Fuel cell system and motor vehicle

Abstract

The invention relates to a fuel cell system (2) for a motor vehicle (1), comprising a fuel cell stack (4) having an air inlet (5) and an exhaust air outlet (6), and an exhaust air system (7) for removing exhaust air (8) from the fuel cell stack (4), which is fluidically connected to the exhaust air outlet (6) of the fuel cell stack (4) and leads to an environment (9), wherein the exhaust air system (7) has an exhaust air heater (10) for heating the exhaust air (8). The energy efficiency of the fuel cell system (2) can be improved by integrating the exhaust air heater (10) into a cooling circuit (11) carrying a coolant and transferring heat from the coolant to the exhaust air (8).

Description

[0001] The present invention relates to a fuel cell system for a motor vehicle according to the preamble of claim 1. The invention further relates to a motor vehicle equipped with such a fuel cell system.

[0002] A generic fuel cell system is known, for example, from DE 10 2004 051 751 B4 and comprises a fuel cell stack having an air supply inlet and an exhaust air outlet, as well as an exhaust air system for removing exhaust air from the fuel cell stack, which is fluidically connected to the exhaust air outlet and leads to an environment. The exhaust air system is equipped with an exhaust air heater for heating the exhaust air, which in the known fuel cell system is configured as an electric heater.

[0003] During the operation of a fuel cell system, water is produced, which is carried in the exhaust air as water vapor and liquid. Particularly at low ambient temperatures, the water vapor in the exhaust air can condense upon release into the environment, forming fog. In a vehicle application with a fuel cell system, this fog can impair visibility for other road users. An exhaust air heater can be used to heat the exhaust air, reducing its relative humidity and thus minimizing fog formation in the surrounding area.

[0004] Further fuel cell systems are known from DE 199 53 404 B4, from EP 3 047 533 B1, from JP 6 926 975 B2, from JP 2021 136217 A and from JP 6 996 237 B2.

[0005] The present invention addresses the problem of providing an improved or at least a different embodiment for a fuel cell system of the type mentioned above or for a motor vehicle equipped therewith, which is characterized in particular by an improved energy efficiency.

[0006] This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0007] The invention is based on the general concept of designing the exhaust air heater as a heat exchanger and integrating it into a cooling circuit in which a coolant circulates. This allows the use of an existing cooling circuit within the fuel cell system or the vehicle, utilizing the heat already present and being dissipated to heat the exhaust air. Since the heat transported in the cooling circuit must be dissipated into the environment anyway for the coolant to perform its cooling function, using the heat from the cooling circuit to heat the exhaust air requires no additional energy, thus improving the energy efficiency of the fuel cell system or the vehicle equipped with it.

[0008] Specifically, the invention proposes that the exhaust air heater is integrated into a cooling circuit containing a coolant and transfers heat from the coolant to the exhaust air. The exhaust air heater is thus configured as a heat exchanger.

[0009] In the present context, a “configuration” corresponds to a “design” and / or a “setup”, so that the phrase “configured so that” is synonymous with the phrase “designed so that” and / or “set up so that”.

[0010] According to an advantageous embodiment, the exhaust air heater can have two concentric tubes, forming an inner tube and an outer tube enclosing the inner tube. In particular, the outer tube can coaxially enclose the inner tube. One of the two tubes is fluidically connected to the exhaust air system and carries the exhaust air through the exhaust air heater. The other of the two tubes is fluidically connected to the cooling circuit and carries the coolant through the exhaust air heater. In this way, the exhaust air heater has an extremely simple design that enables sufficient heat transfer between the coolant and the exhaust air without affecting the flow resistance of the exhaust air system. Accordingly, the exhaust air heater can be integrated into the fuel cell system particularly easily. Advantageously, at least the inner tube is configured as a metal tube. The outer tube can be configured as either a metal or a plastic tube.

[0011] A preferred embodiment involves the inner pipe being fluidically connected to the exhaust system, so that it carries the exhaust air through the exhaust air heater, while the outer pipe is fluidically connected to the cooling circuit, so that it carries the coolant through the exhaust air heater. Due to the arrangement of the inner and outer pipes within each other, in this configuration the coolant flowing through the outer pipe comes into direct contact with the inner pipe. In other words, the coolant flows through the outer pipe and around the inner pipe. This results in improved heat transfer.

[0012] In an alternative embodiment, the outer pipe can be fluidically connected to the exhaust system, so that it carries the exhaust air through the exhaust air heater, while the inner pipe is fluidically connected to the cooling circuit, so that it carries the coolant through the exhaust air heater. In this configuration, the inner pipe is in contact with the coolant on the inside and with the exhaust air flowing in the outer pipe on the outside.

[0013] In another embodiment, the exhaust air heater can again have an inner tube and an outer tube, in which case the outer tube is arranged or wound helically around the inner tube. In particular, the outer tube can be in indirect contact with the inner tube via a heat-conducting material or directly. In this case, the inner and outer tubes can advantageously be made of metal. The exhaust air flows through one of the inner and outer tubes, while the coolant flows through the other. In a first alternative, the exhaust air flows through the inner tube, while the coolant flows through the outer tube, thus simplifying the integration of the exhaust air heater into the exhaust system. In a second alternative, the exhaust air flows through the outer tube, while the coolant flows through the inner tube, thus improving the thermal efficiency of the exhaust air heater.

[0014] According to an advantageous embodiment, the cooling circuit can be a high-temperature cooling circuit configured to cool at least one component of the fuel cell system or the motor vehicle equipped with the fuel cell system. As a high-temperature cooling circuit, the coolant temperature at the inlet to the component to be cooled is at least 60°C. For example, the high-temperature cooling circuit can be configured to cool the fuel cell stack. In other words, the cooling circuit is coupled to the fuel cell stack via heat transfer and can dissipate waste heat generated there. The coolant absorbs heat from the fuel cell stack and dissipates it to the environment via an ambient cooler.

[0015] In another embodiment, the exhaust air system can include an exhaust air cooler for cooling the exhaust air, which is arranged upstream of the exhaust air heater in the exhaust air system. The exhaust air cooler can then be integrated into a further cooling circuit carrying a refrigerant and transfer heat from the exhaust air to the refrigerant. With the help of the exhaust air cooler, the moist exhaust air can be supercooled, i.e., cooled below the dew point of water vapor, so that the entrained moisture can condense and be separated from the exhaust air. This significantly reduces the absolute humidity of the exhaust air, which increases the efficiency of the exhaust air heater located downstream of the exhaust air cooler.

[0016] According to a preferred embodiment, the additional cooling circuit can be a low-temperature cooling circuit configured to cool at least one component of the fuel cell system or the motor vehicle equipped with the fuel cell system. As a low-temperature cooling circuit, the coolant temperature at the inlet to the component to be cooled is less than 60°C. For example, the low-temperature cooling circuit can be configured to cool electrical and / or electronic components, in particular power electronics, of the fuel cell system and / or the motor vehicle. The power electronics can, for example, include at least one inverter and / or at least one converter. In particular, the low-temperature cooling circuit can be configured to cool an electric traction motor of the motor vehicle and / or to cool a braking system of the motor vehicle and / or to cool a main fan.

[0017] According to an advantageous embodiment, the exhaust air system upstream of the exhaust air cooler can include an expansion device for expanding the exhaust air. The expansion device can, in particular, operate mechanically and include an impeller that can be driven by the flow of the exhaust air, wherein the impeller is non-rotatably connected to a drive shaft, so that the rotating impeller drives the drive shaft. The expansion of the exhaust air extracts kinetic energy from it, which drives the impeller.

[0018] According to another embodiment, the exhaust air system can have a condensate drain upstream of the exhaust air heater and downstream of the exhaust air cooler for removing condensate that accumulates in the exhaust air cooler. In this way, the condensate is removed before the exhaust air is reheated in the exhaust air heater, thus preventing the condensate from re-evaporating.

[0019] According to another embodiment, the fuel cell system can include an air supply system for delivering fresh air to the fuel cell stack, which is fluidically connected to the fuel cell stack's fresh air inlet. The air supply system can include an air cooler for cooling the fresh air, which is integrated into a cooling circuit containing a coolant and transfers heat from the fresh air to the coolant. This allows an existing cooling circuit to be used to cool the fresh air, thus increasing the efficiency of the fuel cell system.

[0020] Preferably, the supply air cooler is integrated into the same cooling circuit as the exhaust air heater. The supply air cooler and the exhaust air heater can be connected in series within the cooling circuit, with the supply air cooler located upstream of the exhaust air heater. In particular, the supply air cooler can be located in the supply line of the cooling circuit leading to the component being cooled, while the exhaust air heater is located in the return line of the cooling circuit leading away from the component being cooled. Alternatively, the supply air cooler and the exhaust air heater can also be connected in parallel within the cooling circuit.

[0021] Advantageously, the air supply system can include a compression device upstream of the air supply cooler to compress the supply air. For example, the compression device can be electrically driven and include an impeller for compressing the supply air and an electric motor to drive the impeller. Compression increases the density of the supply air, thereby increasing its mass flow rate and ultimately boosting the electrical output of the fuel cell system.

[0022] According to an advantageous embodiment, the expansion unit and the compression unit can be coupled to each other for drive purposes and form a drive unit. For example, the two impellers can be coupled to each other for drive purposes via the drive shaft, so that the impeller driven by the exhaust air assists the electric motor drive of the impeller driving the supply air. The drive unit thus acts like a turbocharger, with the expansion unit acting as a turbine, while the compression unit acts as a compressor, and the impellers forming a turbine wheel and a compressor wheel, which are connected to each other for drive purposes via the drive shaft.

[0023] In another embodiment, where the fuel cell system also includes an air supply system for delivering fresh air to the fuel cell stack, which is fluidically connected to the fuel cell stack's air supply inlet, the fuel cell system can additionally include a humidifier for humidifying dry supply air using moist exhaust air, which is fluidically connected to both the supply and exhaust air systems. This allows a large portion of the moisture carried in the exhaust air to be transferred to the supply air, thereby improving the energy efficiency of the fuel cell system. Simultaneously, this reduces the water content in the exhaust air, thus improving the efficiency of the exhaust air heater.

[0024] According to an advantageous embodiment, the supply air system can have a humidifier bypass in which the supply air bypasses the humidifier and which includes a control valve for controlling the humidifier bypass. Under certain operating conditions of the fuel cell system, it may be necessary to supply the fuel cell stack with comparatively dry supply air, which is particularly easy to achieve by bypassing the humidifier.

[0025] According to another embodiment, in which the fuel cell system also includes an air supply system for delivering air to the fuel cell stack, which is fluidically connected to the air supply inlet of the fuel cell stack, the fuel cell system can also include a cathode bypass in which the air supply bypasses the fuel cell stack and enters the exhaust system, and which includes a control valve for controlling the cathode bypass. Under certain operating conditions of the fuel cell system, particularly during a start-up phase, it may be necessary not to supply the fuel cell stack with the entire volume flow of the air supply. This can be achieved particularly easily using the cathode bypass, since the control valve allows the volume flow to be divided as desired between the fuel cell stack and the cathode bypass.

[0026] The humidifier can be conveniently located in the supply air system and in the exhaust air system between the fuel cell stack and the cathode bypass. This allows the cathode bypass to bypass the humidifier, meaning that regardless of whether the cathode bypass is more or less open, the conditions within the humidifier are not affected or only minimally affected. Therefore, the humidifier is available for humidifying the supply air via the exhaust air for any volume flow of supply air to the fuel cell stack and of exhaust air from the fuel cell stack.

[0027] The supply air system may also expediently include an air filter for filtering the supply air, whereby the air filter may in particular be arranged upstream of the compression device in the supply air system.

[0028] Additionally, the exhaust system can include a pressure control valve to regulate the exhaust air flow. The pressure control valve can be located upstream of the exhaust air heater and / or upstream of the exhaust air cooler and / or upstream of the expansion device and / or downstream of the humidifier and / or downstream of the cathode bypass.

[0029] A motor vehicle according to the invention is equipped with a fuel cell system of the type mentioned above. The fuel cell system can be integrated into the vehicle's electrical system.

[0030] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0031] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention as defined by the claims. Components of a higher-level unit, such as a device, apparatus, or arrangement, mentioned above and those to be mentioned below, which are designated separately, can form separate parts or components of this unit or be integral areas or sections of this unit, even if this is depicted differently in the drawings.

[0032] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0033] They show, schematically, Fig. 1. A schematic diagram-like representation of a motor vehicle in the area of ​​a fuel cell system, Fig. 2 a circuit diagram-like schematic representation of a thermal management system of a motor vehicle with a fuel cell system.

[0034] According to the Fig. 1 and Fig. Figure 2 comprises a motor vehicle 1 (only partially shown here), a fuel cell system 2, and an electrical system 3, the electrical system 3 being electrically coupled to the fuel cell system 2. The fuel cell system 2 serves as an electrical energy source to supply the electrical system 3 with electrical energy.

[0035] The fuel cell system 2 comprises at least one fuel cell stack 4, which has an air inlet 5 and an exhaust outlet 6. The air inlet 5 and the exhaust outlet 6 belong to a cathode side of the fuel cell stack 4, which is separated in the usual manner by means of an electrolyte from an anode side of the fuel cell stack 4, to which hydrogen gas can preferably be supplied during operation of the fuel cell system 2.

[0036] Accordingly Fig. 2. The fuel cell system 2 can have two fuel cell stacks 4. Furthermore, the motor vehicle 1 is according to Fig. 2 is equipped with a thermal management system 35, which provides the heating and cooling requirements of the vehicle 1 with the highest possible energy efficiency. The thermal management system 35 exhibits, in the example of the Fig. 2 a first refrigeration circuit 36, which is intended for air conditioning a vehicle cabin 37. The first refrigeration circuit 36 ​​has an evaporator 38, which is arranged in an air conditioning unit 39 for air conditioning the vehicle cabin 37. A condenser 40 of the first refrigeration circuit 36 ​​dissipates the heat to an environment 9 of the fuel cell system 2 or the motor vehicle 1.

[0037] The thermal management system 35 also includes a high-temperature cooling circuit 41, which is configured for cooling the fuel cell stacks 4. The high-temperature cooling circuit 41 can also be used for heating anode gas, particularly hydrogen. The high-temperature cooling circuit 41 includes a high-temperature heat exchanger 42, which dissipates heat to the environment 9. The coolant in the high-temperature cooling circuit 41 has a temperature of at least 60°C in the supply line, i.e., on the way from the high-temperature heat exchanger 42 to the respective fuel cell stack 4. A heater 51 of the air conditioning unit 39 is also integrated into the high-temperature cooling circuit 41. Furthermore, another cooling circuit 53, configured for cooling an auxiliary brake system 54, is thermally coupled to the high-temperature cooling circuit 41 via a heat exchanger 52.Furthermore, the high-temperature cooling circuit 41 can be equipped with an additional heat exchanger 55, which can be activated as required in addition to the high-temperature heat exchanger 42 to release excess heat to the environment 9.

[0038] The thermal management system 35 also includes a low-temperature cooling circuit 43, which is configured for cooling electrical and / or electronic components 44 of the vehicle electrical system 3. In the example of the Fig. Components 44 2, including an electric traction motor 56 and power electronics for the fuel cell system 2 and the vehicle 1, are identifiable. The low-temperature cooling circuit 43 has a low-temperature heat exchanger 45, which dissipates heat to the environment 9. The coolant in the low-temperature cooling circuit 43 has a temperature of less than 60°C in the supply line, i.e., on the way from the low-temperature heat exchanger 45 to the respective component 44. A second cooling circuit 47, configured for cooling a traction battery 48, is thermally coupled to the low-temperature cooling circuit 43 via a second refrigeration circuit 46. The second refrigeration circuit 46 is thermally coupled to the low-temperature cooling circuit 43 via a condenser 49 and to the second cooling circuit 47 via an evaporator 50.

[0039] A lubricating oil circuit 57 is used to cool the traction motor 56, which is thermally coupled to the low-temperature cooling circuit 41 via a heat exchanger 58.

[0040] Returning to Fig. 1. The fuel cell system 2 also has at least one exhaust air system 7 for removing exhaust air 8 from the respective fuel cell stack 4. The exhaust air 8, or an exhaust air flow, is in Fig. 1 indicated by an arrow. The exhaust air system 7 is fluidically connected to the exhaust air outlet 6 of the respective fuel cell stack 4 and leads to the environment 9 of the fuel cell system 2 or the motor vehicle 1. In the example of the Fig. 2. Each fuel cell stack 4 is assigned its own exhaust air system 7. According to [reference to relevant section], each exhaust air system 7 has... Fig. 1. An exhaust air heater 10 is configured to heat the exhaust air 8. In the fuel cell system 2 presented here, the exhaust air heater 10 is configured as a heat exchanger. For this purpose, the exhaust air heater 10 is integrated into a cooling circuit 11, which carries or circulates a coolant. The exhaust air heater 10 is configured such that heat is transferred from the coolant to the exhaust air 8. The coolant in the cooling circuit 11 is cooled in the exhaust air heater 10, while the exhaust air 8 is warmed or heated. By warming the exhaust air 8, its relative humidity is reduced, which correspondingly reduces fog formation in the surrounding area 9.

[0041] The exhaust air heater 10 has according to Fig. 1 Two pipes 12, 13 are connected, running inside one another and thus forming an inner pipe 12 and an outer pipe 13. The outer pipe 13 surrounds the inner pipe 12, forming an annular space 14, preferably coaxially. The inner pipe 12 is preferably fluidically connected to the exhaust air system 7 and carries the exhaust air 8 through the exhaust air heater 10. The outer pipe 13 is preferably fluidically connected to the cooling circuit 11 and carries the coolant through the exhaust air heater 10. The coolant flows through the annular space 14 and is in direct contact with the inner pipe 12 inside the outer pipe 13. In an alternative embodiment, the outer pipe 13 can be fluidically connected to the exhaust air system 7 and carries the exhaust air 8 through the exhaust air heater 10. The inner pipe 12 is then fluidically connected to the cooling circuit 11 and carries the coolant through the exhaust air heater 10.In this configuration, the exhaust air 8 flows through the annular space 14 and is in direct contact with the inner pipe 12 inside the outer pipe 13. The inner pipe 12 and outer pipe 13 are configured as straight lines. The cooling circuit 11 can, for example, be the high-temperature cooling circuit 41 of the thermal management system 35.

[0042] The exhaust air system 7 can also include an exhaust air cooler 15 for cooling the exhaust air 8, which is advantageously arranged upstream of the exhaust air heater 10 in the exhaust air system 7. Preferably, the exhaust air cooler 15 can be integrated into a further cooling circuit 16 carrying a coolant, wherein the exhaust air cooler 15 transfers heat from the exhaust air 8 to the coolant. The cooling of the exhaust air 8 causes the vapor to condense within the coolant, thus reducing the absolute humidity of the exhaust air 8. Advantageously, the further cooling circuit 16 can be the low-temperature cooling circuit 43 of the thermal management system 35.

[0043] The exhaust air system 7 can have an expansion device 17 upstream of the exhaust air cooler 15 for expanding the exhaust air 8. Preferably, an expansion device 17 is used which has an expansion impeller (not shown) for driving a drive shaft 23, wherein the expansion impeller is driven by the flow of the exhaust air 8. According to Fig. 1. The exhaust air system 7 can have a condensate drain 18 upstream of the exhaust air heater 10 and downstream of the exhaust air cooler 15, which is configured to remove condensate accumulating in the exhaust air cooler 15. In principle, it is also conceivable to arrange the condensate drain 18 directly at the exhaust air cooler 15. However, arranging the condensate drain 18 between the exhaust air cooler 15 and the exhaust air heater 10 simplifies the routing of the condensate drain pipes.

[0044] The fuel cell system 2 also has at least one air supply system 19 for supplying air 20 to the fuel cell stack 4. The air 20, or an air flow, is in Fig. 1 indicated by an arrow. The supply air system 19 is fluidically connected to the supply air inlet 5 of the respective fuel cell stack 4. In the example of the Fig. 2. Each fuel cell stack 4 is assigned its own air supply system 20. The air supply system 19 can be configured according to Fig. 1. Advantageously, the system includes a supply air cooler 21 for cooling the supply air 20. The supply air cooler 21 can advantageously be integrated into the cooling circuit 11, which also includes the exhaust air heater 10, i.e., in particular, the high-temperature cooling circuit 41. The supply air cooler 21 is configured such that heat is transferred from the supply air 20 to the coolant. Advantageously, in a series connection, the supply air cooler 21 is arranged upstream of the exhaust air heater 10 in the cooling circuit 11. However, a parallel connection of the supply air cooler 21 and the exhaust air heater 10 is preferred.

[0045] The air supply system 19 can have a compression device 22 upstream of the air supply cooler 21 for compressing the supply air 20. Preferably, this is an electric compression device 22, which includes a compression impeller (not shown) for compressing and driving the supply air 20 and an electric motor (not shown) for driving the compression impeller. In particular, the expansion device 17 and the compression device 22 can be coupled to each other for drive purposes and form a drive unit 59. For this purpose, the expansion impeller can be connected to the compression impeller for drive purposes via the drive shaft 23. This allows the drive unit 59 to operate in the manner of a turbocharger, so that the flow of the exhaust air 8 via the expansion impeller and the drive shaft 23 assists in driving the electrically driven compression impeller and thus the compression of the supply air 20.

[0046] Fuel cell system 2 is used in the example of the Fig. 1 is also equipped with at least one humidifier 24, which is configured to humidify dry supply air 20 using moist exhaust air 8. For this purpose, the humidifier 24 is fluidically connected to the supply air system 19 and to the exhaust air system 7 in a suitable manner. In the example of the Fig. 2. Each fuel cell stack 4 is assigned its own humidifier 24. According to Fig. Dry supply air 20 from the environment 9 is fed to the humidifier 24 via a first connection 25, while moist exhaust air 8 from the fuel cell stack 4 is fed to the humidifier 24 via a second connection 26. Within the humidifier 24, moisture transfer from the exhaust air 8 to the supply air 20 takes place in a media-separated manner. At a third connection 27, humidified supply air 20 is discharged from the humidifier 24 and fed to the fuel cell stack 4, while dehumidified exhaust air 8 is discharged from the humidifier 24 via a fourth connection 28 and ultimately fed to the environment 9. The terms "dry", "moist", "dehumidified" and "humidified" are to be understood relatively, such that the moisture in the humidified supply air 20 is greater than in the dry supply air 20, while the moisture in the moist exhaust air 8 is greater than in the dehumidified exhaust air 8.

[0047] The supply air system 19 can include a humidifier bypass 29, through which the supply air 20 can bypass the humidifier 24 as required and in a controlled manner. To control the humidifier bypass 29, it has a control valve 30, which controls the distribution of the supply air 20 between the humidifier bypass 29 and the humidifier 24. A cathode bypass 31 can also be provided, through which the supply air 20 can bypass the fuel cell stack 4 as required and in a controlled manner, and be transferred to the exhaust air system 7. The cathode bypass 31 includes a control valve 32, which controls the distribution of the supply air 20 between the exhaust air system 7 and the fuel cell stack 4. Advantageously, the humidifier 24 is arranged in both the supply air system 19 and the exhaust air system 7 between the fuel cell stack 4 and the cathode bypass 31. This means that with the cathode bypass 31 open, the supply air 20 also bypasses the humidifier 24.

[0048] According to Fig. 1 The exhaust air system 7 also has a pressure control valve 33, which is configured to control the pressure in the exhaust air 8. In the example of the Fig. 1 The pressure regulating valve 33 is arranged upstream of the exhaust air heater 10, in particular upstream of the exhaust air cooler 15, preferably upstream of the expansion device 17, and in particular downstream of the air humidifier 24, preferably downstream of the cathode bypass 31, in the exhaust air system 7.

[0049] The supply air system 19 can also include an air filter 34 through which the supply air 20 flows in order to clean it of particles and the like. The supply air system 19 advantageously draws the supply air 20 from the environment 9. The compression device 22 is advantageously arranged downstream of the air filter 34 in the supply air system 19. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2004 051 751 B4

[0002] DE 199 53 404 B4

[0004] EP 3 047 533 B1

[0004] JP 6 926 975 B2

[0004] JP 2021 136217 A

[0004] JP 6 996 237 B2

[0004]

Claims

[1] Fuel cell system (2) for a motor vehicle (1), - with at least one fuel cell stack (4) having an air inlet (5) and an exhaust outlet (6), - with at least one exhaust air system (7) for removing exhaust air (8) from the fuel cell stack (4), which is fluidically connected to the exhaust air outlet (6) of the fuel cell stack (4) and leads to an environment (9), - wherein the exhaust air system (7) has an exhaust air heater (10) for heating the exhaust air (8), characterized by , - that the exhaust air heater (10) is integrated into a cooling circuit (11) carrying a coolant and transfers heat from the coolant to the exhaust air (8). [2] Fuel cell system (2) according to claim 1, characterized by , - that the exhaust air heater (10) has two interlocking pipes (12, 13) which form an inner pipe (12) and an outer pipe (13) surrounding the inner pipe (12), - that one of the two pipes (12, 13) is fluidically connected to the exhaust air system (7) and the exhaust air (8) is routed through the exhaust air heater (10), - that the other of the two pipes (12, 13) is fluidically connected to the cooling circuit (11) and carries the coolant through the exhaust air heater (10). [3] Fuel cell system (2) according to claim 2, characterized by , - that the inner pipe (12) is fluidically connected to the exhaust system (7) and the exhaust air (8) is routed through the exhaust heater (10), - that the outer pipe (13) is fluidically connected to the cooling circuit (11) and the coolant is routed through the exhaust air heater (10), - that the coolant in the outer tube (13) comes into direct contact with the inner tube (12). [4] Fuel cell system (2) according to any one of the preceding claims, characterized by , - that the cooling circuit (11) is a high-temperature cooling circuit (41) configured to cool the respective fuel cell stack (4). [5] Fuel cell system (2) according to any one of the preceding claims, characterized by , - that the exhaust air system (7) has an exhaust air cooler (15) for cooling the exhaust air (8), which is arranged upstream of the exhaust air heater (10) in the exhaust air system (7), - that the exhaust air cooler (7) is integrated into a further cooling circuit (16) carrying a coolant and transfers heat from the exhaust air (7) to the coolant. [6] Fuel cell system (2) according to claim 5, characterized by , - that the further cooling circuit (16) is a low-temperature cooling circuit (43) configured to cool electrical and / or electronic components (44) of the fuel cell system (2) and / or the motor vehicle (1). [7] Fuel cell system (2) according to claim 5 or 6, characterized by , - that the exhaust air system (7) upstream of the exhaust air cooler (10) has an expansion device (17) for expanding the exhaust air (8). [8] Fuel cell system (2) according to any one of claims 5 to 7, characterized by , - that the exhaust system (7) has a condensate drain (18) upstream of the exhaust heater (10) and downstream of the exhaust cooler (15) for the removal of condensate accumulating in the exhaust cooler (15). [9] Fuel cell system (2) according to any one of the preceding claims, characterized by , - that the fuel cell system (2) has at least one air supply system (19) for supplying air (10) to the fuel cell stack (4), which is fluidically connected to the air supply inlet (5) of the fuel cell stack (4), - that the supply air system (19) has a supply air cooler (21) for cooling the supply air (20), which is integrated into a cooling circuit (11) and transfers heat from the supply air (20) to the coolant. [10] Fuel cell system (2) according to claim 9, characterized by , - that the supply air cooler (21) and the exhaust air heater (10) are integrated into the same cooling circuit (11). [11] Fuel cell system (2) according to claim 9 or 10, characterized by , - that the supply air system (19) upstream of the supply air cooler (21) has a compression device (22) for compressing the supply air (20). [12] Fuel cell system (2) according to claims 7 and 11, characterized by , - that the expansion device (17) and the compression device (22) are coupled to each other in terms of drive. [13] Fuel cell system (2) according to any one of the preceding claims, characterized by , - that the fuel cell system (2) has at least one air supply system (19) for supplying air (20) to the fuel cell stack (4), which is fluidically connected to the air supply inlet (5) of the fuel cell stack (4), - that the fuel cell system (2) has at least one humidifier (24) for humidifying dry supply air (20) by means of moist exhaust air (8), which is fluidically connected to the supply air system (19) and to the exhaust air system (7). [14] Fuel cell system (2) according to claim 13, characterized by , - that the supply air system (19) has a humidifier bypass (29) in which the supply air (20) bypasses the humidifier (24) and which has a control valve (30) for controlling the humidifier bypass (29). [15] Fuel cell system (2) according to any one of the preceding claims, characterized by , - that the fuel cell system (2) has at least one air supply system (19) for supplying air (20) to the fuel cell stack (4), which is fluidically connected to the air supply inlet (5) of the fuel cell stack (4), - that the fuel cell system (2) has a cathode bypass (31) in which the supply air (20) bypasses the fuel cell stack (4) and enters the exhaust system (7) and which has a control valve (32) for controlling the cathode bypass (31). [16] Motor vehicle (1) with a fuel cell system (2) according to any of the preceding claims.

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