Patent Application
20080202735
The invention relates to a heat exchanger as claimed in the precharacterizing clause of patent claim 1, known from DE 100 60 102 A1.
US 2003/0010479 A1 discloses a heat exchanger which can be used as an exhaust-gas cooler in an exhaust-gas feedback system. Exhaust-gas tubes are arranged in a housing through which liquid coolant in the cooling circuit of an internal combustion engine flows and are held at the end in tube bases which are themselves connected to the housing. The exhaust gas is supplied to the exhaust-gas cooler via a diffusor, then flows through the exhaust-gas tubes around which the coolant flows, and emerges from the cooler via an exhaust-gas connecting stub. All the parts of the exhaust-gas cooler are soldered to one another. This design with tube bases in which the tube ends are held has the disadvantage that the tubes are fixed in the tube bases during the soldering process and therefore cannot move towards one another during soldering and during melting of the solder layer which, inter alia, also has a disadvantageous effect on the soldering of the turbulence inserts to the tube inner walls. This disadvantage is avoided by systems without tube bases, as shown by the following example:
DE 100 60 102 A1 discloses a heat exchanger which can likewise be used as an exhaust-gas cooler in an exhaust-gas feedback system. In this case, fed-back exhaust gas is cooled by coolant which is taken from the cooling circuit of the internal combustion engine for the motor vehicle. The known exhaust-gas cooler has a housing which is essentially in two parts and in which a heat sink is arranged, through whose primary side coolant can flow and which comprises a multiplicity of flat small tubes and through whose secondary side exhaust gas flows. In this case, the exhaust gas is passed through the housing in a relatively straight line, that is to say without any significant direction changes. The coolant is input and output at right angles to the flat small tubes, thus resulting in 90° direction changes in each case. In order to improve the heat transfer between the exhaust gas and the coolant, so-called turbulence sheets are arranged between the flat small tubes. The entire exhaust-gas cooler comprising the housing, small tubes and turbulence sheets is produced by “integral soldering”.
The application subject matter of DE 100 60 102 A1 results from the prior art as shown in
One object of the present invention is to design a heat exchanger of the type mentioned in the introduction on the one hand to be suitable for joining techniques, in particular soldering, welding, adhesive bonding etc., and on the other hand to keep its external temperature low when using hot media to be cooled.
This object is achieved by the features of patent claim 1.
The invention provides that the flow channels, which are preferably in the form of plate pairs, are preferably integrally connected on the longitudinal faces to the walls of the housing, that is to say by soldering, welding, adhesive bonding etc. The plate pairs are placed in layers on top of one another to form a pack, and are connected to one another for flow purposes by means of lateral channels. When the flow passes through these lateral channels, this results in a comparatively high pressure loss, on the one hand as a result of the direction of the fluid being changed from the lateral channel into the channels which are enclosed by the plate pairs, but in particular because the lateral channels normally have sharp end edges between the plate pairs which lead to severe vortexing of the fluid, and thus to high pressure losses. A first fluid, preferably a liquid coolant, therefore flows through the plate pairs, with this first fluid being less critical in terms of the pressure losses in the cooler. At the end, a second fluid, in particular a hot medium to be cooled, flows into and through the pack of the plate pairs, thus resulting in the flow passing in a relatively straight line through the plate pack, that is to say without any significant direction changes. This results in little pressure loss for the second, preferably gaseous, fluid. Turbulence-generating devices are provided between the plates as appropriate for the heat-transfer conditions. The heat exchanger according to the invention is preferably soldered, welded, adhesively bonded etc. in one process. Those parts which are to be soldered, welded or adhesively bonded are in this case arranged flexibly with respect to one another, that is to say such that they can move with respect to one another, and can therefore in particular move relative to one another when the soldered layers are melted during the soldering process, thus resulting in minimal solder gaps and good soldering. The plate pairs can advantageously be prefolded in a method step which precedes the joining process, in particular the soldering process, welding process, adhesive-bonding process etc., and/or can be crimped, that is to say the plate pair comprising two plates and if appropriate including any turbulence inserts to be provided can be prefabricated in such a way that the plate pair is fixed by means of lugs which are formed from one plate and surround the rim of the other plate, so that the two plate sheets of the plate pair can no longer slide with respect to one another, can no longer be moved with respect to one another, or can no longer gape open during the actual soldering process, thus ensuring that the plate pair is soldered such that they are sealed. Crimped plates can prevent, for example, relative movements between the housing and the plate pair resting on it along it as a result of the components being heated at different rates and the solder layers melting leading to inadequate soldering of the plate pair. This also simplifies tolerance matching between the longitudinal face of the plate pair and the housing since, essentially, all that is necessary is to ensure that the crimped plate pair rest on the housing during the soldering process, without any need to consider possible movements of the two plates with respect to one another. This ensures that the integral connection of the flow channels and plate pairs results in thermal conduction between the first flow, the cooling medium, and the housing walls. Because of the thermal coupling, the housing wall also contributes to the heat transfer, and the linking of the plate pairs makes it possible to considerably increase the heat-transfer area for the second fluid, depending on the heat-exchanger geometry and the configuration of the turbulence generators: from about 2% to more than 10% when one turbulence sheet is provided in the channel for the second fluid, and even up to more than 25% when turbulence generators (for example a vortex body that is stamped into the plate) are used in the channel of the second fluid. This results in an increase in the heat-exchanger performance, which may be considerable. Furthermore, when using a hot medium to be cooled, the housing wall can be adequately cooled and can be kept at a relatively low temperature level. However, particularly in the case of exhaust-gas coolers and boost-air coolers, adequate cooling of the housing is often absolutely essential in many other heat-exchanger applications since, otherwise, very large thermal stresses will occur at the connecting points between the housing and the plate pairs, caused by the large temperature differences and the correspondingly different thermal expansions of the housing carrying exhaust gas, and the cooled plate pairs. A further major advantage of linking the longitudinal faces of the plate pairs to the housing is the considerable increase in the pressure resistance of the heat exchanger with respect to the second fluid, since the plates represent a tie rod between the two housing sides, opposing the internal pressure. The proposed heat-exchanger concept is therefore particularly suitable for media in which the pressure-loss requirements for the second fluid are highly restrictive, the second fluid is very hot, or the pressures of the second fluid are high, or combinations of these requirements.
In one development of the invention, the flow channels are integrally connected to the housing essentially over the entire length of the longitudinal faces. The integral connection is produced in particular by soldering, welding, adhesive bonding etc., but in principle it is also possible to use any other type of connection, such as an interlocking connection or a combination of an integral connection and an interlocking connection.
In one development of the invention, the flow channels are in the form of plate pairs. The plate pairs form channels for a second fluid to pass through. There is a connection between the plate pairs and the housing, so that the second fluid has access to the housing and to the housing wall, and therefore, for example, cools or heats the housing wall and the housing.
In one development of the invention the flow channels and/or the channels for the second fluid to pass through are essentially held in their entirety by the housing, so that the heat transfer between the first and the second fluid takes place essentially entirely in the interior of a housing which can be closed by a cover, with heat likewise being transferred between the second fluid and the housing and/or the cover, as well as between the first fluid and the housing and/or the housing cover.
In one development of the invention, at least one flow channel for a fluid, in particular the first fluid, is formed between the cover of an adjacent plate, in particular a lower plate, thus saving an upper plate, with the cover being additionally cooled at the same time. Since the cover is integrally connected to the housing, for example by soldering, welding, adhesive bonding etc., and/or is connected by means of an interlock such as forming, heat is transferred between the cover and the housing, and vice versa, so that the housing is also cooled.
In another development of the invention, at least one flow channel for the first fluid is formed between the base section of the housing or the housing shell and an adjacent plate, in particular the upper plate, and between the base section of the housing shell, in this way likewise saving one plate, in particular a lower plate. In particular, the first fluid then cools the housing and the housing shell. Furthermore, however, it is also possible to connect the upper plate to a lower plate, in particular integrally, thus forming a plate pair which is integrally connected, in particular by soldering, welding, adhesive bonding etc., via at least one plate to the housing shell in the base area, in particular to the lower plate adjacent to the base area.
In one development of the invention, the lower plate and upper plate which in each case form a plate pair are connected to one another by means of a fold that is formed at the rim, with the plates therefore being connected to one another in an interlocking manner, in particular by bending. In this case, at least one plate, in particular the lower plate, clasps the other plate, in particular the upper plate, thus resulting in the plates being hooked to one another with tolerance compensation at the same time being possible in the stacking direction of the plates and of the plate pairs, so that, during the joining process, for example soldering, welding, adhesive bonding etc., by means of which the integral connection is produced, it is possible to compensate for any openings or gaps between the plates, so that the joining process can be carried out successfully by means of a reliable process, thus resulting in a complete, integral connection between the plates, in particular the upper plate and the lower plate, as well as between adjacent plate pairs and between adjacent upper plates and lower plates.
In one development of the invention, an inlet flow channel and/or at least one outlet flow channel run/runs transversely through the plate pairs, and in this case the inlet flow channel and/or the outlet flow channel may run through the plate pairs, at an angle of 0° to 360°, or −360°, to the stacking direction of the plates and/or to the longitudinal direction of the plates, in particular at an angle of −50° to +500 to the stacking direction, and particularly advantageously at an angle of 0° to the stacking direction, that is to say the inlet flow channel and/or the outlet flow channel run essentially parallel to the stacking direction. The angles of the outlet flow channel and of the inlet flow channel to the stacking direction and/or to the longitudinal direction may in this case differ, and may assume values between 0° and 360° or −360°.
In one development of the invention, the plate pairs have at least one depression or at least one protrusion. The depression or the protrusion is in this case incorporated in at least one plate of a plate pair in each case, preferably by forming techniques such as bending, stamping, etc., or by primary forming, etc.
In one development of the invention, the protrusion or the depression on or in a plate pair extends to an adjacent plate pair, with the plates and the plate pairs touching, and in particular being integrally connected to one another by soldering, welding, adhesive bonding etc. Furthermore, an interlocking connection and/or a combination of an interlocking connection and an integral connection are also possible, in the same way as other connections.
In one development of the invention, the protrusion or the depression is incorporated in the upper plate, in particular by forming or primary forming, in the same way as an upper plate annular surface which touches a lower plate annular surface, which is incorporated by forming or primary forming, of the lower plate of an adjacent plate pair and, in particular, is integrally connected to the lower plate annular surface by soldering, welding, adhesive bonding, etc. and/or by means of an interlock, such as hooking.
In another development of the invention, another protrusion is incorporated in the lower plate, in particular by forming and/or primary forming, in the same way as a lower plate annular surface which touches an upper plate annular surface of the upper plate of an adjacent plate pair and in particular is integrally connected to the upper plate annular surface by soldering, welding, adhesive bonding etc., and/or by an interlock, for example by hooking.
In one development of the invention, the flow channels are stacked. The channels for the second fluid to pass through can likewise also be stacked. In one development, the plates are stacked such that one plate is stacked on another adjacent plate and such that, in particular, an upper plate is placed on a lower plate and the upper plate has a further lower plate placed on it, on which, in turn, a further upper plate is placed, so that adjacent plate pairs are stacked one on top of the other. The stack formed by the plates, or the stack of plate pairs, is itself inserted into the housing shell, which is closed by a cover. The cover is in this case placed on the housing such that it is placed on the housing in a stacking direction and is connected to it by an interlock, in particular by soldering, welding, adhesive bonding etc., and/or integrally, in particular by forming, hooking, etc., thus allowing tolerances to be compensated for in the stacking direction of the flow channels and of the channels for the second fluid to pass through, during the joining process, in particular the soldering, welding or adhesive bonding.
In one development of the invention, the plates in a plate pair have plate rim surfaces such that the upper plate of a plate pair has an upper plate rim surface, and the adjacent lower plate has a lower plate rim surface, with the upper plate rim surface corresponding to the lower plate rim surface and being integrally connected in particular by soldering, welding, adhesive bonding etc. The upper plate rim surface runs in the longitudinal direction of the plate essentially parallel to the lower plate rim surface, and the upper plate rim surface likewise runs in the same way in the direction of the plate width which, in particular, is formed essentially at right angles to the longitudinal direction of the plate and essentially at right angles to the stacking direction of the plates, as well as essentially parallel to the lower plate rim surface. An abutment between the lower plate rim surface and the upper plate rim surface is formed in those sections of the upper plate rim surface and of the lower plate rim surface in which the longitudinal face of the plate merges into the plate width in the stacking direction, such that the abutment of a plate rim surface in the longitudinal direction is essentially in the form of a quarter cylinder, and such that the quarter cylinders of the lower plate and upper plate essentially touch like two concentric quarter cylinders that are pushed one inside the other, and are integrally connected, in particular by soldering, welding, adhesive bonding etc.
In one development of the invention, the longitudinal faces of two plate pairs which form a flow channel clasp one another at least in places, in particular over the entire plate length, such that the longitudinal face which touches the housing clasps the longitudinal face of an adjacent plate, in particular the other plate of the respective plate pair, and such that the two plates are in this way crimped to one another.
In one development of the invention, broader faces of two plate pairs which form a flow channel clasp one another at least in places, in particular over the entire plate width. In this way, the two plates, in particular the upper plate and the lower plate of a plate pair, are crimped to one another.
In one development of the invention, the plate pairs have turbulence-generating devices, in particular turbulence inserts or stamped-in structure elements. In this case, the turbulence inserts may be designed such that they are sheets with stamped-out areas and/or meshes composed of wire. The content of the unpublished DE102004037391.4, DE19718064B4 and DE19709601C2 is hereby expressly disclosed.
In one development of the invention, the protrusions are conical and are in the form of truncated cones which are produced from a plate, preferably by forming techniques such as stamping or primary forming. That side surface of the truncated cone which has the smaller of the two diameters is in the form of an annular surface, which touches the adjacent plate, preferably the lower plate of the next plate pair, and in particular is integrally connected to it by soldering, welding, adhesive bonding etc.
In one development of the invention, the protrusions are streamlined, in particular with an elongated, elliptical or round cross section.
In one development of the invention, turbulence-generating devices are incorporated between flow channels and/or in the channels for the second fluid to pass through. The contents of the unpublished DE102004037391.4, DE19718064B4 and DE19709601C2 are expressly disclosed in this context.
In one development of the invention, the folded connections are connected to the housing, in particular to the inner surface of the housing, with the connection being produced in particular integrally by soldering, welding, adhesive bonding etc.
In one development of the invention, the inlet area of the housing is arranged in front of the plate pairs in the flow direction of the second fluid.
In one development of the invention, the outlet area of the housing is arranged behind the plate pairs in the flow direction of the second fluid.
In one development of the invention, the second fluid can flow around the plate pairs essentially parallel to their longitudinal faces.
In one development of the invention, the fold on the longitudinal face is formed by rims of an upper plate and lower plate in the same sense that are bent. The fold on the longitudinal face furthermore forms a contact surface for the housing.
In one development of the invention, the fold on the longitudinal face is formed by rims of an upper plate and lower plate in opposite senses that are bent. The fold on the longitudinal face furthermore forms a contact surface for the housing.
In one development of the invention, the plate pairs have side channels for the first fluid on the longitudinal face in the area of the housing walls.
In this case, the side channels are in the form of an extension of the flow cross section of the plate pairs. The extension has a channel height which corresponds essentially to the distance between the plate pairs.
In one development of the invention, the plate pairs have a flow cross section with a channel width b, and the housing walls are separated by a distance w, where b<w and material bridges are arranged between the flow cross sections and the housing wall, and are in particular formed from a lower plate and/or an upper plate.
In one development of the invention, the housing is formed in at least two parts, and has a housing shell as well as a cover.
In one development of the invention, the inlet area of the housing has an inlet connecting stub which is arranged in the housing shell or in the cover. Moreover the outlet area of the housing has an outlet connecting stub which is arranged in the housing shell or in the cover.
In one development of the invention, the housing has an inlet connecting stub and an outlet connecting stub for the first fluid, with the inlet and outlet connecting stubs for the first fluid being arranged in the cover or in the housing shell, and having longitudinal axes which are at an angle to the plate pairs.
In one development of the invention, the heater exchanger has a bypass. A bypass channel for the second fluid is arranged within the housing and parallel to the plate pairs. The mass flow of the second fluid is for this purpose split into at least two mass flow elements, in particular by means of a separating wall, with at least one first mass flow element of the second fluid flowing through the channels for the second fluid to pass through, and with at least one second mass flow element of the second fluid flowing through the bypass.
In one development of the invention, the plate pairs form a pack through which the second fluid flows on two paths. A separating wall is arranged in the inlet area for the second fluid and/or in the outlet area for the second fluid. In this case, in particular, the separating wall is arranged such that it can rotate, so as to make it possible to set an angle of between 0° and 360° between the flow direction of the second fluid and a longitudinal face of the separating wall.
In one development of the invention, the heat exchanger contains at least one non-return valve, which is preferably integrated in the housing and is located in the outlet area.
In one development of the invention, the bypass channel is arranged above or below the plate pairs in the heat exchanger.
In one development of the invention, the bypass channel is in the form of a bypass tube which can be inserted into the housing. The bypass tube is in this case thermally insulated from the flow channels (3) and/or from the channels for the second fluid to pass through, in particular in such a way that as little heat as possible is transferred between the second mass flow element, which flows through the bypass channel and/or the bypass tube, and the first mass flow element which, in particular, is cooled.
In one development of the invention, the bypass tube is essentially arranged at a distance from the flow channels and/or from the channels for the second fluid to pass through. The separation is preferably provided by protrusions or stamped-out areas which are incorporated in the bypass tube and/or in the flow channels and/or the channels for the second fluid to pass through.
In one development of the invention, the bypass tube comprises at least one partial element which is preferably in the form of an open profile and particularly advantageously is in the form of a U-profile or half-tube.
In one development of the invention, the bypass tube comprises two tube halves, which are preferably integrally connected to one another by soldering, welding, adhesive bonding, etc.
In one development of the invention, the bypass tube has at least one longitudinal separating wall.
In one development of the invention, at least one bypass flap is integrated in the inlet or outlet area of the housing. The bypass flap is variable and may assume an angle from 0° to 360°, thus splitting the mass flow of the second fluid into the first mass flow element and the second mass flow element. The first mass flow element flows through the channels for the second fluid to pass through and, in particular, is cooled in the process. The second mass flow element flows, in particular without being cooled, through the bypass. The bypass valve can be used to adjust and/or to provide open-loop and/or closed-loop control for the first mass flow element of the second fluid through the channels for the second fluid to pass through. The second mass flow element of the second fluid through the bypass is a function of the set first mass flow element, and can therefore likewise be subjected to open-loop and/or closed-loop control.
In one development of the heat exchanger, the inlet area has two separate inlet connecting stubs as well as one separating wall.
In one development of the invention, the plate pairs form a pack through which the second fluid flows on two paths. An inlet chamber and an outlet chamber are arranged on one side of the plate pack. A deflection chamber for the second fluid is arranged on the other side of the plate pack.
In one development of the invention, the bypass is integrated in the housing. In particular, the bypass is formed integrally with the housing.
In one development of the invention, the bypass is integrated in the cover. In particular, the bypass is formed integrally with the cover.
A heat exchanger as claimed in one of the preceding claims, characterized in that the flap is arranged in the inlet area or in the outlet area.
In one development of the invention, the heat exchanger has at least one bypass valve which provides open-loop and/or closed-loop control for the volume flow and/or mass flow in particular of the second fluid through the bypass. The bypass valve is preferably integrated in the housing and, in particular, is formed integrally with it. The bypass valve is arranged in the inlet area and/or in the outlet area.
In one development of the invention, the bypass valve is a combination valve, which is referred to in the following text as a heat-exchanger valve device. The heat-exchanger valve device is characterized in that the valve plate can be rotated between a first open position, in which the bypass output is closed and the heat-exchanger output is open, and a second open position, in which the bypass output is open and the heat-exchanger output is closed. The rotating valve plate makes it possible to ensure adequate sealing, even at high pressures.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the rotating valve plate has an opening through which fluid can pass, which, by at least partial rotation, can be made to coincide with one of two further openings through which fluid can pass, and which are provided in a valve plate which is fixed relative to the valve housing. The three openings through which fluid can pass are preferably designed to be coincident with one another.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that one of the openings through which fluid can pass in the fixed valve plate is connected to the heat-exchanger output, and the other opening through which fluid can pass is connected to the bypass output. Depending on the extent to which the openings through which fluid can pass in the valve plates cover one another, more or less or even no fluid is passed to the bypass output and/or to the heat-exchanger output.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the fixed valve plate has a depression in which the rotating valve plate is guided. This results in the advantage that there is no need for the valve plate to be guided on the valve housing.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the fixed valve plate has an external thread by means of which the fixed valve plate can be screwed into a complementary internal thread in the valve housing. This makes it easier to fit the fixed valve plate.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that an actuator rod projects from the rotating valve plate. The actuator rod, which is preferably passed out of the valve housing, makes it easy to operate the rotating valve plate.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the valve plates are at least partially formed from ceramic. Stainless steel can also be used instead of ceramic.
One preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the valve slide can be moved backwards and forwards between a first extreme position, in which the bypass output is closed and the heat-exchanger output is open, and a second extreme position, in which the bypass output is open and the heat-exchanger output is closed. The valve slide makes it possible to ensure adequate sealing even at high pressures.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the valve slide is formed partially from ceramic. Stainless steel can also be used instead of ceramic.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the valve housing is formed partially from ceramic. The contact surface for the valve slide is preferably formed from ceramic.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the valve slide is equipped with a sealing element for the input. The input is preferably equipped with a sealing seat for the sealing element.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the sealing element has a sealing surface facing the input, in the form of a spherical section. The use of a spherical section with a large diameter makes it easier for the valve slide to move.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the sealing element is guided such that it can move backwards and forwards on the valve slide. This makes it easier to close the input by means of the sealing element, which is also referred to as a closing element.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the sealing element is prestressed against the input by a spring device. This allows the input to be closed to form a seal.
A further preferred exemplary embodiment of the heat-exchanger valve device is characterized in that the valve slide has a pressure equalizing channel. This makes it easier to move the valve slide in the valve housing.
In one development of the invention, the integrated bypass has a separating wall which can pivot and by means of which the inlet connecting stub and the outlet connecting stub can be short-circuited.
In one development of the invention, the first fluid is a liquid coolant, in particular the coolant from the cooling circuit of an internal combustion engine for a motor vehicle, and the second fluid is fed-back exhaust gas from the internal combustion engine.
In one development of the invention, the first fluid is air, and the second fluid is fed-back exhaust gas from an internal combustion engine for a motor vehicle.
In one development of the invention, the plate pack is preceded by an oxidation catalytic converter, for example as disclosed in the unpublished DE 10 2005 014 295.8. The entire content of the unpublished DE 10 2005 014 295.8 is hereby disclosed expressly.
In one development of the invention, the first fluid is a liquid coolant, in particular the coolant in the cooling circuit of an internal combustion engine for a motor vehicle, and the second fluid is boost air which can be supplied to the internal combustion engine.
In one development of the invention, the first fluid is air and the second fluid is boost air which can be supplied to an internal combustion engine for a motor vehicle.
In one development of the invention, the heat exchanger is used as an exhaust-gas cooler in an exhaust-gas feedback system for an internal combustion engine for a motor vehicle or as a heater for heating the interior of a motor vehicle, in which case the heat transferred from the second fluid to the first fluid is used to heat the interior of the passenger compartment of a vehicle.
In one development of the invention, the heat exchanger is used as an oil cooler for cooling engine oil for an internal combustion engine or gearbox oil for a motor vehicle by means of a liquid coolant, preferably the coolant in the cooling circuit of the internal combustion engine.
In one development of the invention, the heat exchanger is used as a coolant condenser in the coolant circuit of a climate-control system for motor vehicles.
In one development of the invention, the heat exchanger is used as a coolant exhaust-gas cooler in the coolant circuit of a climate-control system for motor vehicles.
In one development of the invention, the heat exchanger is used as a coolant vaporizer in the coolant circuit of a climate-control system for motor vehicles.
Further advantageous refinements of the invention are specified in the dependent claims.
One particularly advantageous refinement of the invention is represented by concepts in which the rims of both plates of the plate pair are formed circumferentially and without any interruptions such that they make flat contact with one another everywhere (
According to a further advantageous refinement of the invention, the housing is formed in at least two parts, that is to say for example from a first housing part in the form of a trough, a housing shell, and a second part in the form of a cover. The two parts can be placed one inside the other and can easily be joined to one another, in particular by soldering, welding, adhesive bonding etc. A housing concept such as this also results in an optimum joining process, in particular a soldering process, welding process, adhesive-bonding process, etc., between the stacked plate pairs, when the housing parts are likewise pushed one inside the other, or placed one on top of the other, in the stacking direction of the plate pairs, and are joined to the housing by soldering, welding, adhesive bonding etc. during the joining process, in particular the soldering process, welding process, adhesive-bonding process etc. In one suitable embodiment, the housing parts can then also move towards one another to the same extent with the plate pairs so that, for example, no gaps or solder, welding and/or adhesive bonding faults occur as a result of the melting solder layers. Like the cover, the housing shells can advantageously be produced as formed and/or primary-formed parts such as thermoformed or deep-drawn parts, in which case the housing shells may also form the inlet and outlet areas for the second fluid. Furthermore, inlet and outlet connecting stubs both for the first and the second fluid can be integrally formed, for example in the form of passages, on the housing, irrespective of whether this is the housing shell or the housing cover. The position and shape of the connecting stubs can be chosen as required, depending on the requirements for the heat exchanger. For example, the inlet and outlet connecting stubs for the second fluid may be located at the same cooler end or at opposite ends (see the explanatory notes relating to this further below), and the inlet and outlet may be provided in any desired direction, that is to say for example in the longitudinal direction of the cooler, upwards—in this case out of the cover, downwards from the housing or at the side out of the housing.
According to a further advantageous refinement of the invention, a bypass channel can be arranged parallel to the plate pack in the housing, in which case, for example, the bypass may be in the form of a tube which is inserted into the housing and is soldered to the other parts. A bypass such as this is particularly advantageous when using the heat exchanger as an exhaust-gas cooler in an exhaust-gas feedback system. Bypass arrangements such as these in conjunction with appropriate bypass flaps for control of the exhaust-gas flow through the heat exchanger or through the bypass are known per 5e from the prior art. The design of the heat exchanger according to the invention allows a bypass channel and a bypass flap to be integrated in the exhaust-gas cooler, using simple means. The fluid flow which is carried in the bypass must also be carried separately from the fluid flow in the inlet area, which flows through the heat-exchanger channels. For this purpose, a separating plate or separating element, in the simplest form a separating plate, can be provided in the inlet area for the second fluid, separating the inlet area into two areas, one for the bypass fluid flow and the other for the heat-exchanger fluid flow. By way of example, separating elements may be clamped, welded or soldered in one housing part or between housing parts. The separated inlet areas may either each have their own inlet openings in the housing or may be supplied with the fluid flows through a common inlet opening, but which is split in two by the separating element. In the case of the common inlet opening, of course, the two fluid flows must also be separated in the supply line of the second fluid, or a bypass flap must be fitted directly to the inlet opening in a manner such that it is directly closed by the separating element and no unacceptable leakages can occur from the bypass side to the heat-exchanger side, and vice versa. For example, this can be achieved by flange connection or a flange-connected module comprising a flap, housing and actuator. Furthermore, the bypass flap can also be integrated in the inlet area of the second fluid such that the gas flow is passed directly into the bypass channel or into the heat-exchanger channels, as required. In the case of an integrated bypass flap such as this as well, an additional separating element may also be required between the start of the bypass and the flap for sealing purposes. All the described solutions can likewise be provided with the same functionality in the outlet area for the second fluid, that is to say a separating element and bypass flap in the described arrangements and combinations. The statements relating to the need to separate the fluid flows in the supply line then apply in a corresponding manner to the output line. All the solutions are also possible with a combination valve instead of a bypass flap, that is to say it is also possible to completely block the second fluid, in addition to the fluid being passed into the heat-exchanger channels or into the bypass. For example, the described bypass flaps or valves can be operated via an electrical actuator or via a pressure control element.
The heat exchanger according to the invention allows the bypass channel to be embodied in widely differing ways. In one development of the invention, the bypass is inserted underneath the lowermost plate or above the uppermost plate in the stacking direction of the plate pairs. It is directly adjacent to the housing. In one development of the invention, the bypass is inserted into the housing at the side, alongside the stacked plate pairs. In one development of the invention, the bypass channel is formed integrally with the housing by impressing one or more longitudinal beads into the housing such that the bypass channel is formed in this way and is bounded on one side by the housing wall and on the other side by the first plate of the plate stack. In one development of the invention, a bypass is formed such that an essentially U-shaped shell is placed on one housing side, and in particular is joined to it, and in particular is soldered, welded, or adhesively bonded, etc., to it. In this case, the bypass is enclosed between the fitted shell and the housing wall. Furthermore, a heat exchanger according to the invention can also be combined with a completely external bypass, that is to say a closed flow channel for the second fluid, which can be connected to the heat exchanger, for example by welding or soldering, or can be fixed with the heat exchanger in common holders. However, an external bypass may also be routed completely separately from the heat exchanger.
In one development of the invention, any form of spacer may be used between the plate stack and the housing wall, such as a corrugated plate or a ribbed plate. Furthermore, it is possible to use permeable structures such as wire meshes, porous materials or the like. A shell extending in the longitudinal direction may also be particularly advantageous, having a U-profile and being open towards a housing wall. It supports the plate stack by means of the closed side.
In one development of the invention, the structures which form the channel project in the longitudinal direction beyond the heat-exchanger channels formed by the stacked plates into the inlet and/or outlet area of the second fluid. This means there is no need for a separating element between the bypass fluid flow and the heat-exchanger fluid flow. In one development of the invention, the integrated bypass flap is designed such that no additional separating element is required for the bypass channel.
The bypass channel is intended to allow the second fluid to bypass the heat-exchanger channels without any major energy transfer from or to the first fluid, and it should therefore be thermally decoupled as well as possible from the first fluid. The decoupling can be achieved, for example, by a stud or bead support for the bypass channel against the housing wall and/or against the plate stack. The studs or beads may in this case be stamped out both from a structure which forms the bypass channel, for example a tube, and/or from the housing wall or the adjacent first plate in the plate stack. Additional insulation can also be inserted between the bypass channel and adjacent structures as an insulating element with poor thermal conductivity (a good insulating effect). The insulating effect is achieved by insulating materials and/or by shaping, in particular by means of a ribbed structure.
In one development of the invention, the bypass channel has double walls, in particular with a thicker, load-bearing outer wall and a thinner, inner wall. The two walls are designed such that the outer wall is subject to less thermal stresses than the inner wall.
A further refinement of the invention provides for the flow to pass through the heat exchanger on two or more paths, that is to say for the second fluid to be split into flow elements which are each passed through some of the heat-exchanger channels parallel or in opposite directions. The same requirements for separating plates and inlet/outlet openings may be used to separate the flow elements as those already described in conjunction with integration of the bypass tube.
In one development of the invention, the exhaust-gas flow elements are each passed in one flow from two cylinder banks. The respective pressure surges which result in the two paths can thus be used to increase the exhaust-gas feedback rate and the fuel efficiency, provided that a return flow into the other path is avoided. The return flow is therefore prevented by non-return valves which, in particular, are integrated in the exhaust-gas cooler in the outlet area of the second fluid or are arranged in conjunction with a separating plate in the outlet area adjacent to the outlet opening of the cooler housing, for example by flange connection.
In one development of the invention, multiple-path heat exchangers are formed with a minimum of one direction change for the second fluid. In this case, the second fluid is not split into flow elements but is passed through some of the fluid channels from the inlet end of the second fluid to the other end, where this direction is changed, in particular being changed essentially through 180°, then being passed again through others of the fluid channels. In this case, the direction may be changed in a plurality of step elements. However, it is also possible to provide a plurality of direction changes, with the second fluid being output at the inlet end of the heat exchanger if there are an odd number of direction changes, or with the outlet being at the other end of the heat exchanger if there are an even number of direction changes.
In one development of the invention, the direction change is in the form of a U-flow, with the inlet and the outlet for the second fluid being located closely adjacent to one another at one cooler end, thus allowing the heat exchanger to be integrated to optimize the physical space.
In one development of the invention, the heat exchanger is in the form of a boost-air intercooler between the compressor stages of a turbine engine, in particular with no separating elements or other direction-changing elements being formed in the direction-changing area, since the direction change is produced by a housing that is closed at this end.
In one development of the invention, no separate bypass tube is required for the U-flow embodiment since, in the bypass mode, the connection between the inlet and outlet connecting stubs is short-circuited in the combined inlet/output area of the cooler. In the case of cooled exhaust-gas feedback, the path between the inlet and outlet connecting stubs is blocked, and the second fluid, in particular the exhaust gas, is passed through the heat-exchanger channels.
In one development of the invention of the heat exchanger with a U-flow, the design has an internal bypass flap and/or a combination valve and/or an external bypass flap and/or a combination valve. When using an external bypass flap in conjunction with a U-flow cooler, the inlet/output area must be split by means of a separating element, and the bypass flap is then integrated in particular in a module which can directly short-circuit the path through the exhaust-gas cooler.
As mentioned, the heat exchanger according to the invention can be used particularly advantageously as an exhaust-gas cooler; in this case, in particular, it is advantageous to cool the housing casing, because the coolant makes direct contact with the housing wall in places and is indirectly connected to the housing wall via material bridges. Depending on whether it is being used for high-pressure or low-pressure exhaust-gas feedback (exhaust-gas extraction before or after the exhaust-gas turbine), the exhaust-gas cooler can be cooled by the coolant in the cooling circuit of the internal combustion engine or by air, in which case the flow cross sections and the heat transfer are matched, for example by means of turbulence inserts. When used as an exhaust-gas cooler, it is also advantageous to arrange an oxidation catalytic converter in the flow direction of the exhaust gas upstream of the plate pairs, that is to say in the inlet area of the exhaust-gas cooler. It is particularly worthwhile integrating an oxidation catalytic converter upstream of the heat-exchanger tubes and any bypass flap which may be required in the outlet area of the cooler, since the flap/combination valve is then protected against dirt.
The heat exchanger according to the invention can also advantageously be used as a boost-air cooler, either with direct cooling (air) or with indirect cooling (liquid coolant). Furthermore, the heat exchanger according to the invention can advantageously be used as a coolant-cooled oil cooler or as an air-cooled condenser for a motor vehicle climate-control system. All that is necessary for the various applications is matching to the various media and heat-transfer relationships.
Furthermore, in addition to the two simple types of connection comprising flow in the same direction between the first and the second fluid or flow in the opposite direction between the first and the second fluid (with the U-flow cooler representing a combination of the two), it is also possible to provide more than one circuit for the first fluid, that is to say for the first medium. For example, in an exhaust-gas cooler application, the coolant flow may be carried parallel to the exhaust gas in the inlet area of the exhaust gas, thus achieving effective boiling prevention, and the coolant flow can be carried in the opposite direction to the exhaust gas in the outlet area of the exhaust gas, thus achieving particularly efficient heat transfer in the rear part of the heat exchanger, see DE10328746, whose content is hereby expressly disclosed. The first fluid can be tapped off in the center of the heat exchanger through a common outlet for the two circuits, or through separate outlets. However, in order to improve the heat transfer, it is also possible, for example, to arrange two circuits one behind the other for the first medium, with the flow passing through both of them in the opposite direction to the second fluid. In this case, both circuits for the first medium have their own inlet and outlet.
Concepts with two circuits for the first fluid flowing in the opposite direction to the second fluid are particularly worthwhile when the first and second media have similar thermal capacities, or the second medium has a higher thermal capacity than the first, and in particular also when both media are gaseous.
Exemplary embodiments of the invention will be explained in more detail in the following text, and are illustrated in the drawing, in which:
a, 2b, 2c show further exemplary embodiments of the design of the coolant channels with direct cooling of the housing wall,
a, 3b, 3c show further exemplary embodiments of the design of the coolant channels with indirect cooling of the housing walls,
a shows an exploded illustration of the plate pairs and of the cover,
b shows an exploded illustration of an unjoined plate pair which comprises at least one upper plate and at least one lower plate, and a further lower plate of an adjacent plate pair,
c shows a section C-C through an exploded illustration of an unjoined plate pair, which comprises at least one upper plate and at least one lower plate,
d shows a perspective illustration of a joined plate pair,
e shows a view of a joined plate pair in the flow direction of the second fluid,
a, 6b, 6c show embodiments of a two-part housing for the exhaust-gas cooler,
a, 7b show longitudinal sections through the exhaust-gas cooler with different exhaust-gas and coolant routing,
a, 8b show longitudinal sections through the exhaust-gas cooler with an integrated bypass tube and separating wall in the inlet or outlet area,
a shows a further exemplary embodiment of the invention in the form of a detail comprising an exhaust-gas cooler, with the same reference numbers as in
b shows a further exemplary embodiment of the invention relating to the design of a plate pair 8 which is composed of an upper plate 8a, 80b and a lower plate 8b, 80c and is closed at the side by a respective fold 8c. The flow cross section of the plate pair 8 is extended at the side to form side channels 8d, 8e which are approximately the same height as the exhaust-gas channels 5 and the turbulence inserts 6 which are arranged in the exhaust-gas channels 5. The side channels 8d, 8e through which the coolant flows therefore extend from one plate pair 8 to the adjacent plate pair, and rest over their entire area on the housing walls 2c, 2d. This results in very good cooling of the housing walls 2c, 2d, which are therefore insulated from the exhaust-gas flow. The same features are provided with the same reference symbols as in the previous figures.
c shows a further embodiment of the plate pairs 9, comprising an upper plate 80b and a lower plate 80c, between housing walls 2c, 2d, with an extension of the flow cross section forming side channels 9a, 9b, although these are not as high as the exhaust-gas channels, but are only a portion of its height, for example 50%, with the rest of the channel height in each case being bridged by a longitudinal fold 9c, 9d. This embodiment also results in very good cooling of the housing walls 2c, 2d, since coolant flows around them. The same features are provided with the same reference symbols as in the previous figures.
a, 3b, 3c show further exemplary embodiments of the invention of embodiments of plate pairs 10, 11, 12 which are each formed from an upper plate 80b and a lower plate 80c, whose flow channels have a width b which is less than the unobstructed width w of the housing—material bridges 10a, 10b, 11a, 11b, 12a, 12b which each run in the longitudinal direction are arranged between the flow channels of the plate pairs 10, 11, 12 and, in each case in different embodiments, rest on the housing walls 2c, 2d and are soldered to them. This likewise results in a good cooling effect, that is to say the housing walls 2c, 2d are cooled indirectly, that is to say by thermal conduction via the material bridges 10a, 10b, 11a, 11b, 12a, 12b. The same features are provided with the same reference symbols as in the previous figures.
a shows a further illustration of the plate pairs 14 shown in
b shows an exploded illustration of an unjoined plate pair 3, 14 which comprises at least one upper plate 80b and at least one lower plate 80c, as well as a further lower plate 80c of an adjacent plate pair. The same features are provided with the same reference symbols as in the previous figures. The upper plate 80b and the lower plate 80c each have a plate opening 81, which is in the form of a hole. The upper plate 80b has at least one protrusion 14b, in particular two protrusions 14b, which are in the form of truncated cones in the stacking direction. The truncated cone has an upper plate annular surface 82, 82c on the side with the smallest external diameter, which upper plate annular surface 82, 82c is arranged parallel to the plate surface 92 of the upper plate 80b and of the lower plate 80c, and at right angles to the stacking direction of the plate pairs 3, 14. The lower plate 80c has a lower plate annular surface 83, 83c, which is formed integrally with the plate surface 92 and is identical to it in the area of the plate opening. In the joined state, in particular in the soldered, welded, adhesively bonded, etc. state, the upper plate annular surface 82, 82c of a plate pair 3, 14 and the lower plate annular surface 83, 83c of an adjacent plate pair 3, 14 touch, and are integrally connected to one another. The upper plate 80b has an upper plate rim surface 85 at the plate rims. The lower plate 80c has a lower plate rim surface 86 at the plate rims. The upper plate rim surface 85 and the lower plate rim surface 86 correspond to one another and are integrally connected to one another, in particular by soldering, welding, adhesive bonding etc. The upper plate rim surface 85 runs in the longitudinal direction of the plate essentially parallel to the lower plate rim surface 86, in the same way as the upper plate rim surface 85 in the direction of the plate width, which runs essentially parallel to the lower plate rim surface, in particular aligned essentially at right angles to the longitudinal direction of the plate and essentially at right angles to the stacking direction of the plates. An abutment 93 between the lower plate rim surface and the upper plate rim surface is formed in those sections of the upper plate rim surface and of the lower plate rim surface in which the longitudinal face of the plate merges into the plate width in the stacking direction, such that the abutment 93 of one plate rim surface is essentially in the form of a quarter cylinder in the longitudinal direction, and such that the quarter cylinders of the lower plate and upper plate touch essentially like two concentric quarter cylinders which have been pushed one inside the other, and are integrally connected to one another, in particular by soldering, welding, adhesive bonding etc.
c shows a section C-C through the exploded illustration in
d shows a perspective illustration of a joined plate pair 3, 14. The same features are provided with the same reference symbols as in the previous figures. In the joined state, in particular in the soldered, welded, adhesively bonded etc. state, the upper plate annular surface 82, 82c of a plate pair 3, 14 and the lower plate annular surface 83, 83c of an adjacent plate pair 3, 14 touch and are integrally connected to one another. At the plate rims, the upper plate 80b has an upper plate rim surface 85. The lower plate 80c has a lower plate rim surface 86 at the plate rims. The upper plate rim surface 85 and the lower plate rim surface 86 correspond to one another and are integrally connected to one another, in particular by soldering, welding, adhesive bonding etc. The upper plate rim surface 85 runs essentially parallel to the lower plate rim surface 86 in the longitudinal direction of the plate, in the same way as the upper plate rim surface 85 runs in the direction of the plate width, essentially parallel to the lower plate rim surface, and in particular is aligned essentially at right angles to the longitudinal direction of the plate and essentially at right angles to the stacking direction of the plates. An abutment 93 between the lower plate rim surface and the upper plate rim surface is formed in those sections of the upper plate rim surface and of the lower plate rim surface in which the longitudinal face of the plate merges into the plate width in the stacking direction, such that the abutment 93 of the plate rim surface is essentially in the form of a quarter cylinder in the longitudinal direction, and in such a way that the quarter cylinders of the lower plate and upper plate essentially touch one another like two concentric quarter cylinders which have been pushed one inside the other, and are integrally connected to one another, in particular by soldering, welding, adhesive bonding etc.
e shows a view of a joined plate pair in the flow direction of the second fluid. The same features are provided with the same reference symbols as in the previous figures.
a, 6b, 6c show different forms of the embodiment of housings 17, 18, 19, which each have housing shells 17a, 18a, 19a in the form of boxes or troughs. The same features are provided with the same reference symbols as in the previous figures. The cover shapes 17b, 18b, 19b are different. The cover 17b has a circumferential bead (groove) 17c, which can be placed on the circumferential upper edge of the housing shell 17a, and can thus be soldered. The cover 18b has a circumferential rim 18c which projects upwards and rests on the inner wall of the housing shell 18a. The cover 18b can thus “sag” during soldering (during melting of the solder layers in the plate pack). The cover 19b has an angled rim 19c, which clasps the outside of the upper edge of the housing shell 19a and can therefore also be soldered circumferentially. All the illustrated parts can be produced at low cost as deep-drawn or thermoformed parts.
a shows an exhaust-gas cooler 20 in the form of a longitudinal section with a housing 21, comprising a housing shell 21a, a cover 21b, an inlet for the first fluid 90 and an outlet for the first fluid 91. A pack 22 (illustrated by dashed lines) comprising the already mentioned plate pairs, which are not illustrated here but through which coolant can flow, is arranged in the housing 21. The same features are provided with the same reference symbols as in the previous figures. The relevant coolant connections are arranged as connecting stubs 23, 24 in the cover 21b of the housing 21. The exhaust gas, represented by arrows A, enters the exhaust-gas cooler 20 through an inlet connecting stub 25, and leaves it via an outlet connecting stub 26. An inlet area 27 is incorporated in the exhaust-gas flow direction upstream of the plate pack 22 and acts as a diffuser, and an outlet area 28 is incorporated in the housing 21 downstream from the plate pack 22, and merges into the outlet connecting stub 26. The exhaust gas, represented by the arrows A, therefore flows essentially in the longitudinal direction (“axially”) through the exhaust-gas cooler 20 and through the plate pack 22.
b shows a similar exhaust-gas cooler 29 with the difference that the coolant connections 30, 31 are arranged in the base part of the cooler, and the exhaust-gas connecting stop 32 on the outlet side is arranged in the cover part of the housing, thus making it possible to change the direction of the emerging exhaust gas through 90°, represented by an arrow A. The same features are provided with the same reference symbols as in the previous figures. Changes such as these in the exhaust-gas and coolant inlet and outlet are therefore possible by simple measures on the housing.
a and 8b show further exemplary embodiments of the invention, to be precise an exhaust-gas cooler 33 with a bypass channel 34 arranged at the bottom, and an exhaust-gas cooler 35 with a bypass channel 36 arranged at the top. The same features are provided with the same reference symbols as in the previous figures. The two bypass channels 35, 36 may be in the form of a tube and may be introduced into the housing, in each case parallel to the plate packs 37a, 37b, which are illustrated in shaded form. In the exhaust-gas inlet area, the exhaust-gas cooler 33 shown in
As a further exemplary embodiment of the invention,
The turbulence-generating elements and the turbulence inserts are in the form of web ribs in a further embodiment, which is not illustrated.
Turbulence inserts with web ribs have comparatively less tendency to accumulate deposits despite their flow cross sections being fundamentally smaller than those of other inserts. In principle, there was a concern that turbulence inserts with web ribs would lead to increased blocking of individual channels for the flow to pass through, owing to the fine-element structure of the web ribs. However, this is true to a surprisingly small extent, particularly if the webs of the web ribs are relatively short. One possible explanation for this could be that the turbulent flow which is created over large parts of the web-rib insert in the exhaust gas reduces the deposition of particles while in contrast organized flows are formed in longer, single-form channels, which promote the deposition of particles close to walls, because the flow speed is very low there.
In one preferred embodiment, the webs of the web ribs have a length which is no more than about 10 mm, preferably no more than about 5 mm, and particularly preferably no more than about 3 mm. Depending on the available physical space and the internal combustion engine, there may be specific requirements for the pressure drop across the exhaust-gas heat exchanger. One of the abovementioned length ranges may be preferred, depending on these requirements.
Furthermore, the density of the web ribs transversely with respect to the exhaust-gas flow direction is preferably between about 20 web ribs per dm and about 50 web ribs per dm, preferably between about 25 web ribs per dm and 45 web ribs per dm. These web rib densities have been found to be particularly suitable in trials. In particular, the web ribs particularly advantageously represent a good compromise between the risk of blocking and cooling performance.
With respect to the height of the web ribs, it should be remembered that, if they are high, only relatively small primary areas, that is to say surfaces cooled by coolant, are available, via which all of the heat must be dissipated into the coolant. If the primary areas are relatively small, the risk of a liquid coolant burning is then increased. Furthermore, the efficiency of the inserts decreases as the height of the web ribs increases. A preferred height for the insert or web rib is therefore between about 3.5 mm and about 10 mm, particularly preferably between about 4 mm and about 8 mm, and in particular preferably between about 4.5 mm and about 6 mm.
In one preferred development of the apparatus according to the invention, it is possible for an oxidation catalytic converter to be arranged upstream of the plurality of flow channels. In general, a catalytic converter such as this makes it possible to reduce the particle sizes, particle densities and the proportions of hydrocarbons in the exhaust gas, by oxidation. In this case, additionally or alternatively, it is possible to provide for the inserts themselves to be provided with a coating for catalytic oxidation of the exhaust gas. Particularly in conjunction with oxide-catalytic means, the web rib densities that can sensibly be used transversely with respect to the exhaust-gas flow direction may be more than about 50 web ribs per dm, in particular about 75 web ribs per dm. This will result in particularly good heat-exchanger performance for a given physical space without the long-term risk of blocking as a result of deposits.
In one particularly preferred embodiment, the web ribs have inclined teeth. Ribs with inclined teeth have been found experimentally to be particularly suitable for ensuring good long-term stability of the exhaust-gas heat exchanger against deposits. In this case, in one preferred embodiment, the angle between the web walls and a main direction of the web ribs is between about 1° and about 45°. In one particularly preferred embodiment the angle is between about 5° and about 25°, although, in an alternative preferred embodiment, it may also be between about 25° and about 45°. The first-mentioned value range from 5° to 25° is particularly highly suitable for normal applications, which are particularly sensitive to pressure losses, with the second-mentioned value range being suitable to achieve an optimized power density, in particular for applications which are less sensitive to pressure losses.
In general, a correlation can be found between the angle of the walls and a longitudinal pitch of the web ribs for optimization of an insert with obliquely toothed web ribs. In this case, in particular, optimum embodiments with small angles may have greater pitches 1 than optimized embodiments with large angles. Embodiments with a moderate pressure loss result in particular with small inclination angles. Embodiments with optimized power density can be obtained in particular with large inclination angles. Particularly in the case of small inclination angles, the longitudinal pitch may be greater while, for large inclination angles, the longitudinal pitch may in particular be less, in order to obtain optimized embodiments.
In one preferred embodiment, the apparatus is in the form of a stacked-plate heat exchanger. This embodiment is particularly appropriate both in terms of the width of a flow channel and in terms of cost-effective manufacture and the capability to combine a heat-exchanger housing with web-rib inserts. Alternatively, the apparatus may, however, also be in the form of a tube-bundle heat exchanger, or may be some other heat-exchanger form that is known per se.
It is generally preferable for the insert to be manufactured from a stainless steel, in particular from an austenitic steel, in order to prevent corrosion being caused by the corrosive exhaust gas.
In a further advantageous refinement, aluminum materials may be used, in which case it may then be particularly advantageous to provide suitable corrosion protection, in particular such as an alloy and/or a coating.
In one advantageous embodiment, the insert is formed from aluminum. Inserts formed from aluminum have a particularly light weight. It is particularly advantageous to form the inserts from aluminum by means of an alloy or coating, for corrosion protection.
Depending on the flow parameters, in particular the Reynolds number, the length of inlet area of the flow channels, in particular tubes and/or stacked-plate pairs, 1/s is approximately 2.5 to 5, and the length of the web ribs must be chosen to be below this limit value. S denotes the mean cross-sectional width between two webs, and is therefore b/2-t, where t is the metal-sheet thickness. This results in a required ratio 1/s of less than 4, in particular 1/s of less than 2. If there is a high risk of blocking as a result of a critical exhaust-gas composition, 1/s should be chosen to be less than 1.5, in particular 1/s<1.
The inclined position of the webs results in a higher flow speed on the wall on the swirl side, counteracting particulate deposits. A further major advantage of web ribs with inclined teeth is that, in situations in which a low web-rib density in the direction at right angles to the flow is necessary in order to avoid blocking, particularly with a poor exhaust-gas composition, adequate cooler performance can be ensured despite a small rib surface area.
The stacked-plate heat exchanger according to the invention has an outer housing with a cover, with an inlet and an outlet being provided for the exhaust gas, as well as an inlet and an outlet for a liquid coolant. A plurality of plate elements are provided within the housing, with each of the plate elements comprising an upper half and a lower half. The plate elements are welded to one another and to the housing by means of collars that are placed on them, such that the coolant in each case flows from the inlet to the outlet between the two halves of one plate element. An insert, which is not shown but has web ribs, is arranged between two plate elements in each case, with the intermediate space between two plate elements in each case forming a flow channel for the exhaust gas. The inserts are not illustrated, for clarity reasons. The inserts are composed of a stainless steel. In order to improve the thermal contact between the inserts and the plate elements and/or the housing, the inserts may be welded or soldered flat to the said elements.
In a further embodiment, the turbulence insert is formed from a thin sheet-metal material, in which parallel web ribs are incorporated by forming measures. Each of the web ribs has a row of webs arranged one after the other in the exhaust-gas flow direction. Two webs which follow one another in the exhaust-gas flow direction are in each case arranged offset with respect to one another through half the web width transversely with respect to the exhaust-gas flow direction, so that each web is followed by a sharp edge followed by a web. In the present example, the walls are aligned parallel to the flow direction of the exhaust gas and form an angle of 0° with an axis B of the web ribs and the main flow direction of the exhaust gas A. A web rib insert such as this is referred to as a straight-toothed web rib.
In the first exemplary embodiment, the length 1 of a web is about 4 mm. The width b of a single web rib is defined as the width of the cyclic unit of the periodic structure transversely with respect to the main flow direction of the exhaust gas. The web rib density 2/b in the present example is about 40 web ribs per dm. The width b of a web rib is thus about 5 mm.
The height h of the web ribs corresponds to the distance between two adjacent plate elements of the heat exchanger, and in the present case is about 5 mm.
In a further refinement of the web-rib insert, the side walls of the individual webs are in this case not aligned parallel to the main direction B of the web ribs. In fact, each of the walls of the webs includes an angle W of about 30° with the main direction B of the web ribs. The further dimensions of the obliquely toothed web-rib inserts correspond to the dimensions of the straight-toothed web rib.
Suitable longitudinal pitches 1 for corresponding angles of the walls W in suitable embodiments are 10° with longitudinal pitches 1 of less than about 10 mm, 20° with 1 less than about 6 mm, 30° with 1 less than about 4 mm, and 45° with 1 less than about 2 mm.
The minimum longitudinal pitch 1 is about 1 mm for all angles. The permissible channel extent 1/s is within approximately the same limit as that for straight-toothed web ribs, with s being the web separation transversely with respect to the main flow direction B. It is generally difficult to produce longitudinal pitches 1 of less than 1 mm, for manufacturing reasons.
The at least one heat exchanger is at least one exhaust-gas heat exchanger and/or a boost-air cooler and/or an oil cooler and/or a coolant cooler and/or a coolant condenser for a climate-control system and/or a gas cooler for a climate-control system and/or a coolant vaporizer for a climate-control system and/or a cooler for cooling electronic components.
In a first embodiment, the boost-air cooler and/or exhaust-gas cooler is a direct boost-air cooler and/or direct exhaust-gas cooler. In this case, direct should be understood as meaning that at least one medium to be cooled, such as exhaust gas and/or boost air, is cooled directly by a cooling medium such as air.
In a second embodiment, the boost-air cooler and/or exhaust-gas cooler is an indirect boost-air cooler and/or indirect exhaust-gas cooler. In this case, indirectly should be understood as meaning that at least one medium to be cooled, such as exhaust gas and/or boost air, is cooled by a coolant such as a fluid containing water and/or a liquid such as cooling water, with this fluid containing water and/or the liquid such as cooling water being cooled by some other cooling medium, such as ambient air.
The at least one boost-air cooler in another embodiment is cooled directly and the at least one exhaust-gas cooler is cooled indirectly, or vice versa the at least one boost-air cooler in another embodiment is cooled indirectly, and the at least one exhaust-gas cooler is cooled directly.
In order to improve the heat transfer, in a further embodiment, at least two circuits, in particular two, three, four or more circuits, for the first medium are stacked one behind the other, that is to say in particular they are stacked in the direction A and/or in the stacking direction in which the plates are stacked, which in particular farms an angle 0° to 90° with the direction A. For example, the two, three, four or more than four circuits may have flow passing through them in opposite directions or in the same direction, or at an angle of 0° to 90° to the second fluid, in particular to the flow direction of the second fluid.
If the at least two circuits, in particular two, three, four or more than four circuits, for the first medium are arranged one behind the other, that is to say in particular in the direction A, at least one high-temperature circuit is arranged first flowing in the direction A, and is at a higher temperature than an at least second low-temperature circuit. In particular, the temperature difference between the high-temperature circuit and the low-temperature circuit is 10K to 100K, in particular 30K to 80K, more particularly 30K to 60K.
The high-temperature circuit is at temperatures between 70° C. and 100° C., in particular between 80° C. and 95° C., in particular in the operating state. The low temperature is at temperatures between 10° C. and 70° C., in particular between 20° C. and 60° C., in particular between 30° C. and 65° C., and more particularly between 40° C. and 50° C., in particular in the operating state.
In this way, the exhaust gas that is fed back and/or the boost air or at least one medium to be cooled is cooled in two, three, four or more stages.
The at least two circuits, in particular two, three, four or more circuits for the first medium are in the form of at least one U-flow circuit and/or at least one I-flow circuit. For example, at least two I-flow circuits or at least two U-flow circuits are arranged in series, in particular one after the other. In another example, at least one U-flow circuit follows at least one I-flow circuit, or vice versa. In particular, when at least two U-flow circuits are provided, the coolant connections for the at least two circuits are in one example arranged on one side of the cooler, for example at the top or bottom in the stacking direction of the plates, or at an angle of between 0° and 90° to the stacking direction.
In another example, the forward flow takes place in at least one high-temperature circuit, and the return flow in the at least one low-temperature circuit, or vice versa.
Furthermore, in another embodiment, a combination valve is integrated in the at least one heat exchanger, for example in the exhaust-gas heat exchanger and/or in the at least one boost-air cooler and/or in the at least one oil cooler and/or in the at least one coolant cooler and/or in the at least one coolant condenser for a climate-control system and/or in the at least one gas cooler for a climate-control system and/or in the at least one coolant vaporizer for a climate-control system and/or in the at least one cooler for cooling electronic components, in particular integrated in the housing of the heat exchanger, and/or formed integrally with it. The combination valve combines the function of at least one exhaust gas feedback valve for open-loop and/or closed-loop control of the fed-back exhaust gas or exhaust gas/air mixture, and/or the function of at least one bypass valve, in particular a bypass flap, for bypassing exhaust gas that has been fed back around the at least one heat exchanger, in particular the exhaust-gas heat exchanger and/or one of the other heat exchangers mentioned further above, so that a medium which is fed back, in particular exhaust gas and/or air, is not cooled in the at least one heat exchanger, in particular the exhaust-gas heat exchanger and/or one of the other heat exchangers mentioned further above. A combination valve such as this is disclosed in the unpublished DE 10 2005 034 136.5, the unpublished DE 10 2005 041 149.5, the unpublished DE 10 2005 041 150.9, the unpublished DE 10 2005 034 135.7 and in the published DE 103 21 636, the published DE 10321637 and the published DE 10 2005 041 146, whose entire content is hereby expressly regarded as disclosed.
The features of various exemplary embodiments can be combined with one another as required. The invention can also be used for fields other than those described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 034 137.3 | Jul 2005 | DE | national |
| 10 2006 014 187.3 | Mar 2006 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2006/006997 | 7/17/2006 | WO | 00 | 3/17/2008 |
