Cooling system of fuel battery

Abstract

To provide a cooling system for a fuel battery that can appropriately manage the conductivity of a coolant.SOLUTION: A cooling system for a fuel battery includes a control device 60 that calculates the conductivity of a coolant W on the basis of the capacitance measured by a capacitance sensor 27 and controls a switching valve on the basis of the calculated conductivity. When the measured capacitance falls outside a calculable range in which the conductivity can be calculated, the control device 60 controls the oscillation frequency of the capacitance sensor 27 such that the capacitance falls within the calculable range, and controls the switching valve 25 such that the coolant W flows through the ion exchanger 24 when the calculated conductivity becomes equal to or greater than a predetermined threshold.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a cooling system for cooling a fuel cell. [Background technology]

[0002] Conventionally, fuel cells are cooled by a refrigerant since they generate heat during power generation. Ions contained in the single cells of the fuel cell may be present in the refrigerant, which may increase the conductivity of the refrigerant. In view of this, for example, Patent Document 1 discloses a fuel cell cooling system that includes an ion exchanger that removes ions from the refrigerant that cools the fuel cell, and a conductivity measuring sensor that measures the conductivity of the refrigerant. When the conductivity measured by the conductivity measuring sensor reaches or exceeds a predetermined value, this cooling system uses the ion exchanger to adsorb ions contained in the refrigerant, thereby reducing the conductivity of the refrigerant. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-018841 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, a cooling system for a fuel cell is required to ensure a necessary insulation resistance and to prevent electrolytic corrosion of the fuel cell separator, and the conductivity of the refrigerant is managed to satisfy both of these requirements. However, for example, the conductivity of the refrigerant may vary before and after use of an ion exchanger, or the conductivity of the refrigerant to be managed may change due to a change in the material of the fuel cell separator. In the technology of Patent Document 1, the measurement range of the conductivity of the refrigerant that can be measured by the conductivity sensor is limited, so when the variation in the conductivity of the refrigerant becomes large or the conductivity of the refrigerant to be managed is changed, it is difficult for the conductivity measurement sensor to appropriately manage the conductivity of the refrigerant.

[0005] The present invention has been made in view of the above circumstances, and has an object to provide a cooling system for a fuel cell that can appropriately manage the electrical conductivity of the coolant. [Means for solving the problem]

[0006] In consideration of the above problems, the fuel cell cooling system of the present invention comprises an ion exchanger that removes ions from a refrigerant that cools the fuel cell, a cooler that cools the refrigerant that has passed through the fuel cell, a capacitance sensor that measures the capacitance of the refrigerant, a switching valve that switches the refrigerant path so that the refrigerant flows to either the ion exchanger or the cooler, and a control device that calculates the conductivity of the refrigerant based on the measured capacitance and controls the switching valve based on the calculated conductivity, wherein the control device controls the oscillation frequency of the capacitance sensor so that the capacitance falls within the calculable range when the measured capacitance falls outside a calculable range in which the conductivity can be calculated, and controls the switching valve so that the refrigerant flows to the ion exchanger when the calculated conductivity becomes equal to or greater than a predetermined threshold value. Effect of the Invention

[0007] According to the present invention, the electrical conductivity of the coolant that cools the fuel cell can be appropriately controlled. [Brief description of the drawings]

[0008] [Figure 1] (a) is a system diagram of a fuel cell system equipped with a fuel cell cooling system, (b) is a schematic diagram showing a capacitance sensor attached to a tank, and (c) is a schematic diagram showing a capacitance sensor attached to an inner tube. [Diagram 2] 4 is a graph for explaining characteristics of a capacitance sensor. [Diagram 3] FIG. 2 is a control flow diagram of the cooling system shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A cooling system 20 for a fuel cell 10 according to an embodiment of the present invention will be described below with reference to Figures 1 to 3. As shown in Figure 1(a), the cooling system 20 for a fuel cell 10 according to this embodiment constitutes a part of a fuel cell system 1.

[0010] The fuel cell 10 is a stack of fuel cell units (single cells) stacked in the thickness direction, and although not shown, each single cell has a structure in which a membrane electrode assembly having gas diffusion layers formed on both sides is sandwiched between a pair of separators. Hydrogen gas H is supplied to the fuel cell 10 from a high-pressure tank 41 as a fuel gas, and air G is supplied to the fuel cell 10 via a compressor 31 as an oxidizing gas.

[0011] Hydrogen gas H and air G are supplied to each unit cell, and the unit cell generates power. Hydrogen off-gas discharged from the fuel cell 10 is circulated through the fuel cell 10 by a hydrogen pump 42. When the fuel cell 10 generates power, generated water and the like are discharged to the outside via an exhaust path 50 together with the oxidant off-gas.

[0012] Since the fuel cell 10 generates heat during power generation, the fuel cell system 1 is equipped with a cooling system 20 that supplies a coolant W to the fuel cell 10. The cooling system 20 is provided with a cooling path 20A through which the coolant W flows so as to circulate in the fuel cell 10. A pump 21 that pumps the coolant W and a tank 22 that stores the coolant W are disposed in the cooling path 20A.

[0013] The cooling path 20A further includes a cooler (radiator) 23 that cools the refrigerant that has passed through the fuel cell 10. The cooling path 20A further includes an ion exchanger 24 that removes ions contained in the refrigerant W, disposed in a path 20a leading to the cooler 23 and a bypass path 20b. The ion exchanger 24 includes an ion exchange resin therein, and removes ions (e.g., potassium ions and fluorine ions) present in the refrigerant W by adsorbing them to the ion exchange resin. The cooling path 20A further includes a switching valve 25 that switches the cooling path 20A so that the refrigerant flows through either the ion exchanger 24 or the cooler 23.

[0014] In this embodiment, as shown in Fig. 1(b), a capacitance sensor 27 for measuring the capacitance of the refrigerant W is disposed in the tank 22. Alternatively, for example, as shown in Fig. 1(c), the capacitance sensor 27 may be disposed inside the pipe 20c of the cooling path 20A through which the refrigerant W discharged from the fuel cell 10 flows.

[0015] Information on the capacitance measured by the capacitance sensor 27 is transmitted to the control device 60. The control device 60 calculates the conductivity of the refrigerant W based on the measured capacitance of the refrigerant W, and controls the switching operation of the switching valve 25 based on the calculated conductivity of the refrigerant W. In addition, the control device 60 receives signals related to the operating state of the fuel cell 10, and controls the oscillation frequency of the capacitance sensor 27, starts and stops the pump 21, and starts and stops the fan 23a of the radiator 23.

[0016] 2 and 3, the flow of control of the cooling system 20 will be described below. First, in step S1, a threshold value of conductivity (see step S7) is set based on the conductivity KC for maintaining the insulation resistance of the cooling system 20 and the conductivity KA (KB) at which electrolytic corrosion occurs in the separator material. In step S2, the oscillation frequency of the capacitance sensor 27 and the threshold value of the conductivity of the refrigerant W are set based on the setting of the threshold value of conductivity.

[0017] Specifically, as shown in FIG. 2, in the case of separator material A, the conductivity KA at which electrolytic corrosion occurs in the separator is smaller than the conductivity KC for maintaining the insulation resistance of the fuel cell system 1, so the threshold value is set based on the conductivity KA. In this case, in step S2, an oscillation frequency A at which the conductivity KA can be measured is set. On the other hand, in the case of separator material B, the conductivity KC for maintaining the insulation resistance of the fuel cell system 1 is smaller than the conductivity KB at which electrolytic corrosion occurs in the separator, so the threshold value is set based on the conductivity KC. In this case, in step S2, an oscillation frequency B at which the conductivity KC can be measured is set. Note that the conductivity KC for maintaining the insulation resistance of the fuel cell system 1 may also change depending on the system configuration.

[0018] In step S3, the control device 60 causes the capacitance sensor 27 to measure the capacitance of the refrigerant W at the set oscillation frequency. Here, as shown in FIG. 2, in the capacitance sensor 27, when the measured capacitance (capacitance value) is in the range of C1 to C2, the capacitance and conductivity are approximately directly proportional to each other regardless of the oscillation frequency. Therefore, the range of capacitance from C1 to C2 is the range in which the conductivity can be calculated. Therefore, in step S4, it is determined whether the measured capacitance value is equal to or greater than C1 and equal to or less than C2.

[0019] If the measured capacitance is outside the calculable range in step S4 (if NO), the process proceeds to step S5, where the control device 60 controls (changes) the oscillation frequency of the capacitance sensor 27 so that the capacitance falls within the calculable range. On the other hand, if the measured capacitance is within the calculable range (if YES), the process proceeds to step S6, where the control device 60 calculates the conductivity of the refrigerant W based on the capacitance measured by the capacitance sensor 27.

[0020] In step S7, it is determined whether the calculated conductivity of the refrigerant W is equal to or lower than the threshold value described above, and if it is not equal to or lower than the threshold value (if NO), the conductivity of the refrigerant W is high, so the control device 60 controls the switching valve 25 to allow the refrigerant W to flow through the ion exchanger 24. As a result, ion cleaning of the refrigerant W is performed by the ion exchanger 24. On the other hand, if the conductivity of the refrigerant W is equal to or lower than the threshold value (if YES), a series of flows are performed.

[0021] In this way, the control device 60 can calculate the conductivity of the refrigerant W by the capacitance sensor 27 by controlling the oscillation frequency of the capacitance sensor 27, regardless of the material of the separators of the fuel cell 10. As a result, the control device 60 can remove ions from the refrigerant by the ion exchanger 24 and reduce the conductivity of the refrigerant by controlling the switching valve 25 at an appropriate timing based on the calculated conductivity. [Explanation of symbols]

[0022] 10: fuel cell, 23: cooler, 24: ion exchanger, 25: switching valve, 27: capacitance sensor, 60: control device, W: refrigerant

Claims

[Claim 1] an ion exchanger for removing ions from a coolant for cooling the fuel cell; a cooler for cooling the refrigerant that has passed through the fuel cell; a capacitance sensor for measuring the capacitance of the refrigerant; a switching valve that switches a refrigerant path so that the refrigerant flows through either the ion exchanger or the cooler; a control device that calculates a conductivity of the refrigerant based on the measured capacitance and controls the switching valve based on the calculated conductivity, the control device controls an oscillation frequency of the capacitance sensor when the measured capacitance falls outside a calculable range in which the conductivity can be calculated, so that the capacitance falls within the calculable range; and A cooling system for a fuel cell, comprising: a switching valve that controls the refrigerant to flow through the ion exchanger when the calculated electrical conductivity becomes equal to or greater than a predetermined threshold value.

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