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
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/10—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses
  • F28F1/12—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element
  • F28F1/14—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending longitudinally
  • F28F1/16—Tubular elements and assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with projections, with recesses the means being only outside the tubular element and extending longitudinally the means being integral with the element, e.g. formed by extrusion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
  • F24H1/22—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating
  • F24H1/40—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water tube or tubes
  • F24H1/43—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water tube or tubes helically or spirally coiled
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D7/02—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being helically coiled
  • F28D7/024—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being helically coiled the conduits of only one medium being helically coiled tubes, the coils having a cylindrical configuration
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F1/00—Tubular elements; Assemblies of tubular elements
  • F28F1/02—Tubular elements of cross-section which is non-circular
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/007—Auxiliary supports for elements
  • F28F9/013—Auxiliary supports for elements for tubes or tube-assemblies
  • F28F9/0132—Auxiliary supports for elements for tubes or tube-assemblies formed by slats, tie-rods, articulated or expandable rods
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
  • F28F9/00—Casings; Header boxes; Auxiliary supports for elements; Auxiliary members within casings
  • F28F9/22—Arrangements for directing heat-exchange media into successive compartments, e.g. arrangements of guide plates
  • F28F2009/222—Particular guide plates, baffles or deflectors, e.g. having particular orientation relative to an elongated casing or conduit
  • F28F2009/226—Transversal partitions

Definitions

• the present Invention relates to a heat exchanger. More specifically, the present invention relates to a heat exchanger for a gas boiler for producing hot water. BACKGROUND ART
• a gas boiler for producing hot water normally comprises a gas burner, and at least one heat exchanger through which combustion fumes and water flow.
• Some types of gas boilers known as condensation boilers, condense the steam in the combustion fumes and transfer the latent heat in the fumes to the water.
• Condensation boilers are further divided into a first type, equipped with a first exchanger close to the burner, and a second exchanger for simply condensing the fumes; and a second type, equipped with only one heat exchanger which provides solely for thermal exchange along a first portion, and for both thermal exchange and fume condensation along a second portion.
• Condensation or dual-function exchangers of the above type normally comprise a casing extending along a first axis and through which combustion fumes flow; and a tube along which water flows, and which extends along a second axis and coils about the first axis to form a succession of turns.
• the combustion fumes flow over and between the turns to transfer heat to the water flowing along the tube.
• the spiral tube has fins extending perpendicularly to the tube axis. This technical solution provides for a high degree of thermal exchange, but the fins are expensive to produce.
• the spiral tube has a depressed flow section, which is a cheaper technical solution, though much less effective in terms of heat exchange than the finned-tube solution .
• the present invention also relates to a method of producing a heat exchanger.
• the present invention also relates to a gas boiler. According to the present invention, there is provided a gas boiler as claimed in Claim 20.
• Figure 1 shows a schematic front view, with parts in section and parts removed for clarity, of a gas boiler equipped with a heat exchanger in accordance with the present invention
• Figure 2 shows a larger-scale section of a detail of the Figure 1 heat exchanger
• Figure 3 shows a view in perspective of a tube used to produce the Figure 1 exchanger
• Figure 4 shows the Figure 3 tube partly coiled
• Figure 5 shows a larger-scale view in perspective of a component part of the Figure 1 exchanger
• Figure 6 shows a view in perspective, with parts removed for clarity, of the heat exchanger being assembled;
• Figure 7 shows a lateral view of the Figure 6 heat exchanger;
• Figure 8 shows a section of a variation of the Figure 3 tube .
• Boiler 1 is a wall-mounted condensation boiler, i.e. in which the vapour in the combustion fumes is condensed, and comprises an outer structure 2 in which are housed a burner 3; a heat exchanger 4; a gas supply conduit 5; a pipe 6 for supplying an air-gas mixture to burner 3; a combustion gas exhaust pipe 7; a fan 8 connected to supply pipe 6, and which performs the dual function of supplying the air-gas mixture to burner 3, and expelling the combustion fumes; and a water circuit
• Structure 2 comprises a rear wall 10 fixed to a supporting wall (not shown) and supporting the component parts of boiler 1; a top wall 11; two lateral walls 12; and a front wall not shown in the accompanying drawings .
• Burner 3 is connected to pipe 6, is cylindrical in shape, and comprises a lateral wall with holes (not shown) for emitting the air-gas mixture and feeding the flame.
• Burner 3 is housed inside exchanger 4 which, in fact, also acts as a combustion chamber.
• Heat exchanger 4 is substantially cylindrical in shape, extends along a substantially horizontal axis Al parallel to rear wall
• Casing 13 comprises a cylindrical lateral wall 16 about axis Al; an annular wall 17 connected to lateral wall 16, to supply pipe 6, and to burner 3; and an annular wall 18 connected to lateral wall 16 and to exhaust pipe 7.
• Burner 3 extends, coaxially with exchanger 4, inside of exchanger 4 for a given length.
• Tube 14 coils about axis Al to form a succession of adjacent turns 19, each located close to lateral wall 16, and has two opposite ends with known fittings (not shown) for connecting tube 14 to water circuit 9 outside exchanger 4.
• Disk 15 has a thin lateral edge 20 engaging turns 19. That is, disk 15 is screwed to turns 19 into the desired position along axis Al and in a position substantially perpendicular to axis Al .
• Exchanger 4 comprises three comblike spacers 21 for keeping turns 19 a given distance apart and a given distance from lateral wall 16.
• each spacer 21 comprises a straight portion 22 parallel to axis Al, and from which project teeth 23, each of which is interposed between two adjacent turns 19.
• Tube 14, disk 15, and spacers 21 define, inside casing 13, a region Bl housing burner 3; a region B2 communicating directly with exhaust pipe 7; and three regions B3, each extending between two spacers 21, turns 19, and lateral wall 16.
• Tube 14 is preferably made of aluminium or aluminium-based alloy. With reference to Figure 3, finned tube 14 is extruded, extends along an axis A2, and comprises an oval-section wall 24; two fins 25 on one side of tube 14; two fins 26 on the opposite side to fins 25; a fin 27 between fins 25; and a fin 28 between fins 26.
• the cross section of tube 14 has a major axis X and a minor axis Y. Fins 25, 26, 27, 28 are all parallel to axis A2 of tube 14 and to major axis X, and are therefore parallel to one another. Fins 27 and 28 are coplanar with each other, and substantially lie in the same plane as axis A2 of tube 14 and major axis X.
• Fins 25 and 26 are arranged so that each fin 25 is coplanar with an opposite fin 26, and wall 24 of tube 14 forms a slight convexity between the coplanar fins 25 and 26.
• the maximum extension of fins 25 and 26, in a direction parallel to major axis X, is roughly a quarter of the length of major axis X.
• tube 14 is coiled about axis Al, so that axis A2 of tube 14 also assumes a spiral shape.
• This operation actually comprises calendering tube 14, with the minor axis Y of the section of tube 14 maintained substantially parallel to axis Al .
• the relatively small size of fins 25, 26, 27, 28 does not hinder the calendering operation, and does not call for notching fins 25, 26, 28, 28.
• the three spacers 21 are then fitted between fins 26 of adjacent turns 19, and arranged 120 degrees apart, so as to form, with the coiled tube 14, an assembly which is inserted inside cylindrical wall 16 of casing 13 ( Figures 6 and 7) .
• Annular walls 17 and 18 are then fitted to the opposite ends of cylindrical wall 16.
• Tube 14 is coiled with a constant pitch and radius, so that fins 25 and 26 of each turn 19 face and are parallel to fins 25 and 26 of the adjacent turns 19, as shown in Figure 2.
• a gap is thus formed between each two adjacent turns 19, is of constant width at fins 25 and 26, and narrows at the convexities of walls 24.
• the fumes flow from region Bl to regions B3 in direction Dl towards wall 16, then flow in direction D2 between turns 19 and wall 16, flow between turns 19 in direction Dl from regions B3 to region B2, and are finally expelled by exhaust pipe 7.
• the successive gaps therefore define compulsory fume paths, and are so shaped as to produce a venturi effect which rapidly accelerates the fumes .
• Fins 25 and 26 therefore not only increase the exchange surface of tube 14, but also accelerate and so produce turbulent motion of the fumes.
• fins 27 and 28 provide mainly for enhancing heat exchange, and play no part in accelerating the fumes.
• one fin 25 and one fin 26, on opposite sides of tube 14 are sufficient to produce the venturi effect.
• at least two fins 25 and two fins 26 are required to avoid too marked a convexity on wall 24 between one fin 25 and a coplanar fin 26, which would prevent the gap from producing a venturi effect.
• the gap provides for optimum heat exchange when given dimensional ratios of the gap are conformed with.
• Zl indicates the distance between two facing fins 25 or 26 of two adjacent turns 19, and Z2 the minimum distance between the facing walls 24 of the same two adjacent turns 19.
• Tests conducted by the Applicant show the best Z2/Z1 ratio, in terms of thermal efficiency of the exchanger, to be 1/3, whereas Z2/Z1 ratios of 0.2 to 0.4 are considered acceptable.
• Exchanger 4 as described above may also be used in condensation boilers comprising a main exchanger, and in which exchanger 4 provides solely for condensing the fumes, as opposed to acting as a combustion chamber as in the example described.
• Exchanger 4 as described above has numerous advantages, by combining straightforward construction - as a result of the fins being formed directly by the tube extrusion process, as opposed to being added on after extrusion - with a high degree of thermal efficiency - by virtue of the fins increasing the exchange surface, and the dynamic effect on the fumes of the fins in combination with the tube .
• exchanger 4 is relatively easy to produce, and can be produced in different lengths to meet different power requirements.
• lengths along axis Al can be produced which are multiples of a base length, and spacers 21 of a length equal to the base length can be produced to standardize spacer manufacture.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Geometry (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)
• Physical Or Chemical Processes And Apparatus (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

Country Status (7)

Cited By (4)

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• 2003
  • 2003-04-11 IT IT000769A patent/ITMI20030769A1/it unknown
• 2004
  • 2004-03-19 DE DE602004013574T patent/DE602004013574D1/de not_active Expired - Lifetime
  • 2004-03-19 EP EP04721907A patent/EP1627190B1/fr not_active Expired - Lifetime
  • 2004-03-19 ES ES04721907T patent/ES2305755T3/es not_active Expired - Lifetime
  • 2004-03-19 WO PCT/EP2004/050332 patent/WO2004090434A1/fr active IP Right Grant
  • 2004-03-19 DK DK04721907T patent/DK1627190T3/da active
  • 2004-03-19 AT AT04721907T patent/ATE394640T1/de not_active IP Right Cessation

Non-Patent Citations (1)

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