JP3141908B2 - Fuel cell temperature controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell temperature controller and a temperature control method for controlling the temperature during operation of a fuel cell by using latent heat of vaporization of a liquid.

[0002]

2. Description of the Related Art Conventionally, in the temperature control in a fuel cell power generation system, cooling water is circulated through a fuel cell to a fuel cell to control the temperature of the fuel cell. Such a fuel cell is disclosed in, for example, JP-A-4-47674.
JP, JP-A-4-26069, JP-A-4-2669
No. 070 publication.

[0003]

In the above-described conventional cooling water circulation system, heat exchange is performed by contact between the cooling water and the fuel cell. Therefore, the heat transfer rate (= cooling speed) effective for cooling is as follows. 1000-5000 kcal /
m ² h ° C., and the heat transfer coefficient is not very large. In addition, if added, the heat transfer coefficient of the cooling system by blowing air is 20 to 80 kcal / m ² h ° C., and the heat transfer coefficient is further small. In such a conventional cooling water circulation system, the heat transfer coefficient of the heat medium used for cooling is low, so that the cooling efficiency is poor.

The conventional temperature control means of a fuel cell for circulating cooling water includes a tank for containing at least cooling water, a pump for circulating cooling water in the tank to the fuel cell, and cooling the cooling water in the tank. Since a blower or a heat exchanger is required, considerable energy is required for the entire system, and the structure is complicated. Therefore, an object of the present invention is to provide a temperature control device and a temperature control method for a fuel cell, which solve the above-mentioned problems and reduce the energy used for cooling water and simplify the system.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a fuel cell unit having at least one unit cell in an airtight container, wherein the operating temperature of the fuel cell is reduced. A fuel cell wherein a liquid having an upper limit of the boiling point is contained in the hermetic container in a state where a part of the space in the hermetic container is left and in a state where a part of the fuel cell unit is immersed. Temperature control device.

Further, the present invention is characterized in that various kinds of liquids having different boiling points are selectively mixed, and the fuel cell is cooled by the latent heat of vaporization of the mixed liquid to control the temperature during operation of the fuel cell. Temperature control method.

[0007]

In the present invention, since the heat transfer is performed by boiling the liquid, the heat transfer coefficient is 10,000 to 20,000 kcal.
/ M ² h ° C. At the time of boiling, heat is taken away by latent heat, so that the fuel cell can be cooled. According to the present invention, since the heat transfer coefficient due to the boiling of the liquid is such a large value, the Joule heat generation of the electrolytic solution,
The heat generated by the electrochemical reaction and catalytic combustion in the cell can be efficiently removed, and the operating temperature of the fuel cell can be kept stable during operation by selectively mixing various liquids having different boiling points. it can.

[0008]

1 shows the structure of one stack of a fuel cell temperature control device according to the present invention. In FIG. 1, reference numeral 1 denotes a closed container made of a heat insulating material. One or more fuel cell units 2 are accommodated in the sealed container 1, and a part of the fuel cell unit 2 is immersed in a state where a part of the space 3 is left inside. Is filled with the liquid 4 for cooling. A vent is provided on one side of the closed container 1 constituting the stack, and a safety device 5 for reducing a surge pressure generated in the closed container 1 is attached.
As the safety device 5, a surge tank, a safety valve, or the like is used. The lid 6 of the closed vessel 1 is a heat exchanger, and both sides thereof are fin-finished to increase the area.

FIG. 2 shows the whole fuel cell system when a plurality of the above-mentioned stacks are employed. Stack definitive in Figure 2, the stack 61, the stack 62, and so the stack 63 ..., a plurality of each stack connected to the fuel input line 64 and the electrolyte output line 65, the fuel input line 64 and the electrolyte The liquid input / output line 65 is arranged in parallel. Furthermore, each stack 61, 62,
63 are provided with safety devices 51, 52 and 53 for alleviating surge pressure caused by the vapor of the cooling liquid. A fuel tank 66 is provided on the fuel input / output line 64.
And a gas-liquid separator 67. In the electrolyte input / output line 65, a gas-liquid separator / electrolyte purification tank 68 is disposed.

In the overall view of the fuel cell system shown in FIG. 2, fuel stored in a fuel tank 66 is supplied to each stack by a pump 69 through a fuel input / output line 64, and further discharged from each stack. The fuel thus obtained is turned into a liquid in a gas-liquid separator 67 through a fuel input / output line 64, collected in the fuel tank 66, and circulated.

On the other hand, the electrolytic solution purified in the gas-liquid separator / electrolyte purifying tank 68 is passed through an electrolytic solution input / output line 65.
Electrolyte supplied to each stack by the pump 70, and from each stack, a contaminated electrolyte is supplied to the electrolyte input / output line 6.
5 and is again collected and circulated to the gas-liquid separator / electrolyte purification tank 68. In this fuel cell system, the blower 71
Ventilation may be performed in each stack, or forced convection 72 by REM wind or a fan may be performed on the entire fuel cell system.

An application example in which water is used as a liquid utilizing latent heat of vaporization in the fuel cell temperature control apparatus according to this embodiment will be described. Since the operating temperature of the fuel cell (the electrolytic solution is sulfuric acid) is 100 ° C., the cooling liquid 4 (water) starts to boil shortly after the operation of the fuel cell is started, and then continues to boil. The steam condenses in the vicinity of the fin of the lid 6 which is a heat exchanger, and returns in the space 3.

Therefore, when the temperature of the fuel cell rises to 100 ° C. or higher, the fuel cell is cooled by the cooling liquid 4 and the operating temperature is kept at the boiling point of water of 100 ° C. The cooling rate at this time corresponds to the heat transfer coefficient shown in the following Table 1. For example, in the present embodiment, while cooling at a rate of 10,000 kcal / m ² · h · ° C., water at normal temperature is convected. In the comparative example, 100
0 kcal / m ² · h · ° C. In this case, in this embodiment, cooling can be performed ten times faster. Table 1 below
As shown in the figure, the present embodiment can achieve a cooling rate 4 to 10 times that of the comparative example.

On the other hand, since the latent heat of boiling water has a heat capacity of 539 times that of vaporized sensible heat, the heat capacity of the method of continuing boiling in a closed vessel as in this embodiment is 539 times that of the comparative example. Can be estimated. Therefore, it is possible to sufficiently cope with the heat generated by the plurality of battery units.

[0015]

[Table 1]

In the present invention, as the liquid used for cooling, a liquid having a boiling point at the operating temperature of the fuel cell is selected in order to utilize the latent heat of the liquid. For example, Table 2 below shows application examples of the refrigerant.

[0017]

[Table 2]

As shown in Table 2 above, the electrolytic solution was sulfuric acid,
Water can be used as a cooling liquid for a fuel cell with an operating temperature of 100 ° C. Further, in a fuel cell in which the electrolytic solution is a solution containing sulfuric acid and methanol and the operating temperature is 100 ° C. or lower (for example, 60 ° C.), an aqueous solution containing water and methanol can be used as a cooling liquid.

In a fuel cell in which the electrolyte is an aqueous phosphoric acid solution and the operating temperature is 100 ° C. or higher (for example, 100 to 200 ° C.), an aqueous solution of ethylene glycol or a salt can be used as a cooling liquid. In the present invention, the fuel cell housed in the sealed container 1 is, for example, a fuel cell unit 2 in which four unit cells are stacked.

FIG. 3 shows an example of the fuel cell unit 2 of the present invention in which unit cells are assembled, and FIG.
FIG. The fuel cell unit 2 is configured by combining four unit cells, namely, a unit cell (a), a unit cell (b), a unit cell (c), and a unit cell (d). The unit cell (a) has an oxidizer electrode chamber 14, an oxidizer electrode 12, an electrolyte 1
1, a fuel electrode 13 and a fuel electrode chamber 15. Subsequently, a unit cell (b) includes a fuel electrode chamber 15, a fuel electrode 23, an electrolyte 21, an oxidant electrode 22, and an oxidant electrode chamber 24. ing. The other cells (c) and (d) have the same configuration.

These unit cells are stacked back-to-back with each other or with each other so that the fuel cell compartments or oxidant cell compartments of adjacent cells are shared. Together, they form one fuel electrode chamber or one oxidant electrode chamber. That is, the unit cell (b) shares the fuel electrode chamber 15 with the unit cell (a), and the structure of the unit cell (b) includes the fuel electrode chamber 15, the fuel electrode 23, the electrolyte 21, and the oxidant electrode. 22 and the oxidant electrode chamber 24 are stacked in this order, and the oxidant electrode chamber 24 is shared by the unit cells (c) arranged subsequently.

The structure of the electrodes used in each cell is shown in FIG. 5 as an example. FIG. 5 shows a configuration diagram of the oxidizer electrode 22 of the unit cell (b) and the fuel electrode 33 of the unit cell (c).
It is configured by joining current collectors 221 and 331 having lattice-shaped openings and electrode reactants 223 and 333. At the edges of the current collectors 221 and 331, two external lead-out terminals 222 and 332 for electrically connecting the single cells are provided at two points symmetrically in one current collector. The configuration of the electrodes is the same in other single cells.

As shown in FIG. 3, an external lead-out terminal 132 is provided at the edge of the fuel electrode 13 of the unit cell (a). In the unit cell (d), the external lead-out terminal 132 is connected to the oxidant electrode 42. It is shown that the terminal 422 is provided.
These external lead-out terminals 132 and 422 can be connected to adjacent fuel cell units of the integrated fuel cell.

Adjacent cells are connected in series by a current collector 100 at each external lead-out terminal provided on each electrode. A connection block or cable or the like made of a good conductor metal is used for the current collection connector 100, and is connected to form a bridge-like path. 3, the current collector connector 100 illustrated in FIG. 4, have been used U-shaped flat cable, by screwing the external lead terminal foot portion of the flat cable as a leaf spring, adjacent The fitted single cells can be fixed by crimping. The electrical connection is made by connecting the external lead terminals of different electrodes of adjacent cells to form a bridge-like path. Routes that are close to each other are arranged so that their positions are far from each other, that is, are shifted and arranged.
Separating the connection positions in this manner has the effect of preventing electrical interference caused by the same-polarity external lead-out terminals of adjacent cells.

As shown in FIG. 5, the current collector 221 has two external lead terminals 222, 222.
31 also has two external lead-out terminals 332 and 332. When connecting a plurality of cells, each of the current collectors 221 and 221 is connected to reduce the contact resistance between adjacent cells.
It is necessary to connect both of the two external lead terminals 222, 222, 332, 332 formed on both sides of the periphery of 331 to another unit cell. FIG. 4 shows a current collector 221,
331 at the external lead-out terminals on both sides.
0 indicates electrical connection.

FIG. 6 is a perspective view of the entire fuel cell unit 2. A fuel discharge / oxidant supply manifold 54 is provided above the fuel cell unit 2, and a fuel supply / oxidant discharge manifold 55 is provided below the unit. The temperature control device and the temperature control method for a fuel cell according to the present invention are not limited to the above embodiments, and various modifications are possible based on the spirit of the present invention. For example, in the example of the fuel cell, one unit is formed by stacking four unit cells.
It can be a unit.

[0027]

The present invention has the following effects by adopting the above-described configuration. In the present invention, the heat transfer is performed by boiling the liquid.
It can be improved to 0 to 20000 kcal / m ² h ° C. At the time of boiling, heat is taken away by latent heat, so that the fuel cell can be cooled. Therefore, it is possible to reduce the energy used for circulating the cooling water used for cooling the conventional fuel cell, and to simplify the system for that purpose.

Since the heat transfer coefficient in the present invention is thus large, it is possible to efficiently remove the heat generated by the Joule heat of the electrolytic solution, the electrochemical reaction in the battery, the catalytic combustion, etc., during the operation of the fuel cell. The operating temperature can be kept stable.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a fuel cell temperature control device of the present invention.

FIG. 2 is an overall view of a fuel cell system when a plurality of stacks are employed.

FIG. 3 shows an example of a fuel cell unit used in the present invention.

FIG. 4 is a sectional view taken along line AA of FIG. 3 ;

FIG. 5 shows a configuration of an electrode used for each unit cell.

FIG. 6 is a perspective view of the entire fuel cell unit assembled in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Closed container 2 Fuel cell unit 3 Space 4 Liquid 5,51,52,53 Safety device 6 Lid 11,21,31,41 Electrolyte 12,22,32,42 Oxidizer electrode 13,23,33,43 Fuel electrode 14 , 24, 44 Oxidant electrode chamber 15, 35 Fuel electrode chamber 54 Manifold for fuel discharge and oxidant supply 55 Manifold for fuel supply and oxidant discharge 61, 62, 63 Stack 64 Fuel input / output line 65 Electrolyte input / output line 66 Fuel tank 67 Gas-liquid separator 68 Gas-liquid separator / electrolyte purifying tank 69, 70 Pump 71 Blower 72 Forced convection by REM style or fan 100 Current collector 221 331 Current collector 132, 222, 332, 422 External drawer Terminal 223, 333 Electrode reactant

Claims (1)

(57) [Claims] 1. A fuel cell unit having at least one unit cell is disposed in an airtight container, and a liquid having a boiling point at an upper limit of an operating temperature of the fuel cell partially occupies a space in the airtight container. A temperature control device for a fuel cell, wherein the temperature control device is stored in the closed container with the fuel cell unit left and with a part of the fuel cell unit immersed.