The invention relates to a stacked-plate heat exchanger.
Stacked-plate heat exchangers come into use as so-called exhaust gas evaporators in the exhaust gas aftertreatment of internal combustion engines. Such an exhaust gas evaporator enables a recovery of thermal energy from the exhaust gases which are discharged from the internal combustion engine. In an exhaust gas evaporator, heat is extracted from the exhaust gas and is fed to a coolant or refrigerant, the so-called working medium, which is typically evaporated here.
Such a stacked-plate heat exchanger is known for example from DE 10 2009 012 493 A1.
In order to achieve as high an efficiency as possible in the heat recovery, an optimized geometry of the channel structure in which the working medium is directed through the evaporator or respectively stacked-plate heat exchanger is of central importance.
It is an object of the present invention to provide an improved embodiment for a stacked-plate heat exchanger, which in particular has an improved efficiency.
This problem is solved by the subject of the independent claims. Preferred embodiments are the subject of the dependent claims.
Accordingly, it is a basic idea of the invention to provide the channel structure, formed in the stacked-plate heat exchanger, which is to be flowed through by a fluid—the working medium of the heat exchanger—partially with a zigzag-like channel geometry. The changes to the flow direction of the working medium, entailed thereby, when flowing through the zigzag-like channel geometry, are accompanied by an increased heat exchange between the working medium and the exhaust gas which is directed through the stacked-plate heat exchanger. Therefore, such a zigzag-like channel geometry is suitable in a region of the channel structure in which the working medium is present in liquid phase. This is because in this region, at low speeds of flow of the working medium, the heat transmission to the working medium is itself reduced. The zigzag-like channel geometry essential to the invention can at least compensate this reduced heat transmission with working medium present in liquid phase, and therefore leads, as a result, to an improved efficiency of the heat exchanger.
In the regions of the channel structure in which the working medium is two-phase, therefore is also present in gaseous form, the heat transmission is also sufficiently high without a zigzag-like geometry, so that there the said zigzag-like channel geometry can be dispensed with. Therefore, in these regions of the channel structure, an unnecessary pressure loss in the working medium, which always accompanies the zigzag geometry, is avoided.
A stacked-plate heat exchanger according to the invention comprises a plurality of stacked plates which are stacked on top of each other along a stacking direction. A channel structure, which is to be flowed through by a fluid, is formed in at least one stacked plate. The channel structure, when the stacked plate is viewed from above, comprises at least one fluid channel along the stacking direction, said fluid channel having at least one channel section with a zigzag-like geometry.
In a preferred embodiment, the at least one channel section with a zigzag-like geometry has a first partial section, which continues into a second partial section. The two partial sections form together an angle of between 90° and 165°. Experimental investigations have shown that with the said angle range a particularly high heat exchange can be achieved between the working medium and the exhaust gas.
In an advantageous further development, the first and the second partial section are configured so as to be substantially rectilinear along the stacking direction, when viewed from above, and continue into one another by means of a curved formed transition section. By means of such a geometry, an undesired pressure loss in the working medium when flowing through the fluid channel can be kept low.
Particularly preferably, the at least one fluid channel of the channel structure is formed in a meander-like manner and has a plurality of channel sections with a zigzag-like geometry. Such a geometry permits the arrangement of the fluid channel on a stacked plate with relatively small surface dimensions. Therefore, the stacked-plate heat exchanger can be realized with particularly compact exterior dimensions.
In a further preferred embodiment, at least one fluid channel has a plurality of U-shaped channel sections.
In this variant, at least one channel section with a zigzag-like geometry is provided between at least two adjacent U-shaped channel sections along an extent direction of the at least one fluid channel. This variant also permits a high heat exchange with, at the same time, a small installation space requirement.
Because it is likewise able to be realized in a particularly compact construction, a variant may be considered to be particularly preferred in which, between the at least two U-shaped channel sections following one another along the extent direction of the at least one fluid channel, two channel sections with a zigzag-like geometry are provided following one another along the extent direction.
In an advantageous further development, the channel structure comprises at least two fluid channels extending substantially parallel to and at a distance from one another. In this way, a high compressive strength can be ensured in the individual fluid channels. For a variety of working media, such as for instance cyclopentane, ethanol, acetone, it proves to be advantageous if precisely three fluid channels are provided, which extend substantially parallel to and at a distance from one another.
In a further advantageous further development, at least one connecting channel is formed between the at least two fluid channels, which connecting channel is provided with a zigzag-like geometry in the region of the channel section and fluidically connects the at least two fluid channels with one another. This enables a pressure equalization of the fluid pressure which is present in the working medium in the individual fluid channels. This, in turn, promotes a laterally particularly homogeneous heat exchange between working medium or respective the fluid, and the exhaust gas.
Particularly preferably, a plurality of connecting channels is provided, which are arranged at a distance from one another along the extent direction of the at least two fluid channels. In this way, the desired pressure equalization can be guaranteed over the entire extent of the fluid channels.
In a further advantageous further development, at least one connecting channel, preferably respectively all connecting channels, fluidically connects to one another all the fluid channels which are present. This provision also promotes a pressure equalization in the working medium or respectively fluid which is advantageous for a homogeneous heat exchange.
In another preferred embodiment, the channel structure is formed to be flowed through by water. For this, all the fluid channels which are present have, together, in a cross-section of the stacked plate perpendicularly to the extent direction of the fluid channels, a cross-section area of between 2 mm2 and 8 mm2. Alternatively thereto, the channel structure is formed to be flowed through by ethanol. For this, all the fluid channels which are present have, together, in the cross-section of the stacked plate perpendicularly to the extent direction of the fluid channels, a cross-section area of between 3 mm2 and 15 mm2. It is also conceivable to use a mixture of ethanol and water. Alternatively thereto, the channel structure can be formed to be flowed through by cyclopentane. In this case, all the fluid channels which are present have, together, in the cross-section of the stacked plate perpendicularly to the extent direction of the fluid channels, a cross-section area of between 6 mm2 and 20 mm2. Alternatively thereto, the use of acetone is also conceivable. Alternatively thereto, the channel structure is formed to be flowed through by hydrofluorocarbons (HFC). In this variant, all the fluid channels which are present have, together, in a cross-section of the stacked plate perpendicularly to the extent direction of the fluid channels, a cross-section area of between 15 mm2 and 40 mm2. Depending on the choice of the working medium, therefore, an individual design of the cross-section area of the individual fluid channels takes place. In this way, an efficient heat exchange is ensured, with, at the same time, little pressure loss in the working medium. All the named substances can also be used as a mixture with an oil.
A further preferred embodiment proves to be technically particularly simple to realize and therefore to be produced at a favourable cost, in which the channel structure is formed by corrugation-like elevations or depressions present in the stacked plate. This permits a realizing of the stacked plates with the channel structure essential to the invention as shaped sheet metal parts, in particular by means of deep drawing.
In a further preferred embodiment, a channel structure is present in at least two stacked plates. The more stacked plates are provided with a channel structure with the zigzag-like flow geometry essential to the invention, the higher is the efficiency which is able to be achieved with the stacked-plate heat exchanger, in particular if the latter is used as an exhaust gas evaporator in interaction with an internal combustion engine.
Expediently, the stacked-plate heat exchanger can have a shared fluid inlet for distributing the fluid to the at least two, preferably three, fluid channels, and a shared fluid outlet for directing the fluid out after flowing through the respective fluid channels. This provision simplifies the structure of the stacked-plate heat exchanger, in particular when several separate fluid channels are provided.
Further important features and advantages of the invention will emerge from the subclaims, from the drawings and from the associated figure description with the aid of the drawings.
It shall be understood that the features mentioned above and to be explained further below are able to be used not only in the respectively indicated combination, but also in other combinations or in isolation, without departing from the scope of the present invention.
Preferred example embodiments of the invention are illustrated in the drawings and are explained further in the following description, wherein the same reference numbers refer to identical or similar or functionally identical components.
There are shown, respectively diagrammatically:
In the stacked plate 2 shown in
For the formation of the stacked-plate heat exchanger 1, several stacked plates 2 with respective cover plates 11a, 11b can be stacked on top of each other. This is shown in
Observing
As
The channel sections 5 with a zigzag-like geometry are arranged in the stacked-plate heat exchanger 1 such that in the channel sections 5 the fluid F is present entirely in liquid phase. In addition, the two fluid channels 4a, 4b can respectively have two channel sections 20a, 20b that are different from the channel sections 5 with a zigzag-like geometry, in which the fluid channels 4a, 4b do not have a zigzag-like geometry, but rather can be formed so as to be rectilinear or differently.
As
As
Preferably, the cross-sectional area A is adapted to the working medium flowing through the channel structure 3, therefore to the fluid which is used. In this way, an efficient heat exchange can be ensured with, at the same time, a small pressure loss in the working medium/fluid.
If the channel structure 3 is to be flowed through by fluid/working medium, a range of values of between 2 mm2 and 8 mm2 is recommended for the cross-sectional area A defined above.
If the channel structure 3 is to be flowed through by ethanol as fluid/working medium, then a range of values of between 3 mm2 and 15 mm2 proves to be advantageous for the cross-sectional area A defined above. The use of a mixture of ethanol and water is also conceivable.
If the channel structure 3 is to be flowed through by cyclopentane as fluid/working medium, then a range of values of between 6 mm2 and 20 mm2 is recommended for the cross-sectional area A defined above. Acetone can be used as an alternative substance to cyclopentane.
If the channel structure 3 is to be flowed through by hydrofluorocarbons (HFC) as fluid/working medium, then a range of values of between 15 mm2 and 40 mm2 is recommended for the cross-sectional area A defined above.
In further variants, a mixture of one of the previously mentioned substances with an oil is also possible.
Number | Date | Country | Kind |
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10 2016 205 353.1 | Mar 2016 | DE | national |
This application claims priority to International Patent Application No. PCT/EP2017/057536, filed on Mar. 30, 2017, and German Patent Application No. DE 10 2016 205 353.1, filed on Mar. 31, 2016, the contents of both of which are hereby incorporated by reference in their entirety.
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/057536 | 3/30/2017 | WO | 00 |