Patent Application
20190003785
The present invention relates to a method for producing a heat exchanger comprising tubes. The invention furthermore relates to such a heat exchanger.
For decades now, cooling modules have been manufactured for use of refrigerant and use of coolant, the cooling modules generally being manufactured with materials which are suitable for brazing, for example stainless steel, copper or aluminum. Said materials as semifinished products are coated with brazing metal. The braze plating of the semifinished products consists of a material layer which has a lower melting point than the basic material. For the brazing, the parts are braced and are subsequently brazed in the furnace at a temperature which reaches close to the melting point of the basic material. Among items needed for this purpose are, for example, fluxing agents which break open or dissolve the oxide layer located on the outside. However, fluxing agents have the disadvantage of being harmful to health; in addition, residues can remain on the components, the residues having a negative effect on the required purity of the component. In addition, the brazing can usefully only connect materials of the same type to one another in order, for example, to absorb thermal elongations or not to allow the latter to arise at all. Similarly, from a corrosion aspect, there should not be any differences in potential between components of varying materials. The brazing can proceed successfully only if various boundary conditions, as follows, are observed: degreasing the parts, stacking and bracing the braze-plated semifinished products by means of brazing frames, brazing in the furnace at around 650° C. for several hours, checking the tightness of the parts and optionally re-brazing the parts should they not be tight.
This process is highly time-consuming, costly and resource-intensive, which has a negative effect on the CO2 balance. During the connection of two joining partners composed of different materials, different thermal expansions have to be taken into consideration and compensated for, which can ensure brazing only to a limited extent or has only a certain creep strength.
Such heat exchangers are therefore disadvantageous in that the production thereof is highly costly and resource-intensive and damaging to the environment. Furthermore, only a limited number of materials are suitable for brazing, wherein the components have to be produced from materials of the same type or similar materials in order to achieve reliable brazing. In addition, components composed of different materials cannot be connected to one another at the required quality, if at all.
The present invention is therefore concerned with the problem of specifying, for a method for producing a heat exchanger and for such a heat exchanger, an improved or at least a different embodiment which is distinguished in particular by more economical production.
This problem is solved according to the invention by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.
The present invention is based on the general concept of, in the case of a heat exchanger according to the invention comprising tubes, for the first time deforming and expanding a longitudinal end region of such tubes by means of an expanding mandrel in such a manner that to connection of the individual tubes is possible exclusively via the expanded, in particular plane, connecting regions, and therefore, in this case, a tube plate which up to now has been used in this region can be entirely dispensed with. This makes it possible not only to reduce the diversity of parts, but in addition also to reduce the manufacturing costs. The heat exchanger according to the invention is produced by an adhesive layer first of all being applied to an outer side of the individual tubes by lamination of an adhesive sheet or an adhesive film. The lamination of the adhesive layer onto the outer side of the tubes constitutes a particularly economical manufacturing process which also makes it possible to apply a particularly thin, but nevertheless uniform adhesive layer. The tubes are subsequently expanded on the longitudinal end sides in the respective connecting region by means of an expanding mandrel, thus resulting in flat connecting regions via which the individual tubes can later lie against one another and can be adhesively bonded to one another. The tubes are then arranged parallel to one another such that they lie against one another via their respective connecting regions and at the same time form channels between the individual tubes and outside the connecting regions, through which channels a fluid can flow perpendicularly to the tubes. In order then to be able to connect the individual tubes to one another, the adhesive layer is heated at least in the connecting regions, whereupon the individual tubes are fixed to one another via their respective connecting regions. By means of the expanded connecting regions, the individual tubes are already held at a distance from one another, and therefore a tube plate which has been used up to now in the longitudinal end region of the tubes can now be completely omitted. In addition, by means of the use of an adhesive layer for connecting the individual tubes, a brazing connection which has been used up to now in this region can be dispensed with, as a result of which, in turn, considerable advantages can be realized. For example, different materials, in particular materials with different coefficients of thermal expansion, can now also be easily connected to one another without there needing to be concern about stresses or cracks in the region of the connection. Furthermore, the adhesive layer constitutes an electrical isolator which prevents galvanic corrosion (contact corrosion) in metals of different potentials. In addition, removal of fluxing agent residues can also be omitted, as can a complicated preparation of the brazing points, for example by degreasing.
The heating of the adhesive layer preferably leads to a change in shape and/or change in structure of the adhesive layer, which permits and/or facilitates connection of the tubes. Such a change to the adhesive layer is, for example, softening and/or melting and/or expansion and/or hardening of the adhesive layer. The connection between the components by means of the adhesive layer preferably achieves a stable state after the adhesive layer cools following the heating. This is the case in particular whenever the adhesive layer cures.
The connection of the tubes by means of thermal adhesive bonding furthermore has the advantage that they can be separated from one another when required simply and/or without residues of the adhesive layer. This advantageously takes place by the fact that the adhesive layer is heated again, wherein the adhesive layer is heated in such a manner that the adhesive layer can be separated from at least one of the components. It is thereby in particular possible to dismantle the heat exchanger after expiry of its service life into its individual parts simply and neatly and also according to type and to thereby better recycle said heat exchanger.
The adhesive layer has at least one adhesive means which, for curing, requires a temperature of between 80° C. and 400° C. in order to connect the associated connecting regions. Examples of such adhesive means are Makrofol®, Bayfol®, Kleberit 701.1-701.9 and the like. The adhesive layer advantageously has an adhesive which has thermoplastic properties. That is to say that the adhesive can be deformed above an adhesive-specific temperature which preferably corresponds to the temperature during heating of the adhesive layer in order to connect the components.
The method according to the invention for connecting the tubes furthermore makes it possible to heat the adhesive layer for a relatively short time. The duration of the heating is advantageously selected here in such a manner that a sufficient connection is achieved. In particular, it is possible by means of the method according to the invention to heat the adhesive layer for fewer than 10 minutes. Such a short duration of heating the adhesive layer leads to reduced consumption of energy, and therefore the heat exchanger can be produced in a cost-effective and environmentally friendly manner. Such a short heating duration is achieved in particular by an appropriate choice of the adhesive layer and/or of the layer thickness of the adhesive layer.
Use is preferably made of adhesive layers which have a relatively small layer thickness. The method according to the invention permits adhesive layers with a layer thickness of 5 μm or less to be used. In particular, use is made of adhesive layers with a layer thickness of between 5 μm and 500 μm.
In order to improve the connection between the tubes and/or in order to achieve a desired relative positioning of the tubes relative to each other, the tubes are pressed against each other via their connecting regions with a contact pressure. It is also conceivable to press the tubes against one another during and/or after heating.
The contact pressure here can be arbitrarily large or small. The limits of the contact pressure are provided here firstly by the fact that the contact pressure is intended to lead to an improved connection of the tubes, and, secondly, undesirable damage to same is not intended to be caused. The method is preferably configured in such a manner here that contact pressures of between 0.1 N/mm2 and 0.7 N/mm2 are used for this purpose.
In preferred variants, the contact pressure is produced by the expanding mandrels which are already used for expanding the longitudinal end regions and which are pushed into the respective tubes, wherein the contact pressure is realized by expansion of the tube. Refinements in which the expanding mandrel is additionally used for heating the adhesive layer are particularly preferred. That is to say that the expanding mandrel can be heated, and therefore upon or during the pushing of the expanding mandrel into the associated tube, the adhesive layer is heated and the contact pressure realized at the same time. As a result, the connection of the tubes is realized in just a few method steps and as simply and effectively as possible, in particular within a reduced time.
The adhesive layer can also be heated in any other manner. For example, it is possible to heat the adhesive layer in an furnace. The heating of the adhesive layer in an furnace makes it possible in particular to carry out other method steps for producing the heat exchanger in the furnace.
In order to improve the adhesive connection and/or in order to shorten the time required for producing the adhesive connection, the adhesive layer can be cooled after heating. This cooling can be realized in any manner. For example, cooling can be achieved by the fact that the heating of the adhesive layer is time-limited. The cooling can also take place actively by the components being guided or arranged in an environment having a reduced temperature.
Specific cooling of the adhesive layer can also take place by the fact that a cooling device is brought into contact with the components or the adhesive layer.
In an advantageous development of the solution according to the invention, a fin structure, for example corrugated fins, is introduced between two adjacent tubes and is adhesively bonded to said tubes via the adhesive layer arranged in each case on the outside of the tubes. This makes it possible to achieve a particularly good transfer of heat into the flow channel formed by two adjacent tubes in each case.
Expediently, at least part of a collector is arranged in the region of the connecting regions, said part comprising the connecting regions which are each arranged on the same side, and said part lying with an edge against the adhesive layer of a connecting region of a tube and being adhesively bonded to the latter. In this case, it is therefore possible not only to connect, that is to say to adhesively bond, the individual tubes to one another via their respective connecting regions, but additionally also to adhesively bond a collector, for example a water box or at least part of same, thereto. By this means, the production of the heat exchanger according to the invention is considerably further simplified, as a result of which the economical efficiency thereof can be increased in turn.
The advantages of the heat exchanger according to the invention and of the production method thereof reside in a simpler and more cost-effective design. By means of this method, as known in general in adhesive bonding, a wide variety of materials having different coefficients of thermal expansion and corrosion potential can be connected to one another, with at the same time extremely thin layer thicknesses. For the electronic cooling, for example, the processing of copper material as a functional surface for the brazing or sintering of electronic components is required time and again. However, this processing is not possible with current brazing furnaces since impurities due to the processed copper lead to corrosion to the aluminum components. On account of the thin thicknesses of the adhesive layer, high thermal conductivity is ensured, which is of great advantage in particular in stacked-plate coolers. In addition, the required high tightness, which is generally produced only in the case of welded or brazed components, is also ensured. By means of the small thickness of the adhesive layer, in particular in the form of an adhesive sheet, the adhesive bond is substantially more cost-effective than, for example, epoxy or silicone adhesive. Application of the adhesive in bead form would require a much higher amount of material than is necessary. This therefore saves material, resources and therefore ultimately costs. Furthermore, the processing of the adhesive is considerably simplified since the processing of the adhesive does not require any machines (pump, nozzle, valve), merely the pressing together of the parts. Furthermore, savings are produced by means of a more rapid and simpler processing of the parts; in particular, curing times in the furnace, of several hours, for the crosslinking are not required. The laminated adhesive layer requires only approx. 3 minutes under a corresponding heated device for the adhesive bonding of the individual parts, said device applying the pressure for the time mentioned.
Further important features and advantages of the invention emerge from the dependent claims, from the drawings and from the associated description of the figures with reference to the drawings.
It goes without saying that the features mentioned above and those which have yet to be explained below are usable not only in the respectively stated combination but also in other combinations or on their own without departing from the scope of the present invention.
Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the description below, wherein the same reference numbers refer to identical or similar or functionally identical components.
In the drawings, in each case schematically:
According to
The heat exchanger 1 according to the invention is produced here as follows: first of all, in a method step a), an adhesive layer 7 is applied to an outer side of the individual tubes 2 by lamination of an adhesive sheet 8 or an adhesive film 9. Such a lamination of the adhesive layer 7 can not only take place here economically, but also extremely precisely and with an extremely small layer thickness. Subsequently, the tubes 2 in method step b) are expanded on the longitudinal end sides in their respective connecting region 5 by means of an expanding mandrel 10, specifically in such a manner that the connecting regions 5 of two adjacent tubes 2 lie flat against each other via the adhesive layer 7 arranged in between. The tubes 2 in method step c) are now arranged parallel to one another such that they lie against one another via their respective connecting regions 5. Subsequently, in method step d), the adhesive layer 7 is heated at least in the connecting regions 5 for the adhesive bonding of the tubes 2 and, as a result, the individual tubes 2 are fixed with respect to one another.
The adhesive layer 7 can be heated here, for example, to a temperature of between 80° C. and 400° C., wherein the warming or heating has to be applied only for a short time, for example less than 10 min, in particular 2 to 3 min. During the adhesive bonding, the connecting regions 5 can be pressed against one another with a contact pressure of between 0.1 N/mm2 and 0.7 N/mm2, for example by means of the individual expanding mandrels, as a result of which a more stable adhesive bond can be achieved. Customarily, however, the pressure in terms of the manufacturing is not applied by the expanding mandrels 10, but rather onto the stack from above and then the latter is brought to a temperature (cf.
The adhesive layer 7 is preferably applied here with a layer thickness of between 5 μm and 500 μm, that is to say partly with a very small layer thickness which, however, permits electrical insulation and a reliable connection and a certain elasticity between the components adhesively bonded to one another. The electrical insulation is particularly of great advantage here if, for example, tubes 2 and/or other components of different materials, that is to say with different electrical potentials, are intended to be connected to one another.
For example, a fin structure 11, in particular in the manner of corrugated fins, can be introduced in the channels 6, that is to say between the individual tubes 2, said fin structure likewise being fixed to the opposite outer sides of two adjacent tubes 2 via the adhesive layer 7. The fin structure 11 can be introduced here before the tubes 2 are adhesively bonded to one another or after same.
Looking once again at
With the production method according to the invention and the heat exchanger 1 according to the invention, the latter can therefore be produced simply and more cost-effectively, with it being possible at the same time to connect a wide variety of materials having different coefficients of thermal expansion and corrosion potential to one another, with at the same time a minimum use of adhesive. In addition, the lamination of the adhesive layer 7 onto an application of such an adhesive in bead form, which is associated with a significantly increased requirement of material, can be dispensed with. This also simplifies the processing of the adhesive considerably since, for example, no pumps, nozzles or valves which have to be cleaned in a complicated manner retrospectively are required. By means of the comparatively rapid curing time of the adhesive layer 7 according to the invention, the cycle time for the production of the heat exchanger 1 according to the invention can also be reduced, which likewise has an advantageous effect on the production costs. In comparison to brazing connections which have been used up to now in this region, the adhesive layer 7 which is used is also significantly more cost-effective than, for example, expensive brazing metal and, in addition, a complicated removal of fluxing agent residues is omitted. The significantly reduced amount of energy which is required can also be considered to be a further advantage of the adhesive connections. It is above all also possible to use materials which cannot be brazed but which can be tightly connected to one another by means of the adhesive connection according to the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102015215045.3 | Aug 2015 | DE | national |
This application claims priority to International Application No. PCT/EP2016/068667 filed on Aug. 4, 2016, and to German Application No. DE 10 2015 215 045.3 filed on Aug. 6, 2015, the contents of each of which are hereby incorporated by reference in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/068667 | 8/4/2016 | WO | 00 |
