TUBE FOR HEAT EXCHANGER

TECHNICAL FIELD

[0001]The invention relates to a tube for a heat exchanger. In particular, the invention relates to the tube for heat exchanger for a motor vehicle.

BACKGROUND OF THE INVENTION

[0002]The present invention relates to the field of heat exchanger and in particular to heat exchangers for which is typical high temperature difference between inlet and outlet refrigerant temperature. These heat exchangers are especially condensers, gas coolers (where temperature gradient is especially high), but invention is possible and have benefit also for evaporators.

[0003]A known fluid refrigerant circuit forms a closed loop in which the refrigerant fluid flows in order to dissipate or collect calories through heat exchangers. The heat exchanger comprises the manifold to connect said heat exchanger to the fluid refrigerant circuit, said manifold linking pipes from the fluid refrigerant circuit to the heat exchanger core, in order for the refrigerant fluid to flow through heat exchanger tubes.

[0004]In fluid refrigerant circuit traversed by a refrigerant fluid could be in gaseous, mixture, and liquid state for loops working with R1234yf or R134a refrigerants (condensers). The working pressure inside condenser is up to 20 bar to apply safety coefficient prove burst pressure is 100 bar. For working fluid R744 (gas coolers) is the fluid dominantly in supercritical gaseous. Working pressure is around 100 bars but 170 bar can occur. The burst pressure with safety coefficient 2 could be required and in such a case, burst pressure is 340 bar.

[0005]A known heat exchangers comprise the manifolds and the heat exchange tubes allowing the refrigerant fluid to migrate between the manifolds. The heat exchange tubes also allow a thermal exchange between the refrigerant fluid, flowing inside said heat exchange tubes, and an air flowing outside the heat exchanger, thus capturing calories from the air flowing across the heat exchanger core in case of evaporators and dissipating calories in case of condensers and gas coolers.

[0006]The manifold comprises a tank, a header plate and a distribution plate localized between the tank and the header plate. The tank plate of the manifold is configured to delimit said manifold. The header plate of the manifold is designed to allow the refrigerant fluid to flow between the first manifold or the second manifold and the heat exchange tubes. The distribution plate is intended to allow the refrigerant fluid to flow between a connector connected to said distribution plate and the header plate.

[0007]The tank plate, the distribution plate and the header plate are brazed together to insure the sealing of the manifold, avoiding leaks of the refrigerant fluid. The header plate comprises teeth configured to secure the assembly of the header plate, the distribution plate and the tank plate together, in order to help the brazed manifold to withstand the very high pressure generated into the fluid refrigerating circuit.

[0008]In known heat exchangers, the tubes are arranged in one stack, or two stacks arranged next to each other. The individual tubes are located in respective manifolds and they are not in a direct contact with each other. This brings many drawbacks, starting from the assembling process of the heat exchanger. Individual tubes are difficult to introduce into tight slots in the manifolds. Moreover, the stack of tubes is not robust as such, since there is no interaction between the tubes forming said stack. Thus, during for example, thermal expansion of the heat exchanger, the individual tubes are prone to damage. Further, implementing many tubes arranged in one stack requires having at least one manifold on each side of the open ends of the tubes. This could be resolved by bending the tubes to form a U-turn. However, bending the tube is as such is very difficult, since it may decrease the robustness thereof. Moreover, the tubes are usually bent so that one sidewall forms a tight turn of a U-turn, and the other sidewall forms a wide turn of the U-turn. This may lead not only to the leakage, but it may also negatively impact the flow of the fluid within each tube. Consequently, it will also negatively impact the overall efficiency of the heat exchanger.

[0009]Furthermore, the heat exchanger has limited efficiency especially due to two factors. First is that heat exchanger is not (in case of one stack) or only partially (in case of two stacks) counter flow. In case of adding additional tube stack or stacks, the counter flow effect will increase, what moves refrigerant outlet temperature closer to air outlet temperature with efficiency increase as consequence. The second factor are compartments (or zones) with different temperature caused by refrigerant temperature change due to its interaction with the air. If such temperature gradient occurs, the internal heat exchange in these compartments occurs due to heat conduction with consequence of less heat exchange between refrigerant and the air. Consequently, the efficiency of the heat exchanger may degrade again.

[0010]The above-mentioned tube may be improved so that the robustness of the tube is increased and assembling process the of the heat exchanger is facilitated. Moreover, the overall cost of the tube and/or the heat exchanger may be easily reduced without impacting the performance of the heat exchanger.

SUMMARY OF THE INVENTION

[0011]The object of the invention is, among others, a tube for a heat exchanger, comprising: a first tubular element and at least one second tubular element each tubular element comprising two juxtaposed longer walls having essentially flat surface connected by a pair of shorter walls to form a closed profile of each tubular element, wherein the tube further comprises at least one reversal element configured to fluidly connect the first tubular element and the second tubular element, wherein the tubular elements are arranged next to each other, so that the respective longer walls are coplanar with respect to each-other, wherein the reversal element is made integral with the tubular elements.

[0012]Advantageously, the reversal elements comprise a first twisted section and at least one second twisted section, wherein the first twisted section protrudes directly from first tubular element, and the second twisted section protrudes directly from the second tubular element.

[0013]Advantageously, the reversal element comprises an essentially U-shaped section configured to fluidly connect the first twisted section and the second twisted section.

[0014]Advantageously, the reversal element comprises an essentially straight section configured to fluidly connect the first twisted section and the second twisted section.

[0015]Advantageously, the second twisted section protrudes helically in one direction, wherein the first twisted section protrudes helically in the same direction as the second twisted section.

[0016]Advantageously, the second twisted section protrudes helically in one direction, wherein the first twisted section protrudes helically in different direction than the second twisted section.

[0017]Advantageously, the first tubular element forms a first pass or the fluid, the second tubular element comprises a second pass for the fluid, wherein the intended fluid flow direction in the second pass is in counterflow with respect to the intended fluid flow in the first pas.

[0018]Advantageously, the reversal section comprises an essentially the same hydraulic cross-section as any of the first tubular element or the second tubular element.

[0019]Advantageously, the tube is an extruded tube comprising a plurality of micro channels.

[0020]Advantageously, the heat exchanger further comprises: at least one first manifold group configured to receive one end of the tube and a second manifold group configured to receive the other end of the tube, wherein the first manifold group comprises at least a first channel fluidly connected with the first tubular elements, so that a fluidal communication between at least two tube bundle is provided, and in that the second manifold group comprises a second channel fluidly communicated with at least second tubular elements, wherein the manifold groups are arranged next to each-other.

[0021]Advantageously, the first and the second manifold groups comprise a header plate comprising slots for receiving the tubes, a distribution plate configured to form the first and the second channel in the manifold groups, and the tank plate for closure of the manifold groups.

[0022]Advantageously, the header plate comprises a plurality of teeth configured to fix the distribution plate and the tank plate.

[0023]Advantageously, the tub further comprises a third tubular element and a fourth tubular element, wherein the third and fourth tubular elements are fluidly connected by corresponding reversal elements.

[0024]The reversal elements allow to change the intended flow direction of the fluid, without the necessity to provide additional manifolds. It may significantly reduce the overall cost and weight of the heat exchanger while keeping the desired packaging. The reversal elements having the twisted sections further allow to form the substantially equidistant path for the fluid throughout the tube, unlike in the tube comprising direct U-turn, wherein the sidewalls are at some point of different length.

BRIEF DESCRIPTION OF DRAWINGS

[0025]Examples of the invention will be apparent from and described in detail with reference to the accompanying drawings, in which:

[0026]FIG. 1 shows a side partial view of the tube having a reversal section;

[0027]FIG. 2 shows a side view of the tube having reversal section of at least two different types;

[0028]FIG. 3 shows a detailed view of the reversal section in one of the examples;

[0029]FIG. 4 shows a detailed view of another reversal section in one of the examples;

[0030]FIG. 5 shows a perspective view of the heat exchanger having at least one tube of FIG. 1, FIG. 2, FIG. 3 and FIG. 4; and

[0031]FIG. 6 shows a side view of the tube-manifolds assembly in one of the examples.

DETAILED DESCRIPTION OF THE INVENTION

[0032]The subject-matter of an invention is a tube 10 for the heat exchanger 1 which is adapted for heat exchange between a first fluid and a second fluid. The first fluid may be for, example pressurized refrigerant such as carbon-dioxide circulating within the heat exchanger 1, whereas the second fluid may be, for example, an air. The heat exchanger 1 aims to decrease the temperature of the first fluid. It can therefore be associated with the gas coolers, inner gas coolers, evaporators and alike. Further paragraphs discuss the main components of the tube 10 suitable for being implemented in such heat exchanger, and the mechanical or structural features thereof which ensure improvement in terms of efficiency with respect to know heat exchangers.

[0033]FIG. 1 shows a partial side view tube 10 for a heat exchanger 1. The term “tube” is not limited to straight piece of tubular element with two open ends. Here the term “tube” means that there may be more than one tubular element suitable for fluid transportation, whereas the tubular elements are at least partially integrated to form one sub-component. The partial view does not show the open ends of the tube 10 since it aims to show more in detail other characteristic features.

[0034]Referring to FIGS. 1 and 2, the tube 10 may comprise first tubular element 11, and at least one second tubular element 12. An embodiment in which more tubular elements are introduced, i.e. a third tubular element 30 and a fourth tubular element 40, is also envisaged, as shown in FIG. 2. It is to be noted that the number of implemented tubular elements is not limiting. The third tubular element 30 and a fourth tubular element 40 are essentially the same as the first tubular element 11 and the second tubular element 12, yet throughout the description they have different reference numbers to avoid reader's confusion. Each tubular element 11, 12, 30, 40 may comprise two juxtaposed longer walls 13 having essentially flat surface. In other words, the longer walls 13 are substantially identical wall portions arranged in parallel and facing each other with their respective flat surfaces. The tubular elements 11, 12, 30, 40 may also comprise two shorter walls 14 connecting the longer walls 13 to form a closed profile, and an axis of elongation. The tube 10 may further comprise two open ends 19. The term open end refers to a terminal ends of the tubular element 11, 12, 30, 40 which allows the fluid to enter or exit the entire tube 10.

[0035]The open ends 19 of the tube 10 are arranged on the same side and at the same level, whereas the longer walls 13 of the adjacent tubular elements 11, 12 are arranged so that their flat surfaces are coplanar with respect to each other. In order to achieve such configuration, the tube 10 may further comprise at least one reversal element 15 configured to fluidly connect the first tubular element 11 and the second tubular element 12. The reversal element 15 may be made integral with both tubular elements 11, 12. In other words, the reversal element 15 is made in a process of bending a piece of tube, providing reversed flow of the fluid in the unitary piece thereof. Alternatively, the reversal element 15 may be a separate element fixed to both tubular elements 11, 12. However, this embodiment is not preferred due to worse durability of such assembly, in comparison to unitary one.

[0036]The reversal elements 15 may thus be interpreted as any integral section of the tube 10 which is configured to change the intended flow of the fluid within the tube 10. In particular, the reversal elements 15 may be configured to provide the counter flow of the fluid within two neighboring straight sections of the tube 10, i.e. the first tubular element 11 and the second tubular element 12, et cetera.

[0037]Referring to FIGS. 3 and 4, the reversal element 15, may comprise, inter alia, a first twisted section 15A and at least one second twisted section 15B. A term “twisted” refers to essentially helical or semi-helical shape of the section. The twisted section 15A, 15B allow smoother transition of the channel of the fluid, without drastic change of the hydraulic diameter within the reversal element 15. Moreover, if the tube 10 is an extruded tube comprising micro channels, said channels remain their desired shape.

[0038]The integrity between the tubular elements 11, 12, 30, 40 and the reversal element 15 may be described, so that the first twisted section 15A may protrude directly from first tubular element 11, and the second twisted section 15B may protrude directly from the second tubular element 12. The twisted sections 15A, 15B may be then joined together to form a fluidal communication between the neighboring tubular elements 11, 12, 30, 40. Naturally, it is also true that the second twisted section 15B may protrude directly from the first twisted section 15A, so other ways of describing the twisted sections 15A 15B are also possible. It depends mainly on the point of reference. For example, the first twisted section 15A may protrude in helical manner in the counterclockwise direction with respect to the first tubular element 11, yet with respect to the second twisted section 15B it may protrude in a clockwise direction. Similarly, the second twisted section 15B may protrude in helical manner in the counterclockwise direction with respect to the second tubular element 12, yet with respect to the first twisted section 15B it may protrude in a clockwise direction.

[0039]The reversal element may comprise an essentially U-shaped section 16A which connects the first twisted section 15A and the second twisted section 15B. The U-shaped section 16A may be of relatively small curvature, or of bigger curvature. The smaller curvature of the U-shaped section is formed to the extent which is allowed by mechanical properties of the material from which the tube 10 is made of. Small curvature allows to pack the consecutive tubular elements 11, 12, 30, 40 closer to each other which improves packaging. The bigger curvature on the other hand facilitates thermal decoupling of the consecutive tubular elements 11, 12, 30, 40 and allows relatively smoother transfer of the fluid therein.

[0040]The reversal element 15 may also comprise an essentially straight section 16B. Similarly to U-shaped section 16A, the straight section 16B may be configured to fluidly connect the first twisted section 15A and the second twisted section 15B between the tubular elements 11, 12, 30, 40. As mentioned in previous paragraphs, the second twisted section 15B protrudes helically in one direction, wherein the first twisted section 15A protrudes helically in the same direction as the second twisted section 15B. Alternatively, the second twisted section 15B protrudes helically in one direction, wherein the first twisted section 15A protrudes helically in different direction than the second twisted section 15B. The helical direction of protrusion means that the sidewalls 14 remain substantially equidistant with respect to each other, but the axis of elongation of the tubular element 11, 12, 30, 40 is disordered.

[0041]The reversal elements 15 allow to change the intended flow direction of the fluid, without the necessity to provide additional manifolds. It may significantly reduce the overall cost and weight of the heat exchanger 1 while keeping the desired packaging. The reversal elements 15 having the twisted sections 15A 15B further allow to form the substantially equidistant path for the fluid throughout the tube 10, unlike in the tube comprising direct U-turn, wherein the sidewalls 14 are at some point of different length.

[0042]Each tube 10, including both the tubular element 11, 12, 30, 40 and the reversal elements 15 may comprise a set of micro channels extending between the open ends of the tube 10. Naturally, the micro channels are continuous throughout the reversal elements 15, i.e. the micro channels in the reversal elements are configured to link fluidly the corresponding micro channels in respective tubular elements 11, 12, 30, 40. The tubular elements 11, 12, 30, 40 may be of the same size, i.e. their external dimensions such as: width, measured as the distance between the outer faces of the shorter walls 14; the length-measured along the longer walls 13, as the distance between the open ends of the tube; or as the height, measured as the distance between the outer faces of the longer walls of the same tubular element 11, 12, 30, 40.

[0043]The tube 10 may be implemented in a heat exchanger 1. The exchanger 1 may comprise, inter alia: the plurality of tubes 10 which arranged in a stacking direction, wherein the stacking direction is perpendicular to the flat surfaces of the tubes 11, 12, 30, 40.

[0044]The heat exchanger 1 may further comprise at least one first manifold group 100 and at least one second manifold group 200. The first manifold group 100 may be configured to receive one open end of the tube 10 and the second manifold group 200 may be configured to receive the other open end of the tube 10. As the open ends of the tube 10 may be arranged next to each other, the tubes 10 may be connected to single, mutual manifold group, for example the first manifold group 100, so that the first manifold group comprises at least two separate channels for the fluid. In other embodiment, also not presented in the figures, the heat exchanger 1 may also comprise a first set comprising the tubes 10 and a second set comprising plurality of individual tubes arranged in a stack. Term individual tubes refers to the tubes having a substantially straight structure with two opposite open ends. In this embodiment, the heat exchanger 1 may comprise a third manifold group in order to provide a U-turn for the fluid, so that said fluid may circulate between the stacks of individual tubes.

[0045]The first manifold group 100 may comprise at least a first channel 101 fluidly connected with the first tubular elements 11, so that a fluidal communication between at least two tubes 10 is provided. The second manifold group 200 may comprise a second channel 202 fluidly communicated with at least two second tubular elements 12, or any tubular elements 30, 40 which should be regarded as last in the series.

[0046]FIGS. 5 and 6 shows the heat exchanger 1, wherein the tube bundle 10 further comprises a first tubular element 11, a second tubular element 12, a third tubular element 30 and a fourth tubular element 40, wherein the first tubular elements 11 form a first pass P1 for a fluid, the second tubular elements 12 form a second pass P2 for the fluid, wherein the reversal element 15 is fluidly communicating said passes, the third tubular elements 30 form a third pass P3 for the fluid, and the fourth tubular elements 40 form a fourth pass P4 for the for the fluid, wherein the one reversal element 15 is fluidly communicating the second pass P2 and the third pass P3, and the other reversal element is fluidly communicating the third pass P3 and the fourth pass P4. The term pass refers to intended direction of the fluid moving in said pass in the same sense. The heat exchanger 1 comprising four passes arranged as in present invention allow better heat evacuation, increased heat transfer and generally, increased performance of the heat exchanger while keeping relatively small packaging.

[0047]It is apparent from FIG. 6, that at least one reversal element 15 may be located between the first manifold group 100 and the second manifold group 200. Further, the reversal element 15, may be essentially at the same level as the manifold groups 100, 200. Alternatively, at least one reversal element 15 may protrude beyond the level of the manifold groups 100, 200, so that at least part of said reversal element protruded beyond the level of teeth 160.

[0048]Term “manifold group” may refer to one or more manifolds arranged in the vicinity one to another. For example, “first manifold group” may refer to two manifolds arranged next to each other, wherein these manifolds share the same structural features.

[0049]The first and the second manifold groups 100, 200 may comprise a header plate 100a, 200a comprising slots 150 for receiving open ends of each tubular element 11, 40, a distribution plate 100b. 200b configured transfer the fluid between the tube 10 and the channel, and the tank plate 100c, 200c configured to form the first and the second channel 101, 202 in the manifold groups 100, 200.

[0050]Referring to FIG. 6, since the manifold groups 100, 200 may be manufactured by crimping and brazing the latter components, they may comprise plurality of teeth 160 configured to fix the distribution plate 100b, 200b and the tank plate 100c, 200c to the header plate 100a, 200a.

[0051]The heat exchanger 1 may comprise an inlet and an outlet for the first fluid. Both inlet an outlet may be in form of openings fluidly connected to respective pipes of the refrigerant loop. The openings may also be connected indirectly, for example by means of connection block or other types of connectors, as shown in FIG. 5. The pipes or the connection blocks may be fixed wherever suitable, depending on desired flow pattern or location of the inlet and outlet.

[0052]Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of drawings, the disclosure, and the appended claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to the advantage.