IT202100006266A1 - HEAT EXCHANGER TUBE WITH IMPROVED CONDUCTIVITY CHARACTERISTICS - Google Patents

Description

HEAT EXCHANGER TUBE WITH IMPROVED

CONDUCTIVITY CHARACTERISTICS?

DESCRIPTION

TECHNICAL FIELD

The present invention falls within the scope of the production of heat exchangers particularly, but not exclusively, for the petrochemical sector. In particular, the invention refers to a heat exchange tube of the bi-component type, i.e. made up of at least two components. Does the heat exchange tube have improved conductivity characteristics? of the heat. The invention? otherwise? relating to a heat exchanger comprising a plurality? of heat exchange tubes according to the invention and to a process for manufacturing a heat exchange tube.

STATE OF THE ART

As known, heat exchangers are used whenever there is a need? to transfer heat from a high temperature fluid to a low temperature fluid. In particular, in a vast typology of plants (for example in the petrochemical, energy, manufacturing, production sectors in general) heat exchangers are used comprising a plurality of heat exchangers. of finned type heat exchange elements.

Among the various types of exchangers known on the market, those formed by batteries of heat exchange tubes of the bi-component type are considered. In particular, with the term ?two-component? it is meant to indicate that the pipe comprises at least two components: an internal component (or base) intended to be crossed by a first fluid, and an external component intended to be lapped by a second fluid.

Typically, the basic component ? made of a conductive metallic material with high mechanical resistance (normally steel), while the external component? made of a high conductivity metallic material? thermal (usually aluminum, copper or its alloys). In a known embodiment thereof, the two components are formed by two coaxial tubular bodies with a cylindrical section.

In the context of bi-component heat exchange tubes, those with radial fins are identified, normally also known by the English denomination ?finned tube?. In a first known embodiment, described for example in the granted patent IT0001349756, the two components of the heat exchange tube both have a tubular configuration and are coaxially connected. In particular, does the base component define a cavity? longitudinal section intended to be crossed by a first fluid, usually at a high temperature. The external component? instead shod on the base one, so what? that the surface pi? external part of the internal component is connected and in contact with the surface pi? internal part of the external component.

The external component comprises a shaped portion defining, in a single piece, the tabs indicated above. These fins have a circular profile if observed on a section plane orthogonal to the axis around which the two elements develop. Instead, if considered on a plane containing the axis of the exchanger tube, they define a continuous spiral coaxial with said longitudinal axis. In particular, the flaps are made through an expansion and plastic deformation operation carried out with suitable forming means. A heat exchange tube of this type is usually referred to by the English term ?extruded? and the operating temperatures can even be higher than 250?.

In another known embodiment, the exchanger tube differs from the ?extruded? described above for a different configuration of the external component, while the internal one ? always tubular in shape. In fact, in this case the external component ? defined by a ribbon of thermally conductive material that is connected in a continuous spiral around the outer surface of the base component. As a result of the spiral arrangement, the body of the strip also defines the fins in this case with a circular shape if observed on a plane transverse to the axis of the tube. The tubes based on this constructive principle are normally also referred to as ?applied fin tubes?.

Pi? precisely, the tape is connected, at one of its edge surfaces, to the outer surface of the base component. Depending on the mode with which this connection is implemented, the heat exchange tubes take on different names. In this regard, in figure 2 ? shown is an embodiment commonly indicated by the English denomination ?L finned tube?, in which the edge portion of the strip defining the fins ? folded 90?, cos? to give the fins themselves an L-shaped profile, if evaluated on a longitudinal section plane. In particular, for each? fin, the edge portion coincides with the foot portion of the fin, while the body of the fin? defined by the remainder of the tape.

The edge portion of the web is bonded to the outer surface of the base component typically by swaging or welding. The extension of the edge portion identifies the pitch of the spiral, ie? the longitudinal distance between one flap and the other.

In another embodiment, shown in figure 3 and known in the sector with the English denomination ?KL finned tube?, the edge portion of the fin ? folded in a similar way to what is foreseen for a ?L finned tube? described above. In this case however, to favor the connection, before the connection of the tape, the outer surface of the component is knurled. Following the connection, the edge portion of the flap also undergoes a knurling or in any case an upsetting process, in order to increase adhesion against the surface of the base component.

In a further known embodiment, shown in figure 4 and known by the English denomination ?LL finned tube?, the edge portion of the strip, in addition to being folded at 90? compared to the body as in the previous cases, ? shaped so as to define a first region and a second region, on different planes, respectively adjacent and distal to the body of the tape. In this case, the edge portion is fixed so that, for each tab, the second region is in contact with the outer surface of the base component, while the first region overlaps a second region of an adjacent tab. Therefore, in a longitudinal sectional view such as that of figure 4, for each flap, the edge portion is connected to the internal surface of the base component and contextually connected and superimposed on a part of the foot portion of an adjacent flap.

Figure 5 refers to a further embodiment, in which the edge portion ? inserted in a spiral groove previously made on the external surface of the base component. In this embodiment, normally known by the English denomination ?G embedded finned tube?, after being inserted into the spiral groove, the edges of the same groove are pressed, using a suitable tool, against the opposite sides of the edge portion, in order to ensure the mechanical fastening of the tape.

In general, regardless of their specific configuration (L, LL; KL, G embedded, extruded), the heat exchange tubes of the types described above, and others related to them, are used in batteries in heat exchangers, typically coolers, large in size. The ?extruded? type pipes, for example, are used for the construction of air coolers for the petrochemical sector with operating temperatures up to 280 C?. In the case of arrays of ?embedded? G tubes, the operating temperatures can be even higher, even reaching 450 C?. In any case, in these coolers, the basic component of the exchanger tube? crossed by a high temperature liquid and the fins defined by the external component (in the form of tubular or applied tape) are lapped by air normally forced through a blower or other equivalent means.

? It is known that to perform their function effectively, these cooling devices require a large number of heat exchange tubes. To provide an example, in a medium-sized exchanger several heat exchange tube banks are typically provided, the number of which typically varies between 70 and 400 tubes for each bank. The batteries can be arranged in series or in parallel, or even work individually, that is? independently from other batteries. In these devices, the length of the pipes ? typically between 2.5 and 18 metres, regardless of their configuration.

The capacity? of heat exchange, or the conductivity? thermal, of each tube ? a determining factor, not only in terms of general efficiency, but also in reference to the construction costs and to the final size of the cooling device, as well as? to all aspects related to it (quantity and costs of the material used, costs of installation and transport, costs of the foundations and in general of the structures necessary for implementation in the plant which includes the cooling device, difficulties in the design and in the subdivision of the spaces of the plant itself).

? therefore felt the need to supply exchanger tubes with high performance and at the same time to improve the conductivity? thermal of the individual exchanger tubes, in the configurations already? notes (such as those described above). This is not only for the purpose of improving, on equal terms? in size, the performance of a cooler, but also for the purpose of decreasing, parity? performance, the size of the device itself by eliminating or at least mitigating the other drawbacks related to the size itself.

Although this need has been felt for many years, the proposed solutions have so far not allowed to achieve acceptable results or in any case such as to represent a significant step forward in the sector. In the aforementioned patent IT0001349756, for example, ? a solution has been proposed to improve the heat exchange between the two elements constituting an ?extruded? type pipe. In particular, the creation of reliefs on the surface more? external part of the internal component, which are anchored to the external component following the forces that are generated during its deformation aimed at making the fins.

Other solutions proposed in the sector intend to improve the performance of the exchanger tube by resorting to the combination and/or choice of more performing materials. In particular, some proposed solutions concern particular geometries and/or configurations envisaged for the fins. In this regard, shaped fins have been proposed, for example perforated, cut, made of two materials (for example partially copper and partially other conductive material). Other solutions plan to improve the conductivity? of the components of the exchanger tube through machining of the surface pi? internal part of the basic component, for example a helical rifling designed to increase turbulence.

These solutions find for? limits in reference to the times and costs necessary for their realization and/or the costs relating to the raw materials necessary for their implementation. All in all, ? was therefore established the need? to have a new technical solution that allows to significantly increase the performance of the heat exchange tubes without upsetting the production process at the basis of their realization.

SUMMARY

Main task of the present invention ? to provide a solution that allows to overcome or at least mitigate the problems indicated above. Within the scope of this task, a first object of the present invention is that of providing a two-component heat exchange tube with improved performance, in terms of conductivity? thermal, compared to known type exchanger tubes of the same type. Other purpose? to provide a heat exchange tube in which the best performance in terms of conductivity? are obtainable without significantly increasing the process costs compared to the current ones. Additional purpose? that of providing an exchanger tube that is reliable and easy to make at competitive costs.

The Applicants have found that the above proposed aim and objects can be achieved by providing a conductive interface layer in the region or regions in which the connection between the two elements constituting the exchanger tube is achieved. In fact, measurements and microscopic analyzes conducted in this, or in these, regions have revealed that between the surfaces of the two elements (base and exterior) ? detectable a cavity or ?gap? (in the order of microns) determined by the morphology and finish of the surfaces themselves. This ?gap? it inevitably limits the heat exchange between the two elements of the pipe since, due to the lack of continuity, the transmission of heat from the base component to the external one does not occur by conduction, but by convection and/or radiation. Regardless of its specific configuration (L, LL, KL, G, etc.), in the case of an "embedded" type exchanger tube, the critical region is found between the foot portion of the fins and the external surface of the base component, while in an ?extruded? type tube, the microscopic gap between the inner surface of the outer tube and the outer surface of the base component affects the maximum thermal power that can be used? be disposed of.

The idea behind the present invention ? therefore that of providing a highly conductive interface formed by a layer comprising graphene in pure form or in the form of a derivative, wherein this layer annuls or at least strongly limits the microscopic gap indicated above. Pi? precisely, the Applicant has found that the intended aim and objects can be achieved by means of a bi-component heat exchanger tube comprising:

- at least one internal component in metallic material of tubular shape comprising at least one surface more? external and at least one surface pi? internal, where the latter defines a cavity? longitudinal for the passage of a first fluid;

- at least one external component made of metallic material comprising a base surface at which it is connected to said first component, wherein said external component ? capable of being lapped by a second fluid.

The heat exchange tube according to the invention is characterized by the fact that between the most? exterior of the inner component and the base surface of said outer component ? a layer comprising graphene in pure form or in derivative form is provided.

Advantageously, the graphene layer acts as a thermal bridge between the two components that form the heat exchange tube, greatly increasing the thermal conductivity. thermal between them. During the production process of the exchanger tube, graphene in pure form or in the form of a derivative can be applied to the base surface of the component pi? external and/or to the surface pi? exterior of the internal component so as to give rise to said layer following the connection of the two components.

According to a preferred embodiment, the external component ? configured so as to define at least one heat exchange fin, capable of being lapped by said second fluid, which develops around the internal component.

According to a possible embodiment, the external component ? configured to define a plurality? of fins, which develop around the base component in a continuous manner according to a spiral profile, evaluated on a longitudinal section plane containing a longitudinal axis of said internal component. Said fins have a circular shape considered on a transversal plane orthogonal to said longitudinal axis.

In a possible embodiment variation, the external component ? defined by a tubular body defining a cavity? cylindrical in which ? housed the internal tubular component; in this embodiment variant, the base surface of the external component delimits said cavity? cylindrical.

In another possible embodiment, the exchanger tube comprises a plurality of of outer components each comprising a collar defining an inner surface at which it is connected to the outer surface of said inner component, each outer component defines a lug extending from said collar surrounding it. These external components are connected to the internal component so as to be longitudinally side by side. For each of them ? foreseen a layer of graphene, in pure or derivative form, between the inner surface of the collar and the outermost surface. external part of the internal component. According to a possible embodiment, the second component ? defined by a tape in metallic material applied, in correspondence with one of its edge portions, on said surface more? exterior of said internal component according to a spiral pattern.

In a possible variant, called edge portion ? a longitudinal portion folded with respect to the body of the tape so that said fins, generated following the spiral application of said tape on said internal component, have a substantially L-shaped shape, evaluated on a longitudinal section plane containing the longitudinal axis of the internal component; for each fin, considered on said sectional plane, a foot portion and a body portion are identified, wherein said foot portion ? defined by a section of the edge portion of the tape. In this variant, the layer comprising graphene is provided between at least one first side of the foot portion, facing the internal component, and the outermost surface. external part of the same internal component.

In a further possible variant, for each of the wings, considered on the longitudinal section plane indicated above, the foot portion comprises a first region and a second region, wherein the second region is comprised between the first region and the body portion. These regions are configured to be ?staggered? whereby an inner side of the first region and an inner side of the second region are respectively adjacent and distal to the outermost surface? external part of the internal component. As a result of spiraling the web around the inner component, the second region of the foot portion overlaps the first region of an adjacent flap. In this variant, the graphene layer? provided between the outer surface of the base component and the inner side of the first region of the foot portion of each fin.

Preferably, a further layer of graphene, in pure or derivative form, is provided between the overlapping regions of two adjacent fins.

According to another embodiment, the edge portion of the tape is inserted into a predefined spiral groove on the outer surface of the inner component; in this case, the graphene layer? defined at least between the surfaces of said spiral groove and the edge portion of said belt inserted therein.

According to a further embodiment, the body of said tape is folded on s? itself so that at least two of its portions face each other, defining a space inside which ? a further layer of graphene is provided in pure form or in the form of a derivative.

In the context of this embodiment, according to a first possible variant, the body of the tape is folded so that said two portions face each other according to a U configuration, where such a U ? facing the outer surface of the base component. According to another possible variant, the portion of the body ? folded in such a way that said two portions face each other and connected in such a way that said further layer is completely surrounded by the body of the tape.

According to a further possible variant, the body portion of the tape ? folded in such a way that said flaps, defined following the application of said tape on said internal component, have a substantially ?tuning fork? for which a base part and a top part are identified, in which each part is defined by two mutually facing portions of tape, in which said further layer of graphene ? defined between the two portions defining the base part.

LIST OF FIGURES

Further characteristics and advantages of the invention will become more apparent from an examination of the following detailed description of some preferred, but not exclusive, embodiments of the heat exchange tube according to the invention, illustrated by way of non-limiting example, with the support of the drawings attachments, in which:

- figures 1 to 5 refer to known embodiments of exchanger tubes of the two-component type with fins;

- figures 6 to 15 each show a possible embodiment of a heat exchanger tube according to the present invention;

The same reference numbers and letters in the figures identify the same elements or components.

DETAILED DESCRIPTION

With reference to the cited figures, the present invention ? therefore relative to a heat exchange tube indicated generically with the reference 1. The heat exchange tube 1 will be? hereinafter also indicated with the expression ?exchanger tube 1? or more simply ?tube 1?. The heat exchange tube 1 ? intended for the construction of a heat exchange device, for example a liquid-air cooler, preferably operating in a temperature range between 100 and 500°C.

In any case, the heat exchange tube 1 according to the invention is of the two-component type, that is? comprising at least two components (or elements) connected to each other, which define its structure.

In particular, the tube 1 comprises at least one internal component 10 (hereinafter also referred to as the "base component 10") having a tubular shape and made of a metallic material. The ?tubular? provides a surface more? external 11 and at least one surface more? internal 12; the latter defines a cavity? longitudinal for the passage of a first fluid, preferably at a high temperature.

In accordance with a preferred embodiment, visible in the attached figures, the two surfaces 11, 12 are cylindrical and therefore the base component 10? a hollow cylinder with a straight longitudinal axis 100. However, the term ?tubular? Not ? limited to this configuration. In fact, the basic component 10 could have a cross section, that is? orthogonal to the longitudinal axis, different from the cylindrical one, for example rectangular, elliptical or other. At the same time, the shape of the surface is also more? external 11 could differ from the shape of the surface pi? internal 12.

The exchanger tube 1 comprises at least one external component 20 comprising a body made of metallic material defining at least one base surface 21B in correspondence with which this body is connected to the base component 10. Pi? precisely, in correspondence with this base surface 21B, the body made of metallic material of the external component 20 is connected to the surface pi? external 11 of the basic component 10. The external component 20 ? intended to be lapped by a second fluid, preferably at a low temperature, cio? at a lower temperature than that of the fluid passing through the cavity? of the basic component 10. Preferably, in fact, the heat transmission performed by the exchanger tube 1 takes place from the first fluid to the second fluid.

In any case, within the scope of the present invention, the exchanger tube 1 and the two components 10, 20 which compose it are configured, in terms of materials and structure, chosen so as to allow use, single or in series with other exchanger tubes , for example for the construction of a cooler with operating temperatures between 100 C? and the 500 C?.

In accordance with a preferred embodiment, the outer component body 20 is configured in such a way as to define at least one heat exchange fin, which develops around the base component 10, to be lapped by the second fluid, preferably at a low temperature, i.e. at a lower temperature than that of the fluid passing through the cavity? of the basic component 10. Preferably, the external component 20 configures a plurality? of fins 25 side by side in the longitudinal direction, that is? according to a direction parallel to the longitudinal axis 100 of the basic component 10.

In any case, according to the present invention, at least between the base surface 21B of the external component 20 and the outermost surface? external 11 of the basic component 10, ? a layer 5 comprising graphene in pure form or in the form of a derivative is provided. This layer essentially constitutes a highly conductive interface between the two elements constituting the tube 1, since graphene has a conductivity index of very high thermal, between 1000 W/mK and 5000 W/mK. Through the layer comprising graphene, a thermal bridge is formed which greatly increases the transmission of heat by conduction between the two components of the exchanger tube 1.

Preferably, the graphene present in the layer indicated above is in pure form, also called ?original? (or ?pristine? in English). Alternatively, can be present in the form of a derivative, mainly as graphene oxide (or ?GO? from the English ?Graphene Oxide?). In this regard, in one of its possible modalities? of use, graphene pu? also be functionalized with other atoms or groups of atoms in addition to oxygen. In the event that the graphene is present in the form of a derivative, the carbon preferably constitutes at least 90% by weight of the derivative, even more? preferably at least 95% by weight.

According to an embodiment visible in the figures, the external component 20 is configured to define a plurality? of fins 25, which develop around the base component 10 in a continuous manner according to a spiral profile, evaluated on a longitudinal section plane containing the longitudinal axis 100 of the tube 1. These fins 25 have a circular shape considered on a transversal plane , orthogonal to said longitudinal axis 100.

Figure 6 refers to a first embodiment of an exchanger tube 1 according to the present invention, the structure of which ? substantially referable to that of an ?extruded? type pipe. In particular, the base component 10 ? formed by a cylindrical body in metallic material, preferably steel. Also the external component 20 ? defined by a tubular body defining a cavity? cylindrical 25, in which ? the cylindrical body defining the base component 10 is housed. In this embodiment, the base surface 21B of the external component 20 coincides with the outermost surface? inside of the external component 20 delimiting the cavity? cylinder 25 for housing the base component 10. Therefore, according to the present invention, the layer 5, comprising graphene, is provided between the inner cylindrical surface of the outer component 20 and the outer cylindrical surface 11 of the base component 10.

In figure 6, the graphene layer 5 extends for a shorter length than the longitudinal extension of the exchanger tube 1. In any case, preferably, the graphene layer 5 extends for the whole length of the exchanger tube 1, a length measured parallel to the its longitudinal axis 100.

Still with reference to figure 6, the external component 20 is defined by a body in high conductivity metal material? thermal and easily deformed. In this regard, preferred materials for the external component 20 are aluminium, copper or alloys thereof. In any case, the external component 20 comprises a plurality of fins 25 which develop around the base component 10 in a continuous manner according to a spiral profile, evaluated on a longitudinal section plane containing the longitudinal axis 100 of the tube 1. These fins 25, on the other hand, have a circular shape considered on a plane transversal, orthogonal to said longitudinal axis 100.

A possible embodiment of a process for making the exchanger tube of Figure 6 is described below. In particular, the process involves the steps of:

a) preparing a first tubular body, preferably made of metallic material with high mechanical resistance, defining the base component 10 and preparing a second tubular body, made of a material with a high conductivity index? thermal, defining the external component 20; b) applying a layer comprising graphene in pure form or in the form of a derivative on the surface of the? outer surface 11 of the base component 10 and/or on the base surface 21B of the outer component 20;

c) inserting the base component 10 inside the external component 20;

d) deforming, hot or cold, the second component 20 so as to form said fins 25, wherein this deformation is carried out through the action of forming means which generate a pressure on said external component 20 as a result of which the base surface 21B of the same adheres to the surface pi? external part of the base component 10.

According to a preferred embodiment, before step b), the process provides for the step of cleaning the surface most? outer 11 of the base component 10 and/or on the base surface 21B of the outer component 20. This step is implemented to limit the most? possible the presence of impurities? which could reduce the efficiency of graphene. In a first embodiment, this cleaning takes place through a mechanical action (for example through sanding, brushing, traditional sandblasting, carbon dioxide sandblasting). Alternatively, chemical means can be used, such as for example chemical bugs, solvents or reagents.

In a preferred embodiment of the process described above, in step b) the graphene is applied dispersed in a liquid which may be be water or an organic solvent. Preferably, the application of this dispersion on the selected surfaces (the outermost surface 11 of the base component 10 and/or on the base surface 21B of the external component 20) is carried out through a mechanical deposition technique, which can be be for example coating, spraying, application using an impregnated pad, painting, deposition by dipping or glazing or other equivalent deposition techniques carried out by mechanical means.

In an alternative embodiment, however falling within the scope of the present invention, the graphene dispersed in the liquid can also be applied through a chemical deposition technique (for example by means of PVD, CVD, ALD, PLD deposition) or electrochemical/electrophoretic (use of galvanic means and/or currents between anode and cathode).

Regardless of the mode with which the graphene dispersion is applied, in step d), the plastic deformation carried out on the external component 20 leads to a rise in the temperature of the two components 10 and 20 as a result of which the liquid or solvent of the above dispersion evaporates. Therefore, at the end of the production process, the conductive interface between the two components 10,20 ? formed by graphene alone in pure form or in the form of a derivative depending on the case.

In a possible embodiment, however falling within the scope of the present invention, the liquid in which it is dispersed graphene could be evaporated before inserting the base component 10 into the external component 20.

In a further embodiment, the graphene could be applied to the surfaces of interest in the powder state, i.e. without dispersed in liquid, solvent or in an organic matrix. In this regard, graphene powder could be applied through scattering, using magnetic and/or electrostatic fields. For the same purpose, a galvanic technique could be used by providing for the deposit of a compatible base on the surfaces to be coated with graphene and conveying the latter through electric currents. A further technique that can be used for the deposition of graphene powder could be that of plasma spray or cold plasma. In accordance with a preferred embodiment of the process described above, the base component 10 is fitted onto a mandrel which remains inside it during the execution of step c). In particular, in the context of phase c) is the spindle rotated so? to make the base component 10 rotate. Therefore, the latter is kept in rotation during its insertion inside the second component 20 which instead remains stationary during this phase.

In this regard, preferably, the mandrel is inserted into the basic component 10 before the application of the graphene layer on the surface more? outer 11 of the base component 10 and/or on the base surface 21B of the outer component 20. In an alternative embodiment, the mandrel could be inserted into the base component 10 after applying the graphene layer on the affected surface or surfaces.

In an alternative embodiment, the base component 10 ? pushed and is rotated through a system of external wheels without resorting to the use of a spindle.

With reference again to step c), the base component 10 is inserted into the external component 20 according to a first insertion direction. At the end of this insertion, the set of two components 10, 20 is moved in a second direction, opposite to the first, so as to be subjected to the action of the forming means.

In this regard, according to a possible form of the manufacturing process, in step d) the forming means have a conformation substantially attributable to that described in document US 2779223. In essence, they comprise a group formed by three units? tools with blades arranged in equally spaced angular positions of 120? around the longitudinal axis 100 of the exchanger tube 1. During the movement in said second direction, the units? tools act on the external component 20 by pressing it against the base component 10 and deforming its external surface so? to be defined the fins 25, which have the configuration indicated above.

The manufacturing process just described above could also be carried out online. In this hypothesis, the set of components 10, 20 would be made to advance in the same movement direction already? previously followed by the base component 10 to fit into the external component 20.

In a possible embodiment of the manufacturing process, in step d) the use of lubricant containing graphite (also of the intercalated or expandable type) is envisaged, which is deposited on the external surface of the external component 20 during the action of the means formers and/or on the fins 25 generated following the action of said former means. Advantageously, the high temperatures and the shear stresses, which are generated on the surfaces where the forming means act, allow an in-situ conversion, on the same surfaces, of the graphite into graphene, with a further increase in the thermal conductivity. temperature of the exchanger tube. In a further possible embodiment of the manufacturing process, at the end of step d), on one or more? regions of the external component 20 is applied a further layer of graphene to increase the conductivity? of its external surface. This additional layer, for example, could be applied to a region or more? regions of the surface of the fins 25, for example in the vicinity? of the extremities? of the fins and/or in the vicinity? of the foot of the fins themselves.

This additional layer pu? be applied according to any of the techniques indicated above with reference to the layer of graphene provided between the two components 10, 20. In a possible embodiment, for example, the application of said further layer of graphene could take place by painting the fins 25 in the regions of interest. This painting could affect the whole surface of the external component 20 so? as any portions of the ends? of the base component 10 not covered by the external component 20.

In one possible embodiment thereof, the manufacturing process could also comprise the further step of making incisions on the fins 25 to increase the turbulence and therefore the heat exchange with the fluid which laps them. In this regard, these incisions could be made with the technique known in the sector with the term ?serrated? for which the incisions are made through blades that act on the top? of the fins in a direction parallel to the longitudinal axis 100 of the tube 1. The incisions defined with this technique appear to be substantially radial on an observation plane substantially orthogonal to said longitudinal axis 100.

In other possible embodiments, the wings 25 could also be perforated or punched, in combination or not with incisions such as those described above or of other types.

Figures 7 to 13 refer to further possible embodiments of a heat exchange tube according to the invention. In particular, these embodiments are of the ?applied flap? the fins are defined as a result of the application in a spiral, on the surface pi? outer 11 of the base component 10, of the second component 20, which for this purpose is defined in the form of a tape made of conductive metallic material, preferably an aluminum or copper tape. With reference to figures 7 to 10, hereinafter to indicate the ?second component 20? will come the expression ?tape 20? is used.

Specifically, figure 7 refers to an embodiment attributable to an exchanger tube of the "L finned" type. In particular, the tape 20 ? applied, in correspondence with one of its edge portions 31B, to the surface more? outer 11 of the base component 10. This edge portion 31B, ? defined by the folding of an edge of the strip 20, whereby the fins 25, generated following the spiral application of the strip 20, have a substantially L-shaped shape, evaluated on a longitudinal section plane containing the longitudinal axis of the exchanger tube 1. Considering the fins 25 on a longitudinal sectional view, as in figure 7, for each fin 25 a foot portion 41B and a body portion 41C are identified. The foot portion 41B of each flap 25 is therefore defined by a section of the edge portion 31B of the tape, while the body portion 41C is defined by the body of the strip 20 with respect to which the edge portion 31B is folded.

For each flap 25, on the foot portion 41B a first side L1 is identified facing the surface more? outer 11 of the base component 10 and a second side L2 opposite the first side L1. In this embodiment, the layer 5 comprising graphene is provided between the first L1 side of the foot portion 41B and the outer surface 11 of the base component 10.

A possible manufacturing process of the heat exchanger tube shown in figure 7 is described below which essentially involves the steps of:

a1) providing a first tubular body made of metallic material, preferably with high mechanical resistance, defining the base component 10;

a2) prepare a tape in metallic material, preferably with a high conductivity index? thermal, defining the external component 20;

a3) folding an edge portion 31B of the tape along its entire length according to an L-shaped configuration;

a4) apply a layer comprising graphene in pure form or in the form of a derivative on the surface more? external 11 of the base component 10 and/or on the side of the edge portion 31B, intended to be connected to the outermost surface? external 11 of the basic component 10;

a5) mechanically connecting, according to a spiral winding, the edge portion 31B of the tape 20 to said external surface 11 of the base component 10 so that said layer 5 comprising graphene is placed between said edge portion 31B and said uppermost surface; external 11 of the basic component 10.

In accordance with a preferred embodiment, the mechanical connection of the edge portion 31B occurs through its upsetting against the external surface of the base component 10. This connection could also be effected through spot welding or in any case any other technique suitable for scope.

Figure 8 shows another possible embodiment of an exchange tube according to the invention attributable to an exchange tube of the ?KL finned? type. Similarly to what is foreseen in figure 7, also in this case the belt 20 is connected to the outer surface 11 of the base component 10 through a portion of its edge 31 folded with respect to the body of the tape 20 so that, following the spiral winding, the fins 25 assume a substantially L-shaped shape. Therefore also in this case the layer comprising graphene in pure or derivative form? provided between the edge portion 31B and the outer surface 11 of the base component 10.

In fact, the embodiment of figure 8 differs from that in figure 9 due to the manufacturing process, which envisages knurling the uppermost surface. external 11 of the base component 10 before applying the layer of graphene on it and in any case before applying the tape 20 defining the fins 25.

In any case, the edge portion 31B of the belt 20, or the foot portion 41B of the wings 25, is pressed against the outer surface 11 of the base component 10, possibly again through a knurling, until the two parts are stably fixed.

Therefore, with respect to the manufacturing process described above comprising steps a1) -a5), for making the exchanger tube 1 of figure 8? expected, before the phase a5), also the phase of knurling the surface pi? outer 11 of the base component 10. Preferably, following step a5) the further step of knurling the edge portion 31B on the side opposite to that in contact with the graphene layer 5 is also provided.

Figure 9 refers to a third embodiment of an exchange tube according to the invention attributable to an exchange tube of the "LL finned" type. Also in this case the tape 20 ? connected to the outer surface 11 of the base component 10 through an edge portion 31 thereof folded with respect to the body of the tape 20 according to an L-shape. Differently from the embodiment described in figure 9, in this case, for the edge portion 31, identifies a first region 31-1 and a second region 31-2, wherein said second region 31-2 is included between the first region 31-2 and the body of the tape 20. In particular, the two regions 31-1, 31- 2, although connected, are ?staggered? so that the internal side (that is, the one facing the base component 10) of the first region 31-1 is substantially adjacent to the external surface 11 of the base component 10, while the internal side of the second region 31-2 is spaced from it.

As can be seen from figure 9, following the spiral winding around the base component 10, the two regions 31-1, 31-2 indicated above are recognized in the foot portion 41B of each of the fins 25 considered on a longitudinal section plane . Pi? precisely, for each flap 25, the second region 31-2 of the foot portion 41B is superimposed on the first region 31-1 of an adjacent flap.

In this embodiment, at least one first layer 5 comprising graphene? expected between the surface pi? outer side 11 of the base component 10 and the inner side of the first region 31-1 of the foot portion 41B. Preferably, a second layer 51 of graphene is provided between the overlapping regions of two adjacent fins.

With respect to the manufacturing process described above comprising steps a1) -a5), in the case of manufacturing the pipe 1 of Figure 9, the process provides for shaping the edge portion 31B of the strip 20 so as to configure the two regions 31-1 , 31-2 defined above. This shaping could be performed in the context of step a3) indicated above or alternatively before or after step a3). Preferably, in step a4) the graphene in pure form or in derivative form is applied on the whole internal side of the edge portion 31 of the tape 20 so as to define said first layer 5 between the external surface 11 of the base component 10 and the inner side of the first region 31-1 of the edge portion 31 and said second layer 51 between the superimposed regions of two adjacent flaps, considered on a plane of longitudinal section. Figure 10 ? relating to a further embodiment of the tube according to the invention, attributable to a ?G embedded? tube. In this case, the edge of the tape 20 is not folded, but inserted into a predefined spiral groove on the outer surface 11 of the base component 10. In a preferred embodiment, before proceeding with this insertion, graphene is deposited in the groove in pure form or in derivative form. Once the tape 20 ? been inserted in the groove, the edges of the same are pressed / pressed against the two opposite sides of the tape 20 thus fixing? the latter to the basic component 10. In a possible embodiment, also on the tape 20, at least on its edge portion 31, graphene is previously applied in pure form or in the form of a derivative.

In any case, following the fastening of the tape 20, a layer comprising graphene is defined in the interface between the cavity spiral defined on the outer surface 11 of the base component and the edge portion 31 of the tape 20 inserted therein.

A manufacturing process of the exchanger tube 1 of figure 10 is described below. This process includes the steps of:

b1) providing a first tubular body made of metallic material, preferably with high mechanical resistance, defining the base component 10;

b2) prepare a tape in metallic material, preferably with a high conductivity index? thermal, defining said external component 20;

b3) making a spiral groove on the outer surface 11 of the base component 10; b4) depositing graphene in pure form or in derivative form, in said spiral groove and/or in correspondence with an edge portion 31B, intended to be connected to said external surface 11 of said base component 10;

b5) mechanically connecting said tape 20 to said outer surface 11 of said base component 10 by inserting the edge portion 31B of the tape in said spiral groove and following this insertion, tracing/pressing the edges of the groove against the opposite surfaces of said tape 20 blocking it cos? in the spiral groove.

In accordance with a preferred embodiment, before step b5) the tape 20 is preformed so as to give it a circular shape suitable for connection to the surface most? external 11 of the basic component 10. The preforming of the tape can? be made before or after the graphene deposit, the cio? before or after execution of phase b4). In the context of step b3), the spiral groove is made by means of a suitable tool which acts on the external surface 11 while the base component 10 ? rotated about its longitudinal axis 100. In the context of step b5), the base component 10 is made to advance along a movement direction, keeping it always in rotation. The tape 20 is brought around the base component 10 and is inserted into the spiral groove after having brought it to the same speed ring road. Immediately afterwards, the edges of the groove are pressed/upset so? to block the tape 20 stably.

Figures 11, 12 and 13 refer to further possible embodiments of an exchanger tube 1 with inserted fin. In particular, with respect to the embodiments shown in figures 7 to 10, in this case the body of the tape 20 is folded over itself? itself so as to define a space between at least two portions which face each other as a result of this folding. Inside this space, a layer of graphene 55 is provided in pure form or in the form of a derivative. Preferably, the folding of the tape 20 and the deposition of the graphene in said space are operations carried out before the fixing of the tape 20 on the external surface 11 of the base component 10.

In this regard, for each of the embodiments shown in figures 11, 12 and 13, the tape 20 could be applied according to one of the principles described above as a comment on the embodiments shown in figures 7 to 11.

In the embodiment shown in Figure 11, the body of the tape 20 is fixed to the surface pi? external 11 of the basic component 10 according to the same principle described above as a comment of figure 10. The body of the tape 20 is instead folded on s? same so that for each fin 25, evaluated on a longitudinal section plane, two portions 25-1, 25-2 face each other according to a U-shaped configuration, where this U ? facing the surface pi? external 11 of the base component 10. In this space, said further layer 55 of graphene is provided. In this regard, according to a possible embodiment, graphene is more? be applied, before folding the tape 20, on one or both surfaces of the portions 25-1, 25-2 which will then be facing following the folding of the tape itself.

Differently from the solution just described, in the one shown in figure 12, the body of the tape 20 is always folded so as to define, for each flap 25, two mutually facing portions 25-1, 25-2 which in this case for? are connected so that the space defined between them is closed, where this space ? always evaluated in the same longitudinal section plane in which the fins are considered. Graphene in pure or derivative form is provided in this enclosed space and is therefore completely surrounded by the body of the fin 25.

Also in this case, the folding of the body of the tape 20 and the application of the graphene are operations carried out before the application of the tape 20 to the base component 10. In this regard, the edge portion 31B can? be applied according to the principle described for the exchanger tube in figure 10 or according to one of the principles described for any of the embodiments in figures 7 to 10.

In the embodiment shown in figure 13, considering the fins 25 on a longitudinal sectional plane, these have a substantially "tuning fork" shape, in which ? It is possible to identify a base part 251 and a head part 252. The base portion 251 defines the edge portion 31 which is applied to the external surface 11 of the base component 10, according to any of the methods? described above.

The two parts 251, 252 have a substantially symmetrical shape with respect to a transversal plane orthogonal to the longitudinal axis 100. This shape is? obtained following a folding of the ribbon 20 so that both parts 251, 252 are defined by two facing portions of ribbon 20, respectively 251A-251B and 252A-252B. Between the two portions of tape 251A-251B defining the first part 251 ? said further layer 55 of graphene in pure or derivative form is provided.

Advantageously, in the embodiments shown in figures 11 to 13, the presence of said further layer of graphene 55 further increases the conductivity of the graphene. of the fins 25 and therefore the performance of the exchanger tube 1.

Figure 14 ? relating to a further possible embodiment of a heat exchange tube according to the invention. In particular, in this case the exchanger tube 1 comprises a plurality of external components 20 each comprising a collar 23 defining an internal surface correspondingly connected to the external surface 11 of the base component 10. Each external component 20 defines a fin 25 which develops from said collar 23 surrounding it and therefore surrounding the base component 10. The external components 20 are connected to the base component 10 so as to be longitudinally side by side along a development direction of the exchanger tube 1. For each external component 20 ? a layer of graphene is provided between the inner surface of the collar 23 and the outer surface 11 of the base component 10.

In the embodiment of figure 14, the fins 25 defined by the external components 20 have a square shape evaluated according to an observation plane orthogonal to the longitudinal axis 100 of the tube 1. However, the possibility of that the fins have a different shape, for example circular or elliptical. In this regard, the flaps 25 could have incisions made according to the ?serrated? indicated above with reference to the possible alternative embodiment of the solution shown in figure 6.

With reference to the embodiments shown in figures from 1 to 14, for each of these the application of further layers of graphene in pure form or in derivative form could be envisaged in one or more? regions of the external component 20 or of the external components 20, in a completely analogous way to what is indicated above with reference to the alternative embodiment of the solution shown in figure 6.

Figure 15 shows a further possible embodiment of a tube 1 in which the external component 20 does not define fins, presenting a tubular configuration defining a cavity cylindrical in which ? inserted the basic component 10. In this embodiment, the layer of graphene, in pure form or in the form of a derivative, is therefore provided between the surface more? external 11 of the basic component 10 and the surface pi? internal (basic 21B) of the component pi? external 20. The surface pi? external 22 of the external component 20 ? intended to be lapped by the second fluid and could be completely or partially covered by a further layer of graphene.

The present invention ? therefore also related to a heat exchanger comprising a plurality? of heat exchange elements 1 according to the invention. Pi? precisely, a heat exchanger according to the invention can? understand a plurality of exchanger tubes 1 according to any one of the embodiments described and shown in the figures so? as other possible equivalent embodiments in any case falling within the scope of the present invention.

In a possible embodiment, a heat exchanger according to the invention can including one or more batteries of exchanger tubes of the type shown in figure 10, and one or more? coils of exchanger tubes without fins of the type shown in figure 15. The coils of tubes are arranged so as to work in series, ie? so that the exchanger tubes without fins make a first thermal jump, the cio? to reduce the thermal head required for those including fins.

The technical solutions indicated above make it possible to fully achieve the pre-established tasks and purposes. The use of graphene between the interface surfaces of the two components increases the conductivity? heat exchanger tubes allowing therefore to achieve, parity? in size, devices heat exchangers pi? performing or to reduce, on equal terms? of performance, the size of said heat exchanger devices.

Claims (12)

1. Pipe (1) two-component heat exchanger, comprising: - at least one internal component (10) in metallic material of tubular shape comprising at least one surface more? external (11) and at least one surface pi? internal (12), where the latter defines a cavity? longitudinal for the passage of a first fluid; - at least one external component (20) in metallic material comprising a base surface (21B) at which ? connected to said internal component (10), said external component (20) being capable of being externally lapped by a second fluid, in which between said surface pi? exterior (11) of said inner component (10) and said base surface (21B) of said outer component (20) ? a layer (5) comprising graphene in pure form or in derivative form is provided. The heat exchanger tube (1) according to claim 1, wherein said external component (20) is configured so as to define at least one heat exchange fin (25) capable of being lapped by said second fluid, said at least one fin (25) which develops around said internal component (10). The tube (1) according to claim 2, wherein said external component (20) is configured to define a plurality? of fins (25), which develop around the internal component (10) according to a spiral profile evaluated on a longitudinal section plane containing a longitudinal axis (100) of said internal component (10), in which said fins (25) they have a circular shape considered on a transversal plane orthogonal to said longitudinal axis (100). 4. Pipe (1) according to claim 3, wherein also said external component (20) is defined by a tubular body defining a cavity? cylindrical (25), in which ? housed said internal component (10) of tubular shape, in which said base surface (21B) of said external component (20) delimits said cavity? cylindrical (25). 5. Pipe (1) according to claim 2, wherein said pipe (1) comprises a plurality of of external components (20) each comprising a collar (23) defining an internal surface correspondingly connected to said outermost surface? external component (11) of said internal component (10), wherein each external component (20) defines a flap (25) which develops from said collar (23) surrounding it, said external components (20) being connected to said internal component ( 10) so as to be longitudinally side by side, wherein for each of said external components (20) ? a layer of graphene in pure or derivative form is provided between said inner surface of said collar (23) and said outer surface (11) of said inner component (10). 6. Process for making an exchange tube (1) according to claim 3, wherein said process comprises the steps of: a) providing a first tubular body defining said internal component (10) and a second tubular body defining said external component (20); b) applying said layer comprising graphene on said surface more? surface (11) of said base component (10) and/or on the base surface (21B) of said external component (20); c) inserting said inner component (10) into said outer component (20); d) deforming said second component (20) so as to form said fins (25), wherein said deformation ? implemented through the action of forming means which generate a pressure on said external component (20) as a result of which the base surface (21) of the same remains connected to the surface more? outer part of the inner component (10). 7. Process according to claim 6, wherein before said step b), ? foreseen the phase of cleaning this surface more? surface (11) of said inner component (10) and/or of the base surface (21B) of said outer component (20). 8. Process according to claim 6 or 7, wherein in said step b) said graphene is dispersed in a liquid to be applied on said surface more? outside (11) and/or on the base surface (21B). The method according to claim 8, wherein said dispersion is applied through a mechanical deposition technique, a deposition technique or an electrochemical/electrophoretic deposition technique. 10. Process according to claim 8 or 9, wherein in said step b) said graphene is applied in the powder state on said surface more? surface (11) of said inner component (10) and/or of the base surface (21B) of said outer component (20). 11. Process according to any one of claims from 6 to 10, wherein in said step d) the use of graphite-containing lubricant is envisaged, wherein said lubricant is deposited on the outer surface of said outer component (20) during the action of said forming means and/or on said fins (25) generated following the action of said forming means. 12. Process according to any one of claims from 6 to 11, wherein, after said step d), ? the phase of applying a further layer of graphene in pure form or in the form of a derivative on one or more? regions of the surface of said external component (20).