid flow space B without flowing through the hollow fiber membrane module, thereby preventing a decrease in humidification efficiency.

[0018] Meanwhile, in the conventional fuel cell membrane humidifier as shown in FIG. 4, when the pressure (internal pressure P1) of the second fluid flowing in from the fluid inlet (not shown) formed in the middle case 10 is much higher than the atmospheric pressure (external pressure P2) outside the membrane humidifier (P1>>P2) due to the high output state or abnormal output state of the fuel cell, as shown in FIG. 5A and FIG. 5B, the middle case 10 receives an outward pressure due to the pressure difference and can expand outward (indicated as E1). At this time, since the outer partition wall 12b is connected to the connection part 21, the outer partition wall 12b can also expand outward (indicated as E2). If the outer partition wall 12b expands outward, a gap may occur between the hollow fiber membrane cartridge C and the outer partition wall 12b. Therefore, there is a problem that the second fluid that does not flow through the hollow fiber membrane module 11 is generated, and the humidification efficiency decreases. Summary of the Invention [Problem to be solved by the invention]

[0019] An object of the present invention is to provide a fuel cell membrane humidifier that can prevent a decrease in humidification efficiency caused by a pressure difference between the inside and outside of the membrane humidifier. [Means for solving the problem]

[0020] The fuel cell membrane humidifier according to one embodiment of the present invention comprises: The fuel cell comprises: a middle case having a module insertion section formed therein, the module insertion section having an outer partition wall spaced apart from the inner wall of the middle case; a cap case coupled to the middle case; a hollow fiber membrane module inserted into the module insertion section, the hollow fiber membrane module including at least one hollow fiber membrane bundle having a plurality of hollow fiber membranes integrated therein or at least one hollow fiber membrane cartridge containing a plurality of hollow fiber membranes; and an active pressure buffer section formed between the middle case and the module insertion section for preventing expansion of the module insertion section due to a pressure difference between the inside and outside of the middle case or for eliminating the pressure difference depending on the output status of the fuel cell.

[0021] In the fuel cell membrane humidifier according to an embodiment of the present invention, the active pressure buffer unit may include a bypass structure formed between the outer partition and an inner wall of the middle case.

[0022] In one embodiment of the fuel cell membrane humidifier according to the present invention, the bypass structure may include a pair of protruding members fixed to the outer partition and protruding toward the middle case but spaced apart from the inner wall of the middle case, a sliding space formed between the pair of protruding members, and an insertion member formed on the inner wall of the middle case and protruding toward the outer partition but inserted into the sliding space.

[0023] In the fuel cell membrane humidifier according to an embodiment of the present invention, the insert member may include a bypass hole that can be opened or closed depending on the size of an expansion pressure between the outer partition and the middle case.

[0024] In the fuel cell membrane humidifier according to an embodiment of the present invention, when the expansion pressure gradually increases, the insert member may expand outward together with the middle case, and the bypass hole may be opened.

[0025] In the fuel cell membrane humidifier according to an embodiment of the present invention, first sliding protrusions protruding in opposing directions may be formed on ends of the pair of protruding members on the middle case side.

[0026] In the fuel cell membrane humidifier according to an embodiment of the present invention, a second sliding protrusion protruding toward the protruding member may be formed at an end of the insertion member on the outer partition side. Further details of implementations of various aspects of the present invention are included in the following detailed description. Effect of the Invention

[0027] According to an embodiment of the present invention, it is possible to prevent a decrease in humidification efficiency caused by a pressure difference between the inside and outside of a membrane humidifier. In addition, even in a high output state or an abnormal output state of a fuel cell, it is possible to prevent a gap from occurring between a hollow fiber membrane cartridge and an outer partition or to eliminate the pressure difference, thereby preventing a decrease in humidification efficiency. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 is a diagram for explaining problems with a fuel cell membrane humidifier according to the prior art. [Diagram 2] FIG. 1 is a diagram for explaining problems with a fuel cell membrane humidifier according to the prior art. [Diagram 3] FIG. 1 is a diagram for explaining problems with a fuel cell membrane humidifier according to the prior art. [Figure 4] FIG. 2 is a diagram showing a fuel cell membrane humidifier according to still another prior art for solving the problems of the prior art fuel cell membrane humidifier shown in FIG. [Figure 5A] 5 is a diagram for explaining a problem of the fuel cell membrane humidifier according to still another conventional technique shown in FIG. 4. [Figure 5B] 5 is a diagram for explaining a problem of the fuel cell membrane humidifier according to still another conventional technique shown in FIG. 4. [Figure 6] 1A-1C are diagrams illustrating various configurations of a fuel cell membrane humidifier according to an embodiment of the present invention. [Figure 7] 1A-1C are diagrams illustrating various configurations of a fuel cell membrane humidifier according to an embodiment of the present invention. [Figure 8] 1A-1C are diagrams illustrating various configurations of a fuel cell membrane humidifier according to an embodiment of the present invention. [Figure 9] 1A-1C are diagrams illustrating various configurations of a fuel cell membrane humidifier according to an embodiment of the present invention. [Figure 10] 2 is a cross-sectional view showing a portion of a middle case of a fuel cell membrane humidifier according to an embodiment of the present invention; [Figure 11] 4 is an enlarged cross-sectional view showing a change in state due to expansion pressure of a bypass structure, which is one component of an active pressure buffer unit of a fuel cell membrane humidifier according to an embodiment of the present invention; FIG. [Figure 12] 4 is an enlarged cross-sectional view showing a change in state due to expansion pressure of a bypass structure, which is one component of an active pressure buffer unit of a fuel cell membrane humidifier according to an embodiment of the present invention; FIG. [Figure 13] 4 is an enlarged cross-sectional view showing a change in state due to expansion pressure of a bypass structure, which is one component of an active pressure buffer unit of a fuel cell membrane humidifier according to an embodiment of the present invention; FIG. [Figure 14] 4 is a cross-sectional view for explaining an operating state of the fuel cell membrane humidifier according to one embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] The present invention can be modified in various ways and can have various embodiments, and a specific embodiment will be illustrated and described in detail in the detailed description. However, this is not intended to limit the present invention to the specific embodiment, and it should be understood that the present invention includes all modifications, equivalents, and alternatives within the spirit and technical scope of the present invention.

[0030] The terms used in the present invention are merely used to describe certain embodiments and are not intended to limit the present invention. A singular expression includes a plural expression unless the context clearly indicates otherwise. In the present invention, the terms "include" or "have" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations 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 fuel cell membrane humidifier according to an embodiment of the present invention will be described with reference to the drawings.

[0031] 6 to 9 are diagrams showing various forms of a fuel cell membrane humidifier according to an embodiment of the present invention. As shown in Fig. 6 to 9, a fuel cell membrane humidifier according to an embodiment of the present invention (hereinafter, also referred to as "membrane humidifier") includes a middle case 110 and a cap case 120.

[0032] The middle case 110 is combined with the cap case 120 to form the outer shape of the membrane humidifier. The middle case 110 and the cap case 120 may be made of hard plastic such as polycarbonate or metal. The middle case 110 and the cap case 120 may have a polygonal cross-sectional shape in the width direction as shown in Figs. 6 and 7. The polygon may be a rectangle, a square, a trapezoid, a parallelogram, a pentagon, a hexagon, or the like, and the polygon may have rounded corners. Alternatively, the middle case 110 and the cap case 120 may have a circular cross-sectional shape in the width direction as shown in Figs. 8 and 9. The circular shape may be an ellipse. Figs. 6 to 9 are exemplary shapes of the membrane humidifier, and the shape is not limited thereto.

[0033] The middle case 110 is formed with a second fluid inlet 111 through which the second fluid is supplied and a second fluid outlet 112 through which the second fluid is discharged, and a hollow fiber membrane module F containing a plurality of hollow fiber membranes is disposed inside the middle case 110. Depending on the design, reference numeral 111 may be the second fluid outlet through which the second fluid is discharged, and reference numeral 112 may be the second fluid inlet through which the second fluid is supplied. That is, one of reference numerals 111 and 112 may be the second fluid inlet, and the other may be the second fluid outlet. In the following description, reference numeral 111 is the second fluid inlet, and reference numeral 112 is the second fluid outlet, but the present invention is not necessarily limited thereto.

[0034] The hollow fiber membrane module F may be a hollow fiber membrane bundle in which a plurality of hollow fiber membranes are integrated as shown in Figs. 7 and 9, or a hollow fiber membrane cartridge in which a hollow fiber membrane or a hollow fiber membrane bundle is housed as shown in Figs. 6 and 8. In Figs. 6 and 8, a hollow fiber membrane module F is formed by a plurality of hollow fiber membrane cartridges, but the present invention is not limited thereto, and a hollow fiber membrane module F may be formed by one hollow fiber membrane cartridge. In the following description, a membrane humidifier in which a hollow fiber membrane module F is formed by a plurality of cartridges C shown in Fig. 6 and the cross-sectional shape in the width direction is polygonal will be described as an example, but this can be substantially similarly applied to the membrane humidifiers in Figs. 7 to 9. In addition, the cross-sectional shape of the cartridge C is also exemplified as a circle or a square, but the shape of the cartridge C is not limited thereto.

[0035] The cap cases 120 are coupled to both ends of the middle case 110. Each cap case 120 is formed with a fluid inlet / outlet 121, one of which is a first fluid inlet and the other is a first fluid outlet. The first fluid that flows into the fluid inlet / outlet 121 of one cap case 120 passes through an internal channel of the hollow fiber membrane housed inside the hollow fiber membrane cartridge C, and then flows out of the fluid inlet / outlet 121 of the other cap case 120. The hollow fiber membrane may be made of, for example, Nafion, polyetherimide, polyphenylsulfone, polyimide (PI), polysulfone (PS), or polyethersulfone (PES).

[0036] A first mesh part (M1, see FIG. 1) is formed at one end of the hollow fiber membrane cartridge C, which allows the second fluid that has flowed into the membrane humidifier through the second fluid inlet 111 to flow into the inside of the hollow fiber membrane cartridge, and a second mesh part (M2, see FIG. 1) is formed at the other end, which allows the second fluid that has undergone moisture exchange inside the hollow fiber membrane cartridge to flow out of the hollow fiber membrane cartridge. Both sides of the hollow fiber membrane cartridge C are sandwiched between partition walls (211, 212, see FIG. 10) and inserted into the module insertion part 210. Optionally, locking pieces (not shown) may be formed on both sides of the hollow fiber membrane cartridge, and when the hollow fiber membrane cartridge is inserted into the module insertion part 210, the locking pieces may be sandwiched across the partition walls 211, 212 that form the module insertion part 210.

[0037] At both ends of the hollow fiber membrane cartridge or hollow fiber membrane bundle, potting parts P are formed to bind the hollow fiber membranes and fill the gaps between the hollow fiber membranes. As a result, both ends of the hollow fiber membrane module are closed with the potting parts P, and a flow path through which the second fluid passes is formed inside the potting parts. The material of the potting part is well known, and a detailed description thereof will be omitted in this specification. A resin layer E that fills the space between the potting part P and the middle case 110 may be formed around the potting part P, or a gasket assembly (not shown) that hermetically connects the potting part P and the middle case 110 through mechanical assembly may be formed.

[0038] 10 is a cross-sectional view showing a part of a middle case of a fuel cell membrane humidifier according to an embodiment of the present invention. As shown in FIG 10, a module insertion part 210 and an active pressure buffer part 220 are formed inside the middle case 110.

[0039] A hollow fiber membrane cartridge C containing a plurality of hollow fiber membranes is inserted into the module insertion part 210. The module insertion part 210 is composed of a plurality of partitions 211, 212 so that a plurality of hollow fiber membrane cartridges C can be inserted therein. Meanwhile, when a hollow fiber membrane module F is formed from a single hollow fiber membrane cartridge, the inner partition 211 may be omitted. In this case, the module insertion part 210 may have only the outer partition 212.

[0040] The inner wall 110a of the middle case is spaced apart from the outer partition wall 212 of the module insertion section 210. A space S formed by the outer partition wall 212 and the inner wall 110a of the middle case forms an active pressure buffer section 220. The active pressure buffer section 220 may further include a bypass structure 221 formed between the outer partition wall 212 and the inner wall 110a of the middle case.

[0041] The active pressure buffer section 220 can be formed around the outer partition wall 212. The active pressure buffer section 220 separates the fluid flow space A from the fluid flow space B, and allows the fluid to flow only through the hollow fiber membrane cartridge C.

[0042] In addition, the bypass structure 221, which is one component of the active pressure buffer unit 220, can prevent the outer expansion of the outer partition 212 due to the pressure difference or eliminate the pressure difference to prevent a decrease in humidification efficiency even when the pressure (internal pressure P1) of the second fluid flowing in from the fluid inlet 111 formed in the middle case 110 is significantly greater than the atmospheric pressure (external pressure P2) outside the membrane humidifier depending on the high output state or abnormal output state of the fuel cell.

[0043] Hereinafter, the bypass structure 221 will be described with reference to Figures 11 to 13. Figures 11 to 13 are enlarged cross-sectional views showing changes in state of the bypass structure 221, which is one component of the active pressure buffer portion 220, due to the expansion pressure.

[0044] 11, the bypass structure 221 includes a pair of protruding members 221a and an insertion member 221b. The pair of protruding members 221a are fixed to the outer partition 212 and protrude toward the middle case 110, but are formed so as to be spaced apart from the inner wall 110a of the middle case 110. A sliding space SS is formed between the pair of protruding members 221a. The insertion member 221b is formed on the inner wall 110a of the middle case 110 and protrudes toward the outer partition 212, but is formed so as to be inserted into the sliding space SS between the pair of protruding members 221a.

[0045] First sliding protrusions 221aa protruding in opposing directions are formed on the ends of the pair of protruding members 221a on the middle case 110 side, and an insertion member 221b is inserted between the pair of first sliding protrusions 221aa.

[0046] A second sliding protrusion 221ba protruding in the direction of the protruding member 221a is formed on the end of the insertion member 221b on the side of the outer partition wall 212. The outward movement of the second sliding protrusion 221ba is restricted by the first sliding protrusion 221aa.

[0047] The insert member 221b includes at least one bypass hole 221bb. When the insert member 221b moves out of the sliding space SS due to the expansion pressure between the outer partition 212 and the middle case 110, the bypass hole 221bb can be opened or closed.

[0048] For example, when the expansion pressure between the outer partition 212 and the middle case 110 is not large and the sliding space SS is relatively large, the bypass hole 221bb is closed by the pair of protruding members 221a (see FIG. 11). If the expansion pressure between the outer partition 212 and the middle case 110 gradually increases depending on the output status of the fuel cell, the insertion member 221b expands outward together with the middle case 110, and the bypass hole 221bb is opened (see FIGS. 12 and 13).

[0049] The pressure of the second fluid is relatively greater in a high power state compared to a low power state of the fuel cell, and the pressure of the second fluid is relatively much greater in an abnormal power state compared to a normal power state of the fuel cell.

[0050] When the pressure of the second fluid becomes relatively large due to high output or abnormal output of the fuel cell, the middle case 110 receives an expansion pressure due to the large pressure difference, and expands outward (indicated as E1). At this time, the insert member 221b formed in the middle case 110 expands outward together with the middle case 110 (see FIG. 12).

[0051] If the high output state or abnormal output state continues or worsens, the pressure of the second fluid increases further, and the insert member 221b continues to expand outward, gradually opening the multiple bypass holes 221bb that were closed by the pair of protruding members 221a one by one (see FIG. 13).

[0052] As shown in FIG. 13, when the bypass hole 221bb is opened, the fluid in the fluid flow space A flows through the bypass hole 221bb into the fluid flow space B, and then is discharged through the second mesh portion M2 and the second fluid outlet 112, thereby releasing the pressure of the fluid flowing through the fluid flow space A.

[0053] Thereafter, when the high output state or abnormal output state is resolved, i.e., when the fuel cell returns to a low output state or normal output state, the pressure of the second fluid becomes relatively small, so the expansion pressure gradually decreases and the insertion member 221b returns toward the outer partition wall 212. As a result, the bypass hole 221bb is closed again, and it becomes possible to prevent the fluid in the fluid flow space A from flowing into the fluid flow space B without flowing through the hollow fiber membrane module F (see FIG. 11).

[0054] The active pressure buffer unit 220 configured in this manner enables the pressure on both sides of the outer partition wall 212 to be maintained substantially the same even when the fuel cell is in an abnormal output state that generates abnormal pressure. Because the active pressure buffer unit 220 prevents a pressure gradient from being formed on both sides of the outer partition wall 212, the outer partition wall 212 is not deformed.

[0055] 14, a hollow fiber membrane cartridge C is disposed between the partition walls 211 and 212, and the second fluid discharged from the fuel cell stack (not shown) and flowing into the second fluid inlet 111 flows into the cartridge C through the first mesh part M1, exchanges moisture while flowing outside the hollow fiber membrane, and then flows out to the outside of the cartridge through the second mesh part M2. At this time, the pressure P1 of the fluid flowing through the hollow fiber membrane cartridge C is the same, so the pressures on both sides of the inner partition wall 211 are balanced and no deformation occurs.

[0056] Meanwhile, in the outer partition 212, the second fluid at high pressure P1 flows on one side through the hollow fiber membrane cartridge C, and the second fluid at high pressure P1' flows on the other side without passing through the hollow fiber membrane cartridge C. Since the second fluids flowing on both sides of the outer partition 212 have substantially the same pressure (P1=P1'), the pressures on both sides of the outer partition 212 are balanced and no deformation occurs.

[0057] On the other hand, when the fuel cell is in a high output state or an abnormal output state and there is a large pressure difference between the pressure P1 of the second fluid flowing through the active pressure buffer unit 220 and the atmospheric pressure P2 outside the middle case 110, the insertion member 221b of the bypass structure 221 simply expands outward together with the middle case 110, and the protruding member 221a maintains a state of being fixed to the outer partition wall 212. Therefore, the airtightness between the outer partition wall 212 and the hollow fiber membrane cartridge C is maintained, and the second fluid does not leak out between the outer partition wall 212 and the hollow fiber membrane cartridge C.

[0058] Meanwhile, the second fluid that has flowed into the active pressure buffer unit 220 turns at the bypass structure 221 and then flows into the hollow fiber membrane cartridge C. Therefore, unlike the prior art, even in a high output state or an abnormal output state of the fuel cell, no gap is generated between the hollow fiber membrane cartridge C and the outer partition wall 212, and the fluid in the fluid flow space A is prevented from flowing into the fluid flow space B without flowing through the hollow fiber membrane module F, and as a result, a decrease in humidification efficiency is prevented.

[0059] Furthermore, if the high output state or abnormal output state continues or worsens, the pressure of the second fluid increases further, and the bypass holes 221bb formed in the insert member 221b gradually open to an open state. When the bypass holes 221bb open, the fluid in the fluid-flow space A flows through the bypass holes 221bb to the fluid-flow space B, and is then discharged through the second mesh portion M2 and the second fluid outlet 112, thereby releasing the pressure of the fluid flowing through the fluid-flow space A.

[0060] Although one embodiment of the present invention has been described above, a person having ordinary knowledge in the art would be able to modify and change the present invention in various ways by adding, changing, deleting, or adding components without departing from the concept of the present invention described in the claims, and this would also be considered to be within the scope of the claims of the present invention. [Explanation of symbols]

[0061] 110: Middle case 120: Cap case 210: Module insertion section 211: Inner bulkhead 212: Outer bulkhead 220: Active pressure buffer section 221: Bypass structure 221a: Protruding member 221b: Insertion member 221aa, 221ba: Sliding protrusions 221bb: Bypass hole SS: Sliding space A, B: Fluid flow space C: Hollow fiber membrane cartridge F: Hollow fiber membrane module

Claims

1. a middle case having a module insertion section formed therein, the module insertion section having an outer partition wall spaced apart from an inner wall of the middle case; a cap case coupled to the middle case; a hollow fiber membrane module that is inserted into the module insertion section and includes at least one hollow fiber membrane bundle in which a plurality of hollow fiber membranes are integrated or at least one hollow fiber membrane cartridge in which a plurality of hollow fiber membranes are housed; an active pressure buffer unit formed between the middle case and the module insertion part, for preventing expansion of the module insertion part due to a pressure difference between the inside and outside of the middle case or for eliminating the pressure difference according to an output state of the fuel cell; Equipped with the active pressure buffer portion includes a bypass structure formed between the outer partition wall and an inner wall of the middle case, The bypass structure includes: a pair of protruding members fixed to the outer partition wall and protruding toward the middle case but spaced apart from an inner wall of the middle case; A sliding space formed between the pair of protruding members; an insertion member formed on an inner wall of the middle case, protruding toward the outer partition wall and inserted into the sliding space; Equipped with The insert member is a bypass hole that can be opened or closed depending on the size of the expansion pressure between the outer partition and the middle case; Fuel cell membrane humidifier.

2. 2. The fuel cell membrane humidifier of claim 1, wherein when the expansion pressure gradually increases, the insert member expands outward together with the middle case, and the bypass hole opens.

3. 2. The fuel cell membrane humidifier according to claim 1, wherein first sliding protrusions protruding in opposing directions are formed on the ends of the pair of protruding members on the side of the middle case.

4. 4. The fuel cell membrane humidifier according to claim 3, wherein a second sliding protrusion is formed on an outer partition wall side end of the insertion member, protruding toward the protruding member.

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