Heat exchanger arrangement

Abstract

The invention relates to a heat exchanger arrangement (1), - with a main air path (2) through which air (L) flows along a main flow direction (H), - with at least one heat exchanger (3) arranged in the main air path (2), which has a plurality of heat exchanger air paths (4) communicating fluidically with the main air path (2) and thus through which the air (L) can flow, as well as a plurality of fluid paths (5) that are fluidically separated from the heat exchanger air paths (4) and through which a fluid (F) can flow for thermal coupling of the fluid (F) with the air (L), - with a fan (6) arranged in the main air path (2) to drive the air (L) in the main air path (2), - with a separating device (8) arranged upstream of the heat exchanger (3) with respect to the main flow direction (H) in the main air path (2), which divides the main air path (2) upstream of the at least one heat exchanger (3) to the heat exchanger (3) into a first air path zone (7a) and into at least one second air path zone (7b-7h) fluidically separated from the first air path zone (7a), so that the air path zones (7a-7f) communicate fluidically separately from each other with the heat exchanger air paths (4).

Description

[0001] The present invention relates to a heat exchanger arrangement.

[0002] Heat exchangers are often used as evaporators in air conditioning systems. In this case, heat is supplied to a refrigerant flowing through the heat exchanger, causing the refrigerant to evaporate. The heat of vaporization supplied to the refrigerant is transferred to it by air also flowing through the heat exchanger. This reduces the temperature of the air. This can also occur in a refrigerant chiller, for example, when it absorbs heat from the environment and supplies it to the refrigeration circuit for use in a heat pump system with a chiller (i.e., an indirect evaporator).

[0003] In practice, it often occurs that the air temperature is below its dew point, allowing the moisture in the air to condense into water in the heat exchanger. However, this water increases the flow resistance of the air passing through the heat exchanger, hindering its flow. Therefore, it is essential to remove any condensation that accumulates in the heat exchanger as quickly and completely as possible.

[0004] In conventional air conditioning systems, this is usually achieved using a fan to circulate air through the heat exchanger. Such a fan can also be used to blow or extract the water that has accumulated in the heat exchanger, depending on whether the fan is located upstream or downstream of the heat exchanger.

[0005] A disadvantage of this configuration is that the fan typically removes the condensate from the heat exchanger unevenly. This results in areas within the heat exchanger where airflow is minimal, while other areas remain heavily saturated. Consequently, the fan directs most of the air entering the heat exchanger through these areas. As a result, the remaining condensate in these areas is poorly or not at all removed due to insufficient airflow, thus permanently reducing the heat exchanger's efficiency.

[0006] It is therefore an object of the present invention to demonstrate new approaches in the development of heat exchanger arrangements comprising a heat exchanger and a fan for conveying air through the heat exchanger. In particular, an improved embodiment of such a heat exchanger arrangement is to be created in which the aforementioned disadvantage is at least partially, and ideally even completely, eliminated.

[0007] This problem is solved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent patent claims.

[0008] The basic idea of ​​the invention is therefore to provide, in a heat exchanger arrangement described above, a separating device with at least one separating element in the air path between the fan and the heat exchanger – this air path is hereinafter also referred to as the “main air path” – which divides the main air path into at least two fluidically separated air path zones. Air conveyed by the fan thus enters one of the existing air path zones and, due to the separating element present there, remains in that air path until it reaches the heat exchanger and, in particular, until it enters the air paths provided in the heat exchanger – these are hereinafter referred to as “heat exchanger air paths”.

[0009] Once air has entered a specific air path zone, it cannot move to another air path zone before reaching the heat exchanger or its air paths. If condensation has accumulated in a particular area of ​​the heat exchanger, the air moved by the fan cannot simply bypass the water by moving to another air path zone. Instead, due to the existing separation mechanism, it must remain in the selected air path zone and thus inevitably encounters any condensation present, carrying it away from the heat exchanger.

[0010] As a result, any residual water present in the heat exchanger is captured and carried away by air and thus transported out of the heat exchanger.

[0011] In this way, effective removal of a large proportion of the condensate that forms in the heat exchanger is ensured, thereby improving the efficiency of the heat exchanger, as the heat exchanger air path can be efficiently kept free of water.

[0012] Furthermore, comparatively little energy and time is required to remove the water from the heat exchanger, and the risk of damaging icing of the heat exchanger by frozen water is reduced.

[0013] Advantageously, the cycle time at which water needs to be removed again is also increased. Finally, the pressure drop generated by the heat exchanger in the air is reduced. In addition, the air distribution is improved, thus increasing the efficiency of the heat exchanger.

[0014] The effect described above, which is essential to the invention, can be further enhanced if not just a single separating element, but two or more separating elements and thus a corresponding number of air path zones are created.

[0015] Following the above inventive concept, a heat exchanger arrangement according to the invention comprises a main air path through which air flows along a main flow direction, and a heat exchanger arranged in the main air path. The heat exchanger has a plurality of heat exchanger-air paths that communicate fluidically with the main air path and are thus permeable to air flow. Furthermore, the heat exchanger has a plurality of fluid paths, fluidically separated from the heat exchanger-air paths, through which a fluid can flow, for thermally coupling the fluid to the air flowing through the heat exchanger. The heat exchanger is therefore advantageously a direct heat exchanger in which heat is transferred from one fluid – for example, air – to another fluid – for example, a refrigerant or coolant.The fluid can therefore be a refrigerant, in particular if the heat exchanger is part of an air conditioning system and is used there as an evaporator, at least in certain operating conditions.

[0016] The fluid paths in the heat exchanger are fluidically separated from the heat exchanger air paths and also from the main air path. For this purpose, the fluid paths can be formed, for example, by pipe sections through which the fluid flows and which are arranged at a distance from one another. The spaces formed between the pipe sections can constitute the heat exchanger air paths through which the air flows.

[0017] The fluid paths can all extend along a common longitudinal direction, which may run transversely, and in particular perpendicularly, to the main flow direction. The pipe bodies used to delimit the fluid paths can, in particular, be formed by flat tubes. A heat exchanger described above is known to those skilled in the art as a "tube bundle heat exchanger".

[0018] Furthermore, the heat exchanger arrangement according to the invention comprises a fan arranged in the main air path for driving the air in the main air path. According to the invention, the heat exchanger arrangement includes a separating device arranged upstream of the heat exchanger in the main air path with respect to the main flow direction, which divides the main air path in the area upstream of the heat exchanger up to the heat exchanger into a first air path zone and into at least one second air path zone fluidically separated from the first air path zone, so that the two air path zones communicate fluidically separately with the heat exchanger air paths of the heat exchanger.

[0019] In a preferred embodiment of the heat exchanger according to the invention, the fan is arranged upstream of the heat exchanger in the main air path with respect to the main flow direction. Alternatively, the fan can also be arranged downstream of the heat exchanger in the main air path with respect to the main flow direction.

[0020] In a further preferred embodiment, the first air path zone communicates fluidically with a first part of the heat exchanger air paths, which is distinct from at least a second part of the heat exchanger air paths, with which the first air path zone does not communicate. Correspondingly, the second air path zone communicates fluidically with a second part of the heat exchanger air paths, but not with the first part. In this way, it is ensured that air from the first air path zone enters a different part of the heat exchanger than air from the second air path zone.

[0021] Particularly advantageous is the separation device comprising at least one separating element arranged between the first air path zone and at least one second air path zone. Such a separating element ensures the fluidic separation of the air path zones essential to the invention. The separating element can, in particular, be designed in the form of struts.

[0022] Particularly advantageous is the design of at least one partition element as a fluid-tight partition wall. Such a partition wall is technically feasible and therefore cost-effective to manufacture, and also requires very little installation space. This also prevents the flow cross-section of the main air path from being unnecessarily reduced.

[0023] Particularly advantageously, the separating element or partition extends, preferably along the main flow direction, from the fan to the heat exchanger. This advantageously ensures that the air, once it has entered a specific air path zone, cannot leave that air path zone and pass into another air path zone before reaching the heat exchanger. This achieves the effect described above, which is essential to the invention.

[0024] According to an advantageous embodiment, the fan comprises a housing with an opening through which air can flow, in which a rotatable fan wheel is arranged. In this embodiment, the fan wheel is rotatable about an axis of rotation extending along the main flow direction and along a circumferential direction extending perpendicular to the main flow direction and rotating about this axis. In this embodiment, at least one separating element or partition wall is arranged at least partially within an extension of the housing opening along the main flow direction or the axis of rotation in a cross-section perpendicular to the main flow direction and, alternatively or additionally, in the viewing direction of an observer looking at the housing opening along the main flow direction. Particularly preferably, the separating element or partition wall can be arranged completely within the extension.This advantageously ensures that a significant proportion of the air conveyed by the fan or its impeller is divided among the air path zones formed by the separation device.

[0025] In another preferred embodiment, at least one separating element or partition extends along the circumferential direction. In an alternative, yet equally preferred embodiment, in which the radial direction is perpendicular to both the main flow direction and the circumferential direction away from the axis of rotation, at least one separating element or partition extends along the radial direction. The person skilled in the art can thus select from different geometries depending on the application. This allows for maximum flexibility in the configuration of the separating device.

[0026] According to an advantageous refinement, the fluid paths extend along a common longitudinal direction. In this refinement, at least one separating element extends along the longitudinal direction and / or orthogonally to this longitudinal direction.

[0027] Preferably, a first separating element extends along the longitudinal direction and a second separating element extends perpendicular to the longitudinal direction. These two separating elements thus divide the main air path into at least four air path zones. Particularly preferably, in this variant, the two separating elements can intersect at a point located on the axis of rotation.

[0028] In another advantageous embodiment, the heat exchanger, and in particular its fluid paths, extends perpendicular to the main flow direction along a vertical axis from a lower end to an upper end. In this embodiment, at least one separating element or partition wall is arranged in a lower end section facing the lower end with respect to the vertical direction. Thus, this separating element or partition wall divides the main air path with respect to the vertical direction into a first air path zone facing the lower end of the heat exchanger and a second air path zone facing the upper end of the heat exchanger.

[0029] Particularly advantageous in the aforementioned further development, the heat exchanger can be arranged relative to a direction of gravity such that the vertical direction extends parallel to the direction of gravity. In this way, a lower air path zone with respect to the vertical direction is created, in which, due to gravity, a large proportion of the water from the condensed air will accumulate.

[0030] According to a further preferred embodiment, at least one separating element or at least one partition wall is curved and preferably has the geometry of a circular arc.

[0031] Advantageously, the separating device can be connected, preferably permanently, to the fan, in particular to the housing, and / or to the heat exchanger.

[0032] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0033] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0034] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0035] They show, schematically: Fig. 1. A rough schematic of the structure of a heat exchanger arrangement according to the invention, Fig. 2-4 a further development of the example of the heat exchanger arrangement of the Fig. 1 each in a perspective representation and from different perspectives, Fig. 5 the separation device of the heat exchanger arrangement according to the Fig. 2 to 4 in a cross-section and in a highly simplified representation, Fig. 6 another variant of a heat exchanger arrangement according to the invention,

[0036] The Fig. Figure 1 shows a schematic diagram of the structure of a heat exchanger arrangement 1 according to the invention. The heat exchanger arrangement 1 comprises a main air path 2 through which air L flows along a main flow direction H, and a heat exchanger 3 arranged in the main air path 2.

[0037] The heat exchanger 3 has a plurality of heat exchanger-air paths 4 that communicate fluidically with the main air path 2 and are thus permeable to air L. Furthermore, the heat exchanger 3 has a plurality of fluid paths 5, fluidically separated from the heat exchanger-air paths 4, through which a fluid F can flow, for thermally coupling the fluid F with the air L.

[0038] The heat exchanger 3 can expediently be a direct heat exchanger in which heat of vaporization is transferred from the air L to the fluid F present in liquid phase - in the example a refrigerant - in order to evaporate the fluid F or the refrigerant.

[0039] The fluid paths 5 are fluidically separated from the heat exchanger air paths 4 and also from the main air path 2. In this example, the fluid paths 5 are bounded by tube bodies 16, through which the fluid F can flow and which are arranged at intervals along a stacking direction S perpendicular to the main flow direction H. Thus, the spaces 17 formed between the individual tube bodies 16 constitute the heat exchanger air paths 4 through which the air L can flow. The tube bodies 16 can, for example, be flat tubes.

[0040] The fluid paths 5, and thus also the pipe bodies 16, all extend along a common longitudinal direction LR, which is perpendicular to the main flow direction H and also perpendicular to the stacking direction S. A vertical direction V can run parallel to the stacking direction S and can also extend along a direction of gravity G. The fluid F therefore flows through the pipe bodies 16 along the longitudinal direction LR.

[0041] As the Fig. As can also be seen in Figure 1, the heat exchanger arrangement 1 according to the invention comprises a fan 6 arranged in the main air path 2 for driving the air L in the main air path 2. In the example, the fan 6 is arranged upstream of the heat exchanger 3 in the main air path 2 with respect to the main flow direction H.

[0042] The fan 6 has a housing 11 through which air L can flow. For this purpose, the housing 11 includes an opening 12 through which air L can flow, in which a rotatable fan wheel (not shown) is arranged. The fan wheel can be rotatable about an axis of rotation D extending along the main flow direction H and, for this purpose, can be rotatably mounted on a fan hub 13 fixed to the housing 11. The fan hub 13 can be rigidly connected to the housing 11 by means of strut-like fastening elements 22. Furthermore, the fan wheel can be rotatable along a circumferential direction U extending perpendicular to the main flow direction H and rotating about this axis of rotation D. For this purpose, the fan wheel can be rotatably mounted on the housing 11.

[0043] In this example, the fan 6 is arranged upstream of the heat exchanger 3 in the main air path 2. In a variant not shown, however, it is also conceivable that the fan 6 is arranged downstream of the heat exchanger 3 in the main air path 2.

[0044] Furthermore, the heat exchanger arrangement 1 includes a separating device 8 arranged between the heat exchanger 3 and the fan 6 in the main air path 2. In the example of the Fig. 1. The separation device 8 divides the main air path 2 in the area between the heat exchanger 3 and the fan 6 up to the heat exchanger 3 into a first air path zone 7a and a second air path zone 7b, which is fluidically separated from the first air path zone 7a. The division is implemented such that the two air path zones 7a and 7b communicate with the heat exchanger air paths 4 in a fluidically separate manner.

[0045] For the fluidic separation of the two air path zones 7a, 7b, the separation device 8 can be used as in the Fig. Figure 1, shown graphically, comprises a separating element 9a arranged between the first air path zone 7a and the second air path zone 7b. The separating element 9a can be designed as a preferably fluid-tight partition 10a and / or in the form of a strut. The separating element 9a or the partition 10a extends, as schematically shown, along the main flow direction H from the fan 6 to the heat exchanger 3.

[0046] In the example of the Fig. 1 The first air path zone 7a communicates fluidically with a first part 4a of the heat exchanger air paths 4, which is different from a second part 4b of the heat exchanger air paths 4a, with which the second air path zone 7b communicates fluidically.

[0047] The Fig. Figures 2 to 4 illustrate a further development of the example of Fig. 1 each in a perspective view and from different perspectives. For the sake of clarity, in the Fig. Figures 2 to 4 of the heat exchangers 3 have been omitted; that is, these figures only show the fan 6 and the separating device 8 essential to the invention. The longitudinal direction LR of the in the Fig. The fluid paths 2 to 4 of the heat exchanger 3, which are not shown, are each indicated in these figures in the form of an arrow.

[0048] As the Fig. As can be seen from Figures 2 to 4, the separating device 8 can comprise a housing frame 18 that encloses the main air path 2 and surrounds an interior frame space 19 through which the air L can flow. A first and a second separating element 9a, 9b are arranged in the interior frame space 19, each forming a first and second partition wall 10a, 10b, respectively.

[0049] To illustrate, the Fig. 5 in a cross-section perpendicular to the main flow direction H the contour of the separating elements 9a, 9b.

[0050] According to the Fig. From 2 to 5, the first separating element 9a or the first partition wall 10a extends along the longitudinal direction LR, whereas the second separating element 9b or second partition wall 10b extends perpendicular to the first separating element 7a and thus also orthogonally to the longitudinal direction LR. Both separating elements 9a, 9b are designed in a strut-like manner.

[0051] How in particular the Fig. As can be seen in Figure 5, the two separating elements 9a, 9b intersect at a point Z located on the axis of rotation D of the fan wheel. Thus, the two separating elements 9a, 9b each extend along the radial direction R. In doing so, the two separating elements 9a, 9b divide the main air path into four air path zones 7a-7d, each with approximately the same extent.

[0052] As the Fig. As can also be seen from Figures 2 to 5, the separating device 8 comprises, in addition to the two separating elements 9a, 9b, four further third separating elements 9c-9f, which are also each designed as partition walls 10c-10f. These separating elements 9c-9f each essentially have the geometry or shape of a circular arc, with two separating elements 9c, 9e or 9d, 9f opposing each other in the cross-section shown perpendicular to the main flow direction H or to the axis of rotation D. In this way, as is particularly evident from the Fig. 5 removable, four further air path zones 7e-7h created, so that a total of eight air path zones 7a to 7h are provided.

[0053] The Fig. Figure 6 illustrates a further variant of the heat exchanger arrangement 1 according to the invention and shows it in a view direction B from an observer's perspective along the main flow direction H towards the heat exchanger 3. Since the fan 6 and the separating device 8 are hidden in this top view of the heat exchanger, both components of the heat exchanger arrangement 1 are shown separately and at a distance from the heat exchanger 3 in a highly simplified representation. Fig. 6 shown offset to the left of heat exchanger 3.

[0054] According to Fig. In section 6, the heat exchanger 3, with its spaced-apart pipe bodies 16 that define the fluid paths 5, extends along a vertical direction V from a lower end 14a to an upper end 14b. The vertical direction V extends along a direction of gravity G. Furthermore, the vertical direction V is also perpendicular to the main flow direction H and parallel to the longitudinal direction LR of the fluid paths 5 and the pipe bodies 16, so that the longitudinal direction LR also extends along the vertical direction V and along the direction of gravity G. The lower end 14a and the upper end 14b of the heat exchanger 3 are thus opposite each other along the vertical direction V and also along the direction of gravity G.

[0055] The lower end 14a of the heat exchanger 3 can be formed by a fluid distributor 20, which communicates fluidically with the fluid paths 5, so that the fluid F can be distributed from the fluid distributor 20 to the individual fluid paths 5. Similarly, the upper end 14b of the heat exchanger 3 can be formed by a fluid collector 21, which is located opposite the lower end 14a with the fluid distributor 20 along the vertical direction V and thus the direction of gravity G, and also communicates with the fluid paths 5, so that fluid F flowing through the fluid paths 5 can be collected in the fluid collector 21.

[0056] As shown in the diagram of heat exchanger 3 Fig. As illustrated in Figure 6, due to the effect of gravity G, condensed air in the form of (condensed) water W will accumulate in an end section 15 of the heat exchanger 3 facing the lower end 14a, in which the fluid distributor 20 is also located.

[0057] Therefore, in heat exchanger arrangement 1 of the Fig. 6 in the lower end section 15 analogous to the example of the Fig. 1. A separating element 9a in the form of a partition wall 10a is provided. This separating element 9a or partition wall 10a divides the main air path 2 into a first air path zone 7a facing the lower end 14a and a second air path zone 7b facing the upper end 14b.

[0058] In the example of the Fig. In section 6, the separating element 9a or the partition wall 10a is curved and has the geometry of a circular arc. The separating element 9a or the partition wall 10a can be arranged completely in the lower end section 15, as shown. Reference symbol list 1 heat exchanger arrangement 2 main air paths 3 heat exchangers 4 Heat exchanger air path 5 Fluid path 6 fans 7a, b Air path zone 8 Separating device 9a, b Separating element 10a, 10b Partition wall 11 cases 12 Case opening 13 fan hub 14a lower end 14b upper end 15 lower end section 16 pipe bodies 17 spaces 18 housing frames 19 Frame interior 20 fluid distributors 21 fluid collectors 22 fasteners L air F Fluid W water H Main flow direction B View direction U circumferential direction R radial direction V Vertical direction LR longitudinal direction G direction of gravity D axis of rotation

Claims

Heat exchanger arrangement (1),- with a main air path (2) through which air (L) flows along a main flow direction (H),- with at least one heat exchanger (3) arranged in the main air path (2), which has a plurality of heat exchanger air paths (4) communicating fluidically with the main air path (2) and thus through which the air (L) flows, as well as a plurality of fluid paths (5) through which a fluid (F) flows, fluidically separated from the heat exchanger air paths (4), for thermally coupling the fluid (F) with the air (L),- with a fan (6) arranged in the main air path (2) for driving the air (L) in the main air path (2),- with athe main flow direction (H) upstream of the at least one heat exchanger (3) in the main air path (2) a separating device (8) which divides the main air path (2) upstream of the at least one heat exchanger (3) to the at least one heat exchanger (3) into a first air path zone (7a) and into at least one second air path zone (7b-7h) fluidically separated from the first air path zone (7a), so that the air path zones (7a-7f) communicate fluidically separately from each other with the heat exchanger air paths (4). Heat exchanger arrangement according to claim 1, characterized in that the first air path zone (7a) communicates fluidically with a first part (4a) of the heat exchanger air paths (4) which is different from at least a second part (4b) of the heat exchanger air paths (4a) with which the at least one second air path zone (7b-7h) communicates fluidically. Heat exchanger arrangement according to claim 1 or 2, characterized in that the separating device (8) comprises at least one separating element (9a-9f) arranged between the first air path zone (7a) and the at least one second air path zone (7b-7h), preferably at least one separating element (9a-9f) is designed as a fluid-tight partition wall (10a-10d). Heat exchanger arrangement according to one of claims 1 to 3, characterized in that the separating element (9a-9f) or the partition wall (10a-10f) extends, preferably along the main flow direction (H), from the fan (6) to the at least one heat exchanger (3). Heat exchanger arrangement according to one of the preceding claims, characterized in that: - the fan (6) comprises a housing (11) with a housing opening (12) through which the air (L) can flow, in which a rotatable fan wheel is arranged; - the fan wheel is rotatable about an axis of rotation (D) extending along the main flow direction (H); - the fan wheel is rotatable along a circumferential direction (U) extending perpendicular to the main flow direction (H) and rotating about this axis of rotation (D); - in a cross-section perpendicular to the main flow direction (H) and / or in a viewing direction (B) towards the housing opening (12) along the main flow direction (H), at least one separating element (9a-9) or at least one partition wall (10a-10d) is arranged at least sectionally in an extension of the housing opening (12) along the axis of rotation (D). Heat exchanger arrangement according to one of the preceding claims, characterized in that at least one separating element (9a-9f) or at least one partition wall (10a-10d) extends along the circumferential direction (U); or / and that a radial direction (R) extends perpendicularly from the axis of rotation (D) both to the main flow direction (H) and to the circumferential direction (U), and at least one separating element (9a-9f) or at least one partition wall (10a-10d) extends along the radial direction (R). Heat exchanger arrangement according to one of the preceding claims, characterized in that - the fluid paths (7) extend along a longitudinal direction (LR); - at least one separating element (9a, 9b) or at least one partition wall (10a, 10b) extends along the longitudinal direction (LR) and / or orthogonally to the longitudinal direction (LR). Heat exchanger arrangement according to claim 7, characterized in that a first separating element (9a) extends along the longitudinal direction (LR) and a second separating element (9b) extends perpendicular to the longitudinal direction (L), such that these two separating elements (9a, 9b) divide the main air path (2) into at least four air path zones (7a-7d), preferably the two separating elements (9a, 9b) intersect at a point (Z), which is particularly preferably arranged on the axis of rotation (D). Heat exchanger arrangement according to one of the preceding claims, characterized in that: - the at least one heat exchanger (3), in particular the fluid paths (5), extends perpendicular to the main flow direction (H) along a vertical direction (V) from a lower end (14a) to an upper end (14b); - at least one separating element (9a-9f) or at least one partition wall (10a-10d) is arranged in a lower end section (15) facing the lower end (14a) with respect to the vertical direction (V), which divides the main air path (2) into a first air path zone (7a) facing the lower end (14a) and a second air path zone (7b) facing the upper end (14b). Heat exchanger arrangement according to claim 9, characterized in that the at least one heat exchanger (3) is arranged relative to a direction of gravity (G) such that the vertical direction (V) extends parallel to the direction of gravity (G). Heat exchanger arrangement according to one of the preceding claims, characterized in that at least one separating element (9a-9f) or at least one partition wall (10a-10d) is curved and preferably has the geometry of a circular arc.

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