EP2926077B1 - Gas heat exchanger, in particular for exhaust gases of an engine - Google Patents

Description

The present invention relates to a heat exchanger for gas, in particular for the exhaust gases of an engine. The invention is particularly applicable in heat exchangers of engine exhaust gas recirculation (EGRC).

Context of the invention

In some heat exchangers for gas cooling, for example those used in exhaust gas recirculation systems to the inlet of an internal combustion engine, the two heat exchanging media are separated by a wall.

The current configuration of EGR exchangers on the market is a metal heat exchanger typically made of stainless steel or aluminum.

Basically, there are two types of EGR heat exchanger: a first type consists of a housing inside which there is a bundle of parallel tubes for the passage of gases, the refrigerant circulating in the housing, outside tubes, and the second type consists of a series of parallel plates which constitute the heat exchange surfaces, so that the exhaust gases and the refrigerant circulate between two plates, in alternating layers, with the possibility of include fins to improve heat exchange.

In the case of tube bundle heat exchangers, the assembly between the tubes and the housing can be of different types. Generally, the tubes are fixed at their ends between two support plates connected to each end of the housing, the two support plates having a plurality of orifices for the installation of the respective tubes.

Said support plates are in turn fastened to connection means with the recirculation line, which may consist of a V-shaped connection or a peripheral collar or flange, depending on the design of the recirculation line in which is connected the exchanger. The peripheral collar can be assembled with a gas tank, so that the gas tank is a part intermediate between the housing and the collar, or the collar can be assembled directly to the housing.

In both types of EGR exchangers, most of their components are metallic, so that they are assembled by mechanical means and then oven-welded or arc-welded or laser-welded to ensure the proper sealing required this application. In some cases, they may also include some plastic components, which may have a single function or several functions integrated in one piece.

One of the conditions to be fulfilled by the EGR heat exchangers is to maintain an appropriate distribution of the coolant flow to ensure good efficiency and sufficient durability. If the distribution of the coolant flow is not good enough, the efficiency may decrease and may appear a boiling phenomenon, which will affect the durability of the heat exchanger subjected to thermal fatigue.

The distribution of the coolant flow depends fundamentally on the location of the inlet and outlet conduits of the refrigerant. A general recommendation is that the coolant outlet duct must be located in the upper part of the exchanger, while the coolant inlet duct must be located opposite in the lower part of the exchanger, and the greater the distance between the two inlet and outlet conduits of the coolant, the better the distribution of the coolant.

It is possible that the configuration of the refrigerant circuit of the engine is not designed to be able to comply in a simple manner with the recommendations cited; it is then necessary to use additional baffles to obtain that the flow of refrigerant fluid reaches the entire interior space of the heat exchanger. On the other hand, the use of baffles increases the price of the exchanger and makes more complex the assembly process, which involves significant investments to allow the assembly of the deflector.

Licences JP2000292089 and JP2000283666 disclose tube bundle heat exchangers which comprise a plurality of plate-shaped cross deflectors disposed within a circular section housing. The design of said baffles is very similar to the configuration of the support plates at both ends of the housing; the diameter of these baffles is equal to the inside diameter of the housing and they include openings to allow the refrigerant fluid to pass through. The positions of said passage openings in the different deflectors are distributed alternately.

The patent KR20080013457 discloses a tube bundle heat exchanger which comprises a helical shaped baffle inserted along a circular section housing.
The patent US2005161206 A1 discloses a stacked plate heat exchanger whose coolant inlet and outlet conduits are located at opposite ends but in the same side face of the housing. Each plate includes a transverse protuberance embossed in the lateral entry zone of the refrigerant fluid, as well as a plurality of shorter protuberances stamped along the plate, capable of distributing the refrigerant fluid from its lateral entry zone through any the surface of the plates.
The patent US2008169093 A1 discloses a stacked plate heat exchanger having the coolant inlet and outlet conduits at opposite ends and opposite sides of the exchanger housing. Each plate includes a transverse protuberance embossed in the lateral entry zone of the refrigerant fluid, as well as a plurality of shorter protuberances stamped along the plate, capable of distributing the refrigerant fluid from its lateral entry zone through any the surface of the plates.

The documents JP 2004 263616 A , US 2009/126918 A1 , US 2010/044019 A1 , US 3,291,081 and FR 2 936 043 also describe such exchangers.

However, there are no known heat exchangers tube bundle which have on the tubes protrusions transverse to the direction of the gas, to improve the distribution of the coolant flow, which would be desirable.

Description of the invention

The objective of the gas heat exchanger, in particular the exhaust gases of an engine, according to the present invention is to solve the disadvantages that the exchangers known in the art present by proposing a heat exchanger which allows improve the distribution of the flow of refrigerant through it while avoiding the use of deflectors.

The gas heat exchanger, in particular for the exhaust gas of an engine, according to the present invention is of the type which comprises a plurality of parallel tubes, arranged inside a housing, through which the gases circulate. cooling by heat exchange with a cooling fluid and wherein the refrigerant inlet and outlet conduits are each disposed at an opposite end of the housing, preferably on the same side of said housing; each tube comprises a protuberance facing the direction of the gases, said tubes being capable of being stacked together so that the protuberances of the respective tubes define a barrier, in the form of a baffle, for creating a predetermined path capable of ensuring an appropriate distribution of the flow of refrigerant fluid from its inlet to its exit around the tubes and along the exchanger; the parallel tubes have a substantially rectangular section, each tube comprising a protuberance transverse to the direction of the gases, so that said transverse protuberances of the respective tubes define a substantially vertical transverse barrier, it is characterized in that the tubes are oriented from whereby the upper half of the tube bundle has respective transverse protuberances located at a distance of about one-third of the length of the tube from the gas inlet, thereby defining a first vertical transverse barrier, while that the lower half of the tube bundle has its respective transverse protuberances located at a distance of about two-thirds of the length of the tube from the gas inlet, thereby defining a second vertical transverse barrier, so that the two transversal barriers define a trajec in the form of "Z" for the refrigerant flow, the refrigerant inlet duct being located in the upper part at one end of a lateral face of the casing, upstream of said first transverse barrier, and the duct coolant outlet outlet being located in the lower portion of the opposite end of the same side face of the housing, downstream of said second transverse barrier.

Thanks to the use of the protuberances on the tubes, the use of deflectors such as those known in the state of the art is avoided. In this way, by orienting the protuberance of each tube in a suitable manner during the assembly process of the bundle of tubes, it is possible to create a barrier which acts as a deflector, capable of directing the flow of refrigerant fluid. through the interior of the heat exchanger, thus allowing an improved distribution of said refrigerant flow.

The above-mentioned deflecting effect is obtained by contacting the protuberances of the respective tubes, so that the barrier or deflector obtained forces the circulation of the refrigerant fluid so that it flows along a path suitable for obtaining a good distribution of the refrigerant fluid.

Thanks to this deflector effect, the turbulence created in all directions and the improved trajectory from the inlet to the outlet of the refrigerant fluid makes it possible to increase the cooling of the bundle of tubes. It should be emphasized that without this deflector effect, the flow of refrigerant would flow directly from the inlet to the outlet without circulating around the tubes, which is undesirable.

This solution is particularly advantageous when the refrigerant enters and leaves the exchanger on the same side of the housing.

The deflectors or cross barriers created force the flow of refrigerant fluid to fill the inside of the exchanger in all directions, but with an appropriate distribution of the refrigerant flow from the inlet to the coolant outlet, thus avoiding a direct flow of refrigerant flow from the inlet to the outlet thereof. In addition, the flow generated within the housing has a "Z" shape, which differs completely from the refrigerant flow paths in the stacked plate heat exchangers known in the art that utilize a transverse protuberance.

According to one embodiment, each tube comprises a single transverse protuberance located on one of its faces.

According to another embodiment, each tube comprises two transverse protuberances located on the opposite faces of the tube.

Advantageously, each tube comprises a plurality of projections, preferably of circular section, distributed along the tube, intended for support and assembly between the adjacent tubes, which in turn delimit a predetermined space between the tubes for the passage refrigerant.

Brief description of the drawings

• la Figure 1 est une vue en perspective de l'échangeur thermique selon la présente invention, montrant le boîtier avec le faisceau de tubes et les deux conduits d'entrée et sortie de fluide réfrigérant;
• la Figure 2 est une vue en perspective d'un tube, montrant la protubérance transversale et les saillies d'appui;
• la Figure 3 est une vue de profil d'un tube avec une seule protubérance transversale, selon un mode de réalisation de l'invention;
• la Figure 4 est une vue de profil du tube avec deux protubérances transversales disposées sur des faces opposées, selon un autre mode de réalisation de l'invention;
• la Figure 5 est une vue en perspective de l'échangeur thermique de la Figure 1, montrant un plan de coupe longitudinale T; et
• la Figure 6 est une section longitudinale de l'échangeur thermique suivant plan de coupe T représenté sur la Figure 5.

In order to facilitate the description of what we have explained above, we enclose drawings in which, schematically and solely by way of non-limiting example, is shown a practical case of embodiment of the gas heat exchanger, in particular for the exhaust gases of an engine, according to the invention, among which:

• the Figure 1 is a perspective view of the heat exchanger according to the present invention, showing the housing with the tube bundle and the two refrigerant inlet and outlet conduits;
• the Figure 2 is a perspective view of a tube, showing the transverse protuberance and the support projections;
• the Figure 3 is a profile view of a tube with a single transverse protuberance, according to one embodiment of the invention;
• the Figure 4 is a profile view of the tube with two transverse protuberances disposed on opposite sides, according to another embodiment of the invention;
• the Figure 5 is a perspective view of the heat exchanger of the Figure 1 , showing a longitudinal sectional plane T; and
• the Figure 6 is a longitudinal section of the heat exchanger along sectional plane T shown in FIG. Figure 5 .

Description of a preferred embodiment

If we go back to Figure 1 , the heat exchanger 1 for gas, in particular for the exhaust gases of an engine, according to the present invention is of the type which comprises a plurality of parallel tubes 2 of substantially rectangular section, arranged inside a housing 3, through which circulate the gases to be cooled by heat exchange with a cooling fluid. Similarly, it comprises two inlet ducts 4 and 5 of coolant outlet arranged at the opposite ends and in one and the same side of said casing 3.

As can be discerned on the Figure 2 each tube 2 comprises a transverse protuberance 6 with respect to the direction of the gases, situated, starting from one of its ends, at a distance of approximately one-third of the length of the tube.

The tubes 2 may comprise a single transverse protuberance 6 located on one of their faces (see Figure 3 ) or may comprise two transverse protuberances 6 located on the opposite faces of the tube 2 (see Figure 4 ).

Each tube 2 also comprises a plurality of projections 7 of circular section distributed along the tube 2, intended for support and assembly between the adjacent tubes 2, which in turn delimit a predetermined space between the tubes 2 for the passage refrigerant.

On the Figure 6 there is shown a longitudinal section of the heat exchanger 1 according to a sectional plane T illustrated on the Figure 5 . In this case, the tubes 2 are assembled by stacking one on the other and oriented so that the upper half of the tube bundle 2 has its respective transverse protuberances 6 located at a distance from to about a third of the length of the tube 2 relative to the gas inlet, thereby defining a first vertical transverse barrier 6a, while the lower half of the tube bundle 2 has its respective transverse protuberances 6 at a distance of approximately two thirds of the length of the tube 2 relative to the gas inlet, thus defining a second vertical transverse barrier 6b. In this way, the two transverse barriers 6a and 6b define a "Z" -shaped path for the coolant flow, as shown by the arrows shown in FIG. Figure 6 .

In this case, the coolant inlet duct 4 is situated in the upper part at one end of a lateral face of the casing 3, upstream of said first transverse barrier 6a, while the refrigerant outlet duct 5 is located in the lower part of the opposite end of the same side face of the housing 3, downstream of said second transverse barrier 6b.

The above-mentioned deflecting effect is obtained thanks to the contact between the transverse protuberances 6 of the respective tubes 2, so that the deflectors or transverse barriers 6a and 6b created force the flow of refrigerant fluid to fill the inside of the exchanger 1 in all the directions, but with an appropriate distribution of the refrigerant flow from the inlet 4 to the outlet 5 of refrigerant, thus avoiding a direct flow of coolant flow from the inlet to the outlet thereof. In addition, the flow generated within the housing has a "Z" shape, which differs completely from the refrigerant flow paths in the stacked plate heat exchangers known in the art that utilize a transverse protuberance.

Although reference has been made to a concrete embodiment of the invention, it is obvious to a person skilled in the art that the heat exchanger for gas, in particular for the exhaust gases of an engine, is described here. is subject to many variations and modifications and that all the details mentioned may be replaced by other technically equivalent ones, without departing from the scope of protection defined by the appended claims.

Claims (4)

1. Gas heat exchanger (1), in particular for the exhaust gases of an engine, that includes a plurality of parallel tubes (2) that are arranged inside a casing (3) and through which flow the gases to be cooled by heat exchange with a coolant, and in which the coolant inlet and outlet conduits (4, 5) are each arranged at an opposing extremity of the casing (3), preferably on a single side of said casing (3), wherein each tube (2) has a protuberance (6) opposing the direction of the gases, it being possible to assemble said tubes (2) by stacking same on one another such that the protuberances (6) of the respective tubes (2) form a barrier (6a, 6b), in the form of a deflector, intended to create a predetermined pathway guaranteeing an appropriate distribution of the coolant flow from the inlet (4) of same to the outlet (5) of same about the tubes (2) and along the entire length of the exchanger (1), and wherein the parallel tubes (2) have a substantially rectangular section, each tube (2) having a protuberance (6) transverse to the direction of the gases, such that said transverse protuberances (6) of the respective tubes (2) form a substantially vertical transverse barrier (6a, 6b), characterized in that the tubes (2) are oriented such that the respective transverse protuberances (6) of the top half of the set of tubes (2) are located at a distance of approximately one third of the length of the tube (2) from the gas inlet, thereby forming a first vertical transverse barrier (6a), while the respective transverse protuberances (6) of the bottom half of the set of tubes (2) are located at a distance of approximately two thirds of the length of the tube (2) from the gas inlet, thereby forming a second vertical transverse barrier (6b), such that the two transverse barriers (6a, 6b) form a Z-shaped pathway for the coolant flow, the coolant inlet conduit (4) being located in the upper portion at one extremity of a side face of the casing (3), upstream of said first transverse barrier (6a), and the coolant outlet conduit (5) being located in the lower portion of the opposing extremity of the same side face of the casing (3), downstream of said second transverse barrier (6b).
2. Exchanger (1) according to Claim 1, characterized in that each tube (2) has just one transverse protuberance (6) located on one of the faces of same.
3. Exchanger (1) according to Claim 1, characterized in that each tube (2) has two transverse protuberances (6) located on opposing faces of the tube (2).
4. Exchanger (1) according to Claim 1, characterized in that each tube (2) has a plurality of projections (7), preferably of circular section, that are distributed along the tube (2) and used to support and assemble adjacent tubes (2) on one another, said tubes (2) in turn delimiting a predetermined space between the tubes (2) for the coolant to pass through.

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