JPH03230478A - Cooling method for phosphoric acid type fuel cell - Google Patents

Abstract

PURPOSE:To effectively improve the temperature distribution in a cell, prevent the deterioration of electrodes, and improve power generation performance by properly specifying the flow direction of air and the flow direction of cooling water for pressure water cooling and two-phase water cooling. CONSTITUTION:Fuel gas is fed from this side of a hydrogen electrode 3 and flows in a passage 6 and is discharged from the opposite side. Air is fed from the left side of an air electrode 4 and flows in a passage 7 and is discharged from the right side. The cooling water pressurized to about 4atm is fed from a pipe 12 and flows in a water passage in the opposite direction to the air and collected by fine pipes 13b and a branch pipe 13a and discharged from a pipe 13. The pressure cooling water is fed to a cooling plate in the opposite direction to the air, the heating of the low-temperature inlet side air by the high-temperature outlet side cooling water and the cooling of the high- temperature outlet side air by the low-temperature inlet side air are effectively combined, and the temperature distribution in the face direction of the electrodes 3, 4 is kept near the middle temperature. The temperature distribution in the face direction of the electrodes 3, 4 is also kept at the middle temperature for two-phase water cooling.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a cooling method for improving the temperature distribution in the surface direction of an electrode in a water-cooled phosphoric acid fuel cell.

[Conventional technology]

In phosphoric acid fuel cells, which have a large number of stacked large-area single cells, cooling plates are inserted every few cells, and pure water is passed through these to maintain the inside of the cells at the optimal temperature for reaction. FIGS. 4 and 5 schematically show the structure of a cell stack of such a water-cooled fuel cell, with FIG. 4 being a plan view and FIG. 5 being a sectional view taken along the line V-■. In the figure, 1 is a rectangular single cell in which a hydrogen electrode 3 and an air electrode 4 are arranged with a matrix 2 impregnated with phosphoric acid sandwiched between them. The cells are stacked and a cooling plate 5 is inserted every few cells. The hydrogen electrode 3 has countless square groove-shaped fuel passages 6 formed in the front-back direction of the figure (perpendicular to the plane of the drawing), and the air electrode 4 also has square groove-shaped air passages 6 formed in the left-right direction of the figure perpendicular to the fuel passages 6. A countless number of passages 7 are formed. Fuel gas containing hydrogen as a main component is supplied from a fuel inlet manifold 8 to the hydrogen electrode 3 as shown by the arrow, and after passing through a fuel passage 6, it is collected at a fuel outlet manifold 9 and discharged. Similarly, air is supplied to the air electrode 4 from the air inlet manifold 1° as shown by the arrow, and this air is supplied to the air passage 7.
After passing through the air outlet manifold 11, the air is collected and discharged. In addition, in the case of pressurized water cooling (a cooling method in which pressurized cooling water is supplied to suppress boiling during flowing water), the cooling water is supplied through a cooling water supply pipe vertically installed on one side of the air inlet manifold 10. 12, and is introduced into each cooling plate 5 through a branch pipe 12a that is piped along the front end surface of each cooling plate 5, and a large number of thin tubes 12b led out at right angles from the branch pipe 12a. This cooling water flows from left to right in the figure through a large number of passageways (not shown) provided in parallel with the flow of air in the cooling plate 5, and thin tubes 13b similarly provided in the air outlet manifold 11. is collected in a branch pipe 13a,
The cooling water is discharged through a vertical cooling water discharge pipe 13. An example of temperature settings for cooling water, fuel gas, and air at the cell stack inlet and outlet in such a fuel cell is as follows. First, coolant water pressurized to about 4 atmospheres is heated to about 16
The cooling water is supplied from the cooling water supply pipe 12 at 7°C, and is discharged from the cooling water discharge pipe 13 at about 172°C. The fuel gas is then supplied to the inlet manifold 8 at about 160°C and at about 175°C.
and discharge from the outlet manifold 9. In addition, air is supplied to the inlet manifold 10 at about 130°C, where it is brought into contact with the cooling water pipes 12.12a and 12b, heated to about 150°C, and then put into the cell stack and heated to about 170°C.
C to discharge from the outlet manifold 11. In this case, the required temperature distribution in the surface direction on the surface of the single cell 1 is 185 to 19
Within the range of 5°C.

[Problem to be solved by the invention]

As mentioned above, fuel gas, air, and cooling water at various temperatures are supplied from each direction to the cell stack in order to maintain the optimal temperature for power generation. The combination of water flow direction and cooling water flow direction is not appropriate, and the temperature distribution actually exceeds 175-20°C for the above required temperature distribution.
A large temperature distribution in the range of 5°C occurs. As a result, power generation performance deteriorates, voltage drops locally, and battery life decreases in high temperature ranges. Furthermore, conventionally, the fuel gas and air are made to flow in one direction orthogonally to each other, but for this reason, the inlet portion of FIG. 4 where the low-temperature fuel gas and air that have just been introduced into the cell stack are opposed to each other. There is a large temperature difference between the electrodes A and the outlet section B, where the high temperature fuel gas and air, which have been heated by the reaction, face each other. Therefore, an object of the present invention is to provide a cooling method for a phosphoric acid fuel cell in which the temperature distribution of the electrodes is improved by devising a combination of the air flow direction and the cooling water flow direction. It is. Another object of the present invention is to provide a method for cooling a phosphoric acid fuel cell in which the temperature distribution of the electrodes is improved by devising the direction of flow of fuel gas and air.

[Means to solve the problem]

In order to achieve the above object, the present invention has a plurality of stacked single cells to which fuel gas and air are supplied in directions orthogonal to each other, and cooling water is passed through every few cells along the flow of the air. In a phosphoric acid fuel cell in which a cooling plate is inserted, the cooling water flow direction in the case of pressurized water cooling is made opposite to the air flow direction. In addition, in the above-mentioned phosphoric acid fuel cell, in the case of two-phase water cooling (a cooling method in which a part of the cooling water is boiled in the piping and the heat of evaporation is also absorbed), the direction in which the cooling water flows is shall match the direction of air flow. Furthermore, in the above-mentioned phosphoric acid fuel cell, the inlet manifold for fuel gas and air is provided with a partition plate that divides the passage into left and right parts, and the fuel gas and air supplied from one passage are reversed in the outlet manifold to separate the passages from the inlet manifold. so that it is discharged from the other passage.

[For use]

If the air supplied to the inlet manifold were directly introduced, the temperature of the air electrode would drop. Therefore, the temperature of the air is raised by bringing it into contact with the cooling water piping inside the air inlet manifold, but in order to ensure this temperature rise, in the case of pressurized water cooling, the cooling water is cooled on the outlet side through which the heated cooling water passes. Place the water piping into the air inlet manifold. On the other hand, the air on the outlet side whose temperature has increased due to the reaction is brought into contact with the cooling water pipe on the inlet side through which low-temperature cooling water passes. That is, in the case of pressurized water cooling, the cooling water flow direction is opposite to the air flow direction. On the other hand, in the case of two-phase water cooling, there is not much difference in the temperature of the cooling water between the inlet and outlet of the cell stack due to heat absorption due to heat of evaporation, so the water is supplied at a higher temperature than in the case of pressurized water cooling. can. Therefore, even if the cooling water pipe on the inlet side is disposed within the air inlet manifold, there is no problem in heating the supplied air. Furthermore, if the cooling water piping on the inlet side is suddenly brought into contact with the air on the outlet side, the flow rate is less than 1/2 compared to pressurized water cooling, so there is a possibility that boiling will proceed too much and the water cannot flow. Therefore, in the case of two-phase water cooling, the flow direction of the cooling water is made to match the flow direction of the air. Next, a partition plate is provided in the fuel gas and air inlet manifold to divide the passage into left and right parts, and the fuel gas and air supplied from one passage are reversed within the outlet manifold and discharged from the other passage of the inlet manifold. By doing this, the fuel gas and air are in a relationship such that the low-temperature one on the inlet side is opposed to the one on the outlet side where the reaction has progressed and the temperature has risen, creating a temperature difference in the plane direction of the single cell. is spelled. Since hydrogen in the fuel gas and oxygen in the air are consumed by the reaction, the flow rates of the fuel gas and air decrease downstream. Therefore, when dividing the inlet manifold into sections using partition plates, the width of the passages on the inlet side is wider than on the outlet side, rather than equally on the left and right sides.

【Example】

Hereinafter, the present invention will be explained in detail based on the drawings. In addition,
The same reference numerals are used for parts corresponding to those in the conventional example. FIG. 1 is an exploded perspective view of a cell stack for explaining the cooling method in pressurized water cooling, and for simplicity, the cooling plate 5.
Single cell 1 between 5 shows only one layer. Furthermore, the symbols high, medium, and low in the figure indicate relative temperature comparisons in the plane directions of the electrodes 3 and 4 and the cooling plate 5, and represent high temperature, medium temperature, and low temperature, respectively. In the figure, a single cell 1 consists of a matrix 2 impregnated with phosphoric acid as an electrolyte, and a hydrogen electrode 3 and an air electrode 4 placed above and below the matrix. A countless number of parallel fuel passages 6 are formed in the direction. Similarly, on the anti-matrix side of the air electrode 4, countless parallel air passages 7 are formed in the left-right direction in the figure. A cooling plate 5 is inserted every several layers of this single cell 1, and there are 20 to 30 cooling plates parallel to the passage 7 of the air electrode 4 (not shown).
Book passageways are formed in the left and right directions of the figure. Reference numerals 12 and 13 denote a cooling water supply pipe and a discharge pipe, which are vertically installed in an air outlet manifold and an air inlet manifold (not shown), respectively, and branch pipes 12a and 1
3a is piped, and thin tubes 12b and 13b led out from the pipe are connected to both ends of each water passage. Fuel gas is supplied from the front side of the hydrogen electrode 3 as shown by the arrow, flows through the passage 6, and is discharged from the opposite side. On the other hand, air is supplied from the left side of the air electrode 4 as shown by the arrow, flows through the passage 7, and is discharged from the right side. In addition, the cooling water pressurized to about 4 atmospheres is supplied to the cooling water supply pipe 12.
The cooling water is supplied from the cooling water, flows through the water passage from right to left in the figure in the opposite direction to the air through the branch pipe 12a and the thin tube 12b as shown by the arrow, is collected by the thin tube 13b and the branch pipe 13a, and is discharged from the cooling water discharge pipe 13. be done. The temperature distribution in the plane direction of each part in such a cell stack is as shown in the figure. First, the cooling plate 5 at the top of the figure adjacent to the hydrogen electrode 3 is supplied with cooling water from the right side of the figure at, for example, about 167°C, but this cooling water absorbs reaction heat while flowing toward the left. , the temperature distribution goes from right to left: low temperature → medium temperature → high temperature. The hydrogen electrode 3 is supplied from the front side at about 160°C, for example, and is sandwiched between low-temperature air from the left side and low-temperature cooling water from the right side, and becomes almost medium temperature as shown in the figure, and at the central part on the fuel gas inlet side. Some parts are low in temperature, and some parts are high in the central part on the fuel gas outlet side and the central part on the cooling water outlet side. The reason why the temperature is high in the center is that heat dissipation is lower than that in the periphery. On the other hand, air is supplied to the air electrode 4 from the left side of the figure, and this air is supplied to the high temperature outlet side cooling water pipes 13.13a and 1.
3b, the air electrode 4 changes from medium temperature to medium temperature (from the left).
The central part becomes partially high temperature), and the outlet side becomes even hotter, but it is cooled by the cooling water on the low temperature inlet side and becomes medium temperature. In addition, the lower cooling plate 5 adjacent to the air electrode 4 has a low temperature at the inlet side due to the low temperature cooling water supplied from the right side, similar to the upper cooling plate 5, but is heated by the high temperature outlet side air to a medium temperature. becomes. By the way, since air has only about 20% oxygen that contributes to the reaction, the required flow rate is increased compared to fuel gas that contains 65-80% hydrogen, and the heat capacity is correspondingly large. According to the illustrated cooling method, the pressurized cooling water is passed through the cooling plate 5 along the flow of air with a large heat capacity so that the water flow direction is opposite to the air flow direction, so that the low temperature The temperature increase of the inlet side air by the high temperature outlet side cooling water and the cooling of the high temperature outlet side air by the low temperature inlet side cooling water are effectively combined, and the temperature distribution in the surface direction of the hydrogen electrode 3 and the air electrode 4 is improved. The temperature is mostly around medium temperature. Next, FIG. 2 is a perspective view similar to FIG. 1 showing a cooling method in two-phase water cooling. In this case, the cooling water pipes 12.12a, 12b on the population side are arranged in the air inlet manifold, and the cooling water pipes 13.13a, 13b on the outlet side are arranged in the air outlet manifold. Since this is the same as in the case of , the explanation of the configuration will be omitted. Two-phase water cooling is expected to absorb heat due to the heat of evaporation of the cooling water, so the flow rate is small. Therefore, it is necessary to make the cooling water flow as a gas-liquid mixture containing 2 to 3% air bubbles while gradually absorbing heat. Water. Since the heat absorbed by this cooling water is consumed as heat of evaporation, the temperature is almost the same between the inlet side and the outlet side, and therefore the temperature distribution of the upper and lower cooling plates 5 also changes from medium temperature to medium temperature to medium temperature as shown in the figure. . In the hydrogen electrode 3, a part of the part where the fuel gas inlet side and the air inlet side face each other becomes low temperature, and a part of the center part on the fuel outlet side becomes high temperature, but the overall temperature distribution is almost the same as in the case of pressurized water cooling. does not change. In the case of two-phase water cooling, the temperature on the inlet side of the cooling water can be higher than in the case of pressurized water cooling, so the temperature of the low temperature air supplied from the same side is raised, and the central part of the inlet side of the air electrode 4 becomes medium temperature. Become. However, the surrounding area before and after it will be cold. Air flows inside the air electrode 4 from left to right and is heated by the reaction heat, but this heat is absorbed by the cooling water flowing in the same direction while gradually increasing bubbles, so the air electrode 4 moves from the middle to the right. It becomes medium temperature → medium temperature. However, some parts of the central part on the exit side become hot. As mentioned above, even in the case of two-phase water cooling, the temperature distribution in the surface direction of the hydrogen electrode 3 and the air electrode 4 is maintained mainly at medium temperature. Finally, FIG. 3 shows a cooling method in which the fuel gas and air inlet manifolds are provided with partition plates 14 and 15 that divide the passage into left and right sections. The cooling water may be either pressurized water or two-phase water, but the figure shows the case of two-phase water cooling. In the figure, the fuel gas is transferred to the hydrogen electrode 3 as shown by the arrow.
The hydrogen is supplied from the right side of the partition plate 14 in front of the partition plate 14, and after passing through the hydrogen electrode 3, it is reversed in an outlet manifold (not shown), enters the hydrogen electrode 3 again, and is discharged from the left side of the partition plate 14. As mentioned above, fuel gas contains 65 to 80% hydrogen, but this hydrogen is consumed in the reaction and becomes 30 to 45% on the exit side, so the fuel gas decreases as it approaches the exit side. Flow rate decreases. Therefore, the ratio of the width of the left and right passages of the partition plate 14 is set to 70% on the inlet side and 30% on the outlet side. On the other hand, air is supplied from the back side of the left partition plate 15 of the air electrode 4 as shown by the arrow, is reversed in the outlet manifold (not shown) on the right side, enters the air electrode 4 again, and then enters the air electrode 4 through the partition plate 15.
is discharged from the front side. Air contains about 20% oxygen, but this oxygen is about 10% on the outlet side, so the ratio of the width of the left and right passages of the partition plate 15 is 60% on the inlet side and 40% on the outlet side. be. In this way, the reactant gas in the hydrogen electrode 3 and the air electrode 4 is
In the turn system, the fuel gas and air, whose temperature gradually rises from the population side to the exit side, face each other across the matrix 2 so as to compensate for each other in terms of temperature, so that low temperatures do not overlap or high temperatures do not overlap. . Therefore, extremely high or low temperatures do not occur within the electrodes 3.4, and the temperature distribution is generally gentle as shown in the figure. Note that the symbol ``medium high'' indicates a temperature slightly higher than medium temperature. In addition, in this method, when the fuel gas and air are reversed at the outlet manifold, the gas that has undergone half the reaction is stirred, so the gas that undergoes the second half of the reaction becomes homogeneous, improving power generation performance. .

【Effect of the invention】

If there is an imbalance in the temperature distribution within the cell, electrochemical reactions will proceed at different levels within the same electrode, and the high-temperature portion will initially generate electricity centrally, scattering phosphoric acid, and rapidly deteriorating the electrode. This will reduce the effective area for power generation. According to this invention, by appropriately regulating the air flow direction and the cooling water flow direction using pressurized water cooling and two-phase water cooling, and by stirring the reaction gas within the electrode, the temperature inside the cell can be increased. It is possible to effectively improve the distribution, improve power generation performance, and prevent electrode deterioration.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view of a cell stack for explaining a first embodiment of the invention, FIG. 2 is an exploded perspective view of a cell stack for explaining a second embodiment of the invention, and FIG. The figure is an exploded perspective view of a cell stack for explaining a third embodiment of the present invention, FIG. 4 is a plan view of a cell stack for explaining a conventional example, and FIG. 5 is a V-V in FIG. It is a phase cross-sectional diagram along the line. DESCRIPTION OF SYMBOLS 1... Single cell, 2... Matrix, 3... Hydrogen electrode, 4... Air electrode, 5... Cooling plate, 8... Fuel inlet manifold, 9... Fuel outlet manifold, 10・
... Air inlet manifold, 11... Air outlet manifold, 12... Cooling water supply pipe, 13... Cooling water discharge pipe. commode

Claims (1)

[Claims] 1) A cooling plate in which a large number of unit cells to which fuel gas and air are supplied in directions orthogonal to each other are stacked, and cooling water is passed through every few cells along the flow of the air. 1. A method for cooling a phosphoric acid fuel cell, characterized in that in the inserted phosphoric acid fuel cell, the flow direction of cooling water in the case of pressurized water cooling is opposite to the flow direction of air. 2) A phosphoric acid type in which a large number of single cells are stacked to which fuel gas and air are supplied perpendicularly to each other, and a cooling plate is inserted every few cells to allow cooling water to flow along the flow of the air. A method for cooling a phosphoric acid fuel cell, characterized in that in the case of two-phase water cooling, the direction of water flow of cooling water in the fuel cell is made to match the direction of flow of air. 3) A phosphoric acid type in which a large number of single cells are stacked to which fuel gas and air are supplied perpendicularly to each other, and a cooling plate is inserted every few cells to allow cooling water to flow along the flow of the air. In a fuel cell, an inlet manifold for fuel gas and air is provided with a partition plate that divides the passage into left and right halves, and the fuel gas and air supplied from one passage are reversed within the outlet manifold and discharged from the other passage of the inlet manifold. A method for cooling a phosphoric acid fuel cell, characterized in that: