JP2019046720A - Fuel cell system - Google Patents

Abstract

To provide a fuel cell system that secures the amount of evaporation of liquid water at a humidifier for humidifying cathode gas.SOLUTION: A fuel cell system comprises: a fuel cell; a compressor for compressing cathode gas and supplying the compressed cathode gas to the fuel cell; a radiator for promoting heat radiation of cooling water for cooling the fuel cell; a storage unit for storing liquid water in cathode off-gas discharged from the fuel cell; a heat exchanger for performing heat exchange between the liquid water and the cooling water that is discharged from the fuel cell and to be supplied to the radiator; and a humidifier for evaporating the liquid water discharged from the heat exchanger, by using the cathode gas that is compressed by the compressor and to be supplied to the fuel cell and the cooling water that is discharged from the heat exchanger and to be supplied to the radiator, to humidify the cathode gas to be supplied to the fuel cell.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a fuel cell system.

  In Patent Document 1, the liquid water in the cathode off-gas discharged from the fuel cell is stored, and the temperature of the liquid water is raised by a heat exchanger that exchanges heat between the stored liquid water and the cooling water of the fuel cell. There is known a humidifier which humidifies the cathode gas supplied to the fuel cell by the heated liquid water. In the humidifier, the cathode gas compressed to a high temperature by the compressor is supplied, and the liquid water is evaporated by receiving the heat of the cathode gas.

JP 2004-362806 A

  In the humidifier, the temperature of the cathode gas is lowered because the latent heat of vaporization of liquid water is taken away from the cathode gas. Due to the decrease in the temperature of the cathode gas, the amount of evaporation of liquid water may not be sufficiently secured. In particular, when the heat exchange between the liquid water and the cooling water in the heat exchanger is not sufficient, the liquid water does not heat up sufficiently, the latent heat of vaporization of the liquid water increases, and the temperature of the cathode gas is more It may decrease and the evaporation of liquid water may further decrease.

  An object of the present invention is to provide a fuel cell system in which the amount of evaporation of liquid water in a humidifier that humidifies a cathode gas is secured.

  The above object is to provide a fuel cell, a compressor for compressing a cathode gas and supplying the fuel cell to the fuel cell, a radiator for promoting heat radiation of cooling water for cooling the fuel cell, and a cathode off gas discharged from the fuel cell. A reservoir for storing liquid water, a heat exchanger for exchanging heat between the cooling water and the liquid water before being discharged from the fuel cell and supplied to the radiator, and after being compressed by the compressor The liquid water discharged from the heat exchanger is evaporated by the cathode gas before being supplied to the fuel cell and the cooling water discharged from the heat exchanger and before being supplied to the radiator. And a humidifier for humidifying the cathode gas before being supplied to the fuel cell.

  According to the present invention, it is possible to provide a fuel cell system in which the amount of evaporation of liquid water in the humidifier humidifying the cathode gas is secured.

FIG. 1 is a schematic view of a fuel cell system. FIG. 2: is the graph which showed the trial calculation result of the cumulative evaporation of the liquid water according to the heat source. FIG. 3 is a schematic view of a fuel cell system of a modification.

  FIG. 1 is a schematic view of a fuel cell system 1 (hereinafter referred to as a system). The system 1 includes a control device 10, a fuel cell 20, an air supply system 30, a cooling system 40 and the like. The system 1 supplies the generated power of the fuel cell 20 to a motor or the like (not shown). The control device 10 is a computer provided with a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), etc., and is electrically connected to respective devices described later to control the entire system 1 . The system 1 includes a hydrogen gas supply system (not shown) that supplies hydrogen gas, which is an anode gas, to the fuel cell 20, and a power control system that controls the generated power of the fuel cell 20.

  The air supply system 30 supplies air to the fuel cell 20, and is configured as follows. The cathode gas, which is air containing oxygen taken from the outside air, is compressed by the air pump 33 through the supply path 31, is humidified by the humidifier 35, and is supplied to the fuel cell 20. The discharge path 32 releases the cathode off gas discharged from the fuel cell 20 to the atmosphere. The air pump 33 is an example of a compressor that compresses the cathode gas and supplies it to the fuel cell 20. The gas-liquid separator 37 is disposed on the discharge path 32 and allows passage of the cathode off gas discharged from the fuel cell 20 and stores liquid water in the cathode off gas. In the liquid water in the cathode off gas, generated water produced by the power generation reaction of the fuel cell 20 and discharged from the fuel cell 20 together with the cathode off gas, and water in the cathode gas are condensed in the fuel cell 20 and Includes drained condensed water. Although described in detail later, liquid water stored in the gas-liquid separator 37 is used for humidifying the cathode gas in the humidifier 35.

  A liquid-water path 51 is connected between the gas-liquid separator 37 and the humidifier 35. Specifically, one end of the liquid-water path 51 is connected to the end on the vertically lower side of the gas-liquid separator 37. A liquid water pump 55 is provided in the liquid water path 51. The liquid water pump 55 is electrically connected to the control device 10 and controlled. A heat exchanger 57 is provided straddling the circulation path 41 and the liquid / water path 51 described later.

  The cooling system 40 cools the fuel cell 20 by circulating cooling water through a predetermined path. Specifically, the cooling water flows through the circulation path 41 by the circulation pump 45, passes through the heat exchanger 57, is heat-exchanged by the radiator 46, is cooled, and is supplied to the fuel cell 20.

  Next, humidification of the cathode gas by liquid water stored in the gas-liquid separator 37 will be described. The liquid water stored in the gas-liquid separator 37 is supplied in order of the heat exchanger 57 and the humidifier 35 through the liquid-water passage 51 by driving the liquid-water pump 55. As described above, cooling water is supplied to the heat exchanger 57 via the circulation path 41. In the heat exchanger 57, the liquid water and the cooling water are subjected to heat exchange. Specifically, in the heat exchanger 57, cooling water flows in a metal tube provided so as to penetrate the inside of the case, and liquid water is supplied inside the case and outside the tube. It is configured. According to this configuration, the heat of the cooling water is transferred to the liquid water through the outer wall of the tube without mixing the liquid water and the cooling water. Here, the cooling water supplied to the heat exchanger 57 is after being discharged from the fuel cell 20 and before being supplied to the radiator 46, and has a relatively high temperature, for example, about 100.degree. Therefore, in the heat exchanger 57, the temperature rise of the liquid water is promoted by the cooling water.

  Next, the liquid water and the cooling water are introduced into the humidifier 35. Here, the cathode gas, which is compressed by the air pump 33 and becomes high temperature, is supplied to the humidifier 35. The temperature of the compressed cathode gas is, for example, about 200.degree. For this reason, in the humidifier 35, the liquid water is also heat-exchanged with the cooling water as well as the high temperature cathode gas, evaporation is promoted and the cathode gas is humidified. The humidifier 35 also has a configuration similar to that of the heat exchanger 57, and the cooling water flows in a metal tube provided so as to penetrate the inside of the case, and the liquid water is supplied to the outside of the tube in the case. In the case, the cathode gas is configured to pass through the outside of the tube. Further, the cooling water in the tube and the liquid water and the cathode gas outside the tube are not mixed.

  In the humidifier 35, a heat quantity corresponding to the latent heat of vaporization of liquid water is removed from both the cooling water and the cathode gas. Here, assuming that the heat amount corresponding to the latent heat of vaporization of liquid water is deprived only from the cathode gas, the temperature of the cathode gas is greatly reduced, and the amount of evaporation of liquid water may not be sufficiently secured. In particular, due to factors such as the amount of liquid water, the flow rate of the cooling water, and the structure of the heat exchanger 57, the heat exchanger 57 can not sufficiently exchange the heat of the liquid water with the cooling water. It is also conceivable that the temperature can not be raised. In this case, the temperature of the liquid water supplied to the humidifier 35 decreases, the latent heat of evaporation of the liquid water in the humidifier 35 increases, and the temperature of the cathode gas further decreases. May be further reduced. In the present embodiment, heat exchange with the cooling water is performed in the heat exchanger 57 before the liquid water is supplied to the humidifier 35, and the heat exchange between the liquid water and the cooling water is also performed in the humidifier 35. Thereby, even if the heat exchange between the liquid water and the cooling water in the heat exchanger 57 is not sufficient, the liquid water is evaporated by the cooling water and the cathode gas in the humidifier 35. Therefore, as described above, the target from which the heat quantity corresponding to the latent heat of vaporization of liquid water in the humidifier 35 is taken includes not only the cathode gas but also the cooling water, so that the temperature decrease of the cathode gas is suppressed. As a result, the evaporation amount of liquid water can be secured.

  FIG. 2: is the graph which showed the trial calculation result of the cumulative evaporation of the liquid water according to the heat source. The vertical axis indicates the cumulative evaporation of liquid water in the humidifier 35, and the horizontal axis indicates the position in the humidifier 35. On the horizontal axis, the left side is the inlet side of the humidifier 35, and the right side is the outlet side of the humidifier 35. In FIG. 2, as a heat source for evaporating liquid water, in the case of cooling water alone, in the case of cathode gas after compression only, and in the case of cooling water and cathode gas after compression, after heat exchange with liquid water beforehand. The case of cooling water and cathode gas after compression is shown. The evaporation rate of liquid water and the accumulated evaporation amount increase in the above order. Therefore, according to the configuration of this embodiment, the liquid water can be efficiently evaporated, and the cathode gas can be sufficiently humidified. Further, as shown in FIG. 2, the accumulated evaporation amount of liquid water increases as the distance from the inlet to the outlet of the humidifier 35 increases, but the evaporation rate of liquid water is fast due to the configuration of the present embodiment. The amount of evaporation of liquid water can be secured while suppressing the enlargement of the humidifier 35.

  Next, a system 1a of a modification will be described. The same components of the system 1a will be assigned the same reference numerals and redundant explanations will be omitted. Unlike the above embodiment, in the system 1a, an on-off valve 56 is provided instead of the liquid water pump 55. Further, in the air supply system 30a, an air pump 33a is provided instead of the air pump 33, and an air pump 33b is provided on the supply path 31 between the humidifier 35 and the fuel cell 20. The air pumps 33a and 33b and the on-off valve 56 are also electrically connected and controlled by the control device 10a. The cathode gas compressed by the air pump 33 a is supplied to the humidifier 35, and the cathode gas is further compressed by the air pump 33 b and supplied to the fuel cell 20. Here, the inside of the liquid water path 51 has a negative pressure by the air pump 33 b, and while the on-off valve 56 is open, the liquid water stored in the gas-liquid separator 37 is sucked toward the humidifier 35. For this reason, it is not necessary to provide a liquid water pump only for conveying liquid water, and the manufacturing cost of the system 1a is reduced.

  As mentioned above, although the embodiment of the present invention has been described in detail, the present invention is not limited to such a specific embodiment, and various modifications may be made within the scope of the subject matter of the present invention described in the claims. Changes are possible.

DESCRIPTION OF SYMBOLS 1 fuel cell system 20 fuel cell 35 humidifier 37 gas-liquid separator (storage part)
46 Radiator 57 Heat Exchanger

Claims (1)

With fuel cells,
A compressor that compresses a cathode gas and supplies it to the fuel cell;
A radiator promoting heat dissipation of cooling water for cooling the fuel cell;
A storage unit for storing liquid water in cathode off gas discharged from the fuel cell;
A heat exchanger that exchanges heat between the cooling water and the liquid water before being discharged from the fuel cell and supplied to the radiator;
From the heat exchanger by the cathode gas after being compressed by the compressor and before being supplied to the fuel cell, and by the cooling water being discharged from the heat exchanger and being supplied to the radiator A humidifier for evaporating the discharged liquid water to humidify the cathode gas before being supplied to the fuel cell.

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