Heat exchanger element

Abstract

Heat exchanger element with two plates (4, 5) arranged at least substantially parallel to each other, namely a first plate (4) and a second plate (5), wherein the first plate (4) has a higher strength than the second plate (5), wherein the first and the second plate (4, 5) are permanently connected to each other by a plurality of insulated connection points (6) distributed over the plate surface, creating a plate composite, wherein the second plate (5) has expansion areas (8) between the connection points (6) of the plates (4, 5) created by plastic pressure expansion, and the expansion areas (8) form several interconnected fluid-flowable spaces (9), wherein several connection points (6) are arranged circumferentially around each expansion area (8), and wherein the plate composite is also multiaxially curved in its shape.forming convex and concave curved areas of the plate composite, characterized in that the second plate (5) with the widening areas (8) is arranged on multiaxially convex curved areas of the first plate (4) and the widening areas (8) of the second plate (5) project from the second plate (5) opposite to the multiaxially convex curvature of the first plate (4), wherein the multiaxially convex curved areas of the first plate (4) are spherically curved.

Description

[0001] The invention relates to a heat exchanger element with two plates arranged at least substantially parallel to each other, namely a first and a second plate, wherein the first plate has a higher strength than the second plate, wherein the first and the second plate are permanently connected to each other by a plurality of insulated connection points distributed over the plate surface, thereby creating a plate composite, wherein the second plate has expansion areas between the connection points of the plates created by plastic pressure expansion, and the expansion areas form several interconnected fluid-flowable spaces, wherein several connection points are arranged circumferentially around each expansion area, wherein furthermore the plate composite is shaped in a multiaxially curved form, creating convex and concave curved areas of the plate composite.Furthermore, the invention relates to a method for manufacturing a heat exchanger element.

[0002] Such heat exchanger elements are known, forming, for example, the side walls of containers or the walls of pipelines. The plate assembly is uniaxial, forming a cylindrical wall section. The pressure expansion of the expansion zones, achieved by inserting a fluid pressure expansion medium such as water between the plates, is sometimes carried out at very high pressure, for example, ≥ 20 MPa (200 bar). The second plate with the pressure expansion zones is usually located on the outside of the heat exchanger element, i.e., in the area of ​​a concave curvature of the first plate that forms the respective component; in some cases, it is also located on the inside.Furthermore, it is known that in the case of multiaxially or spherically curved heat exchanger elements, for example in the base of a reactor, the base is at least partially formed from heat exchanger elements, whereby the second plate with the expansions is generally arranged on the outside of the respective device, such as a vessel or reactor, since the multiaxial curvature of the heat exchanger element requires a significantly higher expansion pressure than the aforementioned heat exchanger elements with uniaxial curvature. The bulging of the expansion areas thus occurs in the direction in which the plate assembly is also concavely curved, i.e., for example, on the outside of a curved vessel base.

[0003] There is often a need to provide effective cooling of the vessel bottom in containers, especially reactors, which are operated at very high internal pressures. This is particularly relevant for chemical reactors, where rapid and effective cooling of the contents is desired, for example, when the reactor is charged in batches and the freshly added contents must be cooled to the desired temperature as quickly as possible. This is especially critical when the contents are highly temperature-sensitive or when undesirable temperature-sensitive side reactions that could impair the quality of the reaction product must be avoided, as is often the case in the production of chemical products.

[0004] It is particularly important to consider that these reactors are often operated under high internal pressure and are frequently subjected to high cyclic stresses, especially temperature and / or pressure fluctuations. The heat exchanger element is often an integral part of the device's wall, such as that of a reactor, for example, forming part of the side wall and / or bottom. The stability of the device is therefore significantly determined by the stability of the heat exchanger element. One of the two plates of the heat exchanger element thus exhibits comparatively high strength, particularly a thick wall, to ensure the stability of the device, while the other plate provides only the necessary strength to create a fluid-filled space for the heat exchange medium.

[0005] Especially in vessels like reactors, there is a need to improve the temperature control of the vessel contents. Simply using the reactor's side wall as a heat exchanger element is often insufficient, as this can lead to localized overheating at the reactor base, or, if the vessel is only partially filled (e.g., less than 20%), the shell may be ineffective. However, even conventional reactors, due to their thick base walls, require further improvement, particularly for temperature-sensitive chemical reactions. This is because the heat to be transferred or removed from the vessel contents must first penetrate the thicker first plate, which is crucial for vessel stability. The wall thickness significantly influences the heat flow, including the amount of heat that can be transferred. Consequently, localized overheating of the vessel contents in the base region can also occur in these cases.To achieve better temperature control of the container contents, an additional heat exchanger element could be installed inside the container. However, this would require a very high level of equipment complexity, and this additional heat exchanger element would also significantly alter the flow conditions within the reactor. Furthermore, the interior of the container would be very difficult to clean when replacing the contents, for example, with a new batch.

[0006] DE 10 2006 029 821 B3 describes a heat exchanger element with two plates arranged parallel to each other, which can be arc-shaped, and wherein one of the plates has expansion areas to form fluid-flowable spaces.

[0007] GB 873 881 A describes a pressing machine with an inner cylinder to which several curved plate sections are welded on the outside in order to form flow channels between the inner cylinder and the welded plate sections.

[0008] US 2008 / 0128526 A1 describes a tank container with a cylindrical container wall consisting of two plates designed as a heat exchanger element, wherein the radially outer plate has a lesser wall thickness than the inner plate and the outer plate has bulging areas to form fluid-flowable spaces between the plates.

[0009] US 7,691,337 B2 describes a container with a cylindrical side wall, wherein the side wall is formed from a radially outer thicker plate and a radially inner thinner plate, and wherein the inner plate has expansion areas to form flow channels.

[0010] The invention is based on the objective of providing a heat exchanger element for a device or a device with such an element, which enables particularly effective cooling of the medium subjected to the heat exchanger element and which is structurally simple and inexpensive to manufacture. Furthermore, the invention is based on the objective of providing a method for manufacturing structurally simple and inexpensive heat exchanger elements that enable particularly effective cooling of the medium subjected to the heat exchanger element.

[0011] The object of the invention is achieved by a heat exchanger element according to claim 1, in which the second plate with its expansion areas is arranged on multiaxially convex curved regions of the first plate, and the expansion areas of the second plate project from the second plate opposite to the multiaxially convex curvature of the first plate, wherein the multiaxially convex curved regions of the first plate are spherically curved. Furthermore, the object of the invention is achieved by a method according to claim 10.

[0012] This enables particularly effective cooling of the medium exposed to the heat exchanger element. Surprisingly, such a heat exchanger element, in which several connection points are arranged circumferentially around an expansion area provided on a multiaxially convex curved region of the first plate, can be manufactured by pressure expansion. This was not foreseeable prior to knowledge of the invention. In the inventive arrangement of the expansion areas of the second plate, the expansion areas must be bulged in the opposite direction to the multiaxially convex curvature of the first plate. This means that the area of ​​the second plate to be expanded must first be transformed from a spherical bulge into an at least substantially flat area before it can bulge in the opposite direction to the curvature of the first plate.This is the case, for example, with a container bottom that is spherically curved outwards, where the second plate is located on the inside of the container and is therefore also curved outwards before the expansion. During the expansion, a three-dimensional, multi-axial cross-sectional constriction must first be overcome, which is formed by the connection points nearest to the expansion area, which completely surround and constrict it. This also generates extremely high stresses at the connection points, which are significantly higher than, for example, during the bulging of a cylindrical wall in conventional heat exchangers. It has become apparent during the course of the invention that the aforementioned pressure expansion must be carried out almost to the load or bursting limits of the connection areas.Due to the necessary operational reliability of the devices containing the heat exchanger element, such as a reactor bottom, it was not conceivable before the invention that such heat exchanger elements could be designed.

[0013] In the course of developing the invention, it has been found that the pressure expansion of the expansion zones in a heat exchanger element according to the invention proceeds differently than in conventional heat exchanger elements. In conventional heat exchanger elements, where the plate assembly is only monoaxially curved, as with cylindrical side walls, the expansion of the expansion zones occurs essentially uniformly during pressure expansion. This means that the expansion zones expand continuously and to a substantially uniform extent over practically the entire surface of the plate assembly. This is what those skilled in the art are familiar with as the normal expansion process. In contrast, in the heat exchanger element according to the invention, the expansion surprisingly occurs discontinuously and locally abruptly. It is observed that initially only a few expansion zones are affected by the expansion, and these initially expand only partially.The expansion process occurs abruptly and with strong acoustic effects, which is completely unusual for the expansion of conventional heat exchanger elements and indicates the extremely high stresses in the expansion areas and connection points. Even though the expansion has already affected numerous expansion points, some of which are thus partially expanded, the expansion is still irregular, meaning that different expansion points exhibit varying expansion heights. Initially, an irregular surface is created on the expanded second plate, which in this form is unsuitable as an insert for a heat exchanger element, as this would lead to undefined flow conditions during operation of the corresponding device, such as a reactor. Only towards the end of the expansion process is a uniform expansion of all expansion areas of the plate assembly observed.Overall, it was therefore surprising to the person skilled in the art that it was even possible to manufacture the heat exchanger element according to the invention.

[0014] In the course of the invention, it was found that the heat exchangers according to the invention can be manufactured if the expansion areas are generated at a significantly higher pressure than in conventional heat exchanger elements, which may be ≥ 80% or ≥ 90% of the burst pressure of the connection points or approach the burst pressure. Thus, surprisingly, heat exchanger elements can be manufactured according to the invention in which the second plate with pressure expansions is arranged on multiaxially convex curved areas of the first plate.

[0015] In general, within the scope of the invention, the convex curvature of the first plate extends over a plurality of expansion areas of the second plate, for example, over ≥ 25% or ≥ 50%, preferably also ≥ 75%, or over the entire surface area of ​​the second plate. The first plate preferably has no local expansion areas. The pattern of expansion areas of the second plate forms concave and convex curved local areas, whereby the body of the second plate can be convex overall. In contrast, the first plate can, for example, be completely convex.

[0016] Advantageous embodiments result from the dependent claims.

[0017] Within the scope of the invention, the multiaxially convex curved areas of the first plate are spherically curved, e.g., in the shape of a spherical cap, a revolution ellipsoid, or the like. Preferably, the first plate or the plate assembly has only one spherically curved area or is continuously convexly spherically curved, i.e., without concave curved areas. Each axis perpendicular to the central axis of the spherical surface represents an axis of curvature. This necessitates that the expansion areas of the second plate between the connection points of the plates are particularly constricted, thus requiring the application of particularly high expansion pressures, which place a particularly high load on the expansion areas and especially on the connection points of the two plates around the expansion area.

[0018] Preferably, the first plate of the plate assembly is part of a curved vessel bottom, particularly a reactor bottom, with the second plate arranged on the inside of the vessel. It is understood that the vessel bottom curves outwards. The first plate contributes significantly to the stability of the vessel bottom, while the second plate on the inside of the bottom merely separates the spaces between the heat exchange medium and the interior of the vessel. This allows for the design of vessels, particularly reactors, in which especially effective temperature control of the vessel contents is possible, particularly in the bottom region.

[0019] In particular, according to the invention, the container bottom can be designed as a dished end, basket-arch end, elliptical end, or hemispherical end. In these cases, special curvature conditions of the plate composite are present, under which, surprisingly, the heat exchanger element according to the invention can be manufactured under pressure expansion of the expansion areas of the second plate on the inner side of the bottom. The curved container bottom can, in particular, have or be formed from two curvature areas of different radii R1 and R2. For example, a radius R1 can be present in the middle area of ​​the bottom, where R1 can be 0.5 Da to 1.2 Da, preferably 0.7 Da to 1.1 Da, for example 0.8 Da or 1.0 Da, where Da is the outer diameter of the container to which the bottom is attached. The second radius R2 can be in the range of 0.03 to 0.25 Da, for example 0.05 to 0.15 Da, in particular 0.06 Da or 0.1 Da or approximately 0.15 Da.For a dished end according to DIN 28011, R1 = Da and R2 = 0.1 Da. For a dished end according to ASME F&D, R1 = Da and R2 = 0.06 Da. For a basket-arch end according to DIN 28013, R1 = 0.8 Da and R2 = 0.154 Da. It is understood that, according to the invention, corresponding vessel ends can also be designed according to other relevant standards or configurations. The aforementioned standards refer in particular to those valid as of January 1, 2016. An elliptical end can, for example, have a radius of curvature as described above in a partial area, such as a radius of curvature like that of a dished end or basket arch, without being limited to this. The widenings of the second plate can be provided in the area with the larger and / or smaller radius of curvature of the end.

[0020] The connection points can be arranged in an irregular but preferably uniform grid across the plate surfaces, for example with a hexagonal or orthogonal grid, particularly in the form of a square or, optionally, rectangular pattern of connection points. A square pattern is preferred because this results in particularly favorable flow spaces for the heat exchanger medium, while the expansion areas are somewhat less constricted than, for example, with a pattern of equilateral triangles. The individual expansion areas can thus each be directly surrounded by 3 to 6 connection points, preferably 3, 4, or even 6 connection points. Preferably, the connection points are arranged at a uniform distance from each other around the respective expansion area. The distance between the individual connection points can be at least substantially constant.

[0021] Preferably, the expansion areas form a two-dimensional network of fluid-carrying interconnected spaces, which form intersecting flow channels for the heat exchanger medium, for which the insulated connection points can be arranged distributed over the plate surfaces.

[0022] The expansion areas of the second plate between the connection points preferably have an at least substantially isometric shape, for example, with a ratio of the largest and smallest widths of the respective expansion area along the surface of the first plate in the range of 5:1 to 1:1, 3:1 to 1:1, or 2:1 to 1:1, and in particular also approximately 1:1, as is the case with connection points with a square pattern. The expansion areas are bounded by the connection points between the plates surrounding them. The aforementioned expansion ratios are particularly advantageous for the formation of the network of intersecting flow channels for the heat exchange medium and for a heat exchanger-effective design of the side of the second plate facing the vessel contents. On the other hand, this makes the aforementioned problem of generating the expansion areas under the constraints of the connection points particularly evident.

[0023] Using the method according to the invention, for example containers with a diameter in the range of 0.3m to 8m can be produced, for example with a diameter ≥ 1m or in the range of 2 to 6m.

[0024] The connection points can, for example, have a distance of 20-150 mm or in the range of 30-100 mm, for example approximately 50 mm, without being limited to this.

[0025] In the heat exchanger element according to the invention, the joints can be designed as welds, with the weld beads preferably being smoothed. Smoothing can be achieved, for example, by grinding, and optionally also by polishing. It has been found that such joints exhibit increased strength during plate expansion compared to untreated welds, so that the heat exchanger elements according to the invention can be manufactured with expansion areas on the convexly curved regions of the plate assembly particularly advantageously. This material treatment of the welds apparently results in better force distribution under load and avoids notch effects during expansion, without being bound by theory.The aforementioned material treatment of the welded joints is therefore preferably carried out before the partial or final expansion of the second plate. Due to the treatment of the welded joints, the expansion areas of the second plate can be produced more efficiently and with a lower risk of damage to the joints during expansion.

[0026] It is often necessary to subject the plate assembly to an annealing treatment. The expansion areas of the second plate can be expanded to at least a portion of their final expansion height, which is present when the heat exchanger is ready for use, before the annealing treatment is carried out. This often facilitates the expansion process, particularly if the plates tend to stick together due to the annealing treatment. However, this procedure is not essential for carrying out the invention.

[0027] The heat exchanger element according to the invention can be operated with an operating pressure of the heat exchange medium of ≥ 3 bar, ≥ 10 bar, or ≥ 30 bar. The internal pressure of the device, which acts on the second plate provided with expansions, can in particular be ≥ 5 bar, ≥ 10 bar, or often also ≥ 16 bar or ≥ 40 bar, without being limited thereto. Thus, a pressure differential between the internal and external pressure of ≥ 10 bar, ≥ 20 bar, or even ≥ 40 bar can act on the second plate due to the contents of the container. It is understood that the second plate provided with the expansions must withstand the differential pressure, but also the internal pressure of the device, e.g., if the heat exchanger circuit fails.Therefore, the expansions of the second plate must be designed with a corresponding material stiffness, such as plate thickness, which in turn necessitates a correspondingly high expansion pressure during the creation of the expansion areas, particularly in connection with the problems described at the outset. Surprisingly, however, such heat exchangers or vessel bottoms can be manufactured according to the invention.

[0028] The wall thickness of the first plate is greater than the wall thickness of the second plate, usually by a factor of ≥ 2.5 or ≥ 5, but often also ≥ 10 or ≥ 20 or higher.

[0029] It is understood that the heat exchanger according to the invention is not limited to the manufacture of container bottoms, but can also be used for other devices with heat exchangers, e.g. pipe bends, elbows, collectors or the like, in which case the same may apply.

[0030] The plates of the heat exchanger element can be made of steel, for example, especially austenitic steel or dupex steel, but also of ferritic steel or other suitable materials or alloys, including non-ferrous materials such as Hastelloy.

[0031] The invention is described below with reference to an exemplary embodiment. The individual features of this exemplary embodiment can also be implemented generally within the scope of the invention, independently of other features of the same embodiment. The figures show: Fig. 1: A perspective view of a reactor in elevation with a bottom designed according to the invention, Fig. 2: a cross-sectional view of an area of ​​the ground according to Fig. 1.

[0032] A device comprising the heat exchanger according to the invention is described in the Fig. 1 and Fig.Figure 2 shows a container 1 configured as a reactor. The heat exchanger 3 according to the invention forms at least part of the outwardly convex bottom 2 of the reactor. It is understood that the heat exchanger described here can optionally also be part of another device.

[0033] The heat exchanger element 3 has two plates arranged at least substantially parallel to each other, namely a first and a second plate 4, 5, wherein the first plate has a higher strength than the second plate, in particular a significantly greater wall thickness. The first and the second plate 4, 5 are permanently connected to each other by a plurality of insulated connection points 6 distributed over the plate surface, forming a plate composite 7, wherein the second plate 5 has expansion zones 8 between the connection points 6 of the plates, created by plastic pressure expansion, and the expansion zones 8 form several interconnected fluid-flowable spaces 9. Several connection points 6 are arranged circumferentially around each expansion zone 8.The connection points are arranged in a square pattern, so that an expansion area is uniformly surrounded or bounded by four connection points. The expansion areas 8 of the second plate thus have an at least substantially isometric shape between the connection points. The spaces 9 form a two-dimensional network of intersecting and fluid-connected channels for the heat exchanger medium.

[0034] The plate assembly 7 is multiaxially curved, specifically spherically curved, forming convex and concave curved areas of the plate assembly: a concave outer surface, which forms the outer surface of the container bottom, and a convex inner surface, which forms the inner surface of the container bottom. The second plate 5, with its flared areas 8, is arranged on multiaxially convex curved areas of the first plate, namely on the spherically convex curved inner surface of the plate assembly or bottom. The flared areas 8 of the second plate thus project from the second plate in the opposite direction to the curvature of the first plate, namely towards the interior of the container. The container bottom 2 is therefore bulged outwards from the container 1.

[0035] According to the exemplary embodiment, the container bottom 2 is designed as a dished bottom, but can also be designed, for example, as a basket-arch bottom, elliptical bottom or hemispherical bottom.

[0036] The joints 6 are designed as circumferential weld lines, which are completely closed, here in the form of circular arcs. The weld lines have a surface that is at least substantially smooth, which may, for example, have been finished by grinding. It has been found that this increases the strength of the welded joints during the partial expansion of the second plate, which is particularly advantageous due to the expansion occurring under very high pressure – possibly close to the bursting limits of the joints.

[0037] The expansion areas of the second plate can, if necessary, be formed with at least part of their respective final expansion height or with their entire expansion height before carrying out an annealing treatment, which is often particularly advantageous to avoid the plates sticking together, but is not essential for carrying out the invention.

[0038] The heat exchanger element is designed for an operating pressure of ≥ 10 bar or ≥ 40 bar for the medium located outside the heat exchanger element and with which it exchanges heat (in this case, the container contents). The heat exchange medium within the heat exchanger can, for example, be pressurized to > 10 bar or > 20 bar. This places high mechanical demands on the plate assembly, particularly the expansion areas and connection points.

Claims

[1] Heat exchanger element with two plates (4, 5) arranged at least substantially parallel to each other, namely a first plate (4) and a second plate (5), wherein the first plate (4) has a higher strength than the second plate (5), wherein the first and the second plate (4, 5) are permanently connected to each other by a plurality of insulated connection points (6) distributed over the plate surface, forming a plate composite, wherein the second plate (5) has expansion areas (8) between the connection points (6) of the plates (4, 5) created by plastic pressure expansion, and the expansion areas (8) form several interconnected fluid-flowable spaces (9), wherein several connection points (6) are arranged circumferentially around each expansion area (8), and wherein the plate composite is also multiaxially curved in its shape.with the formation of convex and concave curved areas of the plate composite, , characterized by , that the second plate (5) with the widening areas (8) is arranged on multiaxially convex curved areas of the first plate (4) and the widening areas (8) of the second plate (5) project from the second plate (5) opposite to the multiaxially convex curvature of the first plate (4), wherein the multiaxially convex curved areas of the first plate (4) are spherically curved. [2] Heat exchanger element according to claim 1 characterized by , that the first plate (4) is part of or forms a curved container bottom (2) and that the second plate (5) is arranged on the inside of the bottom. [3] Heat exchanger element according to claim 2 characterized by , that the container bottom (2) is a dished end, basket arch bottom, elliptical bottom or hemispherical bottom. [4] Heat exchanger element according to one of claims 1 to 3, characterized by, that the widening areas (8) of the second plate (5) between the connection points (6) have an at least substantially isometric shape. [5] Heat exchanger element according to any one of claims 1 to 4, characterized by , that the joints (6) are formed as weld lines and that the weld lines have a surface that is at least substantially smooth. [6] Heat exchanger element according to any one of claims 1 to 5 characterized by , that the expansion areas (8) of the second plate (5) are formed at least to a part of their respective final expansion height before the performance of an annealing treatment. [7] Heat exchanger element according to any one of claims 1 to 6, characterized by , that the heat exchanger element (3) is designed for a pressure of the medium which is arranged outside the heat exchanger element (3) and is in heat exchange with it, of ≥ 4 MPa (40 bar). [8] Device with a heat exchanger element according to any one of claims 1 to 7. [9] Device according to claim 8, characterized by , that the device is designed as a reactor and that the heat exchanger element (3) forms at least part of a domed bottom (2) of the reactor. [10] Method for manufacturing a heat exchanger element according to any one of claims 1 to 7, wherein the first and the second plate (4, 5) are permanently connected to one another by a plurality of insulated connection points (6) distributed over the plate surface, forming a plate composite, wherein the plate composite is furthermore formed in its shape with a multiaxially spherically curved shape, forming convex and concave curved areas of the plate composite, wherein the second plate (5) is arranged on multiaxially convex curved areas of the first plate (4), wherein the second plate (5) is expanded by plastic pressure expansion, generating expansion areas (8) between the connection points (6) to form several interconnected fluid-flowable intermediate spaces (9), and wherein the expansion areas (8) are formed on multiaxially convex curved areas of the first plate (4).so that the widening areas (8) of the second plate (5) project from the second plate (5) in the opposite direction to the multiaxially convex curvature of the first plate (4).

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