Heat exchanger

Abstract

Heat exchanger (200, 200', 200") with a first end region (250), with a second end region and with a central region, wherein the first end region (250) and the second end region are connected to each other via the central region, characterized in that a temperature unit (300, 300', 300") is arranged in the first end region (250) and / or in the second end region and is configured to influence a temperature of the respective end region (250) during a shutdown of the heat exchanger (200, 200', 200") such that this temperature reaches a predetermined value or lies within a predetermined range of values.

Description

[0001] The invention relates to a heat exchanger. State of the art

[0002] In a variety of applications, heat exchangers are operated with cryogenic fluids, i.e. fluids with temperatures significantly below 0°C, in particular significantly below -100°C, for example in process engineering plants, e.g. in air separation plants, in plants for storing and recovering energy using liquid air, in natural gas liquefaction plants, etc. For example, such heat exchangers can be designed as brazed aluminum plate-fin heat exchangers (PFHE), as used, for example, in Fig. 2 of ISO 15547-2:3005 and on page 5 of the ALPEMA publication “The Standards of the Brazed Aluminium Plate-Fin Heat Exchanger Manufacturers' Association”, 3rd edition 2010.

[0003] Without additional measures, the temperature profiles of such heat exchangers will equalize during shutdown or a standstill of the associated system. If, for example, cryogenic gas is fed into a heated part of the heat exchanger during restart, or conversely, warm gas is fed into a cooled part of the heat exchanger, high thermal stresses arise, which can lead to damage to the heat exchanger or require disproportionately high material or manufacturing costs.

[0004] In particular, when a heat exchanger is taken out of service, before it has warmed up overall, the temperatures at the previously warm end and the previously cold end equalize due to the good thermal conductivity (longitudinal thermal conduction) in its metallic material. In other words, the previously warm end of the heat exchanger becomes colder over time, and the previously cold end warms up, until the temperatures are at or close to an average temperature. For example, the temperatures of the heat exchanger ends may be approximately -175°C and +20°C respectively at the time of decommissioning and will equalize over several hours, reaching almost an average temperature.

[0005] This behavior can be observed, for example, when shutting down an air separation plant, the main heat exchanger, which is housed in a cold-insulated enclosure, is blocked off along with the rectification unit, i.e., when no more gas is supplied from the outside. In such a case, typically only gas resulting from thermal insulation losses is blown off cold.

[0006] If warm fluid is subsequently fed into the cooled warm end of the heat exchanger upon restarting, the temperature there will rise dramatically. Correspondingly, the temperature at the heated cold end will drop dramatically upon restarting if correspondingly cold fluid is fed there. This leads to the aforementioned material stresses and thus potentially to damage.

[0007] The present invention therefore has the object of specifying measures which enable a corresponding heat exchanger to be put back into operation after a long period of decommissioning, if possible while avoiding the disadvantageous effects mentioned. Disclosure of the invention

[0008] Against this background, the present invention proposes a heat exchanger with the features of the independent patent claim. Further embodiments are the subject of the dependent patent claims and the following description.

[0009] The heat exchanger has a first end region or a first end, a second end region or a second end, and a central region, wherein the first end region and the second end region are connected to each other via the central region. One of the two end regions expediently represents a hot end of the heat exchanger, and the other end region expediently represents a cold end, wherein an operating temperature of the hot end during operation of the heat exchanger is higher than an operating temperature of the cold end.

[0010] For example, the heat exchanger can be designed as a brazed aluminum plate-fin heat exchanger (PFHE), as is generally used, for example, in Fig. 2 of ISO 15547-2:3005 and on page 5 of the ALPEMA publication "The Standards of the Brazed Aluminium Plate-Fin Heat Exchanger Manufacturers' Association", 3rd edition 2010. The first end region and the second end region can each, for example, at least partially comprise a respective header with nozzles for supplying and discharging process media. The middle region can, for example, at least partially comprise heat exchange passages for heat exchange between the process media, wherein these individual heat exchange passages can be defined by baffles arranged parallel to one another and by structured sheets with fins arranged between these baffles.

[0011] According to the invention, a temperature unit is arranged in or on the first end region and / or in or on the second end region and is designed to influence a temperature of the respective end region during decommissioning or standstill of the heat exchanger in such a way that this temperature of the respective end region, i.e. the end region at which a temperature unit is arranged, reaches a predetermined value or temperature value or lies within a predetermined value range or temperature interval.

[0012] This temperature unit represents, in particular, a modification or a structural unit which can be arranged, in particular, in a structurally simple manner, at the respective end region or connected to the heat exchanger there. The temperature unit can expediently keep the temperature of the respective end region constant at the predetermined value or at least within the predetermined value range during decommissioning. This predetermined temperature value can, for example, at least substantially correspond to the operating temperature of the respective end, or the operating temperature of the respective end can lie within the predetermined value range. The temperature value orthe value range is selected in such a way that high thermal stresses do not occur when the heat exchanger is put back into operation or that such thermal stresses can at least be reduced, which could lead to damage to the heat exchanger in the long term.

[0013] The invention makes it particularly useful to completely or at least partially avoid temperature equalization during downtime phases. This allows for rapid restart of the heat exchanger after its shutdown. High thermal stresses resulting from differential thermal expansion caused by existing temperature differences can be avoided or at least reduced. The service life of the heat exchanger can thus be increased. Furthermore, it can be ensured that the service life is not impaired by flexible, intermittent operation of the heat exchanger.

[0014] According to one embodiment, the temperature unit has a thermal contact unit that brings the respective end region into thermal contact with a housing of the heat exchanger or with a housing of a device comprising the heat exchanger. Through the thermal contact between the respective end region and the housing with the aid of the contact unit, the temperature of the respective end region can expediently be adjusted to the temperature of the housing. For example, heat can be transferred from the environment to the outer wall of the housing by convection, and a corresponding heat flow can flow from the housing to the respective end of the heat exchanger through the thermal contact unit.

[0015] The housing can be made of steel, for example, or, in particular, of a material with better heat conduction, such as aluminum or an aluminum alloy. In the latter case, the material can be protected from damage if, in the event of a failure, the heat exchanger becomes too cold, i.e., reaches temperatures that could lead to embrittlement and fracture in steel sheets.

[0016] The device comprising the heat exchanger is designed, in particular, as a process plant, for example, as an air separation plant, as a plant for storing and recovering energy using liquid air, as a plant for liquefying natural gas, etc. For example, the heat exchanger can be arranged together with other components of the device within the housing. In the case of an air separation plant, the heat exchanger can, for example, be arranged together with a distillation column system within the common housing. The housing and the plant components arranged therein can, for example, be provided as a structural unit, for example, as a cold chamber or so-called cold box.

[0017] According to one embodiment, the contacting unit has at least one contacting element, which is connected to the respective end region and to the housing. This contacting element is particularly thermally conductive and has, in particular, a predetermined thermal conductivity. The contacting elements can each be connected to the respective end region and the housing, for example, by means of a material bond, e.g., by a soldered or welded connection.

[0018] According to one embodiment, the at least one contacting element comprises at least one plate, e.g., flat, soldered plates, and / or at least one cable and / or at least one strip. For example, these cables and strips can each be made of a solid material or a fabric, e.g., copper or aluminum. Such contacting elements can be connected, in particular, over a large area to the respective end region of the heat exchanger, from there to the outer wall of the housing, and there, in particular, also connected to the outer wall over a large area.

[0019] According to one embodiment, the respective end region is separated from an insulating material within the housing by a separating element. As explained above, for example, a perlite bed can be provided within the housing around the system components as the insulating material. The contacting unit has a filling material, for example a knitted fabric made of copper and / or aluminum, which is arranged within the separating element. Particularly expediently, the separating element encloses the respective end region and can, for example, be cuboid or box-shaped. The respective end region can be arranged within the housing, in particular close to one or more housing walls, e.g. to a roof, a floor or one or more side surfaces. Expediently, the separating element extends as far as this one or these several housing walls.

[0020] The filling material can in particular create a good heat-conducting connection between the respective end area and the respective housing wall or walls.

[0021] According to one embodiment, the respective end region protrudes at least partially from the housing. For example, in this case, the contacting unit can be designed as a highly thermally conductive connecting element with a predetermined thermal conductivity, which connects the respective end region to the housing. In particular, the temperature of the respective protruding end region can be adjusted to the outside or ambient temperature.

[0022] According to one embodiment, the temperature unit further comprises a fin arrangement or a rib arrangement arranged on a region of the respective end region located outside the housing. This fin arrangement can expediently increase the surface area of ​​the respective end region that communicates with the environment.

[0023] According to one embodiment, the temperature unit comprises a fluid unit, wherein this fluid unit has a fluid supply and a fluid discharge and is configured to supply a fluid to the respective end region by means of the fluid supply and to discharge the fluid from the respective end region again by means of the fluid discharge, in particular by means of an open or closed circuit. The fluid can expediently be provided as a cooling fluid for cooling the respective end region or as a heating fluid for heating the respective end region. For example, dry air or ambient air can be used as the fluid.

[0024] According to one embodiment, the fluid unit is arranged within the respective end region. In this case, the fluid unit can be provided, in particular, as additional, internal heat exchange passages within the respective end region. In this case, the overall height of the heat exchanger can be increased by these additional, internal passages.

[0025] According to one embodiment, the fluid unit is arranged outside the respective end region. In this case, the fluid unit can be provided, in particular, as an attachment that can be flexibly placed on the respective end region or arranged around the respective end region.

[0026] According to one embodiment, the fluid unit further comprises a circulation element that connects the fluid discharge to the fluid supply and is configured to bring the temperature of the fluid discharged by the fluid discharge to a predetermined fluid temperature value and to return the fluid, brought to the predetermined fluid temperature value, to the respective end region via the fluid supply. In particular, a closed fluid circuit can thus be created. The fluid discharged from the end region can expediently be heated or cooled by means of the circulation element in order to heat or cool the end region again upon re-supply. For example, the circulation element can be designed as a heating fan.

[0027] According to one embodiment, the temperature unit has at least one sidebar element arranged between adjacent sidebars of the heat exchanger. The heat exchanger expediently has a plurality of sidebars, wherein the separating plates can be kept at a distance by these sidebars and wherein the sidebars can also provide mechanical reinforcement of the pressure chamber. The respective adjacent sidebars can be modified at the respective end region, for example, such that the respective sidebar element can be placed between them. Furthermore, the respective sidebars can also be installed at the respective end region, for example, with a corresponding distance from one another in order to be able to insert or push in the respective sidebar element between them. The respective sidebar element can then directly influence the temperature of the respective end region.For example, the sidebar element can be designed as a heating element, in particular as an electrical heating element.

[0028] According to one embodiment, a thermally conductive paste is applied between the at least one sidebar element and the respective sidebars. For example, this thermally conductive paste can improve contact between the sidebar element, e.g., designed as a heating element, and the end region.

[0029] According to one embodiment, an operating temperature of the first end region during operation of the heat exchanger is higher than an operating temperature of the second end region. The first end region thus represents, in particular, a warm end, and the second end region represents, in particular, a cold end. A temperature unit designed as a heating unit can be arranged in the first end region and configured to introduce heat into this warm end of the heat exchanger during shutdown. Alternatively or additionally, a temperature unit designed as a cooling unit can be arranged in the second end region and configured to cool this cold end during shutdown.For example, depending on the operating temperatures and material properties of the end regions and also, for example, depending on the operating temperatures and properties of the process fluids passed through the heat exchanger during operation, only the heating unit at the warm end or only the cooling unit at the cold end or both the heating and the cooling unit may be provided.

[0030] Furthermore, a method for decommissioning a corresponding heat exchanger is discussed herein. Advantages and embodiments of the method and the heat exchanger according to the invention will become apparent from the present description.

[0031] Within the scope of the method, the heat exchanger is initially operated in a regular operating mode, wherein process media are supplied to the heat exchanger and heat is exchanged between the process media. The temperature unit of the heat exchanger is expediently deactivated in this regular operating mode. The heat exchanger is then taken out of operation or deactivated, wherein in particular the supply of process media is stopped. For example, the decommissioning can take place during a deactivation or shutdown of the device or system comprising the heat exchanger. During decommissioning, the temperature of the first end region and / or the second end region is influenced by means of the temperature unit arranged in the respective end region in such a way that this temperature of the respective end region reaches the respective predetermined value or lies within the predetermined value range.For example, the temperature unit that was deactivated during regular operating mode can now be activated and controlled to influence the temperature of the respective end area accordingly.

[0032] According to one embodiment, the heat exchanger is restarted and operated in its regular operating mode. Since temperature equalization can be avoided by influencing the temperature of the respective end zone during shutdown, a rapid restart can be carried out particularly effectively. The temperature unit can then be conveniently deactivated again.

[0033] The invention is explained in more detail below with reference to the accompanying drawings, which illustrate the present invention and its features compared to the prior art. Short description of the drawings Fig. 1 shows schematically a heat exchanger not according to the invention in a simplified isometric representation. Fig. 2 shows schematically an embodiment of a heat exchanger according to the invention in a perspective view. Fig. 3 shows schematically an embodiment of a heat exchanger according to the invention in a perspective view. Fig. 4 shows schematically an embodiment of a heat exchanger according to the invention in a sectional view. Embodiment(s) of the invention

[0034] Fig. Figure 1 schematically shows a prior art heat exchanger 100. The heat exchanger 100 is designed as a brazed aluminum fin-plate heat exchanger, as described, for example, in Fig. 2 of ISO 15547-2:3005 and on page 5 of the publication “The Standards of the Brazed Aluminium Plate-Fin Heat Exchanger Manufacturers' Association” of ALPEMA, 3.

[0035] Edition 2010. An illustration that essentially corresponds to the illustrations there is included in this Fig. 1 shown.

[0036] The Fig. 1 partially opened plate heat exchanger 100 according to the prior art is used for the heat exchange of, in the example shown, five different process media A to E. For the heat exchange between the process media A to E, the plate heat exchanger 100 comprises a plurality of separating sheets 4 arranged parallel to one another (referred to in English as parting sheets in the aforementioned publications, to which the following information in brackets also refers), between which heat exchange passages 1 are formed, each for one of the process media A to E, which can thereby enter into heat exchange with one another.

[0037] The structural sheets with the slats 3 are typically folded or corrugated, whereby flow channels are formed by the folds or waves, as in Fig. 1 of ISO 15547-2:3005. Compared to plate heat exchangers without fins, the provision of structured plates with fins 3 offers the advantage of improved heat transfer, more targeted fluid flow, and increased mechanical (tensile) strength. In the heat exchange passages 1, the process media A to E flow separately from one another, particularly through the separating plates 4, but can possibly pass through the latter in the case of perforated structured plates with fins 3.

[0038] The individual passages 1 or the structural plates with the slats 3 are each surrounded laterally by so-called sidebars 8, which, however, leave open feed and discharge openings 9. The sidebars 8 keep the separating plates 4 at a distance and provide mechanical reinforcement for the printing chamber. Reinforced cover plates 5 (cap sheets), arranged parallel to the separating plates 4, serve as the closure on at least two sides.

[0039] By means of so-called headers 7, which are equipped with nozzles 6, the process media A to E are fed in and out via feed and discharge openings 9. In the inlet area of ​​the passages 1, there are further structured plates with so-called distributor fins 2, which ensure even distribution across the entire width of the passages 1. At the end of the passage 1, viewed in the direction of flow, there may be further structured plates with distributor fins 2, which guide the process media A to E from the passages 1 into the headers 7, where they are collected and withdrawn via the corresponding nozzles 6.

[0040] The structural plates with the fins 3, the further structural plates with the distributor fins 2, the sidebars 8, the separating plates 4 and the cover plates 5 form a cuboid-shaped heat exchanger block 20, whereby a "heat exchanger block" is understood to mean the aforementioned elements without the headers 7 and nozzles 6 in an interconnected state. As in Fig. 1, the plate heat exchanger 300 can be formed from a plurality of corresponding cuboid-shaped and interconnected heat exchanger blocks 20, particularly for manufacturing reasons.

[0041] Corresponding plate heat exchangers 300 are brazed from aluminum. The individual passages 1, comprising the structural sheets with the fins 3, the further structural sheets with the distributor fins 2, the cover sheets 5, and the sidebars 8, are each coated with solder, stacked one on top of the other or arranged accordingly, and heated in a furnace. The headers 7 and the nozzles 6 are welded onto the heat exchanger block 20 produced in this way. The headers 7 are manufactured using semi-cylindrical extruded profiles, which are cut to the required length and then welded onto the heat exchanger block 20.

[0042] Such heat exchangers can be used in process engineering plants, for example, in an air separation plant, which may also have a distillation column system, where, for example, a high-pressure column and a low-pressure column of the distillation column system can be connected to each other via the heat exchanger for heat exchange. The heat exchanger and other plant components can, for example, be arranged in a common housing and provided as a common structural unit, e.g., as a so-called cold box. Such air separation plants are described, for example, in H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH, 2006, in particular Section 2.2.5, "Cryogenic Rectification." For detailed explanations of the structure and operation, please refer to the relevant specialist literature.

[0043] During operation of the heat exchanger in the respective system, a first end area or a first end, e.g. an upper end area having the headers and nozzles there, can have a higher operating temperature than a second end area or a second end, e.g. a lower end area having the headers and nozzles there. For example, the operating temperature in the first (warm) end can be approx. 20°C and in the second (cold) end approx. -175°C. When the heat exchanger is taken out of service, e.g. when the system is at a standstill, the temperatures of these two end areas can increasingly equalize over time due to the high thermal conductivity of the materials used in the heat exchanger. For example, strong thermal stresses can arise if the first (warm) end of the heat exchanger is exposed to a warm fluid again after a period of regeneration without further measures.

[0044] In order to counteract such effects, the invention proposes arranging a temperature unit in one or both end regions of the heat exchanger, which temperature unit influences a temperature of the respective end region during shutdown in such a way that this temperature reaches a respective predetermined value or lies within a predetermined value range, as described below with reference to the Fig. 2 to 4 will be explained.

[0045] In Fig. 2, an embodiment of a heat exchanger according to the invention is shown schematically in a perspective view and designated 200. The heat exchanger 200 can be designed as a brazed fin-plate heat exchanger, as described above with reference to Fig. 1. The heat exchanger 200 has headers with nozzles 210 for the supply and discharge of process media 220.

[0046] An upper end region 250 of the heat exchanger 200 represents, for example, the warm end, whose operating temperature during regular operation is approximately +20°C, for example. A configuration of a temperature unit 300 is arranged at this end region 250. The temperature unit 300 is configured, for example, to maintain the temperature of the warm end 250 during shutdown essentially at the operating temperature of +20°C or at least within an interval around this operating temperature, e.g., between +15°C and +25°C.

[0047] The temperature unit 300 comprises, for example, a fluid unit 310 with a fluid supply 311 and a fluid discharge 312 for supplying a fluid 313, e.g., dry (ambient) air, to the end region 250 via the fluid supply 311 and for discharging the fluid 313 from the end region 250 via the fluid discharge 312. The fluid unit 310 is arranged outside the end region 250 and is provided, for example, as an attachment that is applied to the end region 250.

[0048] In a corresponding manner, a corresponding temperature unit can also be provided at the lower, cold end region of the heat exchanger 200 in order to cool this cold end during shutdown, wherein, for example, a cryogenic fluid can then be supplied and discharged.

[0049] Also in Fig. 3, an embodiment of a heat exchanger according to the invention is shown schematically in a perspective view and designated 200'. Identical reference numerals in the Fig. 2 to 4 refer to identical or identically constructed elements and are not explicitly explained again to avoid repetition.

[0050] Also the Fig. The heat exchanger 200' shown in Figure 3 has a configuration of a temperature unit 300' at its warm end 250, which also has a fluid unit 320 arranged outside the warm end 250 and having a fluid supply 321 and a fluid discharge 322. This fluid unit 320 further has a circuit element 323, which connects the fluid discharge 322 to the fluid supply 321 and is configured to bring the temperature of the fluid discharged by means of the fluid discharge 322 to a predetermined fluid temperature value and to feed the fluid, brought to the predetermined temperature value, back to the respective end region via the fluid supply 321. For example, a heating fan 324 can be provided for this purpose to heat the discharged fluid.

[0051] The warm end 250 stands out in the example of Fig. 3 at least partially out of a housing 240 of the system comprising the heat exchanger 200'. The temperature unit 300' further comprises a contacting unit 330, which brings the end region 250 into thermal contact with the housing 240. For example, the contacting unit 330 can comprise plates, cables and / or strips, which are each connected to the warm end 250 and the housing 240, e.g., by means of a soldered or welded connection. By convection, heat from the environment can be transferred to the outer wall of the housing 240, and a heat flow can flow through the contacting unit 330 from the housing 240 to the warm end 250. The temperature of the warm end 250 can thus be adjusted to the outside or ambient temperature.

[0052] The temperature unit 300' further includes a fin arrangement 340 arranged on the area of ​​the warm end 250 located outside the housing 240. The fin arrangement 340 can increase the area of ​​the warm end 250 that is in contact with the environment.

[0053] Fig. 4 shows an embodiment of a heat exchanger 200" according to the invention in a schematic sectional view. The Fig. 4 has a configuration of a temperature unit 300" which has a sidebar element 350 which is arranged in the warm end 250 between adjacent sidebars 230 (in Fig. 1 designated 8). For example, sidebar element 350 can be designed as an electrical heating element.

[0054] The individual temperature units 300, 300', and 300" can be used to partially or completely avoid temperature equalization of the warm end during shutdown, thus enabling rapid recommissioning of the heat exchanger after its shutdown. High thermal stresses can be reduced or avoided, and the service life of the heat exchanger can be increased. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] The Standards of the Brazed Aluminum Plate-Fin Heat Exchanger Manufacturers' Association” of ALPEMA, 3rd edition 2010 [0002, 0010] Page 5 of the publication “The Standards of the Brazed Aluminium Plate-Fin Heat Exchanger Manufacturers' Association” of ALPEMA, 3

[0034] H.-W. Häring (ed.), Industrial Gases Processing, Wiley-VCH, 2006

[0042]

Claims

[1] Heat exchanger (200, 200', 200") with a first end region (250), with a second end region and with a central region, wherein the first end region (250) and the second end region are connected to one another via the central region, characterized by in that a temperature unit (300, 300', 300") is arranged in each of the first end region (250) and / or in the second end region and is configured to influence a temperature of the respective end region (250) during decommissioning of the heat exchanger (200, 200', 200") such that this temperature reaches a predetermined value or lies within a predetermined value range. [2] Heat exchanger according to claim 1, wherein the temperature unit (300') has a contacting unit (330) which brings the respective end region (250) into thermal contact with a housing of the heat exchanger or with a housing (240) of a device comprising the heat exchanger. [3] Heat exchanger according to claim 2, wherein the contacting unit (330) has at least one contacting element which is connected to the respective end region (250) and to the housing (240). [4] Heat exchanger according to claim 3, wherein the at least one contacting element comprises at least one plate and / or at least one cable and / or at least one band. [5] Heat exchanger according to one of claims 2 to 4, wherein the respective end region (250) is sealed off from an insulating material within the housing (240) by a separating element, wherein the contacting unit (330) comprises a filling material which is arranged within the separating element. [6] Heat exchanger according to one of claims 2 to 5, wherein the respective end region (250) protrudes at least partially from the housing (240). [7] Heat exchanger according to claim 6, wherein the temperature unit (300') further comprises a fin arrangement (340) arranged on a region of the respective end region (250) arranged outside the housing (240). [8] Heat exchanger according to one of the preceding claims, wherein the temperature unit (300, 300") comprises a fluid unit (310, 320), wherein the fluid unit (310, 320) comprises a fluid supply (311, 321) and a fluid discharge (312, 322) and is configured to supply a fluid to the respective end region (250) by means of the fluid supply (311, 321) and to discharge the fluid from the respective end region (250) again by means of the fluid discharge (312, 322). [9] Heat exchanger according to claim 8, wherein the fluid unit (310, 320) is arranged within the respective end region (250) and / or is arranged outside the respective end region. [10] Heat exchanger according to claim 8 or 9, wherein the fluid unit (320) further comprises a circuit element (323, 324) which connects the fluid discharge (322) to the fluid supply (321) and is adapted to bring a temperature of the fluid discharged by means of the fluid discharge (322) to a predetermined fluid temperature value and to supply the fluid via the fluid supply (321) back to the respective end region (250). [11] Heat exchanger according to one of the preceding claims, wherein the temperature unit (300") comprises at least one sidebar element (350) which is arranged between sidebars (8, 230) of the heat exchanger. [12] Heat exchanger according to claim 11, wherein a thermally conductive paste is applied between the at least one sidebar element (350) and the respective sidebars (8, 230). [13] Heat exchanger according to one of the preceding claims, wherein an operating temperature of the first end region (250) during operation of the heat exchanger is higher than an operating temperature of the second end region, wherein a temperature unit (300, 300', 300") designed as a heating unit is arranged in the first end region (250) and is configured to introduce heat into the first end region (250) during decommissioning and / or wherein a temperature unit designed as a cooling unit is arranged in the second end region and is configured to cool the second end region during decommissioning.

Images