WO2024149514A1

WO2024149514A1 - Cell frame, electrochemical cell, and electrochemical flow reactor

Info

Publication number: WO2024149514A1
Application number: PCT/EP2023/083690
Authority: WO
Inventors: Jan GIRSCHIK; Thomas Markmann
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
Priority date: 2023-01-10
Filing date: 2023-11-30
Publication date: 2024-07-18
Also published as: DE102023100399A1; DE102023100399B4

Abstract

The invention relates to a cell frame (4) for an electrochemical flow reactor (1), in particular a redox flow battery, wherein the cell frame (4) circumferentially surrounds at least one cell interior (5), wherein the cell frame (4) has at least one flow channel (13, 14) connected to the at least one cell interior (5) to supply and/or remove a fluid to the cell interior (5) and/or from the cell interior (5), wherein the at least one flow channel (13, 14) has at least one redirection mechanism (17) comprising a bend (18) for redirecting the fluid flow, in particular by at least approximately 90°, wherein the flow channel (13, 14) has an inlet region (19), a redirection region (20), a vortex region (21), and an outlet region (22) successively in the flow direction of the fluid, and wherein the flow directions (R1, R2) of the fluid in the inlet region (19) and in the outlet region (22) are oriented at least substantially opposite to one another. In order to avoid undesirably high pressure losses along flow channels, according to the invention the flow cross-section (QW) of the flow channel (13, 14) in the vortex region (21) is larger than the flow cross-section (QE, QA) in the inlet region (19) and in the outlet region (22).

Description

Cell frame, electrochemical cell and electrochemical flow reactor

The invention relates to a cell frame for an electrochemical flow reactor, in particular a redox flow battery, wherein the cell frame surrounds at least one cell interior, wherein the cell frame has at least one flow channel connected to the at least one cell interior for supplying and/or discharging a fluid to the cell interior and/or from the cell interior, wherein the at least one flow channel has at least one deflection comprising an arc for deflecting the fluid flow, in particular by at least approximately 90°, wherein the flow channel has an inlet region, a deflection region, a vortex region and an outlet region in the flow direction of the fluid, one after the other, and wherein the flow directions of the fluid in the inlet region and in the outlet region are aligned at least substantially opposite to one another. The invention further relates to an electrochemical cell for a flow reactor, in particular a redox flow battery, with at least one such cell frame and an electrochemical flow reactor, in particular a redox flow battery, with such a cell.

Electrochemical cells are known in various designs and are sometimes also referred to as electrochemical reactors because electrochemical reactions take place in the electrochemical cells. Depending on their use, the electrochemical cells can be designed as galvanic cells in the form of electrochemical power sources, for example, which supply usable electrical energy through chemical reactions at the various electrodes. Alternatively, the electrochemical cells can also be used to produce certain products by applying an external voltage. Like galvanic cells, accumulator cells serve alternately as a power source and also as a power storage device.

The present invention can be used in all types of electrochemical cells through which at least one fluid flows. In this context, one also speaks of cells of an electrochemical flow reactor. Such electrochemical flow reactors are, for example, fuel cells, electrolysis cells, electrosynthesis cells and redox flow batteries.

Working fluids flow through fuel cells, which can be either liquid or gaseous media. The working fluids flow through an anode chamber and a cathode chamber, which are separated by a separator. The anode chamber and the cathode chamber are usually each provided by a cell frame, which closes off the interior of the cell from the outside in the plane of the cell frame. Contrary to their usual name, fuel cells are typically designed as a cell stack with a large number of electrochemical cells stacked on top of one another. An electrolyzer comprises a series of electrolysis cells, which can also be combined to form a cell stack. With the help of an electric current, a chemical reaction in the form of electrolysis is carried out in the individual electrochemical cells to produce a product, for example in the form of hydrogen.

Electrosynthesis cells are constructed in a similar way to the electrochemical cells of an electrolyzer. The fundamental difference here, however, is that the reactants are not split electrochemically. Instead, a synthesis reaction takes place. Depending on the desired reaction and thus dependent on the corresponding reactants and products, the cell interiors of the half-cells of the corresponding electrochemical cells, which are separated by a separator, are flowed through by liquid or gaseous media. Here, too, the cell interiors are typically provided essentially by a cell frame, which closes off the respective cell interior from the outside in the plane of the cell frame. In batteries, particularly redox flow batteries, the redox reactions taking place in the electrochemical reactor can be used to generate an electrical voltage. By applying an external voltage, the redox flow batteries can also be recharged, which is why redox flow batteries are essentially accumulators. Redox flow batteries themselves have been known for a long time and in various designs. Such designs are described as examples in EP 0 051 766 Al and US 2004/0170893 Al. An important advantage of redox flow batteries is the flexible scalability of performance and capacity and thus their suitability to store very large amounts of energy even with a low selected performance and vice versa. The energy is stored in electrolytes that can be kept ready in external tanks. The electrolytes usually contain metallic ions of different oxidation states. To extract electrical energy from the electrolytes or to recharge them, the electrolytes are pumped through a so-called electrochemical cell. The structure of redox flow batteries is usually less well known than the structure of the other electrochemical reactors mentioned above, although the structure of the different electrochemical reactors is basically similar. The structure of redox flow batteries is therefore discussed in more detail below using an example.

The electrochemical cell of redox flow batteries is usually made up of two half-cells that are separated from each other by a separator in the form of a semi-permeable membrane and each have an electrolyte and an electrode. The semi-permeable membrane has the task of spatially and electrically separating the cathode and the anode of an electrochemical cell. The semi-permeable membrane must therefore be permeable to ions that cause the conversion of the stored chemical energy into electrical energy or vice versa. Semi-permeable membranes can be made of microporous plastics, as well as nonwovens made of glass fiber or polyethylene and so-called Diaphragms are formed. Redox reactions take place at both electrodes of the electrochemical cell, with electrons being released from the electrolytes at one electrode and absorbed at the other electrode. The metallic and/or non-metallic ions of the electrolytes form redox pairs and thus generate a redox potential. Examples of redox pairs include iron-chromium, polysulfide-bromide or vanadium. These or other redox pairs can basically be present in aqueous or non-aqueous solution.

The electrodes of a cell, between which a potential difference develops as a result of the redox potentials, are electrically connected to one another outside the cell, e.g. via an electrical consumer. While the electrons pass from one half-cell to the other outside the cell, ions of the electrolytes pass directly from one half-cell to the other half-cell through the semipermeable membrane. To recharge the redox flow battery, a potential difference can be applied to the electrodes of the half-cells instead of the electrical consumer, e.g. using a charger, which reverses the redox reactions taking place at the electrodes of the half-cells.

To form the cell described, cell frames are used, among other things, which enclose a cell interior. The cell frames typically do not enclose the cell interior completely, but only along a circumferential narrow side. The cell frame therefore runs circumferentially around the cell interior and separates two opposite, larger-area sides from each other, which in turn are assigned to a semipermeable membrane or an electrode. The thickness of the cell frame, which is formed by the edge of the cell frame, is typically significantly less than the width and height of the cell frame, which define the larger-area opposite sides. Each half-cell of the electrochemical cell comprises such a cell frame, which is manufactured from a thermoplastic material, for example, using an injection molding process. A semi-permeable membrane is arranged between two cell frames, which separates the electrolytes of the half-cells from one another with regard to convective mass transfer, but allows diffusion of certain ions from one half-cell into the other half-cell. An electrode is also assigned to each of the cell interiors in such a way that they are in contact with the electrolytes flowing through the cell interiors. The electrodes can, for example, close off the cell interior of each cell frame on the side facing away from the semi-permeable membrane. The cell interior can remain essentially free and only be filled with one electrolyte at a time. The respective electrode can also, however, be provided at least partially in the cell interior. The electrode is then typically designed in such a way that the electrolyte can partially flow through the electrode.

In many cases, electrodes with a high specific surface area are used, where the corresponding electrochemical reactions can take place quickly and/or comprehensively. This ultimately leads to a high volume-specific output of the cell. However, even if the electrode extends into the cell interior, the cell interior is usually closed by the electrode on the side facing away from the semi-permeable membrane. So-called bipolar plates, which can be coated with a catalyst or another substance, for example, can also be used as a non-porous part of the electrode. Each cell frame has openings and channels through which the corresponding electrolyte can flow from a supply line into the respective cell interior and from there be withdrawn again and fed into a disposal line.

If the redox flow battery only comprises a single cell, supply lines for each half cell and disposal lines for each half cell are located outside the cell frames forming the half cells. Each cell frame has at least two openings, of which at least one is connected to a supply line, while the at least one other opening is connected to the disposal line. Within the cell frame, each opening is connected to a flow channel that is open to the cell interior. This allows electrolyte to be supplied from the supply line to the cell interior via a supply channel and the electrolyte that has flowed through the cell interior to be discharged via a discharge channel. The flow channel can also be branched.

If required, a number of similar electrochemical cells are combined in a redox flow battery. The cells are usually stacked on top of one another, which is why the entirety of the cells is also referred to as a cell stack. The electrolytes usually flow through the individual cells in parallel, while the cells are usually connected electrically in series. The cells are therefore usually connected hydraulically in parallel and electrically in series. In this case, the charge state of the electrolytes in each of the half cells of the cell stack is the same. To distribute the electrolytes to the corresponding half cells of the cell stack and to drain the electrolytes from the respective half cells, half cells are connected to one another with supply and disposal lines. Since each half cell or each cell interior of a cell is flowed through by a different electrolyte, the two electrolytes must be separated from one another as they pass through the cell stack. For this reason, two separate supply lines and two separate disposal lines are usually provided along the cell stack. Each of these channels is usually partially formed by the cell frames themselves, which have four openings. The openings extend along the cell stack and form the supply and disposal lines, arranged one behind the other and separated from each other by sealing materials if necessary.

In many cases, the flow channels for supplying and removing fluids to and from the cell interiors are at least partially meander-shaped in the associated cell space. The cell frames can have the flow channel as a closed channel, and therefore completely, or just as an open channel, which is then closed by at least one other component when the cell frame is connected to other components of the cell. However, this distinction is not of essential importance in the present case, so that this distinction is not always discussed in detail below. This is intended to improve understanding and avoid unnecessary repetition.

The meandering flow channels usually have several bends that serve to reverse the flow direction. The flow direction is regularly reversed by 180°. However, such an exact flow reversal is not important in this case. Alternatively or additionally, deflections are used to deflect the flow direction at a right angle, i.e. around 90°. The deflections of the flow channels each have a bend to deflect and/or reverse the flow direction. This applies to deflecting the flow direction by around 90°, reversing the fluid flow in the opposite direction by around 180°, or deflecting the flow direction in an angular range in between. These deflections can be divided into different sections in the flow direction, which can but do not necessarily have to be directly adjacent to one another. In an inlet area, the fluid with an original flow direction is fed to a deflection area in which the actual reversal of the flow direction takes place and which includes a bend for this purpose. From the bend or the deflection area, the flow enters a vortex area in which the reversal of the flow direction may already be complete, but does not have to be. In this vortex area, the flow is regularly swirled. In an outlet area, the reversal of the flow direction is at least essentially complete, so that the redirected flow direction in the outlet area points in a different direction, if necessary at least essentially in the opposite direction to the original flow direction of the flow in the inlet area. The meandering design of the flow channels is done in order to be able to position the deliberately long distances of the flow channels in the cell frame in the most space-saving way possible in order to increase the electrical resistance across the fluid lines and thus reduce short-circuit currents between the hydraulically connected half-cells in a stack. However, this has the disadvantage that sometimes quite high and undesirable pressure losses along the flow channels have to be accepted.

Therefore, the object of the present invention is to design and further develop the cell frame, the electrochemical cell and the electrochemical flow reactor, each of the type mentioned at the beginning and explained in more detail above, in such a way that undesirably high pressure losses along flow channels are avoided.

This object is achieved in a cell frame according to the preamble of claim 1 in that the flow cross-section of the flow channel in the vortex region is larger than the flow cross-section in the inlet region and in the outlet region.

The above object is further achieved according to claim 12 by an electrochemical cell for a flow reactor, in particular a redox flow battery, with at least one cell frame according to one of claims 1 to 11.

The aforementioned object is further achieved according to claim 14 by an electrochemical flow reactor, in particular a redox flow battery, with at least one cell according to claim 12 or 13.

The invention has recognized that the pressure loss due to the deflections in the meandering flow channels can be reduced if the flow cross section of the flow channel is made larger in the vortex area. than is the case in both the inlet area and the outlet area. The flow cross-sections in the inlet area and in the outlet area are preferably designed to be at least essentially the same. The flow cross-section is selected such that the meandering flow channel does not require too much space and at the same time does not generate too high a pressure loss. A small flow cross-section can usually be provided here, since the main pressure loss is generated by the deflection of the flow direction in the deflections of the flow channel. In order to reduce this pressure loss, however, it is not necessarily advisable to enlarge the flow cross-section in the area of the deflection. On the one hand, this requires more installation space and, on the other hand, the changes in cross section initially slow down the flow and then accelerate it again, which in itself increases the pressure loss of the flow. Nevertheless, the invention has recognized that a targeted widening of the flow channel can contribute to a reduction in the pressure loss without significantly increasing the space required for the flow channel.

The flow cross-section of the flow channel is enlarged precisely in the vortex area of the flow channel, because a vortex area forms in the flow there as a result of the bend, particularly on the inside of the flow channel. This vortex area reduces the flow cross-section for the less or not vortexed part of the flow, which is consequently initially accelerated adjacent to the vortex area and then decelerated again. By enlarging the flow cross-section in the area of the vortex area, an approximately constant flow cross-section can be provided for the less or not vortexed part of the flow despite the vortex area. This part of the flow is therefore not or only slightly decelerated and/or accelerated as a result of the vortex area in the vortex area of the flow channel, which ultimately leads to a reduced pressure loss of the flow as a whole. It has proven particularly useful with regard to the fluid dynamic properties of the flow channel and the space required for the flow channel in the cell frame if the flow cross-section in the vortex area is reduced by at least 10%, preferably at least 20%, in particular at least 30%, greater than in the inlet area and/or in the outlet area.

The cell frames will preferably have two different flow channels to supply the fluid in question to the cell interior and to remove it from the cell interior. It is then advisable if both flow channels are designed in a similar manner to that described above. However, this is not mandatory, just as the cell frame is not limited to a maximum of two such flow channels. For example, for a more even distribution of the fluid in the cell interior, it may be advisable to provide several flow channels for supplying and removing fluid to or from the cell interior. Alternatively or additionally, the flow channels can also be branched in order to be able to introduce the fluids into the cell interior and/or remove them from the cell interior over a wider area.

The advantages according to the invention are particularly, but not necessarily exclusively, applicable to deflections in which the fluid flow is deflected by at least about 90°, i.e. at least about a right angle. However, it is possible that the right angle or the corresponding 90° is more or less clearly undercut. Even then, a more or less meandering flow channel can be formed that prevents short-circuit currents.

In a first particularly preferred embodiment of the cell frame, the deflection encompassing the arc for deflecting the fluid flow is designed in such a way that it serves to deflect the fluid flow approximately at a right angle or by approximately 90°. This makes it easy to provide a fairly long flow channel in the cell frame. However, it is not necessarily important whether the deflection takes place at a right angle or only approximately at a right angle. However, it can be particularly preferred for the formation of a meandering design of the flow channel if the deflection is at least in the is designed essentially to reverse the fluid flow in the opposite direction. Here, too, an actual reversal of the flow direction by at least essentially 180° is preferred but by no means mandatory. Deflections at an angle between 90° and 180° can also be provided if this is expedient for the design of the flow channel. in a common central plane, the width of the flow channel in the vortex region is designed to be larger than the width of the flow channel in both the inlet region and the outlet region. The central plane intersects the inlet region, the deflection region, the vortex region and the outlet region. It is particularly preferred if the common central plane intersects the inlet region, the deflection region, the vortex region and the outlet region in the region of the center of the flow channel and/or in the region of a center line of the flow channel. The widening of the flow cross-section in the vortex area compared to the inlet area and the outlet area is therefore carried out in such a way that the flow channel in a common central plane is wider in the vortex area than in the inlet area and than in the outlet area. This ultimately leads to a fluid-dynamically preferred shape of the flow channel as a whole. It has proven particularly expedient with regard to the fluid-dynamic properties of the flow channel and the space required for the flow channel in the cell frame if the width of the flow channel in the common central plane in the vortex area is at least 10%, preferably at least 20%, in particular at least 30%, wider than in the inlet area and/or in the outlet area.

Alternatively or additionally, it contributes to a reduction in the pressure loss across the flow channel as a whole if the flow cross-section of the flow channel in the vortex area is larger than the flow cross-section in the deflection area. In this way, a fluid-dynamically favorable, slow widening of the flow channel can be achieved, which particularly preferably corresponds to the Formation of a vortex area in the flow channel can also be accompanied by a flow separation on the outside of the flow channel. The difference in size of the flow cross sections of the vortex area and the deflection area is preferably at least 10%, more preferably at least 15%, in particular at least 20%.

Irrespective of this, in the common center plane the width of the flow channel in the vortex area can be made larger than the width of the flow channel in the deflection area. In this case too, the fluid dynamic advantages described are achieved without the flow channel itself taking up significantly more space. The difference in width of the flow channels in the vortex area and in the deflection area is preferably at least 10%, more preferably at least 15%, in particular at least 20%.

Alternatively or additionally, in the common center plane, the distance between the inlet area and the outlet area in a direction transverse to the flow direction in the inlet area can be smaller than the width of the inlet area and/or the outlet area. This enables a space-saving arrangement of the meandering flow channel without this necessarily leading to excessive pressure losses. The aforementioned size difference is preferably at least 10%, more preferably at least 15%, in particular at least 20%.

If, in the common center plane, the distance between the inlet area and the outlet area in a direction transverse to the flow direction in the inlet area is greater than the distance between the inlet area and the vortex area, also in a direction transverse to the flow direction in the inlet area, the space required by the flow channel can be reduced. Contrary to expectations, the increase in the flow cross-section in the vortex area can be achieved at the expense of the corresponding distance between the inlet area and the vortex area, without thereby increasing the reduced pressure loss overall. The difference in size of the distances mentioned is preferably at least 10%, more preferably at least 15%, in particular at least 20%.

A good compromise between pressure loss and space requirements of the flow channel can also be achieved if the inner radius of the deflection region in the common center plane is larger than the distance between the inlet region and the vortex region in a direction transverse to the flow direction in the inlet region. The larger inner radius reduces the tendency for flow separation and the formation of a subsequent, wider vortex region. Contrary to expectations, the return of the vortex region to the inlet region does not affect this, but can be used to reduce the space requirements of the flow channel overall. The corresponding inner radius is preferably at least 10%, more preferably at least 15%, in particular at least 20%, larger than the corresponding distance.

Alternatively or additionally, the inner radius of the deflection region in the common center plane can be made larger than the distance between the inlet region and the outlet region in a direction transverse to the flow direction in the inlet region. In this case too, the fluid dynamic advantages described are achieved without the flow channel itself taking up significantly more space. The corresponding inner radius is preferably at least 10%, more preferably at least 15%, in particular at least 20%, larger than the corresponding distance.

A fluid dynamically appropriate flow channel, which at the same time takes up little space, can also be achieved alternatively or additionally if, in the common central plane, the width of the deflection in a direction transverse to the flow direction in the inlet area is larger in the deflection area than at the level of the outlet area. The larger width in the deflection area primarily serves to reduce the pressure loss, while the small distance between the Inlet area and outlet area contributes to a smaller space requirement without these two measures hindering each other too much. This can be exploited even more comprehensively if, in the common central plane, the width of the deflection in a direction transverse to the flow direction in the inlet area is larger in the deflection area than at the level of the vortex area. The vortex area can thus contribute both to reducing the pressure loss and to reducing the space required by the flow channel. The corresponding width difference is preferably at least 10%, more preferably at least 15%, in particular at least 20%.

If in the common central plane the width of the deflection in a direction transverse to the flow direction in the inlet area is larger at the level of the vortex area than at the level of the outlet area, this can ensure a flow with low pressure loss. At the same time, however, the flow channel can be designed in such a way that the space required by the flow channel remains small. The corresponding difference in width is preferably at least 10%, more preferably at least 15%, in particular at least 20%.

The space requirement of the flow channel can also be kept low without this being excessively detrimental to the pressure loss in the flow channel if the width of the vortex area perpendicular to the flow direction in the inlet area is greater than one and a half times the width of the inlet area and/or the outlet area in the common center plane. The space requirement is then, if necessary, at most insignificantly larger than with standard deflections with a constant flow cross-section.

In a first particularly preferred embodiment of the electrochemical cell, at least one cell frame according to one of claims 1 to 11 is provided per half cell. In this way, the previously described advantages can be achieved in particularly in both half-cells of the electrochemical cell.

In a first particularly preferred embodiment of the electrochemical flow reactor, a cell stack of electrochemical cells according to one of claims 12 or 13 is provided. This leads overall to a high power density and efficiency of the electrochemical flow reactor.

The invention is explained in more detail below with reference to a drawing which merely represents an exemplary embodiment. The drawing shows

Fig. 1A-B an electrochemical flow reactor according to the invention in the form of a redox flow battery in a longitudinal section,

Fig. 2 shows a cell frame according to the invention of the electrochemical flow reactor from Fig. 1 in a plan view and

Fig. 3 A deflection of a flow channel of the cell frame from Fig. 2 in a plan view.

In Fig. 1A and 1B, an electrochemical flow reactor 1 in the form of a redox flow battery with a cell stack comprising several electrochemical cells 2 is shown in a longitudinal section. The electrochemical flow reactor 1 comprises three cells 2, each of which has two half cells 3 with corresponding electrolytes. Each half cell 3 has a cell frame 4, which comprises a cell interior 5 through which an electrolyte stored in a storage container can be passed and into which an electrode 6 engages at least partially, which also closes and seals the cell interior 5 on one side. The electrolytes flowing through the cell interiors 5 differ from one another. The respective cell interior 5 is on the The side facing away from the electrode 6, adjacent to the cell frame 4 of the second half-cell 3 of the same electrochemical cell 2, is closed by a semi-permeable membrane 7 provided between the cell frames 4 of the two half-cells 3. Convective transfer of the two different electrolytes of the two half-cells 3 into the cell interior 5 of the cell frame 4 of the other half-cell 3 is thus prevented. However, ions can pass from one electrolyte to the other electrolyte via the semi-permeable membrane 7 by diffusion, thereby transporting charges. Redox reactions of the redox pairs of the electrolytes at the electrodes 6 of the half-cells 3 of a cell 2 either release or absorb electrons. The released electrons can flow from one electrode 6 to the other electrode 6 of a cell 2 via an electrical connection provided outside the flow reactor 1 and, if required, having an electrical consumer. Which reactions take place at which electrode 6 depends on whether the electrochemical flow reactor is charged or discharged.

In the electrochemical flow reactor 1 shown, the electrodes 6 lie flat on an outer side 8 of the cell frame 4. The electrode 6 thus forms a frame surface in the contact area with the outer side 8 of the cell frame 4, which acts as a sealing surface 9. Between the mutually facing outer sides 8 of the cell frames 4 of a cell 2 there is a sealing material 10 in which the membrane 7 is sealed. The sealing material 10 lies flat on the outer sides 8 of the adjacent cell frames 4 and thus forms frame surfaces that act as sealing surfaces 9.

Four channels extend lengthways to the electrochemical flow reactor 1. Two of these are supply lines 11 for supplying the two electrolytes to the cell interiors 5 of the cell frames 4. The other two channels are disposal lines 12 for removing the electrolytes from the cell interiors 5 of the cell frames 4. In Fig. 1A, one supply line 11 and one disposal line 12 are shown. A flow channel 13 branches off from the supply line 11 in each half cell 3 of each cell 2 as a feed channel, via which the Electrolyte can be supplied to the corresponding cell interior 5 of the half-cell 3. On opposite sections of the corresponding cell frames 4, a flow channel 14 is provided as a discharge channel, via which the electrolyte can be drained from the cell interior 5 into the disposal line 12. The supply line 11 (not shown in Fig. 1A) and the disposal line 12 (also not shown) enable the second electrolyte to flow through the other cell interiors 5 of the other half-cells 3 via similar flow channels 13, 14.

Fig. 2 shows a plan view of a cell frame 4. Four openings 15 are provided in the corners of the cell frame 3, each opening 15 of which forms part of a supply line 11 or a disposal line 12. The flow channel 13 for supplying and the flow channel 14 for discharging electrolyte are let in as depressions or open channels in the shown outer side 8 of the frame casing 16 of the cell frame 4, which runs around the cell interior 5. The flow channels 13, 14 are closed off to form circumferentially closed lines when assembled to form an electrochemical flow reactor 1. In the electrochemical flow reactor 1 shown, this is done, for example, and in sections, by the sealing materials 10 and the electrodes 6. The flow channels 13, 14 could also be provided as closed channels in the cell frame or closed off by other components of the electrochemical flow reactor 1.

The flow channels 13, 14 are shown only very schematically in Fig. 2 and are branched in the embodiment shown, so that the electrolyte can be supplied via the flow channel 13 in a distributed manner over the cell interior 5 and can be discharged via the other flow channel 14. However, this is not necessary. Flow channels 13, 14 leading separately from the supply line 11 could also be provided. The flow channels 13, 14 are designed in a meandering manner with a number of deflections 17, of which one deflection 17 is shown in detail in Fig. 3 as an example. The deflection 17 comprises a bend 18, which ensures that the original flow direction RI of the flow in the flow channel 13, 14 is at least substantially reversed into a reverse flow direction R2 after the bend 18. The deflection 17 is divided into four different sections, which are provided one after the other in the flow direction R1, R2 of the fluid, in the present embodiment an electrolyte. In an inlet region 19, the fluid is fed in the original flow direction RI to a deflection region 20 for the actual deflection of the flow direction RI of the flow of the fluid. In the deflection region 20, the flow is therefore deflected and leaves the deflection region 20 in a flow direction that is at least partially oriented opposite to the original flow direction RI. As a result of the deflection, vortex regions form in the flow, particularly on the inside of the flow channel 13, 14, which at least essentially occur in the vortex region 21. After the vortex regions have at least largely subsided, the vortex region 21 is followed by an outlet region 22 in which the deflected flow direction R2 points at least essentially opposite to the original flow direction RI. The flow direction R2 of the flow can be reversed by 180°. However, an exact reversal of the flow direction is not important. In the illustrated and in this respect preferred embodiment, it is sufficient if the flow flows back in the direction from which the flow originally flowed. This is intended to achieve a meandering design of the flow channel 13, 14.

In the deflection 17 of the flow channel 13,14 shown in Fig. 3, the flow cross section QW of the flow channel 13,14 in the vortex area 21 is larger than the flow cross section QE,QA in both the inlet area 19 and the outlet area 22. In a common center plane ME, the width BW of the flow channel 13,14 in the vortex area 21 is larger than the width BE,BA of the flow channel 13,14 in both the inlet area 19 and the outlet area 22. The common center plane ME intersects the inlet region 19, the deflection region 20, the vortex region 21 and the outlet region 22, in each case in the region of the center of the flow channel 13, 14 and/or in the region of a center line ML of the flow channel 13, 14. In addition, the flow cross section QW of the flow channel 13, 14 in the vortex region 21 is larger than the flow cross section QU in the deflection region 20.

Viewed in a direction transverse to the flow direction RI in the inlet region 19, the width BW of the flow channel 13,14 in the common center plane ME in the vortex region 21 is greater than the corresponding width BU of the flow channel 13,14 in the deflection region 20. In addition, viewed in the common center plane ME in a direction transverse to the flow direction RI in the inlet region 19, the distance Al between the inlet region 19 and the outlet region 22 is smaller than the width BE,BA of the inlet region 19 as well as the outlet region 22. In the common center plane ME, the distance Al between the inlet region 19 and the outlet region 22 is also viewed in a direction transverse to the flow direction RI in the inlet region 19 greater than the corresponding distance A2 between the inlet region 19 and the vortex region 21.

Furthermore, in the common center plane ME, the inner radius 1R of the deflection region 20 is greater than the distance A2 between the inlet region 19 and the vortex region 21 and greater than the distance Al between the inlet region 19 and the outlet region 22 if the respective distance A1,A2 is measured in a direction transverse to the flow direction RI in the inlet region 19 along the common center plane ME. Measured in the same direction, the width B1,B2 of the deflection 17 in the deflection area 20 as well as in the vortex area 21 is greater than the width B3 of the deflection 17 at the level of the outlet area 22 and the width Bl of the deflection 17 transverse to the flow direction RI in the inlet area 19 in the deflection area 20 is greater than the width B2 of the deflection at the level of the vortex area 21. In addition, in the common center plane ME, the width BW of the vortex area 21 in a direction transverse to the flow direction RI in the Inlet area 19 seen larger than one and a half times the width BE,BU,BA of the inlet area 19 and/or the outlet area 22.

List of reference symbols

1 flow reactor

2 Cell

3 half cell

4 cell frames

5 Cell interior

6 Electrode

7 semipermeable membrane

8 Outside

9 Sealing surface

10 Sealing material

11 Supply line

12 Disposal line

13 Flow channel

14 Flow channel

15 Opening

16 Frame casing

17 Deflection

18 sheets

19 Inlet area

20 Deflection area

21 Vertebral area

22 Run-off area

Al-2 distance

Bl-3 Wide deflection

BA Width run-off area

BE Width inlet area

BU Width deflection area

BW Width Vertebral Area

1R inner radius

ME Middle Level

QA Flow cross section outlet area

QE Flow cross section inlet area

QU Flow cross section deflection area

QW Flow cross section Vortex area

RI original flow direction R2 redirected flow direction

Claims

Patent claims

1. Cell frame (4) for an electrochemical flow reactor (1), in particular a redox flow battery, wherein the cell frame (4) encircles at least one cell interior (5), wherein the cell frame (4) has at least one flow channel (13, 14) connected to the at least one cell interior (5) for supplying and/or discharging a fluid to the cell interior (5) and/or from the cell interior (5), wherein the at least one flow channel (13, 14) has at least one deflection (17) comprising a bend (18) for deflecting the fluid flow, in particular by at least approximately 90°, wherein the flow channel (13, 14) has, in the flow direction of the fluid, one after the other an inlet region (19), a deflection region (20), a vortex region (21) and an outlet region (22), and wherein the flow directions (R1, R2) of the fluid in the inlet region (19) and in the Outlet region (22) are aligned at least substantially opposite to one another, characterized in that the flow cross-section (QW) of the flow channel (13,14) in the vortex region (21) is larger than the flow cross-section (QE,QA) in the inlet region (19) and in the outlet region (22).

2. Cell frame according to claim 1, characterized in that the deflection (17) comprising the arch (18) for deflecting the fluid flow approximately at a right angle, preferably at least substantially for reversing the fluid flow in the opposite direction.

3. Cell frame according to claim 1 or 2, characterized in that in a common center plane (ME) the width (BW) of the flow channel (13,14) in the vortex region (21) is greater than the width (BA,BE) of the flow channel (13,14) in the inlet region (19) and in the outlet region (22) and/or that the flow cross section (QW) of the flow channel (13,14) in the vortex region (21) is greater than the flow cross section (QU) in the deflection region (20).

4. Cell frame according to one of claims 1 to 3, characterized in that in the common center plane (ME) the width (BW) of the flow channel (13,14) in the vortex region (21) transverse to the flow direction (RI) in the inlet region (19) is greater than the width (BU) of the flow channel (13,14) in the deflection region (20) transverse to the flow direction (RI) in the inlet region (19).

5. Cell frame according to one of claims 1 to 4, characterized in that in the common center plane (ME) the distance (Al) between the inlet region (19) and the outlet region (22) transverse to the flow direction (RI) in the inlet region (19) is smaller than the width (BA,BE) of the inlet region (19) and the outlet region (22) transverse to the flow direction (RI) in the inlet region (19).

6. Cell frame according to one of claims 1 to 5, characterized in that in the common center plane (ME) the distance (Al) between the inlet region (19) and the outlet region (22) transverse to the flow direction (RI) in the inlet region (19) is greater than the distance (A2) between the inlet region (19) and the vortex region (21) transverse to the flow direction (RI) in the inlet region (19).

7. Cell frame according to one of claims 1 to 6, characterized in that in the common center plane (ME) the inner radius of the deflection region (20) is greater than the distance (A2) between the inlet region (19) and the vortex region (21) transverse to the flow direction (RI) in the inlet region (19).

8. Cell frame according to one of claims 1 to 7, characterized in that in the common center plane (ME) the inner radius of the deflection region (20) is greater than the distance (Al) between the inlet region (19) and the outlet region (22) transverse to the flow direction in the inlet region (19).

9. Cell frame according to one of claims 1 to 8, characterized in that in the common center plane (ME) the width (Bl) of the deflection transverse to the flow direction (RI) in the inlet region (19) in the deflection region (20) is greater than at the level of the outlet region (22) and that, preferably, in the common center plane (ME) the width (B2) of the deflection transverse to the flow direction (RI) in the inlet region (19) in the deflection region (20) is greater than at the level of the vortex region (21).

10. Cell frame according to one of claims 1 to 9, characterized in that in the common center plane (ME) the width (Bl) of the deflection transverse to the flow direction (RI) in the inlet region (19) at the level of the vortex region (21) is greater than the width (B3) of the deflection transverse to the flow direction (RI) in the inlet region (19) at the level of the outlet region (22).

11. Cell frame according to one of claims 1 to 10, characterized in that in the common center plane (ME) the width (B2) of the vortex region (21) transverse to the flow direction (RI) in the inlet region (19) is greater than one and a half times the width (BE,BA) of the inlet region (19) and/or the outlet region (22) transverse to the flow direction (RI) in the inlet region (19).

12. Electrochemical cell (2) for a flow reactor (1), in particular a redox flow battery, with at least one cell frame (4) according to one of claims 1 to 11.

13. Electrochemical cell according to claim 12, characterized in that at least one cell frame (4) according to one of claims 1 to 11 is provided per half-cell (3).

14. Electrochemical flow reactor (1), in particular redox flow battery, with at least one cell (2) according to claim 12 or 13.

15. Electrochemical flow reactor according to claim 14, characterized in that a cell stack of electrochemical cells (2) according to one of claims 12 or 13 is provided.