Cell frame, electrochemical cell and electrochemical flow reactor

Abstract

The present invention describes and illustrates a cell frame (4) for an electrochemical flow reactor (1), particularly for a redox flow battery, the cell frame (4) circumferentially surrounding at least one cell chamber (5), the cell frame (4) having at least one flow channel (13, 14) connected to the at least one cell chamber (5) for supplying fluid to the cell chamber (5) and / or removing fluid from the cell chamber (5), the at least one flow channel (13, 14) having at least one deflection section (17) with a bend (18) for deflecting the fluid flow, particularly by at least about 90°, the flow channel (13, 14) having, successively in the fluid flow direction, an inlet region (19), a deflection region (20), a vortex region (21), and an outlet region (22), the fluid flow directions (R1, R2) in the inlet region (19) and the outlet region (22) being oriented at least substantially opposite to each other. Here, in order to avoid undesirably high pressure losses along the flow channels, the flow cross-sectional area (QW) of the flow channels (13, 14) in the vortex region (21) is configured to be larger than the flow cross-sectional areas (QE, QA) in the inlet region (19) and outlet region (22).

Description

[Technical Field]

[0001] The present invention relates to a cell frame for an electrochemical flow reactor, particularly for a redox flow battery, the cell frame circumferentially including at least one cell chamber, the cell frame having at least one flow channel connected to the at least one cell chamber for supplying and / or removing fluid from the cell chamber, the at least one flow channel having at least one deflection portion including a bend for deflecting the fluid flow, particularly by at least about 90°, the flow channel having, successively in the fluid flow direction, an inlet region, a deflection region, a vortex region, and an outlet region, the fluid flow directions in the inlet region and the outlet region being at least substantially opposite to each other. Furthermore, the present invention relates to an electrochemical cell for a flow reactor, particularly for a redox flow battery, comprising at least one such cell frame, and to an electrochemical flow reactor, particularly a redox flow battery, comprising such a cell.

[0002] Electrochemical cells are known in various configurations and are sometimes referred to as electrochemical reactors because electrochemical reactions occur within them. Depending on their application, electrochemical cells can be designed, for example, as galvanic cells, a form of electrochemical power source that provides usable electrical energy through chemical reactions at various electrodes. Alternatively, electrochemical cells can be used to produce specific products by applying an external voltage. Battery cells, like galvanic cells, function as power sources and also as power storage devices.

[0003] The present invention can be used in any type of electrochemical cell through which at least one fluid flows. In this context, the cell is also referred to as an electrochemical flow reactor. Such electrochemical flow reactors are, for example, fuel cells, electrolysis cells, electrosynthesis cells, and redox flow batteries.

[0004] A working fluid, which can be either a liquid or gaseous medium, flows through a fuel cell. The working fluid flows through the anode and cathode chambers, which are separated by a separator. The anode and cathode chambers are usually substantially provided by a cell frame, which closes the cell interior from the outside in its plane. Contrary to their usual designation, fuel cells are typically designed as a cell stack with a number of stacked electrochemical cells. Electrolyzers contain a series of electrolysis cells, which can also be combined to form a cell stack. A chemical reaction in the form of electrolysis is carried out using an electric current, thereby producing a product, for example, in the form of hydrogen, in each electrochemical cell. Electrosynthesis cells have a structure similar to that of electrolyzer electrochemical cells. However, the fundamental difference here is that the reactants are not electrochemically divided. Instead, a synthesis reaction takes place. Depending on the desired reaction, and therefore the corresponding reactants and products, a liquid or gaseous medium flows through the cell interiors of the corresponding electrochemical cell half-cells, separated by separators. In this case too, the cell chambers are typically substantially formed by the cell frame, and the cell frame closes off each cell chamber from the outside at its plane.

[0005] Batteries, particularly redox flow batteries, can generate voltage using oxidation-reduction reactions that occur within an electrochemical reactor. However, redox flow batteries can also be recharged by applying an external voltage, since they are essentially rechargeable batteries. Redox flow batteries themselves have been known for a long time in various designs. Examples of such designs are described in U.S. Patent Nos. 5,629,997 and 5,629,997. A key advantage of redox flow batteries is their flexible scalability in performance and capacity, and therefore their adaptability to store very large amounts of energy even when low performance is selected, and vice versa. Energy is stored in an electrolyte, which can be held in an external container. The electrolyte typically contains metal ions in different oxidation states. To extract electrical energy from the electrolyte or to recharge it, the electrolyte is pumped through an electrochemical cell. While the structure of redox flow batteries is generally less well known than the structures of the other electrochemical reactors mentioned above, the structures of various electrochemical reactors are fundamentally similar. Therefore, the structure of a redox flow battery will be described in more detail below as an example.

[0006] The electrochemical cell of a redox flow battery typically consists of two half-cells, each containing an electrolyte and an electrode, separated from each other by a separator in the form of a semipermeable membrane. The semipermeable membrane serves to spatially and electrically separate the cathode and anode of the electrochemical cell. Therefore, the semipermeable membrane must be permeable to ions that convert stored chemical energy into electrical energy, or vice versa. Semipermeable membranes can be formed, for example, from microporous plastics and nonwoven fabrics made of glass fiber or polyethylene, known as diaphragms. Redox reactions occur at both electrodes of the electrochemical cell, with electrons being released from the electrolyte at one electrode and absorbed at the other. Metal and / or nonmetal ions in the electrolyte form redox pairs, resulting in a redox potential. Possible redox pairs include iron-chromium, polysulfide-bromide, or polysulfide-vanadium. These and other redox pairs can exist in aqueous or nonaqueous solutions.

[0007] The electrodes of a cell, which experience a potential difference as a result of the redox potential, are electrically connected to each other outside the cell, for example, via an electrical consumer. Electrons pass from one half-cell to the other outside the cell, while electrolyte ions pass directly from one half-cell to the other through a semipermeable membrane. To recharge a redox flow battery, a potential difference can be applied to the half-cell electrodes instead of the electrical consumer, for example, by a charger that reverses the redox reaction occurring at the half-cell electrodes.

[0008] In particular, to form the described cell, a cell frame is used that surrounds the cell chamber. Typically, the cell frame does not completely surround the cell chamber, but only along its narrow circumferential sides. As a result, the cell frame extends around the periphery of the cell chamber, separating the two opposing sides with larger surface areas, which are assigned to the semipermeable membrane or electrodes. The thickness of the cell frame, defined by the edges of the cell frame, is typically significantly smaller than the width and height of the cell frame that define the opposing sides with larger surface areas.

[0009] Each half-cell of the electrochemical cell has a cell frame of the type described above, manufactured from a thermoplastic material, for example, by injection molding. A semipermeable membrane is disposed between the two cell frames. This semipermeable membrane separates the electrolytes of the half-cells from each other with respect to convective mass transfer, but allows the diffusion of certain ions from one half-cell to the other. Furthermore, an electrode is assigned to each of the cell chambers so as to be in contact with the electrolyte flowing through the cell chamber. Each electrode can close the side of the cell chamber of each cell frame facing away from the semipermeable membrane, for example. The cell chamber remains substantially open and can be filled with only one type of electrolyte at a time. However, each electrode can also be at least partially disposed within the cell chamber. In this case, the electrodes are typically designed to allow the electrolyte to partially flow through them.

[0010] Electrodes with a high specific surface area are often used here, allowing the corresponding electrochemical reactions to occur quickly and / or comprehensively. This ultimately increases the cell's performance per volume. However, even if the electrodes protrude into the cell interior, the cell interior is usually sealed by the electrode on the side opposite the semipermeable membrane. The non-porous part of the electrode may be a so-called bipolar plate, which can be coated with, for example, a catalyst or other substance. Each cell frame has openings and channels through which the corresponding electrolyte can flow from the supply channel into each cell interior and from there, can be withdrawn and supplied to the discharge channel.

[0011] When a redox flow battery includes only a single cell, the supply and discharge channels of each half-cell are located on the outer surface of the cell frame that forms the half-cell. Each cell frame has at least two openings, at least one of which is connected to the supply channel, while at least one other opening is connected to the discharge channel. Within the cell frame, each opening is connected to a flow channel that opens into the cell interior. This allows electrolyte to be supplied from the supply channel to the cell interior via the supply channel and electrolyte flowing through the cell interior via the discharge channel. The flow channels can also be branched.

[0012] If necessary, several similar electrochemical cells can be combined into a redox flow battery. The cells are typically stacked one on top of the other, often referred to as a cell stack. While the electrolyte typically flows parallel to each other through the individual cells, the cells are typically connected electrically in series. Therefore, the cells are typically connected hydraulically in parallel and electrically in series. In this case, the state of charge of the electrolyte is the same in each half-cell of the cell stack. To distribute the electrolyte to the corresponding half-cells of the cell stack and to simultaneously drain the electrolyte from each half-cell, the half-cells are interconnected by supply and drain channels. If different electrolytes flow through each half-cell or cell chamber of a cell, the two electrolytes must be kept separate as they pass through the cell stack. For this purpose, two separate supply and drain channels are typically provided along the cell stack. Each of these channels is typically formed in part by the cell frame itself, which typically has four openings for this purpose. The openings extend along the cell stack to form supply and exhaust channels arranged one behind the other, which are separated from one another by sealing material as required.

[0013] In many cases, the flow channels for supplying and removing fluids to and from the cell interiors are formed at least partially in a meandering pattern in the associated cell space. The cell frame may define the flow channels as closed channels, i.e., completely closed channels, or as open channels only in the sense that they are closed by at least one other component when the cell frame is connected to other components of the cell. However, this distinction is not essential here and therefore will not necessarily be explained in detail below. This is done to improve understanding and avoid unnecessary repetition.

[0014] A meandering flow channel typically has multiple bends that function to reverse the flow direction. The flow direction is regularly reversed by 180°. However, the exactness of the flow reversal is not critical here. Alternatively or additionally, deflection sections that deflect the flow direction at a right angle, i.e., by approximately 90°, are also used. To deflect and / or reverse the flow direction, the deflection sections of the flow channel each have a bend. This applies to deflecting the flow direction by approximately 90°, reversing the fluid flow in the opposite direction by approximately 180°, or deflecting the flow direction in an intermediate angular range. The deflection section here can be divided into different sections in the flow direction, which may, but need not, be immediately adjacent to each other. In the inlet region, the fluid with its original flow direction is fed into the deflection region, where the actual reversal of the flow direction occurs and where the bends are provided. From the bend or deflection region, the flow enters a vortex region, where the reversal of the flow direction may or may not be complete. The flow is swirled in a regular manner in the vortex region, and in the outlet region, the reversal of the flow direction of the flow is at least substantially complete so that the reversed flow direction in the outlet region is in a different direction from the original flow direction of the flow in the inlet region, i.e., at least substantially opposite as required.

[0015] The meandering of the flow channels is implemented to allow for the space-saving arrangement of intentionally long flow channels in the stack in order to increase the electrical resistance through the flow paths and thus reduce short-circuit currents between hydraulically connected half cells in the cell frame, but this sometimes has the disadvantage of having to accept undesirably high pressure losses along the flow channels. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] European Patent Application Publication No. 0 051 766(A1) [Patent Document 2] U.S. Patent Application Publication No. 2004 / 0170893(A1)

[0017] The object underlying the present invention is therefore to configure and further develop cell frames, electrochemical cells and electrochemical flow reactors of the type mentioned at the beginning and described in detail above in such a way that undesirable high pressure losses along the flow channels are avoided.

[0018] This object is achieved in a cell frame according to the preamble of claim 1 in that the flow cross-sectional area of ​​the flow channel in the vortex region is larger than the flow cross-sectional area in the inlet and outlet regions.

[0019] According to claim 12, the above object is also achieved by an electrochemical cell for a flow reactor, in particular an electrochemical cell for a redox flow battery, which comprises at least one cell frame according to any one of claims 1 to 11.

[0020] The above object is also achieved according to claim 14 by an electrochemical flow reactor, in particular a redox flow battery, comprising at least one cell according to claim 12 or 13.

[0021] The present invention recognizes that pressure losses due to the deflection of a meander-shaped flow channel can be reduced if the cross-sectional flow area of ​​the flow channel in the vortex region is larger than the cross-sectional flow areas of both the inlet and outlet regions. The cross-sectional flow areas in the inlet and outlet regions are preferably at least substantially equal. The cross-sectional flow area is selected so that the meander-shaped flow channel does not require excessive space and does not generate excessive pressure losses. Since the main pressure loss typically occurs due to the deflection of the flow direction at the bend in the flow channel, a small cross-sectional flow area can be provided. It should be noted that increasing the cross-sectional flow area in the region of the deflection to reduce such pressure losses is not necessarily recommended. This requires more installation space, and on the other hand, increases the pressure loss of the flow due to the initial deceleration and subsequent reacceleration of the flow resulting from the change in cross-sectional area. Nevertheless, the present invention recognizes that targeted widening of a flow channel can contribute to reducing pressure losses without significantly increasing the space required for the flow channel.

[0022] The cross-sectional flow area of ​​the flow channel is increased in the vortex region of the flow channel because, particularly within the flow channel, a vortex region forms in the flow at that point as a result of the bend. The vortex region reduces the cross-sectional flow area of ​​the flow in the less vortex-rich or vortex-free region, so that the flow first accelerates in contact with the vortex region and then decelerates again. By increasing the cross-sectional flow area in the region of the vortex region, a substantially constant cross-sectional flow area can be provided for the less vortex-rich or vortex-free region of the flow despite the vortex region. Thus, the flow portion is not decelerated and / or accelerated in the vortex region of the flow channel as a result of the vortex region, or is only decelerated and / or accelerated to a lesser extent, ultimately reducing the overall pressure loss of the flow. With regard to the hydrodynamic properties of the flow channel and the spatial requirements of the flow channel within the cell frame, it has proven particularly advantageous if the cross-sectional flow area in the vortex region is at least 10%, preferably at least 20%, and in particular at least 30% larger than the cross-sectional flow area in the inlet and / or outlet regions.

[0023] The cell frame preferably has two different flow channels for supplying and removing the target fluid to and from the cell chamber. In this case, it is advantageous for both flow channels to be configured in a similar manner as described above. However, this is not essential, just as the cell frame is not limited to a maximum of two such flow channels. For more uniform distribution of the fluid in the cell chamber, it may be advisable, for example, to provide multiple flow channels for supplying and removing the fluid from the cell chamber. However, alternatively or additionally, the flow channels may branch to allow the fluid to be introduced into and / or removed from the cell chamber over a wider area.

[0024] The advantages of the present invention are particularly applicable to deflectors where the fluid flow is deflected at least approximately 90°, i.e., at least approximately at a right angle, although this is not required. However, the right angle or the corresponding 90° may be explicitly undercut to a greater or lesser extent. Also, more or less meandered flow channels may be formed, thereby preventing short-circuiting.

[0025] In a first particularly preferred embodiment of the cell frame, the deflection section, including the bend that deflects the fluid flow, is configured to deflect the fluid flow at an approximately right angle or approximately 90°. This facilitates the creation of fairly long flow channels within the cell frame. It is not essential whether the deflection section is a right angle or approximately a right angle. However, if the deflection section is designed to at least substantially reverse the fluid flow in the opposite direction, this may be particularly advantageous for the creation of meander-shaped designs of the flow channels. Again, it is preferable to actually reverse the flow direction by at least substantially 180°, but this is not essential. If appropriate for the design of the flow channel, deflection sections at angles between 90° and 180° may also be provided.

[0026] In the common mid-plane, the width of the flow channel in the vortex region is greater than the width of the flow channel in both the inlet and outlet regions. The mid-plane intersects the inlet region, the deflection region, the vortex region, and the outlet region. It is particularly preferred that the common mid-plane intersects the inlet region, the deflection region, the vortex region, and the outlet region in the central region of the flow channel and / or in the region of the centerline of the flow channel. Therefore, the enlargement of the flow cross-sectional area in the vortex region compared to the inlet and outlet regions is designed so that, in the common mid-plane, the flow channel in the vortex region is wider than the flow channel in the inlet and outlet regions. This ultimately results in a hydrodynamically favorable shape of the entire flow channel. It has been found to be particularly significant in terms of the hydrodynamic properties of the flow channel and the space requirements of the flow channel within the cell frame if the width of the flow channel in the vortex region in the common mid-plane is at least 10%, preferably at least 20%, and in particular at least 30% wider than the width of the flow channel in the inlet and / or outlet regions.

[0027] Alternatively or additionally, if the cross-sectional flow area of ​​the flow channel in the vortex region is larger than the cross-sectional flow area in the deflection region, this contributes to reducing the pressure loss across the entire flow channel. In this way, a gradual widening of the flow channel that is hydrodynamically favorable can be achieved, which can particularly preferably correspond to the formation of a vortex region within the flow channel. In this way, stall outside the flow channel can also be avoided or reduced. The difference in size between the cross-sectional flow area of ​​the vortex region and the cross-sectional flow area of ​​the deflection region is preferably at least 10%, more preferably at least 15%, and in particular at least 20%.

[0028] Independently of the above, the width of the flow channel in the vortex region can be greater than the width of the flow channel in the deflection region at the common mid-plane. Again, this achieves the aforementioned hydrodynamic advantages without the flow channel itself taking up significantly more space. The difference between the width of the flow channel in the vortex region and the width of the flow channel in the deflection region is preferably at least 10%, more preferably at least 15%, and especially at least 20%.

[0029] Alternatively or additionally, the distance from the inlet region to the outlet region in a common mid-plane, seen transversely to the flow direction in the inlet region, may be smaller than the width of the inlet and / or outlet region, thereby realizing a space-saving arrangement of the meander flow channels without incurring excessive pressure losses. The aforementioned dimensional difference is preferably at least 10%, more preferably at least 15%, in particular at least 20%.

[0030] The spatial requirements of the flow channel can be reduced if the distance from the inlet region to the outlet region, measured transversely to the flow direction of the inlet region, is greater than the distance from the inlet region to the vortex region, also measured transversely to the flow direction of the inlet region. Contrary to expectations, an increase in the cross-sectional flow area in the vortex region can be achieved without compromising overall pressure loss reduction at the expense of a corresponding increase in the distance from the inlet region to the vortex region. The difference in size between the aforementioned distances is preferably at least 10%, more preferably at least 15%, and especially at least 20%.

[0031] A good compromise between pressure loss and space requirements in the flow channel can also be achieved if the inner radius of the deflection region at the common mid-plane is larger than the distance from the inlet region to the vortex region transverse to the flow direction in the inlet region. A larger inner radius reduces the tendency for the flow to stall and form a wider vortex region behind it. Contrary to expectations, this does not affect the return flow from the vortex region to the inlet region, yet can be used to reduce the space requirements of the overall flow channel. The corresponding inner radius is preferably at least 10%, more preferably at least 15%, and especially at least 20% larger than the corresponding distance.

[0032] Alternatively or additionally, in a common mid-plane, the inner radius of the deflection region can be greater than the distance from the inlet region to the outlet region, as viewed transversely to the flow direction in the inlet region. Again, the hydrodynamic advantages described above 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%, and especially at least 20% greater than the corresponding distance.

[0033] Alternatively or additionally, if the width of the deflection section in the deflection region, seen in a common central plane transverse to the flow direction in the inlet region, is greater than the width of the deflection section at the level of the outlet region, a flow channel with high hydrodynamic functionality and occupying little space can be achieved. The larger width in the deflection region primarily serves to reduce pressure losses, while the small distance from the inlet region to the outlet region contributes to a smaller space requirement, with these two measures not interfering significantly with each other. This can be utilized even more extensively if the width of the deflection section, seen in a common central plane transverse to the flow direction in the inlet region, is greater than the width of the deflection region at the level of the vortex region. In this way, the vortex region can contribute both to a reduction in pressure losses and a reduction in the space requirement of the flow channel. The corresponding width difference is preferably at least 10%, more preferably at least 15%, and in particular at least 20%.

[0034] If the width of the deflection section at the level of the vortex region, seen transversely to the flow direction in the inlet region, is greater than the width of the deflection section at the level of the outlet region in a common mid-plane, this can ensure a flow with low pressure loss. At the same time, the flow channel can be designed so that it requires less space. The corresponding width difference is preferably at least 10%, more preferably at least 15%, in particular at least 20%.

[0035] Similarly, if the width of the vortex region transverse to the flow direction at the inlet region at the common mid-plane is greater than 1.5 times the width of the inlet and / or outlet regions, the space requirements of the flow channel can be kept to a minimum without excessively degrading the pressure loss through the flow channel, and the space requirements will be at most only slightly greater than for a standard deflector with a constant flow cross-sectional area.

[0036] In a first particularly preferred embodiment of the electrochemical cell, at least one cell frame according to any one of claims 1 to 11 is provided for each half-cell, so that the advantages already mentioned above can be utilized to a certain extent in both half-cells of the electrochemical cell.

[0037] In a first particularly preferred embodiment of the electrochemical flow reactor, a cell stack of electrochemical cells according to claim 12 or 13 is provided, which results in a high overall power density and efficiency of the electrochemical flow reactor.

[0038] In the following the invention will be explained in more detail with the aid of drawings which show only one embodiment. [Brief explanation of the drawings]

[0039] [Figure 1A] FIG. 1 is a longitudinal cross-sectional view of an electrochemical flow reactor according to the present invention in the form of a redox flow battery. [Figure 1B]FIG. 1 is a longitudinal cross-sectional view of an electrochemical flow reactor according to the present invention in the form of a redox flow battery. [Figure 2] FIG. 2 is a plan view showing a cell frame of the electrochemical flow reactor according to the present invention shown in FIG. 1. [Figure 3] FIG. 3 shows the deflector of the flow channel of the cell frame from FIG. 2 in a plan view.

[0040] 1A and 1B show longitudinal cross-sectional views of an electrochemical flow reactor 1 in the form of a redox flow battery with a cell stack including multiple electrochemical cells 2. The electrochemical flow reactor 1 includes three cells 2, each of which has two half-cells 3 containing a corresponding electrolyte. Each half-cell 3 has a cell frame 4 containing a cell chamber 5 through which an electrolyte stored in a storage container can flow. An electrode 6 is at least partially engaged in the cell chamber 5, and the electrode 6 also closes and seals the cell chamber 5 on one side. The electrolytes flowing through the cell chambers 5 are different from each other. Each cell chamber 5 is closed by a semipermeable membrane 7 provided between the cell frames 4 of the two half-cells 3 on the side opposite the electrode 6 that contacts the cell frame 4 of the second half-cell 3 of the same electrochemical cell 2. This prevents convective migration of the two different electrolytes from the two half-cells 3 into the cell chamber 5 of the cell frame 4 of the other half-cell 3. However, ions can pass from one electrolyte through the semipermeable membrane 7 to the other electrolyte by diffusion, resulting in charge transport. The redox reaction of the electrolyte's redox couple at electrode 6 of half-cell 3 of cell 2 releases or absorbs electrons. The released electrons can flow from one electrode 6 of cell 2 to the other electrode 6 via an electrical connection provided on the outside of flow reactor 1, which may have an electrical consumer. The reaction occurring at electrode 6 depends on whether the electrochemical flow reactor is being charged or discharged.

[0041] In the illustrated electrochemical flow reactor 1, the electrodes 6 lie flat against the outer surfaces 8 of the cell frames 4. Thus, the electrodes 6 form frame surfaces in the contact areas with the outer surfaces 8 of the cell frames 4, which function as sealing surfaces 9. A sealing material 10 is provided between the opposing outer surfaces 8 of the cell frames 4 of the cells 2, and the membranes 7 are sealed within this sealing material 10. The sealing material 10 lies flat against the outer surfaces 8 of the cell frames 4 that it contacts, thus forming frame surfaces that function as sealing surfaces 9.

[0042] Four channels extend along the electrochemical flow reactor 1. Two of these channels are supply paths 11 for supplying two electrolytes to the cell chambers 5 of the cell frame 4. The other two channels are drain paths 12 for discharging the electrolytes from the cell chambers 5 of the cell frame 4. One supply path 11 and one drain path 12 are shown in FIG. 1A . A flow channel 13 branches from the supply path 11 to one half cell 3 of each cell 2 as a supply channel, through which electrolyte can be supplied to the corresponding cell chamber 5 of the half cell 3. The opposite portion of the corresponding cell frame 4 is provided with a flow channel 14 as a drain channel, through which electrolyte can be discharged from the cell chamber 5 to the drain path 12. The supply path 11 (not shown in FIG. 1A ) and the drain path 12 (not shown in FIG. 1A ) allow the second electrolyte to flow through the other cell chamber 5 of the other half cell 3 via the same flow channels 13 and 14.

[0043] FIG. 2 shows a top view of the cell frame 4. Four openings 15 are provided at each corner of the cell frame 4, and each opening 15 forms part of a supply channel 11 or a drain channel 12. The flow channels 13 for supplying electrolyte and the flow channels 14 for draining electrolyte are recessed or open channels in the illustrated outer surface 8 of the frame shell 16 of the cell frame 4, which surrounds the cell chamber 5. The flow channels 13, 14 are closed at their peripheries when assembled to form the electrochemical flow reactor 1. In the illustrated electrochemical flow reactor 1, this closure is achieved, for example, by sealing material 10 and electrodes 6 in sections. However, the flow channels 13, 14 can also be provided as closed channels within the cell frame or can be closed by other components of the electrochemical flow reactor 1.

[0044] 2 only diagrammatically and in the illustrated embodiment are branched so that electrolyte can be supplied through one flow channel 13 distributed over the cell interior 5 and discharged through another flow channel 14 distributed over the cell interior 5, although this is not required. The flow channels 13, 14 can also be provided separately from the supply channel 11.

[0045] The flow channels 13, 14 are designed to have a meander shape with multiple deflection sections 17, one of which is shown in detail in FIG. 3 by way of example. The deflection sections 17 include bends 18, which ensure that the original flow direction R1 of the flow in the flow channels 13, 14 is at least substantially reversed after the bends 18 into an opposite flow direction R2. The deflection sections 17 are divided into four distinct sections arranged in succession with respect to the flow direction R1, R2 of the fluid, in this example, the electrolyte. In the inlet region 19, the fluid is fed in the original flow direction R1 to a deflection region 20, which performs the actual deflection of the flow direction R1 of the fluid stream. In the deflection region 20, the flow is then deflected away from the deflection region 20, at least partially in a flow direction opposite to the original flow direction R1. As a result of the deflection, multiple vortex regions are formed in the flow, particularly within the flow channels 13, 14, and these vortex regions occur at least substantially in vortex region 21. After at least most of the vortex region has disappeared, the vortex region 21 is followed by an outlet region 22 in which the deflected flow direction R2 is at least substantially opposite to the original flow direction R1. The flow direction R2 here can be reversed by 180°. However, the exact reversal of the flow direction is not important. In the preferred design shown, it is sufficient for the flow to flow back in the original inflow direction. This allows a meander-shaped design of the flow channels 13, 14 to be realized.

[0046] 3, the cross-sectional flow area QW of the flow channels 13, 14 in the vortex region 21 is greater than the cross-sectional flow areas QE, QA in both the inlet region 19 and the outlet region 22. At a common mid-plane ME, the width BW of the flow channels 13, 14 in the vortex region 21 is greater than the widths BE, BA of the flow channels 13, 14 in both the inlet region 19 and the outlet region 22. The common mid-plane ME intersects the inlet region 19, the deflection region 20, the vortex region 21, and the outlet region 22 in central regions of the flow channels 13, 14 and / or in the region of the centerline ML of the flow channels 13, 14, respectively. Furthermore, the cross-sectional flow area QW of the flow channels 13, 14 in the vortex region 21 is greater than the cross-sectional flow area QU in the deflection region 20.

[0047] When viewed transversely to the flow direction R1 at the inlet region 19, the width BW of the flow channels 13, 14 at the common mid-plane ME in the vortex region 21 is greater than the width BU of the corresponding flow channel 13, 14 in the deflection region 20. Furthermore, when viewed transversely to the flow direction R1 at the inlet region 19 at the common mid-plane ME, the distance A1 from the inlet region 19 to the outlet region 22 is less than the widths BE, BA of the inlet region 19 and the outlet region 22. When viewed transversely to the flow direction R1 at the inlet region 19 at the common mid-plane ME, the distance A1 from the inlet region 19 to the outlet region 22 is similarly greater than the distance A2 from the corresponding inlet region 19 to the vortex region 21.

[0048] Furthermore, at the common mid-plane ME, the inner radius IR of the deflection region 20 is greater than the distance A2 from the inlet region 19 to the vortex region 21 and is greater than the distance A1 from the inlet region 19 to the outlet region 22, when the respective distances A1, A2 are measured transversely to the flow direction R1 at the inlet region 19 along the common mid-plane ME. When measured in the same direction, the widths B1, B2 of the deflection portions 17 in the deflection region 20 and the vortex region 21 are greater than the width B3 of the deflection portion 17 at the level of the outlet region 22, and further, the width B1 of the deflection portion 17 in the deflection region 20 transversely to the flow direction R1 at the inlet region 19 is greater than the width B2 of the deflection portion at the level of the vortex region 21. Furthermore, at the common mid-plane ME, the width BW of the vortex region 21 transversely to the flow direction R1 at the inlet region 19 is greater than 1.5 times the widths BE, BU, BA of the inlet region 19 and / or the outlet region 22. [Explanation of symbols]

[0049] 1 Flow reactor 2 cells 3 Half Cell 4 Cell Frame 5 Cell Inner Chamber 6 electrodes 7 Semi-permeable membrane 8 External surface 9 Sealing surface 10 Sealing material 11 Supply route 12 Exhaust channel 13 Flow Channel 14 flow channels 15 Aperture 16 Frame shell 17 Deflection section 18 Bend 19 Entrance area 20 deflection area 21 Vortex region 22 Exit area A1, A2 distance B1~B3 Width of deflection section BA Exit Area Width BE Width of entrance area BU deflection area width BW Width of the vortex region IR Inner Radius ME midplane QA Cross-sectional flow area of ​​the outlet region QE Cross-sectional flow area of ​​the inlet region QU Flow cross-sectional area of ​​deflection region QW vortex region flow cross section R1 Original flow direction R2 Deflected flow direction

Claims

1. A cell frame (4) for an electrochemical flow reactor (1), in particular for a redox flow battery, the cell frame (4) circumferentially surrounding at least one cell chamber (5), the cell frame (4) having at least one flow channel (13, 14) connected to the at least one cell chamber (5) for supplying fluid to the cell chamber (5) and / or removing fluid from the cell chamber (5), the at least one flow channel (13, 14) having at least one deflection section (17) with a bend (18) for deflecting the fluid flow, in particular by at least about 90°, the flow channel (13, 14) having, successively in the fluid flow direction, an inlet region (19), a deflection region (20), a vortex region (21) and an outlet region (22), the fluid flow directions (R1, R2) in the inlet region (19) and the outlet region (22) being oriented at least substantially opposite to each other. In the cell frame (4), A cell frame (4) characterized in that the flow cross-sectional area (QW) of the flow channels (13, 14) in the vortex region (21) is larger than the flow cross-sectional areas (QE, QA) in the inlet region (19) and the outlet region (22).

2. 2. The cell frame of claim 1, wherein the deflecting portion (17) comprises a bend (18) for deflecting the fluid flow at approximately a right angle, preferably for at least substantially reversing the fluid flow in the opposite direction.

3. 3. A cell frame according to claim 1 or 2, characterized in that in a common mid-plane (ME), the width (BW) of the flow channels (13, 14) in the vortex region (21) is greater than the widths (BA, BE) of the flow channels (13, 14) in the inlet region (19) and the outlet region (22) and / or the flow cross-sectional area (QW) of the flow channels (13, 14) in the vortex region (21) is greater than the flow cross-sectional area (QU) in the deflection region (20).

4. 4. A cell frame according to claim 1, wherein in a common mid-plane (ME), the width (BW) of the flow channels (13, 14) in the vortex region (21) in a direction transverse to the flow direction (R1) in the inlet region (19) is greater than the width (BU) of the flow channels (13, 14) in the deflection region (20) in a direction transverse to the flow direction (R1) in the inlet region (19).

5. 5. Cell frame according to any one of claims 1 to 4, characterized in that in a common mid-plane (ME), the distance (A1) from the inlet region (19) to the outlet region (22) in a direction transverse to the flow direction (R1) in the inlet region (19) is smaller than the widths (BA, BE) of the inlet region (19) and the outlet region (22) in a direction transverse to the flow direction (R1) in the inlet region (19).

6. 6. A cell frame according to claim 1, characterized in that in a common mid-plane (ME), a distance (A1) from the inlet region (19) to the outlet region (22) in a transverse direction to the flow direction (R1) in the inlet region (19) is greater than a distance (A2) from the inlet region (19) to the vortex region (21) in a transverse direction to the flow direction (R1) in the inlet region (19).

7. 7. A cell frame according to any one of claims 1 to 6, characterized in that, in a common mid-plane (ME), the inner radius of the deflection region (20) is greater than the distance (A2) from the inlet region (19) to the vortex region (21) in a transverse direction to the flow direction (R1) in the inlet region (19).

8. 8. Cell frame according to any one of claims 1 to 7, characterized in that, in a common mid-plane (ME), the inner radius of the deflection area (20) is greater than the distance (A1) from the inlet area (19) to the outlet area (22) in a direction transverse to the flow direction in the inlet area (19).

9. 9. Cell frame according to any one of claims 1 to 8, characterized in that, in a common mid-plane (ME), the width (B1) of the deflection section in the deflection area (20) in a direction transverse to the flow direction (R1) in the inlet area (19) is greater than the width of the deflection section at the level of the outlet area (22), preferably in a common mid-plane (ME), the width (B2) of the deflection section in the deflection area (20) in a direction transverse to the flow direction (R1) in the inlet area (19) is greater than the width of the deflection section at the level of the vortex area (21).

10. 10. Cell frame according to any one of claims 1 to 9, characterized in that, in a common mid-plane (ME), the width (B1) of the deflection section in the transverse direction to the flow direction (R1) in the inlet region (19) at the level of the vortex region (21) is greater than the width (B3) of the deflection section in the transverse direction to the flow direction (R1) in the inlet region (19) at the level of the outlet region (22).

11. 11. Cell frame according to any one of claims 1 to 10, characterized in that, in a common mid-plane (ME), the width (B2) of the vortex region (21) in a transverse direction to the flow direction (R1) at the inlet region (19) is greater than 1.5 times the width (BE, BA) of the inlet region (19) and / or the outlet region (22) in a transverse direction to the flow direction (R1) at the inlet region (19).

12. 12. An electrochemical cell (2) for a flow reactor (1), in particular an electrochemical cell (2) for a redox flow battery, comprising at least one cell frame (4) according to any one of claims 1 to 11.

13. 13. An electrochemical cell according to claim 12, characterized in that at least one cell frame (4) according to any one of claims 1 to 11 is provided for each half cell (3).

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

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

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