JP2004119215A - Cooling medium for cooling fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly stable cooling medium into which aluminum is not dissolved and corroded, for cooling a fuel cell driven at high temperatures of 90°C or more. <P>SOLUTION: This cooling medium for cooling the fuel cell of the high-temperature driven type is constituted by adding propylene glycol to pure water. Because the cooling medium does not dissolve the aluminum even if it exceeds a constant period of time at 90°C or more like a curve (a) of the figure, electric conductivity is not rapidly elevated. On the other hand, the electric conductivity of a conventional cooling medium is rapidly elevated when the constant period of time is exceeded at 90°C or more like a curve (b). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a refrigerant used for cooling a fuel cell, and more particularly to a refrigerant for cooling a high-temperature driven fuel cell.
[0002]
[Prior art]
In recent years, the development of fuel cells using hydrogen or the like as fuel has been accelerated. Fuel cells are extremely large in use as driving power sources for vehicles such as automobiles in addition to ordinary households.
[0003]
FIG. 1 is a diagram illustrating an example of a general fuel cell. The stack of the fuel cell 1 is formed by stacking a number of cells 2, and the cell 2 mainly includes a matrix (electrolyte) 3 sandwiched between an air electrode and a fuel electrode, and separators 4 and 5 disposed on both sides of the matrix. It is a constituent member. Each time a plurality of the unit cells 2 are stacked, a cooling separator 6 is disposed.
[0004]
The cooling separator 6 is provided with an inlet portion 7 and an outlet portion 8 for the refrigerant, a pipe 9 is connected to the inlet portion 7, and a refrigerant supplied from an external cooling device 10 is supplied through the pipe 9. A pipe 11 is connected to the outlet 8, and the refrigerant cooled by heat exchange through the pipe 11 is returned to the cooling device 10.
[0005]
On the other hand, a communication path for circulating a refrigerant is formed between the cooling stack 6 and the unit cells 2, and the refrigerant supplied to the stack 6 flows evenly inside the unit cells 2, and the refrigerant exchanged and heated is heated. Return to the stack 6 again.
[0006]
It is required that a fuel cell mounted on a vehicle is reduced in size and weight, and that a cooling refrigerant does not freeze even in a severe cold season. Therefore, conventionally, the components such as the cooling stack 6 are made of a relatively strong and lightweight aluminum material for the purpose of miniaturization and weight reduction, and an antifreeze liquid used for a vehicle radiator or the like for the purpose of preventing freezing, That is, a refrigerant obtained by adding ethylene glycol to pure water is employed.
[0007]
However, it has been strongly desired that further improvements have been made in the vehicle-mounted fuel cells that have not been sufficiently reduced in size and weight, and one of the solutions is to solve the problem per unit weight of the fuel cell. Attention has been focused on technologies for improving the amount of power generation. However, when the amount of power generation per unit weight is increased, the current flowing through each cell increases, and the internal temperature increases. Therefore, a recent development direction aims to solve this problem by further improving the heat resistance of the separation membrane constituting the separator of the unit cell, and has already achieved the objective at the experimental level.
[0008]
[Problems to be solved by the invention]
However, according to the experiments of the present invention, when the high-temperature drive type fuel cell with improved heat resistance as described above is operated for a long time, the corrosion of the aluminum portion employed for miniaturization and weight reduction increases, It has been found that this causes another problem that the electric insulation inside the fuel cell is greatly reduced.
[0009]
When the cause was investigated and analyzed in detail, the temperature of the refrigerant in which ethylene glycol was added to pure water increased due to heat exchange, and especially when operated at 90 ° C or higher for a long time, ethylene glycol changed to formic acid and dissolved in aluminum. It has been found that the electrical conductivity sharply increases, thereby causing the corrosion of aluminum to progress, the electrical conductivity to increase rapidly due to the dissolved aluminum, and the electrical insulation inside the fuel cell to deteriorate.
Accordingly, an object of the present invention is to solve such a problem in the conventional refrigerant, and an object of the present invention is to provide a refrigerant suitable for cooling a high-temperature driven fuel cell.
[0010]
[Means for Solving the Problems]
The refrigerant according to the present invention that solves the above-mentioned problems is a refrigerant for cooling a high-temperature driven fuel cell, which is obtained by adding propylene glycol to pure water, and in particular, a high-temperature refrigerant that is driven at a high temperature of 90 ° C. or higher. It is a cooling refrigerant for a driving type fuel cell. In the present invention, “pure water” refers to pure water produced by a pure water producing apparatus using a reverse osmosis membrane or the like, and water having a purity equivalent thereto.
[0011]
The refrigerant according to the present invention has an excellent effect for cooling a high temperature drive type fuel cell operating at a high temperature of, for example, 90 ° C. or more, preferably 100 ° C. or more. That is, by using the refrigerant of the present invention for cooling a fuel cell, corrosion of aluminum is significantly suppressed even in the high-temperature region as described above, thereby preventing a decrease in electrical insulation inside the fuel cell. .
[0012]
The addition ratio of propylene glycol to pure water in the refrigerant is in the range of 0.3 to 1.5 parts by weight, preferably 0.4 to 1.0 part by weight per 1 part by weight of pure water. If the amount is less than 0.3 part by weight, the freezing resistance decreases, and if the amount is more than 1.5 parts by weight, the freezing resistance does not increase so much. As a method for producing the refrigerant, an appropriate amount of propylene glycol may be mixed into pure water and stirred and homogenized as in the conventional method.
[0013]
【Example】
Next, examples of the refrigerant of the present invention will be described.
The fuel cell 1 was assembled by stacking a plurality of unit cells 2 as shown in FIG. 1 and connected to an external cooling device 10 via pipes 9 and 11. The fuel cell 1 is of a high-temperature drive type, and the internal temperature reaches about 100 ° C. at the maximum when the operation is continued at the rated operation. Most of the cooling passages formed inside the fuel cell 1 are made of an aluminum material. Further, a thermometer for measuring the refrigerant temperature and an electric conductivity meter for measuring the electric conductivity of the refrigerant were installed in the pipe 11.
[0014]
The cooling device 10 was provided with a storage tank and a circulation pump, and the refrigerant stored in the storage tank was adjusted by adding 1 part by weight of propylene glycol per 1 part by weight of pure water and uniformly mixing. In the experiment, first, the pump of the cooling device 10 was started, and the refrigerant in the storage tank was circulated to the fuel cell 1. Next, fuel was supplied to the fuel cell 1 to generate power, and power was supplied to load equipment connected to the output circuit. By continuing to supply power, the internal temperature of the fuel cell 1 gradually increased, and the temperature of the thermometer provided in the pipe 11 also increased accordingly.
[0015]
FIG. 2 shows the relationship between the test time and the electric conductivity measured by an electric conductivity meter when the temperature of the refrigerant is tested at 90 ° C. or higher (as an example, 100 ° C.) by a curve (a). As can be seen, the electrical conductivity of the coolant is almost linearly and gradually increases in proportion to the lapse of time, T ₁ hour electrical conductivity even beyond (in this case 400 to 700 hours) is rapidly Never rise. Thus reason the electric conductivity is not rapidly increased even beyond ₁ hour T without refrigerant according to the present invention is reached at that time has a stability, changes in formic acid, constituting a cooling passage This is because the effect of dissolving and corroding the aluminum material is extremely small.
[0016]
[Comparative example]
On the other hand, for comparison, an experiment was performed in the same manner as in the example using a conventional refrigerant in which ethylene glycol was added to pure water (for example, an antifreeze liquid in which 1 part by weight of ethylene glycol was added to 1 part by weight of pure water). . The relationship between the test time and the electric conductivity measured by the electric conductivity meter is shown by a curve (b). As can be seen, the electric conductivity up to around ₁ hour T is substantially linearly and gradually increases in proportion to the temperature rise, but it can be seen that the rapid rise exceeds it. This indicates that the conventional refrigerant to which ethylene glycol is added significantly dissolves and corrodes aluminum when operated at 90 ° C. or higher for a long time.
[0017]
【The invention's effect】
As described above, the refrigerant according to the present invention has an excellent effect for cooling a high temperature drive type fuel cell operating at a high temperature of 90 ° C. or more, preferably 100 ° C. or more. That is, even in a high-temperature region, corrosion of aluminum is significantly suppressed, thereby preventing a decrease in electric insulation inside the fuel cell.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating an example of a general fuel cell.
FIG. 2 is a diagram showing a change in electric conductivity over time when a refrigerant according to the present invention and a conventional refrigerant are used at 90 ° C. or higher (test temperature 100 ° C.) for cooling a fuel cell. .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fuel cell 2 Single cell 3 Matrix 4 Separator 5 Separator 6 Separator for cooling 7 Inlet part 8 Outlet part 9 Pipe 10 Cooling device 11 Pipe

Claims (2)

A refrigerant for cooling a high temperature drive type fuel cell, wherein propylene glycol is added to pure water. 2. The cooling medium according to claim 1, wherein the fuel cell is operated at a high temperature of 90 ° C. or higher.

Images