Cooling device for fuel cell systems

Abstract

The present invention provides a cooling device for a fuel cell system that can reduce the time required for air bleeding and ensure more reliable air bleeding. [Solution] The refrigerant piping 4 includes module piping 4M which forms an annular pipeline for supplying and discharging refrigerant to and from the power generation unit 5, and system piping 4S which is connected in parallel with a plurality of module pipings 4M and forms an annular pipeline for supplying and discharging refrigerant to and from the radiator 1 and the module piping 4M, an air vent line 8 provided for each module piping 4M which discharges air bubbles in the refrigerant piping 4 to the outside, and a pump 6 which circulates refrigerant in the refrigerant piping 4, and performs air vent circulation in which refrigerant circulates between the radiator 1 and one power generation unit 5 that is not generating power, selected from a plurality of units.

Description

TECHNICAL FIELD

[0001] The present invention relates to a cooling device that cools a fuel cell system using a refrigerant.

BACKGROUND ART

[0002] In recent years, fuel cell systems that output large electric power by combining a plurality of fuel cell modules have been proposed. For example, in the fuel cell system disclosed in Patent Document 1, three fuel cell modules are connected in parallel to one radiator, and a refrigerant circulates between the radiator and the fuel cell modules. In such a configuration that cools the fuel cell modules by circulating the refrigerant, it is unavoidable that air bubbles are mixed into the piping when the refrigerant is injected into the piping. For this reason, in order to remove the mixed air bubbles, the refrigerant is circulated without performing power generation. For example, in a fuel cell system in which a plurality of fuel cell modules are connected in parallel as in Patent Document 1, a method is adopted in which the refrigerant is circulated simultaneously through all refrigerant pipes to remove air bubbles.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0003]

PATENT DOCUMENT 1

SUMMARY OF INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0004] Incidentally, as described above, when the method of circulating the refrigerant simultaneously through all the pipes is used, air bubbles separated from one fuel cell module may move to another fuel cell module and adhere thereto. If this separation and adhesion are repeated, there is a possibility that the air bubbles cannot be completely eliminated even though the air bleeding takes a long time.

[0005] This invention has been made in view of the above-mentioned points, and aims to provide a cooling device for a fuel cell system that can shorten the time required for air bleeding and perform air bleeding more reliably. Furthermore, by shortening the time required for air bleeding, it contributes to energy efficiency. [Means for solving the problem]

[0006] To achieve the above objective, the cooling device for a fuel cell system according to the present invention comprises a refrigerant piping having modular piping that forms an annular conduit for supplying and discharging refrigerant to and from a power generation unit, and system piping that is connected in parallel with a plurality of the modular pipings and forms an annular conduit for supplying and discharging refrigerant to and from a heat sink and the modular piping, an air vent line provided for each of the modular pipings for discharging air bubbles in the refrigerant piping to the outside, and a pump for circulating refrigerant in the refrigerant piping, and is characterized by performing air vent circulation in which the refrigerant circulates between the heat sink and one power generation unit that is not generating power, selected from a plurality of units. [Effects of the Invention]

[0007] The present invention aims to provide a cooling device for a fuel cell system that can shorten the time required for air bleeding and perform air bleeding more reliably. This will ultimately contribute to energy efficiency. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram shows the cooling device for the fuel cell system of the first embodiment and represents the first step. [Figure 2] This diagram shows the cooling device for the fuel cell system of the first embodiment and represents the second step. [Figure 3] This diagram shows the cooling device for the fuel cell system of the first embodiment and represents the third step. [Figure 4]This diagram shows the cooling device for the fuel cell system of the first embodiment and represents the fourth step. [Figure 5] This diagram shows another air bleeding method in the cooling device of a fuel cell system according to the first embodiment, and represents the configuration of the first step. [Figure 6] This diagram shows an alternative air venting method in the cooling device of the fuel cell system of the first embodiment, and represents the second step. [Figure 7] This diagram shows the cooling device for the fuel cell system of the second embodiment and represents the configuration of the first step. [Figure 8] This diagram shows the cooling device for the fuel cell system of the third embodiment and represents the first step. [Modes for carrying out the invention]

[0009] The cooling device S1 of the fuel cell system according to the first embodiment of the present invention will be described in detail with reference to Figures 1 to 4. In the explanations, identical elements will be given the same symbols, and redundant explanations will be omitted.

[0010] The cooling device S1 of this embodiment is a device for cooling a fuel cell system. It is equipped with a radiator 1, a fuel cell module 2, a switching valve 3, and refrigerant piping 4. The heat sink 1 is configured to cool the refrigerant that has been heated as it passes through the fuel cell module 2.

[0011] The fuel cell module 2 comprises a power generation unit 5, a pump 6, and a control unit (not shown). In this embodiment, four fuel cell modules 2 of the same standard and specifications are provided. Therefore, we will refer to each of the four fuel cell modules 2, in order from left to right in Figure 1, as Module 1 21, Module 22, Module 3 23, and Module 4 24, and continue the explanation. Furthermore, the control unit (not shown) controls each power generation unit 5, each pump 6, and each switching valve 3.

[0012] The power generation unit 5 is a unitized structure of components necessary for generating power as a fuel cell, and includes a stack (not shown), fuel gas supply means (not shown), oxidizing gas supply means (not shown), and the like. The power generation unit 5 of each fuel cell module 2 has the same standard and the same specifications, and is configured to be capable of generating power independently for each power generation unit 5. The power generation unit 5 is configured such that a refrigerant can circulate inside thereof to cool the stack. Note that the power generation unit 5 of the first module 21 is referred to as the first unit 51, the power generation unit 5 of the second module 22 is referred to as the second unit 52, the power generation unit 5 of the third module 23 is referred to as the third unit 53, and the power generation unit 5 of the fourth module 24 is referred to as the fourth unit 54, and the description will be continued.

[0013] The pump 6 is for transferring the refrigerant within the refrigerant pipe 4. The pump 6 is configured to allow control of the discharge flow rate. Therefore, for convenience of description, the pump 6 of the first module 21 is referred to as the first pump 61, the pump 6 of the second module 22 is referred to as the second pump 62, the pump 6 of the third module 23 is referred to as the third pump 63, and the pump 6 of the fourth module 24 is referred to as the fourth pump 64, and the description will be continued.

[0014] The refrigerant pipe 4 is a pipe for circulating the refrigerant while sealing the refrigerant inside the cooling device S1. The refrigerant pipe 4 includes a module pipe 4M, a system pipe 4S, an EXP tank 7, an air vent line 8, and a water injection line 9. The module pipe 4M is a pipe for allowing the refrigerant to circulate inside the fuel cell module 2. The module pipe 4M connects the pump 6 and the power generation unit 5 in series while forming an annular pipeline. The module pipe 4M forms an annular pipeline, and circulates the refrigerant discharged by the pump 6 while supplying the refrigerant to and discharging the refrigerant from the power generation unit 5. Therefore, for the sake of explanation, we will refer to the module piping 4M of the first module 21 as the first piping 4M1, the module piping 4M of the second module 22 as the second piping 4M2, the module piping 4M of the third module 23 as the third piping 4M3, and the module piping 4M of the fourth module 24 as the fourth piping 4M4, and continue the explanation.

[0015] System piping 4S is the piping for circulating the refrigerant between the fuel cell module 2 and the radiator 1. System piping 4S connects four fuel cell modules 2 in parallel, while connecting the radiator 1 and the four fuel cell modules 2 in series, forming a ring-shaped conduit. System piping 4S circulates the refrigerant discharged by pump 6, supplying and discharging it to the fuel cell module 2 and the heat radiator 1.

[0016] The switching valve 3 is used to open and close the conduits leading to the system piping 4S and each module piping 4M. The switching valves 3 are valves located at the connection points between the system piping 4S and each module piping 4M, and four of them are provided for each fuel cell module 2. Therefore, for the sake of explanation, we will refer to the switching valve 3 that opens and closes the conduit connecting system piping 4S and first piping 4M1 as the first valve 31, the switching valve 3 that opens and closes the conduit connecting system piping 4S and second piping 4M2 as the second valve 32, the switching valve 3 that opens and closes the conduit connecting system piping 4S and third piping 4M3 as the third valve 33, and the switching valve 3 that opens and closes the conduit connecting system piping 4S and fourth piping 4M4 as the fourth valve 34, and continue the explanation.

[0017] When the switching valve 3 (first valve 31) is open, the conduit connecting the system piping 4S and the module piping 4M (first piping 4M1) opens. In this state, when pump 6 (first pump 61) is driven, the refrigerant circulates between the heat exchanger 1 and the power generation unit 5 (first unit 51). Furthermore, when the switching valve 3 (first valve 31) is closed, the conduit connecting the system piping 4S and the module piping 4M (first piping 4M1) is closed. In this state, when pump 6 (first pump 61) is activated, the refrigerant circulates within fuel cell module 2 (first module 21).

[0018] EXP tank 7 (Expansion tank) is a pressurized reserve tank, and the pressure inside the tank is set to the same pressure as inside refrigerant piping 4. The bubbles in the refrigerant are sent to the EXP tank 7, where they are separated into gas and liquid and then discharged to the outside. Air vent line 8 is a pipe used to discharge air bubbles from the refrigerant. The air bubbles move from the refrigerant piping 4 to the EXP tank 7 through the air vent line 8. The air vent line 8 includes a first air vent line 81 and a second air vent line 82 on the upstream and downstream sides of the power generation unit 5. The first air vent line 81 has one end connected to the EXP tank 7 and the other end connected to the module piping 4M between the pump 6 and the power generation unit 5. The second air vent line 82 has one end connected to the EXP tank 7 and the other end connected to the power generation unit 5. The water injection line 9 is a pipe used to inject refrigerant into the refrigerant piping 4. One end of the water injection line 9 is connected to the EXP tank 7, and the other end of the water injection line 9 is connected to the module piping 4M between the switching valve 3 and the pump 6.

[0019] Next, we will explain the procedure for bleeding air (see Figure 1). Note that the following procedure is for bleeding air, so none of the fuel cell module 2's power generation units 5 are generating power. First, refrigerant is injected into the empty refrigerant pipe 4 through the water injection line 9. Next, the first valve 31 is opened, and the second valve 32 to the fourth valve 34 are closed. Next, the first pump 61 is driven to circulate the refrigerant through the first piping 4M1 and the system piping 4S, thereby performing air bleeding (air bleeding circulation) of the first module 21.

[0020] The refrigerant flow rate at this time is the air bleed rate. The air bleeding speed is the flow velocity sufficient to detach and flush away air bubbles adhering to various parts of the refrigerant piping 4 and the power generation unit 5. Then, regarding the air bleeding of the first module 21, when the remaining time required for the expected air bleeding reaches the set time, the second pump 62 is driven at idle speed to circulate the refrigerant in the second module 22 (idle circulation). In other words, the second module 22 transitions continuously from idle circulation to air bleed circulation without interruption. Furthermore, the idling speed is set lower than the air bleeding speed.

[0021] Furthermore, regarding the refrigerant flow rate, the pumps 6 may be controlled to change the flow rate of the refrigerant circulating in the air bleed circulation and the flow rate of the refrigerant circulating at idle in small increments, thereby generating a pulsating flow. By creating a pulsating flow of the refrigerant, it is possible to promote the detachment of air bubbles attached to various parts from their attachment points. Then, after a predetermined time has elapsed since the start of operation of the first pump 61, it is determined that the air bleeding of the first module 21 is complete, and the first pump 61 is stopped and the first valve is closed.

[0022] Next, the second valve 32 is opened and the second pump 62 is driven at the air-bleeding speed to circulate the refrigerant through the second pipe 4M2 and the system piping, thereby bleeding the air from the second module 22 (see Figure 2). Furthermore, the second pump 62 may be controlled to generate pulsating flow, similar to the air venting mechanism for the first module 21. Then, regarding the air bleeding of the second module 22, when the remaining time required for the expected air bleeding reaches the set time, the idle circulation of the third module 23 is performed. Next, after a predetermined time has elapsed since the start of operation of the second pump 62, it is determined that the air bleeding of the second module 22 is complete, and the second pump 62 is stopped and the second valve is closed.

[0023] Next, the third valve 33 is opened and the third pump 63 is driven at the air-bleeding speed to circulate the refrigerant through the third pipe 4M3 and the system piping, thereby bleeding the air from the third module 23 (see Figure 3). Furthermore, the third pump 63 may be controlled to generate pulsating flow, similar to the air venting mechanism for the first module 21. Then, regarding the air bleeding of the third module 23, when the remaining time required for the expected air bleeding reaches the set time, the idle circulation of the fourth module 24 is performed. Next, after a predetermined time has elapsed since the start of operation of the third pump 63, it is determined that the air bleeding of the third module 23 is complete, and the third pump 63 is stopped and the third valve is closed.

[0024] Next, the fourth valve 34 is opened and the fourth pump 64 is driven at the air-bleeding speed to circulate the refrigerant through the fourth pipe 4M4 and the system piping, thereby bleeding the air from the fourth module 24 (see Figure 4). Furthermore, the second pump 62 may be controlled to generate pulsating flow, similar to the air venting mechanism for the first module 21. Then, after a predetermined time has elapsed since the start of operation of the fourth pump 64, it is determined that the air bleeding of the fourth module 24 is complete, and the fourth pump 64 is stopped and the fourth valve is closed. This completes the air bleeding process for all modules.

[0025] Next, the effects and advantages of this embodiment will be described. In this embodiment, the cooling device S1 of the fuel cell system selects the fuel cell module 2 that performs air venting circulation by opening and closing the switching valve 3. This prevents air bubbles in the selected fuel cell module 2 from flowing into and transferring to other fuel cell modules 2, thereby reducing the time required for air bleeding.

[0026] In this embodiment, the fuel cell module 2 through which the refrigerant flows is switched by opening and closing the switching valve 3, but the method is not limited to this. For example, in this embodiment, a pump 6 is provided for each fuel cell module 2. Furthermore, when each pump 6 is not operating, it creates resistance in the piping, hindering the circulation of the refrigerant. Therefore, without opening or closing the switching valve 3, the fuel cell module 2 to which the refrigerant circulates can be selected and switched by operating or stopping the pump 6.

[0027] Furthermore, in this embodiment, the discharge rate of the pump 6 is controlled to generate pulsating flow when performing air venting circulation and idle circulation. This promotes the detachment of air bubbles attached to various parts, thereby further reducing the time required for air removal.

[0028] Furthermore, in this embodiment, idle circulation is performed by a fuel cell module 2 separate from the fuel cell module 2 that performs air venting circulation. By using this method, conditions are created that make it easier for air bubbles attached to the module piping (4M) to detach, thereby increasing the efficiency of bubble removal. This reduces the time required for air bleeding and circulation.

[0029] Furthermore, in this embodiment, the fuel cell module 2 that performs idle circulation is limited to the fuel cell module 2 that then performs air venting circulation. This reduces the number of modules that perform idle cycles, thereby suppressing unnecessary energy consumption.

[0030] Furthermore, in this embodiment, the idling speed during idle circulation is set to a lower speed than the air bleeding speed. This further reduces energy consumption during idle cycles.

[0031] Furthermore, in this embodiment, for the fuel cell module 2 performing air purging circulation, idle circulation is started when the remaining time required for the expected air purging reaches the set time. By using this method, the refrigerant can be circulated only for the time required for idle circulation, and the transition from idle circulation to air bleed circulation can be made without interruption. This improves efficiency in terms of both energy consumption and the time required for air bleeding.

[0032] In this embodiment, the method involves controlling the discharge rate of the pump 6 and changing the flow velocity of the refrigerant to create pulsating flow, but the method is not limited to this approach. For example, it is possible to use a method that controls the opening degree of the switching valve 3 to change the flow rate of the refrigerant flowing through the module piping 4M, thereby causing pulsation. Even when using such a method, the same effects and advantages as in this embodiment can be obtained.

[0033] Next, we will describe another air bleeding method using a cooling device S1 of a fuel cell system having the same configuration as the first embodiment described above (see Figures 5 and 6). The difference between the previously mentioned method and this method lies in the fuel cell module 2 that performs idle circulation. In this method, idle circulation is performed in all fuel cell modules 2 except for the fuel cell module 2 that is performing air venting circulation. In other words, the first module 21 performs air bleeding circulation while the second to fourth modules 24 perform idle circulation. Then, the refrigerant flow rate during idle circulation is set to the air bleed speed. Therefore, air bubbles in modules 2 through 4 escape even during idle circulation. Therefore, the air purging circulation in the second to fourth modules 24 mainly involves purging air from the system piping 4S after it branches off to each fuel cell module 2 and from the system piping 4S where the systems from each fuel cell module 2 converge. This makes it possible to shorten the time required for bleeding air from the second to fourth modules 24 after the air bleeding from the first module 21 has been completed.

[0034] Next, the cooling device S2 of the fuel cell system in the second embodiment will be described (see Figure 7). The configuration of the module piping 4M of each fuel cell module 2 and the configuration of each switching valve 3 differ between this embodiment and the first embodiment described above. In this embodiment, module piping 4M branches off downstream of the power generation unit 5 and is always connected to system piping 4S without going through the switching valve 3. Then, in the fuel cell module 2 (the first module 21 in Figure 7) which performs air venting and circulation, the switching valve 3 (the first valve 31) is switched so that the system piping 4S and the module piping 4M are in communication.

[0035] Furthermore, in the fuel cell module 2 (second module 22) which performs idle circulation, the switching valve 3 is switched so that the refrigerant circulates within the module. Then, the first to fourth steps are performed while sequentially switching between air venting circulation and idle circulation, similar to the first embodiment. In addition, in the fuel cell module 2 that performs idle circulation, the pump 6 is controlled to operate at the minimum discharge rate so that the following relationship holds true. (Refrigerant flow rate during air venting circulation) >> (Refrigerant flow rate during idle circulation) Even with this configuration, the same effects and advantages as in the first embodiment can be obtained.

[0036] Next, the cooling device S3 of the fuel cell system in the third embodiment will be described (see Figure 8). The location where the pump 6 is installed differs between this embodiment and the first embodiment described above. In this embodiment, the pump 6 is not located in each fuel cell module 2, but rather in only one unit in the system piping 4S. Furthermore, the switching valve 3 only opens and closes without switching the pipeline. Even with this configuration, the same effects and advantages as in the first embodiment can be obtained. [Explanation of symbols]

[0037] S1, S2, S3 Fuel cell system cooling devices 1 Heatsink 3. Switching valve 4 Refrigerant piping 4M Module Piping 4S System Piping 5. Power generation unit 6 pumps 8. Air bleed line

Claims

1. Module piping that forms a ring-shaped conduit for supplying and discharging refrigerant to the power generation unit, A system piping system that forms an annular conduit for supplying and discharging refrigerant to and from a heat sink and the module piping, while being connected in parallel to multiple module piping systems, Refrigerant piping having, Each module piping is provided with an air vent line that discharges air bubbles from the refrigerant piping to the outside, A pump for circulating refrigerant within the refrigerant piping, Equipped with, The refrigerant is circulated through the heat sink and one of the non-power-generating power generation units selected from a group, in an air-bleeding circulation process. A cooling device for a fuel cell system characterized by the following features.

2. The aforementioned refrigerant piping is Each of the aforementioned module pipes is equipped with a switching valve for opening and closing the pipeline, The switching valve is, The system is controlled to open the selectable valve leading to the non-power-generating power unit while closing the remaining valves. A cooling device for a fuel cell system characterized by the following features.

3. In the cooling device for the fuel cell system according to claim 2, The aforementioned pump, Arranged for each module piping, The pump, located in the module piping with the aforementioned switching valve closed, is activated to perform idle circulation, circulating the refrigerant within the module piping. A cooling device for a fuel cell system characterized by the following features.

4. In the cooling device for the fuel cell system according to claim 3, The aforementioned idle cycle is, In the module piping with the switching valve closed, the pump located in one of the selected module pipes operates. A cooling device for a fuel cell system characterized by the following features.

5. In the cooling device for the fuel cell system according to claim 1, The aforementioned pump, It is possible to accelerate and decelerate from an air bleed speed that is sufficient to flush out air bubbles adhering to the inside of the refrigerant piping and the inside of the power generation unit. A cooling device for a fuel cell system characterized by the following features.

6. In the cooling device for the fuel cell system according to claim 3, The refrigerant flow rate during idle circulation is, The air bleed speed is set to a flow rate sufficient to flush out air bubbles adhering to the inside of the refrigerant piping and the power generation unit, or to an idling speed lower than the air bleed speed. A cooling device for a fuel cell system characterized by the following features.

7. In the cooling device for the fuel cell system according to claim 3, The time required for idle cycles is It is set to be shorter than the time required for air bleeding and circulation. The transition from idle circulation to air bleed circulation is, It continues without interruption A cooling device for a fuel cell system characterized by the following features.

Images