EP0612858A2 - Fabrication d'un élément de transfert de chaleur - Google Patents

Fabrication d'un élément de transfert de chaleur Download PDF

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Publication number
EP0612858A2
EP0612858A2 EP94301175A EP94301175A EP0612858A2 EP 0612858 A2 EP0612858 A2 EP 0612858A2 EP 94301175 A EP94301175 A EP 94301175A EP 94301175 A EP94301175 A EP 94301175A EP 0612858 A2 EP0612858 A2 EP 0612858A2
Authority
EP
European Patent Office
Prior art keywords
substrate
carbon dioxide
metal particles
liquid carbon
heat transfer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP94301175A
Other languages
German (de)
English (en)
Other versions
EP0612858B1 (fr
EP0612858A3 (fr
Inventor
Stephen Forbes Pearson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Star Refrigeration Ltd
Original Assignee
Star Refrigeration Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Star Refrigeration Ltd filed Critical Star Refrigeration Ltd
Publication of EP0612858A2 publication Critical patent/EP0612858A2/fr
Publication of EP0612858A3 publication Critical patent/EP0612858A3/fr
Application granted granted Critical
Publication of EP0612858B1 publication Critical patent/EP0612858B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F13/00—Arrangements for modifying heat-transfer, e.g. increasing, decreasing
    • F28F13/18—Arrangements for modifying heat-transfer, e.g. increasing, decreasing by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing
    • F28F13/185—Heat-exchange surfaces provided with microstructures or with porous coatings
    • F28F13/187—Heat-exchange surfaces provided with microstructures or with porous coatings especially adapted for evaporator surfaces or condenser surfaces, e.g. with nucleation sites
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying

Definitions

  • the present invention relates to a process for the production of a heat transfer element for boiling a liquid, to the heat transfer element produced in this way, and to an apparatus for carrying out the process.
  • the heat transfer co-efficient for boiling a liquid may be improved by coating the heat transfer surface of a heat exchanger with a matrix of small heat-conductive particles which produce a network of linked re-entrant cavities.
  • the cavities act as nucleation centres for the production of bubbles of vapour.
  • High flux tubing So called "high flux" (trademark) tubing having a high co-efficient of heat transfer is available but its production is complex and the tubing is correspondingly expensive.
  • High flux tubing is generally produced by coating a tube with petroleum jelly and depositing particles of a cupro-nickel powder onto the tube so that the particles become embedded in the petroleum jelly.
  • the cupro-nickel powder is made up of two components having different melting points.
  • the coated tube is then heated in a furnace to a temperature such that one of the components just melts and adheres the other non-melted powder to the tube. In this way, a matrix of metal particles firmly adhered to the tube is produced.
  • European Patent application 88307468.4 describes a method of coating heat transfer surfaces by spraying a particulate mixture of metal and a plastics material onto a thermally conductive surface to form a coating comprising particles of plastics material embedded in metal, and heating to a temperature sufficient to volatilise the plastics material, thereby forming pores in the metal coating.
  • US Patent 3,384,154 describes a method of coating heat transfer surfaces with small metallic particles which are subsequently sintered onto the substrate material.
  • US Patent 4,753,849 describes a process of coating an evaporator tube which involves arc spraying two dissimilar metals onto the tube and then etching out one of the metals.
  • European application 80101983.7 describes the production of a porous boiling surface by spraying liquified aluminium onto a substrate under inert gas according to certain specified conditions.
  • the important parameters include particle size, pore size, range of pore sizes, activity of the particles, surface tension of the liquid being boiled and the angle of contact between liquid and particle surface in the presence of vapour.
  • the present invention is based on the discovery that co-spraying liquified metal and liquid carbon dioxide results in a surface having good heat transfer properties.
  • the present invention provides a process for the production of a heat transfer element for boiling a liquid which comprises:
  • spraying is to be interpreted broadly to include processes wherein substantially semi-solid or liquid metal is impacted onto a substrate.
  • liquid carbon dioxide and metal may be sprayed onto the substrate from closely spaced adjacent locations (e.g.nozzles) it is preferred to move the substrate relative to the liquified metal spray (by moving the spray locations, the substrate, or both), such that the liquid carbon dioxide is sprayed onto a given area of the substrate slightly before the liquified metal particles impinge on that area of the substrate.
  • This has the effect of pre-cooling the substrate and also cooling the liquified metal particles somewhat so that the particles may become skinned or semi-solid. In this way, the particles have sufficient adherent nature to adhere firmly to the substrate, yet are not so liquid that they flow and lose their particle-like nature when they hit the substrate.
  • liquid carbon dioxide is sprayed into a shroud which directs the liquid carbon dioxide first onto the substrate and then the cold carbon dioxide is directed (usually sideways) into the spray of liquified metal particles.
  • Liquified carbon dioxide has been found to be uniquely effective in the practising of the invention. It is possible that some thermal decomposition of the carbon dioxide takes place leading to the production of carbon. However, this is merely a hypothesis and should not be used to limit the generality of the present invention.
  • the liquid carbon dioxide forms a powder which then vapourises to provide a cooling effect. The formation of the fine powder and its subsequent vapourisation may assist in the formation of pores in the matrix.
  • other liquids such as water, liquid nitrogen, or sulphur hexafluoride.
  • the metal particles are preferably formed of a heat conductive material such as aluminium or other high conductivity metal or alloy known in the art.
  • the particle size is usually in the range 1 to 100 microns, particularly 10 to 60 microns, and the thickness of the layer is preferably less than 250 microns. Thus, on average, the layer will usually be about 2 to 5 metal particles deep.
  • the substrate is grit-blasted prior to spraying.
  • the substrate is in the form of a heat transfer tube but may also be a plate or other heat transfer element.
  • the substrate is usually of metal, for example cupro-nickel, copper, steel or stainless steel. Generally, it is not possible to produce "high flux" tubing from stainless steel according to conventional technology.
  • the heat transfer element of the invention allows heat exchangers for boiling liquids to be fabricated, which have high co-efficients of heat transfer.
  • the heat transfer element finds particular use in the refrigeration field.
  • a heat transfer tube according to the invention was produced as follows.
  • a cupro-nickel tube (90% copper and 10% nickel) was cleaned by grit blasting and was then mounted in the apparatus shown in Figure 1.
  • the tube 2 was mounted in a lathe for rotation about its longitudinal axis.
  • a spraying device 1 which is arranged so as to be moveable along the length of the tube in the direction indicated by the arrow for concurrently spraying the tube with metal particles and liquid carbon dioxide. It comprises a plasma spray gun 4, equipped for spraying aluminium metal in a flow of inert gas onto the tube, and a shroud 6 having a central aperture 10 for receiving the tube and an inlet nozzle 8 for spraying liquid carbon dioxide into the shroud and onto the tube.
  • the shroud is arranged slightly upstream of the plasma spray of aluminium particles, such that the liquid carbon dioxide first cools the pipe surface and then exits from the shroud in a direction towards the plasma spray, so that the cold carbon dioxide then cools the plasma spray also.
  • the flow rate of liquid carbon dioxide and the spacing of the shroud from the plasma stream is chosen such as to provide good adhesion of the aluminium metal particles 12 to the tube surface and to provide a high co-efficient of heat transfer.
  • the coating of aluminium particles was typically around 100 microns thick.
  • the heat transfer ability of the tube was then tested in an apparatus as shown in Figures 2 and 3.
  • the heat transfer tube 2 was fitted with a heater 34 as shown in Figure 3, and a low melting point alloy Ostalloy 158 (trademark) was poured into the space 39 between the heater and the tube to provide good thermal contact.
  • the tube was equipped with a surface thermocouple pair 36 to measure the temperature at the surface of the tube.
  • FIG. 2 shows a test rig for measuring temperature difference between the tube surface and a boiling liquid, in this case refrigerant R11 (trichlorofluoromethane).
  • a sealed container 10 is filled with liquid R11.
  • the surface temperature of the tube is measured by thermocouple 36 and the temperature of the refrigerant R11 measured by a series of thermocouples (not shown) placed in the bulk of the liquid.
  • the liquid is boiled by three heated tubes A, B and C each equipped with a heater and variable power supply. Each power supply is fed through a varistor 22.
  • a watt meter 20 is fitted to measure the power drawn by the heater.
  • the vapour produced is condensed using cooling water supplied to a cooler via inlet 12 and returned via outlet 14.
  • Heat transfer tube B is provided with an aluminium particle coating according to the invention, as described above.
  • Tube A is a shot blasted cupro-nickel tube
  • tube C is a high flux tube, for comparison purposes. The temperature difference between the tube surface and the R11 liquid was measured.
  • Figure 4 shows the test results.
  • the shot blasted cupro-nickel tube A shows a temperature difference of typically around 6 to 9°C depending on the power.
  • the temperature difference of the tube B according to the present invention is relatively low, indicated good heat transfer, and is comparable to the conventional high-flux tube C.
  • the tube of the present invention is simpler and cheaper to produce.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Plasma & Fusion (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Coating By Spraying Or Casting (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
EP19940301175 1993-02-23 1994-02-18 Fabrication d'un élément de transfert de chaleur Expired - Lifetime EP0612858B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB939303655A GB9303655D0 (en) 1993-02-23 1993-02-23 Production of heat transfer element
GB9303655 1993-02-23

Publications (3)

Publication Number Publication Date
EP0612858A2 true EP0612858A2 (fr) 1994-08-31
EP0612858A3 EP0612858A3 (fr) 1995-04-19
EP0612858B1 EP0612858B1 (fr) 1999-06-09

Family

ID=10730921

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19940301175 Expired - Lifetime EP0612858B1 (fr) 1993-02-23 1994-02-18 Fabrication d'un élément de transfert de chaleur

Country Status (3)

Country Link
EP (1) EP0612858B1 (fr)
DE (2) DE612858T1 (fr)
GB (1) GB9303655D0 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998033031A1 (fr) * 1997-01-29 1998-07-30 Deutsches Zentrum für Luft- und Raumfahrt e.V. Tube echangeur de chaleur et procede permettant de le produire

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10141524C2 (de) * 2001-08-24 2003-10-30 Zae Bayern Bayerisches Zentrum Fuer Angewandte Energieforschung Ev Stoff- und Wärmeaustauscherfläche
WO2003019081A1 (fr) 2001-08-24 2003-03-06 Zae Bayern Bayrisches Zentrum Für Angewandte Energieforschung E.V. Surface de transfert de matiere et d'echange thermique et reacteur de transfert de matiere et d'echange thermique comprenant une telle surface de transfert de matiere et d'echange thermique

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0017944A1 (fr) * 1979-04-16 1980-10-29 Union Carbide Corporation Procédé de pulvérisation thermique pour la production de surfaces d'ébullition poreuses en aluminium
EP0263469A1 (fr) * 1986-10-07 1988-04-13 Linde Aktiengesellschaft Procédé pour l'enduction thermique de surfaces
EP0375914A1 (fr) * 1988-12-30 1990-07-04 URANIT GmbH Procédé pour le revêtement de matériaux composites contenant des fibres

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2615022C2 (de) * 1976-04-07 1978-03-02 Agefko Kohlensaeure-Industrie Gmbh, 4000 Duesseldorf Verfahren zum Beschichten einer Oberfläche mittels eines Strahles aus erhitztem Gas und geschmolzenem Material

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0017944A1 (fr) * 1979-04-16 1980-10-29 Union Carbide Corporation Procédé de pulvérisation thermique pour la production de surfaces d'ébullition poreuses en aluminium
EP0263469A1 (fr) * 1986-10-07 1988-04-13 Linde Aktiengesellschaft Procédé pour l'enduction thermique de surfaces
EP0375914A1 (fr) * 1988-12-30 1990-07-04 URANIT GmbH Procédé pour le revêtement de matériaux composites contenant des fibres

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998033031A1 (fr) * 1997-01-29 1998-07-30 Deutsches Zentrum für Luft- und Raumfahrt e.V. Tube echangeur de chaleur et procede permettant de le produire
US6303191B1 (en) 1997-01-29 2001-10-16 Deutsches Zentrum Fuer Luft -Und Raumfahrt E.V. Process for the production of a heat pipe

Also Published As

Publication number Publication date
DE612858T1 (de) 1995-04-20
EP0612858B1 (fr) 1999-06-09
DE69418915D1 (de) 1999-07-15
DE69418915T2 (de) 2000-01-27
GB9303655D0 (en) 1993-04-07
EP0612858A3 (fr) 1995-04-19

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