Classifications

• • 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
  • F28D7/06—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 having a single U-bend
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C37/00—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape
  • B21C37/06—Manufacture of metal sheets, bars, wire, tubes or like semi-manufactured products, not otherwise provided for; Manufacture of tubes of special shape of tubes or metal hoses; Combined procedures for making tubes, e.g. for making multi-wall tubes
  • B21C37/15—Making tubes of special shape; Making tube fittings
  • B21C37/28—Making tube fittings for connecting pipes, e.g. U-pieces
  • B21C37/283—Making U-pieces

Definitions

• the present invention relates to tubular members, par ⁇ ticularly tubes forming a continuous path for the circulation of a heat exchanging fluid in heat exchangers, and methods for manufacture of such tubes.
• This invention relates more particularly to metallic hairpin tubes provided with secondary heat exchanger elements or fins fixed to the tubes normally by brazing/soldering, crimping, expansion or gluing.
• tubes commonly used in heat exchangers with this type of connection have a circular cross-section which facilitates the assembly of the tube ends, e.g. with U-shaped bends, as disclosed in DE 2952736.
• Another object of the invention is to provide tubes for heat exchanger units resulting in better heat rejection perform ⁇ ance, reduced number of tube joints and to avoid or facili ⁇ tate connections between tubes of different cross-sectional shape in heat exchangers.
• Still another object of the invention is to provide a simple and low cost method of manufacturing oblong hairpin tubes.
• a one-piece hairpin configured tube comprising two sub ⁇ stantially parallel leg portions of oblong cross-section connected by an U-shaped bend portion having a cross-section area larger than or equal to the cross-section of the leg portions.
• thermoly conductive tubes including hairpin configured U-shaped bends, comprising the steps of providing a (straight) tubular member of substantially circular cross-section, bending the said tubular member providing an U-shaped hairpin tube with two parallel leg por ⁇ tions which are subsequently exposed to a radial deformation operation resulting in an oblong cross-section of the entire length or parts of the leg portions.
• Fig. 1 is a plan view of a hairpin configured tube.
• Fig. 2 is a sectional view of the hairpin tube taken along line I-I of Fig. 1.
• Fig. 3 is another sectional view taken on line " II-II of Fig. 1.
• Fig. 4 is a sectional view of a tool for accomplishing the step of radial deformation according to the present invention.
• Fig. 5 is a sectional view of the tool from Fig. 4 after performance of the deformation step.
• Fig. 6 is a planar view of the hairpin tube in a die after accomplished deformation step.
• Fig. 7 illustrates the step of conforming of a pre- deter inated part of an oblong tube to a circular cross-section in a modified method of manufacturing the hairpin tubes.
• Fig. 8 is a sectional view of a tool for accomplishing the conforming operation taken on line I-I of Fig. 7.
• Figs. 9 and 10 represent modifications in the manner of configuration of the leg portions of the hairpin tubes with regard to the U-bend portion.
• the new one-piece hairpin tube (1) provided according to the present invention comprises two parallel leg portions (2,2') of the oblong cross-section connected together by an U-shaped bend portion (3) having a substantially circular cross-section - see Fig. 2.
• the new and unique configuration of the hairpin tubes is thus provided based upon a new inventive approach to solve the problem connected to bending thin-walled oblong tubes.
• Dm largest diameter of the tube
• c central distance between the leg portions
• d wall-thickness should be ⁇ 10 to ensure smooth quality tubes, at f in a range from 11-14 problems can arise and at f > 14 the problems with formation of wrinkles are unavoidable.
• a typical Al-tube to be used in a motor vehicle radiator or heater core will have a wall thickness of 0.4 mm, central tube distance 22.0 mm and largest diameter of the oblong cross—section 13.0 mm (short diameter 6.0 mm)
• the tubes are subjected to a bending operation while retaining a substantially circular cross-section over the deformed part of the tubes.
• a circular tube with a diameter of 10 mm is provided and then by means of com ⁇ flashally available apparatuses, e.g. hydraulically powered tube benders, a bend of 180° is formed as the first step in the manufacture of oblong hairpin tubes.
• Figs. 4 and 5 show schematically the subsequent step of radial deformation of the just provided hairpin tube from the circular cross-section to an oblong/elliptical cross-section along the parallel leg portions.of the tube.
• the hairpin tube of circular cross-section (1) is inserted between the open jaws (51,52) of a pressure die (5) so that a predetermined part or the whole leg portions (2,2") of the hairpin tube being conformed to an oblong cross-section having diameters of 13.0 and 5.7 mm respectively, see Fig. 5, showing a sec ⁇ tional view of the pressure die from Fig. 4 after performance of the deformation step.
• the hairpin tube provided in the above example exhibits no surface irregularities in the U-bend portion (3) and transition curves of intermediate portions of the tube between the oblong parts and the circular U-bend being smooth without sharp edges. Furthermore, the circular cross-section of the U-bend portion is larger than the cross-section of the leg portions so that the result is a hairpin tube of sub ⁇ stantially oblong cross-section body ensuring improved heat exchanging efficiency at a minimal pressure drop in the heat exchanger.
• Fig. 6 illustrates in planar view the hairpin tube in the pressure die (5) comprising an U-bend portion (3) of the substantially circular cross-section outside the pressure die and the leg portion ' s (2,2') of the oblong cross-section having free ends (21,21') retaining the original, circular cross-section.
• This configuration of the hairpin tube offers a special advantage allowing direct connection to a terminat ⁇ ing plate of headers provided with circular apertures.
• Figs. 3, 9 and 10 represent the most usual patterns of the -hairpin tube configuration with regard to the assembling of the heat exchanger cores - so-called parallel, staggered parallel or series connection, respectively.
• FIG. 7 and 8 An .alternative manufacturing method to the one described with reference to the above example is illustrated in Figs. 7 and 8.
• a tube (11) of the required oblong cross-section and dimensions is provided by extrusion, extrusion followed by a drawing operation or by welding.
• the thus provided tube (11) is then subjected to a local radial deformation over a pre- determinated part (3 1 ) of the tube.
• the cross-section of this part (3') being conformed to a circular shape in a pressure die (5) - see Fig. 8 showing the die (5) in a vertical sec ⁇ tional view taken along line I-I of Fig. 7, facilitates the subsequent bending operation conducted by means of adapted commercial benders.
• the bending operation in this- case is a final step in the manufacture of oblong hairpin configurated tubes.
• the cross—section of the U-bend parts (3) can also exhibit other shapes deviating from the circular one shown in the drawings without departing from the scope of the present in ⁇ vention. Even if the circular cross-section offers advantages such as direct use of commercially available benders without any need for adaptation of the apparatuses or special acces ⁇ sories (mandrels), tubes with other cross-sectional shapes in the bending area can be used. It is, however, important that such cross-sectional shapes comply with the requirements to a cross-section of the U-bend being larger than or equal to a cross-section of.the leg portions, and furthermore that the relation between the wall thickness, the bend radius and the largest diameter of the tube according to the above empiric formula ensures avoidance of surface defects on the tube wall.

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Bending Of Plates, Rods, And Pipes (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Priority Applications (1)

Applications Claiming Priority (2)

Publications (2)

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• 1985
  • 1985-03-12 DE DE8585901607T patent/DE3563263D1/de not_active Expired
  • 1985-03-12 WO PCT/NO1985/000015 patent/WO1985004242A1/en not_active Application Discontinuation
  • 1985-03-12 BR BR8505815A patent/BR8505815A/pt not_active IP Right Cessation
  • 1985-03-12 JP JP50120385A patent/JPS61501467A/ja active Pending
  • 1985-03-12 EP EP85901607A patent/EP0175743B1/de not_active Expired
• 1994
  • 1994-02-02 JP JP33194U patent/JPH0684173U/ja active Pending

Non-Patent Citations (1)

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