WO2015132086A1

WO2015132086A1 - Method and device for manufacturing a heat exchanger

Info

Publication number: WO2015132086A1
Application number: PCT/EP2015/053623
Authority: WO
Inventors: Steffen Ensminger; Andreas Jünemann; Michael Schmidt; Klaus Irmler
Original assignee: MAHLE Behr GmbH & Co. KG
Priority date: 2014-03-07
Filing date: 2015-02-20
Publication date: 2015-09-11
Also published as: DE102014204259A1

Abstract

The invention relates to a method for manufacturing a heat exchanger, comprising the following steps: a) making available a heat exchanger arrangement (1) with at least two components which are arranged adjacent to one another in an arrangement direction (A) and are to be soldered to one another, b) arranging a first contact pressure plate (6a) on the heat exchanger arrangement (1), which contact pressure plate (6a) bounds said heat exchanger arrangement (1) in the arrangement direction (A), and arranging a second contact pressure plate on the heat exchanger arrangement (1), which second contact pressure plate bounds said heat exchanger arrangement (1) counter to the arrangement direction (A), with the result that the heat exchanger arrangement (1) is arranged in a sandwich-like manner between the two contact pressure plates (6a, 6b), c) providing a clamping device (7) which comprises at least one clamping belt (8a, 8b, 8c) on the contact pressure plates (6a, 6b) in such a way that said clamping device (7) generates in each case a contact pressure acting inwards on the two contact pressure plates (6a, 6b) towards the heat exchanger arrangement (1), with the result that said contact pressure is transmitted by the two contact pressure plates (6a, 6b) onto the components to be soldered, d) soldering the at least two components of the heat exchanger arrangement (1) which are adjacent in the arrangement direction (A).

Description

Method and device

for producing a heat exchanger

The invention relates to a method and an apparatus for producing a heat exchanger.

In addition to the simple principle of direct heat transfer, which is accompanied by an immediate heat transfer between the streams, use heat exchangers of indirect heat transfer, in which the respective streams are separated by a heat-permeable wall. A typical field of application is found in modern heat exchangers, for example as a waste heat utilization device or as a cooling system of conventional internal combustion engines. Such heat exchangers can be designed in an application-specific manner in the form of so-called plate heat exchangers or layer heat exchangers, but also in the form of so-called tube heat exchangers. For heat exchangers of the latter category, a distinction can be made between shell-and-tube heat exchangers, U-tube heat exchangers and jacket tube heat exchangers.

All these types of heat exchangers have in common that they comprise a plurality of metallic components, such as in the form of flat tubes or metal fins, which are soldered together during the assembly of the heat exchanger. Exhaust gas heat exchangers are usually made of stainless steel for corrosion reasons. As part of an industrial series production of such heat exchangers, the entire soldering process is usually carried out in a high temperature soldering oven. For this purpose, the components before the actual soldering in a kind of clamping frame made of a material with a low coefficient of thermal expansion, for example, a carbon fiber reinforced carbon - known in the art as "CFC" - be installed. If the components are heated in a brazing furnace, their thermally induced expansion causes them to fail. S pressed against the frame. This means that an external pressure is exerted on the components to be soldered within the frame by said frame, which favors the formation of high-quality solder joints.

Against this background, DE 103 28 274 A1 describes a method for producing a Schichtwärmeübertragers, the stacked separating and cover plates and collection boxes composed. To produce the Schichtwärmeübertragers the separation and cover plates are first stacked to form a layer block and then attached solder on or between the plates to be soldered. In a next step, we fixed the layer block by means of gluing or welding and then soldered the layer block. Finally, the headers are welded or soldered to the layer block.

Another heat exchanger is described in DE 10 2009 050889. In this alternately belotete plates and ribs are piled into a block and then soldered in a high temperature soldering oven.

DE 41 20 748 discloses a similar process for the production of heat exchangers, the pipe system consists of flat tube coils.

As problematic in such soldering processes, however, prove that the components to be soldered typically have not inconsiderable component tolerances, which in the individual embodiments of the heat exchanger has different pronounced expansion effects and thus significantly varying, acting on the components contact pressures result if these in be heated to said frame. Ultimately, this can lead to significant quality variations of the solder joints produced during soldering in the individual embodiments of the heat exchanger. In extreme cases, for example, if the components to be soldered Have excess pressure, the contact pressure can assume such high levels that it leads to a plastic deformation and thus damage to the heat exchanger.

It is therefore an object of the invention to provide an improved embodiment of a method and an apparatus for producing a heat exchanger, in which in the course of mass production in large numbers heat exchangers can be produced, whose components are connected by high-quality solder joints cohesively.

The basic idea behind the invention is therefore to sandwich the heat exchanger arrangement between two pressure plates before carrying out the soldering process and to exert a well-defined contact pressure on the heat exchanger arrangement from outside using a tensioning device via the two pressure plates. This is transferred to the components to be soldered the heat exchanger assembly, which can be reliably produced a high-quality solder joint.

Another advantage of the invention is that the clamping bands essential to the invention, in contrast to conventional rigid solder racks made of a ceramic or carbon elastic properties. In this way it can be prevented that the contact pressure generated exceeds a maximum permissible value, whereby an undesired plastic deformation of the heat exchanger can be prevented.

A method according to the invention comprises the following steps:

a) providing a heat exchanger assembly with at least two along a direction of arrangement adjacent to each other and to be soldered together components. These components may be any components of the heat exchanger made of a metal, which in the course of the soldering process still to be performed to be materially connected to each other. Depending on the design of the heat exchanger, these components may have a certain geometric shape. For example, in the case of a plate heat exchanger, the components to be soldered may be components of a conventional fin-disc arrangement. Such a rib-disk arrangement may comprise a plurality of fluid disks stacked on top of one another in a stacking direction, wherein between two adjacent fluid disks a rib structure is provided which is to be soldered to the fluid disks.

b) placing a first pressure plate on the heat exchanger assembly, which limits these along the arrangement direction, and arranging a second pressure plate on the heat exchanger assembly, which limits this against the arrangement direction, so that the heat exchanger assembly is sandwiched between the two pressure plates , The pressure plates themselves may be made of a metal, a ceramic or a carbon, in the latter case, for example, carbon fiber reinforced carbon.

c) attaching a clamping device, which comprises at least one clamping band, on the heat exchanger assembly, such that each generates a force acting on the two pressure plates inwardly to the heat exchanger assembly back pressure. The use of a tension band allows a reproducible generation of a well-defined and homogeneous, acting on the pressure plates and thus on the components of the heat exchanger contact pressure. In the present context, the term "pressure plates" also includes components with a not completely planar, ie plate-like, geometric shape The term "pressure plates" also includes plate-like embodiments in the present context, on the top or bottom of which elevations or depressions are provided give the plate a three-dimensional shape. d) soldering at least two adjacent to the arrangement direction of adjacent components of the heat exchanger assembly. Typically, the soldering may take place in a high-temperature soldering furnace, in which the components to be soldered of the heat exchanger assembly are heated above 900 ° C.

In a preferred embodiment, it is proposed to attach the at least one tension band to the heat exchanger arrangement in such a way that it encloses it along a circumferential direction. In a manner that can be produced by tensioning the tension band, a uniform contact pressure acting on the pressure plates and on the heat exchanger arrangement arranged between them, from the tensioning band.

According to an advantageous development, it is advisable to include in method step c) the following two substeps c1) and c2:

c1) lashing and tensioning of the at least one tension band; and

c2) joining the two ends of the at least one tension band, in particular by means of welding, crimping or Aneinanderklammern.

When lashing and the associated clamping according to step c) can be exploited that the tension or tension applied during lashing scales directly with the force acting on the heat exchanger assembly contact pressure. In other words, the harder the strap is lashed around the heat exchanger assembly, the higher the applied contact pressure. By said clamping or lashing so can be set in a flexible manner, the desired contact pressure. The joining together of the two ends of the at least one strap, such as by welding, crimping or Aneinanderklammern makes sure that the strap does not yield when the components to be soldered expand when heated and press outward on the strap. For the automated and comfortable execution of lashing and tightening according to step c1) is proposed in a particularly preferred embodiment, this a compressed air or electrically driven

Use clamping mechanism by means of which the contact pressure generated by the clamping band can be set very precise and reproducible.

For the reproducible generation of a predetermined contact pressure - for example, in the course of mass production of the heat exchanger in large quantities - it is essential that the tension band, before it is stretched, is also attached in a reproducible manner to the individual heat exchanger assemblies. This can be achieved in an advantageous manner by at least one guide device is provided on a remote from the heat exchanger assembly outside of the two pressure plates at least one guide means, in which the clamping band for clamping according to step c) can be inserted.

In order to be able to place the at least one strap quickly and easily in the guide device, it is further proposed to provide this with a guide block which extends along the transverse direction on the outside of the pressure plate, in such a way that the guide block with a first Side on the outside of the pressure plate is applied. The tension band can then be brought to bear against the second block on the guide block on one of the first side opposite, facing away from the pressure plate.

In a further preferred embodiment, the two pressure plates have a substantially rectangular shape with respect to a plan view of the heat exchanger arrangement defined by the arrangement direction. With regard to this plan view, the at least one tension band on the two pressure plates then extends in each case along an orthogonal to the arrangement direction of the components to be soldered transverse direction of the pressure plates. If the heat exchanger arrangement is considered in a cross section along the longitudinal direction tion, so summarizes the clamping band, the heat exchanger assembly including the two pressure plates of the heat exchanger assembly completely circumferential. Such a geometric configuration allows easy mounting or dismounting of the tension band on the heat exchanger assembly;

Particularly expedient, the pressure plates and / or the clamping bands can also be designed such that they remain after the soldering process on the heat exchanger. An elaborate disassembly of the pressure plates or the clamping bands can be omitted in this case, which not insignificantly simplifies the industrial production of the heat exchanger.

A particularly uniform surface pressure acting on the components to be soldered contact pressure can, however, be achieved if on the outer sides of the two pressure plates along the longitudinal direction at least two, preferably three, spaced apart clamping bands are provided, located on the outer sides of the two pressure plates each extend along the transverse direction.

An additional contact pressure can be generated if a material is selected for the tension band which has a lower coefficient of thermal expansion than the material of the components of the heat exchanger arrangement to be soldered. Upon heating of the heat exchanger assembly including the tension band, such as in a brazing furnace, this causes the components of the heat exchanger assembly to expand more than the surrounding tension band.

It is therefore particularly expedient to use an austenitic stainless steel as the material for the at least two components of the heat exchanger arrangement and another steel, preferably a ferritic steel, as the material for the tension band, since austenites have a higher coefficient of thermal expansion than ferrites. In a further preferred embodiment, the heat exchanger assembly is part of a plate heat exchanger or a layer heat exchanger or a tube heat exchanger, in the latter case in particular a Rohrbündelwärmeübertragers, U-tube heat exchanger or Mantelrohrwärmeübertragers.

In a further embodiment, the pressure plates can be made of the same material as the heat exchanger to be soldered, that is, for example austenitic stainless steel, and remain after the soldering process on the heat exchanger, whereas the tension bands are removed again. In one variant, the clamping straps remain on the heat exchanger.

The invention further relates to an arrangement for soldering components of a heat exchanger. The arrangement according to the invention comprises a heat exchanger arrangement which has at least two components arranged adjacent to one another and to be soldered to one another along an arrangement direction. Furthermore, the arrangement comprises a first and a second pressure plate, which limit the heat exchanger arrangement along the arrangement direction, wherein the heat exchanger arrangement is provided along the arrangement direction between the two pressure plates. Finally, the arrangement according to the invention also has a clamping device which has at least one clamping band and surrounds the heat exchanger arrangement including the two pressure plates in such a way that it generates a contact pressure acting inwardly on the two pressure plates for the heat exchanger arrangement.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawings and from the associated figure description with reference to the drawings. It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components.

It show, each schematically

1 shows an example of a heat exchanger arrangement according to the invention, by means of which the method according to the invention can be carried out, in a perspective view,

2 shows the arrangement of Figure 1 in a cross section,

3 shows an expansion temperature diagram for ferritic and austenitic materials.

Figures 1 and 2 illustrate an example of a heat exchanger assembly 1 according to the invention, based on which the inventive method - also exemplified - will be explained. The heat exchanger assembly 1 comprises a plate heat exchanger 2 with a fin-disc arrangement 3.

In alternative variants of the example, the heat exchanger assembly 1 may be part of a shell and tube heat exchanger. The rib-disk arrangement 3 of the heat exchanger arrangement 1 shown in the figures has a plurality of disk tubes arranged adjacent to each other along an arrangement direction A in the form of fluid disks 4 which form fluid channels for a first working medium of the plate heat exchanger 2. A respective rib structure 5 is provided between two adjacent fluid disks 4, on which the two fluid disks 4 are supported and which each form a fluid channel for a second working medium.

Both the fluid disks 4 and the rib structures 5 represent components that are soldered together by means of the method according to the invention in a soldering oven (not shown). For this purpose, the heat exchanger assembly 1 comprises a first and a second pressure plate 6a, 6b, which limit the heat exchanger arrangement 1 along the arrangement direction A. In other words, the heat exchanger assembly 1 is arranged along the arrangement direction A between the two pressure plates 6a, 6b.

As can be seen from FIG. 1, these have a substantially rectangular shape with respect to a plan view of the two pressure plates 6a, 6b. The pressure plates 6a, 6b themselves can be made of a metal, a ceramic o- or a carbon, for example, carbon fiber reinforced carbon. In the present context, the term "pressure plates" also includes components with not completely flat, so plate-like geometric shape, explicitly with a.

For soldering the fluid disks 4 with the rib structures 5, the heat exchanger assembly is equipped with a clamping device 7, which has three clamping bands 8a, 8b, 8c. The latter are provided along a longitudinal direction L on the outer sides 9a, 8b of the two pressure plates 6a, 6b and extend along a transverse direction Q orthogonal to both the arrangement direction A and the longitudinal direction L. The tension bands 8a-8c of the tensioning Direction 7 are in such a way attached to the pressure plates 6a, 6b that they each produce a force acting on the two pressure plates 6a, 6b inside, the rib-disk assembly 3 acting contact pressure p.

For this purpose, each of the three tension bands 8a-8c has a guide device 10a-10f mounted on each of the two outer sides 9a, 9b of the pressure plates 6a, 6b. Each of the guide devices 10a-10f has a guide block 11a-11f which extends along the transverse direction Q onto the outer side 9a or 9b of the pressure plates 6a, 6b. Each guide block 1 1 a-1 1f rests with a first side on the respective outer side 9a, 9b of the two pressure plates 6a, 6b. In contrast, the clamping bands are 8a-8c on one of the first side opposite, facing away from the respective pressure plate 6a, 6b second side on their associated guide block 1 1 a-1 1f. For this purpose, the tension bands 8a-8c, for example, by means of a compressed air or electrically driven tensioning mechanism (not shown) are tensioned, which allows a flexible adjustment of the force acting on the two pressure plates 6a, 6b and this in turn exerted on the heat exchanger assembly 1 contact pressure p ,

In the context of the method according to the invention presented here, the tensioning straps 8a-8c - in the guide blocks 1 1 a-1 1f fitting - are lashed to the heat exchanger assembly 1 and tightened. After such lashing, the two ends of a respective tightening strap 8a, 8c are fixed to each other by means of welding, crimping, abutting one another or another suitable method.

Subsequently, the heat exchanger assembly 1 is introduced in a further process step in a high-temperature brazing furnace, in which the components to be soldered - in particular the fluid disks 4 and the rib structures 5 of the heat exchanger assembly 1 - are soldered together. In a variant of the method, the pressure plates 6a, 6b and, alternatively or additionally, also the clamping bands 8a-8c may remain on the heat exchanger after the soldering process.

An additional contact pressure acting on the rib-disc arrangement 3 during soldering in a soldering oven can be generated by the three clamping bands 8a-8c if a material is selected for them which has a lower coefficient of thermal expansion than the material of the components of the heat exchangers to be soldered Arrangement 1. Because the heating of the heat exchanger assembly 1 including the clamping bands 8a-c in the soldering oven causes the components of the heat exchanger assembly 1 to expand more outwardly than the surrounding clamping band, whereby said additional contact pressure is generated.

It is therefore particularly expedient to use an austenitic stainless steel as the material for the components of the heat exchanger arrangement 1 to be soldered and a ferritic steel as the material for the tension band, since austenites generally have a higher coefficient of thermal expansion than ferrites. This is evidenced by FIG. 3, which shows an expansion-temperature diagram in which the relative change in length of a metal - at an initial length of 100 mm - is shown as a function of its temperature T, on the one hand for a ferritic metal - the corresponding graph is in FIG Figure 3 denoted by the reference numeral 20a - and secondly an austenitic metal whose graph is indicated in Figure 3 by the reference numeral 20b. The graph 20c shows the difference of the graphs 20a, 20b.

Since the crystal structure of a ferrite changes from α (krz) to γ (kfz) at about 900 ° C., this transformation is associated with a volume contraction, for example of about 1% and a length shrinkage, for example of about 0.35% is he- drive the clamping bands 8a-8c at the temperature mentioned an additional contraction. This effect can be exploited in a high temperature soldering oven in which the entire assembly 1, including the clamping bands 8a-8c, is heated to a temperature above 1000 ° C. Said effect causes in the tension bands 8a-8c an additional contraction, whereby the contact pressure generated by them can be increased again.

Claims

claims

1 . Method for producing a heat exchanger,

comprising the following steps:

a) providing a heat exchanger arrangement (1) with at least two components arranged adjacent to one another and to be soldered along an arrangement direction (A),

b) arranging a first pressure plate (6a) on the heat exchanger assembly (1), which limits this along the arrangement direction (A), and arranging a second pressure plate (6b) on the heat exchanger assembly (1), this opposite to the arrangement direction (A) limited, so that the heat exchanger assembly (1) along the arrangement direction (A) between the two pressure plates (6a, 6b) is arranged,

c) attaching a clamping device (7), which comprises at least one clamping band (8a, 8b, 8c), to the pressure plates (6a, 6b), such that these in each case one on the two pressure plates (6a, 6b) inwardly, to Heat exchanger assembly (1) towards acting contact pressure generated so that it is transmitted from the two pressure plates (6 a, 6 b) on the components to be soldered,

d) soldering the at least two along the arrangement direction (A) adjacent components of the heat exchanger assembly (1).

2. The method according to claim 1,

characterized in that the at least one tension band (8a-8c) is attached to the heat exchanger arrangement (1) in such a way that it encloses it completely circumferentially along a circumference.

3. The method according to claim 1 or 2,

characterized in that

the method step c) has the following two sub-steps c1) and c2):

c1) lashing and tensioning of the at least one tension band (8a-8c), c2) joining the two ends of the at least one tension band (8a-8c), in particular by means of welding, crimping or clipping together.

4. The method according to claim 3,

characterized in that

the lashing and clamping according to step c1) using a compressed air or electrically driven clamping mechanism, wherein by means of the clamping mechanism of the pressure plates (6a, 6b) acting contact pressure can be adjusted.

5. Method according to one of the preceding claims,

characterized in that

the two pressure plates (6a, 6b) have a substantially rectangular shape with respect to a plan view of the heat exchanger arrangement (1) defined by the arrangement direction (A),

the at least one tension band (8a-8c) extends in each case along an orthogonal to the arrangement direction (A) transverse direction (Q) on the two pressure plates (6a, 6b) with respect to this plan view, the tension band (8a-8c) encloses the heat exchanger arrangement (1) including the two pressure plates (6a, 6b) in a completely circumferential manner in a cross-section of the heat exchanger arrangement (1).

6. The method according to claim 5,

characterized in that

on the outer sides (9a, 9b) of the two pressure plates (6a, 6b) along a longitudinal direction (L) which extends both transversely to the arrangement direction (A) and to the transverse direction (Q), at least two, preferably three, spaced apart Tension bands (8a-8c) are provided, which extend on the outer sides (9a, 9b) of the two pressure plates (6a, 6b) respectively along the transverse direction (Q).

7. The method according to any one of the preceding claims,

characterized in that

the pressure plates (6a, 6b) and / or the tension bands (8a-8c) remain on the heat exchanger arrangement (1) after the soldering process.

8. The method according to any one of the preceding claims,

characterized in that

on one of the heat exchanger assembly (1) facing away from the outside (9a, 9b) of the two pressure plates (6a, 6b) each have at least one guide means (10a-10f) is provided, in which the clamping band (8a-8c) in step c) is inserted.

9. The method according to claim 8,

characterized in that

the guide device (10a-10f) comprises a guide block (1 1 a-1 1 f) which extends along the transverse direction (Q) on the outer side (9a, 9b) of the pressure plate (6a, 6b), the guide block (1 1 a-1 1 f) rests with a first side on the outer side (9a, 9b) of the pressure plate (6a, 6b),

the clamping band (8a-8c) on one of the first side opposite, from the pressure plate (6a, 6b) facing away from the second side on the guide block (1 1 a-1 1f) is applied.

10. The method according to any one of the preceding claims,

characterized in that

the material of the tension band (8a-8c) has a lower thermal expansion coefficient than the material of the components to be soldered of the heat exchanger assembly (1).

1 1. Method according to one of the preceding claims,

characterized in that

the at least two components of the heat exchanger assembly (1) are made of a stainless steel, preferably austenitic stainless steel, and / or

the at least one tension band (8a-8c) are made of another steel, preferably of a ferritic steel.

12. The method according to any one of the preceding claims,

characterized in that

the heat exchanger assembly (1) is part of a plate heat exchanger or a layer heat exchanger or a tube heat exchanger, in particular a Rohrbündelwärmeübertragers, U-tube heat exchanger and Mantelrohrwärmeübertragers.

13. Arrangement for soldering components of a heat exchanger, comprising a heat exchanger arrangement (1) which has at least two components arranged adjacent to one another and to be soldered together along an arrangement direction (A),

with a first and a second pressure plate (6a, 6b) which delimit the heat exchanger arrangement (1) along the arrangement direction (A), the heat exchanger arrangement (1) being arranged along the arrangement direction (A) between the two pressure plates,

with a tensioning device (7) which comprises at least one tension band (8a-8c) and surrounds the heat exchanger arrangement (1) including the two pressure plates (6a, 6b) in such a way that they move towards the two pressure plates (6a, 6b) inside, to the heat exchanger assembly (1) towards acting contact pressure generated so that it is transferable from the two pressure plates (6a, 6b) on the components to be soldered.