A heat exchanger and a method for shutting down a heat exchanger

Abstract

The present invention relates to a heat exchanger (200), comprising a heat exchanger block (205), wherein a distance from a first end position (215) of the heat exchanger block (205) to a second end position (225) of the heat exchanger block (205) in a longitudinal direction corresponds to a height of the heat exchanger block (205); wherein at least one first header (211, 212) is covering a first end section (210) of the heat exchanger block (205) and / or is arranged adjacent to the first end position (215) outside of the heat exchanger block (205) and wherein at least one second header (221, 222) is covering a second end section (220) of the heat exchanger block (205) and / or is arranged adjacent to the second end position (225) outside of the heat exchanger block (205); wherein the heat exchanger (200) further comprises at least one heat transfer unit (250, 260) configured to introduce heat into the heat exchanger block (205) over a predefined first area (255) of the heat exchanger block (205) or configured to extract heat out of the heat exchanger block (205) over a predefined second area (265) of the heat exchanger block (205); wherein a respective first distance in the longitudinal direction of the predefined first area (255) to the first end position (215) of the heat exchanger block (205) corresponds to at least 5% of the height of the heat exchanger block (205) and the predefined first area (255) is located outside the first end section (210) and / or wherein a respective second distance in the longitudinal direction of the predefined second area (265) to the second end position (225) of the heat exchanger block (205) corresponds to at least 5% of the height of the heat exchanger block (205) and the predefined second area (265) is located outside the second end section (220).

Description

[0001] P40391 -EPP40391 PIF

[0002] 09.12.2025 - Dietmar Imhof

[0003] 1

[0004] Description

[0005] A heat exchanger and a method for shutting down a heat exchanger

[0006] The present invention relates to a heat exchanger and to a method for operating a heat exchanger.

[0007] Background of the invention

[0008] Heat exchangers can be operated with cryogenic fluids, i.e. fluids with temperatures well below 0°C, in particular well below -100°C, in a multitude of technical applications, for example in engineering plants, e.g. air separation plants, plants for storing and recovering energy using liquid air, natural gas liquefaction plants, etc. Heat exchangers of that kind can be provided as brazed aluminium plate-fin heat exchangers (PFHE) with a heat exchanger block and headers, as for example shown and described in Figure 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, 3rd edition 2010.

[0009] Without additional measures, the temperature profiles in a heat exchanger block of a corresponding heat exchanger equalises when the associated system is shut down or turned down or at a standstill (in the following all encompassed by the term "shut down"). If, for example, cryogenic gas is then fed into a heated part of the heat exchanger block when it is restarted and put back into operation, or, conversely, if warm gas is fed into a cooled part of the heat exchanger block, high thermal stresses can occur that can damage the heat exchanger block or that can require a disproportionately high amount of material or manufacturing effort.

[0010] In particular, if a heat exchanger is shut down before it has warmed up, the good heat conduction (heat longitudinal conduction) in its metallic material causes the temperatures at the previously warm end and at the previously cold end to equalise. In other words, the previously warm end of the heat exchanger block becomes colder over time and the previously cold end of the heat exchanger block becomes warmer, until the respective temperatures are at or near an average temperature. For example, the temperatures of the heat exchanger block end sections at the time of shutdownP40391 -EPP40391 PIF

[0011] 09.12.2025 - Dietmar Imhof

[0012] 2

[0013] may be approximately -195°C and +20°C, respectively, and may converge over several hours to almost reach an intermediate temperature.

[0014] This behaviour can be observed during shutdown of air separation plant, for example, when the main heat exchanger, which is housed in a cold-insulated manner, is blocked together with a rectification unit, i.e. when no more gas is supplied from the outside. In such a case, typically only gas that is produced by thermal insulation losses is blown cold.

[0015] If warm fluid is subsequently fed in at the cooled warm end of the heat exchanger block when it is restarted and put back into operation, the temperature there will suddenly increase. Accordingly, if the corresponding cold fluid is fed in at the heated cold end when it is put back into operation, the temperature there will suddenly decrease. This leads to the already mentioned material stresses and thus possibly to damage.

[0016] Document US 5233839 A discloses a heat exchanger, wherein during rest periods, when the heat exchanger is not in operation, heat is introduced at a hot end section and a cooling medium is introduced at a cold end section of the exchanger so as to maintain these two ends at temperatures, which are relatively close to those corresponding to active periods of the heat exchanger. In an embodiment, electrical resistances are provided for heating the hot end section. Further, coils for a flow of cold gaseous nitrogen are mounted in heat exchange relationship on two opposite vertical faces of the heat exchanger over the entire width and length of said faces.

[0017] Further, document WO 2021 / 037391 A1 discloses a method for operating a heat exchanger, wherein in a first operating mode, fluid flows are fed into the heat exchanger for performing a heat exchange between the fluids. In a second operating mode, the feeding of the fluid flows is partially or completely halted. In this second operating mode, a hot end of the heat exchanger is heated by introducing heat and a cold end of the heat exchanger is cooled using a cooling fluid that is conducted through passages in or on the heat exchanger’s cold end.

[0018] However, providing external heating or cooling mechanism at the warm end and the cold end of a heat exchanger, as it is disclosed in documents US 5233839 A and WO 2021 / 037391 A1 might yield difficulties. As a number of headers is usuallyP40391 -EPP40391 PIF

[0019] 09.12.2025 - Dietmar Imhof

[0020] 3

[0021] provided in these end sections, particularly as the end sections are typically mostly occupied with headers, there is usually not much space or no space at all for external heating or cooling mechanisms of that kind, which thus become quite ineffective.

[0022] It is therefore desirable to restart a heat exchanger after a shutdown period, while avoiding the aforementioned disadvantageous effects as far as possible.

[0023] Disclosure of the invention

[0024] The present invention relates to a heat exchanger and to a method for operating a heat exchanger with the features of the independent claims. Embodiments and advantages form the subject-matter of the dependent claims and of the subsequent description.

[0025] The heat exchanger can for example be provided as a brazed aluminium plate-fin heat exchanger (PFHE), as e.g. shown and described in Figure 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, 3rd edition 2010.

[0026] The heat exchanger comprises a heat exchanger block, wherein the term “heat exchanger block” is particularly to be understood as a cuboid block formed by structured sheets with the fins, structured sheets with the distributor fins, sidebars, parting sheets and cap sheets. During a regular operating mode of the heat exchanger, a number of different process media can be guided through the heat exchanger block such that a heat exchange between these process media can be performed. For this purpose, the heat exchanger block particularly comprises a plurality of parallel arranged parting sheets, between which heat exchange passages, e.g. defined by structured sheets with fins, are formed for each one of the process media, which can thereby exchange heat with one another. The individual passages and the structured sheets with the fins can each be surrounded laterally by so-called sidebars. These sidebars can keep the parting sheets at a distance and can provide a mechanical reinforcement of the pressure chamber. At least two sides can be closed off by reinforced cap sheets, which can be arranged parallel to the parting sheets. In the entrance area of the passages, structured sheets with so called distributor fins can be provided, which can ensure even distribution over the entire width of the passages. At the end of the passages, there may be further structured sheets with distributor fins.P40391 -EPP40391 PIF

[0027] 09.12.2025 - Dietmar Imhof

[0028] 4

[0029] A distance from a “first end position” or a first outermost position of the heat exchanger block to a “second end position” or a second outermost position of the heat exchanger block in a longitudinal direction corresponds to a height of the heat exchanger block. The longitudinal direction can especially be parallel or at least essentially parallel to the flow direction of the process media guided though the heat exchanger block during its regular operating mode. For example, without loss of generality, the first end position can correspond to an uppermost position of the heat exchanger block, e.g. to a position of a top surface or an upper edge of the heat exchanger block. Accordingly, without loss of generality, the second end position can correspond to a lowermost position of the heat exchanger block, e.g. to a position of a bottom surface or a lower edge of the heat exchanger block.

[0030] At least one first header is covering a first end section of the heat exchanger block and / or is arranged adjacent to the first end position outside of the heat exchanger block. At least one second header is covering a second end section of the heat exchanger block and / or is arranged adjacent to the second end position outside of the heat exchanger block. Each of these headers can be provided for introducing a respective process medium into the heat exchanger block or for removing a respective process medium from the heat exchanger block. Each of these headers can for example comprise one or several nozzles for supplying and discharging the respective process medium.

[0031] The term "end section" of the heat exchanger block is particularly to be understood as a longitudinal section, region or area of the heat exchanger block, in which respective headers are to be arranged. Particularly, the term "end section" is to be understood as a section, region or area of the heat exchanger block, which extends in the longitudinal direction from the respective end position and where at at least one side surface of which one or more headers are attached. The longitudinal extension of the end section corresponds to the longitudinal extension of the at least one header arranged at this end section. For example, one or more or the first headers can be arranged on the top side or top surface of the heat exchanger block. Furthermore, one or more of the first headers can be provided at a side surface of the heat exchanger block extending from this top surface, i.e. in an area from the first end position of the heat exchanger block downwards. The first end section can therefore comprise this top surface as well as theP40391 -EPP40391 PIF

[0032] 09.12.2025 - Dietmar Imhof

[0033] 5

[0034] longitudinal part of the first end of the heat exchanger block which corresponds to (and includes) the part of the side surface, at which respective first headers are arranged. In this case, a lowermost position of a respective first header provided at the side surface extending from the top surface can be understood as an end or an end position of the first end section. Correspondingly, one or more of the second headers can be arranged on the bottom side or bottom surface of the heat exchanger block as well as at the side surface extending from the bottom surface, i.e. in an area from the second end position upwards. The second end section can thus comprise the bottom surface as well as the longitudinal part of the second end of the heat exchanger block which corresponds to (and includes) the part of the side surface, at which respective second headers are arranged.

[0035] Particularly, a central section or central region of the heat exchanger block connects the first end section and the second end section with each other. One end section of the first end section and the second end section, without loss of generality e.g. the first end section, is a warm end or warm end section of the heat exchanger block and the other end section, without loss of generality e.g. the second end section, is a cold end or cold end section, wherein an operating temperature of the hot end during operation of the heat exchanger block is higher than an operating temperature of the cold end. Further, one of the two end sections, without loss of generality e.g. the first end section, can correspond to an upper end section of the heat exchanger block, whereas the other end section, without loss of generality e.g. the second end section, can correspond to a lower end section of the heat exchanger block. Without loss of generality, the first end position of the heat exchanger block can for example correspond to an outermost position of the warm end section of the heat exchanger block and the second end position of the heat exchanger block can for example correspond to an outermost position of the cold end section of the heat exchanger block.

[0036] According to the present invention, the heat exchanger further comprises at least one heat transfer unit configured to introduce heat into the heat exchanger block locally, i.e. over a predefined first area of the heat exchanger block, or configured to extract heat out of the heat exchanger block locally, i.e. over a predefined second area of the heat exchanger block. A respective first distance in the longitudinal direction of the predefined first area to the first end position of the heat exchanger block correspondsP40391 -EPP40391 PIF

[0037] 09.12.2025 - Dietmar Imhof

[0038] 6

[0039] to at least 5% of the height of the heat exchanger block and the predefined first area is located outside the first end section. Alternatively or additionally, a respective second distance in the longitudinal direction of the predefined second area to the second end position of the heat exchanger block corresponds to at least 5% of the height of the heat exchanger block and the predefined second area is located outside the second end section.

[0040] The term "predefined area" is particularly to be understood as a respective section, region or area of the heat exchanger block in the longitudinal direction, particularly in the central section of the heat exchanger block, wherein this predefined area is locally limited and does not extend over the entire height of the heat exchanger block but rather only over a part of it. Particularly, each predefined area corresponds to a limited area of the heat exchanger block, wherein a height of this limited area corresponds to at most 50% of the height of the heat exchanger block.

[0041] The term of the respective "distance" of the respective predefined area to the respective end position of the heat exchanger block is particularly to be understood as a minimum distance in the longitudinal direction between a middle or a centre, e.g. a geometric centre, of the respective predefined area to the respective end position of the heat exchanger block, particularly the respective edge (upper or lower edge) of the heat exchanger block.

[0042] With this respective distance of each predefined area being at least 5% of the height of the heat exchanger block and with the predefined areas being located outside the end sections of the heat exchanger block, the heat transfer units do not introduce or extract heat in or out of the first or the second end section of the heat exchanger block itself, but rather introduce or extract heat in or out of a limited part of the central section between the first and second end section. Particularly, an extension or a height of the first end section of the heat exchanger block in the longitudinal direction and an extension or height of the second end section of the heat exchanger block in the longitudinal direction can each correspond to less than 5% of the height of the heat exchanger block. Therefore, the respective distance from the respective predefined area towards the respective end position of the heat exchanger block is expediently larger than the distance or height of the respective end section of the heat exchanger block. Each heat transfer unit therefore expediently allows a local introduction orP40391 -EPP40391 PIF

[0043] 09.12.2025 - Dietmar Imhof

[0044] 7

[0045] extraction of heat in or out of a predefined area within the central section of the heat exchanger block.

[0046] Particularly, the at least one heat transfer unit can be used for introducing heat into the predefined first area of the heat exchanger block or for extracting heat out of predefined second area of the heat exchanger block during a shutdown of the heat exchanger. Expediently, by introducing heat into the first predefined area of the heat exchanger block by means of the at least one heat transfer unit, by thermal conduction the warm end section of the heat exchanger block can be heated during the shutdown of the heat exchanger. Correspondingly, by removing heat from the second predetermined area of the heat exchanger block by means of the at least one heat transfer unit, by thermal conduction the cold end section of the heat exchanger block can expediently be cooled during the shutdown of the heat exchanger.

[0047] The invention thus allows to avoid temperature equalisation during shutdown periods of the heat exchanger, either completely or at least to some extent, although the necessary heat transfer is no longer performed directly at the cold end itself and / or at the warm end itself of the heat exchanger block. The inventor found that due to the larger temperature difference, the heat transfer is even better if the predefined area of heat transfer is located at a distance to the warm / cold end. Further, the inventor found that a certain temperature difference, particularly of about 30K is still acceptable for avoiding damage due to thermal stresses. Particularly, the invention allows a warmkeeping of the warm end section of the heat exchanger block and / or a coldkeeping of the cold end section of the heat exchanger block during shutdown by means of the least one heat transfer unit. Thus, the heat exchanger can quickly be restarted after it has been shut down. High thermal stresses resulting from different rates of thermal expansion due to existing temperature differences in the heat exchanger block can be avoided or at least reduced. The service life of the heat exchanger can thus be increased. Furthermore, it can especially be achieved that the service life is not affected by an intermittent operation of the heat exchanger.

[0048] Therefore, the present invention allows to restart the heat exchanger after a shutdown period, while avoiding or at least reducing thermal stresses due to temperature equalisation during shutdown.P40391 -EPP40391 PIF

[0049] 09.12.2025 - Dietmar Imhof

[0050] 8

[0051] Conventionally, external heating or cooling mechanism could be provided at a respective end section of a heat exchanger block in order to keep the respective end section warm or cold during shutdown, as for example described in the US 5233839 A and WO 2021 / 037391 A1 as already discussed above. However, as a number of headers is usually provided in the end section, particularly as the end sections are typically fully occupied with headers, there is usually not much space or no space at all for effective external heating or cooling mechanisms of that kind. Furthermore, providing an external heating mechanism at a respective warm end section might yield further difficulties. For example, due to safety limits, the temperature of an external heating mechanism of that kind might be restricted. The heat transfer is usually directly proportional to the temperature difference between the external heating mechanism and the heat exchanger surface. Since the heat exchanger block temperature is usually the highest at its warm end section, the temperature difference towards the heat exchanger block surface is usually the lowest at the warm end section. As a consequence, the heat transfer from the external heating mechanism to the heat exchanger block is the worst at the warm end section, such that even larger heating mechanism would be needed.

[0052] In contrast to that, according to the present invention, an external heating or cooling mechanism particularly does not need to be provided at the respective end section of the heat exchanger block, but the at least one heat transfer unit is provided for a local introduction or extraction of heat in the central section. Each heat transfer unit can for example comprise elements, which are arranged or attached at the respective predefined area of the heat exchanger block itself, e.g. at the side surface of the exchanger block in the respective predefined area. As particularly a number of headers is provided in the end sections, it is much easier to find a position for fitting respective elements of the heat transfer units without interfering with any headers in the central section than in the end sections. Furthermore, as the temperature of the heat exchanger block is lower in the central section than in its warm end section, a temperature difference between the central section and the heat transfer unit is especially higher than a temperature difference between the warm end section and the heat transfer unit. Thus, a heating of the heat exchanger block by means of the heat transfer unit is for example more effective in the central section than in the warm end section.P40391 -EPP40391 PIF

[0053] 09.12.2025 - Dietmar Imhof

[0054] 9

[0055] Particularly, the temperature of the first end section and / or of the second end section during shutdown does not need to be kept precisely at the temperature value of the respective operating temperature of the respective end section. A certain temperature difference between the temperature of the respective end section during shutdown and the respective operating temperature can be acceptable, while still keeping the mechanical strains within design limits. This respective temperature difference can especially be maintained by means of the heat transfer units.

[0056] With the present invention, it is still possible that one or several headers are provided in the central section. However, such a header in the central section has especially no contact with the first end position or the second end position of the heat exchanger block. If headers are provided in the central section, then a distance in the longitudinal direction from a respective header in the central section to a neighbouring header (either arranged also in the central section or in the first or second end section) is particularly larger than a height of each predefined area in the longitudinal direction. The predefined areas and corresponding elements of the heat transfer units can easily be fit at respective positions in the central section.

[0057] According to an embodiment, the respective first distance in the longitudinal direction of the predefined first area to the first end position of the heat exchanger block and / or the respective second distance in the longitudinal direction of the predefined second area to the second end position of the heat exchanger block each corresponds to at least 5.5% or at least 6% or at least 6.5% or at least 7% or at least 7.5% or at least 8% or at least 8.5% or at least 9% or at least 9.5% or at least 10% or even at least 15% of the height of the heat exchanger block. In particular, each predefined area can be provided in the central section of the heat exchanger block at an individual distance towards the respective end position of the heat exchanger block.

[0058] According to an embodiment, the respective first distance in the longitudinal direction of the predefined first area to the first end position of the heat exchanger block and / or the respective second distance in the longitudinal direction of the predefined second area to the second end position of the heat exchanger block each corresponds to a maximum of 50% of the height of the heat exchanger block or to a maximum of 45% or 40%, preferably to a maximum of 35% or 30% or 25% or 20% of the height of the heat exchanger block. Particularly, each heat transfer unit for introducing heat into heatP40391 -EPP40391 PIF

[0059] 09.12.2025 - Dietmar Imhof

[0060] 10

[0061] exchanger block and for heating the warm end section of the heat exchanger block can be provided in the central section of the heat exchanger block at an individual distance towards the first end position in a respective first half of the heat exchanger block from the first end position towards a middle or centre of the heat exchanger block.

[0062] Correspondingly, each heat transfer unit for extracting heat and for cooling the cold end section can be provided in the central section of the heat exchanger block at an individual distance towards the second end position in a corresponding second half of the heat exchanger block from the second end position towards the middle or centre of the heat exchanger block.

[0063] According to an embodiment, a dimension of each predefined first area in the longitudinal direction and / or a dimension of each predefined second area in the longitudinal direction corresponds to at most 25% or at most 20% or at most 15% or at most 10% or at most 5% of the height of the heat exchanger block. Therefore, each predefined area is particularly smaller than the central section of the heat exchanger block, such that a local introduction of heat into the central section or a local extraction of heat form the central section is possible by means of each heat transfer unit.

[0064] According to an embodiment, the at least one heat transfer unit comprises a heating unit configured to introduce heat into the heat exchanger block over the predefined first area of the heat exchanger block. This heating unit is particularly provided for warmkeeping of the warm end section of the heat exchanger block during shutdown of the heat exchanger. Particularly, the distance from the predefined first area towards the first end position of the heat exchanger block can individually be determined in order to effectively heat the warm end section during the shutdown and further e.g. in order to easily arrange elements of the heating unit at the heat exchanger block without interfering with any header.

[0065] Alternatively or additionally, according to an embodiment, the at least one heat transfer unit comprises a cooling unit configured to extract heat out of the heat exchanger block over the predefined second area of the heat exchanger block. This cooling unit is particularly provided for coldkeeping of the cold end section of the heat exchanger block during the shutdown of the heat exchanger. Correspondingly to the heating unit, the distance from the predefined second area towards the second end position of the heat exchanger block can be individually determined in order to effectively cool the coldP40391 -EPP40391 PIF

[0066] 09.12.2025 - Dietmar Imhof

[0067] 11

[0068] end section during the shutdown and further e.g. in order to easily arrange respective elements of the cooling unit at the heat exchanger block without interfering with any header.

[0069] For example, depending on the operating temperatures, depending on the material properties of the end sections and / or depending on the properties of the process fluids passing through the heat exchanger block during operation, only the heating unit for warming the warm end during shutdown or only the cooling unit for cooling the cool end during shutdown or both the heating and cooling unit may be provided.

[0070] According to an embodiment, the heating unit comprises at least one heating plate, particularly arranged in and more particularly covering an area equal to the predefined first area of the heat exchanger block. For example, these heating plates can be provided as electric heating elements or electric heating plates such that the heating plates can create heat by applying electric energy to the heating plates. The heating plates can for example also be provided as heat transfer elements with high thermal conductivity and with high heat conducting properties, such that heat from an external heat source can be conducted to the warm end section of the heat exchanger block by means of the heating plates. For example, the heating plates can be connected or thermally coupled with a housing, in which the heat exchanger is arranged, such that heat can be conducted from the housing to the warm end section of the heat exchanger block. For example, during fabrication or brazing of heat exchanger, a smooth surface could be manufactured at the intended position of the heating unit to improve heat transfer.

[0071] According to an embodiment, the cooling unit comprises a cooling fluid inlet or a cooling fluid supply for introducing a cooling fluid or cooling medium into the heat exchanger block, particularly into the predefined second area, and a cooling fluid outlet or a cooling fluid removal for removing cooling fluid or cooling medium from the heat exchanger block, particularly from the predefined second area, so to cool the heat exchanger block over the longitudinal length of the predefined second area. This cooling fluid can also be passed through the second end section in order to cool this cold end. For example, liquid nitrogen or cold gaseous nitrogen can be used as the cooling fluid. For example, the cooling unit can further comprise a circulation element, which connects the cooling fluid inlet and the cooling fluid outlet, such that a closedP40391 -EPP40391 PIF

[0072] 09.12.2025 - Dietmar Imhof

[0073] 12

[0074] circuit for circulating the cooling fluid can be provided. For example, the inlet and / or the outlet of the cooling unit can be provided as a respective header, particularly provided in the predefined second area. As the second end section particularly already comprises a number of headers, it is much easier to find a position for fitting the respective headers of the cooling unit without interfering with other headers in the central section of the heat exchanger block than in the second end section itself.

[0075] Furthermore, if the internal passages of the heat exchanger block, where the cooling fluid is fed into, extend downward from the inlet of the cooling unit to the lower end of the heat exchanger block, the transfer of the cooling is not only done by heat conduction in the metal but by the convection of the cooling fluid.

[0076] According to an embodiment, the cooling unit comprises a number of evaporation passages provided at the predefined second area of the exchanger block and a liquid supply, which is in fluid communication with the evaporation passages. The evaporation passages and the fluid supply are configured such that a liquid from the liquid supply is guided through the evaporation passages and evaporated in the evaporation passages. Expediently, the evaporation passages are in thermal contact with the predefined second area of the heat exchanger block such that the heat exchanger block can be locally cooled by evaporation of the liquid in the evaporation passages during the shutdown of the heat exchanger. For example, the evaporation passages can be provided at one side surface or at several side surfaces of the heat exchanger block. For example, a main axis of each evaporation passage can be perpendicular or at least essentially perpendicular to the longitudinal direction. For example, the liquid supply can be provided as a container. For example, gas formed during the evaporation of the liquid can be returned to the fluid supply and re-liquified in the fluid supply, e.g. such that a circulation can be established.

[0077] According to an embodiment, each heat transfer unit of the at least one heat transfer unit is configured to introduce heat into the heat exchanger block over the predefined first area of the heat exchanger block or configured to extract heat out of the heat exchanger block over the predefined second area of the heat exchanger block during a shutdown of the heat exchanger such that a temperature of the first end section of the heat exchanger block and / or of the second end section of the heat exchanger block during the shutdown of the heat exchanger is maintained at a predetermined value or within a predetermined range of values. The heat transfer units can expediently keepP40391 -EPP40391 PIF

[0078] 09.12.2025 - Dietmar Imhof

[0079] 13

[0080] the temperature of the respective warm and / or cold end section constant at the predetermined value or at least within the predetermined value range during the shutdown of the heat exchanger. The respective distance of each predefined area unit towards the respective end position of the heat exchanger block can particularly be determined relative to the respective end section, whose temperature shall be influenced by the respective heat transfer unit during the shutdown. Expediently, the respective distance of each predefined area towards the respective end position of the heat exchanger block can be determined such that the temperature of the respective end section can effectively be influenced by means of the respective heat transfer unit and such that elements of the respective heat transfer unit can easily be arranged without interfering with any header of the heat exchanger.

[0081] The temperature value or the range of values are particularly determined such that, when the heat exchanger is restarted, high thermal stresses, which could lead to damage to the heat exchanger, do not occur or are at least reduced. Particularly, the temperature of the warm end section and / or of the cold end section during shutdown does not need to be kept precisely at the temperature value of the respective operating temperature of the respective end section. A certain temperature difference between the temperature of the respective end section during shutdown and the respective operating temperature can expediently be acceptable, while still keeping the mechanical strains within design limits. This respective temperature difference can especially be maintained by means of the heat transfer units. Thus, the predetermined temperature value to be reached by means of the heat transfer unit for the respective end section can for example lie within an interval around the temperature value of the operating temperature of the respective end section, e.g. an interval of ±30 K around the respective operating temperature value. Correspondingly, the predetermined range of values to be reached by means of the heat transfer unit for the respective end section can for example correspond to an interval around the respective operating temperature value, e.g. an interval of ±30 K around the respective operating temperature value.

[0082] According to an embodiment, the heat exchanger further comprises at least one temperature sensor configured to determine a current temperature value of the heat exchanger block or of a region of the heat exchanger block. For example, a first temperature sensor can be provided in the first end section for determining aP40391 -EPP40391 PIF

[0083] 09.12.2025 - Dietmar Imhof

[0084] 14

[0085] respective first current temperate value in the first end section. Alternatively or additionally, a second temperature sensor can be provided in the second end section for determining a respective second current temperate value in the second end section. This first and second temperature sensor can expediently be used for evaluating the influence of the heat transfer unit on the temperature of the respective end section. Alternatively or additionally, a third temperature sensor can be provided in the central section, e.g. in the first and / or second predefined area itself. This third temperature sensor can for example be used for monitoring the temperature in the central section, for example in order to avoid local overheating in the first and / or second predefined area of the heat exchanger block.

[0086] According to an embodiment, the heat exchanger further comprises a control unit configured to control the temperature of the first end section of the heat exchanger block and / or of the second end section of the heat exchanger block by means of the at least one heat transfer unit and by means of the at least one temperature sensor. From the physical properties of the heat exchanger block, e.g. its heat conduction, a delay time for influencing the temperature in the respective end section from the respective predefined area can be determined or estimated. For example, using the first temperature sensor in the first end section, using the respective third temperature sensor provided in the predefined first area, and using the respective delay time, the temperature in the first end section can be controlled. Alternatively or additionally, using the second temperature sensor provided in the second end section, using the respective third temperature sensor provided in the second predefined area , and using the respective delay time, the temperature in the second end section can be controlled. Particularly, a cascade control can be used for controlling the respective temperature of the first end section and / or of the second end section. Cascade control is a multi-loop control structure, especially with two discrete control loops, e.g. with a primary or main control loop and with a secondary or auxiliary control loop, e.g. wherein one of these two control loops can be used for providing a set point for the one of the two control loops.

[0087] The invention further relates to a method for operating a heat exchanger. Advantages and embodiments of the method according to the invention and of the heat exchanger according to the invention shall a rise from the present description in a corresponding manner.P40391 -EPP40391 PIF

[0088] 09.12.2025 - Dietmar Imhof

[0089] 15

[0090] The heat exchanger to be operated comprises a heat exchanger block, wherein a distance from a first end position of the heat exchanger block to a second end position of the heat exchanger block in a longitudinal direction corresponds to a height of the heat exchanger block. At least one first header is covering a first end section of the heat exchanger block and / or is arranged adjacent to the first end position outside of the heat exchanger block. At least one second header is covering a second end section of the heat exchanger block and / or is arranged adjacent to the second end position outside of the heat exchanger block. Particularly, the heat exchanger to be operated is an embodiment of a heat exchanger according to the invention.

[0091] According to the method, the heat exchanger is operated in a regular operating mode. In this regular operating mode, process media are supplied to the heat exchanger block and a heat exchange is carried out between the process media. The at least one heat transfer unit is expediently deactivated during this regular operating mode. The heat exchanger is shut down or deactivated, particularly by stopping the supply of process media. For example, this shutdown of the heat exchanger can take place in the course of a deactivation or a shutdown of a device or system comprising the heat exchanger, e.g. a process engineering plant.

[0092] During the shutdown of the heat exchanger, heat is introduced by means of at least one heat transfer unit into the heat exchanger block over a predefined first area of the heat exchanger block and / or heat is extracted by means of the at least one heat transfer unit out of the heat exchanger block over a predefined second area of the heat exchanger block. A respective first distance in the longitudinal direction of the predefined first area to the first end position of the heat exchanger block is chosen to be at least 5% of the height of the heat exchanger block and such that the predefined first area is located outside the first end section. Alternatively or additionally, a respective second distance in the longitudinal direction of the predefined second area to the second end position of the heat exchanger block is chosen to be at least 5% of the height of the heat exchanger block and such that the predefined second area is located outside the second end section. By introducing heat into the heat exchanger block, the warm end section of the heat exchanger block can especially be heated during the shutdown. Correspondingly, by removing heat from the heat exchangerP40391 -EPP40391 PIF

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[0095] block, the cold end section of the heat exchanger block can especially be cooled during the shutdown.

[0096] For example, the heat transfer units, which are deactivated during the regular operating mode, can be activated and controlled during the shutdown for warmkeeping of the warm end and for coldkeeping of the cold end. Temperature equalisation of the end sections during the shutdown period can therefore be avoided or at least reduced.

[0097] According to an embodiment, the heat exchanger is restarted and operated in the same or in another regular operating mode. Since temperature equalisation can be avoided or reduced by influencing the temperature of the respective end section during shutdown, the heat exchanger can quickly be restarted after the shutdown period, while avoiding or at least reducing thermal stresses due to temperature equalisation during shutdown. The heat transfer units can now be deactivated again, i.e. heat is no longer introduced and / or removed by means of the heat transfer units, at least as soon as the temperature of the heat exchanger block, especially the temperature of the first end section and / or of the second end section, has reached a respective regular operating temperature of the respective regular operating mode.

[0098] According to an embodiment, the step of introducing heat into the heat exchanger block over the predefined first area during the shutdown of the heat exchanger and / or extracting heat out of the heat exchanger block over a predefined second area of the heat exchanger block during the shutdown of the heat exchanger comprises influencing a temperature of the first end section of the heat exchanger block and / or of the second end section of the heat exchanger block by means of the at least one heat transfer unit during the shutdown of the heat exchanger such that the respective temperature is maintained at a predetermined value or within a predetermined range of values. For example, the heat transfer units which are deactivated during the regular operating mode can be activated during the shutdown and controlled in order to influence the temperature of the respective end section accordingly. Temperature equalisation of the end sections during the shutdown period can therefore be avoided or at least reduced.

[0099] According to an embodiment, at least one temperature sensor is provided in the heat exchanger block. Especially, a first temperature sensor is provided in the first end section of the heat exchanger block and / or a second temperature sensor is provided inP40391 -EPP40391 PIF

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[0102] the second end section of the heat exchanger block and / or a third temperature sensor is provided in the central section between the first end section and the second end. At least one current temperature value of the heat exchanger block is determined by means of the at least one temperature sensor. Particularly, a first current temperature value in the first end section of the heat exchanger block is determined by means of the first temperature sensor and / or a second current temperature value in the second end section of the heat exchanger block is determined by means of the second temperature sensor and / or a third current temperature value in the central section of the heat exchanger block is determined by means of the third temperature sensor. The temperature of the first end section and / or of the second end section is controlled by means of the at least one heat transfer unit and by means of the determined at least one current temperature value, especially by means of a cascade control. The temperature of the respective end section can especially be controlled such that a quick restarted after the shutdown period is possible.

[0103] The heat exchanger can be used in a variety of different technical applications. For example, the heat exchanger can be used in a process engineering plant, e.g. an air separation plant, a plant for storing and recovering energy using liquid air, a plant for liquefying natural gas, etc. For example, the heat exchanger can be arranged together with other components of the plant within a common housing. In the case of an air separation plant, the heat exchanger can e.g. 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 coldbox.

[0104] Further advantages and developments of the invention are specified in the description and the associated drawings.

[0105] It goes without saying, that the features named above and still to be explained below can be used not only in the combination indicated respectively, but also in other combinations or in a stand-alone manner, without going beyond the scope of the present invention.P40391 -EPP40391 PIF

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[0108] The invention is illustrated schematically in the drawings on the basis of exemplary embodiments and will be described in detail in the following with reference to the drawings.

[0109] Description of drawings

[0110] Fig. 1 schematically shows a conventional heat exchanger in a simplified isometric view according to the prior art.

[0111] Fig. 2 schematically shows an embodiment of a heat exchanger according to the invention in a simplified side view.

[0112] Fig. 3 schematically shows a diagram of a temperature of a heat exchanger in dependence of its specific dimension according to an embodiment of the invention.

[0113] Detailed description of the drawing

[0114] Fig. 1 schematically shows a conventional heat exchanger 100 according to the prior art. The heat exchanger 100 is provided as a brazed aluminum plate-fin heat exchanger, such as those shown and described in Figure 2 of ISO 15547-2:3005 and on page 5 of the publication "The Standards of the Brazed Aluminum Plate-Fin Heat Exchanger Manufacturers' Association" of ALPEMA, 3rd edition 2010. A drawing essentially corresponding to the figures therein is shown in the present Fig. 1.

[0115] The heat exchanger 100 according to the prior art, which is shown partially opened in present Fig. 1 , is used for the heat exchange of five different process media A to E. For the heat exchange between the process media A to E, the heat exchanger 100 comprises a plurality of parallel arranged parting sheets 4, between which heat exchange passages 1, defined by structured sheets with fins 3, are formed for each one of the process media A to E, which can thereby exchange heat with one another.

[0116] The structured sheets with the fins 3 are typically folded or corrugated, with the folds or corrugations forming flow channels, as also shown in Figure 1 of ISO 155472:3005. Providing the structured sheets with fins 3 offers the advantage of improved heatP40391 -EPP40391 PIF

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[0119] transfer, more targeted fluid control and increased mechanical (tensile) strength compared to heat exchangers without fins. In the heat exchange passages 1, the process media A to E flow separately, in particular separated by the parting sheets 4, but in the case of perforated structured sheets with fins 3, they can pass through the latter.

[0120] The individual passages 1 and the structured sheets with the fins 3 are each surrounded laterally by so-called sidebars 8, which, however, leave feed and discharge openings 9 free. The sidebars 8 keep the parting sheets 4 at a distance and provide a mechanical reinforcement of the pressure chamber. At least two sides are closed off by reinforced cap sheets 5, which are arranged parallel to the parting sheets 4.

[0121] The process media A to E are supplied and discharged via feed and discharge openings 9 by means of headers 7, which are provided with nozzles 6. In the entrance area of the passages 1, structured sheets with so called distributor fins 2 are provided, which can ensure even distribution over the entire width of the passages 1. At the end of the passages 1 , as seen in the direction of flow, there may be further structured sheets with distributor fins 2 that guide the process media A to E from passages 1 into the headers 7, where they are collected and drawn off via the corresponding nozzles 6.

[0122] The structured sheets with the fins 3, the structured sheets with the distributor fins 2, the sidebars 8, the parting sheets 4 and the cap sheets 5 together form a cuboid heat exchanger block 20, whereby a "heat exchanger block" is to be understood here as the mentioned elements without the headers 7 and nozzles 6 in a state connected to one another. As not illustrated in Figure 1, the plate heat exchanger 100 can be formed from a plurality of corresponding cuboid and interconnected heat exchanger blocks 20, in particular for manufacturing reasons.

[0123] Corresponding plate heat exchangers 100 are brazed from aluminum. The individual passages 1 comprising the structured sheets with the fins 3, the structured sheets with the distributor fins 2, the cap sheets 5, and the sidebars 8 are stacked on one another or arranged accordingly and heated in a furnace, in each case with solder applied. The headers 7 and the connecting pieces 6 are welded onto the heat exchanger block 20 produced in this way. The headers 7 are produced using semi-cylindrical extrudedP40391 -EPP40391 PIF

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[0126] profiles, which are cut to the required length and then welded onto the heat exchanger block 20.

[0127] A heat exchanger 100 of that kind 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 in heat-exchange contact with each other via the heat exchanger. The heat exchanger and other system 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. Haring (ed.), Industrial Gases Processing, Wiley-VCH, 2006, in particular Section 2.2.5, "Cryogenic Rectification". For a detailed description of the design and function, it shall be referred to the respective technical literature.

[0128] During operation of the heat exchanger in the respective plant, a first end section or a first end of the heat exchanger block 20, e.g. an upper end section, may have a higher operating temperature than a second end section or a second end of the heat exchanger block 20, e.g. a lower end section. For example, the operating temperature in the first (warm) end may be about 20°C and in the second (cold) end about -195°C. When the heat exchanger is shut down, e.g. when the plant is shut down, the temperatures of these two end sections can increasingly converge over time due to the high thermal conductivity of the materials used in the heat exchanger. For example, severe thermal stresses can occur if the first (warm) end of the heat exchanger is reexposed to a warm fluid after some time of regeneration without further measures.

[0129] In order to counteract such effects, the invention proposes to locally introduce heat into the heat exchanger block and / or to locally extract heat out of the heat exchanger in a central section between the two end sections of the heat exchanger block, as shall hereafter be explained with reference to Fig. 2.

[0130] Fig. 2 schematically shows an embodiment of a heat exchanger 200 according to the invention in a simplified side view. The heat exchanger 200 can be provided as a brazed aluminum plate-fin heat exchanger, as explained above with reference to Fig. 1.P40391 -EPP40391 PIF

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[0133] The heat exchanger 200 comprises a heat exchanger block 205 with individual passages, structured sheets with fins, structured sheets with distributor fins, sidebars, parting sheets, and cap sheets, as explained above with reference to Fig. 1. A distance from a first end position 215 of the heat exchanger block 205 to a second end position 225 of the heat exchanger block 205 in a longitudinal direction corresponds to a height of the heat exchanger block 205. This longitudinal direction can be parallel or at least essentially parallel to the flow direction of the process media guided though the heat exchanger block 205 during regular operation.

[0134] The heat exchanger block 205 comprises a first end section 210, a second end section 220, and a central section 230, wherein the central section 230 connects the first end section 210 and the second end section 220 with each other.

[0135] A number of first headers 211 , 212 is covering the first end section 210 of the heat exchanger block 205 and is arranged adjacent to the first end position 215 outside of the heat exchanger block. For example, header 211 can be arranged on top of the first end position 215, e.g. on a top surface of the heat exchanger block 205. Header 212 can for example be arranged on a side surface of the heat exchanger block 205 extending from this top surface, i.e. from the first end position 215 downwards. The first end section 210 can for example comprise this top surface of the heat exchanger block 205 as well as the part of the side surface of the heat exchanger block 205, at which the header 212 is arranged. An uppermost or outermost position 215 of the first end section 210 corresponds to the first end position 215 of the heat exchanger block 205, , i.e. to a position of the first end section 210 furthest away from a centre or middle of the heat exchanger block 205. A lowermost or innermost position 216 of the header 212 can correspond to a lowermost or innermost position of the first end section 210, i.e. to a position of the first end section 210 closest to the centre or middle of the heat exchanger block 205.

[0136] Correspondingly, a number of second headers 221, 222 is covering the second end section 220 of the heat exchanger block 205 and is arranged adjacent to the second end position 225 outside of the heat exchanger block 205. For example, header 221 can be arranged on top of the second end position 225, e.g. on a bottom surface of the heat exchanger block 205. Header 222 can be arranged on the side surface of the heat exchanger block 205 extending from the bottom surface, i.e. from the second endP40391 -EPP40391 PIF

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[0139] position 225 upwards. The second end section 220 can comprise the bottom surface as well as the part of the side surface, at which the header 222 is arranged. A lowermost or outermost position 225 of the second end section 220 corresponds to the second end position 225 of the heat exchanger block 205, i.e. to a position furthest away from the centre of the heat exchanger block 205. An uppermost or innermost position 226 of the header 222 can correspond to an uppermost or innermost position of the second end section 210 closest to the centre of the heat exchanger block 205.

[0140] The first end section 210 extends from its outermost position 215 to its innermost position 216. A distance between this outermost position 215 and this innermost position 216 of the first end section 210 corresponds for example to at most 5% of the height of the heat exchanger block 205. Correspondingly, the second end section 220 extends from its outermost position 225 to its innermost position 226. A distance between this outermost and innermost position 225, 226 of the second end section 220 corresponds for example to at most 5% of the height of the heat exchanger block 205. The central section 230 extends from the innermost position 216 of the first end section 210 to the innermost position 226 of the section end section 220. A distance from the innermost position 216 of the first end section 210 to the innermost position 226 of the second end section 220 corresponds to a height of the central section 230 and corresponds for example to at least 90% of the height of the heat exchanger block 205.

[0141] The first end section 210 can correspond to a warm end of the heat exchanger block 205 and the second end section 220 can correspond to a cold end of the heat exchanger block 205. The operating temperature in the first (warm) end section 210 can for example correspond to about 20°C. The operating temperature in the second (cold) end section 220 can for example correspond to about -195°C.

[0142] At least one heat transfer unit 250, 260 is configured to introduce heat into the heat exchanger block 205 over a predefined first area 255 of the heat exchanger block 205 or to extract heat out of the heat exchanger block 205 over a predefined second area 265 of the heat exchanger block 205, expediently during the shutdown of the heat exchanger 200. In particular, the at least one heat transfer unit 250, 260 can be configured to influence a temperature of the first end section 210 and / or of the second end section 220 during the shutdown of the heat exchanger 200 such that theP40391 -EPP40391 PIF

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[0145] respective temperature reaches a predetermined value or lies within a predetermined range of values.

[0146] A respective first distance in the longitudinal direction of the predefined first area 255 to the first end position 215 of the heat exchanger block 205 corresponds to at least 5% of the height of the heat exchanger block 205. Further, the predefined first area 255 is located outside the first end section 210, i.e. in the central section 230. The first area 255 extends in the longitudinal direction between a corresponding first position 251 and a corresponding second position 252. This first position 251 can correspond to an edge of the first area 255, which is closer to the first end position 215 of the heat exchanger block. The first distance corresponds to a minimum distance in the longitudinal direction between a geometric centre of the first area 255, i.e. the middle position between the first position 251 and the second position 252, and the first end position 215. The first distance lies for example within a range between 5% and 20%, preferably between 10% and 15%, of the height of the heat exchanger block 205. The first predefined area 255 is locally limited and does not extend over the entire height of the heat exchanger block 205. Particularly, a height of the first predefined area 255 corresponds to at most 25% of the height of the heat exchanger block 205, particularly at most 15% or 5% or the height of the heat exchanger block 205.

[0147] A respective second distance in the longitudinal direction of the predefined second area 265 to the second end position 225 of the heat exchanger block 205 corresponds to at least 5% of the height of the heat exchanger block 205. Further, the predefined second area 265 is located outside the second end section 220, i.e. in the central section. The second area 265 extends in the longitudinal direction between a corresponding first position 261 and a corresponding second position 262. This first position 261 can correspond to an edge of the second area 265, which is closer to the second end position 225 of the heat exchanger block 205. The second distance corresponds to a minimum distance in the longitudinal direction between a geometric centre of the second area 265, i.e. a middle position between the first position 261 and the second position 262, and the second end position 225. The second distance lies for example within a range between 5% and 20%, preferably between 10% and 15%, of the height of the heat exchanger block 205. Again, the second predefined area 265 is locally limited and does not extend over the entire height of the heat exchanger block 205. A height of the second predefined area 265 can for example corresponds to atP40391 -EPP40391 PIF

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[0150] most 25% of the height of the heat exchanger block 205, particularly at most 15% or 5% or the height of the heat exchanger block 205.

[0151] The at least one heat transfer unit can for example comprise a heating unit 250 configured to introduce heat into the heat exchanger block 205 over the predefined first area 255, for example in order to influence a first temperature of the first end section 210 during the shutdown such that this first temperature reaches a first predetermined value or lies within a first predetermined range of values. This first predetermined value can correspond to the operating temperature of the warm end of 20°C. The first predetermined range of values can correspond to an interval of ±30 K around the respective operating temperature value.

[0152] The heating unit 250 can thus be provided for warmkeeping of the warm end 210 during shutdown. For this purpose, the heating unit 250 can comprise a heating plate arranged on one side surface on several side surfaces of the heat exchanger block 205 in the predefined first area 255, e.g. provided as an electric heating plate creating heat from electric energy or e.g. provided as a heat transfer element for conducting heat from an external heat source to the warm end section 210.

[0153] The at least one heat transfer unit can for example comprise a cooling unit 260 configured to extract heat from the heat exchanger block 205 over the predefined second area 265, e.g. in order to influence a second temperature of the second end section 220 during the shutdown such that the second temperature reaches a second predetermined value or lies within a second predetermined range of values. This second predetermined value can correspond to the operating temperature of the cold end of -195°C. The second predetermined range of values can correspond to an interval of ±30 K around this operating temperature value.

[0154] The cooling unit 260 can thus be provided for coldkeeping of the cold end 220 during shutdown. For this purpose, the cooling unit 260 can comprise a cooling fluid inlet for introducing a cooling fluid into the heat exchanger 200 and a cooling fluid outlet for removing the cooling fluid from the heat exchanger 200. For example, liquid nitrogen or cold gaseous nitrogen as the cooling fluid can be passed through the second end section 220.P40391 -EPP40391 PIF

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[0157] Alternatively or additionally, the cooling unit 260 can also comprise a number of evaporation passages and a liquid supply, e.g. a container, in fluid communication with the evaporation passages. These evaporation passages can be provided at one side surface or at several side surfaces in the predefined second area 265 of the heat exchanger block 205 and are in thermal contact with the heat exchanger block 205. For example, a main axis of each evaporation passage can be perpendicular or at least essentially perpendicular to the longitudinal direction. During the shutdown of the heat exchanger, a liquid from the liquid supply is guided through the evaporation passages and evaporated in the evaporation passages such that the heat exchanger block 205 can be cooled by this evaporation process. Gas formed during the evaporation can be returned to the fluid supply and re-liquified in the fluid supply, e.g. such that a circulation can be established.

[0158] As a multitude of headers 211 , 212, 221 , 222 is provided in each of the end sections 210, 220, it can be difficult to provide elements of the heat transfer units 250, 260 in the end sections 210, 220 itself. However, as only a few headers or no headers at all are provided in the central section 230, it is much easier to find a position for fitting elements of the heat transfer units 250, 260 without interfering with any headers in the central section 230 than in the end sections 210, 220.

[0159] In the example of Fig. 2, no headers are provided in the central section 230. However, it is also possible that one or several headers are provided in the central section 230. If headers are provided in the central section 230, then a distance from a respective header in the central section 230 to a neighbouring header is particularly larger than a dimension, especially a height, of each predefined area 255, 265, such that elements of the heat transfer units 250, 260 can easily be fit in predefined areas 255, 265 in the central section 230.

[0160] The first and second predefined areas 255, 256 are exemplarily arranged symmetrically relative to a horizontal middle axis of the heat exchanger block 205 in the example Fig. 2. However, it shall be understood that the first and second predefined areas 255, 265 can be arranged at individual predetermined positions with individual distances towards the first and second end position 215, 225 of the heat exchanger block 205. At the respective predetermined areas 255, 265, the respective heat transferP40391 -EPP40391 PIF

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[0163] units 250, 260 can for example be arranged inside a perlite filling of the cold box, insulating and reducing heat losses to the exterior.

[0164] The heat exchanger 200 furthermore comprises at least one temperature sensor 271, 272, 273, 274 configured to determine a current temperature value of the heat exchanger 200 or of a region of the heat exchanger 200. For example; a first temperature sensor 271 is provided in the first end section 210 for determining a respective current temperate value in the first end section 210. A second temperature sensor 272 is provided in the second end section 220 for determining a current temperate value in the second end section 220. A third temperature sensor 273 is provided in the central section 230 directly at or in close vicinity to the first predefined area 255. This third temperature sensor 273 can for example be used for monitoring the temperature of the first predefined area 255 in order to avoid local overheating. A fourth temperature sensor 274 is provided in the central section 230 directly at or in close vicinity to the second predefined area 265.

[0165] A control unit 280 is provided and configured to control the temperature of the first end section 210 and the second end section 220 by means of the heat transfer units 250, 260 and by means of the temperature sensors 271, 272, 273, 274, e.g. by means of a cascade control.

[0166] From the physical properties of heat exchanger block 205, e.g. from its heat conduction, a delay time for the heat produced by the heating unit 250 in the first predefined area 255 reaching the first temperature sensor 271 in the warm end 210 can be estimated. Using the first temperate sensor 271 in the warm end section 210, using the third temperature sensor 273 in the first predefined are 255, and using and the respective delay time, a cascade control structure can be implemented that can control the heating unit 250 and the temperature in the warm end section 210 in an optimal way, e.g. without excessive temperature high / low swings.

[0167] Correspondingly, a delay time for the cooling the cold end section 220 by means of the cooling unit 260 can be estimated. Using the second temperate sensor 272 in the cold end section 220, using the fourth temperature sensor 274 in the second predefined area 265, and using and the respective delay time, a cascade control structure can beP40391 -EPP40391 PIF

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[0170] implemented for controlling the cooling unit 260 and for controlling the temperature in the cold end 220.

[0171] As outlined above, providing the heat transfer units 250, 260 for introducing heat and removing heat in the central section 230 allows to easily fit elements of the heat transfer units 250, 260 without interfering with any headers. Further, introducing heat and removing heat in the central section 230 can allow a more effective warm- and coldkeeping than introducing heat and removing heat in the end sections 210, 220 themselves.

[0172] For example, as the temperature of the heat exchanger 200 is lower in the first predefined area 255 than in the warm end section 210, a temperature difference between the heating unit 250 and the heat exchanger 200 is rather high, especially higher than a temperature difference between the heating unit 250 and warm end section 210. For example, the temperature of the heating unit 250 during its operation can correspond to 80°C. The temperature of the heat exchanger block 205 at the warm end 210, e.g. at the position of the first temperature sensor 271 , at the beginning of a shutdown can correspond to 20°C. Therefore, the temperature difference between the heating unit 250 and warm end section 210 would correspond to 60°C. The temperature of the heat exchanger block 205 at the first predefined area 255 at the beginning of a shutdown can for example correspond to -20°C. Therefore, the temperature difference between the heating unit 250 at the predefined area 255 and the heat exchanger block 205 corresponds to 100°C. Thus, heating of the warm end 210 is more effective when the heating unit 250 is arranged in the central section 230 in the predefined area 255 and not in the warm end section 210 itself.

[0173] Further, the cooling by means of the cooling unit 260 is particularly effective, if the internal passages of the heat exchanger 200, where the cooling fluid is fed into, extend downward from the inlet of the cooling unit 260 to the lower end of the heat exchanger 200. That way the transfer of the cooling is not only done by heat conduction in the metal but by the convection of the cooling fluid.

[0174] Figure 3 shows a schematic diagram 300 of a temperature T of the heat exchanger block 205 during its operation in dependence of its specific dimension, in particular in dependence of its height H.P40391 -EPP40391 PIF

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[0177] A value H215 corresponds to the first end position 215 of heat exchanger block 205, e.g. to the uppermost position or to the top of the heat exchanger block 205. A value H225 corresponds to the second end position 225 of the heat exchanger block 205, e.g. to lowermost position or to the bottom of the heat exchanger block 205. The distance between the second end position H225 and the first end position H215 corresponds to the entire height of the heat exchanger block 205.

[0178] A temperature value Ttopcorresponds to the operating temperature at the first end position, i.e. at the top of the heat exchanger block 205 of e.g. +20°C. A temperature value Tbottom corresponds to the operating temperature at the second end position, i.e. at the bottom of the heat exchanger block 205 of e.g. -195°C.

[0179] The value H255 for example corresponds to the corresponding location (as defined above in respect of its distance to the first end position 215) of the first predefined area 255. The distance from this position H255 to the uppermost position H215 of the heat exchanger block 205 corresponds to the first distance in the longitudinal direction of the predefined first area 255 to the first end position 215 of the heat exchanger block 205. This first distance can for example correspond to 5% of the entire height of the heat exchanger block 205.

[0180] The value H265 for example corresponds to the corresponding location (as defined above in respect of its distance to the second end position 225) of the second predefined area 265. The distance from this position H265 to the lowermost position H225 of the heat exchanger block 205 corresponds to the second distance in the longitudinal direction of the predefined second area 255 to the second end position 225 of the heat exchanger block 205. This second distance can for example correspond to 5% of the entire height of the heat exchanger block 205.

[0181] A temperature value Theating corresponds to the operating temperature of the heat exchanger block 205 at the corresponding first position H255 of the first predefined area 255, i.e. at the position 5% below the top of the heat exchanger block 205. This operating temperature Theating can for example correspond to -10°C.P40391 -EPP40391 PIF

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[0184] A temperature value TCOoiingcorresponds to the operating temperature at the corresponding position H265 of the second predefined area 265, i.e. at the position 5% above the bottom of the heat exchanger block 205. This operating temperature TCOoiingcan for example correspond to -165°C.

[0185] Curve 310 represents the temperature of the heat exchanger block 205 during shutdown of the heat exchanger 200. During the shutdown, by means of the heating unit 250, the temperature of the warm end of the heat exchanger block 205 can be maintained at the temperature value Theatingof -10°C. Correspondingly, by means of the cooling unit 260, the temperature of the cold end of the heat exchanger block 205 during the shutdown can be maintained at the temperature value Tcooingof -165°C. The respective temperature differences to Ttop(e.g. +20°C) and Tbottom (e.g. -195°C), respectively, in this embodiment are 30K and thus within an acceptable range as discussed above.

Claims

1. P40391 -EPP40391 PIF09.12.2025 - Dietmar Imhof30Patent Claims1. A heat exchanger (200), comprising a heat exchanger block (205),wherein a distance from a first end position (215) of the heat exchanger block (205) to a second end position (225) of the heat exchanger block (205) in a longitudinal direction corresponds to a height of the heat exchanger block (205); wherein at least one first header (211 , 212) is covering a first end section (210) of the heat exchanger block (205) and / or is arranged adjacent to the first end position (215) outside of the heat exchanger block (205) and wherein at least one second header (221 , 222) is covering a second end section (220) of the heat exchanger block (205) and / or is arranged adjacent to the second end position (225) outside of the heat exchanger block (205);wherein the heat exchanger (200) further comprises at least one heat transfer unit (250, 260) configured to introduce heat into the heat exchanger block (205) over a predefined first area (255) of the heat exchanger block (205) or configured to extract heat out of the heat exchanger block (205) over a predefined second area (265) of the heat exchanger block (205);wherein a respective first distance in the longitudinal direction of the predefined first area (255) to the first end position (215) of the heat exchanger block (205) corresponds to at least 5% of the height of the heat exchanger block (205) and the predefined first area (255) is located outside the first end section (210) and / or wherein a respective second distance in the longitudinal direction of the predefined second area (265) to the second end position (225) of the heat exchanger block (205) corresponds to at least 5% of the height of the heat exchanger block (205) and the predefined second area (265) is located outside the second end section (220),wherein each header comprises one or several nozzles for supplying and discharging a respective process medium.

2. The heat exchanger (200) according to claim 1 , wherein the respective first distance in the longitudinal direction of the predefined first area (255) to the first end position (215) of the heat exchanger block (205) and / or the respective second distance in the longitudinal direction of the predefined second area (265) to the second end position (225) of the heat exchanger block (205) each corresponds to at least 5.5% or at least 6% or at least 6.5% or at least 7% or at least 7.5% or atP40391 -EPP40391 PIF09.12.2025 - Dietmar Imhof31least 8% or at least 8.5% or at least 9% or at least 9.5% or at least 10% or at least 15% of the height of the heat exchanger block (205).

303. The heat exchanger (200) according to claim 1 or 2, wherein the respective first distance in the longitudinal direction of the predefined first area (255) to the first end position (215) of the heat exchanger block (205) and / or the respective second distance in the longitudinal direction of the predefined second area (265) to the second end position (225) of the heat exchanger block (205) each corresponds to a maximum of 50% or 45% or 40% or 35% or 30% or 25% or 20% of the height of the heat exchanger block (205).

4. The heat exchanger (200) according to any one of the preceding claims, wherein a dimension of the predefined first area (255) in the longitudinal direction and / or a dimension of the predefined second area (265) in the longitudinal direction corresponds to at most 25% or at most 20% or at most 15% or at most 10% or at most 5% of the height of the heat exchanger block (205).

5. The heat exchanger according to any one of the preceding claims, wherein the at least one heat transfer unit (250, 260) comprises:a heating unit (250) configured to introduce heat into the heat exchanger block (205) over the predefined first area (255) of the heat exchanger block (205); and / or a cooling unit (260) configured to extract heat out of the heat exchanger block (205) over the predefined second area (265) of the heat exchanger block (205).

6. The heat exchanger according to claim 5, wherein the heating unit (250) comprises at least one heating plate.

7. The heat exchanger according to claim 5 or 6, wherein the cooling unit (260) comprises a cooling fluid inlet for introducing a cooling fluid into the heat exchanger block (205) and a cooling fluid outlet for removing cooling fluid from the heat exchanger block (205).

8. The heat exchanger according to any one of the claims 5 to 7, wherein the cooling unit (260) comprises a number of evaporation passages provided at the predefined second area (265) of the exchanger block (205) and a liquid supply, which is inP40391 -EPP40391 PIF09.12.2025 - Dietmar Imhof32fluid communication with the evaporation passages, configured such that a liquid from the liquid supply is guided through the evaporation passages and evaporated in the evaporation passages.

9. The heat exchanger (200) according to any one of the preceding claims, wherein each heat transfer unit (250, 260) of the at least one heat transfer unit is configured to introduce heat into the heat exchanger block (205) over the predefined first area (255) of the heat exchanger block (205) or configured to extract heat out of the heat exchanger block (205) over the predefined second area (265) of the heat exchanger block (205) during a shutdown of the heat exchanger (200) such that a temperature of the first end section (210) of the heat exchanger block (205) and / or of the second end section (220) of the heat exchanger block (205) during the shutdown of the heat exchanger (200) is maintained at a predetermined value or within a predetermined range of values.

10. The heat exchanger according to any one of the preceding claims, further comprising at least one temperature sensor (271, 272, 273, 274) configured to determine a current temperature value of the heat exchanger block (205), especially a first temperature sensor (271) provided in the first end section (210) and / or a second temperature sensor (272) provided in the second end section (220) and / or a third temperature sensor (273, 274) provided in a central section (230) between and outside of the first end section (210) and the second end section (220).

11. The heat exchanger according to claim 9 and 10, further comprising a control unit (280) configured to control the temperature of the first end section (210) and / or of the second end section (220) by means of the at least one heat transfer unit (250, 260) and by means of the at least one temperature sensor (271, 272, 273, 274), especially by means of a cascade control.

12. A method for operating a heat exchanger (200) comprising a heat exchanger block (205),wherein a distance from a first end position (215) of the heat exchanger block (205) to a second end position (225) of the heat exchanger block (205) in a longitudinal direction corresponds to a height of the heat exchanger block (205);P40391 -EPP40391 PIF09.12.2025 - Dietmar Imhof33wherein at least one first header (211 , 212) is covering a first end section (210) of the heat exchanger block (205) and / or is arranged adjacent to the first end position (215) outside of the heat exchanger block (205) and wherein at least one second header (221 , 222) is covering a second end section (220) of the heat exchanger block (205) and / or is arranged adjacent to the second end position (225) outside of the heat exchanger block (205);wherein the method comprises the steps of:operating the heat exchanger (200) in a regular operating mode;shutting down the heat exchanger (200);introducing heat by means of at least one heat transfer unit (250, 260) into the heat exchanger block (205) over a predefined first area (255) of the heat exchanger block (205) during the shutdown of the heat exchanger (200) and / or extracting heat by means of the at least one heat transfer unit (250, 260) out of the heat exchanger block (205) over a predefined second area (265) of the heat exchanger block (205) during the shutdown of the heat exchanger (205); wherein a respective first distance in the longitudinal direction of the predefined first area (255) to the first end position (215) of the heat exchanger block (205) is chosen to be at least 5% of the height of the heat exchanger block (205) and such that the predefined first area (255) is located outside the first end section (210) and / or wherein a respective second distance in the longitudinal direction of the predefined second area (265) to the second end position (225) of the heat exchanger block (205) is chosen to be at least 5% of the height of the heat exchanger block (205) and such that the predefined second area (265) is located outside the second end section (220).

13. The method according to claim 12, further comprising:restarting the heat exchanger (200) and operating the heat exchanger (200) in the same or in another regular operating mode, wherein heat is no longer introduced into the heat exchanger block (205) over the predefined first area (255) of the heat exchanger block (205) and / or heat is no longer extracted out of the heat exchanger block (205) over the predefined second area (265) of the heat exchanger block (205) at least as soon as a temperature of the heat exchanger block (205), especially a temperature of the first end section (210) and / or of the second end section (220), has reached a respective regular operating temperature of the respective regular operating mode.P40391 -EPP40391 PIF09.12.2025 - Dietmar Imhof3414. The method according to claim 12 or 13, wherein the step of introducing heat by means of the at least one heat transfer unit (250, 260) into the heat exchanger block (205) over the predefined first area (255) of the heat exchanger block (205) during the shutdown of the heat exchanger (200) and / or extracting heat by means of the at least one heat transfer unit (250, 260) out of the heat exchanger block (205) over the predefined second area (265) of the heat exchanger block (205) during the shutdown of the heat exchanger (205) comprises:influencing a temperature of a first end section (210) of the heat exchanger block (205) and / or of a second end section (220) of the heat exchanger block (205) by means of the at least one heat transfer unit (250, 260) during the shutdown of the heat exchanger (200) such that the respective temperature is maintained at a predetermined value or within a predetermined range of values.

15. The method according to claim 14, wherein at least one temperature sensor (271, 272, 273, 274) is provided in the heat exchanger block (205), especially a first temperature sensor (271) in the first end section (210) of the heat exchanger block (205) and / or a second temperature sensor (272) in the second end section (220) of the heat exchanger block (205) and / or a third temperature sensor (273, 274) in a central section (230) of the heat exchanger block (205) between and outside of the first end section (210) and the second end section (220), wherein the method further comprises:determining at least one current temperature value of the heat exchanger block (205) by means of the at least one temperature sensor (271, 272, 273, 274), especially a first current temperature value in the first end section (210) of the heat exchanger block (205) by means of the first temperature sensor (271) and / or a second current temperature value in the second end section (220) of the heat exchanger block (205) by means of the second temperature sensor (272) and / or a third current temperature value in the central section (230) of the heat exchanger block (205) by means of the third temperature sensor (273, 274); and controlling the temperature of the first end section (210) and / or of the second end section (220) by means of the at least one heat transfer unit (250, 260) and by means of the at least one current temperature value , especially by means of a cascade control.

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