EP1654508B1 - 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 it finds particular use in vehicles as oil cooler. Such in the heat exchanger is out DE 19959780 A1 known.

There are known as Platterfwärmeübertrager, which are formed from a stack of adjacent plates. Between the plates cavities are formed, which are alternately traversed by a first and a second medium.

In addition to use as a cooler, in which case, for example, the first medium cooling water and the second medium to be cooled working fluid - in the case of an oil cooler of an internal combustion engine engine oil - is also a use as an evaporator cooling device such as a vehicle air conditioning conceivable, in which case one of 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. In the area of the contact points, the plates are fastened to one another. In addition, the plates are on the outside sealingly against each other, so that the cooling medium or the working medium flows through the cavity exclusively. First and second medium are supplied in each case by a corresponding inflow line and led away via a drain line. In this case, inflow lines and outflow lines each serve as manifolds in which the fluid flow of all corresponding cavities is supplied or removed.

Usually turbulence-rising internals are introduced in Plattenwärmeübertragem to improve the heat transfer and surface enlargement in the fluid channels and firmly connected to the heat transfer plate. As a result, in addition to the thermodynamic property of the channel, the strength property of the radiator is greatly improved.

A Nachteü such turbulence plates is that in the production of the passage openings easily chip formation occurs, which can lead to contamination of the medium flowing through. In addition, dirt accumulates easily in the area of the turbulence plates. As a result, the passage of the cavity can be hindered in an undesirable manner. In addition, they represent an additional component to be produced, which entails an increase in the cost of the heat exchanger due to increased production costs and material costs.

It is therefore the 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 used in particular as an oil cooler in the field of motor vehicles, is formed from interconnected plates. Between the plates outwardly closed cavities are formed. The cavities are alternating over each supplied at least one inflow and outflow line with first or second medium and are also traversed by the corresponding medium. The plates are profiled in such a way that contact points occur between the respective profiles of the plates. In the area of these contact points, the plates are connected to each other. In this case, the plates are designed such that the flow forming between the plates of first or second medium 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 partially diverted 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 ever-changing changes in direction of the fluid in the channel and in the region of the opening wave channel under certain circumstances forming vortices tear the forming boundary layer again and again. This leads to an improved heat transfer.

According to the invention, the plates have a repeating wave profile which then extends at least in a direction transverse to the flow direction, which is the straight connection from the point of entry of the medium to the exit point. Around this direction, the wave profile runs zigzag. Such a wave profile forms in a simple manner Strömungsleitbereiche which are suitable to direct the flow of the medium flowing through the corresponding cavity. The flow is advantageously deflected several times in its course, in particular not only in the plane of the plate, but also out of the plane of the plate. In areas where the distance between the plates is designed to be different in size, the flow rate may vary. At the same time is achieved in an advantageous manner that the medium is distributed over the entire surface of the plates as a whole and as optimized as possible utilization of the entire heat exchange surface takes place.

According to a further embodiment, the wave profile between flow regions on rectilinear legs, wherein the course of the wave profile is characterized by the leg length of the legs, the leg angle between the legs and the profile depth of the wave profile. The profile of a wave profile is determined in its cross section by the course in the region of the legs and in the curvature region, wherein preferred embodiments can provide a deviation of the cross-sectional shape in these areas.

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

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

Here, in a preferred embodiment, a bonding of the plates in the region of the contact points by brazing, for which purpose the plates are coated at least on one side with a soldering agent such as solder. The choice of leg length and leg angle is preferably carried out as a function of the medium flowing through and its viscosity. Thigh length and leg angle have a great influence on the flow velocities occurring and the associated heat exchange, so that they are adaptable to the respective intended use. The above values relate in particular to the use of heat exchangers as oil coolers in vehicles, where the heat exchange between engine oil and cooling water takes place. In addition, of course, they are also dependent on the dimensioning of the plates and the gap resulting from the spacing of 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 the sequence of the profiles defined by the pitch in the course transverse to the extension direction of a wave profile across the plate. Preferred embodiments provide a constant pitch, 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. In particular, the flat area has a width of 0.1 to 0.4 mm. The flat area allows a good, flat contact with each other adjacent plates together and thus a light and stable production of Support or connection - as by brazing - adjacent plates together.

The material of the plates is preferably aluminum. This material has the advantage of having a low density and at the same time to allow the production of the wave profile, for example by embossing in a simple manner. It can be coated over the entire area with soldering aids such as brazing alloy on at least one side to produce the connection between two adjacent plates in the region of the contact points and in the region of the edges. Depending on the choice of soldering agent and the layer thickness of the order of the soldering agent may also be given a double-sided coating with soldering agent. The coating with soldering agent should serve in particular in the region of the edges and the inlet and outlet lines in the block reliable production of a fluid-tight connection of two plates together in a joining process with a joining tool (brazing furnace) without using additional aids or auxiliaries.

In a further embodiment, it can be provided that the plates have bores which serve as inflow and outflow lines in the region of the heat exchanger and whose bore axis runs perpendicular to the plane of the plate. In this case, the bores are introduced, in particular, in a region raised in relation to the ground plane of the plates. In this case, the raised region is preferably raised in such a way that in every second plate gap there is a tight connection between the raised region and the subsequent further plate, so that only every second plate gap creates a fluidic connection between the holes and the plate gap. By virtue of this measure, fluid supply and removal from the plate interspaces is made possible without the use of lines, so that they are flowed through alternately either with cooling medium or with working medium.

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

The raised area and the holes in the raised area can not only have a circular cross section, but also oval or slot-like designs are possible and advantageous. In this case, the longer of the two axes of the slot-like design is preferably to 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 then with the same overall extent of the plates a larger heat transfer surface remains.

Moreover, it is possible that distribution channels are provided in the region of the inflow lines and the bores assigned to the inflow lines, which distribution channels are preferably likewise designed as a wave profile. It is particularly preferred further developments of the invention, when the wave profile of the distribution channels is different from the other wave profiles with respect to the characteristic sizes of the wave profile. In particular, the wave profile of the distribution channels has a leg angle which is less than 45 ° and is in particular in the range of approximately 5 ° and approximately 25 °. It can be formed in the other plate areas both a sudden and a continuous transition in the profile design between the distributor profile and the wave profile. The distribution channels assume the task of the most even distribution of the fluid flow over the entire width of the plate away. This improves the efficiency of the heat exchanger, since in In this case, a larger heat exchange surface is actually used for replacement. Also, to improve the distribution of the medium over the entire area of the heat exchanger, flow channels surround the raised areas. The flow channels are preferably formed by a wave profile-free section, which is guided in particular like a ring around the raised area. It is thus formed a reduced flow resistance section, in which open several wave profiles, so that also a distribution function for the medium is fulfilled.

It corresponds to a particularly simple and inexpensive to manufacture embodiment of a heat exchanger according to the invention, if it is made of a sequence of plates. The plates may have different profiles with respect to their wave profiles on both sides. A heat exchanger may in particular be formed from a stack of such plates designed identically to one another. For it is in this case possible in particular that mutually adjacent plates are rotated by 180 degrees to each other, wherein the axis of rotation extends perpendicular to the plate plane. This type of stack of plates is particularly advantageous if the holes associated with the inflow holes are formed from raised points and these should be assigned to two different different alternating cable guides. In this case, the elevations in the region of the inflow lines can be designed in particular as a substantially frusto-conical dome. Alternatively, dom-shaped elevations, which have an elliptical cross-section.

The plates can be designed to be identical to each other or similar or different. Identically identical plates have the same characteristics as regards the characteristic properties of the wave profile and the shape of the wave profile on. Corresponding plates are structurally equal to each other, however, 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 mutually different values of characterizing sizes, but are in terms of the formation of the edge and formation of front and back of the plates corresponding to each other. The alternating use, for example, of two corresponding plates, which differ only by different leg angle in the characteristic sizes, has the advantage that the position and relative position of contact points of the plates together in the profiled area in view of the required stiffness and the required flow in can be easily optimized.

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 so that at least two mutually adjacent plates abut each other in this edge region and overlap. The number of overlapping in the edge region plates can be up to five. The greater the number of overlapping plates, the stiffer is the wall formed thereby and closing the heat exchanger towards the outside. This simultaneously supports the production of a permanently stable, resistant, fluid-tight closure of the plates to the outside. Preferred further embodiments provide that the wave profile extends into the edge and in particular over its entire width. Care must be taken in the design of the wave profile to ensure that the plates still remain stackable, which is done by the fact that the course of the wave profile in the edge region is matched to the mounting position of two adjacent plates to each other.

The wave profile extends into the edge when the wave profile ends in the root region of the bend, so that the profile with its tread depth extends into the edge. In particular, for reasons of production technology, it may be advantageous if the root of the edge is in a wave profile-free area, since then the bending of the edge can be done in a non-stiffened by profile area. Preferred embodiments then provide that the groove forming between edge and wave profile area is as narrow as possible. In particular, it is selected to be so narrow that, during brazing, a solder flow enters, which completely or at least so far adds this channel that only a negligible amount of medium flows through the channel. The channel must be designed so that it does not serve as a bypass channel for the medium and a significant proportion of media flows through the channel rather than in the region of the wave profile.

To improve the stability of the heat exchanger to the outside and to simplify the connection of the external supply lines and external drainage lines of coolant and working fluid, it may be provided that on at least one of the end faces of the heat exchanger an outer profile-less end plate is arranged. The outside profileless end plate has in particular flanges as connection points. The end plates may in particular also have a greater material thickness than the other plates and thus represent a particular stiffening, stabilizing element which forms a the end faces to the outside final housing part. The lateral housing walls, which close off the heat exchanger to the outside, are formed over the edge, which limits the plates and which coincides with the edge overlapping adjacent plates. The edges are fluid-tightly connected to each other, which can be done in particular by brazing.

One way to characterize the flowability of 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 flow-through channel cross-section and heat exchange surface. 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 free channel cross-section fK to total end face S of the channel between two adjacent plates, the area density Fd from the ratio between heat-transferring area wF to block volume V. $$\mathit{hD}=\frac{4\frac{\mathit{fK}}{S}}{\frac{\mathit{wF}}{V}}$$

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. As a result, a possibly improved and optionally uniform flowability of the plate gap, which forms the channel is achieved.

The hydraulic diameter is according to a preferred embodiment of the invention and in particular when using the heat exchanger as an oil cooler 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 of a pair of plates preferably not more than by 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 stated values apply to an oil cooler in which, on the one hand, water and, on the other hand, an oil flows through the heat exchanger.

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

Heat exchangers according to the invention can on the one hand serve as oil coolers, but also as evaporators or condensers. In this case, the refrigeration cycle of such a device can serve not only for air conditioning a (vehicle) interior, but also for cooling heat sources, such as electrical consumers, energy storage and voltage sources or Ladeiuft a turbocharger. The heat exchanger is a capacitor when, for example, by condensation of the refrigerant of an air conditioner in a coolant-loaded compact heat exchanger takes place and the coolant gives off the heat in a heat exchanger in air as another 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 these applications as a condenser or evaporator, the use of a powerful compact heat exchanger is desirable, in which a coolant as a second medium gives off or absorbs the heat. Due to very high internal cleanliness requirements on the refrigerant side, no stamped turbulence inserts can be used, 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 that is predominantly liquid in the vaporization at the inlet and in vapor form when condensed, is distributed over the entire width of the disc. A special feature of the evaporation and condensation is the often present low temperature difference between the two fluids. In the case of a non-optimal transverse distribution of the liquid fluid to be evaporated or of the vaporous fluid to be condensed, high power losses can quickly occur. Heat exchangers according to the invention offer solutions to these problems.

Fig. 1a, 1b:

die Vorderseite und Rückseite einer 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 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 Platte eines Wärmeübertragers;

Fig. 11a,b

jeweils einen ausschnittsweisen Querschnitt eines Wärmeübertragers;

Fig. 12a,b

jeweils einen ausschnittsweisen Querschnitt eines Wärmeübertragers.

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

Fig. 1a, 1b:

the front and back of a panel according to the invention;

Fig. 2:

the view of a stack of such plates;

3:

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

4:

in an enlarged view the formation of the distribution channels in the region of the holes;

Fig. 5:

a schematic representation of a closure plate with connection bottles;

Fig. 6:

the fluid guide through the plates when one of the fluids is a flow through all the plate interstices;

FIGS. 7a-7d:

the effects of gravity on the liquid 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 plan 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;

8c

a plot of the strength and pressure drop of a heat exchanger versus the density of the interfaces between two plates;

Fig. 9

a section of a heat exchanger plate;

Figure 10

a plate of a heat exchanger;

Fig. 11a, b

each a partial cross section of a heat exchanger;

Fig. 12a, b

each a partial cross section of a heat exchanger.

The FIGS. 1a and 1b show the representation of a front or a back of a plate according to the invention, while the Fig. 2 the representation of a corresponding, from plates according to the FIGS. 1a and 1b formed stack shows.

A plate 10 has a base body 11, which is provided on its front and back in each case with a wave profile 12, which has been introduced by embossing in the base body 11. In the in the FIGS. 1a and 1b illustrated embodiment, the corrugated profile 12 corresponds to the back according to the Fig. 1b the negative profile of the front as shown in Fig. 1a , In this case, the corrugated profile 12 is formed from a plurality of mutually standing in a leg angle 13 legs 10, each having a fixed leg length 15 and the curvature region 16 adjoin one another. The corrugated profile extends across the plate 10. Over the length of the plate 10 across a plurality of wave profiles 12 is formed one behind the other, wherein the wave profiles follow one another in particular at a close distance and in alignment with each other are aligned. The plate 10 in this case has a circumferential bent edge 17, which limits the plate laterally. In this case, the wave profile 12 extends into the edge.

The wave profile 12 can be introduced by embossing in the plate 10. The embossing can be carried out so that the two sides have in the plate 10 differing wave profiles, in particular, the wave profile 12 can represent the negative of the wave profile 12 of the other sides on one side, as for example from the embodiment according to the FIGS. 1 a and 1 b can be seen. It is also possible that a plate 10 has the same wave profile 12 on both sides. Both times, the wave profiles on the two sides of a plate 10 may be aligned with each other or offset from each other. The corrugated profile 12 is characterized in cross-section mainly in that it has a wave back, 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 level. Two of the holes are introduced in a raised area 19. One of the holes serves for the supply of working medium in the area between two plates, while in particular the diametrically opposite bore serves the outflow of working medium. Another pair of holes serves for the inflow and outflow of cooling medium. Be plates 10 as in the Fig. 2 stacked on top of one another, either the lines associated with the working fluid or the cooling medium are alternately fluidly connected to the intermediate space 20 between two plates 10, since the raised area 19 abuts corresponding bores 18 on the adjacent plate 10. The holes 18 thus form through a stack 21 of plates through the supply lines or drain lines for cooling medium and working medium. The Fig. 2 shows in perspective view of such a stack 21 of plates 10 according to the FIGS. 1 a and 1 b ..

In the Fig. 3 is the sectional view through a stack 21 according to the Fig. 2 shown. Plates 10 abut each other and are stacked on top of each other. The bent edge 17 of adjacent plates abut each other and is formed so that the edge of a plurality of plates overlap each other. In order to achieve a fluid-tight connection between the edge 17 of two adjacent plates, these are connected to each other by brazing. In addition, two mutually adjacent plates in different areas of their wave profiles 12 to each other. Even in these areas, the plates are connected by brazing. To produce the solder joints, the plates can be coated on one or both sides with a solder. Between two mutually adjacent plates 10, a gap 20 is formed in each case, wherein the intermediate space is flowed through either by working medium or by cooling medium. In this case, the stack of plates is designed in particular in which the intermediate spaces 20 are alternately flowed through by working medium and cooling medium, so that each of the plates 10 flows around on the one hand by cooling medium and on the other hand by working medium. Thus, a heat exchange between the cooling medium and the working medium on each of the plates 10 away take place.

Due to the fact that the plates have a corrugated profile, the gap 20 is of different width at a plurality of locations. The constantly changing directional changes of the fluid in the channel and the vortex forming in the region of the opening wave channel tear the forming boundary layer over again and again. This results in a greatly improved heat transfer compared to a smooth channel.

This promotes the other exchange between the two media across a disk 10. In addition, it is achieved by the design of the plates 10 that no linear, straight-line flow from the supply line to the discharge line is possible. Depending on the viscosity of the medium, such a design of the intermediate space 20 can also lead to wholly or partly turbulent flows occurring and thus an improved heat exchange between the working medium and the cooling medium is achieved. In addition, by the course of the wave profile 12 transverse to the extension of the plate 10, the corresponding medium is also passed over the entire width of the plate 10, so that the utilization of the heat exchange surface, which provides a plate 10, is improved, whereby the efficiency of such Heat exchanger is further increased. An essential guiding element for the flow guidance is also to be seen in the fact that this always comes between two adjacent plates 10 a Daltongitter to contact points, which act as a flow obstacle and Strömungsumlenkungsstellen. In addition, these contact points act as a support of the plates to each other and thus have a stabilizing function for the plates 10, in particular with respect to the determination behavior of the plates 10. To a in the Fig. 8 To obtain the shown 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 curves. A uniform hydraulic diameter ensures smooth flow of fluid across a corrugated profile and across the entire width of the plate interspace. By constructive design selection of the wave profile optimized for the application hydraulic diameter is achieved.

The Fig. 4 shows an enlarged view of a plate 10 with a wave profile 12, which is formed by the legs 14 which each have a leg angle 13 of 45 °. The plate 10 is replaced by a bent edge 17 is limited, wherein the wave profile 12 extends into the region of the edge 17 into it.

In this figure, in particular, the one between two holes 18, one of which is formed in a dome-shaped raised portion 19 is shown. In the area between the two holes 18, which extends in particular in the region between the holes 18 and the adjacent edge 17, distribution channels 22 are formed. The distribution channels 22 are formed by a wave profile 23, which differs from the wave profile 12 in the remaining region of the plate 10 with respect to the leg angle and the leg lengths. The leg angles are in particular in a range below 45 °. The distribution channels 22 lead in particular in the region of the bore, which is not introduced in a raised portion 19, in the corresponding space entering medium transverse to the main extension of the plate 10 and thus ensure a uniform distribution of the fluid flow over the entire width of the plate. The raised region 19, in which the other bore 18 is introduced, lies in particular sealingly against the bore region of the plate 10 disposed above it in a stack and may be connected thereto by brazing. As a result, a fluid-tight closure to the gap 20 is provided to the overlying plate 10, so that no media flow can take place between this bore 18 and the gap and the medium flowing through this bore 18 only enter behind the overlying plate 10 in the then following gap 20 can. The bores 18 can also be designed as elongated holes for increasing the cross section, the slot axis then preferably extends transversely to the main flow direction H.

Next, as in the FIG. 4a shown, a profile-free annular portion 99 around a dome-shaped raised portion 19 around a channel which connects a plurality of wave profiles 23 and distribution channels 22 together and ensures a good lateral distribution of medium, as it forms a flow-resistant area. In this case, the annular region 19 has an embossing depth which substantially corresponds to the embossing depth of the wave profile 23.

The Fig. 5 shows in a plan view of an end plate 24, which has four connecting flanges 25 which are arranged in alignment with the holes 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 complete it to the outside. The end plate 24 has at least on the outer side no wave profile 12. If a connection plate 24 is arranged on each side of the plate stack, then 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 the 4 connection flanges 25 , The connecting flanges 25 are each assigned to the connection bores. The connecting flanges 25 are used to connect the external lines for the supply and removal of working fluid and cooling medium. In addition, the end plate 24 stiffens the plate stack 21 and forms the frontal housing wall. In this case, the end plate 24 may 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 lateral housing of the heat exchanger. A plate stack according to the Fig. 2 , provided with connecting flanges 25 and a cover plate 24 thus forms - a heat exchanger. Such a heat exchanger can serve in particular as an oil cooler in a vehicle.

The FIG. 6 shows a plate stack 21, consisting of a base plate 88, plates 10 and a cover plate 89 having three holes 18, 18a. The holes 18 serve to guide a first medium, is performed between the plates so that the plate interspaces 20 are flowed through in parallel. Through the bore 18a enters a second medium into the plate stack, which emerges through the bore 18b in the base plate again from the plate stack.

By at least one arranged between the holes 18a and 18b and not visible from the outside partition wall, the flow channels for the second medium are divided into at least two flow paths, which are flowed through successively and each consist of one or more flow channels. By contrast, the flow channels for the first medium are flowed through in parallel. In a modified embodiment, however, the flow channels for the first medium are also divided into at least two flow paths, which are flowed through successively.

The Fig. 7a to 7d show different orientations of the main flow direction H of the plate interspace 20 with respect to the direction of gravity G in the installation position of the heat exchanger, as well as the favorable influence on the distribution of the medium in the plate interspace, in particular when used as a capacitor. The FIGS. 7a and 7c show the application of an evaporator. From the Fig. 7a and 7c It can be seen that the main flow direction H should be transverse or antiparallel to the direction of gravity G, depending on whether the longer L or the narrower side S of the plates is aligned in the direction of gravity G, if it is a liquid medium. By gravity, a transverse distribution of the medium with respect to the main flow direction is supported. In contrast, the show Fig. 7b and 7d in that a gaseous medium is best distributed between the plates 10 when the gravitational direction G counteracts the distribution of the medium between the plates.

The FIG. 8 shows the hydraulic diameter over an entire wave profile in the main flow direction H away, in Fig. 8a the formation of the wave profile 23 is shown with the contact areas of adjacent plates 10 shown as circles 98. It can be seen that over the entire period of the pattern resulting from the wave profiles 23 of the adjacent plates, the wave profile varies in a bandwidth between 1.2 and 1.6 and averages about 1.4. The formation of the wave profiles is preferably selected such that the result is a hydraulic diameter that is as constant as possible in the main flow direction.

In Fig. 8a the contact points between two mutually adjacent plates of the heat exchanger in a plan view of one of the plate are shown as circles. 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 , more preferably 5 to 6 per cm ² . This is based on Fig. 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 surface density of the contact points can be expected a course, which by the broken curve in Fig. 8b is shown, since many points of contact in the main flow direction H seen side by side restrict the flow channel cross-section. This is illustrated by the breaks 40 in the hydraulic diameter. Due to the inventive design, in particular the uniform distribution of the contact points, these burglaries are eliminated or reduced, so that there is a solid line shown for the hydraulic diameter. The fewer of these burglaries have a flow channel, the fewer bottlenecks for the flowing medium, the channel, that is, the pressure loss can be reduced for the same area density of the contact points.

A uniform distribution is achieved, in particular, in that a curvature region between two, in particular straight legs of a wave profile of a plate does not come to lie exactly over a curvature region of an adjacent plate. Rather, it may be advantageous if the areas of curvature of adjacent plates - seen in the main flow direction - are offset from each other so that each curvature region is flanked transversely to the main flow direction of two contact points of the two plates, which advantageously have a same or similar distance from each other as to other points of contact and thus release between them a flow passage which allows appreciable flow and thus does not contribute undesirably to pressure loss of the flow channel formed between the plates. On the other hand, the distance between two points of contact should not be too large, as otherwise local weak points in the strength of the heat exchanger could possibly form.

In Fig. 8c A plot of the strength F and pressure loss DV of a heat exchanger versus 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 as a straight 41 down. In contrast, the pressure loss DV in this plot (42) shows a progression; so that a maximum 43 at a contact point density BD1 results for the ratio F / DV of strength F to pressure loss DV. If now the pressure loss is lowered according to the invention (44), then the mentioned maximum is increased (45) and possibly shifted to a higher contact point density BD2. experimental It has been found that a touch-point density of 4 to 7 per cm ² , preferably 5 to 6 per cm ² , leads to good strength with acceptable pressure loss.

In other words, as in Fig. 8c represented by the arrow 46, are transferred at a constant pressure loss DV 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 achieve that a distance between the plate edge and the near-end crossing points is not too large, it may be advantageous to modify the geometry of the outermost legs with respect to the geometry of the plate-inner legs of the wave profiles. At 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 Fig. 9 can be seen, the half leg angle b in an edge region of the plate 30, for example, 60 ° at 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 bent plate edge 36, wherein a remaining channel 37, which may allow an undesirable bypass flow, has a very small cross-section, so that the bypass flow is reducible. In particular, in a brazed heat exchanger, that is, when the plate 35 is solder plated, form between the outermost legs 38 of the wave profile 34 and the bent edge of the plate 36 Lotmenisken that reduce the edge channel 37 or close particularly advantageous.

In order to effect a reduction of the pressure loss caused by the heat exchanger, the apertures 38 of the plate and thus the cross sections of the collection 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 composed of a plurality of plates 41, as in Fig. 11b displayed. The plates 41 each have a few holes 43 perpendicular to the plate plane as inflow lines and outflow lines, the holes 43 being raised relative to the base plane of the respective plate 41 such that a fluidic connection of one of the two holes exists alternately only to every second plate interspace 44 , As in Fig. 11b can be seen, is in each case a raised bore 43 at a non-raised portion of an adjacent plate 41, so that the height of the raised portion, for example, is as large as the height of a wave profile of the plate 41st

Fig. 12a shows a cross section of a plate 51 of a heat exchanger 52, which is composed of a plurality of plates 51, as in Fig. 12b displayed. The plates 51 each have a few bores 53 perpendicular to the plate plane as inflow and outflow lines, the bores 53 being raised in relation to the base plane of the respective plate 51 in such a way that a fluidic connection of one of the two bores exists alternately only to every second plate interspace 54 , As in Fig. 12b can be seen, is in each case a raised bore 53 at a raised bore 53 of an adjacent plate 51, so that the height of the raised portion, for example, only half as large as the height of a wave profile of the plate 41. This construction reduces under certain circumstances a material thinning when producing the raised areas, so that a tensile strength, ie internal pressure resistance of the heat exchanger 52 is favorably influenced, at least in these areas.

Claims (28)

1. A heat exchanger, in particular 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, the plates being 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.
2. The heat exchanger as claimed in one of the preceding claims, characterised in that 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.
3. The heat exchanger as claimed in one of the preceding claims, characterised in that 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.
4. The heat exchanger as claimed in one of the preceding claims, characterised in that the wavy profile has a flat region on the outside of a wave back.
5. The heat exchanger as claimed in one of the preceding claims, characterised in that the flat region is between 0.1 mm and 0.4 mm in the cross section of the wavy profile.
6. 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°.
7. 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.
8. 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.
9. 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.
10. The heat exchanger as claimed in one of the preceding claims, characterised in that 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).
11. The heat exchanger as claimed in one of the preceding claims, characterised in that the raised region of at least some of the bores is surrounded by a region preferably leading around annularly and free of the wavy profile.
12. The heat exchanger as claimed in one of the preceding claims, characterised in that distribution channels (23) are provided in the region of the bores (18) assigned to the inflow lines, the distribution channels being preferably given by a wavy profile (12) with a leg angle which is raised with respect to the leg angle of the wavy profile.
13. 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.
14. 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.
15. 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.
16. 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.
17. 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.
18. The heat exchanger in particular 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.
19. 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.
20. 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) .
21. 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.
22. 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 profileless 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).
23. The heat exchanger as claimed in one of the preceding claims, characterised in that the hydraulic diameter (hD) has a fluctuation of at least 25%, in particular at least 15%, in particular at least 10% around an average value in the main direction of extension (D).
24. 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.
25. 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.
26. The heat exchanger as claimed in one of the preceding claims, characterised in that the contact points between tow plates adjacent to one another have a surface density of 4 to 7 per cm², in particular of 5 to 6 per cm².
27. 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.
28. 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.

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