US20170131043A1

US20170131043A1 - Heat Exchanger With Reinforced Header Plate

Info

Publication number: US20170131043A1
Application number: US15/322,170
Authority: US
Inventors: Arnaud Contet; Bengt-Ove Birgersson; Ulf Bergman
Original assignee: Titanx Engine Cooling Holding AB
Current assignee: Titanx Holding AB
Priority date: 2014-06-27
Filing date: 2015-06-23
Publication date: 2017-05-11
Also published as: JP2017519181A; SE542001C2; SE1550865A1; WO2015197596A1; BR112016030166B1; BR112016030166A2; EP3161403B1; MX2016017026A; CN106796089A; EP3161403A1; MX389892B

Abstract

The invention relates to a heat exchanger (1) comprising a coolant housing (10) and a header plate (20). The header plate (20) crimps around a border (11) of the coolant housing (10) by encompassing the border (11). The header plate (20) is provided with apertures (22), each aperture (22) receiving a tube (30) for guiding coolant from or to the closed cavity (50). The heat exchanger (1) further comprises a reinforcing plate (40) extending between two opposing crimped locations on the border (11) of the coolant housing (10), and extending on the outside of the header plate (20) in view of the closed cavity (50), wherein the reinforcing plate (40) is joined, at the opposing locations, to an outer surface portion of the header plate (20), and wherein the reinforcing plate (40) is provided with at least one aperture (42) embracing one or more of the tubes (30) received by the header plate (20).

Description

TECHNICAL FIELD

The present invention relates to a heat exchanger and in particular to a heat exchanger of the type comprising a coolant housing, a header plate and a plurality of tubes for transporting coolant from and to the coolant housing. The invention concerns a reinforcement of the heat exchanger in order to withstand high pressures in the coolant housing.

TECHNICAL BACKGROUND

Heat exchangers are used in various applications, such as air conditioners, air compressors, gas turbines, refrigerators, and automotive applications. Heat exchangers for automotive use may be a radiator or a charge air cooler.
Automotive and other heat exchangers may be constructed with a pair of coolant housings which are linked by a core leading a coolant between the coolant housings. The core is typically formed by a plurality of tubes which are located adjacent each other. The tubes may be joined to a header plate which in turn is attached to the coolant housing. The different parts are typically brazed or welded together.
The above exemplified heat exchanger construction can be used for cooling internal combustion engines wherein an engine coolant is circulated through the engine block and thereafter through the heat exchanger where it transfers heat to the through-passing air. The heat exchanger is typically located at an air intake in the front of the vehicle in order to maximize the air flow through the heat exchanger.
The heat exchanger construction may also be provided for cooling air within an engine system between for example a turbocharger and an engine intake.
The coolant pressure may be controlled. By increasing the coolant pressure, vaporization of the coolant can be avoided and the cooling system may thus increase its cooling efficiency. However, an increased coolant pressure puts higher pressure on the mechanical parts of the system, for example on the heat exchanger. In particular, joints between the tubes, the header plate and the coolant housing are exposed to recurrent stress as the coolant pressure repeatedly increases and decreases. In the long run this may cause fatigue and breakdown of the cooling system. One typical area sensitive to fatigue is the joints interconnecting the header plate with the coolant housing since the fluctuating coolant pressure causes the relatively weak coolant housing to repeatedly change dimensions, which changes must be accommodated by the header plate.
One solution to this problem is to reinforce the header plate to make it more rigid. JP9126681 provides an example of a reinforcing clip which is provided on the header plate in a position between the tubes. The free ends of the clips are bent to follow the shape of the header body and clamp against the same. The reinforcing clip is retained by engaging units provided on the header plate. The parts may be brazed to each other. The solution requires modification of the header plate. Further it requires a complex assembly process since multiple reinforcing clips must be oriented and mounted in spaces having a limited access
Thus, there still exists a need for improvement with regards to reinforcement of the components in these types of heat exchangers.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved heat exchanger design, in particular with respect to reinforcement of the header plate.
It is a further object of the invention to provide a heat exchanger which facilitates the production process and which can contribute to cost-efficiency.
The above and other objects are achieved by a heat exchanger according to claim 1.
When pressurized coolant flows through the closed cavity, the walls of the coolant housing tend to bend outward due to the pressure. In particular, the side walls tend to bulge. The inventors have identified portions in the joint between the coolant housing and the header plate which are particularly exposed to fatigue due to such bulging. In order to strengthen the construction, a reinforcing plate is provided. The reinforcing plate is joined to the header plate along the end portion thereof which encompasses the corner between the free edge portion and the outer side surface portion of the border of the coolant housing. Thereby the above mentioned weak portions are strengthened and reinforced so as to increase their resistance to fatigue. The reinforcing plate limits the displacement of the coolant housing in view of the header plate when the heat exchanger is pressurized.
Regardless of the design of the reinforcing plate, the header plate may be designed and manufactured in a standardized manner without care taken to the reinforcement needed for a particular application. Further, the assembly of the reinforcing plate may be made with only minor effects to the assembly line.
The reinforcing plate may be made of the same material as the rest of the components of the heat exchanger, i.e. typically an aluminum alloy. This means that a brazed homogenous joint may be formed along all contact surfaces between the reinforcing plate and the header plate in the very same brazing process that is normally used when joining all components of a heat exchanger. Thus, no extra joining step is required whereby the reinforcing plate easily may be integrated in the assembly line.
Further features and advantages are achieved by embodiments disclosed in the dependent claims.
In one embodiment, the reinforcing plate is joined to one or more tubes embraced by the apertures of the reinforcing plate. This strengthens the overall torsional rigidity of the heat exchanger and further decreases the risk of fatigue related breakdowns.
In another embodiment, the reinforcing plate may be arranged to provide a gap between the reinforcing plate and each of one or more tubes which are embraced by the apertures of the reinforcing plate. This feature may be preferred in order to provide an easy assembling of the components. Also, by a gap tolerances are made of less importance facilitating both production of the reinforcing plate and assembling thereof.
Regardless of if the reinforcing plate is joined to the tubes or provides a gap between the reinforcing plate and the tubes, the apertures of the reinforcing plate may embrace only one tube or embrace a plurality of tubes.
In one embodiment, the opening defined by the border of the coolant housing is oblong. In this case, the reinforcing plate is arranged to extend between two opposing locations on a long side of the border of the coolant housing. It has been found that reinforcement of the header plate along the long side of the border of the coolant housing provides a strong overall reinforcement of the heat exchanger and also provides an improved torsional rigidity. This is particularly the case when the reinforcing plate is located along a central area of the long side.
In one embodiment, the tubes are arranged in a plurality of parallel rows. Each row comprises a plurality of tubes. The rows may extend in the direction of the long side of the border. In such embodiment, the reinforcing plate may be arranged to embrace at least two adjacent tubes in each row. By this configuration, the reinforcing plate may extend along as many tubes along the long side as desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail with reference to the schematic drawings.

FIG. 1 is a three-dimensional view of a typical heat exchanger in line with the present invention.

FIG. 2 is a view of a coolant housing and a part of the core of a heat exchanger according to a first embodiment.

FIG. 3 is an exploded view of the arrangement in FIG. 2.

FIG. 4a is a side view towards the open section of the arrangement in FIG. 2.

FIG. 4b is a cross-sectional view of a section taken along line A-A in FIG. 4 a.

FIG. 5a is side view towards a short side of the arrangement in FIG. 2.

FIG. 5b is a cross-sectional view of a section taken along line B-B in FIG. 5 a.

FIG. 6 is a view of a coolant housing and a part of the core of a heat exchanger according to a second embodiment.

FIG. 7 is an exploded view of the arrangement n FIG. 6.

DETAILED DESCRIPTION

A heat exchanger 1 for heat exchange between a coolant and air is illustrated in FIG. 1. For illustrative purposes the heat exchanger is implemented with the reinforcing plate of the invention. The heat exchanger 1 may be a radiator or a charge air cooler for use in engine cooling systems. A coolant is circulated in a closed system formed by two opposing coolant housings 10 and a plurality of tubes 30 extending between the housings. The disclosed embodiment is provided with a plurality of vertically arranged tubes 30. It is however to be understood that the tubes with remained function may be horizontally arranged. The tubes are arranged side by side in at least one row. A number of parallel rows, each row comprising a plurality of tubes, may be provided.
A header plate 20 is attached to each coolant housing 10 to form a closed cavity. The tubes 30 connect to the closed cavity through apertures in the header plate.
During operation air is allowed to pass by the tubes 30. The tubes 30 are designed to provide a large area relative its volume in order to optimize the heat exchange. To further improve the heat exchanging area, waffled thin metal sheets 70, may be arranged between the individual tubes 30. Turbulator elements may also be provided.
The tubes 30 and the header plates 20 are preferably made of metal such as aluminum. It is however to be understood that also other types of materials may be used. In case of aluminium, the aluminum is preferably of the type provided with a surface treatment facilitating brazing.
The coolant housings are typically made of plastics, composite or metal.
The typical process of manufacturing a brazed heat exchanger of the above type may be briefly explained as follows: A plurality of tubes are stacked with or without intermediate distance forming waffled thin metal material. The stacked plurality of tubes is kept together by arranging two opposing header plates on top of the free ends of the plurality of tubes. The tubes are arranged to extend with their free ends through apertures in the opposing header plates. The resulting stacked arrangement is thoroughly degreased and provided with a fluxing agent in order of dissolving inevitable natural surface oxides of the aluminum. The stacked arrangement is subsequently fed through an oven where all connecting surfaces in the stacked arrangement are brazed together to form a rigid unit with homogenous, brazed joints along all contact surfaces. Finally a coolant housing is arranged on top of each header plate and joined thereto. The coolant housings are typically clamped in place by flanges on the header plate, which flanges clamp the peripheral border of the coolant housing. A gasket is arranged between the coolant housing and the header plate before joining the same. The resulting clamped joint will be made fluid tight by the reactive forces of the thus compressed gasket. Thereby a closed, fluid tight system is provided allowing a closed circulation of a fluid from the first coolant housing, via the plurality of tubes towards the second coolant housing.
A first embodiment of a part of an oblong arrangement 2 forming the fluid side of the heat exchanger 1 is illustrated in FIG. 2. The illustrated part forms an end of the oblong arrangement 2. The part is illustrated as a cut-off to facilitate understanding of the design. The cross section is representative of any part of the arrangement 2 along either one of the coolant housings 10 in FIG. 1.
The arrangement 2 comprises the coolant housing 10, the header plate 20 and the plurality of tubes 30. It is appreciated that these components may take many forms within the scope of the appended claims.
The coolant housing 10 and the header plate 20 form a closed cavity 50 by that the header plate 20 covers an opening of the coolant housing 10. The tubes 30 are in communication with the closed cavity 50 by that their free open ends are arranged to extend into the closed cavity 50 through the header plate 20.
The invention is defined by a reinforcing plate 40. The reinforcing plate 40 is arranged along and at least partly in contact with an outside surface of the header plate 20. By outside surface is meant a surface facing away from the closed cavity 50.
The structural details of the different components in this embodiment and their attachment to each other will now be disclosed with reference to FIGS. 3 and 4 a-4 b.
Starting with the coolant housing 10, the coolant housing 10 comprises a top wall 16 and side walls 17 extending from the top wall 16. The top wall 16 and the side walls 17 define a bowl-shaped inner cavity of the coolant housing 10. The end of the side walls 17 forms a peripheral border which defines an opening in the coolant housing 10. The border 11 is in this embodiment a peripheral rim which extends in an outward direction from the closed cavity 50 along the perimeter of the coolant housing 10. It goes without saying that the border 11 may have a number of different designs within the scope of the invention.
The coolant housing 10 is further provided with a coolant inlet or outlet 18. The inlet/outlet 18 is arranged to be connected to a non-disclosed coolant circulating system.
The opening of the coolant housing 10 is covered by the header plate 20 for separating the closed cavity 50 of the coolant housing 10. The header plate 20 is also provided for connecting the tubes 30 such that the tubes 30 are in communication with the closed cavity 50. To this end, the header plate 20 is provided with apertures 22. Each aperture 22 receives a free open end of a tube 30.
It is important that the attachment between the header plate 20 and the coolant housing 10 is tight in order to prevent leakage. To this end, the header plate 20 is arranged to crimp the border 11 of the coolant housing 10. The crimping is achieved by that an end portion 23, extending from a main portion 21, of the header plate 20 encompasses an inner side surface portion 12, a free edge portion 13, an outer side surface portion 14 and an outer upper surface portion 15 of the border 11 at opposing locations on the border 11. More precisely, the header plate 20 crimps the border 11 along the two opposing long sides and along the two opposing short sides. Thus, in this embodiment, the header plate 20 is arranged to crimp around the border on at least two opposing locations.
By inner side surface portion 12 of the coolant housing 10 within the scope of the invention is meant a surface portion of the border 11 constituting an elongation of the inner envelope surface of the coolant housing 10. The inner envelope surface of the coolant housing 10 faces the closed cavity 50.
By outer side surface portionl4 of the coolant housing 10 within the scope of the invention is meant a surface portion of the border constituting an elongation of the outer envelope side surface of the coolant housing 10. The outer envelope surface of the coolant housing 10 faces away from the closed cavity 50.
By free edge portion 13 of the coolant housing 10 within the scope of the invention is meant a surface portion of the border located between the inner and outer envelope surfaces of the coolant housing 10.
By outer upper surface portion 15 of the border within the scope of the invention is meant a surface portion of the border facing away from the header plate 20.
By encompassing is meant that the end portion 23 of the header plate 20 follows the surface portions of the coolant housing 10, however it is not necessary that the end portion 23 of the header plate 20 abuts the surface along the whole surface portion of the coolant housing 10. Thus, the contact between the end portion 23 of the header plate 20 and the outer side surface portion 14 of the coolant housing 10 may be continuous or discontinuous along the circumference of the coolant housing 10 as long as a fluid tight sealing is achieved. An intermediate flexible sealing may be arranged where necessary.
In the disclosed embodiment, the end portion 23 of the header plate 20 abuts two opposing surface portions of the border 11, being the inner side surface portion 12, the outer side surface portion 14 and the outer upper surface portion 15, so as to achieve the crimping effect. It is appreciated that the crimping effect may be achieved by different configurations of the header plate 20 and its end portion 23. For example, the header plate 20 may encompass only the free edge portion 13 and the outer side surface portion 14 at each opposing location to press the opposing locations of the border 11 toward each other. In other words, the header plate 20 may have a clip-like form and function. Other configurations are also obvious to the skilled person.
The header plate 20 comprises end flaps 24 which encompass the outer upper surface portion 15 of the border 11. This feature strengthens the crimping and thus further increases the tightening of the joint between the header plate 20 and the coolant housing 10. By a non-disclosed gasket being arranged between the header plate 20 and the border 11 such gasket will be compressed by the crimping and the reaction force resulting from the compressed gasket will ensure a fluid tight joint and prevent any significant movements.
During operation, when pressurized coolant flows through the closed cavity 50, the coolant housing 10 tends to bend outward due to the pressure. In particular, the side walls 17 tend to bulge. The bending is typically cyclic, meaning that over time there is a risk of fatigue. The inventors have identified two weak portions on the header plate 20 which are particularly exposed to fatigue stress at high coolant pressures. The first portion is the corner C1 between the main portion 21 and the first part of the end portion 23 which encompasses the inner side surface portion 12 of the coolant housing 10 and thereby the inner envelope surface portion of the coolant housing 10. The second portion is the corner C2 in the end portion 23 which encompasses the corner between the free edge portion 13 of the coolant housing 10 and the outer side surface portion 14 of the coolant housing 10, i.e. the inner envelope surface portion of the coolant housing 10. Moreover, it has been realized that the part of the end portion 23 which runs along the outer side surface portion 14 of the coolant housing 10, i.e. the outer envelope surface portion tends to bend outward due to the border 11 being pressed in an outward direction. Even if the end portion 23 does not break, it will be exposed to wear over time with the consequence that the crimping loosens thus un-tightening the joint between the coolant housing 10 and the header plate 20. There is also a risk that the cyclic stress causes fatigue in the brazed joints between the header plate 20 and the tubes 30.
In order to strengthen the design, the invention provides a reinforcing plate 40. The reinforcing plate 40 comprises a main portion 41 forming a bottom and at least two opposing end portions 43.
The reinforcing plate 40 is formed by stamped sheet metal and is preferably made of the same material as the header plate 20 and the tubes 30 to facilitate joining there between.
The reinforcing plate 40 is arranged on an outside surface of the header plate 20, and extends between two opposing crimped locations on the border 11 of the coolant hosing 10.
The reinforcing plate 40 is in contact with and joined to the header plate 20 at least at two positions: one at each crimped location on the border 11. More precisely, the reinforcing plate 40 is arranged in contact with and joined to each of the end portions 23 of the header plate 12. The joint is arranged along at least the part of the end portion 23 which encompasses the corner C2 between the free edge portion 13 of the coolant housing 10 and the outer side surface portion 14 of the border 11.
By that the reinforcing plate 40 is joined to this particular part of the header plate 20, the above mentioned weak corners C1 and C2 are strengthened and reinforced so as to increase their resistance to fatigue due to high cyclic pressures in the coolant housing 10. The reinforcing plate 40 limits the displacement of the header plate 20 and of the coolant housing 10 when the latter is pressurized. The limited displacement reduces stresses on the coolant housing 10, the header plate 20 and the tubes 30 and also on all joints between these components.
The end portions 43 of the reinforcing plate 40 are curved so as to follow the curvature of the end portions 23 of the header plate 20. The reinforcing plate 40 may be joined to the header plate 20 along other portions as well. In the disclosed embodiment, there is by way of example a joint between the header plate 20 and the reinforcing plate 40 along the main portion 41 of the reinforcing plate 40 and the header plate 20.
The height H of the opposing end portions 43 of the reinforcing plate 40 may vary. As a minimum the reinforcing plate 40 should extend around the corner C2 of the header plate 20 and at least along a portion of the end portion 23 of the header plate 20. It must however not necessarily have the same height and extension as the end portion 23 of the header plate 20.
The reinforcing plate 40 comprises apertures 42. In the disclosed embodiment, each aperture 42 embraces a single tube 30. By the term embrace is within the scope of the invention meant that the tube 30 is located in the aperture 42, however the tube 30 need not abut the reinforcing plate 40 as will be illustrated further on. In this embodiment, however, the reinforcing plate 40 is arranged in contact with and joined to each of the tubes 30. This feature strengthens the torsional rigidity of the heat exchanger as such and may further add to the reinforcement of the relevant corners C1 and C2.
In the disclosed embodiment, the apertures 42 have peripheral rims 42 a which give an extra support and contact surface to the tubes 30. The header plate 20 comprises similar peripheral rims 22 a.
The joint in the contact surfaces between the header plate 20 and the reinforcing plate 40 are preferably brazed, homogenous joints, which joints are formed in the very same process step as is previously disclosed for being used when brazing the stacked components making up the heat exchanger in FIG. 1.
A two-dimensional view toward a short side end of the arrangement 2 in FIG. 2 is illustrated in FIG. 5a . A section taken along the line B-B is illustrated in FIG. 5 b.
The reinforcing plate 40 extends between two opposing locations, being crimped by the header plate 20, on the long side of the border 11 of the coolant housing 10. This positioning of the reinforcing plate 40 may be advantageous when the opening of the coolant housing 10 has an oblong extension with a length considerably exceeding the thickness of the heat exchanger. It has been found that reinforcement of the header plate 20 along the long side of the border 11 of the coolant housing 10, in particular along a central area of the long side, provides a strong reinforcement of the heat exchanger. By central area is meant that the reinforcing plate 40 embraces tubes 30 which are not located at the end of the long side, i.e. adjacent the short side of the order 11.
The reinforcing plate 40 could in other embodiments (not disclosed) also extend between two opposing locations on the short sides of the border 11 of the coolant housing 10.
A second embodiment of a part of the arrangement 3 forming the fluid side of the heat exchanger 1 is illustrated in FIGS. 6 and 7. The components which are similar to the ones illustrated in the first embodiment are provided with the same reference numerals.
The arrangement 3 comprises a reinforcing plate 60 which has a slightly different configuration than the first embodiment of the reinforcing plate 40. The reinforcing plate 60 comprises a main portion 61 forming a bottom and two opposing end portions 63 which extend from the main portion 61.
The reinforcing plate 60 is joined to the header plate in similar manner as in the first embodiment. In other words, the reinforcing plate 60 is joined to each of the end portions 23 of the header plate 20. The joint is arranged along at least the part of the end portion 23 which encompasses the corner C2 between the free edge portion 13 and the outer side surface portion 14 of the border 11. Similar to the first embodiment, the end portions 63 are curved so as to follow the curvature of the end portions 23 of the header plate 20.
The reinforcing plate 60 is provided with apertures 62. Contrary to the first embodiment, each aperture 62 encompasses a pair of adjacent tubes 30. In this embodiment, the tubes 30 are located in a plurality of rows being two rows in the illustrated case. The rows are located in parallel. Each row comprises a plurality of tubes 30. The illustrated part of the arrangement 3 shows three tubes 3 in each row. Each row extends in the direction of the long side of the border 11 which provides an oblong opening of the coolant housing 10.
The reinforcing plate 60 embraces adjacent tubes 30 in adjacent rows. Moreover, the single reinforcing plate 60 is provided with a plurality of apertures 62 which together embrace a plurality of tubes 30 along the rows.
The reinforcing plate 60 differs from the reinforcing plate 40 of the first embodiment also in that it is not joined to the tubes 30. On the contrary, the reinforcing plate 60 is arranged to provide a gap between the reinforcing plate 60 and each of the tubes 30 embraced by the apertures 62. This feature may be preferred in order to facilitate assembling of the components. Further, the tolerances of the apertures 62 of the reinforcing plate 60 may be given a reduced importance.
The two above disclosed embodiments exemplifies the great variety of designs of the reinforcing plate 40 and 60 that is feasible within the scope of the invention. Regardless of the design of the reinforcing plate 40, 60, the header plate 20 may be designed and manufactured in a standardized manner without care taken to the type of reinforcing plate 40, 60 to be used.
The reinforcing plate may be chosen and added during the assembly of the heat exchanger with only minor effect on the assembly line.
It is to be understood that a plurality of reinforcing plates 40, 60 may be arranged side by side along the header plate 20. The reinforcing plates 40, 60 may be arranged side by side in contact with each other or be arranged with an intermediate distance.
By making the reinforcing plates 40, 60 in the very same material as the rest of the heat exchanger with the exception of the coolant housing which typically is made of plastics, the reinforcing plate 40, 60 requires no separate joining step but will be brazed to adjacent components being in contact therewith during the conventional brazing step. Further, by being of the same material as the header plates 20 and the tubes 30, the reinforcing plates 40, 60 will move thermally together with the rest of the heat exchanger causing no additional stress to the brazed joints.
It is appreciated that the embodiments of the invention as disclosed above may be altered in different ways within the scope of the appended claims. For example, the number of apertures 42 and 62 and the geometry thereof may vary depending on the type of tubes and their geometry. Another example is that the border may take any suitable form. It is appreciated that the reinforcing plate according to the invention can be used in any type of heat exchanger where the coolant housings are attached to the header plate by crimping, brazing, welding or the like.

Claims

1. Heat exchanger comprising:

a coolant housing having a border which defines an opening;

a header plate arranged to cover the opening;

wherein the header plate crimps the border of the coolant housing by encompassing a free edge portion, an outer side surface portion and an outer upper surface portion on at least two opposing locations on the border;

whereby a closed cavity for coolant is defined by the coolant housing and the header plate; and

wherein the header plate is provided with apertures, each aperture receiving a tube for guiding coolant from or to the closed cavity;

the heat exchanger further comprising:

a reinforcing plate extending between two opposing locations on the border of the coolant housing, and extending on the outside of the header plate in view of the closed cavity, the reinforcing plate being made of the same material as the header plate and the tubes;

wherein the reinforcing plate is joined, at each of said opposing locations, to an outer surface portion of the header plate encompassing a corner between the free edge portion and the outer side surface portion of the border;

wherein the reinforcing plate is provided with at least one aperture embracing one or more of the tubes which are received by the header plate; and

wherein the reinforcing plate is arranged to provide a gap between the reinforcing plate and each of one or more tubes embraced by the apertures of the reinforcing plate.

2. The heat exchanger according to claim 1, wherein the reinforcing plate is joined to one or more tubes embraced by the apertures of the reinforcing plate.

3. (canceled)

4. The heat exchanger according to claim 1, wherein each of the at least one apertures of the reinforcing plate embraces only one tube received by the header plate.

5. The heat exchanger according to claim 1, wherein each of the at least one apertures of the reinforcing plate embraces a plurality of tubes received by the header plate.

6. The heat exchanger according to claim 1,

wherein the opening defined by the border is oblong; and

wherein the reinforcing plate is arranged to extend between two opposing locations on a long side of the border.

7. The heat exchanger according to claim 6,

wherein the tubes are arranged in a plurality of parallel rows, each row comprising a plurality of tubes;

wherein the rows extend in the direction of the long side of the border; and

wherein the reinforcing plate embraces at least two adjacent tubes in each row.

8. The heat exchanger according to claim 6, wherein the reinforcing plate is arranged at a central area of the header plate with respect to the long side of the border.

9. The heat exchanger according to claim 1,

wherein the tubes have an oblong cross-section and are arranged with the same orientation, and

wherein the reinforcing plate extends along the long sides of the tubes.

10. The heat exchanger according to claim 1, wherein the reinforcing plate is joined to the header plate by brazing.

11. The heat exchanger according to claim 1, wherein the header plate encompasses also an inner side surface portion at each of said two opposing locations on the border.

12. The heat exchanger according to claim 1, wherein the coolant housing comprises a top wall and side walls which extend from the top wall, the top wall and side walls defining a bowl-shaped inner space of the coolant housing.

13. The heat exchanger according to claim 7, wherein the reinforcing plate is arranged at a central area of the header plate with respect to the long side of the border.