Patent Description:
Generally, the heat exchangers are provided in a vehicle for various operations. Particularly, charge air coolers are provided in air inlet circuit of an engine. Generally, the engine may receive air from atmosphere and the atmospheric pressure decreases with the change in elevation of the vehicle, i.e., while the vehicle traveling in elevated area such mountain regions. In such case, the fuel economy and thermal efficiency of the engine may be reduced as the engine may receive inefficient amount/pressure of air. To overcome such problems, air is pressurized (herein referred to as the "charge air") by mechanical or electric compressors, known as superchargers or turbochargers. In the forced induction engines, power output becomes a function of how much air is delivered to the cylinders. Most commonly used methods is to introduce the compressors to recapture energy from gas exhaust manifold through an expansion turbine, which pressurizes air delivered to the engine, or relay part of engine's power to motorize a supercharger, usually by a set of pulleys.

Further, pressurizing the air leads to substantial increase of its temperature. Consequently, the density of the air decreases with the temperature, because hot air is less dense than cold air. The automotive industry, like many other industrial fields, uses heat exchangers to ensure optimal temperature operating conditions for the engine. Therefore, the charge air cooler is provided in the upstream to the engine and downstream to the turbo/super-charger. The charge air cooler may dissipate heat from the charged air flowing from the turbo-charger. The charge air cooler is equipped with a set of tubes forming a heat exchange bundle between a first fluid and a second heat transfer fluid, and the heat exchange bundle being housed in a casing.

The tubes in the charge air cooler can be made of aluminum as it offers significant weight savings, and aluminum alloys also have good thermal and corrosion resistance. Due to the complexity of the charge air cooler and the small dimensions allowed, the components of the charge air coolers are assembled by brazing. Further, the tubes are typically brazed to the housing of the charge air cooler, i.e. joined by adding liquid metal to the metal parts to be joined. As these tubes are brazed over their entire surface in contact with the walls of the housing, the metal thus added forms a continuous line, thereby the assembly lacks in flexibility. It is well known that the charge air coolers are subjected to high and varied stresses during operational mode, such as thermomechanical stresses and chemical reactions with more or less aggressive environments.

In particular, there are thermal shocks caused by a sudden and significant change in temperature, for example when opening valves equipped with sensors that measure engine temperature and allow cold engine cooling water to pass into the warmer engine air intake system. These thermal shocks lead to expansion/contraction phenomena of the tubes of heat exchanger, called thermal cycles. However, the lack of flexibility of tubes generates significant stresses, which can lead to the appearance of rupture zones in tubes. It can then be observed that these fracture zones can lead to leakage of the heat transfer fluid.

In some prior arts, the heat exchange tubes may include some breakable tabs between the tube and the housing which are intended to crack during thermal cycle. However, the breakable tabs tend to form unpredictable shapes and structures which in most cases would cause collision between the housing and the tube, especially during expansion of the tubes. Such collision may lead to mechanical stress, and finally, to malfunction of the charge air cooler due to leakage.

Accordingly, the remains a need for a heat exchanger tube with an original design that ensures greater tube flexibility and which allows to avoid collision between the remaining elements of the breakable fuse element.

The present invention therefore aims to compensate for the disadvantages of the previous art and to meet the above-mentioned constraints by proposing a tube for heat exchanger, simple in its design and in its operating mode, reliable and economical, which makes it possible to limit, or even avoid, the appearance in the tube of rupture zones linked to thermal shocks, and collision between the remaining elements of the breakable fuse element.

Another object of the present invention is such a tube for a heat exchanger providing a support on the opposite walls of the casing with a view to its assembly by brazing with a complementary tube to form a conduit for the circulation of a heat transfer fluid.

The present invention is also intended for a heat exchanger comprising at least one such tube for an exchanger, so as to present enhanced reliability. For this purpose, the invention concerns a tube for a heat exchanger, said tube comprising a coupling edge to another tube.

According to the invention, said edge comprises at least one fusible part for assembling this coupling edge with at least one housing wall, said at least one fusible part being configured to be separated from the rest of said coupling edge by differential expansion/contraction between said tube and said at least one housing wall on which it is intended to be assembled. The tip portion of the fusible part extends beyond the coupling edge of the tube.

In view of forgoing, the present invention relates a tube for a heat exchanger. The tube includes at least one fusible part formed on at least one coupling edge of the tube for assembling with at least one wall of the heat exchanger. Further, the fusible part is parallelly aligned with respect to a general plane (P1) of the tube. The tube is a flat tube assembled of two half-plates so that it comprises two flat walls joined along at least two coupling edges, wherein the two coupling edges define a general plane. The tube further includes a base portion located in the vicinity of the coupling edge and a tip portion located in the vicinity of the wall of the heat exchanger. The tip portion of the fusible part is adapted to be entirely separated from the wall by differential in expansion and contraction between the tube and the wall.

In one embodiment, the tube further includes at least one notch located on the corner area of the tube, in particular the notch being located between the coupling edge and base portion of the fusible part.

Further, the fusible part is formed at the corners of the coupling edge of the tube.

In one embodiment, the tip portion of the fusible part is narrower than the base portion to facilitate separation of the tube from the wall.

Further, the coupling edge is formed to delimit the tube formed by two plates assembled with each other with their respective opposite faces.

Further, the coupling edges are intended to delimit a conduit for the circulation of a heat-transfer fluid within the tube.

In one embodiment, the fusible part is of a trapezoidal shape, wherein the width of the tip portion is smaller than of the width of the base portion.

Further, the fusible part includes sloping edges connecting the tip portion with the base portion.

In another embodiment, the fusible part is of a triangular shape.

Preferably, the fusible part is half the thickness of the tube, wherein the thickness is measured in a direction perpendicular to the general plane (P1) of the tube.

Alternatively, the fusible part is thicker than half the thickness of the tube, wherein the thickness is measured in a direction perpendicular to the general plane (P1) of the tube.

Alternatively, the fusible part is thinner than half the thickness of the tube, wherein the thickness is measured in a direction perpendicular to the general plane (P1) of the tube.

It must be noted that the figures disclose the invention in a detailed enough way to be implemented, said figures helping to better define the invention if needs be. The invention should however not be limited to the embodiment disclosed in the description.

The present invention may disclose a heat exchanger tube having at least one fusible part provided in a heat exchanger. Conventionally, the heat exchanger may include bundle of tubes disposed between two manifolds and forming a fluid channel. The tubes may be brazed to the inner wall of a housing of the heat exchanger. During operation of heat exchanger, the tubes may undergo various thermal cycle. As a result, thermal stress may act on the tubes, which may lead to the appearance of rupture zones in the tubes. Further, such fracture/rupture zones can lead to leakage of the heat transfer fluid. To avoid such problems, tabs are provided at a coupling edge of the tube of the heat exchanger. Such tabs can be fusible part adapted to break when there is a differential expansion and contraction between tubes and corresponding wall of the heat exchanger.

<FIG> illustrates a perspective view of a heat exchanger <NUM>, in accordance with an embodiment of the present invention. The heat exchanger <NUM> may include three walls forming a housing <NUM>. The three walls being a first wall <NUM>, a second wall <NUM> and a third wall <NUM>, wherein the first wall110 and the second wall <NUM> are aligned parallelly and spaced from each other, and the third wall <NUM> may be aligned perpendicularly with respect to the first and the second walls <NUM>, <NUM>, so that the opposite edges of the third wall <NUM> are in contact with the first wall <NUM>, as well as the second wall <NUM>.

The heat exchanger <NUM> may further comprise a manifold <NUM>. The manifold <NUM> may be located parallelly with respect to the third wall <NUM> and perpendicularly with respect to the first and the second walls <NUM>, <NUM>, so that, similarly to the third wall <NUM>, the opposite edges of the manifold <NUM> are in contact with the first wall <NUM>, as well as the second wall <NUM>.

The walls <NUM>, <NUM>, <NUM> and the manifold <NUM> may be joined together, e.g. by brazing, so that the walls <NUM>, <NUM>, <NUM> and the manifold <NUM> form an essentially rectangular fluid tight housing <NUM> which delimits a first fluid circuit for a first fluid, e.g. charge air. The housing <NUM> may further receive intake and outtake (not shown) for the first fluid on its open ends. The exemplary first fluid flow direction from intake to outtake is depicted in <FIG> by Fin and Fout, respectively.

Further, a second fluid circuit for a second fluid may be formed, inter alia, by the manifold <NUM>, which may include an inlet spigot <NUM> and an outlet spigot <NUM> for delivering or collecting second fluid, e.g. coolant. The exemplary second fluid flow direction from the inlet to the outlet is depicted in <FIG> by Win and Wout, respectively. The second fluid circuit further includes at least one tube <NUM> located within the housing <NUM>. In this example, the term "within" means that the tube <NUM> does not protrude beyond the space delimited by the housing <NUM>. The tube <NUM> is aligned substantially in parallel with respect to the first wall <NUM> and the second wall <NUM>, and in perpendicular to the manifold <NUM> and the third wall <NUM>.

Further, the tube <NUM> extends from the manifold <NUM> to the third wall <NUM>, whereas it is fluidly connected only with the manifold <NUM>. The tube <NUM> is formed, so as to enable at least one U-turn at the path of the second fluid flowing there through. Generally, the manifold <NUM> is configured to deliver and/or collect the second fluid to the tube <NUM> through two parallel channels formed therein. Preferably, the channels in the manifold <NUM> are formed as a unitary element with e.g. partition, however other means of providing channels for the second fluid are also envisaged.

Usually, the heat exchanger <NUM> may include a plurality of tubes <NUM> to improve the efficiency thereof. The tubes <NUM> are stacked one on the other in a parallel manner, perpendicularly to the manifold <NUM>, so that the second fluid is distributed as homogenously as possible. The second fluid may flow through the inlet Win and it is directed to respective channel of the manifold <NUM> which feeds the tubes <NUM>. Next, the second fluid flows through the U-shaped tube <NUM> back to the manifold <NUM> and then it is collected by the second fluid outlet Wont.

In order to improve the heat exchange efficiency, the stack of tubes <NUM> may be interlaced with so-called turbulators or fins <NUM>. The number of turbulators or fins <NUM> interlaced between the tubes <NUM> corresponds to the free spaces in the vicinity of the tubes <NUM>. In other words, turbulators or fins <NUM> fill the spaces not occupied by other sub-components within the housing <NUM> in order to maximize the heat exchange efficiency and to reduce bypassing of the tubes <NUM> by the first fluid. In this present example, the heat exchanger <NUM> is a charge air cooler. In such case, the first fluid being a charged air and the second fluid being a heat transfer fluid, i.e., coolant or water or water-glycol mixture.

<FIG> illustrates the heat exchanger <NUM> with plurality of tubes <NUM> in accordance to a prior art. The turbulators or fins <NUM> are omitted for the sake of clarity. The heat exchanger <NUM> may be oriented horizontally. Horizontal orientation of the heat exchanger <NUM> refers to horizontal direction of stacking of its tubes <NUM>. Alternatively, the heat exchanger <NUM> could be oriented at any angle with respect to horizontal orientation as long as the first and second fluids are efficiently delivered to provide effective heat exchange between them. As shown in <FIG>, each tube <NUM> may be formed out of two half-plates produced in the same process, wherein one half-plate is substantially a mirror image of the other to delimit the path for the circulation of a heat transfer fluid between these half-plates. Alternatively, the tube <NUM> may be a folded tube.

<FIG> further shows detailed section "S1" of an assembly of the tube <NUM> with the housing <NUM>. According to the prior art, the tubes <NUM> are stacked and spaced form each other in order to provide good efficiency of the entire heat exchanger <NUM>. During the operational mode the heat exchanger <NUM>, the tubes <NUM> expands and contracts depending on the temperature of the first and the second fluids, as well as the temperature difference between them in different sections of the heat exchanger <NUM>. Further, the different sub-components of the heat exchanger <NUM> may expand or contract to different extent, because the heat is not usually distributed evenly across all sub- components.

Each tube may be formed out of two half-plates produced in the same process, wherein one half-plate is substantially a mirror image of the other to delimit the path for the circulation of a heat transfer fluid between these half-plates. In other words, the tube may be the flat tube assembled of two half-plates so that it comprises two flat walls joined along at least two coupling edges <NUM>.

The tubes <NUM> may be initially, i.e. in a pre-operational mode, secured both to the manifold <NUM> and the third wall <NUM>, yet it may be possible for the tubes <NUM> to be secured only the manifold <NUM>. As the tubes <NUM> are directly connected to the housing <NUM>, the tubes <NUM> may lack flexibility, thereby the tubes may damage and cause leakage of the second fluid. To avoid such problem, a fusible part is introduced in the tubes <NUM>. Schematic and geometry of the fusible part is described in the forthcoming figures.

<FIG> and <FIG> illustrates isometric views of the standalone tube <NUM> and one of the corner areas of the tube <NUM> of <FIG>. In one embodiment, each tube <NUM> may have essentially rectangular shape, so that a general plane (P1) may be defined. In this example, the general plane (P1) of the tube <NUM> is defined along the contact area of two half-plates. In other words, the general plane (P1) of the tube <NUM> runs parallelly and in-between the half-plates of particular tube <NUM>. In other words, the general plane (P1) may cross the median section the tube <NUM>, so that the conduit for the first fluid in both sections thereof is split into two even halves.

As shown in <FIG>, the tube <NUM> may further include a coupling edge <NUM> for coupling two half-plates. As discussed above, the coupling edge <NUM> may delimit the tube <NUM> formed by the two plates assembled with each other with their respective opposite faces and may delimit a conduit for the circulation of the second fluid, i.e., heat-transfer fluid within the tube <NUM>. The coupling edge <NUM> may include at least one fusible part <NUM> for assembling the coupling edge <NUM> with at least one wall of the heat exchanger <NUM>, in particular the third wall <NUM> of the housing <NUM>. Further, the tube <NUM> may include a fluid inlet <NUM> and a fluid outlet <NUM>, as shown in <FIG>. Each of the fluid inlet <NUM> and fluid outlet <NUM> may include a collar configured to provide a fluid-tight connection between tube <NUM> and the manifold <NUM> of the heat exchanger <NUM>.

Thus, in preferred embodiment of an invention, the tube <NUM> is fixed to the housing <NUM> with one end, and the other ought to be a free end during the operational mode of the heat exchanger <NUM>, in order to allow expansion or contraction of the tube <NUM> within the housing <NUM>.

<FIG> illustrates in detail a fragment of the same tube <NUM> as shown in <FIG>. In particular, <FIG> shows one of the corer areas of the tube <NUM> having the fusible part <NUM>. The fusible part <NUM> is parallelly aligned with respect to the general plane "P1" of the tube <NUM>. The fusible part <NUM> includes a base portion <NUM> located in the vicinity of the coupling edge <NUM> and a tip portion <NUM> located/defined in the vicinity of the wall, particularly third wall <NUM>, of the heat exchanger <NUM>. In one embodiment, the tip portion <NUM> of the fusible part <NUM> is in-contact with the third wall <NUM>. In another embodiment, the tip portion <NUM> of the fusible part <NUM> may be formed in such a way that a gap defined in between the tip portion <NUM> and the third wall <NUM>. The tip portion <NUM> is adapted to be entirely separated from the third wall <NUM> by differential in expansion and contraction between the tube <NUM> and the third wall <NUM> of the heat exchanger <NUM>.

<FIG> illustrate top and front views of the fusible part <NUM> of the <FIG>, formed on the coupling edge <NUM> of the tube <NUM>. As shown in <FIG>, the tip portion <NUM> is in-contact with the third wall <NUM> of the housing <NUM>. When the tube <NUM> expands or contracts due to thermal cycles, the fusible part <NUM> may break or entirely separated from the third wall <NUM>, particularly the tip portion <NUM>, which is in contact with the third wall <NUM>, may break, thereby preventing collation of tube <NUM> with the third wall <NUM> and damages of the tube <NUM>. The tube <NUM> further includes at least one notch <NUM> located on the corner area of the tubes <NUM>, particularly, the notch <NUM> being located between the coupling edge <NUM> of the tube <NUM> and the base portion <NUM> of the fusible part <NUM>. In this present embodiment, the tip portion <NUM> of the fusible part <NUM> is narrower than the base portion <NUM> of the fusible part <NUM> to facilitate separation of the tube <NUM> from the third wall <NUM>. The fusible part <NUM> is formed at the corners of the coupling <NUM> of the tube <NUM>. Further, the tip portion <NUM> of the fusible part <NUM> extends beyond the coupling edge <NUM> of the tube <NUM>, so the tube <NUM> can be separated from the walls of the housing <NUM>. As the tip portion <NUM> of the fusible part <NUM> is extended beyond the coupling edge <NUM> of the tube <NUM>, the fusible part <NUM>, particularly the tip portion <NUM>, can break when the tube <NUM> is subjected to differential expansion or contractions due to various thermal cycles.

As shown in <FIG>, the fusible part <NUM> is of a trapezoidal shape, in which the tip portion <NUM> is narrower than the base portion <NUM> of the fusible part <NUM>. Further, the width of the tip portion <NUM> is smaller than of the width of the base portion <NUM>, so that the tip portion <NUM> can be easily separated from the third wall <NUM> by differential in expansion or contraction between the tube <NUM> and the housing <NUM>. Further, the fusible part <NUM> includes sloping edges <NUM> connecting the tip portion <NUM> with the base portion <NUM> of the fusible part <NUM>. In one example, the tip portion <NUM> of the fusible part <NUM> is brazed to the housing <NUM>, particularly to the third wall <NUM>. In another example, the tip portion <NUM> is just in-contact with the housing <NUM>, particularly with the third wall <NUM>. In another embodiment, the fusible part <NUM> is of a triangular shape.

As discussed above, the tip portion <NUM> may be configured to be separated from the fusible part <NUM> by differential in expansion or contraction between the tube <NUM> and at least one wall on which it is intended to be assembled, such as the third wall <NUM>. During the first thermal cycles, the stress put between the tubes <NUM> and the housing <NUM> allows the notch <NUM> to separate the tip portion <NUM> from the fusible part <NUM>, thereby the tip portion <NUM> may break. Consequently, the base portion <NUM> of the fusible part <NUM> is integral with the tube <NUM> and the tip portion <NUM> is integral with the housing <NUM>, in particular the third wall <NUM>, in case the tip portion <NUM> is brazed with the housing <NUM>.

Preferably, the fusible part <NUM> may be half the thickness of the tube <NUM>, in which the thickness is measured in a direction perpendicular to the general plane (P1) of the tube <NUM>. In other words, each fusible part <NUM> protruding from one corner area of the tube <NUM> is of the same thickness as the half-plate of the tube <NUM> from which the fusible part <NUM> protrudes there-from. Alternatively, the fusible part <NUM> protruding from one corner area of the tube <NUM> is thicker than the half-plate of the tube <NUM> from which the fusible part <NUM> protrudes there-from. Alternatively, the fusible part <NUM> protruding from one corner area of the tube <NUM> is thinner than the half-plate of the tube <NUM> from which the fusible part <NUM> protrudes there-from.

As the notch <NUM> is provided between the coupling edge <NUM> of the tube <NUM> and the base portion <NUM> of the fusible part <NUM>, the tip portion <NUM> can be easily separated from the fusible part <NUM> when there is a differential expansion and contraction between the tube <NUM> and the housing <NUM>. In other words, the notch <NUM> allows the tip portion <NUM> be separated from the base portion <NUM> in such a way, that during the operational mode of the heat exchanger <NUM>, the tube <NUM> does not collide with the housing <NUM> or the contact between these elements is very gentle. This allows to significantly improve the thermal resistance of the whole heat exchanger <NUM>. To achieve similar effect, those skilled in the art could, for example, increase the size of the housing <NUM> in the direction parallel to the general plane (P1) of the tube <NUM>, so that the tubes can expand and contract freely, yet it would create several problems, such as increased packaging, reduced thermal efficiency of the heat exchanger, and other.

Claim 1:
A tube (<NUM>) for a heat exchanger (<NUM>) comprising at least one fusible part (<NUM>) formed on at least one coupling edge (<NUM>) of the tube (<NUM>) for assembling with at least one wall (<NUM>) of the heat exchanger (<NUM>) characterised in that the fusible part (<NUM>) is parallelly aligned with respect to a general plane (P1) of the tube (<NUM>), wherein the fusible part (<NUM>) comprises a base portion (<NUM>) located in the vicinity of the coupling edge (<NUM>) and a tip portion (<NUM>) located in the vicinity of the wall (<NUM>) of the heat exchanger (<NUM>), wherein the tip portion (<NUM>) of the fusible part (<NUM>) is adapted to be entirely separated from the wall (<NUM>) by differential in expansion and contraction between the tube (<NUM>) and the wall (<NUM>), wherein the tip portion (<NUM>) of the fusible part (<NUM>) extends beyond the coupling edge (<NUM>) of the tube (<NUM>).