Heat Exchanger

Abstract

The invention relates to a heat exchanger (1), in particular for a motor vehicle, having at least one inlet (2) and one outlet for the medium which is to be cooled or heated and/or the medium which provides the cooling or heating action, wherein the inlet (2) is designed such that, upon entering the heat exchanger (1), the flowing medium has imparted to it a movement component in the tangential direction with respect to the preceding normal movement direction and/or with respect to the main movement direction directly adjacent to the inlet. According to the invention, a swirl body (5) is preferably provided in the inlet (2).

Description

The invention relates to a heat exchanger, in particular an exhaust gas cooler of a motor vehicle, according to the preamble of claim 1.

In order to reduce the emissions of particles and nitrogen oxide in diesel engines it is known to recirculate exhaust gas, both high-pressure exhaust gas recirculation and low-pressure exhaust gas recirculation being possible. In this context, the stream of exhaust gas is cooled to temperatures of approximately 150° C. to 200° C. and added to the intake air. At these temperatures of the cooled intake air, a partial stream of engine coolant is generally used as the coolant in the exhaust gas cooler. The recirculation of exhaust gas is all the more effective here the lower the gas outlet temperatures at the exhaust gas cooler. The same also applies to other coolers, as also to heat exchangers generally.

Taking this prior art as a basis, the object of the invention is to make available an improved heat exchanger. This object is achieved by means of a heat exchanger having the features of claim 1. Advantageous embodiments are the subject matters of the subclaims.

The invention provides a heat exchanger, in particular for a motor vehicle, in particular preferably an exhaust gas cooler or charge air cooler, having at least one inlet and an outlet for the medium to be cooled or to be heated and/or the cooling or heating medium, wherein the inlet is embodied in such a way that the flowing medium is given a movement component in the tangential direction with respect to the previous normal direction of movement and/or the main direction of movement directly adjoining the inlet, when said medium enters the heat exchanger, preferably before the medium which is to be cooled or heated enters the heat exchanger, in particular an inlet diffuser or inlet box. As a result of the tangential component of the flow rate, the flow profile into the heat exchanger is improved by virtue of the fact that, in particular when the flow cross section changes, the flow becomes detached from the wall to a lesser degree and therefore is distributed more uniformly over the entire cross section. In particular the peak flow rates in the center which usually occur can therefore be reduced. In addition, the flow rates in the outer regions are increased somewhat.

The influence of such measures on the entire mass flow rate which is dependent on the pressure loss is, under certain circumstances, positive since as a result of the more uniform distribution in the flow ducts of the heat exchanger the pressure losses due to the embodiment of the inlet according to the invention are possibly more than compensated for. Furthermore, under certain circumstances, more uniform distribution of the flow brings about a more uniform temperature of the components, which contributes to reducing thermally induced mechanical stresses.

A diffuser, which further improves the flow profile in the inlet region, is preferably provided or formed in the region of the inlet.

A flow duct swirl body arrangement, in particular a diffuser with swirl body, is preferably provided in the inlet. The flow is preferably given a tangential component in the flow duct swirl body arrangement, the tangential component being preferably larger at the outer circumference than in the center.

The swirl body preferably has repeating sections which are arranged evenly distributed in the circumferential direction, serve as baffle elements and are embodied such that they extend in the direction of flow in the inflow region, and in the outflow region they are embodied such that they extend obliquely with respect to the direction of flow in the inflow region. In this case preferably two to eight, in particular three to five, particularly preferably four, such sections are provided.

The flow duct swirl body arrangement or the swirl body is preferably composed of a metal or a metal alloy, in particular of aluminum or an aluminum alloy or stainless steel. This material is preferably the same as that which is also used for the heat exchanger. In this context, the arrangement with the inlet or the swirl body is preferably soldered or welded into the inlet. This can be done with one working step with the soldering of the heat exchanger so that the manufacturing costs can be reduced, in particular with respect to the time expended and the necessary energy. Using the same material also enables different thermal expansion rates to be avoided so that the loads on the soldered connections can be reduced and the safety and the service life increased.

According to an exemplary embodiment, one or more components of the heat exchanger are formed from cast metal and a swirl body is directly cast on. Alternatively, a swirl body is formed by punching out from a piece of sheet metal or cast metal.

As an alternative to providing a swirl body, the inflow in the region of the inlet into a flow duct of the inlet region can take place in a tangential direction. In this case, the flow duct may either be a simple pipe or a diffuser. Preferably, in addition to the tangential component a component in the direction of the longitudinal axis of the flow duct is provided in order to optimize the distribution of speed further.

A heat exchanger is explained in detail below by means of two exemplary embodiments and with reference to the drawing, in which:

FIG. 1 is a schematic elevation of an exhaust gas cooler,

FIG. 2a is a diagram clarifying the speed distribution of the flow of coolant in the individual ducts in a conventional exhaust gas cooler, the deviation of the mass flow distribution from the uniform distribution being represented in %,

FIG. 2b is a diagram clarifying the speed distribution of the coolant flow in the individual ducts in an exhaust gas cooler with a swirl body in the inlet, the deviation of the mass flow distribution from the uniform distribution being represented in %,

FIG. 3 is a perspective illustration of a flow duct swirl body arrangement,

FIG. 4 is a perspective elevation of the swirl body from FIG. 3,

FIG. 5 is a plan view of the flow duct swirl body arrangement from FIG. 3,

FIG. 6 is a schematic elevation of the tangential inflow into a diffuser, and

FIG. 7 is a side view of FIG. 6.

According to the first exemplary embodiment, a heat exchanger 1 is provided, formed by an exhaust gas cooler such as is used for cooling recirculated exhaust gas of a turbocharger. In order to permit the most uniform possible distribution of the engine coolant used for cooling the exhaust gas, a flow duct swirl body arrangement 3 such as is illustrated in detail in FIGS. 3 to 5 is provided at the inlet 2 (illustrated schematically in FIG. 1 by the circular dotted region in front of the sectional coolant ducts which are illustrated) of the exhaust gas cooler.

The flow duct swirl body arrangement 3 is composed, like the exhaust gas cooler, of stainless steel and is soldered to the exhaust gas cooler in the region of the inlet opening for the coolant, which is done in the same working step as the soldering or welding of the individual parts which form the exhaust gas cooler.

The flow duct swirl body arrangement 3 is embodied as a diffuser 4 with a swirl body 5, in which case the cross section of the diffuser 4 is widened slightly in the direction of flow. Provided in the interior of the diffuser 4 is the swirl body 5, composed of four baffle elements 6 which are connected on the outside here in one piece to the diffuser 4 and in the center to one another along the longitudinal axis of the diffuser 4. The four baffle elements 6 are each of the same design and are distributed uniformly over the circumference of the diffuser 4. Each baffle element 6 has an inflow region 7 which extends parallel to the normal direction of flow and runs parallel to the longitudinal axis of the diffuser 4. Downstream of the relatively short inflow region 7, which is of rounded design on the inflow side and in which each baffle element 6 runs radially from the center of the diffuser 4 to the diffuser 4, the baffle element 6 is of bent design. The bend in the baffle element 6 starts here in a region in which the diameter of the diffuser 4 is also widened, with the result that in addition to or after the tangential speed component a radial speed component is also imposed on the flow, as a result of which the coolant is distributed better over the following cross section. From the inflow region 7 as far as the outflow region 8, each baffle element 6 runs radially from the center of the diffuser 4 to the diffuser 4 (cf. FIG. 4).

The provision of the flow duct swirl body arrangement 3 results in a flow which also widens to the outside, essentially hugging the wall surfaces, and therefore is distributed relatively uniformly over a relatively large cross section. In particular, the relatively uniform speed distribution over the entire cross section significantly reduces the peak flow speeds which usually occur in the center, the mass flow rate of coolant being overall approximately the same.

The significantly improved distribution of the coolant is apparent from a comparison of the diagrams illustrated in FIGS. 2a and 2b. Here, the flow duct swirl body arrangement 3 is used to produce a significant reduction in the flow speeds in the central region and a corresponding increase in the flow speeds in the outer region so that overall a much more uniform speed distribution is obtained, which allows the efficiency of the exhaust gas cooler to be significantly improved.

FIGS. 6 and 7 are schematic illustrations of a variant for providing a flow duct swirl body arrangement which, given corresponding configuration of the inlet region, can lead approximately to corresponding homogenization of the speed distribution. Here, the inlet 2 into the heat exchanger 1 is arranged laterally at one end of a flow duct 9 (illustrated here as a pipe with a larger cross section than the feed line, but this can also be a diffuser) such that the inflowing medium automatically has a tangential component applied to it and the following flow profile is embodied in the manner of a screw or in such a way that it widens in the manner of a screw so that at the emergence from the flow duct a flow is present which also broadens outwards, essentially hugging the wall surfaces, and is thus distributed relatively uniformly over a relatively large cross section.

Alternatively, in addition to the tangential component, a component in the direction of the following flow duct can also be provided at the same time through a corresponding arrangement of the inlet.

Claims

1. A heat exchanger, in particular for a motor vehicle, having at least one inlet and an outlet for the medium to be cooled or heated and/or the cooling medium or the medium to be heated, wherein the inlet is embodied in such a way that the flowing medium is given a movement component in the tangential direction with respect to the previous normal direction of movement and/or the main direction of movement directly adjoining the inlet, when said medium enters the heat exchanger.

2. The heat exchanger as claimed in claim 1, wherein a diffuser is provided or formed in the region of the inlet.

3. The heat exchanger as claimed in claim 1, wherein a flow duct swirl body arrangement, in particular a diffuser with swirl body, is provided in the inlet.

4. The heat exchanger as claimed in claim 1, wherein the flow is given a tangential component in the flow duct swirl body arrangement, wherein the tangential component is larger at the outer circumference than in the center.

5. The heat exchanger as claimed in claim 3, wherein the swirl body has repeating sections which are arranged evenly distributed in the circumferential direction, serve as baffle elements and are embodied such that they extend in the direction of flow in the inflow region, and in the outflow region they are embodied such that they extend obliquely with respect to the direction of flow in the inflow region.

6. The heat exchanger as claimed in claim 5, wherein two to eight, in particular three to five, such sections are provided.

7. The heat exchanger as claimed in claim 1, wherein the flow duct swirl body arrangement or the swirl body is fabricated from a metal or a metal alloy, in particular from aluminum or an aluminum alloy or stainless steel.

8. The heat exchanger as claimed in claim 1, wherein the flow duct swirl body arrangement or the swirl body is soldered and/or welded to the heat exchanger.

9. The heat exchanger as claimed in claim 1, wherein the inflow in the region of the inlet into a flow duct of the inlet region of the heat exchanger is provided in a tangential direction with respect to the flow duct.

10. The heat exchanger as claimed in claim 9, wherein the inflow in the region of the inlet into a flow duct of the inlet region in the tangential direction is additionally provided with a component in the direction of the longitudinal axis of the flow duct.

11. The heat exchanger as claimed in claim 1, wherein the heat exchanger is an exhaust gas cooler.

12. The heat exchanger as claimed in claim 1, wherein the heat exchanger is a charge air cooler.