EP1654508B2 - Heat exchanger and method for the production thereof - Google Patents

Description

The present invention relates to a heat exchanger according to the preamble of claim 1, as is used in particular in vehicles as an oil cooler. Such a heat exchanger is made of DE 199 59 780 A1 known.

So-called plate heat exchangers are known which are formed from a stack of plates lying side by side. Cavities are formed between the plates, through which a first or a second medium flows alternately.

In addition to being used as a cooler, with the first medium, for example, cooling water and the second medium being the working medium to be cooled - in the case of an oil cooler of an internal combustion engine, the engine oil -, use as an evaporator of a cooling device such as a vehicle air conditioning system is also conceivable, one of which both media is the coolant and the other is the refrigerant.

It is known that the plates are profiled so that contact points occur between the plates. The plates are attached to each other in the area of the contact points. In addition, the plates lie against one another on the outside so that the cooling medium or the working medium flows exclusively through the cavity. The first and second medium are each fed through a corresponding inflow line and led away via a drain line. Inflow lines and outflow lines each serve as collecting lines, in which the fluid flow of all corresponding cavities is fed in or out.

In plate heat exchangers, turbulence-increasing internals for improving the heat transfer and for increasing the surface area are usually introduced into the fluid channels and firmly connected to the heat-transferring plate. As a result, in addition to the thermodynamic property of the duct, the strength property of the cooler is greatly improved.

A disadvantage of such turbulence plates is that during the production of the passage openings, chip formation easily occurs, which can lead to contamination of the medium flowing through. In addition, dirt easily accumulates in the area of the turbulence plates. This can undesirably impede the flow through the cavity. In addition, they represent an additional component to be manufactured, which increases the cost of the heat exchanger due to increased manufacturing costs and material costs.

It is therefore an object of the invention to provide a heat exchanger which does not have the disadvantages of known heat exchangers.

This object is achieved by a plate heat exchanger according to claim 1.

A heat exchanger, as is used in particular as an oil cooler in the field of motor vehicles, is formed from interconnected plates. Cavities which are closed off from the outside are formed between the plates. The cavities are alternately via at least one inflow and outflow line with the first and second medium supplied and are also flowed through by the appropriate medium. The plates are profiled in such a way that contact points occur between the respective profiles of the plates. The plates are connected to one another in the area of these contact points. The plates are designed in such a way that the flow of the first or second medium forming between the plates does not run in a straight line from the corresponding inflow line to the corresponding outflow line.

This measure has the advantage that the medium flowing through is partly redirected several times on its flow path. This improves the distribution of the fluids across the plate width. Depending on the flow behavior (viscosity) of the medium flowing through, turbulent flows may also occur. The repeatedly occurring changes in direction of the fluid in the channel and the eddies that may form in the area of the opening wave channel tear the boundary layer that is formed again and again. This leads to an improved heat transfer.

According to the invention, the plates have a repeating wave profile which then runs at least in a direction transverse to the flow direction, which is the straight connection from the entry point of the medium to the exit point. The wave profile is zigzag around this direction. Such a wave profile easily forms flow guide areas which are suitable for guiding the flow of the medium flowing through the corresponding cavity. The flow is thereby deflected several times in an advantageous manner, in particular not only in the plate plane but also out of the plate plane. In areas in which the distance between the plates is different, the flow rate may vary. At the same time, it is advantageously achieved that the medium as a whole is distributed over the entire surface of the plates, thus making the best possible use of the entire heat exchange surface.

According to the invention, the wave profile between flow regions has straight legs, the course of the wave profile being characterized by the leg length of the legs, the leg angle between the legs and the profile depth of the wave profile. The cross section of the profile of a corrugated profile is determined by the course in the region of the legs and in the region of curvature, preferred configurations being able to provide a deviation in the cross-sectional shape in these regions.

The zigzag wave profile is characterized by the leg length, the leg angle between adjacent legs and the profile depth. Preferred refinements of the invention provide that the leg length is in the range from 8 to 15 mm, preferably in the range from 9 to 12 mm. Typical values of the profile depth - which is measured, for example, from the distance between a shaft crest and the plate center plane - are in the range from 0.3 to 1.5 mm. A profile depth between 0.5 and 1 mm can be advantageous for many applications, values of approximately 0.75 mm being preferred. The leg angle between two legs of the wave profile is preferably between 45 ° and 135 °. Values around 90 ° in particular represent a good compromise with regard to the distribution of the fluid, flow rate and flow rate of the heat exchanger.

The leg length and the leg angle influence on the one hand the flow control function of the wave profile, but on the other hand also the arrangement of points of contact between adjacent plates, which are necessary for the stability of the heat exchanger. The inherent rigidity of the plates against pressurization by the media can be without mutual support cannot be guaranteed if the material thickness of the plate is chosen to be low, as is desirable in many applications for reasons of weight saving and heat exchange.

In a preferred embodiment, the plates are connected in the area of the contact points by brazing, for which purpose the plates are coated at least on one side with a soldering aid, such as solder. The leg length and leg angle are preferably selected as a function of the medium flowing through and its viscosity. Leg length and leg angle have a major influence on the flow velocities and the associated heat exchange, so that they can be adapted to the respective purpose. The values mentioned above relate in particular to the use of heat exchangers as an oil cooler in vehicles, where the heat exchange takes place between engine oil and cooling water. In addition, they are of course also dependent on the dimensioning of the plates and the space resulting from the distance between the plates.

The shape of the wave profile is essentially determined by the shape of the cross section perpendicular to the outer edge of the profile in this area and by the sequence of the profiles determined by the division in the course transverse to the direction of extension of a wave profile across the plate. Preferred refinements provide for a constant division, that is to say a fixed distance between any two adjacent wave profiles. The shape of the wave profile is particularly advantageous if it has a flat area on the outside of the wave back. The flat area in particular has a width of 0.1 to 0.4 mm. The flat area enables good, flat contact of adjacent plates with each other and thus an easy and stable production of the Support or connection - as by brazing - of adjacent plates.

The material of the plates is preferably aluminum. This material has the advantage of having a low density and at the same time making it possible to produce the wave profile in a simple manner, for example by embossing. To produce the connection between two adjacent plates in the area of the contact points and in the area of the edges, it can be coated on at least one side with soldering aids such as hard solder. Depending on the selection of the soldering aid and the layer thickness of the application of the soldering aid, a coating on both sides with soldering aid can also be provided. The coating with soldering aids is intended, in particular in the area of the edges and the inflow and outflow lines in the block, to reliably establish a fluid-tight connection of two plates to one another in a joining process using a joining tool (brazing furnace) without the use of further aids or auxiliaries.

In an embodiment according to the invention, it is provided that the plates have bores which serve as inflow and outflow lines in the area of the heat exchanger and the bore axis of which runs perpendicular to the plane of the plate. The holes are drilled in an area that is raised from the base plane of the plates. The raised area is preferably so raised that there is a tight connection between the raised area and the subsequent further plate in every second plate space, so that a fluidic connection between the bores and the plate space occurs only in every second plate space. This measure enables fluid supply and discharge from the plate interspaces without the use of lines, so that the flow of cooling medium or working medium alternates between them.

The fluid-tight system between an elevated area and an adjacent plate can be achieved not only by positive locking but also by other connection technology, such as brazing. For this purpose, the raised area has, in particular, a preferably flat contact section which is in contact with a preferably flat contact edge of the adjacent plate, to which a fluid-tight connection results.

The raised area and the bores in the raised area can not only have a circular cross section, oval or slot-like designs are also possible and advantageous. The longer of the two axes of the slot-like design should preferably be arranged transversely to the main flow direction of the fluid. This measure also serves to improve the heat exchange between the two media, since a larger heat transfer area then remains with the same overall expansion of the plates.

In addition, distribution channels are provided in the area of the inflow lines and the bores assigned to the inflow lines, which are also designed as a wave profile. It corresponds to particularly preferred further developments of the invention if the wave profile of the distribution channels differs from the other wave profiles with regard to the characteristic sizes of the wave profile. The corrugated profile of the distribution channels has in particular a leg angle that is less than 45 ° and in particular in the range of approximately 5 ° and approximately 25 °. Both an abrupt and a continuous transition in the profile design between the distributor profile and the wave profile can be formed in other plate areas. The distribution channels take on the task of distributing the fluid flow as evenly as possible over the entire width of the plate. This improves the efficiency of the heat exchanger, because in this case a larger heat exchange area is actually used for exchange. Flow channels can also surround the raised areas to improve the distribution of the medium over the entire surface of the heat exchanger. The flow channels are preferably formed by a section without a wave profile, which is guided in particular in a ring-like manner around the raised area. A section of reduced flow resistance is thus formed, into which several wave profiles open, so that this also fulfills a distribution function for the medium.

It corresponds to a particularly simple and inexpensive to manufacture embodiment of a heat exchanger according to the invention if it is manufactured from a sequence of plates. The plates can have profiles that differ from one another on both sides with regard to their wave profiles. A heat exchanger can be formed, in particular, from a stack of such plates which are configured identically to one another. This is because, in particular, it is possible for plates that are adjacent to one another to be rotated by 180 degrees to one another, the axis of rotation extending perpendicular to the plate plane. This type of stack of plates is particularly advantageous if the bores assigned to the inflow lines are formed from raised locations and these are to be assigned alternately to two different line routings. The elevations in the area of the inflow lines can in particular be designed as an essentially frustoconical dome. Alternatively, there are dome-shaped elevations which have an elliptical cross section.

The plates can be designed identically to one another, corresponding to one another, or similar or different. Plates which are identical to one another have identical properties with regard to the characteristic properties of the wave profile and the shape of the wave profile on. Corresponding plates are identical in structure to one another, but it is possible that the plates have, for example, mutually different leg angles. Corresponding plates preferably have a mutually different shape of the wave profile and / or values characterizing values different from one another, but are corresponding to one another with regard to the formation of the edge and the formation of the front and back of the plates. The alternating use of, for example, two corresponding plates, which differ in the characteristic sizes only by different leg angles, has the advantage that the position and relative position of points of contact between the plates in the profiled area with regard to the required rigidity and the required flow in are easy to optimize.

The connection between the plates is made in particular by brazing. In order to achieve a good sealing effect and at the same time a stable construction of the heat exchanger in the region of the edge of the plates, it can be provided that the plates have a bent edge whose height is selected such that at least two plates adjacent to one another abut one another in this edge region and overlap. The number of overlapping plates in the edge area can be up to five. The greater the number of overlapping plates, the stiffer is the wall formed in this way and which closes the heat exchanger to the outside. At the same time, this supports the manufacture of a permanently stable, robust, fluid-tight closure of the panels to the outside. Preferred further developments provide that the wave profile extends into the edge and in particular over its entire width. When designing the wave profile, care must be taken to ensure that the plates remain stackable, which is due to the fact that the wave profile runs in the edge area to match the mounting position of two neighboring panels to each other.

The wave profile extends into the edge when the wave profile ends in the root region of the offset, so that the profile with its profile depth extends into the edge. For reasons of production technology in particular, it can be advantageous if the root of the edge lies in an area free of wave profiles, since the edge can then be bent in an area not stiffened by a profile. Preferred refinements then envisage that the groove which forms between the edge and the wave profile area is as narrow as possible. In particular, it is chosen so narrow that a solder flow occurs during brazing, which closes this channel completely or at least to such an extent that only a negligible amount of medium flows through the channel. The channel must be designed in such a way that it does not serve as a bypass channel for the medium and a significant proportion of the media flows through the channel instead of in the area of the wave profile.

To improve the stability of the heat exchanger to the outside and to simplify the connection of the external inflow lines and external outflow lines of coolant and working medium, it can be provided that at least one end face of the heat exchanger without a profile end plate is arranged. The end plate without profile on the outside in particular has flanges as connection points. The end plates can in particular also have a greater material thickness than the other plates and thus represent an in particular stiffening, stabilizing element which forms a housing part which closes the end faces to the outside. The side walls of the housing, which close off the heat exchanger from the outside, are formed over the edge that delimits the plates and that coincides with the edge adjacent plates overlap. The edges are connected to one another in a fluid-tight manner, which can be done in particular by brazing.

One way to characterize the flow through a stack of plates is to determine the hydraulic diameter between two adjacent plates along the main flow direction of the medium. The hydraulic diameter represents a ratio between the flowable channel cross section and the heat exchange area. The hydraulic diameter hD is defined as four times the ratio of the area ratio Fv to the area density Fd. The area ratio Fv is determined as the ratio of the free channel cross-section fK to the total end face S of the channel between two adjacent plates, the area density Fd from the ratio between the heat-transferring area wF and the block volume V. The following therefore applies: $$\mathit{hD}=\frac{\mathrm{4th}\frac{\mathit{fK}}{S}}{\frac{\mathit{wF}}{V}}$$

According to a preferred embodiment of the invention, the hydraulic diameter should remain as constant as possible over the entire main flow direction of the medium. In this way, an improved and possibly a uniform flow through the plate intermediate space, which forms the channel, is achieved.

According to a preferred embodiment of the invention, and in particular when the heat exchanger is used as an oil cooler, the hydraulic diameter is between 1.1 mm and 2 mm. Preferred values for the hydraulic diameter are around 1.4 mm. The deviation of the hydraulic diameter over the period of profiling a pair of plates preferably not fluctuate by more than 10%, in particular by less than 5%. Of course, the selection of the hydraulic diameter also depends on the media flowing in the spaces between the plates. The values mentioned apply to an oil cooler in which water and oil flow through the heat exchanger.

According to a preferred embodiment, the contact points between two adjacent plates of the heat exchanger are evenly distributed over the plate surface. The contact points between two adjacent plates preferably have a surface density of 4 to 7 per cm ² , particularly preferably 5 to 6 per cm ² . With such a configuration, sufficient strength of the heat exchanger is possible without an excessive increase in pressure loss.

Heat exchangers according to the invention can serve on the one hand as an oil cooler, but also as an evaporator or condenser. The cooling circuit of such a device can not only be used to air-condition a (vehicle) interior, but also to cool heat sources such as electrical consumers, energy stores and voltage sources or charge air of a turbocharger. The heat exchanger is a condenser if, for example, condensation of the refrigerant in an air conditioning system takes place in a compact heat exchanger that is subjected to coolant and the coolant releases the heat in a heat exchanger to air as a further medium. The evaporation or condensation of another medium in a heat exchanger according to the invention can also take place, for example, in applications in fuel cell systems.

In all of these applications as a condenser or evaporator, the use of a powerful, compact heat exchanger is desirable, in which a coolant gives off or absorbs heat as a second medium. Due to very high internal cleanliness requirements, no punched turbulence inserts can be used on the refrigerant side, through which aluminum particles are introduced into the refrigerant circuit. In addition to these purity requirements, an optimal distribution of the fluid at the inlet is also necessary, which then evaporates or condenses in the heat exchanger. Ideally, the fluid, which is predominantly in liquid form during evaporation at the inlet and in vapor form during condensation, is distributed over the entire width of the pane. A special feature of evaporation and condensation is the often low temperature difference between the two fluids. If the transverse distribution of the liquid fluid to be evaporated or the vaporous fluid to be condensed is not optimal, high performance losses can quickly occur. Heat exchangers according to the invention offer solutions to these problems.

A method according to the invention for producing a heat exchanger, in particular a heat exchanger according to the invention, provides that the corrugated profile is produced by embossing the plates, then the plates are stacked accordingly and then connected by brazing. According to a preferred embodiment, the plates are stacked on top of one another in such a way that two plates adjacent to each other are arranged rotated by 180 degrees. The plates are joined by brazing in such a way that the plates are sealingly connected to one another at their edge and, in particular, adjacent plates are connected at the points of contact of profiles. As a result, in a particularly advantageous embodiment, a stable and torsionally rigid element is produced.

Fig. 1a, 1b:

die Vorderseite und Rückseite einer nicht erfindungsgemäßen Platte;

Fig. 2:

die Ansicht eines Stapels von solchen Platten;

Fig. 3:

eine Schnittdarstellung mehrfacher aufeinander gestapelter Platten im Bereich des Randes;

Fig. 4:

in vergrößerter Darstellung die Ausbildung der erfindungsgemäßen Verteilerkanäle im Bereich der Bohrungen;

Fig. 5:

eine schematische Darstellung einer Abschlussplatte mit Anschlussflaschen;

Fig. 6:

die Fluidführung durch die Platten, wenn bei einem der Fluide ein Durchströmen aller Plattenzwischenräume vorliegt;

Fig. 7a-7d:

die Auswirkungen der Gravitation auf die Flüsssigkeitsverteilung;

Fig. 8

den hydraulischen Durchmesser über eine Periode des Wellenprofils in Hauptströmungsrichtung des Mediums im Zwischenraum zweier Platten;

Fig. 8a

eine Aufsicht auf eine Platte eines Wärmeübertragers;

Fig. 8b

den hydraulischen Durchmesser in Hauptströmungsrichtung des Mediums im Zwischenraum zweier Platten;

Fig. 8c

eine Auftragung der Festigkeit und des Druckverlustes eines Wärmeübertragers über der Dichte der Berührungsstellen zwischen zwei Platten;

Fig. 9

einen Ausschnitt aus einer Wärmeübertragerplatte;

Fig.10

eine nicht erfindungsgemäße Platte eines Wärmeübertragers;

Fig. 11a,b

jeweils einen ausschnittsweisen Querschnitt eines Wärmeübertragers;

Fig. 12a,b

jeweils einen ausschnittsweisen Querschnitt eines Wärmeübertragers.

Incidentally, the invention is explained in more detail below with reference to the embodiment shown in the drawing. It shows:

1a, 1b:

the front and back of a plate not according to the invention;

Fig. 2:

the view of a stack of such plates;

Fig. 3:

a sectional view of multiple stacked plates in the region of the edge;

Fig. 4:

in an enlarged view, the design of the distribution channels according to the invention in the area of the bores;

Fig. 5:

a schematic representation of an end plate with connection bottles;

Fig. 6:

the fluid flow through the plates when there is a flow through all plate interspaces in one of the fluids;

7a-7d:

the effects of gravity on fluid distribution;

Fig. 8

the hydraulic diameter over a period of the wave profile in the main flow direction of the medium in the space between two plates;

Fig. 8a

a top view of a plate of a heat exchanger;

Fig. 8b

the hydraulic diameter in the main flow direction of the medium in the space between two plates;

Fig. 8c

a plot of the strength and pressure loss of a heat exchanger over the density of the contact points between two plates;

Fig. 9

a section of a heat exchanger plate;

Fig. 10

a plate of a heat exchanger not according to the invention;

11a, b

each a sectional cross-section of a heat exchanger;

Figures 12a, b

each a section of a cross section of a heat exchanger.

The Figures 1a and 1b show the representation of a front or a back of a plate not according to the invention, while the Fig. 2 the representation of a corresponding, from plates according to the Figures 1a and 1b formed stack shows.

A plate 10 has a base body 11, which is provided on its front and rear side with a corrugated profile 12, which has been introduced into the base body 11 by stamping. In the in the Figures 1a and 1b illustrated embodiment corresponds to the wave profile 12 of the back according to the Fig. 1b the negative profile of the front, as shown in Fig. 1a . In this case, the wave profile 12 is formed from a plurality of legs 10 which are at a leg angle 13 and each have a fixed leg length 15 and connect the curvature region 16 to one another. The wave profile extends across the plate 10. There is a multitude over the length of the plate 10 of wave profiles 12 formed one behind the other, the wave profiles following one another in particular at close spacing and being aligned with one another. The plate 10 has a circumferential cranked edge 17 which laterally delimits the plate. The wave profile 12 extends into the edge.

The wave profile 12 can be introduced into the plate 10 by embossing. The embossing can be carried out in such a way that the two sides in the plate 10 have different wavy profiles, in particular the wavy profile 12 on one side can represent the negative of the wavy profile 12 on the other sides, as is the case, for example, in the exemplary embodiment according to FIGS Figures 1 a and 1b can be seen. It is also possible for a plate 10 to have the same wave profile 12 on both sides. Both times, the wave profiles on the two sides of a plate 10 can be in alignment with one another or offset from one another. The cross section of the wave profile 12 is characterized primarily by the fact that it has a wave ridge which forms a flat region which runs parallel to the plate plane. The flat area preferably has a width between 0.1 mm and 0.4 mm.

In the area of the corners, the plate has a bore 18 which passes through the plate perpendicular to its plane of progression. Two of the bores are made in a raised area 19. One of the holes serves to supply working medium into the area between two plates, while in particular the diametrically opposite hole serves to drain off working medium. Another pair of holes is used for the inflow and outflow of cooling medium. Are plates 10 as in the Fig. 2 shown stacked one on top of the other, either the lines assigned to the working medium or cooling medium are alternately fluidly connected to the intermediate space 20 between two plates 10, since the raised area 19 of corresponding bores 18 abuts the adjacent plate 10. The bores 18 thus form the feed lines or drain lines for the cooling medium and working medium through a stack 21 of plates. The Fig. 2 shows a perspective view of such a stack 21 of plates 10 according to the Figures 1 a and 1b.

In the Fig. 3 is the sectional view through a stack 21 according to the Fig. 2 shown. Plates 10 abut one another and are stacked one above the other. The cranked edge 17 of adjacent plates abuts one another and is designed in such a way that the edge of several plates each overlaps. In order to achieve a fluid-tight connection between the edge 17 of two adjacent plates, these are connected to one another by brazing. In addition, two mutually adjacent plates abut each other in different areas of their wave profiles 12. In these areas, too, the plates are connected to one another by brazing. To make the soldered connections, the plates can be coated on one side or on both sides with a solder. An intermediate space 20 is formed between two mutually adjacent plates 10, the intermediate space being flowed through either by working medium or by cooling medium. The stack of plates is designed in particular in such a way that working medium and cooling medium flow alternately through the interspaces 20, so that cooling medium and working medium flow around each of the plates 10. A heat exchange between cooling medium and working medium can thus take place across each of the plates 10.

Due to the fact that the plates have a wave profile, the intermediate space 20 is of different internal width at a large number of locations. The repeatedly occurring changes in direction of the fluid in the channel and the eddies that form in the region of the opening wave channel tear the boundary layer that forms again and again. this leads to one, compared to a smooth channel, greatly improved heat transfer.

This promotes the other exchange between the two media across a plate 10. In addition, the design of the plates 10 ensures that no linear, rectilinear flow from the supply line to the drain line is possible. Depending on the viscosity of the medium, such a design of the intermediate space 20 can also result in wholly or partly turbulent flows and thus an improved heat exchange between the working medium and the cooling medium. In addition, the course of the wave profile 12 transversely to the extent of the plate 10 also guides the corresponding medium over the entire width of the plate 10, so that the utilization of the heat exchange surface which a plate 10 offers is improved, thereby reducing the efficiency of such a plate Heat exchanger is further increased. An essential guiding element for the flow guidance is also to be seen in the fact that, between two adjacent plates 10, like a Dalton grid, there are always contact points which act as a flow obstacle and flow deflection points. In addition, these points of contact act to support the plates against one another and thus have a stabilizing function for the plates 10, in particular with regard to the determination behavior of the plates 10 Fig. 8 To maintain the uniform value of the hydraulic diameter between two plates, the arrangement of the contact points of the profiles of adjacent plates is important. These result from the wave profiles of mutually facing sides of the plates and from the profile profiles. A uniform hydraulic diameter ensures a uniform flow of the fluid across a wave profile and across the entire width of the plate gap. A hydraulic diameter that is optimized for the application is achieved by constructive design selection of the shaft profile.

The Fig. 4 shows an enlarged view of a plate 10 with a wave profile 12, which is formed by the legs 14, which have a leg angle 13 of 45 ° to each other. The plate 10 is delimited by a cranked edge 17, the wave profile 12 extending into the area of the edge 17.

This figure shows in particular that between two bores 18, one of which is formed in a dome-shaped, raised region 19. Distribution channels 22 are formed in the area between the two bores 18, which in particular also extends into the area between the bores 18 and the nearby edge 17. The distribution channels 22 are formed by a corrugated profile 23, which differs from the corrugated profile 12 in the remaining area of the plate 10 with regard to the leg angle and the leg length. The leg angles are in particular in a range below 45 °. In the region of the bore, which is not introduced in a raised region 19, the distributor channels 22 lead, in particular, medium entering the corresponding space transversely to the main extent of the plate 10 and thus ensure a uniform distribution of the fluid flow over the entire width of the plate. The raised area 19, into which the other hole 18 is made, lies in a sealing manner, in particular, against the hole area of the plate 10 lying above in a stack and can be connected to it by brazing. This creates a fluid-tight seal between the space 20 and the plate 10 lying above it, so that no media flow can take place between this hole 18 and the space and the medium flowing through this hole 18 only enter the space 20 that follows after the plate 10 lying above it can. The bores 18 can also be elongated to increase the cross-section, the elongated axis then preferably extends transversely to the main flow direction H.

Continuing education, as in the Figure 4a shown, a profile-free ring area 99 around a dome-shaped area 19 around a channel, which connects several wave profiles 23 and distribution channels 22 to one another and ensures a good transverse distribution of medium, since it forms a low-flow area. The ring region 19 has an embossing depth which essentially corresponds to the embossing depth of the wave profile 23.

The Fig. 5 shows a top view of an end plate 24, which has four connecting flanges 25, which are aligned with the bores 18 of the plates 10 of a plate stack 21. Such an end plate can be arranged on the one hand or on both sides of the stack 10 and can close it off to the outside. The end plate 24 has no corrugated profile 12 at least on the outside. If a connection plate 24 is arranged on either side of the plate stack, it is possible that one of the two plates has four connection flanges 25 or that one plate has one, two or three connection flanges 25 and the opposite plate has the remaining number of 4 connection flanges 25 . The connection flanges 25 are each assigned to the connection bores. The connection flanges 25 serve to connect the external lines for the supply and discharge of working medium and cooling medium. In addition, the end plate 24 stiffens the plate stack 21 and forms the front housing wall. The end plate 24 can have an edge 17 which is adapted to the edge 17 of the plates 10. The superimposed edges 17 of the plates form in a plate stack 21, as in the Fig. 2 is shown, the side housing wall of the heat exchanger. A stack of plates according to the Fig. 2 , provided with connecting flanges 25 and an end plate 24 thus forms a heat exchanger. Such a heat exchanger can serve in particular as an oil cooler in a vehicle.

The Figure 6 shows a plate stack 21, consisting of a base plate 88, of plates 10 and of a cover plate 89, which has three holes 18, 18a. The bores 18 serve to guide a first medium which is carried out between the plates in such a way that the plate interspaces 20 are flowed through parallel to one another. A second medium enters the plate stack through the hole 18a and exits the plate stack through the hole 18b in the base plate.

The flow channels for the second medium are divided into at least two flow paths, which are flowed through in succession and each consist of one or more flow channels, by at least one partition wall arranged between the bores 18a and 18b and not visible from the outside. In contrast, the flow channels for the first medium are flowed through in parallel. In a modified exemplary embodiment, however, the flow channels for the first medium are likewise divided into at least two flow paths, through which the flow passes one after the other.

The 7a to 7d show different orientations of the main flow direction H of the plate gap 20 with respect to the gravitational direction G in the installed position of the heat exchanger, as well as the favorable influence on the distribution of the medium in the plate gap, especially when used as a condenser. The Figures 7a and 7c show the application of an evaporator. From the 7a and 7c it can be seen that the main flow direction H should be transverse or antiparallel to the gravitational direction G, depending on whether the longer L or the narrower side S of the plates is oriented in the gravitational direction G if it is a liquid medium. The gravitation supports a transverse distribution of the medium with respect to the main flow direction. On the other hand, they show 7b and 7d that there is a gaseous Medium is best distributed between the plates 10 if the direction of gravity G counteracts the distribution of the medium between the plates.

The Figure 8 shows the hydraulic diameter over an entire wave profile in the main flow direction H, wherein in Fig. 8a the formation of the wave profile 23 with the contact points of adjacent plates 10 shown as circles 98 is shown. It can be seen that the wave profile moves in a bandwidth between 1.2 and 1.6 over the entire period of the pattern resulting from the wave profiles 23 of the adjacent plates and is approximately 1.4 on average. The design of the wave profiles is preferably selected such that the hydraulic diameter in the main flow direction is as constant as possible.

In Fig. 8a the points of contact between two adjacent plates of the heat exchanger are shown as circles in a plan view of one of the plates. It can be clearly seen that the contact points are evenly distributed over the plate surface. A preferred areal density of the contact points for sufficient strength is 4 to 7 per cm ² , particularly preferably from 5 to 6 per cm ² . This is based on 8b, 8c clear.

Fig. 8b shows the hydraulic diameter hD of a flow channel between two plates over several profile periods, again in the main flow direction H of the medium. A large areal density of the contact points allows a course to be expected which is shown by the broken curve in Fig. 8b is shown since many points of contact, viewed in the main flow direction H, arranged side by side restrict the flow channel cross section. This is illustrated by the dents 40 in the hydraulic diameter. Due to the configuration according to the invention, in particular the uniform distribution of the contact points these dips are eliminated or reduced, so that the curve for the hydraulic diameter is shown in solid lines. The fewer of these dips in a flow channel, the fewer constrictions for the flowing medium, that is, the pressure loss can be reduced with the same areal density of the contact points.

A uniform distribution is achieved in particular in that a region of curvature between two in particular straight legs of a wave profile of a plate does not come to lie exactly above a region of curvature of an adjacent plate. Under certain circumstances, it is rather advantageous if the curvature areas of adjacent plates - as seen in the main flow direction - are offset from one another in such a way that each curvature area is flanked transversely to the main flow direction by two contact points of the two plates, which advantageously have the same or similar spacing from one another as from other contact points and thus release a flow passage between them which allows a significant flow and thus does not contribute to an undesirable extent to a pressure loss in the flow channel formed between the plates. On the other hand, the distance between two points of contact should not be chosen too large, since otherwise local weak points in the strength of the heat exchanger could otherwise form.

In Fig. 8c a plot of the strength F and the pressure loss DV of a heat exchanger over the density BD of the contact points between two plates is shown. The strength of the heat exchanger increases linearly with the contact point density BD and is reflected in Fig. 8c down as straight line 41. In contrast, the pressure loss DV in this plot (42) shows a progression; so that there is a maximum 43 at a contact point density for the ratio F / DV of strength F to pressure loss DV BD1 results. If the pressure loss is now reduced (44) according to the invention, the aforementioned maximum is increased (45) and possibly shifted to a higher contact point density BD2. It has been shown experimentally that a contact point density of 4 to 7 per cm ² , preferably of 5 to 6 per cm ² , leads to good strength with an acceptable pressure loss.

Viewed differently, as in Fig. 8c represented by the arrow 46, with a constant pressure loss DV, a transition to a higher contact point density BD, which leads to an increased strength F of the heat exchanger.

In Fig. 9 a section of a plate 30 of a heat exchanger is shown. The connection points between two adjacent plates are given by the crossing points of the respective wave profiles of the two plates. In order to ensure that a distance between the edge of the plate and the intersection points near the edge is not too great, it may be advantageous to change the geometry of the outermost legs compared to the geometry of the inner legs of the wave profiles. With the plate in Fig. 9 For this reason, the leg angle 2b of the outer legs 31 differs from the leg angle 2a of the inner legs 32. As in FIG Fig. 9 can be seen, the half leg angle b in an edge region of the plate 30 is, for example, 60 ° with a half leg angle of 45 ° in a central region of the plate. As a result, a more uniform distribution of the connection points and thus an increased pressure resistance of the heat exchanger is achieved in edge regions 33 of the plates.

Fig. 10 shows a plate 35 of a heat exchanger, in which a wave profile 34 extends to the upturned plate edge 36, a remaining channel 37, which under certain circumstances allows an undesirable bypass flow, has a very small cross section, so that the bypass flow is reducible. In particular in the case of a soldered heat exchanger, that is to say when the plate 35 is solder-plated, solder menisci are formed between the outermost legs 38 of the wave profile 34 and the bent-over plate edge 36, which reduce the edge channel 37 or close it particularly advantageously.

In order to bring about a reduction in the pressure loss caused by the heat exchanger, the openings 38 of the plate and thus the cross sections of the collecting channels formed thereby are widened in an oval shape.

Fig. 11a shows a cross section of a plate 41 of a heat exchanger 42, which is constructed from a plurality of plates 41, as in FIG Fig. 11b pictured. The plates 41 each have a few bores 43 as inflow and outflow lines perpendicular to the plane of the plate, the bores 43 being raised in relation to the base plane of the respective plate 41 in such a way that a fluidic connection from one of the two bores alternates only to every second plate space 44 . As in Fig. 11b one can see a raised bore 43 in each case on a non-raised area of an adjacent plate 41, so that the height of the raised area is, for example, as large as the height of a wave profile of the plate 41.

Fig. 12a shows a cross section of a plate 51 of a heat exchanger 52, which is constructed from a plurality of plates 51, as in FIG Fig. 12b pictured. The plates 51 each have a few bores 53 as inflow and outflow lines perpendicular to the plane of the plate, the bores 53 being raised in relation to the base plane of the respective plate 51 in such a way that a fluidic connection from one of the two bores alternates only to every second plate space 54 . As in Fig. 12b can be seen, a raised bore 53 lies against a raised bore 53 of an adjacent plate 51, so that the height of the raised area is, for example, only half as large as the height of a corrugated profile of the plate 41. This design may reduce the thinning of the material when producing the raised areas, so that tensile strength, ie internal pressure resistance of the heat exchanger 52 is favorably influenced at least in these areas.

Claims (23)

1. A heat exchanger as an oil cooler for motor vehicles, wherein the heat exchanger is formed from interconnected plates, wherein there are cavities formed between the plates which are closed off outwardly and through which a first and a second medium flow alternately in each case via at least one inflow line and outflow line, wherein the plates are profiled in such a way that, between the respective profiles of the plates, contact points occur, in the region of which the plates are fastened to one another, characterised in that the profiles of the plates (10) and their contact points are designed in such a way that the flow, formed between the plates (10), of the first and the second medium from the corresponding inflow line to the corresponding outflow line does not run rectilinearly, wherein the plates (10) have a recurring wavy profile (12) which extends substantially transversely with respect to the main throughflow direction (H) and which is waved in a zigzag shape around the direction of extension, wherein the wavy profile (12) has legs (14) extending in a straight line between regions of curvature, wherein the wavy profile (12) is characterised by the leg length (15) of the legs (14), the leg angle (13) given between the legs (14) and the profile depth of the wavy profile, wherein the design of the wavy profile is characterised by the course of the profile in the region of the legs and the regions of curvature, wherein profiles adjacent to one another repeat in a predetermined pitch, wherein the plates (10) have, as inflow lines and outflow lines, in each case a pair of bores (18) which are perpendicular with respect to the plate plane, wherein the bores (18) are raised with respect to the basic plane in such a way that there is a fluidic connection from one of the two bores alternately only to every second plate interspace (20) and wherein the raised region of at least some of the bores is surrounded by a region leading around annularly and free of the wavy profile and wherein distribution channels (23) are provided in the region of the bores (18) assigned to the inflow lines, the distribution channels being given by a wavy profile (12) with a leg angle which is raised with respect to the leg angle of the wavy profile.
2. The heat exchanger as claimed in claim 1, characterised in that the wavy profile has a flat region on the outside of a wave back.
3. The heat exchanger as claimed in claim 1 or 2, characterised in that the flat region is between 0.1 mm and 0.4 mm in the cross section of the wavy profile.
4. The heat exchanger as claimed in one of the preceding claims, characterised in that the leg angle (13) is preferably between 45° and 135°, preferably around 90°.
5. The heat exchanger as claimed in one of the preceding claims, characterised in that the profile depth is between 0.3 mm and 2 mm, in the case of liquid media preferably between 0.5 mm and 1 mm and in particular between 0.7 mm and 0.8 mm and in the case of gaseous media preferably in the range between 0.6 mm and 2 mm and in particular around 1.5 mm.
6. The heat exchanger as claimed in one of the preceding claims, characterised in that the leg length (15) is in the range from 8 mm to 15 mm and in particular in the range from 9 mm to 12 mm.
7. The heat exchanger as claimed in one of the preceding claims, characterised in that the wavy profile (12) is formed as an embossing in the plate (10), wherein the plates (10) preferably consist of a metallic material, in particular aluminium, wherein the plates are preferably coated on at least one side with soldering aid material.
8. The heat exchanger as claimed in one of the preceding claims, characterised in that the bores assigned to the inflow lines are oval, elliptical or rectangular.
9. The heat exchanger as claimed in one of the preceding claims, characterised in that two plates (10) different from one another in terms of the wavy profile (12) are used alternately, wherein the wavy profiles (12) differ from one another at least with regard to one of the features of leg length (15), leg angle (13) and profile depth.
10. The heat exchanger as claimed in one of the preceding claims, characterised in that the wavy profile (12) of one side of the plate (10) differs from the wavy profile (12) of the other side of the plate (10) at least with regard to one of the features of leg length (15), leg angle (13) and profile depth.
11. The heat exchanger as claimed in one of the preceding claims, characterised in that the wavy profiles of adjacent plates are identical to one another.
12. The heat exchanger as claimed in one of the preceding claims, characterised in that the heat exchanger is formed by a stack (21) of plates (10), wherein the plates (10) correspond to one another and are arranged so as to be rotated alternately through 180° with respect to one another.
13. The heat exchanger as claimed in one of the preceding claims, characterised in that the plates (10) have a bent edge (17), wherein the edges (17) of adjacent plates (10) bear one against the other and are preferably connected to one another by brazing.
14. The heat exchanger as claimed in one of the preceding claims, characterised in that the bent edges (17) of several, in particular of up to five plates (10) overlap.
15. The heat exchanger as claimed in one of the preceding claims, characterised in that the wavy profile (12) extends into the edge (17), in particular over the edge (17).
16. The heat exchanger as claimed in one of the preceding claims, characterised in that a profile-free bending portion is formed between the end of the wavy profile and the edge, the width of which is smaller than 2 mm and is preferably determined in such a way that, during the brazing of the plates, braze is added to the bending area in the wave crest sections in such a way that a throughflow of medium in the bending portion is reduced or substantially prevented.
17. The heat exchanger as claimed in one of the preceding claims, characterised in that at least one end face of the heat exchanger is assigned a closing plate (24) which is profile-less in particular at least on the outside and which preferably has connection points (25) for a first and second medium issuing into connection lines and being arranged in alignment with the bores (18) .
18. The heat exchanger as claimed in one of the preceding claims, characterised in that the hydraulic diameter (hD) has a fluctuation of at most 25%, in particular at most 15%, in particular at most 10% around an average value in the main direction of extension (D).
19. The heat exchanger as claimed in one of the preceding claims, characterised in that the hydraulic diameter (hD) has an average value of between 1 mm and 4 mm, wherein it is preferably 1 mm and 2 mm and preferably around 1.4 mm in the case of liquid media and wherein it is preferably around 3 mm in the case of gaseous media.
20. The heat exchanger as claimed in one of the preceding claims, characterised in that the contact points between two plates adjacent to one another are evenly distributed across the plate surface.
21. The heat exchanger as claimed in one of the preceding claims, characterised in that the contact points between two plates adjacent to one another have a surface density of 4 to 7 per cm², in particular of 5 to 6 per cm².
22. The heat exchanger as claimed in one of the preceding claims, characterised in that a phase transition of a medium takes place in plate interspaces.
23. The heat exchanger as claimed in one of the preceding claims, characterised in that the installation position of the heat exchanger is determined such that the transverse distribution of the medium in the plate interspaces is assisted by gravitation.

Images