Heat exchanger and tube

The invention relates to a heat exchanger, particularly for cooling a fluid, comprising a plurality of tubes through which a fluid can flow, an end face of each tube terminating in a collector chamber, said collector chambers being fluidically interconnected by means of the tubes and at least one of said tubes comprising at least one wall section formed from a selectively-permeable membrane. The invention also relates to a tube for a heat exchanger.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a National Stage of International Application No. PCT/EP2015/068487, filed Aug. 11, 2015, which is based upon and claims the benefit of priority from prior German Patent Application No. 10 2014 215 908.3, filed Aug. 11, 2014, the entire contents of all of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The invention relates to a heat exchanger, in particular for cooling a fluid, having a plurality of tubes which can be flowed through by a fluid and open on the end side in each case into a header box, the header boxes being in fluid communication with one another by way of the tubes. Moreover, the invention relates a tube for a heat exchanger.

PRIOR ART

Heat exchangers are used in vehicles, in order to discharge the waste which is produced during operation. Since the required cooling performance continues to increase in modern motor vehicles and, in particular, in vehicles which are driven by electric motors, heat exchangers with higher cooling performance are necessary.

An increased cooling performance requirement also exists, inter alia, in the fuel cell systems which generate large quantities of heat during operation. In order to ensure stable and reliable operation, the heat which is produced has to be discharged.

In order to increase the cooling performance of heat exchangers, apparatuses are known in the prior art which have permeable wall sections, in order to make it possible for a fluid to cross over from the coolant circuit to the outer surface of the heat exchanger. There, the fluid which has crossed over can evaporate, as a result of which the cooling, performance of the heat exchanger overall is increased.

DE 10 2006 048 178 B4 discloses an evaporative cooling, system for a fuel cell system. A conventional cooler is integrated into the evaporative cooling system, which conventional cooler has a selectively permeable wall section, through which water which is contained in the coolant can pass and can evaporate on the outer surface of the cooler.

DE 39 39 867 A1 discloses a composite diaphragm for separating water from a fluid by means of pervaporation. The diaphragm permits the passage of water, while other constituent parts of the fluid are held back.

It is a disadvantage of the apparatuses in the prior art that the production and the construction of heat exchangers with permeable wall sections are not sufficiently disclosed and, in particular, the problems which result from the temperature sensitivity of the permeable diaphragm are not taken into consideration sufficiently during the production.

SUMMARY OF THE INVENTION, PROBLEM, SOLUTION, ADVANTAGES

It is therefore the problem of the present invention to provide a heat exchanger which is improved in comparison with the prior art and can be produced simply and inexpensively. Moreover, it is the problem of the invention to provide a tube in this regard.

The problem with regard to the heat exchanger is solved by way of a heat exchanger having the features of claim1.

One exemplary embodiment of the invention relates to a heat exchanger, in particular for cooling a fluid, having a plurality of tubes which can be flowed through by a fluid and open on the end side in each case into a header box, the header boxes being in fluid communication with one another by way of the tubes, at least one of the tubes having at least one wall section which is configured by way of a selectively permeable diaphragm.

As a result, a heat exchanger is provided which, in addition to the cooling performance which results from the exchange of heat at the outer surface to the air, produces a cooling performance which is produced by way of the evaporation of water on the outer surface. The heat exchanger can advantageously be provided with the aid of a production method which does not require any process temperatures above a limit which is critical for the selectively permeable diaphragm.

Here, all tubes can also have at least one, or more preferably precisely one wall section which is configured by way of a selectively permeable diaphragm.

A wall section of a tube which is formed by way of a selectively permeable diaphragm is particularly advantageous, since the tubes are as a rule part of the heat exchanger block which is flowed around by a cooling fluid. This is the case, in particular, in heat exchangers of tube/fin design. As a rule, high temperatures occur at the heat exchanger block, which high temperatures aid the evaporation on the outer surface of the heat exchanger block. The heat exchanger block also as a rule has a large surface area, as a result of which the evaporation is likewise aided.

It is also be preferred if the selectively permeable diaphragm is connected, such as, in particular, adhesively bonded, to the respective tube. As an alternative, however, the diaphragm can also be connected in some other way, such welded, etc. The adhesive bonding of the selectively permeable diaphragm to the tube is particularly advantageous, since the selectively permeable diaphragms are sensitive to high temperatures, as are produced, for example, during brazing, or welding. If the selectively permeable diaphragm is subjected to high temperatures, permanent damage of the selectively permeable diaphragm can occur, as a result of which the function of the selectively permeable diaphragm is disrupted. Furthermore, an adhesive bond is advantageous, since a fluid-tight connection between the tube and the selectively permeable diaphragm can be produced in a simple way as a result.

A selectively permeable diaphragm is distinguished, in particular, by the fact that it is permeable in one direction for certain fluids, whereas it is impermeable for other fluids. In particular, a selectively permeable diaphragm which is permeable for water is advantageous. In coolant coolers, the fluid which circulates in the heat exchanger as a rule has a water component which can penetrate to the outside through the selectively permeable diaphragm and can evaporate on the outer surface of the heat exchanger, as a result of which an additional cooling performance is produced with a constant installation space requirement.

Furthermore, it is to be preferred if the tubes are received on the end side in tube plates, and fin elements are arranged between the tubes, a cover being arranged on each of the tube plates, which cover forms a header box together with the respective tube plate, the tubes, the tube plates, the covers and the fin elements being adhesively bonded to one another.

On account of the temperature sensitivity of the selectively permeable diaphragm, it is particularly advantageous if all elements of the heat exchanger are connected to one another by way of the use of adhesives. Joining of the elements of the heat exchanger in a brazing furnace, as is the case in conventional heat exchangers, would lead to damage of the selectively permeable diaphragm. Suitable selectively permeable diaphragms, as known in the prior art, are suitable for temperatures up to approximately 120° C.

The heat exchanger is preferably constructed in a tube/fin design, the tubes being received on the end side in each case in tube plates. In alternative refinements, however, heat exchangers without tube plates can also be used, as long as the connection of the individual components which form the heat exchanger to one another is produced by way of adhesive bonding.

It is particularly advantageous if the selectively permeable diaphragm is applied to a supporting structure, the supporting structure and/or the selectively permeable diaphragm being connected, such as, in particular, adhesively bonded, to the tube.

In order to make the selectively permeable diaphragm insensitive to the pressures in the interior of the heat exchanger and, in particular, insensitive to the pressure fluctuations in the heat exchanger, the selectively permeable diaphragm can preferably be applied to a fluid-permeable supporting structure before it is adhesively bonded to the tube. A supporting structure can be formed, for example, by way of a grid-like element. Depending on the embodiment, the supporting structure and/or the selectively permeable diaphragm can be adhesively bonded directly to the tube.

Moreover, it is advantageous if the tube has at least one cutout, the edges of the cutout being formed by way of L-shaped receiving regions which are directed into the tube interior and into which the selectively permeable diaphragm and/or the supporting structure can be inserted.

The receiving regions are particularly advantageous, since they permit simple mounting of the selectively permeable diaphragm and/or the supporting structure on the tube. The L-shaped receiving regions which are directed into the tube interior make it possible for the inserted selectively permeable diaphragm to terminate flush with the outer surface of the tube, which is advantageous, in particular, with regard to an optimum flow around the tubes.

It is also advantageous if the selectively permeable diaphragm makes a transport of fluid out of the tube to the outside possible.

In order to achieve additional cooling performance as a result of the evaporation on the outer surface of the heat exchanger, transport or water from the inside to the outside is particularly advantageous. The selectively permeable diaphragm is preferably impermeable in the opposite direction, in order to avoid a contamination of the coolant in the heat exchanger.

It is also to be preferred if the tube has webs in the interior, the webs connecting two walls of the tube which lie opposite one another to one another.

The tube can be of more stable design as a result of additional webs between the inner surfaces of the tube. In particular, the pressure fluctuations of the coolant which are produced in the heat exchanger can be compensated for in an improved manner in this way.

Furthermore, it is particularly expedient if the webs are configured in one piece with the walls of the tube and/or are adhesively bonded to the inner walls of the tube. In order to avoid the use of brazing methods or welding methods, it is particularly advantageous if the webs are adhesively bonded to the inner walls.

Furthermore, it is expedient if the tube has, on two walls which lie opposite one another, in each case at least one cutout which is covered by way of a selectively permeable diaphragm.

Depending on the design of the tube, a plurality of outer surfaces can also have cutouts which are covered by a selectively permeable diaphragm. This is particularly advantageous, in order to produce as great a surface area as possible which permits a crossover of fluid to the outer surface of the heat exchanger. In this way, the additional cooling performance can be particularly great with a constant installation space requirement.

The problem with regard to the tube is solved by way of a tube having the features of claim11.

One exemplary embodiment of the invention relates to a tube for a heat exchanger according to the invention, the tube having a wall section which is formed by way of a selectively permeable diaphragm.

A tube having a wall section which is formed by way of a selectively permeable diaphragm is particularly advantageous, in order to make the crossover of a fluid which flows through the tube to the outer surface possible. There, additional cooling performance can be produced by way of an evaporation of the fluid which has passed onto the outer surface. A tube of this type can preferably be used in heat exchangers of different design.

It is also expedient if the tube is produced by way or bending from strip stock. This is particularly advantageous, since, in addition to the outer surfaces of the tube, webs in the interior can also be formed in a simple way by way of the bending of the sheet metal strip which forms the strip stock for the tube. The L-shaped receiving regions can also be configured simply in this way, as a result of which an inexpensive rapid production of the tube is made possible overall.

Moreover, it is to be preferred if the tube is produced by way of an extrusion method. An extrusion method can be advantageous, in order for it to be possible to produce the tube profile in large quantities at high speed. Depending on the configuration of the die which is used, the tube profile can be adapted simply, and the webs which lie in the interior and the L-shaped receiving regions can also be produced in addition to the outer walls. The cutouts for the selectively permeable diaphragms can likewise already be produced during the extrusion method or can be made subsequently.

Advantageous developments of the present invention are described in the subclaims and in the following description of the figures.

PREFERRED EMBODIMENT OF THE INVENTION

FIG. 1shows a cross section through a tube1. The tube1has two narrow sides2which lie opposite one another and two broad sides3which lie opposite one another. The narrow sides2are rounded. The tube1is produced from a sheet metal strip by way of bending. To this end, the free end regions of the sheet metal strip are bent over, as a result of which the lower broad side3and the two narrow sides2are configured. The upper broad side is formed substantially by way of a diaphragm4which is inserted into a cutout5.

The edges6,7of the cutout5which lie on the left and the right are formed by way of the free end regions of the sheet metal strip which have been bent over in order to produce the tube. The edges6,7in each case form an L-shaped receiving region8which protrudes into the tube interior. The diaphragm4is inserted into said L-shaped receiving regions8and is adhesively bonded to the tube1. The selectively permeable diaphragm4can extend along the entire length of the tube1or else only over one or more part regions. The length of the tube1is measured inFIG. 1along a surface perpendicular on the plane of the drawing.

The selectively permeable diaphragm4can additionally be applied to a supporting structure which increases the strength and stability of the selectively permeable diaphragm4. The pressure resistance of the diaphragm4, in particular, can be increased by way of the supporting structure which is not shown in figure in order to also ensure a sufficient pressure resistance of the tube1in the region of the diaphragm4. The diaphragm4terminates flush with the outer surface of the tube1.

FIG. 2shows a perspective view of the tube1, as has been shown inFIG. 1.FIG. 2shows a part view of the tube1. The selectively permeable diaphragm4forms the greatest part of the upwardly directed broad side3of the tube1. In alternative embodiments, the selectively permeable diaphragm can also be of less broad configuration or can have a smaller length. The width of the tube1or of the diaphragm4is measured from one to the other narrow side2, whereas the length is measured in a direction parallel to the narrow sides2.

FIG. 3shows a cross section through a tube1, as has already been shown inFIGS. 1 and 2. In addition, the tube1has two webs9in the interior, which webs9run between the broad sides3or the lower broad side3and the selectively permeable diaphragm4.

The webs9are formed in each case by way of the free end regions of the sheet metal strip which have been bent over in order to form the tube1. The L-shaped receiving regions8are configured by way of bending by 90° downward out of the upper broad side3on each of the free end regions and subsequent bending by 90° to the left or to the right. The webs9are configured by way of renewed bending over of the free end regions by 90° downward. Finally, the webs9have a base region10which in turn is configured by way of bending over by 90° to the left or to the right and is seated on the inner side of the lower broad side3.

The webs9are adhesively bonded fixedly with their respective base region10in each case on the inner side of the lower broad side3. The tube1and the webs9are configured in one piece, all of the broad sides3, the narrow sides2, the L-shaped receiving regions8and the webs9with their base regions10being produced by way of bending operations of the free end regions of the sheet metal strip. The webs9increase the stability of the tube1. In addition, the webs form a plurality of chambers11in the interior of the tube1, which chambers11extend along the main throughflow direction of the tube1.

In alternative embodiments, the webs can also be inserted subsequently into the shaped tube and can be adhesively bonded to the tube.

FIG. 4shows a further alternative refinement of a tube1, as has already been shown in the precedingFIGS. 1 to 3. In addition to the webs9, a further web12is configured inFIG. 4. The web12is configured on the lower broad side3and is positioned centrally in the tube1.

The web12is produced by way of bending of the sheet metal strip by 90° upward out of the plane of the lower broad side3, subsequent bending of the sheet metal strip by 180° downward and final bending of the sheet metal strip by 90° back into the plane of the lower broad side3. The web12is therefore also configured in one piece with the remaining tube1and is produced only by way of bending operations of the sheet metal strip which acts as strip stock for the tube1. The web12is supported on the selectively permeable diaphragm4or on the supporting structure below the selectively permeable diaphragm4. The web12is of double-walled configuration.

In the exemplary embodiment ofFIG. 4, the tube1is divided into four chambers13which extend along the main throughflow direction of the tube1.

FIG. 5shows a further alternative embodiment of the tube1. In contrast to the preceding embodiments ofFIGS. 3 and 4, the tube1has three webs14which have been produced from the lower broad side3by means of material doubling operations as a result of bending operations in a manner which is analogous in each case to the web12fromFIG. 4. The webs14are distributed over the width of the tube1. All three webs14support the lower broad side3with respect to the diaphragm4or with respect to the supporting structure below the selectively permeable diaphragm4.

The free end regions of the sheet metal strip inFIG. 5are shaped into L-shaped receiving regions8in an analogous manner toFIG. 1. The two outer webs14adjoin the L-shaped receiving regions8directly with their upper end region. In alternative refinements, a different number of webs can also be provided. The webs can also be provided in a different arrangement within the tube.

The tube fromFIG. 5is divided into four chambers15by way of the webs14. As was also the case in the precedingFIGS. 3 and 4, the webs14are adhesively bonded to the inner surfaces of the tube1or to the supporting structure or the selectively permeable diaphragm4.

FIG. 6shows a cross section through a tube20. The tube20is produced by way of an extrusion method. The tube20has two narrow sides21which lie opposite one another and two broad sides22which lie opposite one another. A cutout23is arranged in the upper broad side22, into which cutout23a selectively permeable diaphragm24is inserted. As was also the case in the preceding figures, the selectively permeable diaphragm24is applied on a supporting structure (not shown) which increases the stability of the selectively permeable diaphragm24.

The cutout23is delimited laterally by way of L-shaped receiving regions into which the selectively permeable diaphragm24is inserted. The selectively permeable diaphragm24is adhesively bonded to the tube20in the region of the L-shaped receiving regions25.

A plurality of webs26are arranged in the interior or the tube20, which webs26are of T-shaped configuration and run from the lower broad side22toward the upper broad side22or the selectively permeable diaphragm24. The section of the webs26which runs parallel to the broad sides22bears against the selectively permeable diaphragm24or against the L-shaped receiving regions25. The webs26are adhesively bonded to the tube20at the contact points between the webs26and the selectively permeable diaphragm24or the upper broad side22. Six chambers27which extend along the main throughflow direction are configured in the tube20by way of the webs26.

The webs26are configured in one piece with the tube20and are already formed into the tube20during the extrusion method. In alternative embodiments, the number, the positioning and the shape of the webs can vary.

FIG. 7shows a further tube30which is produced by way of an extrusion method. The tube30has two narrow sides which lie opposite one another and two broad sides32which lie opposite one another. In each case one cutout33which is covered in each case by way of a selectively permeable diaphragm34is arranged both in the upper broad side32and in the lower broad side32. The edges of both cutouts33are configured by way of inwardly directed L-shaped receiving regions into which the selectively permeable diaphragm34can be inserted and can be adhesively bonded to the tube30.

A plurality of webs36,37are configured in the tube30. The webs36run from the lower broad side32to the upper broad side, whereas the web37runs from the left-hand narrow side31to the right-hand narrow side31. The transversely running web37divides the inner volume of the tube30into an upper half and a lower half. The webs36are configured in the form of I-beams and bear at the top and the bottom in each case against the selectively permeable diaphragms34or the supporting structure (not shown). The two outer webs36in each case directly adjoin the L-shaped receiving regions35. The webs36intersect the transversely running web37. The webs36,37are configured in one piece together with the outer walls of the tube30and are produced in a common extrusion method.

The inner volume of the tube30is divided by way of the webs36and the web37into twelve chambers38which extend along the main throughflow direction of the tube30.

In alternative embodiments, the tubes fromFIGS. 1 to 6can also have in each case a plurality of selectively permeable diaphragms. The selectively permeable diaphragms are preferably arranged in each case on the broad sides, in order for it to be possible to design the selectively permeable membranes with as great a surface area as possible. The larger the selectively permeable diaphragms are configured, the more water can pass through the selectively permeable diaphragms and can evaporate on the outer surface of the tubes, as a result of which additional cooling performance is produced.

It is possible, moreover, to configure the webs in the interior of the tubes by way of inserts which are inserted into the tubes along the main throughflow direction of the latter and are adhesively bonded to the inner sides of the tubes. Flat tubes can also be produced here completely by way of the bending of a sheet metal strip. It is advantageous here that, independently of their production method, the tubes have a cutout on one of the outer surfaces, which cutout can be covered by a selectively permeable diaphragm. The inner side of the selectively permeable diaphragm comes into contact directly with the fluid which flows through the tubes, in order to make a crossover of the fluid or of the water component of the fluid possible.

The exemplary embodiments which are shown inFIGS. 1 to 7do not have any restrictive character, in particular with regard to the design of the tubes and the design and arrangement of the webs.