WO2007017064A1

WO2007017064A1 - Heat exchanger

Info

Publication number: WO2007017064A1
Application number: PCT/EP2006/007087
Authority: WO
Inventors: Walter Aupperle; Volker Döring; Peter Kalisch; Volker Lindemann
Original assignee: Daimler Ag
Priority date: 2005-08-06
Filing date: 2006-07-19
Publication date: 2007-02-15
Also published as: DE102005037156A1

Abstract

The invention relates to a heat exchanger, in particular, for a motor vehicle, comprising a plurality of tubes (1) which extend in a manner parallel to each other, and which are arranged so that they can be cross-flown by a first medium, a housing cover (2) which surrounds the tubes (1) and which is arranged such that it can be cross-flown by a second medium. The tubes (1) are maintained by at least two tube plates (3) which are maintained at a distance from each other, which are also connected to the inner wall (4) of the housing cover (2). According to the invention, at least one of the tube plates (3) is connected to the housing cover (2) by means of an elastic, moulding part (3.1) which can be shaped. The moulding part (3.1) compensates different thermal expansions of the housing cover (2) and the tubes (1) by shaping.

Description

heat exchangers

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

From JP 05187792 Al a multi-tube heat exchanger with a strain joint is known, which is provided around a housing 2 around to compensate for the differences in thermal thermal expansion between the housing side and tube side. The heat exchanger includes a perforated plate for distributing the medium, wherein the one end of the perforated plate is connected to the housing 2 and the other end by a flexible sealing means 7, which is located in a gap between the housing 2 and sealing ring 1 is held.

Such heat exchangers are subjected to high thermal stresses due to high temperatures, the considerable temperature gradient of the individual media between the inlet and the outlet, and, above all, the large temperature differences between the two media, for example between the highly heated exhaust gases and the incoming coolant. The resulting in the components of the heat exchanger high thermal stresses can be superimposed additional stresses due to operational rapid temperature fluctuations, eg load changes of the internal combustion engine. The thermally highly stressed attachment points of the pipes their confluence with the chambers are usually additionally exposed to considerable mechanical stress caused by bending moments and tensile forces caused by the overpressure of a medium.

The invention is therefore based on the object to reduce these thermally induced voltages, i. reduce the resulting stresses in the components of the heat exchanger in order to achieve greater safety and longer life for the heat exchanger mentioned above.

The invention solves this problem by providing a heat exchanger with the features of claim 1. In the heat exchanger according to the invention at least one of the tube sheets is connected via an elastic, deformable molded part to the housing shell, wherein the molding different thermal expansion of the housing shell on the one hand and the tubes on the other compensated by deformation. The molded part absorbs deformations of the housing jacket and the tubes that expand to different degrees under the effect of the hot exhaust gases and the less hot coolant. As a result, damage by voltage peaks in the thermally stressed housing in the region of the junctions of the pipes are advantageously avoided.

In one embodiment of the invention according to claim 2, the tube sheet is elastically deformable. An elastic tube plate allows the expansion of the tubes or tube bundles and avoids favorably critical component stresses in the field of force flow tubes or tube bundles - tubesheet - housing shell. In an alternative development according to claim 3, the molding is an integral part of the tube sheet.

In a preferred embodiment of the invention according to claim 4, the molding additionally has a bead.

In an advantageous development of the invention according to claim 5, the housing shell is arranged at a distance L to the tubes.

In a particularly preferred embodiment of the invention according to claim 6, the housing shell is flared at the ends of the heat exchanger in the region of the tube plate.

In a further development of the invention according to claim 7, the housing shell on several inlet openings and / or outlet openings for the coolant.

Further features, advantages and advantageous embodiments of the invention will become apparent from the claims, as well as from the following description of the invention with reference to the accompanying drawings. By way of example, in a simplified schematic manner:

1 shows a longitudinal section through a heat exchanger according to the invention with just executed molding,

2 shows a longitudinal section through a heat exchanger according to the invention with arched executed molding,

Fig. 3 is a longitudinal section through an inventive

Heat exchanger perpendicular to the sectional plane of Fig. 1, 4 is a second longitudinal section through a heat exchanger according to the invention perpendicular to the sectional plane of Fig. 1,

5 shows preferred embodiments of the elastic molded part according to the invention,

6a is a perspective view of a heat exchanger according to the invention,

6b is a front view of a heat exchanger according to the invention without gas diffuser and coolant inlet: inventive tube sheet with integrated molding and bead,

7 is a second perspective view of a heat exchanger according to the invention,

Fig. 8 is a third perspective view of a heat exchanger according to the invention.

In Fig. 1 and Fig. 2, a heat exchanger according to the invention, here preferably an exhaust gas heat exchanger shown how it is used in motor vehicles in the exhaust gas recirculation (EGR) for cooling the hot exhaust gases. The exhaust gas heat exchanger according to the invention comprises a plurality of mutually parallel tubes 1, which are designed to flow through a first medium, here exhaust gas, a housing jacket 2 enclosing the tubes 1, which for flowing through a second medium, here a coolant, which does not separate shown is designed, wherein the tubes 1 by at least two, spaced tube sheets 3 are held, which in turn are connected to the inner wall 4 of the housing shell 2. In principle, the first and / or the second medium may be gaseous and / or liquid. The individual tubes 1 are also combined to form so-called tube bundles 1.2 (see FIG. 6a). The inlet 5 of the coolant into the heat exchanger, in this case preferably water, is effected by a coolant inlet nozzle 6 placed on the housing jacket 2, which is located near the inlet opening 7 of a gas diffuser 8 for hot exhaust gases (direct current principle). The heat exchanger according to the invention can in principle also be operated in a counterflow principle.

During operation of the exhaust gas heat exchanger tubes 1 and housing shell 2 heat differently because the exhaust gases flowing through the tubes 1 have a higher temperature than the coolant flowing around the housing jacket 2. This results in different strains between the tubes 1 and the tube bundles and the housing shell 2, which leads to thermally induced stresses, ie stresses in the axial direction of the tubes 1 and tensile stresses in the housing shell 2 and bending stresses in the tube sheets. The tubes 1 of the at least one tube bundle, not shown here, the tube ends 1, 3 receiving tube sheets 3 and the housing shell 2 thus form a power flow, in which the tubes 1 are supported on the tube sheets 3 on the housing shell 2. Especially in exhaust gas heat exchangers, such as those used in commercial vehicles, high media flows and high cooling capacities lead to large dimensions. From certain sizes of the different thermal expansion of the gas-conducting tubes 1 relative to the housing shell 2 of the heat exchanger must be increasingly taken into account, since the stresses due to the different strains to failure of individual components or even to Destruction of the tube plate connection of the heat exchanger can lead.

According to the invention, at least one of the tubesheets 3 is therefore advantageously connected to the housing jacket 2 via an elastic, deformable molded part 3.1, wherein the molded article 3.1 compensates for different thermal expansions of the housing jacket 2 on the one hand and the tubes 1 on the other hand due to deformation. Here, the molded part 3.1 may be connected as a separate component with the tube sheet 3, wherein only the molded part can be elastically deformable and the tube sheet largely rigid. In another preferred embodiment, however, the tube sheet 3 may be elastically deformable. Furthermore, in a particularly preferred embodiment, the molded part 3.1 is an integral part of the tube bottom 3, so that both elements, the tube sheet 3 and the molded part 3.1, may be of the same or different elasticity. The elasticity can be controlled, for example, by appropriate thickness ratios or material selection with respect to the molded part 3.1 and tube sheet 3. Tube bottom 3 with molded part 3.1 can also be referred to as expansion compensation device.

The molded part 3.1 can for example be designed as a straight connection (FIG. 1) from the tube bottom 3 to the housing jacket 2 or else in the form of a bead 10 (FIG. 2). The bead 10 has due to their shape by the larger central axis a longer lever arm and thus can respond even more elastic to thermal stresses. Other suitable embodiments of the molded part 3.1 for receiving the different thermal expansions are exemplified in FIG. 5.

The tubes 1 and tube bundle are spaced at a distance L from the housing shell 2, to a deformation of the molding 3.1 to ensure. Particularly preferably, the housing shell 2 is widened at the ends 2.1 of the heat exchanger in the region of the tube bottom 3. Thus, a greater deformation capacity of the molded part 3.1 is made possible in a favorable manner, without having to provide for the core of the heat exchanger large structural changes or further space.

Fig. 3 and Fig. 4 show a longitudinal section through a heat exchanger according to the invention perpendicular to the sectional plane of Fig. 1, wherein Fig. 4 in contrast to Fig. 3 shows a widening of the housing shell 2 at the ends or the edge region of the heat exchanger. In both drawings, the elastic molded part 3.1, where 3.1 ( _K > the undeformed state and 3.1 _(L ) represents the deformed state, deforms by a length change ΔL / L to the thermal stresses in the longitudinal direction of the tubes 1 due to the different thermal expansions between Housing jacket 2 and pipes 1. The tube plate 3 can be made rigid except for the molded part 3.1 or flexible, so that it can also absorb thermal expansion between the individual tubes 1 or tube bundles The order of magnitude depends on the material used for the molded part 3.1 or tube bottom 3. The tubes 1, which are flowed through by the hot exhaust gases in the direction of flow of the arrows, are flowed through the coolant flowing into the coolant channels 9, which preferably flows in the flow direction of the exhaust gases (direct current principle), Is the exhaust gas cooler in the Gleic operated hstromprinzip, are gas inlet and coolant inlet at the same end, preferably arranged in the thermally highly stressed area, ie at the gas inlet. In principle, the heat exchanger according to the invention can also be operated in the countercurrent principle. at Conversely, countercurrent coolers are the gas inlet and the water outlet at the same end, whereby these are preferably arranged in the thermally highly stressed area, ie at the gas inlet.

Fig. 6a shows a perspective view of the heat exchanger according to the invention with at the ends 2.1 and the edge region not flared housing shell 2, at the end, adjacent to the inlet opening 7 of a gas diffuser 8, a coolant inlet nozzle 6 is placed. The heat exchanger consists of at least one of a preferably gaseous medium here flowed through and flowed around by a preferably liquid coolant tube bundle 1.2, the tubes 1 are received with their tube ends in the tube sheets 3 and cohesively connected thereto, wherein the housing shell 2, the end cohesively is connected to the tube plates 3, flows through the coolant. The two tube bundles 1.2 shown here are thus encompassed by the tubesheets 3 and are spaced from the housing jacket 2 by a distance L from the integrated elastic shaped parts 3.1, which have a bead 10. Due to the integrated expansion compensation device 3, 3.1 results in a high stability and long life of the heat exchanger according to the invention, since the expansion compensation device 3, 3.1 is capable of critical component stresses in the field of power flow between "housing shell 2 - tubes 1 and tube bundles 1.2 - tubesheets In this way, in contrast to solutions with an elastic housing jacket, there is the advantage that the exhaust gas heat exchanger and connected exhaust gas exchanger have a high dimensional stability. and Coolant lines can be attached as rigid as desired to the engine, while a stretchable housing always limits the connection options to the engine and requires the appropriate elasticity in the lines. The present inventive solution thus integrates the length compensation in the interior of the heat exchanger and is therefore independent of the outer periphery.

Fig. 6b shows the elastic molded part 3.1, which is provided with recesses 11 which receive the ends of the pipes 1 not shown separately. The bead 10 located in the region of the molded part 3.1 gives the expansion compensation device 3, 3.1 sufficient elasticity to be able to compensate for the thermal expansion or deformation taking place in the longitudinal direction of the tubes 1, so that the molded part 3.1 can follow the greater expansion of the exhaust tubes by elastic stretching , Without this leading to an impermissible deformation and thus to an impairment of the connection between pipes 1 - tube plates 3 and housing shell 2. The

Expansion compensation device 3, 3.1 is also easy to produce and without great expense and is equally suitable for sealing between the liquid and gaseous region of the exhaust gas heat exchanger.

Fig. 7 and Fig. 8 show further perspective views of a heat exchanger according to the invention. The housing jacket 2 has coolant inlet openings 12 and coolant outlet openings, not shown here, and is flowed through by the coolant, wherein in the case of DC coolers, the coolant inlet openings 12 are preferably arranged in the thermally highly stressed part, ie at the gas inlet. The additional water distribution channel in the form of the coolant inlet nozzle 6 with coolant inlet and -Out openings 12 thus allows an optimized inflow and distribution of coolant in the heat exchanger and thus a better cooling effect than would be the case with only a large coolant inlet opening. When operating an exhaust gas heat exchanger, the exhaust pipes 1 are flowed through on the inside of the hot exhaust gas and flows around on the outside of the coolant. This coolant also flows around the inside of the housing shell 2. The exhaust pipes 1 thus reach a much higher temperature than the housing shell 2, resulting in the different strains between exhaust pipes 1 and housing shell 2. This leads to thermal stresses, ie to pressure or tensile stresses in the housing shell 2 and the tubes 1. The tubes press on the tube sheets and cause deformation or even damage the pipe / floor or tube bottom / housing connections, ie the exhaust gas heat exchanger can leak ,

Claims

claims

1. Heat exchanger, in particular for a motor vehicle, with a plurality of mutually parallel tubes (1), which are designed to flow through a first medium, a the tubes (1) enclosing the housing shell (2) designed for flow with a second medium is, wherein the tubes (1) by at least two spaced apart tube sheets (3) are held, which in turn are connected to the inner wall (4) of the housing shell (2), characterized in that at least one of the tube sheets (3) via a (3.1) is connected to the housing shell (2), wherein the molding (3.1) compensates for different thermal expansion of the housing shell (2) on the one hand and the tubes (1) on the other hand by deformation.

2. Heat exchanger according to claim 1, characterized in that the tube sheet (3) is elastically deformable.

3. Heat exchanger according to claim 1 or 2, characterized in that the molded part (3.1) is an integral part of the tube sheet (3).

4. Heat exchanger according to one of the preceding claims, characterized in that the molded part (3.1) has a bead (10).

5. Heat exchanger according to one of the preceding claims, characterized in that the housing jacket (2) with a distance (L) to the tubes (1) is arranged.

6. Heat exchanger according to one of the preceding claims, characterized in that the housing jacket (2) at the ends (2.1) of the heat exchanger in the region of the tube bottom (3) is widened.

7. Heat exchanger according to one of the preceding claims, characterized in that the housing jacket (2) has a plurality of inlet openings (12) and / or outlet openings for the coolant.