Heat exchanger

Abstract

The invention relates to a heat exchanger comprising a first high-pressure channel group (7) and a second low-pressure channel group (6) with a respective plurality of channels (3), wherein the channels (3) of each channel group are arranged on their respective own level, the channel groups (6, 7) are introduced into their respective own films in a fluidically separated manner and these are combined to form a film stack, wherein the channels of the first high-pressure channel group are incorporated in layers and via grooves (2) in first film pairs (9) with two first films lying on top of one another, wherein the grooves extend from a contact surface of the two first films on one another into the at least one first film, without penetrating same, the channels of the second low-pressure channel group are formed in layers via through-openings (11) with strips arranged in-between in a respective second film (10) and are each covered on both sides by a first film (8) of a first film pair (9) or a closing film, and the film stack comprises an alternating stacking of second films (10) and the first film pair (9).

Description

[0001] heat exchanger

[0002] The invention relates to a heat exchanger, preferably a micro heat exchanger with a first high-pressure channel group and a second low-pressure channel group, each with a plurality of channels in a foil stack according to the first patent claim. The heat exchanger is preferably a cocurrent, countercurrent, or crosscurrent micro heat exchanger.

[0003] Heat exchangers of the type mentioned at the beginning are generally known in the art. They have a heat transfer region in which a fluid flow in one channel group is tempered by a fluid flow in another channel group. Each of the channel groups has a large number of channels which are preferably connected in parallel over their entire length and preferably also run parallel. The channels in each channel group are preferably arranged parallel to one another and preferably in a straight line on one plane. The two channel groups are usually arranged alternately in planes, with or without intermediate layers without channels, i.e. cooling or heating of the fluid flow takes place by heat transfer between the overlapping regions of the two channel groups, which thus form the heat transfer regions. The totality of the channels in a channel group preferably forms a passage through the heat exchanger.

[0004] DE 37 09 278 C2 discloses, by way of example, micro heat exchangers and their production, in which the microchannels are incorporated in one side of metal foils as a plurality of parallel grooves. The foils are then placed on top of one another and joined together by gluing, soldering or welding, with the foil sides structured with grooves each resting against one of the adjacent foils. One embodiment provides for the grooves to be covered by an unstructured foil side. Alternative embodiments provide microchannels whose cross-sections extend from grooves into two adjacent foils, with the outer foil surfaces of these two foils remaining unstructured. Heat exchangers are disclosed in which all of the microchannels are aligned in parallel, i.e.as cocurrent or countercurrent heat exchangers, as well as cross-flow microheat exchangers, with foils stacked crosswise, preferably twisted by 90°, depending on the channel group. However, the grooves and channels of the disclosed microheat exchangers are identical for all channel groups.

[0005] One of the embodiments disclosed in DE 37 09 278 C2 provides a microstructured heat exchanger consisting of a stack of single-sidedly structured, diffusion-welded films. A plurality of microchannels, each having an approximately semicircular shape, are incorporated into the films. By stacking two mirror-image structured films face-to-face, almost circular flow cross-sections can be achieved. A further embodiment provides for a monodirectional stacking sequence, wherein the semicircular channel cross-sections incorporated into the films are each open in one direction and are covered by a smooth, unstructured surface of the adjacent film.

[0006] Based on this, one object of the invention is to propose a heat exchanger which is particularly suitable for improved heat transfer of different volume flows and pressures in the channel groups.

[0007] The problem is solved by a heat exchanger with the features of claim 1. Subclaims give advantageous embodiments. To solve the problem, a heat exchanger with two channel groups, a first high-pressure channel group and a second low-pressure channel group, each with a plurality of channels between an inlet and an outlet area is proposed. Consequently, the channels form a fluidically continuous connection between the inlet and outlet areas, each of which is connected to only one of the two channel groups. The channels in each channel group are arranged in their own planes. The channel groups are separated from one another on the fluid side and are each introduced into their own films. The films are assembled to form a film stack.

[0008] The terms "low-pressure" and "high-pressure" channel group each describe a first and a second channel group, which are fluidically separated from each other, including the corresponding inlet and outlet areas. The low-pressure channel group is designed for a lower pressure than the high-pressure channel group, and this is fundamentally independent of the absolute pressure.

[0009] An inlet area is a volume fluidically positioned upstream of a channel group or part of a channel group. It serves as a distribution structure for a fluid from a fluid source (inlet) flowing into the volume into the aforementioned channel group or part of the channel group.

[0010] Corresponding to the inlet areas, an outlet area of ​​a channel group or part of a channel group is a fluidically downstream volume into which the channels open and are passed on to a fluid sink (outlet).

[0011] For each channel group, a number of inlet and outlet areas are provided, preferably one inlet and one outlet area in each plane. It is important that the channels of the first channel group, the high-pressure channel group, are incorporated in planes as grooves in each case in at least one first film of a first film pair with two first films lying flat on top of one another, wherein the grooves extend from a contact surface of the two first films on one another into the at least one, preferably both first films, but do not penetrate the two first films. Preferably, each of the grooves has a semicircular cross-section in both first films, so that when the grooves are placed next to one another, they combine to form a channel with a round flow cross-section.Such a design features a relatively high proportion of foil material around the channels, which in turn advantageously ensures high dimensional stability of the foil pair, even at elevated pressures. This applies in particular to the aforementioned circular flow cross-section, which, although it has a smaller specific wall surface area for heat transfer relative to the channel volume, allows for maximum dimensional stability.

[0012] It is also important that the channels of the second low-pressure channel group are formed in each layer by openings with webs arranged between them, incorporated in one, preferably only one second film in each layer. The channels penetrate the films across their full film thickness and initially form open slits in the films on both sides, which are covered on both sides by a first film of a first film pair or a final film when the film stack is joined. These perforated films thus represent a frame around the slits, with the individual channels being formed by the slits and separated from one another in one layer by webs. This type of design is characterized by a smaller proportion of film material around the channels than in the high-pressure channel group.This facilitates the realization of the largest possible flow cross-sections, on the one hand, and, due to the integration of both adjacent foils into the channel walls, short heat transfer paths and large specific heat transfer areas (relative to the channel volume). Preferably, the second channel group has a flow cross-section that exceeds the cross-section of the webs between the channels by at least twice, more preferably by at least five times or ten times.

[0013] It is also essential that the film stack comprises an alternating stacking of second films and a first film pair, with the uppermost and / or lowermost layer of the film stack being formed by a closure film or a first film pair. Preferably, no two second films and no two first film pairs lie on top of each other during the stacking.

[0014] A preferred embodiment of the first high-pressure channel group provides for its level-wise incorporation by means of grooves in both first foils of the first foil pair, wherein the grooves extend from the contact surface of the two first foils in a mirror image into both first foils and more preferably form round channel cross-sections with the aforementioned advantages.

[0015] Preferably, each of the first and second levels has a plurality of adjacent, continuous channels separated from one another on the fluid side, advantageous for high permeability of the heat exchanger volume with the two channel groups. This applies in particular or alternatively if the channels in each channel group are optionally arranged in parallel and interconnected.

[0016] The channels in each channel group preferably have a uniform length and / or a constant flow cross-section over their entire channel length, whereby the most uniform flow and heat transfer possible can be achieved in all channels of a channel group.

[0017] The proposed heat exchanger with the aforementioned features can basically be designed and implemented both as a cocurrent or countercurrent heat exchanger, in which all channels of both channel groups are arranged at least in sections parallel to one another to form a cocurrent or countercurrent heat exchanger, and as a crosscurrent heat exchanger, in which the channels of the first high-pressure channel group and those of the second low-pressure channel group are arranged at least in sections, preferably completely, skewed to one another, thus intersecting to form a crosscurrent heat exchanger.

[0018] The inlet and outlet regions are preferably arranged in planes at the end of the channels in the respective plane. The channels of one plane are preferably connected to only one and the same inlet region and one and the same outlet region. For this purpose, they are preferably also arranged in this plane and more preferably fluidically connected to the inlet and outlet regions of the same channel group on other planes via the respective inlet region and the respective outlet region via a connecting line.

[0019] It is proposed as a particularly preferred structural design to provide the inlet and outlet regions of the first and second channel groups by means of depressions or grooves in at least one first film of the respective first film pair or by means of openings, grooves or depressions in the respective second films. Preferably, all levels, i.e. all films with channels between one inlet and one outlet region per channel group, have identical dimensions and materials. They are preferably identical for each channel group; they therefore also lead to identical flow conditions in the levels for each channel group.

[0020] Preferably, the inlet and outlet regions of the first and second channel groups are each separately connected to one another on the fluid side in such a way that they each form a common inlet and a common outlet for the high-pressure channel group and the low-pressure channel group of the heat exchanger.

[0021] The proposed heat exchanger is preferably a micro heat exchanger, which is characterized in the context of the invention in that the channels of both channel groups are designed as microchannels of two microchannel groups as grooves or foil openings with narrowest flow cross sections between 0.001 mm 2 or 0.01 mm 2 and 10 mm 2 or 1 mm 2are preferably incorporated into metal foils, and these metal foils are joined together to form a foil stack, preferably by diffusion welding. The foils themselves preferably have a thickness of between 0.25 and 5 mm, more preferably between 0.5 and 1.5 mm.

[0022] In all of the embodiments shown, the foils are preferably metal foils, preferably made of stainless steel or copper. It is important that the materials used are chemically inert to the heat transfer fluid flowing through the channels. A wide variety of substances can be considered as fluids, which are preferably in the liquid or gaseous or in the two-phase state (liquid / gaseous). The fluids can be pure substances or mixtures of substances. The invention therefore achieves the object by means of different flow cross-sections of high-pressure and low-pressure channel groups in order to optimize pressure losses and heat transfer in preferably microstructured heat exchangers, in particular in that the low-pressure channel groups are incorporated in perforated foils (so-called low-pressure frames, second foils) and are directly adjacent to the adjacent (first) foils of the high-pressure channel group on one side, preferably on both sides.The second foils with the low-pressure channel groups can be produced, for example, by punching out sheet metal, laser cutting or milling.

[0023] The low-pressure flow paths closed off by the adjacent foils are always only created by the combination of low-pressure frames with two face-to-face stacked foils (two first foils or one first foil and one end foil), which have smooth joining surfaces for diffusion welding on the outside towards the low-pressure frames and which form the high-pressure flow paths from the etched channels on the inside.

[0024] A heat exchanger with the aforementioned low-pressure frames offers the following advantages over conventional heat exchangers:

[0025] 1 ) Regardless of the stacking sequence in conventional microstructure heat exchangers, one foil wall is always omitted in the above-mentioned high-pressure / low-pressure sequence, which reduces the thermal resistance and improves the heat transfer between the high-pressure and low-pressure media.

[0026] 2) Due to the reduced material cross-sectional area of ​​the low-pressure frame compared to conventional heat exchangers, the longitudinal heat conduction in the walls of the heat exchanger in the direction of the channels is also reduced, which is particularly advantageous in applications with large temperature gradients in the direction of flow, e.g. in refrigeration and cryogenic technology.) Due to the thickness of the second foils and thus the height of the low-pressure frame, the low-pressure flow cross-section can be adapted for a given channel width and number of channels, and thus the pressure loss on the low-pressure side can be minimized and the overall energy efficiency of the foil-frame heat exchanger can be maximized. The thickness of the second foils and thus the frame height is preferably less than or equal to 5 mm and / or less than or equal to a factor of 2-3 of the thickness (i.e.two to three times the thickness) of the first pair of films for the high-pressure channels, more preferably less than or equal to a factor of 5-10 of the thickness of the first pair of films for the high-pressure channels. The minimum frame height is preferably equal to the thickness of the first pair of films.) The preferably parallel channels in the low-pressure frame are separated from one another by webs, the width and spacing of which are determined in particular by manufacturing requirements such as, for example, by the preferred diffusion welding. Since the webs are, for example, diffusion-welded to the adjacent rear walls of the first high-pressure films, their surfaces contribute directly to the heat transfer between the high-pressure and low-pressure medium.) Compared to conventional microstructured heat exchangers, whose design is based on the stacking of etched foils, the proposed heat exchangers with low-pressure frames have a fundamentally improved heat transfer behavior and at the same time an additional degree of freedom, which enables significantly different pressure losses along the flow paths and thus allows the overall energetic optimization of the microstructured heat exchanger with the highest possible power density.

[0027] 6) Like classic microstructure heat exchangers, foil-frame heat exchangers feature a foil stack that is essentially monolithic in design, i.e., the first and second foils, and thus the entire heat exchanger, are preferably made of a single material. This prevents thermal stresses caused by different thermal expansion coefficients, which is particularly advantageous in low-temperature applications with large temperature gradients.

[0028] 7) Due to the small hydraulic diameters of microstructured heat exchangers with the aforementioned foil frames, higher operating pressures are generally possible than with conventional plate heat exchangers. This would allow higher system pressures, for example, in hydrogen liquefaction, which would significantly impact process efficiency.

[0029] The proposed heat exchangers are particularly suitable for process engineering applications with compressible media, where pressure losses have a significant impact on process efficiency. This is especially the case in the low absolute pressure range. A particularly wide range of applications is offered by processes in refrigeration and cryogenics.

[0030] Heat exchangers have a significant influence on the energy efficiency of process engineering applications. The energy efficiency of heat exchangers is mostly determined by the temperature differences of the heat transfer. However, for compressible media and low pressures, the pressure drop also plays an important role. In general, heat transfer can be improved by increasing flow velocities; however, the resulting increase in pressure drops always results in an energy optimization problem.

[0031] In the medium and small power range, conventional plate heat exchangers with a power density in the range of approx. 100-1000 m 2 / m 3 used. Using state-of-the-art microstructured heat exchangers, the power density can be further increased to approximately 1000-10,000 m 2 / m 3increase. This technology, which has great application potential in refrigeration and cryogenics, for example, implies roughly equal flow cross-sections in the fluid flows, the ratio of which can only be influenced within limits, e.g. by the number and stacking sequence of the films in the flow passages. The energetic optimization of many heat exchangers, however, requires in particular the limitation of pressure losses on the low-pressure side. In some applications, due to process reasons, only a few millibars of pressure loss are permissible, whereas on the high-pressure side, much higher pressure losses are often tolerable. A significant improvement is achieved by the invention in that the flow cross-section of the second low-pressure channel group can be adapted to the requirements of the application in such a way that, with improved heat transfer, pressure losses in the flow passages can be realized that can differ by one or two orders of magnitude.

[0032] The advantages of heat exchangers with the foil frames described above are particularly evident in applications where a high energy density of heat transfer is required and where the permissible pressure losses in the flow passages vary greatly. Pressure losses have a negative effect on process efficiency, particularly at low operating pressures (including operation in negative pressure), due to the increase in entropy when compressible media expands. The additional degree of freedom for the hydraulic design of the low-pressure channel group provided by the frame height and the elimination of foil walls open up new possibilities for the thermo-hydraulic optimization of microstructured heat exchangers. This also enables an increase in energy density and the energetic optimization of heat exchangers in a wide variety of system concepts and applications, particularly in refrigeration and cryogenic technology.In refrigeration technology, even small energy improvements are of great economic and ecological importance due to the large quantities involved.

[0033] Furthermore, the proposed heat exchangers make new system concepts conceivable that have not previously been technically feasible. Examples of possible applications include cooled electrical conductors, compact heat transfer systems, ultra-low temperature refrigerators, or hydrogen condensers and helium refrigeration systems.

[0034] The invention is explained in more detail with reference to exemplary embodiments, the following figures and descriptions. All features and their combinations are not limited to these exemplary embodiments and their configurations. Rather, they should be considered representative of other possible configurations that are not explicitly shown as exemplary embodiments and can be combined.

[0035] Fig. 1a to c schematic cross-sectional views of conventional co-current and / or countercurrent heat exchangers with two channel fractions as foil stacks (state of the art),

[0036] Fig. 2a and b are schematic sectional views of cocurrent and / or countercurrent heat exchangers with two modified channel fractions, Fig. 3a to d are several detailed views of a second foil (low-pressure frame) with a number of parallel channels with inlets and outlets,

[0037] Fig. 4a to c various embodiments of a counterflow heat exchanger for use preferably in refrigeration and cryogenic technology as well as

[0038] Fig. 5 is a schematic exploded view of the embodiment shown in Fig. 4a.

[0039] Conventional heat exchangers in layer stack construction, as shown schematically in Fig. 1a to c, have grooves 2 machined into one side of films 1 or plates, which are covered in the stack by an adjacent film with or without machined grooves to form channels. The grooves do not penetrate the films. Common to conventional heat exchangers is that each of the channels extends into only two layers or extends into one layer and is tangent to only one other layer. The wall of each channel is formed in cross-section by only two adjacent layers. Each film has at least one side without machined grooves, preferably as a flat surface. The channels are grouped together in planes to form channel groups.

[0040] Fig. 1a shows a design in which each channel 3 in two adjacent foils 2 of a foil pair (plane ) is formed by two opposing grooves 2 each with semicircular cross-sections. The semicircular cross-sections combine to form round channel cross-sections. The foils of a foil pair are preferably made of a metal, preferably stainless steel or copper or another material with high thermal conductivity and low corrosion tendency towards a heat transfer medium to be passed through the channels. At least the two foils of a foil pair are diffusion-welded or brazed to one another (material bond), which, in conjunction with a round channel cross-section, makes this particularly suitable for passing through media at high pressures.

[0041] Fig. lb and c, on the other hand, represent alternative embodiments in which each channel 3 is formed only by a groove 2 in a film 1, the grooves each being covered in planes by a smooth surface 4 of an adjacent film.

[0042] In Fig . lb these smooth surfaces are formed by the unstructured flat surface of an adjacent foil with channels , thus forming a stack of similar foils .

[0043] Fig. 1c, on the other hand, discloses an embodiment in which, as in Fig. 1a, two foil surfaces structured with grooves are arranged one above the other, but are separated from each other by an unstructured intermediate foil 5. The two grooves do not combine to form one channel as shown in Fig. 1a, but rather form separate channels separated from each other by the intermediate foil.

[0044] Fig. 2a and b, on the other hand, show cross sections of exemplary embodiments of heat exchangers proposed for solving the aforementioned problem, comprising a low-pressure channel group 6 and a high-pressure channel group 7 as a foil stack. The channels of the low-pressure channel group are shown as openings in individual foils (low-pressure frame, second foil), which are covered on both sides by an adjacent foil (belonging to the first foils). The wall of each channel of the low-pressure channel group is thus formed in cross-section by three adjacent layers; these channels border directly on two first foils of the high-pressure channel group on both sides, which is advantageous for heat transfer. The channels in each channel group are arranged parallel to one another and interconnected.

[0045] Fig. 2a shows an exemplary embodiment of a foil stack in which the levels with the high-pressure channel groups, as shown in Fig. 1a, are designed with round channel cross-sections extending over a foil pair 9 (two first foils 8), particularly advantageous for high-pressure applications. In contrast, the levels arranged between them with the low-pressure channel groups 6 are represented in the example by perforated individual foils 10 (low-pressure frames), the perforations 11 being covered on both sides by a smooth surface 4 of one of the aforementioned foil pairs with the high-pressure channel groups.

[0046] Fig. 2b shows a further exemplary embodiment with particularly short heat transfer paths between the high-pressure and low-pressure channel groups. The low-pressure channel groups 6 are represented, as in Fig. 2a, by perforated individual films 10 (low-pressure frame, second film), the openings 11 being covered on both sides by an adjacent first film 8 of the film pair 9 of the high-pressure channel group 7. The channels of the high-pressure channel groups are incorporated as rectangular grooves in only one first film of the film pair and in continuation of the aforementioned openings and are covered by an unstructured cover film 12 which is flat on both sides (second of the two first films). The cover film and films structured with grooves form the film pair (two first films).This, as well as the rectangular cross-sections of the channels of the high-pressure channel groups and the unstructured cover film, favor a particularly large area share of the channel cross-sections in the cross-section of the (first) film pair on the one hand and thus the shortest possible heat transfer paths between the high-pressure and low-pressure channel groups.

[0047] Fig. 3a to d show several schematic detailed views of a perforated film 10 as a second film (low-pressure frame) with a number of parallel openings 11 as channels. Fig. 3c and d contain sectional views of the second film along the section line AA shown in Fig. 3a. The channels (openings 11) open at their ends into a busbar 13 and 14 as inlet and outlet respectively, which are arranged as grooves transverse to the openings and fluidically connect them to one another. Furthermore, fluidic connections 15 and 16 from the busbars 13 and 14 respectively are provided for the introduction and discharge of the media to be conducted through the low-pressure channel group.These fluidic connections are preferably proposed as openings through the second foil, as shown. These openings are arranged one above the other in at least several adjacent foils throughout the foil stack, forming inlet and outlet channels crossing the foils. Inlet and outlet channels thus also connect busbars arranged one above the other.

[0048] Fig. 4a to c show various exemplary embodiments of a countercurrent micro heat exchanger for use preferably in refrigeration and cryogenics in general (Fig. 4a and b) as well as for the temperature control of power supplies for superconducting applications 23 (Fig. 4c). The countercurrent heat exchangers shown each have two end connection areas 17, each with two connections for the extension areas of the high-pressure and low-pressure channel groups 18 arranged between them.

[0049] Fig. 5 shows, by way of example, a schematic exploded view of the first and second films 8 and 10 in a film stack of an embodiment shown in Fig. 4a. The extension of a high-pressure channel group on a first film 27 and of a low-pressure channel group on a second film 28 are shown. While the channels of both channel groups run parallel in layers in the central extension region 18, in the two end connection regions 17 they swing out in channel groups into a connection volume and open into or out of this. The expanded connection volume (stacked openings) in the outflow region is clearly visible, shown in the connection region shown on the right. The second perforated film 10 is closed off at the top with a cover film 25 which is flat on one side.

[0050] Fig. 4a shows an embodiment in which the connections for the outlets for the low-pressure channel group 19 and the high-pressure channel group 21 are significantly wider than their inlets 20 and 22, respectively. Such a configuration is particularly suitable for micro heat exchangers in which the media tempered in the channels experience an increase in volume (e.g. during a reaction or evaporation) or in which only a low flow resistance can be tolerated when discharging the media. This embodiment is characterized by the openings through the film stack described with reference to Figs. 3a to d, which are connected to the aforementioned connections as fluidic connections.

[0051] Fig. 4b shows a further embodiment in which the connections for the outflow lines for the low-pressure channel group 19 and the high-pressure channel group 21 have not been changed or have been changed insignificantly in terms of cross-section compared to their inlets 20 and 22. The aforementioned fluidic connections and the busbars between the high-pressure and low-pressure channel groups 18 and the connections 19 to 22 are replaced here by distribution chambers 24 attached directly to the sides of the foil stack. All of the channels of a channel group preferably open into or out of each of the four distribution chambers and are fluidically connected by these to one of the four connections 19 to 22. Fig. 4c shows a further embodiment in which the connections for the outflow lines for the low-pressure channel group 19 and the high-pressure channel group 21 have not been changed or have been changed insignificantly in terms of cross-section compared to their inlets 20 and 22. 22 were also not or only slightly changed in cross-section.However, the foil stack consists of a highly electrically conductive material, preferably copper, and has current connections 23, so that the electrical current flows preferably parallel to the channels in the central extension region 18. This embodiment is particularly suitable for the temperature control of power supply lines for superconducting applications in order to efficiently transport the electrical current from room temperature to the cryogenic operating temperature of the superconductor.

[0052] List of reference symbols:

[0053] 1 slide

[0054] 2 grooves

[0055] 3 channel

[0056] 4 smooth surface on a foil

[0057] 5 unstructured intermediate film

[0058] 6 Low pressure channel group

[0059] 7 High-pressure channel group

[0060] 8 first slide

[0061] 9 pairs of slides (first two slides)

[0062] 10 perforated single foil (low pressure frame, second foil)

[0063] 11 Breakthrough

[0064] 12 double-sided flat cover film

[0065] 13 Busbar for one introduction

[0066] 14 Busbar for the discharge

[0067] 15 fluid connection to the inlet

[0068] 16 fluid connection to the discharge

[0069] 17 Connection area

[0070] 18 Extension area of ​​the high-pressure and low-pressure channel groups

[0071] 19 Connection for the introduction of low-pressure duct group

[0072] 20 Connection for the discharge of the low-pressure duct group

[0073] 21 Connection for the introduction of high-pressure channel group

[0074] 22 Connection for the discharge of the high-pressure channel group

[0075] 23 Connection flag of the foils for electrical current

[0076] 24 distribution chamber

[0077] 25 one-sided flat cover film

[0078] 26 Extension of a low-pressure channel group on the second foil

[0079] 27 Extension of a high-pressure channel group on the first slide

Claims

Patent claims:

1. Heat exchanger with a first high-pressure channel group (7) and a second low-pressure channel group (6), each with a plurality of channels (3) between an inlet (19, 21) and an outlet region (20, 22), wherein the channels (3) of each channel group are arranged in their own planes, the channel groups (6, 7) are separated from one another on the fluid side and are introduced into their own foils, and these are assembled to form a foil stack, characterized in that a) the channels of the first high-pressure channel group are incorporated in planes by grooves (2) into at least one first foil (8) of a first foil pair (9) with two first foils lying flat on top of one another, wherein the grooves extend from a contact surface of the two first foils into the at least one first foil, but do not penetrate the two first foils,b) the channels of the second low-pressure channel group are formed in planes by openings (11) with webs arranged therebetween in a second film (10) and are covered on both sides by a first film (8) of a first film pair (9) or a closing film (25), and c) the film stack comprises an alternating stacking of second films (10) and first film pair (9), wherein the uppermost and / or lowermost layer of the film stack is formed by a closing film or a first film pair.

2. Heat exchanger according to claim 1, characterized in that the channels of the first high-pressure channel group (7) are incorporated in planes by grooves (2) in both first foils of the first foil pair (9), wherein the Grooves starting from the contact surface of the first two foils extend mirror-inverted into both first foils.

3. Heat exchanger according to claim 1 or 2, characterized in that the second channel group (6) has a flow cross-section which exceeds the cross-section of the webs by at least twice.

4. Heat exchanger according to one of the preceding claims, characterized in that each of the first and second levels has a plurality of adjacently arranged, continuous channels (3) which are separated from one another on the fluid side.

5. Heat exchanger according to one of the preceding claims, characterized in that the channels (3) are arranged and interconnected in parallel in each channel group (6, 7).

6. Heat exchanger according to one of the preceding claims, characterized in that the channels (3) per channel group (6, 7) each have a uniform length and / or a constant flow cross-section over their entire channel length.

7. Heat exchanger according to one of the preceding claims, characterized in that all channels (3) of both channel groups (6, 7) are arranged at least in sections parallel to one another to form a co-current or counter-current heat exchanger.

8. Heat exchanger according to one of claims 1 to 6, characterized in that the channels (3) of the first high-pressure channel group (7) and those of the second low-pressure channel group (6) are each arranged skewed to one another, thus crossing to form a cross-flow heat exchanger. Heat exchanger according to claim 7 or 8, characterized in that the inlet and outlet regions (13, 14, 15, 16) are each arranged plane-wise at the end of the channels (3) in the respective plane. Heat exchanger according to claim 9, characterized in that the inlet and outlet regions (13, 14, 15, 16) of the first and second channel groups (6, 7) are incorporated by depressions or grooves in at least one first film of the respective first film pair or by openings, grooves or depressions in the respective second films. Heat exchanger according to claim 10, characterized in that the inlet and outlet regions of the first and second channel groups are each separately connected to one another on the fluid side in such a way that they each form a common inlet and a common outlet for the high-pressure channel group and the low-pressure channel group of the heat exchanger.Heat exchanger according to one of the preceding claims, characterized in that the channels (3) of both channel groups are designed as microchannels of two microchannel groups as grooves or film openings with narrowest flow cross sections between 0.001 mm. 2 and 10 mm 2 are incorporated into metal foils and the metal foils are joined together to form a foil stack by means of diffusion welding.

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