Heat exchange device for exchanging heat between fluids
09671170 ยท 2017-06-06
Assignee
Inventors
- Xoan Xose Hermida Dominguez (Gondomar, ES)
- Alvaro Sanchez Ragnarson (Gondomar, ES)
- Jose Alberto Blanco Fernandez (Virgo, ES)
- Jose Luis Souto Martinez (Gondomar, ES)
Cpc classification
F28F2009/029
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F2240/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28D9/0081
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F21/084
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F2255/16
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F2275/04
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28D7/0066
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F2009/226
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F9/026
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F9/0219
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28D7/1692
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28D21/0003
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28D7/1684
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28D9/0062
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F21/089
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F2235/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F2225/08
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F02M26/32
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
International classification
F28F3/08
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F9/02
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28F21/08
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28D7/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F28D21/00
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
F02M26/32
MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
Abstract
The present invention relates to a heat exchange device for exchanging heat between two fluids circulating through insulated conduits. In the preferred example the first fluid is a hot gas originating from an exhaust gas recirculation (EGR) system, and the second fluid is a coolant liquid used for removing heat from the hot gas. The device according to the invention has a simple and cheap construction, lacking a shell, formed by a plurality of extruded aluminum profile segments attached by clad plates arranged perpendicularly giving rise to a very compact and light-weight configuration when it is in an operating mode.
Claims
1. A heat exchange device (1) for EGR systems with heat exchange between a first fluid, preferably an EGR gas, circulating through a conduit and a second fluid, preferably a coolant liquid, circulating through a second conduit, where said device is intended for being intercalated between both conduits and comprises: a plurality of extruded aluminium profile segments (1.1) such that: they preferably extend according to a longitudinal direction (X), they have one or more closed inner cavities (1.1.1) giving rise to conduits in the longitudinal direction (X) of the profile intended for conducting the first fluid; and where, this plurality of segments (1.1) are arranged distributed along a direction (Z) transverse to the longitudinal direction (X) and spaced from one another, a first perforated or grooved clad aluminium plate (1.2), i.e., having a layer of aluminium with a melting point lower than the rest of the aluminium of the same plate on at least one of its surfaces, where the perforations (1.2.1) or grooves are suitable for housing one of the ends of the plurality of profile segments (1.1) such that said first plate (1.2) is essentially perpendicular to such profile segments, and where such perforations (1.2.1) or grooves have a configuration according to the section of the profile segments (1.1) which they house, a second (1.3) and a third (1.4) clad aluminium plate where, the second plate (1.3) is in the form of a perimetric ring and is intended for surrounding the plurality of profile segments (1.1), the third plate (1.4) is perforated or grooved, where the perforations (1.4.1) or grooves are suitable for housing the ends of the plurality of profile segments (1.1) opposite the end where the first plate (1.2) is located according to the longitudinal direction (X), and where such perforations (1.4.1) or grooves have a configuration according to the section of the profile segments (1.1) which they house, where both the second (1.3) and the third (1.4) plates are essentially perpendicular to such profile segments (1.1), a first side clad plate and a second side clad plate (1.6, 1.7) extending between the first aluminium plate (1.2) and the second aluminium plate (1.3) and are (1.6, 1.7) suitable for covering the sides of the profile segments (1.1) defining intermediate chambers between consecutive profile segments (1.1), where: the attachment between the side plates (1.6, 1.7) and the profile segments (1.1); and the attachment between the first plate (1.2), the second plate (1.3) and the third plate (1.4) with the profile segments (1.1) is by means of melting the aluminium with lower melting point of the clad plates, at the end of the profile segments (1.1) according to the longitudinal direction (X) where the third plate (1.4) is located, the intermediate chambers between consecutive profile segments (1.1) are in communication with a main chamber (C) which in turn is in communication with connection means (1.5.1, 1.7.1) for the entry/exit of the second fluid; and the device comprises connection means (1.6.1) for connecting with the conduit of the second entering/exiting fluid, where such connection means (1.6.1) have access to the intermediate chambers between the profile segments (1.1); where these connection means (1.6.1; 1.5.1, 1.7.1) allow intercalating the device (1) in the conduit of the second fluid; and, the first plate and the third plate (1.2, 1.4) comprise connection means which allow intercalating the device (1) in the conduit of the first fluid where the connection means of the third plate (1.4) correspond to the inlet of the first fluid and the connection means of the first plate (1.2) correspond to the outlet of the first fluid; and, wherein a tubular distribution body (1.5) is located between the second plate (1.3) and the third plate (1.4), according to the longitudinal direction (X), where the inner face of this tubular distribution body (1.5) is separated at least in one region of the tube segments (1.1) giving rise to the main chamber (C) such that at least one portion of the profile segments (1.1) is housed inside the tubular distribution body (1.5) between the second plate (1.3) and the third plate (1.4).
2. The device according to claim 1, characterized in that the tubular distribution body (1.5) is located between the second plate (1.3) and the third plate (1.4) such that said plates are spaced by said tubular body (1.5).
3. The device according to claim 2, characterized in that it comprises a manifold (1.10) preferably having a conical configuration coupled to the third plate (1.4).
4. The device according to claim 1, characterized in that in at least one outer face of the group of profile segments (1.1) there is a clad plate adjacent to said outer face, being interposed between the profile segments (1.1) and the inner edge of any of the first plate (1.2), second plate (1.3) or third plate (1.4) for improving the attachment.
5. The device according to claim 1, characterized in that the tubular distribution body (1.5) comprises connection means (1.5.1) for the entry/exit of the second fluid where such connection means (1.5.1) have access to the main chamber (C) inside said tubular distribution body (1.5).
6. The device according to claim 1, characterized in that the perimetric surface of the portion of the profile segments (1.1) located between the second plate and the third plate (1.3, 1.4) is inside the inner main chamber (C) of the tubular distribution body (1.5), where the chamber (C) is suitable for distributing the second fluid around said portion of profile segments (1.1).
7. The device according to claim 1, characterized in that the tubular body (1.5) is elongated according to the longitudinal direction (X), in the entry direction of the first fluid by means of an intake manifold (1.10) defining a second chamber (CC) therein such that: the intake manifold (1.10) connecting the inlet of the first fluid and the third plate (1.4) for directing the first fluid from the inlet to the closed inner cavities (1.1.1) of the profile segments (1.1) is housed inside the second chamber (CC), the second chamber (CC) is mainly located between the tubular body (1.5) and the intake manifold (1.10) arranged internally for allowing the perimetric distribution of the second fluid, the second chamber (CC) and the main chamber (C) are communicated with one another for transferring the second fluid between the chamber (CC) and the main chamber (C) mainly according to a longitudinal direction (X), the connection means (1.5.1) for the entry/exit of the second fluid into the tubular body (1.5) have access to the second chamber (CC).
8. The device according to claim 1, characterized in that the profile segments (1.1) have an essentially planar configuration with a preferably rectangular section.
9. The device according to claim 5, characterized in that the connection means (1.5.1) for connecting with the tubular distribution body (1.5) have the inlet/outlet contained in a plane parallel to that defined by the profile segments (1.1).
10. The device according to claim 1, characterized in that it comprises a comb-shaped clad baffle plate (1.8) with at least one main body (1.8.1) and one or more transverse prolongations (1.8.2) such that the main body (1.8.1) is located on the side of the profile segments (1.1) arranged on the side of the inlet/outlet (1.5.1, 1.7.1) of the second fluid and the transverse prolongations (1.8.2) are located between consecutive profile segments (1.1) for distributing the flow of the second fluid throughout the transverse section in the cavities through which said fluid circulates.
11. The device according to claim 10, characterized in that the baffle plate (1.8) is arranged parallel to the second plate (1.3).
12. The device according to claim 10, characterized in that the baffle plate (1.8) is arranged obliquely with the ends of its prolongations (1.8.2) oriented towards the third plate (1.4).
13. The device according to claim 10, characterized in that the baffle plate (1.8) is arranged spaced from the second plate (1.3).
14. The device according to claim 1, characterized in that the second plate (1.3) comprises internal prolongations (1.3.1) located between consecutive profile segments (1.1) for distributing the flow of the second fluid in the cavities through which said fluid circulates.
15. The device according to claim 1, characterized in that the connection means (1.6.1) for connecting with the side plate (1.6) comprise a tubular body attached to the side plate (1.6) by means of a bulked area (1.6.2) such that the bulked area (1.6.2) defines an inner cavity facilitating the access from the tubular body to the cavities located between profile segments (1.1).
16. The device according to claim 15, characterized in that the tubular body of the connection means (1.6.1) is oriented towards the first plate (1.2).
17. An EGR system comprising a heat exchanger according to any of the preceding claims.
18. A vehicle comprising an EGR system according to claim 17.
Description
DESCRIPTION OF THE DRAWINGS
(1) These and other features and advantages of the invention will become more apparent from the following detailed description of the preferred embodiments given only by way of illustrative and non-limiting example in reference to the attached drawings.
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DETAILED DESCRIPTION OF THE INVENTION
(16) The invention is described in a more detailed manner using three embodiments containing, in addition to the essential technical features, other features each giving rise to a shell-less device which can mostly be manufactured by means of welding by passing through an oven to attach the clad parts and which is lightweight in operating mode. Some of the parts, especially when they have a high Mg content are able to be welded for example by means of CMT or TIG welding.
(17) In the three embodiments it is considered that the first fluid to be cooled is a hot gas which originates from a combustion engine and which will be reintroduced into the intake manifold according to an EGR system after being cooled. The coolant fluid is a liquid responsible for removing heat from the hot gas. Both fluids are transported by means of conduits between which the device is intercalated for transferring the heat of the hot gas to the coolant liquid.
(18) However, this is not the only application of this heat exchanger. The first embodiment of the invention, for example, is particularly light-weight and suitable for cooling hot gas which is not at a temperature as high as that of the EGR gas. This is the case of the gas compressed in two steps in a turbo-charged engine. An intermediate cooling is required to go from the first compression step to the second compression step for reducing its density. The first embodiment solves this technical problem by providing a particularly compact and light-weight heat exchanger.
(19) The device according to this embodiment is shown by the components in the exploded perspective view of
(20) The main structure comprises a plurality of extruded aluminium profile segments (1.1) showing a cell structure (1.1.1) intended for the passage of the gas to be cooled therein.
(21) In this embodiment the profile segments are configured according to a rectangular section and are arranged parallel and spaced from one another leaving a space which in an operating mode is occupied by the coolant liquid.
(22) The attachment between profile segments (1.1) is assured by three plates, a first plate (1.2), a second plate (1.3) and a third plate (1.4).
(23) The parallel arrangement between profile segments (1.1) and the spacing therebetween is mainly defined by the two plates arranged at the ends: the first plate (1.2) and the third plate (1.4). These plates (1.2, 1.4) have perforations (1.2.1, 1.4.1) corresponding with the section of the profile segments (1.1) such that the ends of the profile segments (1.1) are housed in said perforations (1.2.1, 1.4.1) after the assembly. The perforations (1.2.1, 1.4.1) can preferably be obtained by means of die-cutting. The surfaces generated by die-cutting are those contacting the perimetric surface of the end of the profile segment (1.1) corresponding to the plate (1.2, 1.4) housing said end.
(24) The second plate (1.3) is ring-shaped given that it is die-cut for coinciding with the perimetric configuration of the assembly of profile segments (1.1). In this case the perimetric shape is rectangular.
(25) The spaces between the profile segments (1.1) are laterally closed by means of a first (1.6) and second (1.7) side clad plate. These side plates (1.6, 1.7) longitudinally elongate from the first plate (1.2) to the second plate (1.3); and transversely extend enough so as to cover the openings between the profile segments (1.1) to thus form inner chambers for the passage of the coolant liquid.
(26) According to this embodiment, the entry and exit of the coolant liquid has been simply achieved generating, by forming, a conical area (1.6.2, 1.7.2) on the elongated side plates (1.6, 1.7) by means of connecting the inlet (1.7.1) and outlet (1.6.1) of the coolant liquid.
(27) The conical configuration allows the inlet conduit and outlet conduit to be in communication with all the cavities arranged between the profile segments (1.1). In this embodiment, using clad plates with the aluminium surface of reduced temperature oriented towards the group of profile segments (1.1) allows the leak-tightness of all the contacting surfaces and particularly of the coolant liquid circuit.
(28) In the case of the conical configuration (1.7.2), a coolant liquid distribution chamber (C) allowing the homogenous entry of flow into all the intermediate chambers between the profile segments (1.1) is internally obtained in the side plate (1.7) corresponding to the inlet conduit.
(29) The other leak-tight attachments which are attached are those corresponding to the die-cut surfaces of the perforations (1.2.1, 1.4.1) of the first plate (1.2) and third plate (1.4), as well as the inner rectangular perforation of the second plate (1.3) with the outer surfaces of the group of profile segments (1.1). The three clad plates (1.2, 1.3, 1.4) perpendicularly intersect with the group of profile segments (1.1); nevertheless, it has been proven that the aluminium adjacent to the contact area of the wet profile segments (1.1) melts when passed through the oven and that the attachment of the die-cut area and the profile segment (1.1) is assured after cooling.
(30) The hot gas enters through the same end of the exchanger in which the coolant liquid inlet is located when used in concurrent flow. The hotter end is thus cooled by the coldest liquid. When used in countercurrent, the hot gas inlet contacts an area where the coolant has a homogenous distribution. In both cases the possibility of hot spots is reduced.
(31) The hot gas enters through a conical-shaped intake manifold (1.10). This first embodiment has a particularly light-weight structure therefore the attachment with the intake manifold (1.10) has been reinforced. The intake manifold (1.10) is usually made of stainless steel. In this embodiment, instead of screwing the intake manifold (1.10) with a stiff part, given that the attachment of the second and third aluminium plates (1.3, 1.4) is not stiff enough, it is screwed to a pair of L-shaped stiffening parts (1.13) arranged on the other side of the assembly of plates formed by the second plate (1.3), the third plate (1.4) and an attachment gasket (1.14). In this embodiment, an additional fourth plate (1.15) made of stainless steel which is welded to the intake manifold (1.10) has been incorporated to assure the support of the attachment gasket (1.14) with the seat of the intake manifold (1.10)
(32) The shape of the L-shape parts (1.13) which are two in number allow the insertion after having weld the components of the heat exchanger such that each L-shaped part (1.13) enters through one side until it is located behind the bundle formed by the second plate (1.3), third plate (1.4) and fourth plate (1.15) and the gasket (1.14). The four elements are not stiff enough for the attachment, therefore the stiff L-shaped parts (1.13) assure a good attachment with the intake manifold (1.10) by means of screws (1.10.1).
(33) The gas exits at the opposite end, where an outlet manifold (1.11) collects the gases which have passed through each of the profile segments (1.1). In this embodiment, the manifold (1.11) is an aluminium moulded part suitable for encircling or at least housing the ends of the profile segments (1.1). The first plate (1.2) is not flush with the ends of the profile segments (1.1), but is slightly out-of-flush so as to allow fitting the manifold (1.11) coinciding with the perimetric shape of the group of profile segments (1.1). The position of the first plate (1.2) is such that the manifold (1.11) contacts the side surface of the first plate (1.2) at least in its perimetric edge. When the manifold (1.11) is made of moulded aluminium with a high Mg content the manifold (1.11) and the first plate (1.2) can be attached by means of CMT welding or alternatively by TIG welding.
(34) In this embodiment, ancillary clad plates (1.12) have been used arranged on the outer face of the externally arranged profile segments (1.1) that are tightly fitted in its edge to the third plate (1.4). This solution is applicable to those points of the perpendicular attachment to be reinforced. To a larger extent, it can also assure the leak-tightness of the attachment since the melting in the tight fitting edge of the ancillary plate (1.12) contributes to the improved attachment of the third plate (1.4) located perpendicularly.
(35) In view of
(36) The lower right corner which is shown in
(37) According to this embodiment, the deflector (1.8) is located parallel to the second plate (1.3); nevertheless, there are embodiments, which can also be combined with those that will be described below, in which arranging this part (1.8) obliquely is of interest or it can even adopt degrees of curvature which allow modifying the flow which is to be imposed in the inlet of the coolant liquid.
(38) In this embodiment, a specific distance has also been maintained between the start of the chamber (C) and the deflector (1.8) since a part of the entering flow passes through the rear part of the deflector (1.8) thus preventing the deflector from giving rise to stagnation points prone to generating thermal fatigue for example because areas reaching boiling temperatures are produced.
(39) In this embodiment, the outlet of the coolant liquid has been arranged with an inclination (). Adopting angles of inclination also modifies the configuration of stagnation areas. Adopting this angle () allows reducing the stagnation region located at the same end but in the corner of the opposite side, which is shown in the upper left in
(40)
(41) In this embodiment, the same structure as in the first embodiment is reproduced in the profile segments (1.1), in the enclosure established by the side plates (1.6, 1.7) and in the attachment solution at the end of outlet of the first fluid where the outlet manifold (1.11) is located.
(42) The changes are mainly seen at the side where the first fluid, the hot gas, is admitted. According to this embodiment, the second plate (1.3) and the third plate (1.4) are separated from one another by means of a tubular distribution body (1.5). This tubular distribution body (1.5) surrounds the end of the group of profile segments (1.1) in which the second (1.3) and third plate (1.4) are located.
(43) In this embodiment, the tubular distribution body (1.5) defines the chamber (C) therein between its inner walls and the end portion of the profile segments (1.1) located between the second plate (1.3) and third plate (1.4). The spaces existing between the profile segments (1.1) intended for the passage of the coolant liquid even exist in the end portion between the second plate (1.3) and third plate (1.4). The chamber (C) communicates all the spaces or intermediate chambers between profile segments (1.1) facilitating the distribution of coolant liquid after entering the chamber (C).
(44) This chamber (C) has a connection (1.5.1) for allowing connection with the coolant liquid conduits. This connection (1.5.1) corresponds to the coolant liquid inlet when the exchanger operates in a concurrent flow. In this configuration it has particularly been observed that the device has great thermal fatigue strength in countercurrent due to the improved distribution of the coolant liquid in the hot area despite it being slightly hotter.
(45) The connection means (1.5.1) for connecting with the tubular distribution body (1.5) have the inlet contained in a plane parallel to that main plane defined by the profile segments (1.1). This configuration allows making the entry direction of the flow coincide with the direction of the cavities formed between consecutive profile segments (1.1).
(46) The configuration of the chamber (C) and how it allows distributing coolant liquid in each of the spaces defined between profile segments (1.1) is clearly shown to the right of
(47) Likewise, the deflector (1.8), given that the chamber (C) is defined between the second plate (1.3) and the third plate (1.4), is slightly spaced from the second plate (1.3) for allowing a small portion of flow to pass behind eliminating possible stagnation areas caused by the deflector (1.8).
(48) With respect to the first fluid, the gas to be cooled, it enters through the openings of the ends of the profile segments (1.1) according to the direction indicated to the right of
(49) The third plate (1.4) prevents the communication between the inner chamber (C) with the coolant liquid and the space where the hot gas is located since the perforations (1.4.1) housing the ends of the profile segments (1.1) coincide with the segment thereof and the attachment with the third clad plate as described above.
(50) In this second embodiment, the connection with the gas conduit is established by means of a conical-shaped intake manifold (1.10) adapting the tubular configuration of the gas conduit with the perimetric configuration of the assembly formed by the second plate (1.3), the tubular intake body (1.5) and the third plate (1.4). The block formed by these three elements (1.3, 1.5, 1.4) has four screws (1.10.1) for attaching with the intake manifold (1.10). In this embodiment, the screws (1.10.1) traverse the block formed by the three parts identified above: the second plate (1.3), the tubular intake body (1.5) and the third plate (1.4). The seat of the intake manifold (1.10) has of a gasket (1.9) assuring the leak-tightness in the screwed attachment of the intake manifold (1.10). Since the tubular distribution body (1.5) in this embodiment is a stiff enough body, a reinforcement such as the L-shaped parts (1.13) described in the first embodiment is not necessary.
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(52) In this embodiment, there is also a second clad plate (1.3) and a third clad plate (1.4) arranged at the end opposite the end where the first clad plate is located; and such plates are spaced from one another leaving a portion of the ends of the profile segments (1.1) therebetween. When operating in a concurrent flow, the coolant liquid enters between these two plates (1.3, 1.4) and along the entire perimeter.
(53) In this embodiment, there is also a tubular distribution body (1.5) defining the chamber (C) which allows distributing the coolant liquid along the periphery of the portion of the ends of the profile segments (1.1) exposed to this chamber (C); nevertheless, this tubular distribution body (1.5) extends beyond the third plate (1.4) from the second plate (1.3).
(54) As seen in detail in the section of
(55) This second chamber (CC) is mainly located between the tubular body (1.5) and the intake manifold (1.10), now arranged internally, for allowing the perimetric distribution of the coolant liquid. When the exchanger is used in a concurrent flow, it is be observed that the coolant liquid enters through the connection means (1.5.1) located in communication with the second chamber (CC) instead of with the first chamber (C). This distribution has the technical effect of cooling the gas which is still in the intake manifold (1.10) even before reaching the closed inner cavities (1.1.1) of the profile segments (1.1) with the coolant liquid of lower temperature.
(56) The coolant liquid goes into the first chamber (C) once it has reduced the temperature of the gas in the intake manifold (1.10). This is possible because the second chamber (CC) and the main chamber (C) are communicated with one another for transferring the coolant liquid distributed perimetrically in the second chamber (CC) towards the main chamber (C). This communication is essentially according to a longitudinal direction (X) such that the perimetric flow of the coolant liquid which in the second embodiment was towards the second plate (1.3) and the third plate (1.4), is now carried out in the second chamber (CC). Therefore, given that the section of the second chamber (CC) imposing the intake manifold (1.10) is greater, the perimetric distribution of the flow of coolant liquid is better and once it has been distributed perimetrically it goes to the first chamber (C) where it is still allowed to flow perimetrically, if necessary.
(57) As in preceding examples, deflectors (1.8) have also been used in this embodiment, in particular two deflectors arranged opposite one another, and slightly spaced from the second plate (1.3) for preventing stagnation areas.
(58)
(59) This third example requires two separated pieces, the second plate (1.3) and the deflector (1.8) wherein the deflector (1.8) needs extra effort when ensuring its position before entering into the oven.
(60) The forth embodiment only requires one piece, a modified second plate (1.3) comprising internal prolongations having the functionality of the deflector (1.3.1) which partially enter between the profile segments (1.1).
(61) It has been tested that, when the exchanger is used in countercurrent, the hottest point within the second fluid is located at the stagnation point located adjacent to the third plate (1.4); therefore, in some particular conditions, the stagnation point behind the deflector (1.3.1) is not the critical point causing the failure of the device. Under this conditions the forth embodiment is cheaper than the exchanger according to the third embodiment.