CN111684230A

CN111684230A - Thermal barrier surface coating for reducing thermal stress on heat exchangers

Info

Publication number: CN111684230A
Application number: CN201980008194.0A
Authority: CN
Inventors: 莱茵霍尔德·霍尔兹尔; 阿克塞尔·莱马赫; 亚历山大·沃塔尔卡
Original assignee: Linde LLC
Current assignee: Messer LLC
Priority date: 2018-01-30
Filing date: 2019-01-17
Publication date: 2020-09-18
Anticipated expiration: 2039-01-17
Also published as: JP2021512267A; ES2930008T3; US20200400392A1; CN111684230B; EP3746728B1; WO2019149446A1; EP3746728A1

Abstract

The invention relates to a plate heat exchanger (10) with a plate heat exchanger block (11) having a plurality of partitions (4, 5) arranged parallel to each other in the form of partition plates forming a plurality of heat exchange channels (1a, 1b) for fluids in indirect heat exchange relationship with each other. The heat exchange channels are closed to the outside by lateral strips (8), and each heat exchange channel (1a, 1b) has an inlet (9) for the inflow of a fluid and an outlet (19) for the outflow of the fluid. According to the invention, one or more partitions (4, 5) and/or one or more heat-conducting elements (2, 3) have a coating (41) made of a heat-insulating material in each case. The invention also relates to a method for producing a polymer laminate and a method for joining prefabricated polymer parts to one another.

Description

Thermal barrier surface coating for reducing thermal stress on heat exchangers

The present invention relates to a plate heat exchanger and a method of producing such a plate heat exchanger.

Plate heat exchangers configured to indirectly transfer heat from a first fluid to another second fluid are known in the art. The fluid in the plate heat exchanger is guided in separate heat exchange channels of the plate heat exchanger block. These heat exchange channels are in each case delimited by two parallel partitions of the plate heat exchanger block, between each of which a heating surface element, also referred to as a fin or a lamella, is arranged.

Such plate heat exchangers are shown and described in the following documents: for example, The Standards of The branched aluminum Plate-Fin Heat exchangers' Association, ALPEMA, third edition, 2010.

Furthermore, such aluminum plate heat exchangers are used in particular in cryogenic processes, for example in air separation units. The partitions or partitions and fins on the one hand form heating surfaces and on the other hand have to absorb forces from internal overpressure. Different spacer and fin types can be used for this purpose, but the design possibilities are limited by the pressure-bearing function. Therefore, it is impossible to arbitrarily narrow a specific heating surface. This is also generally undesirable, since a high heating surface density is generally desired, and therefore a design that is as compact as possible is desired.

Starting up (in particular restarting) a heat exchanger (in particular an aluminum plate heat exchanger) after a short or medium term unit shutdown can lead to very high thermal stresses. This applies in particular to situations where the overall temperature in the plant varies widely, for example in the case of the main heat exchanger of an air separation unit. Thus, such heat exchangers are exposed to a risk of damage even during relatively small numbers of restart due to material fatigue.

In this respect, however, there is a need for a flexibly operable unit, in particular comprising the aforementioned operational interruptions.

The high thermal stress is generated as follows: generally, in the event of a unit shutdown, all process flows are stopped. Starting from a temperature profile with a warm end and a cold end, the material temperature difference slowly equalizes due to heat conduction within the heat exchanger, and the device exhibits a uniform (average) temperature between the highest and lowest temperature of the initial state. The thermal insulation losses are usually small, so that the state changes only slowly.

If the process flows are now started again, they impinge on the heat exchanger with a very high temperature difference. The wall temperature therefore changes rapidly in time, in particular in the region of the inflow opening, and a very steep wall temperature gradient is formed locally in the main flow direction. Temporal and local temperature gradients cause thermal stresses. Especially in the case of large heat exchangers manufactured in a modular manner and having a plurality of plate heat exchanger blocks connected to each other, the thermal stresses may be considerable.

Based on this, it is an object of the present invention to provide a plate heat exchanger which is improved with respect to the aforementioned problems.

This object is achieved by a plate heat exchanger having the features of claim 1.

Thus, a plate heat exchanger is provided with a plate heat exchanger block having a plurality of partitions (for example in the form of separating plates) which are arranged parallel to one another and form a plurality of heat exchange channels for fluids which are to be subjected to indirect heat exchange with one another, wherein the heat exchange channels are delimited (in particular closed to the outside) by lateral strips (for example in the form of sheet metal strips), also referred to as lateral strips (in particular if provided), so as to be flush with the edges of the partitions, and wherein at least one heat conducting element (also referred to as fin) is arranged (in particular) between every two adjacent partitions, and wherein the heat exchange channels (in particular each heat exchange channel) have an inlet for the inflow of a fluid and an outlet for the outflow of a fluid.

According to the invention, it is provided that the one or more spacers and/or the one or more heat-conducting elements and/or the one or more lateral strips each have a coating formed from a heat-insulating material, which is applied to the respective spacer, to the respective heat-conducting element or to the respective lateral strip.

The two outermost partitions of the plate heat exchanger block, which delimit the plate heat exchanger block to the outside, are also referred to as covering walls and, in particular, are formed by covering plates.

The respective heat exchange channel is therefore delimited by two adjacent partitions and has at least one heat-conducting element (fin) arranged between these partitions.

According to one embodiment, the respective heat conducting element forms, together with two adjacent partitions, a plurality of flow channels of the respective heat exchange channel, wherein the coating is applied to the respective heat conducting element and to two adjacent partition plates, such that the respective flow channel has a circumferential inner side coated with a thermal barrier coating. The coating is preferably applied in such a way that the respective flow channel in the first section has an uninterrupted coating (i.e. a continuous coating) on its inner wall.

According to a further embodiment, provision is made for the respective heat-conducting element to have alternating and preferably parallel peaks (or head portions) and valleys (or foot portions), wherein the peaks and valleys are each connected to one another via a web running, in particular, vertically. The alternately arranged peaks and valleys form, together with the web, a corrugated structure of the respective heat-conducting element.

If the peak portion is connected to one of two adjacent partitions, and the valley portion is connected to the other of the two adjacent partitions, a plurality of flow channels are formed in the respective heat exchange channels. The respective flow channel is thus delimited by the partitions, peaks or valleys of the respective heat-conducting element and the web.

Such a plate heat exchanger or an uncoated part of a plate heat exchanger is preferably formed of an aluminium alloy, wherein the parts are preferably connected to each other by brazing. In the production of the plate heat exchanger, the heating surface elements, the partition plate, the cover plate and the side bars, which are partly provided with solder, are preferably stacked one after the other in a cube block and then brazed in a vacuum soldering furnace to form a heat exchanger block. However, other preparation methods can also be envisaged.

The heat-conducting elements, which are optionally coated as described above, can in particular also be so-called distribution fins, which distribute the fluid flow over the entire width of the respective heat exchange channel (i.e. from side bar to side bar). Such distribution fins may also be integrally formed with the downstream heat conducting elements/fins.

According to one embodiment of the invention, it is provided that the respective separator with the coating and/or the respective heat-conducting element with the coating each have a first portion arranged at the respective inlet (which is arranged, for example, adjacent to or adjacent to the inlet), and a second portion connected to the first portion and further away from the inlet than the first portion, wherein in each case only the first portion has the coating, and wherein in each case the second portion has no coating, i.e. in other words the second portion therefore has no thermal barrier coating. In other words, the first portion is thus arranged in such a way that the fluid flows through the first portion before flowing through the second portion.

The flow channel formed by the partition and the heat-conducting element thus has a first portion (closer to the inlet) and a second portion (closer to the outlet), wherein in each case only one inner side or wall of the first portion of the respective flow channel has a thermal barrier coating.

Furthermore, it is provided according to an embodiment of the invention that the plate heat exchanger block has at least a first heat exchange channel for receiving a first fluid and a second heat exchange channel for receiving a second fluid, wherein the partitions and/or the lateral strips assigned to the first heat exchange channel and/or the surface of the heat conducting element assigned to the first heat exchange channel each have (at least in some parts) a coating formed of an insulating material, in particular (in particular) only the partitions and/or the first part of the heat conducting element (and/or the lateral strips) have this coating, and wherein the partitions and/or the lateral strips assigned to the second heat exchange channel and/or the surface of the heat conducting element assigned to the second heat exchange channel do not have a coating formed of an insulating material.

Here, in particular, only the flow channels of the first heat exchange channel have a thermal barrier coating, in particular (in particular) only the inner side or inner surface of the first portion having the flow channels has a thermal barrier coating, while (in particular) the flow channels of the second heat exchange channel do not have a thermal barrier coating.

Furthermore, it is provided according to an embodiment of the invention that the heat insulating material is or has one of the following materials: plastic, polymer or ceramic.

According to a further embodiment of the invention, it is provided that the separator and/or the heat-conducting element and/or the lateral strips (without coating) are formed from or have one of the following materials: aluminum or an aluminum alloy. As the alloy, for example, SB-209(ASME), SB-221(ASME) or EN-AW-3003(EN) can be used.

Furthermore, one embodiment of the present invention provides an insulating material having a thermal conductivity or thermal conductivity of less than 5W/mK, in particular less than 1W/mK.

In contrast, the base material of the respective separator or the respective thermally conductive element or the respective uncoated separator or the respective uncoated thermally conductive element according to an embodiment typically has a thermal conductivity (e.g., at 70K) in a range of about 130W/mK (at 70K) to about 150W/mK (at 300K).

Furthermore, it is provided according to an embodiment of the invention that the respective coating has a thickness (in particular in a normal direction with respect to the surface of the respective separator or the respective heat conducting element or with respect to the plane of extension) of less than or equal to 0.2 mm.

Furthermore, an embodiment of the present invention provides that the respective uncoated separator (in particular, in a normal direction with respect to an extension plane of the respective separator surface) has a thickness in the range of 1mm to 2 mm.

It is further provided according to an embodiment of the invention that the respective uncoated heat-conducting element (in particular, in a normal direction with respect to the extension plane of the surface of the respective substrate) has a thickness in the range of 0.2mm to 0.6 mm.

According to one embodiment of the invention, for the introduction of the fluid, a collector with nozzles is attached in each case above the inlet of the at least one first heat exchange channel and above the inlet of the at least one second heat exchange channel, wherein the nozzles are used for connecting the supply lines.

Such collectors can be designed, for example, as semi-cylinders closed at two opposite end faces. Furthermore, such a collector preferably has a peripheral edge via which the collector is welded to the plate heat exchanger block. The partitions and fins preferably continue perpendicular to the longitudinal axis of the collector when it is welded to the plate heat exchanger block according to the intended purpose of the collector. In this way, the inlet or outlet of the respective heat exchange channel, each delimited by two adjacent partitions, can open into the respective collector. Furthermore, the nozzle associated with the collector is preferably cylindrical and is welded to the collector via an end face of the nozzle, so that the nozzle is in flow connection with the through opening of the collector or with the collector.

According to one embodiment, for each fluid fed into the plate heat exchanger, the plate heat exchanger has at least two collectors with nozzles, wherein the fluid can be introduced into the associated heat exchange channel via one first nozzle and collector and can be discharged again via another second collector or nozzle.

In addition, with respect to the collector/nozzle, one embodiment of the present invention provides that the collector and/or the nozzle of the first heat exchange channel has a coating formed of a heat insulating material on its respective inner side (or inner wall or inner surface). In contrast, the collector and/or the nozzle of the second heat exchange path according to an embodiment of the present invention does not have a coating layer formed of a heat insulating material.

Furthermore, it is provided according to an embodiment of the invention that the respective heat conducting element has a corrugated structure with alternating foot portions and head portions, wherein the respective foot portion is connected to an adjacent head portion via a web such that the corrugated structure is formed. The corrugation may be formed so as to be circular at the transition from the foot portion or the head portion to the respective web. However, the corrugated structure may also have a rectangular or stepped shape. The flow channels for guiding the relevant fluid in the respective heat exchange channels are formed by a corrugated structure together with partitions on both sides.

It is provided according to an embodiment of the invention that the respective heat conducting element, which is connected (in particular brazed) to the adjacent separator via the contact surface, is not coated with a thermal barrier coating at the contact surface.

According to another embodiment it is provided that the web of the respective heat conducting elements, in particular in the first portions of the respective heat conducting elements, has a thermal barrier coating or is coated with a thermal barrier coating.

Furthermore, one embodiment of the invention provides that the respective heat-conducting element has a thermal barrier coating or is coated with a thermal barrier coating only in the region of the web.

Another embodiment provides that the respective heat-conducting element (in particular in the first section) has a thermal barrier coating or is coated with a thermal barrier coating only in the region of the surface facing the respective flow channel.

Due to the preferred corrugated structure of the heat-conducting elements, the coating of the web has proved to be very effective due to the relatively large total surface area of the web (compared to the surface of the respective separator).

Another aspect of the invention relates to a method for producing a plate heat exchanger according to the invention, wherein a flowable material forming a heat insulating material in a hardened state is introduced into the heat exchange channels of a plate heat exchanger block, the partitions and/or the heat conducting elements and/or the lateral strips of which will receive a coating of the layer, wherein the material is cured in order to form the coating. In this case, in particular, a flowable material is introduced into the flow channel of the heat exchange channel, which is formed by the respective heat-conducting element, the two adjacent partitions and optionally the lateral strips.

An embodiment of the method according to the invention provides that at least some parts, in particular the first part, of the plate heat exchanger block are immersed in the flowable material in order to introduce the flowable material into the corresponding heat exchange channel or flow channel. With this immersion method, the dimensions of the area to be coated can advantageously be controlled precisely.

In this respect, it is provided according to one embodiment of the method that the heat exchange channels or flow channels which are not to be coated are suitably sealed beforehand so that no material can penetrate there.

Another aspect of the invention relates to a method for operating a plate heat exchanger according to the invention, wherein at least one first fluid and one second fluid are each introduced into at least one heat exchange channel of the plate heat exchanger, such that the fluids can indirectly exchange heat.

In the context of the present invention, the material composition of the (at least two) fluids or fluid streams may be physically the same or different.

Furthermore, according to an embodiment of the method according to the invention, as in the case of the plate heat exchanger according to the invention, all heat exchange channels (or their flow channels) may have a coating formed of a heat insulating material (in particular a coating of the partitions and/or the heat conducting elements and/or the lateral strips of the respective heat exchange channels).

According to another embodiment of the method/plate heat exchanger according to the invention, only those heat exchange channels or flow channels assigned to a specific fluid (e.g. the first fluid) may have a coating formed by an insulating material (in particular, a coating of the partitions and/or the heat conducting elements and/or the lateral strips of the respective heat exchange channel), while the other heat exchange channels (in particular, their partitions and/or the heat conducting elements) or flow channels do not have a coating formed by an insulating material. In this case, a separate coating layer may be formed or arranged in one of the above-described manners.

Furthermore, an embodiment of the method according to the invention provides that a first fluid is introduced into the at least one first heat exchange channel and a second fluid is introduced into the at least one second heat exchange channel.

An embodiment of the method according to the invention provides in this case also that, when the plate heat exchanger is started up, the first fluid is introduced into the at least one first heat exchange channel before the second fluid is introduced into the at least one second heat exchange channel.

In particular, start-up refers to a process in which the fluid involved in the heat exchange is reintroduced into the plate heat exchanger (e.g. after stopping all fluid previously led through the plate heat exchanger or through the heat exchange channels of the plate heat exchanger, or after the first supply of the heat exchanger has not previously been used for the heat exchanger), wherein the first fluid is introduced into the plate heat exchanger before the second fluid. In particular, the first fluid is first introduced into the plate heat exchanger (i.e. before all the other fluids, or at least simultaneously with the other fluids, if appropriate). Alternatively, the first fluid is at least those fluids that are introduced into the plate heat exchanger before the second fluid.

Furthermore, an embodiment of the method according to the invention provides that the first fluid is introduced into the at least one first heat exchange channel via a nozzle and a collector, which are arranged above the inlet of the at least one first heat exchange channel.

Furthermore, for example, in particular, the at least one first fluid introduced before all the other fluids during start-up may have an inlet temperature in the range of 3K to 360K in the plate heat exchanger, wherein the plate heat exchanger may have a temperature (in particular, a uniform temperature) in the range of 3K to 360K before start-up.

Furthermore, during start-up, the first fluid may have a temperature which differs from the temperature of the plate heat exchanger before start-up by a temperature difference, for example in the range of 10K to 100K (in particular in the range of 20K to 50K).

The technical teaching according to the invention advantageously allows to reduce temporal and local temperature gradients by optionally partially reducing the heat transfer. As a result, thermal stresses are reduced, especially during the aforementioned start-up, in particular during a restart. Thus, the device can withstand a greater number of such processes, thereby extending its useful life.

Further features and advantages of the invention will be described in the following description of the figures of exemplary embodiments of the invention with reference to the figures. Shows that:

FIG. 1, which is a perspective view of a plate heat exchanger according to the invention

FIG. 2, which is a detail of a cross section through the plate heat exchanger of FIG. 1 along the section S-S shown in FIG. 1

Fig. 1 shows a plate heat exchanger 10 according to the invention with partitions in the form of partition plates 4 arranged parallel to each other and forming heat exchange channels, e.g. 1a, 1b, for fluids A, B, C, D, E which are to exchange heat indirectly with each other. Heat exchange between the fluids participating in the heat exchange takes place between adjacent

heat exchange channels

1a, 1b, wherein the

heat exchange channels

1a, 1b and thus the fluids are separated from each other by a partition plate 4.

The heat exchange takes place using heat transfer via the separating plates 4 and via the heat-conducting

elements

2, 3, which are arranged between the separating plates 4 and are also referred to as

fins

2, 3. The fins 2 shown in fig. 1 also serve to distribute the fluid evenly over the respective

heat exchange channels

1a, 1 b.

The

heat exchange channels

1a, 1b are delimited by lateral strips 8 in the form of sheet metal strips 8 (hereinafter also referred to as lateral strips 8), which are arranged in particular flush with the edges of the partition plate 4. In particular, the

heat exchange channels

1a, 1b are closed off externally, i.e. to the surroundings of the heat exchanger 10, by the side bars 8.

Preferably,

corrugated fins

2, 3 are arranged within the

heat exchange channels

1a, 1b, i.e. each between two partitions 4, wherein the cross section of the fins 3 is shown in detail in fig. 2.

Therefore, the fins 3 each have a corrugated structure having alternating foot portions 12 (hereinafter also referred to as valleys 12) and head portions 14 (hereinafter also referred to as peaks 14), wherein the valleys 12 and the peaks 14 are arranged in parallel with each other. The valleys 12 are connected to adjacent peaks 14 via a vertically running web 13, in particular of the relevant fin 3, in order to produce the corrugated structure. At the transition from a valley 12 or a peak 14 to the respective web 13, the corrugation can be formed so as to be circular. However, the corrugated structure may also have a rectangular or stepped shape. The flow channels 40 for guiding the relevant fluid in the respective

heat exchange channels

1a, 1b are formed by a corrugated structure together with the partitions 4 on both sides.

The peaks 14 and valleys 12 of the respective fins 3 are preferably integrally connected to the respective adjacent partition plate 4 by spot welds. The fluid participating in the heat exchange is thus in direct thermal contact with the corrugated structure 3, so that the heat transfer is ensured by the thermal contact between the crests 14 or troughs 12 and the separating plate 4 and thus by thermal conduction. To optimize heat transfer, the orientation of the corrugated structure 3 within the

heat exchange channels

1a, 1b is selected according to the application in such a way that a balanced flow, a cross flow, a counter flow or a cross counter flow between

adjacent channels

1a, 1b is possible.

The plate heat exchanger 10 also has an inlet 9 to the

heat exchange channels

1a, 1b (wherein for the sake of clarity only the inlet 9 to the second heat exchange channel 1b is shown in fig. 1), which is here, by way of example, arranged at an end of the plate heat exchanger 10 (an inlet in the central part is also possible), wherein a fluid A, B, C, D, E can be introduced into or discharged from the

heat exchange channels

1a, 1b via the inlet 9. In the region of these inlets 9, the individual

heat exchange channels

1a, 1b can have fins in the form of distribution fins 2 which distribute the respective fluid to the channels of the fins 3 of the relevant

heat exchange channel

1a, 1 b. However, the distribution fin 2 is not absolutely necessary. Thus, the fluid A, B, C, D, E may be introduced into the assigned

heat exchange channel

1a, 1b via the inlet 9 of the plate heat exchanger block 11 and discharged again from the relevant

heat exchange channel

1a, 1b through the other opening 19 (outlet 19).

The partition plate 4, the fins 3 and the side bars 8 and optionally further components (e.g. the distribution fins 2 shown) are connected to each other, for example by brazing. For this purpose, components such as heating surface elements (fins) 3, separating plates 4, distribution fins 2, cover plates 5 and side bars 8 are partly provided with solder and stacked one after the other in one block and subsequently brazed in a heating furnace to form heat exchanger blocks 11.

For the supply and discharge of the heat exchange fluid A, B, C, D, E, it is preferable to weld the semi-cylindrical collectors 7 (or headers) above the inlet 9 and outlet 19, respectively. Furthermore, the cylindrical nozzles 6 are preferably welded to each collector 7. The nozzles 6 are used to connect supply or discharge pipes to respective collectors 7.

As mentioned above, with plate heat exchangers of the type shown in fig. 1, there is fundamentally the problem that during start-up or re-start-up the flow introduced into the plate heat exchanger has a significant temperature difference compared to the shutdown-related temperature of the block 11. The resulting elongation and thus stress may damage the plate heat exchanger. When the temperatures of the hot and cold ends of the block 11 approach each other by heat transfer due to process flow or fluid down-time, this may result in a down-time related temperature of the block 11 and thus in a uniform temperature of the fluids and components in the plate heat exchanger.

Thus, according to the invention it is provided that the one or more partitions 4, 5 and/or the one or more

heat conducting elements

2, 3 and/or the one or more lateral strips 8 each have a coating 41 of heat insulating material applied to the respective partition 4, 5 or to the respective

heat conducting element

2, 3.

Examples of suitable insulating materials are disclosed herein. Specifically, the base material is an aluminum alloy (e.g., of type 3003). Other suitable aluminum alloys/materials are also contemplated.

The thermal barrier coating 41 is preferably applied to the partitions 4 and the heat conducting elements (fins) 2, 3 and optionally the side bars 8 in such a way that the flow channel 40 is preferably coated with the thermal barrier coating 41 in at least one first portion a1 of the heat exchange channel 1a without gaps (see detail of fig. 1).

In particular, it may be provided according to an embodiment that only certain areas or first portions a1 of the partitions 4, 5 and the

heat conducting elements

2, 3 and/or the lateral strips 8 or the flow channels 40 or the

heat exchange channels

1a, 1b are provided with the thermal barrier coating 41. The first portion a1 may also be incorporated into a second portion a2 of the partition 4, 5 or of the heat-conducting

element

2, 3 or of the lateral strip 8, which is not provided with a coating 41 according to the invention, for example, along a transition plane U indicated by a dashed line in fig. 1. Therefore, in this second portion a2, the inside of the flow passage 40 cannot have a thermal barrier coating.

In this case, the first portion a1 preferably adjoins an inlet 9 for the first heat exchange channel 1a, via which inlet the first fluid B is introduced into the block 11 before the other fluid (e.g. before the second fluid a) during start-up (in particular, restart). Furthermore, such a coating 41 may also be provided on the collector 7 and/or the nozzle 6, via which the first fluid B is introduced into the inlet 9.

List of reference numerals

Claims

1. A plate heat exchanger (10) with a plate heat exchanger block (11) having a plurality of partitions (4, 5) arranged parallel to each other and forming a plurality of heat exchange channels (1a, 1b) for a fluid that is to exchange heat indirectly with each other, wherein the heat exchange channels (1a, 1b) are delimited by lateral strips (8), and wherein heat conducting elements (2, 3) are arranged between adjacent partitions (4, 5), and wherein the heat exchange channels (1a, 1b) each have an inlet (9) for an inflow of fluid and an outlet (19) for an outflow of the fluid,

it is characterized in that

The plurality of separators (4, 5) and/or the plurality of heat conductive elements (2, 3) each have a coating (41) formed of a heat insulating material.

2. A plate heat exchanger according to claim 1, wherein the partition (4, 5) with the coating (41) and/or the heat conducting element (2, 3) with the coating (41) has a first portion (a1) arranged on the inlet (9) and a second portion (a2) connected to the first portion (a1), wherein the second portion (a2) is further away from the inlet (9) than the first portion (a1), and wherein the first portion (a1) has the coating (41), and wherein the second portion (a2) has no thermal barrier coating.

3. A plate heat exchanger according to one of the preceding claims, wherein the plate heat exchanger block (11) has at least a first heat exchange channel (1a) for receiving a first fluid (B) and a second heat exchange channel (1B) for receiving a second fluid (a), wherein the first heat exchange channels (1a) each have a coating (41) of the thermally insulating material, and wherein the second heat exchange channels (1B) do not have a coating of the thermally insulating material.

4. A plate heat exchanger according to one of the preceding claims, wherein the thermally insulating material is or is of one of the following materials: plastics, polymers, ceramics.

5. Plate heat exchanger according to one of the preceding claims, wherein the thermally insulating material has a thermal conductivity of less than 5W/mK, in particular less than 1W/mK.

6. Plate-shaped heat exchanger according to one of the preceding claims, characterized in that the respective coating (41) has a thickness (D1) less than or equal to 0.2 mm.

7. A plate heat exchanger according to one of the preceding claims, wherein for introducing a fluid (B) via the inlet (9) of the first heat exchange channel (1a) and via the inlet (9) of the second heat exchange channel (1B), a collector (7) with a nozzle (6) is attached in each case.

8. A plate heat exchanger according to claim 7, wherein the collector (7) and/or the nozzle (6) of the first heat exchange channel (1a) is provided with a coating (41) of the thermally insulating material.

9. A plate heat exchanger according to one of the preceding claims, wherein the respective heat conducting element (2, 3) has a corrugated structure with alternating foot portions (12) and head portions (14), wherein the respective foot portion (12) is connected to an adjacent head portion (14) via a web (13).

10. Method for producing a plate heat exchanger according to one of the preceding claims, wherein a flowable material forming a heat insulating material in a hardened state is introduced into heat exchange channels (1a) of the plate heat exchanger block (11), the partitions and/or heat conducting elements (2, 3) and/or lateral strips (8) of which will receive the coating (41), wherein the material is solidified in order to form the coating (41).

11. Method according to claim 10, characterized in that at least some parts of the plate heat exchanger blocks (11) are immersed in the flowable material in order to introduce the flowable material into the corresponding heat exchange channel (1).

12. Method for operating a plate heat exchanger according to one of the preceding claims, wherein at least one first fluid (B) and one second fluid (a) are introduced into at least one heat exchange channel (1a, 1B) of the plate heat exchanger such that the fluids (B, A) are able to exchange heat.

13. A method according to claim 12, wherein the first fluid (B) is introduced into the at least one first heat exchange channel (1a) and the second fluid (a) is introduced into the at least one second heat exchange channel (1B).

14. Method according to claim 12 or 13, wherein the first fluid (B) is introduced into the at least one first heat exchange channel (1a) before the second fluid (a) is introduced into the at least one second heat exchange channel (1B) when the plate heat exchanger is activated.

15. The method according to one of claims 12 to 14, wherein the first fluid (B) is introduced into the at least one first heat exchange channel (1a) via the nozzle (7) and collector (6) arranged above the inlet (9) of the at least one first heat exchange channel (1 a).

16. Method according to one of the preceding claims, wherein the temperature of the at least one first fluid (B) introduced into the plate heat exchanger before all other fluids differs from the temperature of the plate heat exchanger before start-up by a certain temperature difference when the plate heat exchanger is started up.