Device for humidifying a gas flow and air system for supplying at least one fuel cell stack with air

Abstract

The invention relates to a device (100) for humidifying a gas flow (1) with the aid of an additional, water-containing gas flow (2), having a housing (3) through which a respective flow path (4) for each of the two gas flows (1, 2) extends, wherein the flow path (4) for the additional, water-containing gas flow (2) runs via a plurality of parallel flow channels (5) by means which a geodetically higher inlet region (6) is connected to a geodetically lower outlet region (7) that is equipped with water-collecting elements (8) in order to separate water from the additional, water-containing gas flow (2). The invention also relates to an air system having a device (100) according to the invention.

Description

[0001] Description for humidifying a gas stream and to at least one with air

[0002] The invention relates to a device for humidifying a gas stream, which may in particular be an air stream that is supplied to a fuel cell stack via an air system. The invention therefore further relates to an air system for supplying at least one fuel cell stack with air, which comprises a device according to the invention.

[0003] The preferred field of application of the invention is mobile fuel cell systems or vehicles in which drive energy is generated by at least one fuel cell stack.

[0004] State of the art

[0005] In vehicles where drive energy is supplied by one or more fuel cell stacks or fuel cell systems, the oxidant oxygen from the ambient air is generally used to react with hydrogen in the fuel cell to form water or water vapor, thereby generating electrical power through electrochemical conversion. The ambient air is fed to the fuel cell stack using an air conveying and compression system, as the electrochemical conversion requires a certain air mass flow and a certain pressure level. The air is generally compressed using a thermal turbomachine driven by an electric motor. Optionally, this can be coupled to a turbine, which is fed with the moist air or exhaust air escaping from the fuel cell stack. In this way, the exhaust gas enthalpy can be used for energy recovery.In multi-stage air compression with several air compressors or shaft-rotor units, at least one shaft-rotor unit is usually connected to an exhaust air turbine.

[0006] Since the air heats up considerably during compression, it is cooled using a cooler before entering the fuel cell stack. For further conditioning, the air is usually humidified. Humidifying the air is intended to prevent the fuel cell membranes from drying out. This is because the proton conductivity of the membranes depends largely on a sufficient amount of water being embedded in their structure. A gas-to-gas membrane humidifier can be used for humidification, in which the air to be humidified is passed past the moist exhaust air. The exhaust air then releases some of the water it contains into the air to be humidified. The remaining water in the exhaust air can be separated from the exhaust air stream using a water separator, which is particularly advantageous if the exhaust air stream is subsequently fed into a turbine for energy recovery.The residual water contained in the exhaust air can damage the turbine through droplet impact or erosion.

[0007] Accordingly, a multitude of different components are used in an air system. Since the available installation space is limited, especially in mobile applications, the present invention aims to reduce the number of components and thus the installation space required.

[0008] To achieve this object, the device having the features of claim 1 and the air system having the features of claim 9 are proposed. Advantageous further developments of the invention can be found in the respective subclaims.

[0009] Disclosure of the invention

[0010] A device for humidifying a gas stream with the aid of a further water-containing gas stream is proposed. The device comprises a housing through which a flow path for each of the two gas streams extends. The flow path for the further water-containing gas stream leads through several parallel flow channels, via which a geodetically higher inlet region is connected to a geodetically lower outlet region, in which water trapping elements are arranged to separate water from the further water-containing gas stream.

[0011] With the help of the proposed device, not only can a gas stream be humidified, but also a humid or water-containing gas stream can be dehumidified or dried. This means that the proposed device performs the function of a humidifier and a water separator. By integrating these functions into one device, the number of components in an air system can be reduced. This helps save space, weight, and costs. When used in an air system to supply a fuel cell stack with air, seals and interfaces can also be reduced. Furthermore, fewer assembly steps are required to manufacture the air system.

[0012] Due to the laminar flow of the water-containing gas stream in the area of ​​the flow channels, a portion of the water contained is already separated. A further portion, preferably the entire remaining portion, is separated from the gas stream in the outlet area by means of the water trap elements. This eliminates the need for a separate downstream water separator.

[0013] Preferably, the flow channels for the additional water-containing gas flow are oriented substantially vertically in the final installation position of the device. This allows gravity to be used for water transport in addition to the gas flow. Since the device may be tilted in mobile applications, for example, when driving uphill, the orientation of the flow channels can vary.

[0014] The installation position of the device should preferably be selected so that the inlet area is always geodetically higher, i.e., above the outlet area. The additional water-containing gas flow is thus guided from the inlet area through the flow channels into the outlet area, essentially from top to bottom. Water contained in the gas flow in the form of water vapor is separated as liquid water through condensation effects, which are attributable, for example, to temperature and / or pressure differences.

[0015] Furthermore, the inlet region and / or the outlet region is / are preferably oriented substantially perpendicular to the flow channels, so that the water-containing additional gas flow is deflected upon entering the flow channels and / or upon exiting the flow channels. This deflection enables a low overall height of the inlet region and / or the outlet region, thus further reducing the installation space requirement. Furthermore, the gas flow can be distributed to all flow channels via the inlet region. The gas flows exiting the flow channels can be combined via the outlet region.

[0016] The flow path for the gas stream to be humidified is preferably oriented substantially perpendicular to the flow channels of the flow path for the water-containing additional gas stream, so that the two gas streams pass each other in crossflow. This gas flow guidance promotes the humidification of the gas stream to be humidified, allowing a large portion of the water contained in the additional gas stream to be separated.

[0017] According to a preferred embodiment of the invention, the water collection elements arranged in the outlet region protrude from a bottom of the outlet region into the flow path of the additional water-containing gas stream, such that the additional water-containing gas stream flows over them. The height of the water collection elements is therefore less than the height of the outlet region, such that the flow path is only partially restricted by the water collection elements. Water droplets carried along by the gas stream cling to the water collection elements and slide down them under the force of gravity, so that they collect at the bottom of the outlet region. The water collection elements are preferably connected in series in the flow direction of the additional water-containing gas stream. This means that the water collection elements are flowed over one after the other, such that the separation rate increases with the number of water collection elements over which the flow occurs.

[0018] Furthermore, the water collection elements are preferably designed to be concave in the flow direction of the additional water-containing gas stream. Alternatively or additionally, it is proposed that the water collection elements be tilted against the flow direction of the additional water-containing gas stream. Both measures – either alone or in combination – lead to the formation of a collection chamber in which water separated from the gas stream can be collected. The flow pressure of the gas stream flowing over the water collection elements simultaneously forces the water collected in the collection chambers to one side, from where it can be drained away.

[0019] In a further development of the invention, it is proposed that the outlet area be connected to a water drain via at least one opening, preferably arranged at the bottom. The at least one opening can, for example, extend along one side of the outlet area, so that water driven to this side flows into the water drain via the opening.

[0020] The water drain is preferably located below the outlet area. The water driven to at least one side of the outlet area can thus be drained into the water drain by gravity. Furthermore, the water drain is preferably funnel-shaped. The water flowing through at least one side of the outlet area can be collected via the funnel shape and drained from the device at a preferably central point. The housing can form a connection piece at this point, which simplifies the connection of a water pipe.

[0021] Since the proposed device can be used in particular in an air system for supplying at least one fuel cell stack with air, an air system comprising a device according to the invention is also proposed. In the air system, the device can be used to humidify an air stream supplied to the fuel cell stack. In particular, the moisture contained in the air or exhaust air exiting the fuel cell stack can be used for humidification. The additional water-containing gas stream is therefore an additional air stream.

[0022] The air system preferably has an air supply path for supplying air and an exhaust path for removing the air escaping from the fuel cell stack. The air supply path leads via the flow path for the gas stream to be humidified, and the exhaust path leads via the flow path for the additional water-containing gas stream through the housing of the device. The device is thus integrated into both the air supply path and the exhaust path of the air system. Thanks to the additional separation function of the device, a separate water separator is no longer required. This helps save space, weight, and costs. Furthermore, seals and interfaces in the air system are reduced.

[0023] The invention and its advantages are explained in more detail below with reference to the accompanying drawings. These show:

[0024] Fig. 1 shows a simplified longitudinal section through a device according to the invention and

[0025] Fig. 2 is a simplified, partially perspective sectional view through a device according to the invention.

[0026] Detailed description of the drawings

[0027] Figure 1 shows a device 100 according to the invention for humidifying a gas stream 1. The gas stream 1 can, for example, be an air stream that is supplied to a fuel cell stack (not shown) via an air supply path of an air system. For humidification, the gas stream 1 is guided past a further water-containing gas stream 2 within a housing 3 of the device 100, wherein the two gas streams 1, 2 use separate flow paths (4). Mixing of the gas streams 1, 2 therefore does not occur. The flow path 4 for the further water-containing gas stream 2 extends over a plurality of parallel flow channels 5, an inlet region 6 upstream of the flow channels 5 and an outlet region 7 downstream of the flow channels 5. The gas stream 2 is distributed to the flow channels 5 via the inlet region 6.The individual gas streams emerging from the flow channels 5 are reunited via the outlet area 7.

[0028] Due to the laminar flow in the flow channels 5, a portion of the water contained in the gas stream 2 is already separated and released into the other gas stream 1. Another portion remains in the gas stream 2 and reaches the outlet region 7 with the gas stream 2. Water collection elements 8 are arranged in the outlet region 7 and extend from a bottom 9 of the outlet region 7 into the flow path 4. The water collection elements 8 are arranged one behind the other in several regions so that the gas stream 2 flows over them one after the other. The water collection elements 8 are also concave in the flow direction of the gas stream 2 so that water droplets 12 carried by the gas stream 2 adhere to the water collection elements 8 and slide down them, collecting at the bottom 9 of the outlet region 7.The flow pressure of the gas stream 2 drives the water droplets 12 collecting at the bottom 9 outward to one side, which is connected via an opening (not shown) running along the side to a water drain 10 located below the outlet area 7 and separated from it only by the bottom 9. The water drain 10 is funnel-shaped and has a centrally located connection piece 11 for connecting a water pipe (not shown). The gas stream 2, freed of water, is discharged via a further opening 13 in the bottom 9 of the outlet area 7.

[0029] Figure 2 shows a further device 100 according to the invention for humidifying a gas stream 1 with the aid of a further water-containing gas stream 2. The device 100 has a housing 3, which is shown in section in Figure 2. The illustration thus allows the internal workings to be seen. In particular, the flow paths 4 for the two gas streams 1, 2 can be seen from Figure 2. The entry and exit of the gas stream 1 to be humidified are each from the side. The further water-containing gas stream 2 is introduced from above into the inlet region 6 and fed via the flow channels (not shown) to the outlet region 7. Instead of the flow channels, a chamber 14 for receiving an insert forming the flow channels 5 is shown. The insert has been omitted in Figure 2.Figure 2 shows the concave water collection elements 8 arranged in rows, as well as an adjoining opening 13 in the base 9 of the outlet area 7, through which the gas stream 2, freed from water, is discharged. The water collecting at the base 9 is driven to one side by the flow pressure and from there, via another opening (not shown), flows into the water outlet 10, which is also funnel-shaped here and ends in a connecting piece 11.

Claims

Claims 1. Device (100) for humidifying a gas stream (1) with the aid of a further water-containing gas stream (2), comprising a housing (3) through which a flow path (4) for each of the two gas streams (1, 2) extends, wherein the flow path (4) for the further water-containing gas stream (2) leads via a plurality of parallel flow channels (5) via which a geodetically higher inlet region (6) is connected to a geodetically lower outlet region (7) in which water collecting elements (8) for separating water from the further water-containing gas stream (2) are arranged.

2. Device (100) according to claim 1, characterized in that the inlet region (6) and / or the outlet region (7) is / are aligned substantially perpendicular to the flow channels (5), so that the water-containing further gas flow (2) is deflected upon entry into the flow channels (5) and / or upon exit from the flow channels (5).

3. Device (100) according to claim 1 or 2, characterized in that the flow path for the gas stream (1) to be humidified is aligned substantially perpendicular to the flow channels (5) of the flow path (4) for the water-containing further gas stream (2), so that the two gas streams (1, 2) are guided past each other in cross flow.

4. Device (100) according to one of the preceding claims, characterized in that the water collecting elements (8) protrude from a bottom (9) of the outlet region (7) into the flow path (4) of the water-containing further gas stream (2) so that they are overflowed by the water-containing further gas stream (2).

5. Device (100) according to one of the preceding claims, characterized in that the water collecting elements (8) are connected in series in the flow direction of the water-containing further gas stream (2).

6. Device (100) according to one of the preceding claims, characterized in that the water collecting elements (8) are concave in the flow direction of the water-containing further gas stream (2) and / or are tilted against the flow direction of the water-containing further gas stream (2).

7. Device (100) according to one of the preceding claims, characterized in that the outlet area (7) is connected to a water drain (10) via at least one opening, preferably arranged on the bottom side.

8. Device (100) according to claim 7, characterized in that the water drain (10) is arranged below the outlet area (7) and / or is funnel-shaped.

9. Air system for supplying at least one fuel cell stack with air, comprising a device (100) according to one of the preceding claims.

10. Air system according to claim 9, characterized in that the air system has an air supply path for supplying air and an exhaust air path for discharging the air emerging from the fuel cell stack, wherein the air supply path leads via the flow path (4) for the gas stream (1) to be humidified and the exhaust air path leads via the flow path (4) for the water-containing further gas stream (2) through the housing (3) of the device (100).

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