Cooling circuit of a fuel cell with optimized electrical insulation

Abstract

The present invention relates to a cooling circuit (1) for a fuel cell (2), comprising components electrically connected to the chassis ground, such as a pump (11) or a radiator (10), and pipes (12, 13, 14) connecting said fuel cell (2) to said components (10, 11), at least one of said pipes (12, 13, 14) comprising at least one pipe portion having a useful cross-sectional area PHI1. According to the invention, at least one of said pipe portions with a useful cross-sectional area PHI1 has a cross-sectional reducer (3), said cross-sectional reducer (3) having a useful cross-sectional area PHI2 smaller than said useful cross-sectional area PHI1. Fig. 2

Description

Title of the invention: Cooling circuit for a fuel cell with optimized electrical insulation 1. Scope of the invention

[0001] The field of the invention is that of fuel cells and in particular that of the cooling of such cells.

[0002] More specifically, the invention relates to the electrical insulation of fuel cell cooling circuits. 2. Prior art

[0003] Fuel cells, especially those operating on hydrogen, are becoming more widespread in various fields such as motor vehicles (cars, trucks, coaches, buses, etc.) or in the nautical sector.

[0004] To operate optimally, the fuel cells are connected to cooling circuits designed so that the operating temperature of the cells is maintained within an ideal range.

[0005] Typically, the cooling circuits used to ensure the cooling of fuel cells include: - a cooling radiator; - pipes connected on one side to the battery and on the other side to the radiator; - a coolant suitable for circulating in the battery, pipes and radiator; - a pump capable of moving the coolant in the cooling circuit.

[0006] Some of the components of these cooling circuits are electrically connected to the chassis ground of the device in which the battery is installed (vehicle, boat, etc.). This is particularly the case for radiators and pumps.

[0007] Since the coolant is conductive, leaks of electrical currents are observed through the coolant, from the battery to ground.

[0008] The majority of current leakage is ensured by the cooling circuit; the insulation value is therefore very closely related to the cooling circuit.

[0009] These electrical current leaks are obviously not desirable, so efforts are made to reduce them by insulating the fuel cell cooling circuits.

[0010] The insulation of fuel cell cooling circuits is achieved at two levels: - electrical insulation, and - physical isolation.

[0011] With regard to electrical insulation, it is required that the cooling circuits of fuel cells have an electrical resistance greater than a predetermined threshold set according to the application area. The value of this threshold, expressed in ohms / volt, is set according to the application area and the maximum voltage level associated with the fuel cell and the nature of the DC / AC voltage. In the automotive sector, this threshold may be set at 100 ohms / volt. Thus, for example, the cooling circuits of 400-volt and 800-volt fuel cells must have an electrical resistance greater than 400 and 800 kΩ, respectively (for a road vehicle).

[0012] With regard to physical isolation, a minimum distance is imposed between the battery and the components of the cooling circuit that are electrically connected to ground.

[0013] In order to increase electrical insulation, additive(s) are added to the coolant to reduce its electrical conductivity or conductance.

[0014] In order to increase physical resistance, the battery is interconnected with the pump and the radiator by means of long pipes which move the pump and the radiator away from the battery.

[0015] All of this contributes to reducing electrical current leakage through the cooling circuit. However, this leakage could be further reduced. Furthermore, the use of long pipes to increase physical insulation results in significant bulk, which complicates the integration of the fuel cells and their cooling circuit within the devices they equip.

[0016] Thus, the cooling of fuel cells, and in particular the insulation of their cooling circuit, can still be optimized. 3. Objectives of the invention

[0017] The invention aims in particular to provide an effective solution to at least some of these different problems.

[0018] In particular, according to at least one embodiment, an objective of the invention is to provide a cooling circuit for a fuel cell which has a good level of insulation.

[0019] In particular, the invention aims, according to at least one embodiment, to provide such a cooling circuit which has significant electrical insulation.

[0020] Another objective of the invention is, according to at least one embodiment, to provide such a cooling circuit which makes it easier to integrate a fuel cell and its cooling circuit into a device incorporating them.

[0021] In particular, an objective of the invention is, in at least one embodiment, to provide such a cooling circuit which is compact.

[0022] Another objective of the invention is, in at least one embodiment, to provide such a cooling circuit which has a good level of overall insulation while reducing its physical insulation, that is to say while reducing the distance between the battery and the components of the cooling circuit which are electrically connected to ground.

[0023] Another objective of the invention is, in at least one embodiment, to provide such a cooling circuit which makes it possible to increase the limiting temperature of the liquid while maintaining the same level of electrical insulation.

[0024] Another objective of the invention is, in at least one embodiment, to provide such a cooling circuit which makes it possible to reduce the frequency of draining operations of the cooling circuit.

[0025] Another objective of the invention is, in at least one embodiment, to provide such a cooling circuit which makes it possible to reduce the cost of cooling.

[0026] In particular, an objective of the invention is, in at least one embodiment, to provide such a cooling circuit which allows the use of a lower quality coolant while guaranteeing an equivalent level of cooling and without increasing the frequency of oil changes.

[0027] Another objective is, according to at least one embodiment, to provide such a technique which makes it possible to implement a lower quality cooling infrastructure, in particular lower quality pipes, without affecting the service life of the cooling system. 4. Presentation of the invention

[0028] For this purpose, the invention proposes a cooling circuit for a fuel cell, comprising components electrically connected to the ground of a chassis, such as a pump or a radiator, and pipes connecting said fuel cell to said components, at least one of said pipes comprising at least a portion of pipe having a useful cross-section PHI1.

[0029] According to the invention, at least one of said portions of pipe with useful cross-section PHI1 has a section reducer, said section reducer having a useful cross-section PHI2 less than said useful cross-section PHI1.

[0030] Thus, according to this aspect, the invention consists of implementing at least one pipe section reducer within a fuel cell cooling circuit.

[0031] Reducing the cross-section allows the conductance of the portion of the circuit with reduced cross-section to be reduced.

[0032] The reduction of conductance is an increase in the electrical resistance of the cooling circuit.

[0033] This increase in the resistance of the cooling circuit allows: - in the case of a cooling circuit that was not sufficiently efficient in terms of insulation and therefore did not comply with the standard, to bring the cooling circuit up to standard; - in the case of a cooling circuit which was sufficiently efficient in terms of insulation and thus complied with the standard, to increase the maximum operating temperature of the coolant; - in the case of a cooling circuit which was sufficiently efficient in terms of insulation and complied with the standard up to a certain mileage, to continue to use more of the coolant and thus allow the use of lower quality pipes and infrastructure and to reduce the frequency of coolant changes without harming the quality of cooling or to maintain the frequency of changes but using a lower quality coolant: reducing the frequency of changes or using a lower quality coolant or implementing lower quality pipes and infrastructure makes it possible to reduce the cost of cooling; - in the case of a cooling circuit which was sufficiently efficient in terms of insulation and complied with the standard but which used long pipes, to shorten the length of the pipes, and consequently to reduce the size of the cooling circuit and to facilitate its installation within a vehicle.

[0034] A person skilled in the art would have assumed that adding a section reducer would induce an unacceptable pressure drop in the cooling circuit. However, the inventors observed, contrary to this assumption, that the section reduction resulted in a perfectly acceptable pressure drop and increased the insulation of the cooling circuit, along with all the resulting advantages that led to optimization of the cooling circuit.

[0035] The invention therefore provides very interesting advantages without generating any constraints.

[0036] According to one possible feature, said section reducer has an inner perimeter smaller than the inner perimeter of said portion of pipeline to which it is connected.

[0037] According to one possible feature, said section reducer houses at least one mesh, said mesh being configured to ensure at least part of the section reduction.

[0038] According to one possible feature, said section reducer houses baffles, said baffles being configured to ensure at least part of the section reduction.

[0039] According to one possible feature, said battery and said components electrically connected to the vehicle ground include input and output interfaces for connection to said piping, at least one section reducer being connected to at least one of said input or output interfaces.

[0040] This allows for maximizing the reduction in pipe length.

[0041] According to one possible feature, a cooling circuit according to the invention includes a section reducer at each of the inlet and outlet interfaces of said stack.

[0042] According to one possible characteristic, said section reducer comprises: - a central portion with a cross-section PHI2 smaller than said useful section PHI1; - two connecting portions of maximum cross-section PHI1 and minimum cross-section PHI2, respectively convergent and divergent, connecting said central portion to said portion of piping or to one of said inlet or outlet interfaces.

[0043] The implementation of a convergent-divergent makes it possible to reduce the impact in pressure loss of the abrupt reduction in section induced by the section reducer.

[0044] According to one possible characteristic: - one of said connecting portions constitutes a coolant inlet connecting portion into said central portion, and - the other of said connecting portions constitutes a connecting portion for the outlet of coolant from said central portion,

[0045] each of said connecting portions comprising: - a first opening for connection to said pipeline or to one of said inlet or outlet interfaces, and - a second connection opening to said central portion,

[0046] the distance between said first and second openings of said input connection portion being less than the distance between said first and second openings of said output connection portion.

[0047] This makes it possible to further minimize the pressure loss induced by the reduction in cross-section

[0048] According to one possible characteristic, said useful cross-section PHI1 is between 12 and 80.

[0049] According to a possible characteristic, which said cross-section PHI2 is between 6 and 40.

[0050] According to one possible characteristic, the length of said central portion is between 6 and 80.

[0051] According to one possible characteristic, said pipe portions and / or central portion and / or connecting portion have a circular cross-section.

[0052] According to one possible characteristic, said connecting portion are of frustoconical shape.

[0053] The invention further relates to a vehicle powered by a fuel cell system equipped with such a cooling circuit.

[0054] This vehicle is in particular, but not exclusively, a transport vehicle, such as a motor vehicle.

[0055] Such a vehicle may be an electric or hybrid vehicle.

[0056] The invention also covers the use of a cooling device for at least one of the applications belonging to the group comprising: motor vehicles; commercial vehicles; buses or trucks; trains; the boats; aircraft. 5. Description of the figures

[0057] Other features and advantages of the invention will become apparent from the following description of particular embodiments, given by way of simple illustrative and non-limiting example, and the accompanying drawings, among which:

[0058] [Fig.1] [Fig.1] illustrates a diagram of a cooling circuit according to the invention;

[0059] [Fig.2] [Fig.2] illustrates the installation within a pipeline of a section reducer whose outer perimeter is less than the outer perimeter of the pipeline;

[0060] [Fig.3] [Fig.3] illustrates the installation within a pipeline of a section reducer whose outer perimeter is equivalent to the outer perimeter of the pipeline;

[0061] [Fig.4] [Fig.4] illustrates the installation, at the end of a pipeline, of a section reducer whose outer perimeter is less than the outer perimeter of the pipeline;

[0062] [Fig. 5] [Fig. 5] illustrates the installation, at the end of a pipeline, of a section reducer whose outer perimeter is equivalent to the outer perimeter of the pipe;

[0063] [Fig.6] [Fig.6] illustrates a section reducer implementing a diverging- converging;

[0064] [Fig.7] [Fig.7] illustrates a curve showing the variation in the length of the part of small section of the section reducer as a function of its inner diameter for an example of an embodiment of a device according to the invention.

[0065] 6. Description of particular embodiments

[0066] The invention relates to a cooling circuit 1 of a fuel cell 2.

[0067] In the example described here, the fuel cell is mounted on a motor vehicle. It is a hydrogen fuel cell.

[0068] Such a cooling circuit 1 comprises at least one radiator 10. This is an air-liquid heat exchanger suitable for cooling a coolant circulating inside it. Alternatively, it could be a liquid-liquid heat exchanger.

[0069] The radiator 10 includes an inlet interface 100 and an outlet interface 101 for connection to piping. This radiator 10 is fixed to the chassis (not shown) of the vehicle and is therefore electrically connected to the vehicle's ground.

[0070] This cooling circuit 1 also includes a pump 11.

[0071] This pump 11 includes an inlet interface 110 and an outlet interface 111 for connection to pipelines. This pump 11 is also fixed to the vehicle chassis and is therefore electrically connected to the vehicle ground.

[0072] The fuel cell 2 is not described in further detail here. It conventionally comprises a network of internal channels allowing the circulation of a coolant to regulate the cell's temperature. The cell also includes an inlet interface 21 and an outlet interface 22, which are connected to the channel network and allow connection to piping.

[0073] The cooling circuit 1 includes pipes for interconnecting the inlet / outlet interfaces of the fuel cell, radiator and pump.

[0074] More specifically, : - a pipe 12 connects the outlet interface 111 of the pump 11 to the inlet interface 21 of the fuel cell 2, - a pipe 13 connects the output interface 22 of the fuel cell 2 to the input interface 100 of the radiator 2, - a pipe 14 connects the outlet interface 101 of the radiator 10 to the inlet interface 110 of the pump 2.

[0075] In one embodiment, the pump 11 could be arranged differently in the cooling circuit 1, in particular upstream of the radiator 10 rather than downstream. The direction of coolant flow could be reversed.

[0076] The pump 2 allows the coolant to be circulated, in one direction or the other, in the pipes 12, 13, 14, the radiator 10 and the fuel cell 2.

[0077] According to the principle of the invention, the cooling circuit 1 includes at least one reducer of section 3 located on at least a portion of one of the pipes 12, 13, 14.

[0078] The portion of the pipe 12, 13, 14 on which the reducer of section 3 is installed has a useful cross-section (i.e. along a plane orthogonal to its longitudinal axis) of a value PHI1.

[0079] The reducer of section 3 has a useful cross section (i.e. along a plane orthogonal to its longitudinal axis) PHI2 less than PHI1.

[0080] As shown in [Fig.2], the outer peripheral contour of the section reducer 3 may have a perimeter smaller than that of the portion of pipe 12, 13, 14 on which it is installed.

[0081] In the example illustrated in [Fig. 3], the outer peripheral contour of the section reducer 3 has a perimeter identical to that of the pipe section 12, 13, 14 on which it is installed. However, the effective cross-sectional area PH12 of the section reducer remains smaller than the effective cross-sectional area PH11 of the pipe section 12, 13, 14.

[0082] In both cases mentioned above, the reduction in section can result from a reduction in the internal perimeter of the section reducer 3 relative to the internal perimeter of the portion of pipe 12, 13, 14 to which it is connected.

[0083] Alternatively, the reduction in cross-section may not result from a reduction in the internal perimeter of the cross-section reducer relative to the internal perimeter of the pipe portion 12, 13, 14. In this case, the cross-section reducer 3 houses a useful cross-section reduction device which induces that the useful cross-section of the cross-section reducer 3 is less than the useful cross-section of the pipe portion on which it is installed even though the internal perimeter of the cross-section reducer is identical to that of the pipe portion.

[0084] In this case, the cross-section reduction device may comprise a mesh, this mesh being configured to ensure the cross-section reduction. Alternatively, it may comprise baffles, these baffles being configured to ensure the cross-section reduction. These two variants can be combined.

[0085] The embodiments of figures 2 and 3 are combinable, the reduction in section being able to result from the combination of a reduction in internal perimeter and the implementation of a section reduction device.

[0086] A section reducer 3 according to the invention can be implanted anywhere along a pipeline 12, 13, 14, i.e. at one of its ends (see [Fig.4] or 5) or between its two ends (see figures 1, 2 and 3).

[0087] Preferably, a section reducer 3 is connected on one side to one end of a pipe 12, 13, 14 and on the other side to an inlet or outlet interface of the stack 2, the radiator 10 or the pump 11.

[0088] Connecting a section reducer directly to an inlet or outlet interface of the stack, pump or radiator maximizes the reduction in pipe length.

[0089] The inventors have found that placing a section reducer at the stack's input interface and a section reducer at the stack's output interface gives excellent results.

[0090] However, various arrangements of one or more section 3 reducers can be envisaged.

[0091] For example, at least one section reducer 3 can be installed along at least one pipe. Thus, the cooling system can include a single section reducer installed on a single pipe, or several section reducers installed each on a different pipe, or several section reducers installed on the same pipe, or several section reducers installed on several pipes.

[0092] At least one section reducer can be placed between two ends of the corresponding pipe.

[0093] Alternatively, at least one section reducer may be connected to at least one inlet and / or outlet interface of the stack and / or radiator and / or pump. Thus, the cooling system may, for example, include: - a single section reducer which will be connected on one hand directly to one of the input or output interfaces of the stack or radiator or pump, and on the other hand connected to the corresponding pipe; - several section reducers each connected on one side to an input or output interface of the stack or radiator or pump and on the other side to the corresponding pipe.

[0094] The number of section reducers connected to the battery, radiator, and pump may be the same or different. Thus, between zero and two section reducers may be connected to the battery, radiator, and pump as long as the system includes at least one section reducer. The number of reducers is therefore preferably between one and six.

[0095] The greater the number of section reducers, the more optimized the cooling system will be.

[0096] In the embodiment of [Fig. 6], the section reducer 3 comprises: - a central portion 30 with a cross-section PHI2 smaller than the useful section PHI1; - two connecting portions 31, 32 of maximum cross-section PHI1 and minimum cross-section PHI2, respectively converging towards the central portion and diverging from the central portion, connecting the central portion 30 to a pipe 12, 13, 14 or to an inlet or outlet interface of the stack, radiator or pump;

[0097] The implementation of a convergent-divergent makes it possible to reduce the impact in pressure loss of the abrupt reduction in cross-section induced by the cross-section reducer.

[0098] Preferably, : - one of the connecting portions 31 constitutes a connecting portion for the inlet of coolant into the central portion 30, and - the other of the connecting portions 32 constitutes a connecting portion for the outlet of coolant from the central portion 30.

[0099] In this case, each of the connecting portions 31, 32 comprises: - a first opening 310, 320 for connection to a pipeline or an inlet or outlet interface, and - a second opening 311, 321 for connection to the central portion.

[0100] In this case also, the distance between the first 310 and second 311 openings of the input connection portion 31 is less than the distance between the first 320 and second 321 openings of the output connection portion 32.

[0101] In other words, the length of the divergent along the longitudinal axis of the section reducer is greater on the side through which the coolant escapes from the section reducer than the length of the convergent through which the coolant enters the section reducer.

[0102] This allows the pressure loss induced by the reduction in cross-section to be minimized even further.

[0103] A pipe may have a non-constant effective cross-section PH11 along its entire length. In this case, the effective cross-section PHL2 of the section reducer is less than the effective cross-section of the portion of pipe to which it is connected.

[0104] The cross-section of the pipes may be circular. In this case, the cross-section of the cross-section reducer will also be circular, and in the case of the implementation of converging-diverging, the central portion will have a circular cross-section and the connecting portions will be frustoconical.

[0105] The useful cross-section PHI1 is preferably between 12 and 80 millimeters (varying according to the power of the fuel cell).

[0106] The cross-section PHI2 is preferably between 6 and 40 (evolving with the need for insulation).

[0107] The length of the central portion is preferably between 6 and 80 (evolving with the need for insulation).

[0108] Fig. 7 shows, by way of illustration and not limitation, the variation of the length of the useful cross-sectional portion PHI2 of the section reducer, as a function of its internal diameter, for a section reducer providing 100 kOhm insulation with a coolant at 8 uS / cm (standard insulation R100 for an 800V vehicle with an "aged" coolant).

Claims

Demands

1. Cooling circuit (1) of a fuel cell (2), comprising components electrically connected to the ground of a chassis, such as a pump (11) or a radiator (10), and pipes (12, 13, 14) connecting said fuel cell (2) to said components (10, 11), at least one of said pipes (12, 13, 14) comprising at least one pipe portion having a useful cross-section PHI1, characterized in that at least one of said pipe portions with a useful cross-section PHI1 has a section reducer (3), said section reducer (3) having a useful cross-section PHI2 less than said useful cross-section PHI1.

2. Cooling circuit according to claim 1 in which said section reducer (3) has an inner perimeter smaller than the inner perimeter of said portion of piping to which it is connected.

3. Cooling circuit according to claim 1 or 2 in which said section reducer (3) houses at least one mesh, said mesh being configured to ensure at least part of the section reduction.

4. Cooling circuit according to any one of claims 1 to 3 in which said section reducer (3) houses baffles, said baffles being configured to ensure at least part of the section reduction.

5. Cooling circuit according to any one of claims 1 to 4 in which said stack (2) and said components (10, 11) electrically connected to said chassis ground comprise inlet and outlet interfaces (100, 101, 110, 111) for connection to said piping (12, 13, 14), at least one section reducer (3) being connected to at least one of said inlet or outlet interfaces (100, 101, 110, 111).

6. Cooling circuit according to claim 5 comprising a section reducer (3) at each of the inlet and outlet interfaces (20, 21) of said stack (2).

7. Cooling circuit according to any one of claims 1 to 6, wherein said section reducer (3) comprises: - a central portion (30) with a cross-section PHI2 smaller than said useful section PHI1; - two connecting portions (31, 32) with a maximum cross-section PHI1 and a minimum cross-section PHI2, respectively convergent and divergent, connecting said central portion (30) to said portion of piping or to one of said inlet or outlet interfaces.

8. Cooling circuit according to claim 7 wherein: - one of said connecting portions constitutes an inlet connecting portion (31) of coolant into said central portion (30), and - the other of said connecting portions constitutes an outlet connecting portion (32) of coolant from said central portion (30), each of said connecting portions 31, 32) comprising: - a first connection opening (310, 320) to said pipe (12, 13, 14) or to one of said inlet or outlet interfaces 100, 101, 110, 111, 20, 21), and - a second connection opening (311, 321) to said central portion (30), the distance between said first and second openings of said inlet connecting portion being less than the distance between said first and second openings of said outlet connecting portion.

9. Cooling circuit according to any one of claims 1 to 8 in which said useful cross-section PHI1 is between 12 and 80 mm.

10. Cooling circuit according to any one of claims 1 to 9 in which said cross section PHI2 is between 6 and 40 mm.

11. Cooling circuit according to claim 7 alone or in combination with any of claims 8 to 10 wherein the length of said central portion (30) is between 6 and 80 mm.

12. Cooling circuit according to any one of claims 1 to 11 in which said piping portions (12, 13, 14) have a circular cross-section.

13. Cooling circuit according to claim 7 alone or in combination with any of claims 8 to 12 in which said central portion (30) and / or said connecting portions have a circular cross-section.

14. Cooling circuit according to claims 8 and 13 in which said connecting portions are frustoconical in shape.

15. Vehicle, powered by a fuel cell, equipped with a cooling circuit according to any one of claims 1 to 14.

16. Vehicle according to claim 15 belonging to the group comprising: - motor vehicles; - commercial vehicles; - buses or trucks; - trains; - boats; - aircraft.

Images