EP1528348B1 - Heat exchanger - Google Patents

Description

The invention relates to a heat exchanger, in particular for a motor vehicle, according to the preamble of claim 1, DE 10060102 discloses such a heat exchanger.

In order to meet the increasing demands on modern engines with regard to emission reduction and fuel consumption, extensive measures, such as increased charging, more precise influence on the combustion conditions, are required. This also leads to harsher operating conditions in motor vehicle heat exchangers, namely higher gas and coolant pressures, elevated temperatures and higher volume throughputs. At the same time, the demands on power density and service life are growing. Partly, therefore, new cooling concepts are required. Thus, in charge air coolers, the air / air coolers conventionally used are at least partially replaced by air / liquid coolers to achieve the required performances and power densities required due to the high engine boost. With exhaust gas heat exchangers, ever higher exhaust gas recirculation rates are required, with ever-increasing operating conditions with regard to pressures, temperatures and power densities. Thus occur in modern heat exchangers ever higher mechanical loads, especially with regard to pressure and vibration.

High temperature differences of the primary medium to be cooled (usually gaseous) and the cooling secondary medium (here usually liquid) lead to different component heating on the primary and Sektundärseite. For exhaust gas heat exchangers, the temperature difference can be up to more than 700K, for charge air coolers up to 300K. This leads to strong thermal stresses as a result of different thermal expansion between the primary and secondary side. In the case of rapid changes of the operating state, these thermoelectric voltages can be exacerbated by uneven temperature distributions (thermal shock).

Due to higher power densities of the heat exchanger also increases the risk of boiling of the coolant, which can lead to strong performance and loss of life.

Finally, the processes and materials used are highly corrosive medium due to the occurrence, e.g. Condensate from the exhaust gas in the exhaust gas heat exchanger, severely limited, which leads to ever greater problems with increasing demands on power density, a durable technical solution to provide sufficient internal and external pressure resistance of the flow channels, avoid boiling and sufficient To combine strength against vibration excitations and thermal voltages.

It is an object of the invention to provide an improved heat exchanger.

This object is achieved by a heat exchanger with the features of claim 1. Advantageous embodiments are the subject of the dependent claims.

According to the invention, a heat exchanger is provided with a housing and at least one tube arranged in the housing, wherein structures are provided between the tubes and the housing and / or the tubes: the primary medium flows through the tubes. The secondary medium is guided in the interstices between the tubes and / or between the tubes and the housing, in which also the structures are arranged are. The structures increase the strength through a stiffening with respect to internal and external pressure stresses of the pipes. The coupling between tubes and housing also provides a continuous compensation of the thermal stresses between the primary and secondary sides over the entire length of the radiator, so that the stresses at the ends of the tubes are significantly reduced. The structures also serve for fluid conduction and distribution in the heat exchanger. The ribbed plates also allow a better heat transfer, so that thermoelectric voltages can be reduced by the improved heat transfer. Due to the increased transfer surface, the tubes are better cooled and boiling can be avoided. Overall, this results in a significant increase in the power density of the heat exchanger over conventional heat exchangers without structures. Preferred structures are sheet metal structures in the form of separate tubes, ribbed plates, dimpled plates, or the like. inserted. The heat exchanger may in particular be an exhaust gas heat exchanger or charge air cooler, but also another heat exchanger, for example another gas-liquid heat exchanger in which hot gas flows through the heat exchanger (cooler) in tubes for cooling, a liquid-gas heat exchanger, in which cold gas in pipes passes through the heat exchanger (heater) for heating, or be a liquid-liquid heat exchanger. Instead of the use of sheet metal structures, the tubes and / or the housing can be correspondingly formed with structures, ie, in particular, the pipe surface may be formed rib-like and / or knob-like. The structures preferably have a height of 1 mm to 5 mm, preferably 1 mm to 3 mm, particularly preferably 1.5 mm. The pitch L of the structures is preferably 0.1 to 6 times, more preferably 0.5 to 4 times the structural height h. The transverse dimension Q is preferably 0.15 to 8 times, more preferably 0.5 to 5 times the structural height h. The ratio of channel height between the tubes and channel height in the tube is in the range of structures preferably 0.1 to 1, preferably 0.2 to 0.7. The hydraulic diameter between the tubes in the region with structures is preferably 0.5 mm to 10 mm, preferably 1 mm to 5 mm.

Preferably, the structures with the housing and / or the pipes are firmly connected, in particular soldered. In particular, a fixed connection over a large length of the heat exchanger without or with interruptions, for example, for better coolant distribution provided. The fixed connection increases the external pressure resistance (overpressure on the secondary side) very efficiently because the structures provide tie rods that prevent the tube from collapsing. Furthermore, vibrations of the tubes, which are relatively unstable in conventional heat exchangers, are damped by the structures, and a very efficient compensation of the thermoelectric voltages is brought about. Furthermore, the fixed connection supports the heat transfer from the tubes to the structures, so that a better cooling of the tubes takes place. By an improved heat transfer can also reduce the number of tubes, so that the production costs can be reduced.

The tubes are preferably at least partially formed by flat tubes. Flat tubes are thermodynamically much more efficient than round tubes, but have a lower pressure resistance, which is why pressure-increasing measures are required for flat tubes, as inventively a support structure on the outside of the tube. The flat tubes in particular have an approximately rectangular cross-section with rounded corners. Furthermore, one-piece rectangular tubes can be provided. These can have a longitudinal seam, which can be welded, for example laser-welded, friction-welded, induction-welded, or soldered. The rectangular tubes can also be constructed of shells that are welded or soldered. The tubes may also have any other shape, for example. Oval, and / or have lateral tabs which are soldered or welded. Furthermore, the tubes for tolerance compensation between the housing and tubes and the structures arranged therebetween may be slightly convex. Turbulizers (winglets) can also be provided in and / or on the pipes. The pipe surface (inside and / or outside) can also be structured to generate turbulence.

The structures preferably have an inhomogeneous structure at least partially, as a result of which coolant can be supplied to critical areas in a targeted manner, so that overheating or boiling can be avoided. A corresponding increased supply of coolant can also be achieved by the partial omission of structures. These measures can be used to optimize the pressure loss of the heat exchanger and the transverse distribution of the coolant in the heat exchanger. The regions with inhomogeneous structures are preferably in the region of the inlet and / or outlet of the fluid. They serve in particular the flow control and to keep the pressure loss as low as possible.

By at least partially toothing can increase the stability of the structures and also optimize the flow paths of the coolant.

For simplified construction of the heat exchanger, the housing is preferably formed in two or more parts, in particular as a U-shaped shell with a lid, wherein a water tank can be formed integrated in the lid. In principle, however, a one-piece construction, for example with a molded-on water tank, possible.

Structures may also be provided in the tubes themselves, with all the above-mentioned structures that may be provided between the tubes also being able to be integrated into the tubes. The structures are preferably formed by rib plates or dimpled sheets, which are connected to the pipe, for example, by welding, soldering or jamming. The structures preferably have a height of 1 mm to 5 mm, preferably 1 mm to 3 mm, particularly preferably 1.5 mm. The pitch L of the structures is preferably 0.5 to 6 times the structural height h. The transverse dimension Q is preferably 0.5 to 8 times the structural height h. The hydraulic diameter in the tube in the region with structures is preferably 0.5 mm to 10 mm, preferably 1 mm to 5 mm.

Fig. 1

einen Schnitt durch einen Abgas-Wärmetauscher,

Fig. 2

eine perspektivische Ansicht des Wärmetauschers von Fig. 1,

Fig. 3

eine schematische perspektivische Ansicht eines Rippenblechs,

Fig. 4

eine schematische perspektivische Ansicht eines Rippenblechs gemäß einer Variante, und

Fig. 5a-d

verschiedene Varianten von Einlaufbereichen.

In the following the invention with reference to an embodiment with reference to the drawings will be explained in detail. In the drawing show:

Fig. 1

a section through an exhaust gas heat exchanger,

Fig. 2

a perspective view of the heat exchanger of Fig. 1 .

Fig. 3

a schematic perspective view of a fin plate,

Fig. 4

a schematic perspective view of a fin sheet according to a variant, and

Fig. 5a-d

different variants of inlet areas.

An exhaust gas heat exchanger 1 has a two-part housing 2 and a plurality of tubes 3 arranged in this housing 2. Ribs 4 are provided as structures between the individual tubes 3 and between the housing 2 and the tubes 3, these ribbed plates 4 being toothed in accordance with the present exemplary embodiment, as in FIG Fig. 3 shown and described in more detail later. The tubes 3 are in the present case flat tubes.

Through the individual tubes 3, the coming from the engine to be cooled exhaust gas (gaseous primary medium) is passed, in Fig. 2 the flow direction is indicated by two continuous arrows. The housing 2, in which the tubes 3 are arranged, consists of a U-shaped first housing part 2 'and a housing cover 2 ", which is set from above onto the first housing part 2.' For the inlet and outlet of the coolant (liquid secondary medium ) are two coolant nozzle 5 in the housing cover 2 "provided, wherein the flow direction of the coolant in DC operation in Fig. 2 is shown by dashed arrows. It is also possible to flow through in countercurrent operation, including the flow direction is reversed. Since the coolant is passed through the housing 2 and around the tubes 3, the fin sheets 4 are arranged on the coolant side.

The straight toothed ribbed plates 4 point in the direction of in Fig. 3 Arrow shown with a solid line a slight passage and in the dashed line arrow on a heavier passage for the coolant. By changing the longitudinal pitch L and the transverse division Q and the rib height h, the flow can be influenced. In addition to a straight toothing and a helical toothing is possible. With appropriate design of the individual fin sheets 4, these can also specifically support the coolant delivery to particularly critical points, including the rib sheets 4 are at least partially formed inhomogeneous.

In Fig. 4 a simple variant of a ribbed plate is shown with a rib running in a straight direction, which has a longitudinal pitch L of 2.4 mm and a rib or structural height h of 1.5 mm. In this case, the ribbed sheet can also be bent from a perforated plate, so that the individual corrugations are permeable due to the perforation.

According to a variant not shown in the drawing, a corresponding structure for a charge air cooler is used.

Fig. 5a-d show various inhomogeneous regions of the rib sheets 4 forming structures. These cause a better distribution of the fluid in the inflow. According to the first variant, the in Fig. 5a is shown, transverse distribution channels are provided by forming or stamping. According to the variants of Fig. 5b and 5c the rib bleaching 4 were partially cut off. Fig. 5d shows a variant with a special formed on the rib sheet 4 manifold structure. A the FIGS. 5a to 5d corresponding inhomogeneous region can also be provided on the outflow side.

Claims (14)

1. A heat exchanger, in particular for motor vehicles, having a housing (2) and tubes (3) arranged in the housing (2), structures being provided in the region between the tubes (3), the structures being formed as sheet-metal structures, the sheet-metal structures being finned metal plates, characterized in that structures are disposed between the tubes (3) and the housing (2), the structures being formed of sheet-metal structures, the sheet-metal structures being finned metal plates (4).
2. The heat exchanger as claimed in claim 1, characterized in that the structures are formed directly on the housing (2) and/or on the tubes (3).
3. The heat exchanger as claimed in one of the preceding claims, characterized in that the structures are fixedly joined to the housing (2) and/or the tubes (3), in particular by soldering.
4. The heat exchanger as claimed in one of the preceding claims, characterized in that the tubes (3) are at least in part formed by flat tubes.
5. The heat exchanger as claimed in one of the preceding claims, characterized in that the tubes (3) have supporting studs on the tube outer side.
6. The heat exchanger as claimed in one of the preceding claims, characterized in that the tubes (3) have a tube surface on the inner and/or outer side which is structured so as to generate turbulence.
7. The heat exchanger as claimed in one of the preceding claims, characterized in that the structures (4) at least in part have an inhomogeneous structure.
8. The heat exchanger as claimed in one of the preceding claims, characterized in that the structures (4) are at least partially toothed.
9. The heat exchanger as claimed in one of the preceding claims, characterized in that the housing (2) is formed in two or more parts.
10. The heat exchanger as claimed in one of the preceding claims, characterized in that the structures are arranged in the interior of at least one tube.
11. The heat exchanger as claimed in one of the preceding claims, characterized in that the structures are formed as at least one fin which is in particular straight or of undulating depth and/or in particular has gills.
12. The use of the heat exchanger as claimed in one of the preceding claims, characterized in that a medium which is to be cooled flows within the tubes (3), and a coolant flows in the space between the housing (2) and the tubes (3) and structures (4).
13. The use of the heat exchanger as claimed in one of the preceding claims, characterized in that the structures (4) are arranged on the coolant side in the housing (2) of the heat exchanger (1).
14. The use of the heat exchanger as claimed in one of claims 1 to 13 as an exhaust-gas heat exchanger or a charge-air cooler of a motor vehicle.

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