Plate package using heat exchanger plates with integral discharge channels and heat exchanger comprising such a plate package

Abstract

The present invention relates to a plate package for a heat exchanger arrangement, wherein the plate package (200) comprises a plurality of heat exchanger plates (100) of a first type (A) and a plurality of heat exchanger plates (100) of a second type (B). At least the heat exchanger plates (100) of the first type (A) comprise discharge channel flanges (109) along at least one section of opposite sides (105). The discharge channel flanges (109) are oriented in the same direction so that the discharge channel flanges (109) of a first heat exchanger plate (100) of the first type (A) abut or overlap the discharge channel flanges (109) of a subsequent heat exchanger plate (100). The discharge channel flanges (109) are formed to the outer wall of an outer discharge portion (DP), thereby converting the outer discharge portion (DP) into a discharge channel (111). The present invention also relates to the use of such a plate package in a heat exchanger arrangement and also to a heat exchanger arrangement such as this.

Description

Technical Field

[0001] The invention relates to a plate package for use in a heat exchanger arrangement, the use of a plate package of this type in a heat exchanger arrangement, and also a heat exchanger arrangement using such a plate package. Background Art

[0002] In applications such as generating cooling, heat exchanger devices are commonly used to evaporate various types of cooling media, such as ammonia. The evaporated medium is fed from the heat exchanger device to a compressor, and the compressed gaseous medium is subsequently condensed in a condenser. The medium is then allowed to expand and recirculated to the heat exchanger device. An example of such a device is a plate and shell type heat exchanger.

[0003] One example of a plate and shell type heat exchanger is known from WO2004 / 111564, which discloses a plate pack consisting of generally semicircular heat exchanger plates. The use of semicircular heat exchanger plates is advantageous because it creates a large volume inside the shell above the plate pack, which improves the separation of liquid and gas. The separated liquid is transferred from the upper portion of the interior space to a collection space in the lower portion of the interior space via a gap between the inner wall of the shell and the outer wall of the plate pack. The gap forms part of a thermosiphon circuit that draws liquid toward the collection space in the shell.

[0004] However, one problem is the transfer of heat from the inner wall of the shell and from the plate pack into the gap. In some cases, this heat can cause the separated liquid fed through it to evaporate within the gap. If this occurs, it can negatively impact the thermosyphon circuit and can even cause it to stop functioning.

[0005] The shell is typically made of carbon steel, while the heat exchanger plates that make up the plate pack are typically made of stainless steel. Furthermore, the medium includes a small amount of compressor oil, which is introduced as a lubricant for the compressor. However, even if the system includes a separator, there is an unavoidable residual amount of compressor oil that cannot be successfully separated. Although this residual amount of compressor oil can be measured in parts per million (ppm), it has a significant impact on the overall efficiency of the plate pack and, therefore, the heat exchanger arrangement.

[0006] Experience has shown that compressor oil has a different affinity for carbon steel than for stainless steel, resulting in a tendency for the oil to conform to the inner wall of the shell. However, because the compressor oil has different temperature-dependent properties than the medium, some of the oil will still come into contact with the heat exchanger plates and form deposits on their main surfaces. This deposit acts as an insulating layer across the main surfaces of the heat exchanger plates, and thus on their heat transfer surfaces. Measurements have shown that, over time, amounts in the range of 2-5 ppm can reduce the efficiency of a heat exchanger system by as much as 20-50 percent.

[0007] The reduced efficiency is typically compensated by making the plate pack larger. This can be accomplished by increasing the plate pack's footprint (i.e., by increasing the surface area of ​​the individual heat exchanger plates). Another known measure is to add more heat exchanger plates to the plate pack to increase the available contact area between the medium and the fluid. Both measures require substantially greater overall material consumption, which adds weight and volume to the plate pack and shell, thereby increasing overall costs. Consequently, commercially available plate packs and shells are often oversized to compensate for the problems caused by inevitable compressor oil residues.

[0008] There is therefore a need for a solution that limits the heat transfer from the shell and plate pack into the liquid conveying gap, thereby preventing or reducing evaporation of the liquid stream.There is also a need for a solution to the problem of compressor oil contact with the heat exchanger plates. Summary of the Invention

[0009] The object of the present invention is to provide a plate pack design as well as a design of the individual heat transfer plates which limits the heat transfer from the shell and the plate pack into the liquid conveying gap formed between them.

[0010] Another object of the present invention is to provide a plate pack design and a design of the individual heat transfer plates that reduces the amount of compressor oil that comes into contact with the heat transfer surfaces of the heat exchanger plates.

[0011] Another object is to allow providing smaller, lighter and therefore cheaper plate packages, wherein the overall efficiency of the heat exchanger arrangement is maintained.

[0012] These objects are achieved by a plate package for a heat exchanger arrangement, wherein the plate package comprises a plurality of heat exchanger plates of a first type and a plurality of heat exchanger plates of a second type arranged alternately one above the other in the plate package, wherein each heat exchanger plate has a geometric main extension plane, wherein the alternately arranged heat exchanger plates form first plate interspaces and second plate interspaces, the first plate interspaces being substantially open and arranged to allow a medium to flow through for evaporation thereof, and the second plate interspaces being closed and arranged to allow a fluid to flow for evaporation of the medium,

[0013] wherein each of the first type and the second type of heat exchanger plates has a circumferential edge portion having an upper portion, a lower portion and two opposing sides interconnecting the upper portion and the lower portion,

[0014] wherein at least one section of the first and second type of heat exchanger plates along opposite sides further comprises cooperating abutment portions extending along and at a distance from the circumferential edge portion, thereby dividing the respective first plate interspace into an inner heat transfer portion and two outer discharge portions,

[0015] wherein at least the first type of heat exchanger plate further comprises, along at least one section of the opposite side, a discharge channel flange extending from the circumferential edge portion in a direction away from the geometrical main extension plane, and

[0016] wherein the discharge channel flanges of the respective heat exchanger plates are oriented in the same direction and have an extension with a component along the normal to the geometric main extension plane, so that the discharge channel flange of a first heat exchanger plate of the first type adjoins or overlaps the discharge channel flange of a subsequent heat exchanger plate, which is a heat exchanger plate of the first type or a heat exchanger plate of the second type,

[0017] Thereby a discharge channel flange is formed to the outer wall of the outer discharge part, thereby converting the outer discharge part into a discharge channel.

[0018] Thus, with the plate pack design of the type described above, the cooling medium, in liquid form, present in the upper portion of the shell can be directed within and along a plurality of drainage channels, which extend along opposite sides of the shell's inner wall, but at a distance therefrom and also at a distance from the first interplate gaps formed between the opposing main surfaces of the heat exchanger plates. Depending on the design of the joints and walls that respectively define the cross-section of the drainage channels, this distance is provided at least by the material thickness of the sheets comprising the heat exchanger plates. The resulting distance acts as a thermal insulator, reducing heat transfer from the shell's inner wall and from the interplate gaps in the plate pack toward the drainage channels. This, in turn, reduces the risk of the liquid medium evaporating within the drainage channels and thereby disrupting or halting the thermosiphon circuit. This promotes a more stable liquid flow.

[0019] Furthermore, the drain channel prevents compressor oil from passing into the first interspace of the plate pack. Compressor oil typically tends to follow the curvature of the shell's inner wall, for example due to its stronger affinity for carbon steel than stainless steel. Instead, the flow of compressor oil into the first interspace is now limited to the longitudinal gap, which faces the upper portion of the shell and opens into the first interspace. The amount of compressor oil in this area is typically low.

[0020] By reducing the amount of compressor oil that can come into contact with the first plate interspace, the risk of insulating deposits forming on the heat transfer surfaces is reduced. This allows the plate pack to be smaller in terms of footprint or the number of heat exchanger plates included in the pack, while maintaining efficiency. This can reduce overall costs.

[0021] As a further advantage, the discharge flange will provide an overall improved stiffness to the heat exchanger plates and will also aid in guiding the heat exchanger plates during stacking and handling of the stack until joining. The fixing means can thereby be made less complex.

[0022] As an alternative or in addition to the statement that the outlet channel flange extends from the circumferential edge portion in a direction away from the geometrical main extension plane, the outlet channel flange may extend from the circumferential edge portion at an angle β to the normal to the geometrical main extension plane.

[0023] The mating abutment portions may be formed by ridges formed in a first type of heat exchanger plate and a second type of heat exchanger plate; or by a first or second type of heat exchanger plate comprising ridges and a heat exchanger plate of the other type comprising a substantially flat surface. Regardless of type, the mating abutment portions will constitute a contact area along which a bond will form when the stack of heat exchanger plates is subjected to heating in a furnace to thereby form a bonded plate pack. It will be appreciated that during stacking, intermediate bonding material may be disposed between the abutment portions. The ridges forming the two mating abutment portions may have the same or different heights.

[0024] The respective discharge channel as seen in a section transverse to its longitudinal extension may be defined by the discharge channel flange, outer discharge portion and adjoining portion of a heat exchanger plate of a first type and by the adjoining portion and outer discharge portion of an adjacent heat exchanger plate of a second type.

[0025] The respective outlet channel can have a uniform cross-sectional geometry along its longitudinal extension, as seen in a section transverse to its longitudinal extension, thereby resulting in no excessive local flow restrictions.

[0026] The abutting portions of the first type of heat exchanger plate can sealably abut the abutting portions of the second type of heat exchanger plate. As seen in the longitudinal extension, this sealed abutment or sealed overlap provides a substantially closed drainage channel. This prevents any outflow or inflow of the drainage channel in any direction transverse to its longitudinal direction. The overlap is advantageous because it further increases the rigidity of the plate package.

[0027] The discharge channel flanges of a heat exchanger plate of a first type can sealingly abut or overlap the discharge channel flanges of a subsequent heat exchanger plate of the first or second type. This sealed overlap eliminates the risk of compressor oil migrating into the discharge channels transversely to the discharge channels via capillary action. Furthermore, overlapping is advantageous because it provides a more rigid plate package.

[0028] Each discharge channel may have an inlet opening facing the upper part of the circumferential edge portion, said inlet opening having a mouth with a substantially horizontal extension.The inlet of the discharge channel will thus face the upper part of the plate pack and thus the free volume of the inner space of the shell above the plate pack.

[0029] Each discharge channel may have an outlet opening facing the lower portion of the circumferential edge portion. When the plate package is used in a heat exchanger arrangement, the lower portion of the circumferential edge portion, and therefore the lower portion of the plate package, is typically arranged to face the collection space for the medium. Thus, the medium that is in the liquid phase or that changes to the liquid phase while being guided along and within the discharge channel is guided toward the collection space and discharged therein.

[0030] The lower portion of the drain channel flange may extend past the transition between the lower portion and the side portions of the circumferential edge portion.The change in flow direction has been shown to be beneficial in facilitating the release of any accumulation of compressor oil.

[0031] In one embodiment of the plate package, the upper portion of each heat exchanger plate is curved and the lower portion of each heat exchanger plate is substantially straight, and

[0032] wherein the first hole is arranged in the lower section of each heat exchanger plate and is located at a distance from the lower part of the circumferential edge portion, thereby defining a first intermediate portion between the substantially straight lower part of the circumferential edge portion and the circumferential edge of the first hole, the first intermediate portion comprising the shortest distance between the center of the first hole and the lower part of the circumferential edge portion,

[0033] wherein the second hole is arranged in an upper section of the heat exchanger plate and is located at a distance from the upper part of the circumferential edge portion, thereby defining a second intermediate portion between the upper part of the circumferential edge portion and the circumferential edge of the second hole, the second intermediate portion comprising the shortest distance between the center of the second hole and the upper part of the circumferential edge portion,

[0034] wherein the first shielding flange is arranged along at least a section of the first middle portion and has an extension along a lower part of the circumferential edge portion, and wherein the first shielding flange has a length as seen in a direction transverse to the shortest distance which is smaller than the diameter of the first hole and more preferably smaller than 80% of the diameter of the first hole, and / or

[0035] Wherein the second shielding flange is arranged along at least one section of the second middle portion and has an extension along the upper portion of the circumferential edge portion, and the second shielding flange has a length of 200-80% of the diameter of the second hole and more preferably 180-120% of the diameter of the second hole as seen in the shortest distance transverse direction.

[0036] When the heat exchanger plates are subjected to heating during the bonding of their stack in the furnace, heat is transferred from the periphery of the plate toward its center. The time required to achieve a uniform temperature gradient across the plate depends on the amount of material that must be heated. In prior art heat exchanger plates, the center portion heats faster than the rest of the plate. This uneven temperature gradient, combined with the fact that the center portion can be weaker than the rest of the plate, creates the risk of thermal buckling of the center portion. Buckling compromises the intended contact surface between adjacent plates, which can lead to inadequate bonding and leaking joints. In a worst-case scenario, the resulting plate stack could leak fluid into the media, an unacceptable defect.

[0037] Arranging a shielding flange at least along the extension of the central portion proximal to the hole provides a heat shielding effect. This heat shielding effect is caused by the locally added material that must be heated before the central portion. By providing the locally added material as a shielding flange, the added material does not form part of the available heat transfer area / footprint of the heat exchanger plates, but instead extends along the circumferential sidewalls of the plate pack. This provides a more uniform temperature gradient. The improved heat distribution results in an overall higher joint quality and, therefore, a lower risk of leakage.

[0038] The shielding flange not only serves as a heat shield but also provides the heat exchanger plates with an overall improved stiffness, making them less limp during handling. This is particularly true for larger heat exchanger plates. Furthermore, the shielding flange facilitates the guidance of the heat exchanger plates during stacking and handling until they are joined. This makes the fixing device less complex.

[0039] The extension of the shielding flange depends on parameters such as the curvature of the circumferential edge portion along which the respective hole is arranged, the shortest distance between the center of the hole and the circumferential edge, the diameter of the hole and the thickness of the material of the heat exchanger plate.

[0040] The substantially straight lower edge portion makes the area of ​​the first middle portion larger than the area of ​​the second middle portion, which is arranged adjacent to the curved upper portion. Assuming the respective shortest distances of the first and second middle portions are the same and the diameters of the first and second holes are the same, the area of ​​the second middle portion will be smaller than the area of ​​the first middle portion. To achieve a corresponding heat shielding effect, the second shielding flange should therefore be longer than the first shielding flange.

[0041] Simulations and experiments have shown that, assuming the lower edge portion is substantially straight, the first shielding flange can have a length, as viewed in a direction transverse to the shortest distance between the lower portion of the circumferential edge portion and the center of the first hole, that is less than the diameter of the first hole, and more preferably less than 80% of the diameter of the first hole. Similarly, the second shielding flange can have a length that is 200-80% of the diameter of the second hole, and more preferably 180-120% of the diameter of the second hole.

[0042] According to another aspect, the present invention relates to the use of a plate package as described above in a heat exchanger arrangement. The plate package is particularly suitable for use in a plate and shell type heat exchanger. The advantages of this use are discussed in the preceding paragraphs, and to avoid excessive repetition, reference is made to them.

[0043] According to a further aspect, the invention relates to a heat exchanger arrangement comprising a shell forming a substantially closed interior space and comprising an inner wall surface facing the interior space, the heat exchanger arrangement being arranged to comprise a plate package comprising

[0044] a plurality of heat exchanger plates of a first type and a plurality of heat exchanger plates of a second type arranged alternately one above the other in a plate package, wherein each heat exchanger plate has a geometric main extension plane and is arranged such that the main extension plane is substantially vertical, wherein the alternatingly arranged heat exchanger plates form first plate interspaces, the first plate interspaces being substantially open to the interior space and arranged to allow a medium to circulate for evaporation from a lower part of the interior space upwards to an upper part of the interior space, and second plate interspaces being closed to the interior space and arranged to allow a fluid to flow for evaporating the medium,

[0045] wherein each of the first type and the second type of heat exchanger plates has a circumferential edge portion having an upper portion, a lower portion and two opposing sides interconnecting the upper portion and the lower portion,

[0046] wherein at least one section of the first and second type of heat exchanger plates along opposite sides further comprises cooperating abutment portions extending along and at a distance from the circumferential edge portion, thereby dividing the respective first plate interspace into an inner heat transfer portion and two outer discharge portions,

[0047] wherein at least the first type of heat exchanger plate further comprises, along at least one section of the opposite side, a discharge channel flange extending from the circumferential edge portion in a direction away from the geometrical main extension plane, and

[0048] wherein the discharge channel flanges of the respective heat exchanger plates are oriented in the same direction and have an extension with a component along the normal to the main extension plane, such that the discharge channel flange of a first heat exchanger plate of the first type abuts or overlaps the discharge channel flange of a subsequent heat exchanger plate, which is a heat exchanger plate of the first type or a heat exchanger plate of the second type,

[0049] Thereby a discharge channel flange is formed to the outer wall of the outer discharge part, thereby converting the outer discharge part into a discharge channel.

[0050] The advantages of a heat exchanger arrangement with this combination of features are discussed comprehensively above in the context of a heat exchanger plate and a plate package comprising such a plate. In order to avoid excessive repetitions, reference is made to the paragraphs given above.

[0051] Preferred embodiments are presented in the dependent claims and in the description. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The invention will be described in more detail, by way of example, with reference to the accompanying schematic drawings, which show currently preferred embodiments of the invention.

[0053] Figure 1 A schematic and cross-sectional view from the side of a plate and shell type heat exchanger arrangement is disclosed.

[0054] Figure 2 Schematically disclosed Figure 1 Another cross-sectional view of the heat exchanger arrangement.

[0055] Figure 3 Expose the heat exchanger plates.

[0056] Figure 4 Publicly included Figure 3 Cross-section of a plate package of a heat exchanger plate of the type disclosed in.

[0057] Figure 5 Disclosed is a cross section of the plate pack as seen transversely to the first shielding flange.

[0058] Figure 6 A schematic cross section of a heat exchanger arrangement is disclosed. DETAILED DESCRIPTION

[0059] Reference Figure 1 and Figure 2 , discloses a schematic cross-section of a typical heat exchanger arrangement of the plate and shell type. The heat exchanger arrangement comprises a shell 1 forming a substantially enclosed interior space 2. In the disclosed embodiment, the shell 1 has a substantially cylindrical shape with a substantially cylindrical shell wall 3 (see Figure 1 ) and two generally planar end walls (e.g. Figure 2 (shown in FIG). For example, the end wall may also have a hemispherical shape. Other shapes of shell 1 are also possible. Shell 1 includes a cylindrical inner wall surface 3 facing interior space 2. Section p extends through shell 1 and interior space 2. Shell 1 is arranged so that section p is substantially vertical. Shell 1 may be made of carbon steel, for example.

[0060] Shell 1 includes an inlet 5 for supplying a two-phase medium in a liquid state to interior space 2, and an outlet 6 for discharging the medium in a gaseous state from interior space 2. Inlet 5 includes an inlet conduit that terminates in a lower space 2' of interior space 2. Outlet 6 includes an outlet conduit that extends from an upper space 2' of interior space 2. In applications for generating cooling, the medium may be, for example, ammonia.

[0061] The heat exchanger arrangement comprises a plate package 200 which is arranged in the inner space 2 and comprises a plurality of heat exchanger plates 100 arranged adjacent to each other. Figure 3 The heat exchanger plates 100 are discussed in more detail in WO 2013 / 144251 A1. The heat exchanger plates 100 are permanently connected to one another in the plate package 200, for example, by welding, brazing (such as copper brazing), fusion bonding, or adhesive bonding. Welding, brazing, and adhesive bonding are well-known techniques, and fusion bonding can be performed as described in WO 2013 / 144251 A1. The heat exchanger plates 100 can be made of a metallic material, such as an iron-, nickel-, titanium-, aluminum-, copper-, or cobalt-based material, i.e., a metallic material (e.g., an alloy) having iron, nickel, titanium, aluminum, copper, or cobalt as a primary component. Iron, nickel, titanium, aluminum, copper, or cobalt can be the primary component and thus the component with the largest percentage by weight. The metallic material can have an iron, nickel, titanium, aluminum, copper, or cobalt content of at least 30% by weight, such as at least 50% by weight, such as at least 70% by weight. The heat exchanger plates 100 are preferably manufactured from a corrosion-resistant material, such as stainless steel or titanium.

[0062] Each heat exchanger plate 100 has a main extension plane q and is arranged in the plate package 200 and in the shell 1 such that the extension plane q is substantially vertical and substantially perpendicular to the section p. The section p also extends transversely through each heat exchanger plate 100. In the disclosed embodiment, the section p thus also forms a vertical center plane through each individual heat exchanger plate 100.

[0063] The heat exchanger plates 100 form first interspaces 12 and second interspaces 13 in the plate package 200, the first interspaces 12 being open toward the interior space 2 and the second interspaces 13 being closed toward the interior space 2. The above-mentioned medium supplied to the shell 1 via the inlet 5 is thus conveyed into the plate package 200 and into the first interspaces 12.

[0064] Each heat exchanger plate 100 includes a first port opening 107 and a second port opening 108. The first port opening 107 forms an inlet channel connected to the inlet conduit 16. The second port opening 108 forms an outlet channel connected to the outlet conduit 17. It should be noted that in an alternative configuration, the first port opening 107 forms the outlet channel and the second port opening 108 forms the inlet channel. The cross section p extends through both the first port opening 107 and the second port opening 108. The heat exchanger plates 100 are connected to each other around the port openings 107 and 108 such that the inlet and outlet channels are closed relative to the first plate interstices 12 but open relative to the second plate interstices 13. Fluid can thus be supplied to the second plate interstices 13 via the inlet conduit 16 and the associated inlet channel formed by the first port opening 107, and discharged from the second plate interstices 13 via the outlet conduit 17 and the outlet channel formed by the second port opening 108.

[0065] like Figure 1 As shown in FIG, the plate group 200 has an upper side and a lower side and two opposite lateral sides. The plate group 200 is arranged in the interior space 2 so that it is substantially located in the lower space 2 ′ and a collecting space 18 is formed below the plate group 200 between the lower side of the plate group and the bottom part of the inner wall surface 3.

[0066] Furthermore, recirculation channels 19 are formed at each side of the plate package 200. These may be formed by gaps between the inner wall surface 3 and the respective lateral sides, or as internal recirculation channels formed within the plate package 10.

[0067] Each heat exchanger plate 100 includes a circumferential edge portion 20 that extends substantially around the entire heat exchanger plate 100 and allows for the aforementioned permanent connection of the heat exchanger plates 100 to one another. These circumferential edge portions 20 will abut the inner cylindrical wall surface 3 of the shell 1 along the lateral sides. The recirculation channels 19 are formed by the inner or outer gaps extending along the lateral sides between each pair of heat exchanger plates 100. It should also be noted that the heat exchanger plates 100 are connected to one another such that the first plate interspaces 12 are closed along the lateral sides (i.e., toward the recirculation channels 19 of the interior space 2).

[0068] The embodiment of the heat exchanger device disclosed in this application can be used to evaporate a two-phase medium supplied in liquid state via the inlet 5 and discharged in gaseous state via the outlet 6. The heat necessary for the evaporation is supplied by the plate package 200, which is supplied with a fluid (e.g. water) via the inlet duct 16, which circulates through the second plate interspaces 13 and is discharged via the outlet duct 17. The evaporated medium is thus at least partially present in the liquid state in the inner space 2. The liquid level can extend to Figure 1 The level indicated in 22. Thus, substantially the entire lower space 2' is filled with the medium in the liquid state, whereas the upper space 2" contains the medium mainly in the gaseous state.

[0069] Now go to Figure 3 , discloses a detailed first embodiment of a heat exchanger plate 100. The heat exchanger plate 100 is intended to form part of a plate package 200 according to the invention. The heat exchanger plate 100 can be easily converted into a heat exchanger plate of the first type A or a heat exchanger plate of the second type B in the manner described below.

[0070] The heat exchanger plate 100 is provided by a pressed thin-walled sheet metal plate. The heat exchanger plate 100 can be made of stainless steel, for example. The heat exchanger plate 100 has a geometric main extension plane q and a circumferential edge portion 101. The circumferential edge portion 101 defines a heat transfer surface 102 that extends substantially across the geometric main extension plane q.

[0071] The circumferential edge portion 101 comprises a curved upper portion 103, a substantially straight lower portion 104 and two opposite sides 105 interconnecting the upper and lower portions 103, 104. The two opposite sides 105 each have a curvature corresponding to the curvature of the inner wall 3 of the shell 1 of the heat exchanger device.

[0072] The heat transfer surface 102 includes a wavy pattern 106 of ridges and valleys. To facilitate understanding of the present invention, the wavy pattern 106 in and around the first and second holes 107, 108 (discussed below) is removed. The wavy pattern 106 extends in different directions at different portions of the heat exchanger plate 100. When a plurality of heat exchanger plates 100 are stacked one on top of another to thereby form a plate pack 200, every other heat exchanger plate 100 (heat exchanger plates of the first type A) is formed with a wavy pattern 106. Figure 3 The heat exchanger plates 100 (heat exchangers of the second type B) are rotated 180 degrees about a substantially vertical rotation axis coinciding with the section p. This causes the corrugations 106 of adjacent heat exchanger plates 100 to intersect with one another. Furthermore, multiple contact points are formed where the ridges of adjacent heat exchanger plates 100 abut against one another. During stacking, a layer of bonding material (not disclosed) may be placed between the heat exchanger plates 100. When the stack is subsequently heated in a furnace, the heat exchanger plates 100 bond to one another along the contact points, thereby forming a complex pattern of fluid channels. In this way, efficient heat transfer from the fluid to the medium is ensured while providing the required mechanical support for the plates included in the plate package 200.

[0073] Depending on how the heat exchanger plates 100 are oriented in the plate package 200, one side of the heat exchanger plates 100 will face the first plate interspaces 12 during operation of the plate package 200 in the heat exchanger arrangement 300 and thus be in contact with the two-phase medium, while the opposite side of the heat exchanger plates 100 will face the second plate interspaces 13 and thus be in contact with the fluid.

[0074] The heat exchanger plates comprise first holes 107 intended to form inlet ports of the plate package 200 and second holes 108 intended to form outlet ports of the plate package 200 .

[0075] In the disclosed embodiment, the first holes 107 are located proximate to the lower portion 104, and the second holes 108 are located proximate to the upper portion 103. When the heat exchanger plates 100 are arranged to form part of the plate package 200, fluid will therefore flow upwards through the second plate inter-plate spaces 12 in the plate package 200 during operation. Alternatively, it is possible to provide the first holes 107 at the upper portion 103 and the second holes 108 at the lower portion 104. It is also possible to provide the holes 107, 108 in other locations on the heat exchanger plates 100.

[0076] Now go to Figure 3 and Figure 4 , the heat exchanger plate 100 comprises a discharge channel flange 109 which extends along two opposite sides 105 of the circumferential edge portion 101. The discharge channel flange 109 also has an extension which extends partly along the lower portion 104 of the circumferential edge portion 101.

[0077] The drain channel flange 109 extends from the circumferential edge portion 101 in a direction away from the geometrical main extension plane q. The drain channel flange 109 extends from the circumferential edge portion 101 at an angle β to the normal to the geometrical main extension plane q.

[0078] Furthermore, the heat exchanger plate 100 comprises ridges 110 extending along two opposite sides 105 of the circumferential edge portion 101. The ridges 110 are located at a distance from the drain channel flange 109 and follow its curvature. In the disclosed embodiment, the ridges 110 also have an extension extending partially along the upper portion 103 of the circumferential edge portion 101.

[0079] Now specifically turn to Figure 4 , discloses a cross-section of a plate package 200 arranged in a housing 1 of a heat exchanger arrangement 300. The discharge channels 111 are disclosed as viewed transversely across their longitudinal extension. In the disclosed embodiment, the discharge flanges 109 of every other heat exchanger plate 100 are cut away, thereby converting the plate into a heat exchanger plate 100 of the second type B. In all other respects, the heat exchanger plates are identical.

[0080] When two heat exchanger plates 100 of the first type A and the second type B are Figure 4 When stacked as disclosed in , the ridges 110 of two subsequent heat exchanger plates 100 will form mating abutment portions 112. In the joined state, the abutment portions 112 of the heat exchanger plates 100 of the first type A will sealingly abut corresponding abutment portions 112 of the heat exchanger plates 100 of the second type B.

[0081] The mating abutment portion 112 extends along and at a distance from the circumferential edge portion 101, thereby dividing the corresponding first inter-plate interspace 12 into an inner heat transfer portion HTP and two outer discharge portions DP. When stacked, the discharge channel flanges 109 of the corresponding heat exchanger plates 100 are oriented in the same direction and have an extension with a component along the normal to the main extension plane, so that the discharge channel flange 109 of a first heat exchanger plate 100 of the first type abuts or overlaps the discharge channel flange 109 of a subsequent heat exchanger plate. It should be understood that the subsequent heat exchanger plate 100 can be a heat exchanger plate 100 of the first type A or a heat exchanger plate 100 of the second type B.

[0082] The drain channel flanges 109 are formed to the outer wall of the outer drain portion DP, thereby converting the outer drain portion DP into a drain channel 111. After joining, the drain channel flanges 109 of a first type of heat exchanger plate 100 sealingly abut or sealingly overlap the drain channel flanges 109 of a subsequent heat exchanger plate 100 of the first or second type.

[0083] The drain channel 111 has a cross section as seen transversely of its longitudinal extension, which is defined by the drain channel flange 109, the outer drain portion DP and the adjoining portion 112 of the heat exchanger plate 100 of the first type A and by the adjoining portion 112 and the outer drain portion DP of the adjacent heat exchanger plate 100 of the second type B.

[0084] The outlet channel 111 , as seen in a section transverse to its longitudinal extension, preferably has a uniform cross-sectional geometry along its longitudinal extension.

[0085] When the resulting plate package 200 is arranged in the shell 1 of the heat exchanger arrangement 300 , the respective discharge channel flanges 109 may be in contact with the inner wall 3 of the shell 1 .

[0086] In the disclosed embodiment, the ridges 110 are of equal height. A skilled person will appreciate that the ridges 110 may be of different heights and that one heat exchanger plate 100 may be provided with ridges 110 while a subsequent heat exchanger plate 100 may include a substantially flat mating abutment 112.

[0087] Now turn to Figure 3 The discharge channel 111 has an inlet opening 113 facing the upper portion 103 of the peripheral edge portion 101. The inlet opening 113 has a mouth 114 with a substantially horizontal extension. In addition, the discharge channel 111 has an outlet opening 115 facing the lower portion 104 of the peripheral edge portion 101. The discharge channel flange 109 extends across the transition between the lower portion 104 and the side portion 105 of the peripheral edge portion 101.

[0088] Now go to Figure 4 When a plate package 200 composed of heat exchanger plates 100 of this type is used in a plate and shell type heat exchanger device 300, the medium in liquid form present in the upper space 2″ of the shell 1 can be directed within and along a plurality of drainage channels 111, which extend along opposite sides of the inner wall surface 3 of the shell 1, but at a distance therefrom and also at a distance from the first interplate spaces 12 formed between the opposite main surfaces of the heat exchanger plates 100. This distance is provided at least by the material thickness of the sheet material constituting the heat exchanger plates 100, depending on the design of the joints and walls that respectively define the cross-section of the drainage channels 111. The resulting distance can be considered a thermal insulator, reducing heat transfer from the inner wall surface 3 of the shell 1 and from the first interplate spaces 12 in the plate package 200 toward the drainage channels 111. This reduces the risk of the liquid medium evaporating within the drainage channels 111 and thereby disrupting or stopping the thermosiphon circuit. This promotes a more stable liquid flow.

[0089] Furthermore, drain channel 111 prevents compressor oil from passing into first interspace 12 of plate pack 200. Compressor oil, typically due to its stronger affinity for carbon steel than stainless steel, tends to follow the curvature of inner wall surface 3 of shell 1. The presence of drain channel 111 prevents compressor oil present within the gap between inner wall surface 3 of shell 1 and the outer boundary of plate pack 200 from passing in a direction transverse to the longitudinal extension of drain channel 111 and into first interspace 12. Instead, the inflow of compressor oil into first interspace 12 is now limited to longitudinal gap 116, which faces upper space 2″ of shell 1 and forms an opening toward first interspace 12.

[0090] Now turn to Figure 3 The first hole 107 is arranged in the lower section of the heat exchanger plate 100 at a distance from the lower portion 104 of the circumferential edge portion 101. This defines a first intermediate portion 117 located between the circumferential edge portion 101 and a circumferential edge 118 of the first hole 107. The first intermediate portion 117 includes a shortest distance d1 between the center of the first hole 107 and the lower portion 104 of the circumferential edge portion 101. Furthermore, the first intermediate portion 117 has a height Y1 along the shortest distance d1 and a width X1 transverse to the shortest distance d1.

[0091] The first shielding flange 119 is arranged to have an extension along the lower portion 104 of the circumferential edge portion 101. The first shielding flange 119 is arranged to extend along at least a section of the first middle portion 117. The first shielding flange 119 extends towards the surface of the heat exchanger plate 100 intended to be in contact with the fluid (i.e. the surface intended to face the second plate interspace).

[0092] The first shield flange 119 has a length L1 as seen in a direction transverse to the shortest distance d1 that is less than the diameter D1 of the first hole 107 , and more preferably less than 80% of the diameter D1 of the first hole 107 .

[0093] The second hole 108 is arranged in the upper section of the heat exchanger plate 100 and is located a distance from the upper portion 103 of the circumferential edge portion 101. This defines a second intermediate portion 120 located between the circumferential edge portion 101 and the circumferential edge 121 of the second hole 108. The second intermediate portion 120 includes a shortest distance d2 between the center of the second hole 108 and the upper portion 103 of the circumferential edge portion 101. Furthermore, the second intermediate portion 120 has a height Y2 along the shortest distance d2 and a width X2 transverse to the shortest distance d2.

[0094] The second shielding flange 122 is arranged to have an extension along the upper portion 103 of the circumferential edge portion 101. The second shielding flange 122 is arranged to extend along at least a section of the second middle portion 120. The second shielding flange 122 extends toward the surface of the heat exchanger plate 100 intended to be in contact with the fluid (i.e., the surface intended to face the second plate interspace 13).

[0095] The second shield flange 122 has a length L2 of 200-80% of the diameter D2 of the second hole 108 and more preferably 180-120% of the diameter D2 of the second hole 108 as seen in a direction transverse to the shortest distance d2 .

[0096] like Figure 3 and Figure 6 As best seen in the figure, the curvature of the upper portion 103 of the circumferential edge portion 101 of the heat exchanger plate 100 differs from the curvature of the lower portion 104 of the heat exchanger plate 100. When the heat exchanger 100 is included in the plate package 200 and used in the heat exchanger device 300, the lower portion 104 is intended to face the collecting space 18 formed in the lower shell 1 of the plate package 200. To allow for a certain volume of the collecting space 18, the lower portion 104 is more or less straight in the disclosed embodiment, while the upper portion 103, intended to face the upper space 2" of the shell 1, has a convex curvature. Consequently, the extension of the circumferential edge portion 101 adjacent to the holes 107; 108 affects the area of ​​the usable intermediate portions 117; 120.

[0097] In the case where the lower portion 104 is substantially straight, the height Y1 of the first intermediate portion 117 between the lower portion 104 and the peripheral edge 118 of the first hole 107 will increase relatively quickly with the distance X1 from the section p. This can be compared to the second hole 108 adjacent the curved upper portion 103, where the height Y2 of the second intermediate portion 120 between the curved upper portion 103 and the peripheral edge 121 of the second hole 108 will increase more slowly with the distance X2 from the section p. The decisive factor in this case is the radius of the curved upper portion 103.

[0098] The impact of this difference can be seen by studying the temperature gradient when a stack of heat exchanger plates 100 is subjected to heating in a furnace. The second middle portion 120, with its curved upper portion 103, will heat up faster than the first middle portion 117, with its straight lower portion 104. By introducing the first and second shielding flanges 119 and 122 and adjusting their lengths L1 and L2 to the diameters D1 and D2 of the corresponding holes 107 and 108, the difference in heating can be compensated. This mitigates the risk of buckling due to uneven thermal expansion and the resulting inadequate bonding.

[0099] Now go to Figure 5 , discloses a schematic cross-section of a plate package 200 consisting of a plurality of heat exchanger plates 100 of the above type. Figure 5 The cross-sections in are taken transversely at the first shield flange 119. For the record, corresponding cross-sections taken transversely at the second shield flange 122 may appear identical.

[0100] As given above, the heat exchanger plate 100 according to the present invention can be easily converted into a heat exchanger plate 100 of the first type A or into a heat exchanger plate 100 of the second type B by simply cutting off the first and second shielding flanges 119 , 122 and the drain channel flange 109 after pressing.

[0101] When the heat exchanger plates 100 are stacked one on top of another to form the plate package 200, every other heat exchanger plate 100 is stacked one on top of another to form the plate package 200. Figure 4 The heat exchanger plates 100 are rotated in the manner disclosed in the prior art, with every other plate rotated 180 degrees about a substantially vertical axis of rotation coinciding with section p. As a result, the wavy patterns 106 of adjacent heat exchanger plates 100 intersect with one another. Furthermore, a plurality of contact points are formed where the ridges 110 of adjacent heat exchanger plates 100 abut one another. As in the prior art, a layer of bonding material (not disclosed) may be placed between the heat exchanger plates 100 during stacking. When the stack is subsequently heated in a furnace, the heat exchanger plates 100 bond to one another along the contact points, thereby forming a complex pattern of fluid channels. It will be appreciated that the width of the joint depends on the cross-section of the wavy pattern 106.

[0102] Depending on how the heat exchanger plates 100 are oriented in the plate package 200, one side of the heat exchanger plates 100 is intended to face the first plate interspaces 12 intended to be in contact with the medium during operation of the plate package 200, while the other side of the heat exchanger plates 100 will face the second plate interspaces 13 intended to be in contact with the fluid, such as water.

[0103] As in Figure 4 and Figure 5 As can be seen in the embodiment of FIG. 1 , the flanges 109; 119 of every other heat exchanger plate 100 (i.e., the heat exchanger plates 100 of the second type B) are cut away. Furthermore, the flanges 109; 119 of the corresponding heat exchanger plates 100 of the first type A are oriented in the same direction and have an extension with a component along the normal to the main extension plane q, such that the flanges 109; 119 of the heat exchanger plate 100 of the first type A abut or overlap the flanges 109; 119 of the second subsequent heat exchanger plate 100 of the first type A. The overlap formed between the two subsequent flanges thus has a length e corresponding to 5-90% of the height f of the flanges 109; 119, as seen in the direction corresponding to the normal to the geometric main extension plane.

[0104] It is to be understood that it may be sufficient if the flange 109 ; 119 of a heat exchanger plate 100 of a first type A abuts the flange 109 ; 119 of a subsequent heat exchanger plate 100 .

[0105] The flanges 109 and 119 are disclosed as extending from the peripheral edge portion 101 at angles α and β relative to the normal to the geometric main extension plane q. The angles α and β are preferably less than 20 degrees relative to the normal, and more preferably less than 15 degrees relative to the normal. It is understood that the angles α and β can be as small as 0 degrees. The angles α and β can be the same or different from each other.

[0106] The angles α, β depend on whether both subsequent heat exchanger plates 100 to be joined are provided with flanges 109; 119 or whether only one of the heat exchanger plates 100 has a flange 109; 119. In case only one of the heat exchanger plates 100 has a flange 109; 119, the angles α, β can be made smaller, such as less than 10 degrees, such as less than 8 degrees, and typically about 6-7 degrees.

[0107] Joining the heat exchanger plates 100 to provide the plate package 200 may be performed by brazing as discussed above or by fusion bonding. Fusion bonding is particularly suitable when the heat exchanger plates are made of stainless steel.

[0108] Now go to Figure 6, an embodiment of a plate package 200 according to the invention is schematically disclosed as being included in a heat exchanger arrangement 300 according to the invention. This view clearly shows how the first and second shielding flanges 109, 122, as well as the two opposing discharge channel flanges 109, form the sealed circumferential side walls of the plate package 200. Due to the limited length of the first and second shielding flanges 119, 122, the communication between the interior of the shell 1 and the first inter-plate gap 12 is not limited to any substantial extent.

[0109] There are numerous modifications of the embodiments described herein which are envisaged and which remain within the scope of the invention as defined by the appended claims.

[0110] For example, the first and second types of heat exchanger plates may be identical except that the first and second flanges and the drain channel flanges 109 on every other heat exchanger plate 100 are cut away, thereby converting them into first and second types of heat exchanger plates. Thus, the same pressing tool may be used.

[0111] It will be appreciated that the second type of heat exchanger plates may also be provided with flanges of the type described above, without these flanges being cut away. This allows the flanges of the first type of heat exchanger plates to sealingly abut the flanges of the second type of heat exchanger plates.

[0112] The plate package is disclosed as being applied to a plate and shell type heat exchanger. A skilled person will appreciate that the concept may also be applicable to other types of heat exchangers.

Claims

1. A plate package for a heat exchanger device, wherein the plate package (200) comprises a plurality of heat exchanger plates (100) of a first type (A) and a plurality of heat exchanger plates (100) of a second type (B) arranged alternately one above the other in the plate package (200), wherein each heat exchanger plate (100) has a geometric main extension plane (q), wherein the alternately arranged heat exchanger plates (100) form first plate interspaces (12) and second plate interspaces (13), the first plate interspaces (12) being substantially open and arranged to allow a medium to flow therethrough for evaporation, and the second plate interspaces (13) being closed and arranged to allow a fluid to flow for evaporation of the medium, wherein each of the heat exchanger plates (100) of the first type (A) and the second type (B) has a circumferential edge portion (101) having an upper portion (103), a lower portion (104) and two opposite side portions (105) interconnecting the upper portion (103) and the lower portion (104), wherein the heat exchanger plates (100) of the first type (A) and the second type (B) further comprise, along at least one section of the opposite side portions (105), cooperating abutment portions (112) extending along and at a distance from the circumferential edge portion (101), thereby dividing the respective first plate interspace (12) into an inner heat transfer portion (HTP) and two outer discharge portions (DP), wherein at least the heat exchanger plate (100) of the first type (A) further comprises, along at least one section of the opposite side (105), a discharge channel flange (109) extending from the circumferential edge portion (101) in a direction away from the geometric main extension plane (q), and wherein the discharge channel flanges (109) of the heat exchanger plates (100) of the first type (A) are oriented in the same direction and have an extension with a component along the normal to the main extension plane (q), so that the discharge channel flange (109) of a first heat exchanger plate (100) of the first type (A) abuts or overlaps the discharge channel flange (109) of a subsequent heat exchanger plate (100) of the first type (A), whereby the discharge channel flange (109) is formed to the outer wall of the outer discharge portion (DP), thereby converting the outer discharge portion (DP) into a discharge channel (111), in, The upper portion (103) of each heat exchanger plate (100) is curved, and the lower portion (104) of each heat exchanger plate (100) is substantially straight, and wherein a first hole (107) is arranged in a lower section of each heat exchanger plate (100) and is located at a distance from the lower portion (104) of the circumferential edge portion (101), thereby defining a first intermediate portion (117) between a substantially straight lower portion of the circumferential edge portion (101) and a circumferential edge (118) of the first hole (107), the first intermediate portion (117) comprising a shortest distance (d1) between a center of the first hole (107) and the lower portion (104) of the circumferential edge portion (101), wherein a second hole (108) is arranged in an upper section of the heat exchanger plate (100) and is located at a distance from an upper portion (103) of the circumferential edge portion (101), thereby defining a second intermediate portion (120) between the upper portion (103) of the circumferential edge portion (101) and a circumferential edge (121) of the second hole (108), the second intermediate portion (120) comprising a shortest distance (d2) between a center of the second hole (108) and the upper portion (103) of the circumferential edge portion (101), wherein a first shielding flange (119) is arranged along at least a section of the first intermediate portion (117) and has an extension along the lower portion (104) of the circumferential edge portion (101), and the first shielding flange (119) has a length (L1) smaller than a diameter (D1) of the first hole (107) as seen in a direction transverse to the shortest distance (d1), and / or wherein a second shielding flange (122) is arranged along at least one section of the second middle portion (120) and has an extension along the upper portion (103) of the circumferential edge portion (101), and the second shielding flange (122) has a length (L2) of 200-80% of the diameter (D2) of the second hole (108) as seen in a direction transverse to the shortest distance (d2).

2. The plate assembly according to claim 1, characterized in that The mating abutment portion (112) is formed by: ridges (110) formed in the heat exchanger plates (100) of the first type (A) and in the heat exchanger plates (100) of the second type (B); or Heat exchanger plates (100) of the first type (A) or the second type (B) comprising ridges (110) and heat exchanger plates (100) of the other type comprising a substantially flat surface.

3. The plate assembly according to claim 1 or claim 2, characterized in that The respective discharge channels (111) are defined by the discharge channel flanges (109), the outer discharge portions (DP) and the adjoining portions (112) of the heat exchanger plates (100) of said first type (A) as seen in a cross section transverse to their longitudinal extension and by the adjoining portions (112) and the outer discharge portions (DP) of the adjacent heat exchanger plates (100) of said second type (B).

4. The plate assembly according to claim 1 or 2, characterized in that The respective outlet channel (111) has a uniform cross-sectional geometry along its longitudinal extension, as seen in a section transverse to its longitudinal extension.

5. The plate assembly according to claim 1 or 2, characterized in that The abutting portions (112) of the heat exchanger plates (100) of the first type (A) sealingly abut the abutting portions (112) of the heat exchanger plates (100) of the second type (B).

6. The plate assembly according to claim 1 or 2, characterized in that Each discharge channel (111) has an inlet opening (113) facing the upper portion (103) of the peripheral edge portion (101), the inlet opening (113) having a mouth (114) having a substantially horizontal extension.

7. The plate assembly according to claim 1 or 2, characterized in that Each discharge channel (111) has an outlet opening (115) facing the lower portion (104) of the peripheral edge portion (101).

8. The plate assembly according to claim 1 or 2, characterized in that The lower portion of the discharge channel flange (109) extends through the transition between the lower portion (104) and the side portion (105) of the peripheral edge portion (101).

9. The plate assembly according to claim 1 or 2, characterized in that The first shielding flange (119) has a length (L1) less than 80% of the diameter (D1) of the first hole (107) as seen in a direction transverse to the shortest distance (d1).

10. The plate assembly according to claim 1 or 2, characterized in that The second shielding flange (122) has a length (L2) of 180-120% of the diameter (D2) of the second hole (108) as seen in a direction transverse to the shortest distance (d2).

11. Use of a plate package according to any one of claims 1 to 10 in a heat exchanger arrangement (300).

12. A heat exchanger device comprising a shell (1) forming a substantially closed interior space (2) and comprising an inner wall surface (3) facing the interior space (2), the heat exchanger device (300) being arranged to include a plate pack (200), the plate pack (200) comprising a plurality of heat exchanger plates (100) of a first type (A) and a plurality of heat exchanger plates (100) of a second type (B) arranged alternately one above the other in the plate pack (200), wherein each heat exchanger plate (100) has a geometrically main extension plane. The heat exchanger plates (100) are arranged such that the main extension plane (q) is substantially vertical, wherein the alternatingly arranged heat exchanger plates (100) form first plate interspaces (12) and second plate interspaces (13), the first plate interspaces (12) being substantially open to the interior space (2) and arranged to allow a medium to circulate for evaporation from a lower part (2') of the interior space (2) upwards to an upper part (2") of the interior space (2), and the second plate interspaces (13) being closed to the interior space (2) and arranged to allow a fluid to flow for evaporation of the medium, wherein each of the heat exchanger plates (100) of the first type (A) and the second type (B) has a circumferential edge portion (101) having an upper portion (103), a lower portion (104) and two opposite side portions (105) interconnecting the upper portion (103) and the lower portion (104), wherein the heat exchanger plates (100) of the first type (A) and the second type (B) further comprise, along at least one section of the opposite side portions (105), cooperating abutment portions (112) extending along and at a distance from the circumferential edge portion (101), thereby dividing the respective first plate interspace (12) into an inner heat transfer portion (HTP) and two outer discharge portions (DP), wherein at least the heat exchanger plate (100) of the first type (A) further comprises, along at least one section of the opposite side (105), a discharge channel flange (109) extending from the circumferential edge portion (101) in a direction away from the geometric main extension plane (q), and wherein the discharge channel flanges (109) of the heat exchanger plates (100) of the first type (A) are oriented in the same direction and have an extension with a component along the normal to the main extension plane (q), so that the discharge channel flange (109) of a first heat exchanger plate (100) of the first type (A) abuts or overlaps the discharge channel flange (109) of a subsequent heat exchanger plate (100) of the first type (A), whereby the discharge channel flange (109) is formed to the outer wall of the outer discharge portion (DP), thereby converting the outer discharge portion (DP) into a discharge channel (111), in, The upper portion (103) of each heat exchanger plate (100) is curved, and the lower portion (104) of each heat exchanger plate (100) is substantially straight, and wherein a first hole (107) is arranged in a lower section of each heat exchanger plate (100) and is located at a distance from the lower portion (104) of the circumferential edge portion (101), thereby defining a first intermediate portion (117) between a substantially straight lower portion of the circumferential edge portion (101) and a circumferential edge (118) of the first hole (107), the first intermediate portion (117) comprising a shortest distance (d1) between a center of the first hole (107) and the lower portion (104) of the circumferential edge portion (101), wherein a second hole (108) is arranged in an upper section of the heat exchanger plate (100) and is located at a distance from an upper portion (103) of the circumferential edge portion (101), thereby defining a second intermediate portion (120) between the upper portion (103) of the circumferential edge portion (101) and a circumferential edge (121) of the second hole (108), the second intermediate portion (120) comprising a shortest distance (d2) between a center of the second hole (108) and the upper portion (103) of the circumferential edge portion (101), wherein a first shielding flange (119) is arranged along at least a section of the first intermediate portion (117) and has an extension along the lower portion (104) of the circumferential edge portion (101), and the first shielding flange (119) has a length (L1) smaller than a diameter (D1) of the first hole (107) as seen in a direction transverse to the shortest distance (d1), and / or wherein a second shielding flange (122) is arranged along at least one section of the second middle portion (120) and has an extension along the upper portion (103) of the circumferential edge portion (101), and the second shielding flange (122) has a length (L2) of 200-80% of the diameter (D2) of the second hole (108) as seen in a direction transverse to the shortest distance (d2).

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