JPS6266574A - Air cooling type fuel cell - Google Patents

Abstract

PURPOSE:To make temperature uniform over the whole area inside a cell by forming in parallel cooling air passages in every layer, dividing into plural sections, and alternately passing cooling air from an opposite direction. CONSTITUTION:Cooling air passage 19 formed in parallel in every layer in a cell stack 1 is formed so that an inlet of the passage and an outlet are alternately positioned in an adjacent section. The flow direction of cooling air introduced from a manifold 4 or 5 is opposite in adjacent flow passages. Since the cooling air passages 19 have an opposite flow direction of cooling air between adjacent passages, heat transfer is made between high temperature region of the outlet and low temperature region of the inlet of adjacent cooling air passages inside a gas separating plate. Thereby, temperature distribution inside the cell is made uniform.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

This invention relates to an air-cooled fuel cell in which heat generated inside the cell during operation is removed by cooling air in a fuel cell that extracts electrical energy by supplying a reaction gas of fuel and an oxidizing agent, and in particular, the cooling of the fuel cell. Regarding the configuration of the air supply system.

[Prior art and its problems]

As is well known, there are two main methods for removing heat generated during power generation by fuel cells: water-cooled and air-cooled. This is a method in which a cooling plate is interposed between four to seven unit cell stacks, a cooling water vibrator is piped to the cooling plate, and cooling water is supplied from the outside. In this case, the higher the operating temperature of the fuel cell, the higher the power generation efficiency can be obtained, but the battery temperature is usually 170
It is operated at a controlled temperature of ~230°C. Therefore, it is necessary to adjust the temperature of the cooling water to about 150 to 200°C, and for this purpose, the cooling water supply system includes a water temperature control device including a boiler, etc., and the formation of scale in the cooling piping is prevented. Ancillary equipment such as a water purification device is required, which increases equipment costs for the entire power generation system. On the other hand, the air-cooled type, like the water-cooled type, is a type in which a cooling plate with a cooling air flow path is provided for each failed unit cell, or a cooling plate is installed in the gas separation plate for each unit cell that makes up the cell stack. There is a method of forming a flow path and supplying cooling air from the outside, but either method does not require the boiler or pure water production equipment required for the water-cooled method mentioned above, and the configuration of the power generation system is simple. This has advantages such as low equipment costs. In this way, compared to water-cooled systems, air-cooled systems have the advantage that the air, which is the heat medium for cooling, is easy to handle, is highly safe, and the equipment is compact and inexpensive.
It is widely used as a cooling method for fuel cells used as OK-scale mobile power sources. However, although air-cooled fuel cells have the above-mentioned advantages, they also have the problem that it is difficult to control the temperature of the fuel cell. This is due to the large difference between the operating temperature of the fuel cell and the air temperature (outside temperature) at which room temperature outside air is used as cooling air. In other words, as mentioned above, it is desirable to control the operating temperature of the fuel cell to the highest temperature within the allowable range of the cell components, but when looking at the temperature distribution inside the fuel cell along the cooling air flow path, it is found that The temperature is low in the area near the inlet side of the cooling air flow path where the cooling air is introduced, and the temperature increases as the heat generated inside the battery is added toward the outlet side area. For this reason, it is necessary to suppress the temperature at the exit portion of the cooling air flow path to the maximum allowable temperature of the battery, and as a result, when the temperature of the entire interior of the battery is averaged, it becomes considerably lower than the maximum allowable temperature. Moreover, as mentioned above, the power generation efficiency of a fuel cell is proportional to the operating temperature, so it is not possible to obtain a sufficiently high power generation efficiency as is. Therefore, in order to increase the power generation efficiency of a fuel cell, the highest temperature point inside the cell must be It is necessary to take a cooling means to equalize the temperature by suppressing the temperature to the maximum allowable temperature and increasing the average temperature throughout the battery interior to a temperature as close to the maximum allowable temperature as possible. On the other hand, as a method to deal with the above problem and to equalize the temperature while increasing the average temperature inside the battery, conventionally, a part of the high temperature cooling air discharged from the outlet of the cooling air flow path inside the battery is transferred to the inlet side. Circulating air L7 is used to increase the temperature of the cooling air introduced from the inlet so as to cause reflux, while at the same time increasing the amount of air passing through the inside of the battery.
Some attempts have been made to reduce the temperature difference at the outlet to increase the average temperature and equalize the temperature distribution. However, with this method of circulating cooling air, the average temperature of the battery can be raised as the amount of circulating air increases.
For this purpose, the power of the proar used for circulating cooling air becomes large, making it difficult to improve the overall efficiency of the power generation equipment as a whole.Also, the diameter of the pipes that carry the circulating air has to be large because it is necessary to flow a large amount of air. As a result, the power generation equipment becomes larger, making it difficult to make it compact, which is a major feature of air-cooled systems. In addition, the circulating blower must be of a large capacity type that can withstand high temperatures of 150 to 180 DEG C. As a result, equipment costs increase and maintainability is undeniably reduced.

[Purpose of the invention]

This invention was developed in consideration of the above points, and it is an object of the present invention to equalize the temperature distribution inside the fuel cell due to the flow of cooling air over the entire area inside the cell by a simple means, thereby further increasing the power generation efficiency of the cell. An object of the present invention is to provide an air-cooled fuel cell, in particular, a configuration of a cooling air supply system thereof.

[Key points of the invention]

In order to achieve the above object, the present invention makes the cooling air flow path formed in the cell stack into a plurality of parallel flow paths aligned left and right for each layer, and divides the parallel flow path into a plurality of sections. The flow path inlet and outlet of each section are opened alternately between adjacent sections, and the cooling air is configured to flow alternately from opposite directions between each flow path section. The heat conduction of the base material constituting the flow path is used to equalize the temperature distribution inside the battery, especially over the entire electrode surface. In other words, according to the above configuration, when looking at each section of the cooling air flow path, the air temperature difference between the inlet side and the outlet side of the flow path is large, but there is a large difference in air temperature between adjacent sections. The inlet and outlet of the air flow path are lined up closely, and therefore, due to the heat conduction of the base material that makes up the flow path, the temperature distribution throughout the battery is from the inlet side to the outlet side of the cooling air flow path. averaged over the entire range. As a result, the electrode surfaces of the fuel electrode and oxidizer electrode, where cell reactions occur, are hardly affected by the temperature of the cooling air flowing through the inlet and outlet sides of the cooling air flow path, and a uniform temperature distribution is achieved over the entire electrode surface. As a result, the electrode reaction becomes uniform over the entire electrode surface, resulting in even higher power generation efficiency.

[Embodiments of the invention]

1 to 3 show embodiments of the present invention, and FIG. 1 is an exploded perspective view showing the arrangement of a fuel cell cell stack and a manifold for supplying reaction gas and cooling air, and FIG. The figure shows a cooling air supply system diagram in Figure 1 shown as a plan view, and Figure 3 is a partial cross-sectional view of the cell stack in Figure 1. In the figure, 1 is a cell stack, and 2 is a fuel gas supply system. 3 is a manifold for supplying air as an oxidant gas, and 4 and 5 are manifolds for supplying cooling air. As is well known, the cell stack 1 is a stack of single cells, and its detailed structure is as shown in FIG. An impregnated matrix 12 and fuel electrodes 13 facing on both sides of the matrix 12.
．． It is a laminate of an oxidizing agent electrode 14 and a gas separation plate 15.16 called a ribbed separator superimposed on the outside of this electrode 13.14. Here, a fuel gas flow path 17° and an oxidant flow path 18 are formed on the inner surface of the gas separation plate 15.16 in contact with the electrodes 13.14. Further, as clearly shown in FIG. 1, this reaction gas flow path is a U-shaped flow path starting from the inlet, making a U turn on the way, and ending at the outlet. 1
The inlet and outlet of 8 are respectively opened on the opposite side of the cell stack 1, and the manifold 2 for supplying fuel gas is respectively opened.
．． Reaction gas is supplied through a manifold 3 for supplying oxidant gas. Note that in FIG. 1, the fuel gas flow path 17 opens on the back side of the cell stack and is not drawn on the drawing. On the other hand, returning to FIG. 3, the above-mentioned fuel gas flow path 17 is provided on the overlapping surface of the gas separation plates 15 and 16 between each unit cell 11.
．． A cooling air flow path 19 is formed which is separated from the oxidizing gas flow path 18 and is made up of a plurality of flow path grooves arranged in parallel from side to side. As shown in FIG. 1, the cooling air flow path 19 is formed to extend between both side surfaces of the cell stack 1 so as to open to the other left and right side surfaces perpendicular to the side surface where the reaction gas flow path is opened. Manifolds 4 and 5 for supplying cooling air are disposed in close contact with the left and right side surfaces of the cell stack 1, respectively, through sealing gaskets, facing the open end of the cooling air passage 19. Here, the manifold 4,
5 is divided into a plurality of small chambers lined up in the horizontal direction via vertical partition walls 41 and 51, and each of the small chambers is filled with air every other time as shown in FIG. A cooling air introduction pipe 21 leading to the blower 20 is branched and connected, and the remaining small chambers to which the cooling air introduction pipe 21 is not connected are opened to the atmosphere through exhaust ports 42 and 52. Moreover, in the left and right manifolds 4 and 5, the connection positions of the cooling air introduction pipes 21 are shifted from each other by one room. In addition, each of the small chambers divided and partitioned inside the manifold 4.5 divides into a plurality of cooling air passages 19 formed in parallel between the gas separation plates 15 and 16 in each layer on the cellus tank side. It is divided into sections and divided into sections via partition walls 41 and 51 so as to correspond to each section. In the illustrated example, the cooling air passage 19 consisting of a plurality of passage grooves is divided into one section, and each small chamber in the manifolds 4 and 5 has one passage groove corresponding to an opening. are doing. Due to the cooling air supply path having such a configuration, the cooling air flow paths 19 formed in line with each layer in the cell stack,
Between adjacent sections (one channel groove in the illustrated example), the channel inlets and outlets are alternately opened,
The flow direction of the cooling air introduced through the manifold 4 or 5 is alternately reversed between adjacent flow paths as shown by the arrows in FIG. That is, as shown in the figure, the cooling air forced into the small chamber IN in the manifold 4 through the air introduction pipe 21 by the air blower 20 is
After flowing from left to right through the channel groove of the cooling air channel 19 in the cell stack 1 whose inlet opens to the cough chamber IN, the small chamber 0 of the manifold 5 is located on the opposite side from the outlet thereof.
tlT, from where it is discharged into the atmosphere through the exhaust port 52. On the other hand, the cooling air introduced into the small chamber IN in the manifold 5 through the air introduction vibrator 21 flows from right to left through the channel groove of the cooling air flow path 19 whose inlet opens into the small chamber IN. Afterwards, it is discharged from the outlet to the small chamber 0υ of the manifold 4 arranged on the opposite side, and from there it is discharged into the atmosphere through the exhaust port 42. Therefore, cooling air flows in opposite directions alternately through each channel in the cooling air channel 19, which is made up of a plurality of channel grooves formed in parallel on the left and right in the cell stack 1. When power generation starts by supplying fuel gas and oxidant gas to the fuel cell, the cell body rises to high temperature due to heat generation due to polarization of the electrodes and internal resistance. The heat of formation of gas separation plate 15.1
6 and reaches the cooling air flow path 19, where the heat is removed to the outside of the system by the cooling air flow flowing there. In this case, looking at each channel groove, the air temperature of the cooling air flowing back here is low at the inlet side and becomes high temperature as it reaches the outlet side, creating a temperature difference between the population and the outlet. However, as described above, since the direction of flow of cooling air is opposite between the adjacent channels in each cooling air channel 19, inside the gas separation plate, these cooling air flows close to each other. Heat transfer occurs between the high-temperature region on the outlet side and the low-temperature region on the inlet side between each flow channel of the channel, and the internal temperature of the entire battery has a temperature distribution over the entire area along the cooling air flow channel 19. will be averaged. Therefore, if we look at the electrode part where the battery reaction takes place, the temperature across the entire f-pole surface is almost unaffected by the temperature difference between the inlet and outlet of the cooling air in each flow channel, and is close to the maximum allowable temperature. As a result, the battery reaction becomes uniform over the entire area of the electrode, resulting in high power generation efficiency. In addition, the Kagaru method eliminates the need for the conventional air circulation system that recirculates cooling air from the outlet to the inlet as a heat equalization measure. There is no need for ancillary equipment or power for the ancillary equipment, and therefore, the equipment cost of the power generation equipment as a whole can be reduced, it can be made more compact, and the overall efficiency of the power generation system can also be improved. In addition, since the temperature of the fuel cell can be controlled only by controlling the air volume by the cooling air blower 20, the
Moreover, maintainability is also improved. Note that in the cooling air path of the illustrated embodiment, the cooling air flow path 19
Although the exhaust air from the outlet of the manifold is configured to be exhausted to the atmosphere via the small chamber OUT in the manifold 4.5, this exhaust air may be directly discharged to the atmosphere without going through the manifold. , and an example in which the cooling air flow path 19 is formed between the gas separation plates 15 and 16 for each unit cell 11 constituting the cell stack 1 is shown, but the cooling air flow path 19 is formed every few cells of the unit cell 1. Of course, it is also possible to use a cooling device provided with a cooling device formed therein. [Effects of the Invention] As described above, according to the present invention, the cooling air wave path is formed into a plurality of parallel flow paths aligned left and right for each layer, and the parallel flow path is divided into a plurality of sections, and each section is flow path inlet,
The outlets are staggered between adjacent sections;
By configuring the cooling air to flow alternately from opposite directions between each flow path section, the temperature distribution inside the battery in the direction of the electrode surface is equalized, and the difference between the maximum temperature and the average temperature is reduced. Therefore, the average temperature inside the fuel cell can be increased to a temperature closer to its maximum allowable temperature during operation. As a result, it is possible to improve the power generation efficiency of the battery and the overall efficiency of the power generation system as a whole without employing the conventional cooling air circulation method, and therefore with low equipment costs and a compact configuration.

[Brief explanation of the drawing]

FIG. 1 is an exploded perspective view showing the arrangement of a cell stack of an air-cooled fuel cell according to an embodiment of the present invention and a corresponding manifold for supplying reaction gas and cooling air;
The figure is a cooling air supply system diagram in Figure 1, and Figure 3 is a partial cross-sectional view of the cell stack in Figure 1. In Figure 0, 1: cell stack, 2: manifold for fuel gas supply, 3: Manifold for supplying oxidant gas, 4
．． 5: Manifold for cooling air supply, 11: Cell battery,
15.16: Gas separation plate, 17: Fuel gas flow path, 18:
M other agent gas flow path, 19: cooling air flow path, 2o: cooling air supply proa, 21: cooling air introduction pipe, 41.51
: Partition wall that separates the small chamber of the manifold, 42.52: Manifold exhaust port. Figure 1 Figure 2

Claims (1)

[Claims] 1) A cooling air flow path is formed in the layer of the cell stack, which is a stack of unit cells, separate from the reaction gas flow path for fuel and oxidizer, and the cooling air flow path is connected to the cooling air flow path from the outside. In an air-cooled fuel cell in which cooling air is supplied to remove heat produced by the cell, the cooling air flow path is formed into a plurality of parallel flow paths arranged left and right in each layer, and the parallel flow paths are After dividing into multiple sections, the flow path inlet and outlet of each section are set to open alternately between adjacent sections, and the cooling air is configured to flow between each flow path section alternately from opposite directions. This air-cooled fuel cell is characterized by: 2) In the air-cooled fuel cell according to claim 1, the cooling air flow path is formed in parallel with the gas separation plate of the unit cell, and the cooling air flow path is formed in parallel with the gas separation plate of the unit cell, and the flow is controlled in each section of the cooling air flow path. An air-cooled fuel cell characterized in that cooling air is introduced from the outside through a manifold for supplying cooling air arranged on the side of the cell stack to the channel entrance, and is discharged from the channel outlet on the opposite side. 3) In the air-cooled fuel cell according to claim 2, the manifold for supplying cooling air is partitioned into small chambers corresponding to each section of the cooling air flow path on the cell stack side, and The air-cooled fuel is characterized in that the small chamber leading to the entrance of the air flow path is connected to a cooling air introduction pipe through an air blower, and the small chamber leading to the outlet of the cooling air flow path is open to the atmosphere through an exhaust port. battery.