RECUPERATOR DEVICE FOR RECOVERING ENERGY FROM EXHAUST GAS HEAT

Abstract

The present invention is a device for recovering energy from exhaust gas heat of an internal combustion engine. Particularly, the invention relates to a recuperator device which makes use of a temperature gradient between two conduits to generate an electric potential by means of a plurality of thermoelectric boards.

Claims

1. A recuperator for recovering energy from exhaust gas heat of an internal combustion engine, there being a first fluid and a second fluid, wherein a temperature of the first fluid is higher than the temperature of the second fluid, wherein the recuperator comprises: at least a first inlet baffle (1) and a first outlet baffle (2) for the first fluid and a second inlet baffle (4) and a second outlet baffle (5) for the second fluid, wherein each of the baffles (1, 2, 4, 5) comprises openings for the passage of the corresponding fluid; a first tube bundle (3) for the passage of the first fluid, wherein these tubes (3) are arranged essentially parallel to one another and, the tubes (3) of the first tube bundle (3) extend from the first inlet baffle (1) to the first outlet baffle (2); a second tube bundle (6) for the passage of the second fluid, wherein these tubes (6): are arranged essentially parallel to one another and, the tubes (6) of the second tube bundle (6) extend from the second inlet baffle (4) to the second outlet baffle (5); a plurality of thermoelectric modules (7.1) comprising a first face (7.1.1) and a second face (7.1.2) arranged opposite the first face (7.1.1), wherein the thermoelectric modules (7.1) are adapted for generating an electric potential based on a temperature gradient between the first face (7.1.1) and the second face (7.1.2); wherein the first tube bundle (3), the second tube bundle (6) and the plurality of thermoelectric modules (7.1) form a stack such that each thermoelectric module (7.1) has the first face (7.1.1) in thermal contact with a tube (3) of the first tube bundle (3) and the second face (7.1.2) in thermal contact with a tube (6) of the second tube bundle (6); characterized in that the tubes (3) of the first tube bundle (3), the tubes (6) of the second tube bundle (6), or both (3, 6), comprise a support element (3.1, 3.2, 6.1, 6.2) at each end of the tube (3, 6) adapted for being supported on a face of the baffle (1, 2, 4, 5) corresponding to said end of the tube (3, 6) and establishing a fluid communication through one or more openings of the baffle (1, 2, 4, 5) between the inside of the tube (3, 6) and the side of the baffle (1, 2, 4, 5) arranged on the side opposite the tube (3, 6).

2. The recuperator according to claim 1, wherein there is a leak-tight attachment between each support element (3.1, 3.2, 6.1, 6.2) and the baffle (1, 2, 4, 5) on which it is supported.

3. The recuperator according to claim 1, wherein the support element (3.1, 3.2, 6.1, 6.2) is an element extending perimetrically around the tube.

4. The recuperator according to claim 1, wherein said recuperator comprises a shell (8).

5. The recuperator according to claim 1, wherein said recuperator comprises a plurality of springs (13) arranged between the shell (8) and the stack and are adapted for applying a compressive force on said stack.

6. The recuperator according to claim 1, wherein: either the tubes (3) of the first tube bundle (3) have a longitudinal configuration and the tubes (6) of the second tube bundle (6) have a U-shaped configuration; or the tubes (6) of the second tube bundle (6) have a longitudinal configuration and the tubes (3) of the first tube bundle (3) have a U-shaped configuration.

7. The recuperator according to claim 1, wherein the tubes (3) of the first tube bundle (3) are transverse to the tubes (6) of the second tube bundle (6).

8. The recuperator according to claim 1, wherein the tubes (3) of the first tube bundle (3) or the tubes (6) of the second tube bundle (6), or both, are flat.

9. The recuperator according to claim 1, wherein the tubes (3) of the first tube bundle (3) are arranged as double tubes in the stack to increase the contact area with the thermoelectric module or modules (7.1).

10. The recuperator according to claim 1, wherein there is a thermal in material between a thermoelectric module (7.1) and the tube (3, 6) with which it is in thermal contact.

11. The recuperator according to claim 10, wherein the thermal insulation material between the thermoelectric module (7.1) and the tube (3) of the first tube bundle (3) is graphite (14.1).

12. The recuperator according to claim 10, wherein the thermal insulation material between the thermoelectric module (7.1) and the tube (6) of the second tube bundle (6) is silicone (14.2).

13. The recuperator according to claim 1, wherein a plurality of thermoelectric modules (7.1) in the stack are grouped together on a board (7) having a flat configuration.

14. The recuperator according to claim 1, wherein one or more baffles (1, 2, 4, 5) are attached to a manifold.

15. The recuperator according to claim 1, wherein the support element (3.1, 3.2, 6.1, 6.2) is a plate transverse to the tube (3, 6).

16. The recuperator according to claim 15, wherein the plate transverse to the tube (3, 6) is a prolongation of the tube (3, 6).

17. A construction method for constructing a recuperator for recovering energy from exhaust gas heat of an internal combustion engine, there being a first fluid and a second fluid, wherein the temperature of the first fluid is higher than the temperature of the second fluid, wherein the recuperator comprises: at least a first inlet baffle (1) and a first outlet baffle (2) for the first fluid and a second inlet baffle (4) and a second outlet baffle (5) for the second fluid, wherein each of the baffles (1, 2, 4, 5) comprises openings for the passage of a fluid; a first tube bundle (3) for the passage of the first fluid, wherein these tubes (3) are arranged essentially parallel to one another and, the tubes (3) of the first tube bundle (3) extend from the first inlet baffle (1) to the first outlet baffle (2); a second tube bundle (6) for the passage of the second fluid, wherein these tubes (6): are arranged essentially parallel to one another and, the tubes (6) of the second tubs bundle (6) extend from the second inlet baffle (4) to the second outlet baffle (5); a plurality of thermoelectric modules (7.1) comprising a first face (7.1.1) and a second face (7.1.2) arranged opposite the first face (7.1.1), wherein the thermoelectric modules (7.1) are adapted for generating an electric potential based on a temperature gradient between the first face (7.1.1) and the second face (7.1.2); wherein the method comprises the following steps: a) providing a support element (3.1, 3.2, 6.1, 6.2) at each end of the tube (3, 6) adapted for being supported on a face of the baffle (1, 2, 4, 5) corresponding to said end of the tube (3, 6); b) establishing a stack of the first tube bundle (3), the second tube bundle (6) and the plurality of thermoelectric modules (7.1) such that each thermoelectric module (7.1) has the first face (7.1.1) in thermal contact with a tube (3) of the first tube bundle (3), the second face (7.1.2) in thermal contact with a tube (6) of the second tube bundle (6) and, the support elements (3.1, 3.2, 6.1, 6.2) are supported on the baffles (1, 2, 4, 5) corresponding to each end of the tube (3, 6), establishing fluid communication through one or more openings of the baffle (1, 2, 4, 5) between the inside of the tube (3, 6) and the side of the baffle (1, 2, 4, 5) arranged on the side opposite the tube (3, 6); to attach each of the support elements (3.1, 3.2, 6.1, 6.2) to the baffle (1, 2, 4, 5) on which it is supported.

18. The recuperator according to claim 1, wherein the first fluid is an exhaust gas and the second fluid is a liquid coolant. c)

Description

DESCRIPTION OF THE DRAWINGS

[0063] 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 given only by way of illustrative and non-limiting example in reference to the attached drawings.

[0064] FIG. 1 is a perspective view of a first preferred embodiment in which the first tube bundle is shown with the tubes supported on their corresponding baffles and without the thermoelectric modules to allow clearly seeing the rest of the components.

[0065] FIG. 2 is a perspective of the same embodiment in which a view of the stack of the first and second tube bundle is shown with their corresponding baffles and manifolds.

[0066] FIG. 3 shows a perspective view of the plurality of thermoelectric module boards in their spatial position in the stack according to the same embodiment.

[0067] FIG. 4 shows a perspective view of a tube of the first tube bundle, together with its corresponding support elements, and its baffle and manifold according to its relative spatial positioning, all of them according to the same embodiment.

[0068] FIG. 5 shows a perspective view of the stack of tubes of the second tube bundle, together with their corresponding support elements, and their baffle and manifold according to their relative spatial positioning, all of them according to the same embodiment.

[0069] FIG. 6 shows three views, i.e., a perspective view, a front view and a plan view, of a separate tube of the second tube bundle according to the same embodiment in perspective view.

[0070] FIG. 7 shows a perspective view of the second tube bundle supported on its corresponding baffles according to the same embodiment.

[0071] FIG. 8 shows a perspective view of the recuperator for recovering energy according to the same embodiment with a quarter section.

[0072] FIG. 9 shows an amplified detail of the quarter section shown in the preceding drawing of the recuperator for recovering energy.

[0073] FIG. 10 shows a still more amplified detail of the preceding drawing in which details of the tube stacks are shown.

[0074] FIG. 11 shows a detail of a section view of the stack according to an embodiment in which the arrangement of the elements forming it can be seen.

DETAILED DESCRIPTION OF THE INVENTION

[0075] According to the first inventive aspect, the present invention is a recuperator for recovering energy or a device for recovering energy from exhaust gas heat of a vehicle by means of converting same into electric energy. To convert heat into a potential difference, the recuperator for recovering energy uses a plurality of thermoelectric modules (7.1) arranged between tubes (3) containing a hot fluid and tubes (6) containing a cold fluid or coolant.

[0076] FIG. 1 shows an embodiment of the invention in which a first inlet baffle (1), a first outlet baffle (2), a first tube bundle (3) extending between the first inlet baffle (1) and the first outlet baffle (2), a first inlet manifold (9) for distributing hot gas into the inlets of the tubes of the first tube bundle (3) and a first outlet manifold (10) receiving the hot gas after it exits the same first tube bundle (3) can be seen.

[0077] This perspective view also shows support elements (3.1, 3.2) located at the ends of the tubes of the first tube bundle (3) in contact with the first baffles (1, 2), and a free space which is located between the tubes of the first tube bundle (3) that are arranged in a stack. It is indicated that the arrangement shown in this drawing is a stack arrangement because the view corresponds to the spatial position of the tubes of the first tube bundle (3) without graphically depicting the rest of the elements in order to more clearly see the separation of the support elements (3.1, 3.2).

[0078] The tubes of a second tube bundle (6) arranged in an alternating manner with respect to the tubes of the first tube bundle (3), and all of them arranged in a stack, have been added to the graphical depiction of the preceding elements in FIG. 2. A second inlet baffle (4) and a second outlet baffle (5) are also shown along with corresponding second manifolds (11, 12) for the fluid coolant: a second inlet manifold (11) for distributing liquid coolant into the inlet of the tubes of the second tube bundle (6) and a second outlet manifold (12) for receiving the liquid coolant that exits the tubes of the second tube bundle (6). Neither the support elements of the second tube bundle (6.1, 6.2) (which are indeed shown in FIG. 5) nor the thermoelectric modules (shown in FIG. 3) can be seen in this view.

[0079] FIG. 3 depicts a plurality of boards (7) having a flat configuration, this plurality of boards (7) being spatially distributed like how they are placed inside the stack. Each board (7) having a flat configuration comprises a plurality of individual thermoelectric modules (7.1) which, in the shown embodiment, are arranged in two rows such that the number of thermoelectric modules (7.1) installed in the available space is maximized.

[0080] The thermoelectric modules (7.1) are the minimum individual element capable of producing a potential difference that can be utilized, and comprises a first face (7.1.1), a second face (7.1.2) and at least two electric terminals; depending on the polarity of the thermoelectric module (7.1), one of the faces is placed in thermal contact with a hot source, and the other face is placed in thermal contact with a cold source. A potential difference is thereby generated between the electric terminals as a result of thermoelectric effect. In the shown embodiment, the board (7) corresponds to a printed circuit board (PCB) comprising electrical connections between the thermoelectric modules (7.1), such that they are connected to one another, and means for converting the type of current generated.

[0081] This spatial distribution of the thermoelectric modules (7.1) on a board (7) results in a part configured in the form of a board with two large surfaces, one intended for being in thermal contact with a cold source and another intended for being in thermal contact with a hot source, generating enough potential in connectors which allow extracting electric energy in a utilizable manner.

[0082] FIGS. 4 and 5 depict two assemblies of parts, one assembly of parts being associated with the first fluid (FIG. 4), i.e., the hot gas, and one assembly of parts being associated with the second fluid (FIG. 5), i.e., the liquid coolant; said assemblies of parts comprising baffles, tube bundles, manifolds and support elements. In the case of FIG. 4, only a double tube for the first fluid has been graphically depicted.

[0083] FIG. 4 shows in detail a tube of the first tube bundle (3) with a flat configuration and having, in this embodiment, two separate conduits of rectangular section with the shortest sides being rounded. These tubes (3) are made by means of known methods. A support element (3.1, 3.2) configured as a plate transverse to the tube is located at each end of the tube. In this embodiment, the support elements (3.1, 3.2) furthermore have the function of serving as a structural support and attaching the two conduits of the tube (3) to one another.

[0084] The same FIG. 4 furthermore shows the first outlet baffle (2) and the first outlet manifold (10). Neither the inlet baffle (1) nor the inlet manifold (9) is shown in this view in order to allow better viewing the shown components which, in this embodiment, would comprise the elements shown in FIGS. 1 and 2, where they are essentially the same as the outlet elements. The first outlet baffle (2) has a plurality of openings with an almost rectangular section, wherein one of the purposes thereof is to establish fluid communication between the conduits of the tubes (3) and the manifolds (9, 10). In turn, the manifolds (9, 10) are attached in a leak-tight manner to the baffles.

[0085] The function of the support elements (3.1, 3.2) is to link each end of the tube (3) with the corresponding baffle (1, 2). As described in the construction method, the attachment between the support elements (3.1, 3.2) and the baffles (1, 2) is initially a support which assures the position between the tube and the baffle with respect to the axial direction defined at the end of the tube while allowing sliding in any of the directions of the plane defined by the baffle (1, 2), and a permanent attachment is made in subsequent steps of the construction method. The degrees of freedom established by the relative sliding between the baffle and the ends of the tubes as a result of the support elements (3.1, 3.2) assure that there is a suitable thermal contact between the tubes and the thermoelectric modules (7.1) when making the attachment between said support elements (3.1, 3.2) and the baffle (1, 2).

[0086] It is advantageous for the attachment between the support elements (3.1, 3.2) and the baffles (1, 2) to be leak-tight, since the fluids contained in the tubes (3, 6) will therefore be prevented from leaking out, where it may cause damage to other elements. In this embodiment, the leak-tight attachment is achieved by extending the welding between the support elements (3.1, 3.2) and the baffles (1, 2) to the entire perimetral area of the support elements (3.1, 3.2).

[0087] In this embodiment, the support elements (3.1, 3.2) are flat transverse plates (3, 6) rigidly attached to the ends of the tubes (3, 6) by means of welding, for example. According to another embodiment, the support elements (3.1, 3.2) are obtained during the manufacturing process by means of extruding or stamping the same end of the tube (3, 6), for example.

[0088] Similarly, the tubes of the second bundle (6), the second baffles (4, 5) and the second manifolds (11, 12) have essentially the same configuration as the assembly described for the first fluid. FIG. 5 shows a plurality of tubes of the second tube bundle (6) and their support elements (6.1, 6.2); the tubes (6) have a flat, U-shaped configuration, i.e., the fluid experiencing a 180 change in direction, such that the inlet and the outlet of the second fluid are parallel to one another.

[0089] The support elements (6.1, 6.2) for this second tube bundle (6) have the same function as the one described for the first tube bundle (3.1, 3.2).

[0090] In the shown embodiment, the recuperator for recovering energy has been configured as a counter-current heat exchanger, but in other embodiments it would also be possible to configure it as a co-current exchanger by interchanging the inlet and the outlet of the assembly of the second fluid.

[0091] FIG. 6 shows a tube of the second tube bundle (6) having a flat configuration and a U-shaped second fluid path or trajectory, with a rectangular section (considering the direction of the fluid path in the conduit). The top view of the tube (6) of this same FIG. 6 shows the shape of the tube (6), formed by an essentially rectangular or trapezoidal cavity divided by a divider element into two chambers communicated with one another, and in turn communicating with the outside through the inlet and the outlet, respectively. This conduit configuration allows the fluid to move following a U-shaped trajectory, with the inlet and the outlet on the same lateral face of the device. The tubes furthermore have a perimetral edge in the form of a flat lateral band; the function of the perimetral edge is to make manufacturing and stacking the boards (7) easier, limiting possible relative movements in any direction of their main plane and simplifying their assembly as they serve as a guide in contact with the shell (8) that will be identified below.

[0092] In one embodiment (not shown in the drawings), the tubes of the second tube bundle (6) have a flat and straight configuration, without the fluid changing direction. In an alternative embodiment, the tubes of the second tube bundle (6) are arranged in the same direction as the tubes of the first tube bundle (3). In another alternative embodiment, the tubes of the second tube bundle (6) are arranged transverse to the tubes of the first tube bundle (3).

[0093] FIG. 7 shows the second tube bundle (6) forming a stack and with the ends of the inlets and outlet showing the support elements (6.1, 6.2) supported on the second baffles (4, 5). The same conditions of attachment between the tubes (3) and the baffles (1, 2) of the first assembly are verified for the attachment between the tubes of the second tube bundle (6) and the second baffles (4, 5).

[0094] FIG. 8 shows a view of the recuperator for recovering energy with a quarter section at the top which allows showing on one hand the stack of tubes (3, 6) and on the other the shell (8). The purpose of the shell (8) is to protect and hold the assembly of the recuperator for recovering energy. Furthermore, the shell (8) allows placing an assembly of springs (13) between the stack of tubes (3, 6) and the shell (8); these springs (13) have the function of producing a compressive stress in the stacking direction.

[0095] According to a preferred way of carrying out the construction method for constructing the recuperator for recovering energy, support elements (3.1, 3.2, 6.1, 6.2) are first provided at the ends of the tubes (3, 6); as described above, the way of constructing these support elements (3.1, 3.2, 6.1, 6.2) depends on the type of tubes (3, 6) and on the type of support elements (3.1, 3.2, 6.1, 6.2) themselves. In one embodiment of the device like the one shown in the drawings in which the tubes (3, 6) are flat and the support elements (3.1, 3.2, 6.1, 6.2) are transverse plates, the support elements (3.1, 3.2, 6.1, 6.2) are welded to the ends of the tubes (3, 6).

[0096] Alternatively, the support elements (3.1, 3.2, 6.1, 6.2) can be constructed by means of stamping the elements making up the flat tubes (3, 6), and subsequently bending the support elements (3.1, 3.2, 6.1, 6.2) such that they form a suitable support surface.

[0097] Secondly, the tubes (3, 6) and the boards (7) comprising the thermoelectric modules (7.1) are stacked. Although it is possible, in principle, to construct the device with independent thermoelectric modules (7.1), it is more convenient to group them together on boards (7) and to stack these boards. The way of stacking the tubes (3, 6) and the boards (7) must allow the first faces (7.1.1) of the thermoelectric modules (7.1) to be in thermal contact with the surface of the first tubes (3), and the second faces (7.1.2) of the thermoelectric modules (7.1) to be in thermal contact with the surface of the second tubes (6). The orientation of the faces (7.1.1, 7.1.2) and the name thereof depends on the polarity of the thermoelectric modules (7.1); for the sake of clarity it will be considered that the first faces (7.1.1) correspond to the hot source, and the second faces (7.1.2) correspond to the hot source and the chosen orientation of the boards (7) is such that the face intended for being in contact with the hot source corresponds to the tube with the hot gas and the face intended for being in contact with the cold source corresponds to the tube with the liquid coolant.

[0098] A favorable way of making the stack according to what has been described is as follows: [0099] firstly, arranging a tube of the second tube bundle (6), [0100] then arranging a board (7), with the second faces (7.1.2) in contact with the tube (6) for the liquid coolant, [0101] arranging a tube of the first tube bundle (3), with the first faces (7.1.1) in contact with the tube (3) for the hot gas, then arranging another board (7), with the first faces (7.1.1) in contact with the tube (3) for the hot gas, [0102] arranging another tube of the second tube bundle (6), with the second faces (7.1.2) in contact with the tube (6) for the liquid coolant, and [0103] repeating the preceding steps.

[0104] A stack of the desired size can thereby be formed depending on the number of tubes of the first tube bundle (3) the recuperator for recovering energy has. An example of stack following the described order (the thermoelectric boards (7) are not visible in this drawing) with six tubes of the first tube bundle (3) and twelve thermoelectric boards (7) can be seen in FIG. 2. To maintain the temperature gradient between the first faces (7.1.1) and the second faces (7.1.2) of the thermoelectric modules (7.1), according to one embodiment, a layer of insulating material is included on the surfaces of thermal contact between the boards (7) and the tubes (3, 6). This layer of insulating material must allow a certain degree of heat transfer by conduction, graphite (14.1) (in contact with the hot side, or first face) and silicone derivatives (14.2) (in contact with the cold side, or second face) being materials suitable for this use. In this manner, only part of the heat generated in the tubes of the first tube bundle (3) is transferred to the first faces (7.1.1) through the insulating layer, preventing thermal equilibrium with the second faces (7.1.2) from being reached.

[0105] FIG. 11 shows the particular arrangement of the elements forming the stack according the embodiment described above. According to the shown embodiment, between a tube of the first tube bundle (3) and a thermoelectric module (7.1) one or more layers of graphite (14.1) are arranged in thermal contact with the first face (7.1.1) of a thermoelectric module (7.1) and with the tube (3), whereas between a tube of the second tube bundle (6) and a thermoelectric module (7.1) one or more layers of silicone (14.2) are arranged in thermal contact with the second face (7.1.2) of a thermoelectric module (7.1) and with the tube (6).

[0106] If graphite (14.1) is used, it will be supplied in the form of a sheet. When the insulating material is a silicone derivative (14.2), the material is applied in the form of a fluid or pasty substance which allows a closer contact between the surfaces between which said material is applied and allows homogenizing the temperature in the contact region of the cold side between the boards (7) and the tubes (3, 6).

[0107] As part of the stacking step, the tubes of both tube bundles (3, 6) must be arranged such that the support elements (3.1, 3.2, 6.1, 6.2) are supported on the corresponding baffles (1, 2, 4, 5).

[0108] In one embodiment, as part of the stacking step, one or more layers of silicone (14.2) are arranged between a tube of the second tube bundle (6) and the second face (7.1.2) of a board (7). Similarly, in one embodiment, as part of the stacking step, one or more graphite sheets (14.1) are arranged between the first face (7.1.1) of a board (7) and a tube of the first tube bundle (3) for the hot gas.

[0109] Given the configuration of the support elements (3.1, 3.2, 6.1, 6.2), the plurality of said support elements which are supported on one and the same baffle configure a flat fragmented surface which is supported on said also flat baffle.

[0110] In this step, the contact between the support elements (3.1, 3.2, 6.1, 6.2) and the baffles (1, 2, 4, 5) must be a sliding contact according to the stacking direction, allowing movements of the support elements (3.1, 3.2, 6.1, 6.2) in the stacking direction and maintaining contact with the baffles (1, 2, 4, 5). Furthermore, it is important that the position of the baffles (1, 2, 4, 5) and the stacked tubes (3, 6) allows for fluid communication between the manifolds (9, 10, 11, 12); to that end, the openings of the baffles (1, 2, 4, 5) must be aligned with the openings of the conduits of the tubes (3, 6); FIGS. 9 and 10 show this configuration. Given that there is possibility that sliding occurs, the openings of the baffles (1, 2, 4, 5) must be large enough so as to assure that the ends of the tubes open into said openings even with the expected movements.

[0111] In a last step of the construction method, the attachments between the support elements (3.1, 3.2, 6.1, 6.2) and the baffles (1, 2, 4, 5) are fixed. In a way of carrying out the invention, this attachment constitutes laser welding which immobilizes the ends of the tubes and assures the leaktightness between the attached elements. To assure a better thermal contact between the thermoelectric modules (7.1) and the tubes (3, 6), the present invention proposes fixing the attachment between the support elements (3.1, 3.2, 6.1, 6.2) and the baffles (1, 2, 4, 5) while applying a compressive stress according to the stacking direction, where the welded attachment is therefore able to maintain the contact pressure and to provide an excellent thermal contact of the thermoelectric modules (7, 1) with the tubes (3, 6).