DE10056673A1 - System for conveying of surface inclusion and/or discharge of substance by fluid e.g. in fuel cell, comprises flow duct forming laminar fluid flow and with flow conducting unit effecting spatial rearrangement of fluid layers - Google Patents

Abstract

The at least one flow conducting unit is so arranged and formed, that the fluid layers (24) are rearranged so that the layer flows (20) of the laminar flow receive a transversal speed component.

Description

The invention relates to a device for promoting Surface absorption and / or surface release of a substance through a fluid comprising a flow channel in which a laminar flow of the fluid can be formed.

The invention further relates to a method for promoting Surface absorption and / or surface release of a substance through a fluid that flows in laminar flow.

A laminar flow of a fluid is internal Friction essentially without turbulence. The Reynolds number such a flow is very low. For a channel flow the flow change is at a Reynolds number of 2300. You can only see friction inside the flowing fluids between adjacent fluid layers. The have individual fluid layers in laminar flows different speed.

For example, laminar flows occur when atmospheric oxygen is supplied as an oxidizing agent in electrochemical cells. In fuel cells, for example, air is supplied with catalytically active, extensively extended electrodes to act as an oxidizing agent in the electrochemical reaction. The air itself is distributed on the surface of the electrodes by means of one or more flow channels. In particular, there is a gas diffusion electrode on one side of the flow channels, so that the oxygen from the air can diffuse over a large area to the gas diffusion electrode. Commercial fuel cells have a high power density and integration density, so that the flow channels have small structures (for example less than 1 × 1 mm ² ). In practice, the flow velocities are relatively low (in the order of a few m / s at most). This results in correspondingly low Reynolds numbers, so that very stable laminar fluid flows form in such flow channels.

The invention has for its object a device and to create a process in which the inclusion and / or delivery of a substance through the laminar flow Fluid over whose surface is optimized.

This object is achieved by the device mentioned at the beginning solved according to the invention in that at least one Flow guide device is provided, which in the Flow channel is arranged and is designed such that in the laminar flow a spatial redistribution of Fluid layers causes.  

Due to the laminar flow of the fluid, there is no turbu lente mixing of the fluid in the flow channel instead. This allows a concentration gradient to be recorded the substance or substances to be dispensed in the fluid starting from the Form the receiving surface or delivery surface. at is for example with air as fluid and oxygen as release substance the air in areas close to the surface of atmospheric acid fabric impoverished. Since the substance in the flow channel over the individual fluid layers essentially only by diffusion transversely to the direction of the laminar flow can, is the uptake or delivery of the substance by the laminar flowing fluid inhibited.

It is known to create turbulence structures like turbula gates or turbulence promoters to promote the through mix the fluid, which in turn creates the upper surface coverage and / or surface release of a substance is promoted because of the formation of a concentration gradient of the substance in the fluid is counteracted. The principle of operation of such turbulence-generating structures lies in an envelope of flow from laminar to door to cause bulent d. H. to generate high Reynolds numbers. To do this, however, the flow rate must be increased and in addition, the dimensions of the flow channel must be sufficient be great. Furthermore, such turbulence-generating Structures causes high pressure drops.

In that, according to the invention, the laminarity of the flow remains, however, fluid layers in the laminar Flow will be shifted, building a conc tion gradient of the substance in the fluid counteracted.  

It is the surface absorption or surface release of the Substance improved by the fluid. The escapement of the Substance in the laminar flowing fluid is thereby ent counteracted. Since there is no turbulent mixing, there are only very small pressure drops.

The device according to the invention can thus be advantageously used use in fuel cells because the surface release of Oxygen is conveyed in a laminar airflow, however on the other hand, the cross section of a flow channel is only mini is narrowed while maintaining the low-loss lamina ren character of the current. Especially for mobile use ed fuel cells (e.g. fuel cells for a motor vehicle), slight pressure drops can become too great Reduce system efficiency. By inventing device according to the invention, which ensures that the laminar The character of the flow is maintained Avoid such harmful pressure losses as much as possible.

The at least one flow guide is advantageously device arranged and designed so that by this Layer currents of the laminar flow a transverse Ge received speed component. This allows ins special stratified currents with respect to the surface of the laminar flow deeper areas towards the Deflect the surface and streams of layers from near the surface Redirect areas into deeper areas so as to build up a concentration gradient of the substance in the fluid counteract and thus the transport inhibition of the substance with regard to surface uptake or surface release reduce.  

Favorably, the at least one flow guide device arranged and designed so that a Umschich device of fluid layers of the laminar flow in such a way follows that fluid layer flows out of the receiving surface or delivery surface of the fluid closer regions of the Flow diverted to more distant areas become. This results in poor fluid layers on the substance rich in surface release or substance Fluid layers during surface absorption in substance-rich or substance-poor areas due to their distance from the Surface deflected.

The at least one flow is then also favorable guide device arranged and designed so that Fluid layer flows from the receiving surface or Ab delivery surface of the fluid more distant areas of the Flow in areas closer to this surface be directed. At the surface absorption of a substance become fluid layer flows from low-substance areas redirected to the surface, where the substance is to be able to take and when dispensing become more substantial Layers of fluid deflected towards the surface in order for to ensure an improvement in substance delivery.

It is particularly advantageous if the at least one Flow control device is arranged and designed that the flow in the flow channel is essentially turbulent free is. As a result, there are no pressure drops or only very much low pressure losses and especially none Pressure oscillations, for example, the efficiency  Fuel cell, which is supplied with atmospheric oxygen, ver could wrestle.

The at least one flow control device is expediently device arranged and designed so that fluid flows cross different fluid layers. This will make one effective spatial shifting of fluid layers, so the formation of a concentration gradient of the Counteracting substance in the laminar flow and thus the surface uptake or surface release of the substance to improve.

It is favorable if the at least one flow guide device comprises a structure whose dimensions are transverse to Flow direction of the laminar flow vary. To this Way, the fluid layer flows of individual fluid layers a transverse speed component is given in order to effect a spatial shift.

It is favorable if the at least one flow guide device is arranged and designed so that along the Flow channel an essentially regular redeployment of fluid layers. The longitudinal direction of the flow channel is defined so that it is parallel to the main flow direction of the laminar flow is. Through one of the like arrangement and training is ensured that at the Receiving surface or discharge surface of the fluid in the Flow channel prevail substantially similar conditions and highly localized increases in concentration or concentration lowering of the substance near the surface Layers are avoided.  

It is advantageous if the at least one flow guide device a plurality of flow-guiding structures includes which with respect to the longitudinal direction of the flow direction are arranged in a regular sequence. Thereby can be an oscillatory space in a simple manner liche redistribution with respect to a medium Concentration of the substance at the surface is low Standard deviation, so that is highly localized Concentration gradients are avoided.

In a first embodiment, the at least one Flow control device a flow turner structure, which gives the fluid a twist in the laminar flow. It has shown in simulation calculations that such Structures with little construction effort a signi noticeable improvement in surface release, for example cause a substance through the laminar flowing fluid. For example, the efficiency of a fuel cell with air as a laminar flowing fluid and oxygen as a substance to be dispensed on electrodes of the fuel cell through a flow turner structure a twelve percent Performance increase in terms of current density at the Flow turner structure reached.

In particular, it is advantageous if the flow turner structure has a spiral structure to the fluid in the to give a laminar flow a swirl.

It is advantageous if a longitudinal axis of the flow turning structure parallel to the longitudinal direction of the flow channel  is aligned. This leaves the main flow direction the laminar flow, while at the same time for the spatial shifting of the fluid layer flows is provided.

In a variant of an embodiment it is provided that the flow turner structure is arranged in the flow channel is. For this purpose, for example, it can enter the flow channel be laid.

In a further variant of an embodiment, the Flow turner structure formed by the channel walls themselves. For this purpose, the channel walls can have a concave structure, d. H. "positive" features emerge from the canal walls. It can also be provided that the channel walls have a convex Have structure for forming the flow turner structure; this means that "negative" traits enter the channel walls are relaxed.

In a further embodiment, the flow guide comprises device one or more displacement bodies, which There are barriers to the flow in the flow channel. On such The laminar flow can partially displace displacement bodies "peel", i.e. H. it will be a redirection of Fluid layer flows of the laminar layer flow causes which in turn leads to a spatial shift. the like displacement body can be particularly cost produce cheaply and easily in one example Use existing flow channel wisely.

In a variant of this embodiment, a Ver urging body is wedge-shaped. simulations  have shown that in fuel cells neglect pressure losses such wedges performance improvements can deliver on the order of 10%.

It is beneficial if a wedge-shaped displacement body is arranged so that its oblique wedge surface of the Flow direction facing the laminar flow. This allows an effective "peeling" to occur effective spatial redeployment of fluid layers cause.

It is particularly advantageous if the flow guide device at least one pair of wedge-shaped displacement body includes. It has been shown that, for example Installation of such a pair of displacers on the ge entire length of a flow channel with an effective Ab pressure drop is negligible and an improvement in performance, for example, in a distillery material cell occurs, which is of the order of 10%.

It is special to effect an effective redeployment advantageous if the inclined wedge surfaces of a ver pair of urging bodies are arranged transversely to one another.

It is also favorable if the displacement body of a ver pair of urging bodies in a transverse direction of the flow channel are arranged offset to each other, so as an effec effective redeployment.  

Furthermore, it is advantageous if the oblique wedge surfaces of one Displacement body pair of opposing components vectors with respect to the longitudinal direction of the flow channel to have an effective "peeling" of Fluid layer flows to cause a spatial cause redistribution.

In a variant of an embodiment, a Ver urging body arranged and designed so that Fluid layer flows from first walls of the flow channel in Are deflectable towards the second walls of the flow channel. In a further variant, a displacement body is like this arranged and designed that fluid layer flows from closed walls of the flow channel towards the open Channel walls can be deflected. In particular, these combine both variants to create an effective one enable spatial exchange of fluid layers.

The invention further relates to a use of the above Device in an electrochemical cell. As a result of that according to the invention the need for a flow turnaround from laminar to turbulent at most a very low pressure drop. You also have to no unfamiliar operating conditions, such as high ones Flow velocities, the electrochemical cell are forced. By the device according to the invention can the electrochemical cells in their optimal Operate parameter range, with an optimal supply is ensured by oxygen. For example, use the device in an electrolytic cell.  

The invention can be very particularly advantageous Use the device in a fuel line. fuel cells and in particular mobile fuel cells for example, in a motor vehicle have high integers density and there are high demands on the System efficiency posed. The flow used there channels have small channel dimensions and the flow speed is relatively low. Through the fiction appropriate device is used for good deployment for example of oxygen from a laminar flow of air Electrode surfaces provided, with pressure losses largely are avoided since there is no flow change from laminar in is turbulent, d. H. the device continues with small Reynolds numbers can be operated. In particular, the Flow channel to an electrode around this oxygen supply. The oxygen comes especially from laminar flowing air.

According to the invention, the above-mentioned object is also used in a solved the above-mentioned method, in which by a Flow guide fluid layers of the laminar Flow can be shifted.

This procedure indicates the already in connection with the Advantages of the device according to the invention.

Further advantageous refinements of the method and their Advantages are already in connection with the Invention according device and its use explained.

The following description of preferred embodiment examples serves in connection with the drawing of the closer Explanation of the invention. Show it:

Fig. 1a, 1b in a schematic representation of a laminar flow in a closed channel with a rectangular cross-section in a longitudinal sectional view ( Fig. 1a) and a cross-sectional view ( Fig. 1b);

FIGS. 2a, 2b, the surface of dispensing a substance from a fluid, which channel flows in a flow in laminar flow, wherein the flow channel of the discharge surface of the fluid facing openly in a longitudinal sectional view (Fig. 2a) and a cross-sectional view (Fig. 2 B);

Fig. 2c shows the profile of the concentration of the substance delivery over the height of the flow channel according to Figures 2a, 2b.

FIGS . 3a, 3b, 3c, 3d in each case variants of a flow turner structure as a flow guiding device which is arranged in a flow channel;

Figure 4 shows the ratio of the local current density of an electrochemical cell, which air is fed in a laminar flow in a flow channel, with a flow turret structure according to Figure 3a is arranged in a portion of the flow channel .

Fig. 5 shows a further variant of a flow turner structure, which is arranged in a flow channel with a semicircular cross section, in a schematic longitudinal sectional view parallel to the surface (right part) and in cross section (left part);

FIG. 6a, the Strömungswenderstruktur in longitudinal sectional view according to FIG surface 5 perpendicular to the fluid.

FIG. 6b is a cross-section of the flow channel according to FIG 6a, in which walls of the flow channel has a concave structure is formed.

FIG. 6c shows a cross section of the flow channel according to FIG 6a, in which the walls of the channel Strö mung a convex structure is formed.

Fig. 7a, a further embodiment of a flow guide which is disposed cut in a flow channel with a square cross, wherein the Strö mungsleiteinrichtung comprises a wedge-shaped displacement body, in longitudinal sectional view parallel to the fluid surface (right part of the picture) and in cross section (left panel);

FIG. 7b the flow channel shown in FIG 7a is a longitudinal sectional view transverse to that of the FIG. 7a.

Fig. 7c drängungskörpern another embodiment arranged in a flow channel Ver;

Fig. 8a shows a further embodiment of a flow guide bodies with displacement, wherein a pair of wedge-shaped Ver displacement body in the flow channel is arranged, in a longitudinal sectional view (right part of the picture) and in cross section (left panel);

FIG. 8b shows a longitudinal sectional view of the flow channel according to Fig 8a transverse to the view of Figure 8a..;

FIG. 8c another embodiment of the paired displacement bodies;

. Fig., The current density of a fuel cell, which is guided through a flow channel according to Fig 8a oxygen as the oxidant by means of air in laminar flow to 9 I, above the channel length P of the flow channel; It compares the current density when a flow control device with paired wedge-shaped displacement bodies is arranged in the flow channel and accordingly without such displacement bodies. The diagram is the result of a simulation;

FIG. 10a is a further embodiment of a flow guide in a longitudinal sectional view (right part of the picture) and a cross-sectional view (left panel);

. FIG. 10b shows the flow channel according to Fig 10a is a longitudinal sectional view transverse to that of Fig. 10a;

Figure 10c is another embodiment of a flow guide which comprises arranged in the flow passage displacement body.

FIG. 11a, 11b a further embodiment in longitudinal sectional views (Figure 11a, right part image; Fig. 11b.) And in cross section (Figure 11a, left panel.) By a cut in a flow channel with a square cross arranged displacement body, wherein in the Shown variants of the Ver displacement body is formed by a bump formed in a sheet;

Figure 11c, 11d a further embodiment in longitudinal sectional views (11c, 11d,.) Bodies arranged in a flow channel with a square cross-section displacement, wherein the displacement body are formed by sheets in insert formed protrusions in the illustrated variants.

Fig. 12a, 12b, 12c, 12d further variants of a further example of execution from a channel being in a flow of square cross section arranged flow guide, wherein the flow guide baffles.

A laminar flow 10 of a fluid 12 ( Fig. 1a) is a flow with internal friction but without vortex formation. The internal friction is a consequence of the force between the molecules of the fluid. The friction occurs only inside the flowing medium between adjacent liquid layers 14 a, 14 b, the individual liquid layers having different speeds and sliding past one another. It then forms as a function of a flow channel 16 , in which the fluid 12 flows, a speed profile 18 , wherein in individual liquid layers 14 a, 14 b fluid layer flows of different speeds are present.

The laminar flow 10 , which is composed of the sum of the fluid layer flows, has a main flow direction 22 .

Since the flow velocity in fluid layers 24 un directly on channel walls 26 of the flow channel 16 is zero, the shape of the speed profile 18 depends on the formation of the flow channel 16 .

In FIGS. 1a, 1b, a flow channel is shown with quadrati schem cross-section 28 which is closed on all sides.

A laminar flow 10 is formed when the Reynolds number of the flow is small and, in the case of a channel flow, is in particular less than 2300. Since the Reynolds number is defined as the product of a characteristic length and the flow rate divided by the kinematic viscosity, there is a laminar flow 10 before when the transverse dimensions of the flow channel 16 are small and the flow velocity is small.

In the case of electrochemical cells and in particular fuel cells, atmospheric oxygen is supplied in an air stream as an oxidizing agent to catalytically active, extensive electrodes (not shown in the drawing). In particular in mobile fuel cells, flow channels with small dimensions are provided in order to achieve a high integration density and power density. Accordingly, the Reynolds number of the air flow is low and the flow itself in such flow channels is laminar with high stability. Such a flow channel 30 for an electrochemical cell is shown schematically in FIG. 2a. This flow channel 30, for example, has a substantially square cross-section 32 (Fig. 2b) and is open in the example shown in Fig. 2 embodiment on a channel side 34 down. As a result, from the laminar air flow 36 as a fluid flow on the open channel side 34, atmospheric oxygen can be removed as a delivery substance, ie a delivery surface of the air flow 36 faces the open channel side 34 , and an oxygen concentration of the air flow takes place via this delivery surface.

The oxygen transport in the air flow 36 between an individual fluid layers of the laminar flow transverse to the main flow direction 38 takes place essentially only by diffusion. Due to the formation of the air flow 36 as a laminar flow, no further material exchange takes place. This means that a concentration gradient with respect to the oxygen content in the air flow 36 is formed perpendicular to the open side 34 ( FIG. 2c). The transport of atmospheric oxygen in a transport direction 40 transverse to the main direction of flow 38 is inhibited and the closer a fluid layer is to the delivery surface and thus to the open channel side 34 , the easier such an air layer can release atmospheric oxygen. Accordingly, as shown in FIG. 2 c, the oxygen concentration as a substance which releases the air as a fluid is reduced in regions 42 near the surface and increased in regions 44 remote from the surface. A concentration gradient is thus formed along the substance transport direction 40 and thus perpendicular to the open channel side 34 in the laminar air flow 36 .

In a first exemplary embodiment of a device according to the invention, as shown in FIG. 3a, a flow guide device, designated as a whole by 48, is arranged in the flow channel 30 .

The flow guide device 48 comprises a flow turner structure 50 , which is of spiral design. This flow turner structure 50 gives a fluid flow 52 in the flow channel 30 a swirl, so that based on the open channel side 34 fluid layers are spatially shifted and in particular with respect to the substance transport direction 40 are shifted.

As a result, fluid layer flows from the open channel side 34 to more distant areas in this area and vice versa fluid layer flows from closer areas to more distant areas. Fluid layers with a lower proportion of substance due to the substance release by the fluid there from the open channel side closer areas are thus led away from the surface of the fluid and more substantial fluid layers are guided to the surface in order to collectively relate the substance to the total flow to care. (The situation is reversed accordingly if a substance is to be taken up on the surface of the fluid.) This spatial shifting of the fluid thus counteracts the formation of a concentration gradient, as shown in FIG. 2c, and thus overall the substance release improves over the surface of the fluid flow 52 . (Accordingly, the substance absorption is improved if a substance is added to the surface.)

In the exemplary embodiment shown in FIG. 3a, a spiral flow turner with a spiral angle of 180 ° is arranged in the flow channel 30 . However, angles of rotation greater or less than 180 ° can also be provided. A longitudinal direction of this flow turner structure 50 is arranged essentially parallel to a longitudinal direction of the flow channel 30 and thus also aligned essentially parallel to a main flow direction of the fluid flow 52 .

The length of the Strömungswenderstruktur 50 corresponds in this embodiment substantially to the length of the open channel side 34, the length of the flow Wender the length of the surface over which the recording substance delivery or substance that is structurally 50 corresponds in its dimensions is performed.

The view 54 shows the flow turner structure 50 in the flow channel 30 in cross section.

In the further exemplary embodiment shown in FIG. 3 b, the flow guiding device comprises a flow turning structure 56 , which comprises a plurality of spiral structures 58 arranged spaced apart in the flow channel 30 . A single spiral structure has an angle of rotation of, for example, 180 °.

In the exemplary embodiment shown in FIG. 3c, a corresponding flow turner structure 60 is constructed in the same way as the flow turner structure 56 according to FIG. 3b, but the individual spiral structures 58 are now connected via webs 62 . As a result, the flow turner structure 60 can be handled more easily and, in particular, it can be mounted in the flow channel 30 in a more simple manner.

In the further exemplary embodiment of a flow turner structure 64 shown in FIG. 3d, this is designed as a spiral belt, which regularly comprises successive spiral structures 66 . A chain of spiral structures 66 is thus formed.

FIG. 4 shows a diagram which is the result of a numerical simulation on a flow channel according to FIG. 3a with a flow turner structure 50 , but this flow turner structure is not arranged over the entire length of the flow channel, but only over a section. P is a location in the flow channel in its longitudinal direction. One end of the flow turner structure 50 is arranged at position 68 and has a length of 4 mm. The flow channel itself has a length of approximately 300 mm, ie the section of the flow channel which is occupied by the flow turner structure 50 is approximately 1.3% based on the total length of the flow channel.

Plotted on the ordinate is a current density distribution V, determined numerically in simulation, which is defined as the current density with flow turner structure 50 in relation to the current density without flow turner structure 50 in relation to 1. The diagram therefore shows the percentage increase due to the flow turner structure 50 .

The current density is the current density in an electro chemical cell due to electrochemical reactions, whereby this is determined by the supply of oxygen as oxidation medium. This oxygen supply is in turn determined by the mass transfer of atmospheric oxygen from the flow of the Air as a laminar flowing fluid.

As can be seen from the diagram in FIG. 4, the flow turner structure 50 in the section of the flow channel causes an increase in the current density locally up to 12%. The increase in current density is not limited to the section itself, but extends over several centimeters of the channel length and approximately over approximately 17% of the channel length, although the flow inverter structure 50 only occupies approximately 1.3% of this channel length.

The flow turner structure 50 thus significantly promotes the release of atmospheric oxygen through the surface of the air flow by spatially shifting fluid layers of the laminar flow and, in particular, fluid layer flow is given a swirl and this receives a transverse velocity component in the area of the flow turner structure 50 .

In a further embodiment, which is shown in FIGS. 5, 6a, there is a tubular flow channel 70 with a semicircular cross section 72 . A spiral structure 76 is arranged on channel walls 74 , which gives the laminar flowing fluid a swirl and thus causes a shifting of fluid layers in relation to a cross-sectional direction 78 .

To an open channel side toward 80 can then be a substance from the fluid and remove this open channel page 80 can be a substance introducing into the fluid, without it being possible to prevent a strong concentration gradient due to the laminar flow, the dispensing or aspirating.

The structure 76 can be formed in a simple manner by integrating it into the channel walls 74 , the structure 76 being able to be produced, for example, by embossing or pressing or injection molding. Undercuts should be avoided if possible.

In Fig. 6b is a variant of a structure 76 is shown which includes a train 82 which is formed convexly in the channel walls 74, that is embedded in it.

In Fig. 6c a concave train 84 is shown as a further example, which emerges from the channel walls 74.

In a further exemplary embodiment, which is shown in FIGS . 7a, 7b, a flow channel 86 has, for example, a square cross section 88 and is open to one side 90. A wedge-shaped displacement body 92 is arranged in the flow channel 86 or it is part of the flow channel 86 .

The displacement body 92 has an oblique wedge surface 94 and a further wedge surface 96 . The other wedge surface 96 is preferably having its normal parallel to the longitudinal direction of the flow channel 86 and thus arranged is transverse to the main flow direction of the fluid in the flow channel 86th

In the embodiment shown in Fig. 7a, 7b he extends the displacement body 92 over the entire cross section of the flow channel; ie a width of the further wedge surface 96 corresponds essentially to the inner distance from walls 98 a, 98 b of the flow channel 86 .

The displacement body 92 occupies only a part 100 of the height of the flow channel 86 , for example half the height of the flow channel 86 (left partial image of FIG. 7a).

In the embodiment shown in FIG. 7a is the oblique wedge surface 94 of the main flow direction of the fluid supplied Wandt, ie the oblique wedge surface 94 is perpendicular to a bottom 102 of the flow channel 86.

A laminar flowing fluid in the flow channel, ie fluid flowing in liquid layers with fluid layer flows of different speeds, strikes the displacement body 92 and in particular its oblique wedge surface 94 and is thereby deflected. This causes fluid layers to "peel" from duct walls and in particular from duct walls 98 a and 98 b, and thus a shifting of fluid layers takes place (compare FIGS . 7a and 7b). Because the displacement body 92 is arranged only in a partial region of the flow channel 86 and thus the laminar flow and in particular the fluid layer flows have to flow around it, at least parts of the fluid layer flows receive a transverse speed component in the direction of the open side 90, that is to say to the receiving surface or delivery surface.

In a variant of an embodiment, which is shown in FIG. 7c, a plurality of wedge-shaped displacement bodies 104 are arranged in the flow channel 86 . Such a displacement body 104 is basically the same out forms as a displacement body 92 described above in connection with FIG. 7a and also arranged in the same way.

The arrangement of the plurality of sinker 104 is particularly regularly, ie the individual displacement body 104 are equally spaced from each other. The plurality of displacement bodies 104 is preferably arranged over the length of the flow channel 86 , over which a receiving surface or delivery surface is to be effective.

In a further exemplary embodiment, which is shown in FIGS. 8a and 8b, a pair 110 of wedge-shaped displacement bodies 112 , 114 are arranged in a flow channel 106 with an open side 108, which is basically of the same design as the flow channel 86 . The displacement body 112 has an oblique wedge surface 116 and a further wedge surface 118 . The latter is oriented with its normal preferably parallel to a longitudinal direction of the flow channel 106 . The further wedge surface 118 , as shown in the left partial image of FIG. 8 a, for example, occupies a partial area both in terms of the height and in relation to the width of the flow channel 106 .

The second displacement body 114 of the displacement body pair 110 is basically of the same design as the first displacement body 112 with an oblique wedge surface 120 and a further wedge surface 122 , which is arranged essentially parallel to the longitudinal direction of the flow channel 106 . This further wedge surface 122 also occupies a portion of the flow channel 106 with respect to its height and width.

The two displacement bodies 112 and 114 of the displacement body pair 110 are offset from one another with respect to the width of the flow channel 106 on their further wedge surfaces 118 , 122 , so that these two further wedge surfaces 118 and 122 lie essentially in one plane.

Furthermore, the displacement bodies 112 , 114 of the pair of displacement bodies 110 are oriented towards one another such that the respective normals of the oblique wedge surfaces 116 and 120 lie transversely to one another.

Is, for example, as shown in Figs. 8a and 8b, the inclined wedge surface 116 of the displacement body 112 is oriented perpendicular to a bottom 124 of the flow channel 106 and the inclined wedge surface 120 of the second displacer 114 is substantially perpendicular to walls 126 of flow channel 106.

The orientation of the oblique wedge surfaces 116 and 120 is in particular such that fluid layer flows which flow parallel to the longitudinal direction of the flow channel 106 flow onto the oblique wedge surface 116 of the first displacement body 112 ; this means that the angle between the oblique wedge surface 116 and the walls 126 is a small positive acute angle. Furthermore, the oblique wedge surface 120 is oriented so that it forms a small negative acute angle with respect to the bottom 124 . As a result, the laminar flow can continue to flow continuously at the further wedge surfaces 118 , 122 even at the transition between the two displacement bodies 112 , 114 .

By arranging a pair of displacers 110 in the flow channel 106 , a shifting of the fluid layer flows of the laminar flow is effected according to the invention in that fluid layer flows maintain a transverse speed transverse to the main flow direction of the laminar flow. In particular, fluid is shifted from closed channel walls to the open side 108, ie in particular from the testicle 124 to the open side 108; however, in particular because of the arrangement of the inclined wedge surface 116, there is also a shifting between adjacent channel walls 126 .

In a variant, which is shown in FIG. 8c, a plurality of displacement bodies 110 are arranged in the flow channel 106 and in particular are arranged regularly.

In Fig. 9 a graph is shown which nits to the resulting based on numerical simulations. Basis is a square channel geometry shown in FIG. 8c with a plurality of regularly spaced-apart Ver drängungskörperpaaren 110 which are respectively formed as shown in Fig. 8a, said displacement body pairs are arranged over the entire length of the flow channel 106th The location P in the longitudinal direction of the channel is given on the abscissa in mm (ie the channel has a length of 300 mm) and on the ordinate the current density I in mA / cm ² . The current density is that of an electrochemical cell, which is supplied via such a flow channel 106 atmospheric oxygen as an oxidizing agent in a laminar air flow.

Curve 128 in the diagram in FIG. 9 shows the current density without displacement body pairs 110 . It can be seen that the current density decreases as expected with increasing distance from the beginning of the channel, since layers near the surface increasingly deplete oxygen in air and the mass transfer of atmospheric oxygen between the laminar layers takes place essentially only by diffusion and thereby the oxygen release via the surface of the laminar air flow worsens with increasing distance.

Curve 130 shows the influence of the flow guide device with the displacement body pairs 110 . The current density I shows an oscillatory behavior in accordance with the regular arrangement of the displacement body pairs 110 and lies above the curve 128 . Local peaks 132 occur at the location of the wedge-shaped displacement body pairs 110 . The total level of current density on curve 130 is higher than on curve 128 , this increase being of the order of 10%, with negligible pressure losses. This increase represents an improvement in the performance of the electrochemical cell.

Another embodiment is shown in FIGS. 10a and 10b. In a flow channel 134 a Ver displacement body pair 136 is arranged with a wedge-shaped displacement body 138 and a wedge-shaped displacement body 140 . The displacement body 138 in turn has an inclined wedge surface 142 and a further wedge surface 144 , the latter being oriented substantially perpendicular to a longitudinal direction of the flow channel. The further wedge surface takes up essentially the entire cross section of the flow channel 134 and a partial area based on its height. The inclined wedge surface 142 is perpendicular to a bottom 146 of the flow channel 134 .

An oblique wedge surface 148 of the displacement body 140 of the displacement body pair 136 is essentially perpendicular to walls 150 of the flow channel 134 . Another wedge surface 152 of the second displacer 140 is arranged in wesent union perpendicular to a longitudinal direction of the flow channel 134 and takes up substantially the entire height of the flow channel 134 based on the distance between the bottom 146 and an open side 154, wherein, based on the cross-section, this further partial area occupies only a partial area of the flow channel (compare the left partial figure in Fig. 10a).

The oblique wedge surface 142 of the first displacement body 138 of the displacement body pair 136 has a small positive acute angle relative to a channel wall 150 and the oblique wedge surface 148 of the second displacement body 140 has a small positive angle relative to the bottom 146 of the flow channel 134 .

The arrangement of displacers 138 , 140 in the flow channel 134 shown in FIGS . 10a and 10b also effects a shifting of fluid layers in the laminar flow of a fluid, so as to increase the surface uptake or release of substances, such as atmospheric oxygen, in one laminar flowing fluid, such as air to improve.

In the variant of an embodiment shown in FIG. 10c, a plurality of displacement body pairs 138 are arranged in the flow channel 134 . These are in particular arranged regularly and thus equally spaced in the flow channel.

In a further exemplary embodiment, which is shown in FIGS. 11a, 11b, an insert body 158, for example in the form of an insert plate, is arranged in a flow channel 156 with a square cross section, for example. This insert body 158 is formed in a hat-shaped manner and has an elevation 160 which acts as a displacement body, ie the fluid cannot penetrate the elevation 160 .

The insert body 158 also has an opening 162 which is adjacent to the elevation 160 , so that at the elevation 160 deflected fluid layer flows can flow through the opening 162 .

The insert body 158 is preferably over the entire cross section of the flow channel 156 arranged (see left panel of Fig. 11a) and in relation to the height of the Strö mung channel 156 between a bottom 164 and an open side 166 located such that the collection 160 through a Part of the height of the flow channel 156 is arranged. For example, the elevation 160 forms an acute angle with respect to the bottom 164 and ends near half the height in relation to the distance between the bottom 164 and the open side 166 of the flow channel 154 .

The elevation 160 is punched out or embossed in a guide plate as an insert body 158 , for example.

The fluid flow in the area of the insert body 158 can enter in the area of the insert body via an open end 168 , is then deflected via the elevation 160 and can exit at the opening 162 . There is thus a stratification of fluid layer flows from the area near the bottom 164 to an area near the open side 166, ie fluid layers are diverted from areas remote from the surface to near-surface areas.

When in Figs. 11c and 11d shown variant 156 insertion body 158 are provided in the flow channel, which are arranged at a regular interval. It can also be provided that the regular insert body 158 is formed by a single insert body which is inserted accordingly into the flow channel 156 .

In particular, the openings 162 are then spaced apart and in particular are arranged at a regular distance from one another. The openings 162 lie in the flow channel 156 in particular essentially on one level.

However, an alternative variant can also be provided in which the height of the individual openings 162 is different from the floor 164 , ie in which the openings 162 are offset with respect to one another with respect to the height.

In particular in the event that the plurality of insert bodies 158 is formed by a single insert body, as shown in FIGS . 11c and 11d, at least one further fluid exchange opening 170 is provided between adjacent openings, which fluid exchange between the region 172 above the insert body 158 (or of an insert body Zigen) and the region 174 below the a lay body 158 (or the single insert body) allowed. As a result, fluid layer currents which are deflected by the elevations 160 into the region 172 can again flow through the fluid exchange openings 170 into the region 174 , so that they can in turn flow into open ends 168 and then be deflected again into corresponding regions 172 via corresponding elevations can.

In a further exemplary embodiment, which is shown in FIG. 12a, the flow channel is basically constructed the same as described with reference to FIGS. 11a to d. The same reference number is therefore used for the flow channel. In the flow channel 156 is in inserted in FIGS. 12a to 12d shown embodiments of an insert body into the flow channel 156. As shown in Fig. 12a, 12b ge, the insert body 176 there comprises a displacement body 178 which, for example, has the shape of a cuboid, the diagonal of which is oriented essentially parallel to the longitudinal direction of the flow channel 156 and which extends over the bottom 164 of the flow channel 156 up to a partial height of the flow channel 156 . The cuboid 178 can be formed by punched and folded sheet metal parts and be open at the top or can also be closed ge.

The insert body 176 with the displacement body 178 is punched out of a sheet metal strip, for example, or is a correspondingly embossed guide plate.

The displacer 178 redirects fluid layer flows so as to redeploy fluid layers of the laminar flow.

In the variant shown in FIG. 12c, an insert body 180 with a displacement body 182 is also provided, which is basically of the same design as the displacement body 178 . However, an edge 184 of the cuboid-shaped displacer, which faces the open side 166, is chamfered, ie the edge is chamfered. This further promotes the diversion of fluid layer flows.

In a variant of an embodiment, which is shown in FIG. 12d, a plurality of insert bodies 186 are arranged in the flow channel 156 over the length of this flow channel 156 . In particular, the insert bodies 186 are arranged regularly and in particular are equally spaced.

In the variant shown, an insert body 188 is provided which, for example, has two spaced displacement bodies 182 , as described in connection with FIG. 12c. The two displacement bodies 182 are aligned so that their diagonals lie on one line.

It can also be provided that a pair of displacers 182 are offset from one another in an insert body 190 , that is to say that their diagonals are in each case spaced apart.

In particular, different combinations of such insert bodies 188 and 190 can be arranged in the flow channel 156 .

The displacement bodies 112 , 114 or 138 , 140 or 158 or 178 can be produced, for example, by deep drawing or stamping metal sheets or, for example, by injection molding or pressing polymer-bonded graphite plates.

The flow devices according to the invention have in common that layered fluid layers of laminar flow become, d. H. there is a shift to one Delivery surface or receiving surface for a substance. In particular, fluid layer flow becomes a transverse one Velocity component across a main flow direction of the laminar flow, so as a rich to effect change in such fluid layer flows.

Claims (36)

1. Device for promoting the surface uptake and / or surface release of a substance by a fluid, comprising a flow channel ( 30 ) in which a laminar flow of the fluid can be formed, at least one flow guide device ( 48 ) being provided, which is in the flow channel ( 30 ) is arranged and is designed in such a way that it causes a spatial shifting of fluid layers ( 24 ) in the laminar flow. 2. Apparatus according to claim 1, characterized in that the at least one flow guide device ( 48 ) is arranged and designed so that through this layer currents ( 20 ) of the laminar flow receive a transversal velocity component. 3. Apparatus according to claim 1 or 2, characterized in that the at least one flow control device ( 48 ) is arranged and designed such that a shifting of fluid layers ( 24 ) of the laminar flow takes place in such a way that fluid layer flows ( 20 ) from the Receiving surface or discharge surface of the fluid nearer areas of the flow can be deflected to more distant areas. 4. Device according to one of the preceding claims, characterized in that the at least one Strö mungsleiteinrichtung ( 48 ) is arranged and designed such that fluid layer flows ( 20 ) from the receiving surface or discharge surface of the fluid remote areas of the flow in this surface closer areas are redirected. 5. Device according to one of the preceding claims, characterized in that the at least one flow guide device ( 48 ) is arranged and designed such that the flow in the flow channel ( 30 ) is essentially free of turbulence. 6. Device according to one of the preceding claims, characterized in that the at least one flow guide device is arranged and designed such that fluid layer flows ( 20 ) of different fluid layers intersect. 7. Device according to one of the preceding claims, characterized in that the at least one flow guide device ( 48 ) comprises a structure ( 50 ; 76 ; 92 ; 158 ; 176 ), the dimensions of which vary transversely to the flow direction ( 22 ) of the laminar flow. 8. Device according to one of the preceding claims, characterized in that the at least one Strö mungsleiteinrichtung ( 48 ) is arranged and designed such that along the flow channel a substantially regular shifting of fluid layers ( 24 ) it follows. 9. The device according to claim 8, characterized in that the at least one flow guide device ( 48 ) comprises a plurality of flow-guiding structures ( 66 ; 104 ; 110 ; 136 ; 158 ; 186 ), which is arranged in a regular sequence with respect to the longitudinal direction of the flow channel , 10. Device according to one of the preceding claims, characterized in that the at least one flow guide device comprises a flow turner structure ( 50 ) which gives the fluid in the laminar flow a swirl. 11. The device according to claim 10, characterized in that the flow turner structure ( 50 ) has a spiral structure ( 58 ). 12. The apparatus of claim 10 or 11, characterized in that a longitudinal axis of the flow turner structure ( 50 ) is aligned parallel to the longitudinal direction of the flow channel ( 30 ). 13. Device according to one of claims 10 to 12, characterized in that the flow turner structure ( 50 ) is arranged in the flow channel ( 30 ). 14. Device according to one of claims 10 to 12, characterized in that the flow turner structure ( 60 ) is formed by means of channel walls. 15. The apparatus according to claim 14, characterized in that channel walls have a concave structure ( 82 ) for forming the flow turner structure. 16. The apparatus according to claim 14, characterized in that channel walls have a convex structure ( 84 ) for forming the flow turner structure. 17. Device according to one of the preceding claims, characterized in that the flow guide device comprises one or more displacement bodies ( 92 ; 112 , 114 ; 138 , 140 ; 158 ; 178 ; 182 ), which are barriers to the flow in the flow channel. 18. The apparatus according to claim 17, characterized in that a displacement body ( 92 ) is wedge-shaped. 19. The apparatus according to claim 18, characterized in that a wedge-shaped displacement body ( 92 ) is arranged so that its inclined wedge surface ( 94 ) faces the flow direction of the laminar flow. 20. The apparatus according to claim 18, characterized in that the flow guide device comprises at least one pair ( 110 ) of wedge-shaped displacement bodies ( 112 , 114 ). 21. The apparatus according to claim 20, characterized in that the inclined wedge surfaces ( 116 , 120 ) of a Ver displacement body pair ( 110 ) are arranged transversely to one another. 22. The apparatus of claim 20 or 21, characterized in that the displacement bodies ( 114 , 116 ) of a pair of displacement bodies ( 110 ) are arranged transversely to one another. 23. Device according to one of claims 20 to 22, characterized in that the displacement bodies ( 112 , 114 ) of a pair of displacement bodies ( 110 ) are arranged offset to one another in a transverse direction of the flow channel ( 106 ). 24. Device according to one of claims 20 to 23, characterized in that the oblique wedge surfaces ( 116 , 120 ) of a pair of displacers ( 110 ) have opposite component vectors with respect to the longitudinal direction of the flow channel ( 106 ). 25. Device according to one of claims 17 to 24, characterized characterized in that a displacement body is arranged and is configured such that fluid layer flows from first Walls of the flow channel towards the second walls of the Flow channel are deflectable. 26. Device according to one of claims 17 to 24, characterized in that a displacement body is arranged and designed such that fluid layer flows ( 20 ) from ge closed walls of the flow channel in the direction of open channel walls can be deflected. 27. Use of the device according to one of the preceding Claims in an electrochemical cell. 28. Use according to claim 27 in an electrolyzer. 29. Use according to claim 27 or 28 in a fuel cell. 30. Use according to one of claims 27 to 29, characterized characterized in that the flow channel to an elec trode leads to supply this oxygen. 31. Process for promoting surface uptake and / or Surface release of a substance through a fluid, wel ches flows in laminar flow, through which a Flow guide fluid layers of the laminar Flow can be shifted. 32. The method according to claim 31, characterized in that Fluid layer flows through the flow guide a transverse speed is given. 33. The method according to claim 31 or 32, characterized records that fluid layer flows from the area of Receiving surface or delivery surface in further distant areas are redirected. 34. The method according to any one of claims 31 to 33, characterized characterized in that fluid layer flows from further ent distant areas in the direction of the recording upper surface or delivery surface are redirected.   35. The method according to any one of claims 31 to 34, characterized characterized in that the fluid is given a swirl. 36. The method according to any one of claims 31 to 35, characterized characterized in that the fluid layer flows essentially be redirected without turbulence.