Patent Application
20140182825
The present invention relates to a heat transfer device for an internal combustion engine, the heat transfer device having an outer housing, an inner housing which has a partition wall by means of which an inner duct through which a fluid to be cooled can flow is separated from an outer coolant duct formed between the inner housing and the outer housing, fins which extend from the partition wall into the duct through which the fluid to be cooled can flow, recesses which are formed on the outer surface of the partition wall of the inner housing, and projections which extend from an inner wall, which point toward the coolant duct, of the outer housing in the direction of the recesses on the partition wall in such a way that a cross section of the coolant duct is substantially constant.
Such heat exchangers are used, for example, as coolers in internal combustion engines. Applications for cooling exhaust gas, as well as for cooling charge air, have previously been described. In both cases, this cooling serves to enhance the combustion process and thus to reduce the content of pollutants in the exhaust gas.
The manufacture of heat exchangers, in particular heat exchangers made from a die cast metal, from a plurality of nested shells from which fins extend in particular into the duct through which the fluid to be cooled can flow, have previously been described. In these cases, the base plate from which the fins extend typically serves as a partition wall between the coolant duct and the duct usually carrying gas.
To increase efficiency, as well as to simplify the casting process, it has previously been described to provide the partition wall of the inner housing with a wave-shaped design to enhance the flow of the molten metal during the casting process and to enlarge the heat transfer surfaces.
With such heat exchangers having recesses in the partition wall, DE 10 2007 008 865 A1 further describes casting the outer housing so that a substantially constant coolant gap is formed by simultaneously casting corresponding projections on the inner wall of the outer housing. It is thereby prevented that different flow resistances occur in the cross section of the main flow direction of the coolant which would cause a non-uniform through-flow so that colder and warmer zones would be formed in the heat exchanger.
This is, however, disadvantageous in that the weight of the outer housing increases due to the material accumulations forming. The housing parts are further often subjected to a high pressure that has the effect that the necessary strength is not achieved with lesser wall thicknesses.
An aspect of the present invention is to provide a heat exchanger which has a maximum strength while at the same time maintaining a low weight of the outer housing. A uniform flow resistance should also be maintained in the coolant jacket.
In an embodiment, the present invention provides a heat transfer device for an internal combustion engine which includes an outer housing comprising an inner wall. An inner housing comprises a partition wall which comprises an outer surface. The inner housing is configured to separate an inner duct, which is configured to have a fluid to be cooled flow therethrough, from an outer coolant duct, which is formed between the inner housing and the outer housing. Fins extend from the partition wall into the inner duct. Recesses are formed on the outer surface. An inner wall is formed on a surface of the outer housing facing the coolant duct. Projections extend from the inner wall. The projections are arranged to extend towards the recess on the partition wall so that a cross section of the coolant duct is substantially constant. The projections on the inner wall of the outer housing are formed by beads on the outer housing.
The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:
The amount of material required is reduced due to the fact that the projections on the inner wall of the outer housing are formed by beads on the outer housing, while the strength is increased due to the beads, and the weight is reduced. The formation may be provided, for example, in a sandcasting process. A coolant duct with uniform through-flow is formed at the same time so that a high degree of efficiency of the cooler is achieved, while the fuel consumption of the internal combustion engine is reduced because of the lower weight.
In an embodiment of the present invention, the recesses can, for example, respectively be formed between the fin bases. The cooling surface is thereby enlarged so that the efficiency can be further enhanced.
In an embodiment of the present invention, the recesses can, for example, respectively be formed at the fin bases. This simplifies manufacturing by improving the flow of the liquid metal during the casting process. Cast parts with a uniform structure are formed, whereby the strength is further enhanced.
In an embodiment of the present invention, the fins can, for example, be arranged one after the other in rows in the flow direction, the fins of respective successive rows being arranged offset to one another and the beads being formed corresponding to this offset. Boundary layers are dissolved in this manner so that a good mixing of the fluid to be cooled is provided in the duct flown through by the fluid to be cooled, whereby the efficiency is enhanced. This embodiment can also include a corresponding design of the beads which has the effect that the flow through the cross section of the coolant duct is uniform, whereby dead spaces, in which the coolant flow velocity is zero, are prevented in the coolant duct and the efficiency is further enhanced.
In an embodiment of the present invention, the surface of the inner housing facing the coolant duct and the inner wall of the outer housing facing the coolant duct can, for example, be formed in a continuous manner so that no sudden variations in cross section occur in the duct flown through by the cooling fluid. The pressure loss is thereby again reduced and dead water regions are avoided. Low-power coolant pumps can be used in this manner.
In an embodiment of the present invention, the inner housing is made in a die-casting process and the outer housing is made in a sandcasting process. The heat exchanger can thus be built from a small number of housing parts and can be manufactured in an economic manner.
With the embodiments of the heat transfer device of the present invention, the cooling efficiency can be maintained while the strength is enhanced and the material effort is reduced. The reduced weight makes it possible to save costs for raw materials and to lower fuel consumption.
An embodiment of a heat transfer device of the present invention is illustrated in the drawings as hereafter described.
The heat transfer device illustrated in
Both the upper shell 6 and the lower shell 8 of the inner housing 4, which are each made in a die-casting process, for example, have a partition wall 10 from which, seen in cross section, fins 12 alternately extend from the upper shell 6 and the lower shell 8 into a duct 14 inside the inner housing 4, which duct 14 is flown through by a fluid to be cooled. This fluid may, for example, be the exhaust gas of an internal combustion engine.
The inner housing 4 is inserted into the outer housing 2 so that a coolant duct 16 is formed between the inner housing 4 and the outer housing 2, through which coolant can flow and which is separated by the partition wall 10 from the duct 14 flown through by the fluid to be cooled. Flange connections 18 provide for a tight connection of the inner housing 4 with the outer housing 2 so that the coolant duct 16 is configured as a close coolant jacket.
The duct 14 flown through by the fluid to be cooled extends from an inlet 20 at the front end side of the heat transfer device to an outlet 22 at the opposite side of the heat transfer device. An intermediate wall 24 divides the duct 14 into a first partial duct 26 and a second partial duct 28, wherein the first partial duct 26 is connected with an exhaust manifold of a first group of cylinders and the second partial duct 28 is connected with an exhaust manifold of a second group of cylinders of the internal combustion engine. This separation prevents interferences between the individual emitted exhaust gas pulses, whereby, given the use of a non-return valve arranged downstream, the overall mass flow can be increased.
The intermediate wall 24 extends continuously from the partition wall 10 of the lower shell 8 into an opposite groove 30 formed in the partition wall 10 of the upper shell 6. The intermediate wall 24 is fixed in the groove 30 by friction stir welding through the partition wall 10 so that an overflow of the intermediate wall 24 is prevented and, at the same time, the stability of the inner housing 4 is significantly increased by halving the existing projected areas.
It can further be seen that the partition wall 10 of both the lower shell 8 and the upper shell 6 of the inner housing 4 comprises a corrugated outer surface 32. The corrugated outer surface 32 is achieved by recesses 34 between fin bases 36 of the successive fin rows 38. In the regions of the corrugated outer surface 32 located between the fin rows 38 in the longitudinal direction, the recesses 34 present an offset 40 extending only over this region so that at the start of the next fin row 38, which is similarly arranged offset to the previous row, the recesses 34 are again arranged in the spaces between the fin bases 36.
The outer housing 2, manufactured, for example, in a sandcasting process, comprises an inner wall 42 designed corresponding to the recesses 34 of the inner housing 4. This means that a projection 44 extends into each recess 34 between the fin bases 36 so that the distance of the corrugated outer surface 32 of the inner housing 4 to the inner wall 42 of the outer housing 2 is substantially the same all over. As a consequence, the flow cross section is substantially the same all over, both in the direction of flow and perpendicular to the through-flow direction. Thereby constant coolant flows with a uniform heat output, since dead water zones can be largely excluded due to the constant flow resistance, whereby a very high cooling efficiency is achieved.
According to the present invention, the projections 44 are formed by beads 46, i.e., by groove-shaped recesses 48 in an outer wall 50 of the outer housing 2, which are provided to increase rigidity. Respectively opposite thereto, i.e., on the inner wall 42, a projection 44 is formed by the displacement of material if the bead 46 is formed subsequently. This bead design can also be formed directly in the casting process, whereby an increase in rigidity is achieved without an increase in required material. Thin-walled outer housings 2 can thus be formed with sufficient strength. The beads here follow the course of the recesses 34 in the outer surface 32 of the inner housing 4.
As shown in
A heat transfer device of such construction has a high degree of efficiency due to the uniform through-flow of coolant and, at the same time, can be manufactured with little material effort. Because of the reduced weight, it is possible to save fuel if the device is used in an internal combustion engine.
It should be clear that the scope of protection is not limited to the embodiment described. The outer housing may, for example, be made from sheet metal instead of sandcast material, and the beads may be formed subsequently. It is also possible to form the recesses in the inner housing at the fin bases, respectively, whereby the castability is significantly enhanced. It is also possible to divide the housing parts in a different manner and, in particular, to shift the joint planes. Further design changes are conceivable. Reference should also be had to the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 050 596.2 | May 2011 | DE | national |
This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2012/055759, filed on Mar. 30, 2012 and which claims benefit to German Patent Application No. 10 2011 050 596.2, filed on May 24, 2011. The International Application was published in German on Nov. 29, 2012 as WO 2012/159806 Al under PCT Article 21(2).
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/055759 | 3/30/2012 | WO | 00 | 1/23/2014 |
