HEAT EXCHANGER FOR GASES , ESPECIALLY ENGINE EXHAUST

GASES

Technical sector

The present invention in general relates to a heat exchanger for gases, especially engine exhaust gases, which comprises a set of heat transfer elements designed for the circulation of exhaust gases and, more particu larly, to a heat exchanger in which the set of heat transfer elements includes two or more heat transfer element subsets of different lengths and/or offset spatially relative to one another in a longitudinal direction .

The invention applies especially to engine exhaust gas recirculation exchangers ("Exhaust Gas Recirculation Coolers" (EGRC) ) .

Prior art

The principle function of EGR exchangers is the exchange of heat between exhaust gases and the coolant fluid in order to cool the gases.

EGR heat exchangers are currently widely used for diesel applications with a view of reducing emissions and are also used in gasoline applications to reduce fuel consumption .

There is a trend on the market to reduce engine size and to use EGR heat exchangers not only in high-pressure (HP) applications but also in low-pressure (LP) applications, both having an impact on the design of the EGR heat exchangers. Vehicle manufacturers require EGR heat exchangers with higher levels of performance and at the same time the space available for fitting the exchanger and its components is increasingly small and more difficult to integrate.

The restriction on the space available for the engine components determines the functionality thereof. This is the case of EGR heat exchangers, since it may be that the space available for a specific application does not enable the exchanger to achieve the functional objective of thermal efficiency and/or pressure drop.

The basic configuration of an EGR heat exchanger is determined by its set of heat transfer elements (tubes, plates or plates plus disrupter) that provide the corres ponding function. The number, length and design of these heat transfer elements is key in terms of the function to be performed. The casing that contains this set of heat transfer elements normally has a rectangular or circular form, although it may also be irregular, if necessary, in order to increase its capacity. Thus, this form determines the cross section and therefore the number of heat transfer elements. As for the length, known applications have an end support plate (or similar) at the end of each side of the casing. In the prior art, this plate means that there is a constant length for all the heat transfer elements. This length is limited by the most restrictive part of the environment, i.e. the space in which the exchanger is to be mounted. The length closely relates to the thermal efficiency achieved.

For that reason, prior art heat exchangers envisaged for fitting in small spaces of this type have their function limited by their implementation in the engine.

It is necessary to offer an alternative to the prior art that makes it possible to cover the gaps found therein, providing a heat exchanger that is able to adapt to the restrictions on space where it is to be located, with greater flexibility than known prior art heat exchangers, with a view to providing greater thermal efficiency.

Explanation of the invention

To that end, the present invention relates to a heat exchanger for gases, especially for engine exhaust gases, which, in a manner known per se, comprises: a set of heat transfer elements designed for the circulation of the exhaust gases; a casing with the form of a hollow elongate body that extends along a longitudinal direction and that is open at its respective opposite ends, which accommodates, within, said set of heat transfer elements, and which comprises an inlet port and an outlet port for coolant fluid for the circulation of a coolant fluid through the interior of the casing in contact with the heat transfer elements of the set of heat transfer elements for the heat exchange with the exhaust gases circulating therethrough; and a first and a second support plate coupled respectively to an inlet end and an outlet end for gases of said casing, the ends of the heat transfer elements of said set of heat transfer elements being attached to said first and second support plates such that they communicate with the exterior of the casing via through-holes therein.

Unlike exchangers known in the prior art, in the exchanger proposed by the present invention, the set of heat transfer elements comprises at least a first subset of heat transfer elements formed by heat transfer elements of a first determined length and a second subset of heat transfer elements formed by heat transfer elements of a second determined length, arranged in parallel and such that at least one of the ends of the heat transfer elements of the first subset extends further than one of the ends of the heat transfer elements of the second subset in said longitudinal direction.

According to one illustrative embodiment, the second determined length is less than the first determined length .

For one alternative illustrative embodiment, the second determined length is equal or substantially equal to the first determined length such that a second end of the heat transfer elements of the second subset extends further than a second end of the heat transfer elements of the first subset in said longitudinal direction, or, in other words, both subsets are spatially offset relative to one another in the longitudinal direction.

In accordance with one preferred illustrative embodiment, at least one of the aforesaid first and second support plates comprises at least a first plate portion and a second plate portion that are distanced in a stepped manner, the first plate portion being attached to ends of the heat transfer elements of the first subset of heat transfer elements and the second plate portion being attached to ends of the heat transfer elements of the second subset of heat transfer elements.

For another illustrative embodiment, applied to the case where the second determined length is less than the first determined length, when both ends of the heat transfer elements of the first subset extend further than the corresponding ends of the heat transfer elements of the second subset, in said longitudinal direction, not only the first but also the second support plate is configured as indicated in the above paragraph, i.e. with plate portions distanced in a stepped manner. For another illustrative embodiment, applied to the case described above where the second determined length is equal or substantially equal to the first determined length such that both subsets of heat transfer elements are spatially offset relative to one another in the longitudinal direction, not only the first but also the second support plate has the aforesaid first and second plate portions distanced in a stepped manner, where the distance between the first plate portions of the first and the second support plate is equal or substantially equal to the distance between the second plate portions of the first and the second support plate. In general, the ends of the heat transfer elements are attached (normally, welded) to the contour of said through-holes such that the aforesaid communication between them and the exterior of the casing is produced. According to one illustrative embodiment, the first and the second determined length differ at most by 30%.

According to one preferred illustrative embodiment, the set of heat transfer elements is a tube bundle and the above-mentioned first and second subsets of heat transfer elements are a first and a second tube sub bundle, respectively .

Alternatively, for another illustrative embodiment, the set of heat transfer elements is a set of stacked plates and the first and second subsets of heat transfer elements are a first and a second subset of stacked plates, respectively. According to one illustrative embodiment, at least some of the heat transfer elements of the first subset occupy a first volume of the interior of the casing and the heat transfer elements of the second subset occupy at least a first volumetric portion of a second volume of the interior of the casing, where at least said first volumetric portion is adjacent to said first volume.

For a variant of said illustrative embodiment where the second determined length is smaller than the first deter mined length, at least the first volumetric portion is shorter, in the aforesaid longitudinal direction, than the first volume.

According to an implementation of said illustrative embodiment, the heat transfer elements of the second subset completely occupy the aforesaid second volume of the interior of the casing.

However, in an alternative manner, for another implement ation of said illustrative embodiment, some of the heat transfer elements of the first subset occupy a second volumetric portion of the aforesaid second volume of the interior of the casing, where said second volumetric portion is substantially equal in length, in said longitudinal direction, to the first volume and is not spatially offset with respect thereto in the aforesaid longitudinal direction.

The first and second volumes are separated, according to one illustrative embodiment, by an imaginary parting line that completely traverses the casing longitudinally, such that, for example, the first volume occupies a larger space of the interior of the casing and the second a smaller space, or vice versa, or the aforesaid first and second volumes occupy different lateral spaces of the interior of the casing.

For one illustrative embodiment, both the first and second plate portions have some of the abovementioned through-holes, are arranged in the manner of a tread and are connected by at least one connection plate portion arranged in the manner of a riser and that lacks through- holes.

According to one implementation of said illustrative embodiment, said connection plate portion arranged in the manner of a riser has a planar form, such that the arrangement of (first, second and connection) plate portions forms a single step.

Alternatively, for another implementation of said illust rative embodiment, the connection plate portion arranged in the manner of a riser is formed by two planar plate subportions arranged perpendicularly relative to one another, forming an angle, or, in other words, the arrangement of the (first, second and connection) plate portions forms a double step, in two perpendicular directions .

According to one illustrative embodiment, the height of the connection plate portion, in a direction perpendi cular to the first and second plate portions, is equal to or greater than 3 mm.

For one illustrative embodiment, the heat transfer elements of the first subset are separated from the respective adjacent heat transfer elements of the second subset, in a determined direction, by a predetermined distance that has a value preferably of at least twice and at most ten times the thickness of the first support plate, and is greater than a separating distance, also in said determined direction, that exists between the heat transfer elements of the first subset. This illus trative embodiment relates to the case where there is no deflector between the two subsets of heat transfer elements .

For another illustrative embodiment, the heat exchanger according to the present invention comprise a deflector arranged in the interior of the casing extending in the aforesaid longitudinal direction between the heat trans fer elements of the set of heat transfer elements, the heat transfer elements of a grouping of heat transfer elements that are adjacent to a side of the deflector being separated, in a direction perpendicular to the deflector, from those of another grouping of heat trans fer elements that are adjacent to the other side of the deflector by a predetermined distance that has a value preferably at least twice and at most ten times the thickness of the first support plate plus the value corresponding to the thickness of the deflector and is greater than a separation distance, also in said direction perpendicular to the deflector, between the heat transfer elements of both of said groupings of heat transfer elements.

For one illustrative embodiment, the exchanger of the present invention comprises at least one gas conveying unit (in general, a gas tank and/or connection flange) coupled to the end of the casing to which the support plate that includes the above-mentioned first and second plate portions distanced in the form of a step is coupled.

Brief description of the drawings

The above and further advantages and features will be more fully understood on the basis of the following detailed description of illustrative embodiments with reference to the attached drawings, which should be taken as an illustration and not a limitation, in which:

Figure 1 is an expanded perspective view that shows the exchanger proposed by the present invention, for one illustrative embodiment; Figure 2 is a perspective view that shows the exchanger proposed by the present invention once mounted, for one illustrative embodiment;

Figure 3 is a view in lateral elevation of a cross section through a parting line traversing the heat exchanger of Figure 2, passing through both inlet and outlet coolant fluid line;

Figure 4 is a perspective view of a cross section similar to that of Figure 3, for the same illustrative embodi ment ;

Figure 5 is a perspective view of one of the support plates of the exchanger of the present invention, for an illustrative embodiment where the latter adopts the form of a double step, unlike the illustrative embodiment in Figures 1, 3, and 4;

Figures 6a and 6b are, respectively, a perspective view and a view in lateral elevation of one of the support plates of the exchanger of the present invention, which also adopts the form of a double step, but, unlike that of Figure 5, this is an embodiment attached to a longi tudinal deflector to be inserted in the interior of the casing;

Figure 7 is a perspective view that shows the exchanger proposed by the present invention once mounted, for another illustrative embodiment;

Figure 8 is a view in lateral elevation of a cross section through a parting line traversing the heat exchanger of Figure 7, in a vertical direction (in accordance with the position illustrated) ; and Figure 9 is a perspective view of a portion of the heat exchanger sectioned transversely in a manner similar to Figure 8, for the same illustrative embodiment. Detailed description of illustrative embodiments

As may be seen from the attached figures, especially Figures 1, 3, 4, 8 and 9, the present invention relates to a heat exchanger for gases, especially engine exhaust gases, which comprises: a set of heat transfer elements designed for the circulation of the exhaust gases, which, for the illustrative embodiments shown, is a tube bundle that includes a first T1 and a second T2 tube subbundle; a casing B with the form of a hollow elongate body that extends along a longitudinal direction and that is open at its respective opposite ends Ba, Bb, which accommodates, within, both tube subbundles Tl, T2, and which comprises an inlet port Oe and an outlet port Os for coolant fluid that are connected to respective ducts Rl, R2, for the circulation of a coolant fluid through the interior of the casing

B in contact with the tube subbundles Tl, T2 for the heat exchange with the exhaust gases circulating therethrough; and - a first PI and a second P2 support plate coupled respectively to an inlet end Ba and an outlet end Bb for gases of the casing B, the ends of the tubes of the tube subbundles Tl, T2 being attached to the first PI and second P2 support plates such that they communicate with the exterior of the casing B via through-holes A therein.

For the illustrative embodiments illustrated in Figures 1, 3, 4, 8 and 9, the tubes of the first tube subbundle T1 have a length greater than that of the tubes of the second tube subbundle T2, and are arranged in parallel and such that one of the ends of the tubes of the first subbundle T1 (the left-hand end, according to the position illustrated in the figures) extends further than one of the ends of the tubes of the second subbundle T2, according to the above-mentioned longitudinal direct ion .

Figures 1, 3, 4, 5, 6a, 6b, 8 and 9 illustrate different illustrative embodiments where the first support plate PI comprises a first plate portion Pla and a second plate portion Plb that are distanced from one another in a stepped manner.

As illustrated in Figures 3, 4, 7 and 8, the first plate portion Pla is attached to ends of the tubes of the first tube subbundle T1 and the second plate portion Plb is attached to ends of the tubes of the second subbundle T2.

For the illustrative embodiments illustrated in Figu res 1, 3, 4, 7 and 8, all the tubes of the first subbundle T1 occupy a first volume of the interior of the casing B (greater volume in Figures 1, 3 and 4 and smaller volume in Figures 7 and 8) and the tubes of the second subbundle T2 fully occupy a second volume of the interior of the casing B (smaller volume in Figures 1, 3 and 4 and greater volume in Figures 7 and 8), where the second volume is adjacent to and shorter, in the aforesaid longitudinal direction, than the first volume.

For such illustrative embodiments illustrated in Figu res 1, 3, 4, 7 and 8, it may be seen how both of the first Pla and second Plb plate portions have some of the through-holes A, are arranged in the manner of a tread and are connected by a connection plate portion Pic arranged in the manner of a riser, which lacks through- holes and has a planar form. For these illustrative embodiments, the support plate PI adopts a single step form.

Alternatively, for the illustrative embodiment illustra ted in Figures 5, 6a and 6b, the support plate PI adopts a double step form in accordance with two perpendicular directions, since the first Pla and second Plb plate portions (which also have some of the through-holes A) are also arranged in the manner of a tread but are connected by a connection plate portion Pic arranged in the manner of a riser (which also lacks through-holes) , but which in turn is formed by two planar plate sub portions arranged perpendicularly relative to one another, forming an angle, in this case a right angle.

Although not illustrated, for one illustrative embodiment of the heat exchanger that includes the first plate PI, such as that illustrated in Figure 5 or that of Figu res 6a and 6b, the tubes of the second subbundle T2 do not occupy the entire second volume of the interior of the casing B but only a first volumetric portion thereof, which is adjacent to and shorter, in the longitudinal direction, than the first volume, and the tubes of the first subbundle T1 do not occupy only the first volume but also occupy part of the second volume, in particular a second volumetric portion thereof that is substantially equal in length, in the longitudinal direction, to the first volume.

In this case, the first volumetric portion of the second volume would correspond to that which is adjacent to the second plate portion Plb, and the second volumetric port ion of the second volume and all the first volume would correspond to the space adjacent to the first plate portion Pla.

In addition, Figures 1 to 4 and 7 to 9 illustrate corres ponding gas tanks Gl, G2 respectively coupled to the ends Ba and Bb of the casing B, and also connection flanges FI, F2 in turn coupled to the gas tanks Gl, G2.

It can also be seen, especially in Figure 1, how the end Ba of the casing B has a form adapted to that of the first plate PI, i.e. with a recessed zone in the lower portion thereof (according to the position illustrated) provided for the coupling of the second plate portion Plb, and how the gas tank Gl also has a lower recessed portion adjacent to the second plate portion Plb such that it can be located in a smaller space than the upper portion of the gas tank Gl .

For one illustrative embodiment where the exchanger does not include a deflector arranged between both tube sub bundles Tl, T2, as is the case of that illustrated in Figures 8 and 9, or one that includes the first plate PI of Figure 5, a distance "d" is defined, which, as may be seen in Figure 5, corresponds to the separation between the through-holes A located in the first plate portion Pla adjacent to and above (according to the position illustrated) the plate portion Plcl (or Pic if this is a single step such as that of Figure 1) and the through- holes A located in the second plate portion Plb adjacent to and below the plate portion Plcl (according to the position illustrated) . Said distance "d" has a value of at least twice and at most ten times the thickness of the first plate PI .

On the other hand, for an illustrative embodiment where the exchanger does indeed include a deflector D arranged between both tube subbundles Tl, T2, such as that illus trated in Figure 1 or that illustrated in Figures 6a and 6b, the distance between the above-mentioned through- holes located on either side of the plate portion Plcl (or Pic if this is a single step such as that of Figure 1) is equal to "d+x", where x is equal to the thickness of the deflector D. Obviously, said distances "d" or "d+x" will also be the distances of separation between the tubes inserted in the above-mentioned through-holes A.

The person skilled in the art would be able to introduce changes and modifications to the illustrative embodiments described without departing from the scope of the invent ion as defined in the attached claims, the aforesaid possible modifications including, for example, other forms, another number and/or other dimensions (absolute and/or relative) of the various elements that make up the exchanger of the present invention.