JP2000149962A - Cooling plate for fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a temperature distribution characteristic of each battery cell in the case of cooling a fuel cell to prevent damage of a cooling pipe. SOLUTION: In this cooling plate for a fuel cell, when a cooling plate comprising two sheets of cooling plates 4 embeded with a cooling pipe 5 in a groove 6 is interposed between respective semi-blocks, and when cooling water is made to flow circulatedly in the cooling pipe 5 to cool a fuel cell, a diameter r1 of the groove 6 in the vicinity of an introducing part and a leading-out part of the pipe 5 to/from the cooling plate, for example, is made larger than that r2 of the other part to prevent the cooling pipe 5 from contacting directly with the cooling plates 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling plate for a fuel cell which is particularly suitable for a phosphoric acid type fuel cell using phosphoric acid as an electrolyte.

[0002]

2. Description of the Related Art In a fuel cell, an electrolyte layer is sandwiched between a fuel electrode and an oxidant electrode, and a fuel gas containing hydrogen is applied to the fuel electrode.
An oxidant gas containing air is caused to flow through the oxidant electrode to generate a cell reaction, thereby generating power. In a phosphoric acid fuel cell, a matrix in which phosphoric acid is held in an electrolyte layer is used. FIG. 4 shows a general configuration example of a fuel cell. The fuel cell stack 1 is put to practical use by stacking a plurality of single cells (single cells) 2 via a cooling plate 3. Manifolds (not shown) are attached to the four circumferences of the fuel cell stack 1 to supply air and hydrogen as reaction gases. Further, cooling water as a cooling medium is supplied to the cooling plate 3 to remove heat generated in the fuel cell.

FIGS. 5 and 6 show a conventional cooling plate 3. FIG. 5 is a plan view, and FIG. 6 is a side view. As shown in FIG. 6, the cooling plate includes two cooling flat plates 4 which can be divided into upper and lower portions, and a cooling pipe 5 through which cooling water as a cooling medium flows. As shown in FIG. 5, the cooling pipe 5
Buried inside. The cooling flat plate 4 is formed with a meandering groove having a predetermined diameter according to the shape of the cooling pipe in order to bury the cooling pipe 5. The cooling water flows in from one of the cooling pipes 5. Generally, the periphery of the cooling plate is covered with a fluororesin (not shown) for the purpose of preventing the intrusion of the reaction gas and the intrusion of phosphoric acid as an electrolyte.

[0004]

However, it has been pointed out that the following problems occur when the above-mentioned phosphoric acid type fuel cell is operated. 1) The temperature distribution is poor in the plane. The phosphoric acid fuel cell operates at about 200 ° C. In order to obtain high efficiency, it is necessary that the temperature within the unit cell is as uniform as possible. On the other hand, phosphoric acid, which is an electrolytic solution, is more likely to be generated as the operating temperature is higher, and scatters out of the system along with the reaction gas, and phosphoric acid in the cell decreases.

On the other hand, the supply of cooling water to the cooling plate is shown in FIG.
As shown by the arrow, supply from the outlet side of the reactant gas, drain from the inlet side of the reactant gas, reduce the temperature of the outlet side of the reactant gas in the surface of the unit cell, and reduce the phosphoric acid scattered. This is usually done. With respect to such an ideal temperature distribution, the air of the reaction gas actually supplied to the fuel cell is close to room temperature, and thus the air supply (inlet) side of the fuel cell operated at about 200 ° C. A low temperature region is formed in the plane, and the efficiency of the fuel cell decreases.

2) Phosphoric acid permeates the cooling flat plate and breaks the cooling pipe. The scattered phosphoric acid or phosphoric acid oozing from the end face of the unit cell adheres to the end face of the cold plate having a low temperature. As described above, the periphery of the cooling plate is covered with a fluorine resin or the like. If the resin has a flaw or the like, phosphoric acid may penetrate into the cooling plate through the resin. As a result, the cooling pipe may be corroded with phosphoric acid within a long period of time, and may be damaged, causing leakage of cooling water. Accordingly, an object of the present invention is to improve the temperature distribution characteristics of a cooling plate for a fuel cell and to prevent corrosion (corrosion prevention) of a cooling pipe.

[0007]

In order to solve such a problem, according to the first aspect of the present invention, a groove is formed in a plane between semi-blocks formed by stacking a plurality of unit cells.
A cooling plate comprising a plurality of cooling flat plates and a cooling pipe which circulates a cooling medium in a groove thereof, wherein the cooling medium is circulated and circulated through the cooling pipe to cool a fuel cell; The heat conductivity between the cooling pipe and the cooling plate is reduced near the inlet and outlet of the cooling pipe to the cooling plate.

According to the first aspect of the present invention, the diameter of the groove of the cooling plate near the inlet and outlet of the cooling pipe to the cooling plate can be made larger than the other portions. Invention). Further, in the first or second aspect of the present invention, the cooling pipe near the inlet and outlet of the cooling pipe to the cooling plate can be covered with a fluororesin (the invention of claim 3).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention reduces the thermal conductivity between a cooling pipe and a cooling plate near the inlet / outlet of a cooling pipe in a cooling plate, and lowers the cooling capacity in this portion. This is to reduce the low temperature region on the supply (inlet) side.
This effect is achieved by reducing the thermal conductivity of the cooling pipe in the cooling plate, particularly between the cooling pipe near the outlet and the cooling plate.

As a specific example of reducing the thermal conductivity between the cooling pipe and the cooling flat plate, first, an example as shown in FIG. 1 is given. FIG.
(A) is a plan view, and (b) is an AA cross-sectional view thereof. That is, as shown in FIG.
The cooling plate 4 is buried in the cooling plate 4 as in the conventional case, but the diameter r1 of the groove 6 at the end of the cooling plate 4 is equal to the internal diameter r.
It is characterized in that it is larger than 2 (r1> r2), and the cooling pipe 5 installed in this large groove is prevented from directly contacting the cooling flat plate 4.

FIG. 2 is a sectional view showing another embodiment of the present invention. In this case, the outer periphery of the cooling pipes arranged at both ends of the cooling plate among the cooling pipes is covered with a fluororesin to form a fluororesin tube 7. The diameter of the groove of the cooling plate is the same as in FIG. 1, and the diameter of the end of the cooling plate is large. FIG. 3 shows the temperature distribution in the flow direction of the reaction air on the single cell surface. When the solid line is the conventional example, the dotted line is the case of the present invention, and it can be seen that the latter can increase the temperature particularly on the air inlet (supply) side.

[0012]

According to the present invention, the heat conductivity between the cooling pipe and the cooling flat plate is reduced in the cooling plate of the phosphoric acid type fuel cell near the inlet and outlet of the cooling pipe to the cooling plate. As a result, the temperature distribution in the plane is poor, a low-temperature area is formed in the plane, and the efficiency of the fuel cell is reduced. The benefits can be obtained.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view showing a modification of FIG.

FIG. 3 is an explanatory diagram of a temperature distribution in a single cell plane.

FIG. 4 is a schematic diagram showing a general structure of a fuel cell.

FIG. 5 is a plan view showing a structural example of a conventional cooling plate.

FIG. 6 is a side view of FIG. 5;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel cell stack, 2 ... Single cell, 3 ... Cooling plate, 4 ...
Cooling flat plate, 5 ... cooling pipe, 6 ... groove, 7 ... fluororesin tube.

Claims (3)

[Claims] 1. A cooling system comprising: two cooling flat plates each having a groove formed in a plane between semi-blocks formed by stacking a plurality of unit cells; and a cooling pipe that circulates a cooling medium in the groove. In a fuel cell cooling plate for burying a plate and cooling a fuel cell by circulating a cooling medium through the cooling pipe and cooling the fuel cell, in the vicinity of an introduction part and a lead-out part of the cooling pipe to the cooling plate,
A cooling plate for a fuel cell, wherein thermal conductivity between a cooling pipe and a cooling plate is reduced. 2. The fuel cell according to claim 1, wherein the diameter of the groove of the cooling plate near the inlet and outlet of the cooling pipe to the cooling plate is larger than that of the other portions. Cooling plate. 3. The fuel cell cooling system according to claim 1, wherein the cooling pipe near the inlet and outlet of the cooling pipe to the cooling plate is covered with a fluororesin. Board.