DE102019110262A1 - Plate-fin heat exchanger - Google Patents

Abstract

The invention relates to a plate-fin heat exchanger (1) with a top and a bottom plate as horizontal boundary plates (2) and side walls (3) as well as an arrangement of several ribs (7) arranged perpendicular to the direction of flow (9), which are perpendicular and extend rod-shaped between the horizontal delimitation plates (2), at least one partition (8) between the horizontal delimitation plates (2) being designed as a plate which is penetrated by the ribs (7) and which has at least two flow channels (6) through which fluid flows can flow. which are materially separated by the partition (8), the ribs (7) having a rib depth (a) and a rib width (b) in the flow direction (9), with several ribs (7) in a row of ribs transversely to the flow direction ( 9) are arranged and several rows of ribs are arranged one behind the other in the flow direction (9) at a row spacing between adjacent rows (c) and that the ribs (7) ben adjacent rows of ribs are offset from one another in such a way that the cross-sections of the ribs (7) overlap in the flow direction (9) and a gap (10) with a gap width (e) through which fluid can flow is formed between adjacent ribs (7).

Description

The invention relates to a plate-fin heat exchanger which can be used in particular for cryotechnical applications or applications in aerospace.

A plate-fin heat exchanger of the generic type has at least two flow channels for the heat-transferring fluids, which are materially separated from one another by a partition wall as a plate. The heat transfer from one fluid to the other fluid takes place through the partition wall, with ribs being provided in the flow channels which enlarge the heat transferring surface area beyond the surface of the partition wall.

In the prior art, highly efficient counterflow heat exchangers of the plate-fin heat exchanger type are known. Brazed plate-fin heat exchangers are used in particular for demanding heat transfer tasks, for example in cryogenics. The individual elements of the heat exchanger are soldered together to achieve good heat transfer and excellent heat transfer properties. An important component of generic heat exchangers are the ribs, which serve to increase the surface area of the heat-transferring surface and which, due to the material, have good thermal conductivity.
The disadvantage of heat exchangers of the plate-fin design is that the choice of fin types is very limited and that the manufacture requires a great deal of manual labor. This makes the heat exchangers relatively expensive. In the case of highly efficient heat exchangers of the known type, there is also the problem that they have a very large structural volume and thus determine the size of the entire system.

In the prior art, heat exchangers are also known which use profile tubes instead of plates to separate the fluid flows, with one fluid flowing in the tubes and the second fluid flowing around the tubes.
From the DE 42 34 006 A1 For example, a profile tube for heat exchangers emerges, a profile tube with a teardrop-shaped outer contour being proposed for the matrix of a tubular heat exchanger. A first fluid flows through the profile tube and the second fluid flows around the matrix of the correspondingly profiled profile tubes.

According to a similar construction, profile tubes according to GB 468,980 are known which also provide profile tubes with a teardrop-shaped contour in a matrix-like arrangement for a heat-transferring fluid to flow around.

The heat exchangers according to the prior art generally have the disadvantage that the individual components cannot be miniaturized as desired in order to reduce the size of the heat exchangers.

The object of the invention is to provide a plate-fin heat exchanger which has good heat transfer properties while at the same time being small in size and which can also be produced with little manufacturing effort in a pressure-stable design, for example for use in cryotechnical systems. The pressure-tight and material-tight separation of the fluid flows in the heat exchanger continues to place particularly high demands on the manufacturing technology and the design of the heat exchanger.

The object is achieved by a plate-fin heat exchanger and by a method for producing such a heat exchanger with the features of the independent claims. Further developments are given in the dependent claims.

The object of the invention is achieved in particular by a plate-fin heat exchanger which is constructed from a top and a bottom plate as horizontal boundary plates and side walls and an arrangement of several ribs arranged perpendicular to the direction of flow. The ribs extend vertically and rod-shaped between the horizontal delimitation plates. At least one partition wall is formed as a plate of the plate heat exchanger between the horizontal delimitation plates, through which the ribs penetrate. The partition wall as a horizontal plane between the horizontal delimitation plates thus forms at least two flow channels through which fluid flows can flow and which are materially separated by the partition wall. If more than one partition is provided, additional flow channels are formed corresponding to the number of partition walls, which can be combined to form different flows. The ribs have a rib depth and a rib width in the flow direction.
Several ribs are arranged in a row of ribs transversely to the flow direction and several rows of ribs are arranged one behind the other at a row spacing in the flow direction. The ribs of adjacent or successive rows of ribs are arranged offset from one another in such a way that the cross sections of the ribs overlap in the flow direction. A gap with a gap width through which fluid can flow is formed between adjacent ribs.

The ribs are preferably designed as a triangle in cross-section and have a pointed leading edge and a pointed trailing edge. A triangle is understood geometrically as a cross section which has two opposite corners with acute angles, which are connected to one another to form a surface without forming a further corner which is effective in terms of fluid mechanics.

The dividing wall between the flow channels is preferably constructed geometrically from a plurality of horizontal surface elements, also called individual surfaces, the transitions of the individual surfaces into the rib being inclined by a fabrication angle alpha with respect to the horizontal.
Particularly preferably, the rib cross-section is designed in a diamond shape, the corners of the rhombus of the rib cross-section advantageously being rounded with the larger angle, thereby forming the cross-section of a delta.

The ratio of the rib depth as the longitudinal diagonal of the rhombus to the rib width as the transverse diagonal of the rhombus of the rib cross-section is advantageously between 1.5 and 3 and preferably 2. The longitudinal diagonal is about twice as long as the transverse diagonal.

A rib capital is advantageously formed at the transition of the ribs into the upper horizontal delimitation plate. The rib capital, comparable to a column capital, is also referred to as the rib head and is the area of transition of the cross section of the rib into the upper horizontal delimitation plate.

The surface elements of the partition, the individual surfaces, are preferably designed as basic diamonds. The rib diamonds are designed to be smaller than the basic diamonds by a reduction factor beta.

The individual surfaces are formed on the upper separating surface in the transition from the basic diamond to the ribbed diamond at a manufacturing angle for generative manufacturing processes with a maximum inclination of 45 °. The inclination is understood to mean the angle to the vertical.

The reduction factor beta from the rib diamond to the basic diamond is advantageously in a range between 0.6 and 0.9.

The heat exchanger is preferably equipped with several essentially horizontal partition walls. Several flow areas are thus designed as floods in which the heat-transferring fluids can be guided in cocurrent, countercurrent or cross-flow.

In a particularly advantageous application, the heat exchanger is designed for fluid flows of different volume flows, for example fluid flows at different pressure levels. In the various flow areas, for example in the area of the high pressure flow, the ribs are preferably provided with a vertical gap in the direction of flow in order to provide an additional flow cross-section with an additional heat transfer surface compared to the area of the low pressure flow.
The horizontal gap is preferably formed in the rib depth, the longitudinal diagonal of the rib diamond of the rib.

The rib advantageously has a different reduction factor beta from the rib diamond to the base diamond in the area of the high pressure flow than in the area of the low pressure flow.
The rib preferably has a larger reduction factor in connection with a gap in the area of the high pressure flow.

Particularly preferably, the reduction factor beta is designed to be variable in the direction of flow from the rib diamond to the base diamond when the volume flow changes along the heat exchanger.

The ribs are preferably made of solid material, a material with the best possible thermal conductivity being selected as the solid material. Metals such as aluminum or copper and corresponding alloys thereof are therefore particularly suitable.

The outer walls of the heat exchanger, that is to say the horizontal delimiting plates and the side walls, are preferably constructed from an outer and an inner layer, the outer layer having a lower thermal conductivity than the inner layer.

The inner layer of the outer walls and the ribs are preferably formed from the same material which is a good conductor of heat.

Furthermore, secondary ribs are advantageously formed on the ribs, the secondary ribs being designed to be inclined relative to the horizontal by a manufacturing angle alpha.

The object of the invention is further achieved by a method for producing a plate-fin heat exchanger in which the outer walls, the partition and the fins are produced as one piece by means of laser sintering or laser melting as a generative production method. As a result, there is excellent heat conduction from the rib of higher temperature across the Flow direction given through the partition wall into the lower temperature rib, with additional heat being transferred through the partition wall.

Particularly preferably, only the horizontal inner layers of the outer walls are produced together with the ribs and the partition wall by means of laser sintering or laser melting as a generative manufacturing process.

The concept of the invention is that a highly efficient plate-fin heat exchanger can be produced by making the plates and fins in one piece and from a material that conducts heat well, such as metal, since between the plate and within the fin there is only heat conduction within one material and there is no heat transfer between different materials or across a gap. The plates, which functionally represent the partition walls for material separation between the flowing fluids, and the rod-shaped ribs penetrating the plates are produced in one piece, i.e. as one piece and in one operation, using generative manufacturing processes. Manufacturing processes are, for example, laser sintering or laser melting.
In this way, optimal heat transfer is achieved by conduction of the ribs from the area of the flowing fluid of higher temperature through the plate as a material partition of the same material into the area of the fluid with lower temperature. The rod-shaped ribs extend on both sides out of the partition wall into the flow paths, or flow areas, of the heat-transferring fluids. The dividing wall of the flow areas is composed of individual geometric surface elements, the surface elements of the dividing wall preferably forming the basis for the geometry of the ribs. The division into surface elements is advantageous as an intermediate stage in the construction; this division then no longer plays a role in manufacture. The ribs are thus made on both sides of the partition and the partition is constructed from a large number of individual surfaces with ribs resulting therefrom.
The ribs are preferably aligned vertically along the flow direction of the fluids and several ribs are designed as a row of ribs transversely to the flow direction. Several rows of ribs are arranged offset to one another along the direction of flow, so that a matrix of ribs around which flow flows is formed.
The matrix is designed in a particularly preferred manner in such a way that the cross sections of the ribs overlap, viewed in the direction of flow, and channels through which the fluids flow are thus formed between the adjacent ribs. The channels are designed in such a way that the arrangement achieves a guiding of the fluid flow which prevents the flow from separating on the rear side of the ribs or the pointed corner of the triangle facing away from the flow.

The laminar flow without flow separation is particularly advantageous due to the forced guidance of the fluids in the channels combined with the optimized heat conduction with the ribs passing through the partition walls.

The heat transfer from one fluid flow to another is also referred to as dual flow transfer, with heat exchangers according to the concept of the invention also being able to be designed in the same way as three or multiple flow heat exchangers.

The advantages of the invention are in particular that heat can be transferred between different fluids in a highly efficient manner via continuous, heat-conducting ribs, the fluids being reliably separated from one another in terms of material by plates or partition walls. Generative manufacturing processes enable the creation of geometrically more complex structures of flow-optimized ribs with partition walls with optimized costs and expenditure of time.

• 1: Platten-Rippen-Wärmeübertrager,
• 2: Querschnitt eines Platten-Rippen-Wärmeübertragers,
• 3: Querschnitt von Einzelfläche und Rippe als Basisraute und Rippenraute im Niederdruckströmungsbereich,
• 4: Querschnitt von Einzelfläche und Rippe als Basisraute und Rippenraute im Hochdruckströmungsbereich,
• 5: Rippe mit Rippenkapitell im Niederdruckströmungsbereich,
• 6: Wandbereich und eine Rippe im Niederdruckströmungsbereich,
• 7: Rippe mit Rippenkapitell im Hochdruckströmungsbereich,
• 8: Wandbereich und eine Rippe im Hochdruckströmungsbereich,
• 9: Rippensäulen mit Trennwänden,
• 10: Ausschnitt Platten-Rippen-Wärmeübertrager mit Primärrippen und Sekundärrippen.

Further details, features and advantages of embodiments of the invention emerge from the following description of exemplary embodiments with reference to the associated drawings. Show it:

• 1 : Plate-fin heat exchanger,
• 2 : Cross section of a plate-fin heat exchanger,
• 3 : Cross-section of individual surface and rib as basic diamond and rib diamond in the low-pressure flow area,
• 4th : Cross-section of individual surface and rib as basic diamond and rib diamond in the high-pressure flow area,
• 5 : Rib with rib capital in the low-pressure flow area,
• 6 : Wall area and a rib in the low pressure flow area,
• 7th : Rib with rib capital in the high pressure flow area,
• 8th : Wall area and a rib in the high pressure flow area,
• 9 : Rib columns with partitions,
• 10 : Detail of plate-fin heat exchanger with primary fins and secondary fins.

In 1 is a plate-fin heat exchanger 1 which essentially consists of three areas. A cuboid heat-transferring area is laterally bounded by a connection and distribution area 11 which have fluid connections and at the same time distribute the fluids to the flow areas. The heat-transferring area is cuboid and is formed from horizontal delimitation plates 2 above and below as well as the side boundary plates as side walls 3 . In the representation according to 1 is only the upper horizontal delimitation plate 2 and a side wall 3 shown. The heat-transferring fluids are supplied via the fluid connection and the distributor of the first connection and distribution area 11 in the plate-fin heat exchanger 1 abandoned and via the second connection and distribution area 11 discharged. The heat transfer takes place during the longitudinal flow of the fluids in the direction of flow 9 , for example in the countercurrent principle. The entire heat exchanger 1 is produced with a generative manufacturing process in one operation, so that no assembly of the otherwise common individual components of the heat exchanger is required. The heat exchanger is particularly advantageously manufactured from aluminum or copper alloys by means of laser melting or laser sintering in order to achieve high thermal conductivity.

In 2 is the plate-fin heat exchanger 1 shown in cross section. The connection and distribution area 11 merges into the heat-transferring area in the cutting plane. The section plane shows the horizontal partition walls 8th those between the horizontal delimitation plates 2 are arranged above and below. Between adjacent partitions 8th are the flow channels 6 , also referred to as flow areas, in which the fluids are guided. In the flow channels 6 are ribs 7th arranged in rows transverse to the direction of flow. Ribs 7th extend vertically and rod-shaped continuously from the lower horizontal delimitation plate 2 up to the upper horizontal delimitation plate 2 through the partitions 8th through. Ribs 7th penetrate the partition walls geometrically in a vertical direction 8th and thus alternately pass through flow channels 6 of the heat-transferring fluids, the fluids being for example under high pressure and high temperatures on the one hand and under low pressure and lower temperatures on the other hand. Heat is transferred from the high pressure fluid to the low pressure fluid between the adjacent flow areas with fluids with different pressures and temperatures. The flow channels 6 for the low-pressure fluid are with a larger flow cross-section due to a larger distance between the flow channel 6 delimiting partitions 8th designed compared to the flow channels 6 for the fluid under high pressure. In the representation according to 2 are alternately flow channels 6 for high pressure and low pressure, which are flowed through in countercurrent, the top and bottom channels each forming half a flow channel for low pressure. In summary, the task of the plate-fin heat exchanger specified by the process is 1 the cooling of a high pressure stream and the warming up of a low pressure stream. For example, the volume flow of the high pressure flow is ten times lower than that of the low pressure flow. Therefore the high pressure channels have lower channel heights.
The plate-fin heat exchanger 1 consists of individual parallel, horizontally stacked flow channels 6 , wherein high pressure and low pressure channels are preferably arranged alternately. The low-pressure flow has two inlets and two outlets, the high-pressure flow has an inlet and an outlet and is arranged between the connections for the low-pressure flow.

In 3 is a detail of a horizontal section in the direction of flow 9 shown in a flow channel for the low pressure flow.
There are two ribs 7th with solid lines with their rib cross-section 13 shown. The geometry of the individual surfaces 12 that make up the partition 8th is constructed is shown with a dashed line. The individual areas 12 and the rib cross-sections 13 are shown as diamonds in the embodiment shown. The basic diamond 15th the single area 12 goes over into the ribbed diamond 16 , which has a pointed leading edge 4th and a pointed trailing edge 5 having. The longitudinal diagonal of the diamond is in relation to the transverse diagonal of the diamond of, for example, two to one. The depth of the ribs a corresponds to the longitudinal diagonal of the rib cross-section 13 the ribbed diamond 16 . The width of the ribs b corresponds to the transverse diagonal of the ribbed diamond 16 minus the length of the rounded edges. Between the ribs 7th adjacent rows in the direction of flow 9 is a crack 10 with a gap width e educated. The row spacing of adjacent rows c denotes the distance between the surface centers of the diamonds.

In 4th is analogous to the representation in 3 the design of ribs 7th shown for the high pressure flow. In addition to the columns 10 between the ribs 7th adjacent rows of ribs within the ribs 7th Longitudinal gaps designed to increase the surface area of the ribs in the high-pressure channels.
The high pressure flow has a significantly smaller volume flow than the low pressure flow. Therefore, the rib height of the channels can be chosen to be lower. With the same rib design, the heat transfer area would decrease more than the heat transfer coefficient would improve. Therefore, the heat transfer area needs to be increased. This is done using a straight channel as a gap 10 through the middle of the rib 7th placed.

The individual areas 12 are in cross-section in proportion to the rib cross-section 13 in the illustrated embodiment as a basic diamond 15th and ribbed diamond 16 executed. This ratio as the quotient of the dimensions of the ribbed diamond 16 to basic diamond 15th is called the reduction factor beta.

In 5a and 5b is each part of a rib 7th with a rib capital 14th , also referred to as the rib head, shown. Ribs 7th are arranged in the area of the fluid flowing under low pressure. As a rib capital 14th becomes the transition between rib 7th and the partition 8th , or the individual areas 12 the partition 8th designated. The section is the rib cross-section 13 in 5a and the single area 12 in 5b shown. The individual areas 12 in turn are part of the partition 8th into which the rib 7th passes over, or that of the rib 7th is penetrated. Are shown in the 5 only one from one side of the partition 8th extending rib 7th .

In 6a and 6b is a perspective in section of the edge or the side rib in the low-pressure channel with the side wall 3 and the partition 8th shown. The appearance of the ribs 7th correspond in the 5a , 5b , 6a and 6b Ribs from the area of the fluid flowing under low pressure. Furthermore are the rib capitals 14th as a transition to the partition 8th analogous to the representations in 5a and 5b shown.

In the 7a and 7b are high pressure ribs with a gap 10 as well as in the 8a and 8b Edge ribs at the transition into the side wall 3 shown. Ribs 7th each go over into the rib capital 14th which in the partition 8th rises.

In 9a, b and c are the ribs 7th shown as rib columns extending from the horizontal delimitation plates 2 Extending vertically like a column and thereby several partitions 8th penetrate. Between the partitions 8th are channels as flow channels 6 formed, in which alternately the heat-transferring fluid flows under high pressure and low pressure. The flow channels 6 with a greater distance between the partition walls 8th to each other are for the higher volume flow at low pressure and the flow channels 6 with a smaller distance between the partitions 8th to each other are for the lower volume flow at high pressure. The flow channels 6 along the upper and lower horizontal boundary plates 2 are half-dimensioned low-pressure channels.

In 10 is a section from a plate-fin heat exchanger 1 shown, with an upper horizontal delimitation plate 2 and a side wall 3 are shown. Ribs 7th are in different levels once as a front row of ribs 17th in a row in section and in between as a back row of ribs 18th shown in the side view. Ribs 7th in 10 are through secondary ribs 19a , 19b , 19c and 19d enlarged in their surface. There are also partitions 8th provided between which the flow channels 6 form. In the area of the horizontal upper limit plate 2 are rib capitals 14th formed which the ribs 7th with the horizontal limiting plate 2 connect. All horizontal or essentially horizontal surfaces are on their underside in a fabrication angle (alpha) α of preferably 45 ° inclination to the vertical executed due to manufacturing. This applies to the partition walls, for example 8th , the secondary ribs 19th and the rib capitals 14th .
In the illustrated embodiment of the invention there is a division of the boundary plates 2 and the side walls 3 . These preferably consist of an inner layer 20th made of the same material that conducts heat well as the ribs 7th and an outer layer 21st made of poorly thermally conductive material, the latter being the outer layer 21st the longitudinal heat conduction is reduced and the plate-fin heat exchanger 1 isolated from the outside.

List of reference symbols

1

Plate-fin heat exchanger

2

Horizontal delimitation plate

3

Side wall

4th

Leading edge

5

Trailing edge

6th

Flow channel

7th

rib

8th

partition wall

9

Direction of flow

10

gap

11

Connection and distribution area

12

Single areas

13

Rib cross-section

14th

Rib capital

15th

Basic diamond

16

Ribbed diamond

17th

Front row of ribs

18th

Posterior row of ribs

19a-d

Secondary ribs

20th

inner layer

21st

outer layer

a

Rib depth

b

Rib width

c

Row spacing between adjacent rows

e

Gap width

α

Alpha manufacturing angle

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 4234006 A1 [0004]

Claims (21)

Plate-fin heat exchanger (1) with a top and a bottom plate as horizontal boundary plates (2) and side walls (3) as well as an arrangement of several ribs (7) arranged perpendicular to the flow direction (9), which extend vertically and rod-shaped between the horizontal delimitation plates (2), at least one partition (8) between the horizontal delimitation plates (2) being designed as a plate which is penetrated by the ribs (7) and which forms at least two flow channels (6) through which fluid flows can flow, which materially are separated by the partition (8), the ribs (7) having a rib depth (a) and a rib width (b) in the flow direction (9), several ribs (7) being arranged in a row of ribs transversely to the flow direction (9) and several rows of ribs are arranged one behind the other in the flow direction (9) at a row spacing (c) and that the ribs (7) of adjacent rows of ribs are offset from one another in such a way are arranged so that the cross-sections of the ribs (7) overlap in the flow direction (9) and a gap (10) with a gap width (e) through which fluid can flow is formed between adjacent ribs (7). Plate-fin heat exchanger (1) according to Claim 1 , characterized in that the ribs (7) are designed as a triangle in cross-section and have a pointed leading edge (4) and a pointed trailing edge (5). Plate-fin heat exchanger (1) according to Claim 1 or 2 , characterized in that the partition (8) is made up of several individual surfaces (12), the individual surfaces (12) being aligned horizontally and the transitions of the individual surfaces (12) into the rib (7) by a manufacturing angle (alpha ) are inclined. Plate-fin heat exchanger (1) according to one of the Claims 1 to 3 , characterized in that the rib cross-section (13) is diamond-shaped. Plate-fin heat exchanger (1) according to Claim 4 , characterized in that the corners of the rhombus of the rib cross-section (13) are rounded with the larger angle. Plate-fin heat exchanger (1) according to Claim 4 or 5 , characterized in that the ratio of the rib depth (a) as the longitudinal diagonal of the rhombus to the rib width (b) as the transverse diagonal of the rhombus of the rib cross-section (13) is between 1.5 and 3. Plate-fin heat exchanger (1) according to one of the Claims 1 to 6 , characterized in that a rib capital (14) is formed at the transition of the ribs (7) into the horizontal upper delimitation plate (2). Plate-fin heat exchanger (1) according to one of the Claims 3 to 7th , characterized in that the individual surfaces (12) of the partition (8) are designed as basic diamonds (15), the rib diamonds (16) being designed to be a reduction factor (beta) smaller than the basic diamonds (15). Plate-fin heat exchanger (1) according to Claim 8 characterized in that the individual surfaces (12) on the upper separating surface in the transition from the basic diamond (15) to the rib diamond (16) are designed with a maximum inclination of 45 °. Plate-fin heat exchanger (1) according to one of the Claims 8 or 9 , characterized in that the reduction factor (beta) from the rib diamond (16) to the base diamond (15) is between 0.6 and 0.9. Plate-fin heat exchanger (1) according to one of the Claims 1 to 10 , characterized in that several partition walls (8) are arranged in the heat exchanger (1) and thus several flow areas are formed as floods. Plate-fin heat exchanger (1) according to one of the Claims 1 to 11 characterized in that a high pressure flow and a low pressure flow are formed as fluid flows and the ribs (7) have a vertical gap (10) in the area of the high pressure flow in the flow direction (9). Plate-fin heat exchanger (1) according to Claim 12 , characterized in that the gap (10) is formed in the rib depth (a), the longitudinal diagonal of the rib diamond (16) of the rib (7). Plate-fin heat exchanger (1) according to Claim 12 or 13 , characterized in that the rib (7) in the area of the high pressure flow has a different reduction factor (beta) from rib diamond (16) to base diamond (15) than in the area of the low pressure flow, wherein in the area of the high pressure flow the reduction factor beta is greater in combination with a gap (10) in the rib (7). Plate-fin heat exchanger (1) according to one of the Claims 8 to 14th characterized in that the reduction factor (beta) from the rib diamond (16) to the base diamond (15) is variable in the flow direction (9). Plate-fin heat exchanger (1) according to one of the Claims 1 to 15th , characterized in that the ribs (7) are made of solid material. Plate-fin heat exchanger (1) according to one of the Claims 1 to 16 , characterized in that the outer walls of the heat exchanger, the horizontal delimitation plates (2) and the side walls (3) are made up of an outer layer (21) and an inner layer (20), the outer layer (21) having a lower thermal conductivity as the inner layer (20). Plate-fin heat exchanger (1) according to Claim 17 , characterized in that the inner layer (20) of the outer walls and the ribs (7) are formed from the same material. Plate-fin heat exchanger (1) according to one of the Claims 1 to 18th , characterized in that secondary ribs (19) are formed on the ribs (7), the secondary ribs (19) being designed to be inclined relative to the horizontal by a manufacturing angle (alpha). Method for producing a plate-fin heat exchanger (1) according to one of the Claims 1 to 19th , characterized in that the outer walls, the partition (8) and the ribs (7) are produced as one piece and in one operation by means of laser sintering or laser melting as a generative manufacturing process. Procedure according to Claim 20 , characterized in that only the inner layer (20) of the horizontal delimitation plates (2) together with the ribs (7) and the partition (8) are produced by means of laser sintering or laser melting as a generative manufacturing process.

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