Patent Application
20170160023
Field of the Invention
The invention relates to a method for producing a heat exchanger. The invention also relates to a heat exchanger.
Description of the Background Art
Heat exchangers are used to transfer heat between different fluids. For this purpose, heat exchangers of different designs are known in the prior art.
The known types include, for example, heat exchangers in tube-fin design, tube bundle heat exchangers or heat exchangers in stacked plate construction. These heat exchangers have in common that they are flowed through and/or surrounded by fluids, causing heat transfer to occur between the fluids involved. These known heat exchangers are used, among other things, as charge air coolers, coolant coolers, oil coolers or as radiators, etc.
Heat exchangers are manufactured from metallic and/or non-metallic materials, which are connected to each other, for example, by means of brazing, welding, form-fitting or adhesive bonding. Elements which are connected to one another by brazing, welding or bonding include, for example, tubes, plate elements, fin members, tube bottoms and cover elements.
For joining individual elements by means of a brazing method, either a brazing material can be applied after the joining of the elements, or elements already coated with brazing material can be used. The brazing material is melted under the application of heat, and a permanent bond is produced by the subsequent solidification of the brazing material.
DE 103 28 274 A1 discloses a method for the production of a layer heat exchanger wherein a plurality of plate elements are stacked on top of one another and are provided with a brazing material. This plate stack is then mechanically fixed before finally the plate elements are welded together and/or brazed.
DE 10 2005 048 452 A1 discloses a heat exchanger in stacked-plate construction, the heat exchanger having a plurality of plate elements which are stacked on one another. The plate stack is closed at the top and at the bottom by a respective base plate. The individual plate elements are brazed together and form flow channels within the plate stack, through which one or more fluids can flow.
Alternatively, individual elements can also be connected to one another by adhesive methods.
For example, DE 10 2008 019 556 A1 discloses a component functioning as a heat exchanger which is produced from a stack of firmly bonded plates. In addition, a method for producing the component is disclosed. A polymeric adhesive is applied to the individual elements for bonding. Said elements are then pressed against one another until the adhesive has hardened.
DE 102 28 697 A1 discloses a method for connecting a tube of metal with circumferential fins of a non-ferrous metal as a component of a heat exchanger. The fins are connected to the tube by bonding.
A disadvantage of the devices and methods from the prior art is, in particular, that complicated mounting racks, which are each designed for a specific heat exchanger, have to be produced for the fixing of the elements to one another for brazing and welding. Furthermore, the racks have to withstand the high temperatures during brazing or welding.
The brazing processes for a heat exchanger often take several ten minutes to several hours and are also very energy-intensive. Moreover, the brazing materials used are very expensive. Before the brazing material is applied, cleaning the surface is also necessary. Following the brazing process, it may also be necessary to clean the heat exchanger in order to remove excess brazing material. Furthermore, brazing methods and welding methods are not suitable for bonding just any materials, which severely limits the material selection for the elements of the heat exchanger and the possible material combinations.
When using adhesives, it is disadvantageous that the adhesives have to be laboriously applied to the elements that are to be connected, which can be done, for example, by injection devices and/or spraying devices. Furthermore, the adhesive surfaces thus produced are either unevenly subjected to the adhesive or a very large amount of the adhesive is applied because the layer thicknesses of the adhesives are partly above 2 mm. As a result, the required curing time is also increased, which causes the production process to become more time-consuming and costly.
It is therefore an object of the present invention to provide a method for producing a heat exchanger which is improved over the prior art. In addition, the object of the invention is to provide an advantageous heat exchanger.
An exemplary embodiment of the invention relates to a method for producing a heat exchanger, comprising a connection between two elements of a heat exchanger, the two elements being connectable to one another in at least one respective one contact surface, with an adhesive film being applied to at least one of the elements in the region of the respective contact surface, wherein the two elements are brought into contact with one another by applying pressure and an adhesive bond is produced between the elements by means of the adhesive film.
It is particularly advantageous to use an adhesive film since this is easy to handle and can be adapted in a simple manner to the respective element or the contact surface between the elements. The adhesive film can be applied to one of the elements in a manual or automated manner. It can also be advantageous if the adhesive film is already applied to the starting material of the elements and the elements are subsequently produced using shaping processes such as, for example, embossing methods, cutting methods or stamping methods.
An adhesive bond can be arranged between the elements by the adhesive film which replaces the usual brazed bond. In this process, the brazing material which is otherwise used is thus replaced by the adhesive film. This is particularly advantageous, since the adhesive film can also be applied to impure surfaces, which can be charged, for example, with greases, oils or dirt particles. The step of cleaning and degreasing the surfaces of the elements, which is otherwise customary when using brazing methods, can thus be omitted.
An adhesive film is also particularly advantageous since layer thicknesses which are very uniform and easily reproducible can be produced in a particularly simple manner. This is particularly advantageous with regard to an automated manufacturing process in the context of a large series production.
It is also advantageous if the adhesive film is dry to the touch, the adhesive effect of the adhesive film being activated and/or highly viscous by the application of a compressive force and/or by heating the adhesive film. A touch-dry or, in technical language, tack-free adhesive film is particularly advantageous since the handling of the adhesive film is significantly facilitated. No special precautions have to be taken to prevent the adhesive film from contacting the elements during the process. The adhesive effect of the adhesive film is only activated and/or highly viscous by the application of a compressive force and/or by heating, so that the adhesive effect is produced only during the process. This also facilitates the positioning of the elements relative to each other since unintentional bonding is avoided.
Also, it is preferable that the adhesive film has a layer thickness between 10 μm and 250 μm. An especially thin adhesive film is particularly advantageous because the amount of material used can be kept very low. In particular, compared to conventional bonding methods in which the adhesive is applied by means of a nozzle in beads, a significantly reduced adhesive application can be achieved. The especially thin layer thicknesses can be produced, in particular, by filler-free adhesives. In the bonded state, the adhesive layer between the two elements is particularly thin and is preferably only a few nanometers to about 250 μm.
Very thin layer thicknesses of the adhesive are also advantageous in order to produce very short curing times for the adhesive bonds. For thermoplastic adhesive substances, the curing time can preferably be in a range from 1 minute to 20 minutes. Curing times of less than 5 minutes are particularly preferred in order to ensure the highest possible process speed.
In addition, it is advantageous if the adhesive film is laminated onto one of the elements and/or is inserted into a recess in one of the elements. For this purpose, the adhesive film can advantageously be adhesively bonded to one of the elements with the aid of a further adhesive or simply applied to the latter. By applying the pressure force and/or by heating, an adhesive bond is finally produced with both elements.
Furthermore, it is advantageous if the adhesive film is applied to one of the elements over the entire area in the region of the contact surface, or that the adhesive film is applied to one of the elements in a precisely tailored manner to the respective contact surface.
Depending on the configuration of the elements and the actual contact area between the elements to be bonded, the adhesive film can be applied over a full area to a region of an element or can be tailored specifically to the contact surface. Elements with a full-surface adhesive film can be produced particularly easily in a scale suitable for large series production. The material insert can be further reduced by means of specially trimmed adhesive films.
It is also expedient if a compressive force of 0.005 N/mm2 and 15 N/mm2 is applied to the elements that are brought into contact in order to form a bond. It is particularly advantageous when the pressing force is applied in a heated state. As a result of the heating, the adhesive film is already softened, which makes it possible to immerse the elements in the adhesive layer.
In addition, it is advantageous if the method comprises the following steps: coating at least one element with an adhesive film; bringing the elements into contact; applying a compressive force to the elements; heating the elements and the adhesive film arranged in the contact surface; cooling the elements and the adhesive film; and checking the tightness of the bond formed between the elements, wherein the adhesive film is softened by the heating, the adhesive film being at least partially displaced by at least one of the elements, whereby the layer thickness between the elements after heating is lower than before heating.
The method is particularly oriented to the already known method for the brazing of heat exchangers. In contrast to brazing methods, however, no brazing material is applied, but only an adhesive film which melts at substantially lower temperatures than the brazing material. All the bonds between the elements of a heat exchanger, which have so far been produced by brazing, can also be produced by the proposed adhesive method.
In particular, different materials can be connected to one another in a simple manner. This is particularly advantageous in the case of materials which have very different longitudinal extensions under the influence of temperature or in the case of materials which can act as a galvanic element through the electrically conductive brazing bond.
An exemplary embodiment of the invention relates to a heat exchanger with at least two elements, wherein the heat exchanger is produced according to a method already described, the elements being formed by tubes and/or tube bottoms and/or plate elements and/or cover elements and/or tube supports and/or fin members.
By means of the adhesive process, all known designs of heat exchangers can be produced. The adhesive film acts as a complete substitute for a brazing material used during brazing. The adhesive film can advantageously also be applied to very differently shaped elements so that virtually no geometrical restrictions exist for the elements to be connected by means of the adhesive film.
Furthermore, it is expedient if the adhesive film is formed from an adhesive which includes at least one component or of only one component, and which can be filled or is free of filler. Suitable fillers are heat-conductive flakes or particles. Materials such as boron nitride, aluminum, copper, steel, brass, graphite etc. can preferably be used. A filler-free adhesive is particularly advantageous in order to produce the smallest possible layer thickness of the adhesive film.
It is also advantageous if the heat exchanger has at least one flow channel through which a fluid can flow, the flow channel being fluid-tightly sealed against the environment by the adhesive film that is arranged between the individual elements of the heat exchanger.
By means of the adhesive bond, flow channels can be produced in a simple manner, which are sealed at their interfaces with other elements of the heat exchanger by the adhesive bond produced. The flow channel itself can also be sealed by the adhesive bond, in that, for example, the flow channel is first produced by adhesively bonding two elements. The sealing against the environment can be effected, for example, at the bonding point between a tube and a tube bottom, at the bonding point between two plate elements or at the bonding point between a tube bottom and a cover element forming a collecting box.
The heat exchanger can also have at least one tube, wherein an adhesive film is applied to the tube on at least one of its outwardly directed end regions, the region which is subjected to the adhesive film being inserted into a recess of a tube bottom, and the adhesive film at least partially covering the contact surface between the tube and the tube bottom and forming a fluid-tight seal between the tube and the tube bottom.
The use of adhesive films for producing the bonds between the elements of a heat exchanger can, among other things, advantageously produce a heat exchanger of a tube-fin-type design, or a tube bundle heat exchanger. It is particularly advantageous that elements made of different materials can be joined together by the adhesive bond. For example, the tubes can be formed from a metallic material with a high thermal conductivity, whereas the tube bottom is formed, for example, from a plastic which has particularly good properties with regard to the absorption of the generated forces. By the use of adhesive films, bonds with a high tightness can be produced. Due to the particularly low layer thickness of the adhesive film, the elements can be mounted similar to the brazed plated elements in a brazing process.
Furthermore, the heat exchanger can be formed from a plurality of stacked plate elements, the plate elements being in contact with one another at their edge region, and an adhesive film being arranged between the individual plate elements in the contact region and forming a fluid-tight seal between the plate elements.
Also a heat exchanger in a stacked plate construction can be produced in a simple manner by the use of adhesive films. For this purpose, the plate elements in particular have an adhesive film in their mutual contact region.
Furthermore, it is advantageous if the heat exchanger has a collecting box, wherein the collecting box is formed from a tube bottom and a cover element inserted into a receiving region of the tube bottom, an adhesive film being arranged in the receiving region of the tube bottom, which at least partially covers the contact surface between the cover element and the tube bottom and forms a fluid-tight seal between the cover element and the tube bottom.
Such a heat exchanger is particularly advantageous since the collecting box can be produced with the same bonding method as the rest of the heat exchanger. In this way, individual process steps can be saved during production, which makes manufacture easier and more cost-effective. Nevertheless, a uniform bond quality can be produced at the different bond points.
It is also expedient for the heat exchanger to have at least one tube through which a first fluid can flow and which can be surrounded by a second fluid, at least one fin member being provided on an outwardly directed surface of the tube and/or on an inwardly directed surface of the tube, which is connected to the tube by the adhesive film.
Fin members can also be connected to the tube on the inner surface or the outer surface of the tube using the adhesive film. This is particularly advantageous in order to enable an improved heat transfer. The low layer thicknesses of the adhesive film are particularly advantageous in this case in order to produce the highest possible thermal conductivity.
Furthermore, it is expedient if the adhesive film can be destroyed by the action of heat. This is particularly advantageous in order to be able to easily dismantle the heat exchangers produced after their use and to be able to supply the individual materials used to a recycling cycle. The required temperature level for the destruction of the adhesive layer is thereby preferably clearly above the temperature level which occurs during the regular operation of the heat exchanger. However, the required temperature level is clearly below the temperature level required for producing a brazed bond.
Brazing joints are produced at temperatures of about 650° C. The temperature required for the destruction of the adhesive film is clearly below this temperature level. The melting of the adhesive film can preferably take place in a temperature range from about 100° C. to about 380° C. The temperature sufficient to destroy the adhesive film is therefore preferably above the melting temperature of the adhesive film and below the usual brazing temperature.
Moreover, it is advantageous if the heat exchanger is manufactured from metallic materials and/or from non-metallic materials.
This is advantageous since, in particular, combinations of different materials are also possible. Here, for example, materials with greatly different coefficients of thermal expansion can be used since the temperatures required to produce the bond are significantly below the temperatures that occur during the brazing process. This leads to a better sealing effect at the bonding points since the heat-induced stresses in the heat exchanger are significantly lower.
The non-metallic materials preferably used include, in particular, plastics or activated carbon. The metallic materials include, inter alia, copper, aluminum, steel and titanium. It is also particularly advantageous that the use of adhesive films also allows for materials to be joined together which cannot be connected to one another by means of conventional brazing processes. This greatly increases the range of available materials.
Furthermore, the adhesive film can be formed of a thermoplastic material.
A thermoplastic material is particularly advantageous because it is very environmentally friendly and easy to recycle as compared to other adhesives. In addition, only minimum requirements for storage and processing have to be met for thermoplastic adhesives. For example, no air extractions have to be provided during the processing of thermoplastic adhesives, since these do not outgas, or only to a very small extent. Since they are not a hazardous substance, the adhesives or the parts coated with an adhesive can also be stored with low safety precautions.
A thermoplastic material is also advantageous because it has high media resistance, which increases the life and failure safety of the produced component. This is especially advantageous particularly with respect to the partially corrosive media in the heat exchangers.
It is also particularly advantageous if all bonds between the individual elements of the heat exchanger are produced using the adhesive film. This makes uniform processing possible and allows for a manufacturing process which is very similar to the usual manufacturing process of brazed heat exchangers. This makes it easier to adapt an existing production line to the new technology.
Furthermore, elements produced at least partially by a brazing process can also be integrated into the otherwise bonded heat exchangers. Since the brazing temperatures lie well above the temperatures for producing an adhesive bond, already brazed elements are not damaged during the bonding process.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes, combinations, and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:
The adhesive film 4 can be laminated onto the tube 2, i.e., connected to the tube 2 with the aid of an adhesive, or simply placed on the outer surface of the tube 2.
In the exemplary embodiment of
In block 20, the adhesive film is applied to at least one of the elements which are to be bonded together. This can be done by an automated process or manually. The adhesive film can in particular be laminated onto an element or inserted into a recess of an element.
In block 21, the elements are brought into contact with one another. For this purpose, they are positioned relative to one another in accordance with the later desired appearance of the heat exchanger. In this case, either only two elements can be positioned relative to one another, or a complete arrangement of all elements forming the heat exchanger block or the heat exchanger can be performed analogously to the known brazing methods.
In block 22, a compressive force is applied to the elements arranged relative to each other. This can preferably be done in a device designed for this purpose.
In block 23, the elements and the adhesive film are heated, thereby melting the adhesive film. The elements are maintained at a predetermined temperature level for a predetermined period of time in order to allow for the elements to be placed in the layer of the adhesive film and finally to ensure curing of the adhesive layer.
Cooling of the elements then takes place in block 24. In the following block 25, the tightness of the produced components is tested. Where applicable, a necessary rework also takes place here.
The exemplary embodiment shown in
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 218 694.3 | Sep 2014 | DE | national |
This nonprovisional application is a continuation of International Application No. PCT/EP2015/070491, which was filed on Sep. 8, 2015, and which claims priority to German Patent Application No. 10 2014 218 694.3, which was filed in Germany on Sep. 17, 2014, and which are both herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2015/070491 | Sep 2015 | US |
| Child | 15431869 | US |
