WO2022233971A1

WO2022233971A1 - Exchanger tube for a heat exchanger

Info

Publication number: WO2022233971A1
Application number: PCT/EP2022/062044
Authority: WO
Inventors: Chris CALHOUN; Roger Fourile; Yang Gao
Original assignee: Estra Automotive Systems Luxembourg S.À R.L.
Priority date: 2021-05-05
Filing date: 2022-05-04
Publication date: 2022-11-10
Also published as: DE212022000196U1; LU500125B1

Abstract

The invention relates to an exchanger tube (10) for a heat exchanger (1), extending in a transversal direction (Y) with a cross-section perpendicular thereto that is elongate in a longitudinal direction (X) with respect to a vertical direction (Z). In order to to provide a multiport exchanger tube for a heat exchanger that has favourable mechanical stability in relation to its weight and that is easy to manufacture, the invention provides that the exchanger tube (10) comprises: an outer shell (20), formed from a single first metal strip (21) and surrounding an inner cavity (40), the outer shell (20) comprising a first sidewall portion (23) on a vertically first side (U) and a second sidewall portion (25) on a vertically second side (L), which extend in the longitudinal direction (X) and are spaced in the vertical direction (Z), a rear portion (24) connecting the sidewall portions (23, 25) on a longitudinally rear side (R), an inner front portion (22) extending towards the second side (L) from the first sidewall portion (23) on a longitudinally front side (F), and an outer front portion (26) extending towards the first side (U) from the second sidewall portion (25) on the front side (F) and at least partially overlapping with the inner front portion (22), wherein the inner front portion (22) comprises an inner convex portion (22.2), and the outer front portion (26) comprises an outer convex portion (26.1) disposed outwards from the inner convex portion (22.2) with respect to the inner cavity (40); and an inner fin (30), formed from a single second metal strip (31), being disposed at least mostly inside the outer shell (20) and extending from a fin rear portion (34) to a fin front portion (32), which is at least partially received between the inner front portion (22) and the outer front portion (26), wherein the outer front portion (26) engages a spring portion (22.4), which comprises the inner convex portion (22.2), from the first side (U) and engages the spring portion (22.4) from the second side (L) via the interposed fin front portion (32), whereby the spring portion (22.4) is bracketed in the vertical direction (Z). The invention also relates to a heat exchanger and to a method of producing an exchanger tube.

Description

EXCHANGER TUBE FOR A HEAT EXCHANGER

Technical Field

[0001 ] The invention relates to an exchanger tube, to a heat exchanger and to a method for producing an exchanger tube.

Background Art

[0002] In vehicles such as passenger cars or trucks, heat exchangers are used as part of cooling circuits, which in turn are needed for cooling vehicle components like the engine, the transmission etc. Some of these cooling circuits employ a liquid heat exchange medium, which receives heat from the vehicle components and transfers heat to ambient air at the main heat exchanger, like a radiator installed in the front of the vehicle. In other cases, the heat exchanger is a condenser, wherein the heat exchange medium (or fluid) enters the condenser in gaseous state, is condensed and cooled in the condenser and exits the condenser in liquid state.

[0003] According to a common design, the heat exchanger comprises an inlet manifold or inlet tank that is connected to a heat exchanger core. The heat exchanger core commonly comprises a plurality of spaced exchanger tubes, which are largely responsible for the heat exchange between the fluid and ambient air. The necessary airflow for cooling the fluid can be provided by forced or natural convection to the exchanger core. One could say that the fluid is received in the inlet tank from where it is distributed to the exchanger tubes. From the exchanger tubes, the fluid is guided to an outlet tank. According to a different design, an inlet cavity and an outlet cavity are provided as separate sections in a single tank.

[0004] External fins are often provided on the exchanger tubes to increase the effective surface and thus the heat transfer to ambient air. It is also known to provide the individual tube with an internal structure sometimes referred to as a turbulator or an internal fin. These structures may serve several purposes. For instance, they increase the surface area available for heat transfer, they may facilitate formation of a non- laminar, turbulent flow and they may increase the structural integrity of the tube. The internal fin usually extends along the length of the exchanger tube and defines a plurality of channels or ports for the flow of a heat transfer fluid.

[0005] Heat exchanger tubes having a plurality of channels are also known as multi-port tubes. A known method of manufacturing multi-port tubes is by extruding a billet of deformable heat conductive material through a die. The extrusion process allows for the formation of the internal fins to have intricate geometric features to improve heat transfer efficiency that other known manufacturing process could not readily provide. However, the extrusion process is expensive, because the extrusion die needs to be replaced frequently in order to maintain the desired dimensions of the intricate geometric features. Extruded tubes are also prone to corrosion attacks from road salt and acidic rain and require extensive corrosion inhibition coatings for motor vehicle applications, which add to the complexity of manufacturing and cost.

[0006] Another known method of forming multi-port tubes is by folding one or several sheets of pliable heat conductive material, normally metal. Multiple ports can be defined by internal corrugated folds of sheet material which form the internal fin. Folded tubes provide numerous advantages over extruded tubes in terms of lower cost and ease of manufacturing for the tube itself as well as for the final assembly of the heat exchanger. One advantage is that folded tubes can be formed from thin strips of clad aluminum, which offers superior corrosion protection without the need for applying additional coatings. Sometimes a single sheet is used for the entire tube, as shown e.g. in WO 2012/106242 A2. According to another design, a thinner sheet is used for the inner fin, while a thicker sheet is used for the outer shell tube, as shown in US 2017/0144212 A1, EP 3 399 267 A1 or US 2007/0095514 A1. Yet another design uses a thinner sheet for the inner fin and two thicker sheets for the outer shell, as disclosed in DE 10 2008 052 785 A1.

[0007] The leading nose of the tube, i.e. the part that is oriented toward the front of the motor vehicle, is exposed to incoming air for increase heat transfer efficiency as the vehicle moves in the forward direction. However, this configuration implies that the leading nose is susceptible to impact damage from road hazards such as rocks and debris, as well as corrosion damage from environmental hazards such as acidic rain, road salt, and wind friction. This is especially true for folded tubes, since the thickness, or gage, of the leading nose is the same as that of the thin strip of clad aluminum material that the folded tube is fabricated from.

[0008] To overcome this problem, it has been proposed to provide several layers of sheet material in the leading nose, either by folding a single sheet in a multilayer fashion or by providing an overlap of several sheets. These measures, however, complicate the forming and assembly process. Also, there is often a tradeoff between maximizing the stability and minimizing the weight of the tube. Another problem arises if a dedicated sheet is used for the inner fin, since the position of the fin with respect to the outer shell needs to be secured during the assembly process before they can be bonded by a final brazing operation.

Technical Problem

[0009] It is thus an object of the present invention to provide a multiport exchanger tube for a heat exchanger that has favourable mechanical stability in relation to its weight and that is easy to manufacture.

[0010] This problem is solved by an exchanger tube according to claim 1 , a heat exchanger according to claim 16 and by a method according to claim 17.

General Description of the Invention

[0011 ] The invention provides an exchanger tube for a heat exchanger. In particular, this can be a heat exchanger for a vehicle, e.g., a passenger car or a truck. The heat exchanger is normally a condenser, to be mounted in a front section of the vehicle or in any other part of the vehicle, as appropriate.

[0012] The exchanger tube, which may also be referred to as a ‘heat exchanger tube’ or for the particular application as ‘condenser tube’, extends in a transversal direction with a cross-section perpendicular thereto that is elongate in a longitudinal direction with respect to a vertical direction. In general, the terms “transversal”, “longitudinal” and “vertical” are used in this context to define a reference system with three pairwise orthogonal directions. Insofar, these terms are not be construed in any limiting manner. However, when the exchanger tube is installed in a heat exchanger in a vehicle, the longitudinal direction normally corresponds to the longitudinal axis (X-axis) of the vehicle, the transversal direction corresponds to the transversal axis (Y-axis) of the vehicle and the vertical direction corresponds to the vertical axis (Z-axis) of the vehicle. The transversal direction normally corresponds to the largest dimension of the exchanger tube. As a rule, the exchanger tube is straight and has a constant cross- section along the transversal direction. The cross-section perpendicular to the transversal direction is elongate in the longitudinal direction with respect to the vertical direction, i.e. , the dimension of the exchanger tube in the longitudinal direction is greater than its dimension in the vertical direction, normally at least three times, at least five times or at least eight times greater. According to the elongate cross-section, the exchanger tube can also be referred to as a flat exchanger tube. More specifically, the exchanger tube is flattened in the vertical direction. [0013] The exchanger tube comprises an outer shell, formed from a single first metal strip and surrounding an inner cavity. The first metal strip may also be referred to as a first metal sheet and is normally made of aluminium or aluminium alloy. It should be noted, though, that one surface or both surfaces of the first metal strip may at least partially be covered with a brazing material, e.g., an aluminum alloy such as AA4343 or generally alloy series AA4XXX. The outer shell surrounds an inner cavity, while it should be understood that the cavity is not completely enclosed by the outer shell, since the exchanger tube needs to have at least one opening on either end in the transversal direction to allow for fluid to enter and exit the tube. It should also be noted that the inner cavity may not be continuous but may be divided into several sections or sub-cavities that are not directly communicating with each other, i.e., that are not adapted for direct fluid exchange. Of course, each of the sections could also be regarded as a cavity. It is understood that the outer shell normally provides a fluid-tight seal around the inner cavity perpendicular to the transversal direction (i.e., on either side in the longitudinal direction and the vertical direction).

[0014] The outer shell comprises a first sidewall portion on a vertically first side and a second sidewall portion on a vertically second side, which extend in the longitudinal direction and are spaced in the vertical direction. The terms “first side” and “second side” only serve to distinguish two opposite sides of the exchanger tube along the vertical direction and are insofar not to be construed in any limiting way. When installed in the vehicle, the side herein referred to as the “first side” could e.g. be facing upwards or downwards with respect to the direction of gravity. In some embodiments, the “first side” could also be referred to as an “upper side”, in which case terms like “towards the first side” could be replaced by “upwards” or “above”. According to a common design, both sidewall portions are straight and parallel to the longitudinal direction. They are spaced in the vertical direction, with the above-mentioned inner cavity (or at least a part thereof) disposed in between. The outer shell further comprises a rear portion connecting the sidewall portions on a longitudinally rear side. The terms “rear side” and “front side” only serve to distinguish two opposite sides of the exchanger tube along the longitudinal direction and are insofar not to be construed in any limiting way. However, when installed in a vehicle, the front side normally faces the front of the vehicle, while the rear side faces its rear. It will be understood that all the portions mentioned herein are part of a single, continuous piece of metal, namely the first metal strip, wherefore the boundary between two neighboring portions may not be clearly identifiable. The rear portion is often arcuate or bent so that there is a smooth transition between the two sidewall portions. However, other designs are possible too. Since the rear portion connects the sidewall portions, it extends along the vertical direction (but is normally not parallel thereto).

[0015] An inner front portion of the outer shell extends towards the second side from the first sidewall portion on a longitudinally front side, and an outer front portion of the outer shell extends towards the first side from the second sidewall portion on the front side and at least partially overlaps with the inner front portion, wherein the inner front portion comprises an inner convex portion, and the outer front portion comprises an outer convex portion disposed outwards from the inner convex portion with respect to the inner cavity. The inner front portion extends towards the second side from the first sidewall portion, but generally not parallel to the vertical direction. It is referred to as the “inner” front portion since it is at least partially disposed closer to the inner cavity. It extends on a (longitudinally) front side from the first sidewall portion, which of course is opposite the above-mentioned rear side. Likewise, the outer front portion extends towards the first side, but generally not parallel to the vertical direction, from the front side of the second sidewall portion. Accordingly, each of the front portions extends from one sidewall portion towards the other sidewall portion. Both front portions overlap at least partially so that they form a double wall that separates the inner cavity from the outside of the exchanger tube. The inner front portion comprises an inner convex portion, whereas the outer front portion comprises an outer convex portion. In this context, the term “convex” refers to the shape as viewed from the outside of the exchanger tube. Each convex portion may be arcuate and continuously bent (or in sections), but it could also comprise at least one sharp bend or kink. Normally, both convex portions overlap partially or even fully. In a configuration where the front side corresponds to the driving direction of the vehicle, the front portions can be regarded as elements of a leading nose.

[0016] The exchanger tube further comprises an inner fin, formed from a single second metal strip, being disposed at least mostly inside the outer shell and extending from a fin rear portion to a fin front portion, which is at least partially received between the inner front portion and the outer front portion. The second metal strip may also be referred to as a second metal sheet and is also normally made of aluminium or aluminium alloy. Like the first metal strip, one surface or both surfaces of the second metal strip may at least partially be covered with a brazing material. The thickness (or gage) of the second metal strip is normally considerably smaller than the thickness of the first metal strip, since the inner fin is mostly or entirely disposed inside the outer shell and therefore does not need to have the same mechanical stability. Without limiting the invention in this regard, the inner fin can have various functions, like increasing the surface area available for heat transfer, facilitating formation of a turbulent flow, and increasing the structural integrity of the tube. The fin rear portion is of course disposed on the longitudinally rear side of the inner fin while the fin front portion is disposed on the front side. The fin front portion is at least partially received between the inner front portion and the outer front portion of the outer shell. One could also say that the fin front portion is at least partially bracketed between the front portions of the outer shell. On the one hand, this serves to secure the position of the inner fin with respect to the outer shell. On the other hand, an effective three-layer structure is established, which enhances the mechanical stability on the front side of the exchanger tube, normally corresponding to the leading nose. Still, a relatively small amount of material is used, wherefore the weight of the exchanger tube can be kept low.

[0017] The outer front portion engages a spring portion, which comprises the inner convex portion, from the first side and engages the spring portion from the second side via the interposed fin front portion, whereby the spring portion is bracketed in the vertical direction. The term bracketed thus designates the fact that spring portion is held at opposite portions by the outer front portion, hence acting as support and/or guide frame. In some embodiments, the spring portion may be formed entirely by the inner convex portion while in other embodiments, it may comprise additional portions. Although the production process of the heat exchanger tube preferably comprises an elastic deformation of the spring portion, as will be discussed below, the term “spring portion” is not to be construed as being limited to such an embodiment. The outer front portion engages the spring portion from the first side, i.e. it is in direct contact with the spring portion from the vertically first side. On the other hand, the outer front portion engages the spring portion from the second side, i.e. from the vertically second side, indirectly via the fin front portion. In other words, the outer front portion directly engages the fin front portion and the fin front portion in turn directly engages the spring portion. As a result, the outer front portion forms a bracket around the spring portion in the vertical direction, i.e. the spring portion is vertically bracketed. Accordingly, precise positioning of the outer front portion, the spring portion and the fin front portion as well as a tight connection between these portions is established. This is particularly helpful during a bonding process, like a brazing process. [0018] According to one embodiment, the spring portion is elastically compressed in the vertical direction (i.e. in the tube thickness direction). In other words, the outer front portion exerts vertical forces on the spring portion that causes an elastic deformation of the spring portion. It should be noted, though, that depending on the material of the outer shell and the conditions of a brazing process, which normally involves heating of the entire exchanger tube, an elastic deformation of the spring portion may turn into a plastic deformation. It will be understood, though, that an elastic compression of the spring portion ensures a tight contact with the outer front portion and the fin front portion, respectively.

[0019] Advantageously, the inner front portion comprises a sloped portion adjacent the inner convex portion, which sloped portion is sloped/bent towards the second side from the first sidewall portion, whereby the inner convex portion is offset towards the second side from the first sidewall portion, and an end portion of the outer front portion is disposed on the first side relative to the inner convex portion. In this embodiment, the inner convex portion is not disposed directly adjacent the first sidewall portion, but the sloped portion is disposed in between. The sloped portion is disposed at an angle with respect to the first sidewall portion, more specifically, it is sloped towards the second side, i.e. towards the second sidewall portion. The sloped portion normally comprises a convex sub-portion adjacent the first sidewall portion and a concave sub portion adjacent the inner convex portion. In other words, the angle between the sloped portion and the first sidewall portion initially increases and then decreases again. At the transition between the sloped portion and the inner convex portion, the inner front portion may even be parallel to the first sidewall portion. By interposing the sloped portion, the inner convex portion is offset towards the second side (i.e. towards the second side) from the first sidewall portion. This leads to additional space available on the first side relative to the inner convex portion, which in this embodiment is occupied by an end portion of the outer front portion.

[0020] Preferably, the sloped portion has an inclination of less than 70° with respect to the first sidewall portion. Since the transition between the sloped portion and the adjacent portions is normally not abrupt, the inclination is usually not constant. Insofar, the statement refers to the maximum inclination (or inclination angle) with respect to the first sidewall portion. Normally, this is identical to the inclination with respect to the longitudinal direction. If the inclination is limited to less than 70°, this helps to avoid an exceedingly sharp bend between the first sidewall portion and the sloped portion, which in turn reduces the stress on the first metal strip during the forming process. In some embodiments, the inclination may even be limited to less than 60°.

[0021 ] It is possible to adapt the cross-section of the end portion so that it fits more closely to the cross-section of the inner front portion. According to one such embodiment, the end portion comprises a tapering cross-section and is disposed adjacent the sloped portion. The cross-section of the end portion tapers, i.e. the thickness of the end portion decreases towards its edge. This makes it possible to position the end portion adjacent and at least close to the sloped portion. In particular, the end portion can be in contact with the sloped portion in several locations and/or over a certain distance. This, in turn makes it possible to bond the end portion to the sloped portion, e.g. by brazing.

[0022] There are various possibilities how the tapering cross-section can be realized. The thickness could decrease gradually and/or stepwise. The decrease could be constant along the length of the end section or it could be varying. According to one embodiment, the tapering cross-section is a wedge-like cross-section with a wedge angle of less than 70°. The wedge angle is normally constant but could also have a variation along the length of the end section. The size of the wedge angle can be chosen according to an inclination of the sloped portion with respect to the first sidewall portion.

[0023] It is highly preferred that the outer front portion is flush with the first sidewall portion with respect to the vertical direction. In other words, the outer front portion extends along the vertical direction to the same position (i.e. the same “height”) as the first sidewall portion. This can result in a straight upper surface of the exchanger tube, which upper surface is mainly formed by the first sidewall portion and to some extent by the outer front portion. It should be noted that this embodiment is preferably combined with (and facilitated by) the above-mentioned embodiment in which the end portion has a tapering cross-section.

[0024] In order to provide a secure connection and also in order to enhance the stability of the front of the exchanger tube, it is preferred that the fin front portion is bonded to the inner front portion and the outer front portion. As a rule, this bonding corresponds to a brazing connection. As explained above, the outer shell and/or the inner fin can be clouded with a brazing material so that after forming and assembling the outer shell and the inner fin, the entire exchanger tube can be heated to melt the brazing material, thereby simultaneously applying all brazing connections in the exchanger tube. [0025] Likewise, it is preferred that the end portion is bonded to the sloped portion. Again, this bonding is normally obtained by brazing. The bonding connection can be facilitated and enhanced by a tapering cross-section of the end portion that is adapted to closely fit the cross-section of the sloped portion.

[0026] One embodiment provides that the fin front portion extends in the vertical direction over 30 - 60% of a height of the inner cavity defined by a distance of the sidewall portions in the vertical direction and the inner front portion and the outer front portion are separated by a gap on the first side relative to the fin front portion. The height of the inner cavity is the vertical distance of the first sidewall portion and the second sidewall portion. If this distance is not constant, the “height” in this context is specifically the vertical distance at the front side of the sidewall portions, adjacent the inner and outer front portion, respectively. As the fin front portion is received between the inner and outer front portion, it extends towards the first side. As mentioned above, the end portion of the outer front portion is preferably directly bonded to the sloped portion, wherefore the fin front portion should not extend to the end portion. In fact, it has been found that the fin front portion should preferably end at a certain distance from the end portion. Due to the finite thickness of the fin front portion, a gap exists between the inner and outer front portion on the first side relative to the fin front portion. This gap can decrease gradually towards the end portion, which can be in contact with the sloped portion, and possibly with the inner convex portion. In order to facilitate this, the fin front portion should extend up to a maximum of 60%, or only 50%, of the height of the inner cavity. On the other hand, the fin front portion should extend up to at least 30% or 40% of the height, which e.g. helps to keep tension on the spring region. It will be noted that in the region with the gap, the outer front portion can be deformed to some extent into the gap without a corresponding deformation of the inner front portion. In other words, there is a region where the deformation of the front portions is (to a certain extent) decoupled, which can be beneficial for the impact resistance of the exchanger tube.

[0027] In one embodiment, the inner front portion comprises a leg portion adjacent the inner convex portion, wherein the fin front portion is at least partially received between the leg portion and the second sidewall portion. The leg portion may be part of the spring portion. Especially during forming and assembly of the exchanger tube, the leg portion may serve to introduce an elastic deforming force into the inner convex portion. The leg portion is disposed opposite the second sidewall portion and, in assembled state, it is normally parallel to the second sidewall portion and the first sidewall portion. It is possible, though, that the leg portion is initially at an angle with respect to the first sidewall portion so that when the upper and second sidewall portion are moved into their final, parallel position, the leg portion needs to be deflected to reach the parallel position, which in turn creates an elastic deformation force on the inner convex portion.

[0028] Preferably, the fin rear portion engages the rear portion in the longitudinal direction. In other words, the inner fin extends over the entire length of the inner cavity so that the fin rear portion is in contact with the rear portion of the outer shell. In particular, the inner fin may be elastically deformed in the longitudinal direction so that the fin rear portion presses against the rear portion of the outer shell.

[0029] Normally, the inner fin comprises a fin middle portion between the fin rear portion and the fin front portion, which fin middle portion is at least partially corrugated and is in contact with both sidewall portions. The cross-section of the fin middle portion is at least partially corrugated, corresponding to a meandering shape, zigzag shape or wavy shape. Correspondingly, the fin middle portion is alternating directed towards the first side and towards the second side between the upper and second sidewall portion and in certain locations is in contact with the first sidewall portion or the second sidewall portion, respectively. It is also possible that the vertical dimension of the fin middle portion before assembly is chosen to be greater than the height of the inner cavity, so that it needs to be (elastically and/or plastically) deformed during assembly of the exchanger tube. It is understood that the fin middle portion separates the inner cavity into subsections are sub-cavities. This effectively creates a plurality of flow channels inside the heat exchanger tube, which facilitates the creation of a turbulent flow. Accordingly, the exchanger tube can be regarded as a multiport tube. Also, the corrugated structure increases the contact surface between the fluid and the heat exchanger tube, thereby enhancing heat transfer. Finally, the corrugated structure enhances the mechanical stability of the heat exchanger tube.

[0030] It is preferred that the fin middle portion is bonded to both sidewall portions. Again, this bonding is normally performed by brazing. By bonding the middle portion to the first sidewall portion and the second sidewall portion, the position of the inner fin relative to the outer shell is secured and the mechanical stability of the exchanger tube is improved. [0031 ] Preferably, the inner fin comprises an abutment portion disposed proximate to the inner front portion and extending in the vertical direction over at least 50% of the height of the inner cavity, which abutment portion at least partially runs at an angle of more than 60° with respect to the longitudinal direction. Such an abutment portion can be easily integrated into a corrugated structure. As will be explained below, during assembly of the exchanger tube, the abutment portion can be in contact with the inner front portion, while the fin rear portion is in contact with the rear portion of the outer shell, so that the inner fin is held in a position near the first sidewall portion before the outer shell is closed. If the angle between the abutment portion and the longitudinal direction is less than 60°, there is an increased risk of the abutment portion sliding off the inner front portion during assembly. The same applies if the abutment portion extends over less than 50% of the height. Further, the nominal distance between the abutment portion and opposite end of the inner fin advantageously exceeds the distance between the inner front portion and the bottom of the rear portion, so that during assembly the inner fin is slightly compressed when the abutment portion is engaged on the inner front portion. The inner fin’s spring force in the tube width direction also helps maintaining the inner fin in place during assembly.

[0032] The invention further provides a heat exchanger, in particular a heat exchanger for a vehicle. The heat exchanger comprises a first tank and a second tank for a fluid, each extending in the vertical direction, the first tank defining an inlet tank cavity and one of the tanks defining an outlet tank cavity. The first and second tank, which at least in some embodiments may be referred to as manifolds or one-piece manifolds, are adapted for containing a fluid during operation. The term “fluid” herein refers to a liquid or gaseous medium. The respective fluid is of course the medium of a cooling circuit to which the heat exchanger belongs, e.g., when installed in the vehicle. The fluid may also be referred to as cooling fluid, cooling medium, coolant or refrigerant. Each tank extends along the vertical direction and normally is elongate with respect to the vertical direction. The term “vertical direction” is to be understood in the sense explained on the first side relative to with respect to the inventive exchanger tube, i.e. , when installed in the vehicle, the vertical direction may correspond to the Z-axis (vertical axis) of the vehicle but it could also correspond e.g. a horizontal axis, like the Y-axis of the vehicle.

[0033] The first tank defines an inlet tank cavity and one of the tanks (the first tank or the second tank) defines an outlet tank cavity of the heat exchanger. The inlet tank cavity, which may also be referred to as an inlet tank space or an inlet tank volume, is a cavity of the heat exchanger that receives fluid e.g. from vehicle components like a water jacket of an engine, a transmission cooler, a battery set, or the like, which fluid is then cooled in the heat exchanger before being returned to the vehicle cooling circuit. To this respect, the first tank has at least one inlet port communicating with the inlet tank cavity. During operation, the fluid is redistributed from the outlet tank cavity to the vehicle components via at least one outlet port of the respective tank. The outlet tank cavity may also be referred to as an outlet tank space or an outlet tank volume. Although the invention is not limited to this, the heat exchanger may in particular be a condenser that is adapted to receive fluid in gaseous state and to discharge fluid in liquid state. In this case, the fluid is in gaseous state inside the inlet tank cavity and in liquid state inside the outlet tank cavity.

[0034] Further, the heat exchanger comprises an exchanger core adapted for heat exchange of the fluid with ambient air and comprising a plurality of inventive exchanger tubes, the exchanger tubes being adapted to guide fluid from the inlet tank cavity towards the outlet tank cavity. The exchanger core may extend along the transversal direction and along the vertical direction, with the exchanger tubes extending along the transversal direction. During operation, ambient air flows along the exchanger core, whereby a heat exchange between the ambient air and the fluid is promoted. In other words, the heat exchange process is almost entirely performed at the exchanger core. The fluid flows through the exchanger tubes, which are adapted to guide fluid from the inlet tank cavity towards the outlet tank cavity. Every exchanger tube is connected so that it receives fluid directly or indirectly from the inlet tank cavity and delivers fluid directly or indirectly to the tank outlet cavity. It is understood that the exchanger core normally comprises structures like external fins in order to increase the surface of the exchanger core and thus enhance the heat exchange with the ambient air. The external fins may be located between the tubes and may partially or totally cover the tube width.

[0035] The invention further provides a method of producing an exchanger tube for a heat exchanger, which exchanger tube extends in a transversal direction with a cross-section perpendicular thereto that is elongate in a longitudinal direction with respect to a vertical direction. As far as these and other terms have been explained above with respect to the inventive exchanger tube, they will not be explained herein again. [0036] The method comprises forming an outer shell from a single first metal strip so that the outer shell comprises a second sidewall portion on a vertically second side, a first sidewall portion on a vertically first side, a rear portion connecting the sidewall portions on a longitudinally rear side, an inner front portion extending towards the second side from the first sidewall portion on a longitudinally front side, and an outer front portion extending towards the first side from the second sidewall portion on the front side, wherein the inner front portion comprises an inner convex portion, and the outer front portion comprises an outer convex portion.

[0037] Further, the method comprises forming an inner fin from a single second metal strip, the inner fin extending from a fin rear portion to a fin front portion. This may be performed before, after and/or during the above-described forming of the outer shell.

[0038] In another step, the inner fin is disposed between the sidewall portions, i.e. between the second sidewall portion and the first sidewall portion. It will be understood that in this state, the sidewall portions are not in their final positions, but one sidewall portion could be at an angle with respect to the other sidewall portion, similar to an open lid. The inner front portion and the outer front portion are also at a distance from each other with an opening in between through which the inner fin can be inserted.

[0039] After the inner fin has been disposed between the sidewall portions, the outer shell is closed so that it surrounds an inner cavity and the inner fin is at least mostly disposed inside the outer shell, the outer front portion at least partially overlaps with the inner front portion, the fin front portion is at least partially received between the inner front portion and the outer front portion, the outer convex portion is disposed outwards from the inner convex portion with respect to the inner cavity, the sidewall portions extend in the longitudinal direction (X) and are spaced in a vertical direction and the outer front portion engages a spring portion, which comprises the inner convex portion, from the first side and engages the spring portion from the second side via the interposed fin front portion, whereby the spring portion is bracketed in the vertical direction.

[0040] Forming of the outer shell may be performed by stepwise deformation of the first metal strip as it is passed in the transversal direction through a series of forming stations. Each forming station may comprise one roller or a plurality of rollers that perform bending processes on the profile of the first metal strip. Closing of the outer shell may also be performed in this way. A similar process may be used to form the inner fin. [0041 ] The method further may comprise, after closing the outer shell, performing at least one bonding process, in particular a brazing process. This normally is performed by subjecting the entire exchanger tube to an elevated temperature to melt a brazing material.

[0042] In general, preferred embodiments of the inventive method correspond to those of the inventive exchanger tube and insofar will not be explained again.

[0043] Preferably, closing the outer shell comprises plastically deforming the outer front portion so that it engages the spring portion, whereby the spring portion is elastically compressed in the vertical direction. This elastic deformation or compression of the spring portion has been mentioned above. It greatly helps to establish a close contact between the spring portion and the outer front portion. As also mentioned above, the elastic deformation could turn into a plastic deformation when the heat exchanger tube is subjected to an elevated temperature during brazing.

[0044] It is also preferred that an end portion of the outer front portion is formed with a tapering cross-section by performing at least one rolling process on the end portion. During the forming process described above, the end portion can be passed through one or several pairs of rollers that for the desired tapering cross-section. For instance, this could be a wedge -shaped cross-section. It is preferred that the end portion is formed by several rolling processes are rolling steps. In comparison to a single rolling step, this reduces the strain on the metal strip as well as on the rollers, which is beneficial for the durability of the exchanger tube and reduces roller wear. Additionally, rolling the end deposits energy into the metal strip, which may facilitate the flow of the brazing material during the brazing process.

[0045] Preferably, an abutment portion is formed on the inner fin and the inner fin is disposed between the sidewall portions so that the fin rear portion engages the rear portion, and the abutment portion engages the inner front portion so that the inner fin is elastically compressed and held between the rear portion and the inner front portion. A possible position and a shape of the abutment portion have been described above with respect to the inventive exchanger tube. During the assembly process, when the inner fin is placed between the first sidewall portion and the second sidewall portion, the fin rear portion is placed in contact with the rear portion of the outer shell, while the abutment portion is placed in contact with the inner front portion. One could also say that the rear portion and the inner front portion serve as abutments for the inner fin. The dimensions are adapted so that the described positioning of the fin rear portion and the abutment portion is only possible by elastically compressing the inner fin in a direction that corresponds to the longitudinal direction of the assembled exchanger tube. This elastic deformation can be largely facilitated by a corrugated structure of the fin middle portion.

[0046] One embodiment provides that at least one cutting operation is performed on the exchanger tube after the outer shell has been closed. According to a common process, the first metal strip is part of endless metal sheet or strip that is passed in the transversal direction through a sequence of forming stations. A certain length of the endless metal sheet corresponds to a single exchanger tube. When all forming steps have been performed for the respective length of metal sheet, the metal strip is cut from the endless metal sheet. The respective cutting operation, which of course involves cutting of the outer shell as well as the inner fin, is a critical operation that places considerable strain on the material. During this step, it is highly beneficial that the fin front portion is received between the front portions of the outer shell and that the spring portion is bracketed by the outer front portion, both of which helps to maintain the proper relative positions of these elements.

Brief Description of the Drawings

[0047] Preferred embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of an inventive heat exchanger;

Fig. 2 is a first perspective view of an inventive exchanger tube;

Fig. 3 is a side view of the exchanger tube from fig. 2;

Fig. 4 is a detail view of fig. 3;

Fig. 5 is a side view of the exchanger tube from fig. 2 in a first stage of a production process;

Fig. 6 is a side view of the exchanger tube from fig. 2 in a second stage of the production process; and

Fig. 7 is a side view of the exchanger tube from fig. 2 in a third stage of the production process. Description of Preferred Embodiments

[0048] Fig.1 illustrates an inventive heat exchanger 1 , which can be used as a radiator in a vehicle like a passenger car or a truck. In particular, the heat exchanger 1 can be a condenser in which an initially gaseous fluid is condensed to liquid state. The heat exchanger 1 comprises a first manifold or first tank 2, which is connected by an exchanger core 8 to a second manifold or second tank 9. The first tank 2 and the second tank 9 each have a roughly cylindrical shape and are elongate along a first axis Z, which is a vertical axis of the vehicle. Both tanks are closed at both ends by respective end walls. The exchanger core 8 extends along a vertical direction Z (corresponding to the height axis of the vehicle) as well as along a transversal direction Y (corresponding to the lateral axis of the vehicle).

[0049] The interior of the first tank 2 is divided by a separator wall 7 into an inlet tank cavity 3 and an outlet tank cavity 4. The inlet tank cavity 3 communicates with an inlet pipe 6 5, through which it receives a gaseous fluid during operation of the heat exchanger 1. The fluid is then distributed to a lower part of the exchanger core 8 and guided to the second tank 9. From there, it is distributed to an upper part of the exchanger core 8 and guided to the outlet tank cavity 4, which communicates with an outlet pipe 5 6. It will be understood that the fluid condenses on its way from the inlet tank cavity 3 to the outlet tank cavity 4. The exchanger core 8 comprises a plurality of exchanger tubes 10, one of which is shown in figs. 2-7 and will now be described.

[0050] Fig. 2 shows a perspective view of the exchanger tube 10 (or condenser tube), while figs. 3 and 4 show side views. The exchanger tube 10 extends along the transversal direction Y, which corresponds to the flow direction of the fluid during operation. Perpendicular to the transversal direction Y, the exchanger tube 10 has a cross-section that is elongate in the longitudinal direction X in relation to the vertical direction Z. In other words, the exchanger tube 10 can be referred to as a flat exchanger tube. It comprises an outer shell 20 that is made from a single first metal strip 21 consisting of aluminium sheet coated with a brazing material. The outer shell 20 surrounds an inner cavity 40. Inside the inner cavity 40, an inner fin 30 (or turbulator) is disposed. Similar to the outer shell 20, the inner fin 30 is made of a single second metal strip 31 consisting of aluminium sheet; in embodiments, the second metal strip cab be provided with a surface cladding - typically on both sides. However, the thickness (or gage) of the second metal strip 31 corresponds to only about 30 - 40% of the thickness of the first metal strip 21.

[0051 ] The outer shell 20 comprises a first sidewall portion 23 and a second sidewall portion 25, both of which extend parallel to the longitudinal direction X and are spaced along the vertical direction Z. The spacing of the sidewall portions 23, 25 defines a height of the inner cavity 40. The first sidewall portion 23 is disposed on a vertically first side U (or upper side), while the second sidewall portion 25 is disposed on a vertically second side L (or lower side). On a longitudinally rear side R, the sidewall portions 23, 25 are connected by an arcuate, convex rear portion 24 of the first metal strip 21. On a longitudinally front side F, an inner front portion 22 of strip 21 extends from the first sidewall portion 23 to the second side U, and an outer front portion 26 of strip 21 extends from the second sidewall portion to the first side U.

[0052] As can best be seen in fig. 4, the inner front portion 22 comprises a sloped portion 22.1 (or bend) that is inclined towards the second side L at an angle of about 60° with respect to the first sidewall portion 23. The sloped portion 22.1 transitions into an inner convex portion 22.2 that has an arcuate shape and corresponds to an arc of approximately 180°. A convex sub-portion 22.5 is disposed at the transition between the first sidewall portion 23 and the sloped portion 22.1 , while a concave sub-portion 22.6 is disposed at the transition between the sloped portion 22.1 and the inner convex portion 22.2. Opposite the sloped portion 22.1, the inner convex portion 22.2 is connected to a leg portion 22.3 that is, in assembled state, substantially parallel to the longitudinal direction X. It may be noted that the inner front portion 22, with convex portion 22.2 and leg portion 22.3, also forms a locking feature that cooperates with one end of the inner fin 30, whereby the inner fin 30 can remain in place along the first side wall portion 23 in an intermediate assembly state as illustrated in Fig.4. The outer front portion 26 almost entirely overlaps the inner front portion 22 on the outside (with respect to the inner cavity 40). It comprises an outer convex portion 26.1 with an end portion 26.2 at its end. The end portion 26.2, which has a wedge-shaped cross-section with a wedge angle of 60°, is in contact with the sloped portion 22.1, while a part of the outer convex portion 26.1 engages the inner convex portion 22.2 from the first side U. The inner convex portion 22.2 and the leg portion 22.3 are parts of a spring portion 22.4. While the outer front portion 26 engages the spring portion 22.4 directly from the first side U, it also engages the spring portion 22.4 indirectly from the second side L via a fin front portion 32. The fin front portion 32 is interposed and received between the inner convex portion 22.2 and the outer convex portion 26.1 as well as between the leg portion 22.3 and the second sidewall portion 25. Effectively, the spring portion 22.4 is bracketed along the vertical direction Z. On the first side U of the fin front portion 32, the inner convex portion 22.2 and the outer convex portion 26.1 are separated by a gap 41 that tapers towards the first side U.

[0053] As will be understood, initially, the first metal strip 21 is typically a rectangular metal sheet, whereby the inner and outer portions 22, 26, with their respective convex portions 22.2 and 26.1, are formed in the longitudinal margin portions (or edge regions) of the metal strip 21.

[0054] During operation of the vehicle, the front side F corresponds to the driving direction, wherefore sand and other particles will mostly impact on the exchanger tube 10 from this side. Accordingly, the exchanger tube 10 has a multi-layered structure on the front side F, with three layers on the second side L and two layers with the interposed gap on the first side U. The three-layered structure provides improved stability, while the two-layer structure with the interposed gap allows for some deformation of the outer front portion 26 that is independent of the inner front portion 22. Accordingly, any particles hitting the exchanger tube 10 from the front side F are unlikely to penetrate the outer shell.

[0055] The inner fin 30 extends from the fin front portion 32 to a fin rear portion 34 that engages the rear portion 24 of the outer shell 20. It also comprises a corrugated fin middle portion 33 that is in contact with both sidewall portions 23, 25 and connected thereto by brazing. The fin middle portion 33 divides the inner cavity 40 into a plurality of sub-cavities 40.1 , each of which corresponds to a separate fluid channel through the exchanger tube 10, corresponding to a multiport configuration.

[0056] A method for producing the exchanger tube 10 will now be outlined with reference to figs. 5 to 7. The outer shell 20 as well as the inner fin 30 can be produced by passing the respective metal strip 21, 31 through a sequence of roll-forming stations. The forming stations are disposed sequentially along a direction that corresponds to the transversal direction Y, and the metal strip 21, 31 is conveyed along this direction. In each forming station, one or several rollers act on the metal strip 21, 31, thereby gradually bending its profile into the shape shown in fig. 5. Also, the wedge-shaped cross-section of the end portion 26.2 is formed by one or several rolling operations. Fig. 5 shows a state of the process in which the sidewall portions 23, 25 are not parallel, but at an angle and the profile of the outer shell 20 is open. Accordingly, the inner fin 30 can be inserted easily between the sidewall portions 23, 25.

[0057] In order to maintain the proper position of the inner fin 30 during the further assembly process, the abutment portion 33.1 is brought into contact with the leg portion 22.3 of the inner front portion 22. This coincides with an elastic compression of the inner fin 30 or, more specifically, of the fin middle portion 33. Since the abutment portion 33.1 is at an angle of about 80° with respect to first sidewall portion 23 (corresponding, in assembled state, to the longitudinal direction X), it is held in place by friction and does not slide off the inner front portion 22.

[0058] While the inner fin 30 is bracketed between the rear portion 24 and the inner front portion 22, the outer shell 20 is closed by moving the sidewall portions 23, 25 into a parallel position as shown in fig. 7. As the inner convex portion 22.2 and the leg portion 22.3 are moved towards the outer convex portion 26.1 and the second sidewall portion 25, the fin front portion 32 is deformed into a bent shape. In this state, the outer convex portion 26.1 and the end portion 26.2 are still out of contact with the inner convex portion 22.2 and the slope portion 22.1.

[0059] With a final forming step, the outer front portion 26 is brought into the position shown in figs. 3 and 4. Now, the spring portion 22.4 is elastically deformed as it is engaged by the outer front portion 26 from the first side U. This elastic deformation, which results in a pre-tensioning of the spring portion 22.4, guarantees a close contact between the spring portion 22.4, the outer front portion 26 and the fin front portion 32. Usually, the forming steps described above are performed on an endless metal sheet and a length corresponding to the transversal dimension of the exchanger tube 10 is afterwards cut from the endless sheet. During this cutting operation, it is highly beneficial that the relative positions of the outer shell 20 and the inner fin 30 are secured as described above. Also, the structure of the exchanger tube 10 is stabilized by the corrugated shape of the fin middle portion 33. Finally, the entire exchanger tube 10 is subjected to an elevated temperature that melts the brazing material, thereby bonding the fin middle portion 33 to the sidewall portions 23, 25. At the same time, the fin front portion 32 is bonded to the leg portion 22.3, the inner convex portion 22.2, the outer convex portion 26.1 and the second sidewall portion 25. Also, the end portion 26.2 is bonded to the sloped portion 22.1 and a part of the outer convex portion 26.1 is bonded to the inner convex portion 22.2. [0060] Remarks on the design and assembly process.

[0061 ] The design of the inventive exchanger tube allows the tube to form on an angle and over several rolling stations, thereby reducing so-called ‘form roll wear’.

[0062] Rolling is thus beneficial for realizing the end portion 26.2 of the outer portion 26, requiring a thickness reduction and taper.

[0063] Additionally, rolling the end deposits energy into the tube that acts as a catalyst for clad flow in brazing process. The present design also allows the material to overlap better since no sharp angles are included in the lap area. This results in almost no gap between inner convex portion 22.2 and outer convex portion 26.1 on the side of the sloped portion 22.1. However, to ensure that the two features stay in close contact during brazing, the lap of the inner convex portion 22 and outer convex portion 26 are kept in tension by the spring design of portion 22.4. The spring portion 22.4 is rolled into the tube and ensure tension between the inner and outer convex portions. It keeps the inside tube compressed again the outside tube surface. Advantageously, oversized the spring feature 22.4 is oversized by a few percent, e.g. 5 to 10%, in the early forming stations, so that it can keep the inner tube wall pressed against the outer surface.

[0064] During assembly of inner fin 30 to the tube, the inner fin 30 is pressed in place and hooks on the inner front portion22 at the spring 22.4 / leg portion 22.3. This helps to keep the inner fin 30 in place like a compressed spring, as the two side walls 23 and 25 are rolled together. Until finally spring portion 22.4 is hooked inside outer front portion 26.

[0065] During the final forming stations, the inner and outer portions 22, 26 of the tube are rolled until the outer portion 26 encapsulates inner portion 22, at which point the tube surfaces are combine and the inner fin 30 is locked in place. The spring portion 22.4 maintains contact between the inner and outer portions while ensuring a small gap of 0 to 0.5mm in between. However, the inner fin 30 should preferably not extend beyond the tube center line to control the gap thickness. Additionally, the inner fin preferably does not extend to far backwards to keep tension on the spring feature 22.4. End portion 26.2 should preferably not extend backwards more beyond the bend radius to maintain the spring effect on feature 22.4. List of Reference Signs:

1 heat exchanger

2 first tank

3 inlet tank cavity

4 outlet tank cavity

5 inlet pipe

6 outlet pipe

7 separator wall

8 exchanger core 9 second tank

10 exchanger tube

20 outer shell

21 first metal strip

22 inner front portion

22.1 sloped portion

22.2 inner convex portion

22.3 leg portion

22.4 spring portion

22.5 convex sub-portion

22.6 concave sub-portion

23 first sidewall portion

24 rear portion

25 second sidewall portion

26 outer front portion 26.1 outer convex portion 26.2 end portion

30 inner fin

31 second metal strip

32 fin front portion

33 fin middle portion

33.1 abutment portion

34 fin rear portion

40 inner cavity

40.1 sub-cavity

41 gap F front side

L second side

R rear side

U first side

X longitudinal direction

Y transversal direction

Z vertical direction

Claims

1. An exchanger tube (10) for a heat exchanger (1), extending in a transversal direction (Y) with a cross-section perpendicular thereto that is elongate in a longitudinal direction (X) with respect to a vertical direction (Z), the exchanger tube (10) comprising:

- an outer shell (20), formed from a single first metal strip (21) and surrounding an inner cavity (40), the outer shell (20) comprising a first sidewall portion (23) on a vertically first side (U) and a second sidewall portion (25) on a vertically second side (L), which extend in the longitudinal direction (X) and are spaced in the vertical direction (Z), a rear portion (24) connecting the sidewall portions (23, 25) on a longitudinally rear side (R), an inner front portion (22) extending towards the second side (L) from the first sidewall portion (23) on a longitudinally front side (F), and an outer front portion (26) extending towards the first side (U) from the second sidewall portion (25) on the front side (F) and at least partially overlapping with the inner front portion (22), wherein the inner front portion (22) comprises an inner convex portion (22.2), and the outer front portion (26) comprises an outer convex portion (26.1) disposed outwards from the inner convex portion (22.2) with respect to the inner cavity (40); and

- an inner fin (30), formed from a single second metal strip (31), being disposed at least mostly inside the outer shell (20) and extending from a fin rear portion (34) to a fin front portion (32), which is at least partially received between the inner front portion (22) and the outer front portion (26), wherein the outer front portion (26) engages a spring portion (22.4), which comprises the inner convex portion (22.2), from the first side (U) and engages the spring portion (22.4) from the second side (L) via the interposed fin front portion (32), whereby the spring portion (22.4) is bracketed in the vertical direction (Z).

2. The exchanger tube according to claim 1, wherein the spring portion (22.4) is elastically compressed in the vertical direction (Z).

3. The exchanger tube according to any of the preceding claims, wherein the inner front portion (22) comprises a sloped portion (22.1) adjacent the inner convex portion (22.2), which sloped portion (22.1) is sloped towards the second side (L) from the first sidewall portion (23), whereby the inner convex portion (22.2) is offset towards the second side (L) from the first sidewall portion (23), and an end portion (26.2) of the outer front portion (26) is disposed on the first side (U) relative to the inner convex portion (22.2).

4. The exchanger tube according to claim 3, wherein the sloped portion (22.1) has an inclination of less than 70° with respect to the first sidewall portion (23).

5. The exchanger tube according to claim 3 or 4, wherein the end portion (26.2) comprises a tapering cross-section performed by at least one rolling process and is disposed adjacent the sloped portion (22.1).

6. The exchanger tube according to claim 5, wherein the tapering cross-section is a wedge-like cross-section with a wedge angle of less than 70°.

7. The exchanger tube according to any one of the preceding claims, wherein the outer front portion (26) is flush with the first sidewall portion (23) with respect to the vertical direction (Z).

8. The exchanger tube according to any one of the preceding claims, wherein the fin front portion (32) is bonded to the inner front portion (22) and the outer front portion (26).

9. The exchanger tube according to any one of claims 3 to 8, wherein the end portion

(26.2) of the outer front portion is bonded to the sloped portion (22.1).

10. The exchanger tube according to any one of the preceding claims, wherein the fin front portion (32) extends in the vertical direction (Z) over 30 - 60% of a height of the inner cavity (40) defined by a distance of the sidewall portions (23, 25) in the vertical direction (Z) and the inner front portion (22) and the outer front portion (26) are separated by a gap (41) on the first side (U) relative to the fin front portion (32).

11. The exchanger tube according to any of the preceding claims, wherein the inner front portion (22) comprises a leg portion (22.3) adjacent the inner convex portion (22.2), wherein the fin front portion (32) is at least partially received between the leg portion

(22.3) and the second sidewall portion (25).

12. The exchanger tube according to claim 11, wherein leg portion (22.3) is straight and extends parallel to the second sidewall portion (25).

13. The exchanger tube according to any one of the preceding claims, wherein the fin rear portion (34) engages the rear portion (24) in the longitudinal direction (X).

14. The exchanger tube according to any one of the preceding claims, wherein the inner fin (30) comprises a fin middle portion (33) between the fin rear portion (34) and the fin front portion (32), which fin middle portion (33) is at least partially corrugated and is in contact with both sidewall portions (23, 25).

15. The exchanger tube according to any one of the preceding claims, wherein the fin middle portion (33) is bonded to both sidewall portions (23, 25).

16. The exchanger tube according to any one of the preceding claims, wherein the inner fin (30) comprises an abutment portion (33.1) disposed proximate to the inner front portion (22) and extending in the vertical direction (Z) over at least 50% of the height of the inner cavity (40), which abutment portion (33.1) at least partially runs at an angle of more than 60° with respect to the longitudinal direction (X).

17. A heat exchanger (1), comprising: a first tank (2) and a second tank (9) for a fluid, each extending in a vertical direction (Z), the first tank (2) defining an inlet tank cavity (3) and one of the tanks (2, 9) defining an outlet tank cavity (4); and an exchanger core (8) adapted for heat exchange of the fluid with ambient air and comprising a plurality of exchanger tubes (10) according to any of the preceding claims, the exchanger tubes being adapted to guide fluid from the inlet tank cavity (3) towards the outlet tank cavity (4).

18. A method of producing an exchanger tube (10) for a heat exchanger (1), extending in a transversal direction (Y) with a cross-section perpendicular thereto that is elongate in a longitudinal direction (X) with respect to a vertical direction (Z), the method comprising:

- forming an outer shell (20) from a single first metal strip (21) so that the outer shell (20) comprises a first sidewall portion (23) on a vertically first side (U), a second sidewall portion (25) on a vertically second side (L), a rear portion (24) connecting the sidewall portions (23, 25) on a longitudinally rear side (R), an inner front portion (22) extending towards the second side (L) from the first sidewall portion (23) on a longitudinally front side (F), and an outer front portion (26) extending towards the first side (U) from the second sidewall portion (25) on the front side (F), wherein the inner front portion (22) comprises an inner convex portion (22.2), and the outer front portion (26) comprises an outer convex portion (26.2),

- forming an inner fin (30) from a single second metal strip (31), the inner fin (30) extending from a fin rear portion (34) to a fin front portion (32),

- disposing the inner fin (30) between the sidewall portions (23, 25),

- closing the outer shell (20) so that it surrounds an inner cavity (40) and the inner fin (30) is at least mostly disposed inside the outer shell (20), the outer front portion (26) at least partially overlaps with the inner front portion (22), the fin front portion (32) is at least partially received between the inner front portion (22) and the outer front portion (26), the outer convex portion (26.1) is disposed outwards from the inner convex portion (22.2) with respect to the inner cavity (40), the sidewall portions (23, 25) extend in the longitudinal direction (X) and are spaced in a vertical direction (Z) and the outer front portion (26) engages a spring portion (22.4), which comprises the inner convex portion (22.2), from the first side (U) and engages the spring portion (22.4) from the second side (L) via the interposed fin front portion (32), whereby the spring portion (22.4) is bracketed in the vertical direction (Z).

19. The method according to claim 18, wherein closing the outer shell (20) comprises plastically deforming the outer front portion (26) so that it engages the spring portion (22.4), whereby the spring portion (22.4) is elastically compressed in the vertical direction (Z).

20. The method according to claim 18 or 19, wherein an end portion (26.2) of the outer front portion (26) is formed with a tapering cross-section by performing at least one rolling process on the end portion (26).

21. The method according to any one of claims 18 to 20, wherein an abutment portion (33.1) is formed on the inner fin (30) and the inner fin (30) is disposed between the sidewall portions (23, 25) so that the fin rear portion (34) engages the rear portion (24), and the abutment portion (33.1) engages the inner front portion (22) so that the inner fin (30) is elastically compressed and held between the rear portion (24) and the inner front portion (22).

22. The method according to any one of claims 18 to 21, wherein at least one cutting operation is performed on the exchanger tube (10) after the outer shell (20) has been closed.

23. The method according to any of claims 18 to 22, wherein the spring portion (22.4) is initially formed to be oversized by 3 to 10%, preferably about 5% in vertical direction.