EP0825406A2 - Echangeurs de chaleur - Google Patents

Echangeurs de chaleur Download PDF

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Publication number
EP0825406A2
EP0825406A2 EP97306110A EP97306110A EP0825406A2 EP 0825406 A2 EP0825406 A2 EP 0825406A2 EP 97306110 A EP97306110 A EP 97306110A EP 97306110 A EP97306110 A EP 97306110A EP 0825406 A2 EP0825406 A2 EP 0825406A2
Authority
EP
European Patent Office
Prior art keywords
tubes
fins
heat exchanger
fin
condensate
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.)
Withdrawn
Application number
EP97306110A
Other languages
German (de)
English (en)
Other versions
EP0825406A3 (fr
Inventor
Roy Bratley
Neville Lucas
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.)
Caradon Ideal Ltd
Original Assignee
Caradon Ideal 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 Caradon Ideal Ltd filed Critical Caradon Ideal Ltd
Publication of EP0825406A2 publication Critical patent/EP0825406A2/fr
Publication of EP0825406A3 publication Critical patent/EP0825406A3/fr
Withdrawn legal-status Critical Current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
    • F28F17/00—Removing ice or water from heat-exchange apparatus
    • F28F17/005—Means for draining condensates from heat exchangers, e.g. from evaporators
    • 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
    • F28F1/24—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 transversely
    • 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
    • F28F1/24—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 transversely
    • F28F1/32—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 transversely the means having portions engaging further tubular elements
    • 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
    • F28F1/34—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 obliquely

Definitions

  • This invention relates to heat exchangers and is mainly concerned with heat exchangers for gas boilers, especially so-called condensing boilers.
  • gas boilers having a cylindrical burner surrounded by an annular heat exchanger enclosing a combustion chamber in which the burner is centrally located.
  • the heat exchanger can comprise several conduits or tubes for conducting the water to be heated extending substantially parallel to the axis of the burner between headers or manifolds located at the opposite ends of the heat exchanger.
  • the tubes are generally equipped with fins or the like to increase the surface area available for heat exchange with hot flue gases flowing from the combustion chamber between the tubes.
  • a heat exchanger comprising a plurality of generally parallel upright tubes, substantially horizontal fins attached to the tubes, and means connected to the fins and extending downwardly therefrom to define a predetermined drainage path for condensate formed on the fins.
  • the means providing for drainage from the fin surfaces and thereby discouraging creation of condensate films covering these surfaces may take various specific forms. Although this arrangement is generally effective in practising the invention, under certain conditions it has been found at the end of a firing period of the burner, a significant proportion of condensate formed at the radially outer areas of the heat exchanger migrates back to the inner edges of the fins instead of draining from them.
  • the condensate tends to be evaporated, and a small amount of corrosion products, e.g. corrosion salts, which are contained in the condensate, can be deposited at edges of the fins. A build up of corrosion products can occur over a prolonged period of operation, and it is not impossible for the deposits to fall from the fins onto the burner igniter electrodes and thus prevent burner ignition.
  • corrosion products e.g. corrosion salts
  • the present invention addresses this problem and accordingly provides a heat exchanger for a boiler comprising several substantially upright tubes for passage of liquid to be heated, and a plurality of fins attached to the tubes for hot gases to flow between the fins from a combustion chamber, wherein the fins are inclined downwardly in the direction away from the combustion chamber at an angle of between 2° and 20° to the horizontal.
  • the fins are inclined to the horizontal at an angle of between 3° and 8°.
  • the total number of fins mounted on the tubes need not be reduced significantly compared to horizontally mounted fins on the tubes of the same length, thereby minimising any loss in the efficiency of the heat exchanger.
  • the invention provides a simple mechanism for improving the overall reliability of the boiler.
  • Each fin may be provided with means to impede further the inward migration of condensate, such as an interruption in the upper surface of the fin.
  • a longitudinal slit defining an inner edge and an outer edge may be provided adjacent the outer sides of the innermost tubes.
  • the inner edge of the slit can be disposed above the outer edge in the assembled heat exchanger to form a physical barrier to reduce or prevent the inward migration of condensate.
  • a plurality of apertures may be provided in the area adjacent the outer sides of the innermost tubes. As with the slit, the apertures form a physical barrier against the migration of condensation.
  • each fin may be reduced or minimised in the region of the innermost row of tubes to impair the efficiency of heat transfer in this region and thereby mitigate or avoid condensate collecting or forming adjacent the innermost edge of the fins.
  • drainage means are provided, the drainage means being connected to the fins and extending downwardly therefrom to define a predetermined drainage path for condensate formed on the fins.
  • Also provided in accordance with the present invention is a method of manufacturing a heat exchanger for a boiler, the heat exchanger comprising several tubes, and a plurality of substantially parallel fins having corresponding apertures proportioned for an interference fit with the tubes, the method comprising the steps of:
  • each fin has a slit or an aperture defining an inner edge and an outer edge, and the fins are deformed during alignment of the tubes such that the inner edge of the slit or aperture is disposed above the outer edge.
  • FIG. 1 to 6 Illustrated in Figures 1 to 6 is a known heat exchanger and gas burner assembly suitable for a domestic gas boiler.
  • the heat exchanger includes several parallel metal tubes 1 arranged in an annular array and fastened between upper and lower tube end plates 2,3.
  • the tube end plates are respectively secured and sealed to upper and lower headers 4,5 to confine within the headers chambers for conducting water to and from the tubes as explained in more detail below.
  • the lower header includes a water inlet 6 for entry of water to be heated into the heat exchanger, and the upper header includes a water outlet 7 for hot water having flowed through the heat exchanger and been heated.
  • the tubes are fitted with fins 8 which in well known manner serve to increase the surface area for heat exchange with hot flue gases passing between the tubes 1.
  • the fins are mounted over the full height of the tubes 1 and are only partially shown in Figures 1 and 2.
  • end plates and fins is manufactured as four equal segments.
  • Each heat exchanger segment includes nine tubes with their axes disposed in two arcuate rows, as best seen in Figure 3, there being five tubes in the inner row and four tubes in the outer row.
  • Each fin plate in each segment surrounds all the tubes of this segment, these fin plates being substantially horizontal in the assembled heat exchanger.
  • the fin plates may be fitted frictionally to the tubes or may be fixed thereon such as by soldering.
  • the upper and lower headers are shaped to form chambers communicating with the tube ends to provide a predetermined flow path for water through the heat exchanger.
  • the incoming cold water first flows upwardly through the four outer tubes (.) of each of the two lower segments as viewed in Figure 3, it is then transferred by the upper header and flows downwardly through the four outer tubes (x) of each of the two upper segments of Figure 3.
  • the water is transferred to flow upwardly through the neighbouring adjacent two of the inner tubes (..) of the two upper segments in Figure 3, following which the water is transferred by the upper header to flow downwardly through the next adjacent pairs of inner tubes (xx) of the two upper segments.
  • each drop of water is constrained to make seven passes along the heat exchanger tubes in flowing from the inlet 6 to the outlet 7.
  • a greater or smaller number of tubes could be used with the chambers in the headers arranged accordingly, and if desired the water may be constrained to make more or less than seven passes along the tubes in flowing through the heat exchanger.
  • the heat exchanger is of annular form enclosing a central combustion chamber wherein a cylindrical burner 10 is disposed.
  • the outer contour of the heat exchanger is defined by the fins and end plates (see Figure 3) is generally circular with flat sides allowing the heat exchanger to be housed in a substantially square casing whereby corner spaces are defined within the casing to form flue ducts extending along the heat exchanger and into which the flue gas passes by flowing between the fins 8 from the combustion chamber.
  • the flue gases On passing through the fin interspaces, the flue gases give up their heat and become cooled.
  • the heat transfer efficiency is such that the flue gases can at least under some operating conditions be reduced in temperature to below the dew point and moisture then condenses out on the surfaces of the fins.
  • FIGS 4A and 4B there is shown an embodiment of a heat exchanger segment in which several rods 12 are arranged to extend vertically through aligned apertures in the fins 8.
  • the rods 12 extend continuously at least from the uppermost fin to below the lowermost fin.
  • the rods contact the fins but do not fill the cross-section of the holes in the fins so that gaps are left through which water drops can pass.
  • the condensate collecting on the upper surface of a fin will be drawn towards a rod adjacent to which a liquid drop will form until it is large enough to run down along the rod under its own weight due to gravity.
  • the rods are disposed in clusters of four around the outer water tubes 1, and three additional rods are located at intermediate positions spaced at greater distances from the water tubes. All the rods are positioned between the inner water tubes and the outer edge of the fins. (In the interest of clarity only two water tubes have been included in Figure 4A, which also applies to Figures 5A and 6A).
  • wicks 13 are arranged to extend longitudinally of the heat exchanger.
  • the wicks could be located as described above in relation to the rods, there are shown two wicks positioned at the outer peripheral edge of the fins.
  • the wicks are inserted into slots 14 which may be conveniently provided at the time of pressing the metal fins.
  • the wicks due to their natural absorbency and ability to conduct liquid provide an effective means of removing condensate from the fin surfaces.
  • additional wicks could for example be inserted in any one or more of the further slots 14 shown formed in the fins in Figure 5B.
  • the fins in the embodiment of Figures 6A and 6B are provided with tabs 15 at the outer edges, these tabs being conveniently formed by slots 14 produced at the time of manufacture of the fins by pressing from metal sheet.
  • the corresponding tabs of all the fins are bent downwardly, so that the deflected tabs define a flow path for water condensing on the fin surfaces.
  • the water is drawn by surface tension towards the tabs and runs down the continuous flow path defined by the tabs.
  • Each tab may be deflected so that it contacts the next tab below, but this is not essential since if gaps are left it merely means that drops of water will collect at the extremities of the tabs and then fall away when they have grown large enough for their weight to overcome the surface tension forces.
  • each tab 115 is defined by a pair of adjacent notches 114 shaped as a circular hole connected to the fin edge by a slot of width less than the hole diameter so that the tab has a waisted neck portion, which may assist in drawing water onto the tab.
  • each water tube hole 143 Around the periphery of each water tube hole 143 are small protrusions 140 for providing a loose interference fit between the fin plate and the tube. Furthermore, additional condensate drainage tabs 145 are provided at the periphery of at least some of the holes. As shown all the holes for the outer tubes, and the holes for the three medial inner tubes are equipped with additional tabs 145. Each tab is defined by a pair of parallel slots 144 and is formed with such a length that its free end projects into the tube hole so that when the tube 1 is inserted, the tab is deflected downwardly and rests with its free end abutting the tube surface as shown in Figure 6F.
  • these downwardly deflected tabs 145 combine with the tubes 1 to define drainage paths for conducting condensate from the fins to the lower region of the heat exchanger. It will be noted that the tabs 145 associated with the outer tubes are positioned so that they are distributed over an outer portion of the fin plate, and the tabs 145 associated with the inner tubes are located at the outer, i.e. cooler, side of these tubes.
  • Figures 4 to 6 could be combined in the same heat exchanger.
  • the fins illustrated in Figure 6B or 6C could have one or more rods inserted through the holes shown, and/or one or more wicks could be inserted in the slots 14 or 114 flanking tabs 15 or 115 which have not been downwardly deflected.
  • additional ones of the tabs not shown bent downwardly in Figure 6B could be deflected to form flow paths for condensate removal and preferably all the tabs are bent down to achieve maximum drainage.
  • FIG 7. A heat exchanger in accordance with the invention is shown in Figure 7.
  • the general arrangement of the tubes 1 and the fins 8 is as described with reference to the known heat exchanger illustrated in Figures 1 to 6.
  • the fins are inclined downwardly in a direction away from the gas burner 10 at an angle between 3° and 8° to the horizontal, and thus condensate which collects on the fins after a firing period flows downwardly and away from the gas burner under its own weight due to the force of gravity.
  • the drainage means associated with the fins and which may be as described above in relation to Figures 1-6, facilitate rapid removal of the condensate from the fins, as hereinbefore described.
  • the fins 8 for a heat exchanger segment are mounted on a jig (not shown) in parallel with one another and the tubes 1 are placed on mandrels prior to being driven by a pneumatic ram through the aligned apertures in a direction orthogonal to the fins 8.
  • the apertures in the fins 8 are proportioned to ensure an interference fit is obtained between the tubes 1 and the fins 8 such that the fins 8 are held in position when they are removed from the jig.
  • the initial stop positions of the tubes 1 in the heat exchanger segment assembly are varied so that tubes positioned at different radial distances from the inner edges of the fins have their ends located in an imaginary plane 30 which is inclined at an angle of between 3° and 8° to the planes of the fins.
  • the ends of the tubes 1 are forced into the end plates 2, 3 of the heat exchanger, thereby bringing the tubes 1 into alignment so that the fins 8 which are firmly attached to the tubes are pivoted on the tubes to an angle approximately equal and opposite to the angle of the plane 30.
  • they can be fixed to the tubes, such as by brazing.
  • each fin 8a has an arcuate slit or cut 20 extending longitudinally between the inner and outer rows 30,31 of tubes 1.
  • the fin plate 8 is deformed such that the inner edge 21 of the slit 20 is disposed above the outer edge 22 when the tubes are oriented vertically as shown in Figure 11.
  • the vertical spacing between the edges increases to maximum at the longitudinal centre of the slit, at which point the spacing is approximately half the pitch between adjacent fins.
  • the vertical gap formed by the slit acts as a physical barrier against the migration of condensate towards the innermost edge 32 of the fin plates 8a, thus enhancing the advantageous effects of the inclination of the fin plates 8a.
  • the slit 20 can be formed by any appropriate cutting or stamping operation, and it may take the form of a continuous arcuate or linear opening. Alternatively, each fin plate could have a series of discrete openings defining a plurality of slits.
  • apertures or slots 25 are cut or stamped in the fins 8b adjacent the outer sides of the inner row 30 of tubes 1. Also segments 26 of the fins 8b are removed from the region adjacent the innermost edge 32 of the fin 8b to reduce or minimise the surface area of the fin 8b in this region.
  • the slots 25 impede the migration of condensate toward the front edge 32 of the fins 8b.
  • the reduction of the surface area of the fin 8b in the region adjacent the innermost row 30 of tubes impairs the efficiency of heat transfer from the flue gases to the fins 8b in this area, thereby reducing or eliminating the formation of condensate on the area of the fin adjacent the inner rows of tubes 30.
  • the slots 25 and segments 26 are generally vee-shaped and they may be formed to leave rings or annuli 27 of substantially uniform radial width for engagement with the tubes.
  • the front edges of the fins 8b project forwardly a substantially uniform distance from the innermost row of tubes 30.
  • the fin 8b illustrated in Figure 12 may be deformed by the preferred process of inclining the fins relative to the tubes such that the inner edges 33 the slots 25 are above the outer edges 34 (as described previously in relation to fin 8a). whilst the deformation of the fin 8b may further enhance the ability of the fin 8b to restrict migration and formation of condensate to the inner edge of the fin, bridging portions 28 of the fin are preferably left between adjacent slots 25 to limit the deformation of the fin 8b and hence to facilitate accurate control of the inclination of the fins 8b during heat exchanger manufacture.
  • Fins 8a,8b with one or more slots 20 or slots 25 can also be used in heat exchangers with substantially horizontal fins.
  • the heat exchanger assembly of the invention provides an improved means for removing condensate water which collects on the heat exchanger, and thus improves the reliability of the boiler. Further the invention provides a simple and effective method of manufacturing the improved heat exchanger.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Geometry (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
  • Details Of Fluid Heaters (AREA)
EP97306110A 1996-08-13 1997-08-12 Echangeurs de chaleur Withdrawn EP0825406A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9616956.0A GB9616956D0 (en) 1996-08-13 1996-08-13 Heat exchangers
GB9616956 1996-08-13

Publications (2)

Publication Number Publication Date
EP0825406A2 true EP0825406A2 (fr) 1998-02-25
EP0825406A3 EP0825406A3 (fr) 1999-03-10

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ID=10798400

Family Applications (1)

Application Number Title Priority Date Filing Date
EP97306110A Withdrawn EP0825406A3 (fr) 1996-08-13 1997-08-12 Echangeurs de chaleur

Country Status (2)

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EP (1) EP0825406A3 (fr)
GB (1) GB9616956D0 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0937952A2 (fr) 1998-02-24 1999-08-25 Caradon Ideal Limited Echangeur de chaleur
CN103503210A (zh) * 2011-05-04 2014-01-08 联合工艺公司 抗冻结燃料电池冷凝器
FR3049048A1 (fr) * 2016-03-21 2017-09-22 Valeo Systemes Thermiques Echangeur de chaleur et son procede de fabrication.
US20180164046A1 (en) * 2016-12-14 2018-06-14 Noritz Corporation Heat exchanger, hot water apparatus, and method of manufacturing heat exchanger
CN114459142A (zh) * 2020-10-30 2022-05-10 芜湖美的厨卫电器制造有限公司 燃烧换热组件及燃气热水器

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB846710A (en) * 1956-11-13 1960-08-31 Babcock & Wilcox Ltd Improvements in or relating to heat exchangers with transversely finned tubes, to transversely finned heat exchanger tubes and to a method of manufacturing such tubes
FR2545585B1 (fr) * 1983-05-05 1989-04-21 Laurent Francois Perfectionnements a des generateurs de chaleur fonctionnant au gaz et susceptibles d'etre raccordes a une aspiration controlee
JPS60216189A (ja) * 1984-04-11 1985-10-29 Hitachi Ltd 横フイン熱交換器
EP0859210A1 (fr) * 1994-06-01 1998-08-19 Caradon Ideal Limited Echangeur de chaleur

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0937952A2 (fr) 1998-02-24 1999-08-25 Caradon Ideal Limited Echangeur de chaleur
CN103503210A (zh) * 2011-05-04 2014-01-08 联合工艺公司 抗冻结燃料电池冷凝器
EP2705561A1 (fr) * 2011-05-04 2014-03-12 United Technologies Corporation Condenseurs résistant au gel pour piles à combustible
EP2705561A4 (fr) * 2011-05-04 2015-01-07 United Technologies Corp Condenseurs résistant au gel pour piles à combustible
CN103503210B (zh) * 2011-05-04 2016-12-21 奥迪股份公司 抗冻结燃料电池冷凝器
US9634337B2 (en) 2011-05-04 2017-04-25 Audi Ag Freeze-resistant fuel cell condensers
FR3049048A1 (fr) * 2016-03-21 2017-09-22 Valeo Systemes Thermiques Echangeur de chaleur et son procede de fabrication.
WO2017162966A1 (fr) * 2016-03-21 2017-09-28 Valeo Systemes Thermiques Échangeur de chaleur et son procédé de fabrication
CN109477700A (zh) * 2016-03-21 2019-03-15 法雷奥热系统公司 热交换器及其制造方法
CN109477700B (zh) * 2016-03-21 2021-05-11 法雷奥热系统公司 热交换器及其制造方法
US20180164046A1 (en) * 2016-12-14 2018-06-14 Noritz Corporation Heat exchanger, hot water apparatus, and method of manufacturing heat exchanger
US10408549B2 (en) * 2016-12-14 2019-09-10 Noritz Corporation Heat exchanger, hot water apparatus, and method of manufacturing heat exchanger
CN114459142A (zh) * 2020-10-30 2022-05-10 芜湖美的厨卫电器制造有限公司 燃烧换热组件及燃气热水器

Also Published As

Publication number Publication date
EP0825406A3 (fr) 1999-03-10
GB9616956D0 (en) 1996-09-25

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