KR20050113713A - Fuel cell system and stack of the same - Google Patents

Abstract

The present invention provides a fuel cell system and a stack thereof that reduce the depth of the cooling channel and the size of the stack while improving the cooling efficiency of the stack.

A fuel cell system according to the present invention includes a fuel supply unit for supplying a fuel containing hydrogen; An air supply unit for supplying air containing oxygen; A heat carrier supply unit supplying a heat carrier; And a stack having electrical generators disposed on both sides of the MEA to electrochemically react hydrogen and oxygen supplied from the fuel supply unit and the air supply unit to generate electrical energy, wherein the stack includes electricity generation. Cooling channels are provided for flowing heat carriers supplied from the heat carrier supply to cool the parts, and the cooling channels are provided with partitions that create turbulence in the flow of the heat carriers.

Description

FUEL CELL SYSTEM AND STACK OF THE SAME

TECHNICAL FIELD The present invention relates to a fuel cell system and a stack thereof, and more particularly, to a fuel cell system and a stack for turbulent flow of a heat carrier in a cooling channel.

In general, a fuel cell is a power generation that directly converts chemical energy into electrical energy by an electrochemical reaction caused by hydrogen contained in a hydrocarbon-based material such as methanol, ethanol or natural gas and oxygen in air as a fuel. System. In particular, the fuel cell is characterized in that it can simultaneously use the electricity generated by the electrochemical reaction of the fuel gas and the oxidant gas and heat by-products thereof without a combustion process.

Polymer electrolyte fuel cells (PEMFCs, hereinafter referred to as PEMFCs), which are being developed in recent years, have excellent output characteristics, low operating temperatures, and fast start-up and response characteristics compared to other fuel cells.

In order for the above PEMFC to basically have a system configuration, a fuel cell body (hereinafter referred to as a stack for convenience) called a stack, a fuel tank, and a fuel pump for supplying fuel from the fuel tank to the stack Etc. are required. In the process of supplying the fuel stored in the fuel tank to the stack, a reformer for reforming the fuel to generate hydrogen gas and supplying the hydrogen gas to the stack is further needed. Therefore, PEMFC supplies the fuel stored in the fuel tank to the reformer by the pumping force of the fuel pump, the reformer reforms the fuel to generate hydrogen gas, and the stack electrochemically reacts the hydrogen gas and oxygen to produce electrical energy. To me.

On the other hand, the fuel cell may employ a direct methanol fuel cell (DMFC, hereinafter referred to as DMFC) that can supply a liquid methanol fuel directly to the stack. This DMFC, unlike PEMFC, excludes the reformer.

In such a fuel cell system, a stack that substantially generates electricity is a unit cell consisting of an electrode-electrolyte assembly (MEA), a bipolar plate, or a separator. This structure has a stacked structure of several to several tens. The MEA has a structure in which an anode electrode and a cathode electrode are attached with an electrolyte membrane interposed therebetween. In addition, the bipolar plate simultaneously serves as a passage for supplying oxygen gas and fuel gas required for the reaction of the fuel cell and a conductor connecting the anode electrode and the cathode electrode of each MEA in series. Accordingly, the anode electrode is supplied with a fuel gas containing hydrogen to the anode electrode, while the oxygen electrode containing oxygen is supplied to the cathode electrode. In this process, the electrochemical oxidation of fuel gas occurs at the anode electrode, the electrochemical reduction of oxygen gas occurs at the cathode electrode, and electricity, heat, and water can be obtained together due to the movement of the generated electrons.

Such a fuel cell system must maintain the stack at an appropriate driving temperature to ensure the stability of the electrolyte membrane and prevent performance degradation. To this end, the stack has a cooling channel therein, and cool air flows through the cooling channel to cool the heat generated in the stack.

10 is a cross-sectional view illustrating a heat layer formed when air flows into a cooling channel according to the related art.

However, as shown in this figure, when the fuel cell system flows air to the cooling channel 51 in the stack, the air flows smoothly in the center of the small pipe friction of the fluid, so that the heat transfer is effectively performed. The heat layer (Tc) of the temperature is formed, the inner surface of the cooling channel 51 having a large friction of the fluid, the air flow is not smooth, the heat transfer is insufficient compared to the central portion, and thus high temperature heat The layer Ts is formed. That is, the cooling channel 51 forms a multi-layer heat layer (laminar flow) distribution in which the temperature increases from the center to the inner surface (Tc <Ts).

Due to the laminar flow distribution as described above, a stack having a plurality of cooling channels 51 has a limitation in heat transfer and thus has a problem in that cooling efficiency decreases as a whole.

Therefore, the fuel cell system must cool the stack to an appropriate driving temperature as a whole so that the stack can be normally operated. For this purpose, the depth d of the cooling channel 51 through which air flows must be further increased, that is, the stack size must be increased. There is a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a fuel cell system and a stack of the same, which reduces the depth of the cooling channel and the size of the stack while improving the cooling efficiency of the stack.

In order to achieve the above object, the fuel cell system according to the present invention,

A fuel supply unit supplying a fuel containing hydrogen;

An air supply unit for supplying air containing oxygen;

A heat carrier supply unit supplying a heat carrier; And

Comprising a stack having electrical generators arranged on both sides of the MEA to generate electrical energy by electrochemically reacting hydrogen and oxygen supplied from the fuel supply and the air supply, respectively,

The stack has cooling channels for flowing a heat carrier supplied from a heat carrier supply to cool the electricity generators,

The cooling channels have partitions that create turbulence in the flow of the heat carrier.

In addition, the stack of the fuel cell system according to the present invention,

Electrical generators having separators disposed on both sides of the MEA to electrochemically react hydrogen and oxygen supplied from the fuel supply unit and the air supply unit to generate electrical energy, and a heat carrier supply unit to cool the electrical generators. Cooling channels for flowing a heat carrier supplied from the

The cooling channels have partitions that create turbulence in the flow of the heat carrier.

The cooling channel is formed in the separator.

The cooling channel is partially formed on one surface of the separator and partially formed on one surface of the separator disposed in close contact with the separator, thereby completing one cooling channel.

The cooling channel is formed opposite the MEA of the separator.

The cooling channel is formed on both sides of the separator.

The cooling channel is formed in the separator corresponding to the inactive region of the MEA.

The cooling channel is formed on a cooling plate interposed between the electrical generators formed by separators disposed on both sides of the cooling channel.

The cooling channel is formed as a quadrilateral or circular passage.

The partition walls are preferably formed in a quadrangular or rectangular band shape to block a portion of the cooling channel of the quadrilateral.

The partitions are preferably formed in the circular cooling channel in a partial circular or circular band shape to block a part thereof.

The partitions are arranged in a zigzag state in the cooling channel.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically showing the overall configuration of a fuel cell system according to the present invention.

Referring to this figure, the fuel cell system generates a reformed gas rich in hydrogen by reforming a hydrocarbon-based fuel such as methanol, ethanol or natural gas, and is produced by electrochemically reacting the hydrogen gas with external air. It can be seen that the PEMFC method of converting chemical energy directly into electrical energy is adopted.

The fuel cell system includes a fuel supply unit 10 for reforming and supplying the hydrocarbon-based fuel, an air supply unit 12 for supplying external air, a heat carrier supply unit 14 for supplying a heat carrier, and the like described above. The chemical energy generated by the reaction of the supplied hydrogen gas and air is converted into electrical energy to produce electricity, wherein the stack 16 is cooled by the heat carrier supplied from the heat carrier supply unit 14.

The fuel supply unit 10 is configured to remove the reformer 18, unlike the PEMFC method, in the case of the DMFC method of supplying liquid fuel directly to the stack 16 to generate electricity. Hereinafter, the fuel cell system to which the above-described PEMFC method is applied will be described as an example. However, the present invention is not necessarily limited thereto.

First, the fuel supply unit 10 is connected to the fuel tank 20 for storing the fuel in the liquid phase containing hydrogen and the fuel tank 20 to discharge the fuel stored in the fuel tank 20 ). The fuel tank 20 and the fuel pump 24 are connected to supply fuel to the stack 16 via the reformer 18.

The air supply unit 12 includes an air pump 26 that sucks and blows external air with a pumping force, and the air pump 26 is connected to supply air to the stack 16.

The heat carrier supply unit 14 includes a pump 28 for sucking and pumping the heat carrier with a pumping force, which is connected to supply the heat carrier to the stack. In the present invention, the heat carrier may be a liquid coolant but is more preferably in a gaseous state. Thus, air which is easily taken in its natural state and lower than the temperature inside the stack 16 during operation can be used as the heat carrier.

In the fuel cell system of the present invention, the fuel includes a hydrocarbon-based fuel, such as methanol, ethanol, natural gas, etc., which is easy to mount and store. However, the fuel may be a mixture of water with methanol, ethanol or natural gas as described above, hereinafter, methanol, ethanol or natural gas is referred to as a liquid fuel for convenience.

The stack 16 for generating electricity by receiving fuel and air from the fuel supply unit 10 and the air supply unit 12 and cooling the generated heat with the heat carrier supplied from the heat carrier supply unit 14 is illustrated in FIG. It demonstrates with reference to 2-9.

2, 3, and 4 are exploded perspective views showing first, second, and third embodiments of the stack 16 shown in FIG. 1, respectively.

Referring to the stack 16 with reference to this figure, the stack 16 is used for the electrical energy by the electrochemical reaction of the reformed hydrogen gas supplied through the reformer 18 and the air supplied from the air supply 12. Electric generators 30 for generating are provided.

The electricity generating unit 30 means a cell of a unit for generating electricity, respectively, a MEA 32 for oxidizing / reducing hydrogen gas and air, and a separator (bipolar) for supplying hydrogen gas and air to the MEA 32, respectively. 34, also called a plate). The electricity generating unit 30 is formed of a separator 34 disposed on both sides of the MEA 32. Such electricity generating units 30 are continuously arranged to form one fuel cell.

The MEA 32 has a conventional structure in which an electrolyte membrane is interposed between an anode electrode and a cathode electrode forming both sides. The anode electrode receives hydrogen gas through the separator 34, and is a catalyst layer for converting hydrogen gas into electrons and hydrogen ions by an oxidation reaction and a gas diffusion layer for smooth movement of electrons and hydrogen ions. It is composed. The cathode electrode receives air through the separator 34 and is composed of a catalyst layer for converting oxygen into electrons and oxygen ions by a reduction reaction and a gas diffusion layer for smooth movement of electrons and oxygen ions. The electrolyte membrane is a solid polymer electrolyte having a thickness of 50 to 200 µm, and has an ion exchange function for transferring hydrogen ions generated in the catalyst layer of the anode electrode to the catalyst layer of the cathode electrode.

The electricity generating unit 30 configured as described above generates electricity, water, and heat according to a reaction as in the following reaction formula.

The anode ^{_{reaction: H 2 → 2H + + 2e}} -

The cathode ^{_{reaction: O 2 + 2H + + 2e}} - → H 2 O

Total reaction: H ₂ + O ₂ → H ₂ O + current + heat

That is, hydrogen gas is supplied to the anode electrode of the MEA 32 through the separator 34 and air is supplied to the cathode electrode. This hydrogen gas flows to the anode electrode and decomposes into electrons and hydrogen ions in the catalyst layer. When the hydrogen ions are moved through the electrolyte membrane, electrons, oxygen ions, and the transferred hydrogen ions are combined at the cathode electrode with the help of a catalyst to generate water. The electrons generated by the anode electrode do not move through the electrolyte membrane but move to the cathode electrode through an external circuit, so that the electricity generator 30 generates electricity.

During the oxidation / reduction reaction, heat is generated in the electricity generating unit 30 of the stack 16. This heat acts as a factor to deteriorate the performance of the stack 16 by drying the MEA 32. Therefore, the stack 16 discharges unreacted air containing a large amount of unreacted moisture from the electricity generating unit 30.

Accordingly, the fuel cell system of the present invention circulates the heat carrier supplied from the heat carrier supply unit 28 into the stack 16 to provide an appropriate temperature gradient for the entire region of the stack 16 by the stack 16 by the heat described above. In addition to preventing the MEA 34 from drying out, it has a structure capable of vaporizing unreacted air.

To this end, the stack 16 has a cooling channel 36 for flowing the heat carrier supplied from the heat carrier supply 28. The cooling channel 36 cools heat generated in the electricity generating unit 30 in the stack 16 as described above, and may be formed in various shapes at various positions in the stack 16.

2 and 3 form the cooling channel 36 in the separator 34, and FIG. 4 illustrates the formation of the cooling channel 36 in the cooling plate 38.

On the other hand, the cooling channel 36 of FIG. 2 is formed a portion 36a on one surface of the separator 34, a portion 26b is formed on one surface of the separator 34 disposed in close contact therewith, and is completed as one. The cooling channel 36 formed in this way is formed on the opposite side of the MEA 32 of the separator 34, thereby cooling the whole area of the MEA 32, that is, the active region 32a and the inactive region 32b, thereby providing excellent cooling. Has performance.

The cooling channel 36 of FIG. 3 is formed on both sides of the separator 34. The separator 34 supplies hydrogen gas to the active region 32a of one side MEA 32 and supplies air to the active region 32a of the other side MEA 32. An air passage 34b is formed. Therefore, the separator 34 cools only the inactive region 32b except for the active region 32a of the MEA 32.

The cooling channel 36 of FIG. 4 is formed in the cooling plate 38. The cooling plate 38 is interposed between the electric generators 3 formed by the separators 34 arranged on both surfaces with the MEA 32 interposed therebetween. That is, the stack 16 of FIG. 4 further includes a cooling plate 38 as compared to the stack 16 of FIGS. 2 and 3. This cooling plate 38 cools over the entire area of the MEA 32 and thus has excellent cooling performance.

(A) and (b) of FIGS. 5 to 8 are exploded perspective views showing a part of the first, second, third and fourth embodiments of the cooling channel formed in the stack shown in FIGS. Sectional view of the combined state.

The cooling channel 36 configured as described above includes partition walls 40 to form a flow of the heat carrier supplied into the turbulence. The barrier ribs 40 may be formed in various ways by forming a turbulence by acting as a resistance to the heat carrier flow in the cooling channel 36. In addition, the partition walls 40 are preferably arranged in a zigzag state with respect to the direction in which the cooling channel 36 is formed. The partition walls 40 in the cooling channel 36 increase the flow length of the heat carrier within the depth d of the limited cooling channel 36 while converting the flow of the heat carrier in the zigzag direction, thereby cooling due to turbulence. In addition to improving the efficiency, the depth d of the cooling channel 36 required for cooling and the size of the entire stack 16 are reduced.

5 and 6 illustrate that the cooling channels 36 are formed in a quadrangle, and portions 36a and 36b of the cooling channels 36 are formed in two separators 34 facing each other, respectively. A rectangular cooling channel 36 may also be formed in the cooling plate 38.

In this case, the partition wall 40 is preferably formed in a square corresponding to the shape of the cooling channel 36, the partition wall 40 is arranged in a zigzag state on the upper and lower sides of the cooling channel 36 in the drawing partition ( At the rear of 40), turbulence t occurs, as shown in FIG. 9.

The partition 40 may be formed only on the upper and lower sides of the cooling channel 36 as shown in FIG. 5. As shown in FIG. 6, the rectangular inner circumference of the cooling channel 36 may have a rectangular band shape.

Thus, in FIG. 5, the turbulence t is formed only on the upper and lower sides of the cooling channel 36, which is the rear of the partition 40, but in the case of FIG. 6, the rear of the partition 40 is formed of the cooling channel 36. Turbulence (t) is formed in the upper, lower, left and right areas.

7 and 8 illustrate that the cooling channels 36 are formed in a circular shape and portions 36a and 36b of the cooling channels 36 are formed in two separators 34 facing each other, respectively. In addition, a circular cooling channel 36 may be formed in the cooling plate 38.

In this case, the partition wall 40 is preferably formed in a partial circle corresponding to the shape of the cooling channel 36, the partition wall 40 is arranged in a zigzag state on the upper and lower sides of the cooling channel 36 in the drawing partition wall At the rear of 40, turbulence t is generated as shown in FIG.

The partition walls 40 may be formed only on the upper and lower sides of the cooling channel 36, as shown in FIG. As shown in FIG. 8, a circular inner circumference of the cooling channel 36 may be formed in a circular shape.

Thus, in FIG. 7, turbulence t is formed only on the upper and lower sides of the cooling channel 36, which is the rear of the partition 40, but in the case of FIG. 8, the rear of the partition 40 is formed of the cooling channel 36. Turbulence (t) is formed in the upper, lower, left and right areas.

9 is a cross-sectional view showing the flow state of the heat carrier in the cooling channel in the present invention.

As shown, supplying the heat carrier hc into the cooling channel 36 causes the heat carrier to impinge on the partition walls 40 and generate heat carrier turbulence t at the rear of the partition walls 40. .

The turbulence t generally forms a uniform temperature distribution in the cooling channel 36 so that the MEA 32 is effectively cooled.

9 illustrates that the partition walls 40 are formed on the upper and lower sides of the cooling channel 36 and the turbulence t is formed on the upper and lower sides of the cooling channel 36. In the case of forming the 40, turbulence t is formed over the entire area.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

According to the fuel cell system and the stack according to the present invention, the cooling channel is formed in the stack, and the partition walls are provided in the cooling channel in a zigzag state, thereby forming turbulence in the heat carrier supplied to the cooling channel, thereby cooling the MEA. And the size of the stack and the depth of the cooling channel.

1 is a block diagram schematically showing the overall configuration of a fuel cell system according to the present invention.

2 is an exploded perspective view showing a first embodiment of the stack shown in FIG.

3 is an exploded perspective view showing a second embodiment of the stack shown in FIG.

4 is an exploded perspective view showing a third embodiment of the stack shown in FIG.

5 (a) and 5 (b) are exploded perspective views and cross-sectional views of a part of a first embodiment of a cooling channel formed in a stack shown in FIGS. 2 to 4.

6A and 6B are exploded perspective views and cross-sectional views of a part of a second embodiment of a cooling channel formed in a stack illustrated in FIGS. 2 to 4.

7 (a) and 7 (b) are exploded perspective views and cross-sectional views of a part of a third embodiment of a cooling channel formed in the stack shown in FIGS. 2 to 4.

8 (a) and 8 (b) are exploded perspective views and cross-sectional views of a portion of a fourth embodiment of a cooling channel formed in the stack shown in FIGS. 2 to 4.

9 is a cross-sectional view showing the flow state of the heat carrier in the cooling channel in the present invention.

10 is a cross-sectional view illustrating a heat layer formed when air flows into a cooling channel according to the related art.

Claims (22)

A fuel supply unit supplying a fuel containing hydrogen; An air supply unit for supplying air containing oxygen; A heat carrier supply unit supplying a heat carrier; And And a stack including electrical generators disposed on both sides of an electrode-electrolyte composite (MEA) to electrochemically react hydrogen and oxygen supplied from the fuel supply unit and the air supply unit to generate electrical energy. , The stack has cooling channels for flowing a heat carrier supplied from a heat carrier supply to cool the electricity generators, And the cooling channels have partitions that create turbulence in the flow of the heat carrier. The method of claim 1, The cooling channel is formed in the separator. The method of claim 2, The cooling channel is partially formed on one surface of the separator, and partially formed on one surface of the separator disposed in close contact with each other, thereby completing one cooling channel. The method of claim 2, The cooling channel is formed on the side opposite the MEA of the separator. The method of claim 2, The cooling channel is formed on both sides of the separator. The method of claim 5, The cooling channel is formed in the separator corresponding to the inactive region of the MEA. The method of claim 1, The cooling channel is formed on a cooling plate interposed between the electricity generating portion formed by separators disposed on both sides with the MEA interposed therebetween. The method of claim 1, The cooling channel is formed by the passage of any one of a quadrilateral and a circular fuel cell system. The method of claim 8, The partition wall is a fuel cell system of any one of a quadrilateral and a rectangular strip shape blocking a portion of the cooling channel of the quadrilateral. The method of claim 8, The partition wall is a fuel cell system of the circular cooling channel is made of any one of a portion of a circular and circular band blocking a portion thereof. The method of claim 1, The partition walls are disposed in a zigzag state in the cooling channel. Electrical generators having separators disposed on both sides of the MEA to electrochemically react hydrogen and oxygen supplied from the fuel supply unit and the air supply unit to generate electrical energy, and from the heat carrier supply unit to cool the electrical generators. Cooling channels for flowing the supplied heat carrier, And the cooling channels have partitions that create turbulence in the flow of the heat carrier. The method of claim 12, And the cooling channel is formed in the separator. The method of claim 13, The cooling channel is partially formed on one surface of the separator and partially formed on one surface of the separator disposed in close contact with each other, thereby completing a cooling channel. The method of claim 13, The cooling channel is formed on the side opposite the MEA of the separator. The method of claim 13, And the cooling channel is formed on both sides of the separator. The method of claim 16, And the cooling channel is formed in the separator corresponding to the inactive region of the MEA. The method of claim 12, And the cooling channel is formed on a cooling plate interposed between electricity generation parts formed by separators disposed on both sides with the MEA interposed therebetween. The method of claim 12, The cooling channel stack of the fuel cell system formed by the passage of any one of a quadrilateral and a circle. The method of claim 19, The partition wall is a stack of the fuel cell system of any one of a quadrilateral and rectangular stripe shape blocking a portion of the cooling channel of the quadrilateral. The method of claim 19, And said partitions comprise one of partial circular and circular bands in a circular cooling channel to block a portion thereof. The method of claim 12, And said partitions are zigzag in the cooling channel.