Heat Exchanger

Abstract

The invention relates to a heat exchanger, particularly in tube bundle-type, panel-type or plate-type design. The heat exchanger has a housing inside of which a number of flow channels are formed for a primary flow and a secondary medium, and the housing has a sandwich design.

Description

The invention relates to a heat exchanger of a tube-bundle type of construction or of a disk type of construction according to preamble of claim 1.

On account of the ever increasing loads with regard to pressure and temperature, ever increasing requirements with regard to the strength of heat exchangers are being imposed. A main problem in this case is the pressure difference between the primary medium in the flow passages provided for it in the heat exchanger and the secondary medium in the respectively adjacent flow passages. The separation between primary medium and secondary medium is normally effected by relatively thin plate walls, which on their own cannot bear the pressure difference between the two media, so that greater wall thicknesses are required, which, however, entail disadvantages, for example with regard to the material and production costs and with regard to the overall weight.

The heat exchanger is normally constructed in such a way that the flow passages of the primary and secondary medium alternate, so that the pressure level of the other medium is present on both sides of the inner flow passages. By introduction of supporting structures into a flow passage, said flow passage can be supported against excess pressure from the other side. Since the pressure on both sides of the passage is the same, the opposite flow passage walls support one another via the supporting structures. If supporting structures are introduced into both flow passages, that is to say into the flow passages of the primary medium and the flow passages of the secondary medium, all the flow passages are supported against excess pressure from the outside, and the heat exchanger is therefore designed for excess pressure of the primary medium relative to the secondary medium, and vice versa. If the supporting structure is firmly connected to the flow passage walls, it provides stiffening not only against excess pressure from outside as a result of the support but also against excess pressure inside the flow passage by acting as a tie rod between the two opposite flow passage walls. Rib structures, supporting plates or supporting studs/beads are normally used.

An example of a known tube-bundle type of construction with stud support is shown in FIGS. 2a and 2b. In the interior of the heat exchanger 101, such stiffening with studs 110 leads to a structure which is very stable under pressure, since a symmetrical load case with equal pressures is present at respectively opposite flow passage walls. However, the outer flow passages present a problem, since only the ambient pressure or the housing wall 102, which itself is not supported, opposes the pressure on the outside of the flow passages. There is therefore a risk of damage to the outermost flow passage as a result of the pressure difference. Furthermore, the outermost passage may inflate as a result of the high internal pressure, so that the shape changes and the flow passage is displaced and/or is no longer supported symmetrically, which has an effect on the adjacent flow passages, so that the entire heat exchanger including the housing “inflates”. On account of expansions, the service life of the heat exchanger may be considerably reduced. To increase the stability, the housing 102 is designed to be relatively thick, which, inter alia, leads to high weight.

In order to prevent inflation, for an oil cooler of a disk type of construction, provision is made in DE 197 11 258 C2 for a base plate of thick design to bear against the outermost disk, this base plate, apart from the thickness, corresponding in its shape approximately to the shape of the outermost disk. However, this base plate has the disadvantage of high weight.

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

This object is achieved by a heat exchanger having the features of claim 1. Advantageous configurations are the subject matter of the subclaims.

A heat exchanger, in particular of a tube-bundle, plate or disk type of construction, is provided according to the invention, the heat exchanger having a housing in which a plurality of flow passages for a primary medium and a secondary medium are formed, and the housing is formed with a sandwich type of construction. The heat exchanger in this case is an exhaust-gas cooler. Instead of an exhaust-gas cooler, any other desired heat exchanger of corresponding construction, for example a charge-air/cooling-medium cooler or an oil cooler, may also be used.

The housing is preferably formed by at least two, preferably three plates, the outer surface of the outer plate forming the housing outer surface. The inner plate is preferably at a distance from the outer plate, a central plate which has a rib structure preferably being arranged between the outer plate and the inner plate. Instead of a rib structure, other structures, for example studs/beads, keeping the two plates at a distance apart are also possible.

The plates are preferably brazed to one another. The brazing in this case may be effected in a single operation, for which purpose the plates are appropriately prepared before assembly.

Preferably arranged in the housing on the inside of the inner plate are tube bundles, plates or disk stacks, which serve for the heat exchange between the two operating media.

A flow passage for one of the operating media is preferably provided between the outer plate and the inner plate, so that this operating medium is also located outside the region in which the actual heat exchanger structures, such as tube bundles for example, are provided and a corresponding pressure prevails.

Due to the configuration of the housing according to the invention, markedly smaller material thicknesses can be used instead of a single housing wall of considerable thickness, at roughly the same costs, said material thicknesses exhibiting increased material strength in such a construction. At comparable strength values, the structural weight can be markedly reduced compared with conventional housings. Furthermore, in the unbrazed state, the components are comparatively flexible and can easily be worked, since no beading or the like is necessary. Due to the flat surfaces of relatively large area, the connection to the adjacent components in the housing, for example by brazing, is assisted. If required, gap dimensions which ensure planar brazing of the two outer plates with the rib structure inbetween to form the housing can be set with low clamping forces and low forces due to weight during the brazing process. It is only in the brazed state that a structure of high bending strength is obtained.

Possibly advantageous is a housing having precisely two plates, of which at least one is provided in an especially preferred manner with spacers such as ribs, webs, corrugations, studs or the like. A reduction in the number of plates simplifies the production of the heat exchanger.

According to a preferred configuration, simplification of the production can likewise possibly be achieved by the housing being formed with a sandwich type of construction only on two sides or in two housing regions opposite one another.

The invention is explained in detail below with reference to an exemplary embodiment with variant, and partly with reference to the drawing, in which:

FIG. 1 shows a section, with only partly shown inner structure, through a heat exchanger according to the invention, and

FIGS. 2 a, b each show a cut-away section in different directions through a heat exchanger of a tube-bundle type of construction with stud support according to the prior art.

A heat exchanger 1 serving as exhaust-gas cooler 1 has a housing 2 which is formed by a sandwich structure consisting of a plurality of plates 3, 4 and 5. The outer plate 3 forms with its outer surface the outer surface of the heat exchanger 1.

The outer plate 3 has a tub-shaped region 3′ and a lid 3″ closing said tub-shaped region 3′. The central plate 4 provided with a rib structure and, on the inner side thereof, the inner plate 5 are arranged so as to run in each case parallel to the outer plate 3, that is to say both in the tub-shaped region 3′ and in the region of the lid 3″, and are brazed to one another, the plates 4 and 5 being designed to be shorter than the outer plate 3.

The tube bundles 6 of the exhaust-gas cooler are arranged on the inside of the inner plate 5. In this case, the outermost tube of the tube bundle 6 in each case bears directly against the inner surface of the inner plate 5 and is brazed to the latter. The joining or brazing of the heat exchanger 1 is effected in one operation in a manner known per se.

A first flow passage, in the present case for the medium to be cooled, namely the exhaust gas (primary medium), is formed by the interior space of the tube bundles 6, and a second flow passage, in the present case for the cooling medium (secondary medium), is formed by the intermediate spaces between the tube bundles 6. The intermediate space of the housing 2, which intermediate space is of hollow design on account of the rib structure of the central plate 4, is assigned to the second flow passage as outermost region of the same, so that a corresponding pressure prevails here too.

According to a variant (not shown in the drawing), a stack of disk pairs is arranged in the interior of a housing of corresponding multi-piece design instead of the tube bundles 6, these disk pairs forming the first flow passage in their interior and the second flow passage in the intermediate spaces and in the intermediate spaces relative to the outermost plate.

LIST OF DESIGNATIONS

• 1, 101 Heat exchanger
• 2, 102 Housing
• 3 Outer plate
• 3′ Tub-shaped region
• 3″ Lid
• 4 Central plate
• 5 Inner plate
• 6 Tube bundle
• 110 Stud

Claims

1. A heat exchanger, in particular of a tube-bundle, plate or disk type of construction, the heat exchanger having a housing in which a plurality of flow passages for a primary medium and a secondary medium are formed, wherein the housing is formed, at least in regions, in particular so as be essentially continuous, with a sandwich type of construction.

2. The heat exchanger as claimed in claim 1, wherein the housing of sandwich type of construction is formed by at least two plates, the outer surface of the outer plate forming the housing outer surface.

3. The heat exchanger as claimed in claim 1, wherein the housing of sandwich type of construction is formed by at least two plates, the inner plate being at a distance from the outer plate forming the housing outer surface.

4. The heat exchanger as claimed in claim 1, wherein the housing of sandwich type of construction comprises a rib structure formed by a central plate, this rib structure being arranged between an outer plate and an inner plate.

5. The heat exchanger as claimed in claim 4, wherein the rib structure is brazed or welded in place between the outer plate and the inner plate.

6. The heat exchanger as claimed in claim 1, wherein, in the housing of sandwich type of construction, a flow passage for one of the operating media is provided between an outer plate and an inner plate.

7. The heat exchanger as claimed in claim 1, wherein, in the housing of sandwich type of construction, tube bundles, plates or disk stacks are arranged on the inside of an inner plate.

8. The heat exchanger as claimed in claim 1, wherein the housing, at least in regions, has precisely two plates which are provided in particular with spacers such as ribs, webs, corrugations, studs or the like.

9. The heat exchanger as claimed in claim 1, wherein the housing is formed in a sandwich type of construction in each case in housing regions arranged opposite one another, in particular in two housing regions.

10. The use of a heat exchanger as claimed in claim 1 as an exhaust-gas cooler, a charge-air/cooling-medium cooler or an oil cooler.