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EP-4308874-B1 - HEAT EXCHANGER TUBE HAVING IMPROVED HEAT CONDUCTIVITY CHARACTERISTICS

EP4308874B1EP 4308874 B1EP4308874 B1EP 4308874B1EP-4308874-B1

Inventors

  • VITALI, Giuseppe
  • MANENTI, GIACOMO
  • SALA, Alessandro Giovanni
  • SALA, RICCARDO

Dates

Publication Date
20260513
Application Date
20220315

Claims (15)

  1. A two-component heat exchanger tube (1) comprising: - at least one inner component (10) made of metallic material in the form of a tube comprising at least one outermost surface (11) and at least one innermost surface (12), where this latter defines a longitudinal cavity for the passage of a first fluid; - at least one outer component (20) made of metallic material comprising a base surface (21B) at which it is mechanically connected to said inner component (10), said outer component (20) being configured for a second fluid to flow over externally, said base surface (21B, L1, L1*) extending around said outermost surface (11) of said inner component (10), characterized in that a layer (5) made of graphene in pure form or in derivative form is provided between said outermost surface (11) of said inner component (10) and said base surface (21B) of said outer component (20).
  2. The tube (1) according to claim 1, wherein said outer component (20) is configured to define at least one heat exchange fin (25) adapted for said second fluid to flow over, said at least one fin (25) extending around said inner component (10).
  3. The tube (1) according to claim 2, wherein said outer component (20) is configured so as to define a plurality of fins (25), which extend around the inner component (10) according to a spiral profile considered in a longitudinal section plane containing a longitudinal axis (100) of said inner component (10), wherein said fins (25) have a circular shape considered in a transverse plane orthogonal to said longitudinal axis (100).
  4. The tube (1) according to claim 3, wherein also said outer component (20) is defined by a tubular body defining a cylindrical cavity (25), in which said inner component (10) of tubular shape is housed, wherein said base surface (21B) of said outer component (20) delimits said cylindrical cavity (25).
  5. The tube (1) according to claim 1, wherein said outer component (20) is defined by a strip made of metallic material mechanically applied to said outermost surface (11) of said inner component (10) at said base surface (L1, L1*) which is defined by an edge portion (31B) of said strip, wherein said strip is applied in a spiral pattern so as to define a plurality of fins (25) extending around said inner component (10), and wherein said layer (5) made of graphene in pure form or in derivative form is arranged between said outermost surface (11) of said inner component (10) and said base surface (L1, L1*) defined by said edge portion (31B).
  6. The tube (1) according to claim 5, wherein said edge portion (31B) is a longitudinal portion folded with respect to the body of said strip, whereby said fins (25), formed following spiral application of said strip (20) around said inner component (10), have a substantially L-shaped configuration, considered in a longitudinal sectional plane containing the longitudinal axis (100) of said inner component (10), wherein for each of said fins (25), considered on said section plane, a foot portion (41B) and a body portion (41C) are identified, wherein said foot portion (41B) is defined by a stretch of said edge portion (31B) of said strip, wherein said layer (5) made of graphene is provided between at least a first side (L1) of said foot portion (41B), facing said inner component (10), and said outermost surface (11) of the same inner component (10).
  7. The tube (1) according to claim 6, wherein for each of said fins (25), considered in said section plane, said foot portion (41B) comprises a first region (31-1) and a second region (31-2), wherein said second region (31-2) is included between said first region (31-1) and the rest of the strip, said regions (31-1, 31-2) being configured so as to be "offset" so that an inner side of said first region (31-1) and an inner side of said second region (31. 2) are respectively adjacent to and spaced apart from said outermost surface (11) of said inner component (10) so that said second region (31-2) of said foot portion (41B) is overlapped with the first region (31-1) of an adjacent fin, said graphene layer (5) being provided between said outermost surface (11) of said inner component (10) and the inner side of said first region (31-1) of said foot portion (41B).
  8. The tube (1) according to claim 7, wherein a further layer (51) of graphene in pure or derivative form being provided between the overlapping regions of two adjacent fins.
  9. The tube (1) according to claim 5, wherein said edge portion (31B) of said strip is inserted into a predefined spiral groove on said outer surface (11) of said inner component (10), wherein said graphene layer (5) is defined at least between the surfaces of said spiral groove and said edge portion (31B) of said strip inserted into the same groove.
  10. The tube (1) according to any one of claims 5 to 9, wherein the body of said strip is folded over itself so that two portions of body are facing each other thereby defining a space inside which a further layer (55) of graphene in pure form or in derivative form is provided.
  11. The tube (1) according to claim 10, wherein said body of said strip is folded so that said two portions (25-1, 25-2) are facing each other according to a U-shaped configuration, wherein said U is facing the outer surface (11) of the base component (10).
  12. The tube (1) according to claim 10, wherein said body is folded in such a way that said two portions (25-1, 25-2) are facing each other and connected in such a way that said further layer (55) is completely surrounded by the body of the strip.
  13. The tube (1) according to claim 10, wherein said strip is folded in such a way that said fins (25), defined following application of said strip onto said inner component (10), have a substantially "tuning fork" configuration for which a base portion (251) and a head portion (252) are identified, wherein each portion (251, 252) is defined by two mutually facing portions (251A-251B, 252A-252B) of the strip, wherein said further graphene layer (55) is defined between the two portions (251A-251B) defining said base portion (251).
  14. A method for producing an exchanger tube (1) according to claim 3, wherein said method comprises the steps of: (a) providing a first tubular body defining said inner component (10) and a second tubular body defining said outer component (20); b) applying said layer made of graphene to said outermost surface (11) of said base component (10) and/or to said base surface (21B) of said outer 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), where said deformation is carried out through the action of forming means generating a pressure on said outer component (20), following which said base surface (21) thereof remains connected to the outermost surface of the inner component (10).
  15. A method for producing an exchanger tube (1) according to claim 5 wherein said method comprises the steps of: (a1) providing a first tubular body made of metallic material defining said inner component (10); a2) providing a strip made of metallic material defining said outer component (20); (a3) folding an edge portion (31B) of said strip along the whole of its length in an L-shaped configuration; (a4) applying a layer made of graphene in pure or derivative form onto said outermost surface (11) of said inner component (10) and/or onto a side (L1) of said edge portion (31B) destined to be connected to said outer surface (11); a5) mechanically connecting, in a spiral pattern, said edge portion (31B) of said strip to said outermost surface (11) of said inner component (10) so that a layer (5) made of graphene remains placed between said first side (L1) of said edge portion (31B) and said outer surface (11) of said inner component (10), wherein said method further comprises the step of knurling said outermost surface (11) of said inner component (10), before carrying out said step a5) and/or further comprises the step of knurling said edge portion (31B) on a second side (L2) opposite said first side (L1).

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 relates to a heat exchanger tube of the two-component type, that is, formed by at least two components. The heat exchanger tube has improved heat conductivity features. The invention also relates to a heat exchanger comprising a plurality of heat exchanger tubes according to the invention and to a method for producing a heat exchanger tube. A two component heat exchanger tube according to the preamble of claim 1 is known e.g. from document WO 2020/073616 A1. BACKGROUND ART As is well 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, heat exchangers comprising a plurality of finned heat exchange elements are used in a wide range of plants (e.g., in the petrochemical, energy, manufacturing and production sectors in general). Among the various types of exchangers known on the market, those formed of bundles of heat exchanger tubes of the two-component type are considered. In particular, the term "two-component" is meant to indicate that the tube comprises at least two components: an inner (or base) component, destined for a first fluid to pass through, and an outer component destined for a second fluid to flow over. Typically, the base component is made of a conductive metallic material with high mechanical strength (usually steel), while the outer component is made of a metallic material with high thermal conductivity (usually aluminium, copper or its alloys). In a known embodiment thereof, the two components are formed by two coaxial tubular bodies with a cylindrical cross section. Within the field of two-component heat exchanger tubes, those with radial fins, usually known as "finned tubes", are identified. In a first known embodiment, described for example in the granted patent IT0001349756, the two components of the heat exchanger tube both have a tubular configuration and are coaxially connected. In particular, the base component defines a longitudinal cavity destined for a first fluid to pass through, usually at high temperature. The outer component is instead fitted on the base component, i.e., so that the outermost surface of the inner component is connected to and in contact with the innermost surface of the outer component. The outer component comprises a shaped portion defining, in one piece, the aforesaid fins. These fins have a circular profile if observed in a section plane orthogonal to the axis around which the two elements extend. Instead, if considered in a plane containing the axis of the exchanger tube, they define a continuous spiral coaxial with said longitudinal axis. In particular, the fins are produced through an expansion and plastic deformation operation carried out with appropriate forming means. A heat exchanger tube of this type is usually also indicated with the term "extruded" and the operating temperatures can be even higher than 250°. In another known embodiment, the exchanger tube differs from the "extruded" one described above due to a different configuration of the outer component, while the inner one is always tubular in shape. In fact, in this case the outer component is defined by a strip of thermally conductive material that is spirally connected in a continuous manner around the outer surface of the base component. As a result of the spiral arrangement, the body of the strip defines the fins, which are also in this case circular in shape when observed in a plane transverse to the axis of the tube. Tubes based on this construction principle are also normally referred to as "applied fin tubes". More precisely, the strip is connected at one of its edge surfaces to the outer surface of the base component. Depending on how this connection is made, the heat exchanger tubes take different names. In this regard, Figure 2 shows an embodiment commonly indicated with the term "L finned tube", in which the edge portion of the strip defining the fins is folded through 90°, to give the fins an L-shaped profile, if considered in 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 is defined by the remaining part of the strip. The edge portion of the strip is connected to the outer surface of the base component typically by mechanical upsetting or welding. The extension of the edge portion identifies the pitch of the spiral, i.e., the longitudinal distance, between one fin and the other. In another embodiment, shown in Figure 3 and known in the field by the term "KL finned tube", the edge portion of the fin is folded in a manner similar to that provided for an "L finned tube" described above. In this case, however, in order to facilitate connection, the outer surface of the component is knurled before conne