DE19907163A1 - Exhaust gas heat exchanger - Google Patents

Abstract

The heat exchanger has the tube bottoms, the tubes of the tube bundle and the casing (15) all made from stainless steel. The tube bottoms (19) are in the form of deep-drawn and stamped parts with a wall running round them which projects outward beyond the ends of the tubes in the tube bundle. These walls are welded to the casing. A diffuser (12) is connected to them.

Description

The invention relates to a heat exchanger, in particular egg N exhaust gas heat exchanger, with ge at both ends in tube plates holding pipes for guiding a gaseous medium and with one adjoining the tube sheets and enclosing the tubes ß housing for carrying a liquid cooling medium, wherein the tube sheets, the tubes and the housing made of heat-resistant austenitic steel sheets are molded into the tubes Tube sheets are welded and the housing with the tube gust which is welded.

A heat exchanger of the type mentioned is from DE 195 40 683 A1 known.

The invention has for its object a heat exchanger of the type mentioned so that it is inexpensive stig and technically advantageous can.

This object is achieved in that the tube sheets as deep-drawn and stamped parts are molded, each one encircling, the ends of the tubes protruding outwards Have wall that is welded to the housing and on each connected by a diffuser.  

The inventive design of the heat exchanger enables a welding, in which in particular when welding the parts of the housing with the tube sheets as little heat as possible me is introduced into the tube sheets, so that a heat deformation of the tube sheets is largely prevented.

In an advantageous embodiment of the invention, that the housing and the tube sheets in the area of the rotating Walls cut to length after making the welded connections are. In this way, a heat exchanger can be created the required installation tolerances with high accuracy complies with who is required in particular for motor vehicles the.

In a further embodiment of the invention it is provided that the housing and the tube sheets by means of a circumferential Auxiliary seam and attached closer to the pipe ends ten sealing seam are welded together, and that the Ge housing and the tube sheets in the area of the auxiliary seam cut to length are. The housing and the tube sheets thus form a tight seal closed edge. Because the actual sealing seam is relatively close at the area of the tube sheet receiving the tube ends can be placed, it is largely excluded that in the Crevice corrosion between the tube sheet and the housing occurs.

In an advantageous embodiment, it is further provided that that a diffuser on the circumferential, cut edge is butt welded. This will be an advantageous one Welded connection between the diffuser and the edge fen, in which length tolerances are also partially evident can be compared.

In a further embodiment of the invention it is provided that the housing then each a size to the tube sheets has a larger cross section than in the intermediate Be  rich, in which it envelops the pipes at a short distance. In the area of the larger cross-sections there is therefore one Kind of water box created, in which the liquid Cooling medium over the entire cross section of the heat exchanger distributed.

In a further embodiment of the invention it is provided that the tubes with protruding, knob-like projections are provided, by means of which they mutually and on the Inner wall of the housing are supported. So he becomes one maintain high stability of the entire heat exchanger, whereby at the same time the emergence of noises due to on conducted oscillations or vibrations largely is closed.

In a further embodiment of the invention it is provided that the housing, which consists of at least two sheet metal parts is set by means of those running parallel to the pipes Is welded. Even when attaching this Weld seams are only small amounts of heat in the pipes or Pipe trays initiated. It is advantageously provided that the welds in the area of the larger housing cross-section are designed as an I-seam. This results in this Be rich a largely smooth outer contour of the heat exchanger. Advantageously, it is further provided that the welds in Area of the smaller housing cross-section than flanged seam are executed. This makes it possible to insulate the weld to go through on one level overall. Especially before it is partial if the housing parts are elastically pretensioned are welded. The elastic preload, on the one hand a tight fitting of the edges of the sheet to be welded brings about parts, also ensures that the housing parts after welding in the area of the lower housing cross cut under tension against the knobs of the outer Create tubes of the tube bundle, so that the risk of Ge Noise generation due to vibrations is further reduced.  

This elastic prestress consists essentially in loading rich in flared seams.

In another embodiment of the invention, it is preseeded hen that the housing is formed from a piece of pipe, the both end areas are widened. This is a one-part ger housing jacket created, which is easy to assemble handle.

In a further embodiment of the invention it is provided that the pipes using laser beam welding or electron beam are welded into the tube sheets. To this To be able to carry out welding exactly is further envisaged hen that the tube sheets with at predetermined locations brought positioning aids are provided. This makes it possible Lich, the tube sheets with the tubes during welding ex act.

In a further embodiment of the invention it is provided that the tubes with a predetermined projection into the tube sheets are plugged in, and that the welds are right next to it the pipe outer walls by means of obliquely incident laser or Electron beam are attached. This measure is particularly important Especially advantageous for larger heat exchangers, d. H. at Heat exchangers with a tube bundle from a variety of Pipes. With a large number of pipes, it can hardly be exclude that when inserting the pipes in the Ausspa tion of the tube sheets the latter can be deformed somewhat. This Deformation can be caused by welding with obliquely incident Beam are encountered, so the danger of an imperfect or leaky welding is largely avoided.

In a further embodiment it is provided that the housing in an area with the larger cross section with an An closing tube for a coolant supply and in the other loading rich with a larger cross section with a connecting tube for egg ne coolant discharge is provided, the housing with after  externally directed passages is provided to which the An tail pipes are welded. This also results in egg ne inexpensive and technically advantageous solution for attaching the connections for the coolant.

Further features and advantages of the invention result from the following description of exemplary embodiments.

Fig. 1 shows a perspective view of a heat exchanger OF INVENTION to the invention,

Fig. 2 is a partial section through the housing of the Wärmetau exchanger along the line II-II,

Fig. 3 is a partial section through the housing of the Wärmetau exchanger along the line III-III of Fig. 1,

Fig. 4 is a partial perspective view of the end portion of a heat exchanger according to the invention prior to completion of its preparation,

Fig. 5 is a partial section along the line VV of Fig. 4,

Fig. 6 shows a partial section along the line VI-VI of Fig. 1,

Fig. 7 shows a partial section in the region of the connection Zvi's tubes and tubesheet of a heat exchanger according to the invention,

Fig. 8 is a partial section similar to Fig. 7 with a planmä lar supernatant of the tubes to the associated tube sheet,

Fig. 9 shows a section along the line IX-IX of Fig. 1,

Fig. 10 is a partial section similar to FIG. 9 of a abgewandel th embodiment,

Fig. 11 is a view of a housing shell formed from a one-piece tube piece and

Fig. 12 is a view of the housing shell in the axial direction Rich.

The partial sections are each shown on a larger scale poses.

The heat exchanger 11 shown in FIG. 1 is used in particular as an exhaust gas heat exchanger in which exhaust gas is cooled. The exhaust gas flows through a diffuser 12 and is guided inside the heat exchanger 11 by means of a tube bundle 13 made of rectangular tubes to a diffuser 14 , from which it flows out. In the area between the diffusers 12 , 14 , the tube bundle 13 is surrounded by a housing composed of two parts 15 , 16 , in which a liquid coolant is guided, which flows around the tubes of the tube bundle 13 . The coolant is supplied to a coolant inlet connection 17 and discharged to a coolant outlet connection 18 , which are arranged essentially diametrically. The coolant flows in direct current to the exhaust gas to be cooled.

The tube bundle 13 consists of rectangular tubes, as are known for example from DE 195 40 683 A1. The right corner tubes have protruding from opposite inner walls, V-shaped pairs of lugs, which are alternately provided on opposite walls. The rectangular tubes are fer ner on its outside with nub-like projections hen, on which they are supported against each other and against the housing 15 , 16 . The ends of the rectangular tubes of the Rohrbün dels 13 are welded tight in tube sheets 19 .

Pot-shaped, deep-drawn sheet metal parts serve as tube sheets 19 , the bottom of which is provided with punched holes for receiving the tubes of the tube bundle 13 . Furthermore, the tube sheets 19 form a circumferential wall 20 which protrudes in the direction of the diffusers 12 , 14 over the ends of the tubes of the tube bundle 13 . As will be explained in more detail below, the sheet metal parts 15 , 16 forming the housing are welded to this wall 20 of the tube sheets 19 .

The housing is composed of two sheet metal parts 15 , 16 sets. It has each of the diffusers 12 , 14 adjoining areas 21 , 22 with a larger cross section, each forming an annular channel-like water distribution box, in the area of which the inlet connection 17 and the outlet connection 18 are arranged. The central area of the housing between the two outer areas 21 and 22 has a smaller cross section. In this area, the Ge maintains a distance from the tubes of the tube bundle 13 , which is determined by the knob-like projections of the tubes. The sheet metal parts 15 , 16 are connected by means of weld seams 23 running in the longitudinal direction. Each weld 23 is in the areas 21 , 22 with a larger cross section than an I-seam ( FIG. 3) and in the intermediate area with a smaller cross section than a flared seam ( FIG. 2). It is thereby achieved that each weld seam 23 runs at a constant height level and can therefore be placed in one go in a simple manner. During the welding of the weld seams 23 , the two sheet metal parts 15 are pressed against one another so that the sheet metal parts lie close together in the area of the I-seam and also in the area of the flanged seam. The sheet metal parts 15 , 16 are deformed somewhat elastically in the region of the flanged seam, so that the housing in the middle, having a smaller cross-section, is rich after welding with an elastic prestress on the nub-like projections of the tubes of the tube bundle 13 .

Before welding the longitudinal seams 23 , the sheet metal parts 15 , 16 are placed against the walls 20 of the tube sheets 19 (FIGS . 4 and 5) which are provided with the tube bundle 13 . The longitudinal seams 23 are also welded in the region of the wall 20 of the tube sheets 19 , so that when the weld seams 23 are attached, the tube sheets 19 are stitched to the housing formed from the two sheet metal parts 15 , 16 . The housing formed from the two sheet metal parts 15 , 16 is then welded to the tube sheets 19 in the region of the walls 20 . First, an auxiliary seam 24 is made at a greater distance from the bottom of the tube sheets 19 . Subsequently, a sealing seam 25 is welded, which is closer to the bottoms of the tube sheets 19 and preferably immediately before the transition between the wall 20 and the bottom of the tube sheets 19th

The rectangular tubes of the tube bundle 13 are welded to the tube sheets 19 before or after the housing has been attached and welded. The tube sheets 19 are plugged onto the ends of the rectangular tubes of the tube bundle 13 . Then who the the ends of the Recheckrohre slightly expanded with plastic deformation, so that only a small gap between the punched recesses of the tube sheets 19 and the rectangular tube Ren is available, which allows a dense laser beam welding or electron beam welding. By means of the widening, a joint connection is created between the tube bundle 13 and the tube sheets 19 , which allows the housing to be attached and welded from the sheet metal parts 15 , 16 , without the tube sheets 19 having already been welded to the tube bundle 13 .

In Figs. 11 and 12 a housing shell 32 is shown, from which a heat exchanger 11 can be manufactured in a corresponding manner. The housing jacket 32 consists of a tube section of a welded rectangular tube. The two end regions 33 , 34 are widened in order to form ring channel-like water distribution boxes. In these widened areas, connections for the water supply and drainage are provided, for example simple punch holes 35 , 36 or outwardly directed passages 28th If a particularly long tubular jacket 32 is provided, it is expedient to stiffen it by means of transverse beads 37 shaped outwards, as shown in FIG. 11.

In this design, a tube bundle 13 made of rectangular tubes is inserted into the housing shell 32 . Thereafter, tube sheets 19 are used, which are pressed into the widened end regions 33 , 34 before, preferably with a light press fit. As a result, a joint is already obtained before welding, which allows good handling of the object so far assembled. The tube sheets 19 are then welded to the housing jacket 32 in the end regions 33 , 34 with the aid of an auxiliary seam 24 and a sealing seam 25 . Likewise, the rectangular tubes of the tube bundle 13 with the tube sheets 19 are welded ver. It can optionally be provided that the welding of the tube sheets 19 to the rectangular tubes is carried out before or after the welding of the tube sheets 19 to the housing jacket 32 .

The tubes of the tube bundle 13 have a relatively small wall thickness, ie a wall thickness on the order of 0.2 mm to 0.6 mm. It is therefore necessary that the welds placed around the tubes of the tube bundle 13 are brought very precisely. For this purpose, it is necessary that the tube sheets 19 are positioned with the tube bundle 13 very precisely to a welding device. To facilitate this positioning, the tube sheets 19 can be provided with positioning aids in a manner not shown.

As already mentioned, the welding of the tubes of the tube bundle 13 into the tube sheets 19 is preferably carried out as a laser beam welding or also as an electron beam welding. If the welding is carried out in a conventional manner so that the laser beam or electron beam, which is indicated in Fig. 7 with an arrow 26, is aligned parallel to the tube axes, it should be ensured that the tube sheets 19 due to the assembly There are no differences in position due to deformation of the tube sheet. In the case of heat exchangers with a tube bundle 13 made up of a large number of tubes, deflections and thus positional displacements in dimensions larger than 0.1 mm can often not be avoided. In this case, it is expedient to produce a projection as planned when the tube sheets 19 are fitted onto the tube ends of the tube bundle 13 , as is shown in FIG. 8. In this case, welding is then carried out by means of an obliquely directed laser beam or electron beam, which is indicated by the arrow 27 . The beam is inclined at an angle between 5 ° and 10 ° to the tube axes and directed towards the tube sheet in the immediate vicinity of the tube outer walls. When welding the tubes of the tube bundle 13 into the tube sheets 19 , the weld seams can be placed according to the tube contour, ie as so-called window welding, or along the lattice contour of the recesses in the tube sheet as so-called lattice welding. If necessary, it makes sense to provide a ring weld as an additional sealing weld in the area of the webs between opposite corners of the rectangular tubes or, if necessary, to provide a weld seam as a cover layer on the webs of the tube sheets 19 between the tubes.

After the base body of the heat exchanger 11 is completed, ie after the housing made of the sheet metal parts 15 , 16 has been attached and welded on and after the tube bundle 13 has also been welded into the tube sheets 19 , or after the base body in the manner explained with the aid of the one-piece housing shell 32 according to FIGS . 11 and 12 has been provided, this base body of the heat exchanger 11 is cut to a predetermined size, as shown in FIGS. 4 and 5. This cutting is preferably carried out in the area of the auxiliary seam 24 by means of a laser cutter. Due to the cutting to length in the area of the auxiliary seams 24 , a tightly closed edge from the end faces of the sheet metal molded parts 15 , 16 and the wall 20 of the tube sheets 19 remains. At this edge, the diffusers 12 and 14 are attached. The diffusers 12 , 14 are preferably butt-welded, as shown in FIG. 6. However, it is also possible to insert the diffusers into the circumferential edge or to place them on the circumferential edge and then to weld them internally to the wall 20 of the tube sheets 19 or externally to the sheet metal parts 15 , 16 . The diffusers 12 , 14 can be manufactured as castings, deep-drawn parts or as welded parts. When attaching them, they are set so that the tolerances created during their manufacture are compensated for to such an extent that the required installation dimensions for the entire heat exchanger 11 are observed.

To form the coolant connections 17 , 18 , the sheet metal parts 15 , 16 are provided with outwardly directed passages 28 . At these passages 28 , a connecting pipe is butt-welded in the exemplary embodiment according to FIG. 9. This welding can be carried out, for example, using TIG welding with an orbital welding gun. In the embodiment of FIG. 10, the connecting pipe 30 is provided with a circumferential bead 31 and inserted into the passage 28 . Welding takes place in the joining area. This welding can be carried out, for example, as a TIG welding with a robot.

A heat-resistant austenitic steel is selected for the tubes of the tube bundle 13 and the tube sheets 19 , which is largely corrosion-resistant, especially against sulfuric acid contained in an exhaust gas. A heat-resistant austenitic steel is also provided for the sheet metal parts 15 , 16 of the housing. The tubes of the tube bundle 13 have a relatively small wall thickness, for example in the order of magnitude of 0.2 mm to 0.6 mm, since in their area the heat transfer takes place between the exhaust gas and the liquid coolant. The tube sheets 19 and the sheet metal parts 15 , 16 or the housing jacket 32 , on the other hand, can have a significantly greater wall thickness, for example in the order of 1 mm. The welding of the sheet metal parts 15 , 16 to one another and to the tube sheets 19 and the welding of the diffusers 12 , 14 can also be carried out as laser beam welding. However, other welding processes can also be used, e.g. B. electron beam welding, MIG welding, TIG welding or plasma welding.

Claims (16)

1. Heat exchanger, in particular exhaust gas heat exchanger, with tubes held at both ends in tube plates for guiding a gaseous medium and with a housing adjoining the tube plates and enclosing the tubes for guiding a liquid cooling medium, the tube plates, the tubes and the housing being made of heat-resistant austenitic steel sheets are formed, the tubes are welded into the tube sheets and the housing is welded to the tube sheets, characterized in that the tube sheets ( 19 ) are formed as deep-drawn and stamped parts, each having a circumferential, the ends of the tubes of the tube bundle ( 13 ) outwardly projecting wall ( 20 ) sen, which is welded to the housing ( 15 , 16 ; 32 ) and to each of which a diffuser ( 12 , 14 ) connects. 2. Heat exchanger according to claim 1, characterized in that the housing ( 15 , 16 ; 32 ) and the tube sheets ( 19 ) in the area of the circumferential walls ( 20 ) are cut to length after the welding connections have been made. 3. Heat exchanger according to claim 2, characterized in that the housing ( 15 , 16 ; 32 ) and the tube sheets ( 19 ) are welded to one another by means of a circumferential auxiliary seam ( 24 ) and by means of a sealing seam ( 25 ) attached closer to the tube ends, and that the housing and the tube sheets ( 19 ) are cut to length in the region of the auxiliary seam ( 24 ). 4. Heat exchanger according to claim 3, characterized in that a diffuser ( 12 , 14 ) is butt welded to the circumferential, cut edge. 5. Heat exchanger according to one of claims 1 to 4, characterized in that the housing ( 15 , 16 ; 32 ) each has an area ( 21 , 22 ; 33 , 34 ) with a cross-section on the tube sheets ( 19 ) is larger than the cross section in the area in between, in which the housing encased the tubes of the tube bundle ( 13 ) with little from. 6. Heat exchanger according to claim 5, characterized in that the tubes of the tube bundle ( 13 ) are provided with outwardly projecting, knob-like projections, by means of which they are supported with each other and on the inner wall of the housing ( 15 , 16 ; 32 ). 7. Heat exchanger according to one of claims 1 to 6, characterized in that the housing, which is composed of at least two sheet metal parts ( 15 , 16 ), is welded by means of parallel lel to the tubes of the tube bundle ( 13 ) running welds ( 23 ) . 8. Heat exchanger according to claim 7, characterized in that the welds in the areas ( 21 , 22 ) are made with a larger cross-section than an I-seam. 9. Heat exchanger according to claim 7 or 8, characterized in that the weld seams ( 23 ) in the region of the smaller housing cross section are designed as a flanged seam. 10. Heat exchanger according to one of claims 7 to 9, characterized in that the housing parts ( 15 , 16 ) are welded elastically before tension. 11. Heat exchanger according to one of claims 1 to 6, characterized in that the housing ( 32 ) has a housing jacket made of a tube piece, the two end regions ( 33 , 34 ) of which are widened. 12. Heat exchanger according to one of claims 1 to 11, characterized in that the tubes of the tube bundle ( 13 ) are welded into the tube sheets ( 19 ) by means of laser beam welding or electron beam welding. 13. Heat exchanger according to claim 12, characterized in that the tube sheets ( 19 ) are provided with positioning aids at predetermined locations. 14. Heat exchanger according to claim 12 or 13, characterized in that the tubes of the tube bundle ( 13 ) are inserted with a pre-given overhang in the tube sheets ( 19 ), and that the weld seams ( 23 ) directly next to the tube outer walls by means of obliquely incident Laser beam or electron beam ( 27 ) are attached. 15. Heat exchanger according to one of claims 1 to 14, characterized in that the housing ( 15 , 16 ; 32 ) in a region ( 21 , 33 ) with a larger cross section with a connecting tube ( 29 , 30 ) for a coolant supply ( 17th ) and in the other area ( 22 , 34 ) with a larger cross section with a connection pipe ( 29 , 30 ) for a coolant discharge ( 18 ) is provided. 16. Heat exchanger according to claim 15, characterized in that the housing ( 15 , 16 ; 32 ) is provided with outwardly directed passages ( 28 ) to the connecting pipes ( 29 , 30 ) are welded.