Fuel cell exhaust system, in particular for commercial vehicles

Abstract

The invention relates to a fuel cell exhaust system, comprising a heat exchanger which extends lengthwise in the longitudinal direction of the heat exchanger and through which fuel cell exhaust gas can flow, said heat exchanger having a first end region and a second end region, the heat exchanger has a fuel cell exhaust gas inlet region in one end region and a fuel cell exhaust gas outlet region in one end region, the heat exchanger has a first flow volume which leads away from the fuel cell exhaust gas inlet region in the longitudinal direction of the heat exchanger and a second flow volume which is connected to the first flow volume and returns in the longitudinal direction of the heat exchanger towards the fuel cell exhaust gas inlet region. The first flow volume is separated from the cooling medium flow volume by the first wall and from the heat exchanger second flow volume by the heat exchanger second wall.

Description

Technical Field

[0001] The invention relates to a fuel cell exhaust gas device which is preferably designed to discharge fuel cell exhaust gas emitted from a fuel cell in a vehicle, in particular a commercial vehicle, into the surrounding environment. Background Art

[0002] The exhaust gas stream discharged from the fuel cell, and in particular also including the cathode exhaust gas, is enriched with product water that accumulates in the cathode region of the fuel cell during fuel cell operation. The temperature of the fuel cell exhaust gas leaving the fuel cell can be in the range of 50°C to 100°C, and the relative humidity can be in the range of 80% to 100%. By cooling the fuel cell exhaust gas, for example, when it is discharged into relatively cold ambient air, the relative humidity increases sharply, causing the water contained in the fuel cell exhaust gas as water vapor to condense into mist.

[0003] In commercial vehicles, the exhaust system is often installed so that it, or a large portion of it, extends substantially vertically upward behind or to the side of the cab. This allows the exhaust gas from the exhaust system to be discharged vertically into the surrounding environment above the cab. During driving, ambient air flows around the substantially vertically extending portion of the exhaust system. If fuel cell exhaust gas is to be discharged to the surrounding environment via such an exhaust system, water condensation can already occur within the exhaust system, forming mist, particularly at relatively low ambient air temperatures. While it is possible to discharge some of the condensed water in liquid form, the majority of the condensed water is discharged to the surrounding environment as mist. Summary of the Invention

[0004] The object of the present invention is to provide a fuel cell exhaust system, in particular for commercial vehicles, in which the formation of mist in the fuel cell exhaust system or when the fuel cell exhaust gas emerges from the fuel cell exhaust system is significantly reduced.

[0005] According to the present invention, the object is achieved by a fuel cell exhaust device, in particular a fuel cell exhaust device for commercial vehicles, which includes a heat exchanger extending longitudinally in a longitudinal direction of the heat exchanger and through which fuel cell exhaust gas can flow, the heat exchanger having a first end region of the heat exchanger and a second end region of the heat exchanger, wherein the heat exchanger has a fuel cell exhaust gas inlet region in one end region of the heat exchanger between the first end region of the heat exchanger and the second end region of the heat exchanger, and has a fuel cell exhaust gas outlet region in one end region of the heat exchanger between the first end region of the heat exchanger and the second end region of the heat exchanger, wherein the heat exchanger has a first flow volume of the heat exchanger guided away from the fuel cell exhaust gas inlet region in the longitudinal direction of the heat exchanger and a second flow volume of the heat exchanger connected to the first flow volume of the heat exchanger and returning in the longitudinal direction of the heat exchanger toward the fuel cell exhaust gas inlet region, the first flow volume of the heat exchanger being separated from the coolant flow volume by a first wall of the heat exchanger and separated from the second flow volume of the heat exchanger by a second wall of the heat exchanger.

[0006] The thermal interaction of the fuel cell exhaust gas with a coolant, such as ambient air circulating through the heat exchanger, in the first flow volume of the heat exchanger, and the resulting cooling of the fuel cell exhaust gas, actively ensures that the relative humidity of the fuel cell exhaust gas in the first flow volume of the heat exchanger increases sharply and reaches a value of 100%. Consequently, a large portion of the water carried in the fuel cell exhaust gas in the form of water vapor can condense in the first flow volume of the heat exchanger and thus be separated from the fuel cell exhaust gas. The dehydrated fuel cell exhaust gas entering the second flow volume of the heat exchanger from the first flow volume of the heat exchanger is heated by the thermal interaction with the fuel cell exhaust gas flowing in the first flow volume of the heat exchanger, which occurs via the second wall of the heat exchanger. This reduces the relative humidity of the fuel cell exhaust gas in the second flow volume of the heat exchanger. Since the fuel cell exhaust gas subsequently discharged to the surrounding environment via the fuel cell outlet region is dehydrated and has a relatively low relative humidity, there is essentially no risk of mist formation, even at relatively low ambient temperatures.

[0007] If the first flow volume of the heat exchanger preferably surrounds the second flow volume of the heat exchanger essentially concentrically with respect to a central axis of the heat exchanger extending essentially in the longitudinal direction of the heat exchanger, a relatively large surface is provided for thermal interaction between the fuel cell exhaust and the cooling medium via the first wall of the heat exchanger, while the second flow volume of the heat exchanger is essentially shielded outwardly or toward the cooling medium by the first flow volume of the heat exchanger surrounding the second flow volume of the heat exchanger.

[0008] In an alternative embodiment, the first heat exchanger flow volume and the second heat exchanger flow volume can be arranged alongside one another in a layered arrangement transversely to the longitudinal direction of the heat exchanger. If the second heat exchanger flow volume is arranged transversely to the longitudinal direction of the heat exchanger between a first portion of the first heat exchanger flow volume and a second portion of the first heat exchanger flow volume, a relatively large surface area is again provided for thermal interaction between the fuel cell exhaust gas flowing in the first heat exchanger flow volume and the coolant, while the dehydrated fuel cell exhaust gas flowing in the second heat exchanger flow volume is effectively shielded by the first heat exchanger flow volume from thermal interaction with the coolant.

[0009] In a compact design, it can be provided that the heat exchanger inlet region and the heat exchanger outlet region are arranged at a first end region of the heat exchanger and that the heat exchanger outlet region is connected to a second flow volume of the heat exchanger.

[0010] In order to achieve a linear design of the fuel cell exhaust system, which is particularly advantageous for installation in commercial vehicles, it is proposed to provide a third heat exchanger flow volume connected to the second heat exchanger flow volume and directed in a direction away from the heat exchanger inlet area, wherein the third heat exchanger flow volume is separated from the second heat exchanger flow volume by a third heat exchanger wall.

[0011] In order to also effectively shield the fuel cell exhaust gas flowing in the third heat exchanger flow volume from thermal interaction with the cooling medium, the second heat exchanger flow volume can surround the third heat exchanger flow volume, preferably substantially concentrically, with respect to the heat exchanger central axis.

[0012] In this linear design of the fuel cell exhaust device, the heat exchanger inlet area can be arranged on the first end area of the heat exchanger, the heat exchanger outlet area can be arranged on the second end area of the heat exchanger, and the heat exchanger outlet area can be connected to the third flow volume of the heat exchanger.

[0013] In order to avoid or reduce the flow resistance inevitably introduced by the heat exchanger when, for example, there is essentially no risk of mist formation even in the case of a high water content in the fuel cell exhaust gas due to a sufficiently high ambient temperature, it is proposed to provide a bypass flow path leading from the first flow volume of the heat exchanger or the heat exchanger inlet area to the heat exchanger outlet area, which can be selectively opened or closed for flow through.

[0014] In particular, when the heat exchanger is designed with three heat exchanger flow volumes that follow one another or are connected to one another in the flow direction, in order to provide such a bypass flow path, at least one bypass flow opening can be provided in the area of the second wall of the heat exchanger, which can be selectively opened or closed for flow through by a closing device.

[0015] If the at least one bypass flow opening is arranged on the second end region of the heat exchanger, then when the bypass flow path is open, the fuel cell exhaust gas basically does not flow through the entire second flow volume of the heat exchanger and the third flow volume of the heat exchanger, thereby significantly reducing the flow resistance introduced through the heat exchanger.

[0016] For efficient thermal interaction between the fuel cell exhaust gas and the coolant flowing in the first flow volume of the heat exchanger, a plurality of first heat transfer ribs may be provided on the outer side of the first wall of the heat exchanger facing the coolant flow volume.

[0017] In order to achieve low flow resistance for the coolant, i.e., the ambient air flowing around the fuel cell exhaust system, for example, while the vehicle is in motion, the first heat transfer ribs can extend substantially perpendicularly to the longitudinal direction of the heat exchanger. This means that the large surface area of the first heat transfer ribs, which is provided for thermal interaction with the coolant, is oriented substantially parallel to the flow direction of the coolant.

[0018] For efficient thermal interaction of the cooling medium with the fuel cell exhaust gas flowing in the first flow volume of the heat exchanger, a plurality of second heat transfer ribs may be provided on the inner side of the first heat exchanger wall facing the first flow volume of the heat exchanger.

[0019] In order to also achieve the lowest possible flow resistance for the fuel cell exhaust gas, the second heat transfer ribs can extend essentially parallel to the longitudinal direction of the heat exchanger. Here, the large surfaces of the second heat transfer ribs provided for thermal interaction are also oriented such that they are parallel to the flow direction or main flow direction of the fuel cell exhaust gas in the first flow volume of the heat exchanger.

[0020] By configuring the heat exchanger inlet region so that the fuel cell exhaust gas enters the first flow volume of the heat exchanger at the heat exchanger inlet region with a fuel cell exhaust gas inflow direction oriented tangentially with respect to the central axis of the heat exchanger, separation of water carried in the fuel cell exhaust gas in the form of droplets in the first flow volume of the heat exchanger can be supported. The fuel cell exhaust gas is thereby forced into an annular or spiral flow path, so that the water droplets carried in the fuel cell exhaust gas can be accelerated radially outward under the action of centrifugal force, collect on the inner surface of the first wall of the heat exchanger, and be discharged therefrom.

[0021] For this purpose, a liquid discharge device for discharging liquid from the heat exchanger can be provided. The liquid discharge device can include an opening in the heat exchanger inlet region, such as the opening through which the fuel cell exhaust gas also enters the first flow volume of the heat exchanger at the heat exchanger inlet region.

[0022] Particularly advantageous for use in conjunction with commercial vehicles is that the fuel cell exhaust device is designed for installation with a substantially vertically oriented heat exchanger longitudinal direction, so that the first end region of the heat exchanger forms the lower end region of the heat exchanger and the second end region of the heat exchanger forms the upper end region of the heat exchanger.

[0023] The invention further relates to a vehicle, in particular a commercial vehicle, which comprises a fuel cell exhaust system designed according to the invention.

[0024] The fuel cell exhaust system is advantageously mounted in the vehicle such that the first end region of the heat exchanger is vertically positioned at the bottom and the second end region of the heat exchanger is vertically positioned at the top. This also ensures that ambient air surrounding the vehicle can flow around the heat exchanger as a cooling medium. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention will be described in detail below with reference to the accompanying drawings.

[0026] Figure 1 A schematic diagram of a vehicle configured as a commercial vehicle and equipped with a fuel cell and a fuel cell exhaust system is shown;

[0027] Figure 2 Shown in Figure 1 A longitudinal sectional view of a heat exchanger of a fuel cell exhaust device shown in;

[0028] Figure 3 Shown for Figure 1 A side view of a heat exchanger of a fuel cell exhaust device shown in ;

[0029] Figure 4 Show Figure 3 A cross-sectional view of a heat exchanger;

[0030] Figure 5 Shows a diagram showing the flow through Figure 2 Graph of the temperature development of the fuel cell exhaust gas of the heat exchanger;

[0031] Figure 6 Shows a diagram showing the flow through Figure 2 Graph of the relative humidity development of the fuel cell exhaust gas from the heat exchanger;

[0032] Figure 7Showing a heat exchanger with Figure 2 Corresponding view showing an alternative design for the heat exchanger inlet area;

[0033] Figure 8 Show Figure 7 A cross-sectional view of a heat exchanger;

[0034] Figure 9 Shows a heat exchanger with an alternative design Figure 2 Another corresponding view;

[0035] Figure 10 Shows a heat exchanger with an alternative design Figure 2 Another corresponding view;

[0036] Figure 11 Shows a heat exchanger with an alternative design Figure 2 Another corresponding view;

[0037] Figure 12 Show Figure 11 Perspective view of a heat exchanger. DETAILED DESCRIPTION

[0038] exist Figure 1 In the figure, a vehicle designed as a commercial vehicle is generally designated by 10. Vehicle 10, which is electrically driven, for example, includes a fuel cell 12 as a source of electrical energy, via which an electric motor (not shown) of vehicle 10 is supplied with electrical energy. Fuel cell exhaust gas B generated by fuel cell 12 is discharged to the surrounding environment via a fuel cell exhaust gas device 16 extending upward in a vertical direction V in the area behind or to the side of a driver's cab 14.

[0039] The fuel cell exhaust device 16 includes a heat exchanger 18 as a main component, which is described in detail below. The ambient air L provided with a cooling medium flows around the heat exchanger, especially when the vehicle 10 is in driving state, so that heat is transferred from the fuel cell exhaust gas B flowing through the heat exchanger 18 to the ambient air L, or the fuel cell exhaust gas B is cooled.

[0040] Figure 2 The heat exchanger 18 is shown in a longitudinal section along the heat exchanger center axis M in the longitudinal direction W of the heat exchanger. Figure 1 The heat exchanger 18 is shown schematically in the figure as a first heat exchanger end region 20 positioned at the bottom when mounted substantially vertically. Thus, the first heat exchanger end region 20 forms the lower region of the heat exchanger. The heat exchanger 18 also has a second heat exchanger end region 22 which provides the upper end region of the heat exchanger when mounted vertically.

[0041] exist Figure 2 The heat exchanger 18 shown in FIG. 1 has three heat exchanger flow volumes that are arranged concentrically with respect to a heat exchanger center axis M. A first heat exchanger flow volume 24 leads from a heat exchanger inlet region 26 formed at the first heat exchanger end region 20 to a second heat exchanger end region 22. The first heat exchanger flow volume 24 is radially outwardly bounded by a first heat exchanger wall 28, so that the fuel cell exhaust gas flowing in the first heat exchanger flow volume 24 essentially in a main flow direction of the fuel cell exhaust gas, which corresponds to the longitudinal direction W of the heat exchanger, is separated from the ambient air L, which serves as a coolant, by the first heat exchanger wall 28. The environment surrounding the heat exchanger 18 here forms the coolant flow volume, which is the coolant ambient air that circulates around the heat exchanger on its outer side.

[0042] Directly following the first heat exchanger flow volume radially inward is a second heat exchanger flow volume 30, which is connected to the first heat exchanger flow volume 24 in the heat exchanger second end region 22 and returns from the heat exchanger second end region 22 to the first heat exchanger end region 20. The second heat exchanger flow volume 30 is separated radially outward from the first heat exchanger flow volume 24 by a second heat exchanger wall 32. In the second heat exchanger flow volume 30, the fuel cell exhaust gas B flows in a fuel cell exhaust gas main flow direction, which is oriented substantially in the direction of the heat exchanger longitudinal direction W and is substantially opposite to the main flow direction of the fuel cell exhaust gas in the first heat exchanger flow volume 24.

[0043] A third heat exchanger flow volume 34 is radially arranged within the second heat exchanger flow volume 30 and is separated radially outward from the second heat exchanger flow volume 30 by a third heat exchanger wall 36. In the third heat exchanger flow volume 34, which is connected to the second heat exchanger flow volume 30 in the first end region 20 of the heat exchanger, the fuel cell exhaust gas B flows substantially along a fuel cell exhaust gas main flow direction oriented in the longitudinal direction W of the heat exchanger. This fuel cell exhaust gas main flow direction also substantially coincides with the fuel cell exhaust gas main flow direction in the first heat exchanger flow volume 24 and is oriented opposite to the fuel cell exhaust gas main flow direction in the second heat exchanger flow volume 30.

[0044] In this regard, it should be noted that in each of the different heat exchanger flow volumes 24, 30, 34, the flow direction components that ensure that the fuel cell exhaust gas B moves from one end region of the heat exchanger to the other end region of the heat exchanger are considered to be the main flow direction. As will be explained below, this does not exclude the possibility of flow direction components that locally deviate from this main flow direction oriented in the longitudinal direction W of the heat exchanger, for example, oriented in the circumferential direction.

[0045] The heat exchanger third flow volume 34 is connected to a heat exchanger outlet region 38 located in the heat exchanger second end region 22, through which the fuel cell exhaust gas B can pass. Figure 1 As shown diagrammatically in FIG, the discharge to the surrounding environment is carried out, for example, via a curved pipe section.

[0046] exist Figure 2 In the illustrated configuration of the heat exchanger 18, the centrally located third heat exchanger flow volume 34 is shielded radially outwards and thus substantially with respect to the ambient air L by the second and first heat exchanger flow volumes 30, 24 located radially outside it. The second heat exchanger flow volume 30, which surrounds the centrally located third heat exchanger flow volume 34 in the form of an annular space, is shielded radially outwards and thus with respect to the ambient air L by the first heat exchanger flow volume 24, which is also designed as an annular space.

[0047] The fuel cell exhaust gas B flowing in the first heat exchanger flow volume 24 and entering the heat exchanger 18 or the first heat exchanger flow volume 24 at the heat exchanger inlet region 26, for example, via the inlet opening 40 provided there, substantially in the heat exchanger longitudinal direction W and having a relatively high temperature, interacts thermally with the ambient air L serving as a cooling medium via the first heat exchanger wall 28. For an efficient thermal interaction, as in Figure 3 As shown in the diagram, a plurality of first heat transfer ribs 42 may be arranged one after another in the direction of the heat exchanger center axis M on the outer side of the first wall 28 of the heat exchanger facing the ambient air L. For effective thermal interaction with the ambient air L, the first heat transfer ribs 42 are oriented substantially orthogonally relative to the heat exchanger center axis M, so that the large surfaces of the heat transfer ribs 42, each oriented in the direction of the heat exchanger center axis M, are oriented substantially parallel to the flow direction of the ambient air L.

[0048] On the inner side of the first heat exchanger wall 28, which faces the first heat exchanger flow volume 24, a plurality of second heat transfer ribs 44 can be provided, in order to improve the thermal interaction between the fuel cell exhaust gas B and the ambient air L, which extend one after another in the circumferential direction and essentially in the direction of the heat exchanger central axis M. Consequently, the large, essentially radially oriented heat transfer surfaces of the second heat transfer ribs 44 extend essentially in the direction of the heat exchanger central axis M and, therefore, also essentially in the direction of the main flow direction of the fuel cell exhaust gas in the first heat exchanger flow volume 24.

[0049] It should be noted that the mutually nested or mutually surrounding structures of the heat exchanger flow volumes can also be realized in their non-circular designs. For example, they can have a flat circular cross section or a polygonal cross section.

[0050] When flowing through the first flow volume 24 of the heat exchanger, the fuel cell exhaust gas B releases heat to the ambient air L and is cooled there, especially when the temperature of the ambient air L is relatively low. Therefore, when flowing through the first flow volume 24 of the heat exchanger from the first end region 20 of the heat exchanger, i.e., position U, toward the second end region 22 of the heat exchanger, i.e., position O, the temperature T of the fuel cell exhaust gas B decreases, as shown by Figure 5 The temperature-travel diagram of branch a is shown schematically. Figure 6 As illustrated by branch a' in the relative humidity-travel diagram, the relative humidity R of the fuel cell exhaust gas B increases or remains at 100%. As a result of the cooling of the fuel cell exhaust gas B, water carried in the form of water vapor in the fuel cell exhaust gas B condenses and settles on the inner surface of the heat exchanger's first wall 28 or on the surfaces of the second heat transfer ribs 44 (if included). The water that accumulates on these surfaces can then flow downward due to gravity and be discharged, for example, to a collection container located below the heat exchanger 18 in the region of the liquid discharge device 46, including the inlet opening 40 of the fuel cell inlet region 26.

[0051] The cooled and dehydrated fuel cell exhaust gas B leaves the heat exchanger first flow volume 24 at the second fuel cell end region 22, i.e., at position O, and enters the heat exchanger second flow volume 30. Since the heat exchanger second flow volume is shielded from the ambient air L by the heat exchanger first flow volume 24, the temperature T of the fuel cell exhaust gas B no longer decreases when flowing through the heat exchanger second flow volume 30. Instead, due to the counterflow generated in the heat exchanger first flow volume 24 with respect to the fuel cell exhaust gas flow, a thermal interaction is generated between the fuel cell exhaust gas B in the heat exchanger second flow volume 30 and the fuel cell exhaust gas B in the heat exchanger first flow volume 24, so that, as shown by Figure 5As schematically represented by branch b in FIG, the temperature T of the fuel cell exhaust gas B rises again and thus, as shown by Figure 6 As shown in the diagram of branch b', the relative humidity R decreases.

[0052] At the lower end of the second heat exchanger flow volume 30, the dehydrated fuel cell exhaust gas B with a low relative humidity R enters the third heat exchanger flow volume 34 and flows through it toward the heat exchanger outlet area 38. Figure 5 As shown schematically in branch c in FIG, the temperature T of the fuel cell exhaust gas B can be slightly reduced again, while at the same time, as in Figure 6 As illustrated by branch c' in FIG, the relative humidity R of the fuel cell exhaust gas B can be slightly increased.

[0053] As this basis Figure 5 and Figure 6 As shown diagrammatically, the temperature T of the fuel cell exhaust gas B decreases as it flows through the heat exchanger 18 due to thermal interaction with the ambient air L serving as a cooling medium, while the relative humidity R of the fuel cell exhaust gas B also decreases due to condensation of water, particularly in the first flow volume 24 of the heat exchanger. Consequently, the fuel cell exhaust gas B dehydrated in this manner enters the surrounding environment at a significantly reduced relative humidity. This significantly reduces the risk of the relative humidity R of the fuel cell exhaust gas B spontaneously increasing to a value of 100%, even at relatively low ambient air temperatures, as the discharged fuel cell exhaust gas B is significantly cooled upon contact with the ambient air L. Accordingly, the risk of mist formation in the outlet region of the fuel cell exhaust gas device 16, particularly at relatively low ambient temperatures, is also significantly reduced.

[0054] Figure 7 and Figure 8 Shown in Figure 2 A modification of the heat exchanger 18 shown in FIG. In this heat exchanger 18, the heat exchanger inlet region is designed such that the fuel cell exhaust gas B enters the heat exchanger 18 or the first heat exchanger flow volume 24 in a fuel cell exhaust gas inflow direction E, which is oriented tangentially with respect to the heat exchanger central axis M. Consequently, the fuel cell exhaust gas B flows into the first heat exchanger flow volume 24 essentially in a circumferential direction. Due to the centrifugal forces that occur here, water droplets contained in the fuel cell exhaust gas B impinge radially outward onto the inner surface of the first heat exchanger wall 28. As a result, the water components entrained in the fuel cell exhaust gas B in the form of droplets and entering the heat exchanger 18 can be separated from the fuel cell exhaust gas B and, as described above, discharged downward or toward a water reservoir, etc., via a liquid discharge device 46, for example, formed in the region of the fuel cell inlet region 26.

[0055] exist Figure 9 The diagram shows Figure 2 Another modification of the heat exchanger 18 is shown in FIG. Figure 9 In the heat exchanger 18, a bypass flow path, generally designated 48, is formed in the heat exchanger second end region 22, i.e., in the region of the downstream end of the heat exchanger first flow volume 24. In the illustrated embodiment, the bypass flow path 48 includes one or more bypass flow openings 50 in the heat exchanger third wall 38, which can be selectively opened or closed for flow by associated closing devices 52. For example, each closing device 52 associated with a bypass flow opening 50 can include a flap, slider, butterfly valve, or similar device that is adjustable by an associated device. For example, these closing devices 52 can be configured such that, when they are positioned to release the associated bypass flow opening 50 for flow, they substantially close the heat exchanger second flow volume 30 in its upstream end region to prevent the ingress of fuel cell exhaust gas B.

[0056] By means of the bypass flow path 48, a flow connection is created from the downstream end of the first heat exchanger flow volume 24 directly into the heat exchanger outlet region 38, so that the fuel cell exhaust gas B flowing through the heat exchanger 18 flows only through the first heat exchanger flow volume 24 and not through the second heat exchanger flow volume 30 and the third heat exchanger flow volume 34. This state can be selected when there is no risk of water condensing from the fuel cell exhaust gas B when it is discharged to the surrounding environment due to thermal conditions. By opening the bypass flow path 48, the flow resistance occurring in the heat exchanger 18 is significantly reduced, since the second heat exchanger flow volume 30 and the third heat exchanger flow volume 34 are not flowed through. However, any water that may condense in the first heat exchanger flow volume 34 and accumulate there can be removed as described above with reference to Figure 2 The liquid is discharged from the heat exchanger 18 via the liquid discharge device 46 in the manner and type described in the embodiment of FIG.

[0057] exist Figure 10 Another modification of the heat exchanger 18 is shown in FIG. Figure 10 In the heat exchanger 18 shown, the heat exchanger first flow volume 24 and the heat exchanger second flow volume 30 are arranged coaxially with each other or coaxially with the heat exchanger central axis M. However, Figure 10The heat exchanger 18 does not have a third heat exchanger flow volume. The heat exchanger outlet region 38 is located at the heat exchanger first end region 20, just like the heat exchanger inlet region 26. Therefore, the fuel cell exhaust gas B leaves the heat exchanger 18 after thermal interaction with the fuel cell exhaust gas B flowing in the first heat exchanger flow volume 24 and cooled by the ambient air L, which occurs via the heat exchanger second wall 32. Figure 5 and Figure 6 This means that the respective last branch c or c' disappears and the fuel cell exhaust gas B emerges / flows out of the heat exchanger 18 at the temperature T or relative humidity R present at the end of the branch b or b' at position U, respectively.

[0058] Figure 10 The heat exchanger 18 can also be integrated into the vehicle in such a way that its heat exchanger center axis M is oriented essentially vertically, for example Figure 1 As shown, it is located to the side or rear of the cab 14. The fuel cell exhaust gas B can then be exhausted to the surrounding environment within the lower area of the vehicle 10.

[0059] It should be pointed out that in Figure 10 In the design variant of the heat exchanger 18 shown, a bypass flow path can also be present, which then leads directly from the heat exchanger inlet area 26 to the heat exchanger outlet area 38, so that no flow flows through the first heat exchanger flow volume 24 and the second heat exchanger flow volume 30 when this is not necessary for thermal reasons.

[0060] In such a Figure 9 Shown and referenced Figure 10 In the embodiment described above, the bypass flow path can be selectively opened or closed. In this embodiment, it can preferably be provided that the closing device used for this is actuated in such a way that the amount of fuel cell exhaust gas B directed via the bypass flow path is selected so as to prevent the formation of mist at the outlet of the fuel cell exhaust gas device 16. Various parameters can be taken into account for this purpose, such as, for example, the temperature of the ambient air L, the humidity of the ambient air L, the temperature of the fuel cell exhaust gas B, or the relative humidity of the fuel cell exhaust gas B.

[0061] Figure 11 and Figure 12 Another modification of the heat exchanger 18 is shown. In this embodiment, the existing heat exchanger flow volumes are not arranged around each other or concentrically with each other, but are arranged with respect to the heat exchanger longitudinal direction W and the heat exchanger central axis M or include the heat exchanger central axis M and are Figure 1 The planes perpendicular to the drawing plane are arranged laterally side by side in a layered, essentially planar arrangement.

[0062] Figure 11 and Figure 12 The heat exchanger 18 shown also has only the first heat exchanger flow volume 24 and the second heat exchanger flow volume 30. The first heat exchanger flow volume 24 is divided into a first portion 241 and a second portion 242. The second heat exchanger flow volume 30 is positioned between the first portion 241 of the first heat exchanger flow volume 24 and the second portion 242 of the first heat exchanger flow volume 24.

[0063] Even in this embodiment, the heat exchanger second flow volume 30 is effectively shielded from thermal interaction with the ambient air L, when the interaction surface between the heat exchanger first flow volume 24 and the surroundings is relatively large. Figure 11 and Figure 12 The heat exchanger 18 can also be installed in the vehicle 10, in particular Figure 1 In the commercial vehicle shown, the heat exchanger center axis M is oriented essentially vertically, so that the fuel cell exhaust gas B can enter the heat exchanger 18 at the first end region 20 of the heat exchanger in the lower position U and can also flow out of the heat exchanger 18 in the lower position U.

[0064] For example, Figure 10 and Figure 11 The heat exchanger 18 can be integrated into the vehicle 10 in such a way that, for efficient circulation of the ambient air L, the first wall 28 of the heat exchanger, which delimits the first portion 241 and the second portion 242 outward, i.e., toward the ambient air L, is oriented substantially parallel to the longitudinal direction of the vehicle and thus substantially parallel to the flow direction of the ambient air L when the vehicle is traveling forward. In this manner and type, efficient thermal interaction with the ambient air L can be achieved on both longitudinal sides of the heat exchanger 18.

[0065] Finally, it should be noted that, as an alternative or in addition to the use of ambient air L, the fuel cell exhaust gas flowing in the first flow volume of the heat exchanger can thermally interact with another, for example, liquid coolant. To this end, a flow volume for this liquid coolant can be provided on the outside of the first wall 28 of the heat exchanger, which can circulate in the coolant circuit of the vehicle.

Claims

1. A fuel cell exhaust system, in particular a fuel cell exhaust system for a commercial vehicle, comprising a heat exchanger (18) extending longitudinally in a longitudinal direction (W) of the heat exchanger and through which fuel cell exhaust gas (B) can flow, the heat exchanger having a first heat exchanger end region (20) and a second heat exchanger end region (22), wherein: The heat exchanger (18) has a fuel cell exhaust gas inlet region (26) in one end region of the heat exchanger between a first end region (20) and a second end region (22) of the heat exchanger and a fuel cell exhaust gas outlet region (38) in one end region of the heat exchanger between the first end region (20) and the second end region (22), wherein the heat exchanger (18) has a first heat exchanger flow volume (24) leading away from the fuel cell exhaust gas inlet region (20) in a longitudinal direction (W) of the heat exchanger and a second heat exchanger flow volume (30) connected to the first heat exchanger flow volume (24) and returning in the longitudinal direction (W) of the heat exchanger toward the fuel cell exhaust gas inlet region (26), the first heat exchanger flow volume (24) being separated from the coolant flow volume by a first heat exchanger wall (28) and separated from the second heat exchanger flow volume (30) by a second heat exchanger wall (32).

2. The fuel cell exhaust device according to claim 1, characterized in that: The first heat exchanger flow volume (24) surrounds the second heat exchanger flow volume (30) preferably substantially concentrically with respect to a heat exchanger center axis (M) extending substantially in the longitudinal direction (W) of the heat exchanger.

3. The fuel cell exhaust device according to claim 1, characterized in that: The first heat exchanger flow volume (24) and the second heat exchanger flow volume (30) are arranged alongside one another in a layered arrangement transverse to the longitudinal direction (W) of the heat exchanger.

4. The fuel cell exhaust device according to claim 3, characterized in that: The heat exchanger second flow volume (30) is arranged transversely to the heat exchanger longitudinal direction (W) between a first portion (241) of the heat exchanger first flow volume (24) and a second portion (242) of the heat exchanger first flow volume (24).

5. The fuel cell exhaust device according to any one of claims 2 to 4, characterized in that: The heat exchanger inlet region (26) and the heat exchanger outlet region (38) are arranged on the first end region (20) of the heat exchanger, and the heat exchanger outlet region (38) is connected to the second flow volume (30) of the heat exchanger.

6. The fuel cell exhaust device according to any one of claims 1 to 4, characterized in that: A third heat exchanger flow volume (34) is provided which is connected to the second heat exchanger flow volume (30) and is directed away from the heat exchanger inlet region (26). The third heat exchanger flow volume (34) is separated from the second heat exchanger flow volume (30) by a third heat exchanger wall (36).

7. When referring back to claim 2, the fuel cell exhaust device according to claim 6 is characterized in that The second heat exchanger flow volume (30) preferably surrounds the third heat exchanger flow volume (34) substantially concentrically with respect to the heat exchanger central axis (M).

8. The fuel cell exhaust device according to claim 6 or 7, characterized in that: The heat exchanger inlet region (26) is arranged on the first end region (20) of the heat exchanger, the heat exchanger outlet region (38) is arranged on the second end region (22) of the heat exchanger, and the heat exchanger outlet region (38) is connected to the third flow volume (34) of the heat exchanger.

9. The fuel cell exhaust device according to any one of claims 1 to 8, characterized in that: A bypass flow path is provided from the first heat exchanger flow volume (24) or the heat exchanger inlet region (26) to the heat exchanger outlet region (38), which can be selectively opened or closed for throughflow.

10. The fuel cell exhaust device according to claim 6 or any one of claims 7 to 9 when referring back to claim 6, characterized in that In the region of the second wall (32) of the heat exchanger, at least one bypass flow opening (50) is provided, which can be selectively opened or closed for throughflow by means of a closing device (52).

11. The fuel cell exhaust device according to claim 10, characterized in that: The at least one bypass flow opening (50) is arranged at the second end region (22) of the heat exchanger.

12. The fuel cell exhaust device according to any one of claims 1 to 11, characterized in that: A plurality of first heat transfer ribs (42) are provided on the outer side of the first wall (28) of the heat exchanger facing the coolant flow volume.

13. The fuel cell exhaust device according to claim 12, characterized in that: The first heat transfer ribs (42) extend substantially perpendicular to the longitudinal direction (W) of the heat exchanger.

14. The fuel cell exhaust device according to any one of claims 1 to 13, characterized in that: A plurality of second heat transfer ribs (44) are provided on the inner side of the first heat exchanger wall (28) facing the first flow volume (24) of the heat exchanger.

15. The fuel cell exhaust device according to claim 14, characterized in that: The second heat transfer ribs (44) extend substantially parallel to the longitudinal direction (W) of the heat exchanger.

16. A fuel cell exhaust device according to claim 2 or any one of claims 3 to 15 when referring back to claim 2, characterized in that The heat exchanger inlet region (26) is designed so that the fuel cell exhaust gas (B) enters the heat exchanger first flow volume (24) at the heat exchanger inlet region (26) with a fuel cell exhaust gas inflow direction (E) oriented tangentially with respect to a heat exchanger central axis (M).

17. The fuel cell exhaust device according to any one of claims 1 to 16, characterized in that: A liquid discharge device (46) is provided for discharging liquid from the heat exchanger (18).

18. The fuel cell exhaust device according to any one of claims 1 to 17, characterized in that: The fuel cell exhaust device (16) is designed for installation with a heat exchanger longitudinal direction (W) oriented essentially vertically, so that the heat exchanger first end region (20) forms the heat exchanger lower end region and the heat exchanger second end region (22) forms the heat exchanger upper end region.

19. A vehicle, in particular a commercial vehicle, comprising a fuel cell exhaust system (16) according to one of claims 1 to 18.

20. The vehicle according to claim 19 in combination with claim 18, characterized in that The fuel cell exhaust device (16) is installed in a vehicle (10) so that the heat exchanger first end region (20) is positioned lower in the vertical direction (V) and the heat exchanger second end region (22) is positioned upper in the vertical direction (V).

21. The vehicle according to claim 19 or 20, characterized in that The fuel cell exhaust device (16) is installed in a vehicle (10) so that the heat exchanger (18) can be circulated by ambient air (L) surrounding the vehicle (10) as a cooling medium.

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