Cooling field for a stacked electrochemical system and electrolyzer

Abstract

The invention relates to a cooling field (1) for a stacked electrochemical system (10), in particular an electrolyzer, and has at least one coolant inlet (2) and at least one coolant outlet (3) which is larger than the at least one coolant inlet, in particular two such inlets (2) and two such outlets (3), wherein: an inlet region (4), a main flow field (7) and an outlet region (9) are formed between the coolant inlet (2) and the coolant outlet (3); the main flow field (7) has a central constricted region (8); in the central constricted region (8), channels (13) are formed which extend parallel to one another in the region in question, whereas a plurality of at least singly bent channel portions (16, 17) are present between the constricted region (8) and the transitions (14, 15) to the inlet region (4) and the outlet region (9), respectively; and the main flow field (7) is adjoined, on the side of the coolant inlet (2), by a rib structure (18) of the inlet region (2) and, on the side of the coolant outlet (3), by a pin structure of the outlet region (3), with distance from the mentioned channel portions (16, 17) being maintained in each case.

Description

[0001] Cooling field for a stacked electrochemical system and electrolyzer

[0002] The invention relates to a cooling field intended for use in a stacked electrochemical system. The invention further relates to an electrolyzer for water electrolysis.

[0003] An electrolyzer for water electrolysis, i.e., for the production of hydrogen from water, is known, for example, from DE 10 2023 109 185 A1. The known electrolyzer includes, among other things, a cooling field frame as a component of a cell stack. Bipolar plates of the electrolyzer according to DE 10 2023 109 185 A1 separate a half-cell of a first electrochemical cell from a half-cell of another electrochemical cell. A channel area is located between a port kept clear by the bipolar plate and an active area of ​​the electrochemical cells, i.e., electrolysis cells. Several groups of protrusions are formed in the channel area by the bipolar plate; these serve as support structures and simultaneously as flow-conducting structures.The port, which is separated from the active area of ​​the electrolyzer by the channel area, lies in an opening of a frame which is arranged in a cooling plane of the stacked electrolyzer, the cooling plane being located between two half-sheets from which the bipolar plate is constructed.

[0004] An electrolyzer described in US 2022 / 0243348 A1 is designed to convert CO and CO2 into other carbon-containing substances, such as chemicals and fuels. US 2022 / 0243348 A1 details the design of flow fields and gas diffusion layers.

[0005] Another electrochemical system is described in DE 10 2022 110 122 A1.

[0006] In this case, it is an electrolysis stack that processes process water, with a coolant circuit separate from the process water for temperature control.

[0007] The invention is based on the objective of further developing the cooling of electrochemical systems, in particular electrolyzers, compared to the prior art, with a particular aim of achieving the most uniform cooling possible.

[0008] This problem is solved according to the invention by a cooling field having the features of claim 1 for a stacked electrochemical system. According to claim 10, the electrochemical system can in particular be an electrolyzer for water electrolysis.

[0009] The cooling field comprises at least one coolant inlet and at least one larger coolant outlet. Water or a liquid containing water as its main component can be used as the coolant. Alternatively, oil, for example, can be used as a coolant.

[0010] Between the coolant inlet and outlet, regardless of the type of coolant, an inlet area, a main flow field, and an outlet area are formed. The main flow field is larger than the inlet area and larger than the outlet area, in particular larger than the sum of the areas of the inlet and outlet areas. The area of ​​the inlet area can be the same as the area of ​​the outlet area. For example, the inlet area, which does not include the area of ​​the coolant inlet, is slightly larger than the outlet area, for example by at least 1% but not more than 10%, whereby, analogous to the definition of the inlet area, the area of ​​the coolant outlet is also not to be included in the outlet area.

[0011] The main flow field, lying in a plane normal to the stacking direction of the electrochemical system comprising at least one cooling field according to claim 1, has a central constriction region in which the main flow field is narrower than the inlet and outlet regions, while regions of greater width of the main flow field are present at the transitions between the main flow field and the inlet and outlet regions. The width of the various regions and fields is to be measured in the plane of the main flow field, and thus also of the inlet and outlet regions, orthogonal to the main flow direction of the coolant.

[0012] In the aforementioned constriction region of the main flow field, channels are formed which run parallel to each other and parallel to a reference line that passes centrally through the coolant inlet and outlet. This reference line defines the main flow direction of the coolant.

[0013] Between the central constriction and the transitions to the inlet and outlet areas, several channel sections, each with at least a simple bend, are formed. These sections are connected to the inlet and outlet areas in different ways: on the coolant inlet side, a ribbed structure, and on the coolant outlet side, a pin structure, are adjacent to the main flow field, maintaining a distance from the aforementioned channel sections. The ribbed structure is part of the inlet area, and the pin structure is part of the outlet area. The pins forming the pin structure are approximately point-like in shape.Geometric elements that deviate from a perfectly circular shape, exhibiting a slightly elongated form, particularly with a length-to-width ratio of no more than five, are also considered pins. Larger length-to-width ratios, such as those found in the inlet area, are referred to as ribs. Ribs can be straight, simply curved, or multiply curved.

[0014] Overall, the ribs structuring the inlet area contribute significantly to a uniform distribution of the coolant across the individual channels of the main flow field. In contrast, such a distribution or collection function is not required in the outlet area to direct the coolant to the outlet. Instead, a static function within the cell stack, which forms the main component of the electrochemical system, takes precedence. This function is fulfilled by the pin-shaped structural elements of the outlet area.

[0015] Various possible configurations of the cooling field provide for the existence of edge channel fragments parallel to the reference line at the two transitions between the main flow field, the inlet area, and the outlet area. These edge channel fragments are attributable to one of the channel sections that are at least singly bent, and in these cases, multiply bent. In addition to the edge channel fragments, further channel fragments, each attributable to a multiply bent channel section, can be arranged. These fragments have a length that decreases with decreasing distance from the reference line, so that the edge channel fragment, together with the other, also doubly bent, channel fragments, forms a triangular sub-area of ​​the main flow field.

[0016] In addition to the doubly bent channel sections, which form, among other things, the aforementioned triangular section, several simply bent channel sections can be arranged, exhibiting an angle of inclination relative to the reference line that decreases with increasing distance from the triangular section. Optionally, several point-like structural elements are formed on the inlet side of the main flow field, within the inlet area, adjacent to the simply bent channel sections.

[0017] Regardless of the precise design of the main flow field, the rib structure of the inlet area can comprise continuous main ribs extending from the coolant inlet to the end of the rib structure on the main flow field side, as well as comparatively short auxiliary ribs. The auxiliary ribs are more prevalent in the section of the inlet area bordering the main flow field, whereas the rib structure in the section of the inlet area bordering the coolant inlet may consist predominantly or exclusively of main ribs. At the transition between the inlet area and the main flow field, the distance measured orthogonally to the reference line between two ribs—whether two main ribs, two auxiliary ribs, or a combination of one main and one auxiliary rib—may be greater than the distance measured between the adjacent channel sections in the main flow field.

[0018] The pin structure formed in the outlet area can consist exclusively of circular pins. Alternatively, configurations are possible in which the outlet pin structure comprises a matrix-like array of round pins adjacent to the main flow field, as well as several, particularly two, rows of oval pins aligned longitudinally with the reference line and adjacent to the coolant outlet. Regarding the distinction between oval pins and ribs, the previously mentioned length-to-width ratios are relevant.

[0019] The number of coolant inlets and outlets is not subject to any theoretical restrictions. For example, the cooling field comprises two coolant inlets and associated coolant outlets, being mirror-symmetrical about a median plane located midway between two reference lines that each intersect a coolant inlet and its associated outlet.

[0020] An electrolyzer according to the invention is designed for water electrolysis and comprises at least one cooling field according to the invention, which conducts cooling water that is separate from the process water of the electrolyzer, i.e., from highly purified water which is electrolytically decomposed into hydrogen and oxygen. The cooling field thus directs the cooling water for cooling an electrolysis cell in a separate plane from the process water through the electrolyzer.

[0021] The uniform cooling of the electrochemical cells via the cooling fields, which essentially cover the entire active area of ​​the cells—that is, the area in which the desired electrochemical reactions take place—particularly benefits the service life of the proton-permeable membranes of the individual cells. In short, a cooling field of an electrochemical system has at least one coolant inlet and at least one larger coolant outlet, in particular two such inlets and outlets each, wherein an inlet region, a main flow field, and an outlet region are formed between the coolant inlet and the coolant outlet, the main flow field having a central constriction region, and channels running parallel to each other in the central constriction region.whereas between the constriction area and the transitions to the inlet area or outlet area there are several channel sections with at least simple bends, and wherein on the side of the coolant inlet a rib structure and on the side of the coolant outlet a pin structure of the respective inlet or outlet area, each maintaining a distance to the aforementioned channel sections, is adjacent to the main flow field.

[0022] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows:

[0023] Fig. 1 shows a cooling field of an electrochemical system, namely an electrolyzer for water electrolysis, in top view.

[0024] Fig. 2 shows a detail from Fig. 1 ,

[0025] Fig. 3 shows a partial view of a plate element forming the cooling field of the electrolyzer in side view.

[0026] An electrochemical system designated by reference numeral 10 is, in this case, configured as an electrolyzer for water electrolysis. The electrolyzer 10 is arranged in a stacked configuration, with the stacking direction, as shown in Figures 1 and 2, perpendicular to the plane of the image. In the arrangement shown in Figure 3, the stacking direction lies in the plane of the image. Any terms such as "top," "bottom," "left," or "right" used in this text refer only to the figures and do not imply any statement about the spatial arrangement of the components of the electrochemical system 10. For the fundamental structure and function of the stacked electrochemical system 10, reference is made to the prior art cited at the outset.

[0027] The electrolyzer 10 is temperature-controlled with cooling water or another coolant that is separate from the process water. Numerous cooling fields are provided for this purpose.

[0028] 1 is provided, which lie in mutually parallel planes. The coolant, in particular cooling water, to be distributed in the cooling field 1 is supplied via a coolant inlet 2 and discharged via a coolant outlet 3. In the present case, a metallic plate element 32, which defines the structure of the cooling field 1, has mirror symmetry with respect to a median plane ME. The plate elements 32 are inserts which are installed above and below the individual cells of the electrochemical system 10.

[0029] The median plane ME is positioned midway between two reference lines G1 and G2, each running between the center of a coolant inlet 2 and the center of the corresponding coolant outlet 3. The main flow direction of the coolant in the cooling field 1 is determined by the orientation of the reference lines G1 and G2. As can be seen in Figure 1, the width of each coolant inlet corresponds to

[0030] 2 the width of the associated coolant outlet 3. However, in the main flow direction of the coolant, the coolant outlet 3 is more extended than the associated coolant inlet 2, so that the coolant outlet 3 has a larger area than the coolant inlet 2.

[0031] The coolant inlet 2 is located in an inlet area 4, which is divided into a narrow section 5 and a wide section 6. The main flow field of the cooling field 1, designated 7, borders the wide section 6 of the inlet area 4. Within the main flow field 7, a constriction area 8 is formed. On the outlet side, an outlet area designated 9 borders the main flow field 7. Analogous to the inlet area 4, the outlet area 9 also has a wide section 30 adjoining the main flow field 7 and a narrow section 29. The coolant outlet 3 is located in the narrow section 29. Within the main flow field 7, above the constriction area 8, there is a wider area 11, which borders the inlet area 4.Below the constriction region 8, there exists another region 12 of greater width, this region 12 of the main flow field 7 bordering the outlet region 9. The outer contours of the plate element 32 are mirror-symmetrical to another mirror plane, which is to be placed midway between the lower and upper edges of the plate element 32 and which intersects the median plane ME at a right angle.

[0032] In the main flow field 7, channels for the coolant, generally designated 13, are formed. All sections of the channels 13 located in the constriction region 8 are parallel to each other, aligned in the main flow direction of the coolant. The inlet end of the channels 13 is located at the transition between the inlet region 4 and the main flow field 7, designated 14. On the outlet side, the channels 13 terminate at a transition 15 between the main flow field 7 and the outlet region 9. The channels 13 have a uniform depth along their entire length, as can be seen in Figure 3. Likewise, the depth of all channels 13 is the same. As Figure 3 further illustrates, all channels 13 are mirror images of each other on the front and back sides of the plate element 32.

[0033] The channels 13 are completely straight in two rectangular sub-areas, designated 31, bordering the central plane ME. Furthermore, there are doubly bent channel sections 16 and singly bent channel sections 17, which together describe a fan-like structure. The doubly bent channel sections 16 correspond to edge channel fragments 19 at the left and right edges of the plate element 32, as shown in Figure 1. Parallel to each edge channel fragment 19, parallel channel fragments 20 are formed, also aligned along the reference lines G1, G2, the length of which decreases in the direction from the edge channel fragment 19 to the nearest reference lines G1, G2. The edge channel fragment 19 thus forms, together with the adjacent channel fragments 20, a triangular sub-area 21 of the main flow field 7. A total of four such triangular sub-areas 21 exist.Two of these sub-areas 21 extend along the upper edge of the main flow field 7 to the transition 14 between the main flow field 7 and the inlet area 4.

[0034] As shown in Figure 1, a rib structure 18 is formed in the inlet area 4. The rib structure 18 comprises main ribs 23 and, in comparison to these, shorter auxiliary ribs 24. Furthermore, several point-like structural elements 22, as shown in Figure 2, exist in the inlet area 4 in the region bordering the main flow field 7.

[0035] In contrast to the inlet area 4, the outlet area 9 features a matrix-shaped pin structure 25, predominantly formed by round pins 26, which together define an array 27 of round pins 26. Additionally, the outlet area 9 contains several oval pins 28 arranged in two rows adjacent to the coolant outlet 3. The oval pins 28 are located in the narrow section 29 of the outlet area 9. The wide section 30 of the outlet area 9 borders, among other things, the sub-area 31 of the main flow field 7, which consists exclusively of straight channels 13. This same sub-area 31 also borders the wide section 6 of the inlet area 4. The rib structure 18, the pin structure 25, and the channels 13 can be produced, for example, by etching.

[0036] Within the inlet area 4, the ribs 23, 24 of different lengths, supplemented by the individual point structural elements 22, are shaped in such a way that the coolant is distributed almost evenly to the various channels 13, regardless of whether these have angled sections 16, 17.

[0037] Additionally, the rib structure 18 of the inlet area 4 within the electrolyzer 10 has a supporting function. In the outlet area 9, a flow-guiding function is primarily performed by the oval pins 28, which are part of the pin structure 25. Otherwise, the pin structure 25 mainly serves a static function. The flow velocity of the coolant in the coolant outlet 3 is lower than in the coolant inlet 2. Together with the described structuring of the inlet area 4, the main flow field 7, and the outlet area 9, this contributes to efficient cooling with low flow resistance and thus low pressure loss.

[0038] List of reference signs

[0039] Cooling area

[0040] Coolant inlet

[0041] Coolant outlet

[0042] Inlet area, narrow section of the inlet area, wide section of the inlet area

[0043] Main flow field

[0044] constriction area

[0045] outlet area

[0046] Electrochemical system, electrolyzer

[0047] Area of ​​greater width of the main flow field, bordering the inlet area

[0048] Area of ​​greater width of the main flow field, bordering the outlet area

[0049] channel

[0050] Transition between the inlet area and the main flow field

[0051] Transition between the outlet area and the main flow field, double-angled channel section, single-angled channel section

[0052] Ribbed structure

[0053] Marginal canal fragment

[0054] Channel fragment, triangular sub-area of ​​the main flow field, point-like structural element

[0055] Main rib

[0056] Additional rib

[0057] Pin structure

[0058] Round pin

[0059] Field of round pins

[0060] Oval pin narrow section of the outlet area 30 wide section of the outlet area

[0061] 31 sub-area with straight channels

[0062] 32 plate elements

[0063] G1, G2 Reference line

[0064] ME Middle Level

Claims

Patent claims 1. Cooling field (1) for a stacked electrochemical system (10), with at least one coolant inlet (2) and at least one coolant outlet (3) larger than the coolant inlet (2), wherein an inlet region (4), a main flow field (7) and an outlet region (9) are formed between the coolant inlet (2) and the coolant outlet (3), wherein the main flow field (7) lying in a plane normal to the stacking direction of the electrochemical system (10) has a central constriction region (8) in which it is narrower than the inlet region (4) and the outlet region (4), while regions (11, 12) of greater width of the main flow field (7) are present at the transitions (14, 15) between the main flow field (7) and the inlet region (4) and the outlet region (9), and wherein channels (13) are formed in the central constriction region (8).which run parallel to each other and parallel to a reference line (G1, G2) in the relevant area, which is placed centrally through the coolant inlet (2) and the coolant outlet (3), whereas between the central constriction area (8) and the transitions (14, 15) to the inlet area (4) and outlet area (9) respectively, there are several channel sections (16, 17) that are at least simply angled, which are connected to the inlet area (4) and the outlet area (9) respectively in different ways, in that a rib structure (18) on the side of the coolant inlet (2) and a pin structure (25) on the side of the coolant outlet (3) of the respective inlet or outlet area (2, 3) are adjacent to the main flow field (7), in each case while maintaining a distance to the aforementioned channel sections (16, 17).

2. Cooling field (1 ) according to claim 1 , characterized in that at transitions (14, 15) between the main flow field (7) and the inlet area (4) on the one hand and the outlet area (9) on the other hand parallel to the reference line (G1 , G2) there exist edge channel fragments (19) which are to be attributed to one of the at least simply bent, in these cases multiple bent, channel sections (16).

3. Cooling field (1 ) according to claim 2, characterized in that, in addition to the edge channel fragments (19), further channel fragments (20) are arranged, each attributable to a multiply bent channel section (16), which have a length that decreases with decreasing distance from the reference line (G1 , G2), so that the edge channel fragment (19) together with the further channel fragments (20) forms a triangular partial area (21 ) of the main flow field (7).

4. Cooling field (1 ) according to claim 3, characterized in that, in addition to the doubly bent channel sections (16), which form among other things the said triangular partial surface (21 ), several simply bent channel sections (17) are arranged, which have an inclination angle relative to the reference line (G1 , G2) that decreases with increasing distance from the triangular partial surface (21 ).

5. Cooling field (1 ) according to claim 4, characterized in that on the inlet side of the main flow field (7) several point structural elements (22) attributable to the inlet area (4) are adjacent to the simply bent channel sections (17).

6. Cooling field (1 ) according to one of claims 1 to 4, characterized in that the rib structure (18) of the inlet area (4) comprises continuous main ribs (23) extending from the coolant inlet (2) to the main flow field side end of the rib structure (18) and comparatively short additional ribs (24), wherein the additional ribs (24) are more frequently present in the section of the inlet area (4) bordering the main flow field (7).

7. Cooling field (1 ) according to claim 6, characterized in that at the transition (14) between the inlet area (4) and the main flow field (7) the distance to be measured orthogonally to the reference line (G1 , G2) between two ribs (23, 24), whether main or additional ribs, is greater than the distance to be measured between the adjacent channel sections (16, 17).

8. Cooling field (1 ) according to one of claims 1 to 7, characterized in that the pin structure (25) of the outlet area (9) comprises a matrix-shaped field (27) of round pins (26) adjacent to the main flow field (7) and several, in particular two, rows of oval pins (28) adjacent to the coolant outlet (3) and aligned in the longitudinal direction of the reference line (G1 , G2).

9. Cooling field (1 ) according to one of claims 1 to 8, characterized in that it comprises two coolant inlets (2) and associated coolant outlets (3) and is designed in a mirror-symmetrical manner with respect to a central plane (ME) which is placed centrally between two reference lines (G1 , G2) which each centrally intersect a coolant inlet (2) and the associated coolant outlet (3).

10. Electrolyzer (10) for water electrolysis, comprising at least one cooling field (1) designed according to one of claims 1 to 9, which is provided for conveying cooling water that is separated from process water to be electrolytically decomposed into hydrogen and oxygen in the electrolyzer (10).

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