Compact heat exchanger

Abstract

The present invention relates to a compact heat exchange device, applicable to either EGR (Exhaust Gas Recirculation) systems for reducing nitrogen oxide emission, or to WHRS systems (Waste Heat Recovery Systems), both in internal combustion engines. The design of the heat exchanger is characterized by a configuration that incorporates technical solutions intended for compensating for the differential expansions between the tube bundle and the shell, as well as other variables relating to thermal fatigue, where said solutions result in a compact device.

Claims

1. A compact heat exchanger for a heat exchange between a hot gas and a liquid coolant comprising: a) a shell extending according to a longitudinal direction to allow a passage of the liquid coolant between a liquid coolant inlet/outlet and a liquid coolant outlet/inlet; b) a heat exchange tube bundle for a passage of the hot gas, housed in the shell, extending according to the longitudinal direction between a first fixing baffle located on a hot gas inlet/outlet side and a second fixing baffle located on a hot gas outlet/inlet side; and c) the second fixing baffle is attached to the shell; wherein d) the first fixing baffle is attached to the shell by means of a tubular-shaped manifold element wherein: i. the end of the manifold element located at a hot gas inlet/outlet end according to the longitudinal direction comprises an elastically deformable perimetral collar with an outer attachment region and an inner attachment region, wherein the outer attachment region has a characteristic diameter that is larger than the characteristic diameter of the inner attachment region, characteristic diameter being defined as four times the area of the cross section divided by the perimeter of said section, such that the first baffle is attached to the manifold element through the inner attachment region of the manifold element, and the outer attachment region of the manifold element is attached to the shell, and ii. at least one tubular segment of the manifold element extends according to the longitudinal direction from the perimetral collar to the hot gas outlet/inlet side and is completely housed inside the shell, establishing a perimetral chamber in fluid communication with the liquid coolant inlet/outlet and in fluid communication with an inside of the shell; wherein the end of the manifold element located at an opposite end of the hot gas inlet/outlet, according to the longitudinal direction, is attached to the surface of the shell, wherein the first fixing baffle and the second fixing baffle are end baffles disposed at opposite ends of the heat exchange tube bundle, and the first fixing baffle and the second fixing baffle are the only ones of the end baffles for the heat exchange tube bundle.

2. The heat exchanger according to claim 1, wherein the perimetral chamber is configured by means of an enlargement of the shell in a segment according to the longitudinal direction in which the at least one tubular segment of the manifold element extends.

3. The heat exchanger according to claim 1, wherein the perimetral collar establishes a fluid barrier between the inside of the shell where the liquid coolant is located and an inlet into the tube bundle where the hot gas is located.

4. The heat exchanger according to claims 1, wherein the end of the manifold element located at an opposite end of the hot gas inlet/outlet according to the longitudinal direction establishes a sliding support with a surface of the shell that slides according to the longitudinal direction, where the sliding support establishes a closure of the perimetral chamber formed between the shell and the manifold element.

5. The heat exchanger according to claim 4, wherein the sliding support is established in an enlarged segment configured according to a step-like section of the shell.

6. The heat exchanger according to claim 1, wherein the tubular segment of the manifold element comprises an elastically deformable segment that is elastically deformable in at least a perimetral region of the tubular segment, preferably configured like a bellows, to reduce stressing due to expansion of the manifold element according to the longitudinal direction.

7. The heat exchanger according to claim 1, wherein the manifold element comprises one or more slots for fluid communication between the perimetral chamber and the inside of the shell where the tube bundle is housed.

8. The heat exchanger according to claim 7, wherein at least one of the slots is located in a position opposite the liquid coolant inlet/outlet with respect to the perimetral chamber.

9. The heat exchanger according to claim 1, wherein the elastic perimetral collar has a section that is: in corrugated form with at least one double transition curve; in multi-step form; straight with stamped protrusions; or a combination of any of the foregoing.

10. The heat exchanger according to claim 1, wherein the manifold element is configured as a single part.

11. An EGR system or WHRS system comprising a heat exchanger according to claim 1.

12. A method of assembly of a heat exchanger configured according to claim 1, comprising the following steps: i) assembling the first fixing baffle on the manifold element, and assembling the second fixing baffle on the shell; ii) assembling the assembly formed by the first baffle and the manifold element on the shell; iii) assembling the heat exchange tubes between the first fixing baffle and the second fixing baffle; wherein brazing paste is incorporated in any of the steps in the assembled parts to be attached, and iv) sending the assembled assembly through the brazing furnace for attaching the assembly by brazing.

13. The method of assembly according to claim 12, wherein the manifold element comprises at least one deflector, configured as an intermediate baffle, of the liquid coolant flowing between tubes of the tube bundle, and wherein step iii) of assembling the exchange tubes is performed by the guided insertion through the at least one deflector.

14. The method of assembly according to claim 12, further comprising, between steps iii) and iv), the step of inserting a manifold at the intake and at the exhaust.

15. The heat exchanger according to claim 1, wherein the first fixing baffle and the second fixing baffle are configured to separate the hot gas and the liquid coolant from one another.

Description

DESCRIPTION OF THE DRAWINGS

(1) The foregoing and other features and advantages of the invention will be more clearly understood based on the following detailed description of a preferred embodiment provided only by way of illustrative and non-limiting example in reference to the attached drawings.

(2) FIG. 1 shows a first embodiment of a heat exchanger. In this figure the heat exchanger is shown according to a front longitudinal section view to allow seeing the internal components.

(3) FIG. 2 shows a perspective view of a quarter section of the same embodiment to allow seeing both the external configuration of the heat exchanger and the internal elements.

(4) FIG. 3 shows two components of the heat exchanger, i.e., the manifold element and an internal deflector, according to one embodiment.

(5) FIG. 4 shows the same two components where the internal deflector is located in its final position with respect to the manifold element.

(6) FIG. 5 schematically depicts various embodiments of the cross section of the elastically deformable perimetral collar as well as a schematic depiction of a detail of the bellows that allows absorbing axial forces in the tubular body of the manifold element.

DETAILED DESCRIPTION OF THE INVENTION

(7) According to a first inventive aspect, the present invention relates to a compact heat exchanger for an EGR system. FIG. 1 shows a first embodiment, depicted in a front view and according to a cross section along a plane containing the longitudinal axis X-X′ to see the elements inside it. FIG. 2 shows a perspective view of a quarter section of the device that allows seeing the chambers formed inside the device by means of the combination of various parts.

(8) This section shows a shell (1) having a rectangular section, with a liquid coolant inlet/outlet (1.1) at one end and an outlet/inlet (1.2), also for the liquid coolant, located at the opposite end. In this case, the inlet/outlet (1.1) is located on the right side according to the position of the section view of FIG. 1 and the outlet/inlet (1.2) is located on the left side. Throughout the description, relative positions such as right, left, up or down are used with respect to the position in which the figures are shown.

(9) According to this embodiment, both inlets/outlets (1.1, 1.2) are located in an enlargement of the shell (1) along a longitudinal segment X-X′, the enlargement (1.3) on the right side being of larger dimensions.

(10) The inside of the shell (1) houses a tube bundle (2) of flat tubes, where the section shows the inside of a flat tube with an assembly of corrugated heat exchange fins (2.1). The flat tubes in this embodiment are arranged parallel to and spaced from one another such that there are formed channels for the passage of liquid coolant according to planes which are shown in this figure to be vertical and parallel to longitudinal direction X-X′.

(11) The tubes of the tube bundle (2) are intended for the passage of hot gas which, through the walls of the tube, transfers heat to the liquid coolant covering the tube bundle (2). These tubes extend between a first baffle (3) and a second baffle (4), where the first baffle (3) is a floating baffle located on the right side of the drawing and the second baffle (4) is a fixed baffle located on the left side of the drawing.

(12) In this embodiment, the first baffle (3) and the second baffle (4) are made from punched and stamped sheet metal with perimetral walls having a cylindrical configuration that allow being fitted in a housing. The second baffle (4) is fitted directly on the end of the shell (1) and the first baffle (3) is fitted on an intermediate part, i.e., the manifold element (5).

(13) In this embodiment, the manifold element (5) is also a part made of punched and stamped sheet metal. The manifold element (5) comprises an elastically deformable perimetral collar (5.1) and a tubular segment (5.5).

(14) In this embodiment, the perimetral collar (5.1) of the manifold element (5) is configured according to its section in corrugated form, particularly being S-shaped. According to other embodiments, the perimetral collar (5.1) is configured according to the cross section in corrugated form with at least one double transition curve allowing a higher degree of deformation with respect to the same stresses.

(15) FIG. 5 shows other alternative shapes for configuring the perimetral collar (5.1). In a simple embodiment, the perimetral collar (5.1) is a straight section in the transverse direction corresponding to a transverse plane, as can be seen in FIG. 5a). Another alternative configuration of the section of the perimetral collar (5.1) is the stepped shape shown in FIG. 5b), which readily allows being stamped. Alternatively, FIG. 5c) shows a straight section configuration in the transverse direction with the surface of the perimetral collar (5.1) having stamped protrusions that allow determining the degree of rigidity of the elastically deformable perimetral collar (5.1). The protrusions do not have to be made on just the sections corresponding to a transverse plane; they could also be made on other sections, for example in a stepped configuration.

(16) FIG. 5d) shows the configuration with a cross section in corrugated form with at least one double transition or S-shaped curve. It is also possible to configure the perimetral collar (5.1) with a combination of the previously indicated shapes.

(17) In any case, the perimetral collar (5.1) has an outer attachment region (5.3) and an inner attachment region (5.4), the first attachment region (5.3) being intended for attachment with the shell (1) and the second attachment region (5.4) being intended for the attachment with the first baffle (3).

(18) In the described embodiments, the attachment between components is by means of brazing, although it would be possible to make use of other types of welding. In a first step, the components to be attached are assembled by incorporating brazing paste on contacting surfaces that are to be attached. Going through the brazing furnace melts the metal part of the brazing paste, giving rise to the brazing of the contacting parts.

(19) In order to facilitate the assembly before going through the furnace, the outer attachment region (5.3) and the inner attachment region (5.4) are configured in the form of a seating. The seating corresponding to the outer attachment region (5.3) allows the insertion and positioning of the manifold element (5) in the shell (1), and the seating corresponding to the inner attachment region (5.4) allows the insertion and positioning of the first baffle (3) in the manifold element (5).

(20) The insertion of each part requires the incorporation of the brazing paste.

(21) The seating receiving the first baffle (3) comprises the inner attachment region (5.4) and a step (5.2) for supporting the first baffle (3) which limits the entry of said first baffle (3) during insertion.

(22) So the elastically deformable perimetral collar (5.1) is sandwiched between the first baffle (3) and the shell (1), thereby allowing the tube bundle (2) to experience greater expansion than the shell (1).

(23) As indicated above, the manifold element (5) is prolonged by means of a tubular segment (5.5) from the perimetral collar (5.1) according to the longitudinal direction to the side where the hot gas outlet is located. This tubular segment (5.5) configures a chamber (C) that is in fluid communication with the inlet/outlet (1.1) and is also in fluid communication with the inside of the shell (1) such that it allows distributing the liquid coolant circulating between the inlet/outlet (1.1) and the inside of the shell (1) and allows access to be gained to said inside of the shell (1) through any perimetral point.

(24) The chamber (C) is demarcated by the tubular segment (5.5), the enlarged segment of the shell (1.3), and by the perimetral collar (5.1).

(25) According to this embodiment, the expansion of the tube bundle (2) due to the increase in temperature caused by the passage of the hot gas through the inside thereof generates a displacement according to longitudinal direction X-X′ of the first baffle (1). In this case, the displacement is to the right, i.e., to the hot gas inlet. Nevertheless, deformation of the perimetral collar (5.1) can be in other directions since said perimetral collar (5.1) allows for deformations in the transverse plane in which it is contained.

(26) The displacement occurs at the expense of a deformation of the elastically deformable perimetral collar (5.1) and pulls the tubular segment (5.5) in the direction in which the expansion occurs, in this case, as indicated, primarily in the axial direction towards the right, shown in the drawing.

(27) The tubular segment (5.5) and shell (1) establish a closure of the chamber (C) that does not necessarily have to be leak-tight since both the inside of the shell (1) and the inside of the chamber (1) contain liquid coolant. To prevent the closure between the tubular segment (5.5) and the shell (1) from imposing restrictions on the pulling effect of the tubular segment (5.5) due to deformation of the perimetral collar (5.1), a closure has been established in this embodiment by means of a sliding support between both parts, i.e., between the tubular segment (5.5) and the shell (1).

(28) The sliding support is formed in this embodiment by means of a seating formed as an enlarged segment (1.4) configured according to a step-like section of the shell (1). The end of the tubular segment (5.5) is supported on this enlarged segment (1.4) such that during expansion, the tubular segment (5.5) slides following the axial movement allowed by the elastically deformable perimetral collar (5.1) without the closure of the chamber disappearing.

(29) According to other embodiments, in order to prevent the closure between the tubular segment (5.5) and the shell (1) from imposing restrictions on the pulling effect of the tubular segment (5.5) due to deformation of the perimetral collar (5.1), the end of the tubular segment (5.5) is welded to the shell (1), particularly to the inner surface of the shell (1), and the tubular segment (5.5) incorporates an elastically deformable segment that allows separation of the end of the tubular segment (5.5) attached to the shell (1) and the end where the perimetral collar (5.1) is located.

(30) A specific way in which an elastically deformable segment is incorporated in the tubular segment (5.5) is by means of a segment configured in the form of a bellows, as schematically depicted in FIG. 5 in the detail identified as e).

(31) In the embodiment shown in FIG. 1, a slot (5.6) through which the passage of the liquid coolant between the inside of the shell (1) and the chamber (C) takes place is shown in the lower portion, i.e., in the portion that is opposite the liquid coolant inlet/outlet (1.1) with respect to the chamber (C).

(32) A relevant case of the heat exchanger is one that operates under co-current flow conditions, such that it is at the end where the manifold element (5) is located where the entry of the liquid coolant takes place. Entry of the liquid coolant through the slot (5.6) allows injecting the liquid at a high speed in a direction parallel to the first baffle (3), such that any stagnation region of the liquid coolant is eliminated, and from a position opposite the entry of the liquid coolant.

(33) In this case, the slot (5.6) introduces the liquid coolant in a direction parallel to the flat tubes. Another arrangement of the tubes can be achieved by simply turning the position of the baffles (3, 4) between which the tubes of the tube bundle (2) are located, and the slot (5.6) must simply be located at a suitable point of entry on the periphery since the chamber (C) extends around the periphery of the end of the exchanger where the hot gas inlet is located.

(34) There is an intake manifold (6) in the hot gas inlet communicating the hot gas conduit with the inside of the tubes of the tube bundle (2), and there is an exhaust manifold (7) at the hot gas outlet communicating the inside of the tubes (2) with the cooled gas outlet conduit.

(35) In this embodiment, the intake manifold (6) and the exhaust manifold (7) are attached to the shell (1). In the case of the intake manifold (6), attachment with the shell is by means of the manifold element (5), although in another alternative the attachment is established by locating the intake manifold (6) between the manifold element (5) and the shell (1).

(36) By means of this configuration, the elastically deformable perimetral collar (5.1) of the manifold element (5) establishes a barrier between the liquid coolant located inside the chamber (C) and the hot gas located inside the intake manifold (6). In other words, the attachment between the intake manifold (6) and the heat exchanger is established in the region where the outer attachment region (5.3) is located.

(37) In an embodiment not shown in drawings, the intake manifold (6) is attached to the manifold element (5) in a region where the inner attachment region (5.4) is located, for example the segment of the intake manifold (6) to be attached being located between the first baffle (3) and the manifold element (5).

(38) In this alternative configuration, the elastically deformable perimetral collar (5.1) establishes a separation between the liquid coolant housed in the chamber (C) and the outside of the heat exchanger.

(39) FIG. 2 also shows a deflector (8) in the form of an intermediate baffle configured as a comb entering part of the channels formed between the flat tubes. This deflector modifies streamlines of the liquid coolant flow by forcing the latter to cling to the inner wall of the first baffle (3) to a higher degree in order to eliminate any stagnation region, which goes against the tendency of the flow to head to the opposite outlet.

(40) According to a preferred embodiment, this deflector (8) is attached to the inside of the manifold element (5) instead of being attached to the inner wall of the shell (1), as shown in FIG. 4. FIG. 3 shows the manifold element (5) and the deflector (8) separated from one another, and FIG. 4 shows the deflector (8) attached in its final position inside the manifold element (5).

(41) The manifold element (5) is preferably manufactured as a single part. In the described embodiments, this part is formed by punched and stamped sheet metal.

(42) In addition to solving the described technical problems, the manifold element (5) facilitates assembly of the heat exchanger for it to later go through the brazing furnace, and even more so when it incorporates the deflector (8).

(43) A second inventive aspect relates to the method of assembly of a heat exchanger according to the first inventive aspect. The method comprises the following steps: i) assembling the first fixing baffle (3) on the manifold element (5), and assembling the second fixing baffle (4) on the shell (1), wherein both assembly operations can be carried out in any order. ii) assembling the assembly formed by the first baffle (3) and the manifold element (5) on the shell (1), at the end opposite where the second baffle (4) is located. The assembly comprising the manifold element (5) and the first baffle (3) is located at the end of the shell (1), opposite to the end where the second baffle (4) is located, and it is housed in the enlargement (1.3) of the shell (1). iii) assembling the heat exchange tubes (2) between the first fixing baffle (3) and the second fixing baffle (4). Both the first baffle (3) and the second baffle (4) have a surface with perforations coinciding with the section of the tubes of the tube bundle (2) they house. When the manifold element (5) comprises a deflector (8), the latter serves as a guide during the operation of inserting the exchange tubes through the perforations, such that after passing the first baffle (3) the tubes reach the second baffle (4) in a guided manner.

(44) Brazing paste is incorporated in any of the steps in the assembled parts to be attached, and as an additional step, iv) sending the assembled assembly through the brazing furnace for attaching the assembly by brazing.

(45) In the described examples, the intake manifold (6) and the exhaust manifold (7) are incorporated before going through the brazing furnace.