Exhaust gas heat transfer device

Abstract

The invention relates to an exhaust gas heat exchanger (1) with a housing (2), in which a tube bundle (3) with multiple tubes (4) is held via headers (5, 6), wherein in the tubes (4) a first flow path for exhaust gas (7) and between the tubes (4) and the housing (2) a second flow path for coolant (8) runs, wherein the first longitudinal ends of the individual tubes (4) of the tube bundle (3) are incorporated in a first header (5) in a fixed manner, in particular welded or brazed. It is substantial to the invention that at least one of the tubes (4) is axially moveable in the region of a second longitudinal end relative to the second header (6) and captive therein.

Claims

1. An exhaust gas heat exchanger comprising a housing, in which a tube bundle with at least two tubes is held via a first header, a second header, and a third header, wherein a first flow path for exhaust gas runs in the tubes and a second flow path for coolant runs between the tubes and the housing and wherein the first longitudinal ends of the individual tubes of the tube bundle are incorporated in the first header in a fixed manner, wherein at least one of the tubes is axially moveable relative to the second header and captive therein, and wherein a second longitudinal end of at least one of the tubes is fixed to the third header; wherein the individual tubes with their second longitudinal ends are incorporated in apertures in a fixed manner, wherein the tubes between the second header and the third header comprise a bellows for compensating longitudinal expansions.

2. The exhaust gas heat exchanger according to claim 1, wherein at least one tube is held captive in an aperture of the second header by means of a clearance fit, transition fit or by means of a press fit.

3. The exhaust gas heat exchanger according to claim 1, wherein all tubes are held axially moveable in the region of their second longitudinal end in the second header.

Description

(1) Preferred exemplary embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein same reference characters relate to same or similar or functionally same components.

(2) It shows, in each case schematically,

(3) FIG. 1 a longitudinal sectional representation through an exhaust gas heat exchanger according to the invention,

(4) FIG. 2 a cross-sectional representation through an exhaust gas heat exchanger according to the invention,

(5) FIG. 3 a seal for a second header of a heat exchanger according to the invention,

(6) FIG. 4 a representation as in FIG. 1, however only in the region of a second longitudinal end of the tubes of the tube bundle, wherein the tubes are axially moveably mounted in the second header and a third header, which is designed as a membrane header, is provided,

(7) FIG. 5 a representation as in FIG. 4, however with tubes equipped with bellows between the second and third header,

(8) FIG. 6 a sectional representation through a possible embodiment of a seal,

(9) FIG. 7 a sectional representation through a second header with individual seals, which are held in a groove of the apertures of the second header.

(10) According to FIGS. 1, 4 and 5, an exhaust gas heat exchanger 1 according to the invention comprises a housing 2, in which a tube bundle 3 with multiple tubes 4 is held via headers 5, 6. On the inlet side a first header 5 is provided here, whereas on the outlet side, a second header 6 is provided. Here, a first flow path for exhaust gas 7 runs in the tubes 4 while a second flow path for coolant 8 runs between the tubes 4 and the housing 2. The individual tubes 4 of the tube bundle 3 in this case are incorporated in a fixed manner in the first header 5 with a first longitudinal end, in particular welded or brazed. In the region of a second longitudinal end the individual tubes 4 of the tube bundle 3 are held captive axially moveably in the second header 6 designed as sliding seat header, i.e. mounted. Because of this it is possible that even in the case of an interruption of the coolant supply and the drying up of individual tubes 4 these can expand in longitudinal direction independently of the neighbouring tubes through which coolant 8 is still flowing, since these can adjust themselves in the second header 6 for the first time in longitudinal direction independently of the outer tubes 4. The first header 5 and the second header 6 in this case are connected to the housing 2 in a fixed manner, for example brazed or welded.

(11) The individual tubes 4 can be captive in the second header 6 by means of a clearance fit, a transition fit or by means of a press fit. Looking at FIG. 1 more closely it is evident that on the side of the second header 6 facing away from the first header 5 a seal 9 (see also FIGS. 3 and 6) for sealing the individual tubes 4 against the second header 6 is arranged. This seal 9 is preferentially arranged between the second header 6 and a third header 10, wherein in the third header 10 the individual tubes 4 are likewise captive in an axially moveable manner. In addition to this, the seal 9 can be clamped in between the two headers 6 and 10 as a result of which it contacts the tubes 4 in a sealing manner. The seal 9 itself can for example be formed as an elastomer gasket with apertures 11 formed complementarily to the tubes 4, wherein the apertures 11 are punched out of a gasket for example by means of a suitable punching tool or are already produced together with the casting of the seal 9. To this end, a suitable injection or casting mould is then required.

(12) The second longitudinal ends of the individual tubes 4 are likewise held in the apertures 11 of the seal 9 by means of a press fit. The apertures 11 of the seal 9 can additionally comprise a raised edge 12 (see in particular FIGS. 3 and 6), wherein such a raised aperture edge 13 can also be provided in the region of apertures 11 of the second or third header 6, 10.

(13) Generally, the seal 9 can be formed as an elastomer gasket, whichas previously mentionedhas apertures 11 corresponding to the tubes 4. Alternatively to this, the seal 9 can be produced as a liquid seal, for example from silicone, wherein during the production the liquid seal is poured onto the second header 6 between the tubes 4 in vertical position, i.e. with vertically orientated tubes 4, where it sets. Here, the viscosity of the still liquid sealing material and the fit of the header 6 have to ensure that the sealing material cannot flow through gaps between the tubes 4 and the apertures 11 in the second header 6 prior to setting. In order to ensure permanent contact pressure, a third header 10 may also be required here which secures the seal 9 against internal pressure. In order to be able to ensure permanent contact pressure, the third header 10 can likewise comprise curvatures 12, wherein it can be practical not to fill out the space between the two headers 6 and 10 with the seal 9 completely, so that overpressure and thus damage to the seal 9 can be avoided.

(14) Generally, the seal 9 can also be formed as a membrane header 13, as is shown with an embodiment version according to FIG. 4. It is likewise conceivable that the seal 9 is realized in the region of a third header 10, which however according to FIG. 5 is not formed as a sliding seat for the tubes 4 but with which the tubes 4 are connected via individual bellows 14. In the third header 10 in turn the tubes 4 are incorporated in a fixed and thus tight manner, in particular welded in or brazed in. In order to be able to ensure a predefined spacing of the third header 10 from the second header 6 one of the tubes 4, in this case the tube 4a can be formed continuously, i.e. without bellows 14. Despite this coupling of the tube 4a to the third header 10 and on the other longitudinal end to the first header 5 an individual length change of each individual tube 4, 4a can be ensured.

(15) In a further advantageous embodiment, as it is shown according to FIG. 7, the second header 6 comprises in each aperture 11 a groove 15 with a ring seal 16 arranged therein, as a result of which a tight connection between the tube 4 and the second header 6 is likewise made possible, but at the same time longitudinal expansion is also permitted.

(16) With the exhaust gas heat exchanger 1 according to the invention it is possible for the first time to mount individual tubes 4 of a tube bundle 3 individually with respect to thermal longitudinal expansions and because of this avoid damage that occurs for example by individual tubes 4 drying up and connected with this intense heating of the same.