Abstract:
Disclosed herein is a heat exchanger with tubes ( 1 ) and at least one end piece, which has a tube bottom that, in turn, has a bottom plate ( 8 ), a baffle plate ( 12 ) and a covering plate ( 16 ).

Description:
BACKGROUND OF THE INVENTION  
   The invention relates to a heat exchanger with tubes and with an end piece which has a tube plate comprising a plurality of individual plates. 
   A heat exchanger of this type is described, for example, in EP 0 563 471 A1. The heat exchanger disclosed by that document is designed as a two-row flat-tube evaporator which has two flows of medium passing through it. Corrugated fins which have ambient air flowing over them are located between the flat tubes. The refrigerant first of all flows through the rear row of flat tubes, as seen in the main direction of flow of the air, from the top downward and is then collected and diverted, by means of a diverter device, in the opposite direction to the direction of flow of the air, entering the first, i.e. front row of flat tubes, through which it flows from the bottom upward. With this design, therefore, the refrigerant is diverted over the depth, i.e. counter to the direction of flow of the air. As a result, the flow paths for the refrigerant in each case comprise two sections, with each section corresponding to a tube length. The refrigerant is distributed and collected by a collection and distribution device, which is formed by a multiplicity of plates which are layered on top of one another and are soldered together. These plates substantially comprise a base plate, a distributor plate above it, with a partition running in the longitudinal direction, and a cover plate with feed and discharge openings for the refrigerant. In a similar way, the diverter device arranged on the opposite side is composed of individual plates. This results in a low overall height of this evaporator. In addition, there is optionally what is known as a stop plate, which is in each case laid onto the base plate and forms a stop for the tube ends. One drawback of this type of evaporator is that the refrigerant, on account of the distribution or collection chamber extending over the entire width of the evaporator, is distributed unevenly to the individual tubes. Furthermore, the two-row design requires increased assembly outlay. 
   What is known as a divider plate with individual openings for distributing the refrigerant between the individual tubes has been proposed for a similar evaporator in EP 0 634 615 A1. This results in more uniform distribution of the refrigerant to the tubes, but this is at the expense of an increased number of plates and therefore higher outlay on materials and assembly. 
   U.S. Pat. No. 5,242,016 describes an evaporator with refrigerant distribution through passages in a large number of plates, which likewise contribute to a more uniform distribution of the refrigerant between heat-exchanger tubes. However, this requires a very large number of plates and high manufacturing costs. 
   DE 100 20 763 A1 has disclosed a further design of evaporator, which is intended for operation with CO 2  as refrigerant and in which a pressure-resistant collector housing is to be achieved by virtue of the fact that a multiplicity of plates provided with apertures are stacked on top of one another and soldered together. This evaporator is of one-row design, specifically with multi-chamber flat tubes through which medium flows both upward and downward, which is made possible by a diverter device located at the lower end of the tubes. One drawback of this design of evaporator is the large number of plates with relatively narrow passages, which firstly entails additional weight and secondly involves the risk of the passages in the collector housing being closed up during soldering, i.e. becoming blocked by solder. 
   EP 1 221 580 A2 has described an evaporator for a fuel cell system, which comprises a header piece which includes a base plate and a cover plate secured to it. Fuel passes via a connection part into a fuel distributor chamber, and from there into guide passages and via apertures in the base plate into heat-uptake passages of the evaporator. In this fuel evaporator, there is a small number of plates in the header piece, but these plates are highly complex to manufacture. Moreover, supply of fuel to the heat-uptake passages is very uneven depending on the pressure distribution in the fuel distributor chamber and in the guide passages. 
   SUMMARY OF PREFERRED EMBODIMENTS 
   The object of the invention is to provide a heat exchanger in which it is possible to realize a simple and/or lightweight design and if appropriate simultaneously a uniform distribution of a medium to a plurality of flow paths and/or a pressure-stable construction of the heat exchanger. 
   This object is achieved by a heat exchanger having the features of one of the independent claims  1 ,  14 ,  26 ,  29 ,  31 ,  33  or  36 . 
   According to these claims, a heat exchanger according to the invention includes tubes through which a first medium can flow and around which a second medium can flow, so that heat can be transferred from the first medium to the second or vice versa through walls of the tubes. For this purpose, heat-exchange passages, through which the first medium can be passed, are located in the tubes, with an individual tube having either one heat-exchange passage or, as what is known as a multi-chamber tube, having a plurality of heat-exchange passages located next to one another. The tubes may in this case have a circular, oval, substantially rectangular or any other desired cross section. By way of example, the tubes are designed as flat tubes. To increase the heat transfer, it is if appropriate possible to arrange fins, in particular corrugated fins, between the tubes, in which case the tubes and the fins can in particular be soldered to one another. There are various conceivable uses for the heat exchanger, for example as an evaporator of a refrigerant circuit, in particular of a motor vehicle air-conditioning system. In this case, the first medium is a refrigerant, for example R 134   a  or R 744 , and the second medium is air, with heat being transferred from the air to the refrigerant. However, the heat exchanger is also suitable for other media, in which case the heat can if appropriate also be transferred from the first medium to the second. 
   If appropriate, there are at least two collection chambers, it being possible for the first medium to be passed from a first collection chamber to a second collection chamber. The first medium can be passed along one or more flow paths which optionally comprise several sections. In the context of the invention, the term flow-path section is to be understood as meaning one or more heat-exchange passages which run from one side of the heat exchanger to an opposite side and are hydraulically connected in parallel with one another. The heat-exchange passages of a flow-path section are, for example, arranged in a single tube, although an arrangement of the heat-exchange passages of a flow-path section which is distributed between a plurality of tubes is also conceivable. 
   Furthermore, the heat exchanger has an end piece with a tube plate which actually comprises a number of plates bearing against one another, namely a base plate, a diverter plate and a cover plate. The base plate can be connected to ends of the tubes by virtue of the base plate having, for example, cutouts, in which the tube ends can be received. Within the context of the invention, it is also conceivable to use other types of connection between tubes and the base plate, for example connections produced by extensions at the edges of cutouts in the base plate, so that the tubes can be plug-fitted onto the extensions. Cutouts in the diverter plate serve to form through-passages and/or diverter passages, which can be closed off in a fluid-tight manner with respect to an environment surrounding the heat exchanger by means of a cover plate. The plate structure of the tube plate allows the end piece and the entire heat exchanger to be of very pressure-stable construction. 
   A first basic idea of the invention is for the end piece which comprises the tube plate to be provided with a collection box which, in a housing, has at least one collection chamber for the first medium. In this way, a component which may in any case be required is integrated in the end piece, ensuring a compact and therefore simple design of the heat exchanger. 
   According to a second basic idea of the invention, flow-path sections are connected to one another by means of diverter passages in the diverter plate. The connection of the flow-path sections to form one or more hydraulically parallel flow paths can then be designed to satisfy any desired requirements, by virtue of a single plate, namely the diverter plate, being configured so as to correspond to the required flow-path connection. Therefore, the heat exchanger can be constructed flexibly for different applications, on account of its modular structure. 
   According to another basic idea of the invention, a tube is introduced into the tube plate as far as a predetermined stop in order to achieve increased manufacturing reliability and therefore simplified production. The stop is realized by a web between two cutouts in the base plate, which web can be received in a cutout in a tube end, with the width of the web being substantially equal to that of the cutout in the tube end. It is advantageous for the cutout to be slightly wider than the web, in order to facilitate insertion of the tube into the base plate. The depth of insertion of the tube is determined by the height of the cutout in the tube end. It is particularly advantageous for the cutout to be higher than the web, thereby reducing the risk of one or more heat-exchange passages undesirably becoming blocked by solder which is present on the base plate during a soldering process. The difference in height is, for example, 1 mm or more, but should on the other hand be less than the thickness of the diverter plate, since the tube otherwise butts against the cover plate. A height difference which is approximately equal to half the thickness of the diverter plate is advantageous. 
   A further basic concept of the invention is for a plurality of individual plates of the tube plate to be configured integrally, in order to reduce the number, the manufacturing costs and if appropriate the materials costs. Under certain circumstances, the tube plate then comprises just one individual plate, into which the base plate, the diverter plate and the cover plate are integrated. 
   According to a further concept of the invention, the outlay on material for the tube plate and therefore also for the heat exchanger is reduced by one or more individual plates, and preferably all the individual plates, of the tube plate having additional cutouts between through-passages and/or diverter passages, which cutouts are formed, for example, as apertures or lateral notches. It is advantageous for the plates to be fully separated between through-passages and/or diverter passages, which means that under certain circumstances the plates may be broken down into many small partial plates. This allows a particularly lightweight design which has beneficial effects both on materials costs and on the weight of the heat exchanger. 
   According to a further basic concept of the invention, a simplified structure is also made possible by tubes which are deformed in a U shape, in which case the tubes are deformed once or, to produce an even simpler design, more than once. As a result, two tube-plate connections and if appropriate a diverter passage are recessed in the region of the U-shaped deformation. If exclusively U-tubes are used, it is even possible to eliminate one end piece, if all the diversions on one side of the heat exchanger are realized by tube deformations. In this case, the ends of in each case one tube can be connected to the same base plate. 
   A further concept of the invention is for the heat exchanger to be provided with precisely one end piece, in which in particular a collection box having two collection chambers is integrated. This can be realized not only by using U-tubes but also by any conceivable hydraulic connection of tubes on the opposite side of the heat exchanger from the precisely one end piece, for example by fitting suitably constructed caps onto in each case a plurality of, in particular two, tubes. 
   Preferred embodiments of the heat exchanger according to the invention form the subject matter of the dependent claims. 
   According to a preferred embodiment, a collection box which is optionally integrated in the end piece is soldered or welded in a fluid-tight manner to the cover plate. According to another advantageous embodiment, the collection box is formed integrally with the cover plate, thereby simplifying production. A particularly lightweight design is achieved by a tubular design of the collection box in accordance with a further configuration of the invention. It is particularly preferable for the cover plate, at edges of apertures, to have extensions which engage in apertures in a housing of the collection box. Conversely, according to a further embodiment, it is possible for apertures in the collection box housing to be provided with extensions which engage in apertures in the cover plate. In both cases, manufacturing reliability is increased by aligning the flush apertures in the cover plate and in the collection-box housing. 
   According to one preferred embodiment, the through-openings which are formed by the flush apertures in the cover plate and in the collection-box housing have different cross sections of flow. This allows simple matching of the distribution of the first medium to the flow conditions in the associated collection chamber. In particular, a uniform distribution between a plurality of flow paths is desirable in this context, but a deliberately nonuniform distribution is also conceivable, for example in the case of a nonuniform mass flow of the second medium over an end face of the heat exchanger. It is advantageous for the through-openings with different cross sections of flow to be arranged upstream of the heat-exchange passages, making it particularly simple to equalize the flow in the flow paths. If quantitative flows through the flow paths are controlled on an inlet side for the first medium, it is possible to make the through-openings on the outlet side larger, for example with a cross section of flow which corresponds to the cross section of flow of the respective flow path. If the heat exchanger is used, for example, as an evaporator in a refrigerant circuit, the pressure ratios along the circuit are more advantageous for the overall performance of the heat exchanger if cross sections of flow are narrowed before the refrigerant is heated than if the cross sections of flow are narrowed after this heating. 
   According to one configuration, the cross sections of flow of the through-openings can be adapted to a pressure distribution of the first medium within the collection chamber in question. In another configuration, the cross sections of flow can be matched to a density distribution of the first medium within the collection chamber in question. In the context of the invention, the density of a medium in the case of single-phase media is to be understood as meaning the physical density, whereas in the case of multi-phase media, for example in the case of media which are partially liquid and partially gaseous, it is to be understood as meaning a density averaged over the volume in question. 
   For similar reasons, in a preferred embodiment the cross-sectional areas of the first and second collection chambers are different than one another. It is particularly preferable for it to be possible to adapt the cross-sectional areas of the collection chambers to the density ratios of the first medium in the chambers. 
   Further embodiments of the heat exchanger according to the invention relate to the connection of the flow-path sections by means of diverter passages in the diverter plate. 
   According to one advantageous configuration, flow-path sections which are arranged next to one another in the main direction of flow of the second medium are connected to one another by a diverter passage. This is then referred to as a diversion over the width. This makes it possible for a plurality of or possibly all flow-path sections within a row or within a tube row to be connected to one another to form a flow path. This leads to an at least partially serpentine design of the heat exchanger. In another configuration, the interconnected flow-path sections are aligned in the main direction of flow of the second medium. This is then known as a diversion over the depth. This makes it possible for flow paths for the first medium to be connected in parallel or antiparallel with the main direction of flow of the second medium. This leads to an at least partially countercurrent design of the heat exchanger. 
   According to a further embodiment, two flow-path sections within a tube are connected to one another by a diverter passage. This means that the first medium flows through the tube in one direction and flows back through the same tube in the opposite direction. The use of tubes with a large number of heat-exchange passages therefore reduces the total number of tubes and therefore the manufacturing costs. 
   According to one preferred configuration, the number of sections of at least one flow path can be divided by two. This means that it is easy to connect up a two-row arrangement of the flow-path sections, by virtue of the first half of the sections of a flow path being arranged in a first row and being connected to one another by diversions over the width, whereas the second half of the sections are arranged in a second row and are likewise connected to one another by diversions over the width, with the two halves of the flow path being connected by a diversion over the depth. This diversion over the depth takes place, for example, in a diverter passage of a diverter plate of a tube plate on the opposite side of the heat exchanger from the collection chambers. It is particularly preferable for the number of sections of the flow path to be divisible by four. This means that with a two-row arrangement of the flow-path sections connected up as described above, the diversion over the depth takes place on that side of the heat exchanger on which the collection chambers are located as well. As a result, it may be possible to configure just one diverter plate of the heat exchanger if the heat exchanger is designed for predetermined requirements, whereas other components are left unchanged. 
   In one configuration, the first and last flow-path sections within one or more tube rows are not acted on as hydraulically the first sections of flow paths, since the flow and/or pressure conditions of the first medium are unfavorable for application to flow paths in the edge region of collection chambers, which are usually arranged along tube rows. 
   According to an advantageous embodiment, two adjacent flow paths run mirror-symmetrically with respect to one another. It is particularly preferable for diverter passages of at least two flow paths to communicate. This results in additional compensation of the through-flow within the flow paths. With a mirror-symmetrical profile of the flow paths communicating with one another, communication between the then optionally adjacent diverter passages is particularly simple to realize, for example by omitting a web which may under certain circumstances otherwise be present between two diverter passages. 
   In a further preferred embodiment, a cross section of flow of a flow path changes over the course of its profile. This is very simple to realize, for example by flow-path sections with a small number of heat-exchange passages being connected, via correspondingly configured diverter passages, to flow-path sections with a large number of heat-exchange passages. It is particularly preferable to match the cross section of flow of one flow path to a density of the first medium which changes along the flow path. 
   A configuration in which all sections of at least one flow path are aligned with one another in the main direction of flow of the second medium is advantageous. It is particularly advantageous for all the flow paths of the heat exchanger to be designed in this way, so that a purely countercurrent construction of the heat exchange is made possible in a simple way, namely by correspondingly configured diverter passages in a diverter plate. 
   In a further embodiment, the heat exchanger comprises flat tubes which have a refrigerant in liquid and/or vapor form flowing through them, corrugated fins arranged between the flat tubes and acted on by ambient air, a collection and distribution device for supplying and discharging the refrigerant, the collection and distribution device comprising a plurality of interrupted plates which are layered on top of one another, so as to form refrigerant passages, with the ends of the flat tubes being held in receiving openings in a base plate, and a diverter device for diverting the refrigerant in the direction of flow of the ambient air, the heat exchanger comprising a series of flat tubes, with in each case one flat tube having two flow sections running parallel, through which medium flows in succession, these flow sections being connected by the diverter device, each flat tube, at the end side, having a groove between the two flow sections in the center of the flat-tube end, and the base plate, between the receiving openings, having webs, the dimensions of which, in terms of height and width, corresponding to the grooves, so as in each case to form a joined connection to the grooves. 
   It is particularly preferable for the diverter device to be formed by a further base plate with receiving openings and webs which form a joined connection to the end-side groove of the flat tubes. 
   It is particularly preferable for the diverter device additionally to have a passage plate with continuous slots and a closed cover plate. 
   It is particularly preferable for the collection and distribution device to have a passage plate with passage openings and webs between the passage openings, a cover plate with refrigerant inlet and outlet openings and a refrigerant feed and refrigerant discharge passage, which are arranged parallel to one another and in the longitudinal direction of the heat exchanger, with the base plate, the passage plate and the cover plate being arranged above one another in such a manner that the openings in the plates are aligned with the flat-tube ends. 
   It is particularly preferable for the refrigerant inlet openings to be designed as calibrated bores, with the diameter of the bores in particular being variable. It is also preferable for the cover plate and the refrigerant feed and discharge passages to be of single-part design. 
   According to a further configuration, the heat exchanger, which can be used in particular as an evaporator for motor vehicle air-conditioning systems, comprises flat tubes which have a refrigerant in liquid and/or vapor form flowing through them, corrugated fins arranged between the flat tubes and acted on by ambient air, a collection and distribution device for supplying and discharging the refrigerant, the collection and distribution device comprising a plurality of interrupted plates layered on top of one another, so as to form refrigerant passages, with the ends of the flat tubes being held in receiving openings in a base plate, and a diverter device for diverting the refrigerant in the direction of flow of the ambient air. The heat exchanger in this case comprises a row of flat tubes, with in each case one flat tube having two flow sections which run parallel, through which medium can flow in succession and which are connected via the diverter device, and the collection and distribution device having a calibration device which is arranged between refrigerant inlet and refrigerant outlet and is designed as a cover plate with calibration openings for the refrigerant distribution. It is preferable for the calibration openings to be arranged on the refrigerant inlet side. 
   According to an advantageous refinement, the calibration openings have different cross sections of flow. The cross sections of flow of the calibration openings preferably increase in size in the direction of the pressure drop of the refrigerant in the feed passage. It is particularly preferable for the cross sections of flow of the calibration openings to be variable as a function of the specific volume of the refrigerant and/or its vapor content. 
   In another embodiment of the heat exchanger, the flat tubes are designed as serpentine segments, and the diverter device is arranged in the collection and distribution device. 
   According to a further configuration, the collection and distribution device has a passage plate with continuous passage openings for diverting the refrigerant, and passage openings with webs, a cover plate with refrigerant inlet and outlet openings and a refrigerant feed passage and a refrigerant discharge passage. The passage openings with webs are in this case each arranged flush with the first flat-tube end of the serpentine segment, whereas the continuous passage openings are arranged flush with the second flat-tube end of the serpentine segment, the refrigerant inlet and outlet openings being flush with the passage openings, and the continuous passage openings being covered by the cover plate. It is preferable for the serpentine segments to have two or three diversions over the width. 
   According to an advantageous embodiment of the heat exchanger, the flat tubes are designed as U-tubes, i.e. with in each case one diversion (over the width). It is preferable for in each case two U-tubes to be connected in series on the refrigerant side, and for in each case two adjacent passage openings, which are assigned to a U-tube outlet and a U-tube inlet, to be in refrigerant communication with one another through a transverse passage in the passage plate. 
   It is preferable for the width b of the passage openings in the passage plate to be greater than the width a of the receiving openings in the base plate. It is also advantageous for the depth of the groove in the flat-tube ends to be greater than the thickness of the base plate. 
   It is advantageous for one or more of the following dimensional stipulations to apply to the heat exchanger: 
   
     
       
             
             
           
         
             
                 
             
           
           
             
               Width: 
               200 to 360 mm, in particular 
             
             
                 
               260 to 315 mm, 
             
             
               Height: 
               180 to 280 mm, in particular 
             
             
                 
               200 to 250 mm 
             
             
               Depth: 
               30 to 80 mm, preferably 
             
             
                 
               35 to 65 mm 
             
             
               Volume: 
               0.003 to 0.006 m 3 , in particular 
             
             
                 
               0.0046 m 3   
             
             
               Number of tubes per refrigerant path: 
               1 to 8, preferably 2 to 4 
             
             
               Diameter of the heat-exchange 
               0.6 to 2 mm, in particular 
             
             
               passages: 
               1 to 1.4 mm 
             
             
               Center-to-center distance of the heat- 
               1 to 5 mm, preferably 2 mm 
             
             
               exchange passages in the depth 
             
             
               direction: 
             
             
               Transverse pitch: 
               6 to 12 mm, in particular 10 mm 
             
             
               Tube height: 
               1 to 2.5 mm, in particular 1.4 
             
             
                 
               to 1.8 mm 
             
             
               End face surface area SF in the main di- 
               0.04 to 0.1 m 2 , in particular 
             
             
               rection of flow of the second medium: 
               0.045 to 0.07 m 2   
             
             
               Free flow cross-sectional area BF for 
               0.03 to 0.06 m 2 , in particular 
             
             
               the second medium: 
               0.053 m 2   
             
             
               Ratio BF/SF: 
               0.5 to 0.9, in particular 0.75 
             
             
               Heat-exchanging surface area: 
               3 to 8 m 2 , in particular 4 to 
             
             
                 
               6 m 2   
             
             
               Lamella density for corrugated fins: 
               400 to 1000 m −1 , in particular 
             
             
                 
               650 m −1   
             
             
               Passage height: 
               4 to 10 mm, in particular 6 to 
             
             
                 
               8 mm 
             
             
               Lamella slot length: 
               4 to 10 mm, in particular 
             
             
                 
               6.6 mm 
             
             
               Lamella slot height: 
               0.2 to 0.4 mm, in particular 
             
             
                 
               0.26 mm 
             
             
               Thickness of the base plate: 
               1 to 3 mm, in particular 1.5 or 
             
             
                 
               2 or 2.5 mm 
             
             
               Thickness of the diverter plate: 
               2.5 to 6 mm, in particular 3 or 
             
             
                 
               3.5 or 4 mm 
             
             
               Thickness of the cover plate: 
               1 to 3 mm, in particular 1.5 or 
             
             
                 
               2 or 2.5 mm 
             
             
               Collection box diameter: 
               4 to 10 mm, in particular 6 to 
             
             
                 
               8 mm 
             
             
               Housing wall thickness of a collection 
               1 to 3 mm, in particular 1.5 to 
             
             
               box: 
               2 mm 
             
             
                 
             
           
        
       
     
   

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is explained in more detail below on the basis of exemplary embodiments and with reference to the drawings, in which: 
       FIG. 1  shows a parallel-flow evaporator in the form of an exploded illustration, 
       FIG. 2  shows an evaporator with serpentine segment (diversion over the width), 
       FIG. 3  shows an evaporator with U-tubes, 
       FIG. 4  shows a section IV-IV through evaporators as shown in  FIG. 3 , 
       FIG. 5  shows a section V-V through evaporators as shown in  FIG. 3 , 
       FIG. 6  shows an evaporator with U-tubes connected in series (diversion over the width), 
       FIG. 7  shows a cross-sectional illustration of a heat exchanger, 
       FIG. 8  shows a partial view of a heat exchanger, 
       FIG. 9  shows a partial view of a heat exchanger, 
       FIG. 10  shows a diverter plate, 
       FIG. 11  shows a partial view of a tube plate, 
       FIG. 12  shows an exploded illustration of a tube plate, 
       FIG. 13  shows a cross-sectional illustration of a tube plate, 
       FIG. 14  shows a longitudinal section illustration of a tube plate, 
       FIG. 15  shows a tube plate, 
       FIG. 16  shows a cross-sectional illustration of a tube plate, 
       FIG. 17  shows a partial view of a heat exchanger, 
       FIG. 18  shows a cross-sectional illustration of a tube plate, 
       FIG. 19  shows a tube plate, 
       FIG. 20  shows a tube plate, 
       FIG. 21  shows a tube plate, 
       FIG. 22  shows a tube plate, 
       FIG. 23  shows a tube plate, 
       FIG. 24  shows a partial view of a heat exchanger and 
       FIG. 25  shows a partial view of a tube plate. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
     FIG. 1  shows, as first exemplary embodiment, an evaporator for a motor vehicle air-conditioning system which is operated with CO 2  as refrigerant, specifically in the form of an exploded illustration. This evaporator  1  is designed as a single-row flat-tube evaporator and has a multiplicity of flat tubes, of which just two flat tubes  2 ,  3  are illustrated. These flat tubes  2 ,  3  are designed as extruded multichamber flat tubes which have a multiplicity of flow passages  4 . All the flat tubes  2 ,  3  have the same length I and the same depth t. A groove  5 ,  6  is machined into the flat tube  2  at each tube end  2   a ,  2   b , symmetrically with respect to the center axis  2   c . Between the individual flat tubes  2 ,  3  there are corrugated fins  7 , which are acted on by ambient air in the direction of the arrow L. The corrugated fins  7  are continuous in the depth direction, although they may also be interrupted, for example in the center of the depth t, in order to ensure improved condensate run-off and/or thermal isolation. 
   In the drawing, a base plate  8 , in which a first row of slot-like apertures  9   a - 9   f  and a second row of similar apertures  10   a - 10   f  are arranged, is illustrated above the flat tubes  2 ,  3 . The openings  9   a  and  10   a ,  9   b  and  10   b , etc. are located one behind the other in the depth direction (airflow direction L) and in each case leave between them webs  11   a ,  11   b - 11   f . In terms of their width in the depth direction, these webs  11   a - 11   f  correspond to the width of the cutout  5  of the tube ends  2   a . The number of openings  9   a - 9   f  and  10   a - 10   f  corresponds to the number of flat tubes  2 ,  3 . 
   What is known as a diverter plate  12 , in which two rows of apertures  13   a - 13   f  and  14   a - 14   f  (partially covered) are arranged, is illustrated above the base plate  8  in the drawing. The arrangement of the apertures  13   a - f  and  14   a - f  corresponds to the arrangement of the apertures  9   a - 9   f  and  10   a - 10   f , respectively, but the width b and depth of the apertures  13   a - f  and  14   a - f  are greater than the corresponding dimensions of the apertures  9   a - 9   f  and  10   a - 10   f , respectively, which in each case only have a width a corresponding to the thickness of the flat tubes  2 ,  3 . Webs  15   a - 15   f  are in each case left between the apertures  13   a ,  14   a ,  13   b ,  14   b - 13   f  and  14   f . The dimensions of these webs  15   a - 15   f  in the depth direction are smaller than the corresponding dimensions of the webs  11   a - 11   f  of the base plate  8 . 
   What is referred to as a cover plate  16 , which includes a first row of refrigerant inlet apertures  17   a - 17   f  and a second row of refrigerant outlet apertures  18   a - 18   f , is illustrated in the drawing above the diverter plate  12 . These apertures  17   a - 17   f  and  18   a - 18   f  are preferably designed as circular bores with a diameter matched to the desired refrigerant distribution and quantitative flow. 
   Finally, a collection box  19  with a housing and in each case one collection chamber  20 ,  21  for supplying and discharging the refrigerant is located above the cover plate  16  in the drawing. The collection box has apertures  22   a - f  and  23   a - f , illustrated by dashed lines, the position and size of which correspond to the apertures  17   a - f  and  18   a - f , at the underside of both collection chambers. 
   In the drawing, a further base plate  24 , which analogously to the first base plate  8  has two rows of slot-like apertures  25   a - f  and  26   a - f , is illustrated beneath the flat tubes  2 ,  3  in the drawing. Between the apertures  25   a  and  26   a  to  25   f  and  26   f  there are likewise webs  27   a - f  (partially covered), the width of these webs in the depth direction corresponding to the width of the cutout  6  in the end of the flat tube  2 . A further diverter plate  28 , which has continuous diverter passages  29   a - 29   f , is illustrated in the drawing below the second base plate  24 . These diverter passages  29   a - f  extend over the entire depth t of the flat tubes  2 ,  3 . 
   Finally, a cover plate  30 , which does not have any apertures, but rather closes off the diverter passages  29   a - 29   f  with respect to the environment surrounding the heat exchanger, is illustrated at the bottom of the drawing. 
   The above-described individual parts of the evaporator  1  are assembled in the following way: the base plate  8  is fitted onto the flat-tube ends  2   a , etc., so that the webs  11   a - 11   f  come to lie in the cutouts  5  in the flat-tube ends. Then, the diverter plate  12 , the cover plate  16  and the collection box  19  with the collection chambers  20 ,  21  are stacked on top of the base plate  8 . In a similar way, the lower base plate  24  is pushed onto the flat-tube ends  2   b , so that the webs  27   a - 27   f  come to lie in the cutouts  6 ; then, the passage plate  28  and the cover plate  29  are attached. After the evaporator  1  has therefore been assembled, it is soldered to form a fixed block in a soldering furnace. During the soldering process, the plates are held in position with respect to one another by a positive or nonpositive clamping action. However, it is also possible firstly to assemble the end piece comprising base plate, diverter plate and cover plate, and then to connect it to flat tubes. 
   The profile of the refrigerant flow is illustrated by way of example on the basis of a row of arrows V 1 -V 5  on the front side of the evaporator, by the diverter arrow U in the diverter passage  29   c  and the arrows R 1 , R 2  and R 3  on the rear side of the evaporator  1 . The refrigerant, in this case therefore CO 2 , thus flows through the evaporator, starting on the front side from the top downward, specifically in the front section  2   d  of the flat tube  2 , is diverted over the depth in the lower tube plate, comprising the individual plates  24 ,  28 ,  30 , and flows from the bottom upward on the rear side of the evaporator  1 , i.e. in the rear flow section  2   e  of the flat tube  2 , as indicated by the arrows R 1 , R 2  and R 3 , into the collection chamber  21 . 
     FIG. 2  shows a further exemplary embodiment of the invention, specifically an evaporator  40  in which the abovementioned flat tubes are designed as serpentine segments  41 . A serpentine segment  41  of this type comprises four flat-tube limbs  42 ,  43 ,  44  and  45 , which are connected to one another by three diverter bends  46 ,  47 ,  48 . Corrugated fins  49  are arranged between the individual flat-tube limbs  42 - 45 . The further parts of the evaporator are likewise illustrated in the form of an exploded illustration, i.e. a base plate  50 , a diverter plate  51 , a cover plate  52  and collection chambers  53 ,  54  for a refrigerant feed and discharge. The base plate  50  has a front row of slot-like apertures  55   a ,  55   b  and  55   c , behind which there is a second row (partially covered) of corresponding apertures. Webs  56   a ,  56   b  and  56   c  are in turn left between the two rows of apertures, these webs corresponding with cutouts  57  and  58  in the ends  42   a  and  45   a  of the serpentine segment  41 . These flat-tube ends are therefore fitted through the apertures in the base plate, with the webs coming to lie in the cutouts. The base plate  50  is followed at the top by the diverter plate  51 , which has an aperture  59   a  which is flush with the aperture  55   a  in the base plate  50 . Behind the aperture  59   a  in the depth direction there is (partially covered) a corresponding aperture, which is separated from the aperture  59   a  by a web  60   a . This web  60   a  is once again smaller than the cutout  58  in the flat-tube limb  42 . Adjacent to the aperture  59   a , at a distance which corresponds to the distance between the flat-tube ends  42   a - 45   a , there is a diverter passage  61  which extends over the entire depth of the flat-tube limb  45 . Adjacent to the diverter passage  61  there then follows an aperture  59   b , the size of which corresponds to the aperture  59   a . It corresponds to the next flat-tube serpentine segment, which is not shown here. Above the diverter plate  51  is the cover plate  52 , which in the front row has two refrigerant feed apertures  62 ,  63  and in the rear row has two refrigerant outlet apertures  64  and  65 . The size and position of the latter correspond to the openings shown in dashed lines in the drawing (without any reference numbers) at the collection chambers  53 ,  54 . 
   The refrigerant flow route is illustrated by arrows: first of all the refrigerant leaves the collection chamber  53  as indicated by the arrow E 1 , then follows the direction of the arrows E 2 , E 3 , E 4  and passes into the front flow section of the flat-tube limb  42  and then flows through the entire serpentine segment  41  on its front side and emerges from the final limb  45  at E 6 , passes into the diverter passage  61 , where it is diverted over the depth in accordance with arrow U, before then flowing through the rear side of the serpentine segment, as indicated by arrow R 1 , i.e. in the opposite direction to on the front side. Finally, this stream of refrigerant passes into the collection chamber  54  as indicated by the arrow R 2 , i.e. through the aperture  64 . 
   This construction therefore diverts the refrigerant over the width of the evaporator, i.e. transversely to the main direction of flow of the air, specifically initially from the right to the left on the front side in the drawing, and then from the left to the right on the rear side. As has already been mentioned above, one or more serpentine segment sections which are not illustrated follow the serpentine segment section  41  illustrated in the drawing. 
     FIG. 2  illustrates just one serpentine segment section  41 , arranged on the right in the drawing. Contrary to the description given above, it is possible for the next serpentine segment section following this serpentine segment section  41  also to have refrigerant flowing through it in the opposite direction over the width, i.e. from the left to the right or from the outside inward in the drawing. On viewing the end face of the evaporator, therefore, the latter would therefore have refrigerant flowing through it symmetrically from the outside inward on the front side, then the two refrigerant streams can then be combined in the center—in a common diverter passage which then functions as a mixing space—and diverted over the depth and can flow from the inside back outward on the rear side. 
     FIG. 3  shows a further exemplary embodiment of the invention, specifically an evaporator  70 , the flat tubes of which are formed from individual U-tubes  71   a ,  71   b ,  71   c  etc. This is therefore a serpentine segment section with a diversion and two limbs  72  and  73 . The ends of these flat-tube limbs  72  and  73  which cannot be seen in the drawing are secured in an analogous way, i.e. as described above, in a base plate  74  with corresponding receiving parts. A diverter plate  75  is arranged above the base plate  74  and has, in alternation, two slot-like apertures  76 ,  77  which lie one behind the other in the depth direction, leaving a web  78  and a diverter passage  79  which continues through in the depth direction. In this illustration, the cover plate—similar to the exemplary embodiments described above—has been omitted. 
   The flow of the refrigerant then follows the direction of the arrows, i.e. the refrigerant enters the front flow section of the U-tube  71   a  at E, initially flows downward, is diverted at the bottom, then flows upward and passes into the diverter passage  79 , where it is diverted as indicated by arrow U before then flowing downward on the rear side, where it is diverted and then flows upward again in order to pass through the aperture  77  as indicated by arrow A. The supply and discharge of the refrigerant is described on the basis of the following figure, corresponding to sections IV-IV and V-V. 
     FIG. 4  shows a section on line IV-IV through the evaporator shown in  FIG. 3 , in the form of an enlarged illustration and with the addition of a cover plate  80  and a collection box  81  and a collection box  82 . The other parts are denoted by the same reference numerals as in  FIG. 3 , i.e. the diverter plate by  75 , the base plate by  74  and the flat-tube limb by  71   c . The diverter plate  75  has two apertures  76   c  and  77   c , which are separated from one another by the web  78   c . In the cover plate  80  there is a refrigerant inlet aperture  83 , which is arranged flush with a refrigerant aperture  84  in the collection box  81 . In a similar way, a refrigerant outlet aperture  85  in the cover plate  80  is arranged flush with a refrigerant aperture  86  in the collection box  82  on the side of the collection box  82 . The collection boxes  81 ,  82  are soldered tightly and in a pressure-resistant manner to the cover plate  80 , as are the other parts  80 ,  75 ,  74  and  71   c.    
     FIG. 5  shows a further section, on line V-V in  FIG. 3 , i.e. through the diverter passage  79   d . Identical parts are once again denoted by identical reference numerals. It can be seen that the refrigerant, illustrated by the arrows, flowing from the bottom upward in the left-hand flat-tube section, is diverted to the right in the diverter passage  79   d  and passes into the right-hand or rear section of the flat-tube limb  71   c , where it flows from the top downward. 
   This mode of design of the evaporator shown in  FIGS. 3 ,  4  and  5  with simple U-tubes therefore in each case allows simple diversion over the width and over the depth. 
     FIG. 6  shows, as a further exemplary embodiment of the invention, an evaporator  90 , which is once again constructed from U-tubes  91   a ,  91   b ,  91   c , etc. The ends of the U-tube limbs are once again—although this is not illustrated in the drawing—received in a base plate  92 , above which there is a diverter plate  93 . The diverter plate  93  has a configuration of apertures in which a pattern repeats itself after in each case two U-tubes, i.e. for example  91   a  and  91   b . The following text describes this pattern, specifically starting in the top left-hand corner of the drawing: two apertures  94  and  95  arranged one behind the other in the depth direction are located there, adjoined in the width direction by the apertures  96  and  97  and  98  and  99 , the apertures  96  and  98 , in the width direction, being in refrigerant communication via a transverse passage  101 , and the apertures  97  and  99  being in refrigerant communication via a transverse passage  100 , resulting in two H-shaped apertures. A continuous diverter passage  102  is arranged adjacent to the H-shaped apertures. The pattern of apertures  94 - 102  which has just been described is then repeated. This configuration of apertures enables in each case two U-shaped refrigerant tubes to be connected in series on the refrigerant side, i.e. in this case the U-tubes  91   a  and  91   b . The refrigerant profile is illustrated by arrows: the refrigerant enters the front part of the left-hand limb of the U-tube  91   a  at A and flows downward, is diverted, flows back upward and is diverted into the next U-tube  91   b  in the diverter plate  93  via the transverse passage  101 , i.e. following the arrow B. In this next U-tube  91   b , it flows downward, is diverted, then flows back upward and passes into the diverter passage  102 , where, following arrow C, it is diverted over the depth and then flows through the rear part of the two flat-tube limbs  91   b  and  91   a , before finally emerging again at D. The cover plate and the refrigerant feed and discharge have been omitted here in order to provide a better illustration of the flow of refrigerant. This series connection of two U-tubes on the one hand allows triple diversion over the width and on the other hand means that each U-tube limb is received in the base plate, resulting in a pressure-stable design. Of course, this pattern can also be used to realize four or more diversions over the width, which merely requires U-shaped flat tubes. The upper diversion therefore in each case takes place in the passage plate  93 . 
     FIG. 1  illustrates collection chambers  20  and  21 , and  FIG. 4  illustrates collection boxes  81  and  82 , for supplying and discharging refrigerant. According to one refinement of the invention, it is possible for a distribution device in accordance with DE 33 11 579 A1, i.e. a coiled profiled-section body, or in accordance with DE 31 36 374 A1 in the name of the present Applicant, known as a push-in body, to be used in particular on the respective refrigerant inlet side, so that a uniform refrigerant distribution and therefore also a uniform temperature distribution is achieved at the evaporator. In this context, it may be advantageous if in each case a plurality of, for example four, adjacent refrigerant inlet apertures are supplied via a common chamber; this enables four times five, i.e. 20, refrigerant inlet apertures to be supplied with refrigerant in the case of a profiled-section body with, for example, five passages. For this purpose, the (five) passages, which initially run axially parallel, are in each case turned (through approximately 72°) behind a group of refrigerant inlet apertures, so that the adjacent chamber comes into communication with the next group of refrigerant inlet apertures. 
     FIG. 7  shows a cross section through a heat exchanger  110  with an end piece  120 , which has a base plate  130 , a diverter plate  140 , a cover plate  150  and collection boxes  160 ,  170 . A tube  180  is received in two apertures  190 ,  200  in the base plate  130 , with a cutout  210  in one end of the tube  180  bearing against a web  220  of the base plate  130 . The cutout  210  is slightly higher than the web  220 , so that the tube end projects slightly above the base plate  130 . Heat-exchange passages (not shown) in the tube  180  communicate with through-passages  230 ,  240  in the diverter plate  140 . The through-passages  230 ,  240  are in turn connected via cutouts  250 ,  260  in the cover plate  150  and cutouts  270 ,  280  in the housings  290 ,  300  of the collection boxes  160 ,  170  to collection chambers  310 ,  320 . To improve manufacturing reliability, the edges of the cutouts  250 ,  260  are provided with extensions  330 ,  340  which engage into the cutouts  270 ,  280 , resulting in an orientation of the collection boxes  160 ,  170  with respect to the cover plate  150 , in such a manner that the cutouts  250  and  260  in the cover plate  150  are flush with the cutouts  270  and  280 , respectively, in the collection-box housings  290 ,  300 . 
     FIG. 8  shows a refinement of the heat exchanger from  FIG. 6 . In the heat exchanger  410 , the configuration of diverter passages likewise adopts a pattern which repeats itself after in each case two U-tubes  420 , corresponding to a flow path through the heat exchanger  410 . In this case, however, in each case two adjacent flow paths are arranged mirror-symmetrically with respect to one another. This means that either the through-passages  430 ,  440  of a flow path  450  come to lie next to the through-passages  460 ,  470  of an adjacent flow path  480 , or a diverter passage  490  of a flow path  500  comes to lie next to a diverter passage  510  of an adjacent flow path  520 . In the latter case, it is possible for the adjacent diverter passages  530 ,  540  to be connected to a connecting passage  545 , so that mixing and flow compensation is realized between the participating flow paths  550 ,  560 . This is particularly effective in a region of the edge of the heat exchanger, since the flow conditions there may otherwise be particularly unfavorable for the performance of a heat exchanger. In other regions of the heat exchanger, mixing of the first medium by means of a connection passage between two adjacent diverter passages is also possible. The flow paths  450 ,  480 ,  485 ,  500 ,  520 ,  550 ,  560  in each case comprise eight sections, whereas the flow path  445  comprises just four sections, in order to reduce a pressure drop along the flow path  445 , likewise on account of the unfavorable flow conditions in the edge regions of a heat exchanger. In this case, mixing with the adjacent flow path  450  is likewise applied. 
     FIG. 9  shows a further example of a connection arrangement for flow-path sections of a heat exchanger  610 . In this case, the flow-path sections  620  on the inlet side  630  of the heat exchanger  610  have a smaller cross section of flow than the flow-path sections  640  on the outlet side  650 . By way of example, if the heat exchanger  610  is used as an evaporator, this asymmetry serves to match the cross sections of flow to the density of the first medium along the flow paths  660 . 
     FIG. 10  shows a further example of a connection arrangement for flow-path sections of a heat exchanger  710 , produced by a configuration of through-passages and diverter passages of a diverter plate  720 . In this case, the flow paths  730  and  740  are in each case oriented in such a way that an inlet and an outlet for the first medium, produced by through-passages  750 ,  760  and  770 ,  780 , respectively, are arranged as far away as possible from edges  790  or  800  of the heat exchanger  710 . 
     FIG. 11  shows a further example of a connection arrangement for flow-path sections of a heat exchanger  810 , produced by a configuration of through-passages  812  and diverter passages  814  of a diverter plate  820 . In this case, the flow-path sections are connected to one another in the following order: 1 (downward)—2 (upward)—3 (downward)—4 (upward)—5 (downward)—6 (upward) etc. 
     FIG. 12  shows a tube plate  1010  with a cover plate  1020  and a plate  1030  formed by integral configuration of a diverter plate with a base plate. The cover plate  1020  has cutouts  1040  for connection to two collection chambers, while through-passages  1050  of the diverter plate and, beneath them, narrower tube-receiving parts  1060  in the base plate can be seen in the plate  1030 . 
     FIG. 13  and  FIG. 14  show the tube plate from  FIG. 12  in a cross section and a longitudinal section, respectively, in each case in the assembled state with a tube  1070 . 
     FIG. 15  shows a similar tube plate  1110 , the cover plate  1120  of which does not have any cutouts. Diverter passages  1140  for diversion over the depth are arranged in the plate  1130  comprising the diverter plate and the base plate. 
     FIG. 16  shows a further possible option for the configuration of a two-part tube plate  1210 . In this case, the diverter plate is formed integrally with the cover plate, producing a plate  1220 . The plate has a diverter passage  1230  for diversion over the depth, which is produced by a curvature. The base plate  1240  is likewise curved, so that the tube  1260  received in the cutout  1250  in the base plate  1240  is held more securely and therefore in a manner which is more resistant to pressure. The tube  1260  in this case butts against the edge  1270 ,  1280  of the diverter passage  1230 , since the curvature in the plate  1220  is not as wide as the curvature in the plate  1240 . 
     FIG. 17  shows a heat exchanger  1310  of purely countercurrent design. The pure countercurrent design is distinguished by the fact that diversions take place only over the depth but not over the width. In this context, it is irrelevant how many sections the flow paths comprise. The flow paths may, for example, comprise in each case four sections, in which case three diversions per flow path are required over the depth. The heat exchanger  1310  has flow paths  1320  with in each case one diversion over the depth and accordingly with in each case two flow-path sections, which are aligned with one another in the main direction of flow of the second medium. The upper end piece  1330  has a tube plate  1340  and two collection boxes, which are not shown for the sake of clarity. The tube plate comprises a base plate  1350 , a diverter plate  1360 , which in this case serves merely to pass through the first medium, and a cover plate  1370  with apertures  1380  for connection to the collection boxes. The lower end piece  1390  comprises only a plate  1400 , in which a base plate, a diverter plate and a cover plate are integrated. The structure of the plate  1400  is explained on the basis of  FIGS. 18 and 19  below. 
     FIG. 18  shows a cross section through and  FIG. 19  a cut-away oblique view of the plate  1400  from  FIG. 17 . A tube  1410  is received in a cutout  1420 , which simultaneously serves as a diverter passage for the first medium, the diverter passage being closed off with respect to the outside by the region  1430  of the plate  1400 . A narrowing provides the cutout  1420  with edges  1440 ,  1450  which serve as a stop for the tube  1410 . This produces a single-part tube plate of very simple design and with a high ability to withstand pressure. The tube  1410  in this case serves to form two sections (downward  1460  and upward  1470 ) of a flow path. 
     FIG. 20  shows a tube plate  1800  of similar construction, which is likewise of single-part structure and over and above the diverter passages  1820  and the tube stops  1830  also has apertures  1810  in the region of the cover plate in order to allow it to be connected to one or two collection boxes. 
   To summarize, the invention allows the production of a heat exchanger which comprises a row of tubes (to realize heat-exchange passages), two plates (the tube plates) and two tubes (the collection boxes). This makes it possible to realize an extremely simple and, moreover, pressure-stable structure of the heat exchanger. 
     FIGS. 21 to 24  show exemplary embodiments of a tube plate which involves little outlay on material and, for this reason, low materials costs and a low weight. 
   The tube plate  2010  in  FIG. 21  has, between the tube-receiving cutouts  2020  with the tube-stop edges  2030 , cutouts formed as apertures  2040  in order to save material. For the same reason, in the case of the tube plate  2110  shown in  FIG. 22 , cutouts formed as lateral notches  2120  are provided. The tube plate  2210  in  FIG. 23  and  FIG. 24  is completely separated between the tube-receiving cutouts  2220 . In this case, the tubes  2230  may under certain circumstances be stabilized by the corrugated fins  2240  alone. 
     FIG. 25  shows a further example of a connection arrangement for flow-path sections of a heat exchanger  2310 , produced by a configuration of through-passages  2320  and diverter passages  2330  of a diverter plate  2340 . In this case, the flow-path sections are connected to one another in the following order: 1 (downward)—2 (upward)—3 (downward)—4 (upward)—5 (downward)—6 (upward). It is possible to provide a tube for each flow-path section. However, it is preferable for a tube to include two or more flow-path sections, for example the flow-path sections  1 ,  4  and  5  or the flow-path sections  2 ,  3  and  6 . In this exemplary embodiment, flat tubes are particularly suitable for this purpose. Any further desired connection arrangements for flow-path sections are also conceivable over and above those illustrated. 
   The present invention has been described in part on the basis of the example of an evaporator. However, it should be noted that the heat exchanger according to the invention is also suitable for other uses.