GB2142857A

GB2142857A - Manufacture of heat exchangers by welding

Info

Publication number: GB2142857A
Application number: GB08414884A
Authority: GB
Inventors: Anthony Gerald Cooper; William Henry Tomlinson
Original assignee: FULTON
Current assignee: FULTON
Priority date: 1983-06-15
Filing date: 1984-06-11
Publication date: 1985-01-30
Also published as: GB8414884D0

Abstract

A heat exchanger having a tubular element 10 mounted in thermal engagement with a heat collecting or emitting panel 13 is formed by superimposing the tubular element and panel and clamping them together between a pair of roller-type welding electrodes 20,23. The electrode engaging the tubular element is contoured at 21, so as to engage a substantial part of the circumference of the tubular element over a short length thereof, while the other electrode engages a small area of the panel. A current is applied between the electrodes to form a spot weld between the tubular element and the panel and the tubular element and panel are advanced between the electrodes to form a series of spot welds at spaced locations along their interengaging lengths. <IMAGE>

Description

SPECIFICATION Heat exchangers The present invention relates to heat exchangers and in particular to a method and apparatus for producing heat exchangers comprising a tubular element forming a closed channel through which a heat exchange fluid may flow, said tubular element being mounted in thermal contact with a heat col lecting or emitting panel.

According to one aspect of the present invention, a method of forming a heat exchanger having a tubular element in thermal engagement with a heat collecting or emitting panel comprises superimposing the tubular element onto the heat collecting or emitting panel, so that said tubular element engages said panel along a substantial continuous part of its length; clamping the tubular element and panel between a pair of welding electrodes, one electrode engaging about a substantial part of the circumference of the tubu lar element over a short length thereof and the other engaging a small area of the panel; applying a current between the electrodes to form a spot weld between the tubular element and the panel; and advancing the superimposed tubular element and panel between the welding electrodes, so that a series of spot welds are produced along the interengaging lengths of tubular element and panel.

According to a further aspect of the present invention, an apparatus for forming heat exchangers having a tubular element spot welded to a heat collecting or emitting panel comprises a pair of electrodes arranged to engage opposite sides of the superimposed tubular element and panel and clamp them together, one electrode engaging the tubular element, the other the panel; the portion of the electrode engaging the tubular element being grooved so that it engages a substantial part of the circumference of the tubular element over a short length thereof.

The form of the electrodes engaging the tubular element, allows pressure to be spread over a relatively large area of the surface of the tube, so that the necessary pressure can be applied over a small area between tubular element and panel to effect the spot weld, without crushing the tubular element. Conveniently, the electrode in engagement with the tubular element is in the form of a circumferentially grooved roller which will roll along the tubular element as the superimposed tubular element and panel are passed between the electrodes. The groove in the roller preferably has a semi-circular configuration, its diameter being slightly greater than the diameter of the tubular element to allow for expansion of the tubular element during the welding process.

In particular, the diameter of the groove should be of the order of 0.05 mm greater than the maximum OD of the tubular element.

The semi-circular groove may also have a parallel sided lead-in portion which may be of the order of 0.25 mm deep. The electrode engaging the panel may be in the form of a plain roller, so that the superimposed plate and tubular element may be fed between the electrode rollers, the rollers being energised intermittently to provide spot welds at the required intervals. Alternatively, the electrode engaging the panel may be in the form of a roller with radial projections, the pitch of these projections being such that as the panel and tubular element are passed between the electrodes, the radial projections will engage the panel and produce spot welds at the required intervals. In this case, the rollers may be energised continuously, but will only produce spot welds when one of the radial projections engages the panel.

Conveniently the tubular element may be in the form of a serpentine, having a plurality of substantially parallel straight runs interconnected by curved sections. However, other configurations of tube, for example, several parallel lengths interconnected by header tubes, or even a plurality of individual tubes, may be used.

According to a preferred arrangement a plain panel is arranged to overlap the whole of the tubular element, so that it engages the panel over its whole length and may be spot welded thereto at regular intervals along its length. With this arrangement, there is heat exchange between the whole of the tubular element and the panel. Alternatively, with, for example, a serpentine tubular element, the curved sections may protrude beyond the panel, so that only the straight runs will engage and may be spot welded to the panel.

The panel is preferably a plain sheet. However, the panel may be formed with perforations, particularly louvres, in between the portions thereof engaged by the tubular element, in order to modify the convectional flow over the surface of the panel. These perforations should be formed in a manner which does not result in any significant thinning of the sheet material about the periphery of the perforations. For example, a louvred panel may be formed using a shearing technique in which a sheet of material is stamped between a pair of dies in a press.

An embodiment of the invention is now described by way of example only, with reference to the accompanying drawings in which: Figure 1 illustrates a condenser for a refrigerator typical of the heat exchangers that may be formed by the method of the present invention; Figure 2 illustrates one form of apparatus that may be used to produce the condenser illustrated in Figure 1; and Figure 3 is a section along the line Ill-Ill in Figure 2.

The condenser illustrated comprises a serpentine tube 10, having four parallel runs 11, interconnected by curved sections 12. The tube 10 is mounted on a heat emitting panel 13, so that the runs 11 engage the surface of the panel 13, continuously along their lengths and the curved sections 12 protrude beyond the ends of the panel 13. The runs 11 are secured to the panel 13 by means of spot welds 14, spaced at about 25 mm intervals along the lengths of the runs 11.

A pair of bracket members 15 are welded, one to each of the longitudinal edges of the panel 13. These bracket members 15 enable the condenser to be fitted to the back of a refrigerator cabinet, leaving space between the condenser and the back of the cabinet, for circulation of air over the panel 13. These bracket members 15 may also be provided with projections which will extend away from the refrigerator cabinet and will ensure that an adequate gap is maintained at the back of the cabinet when, for example, it is placed against a wall.

The use of separate bracket members 15, in the manner described above, enables a standard width condenser to be used on cabinets of varying widths, the width of the bracket member 15 being adjusted to suit the cabinet.

However, the panel 13 may alternatively be bent to form the bracket members 15 integrally thereof.

As illustrated in Figures 2 and 3, the condenser described above may conveniently be formed using a pair of welding electrodes in the form of rollers 20, 23. The roller 20 engaging the tube 10 is formed with four circumferential grooves 21, these grooves 21 corresponding in position to the position of the four runs 11 of tube 10. The grooves 21 are of semi-circular configuration having a diameter 0.05 mm larger than the OD of the tube 10, and have a parallel sided lead-in portion 22, 0.25 mm deep, so that they engage around something of the order of 140 of the circumference of the tube 10.

The other roller 23, which engages the panel 13 is of plain configuration. The parallel runs 11 of tube 10 and panel 13 are clamped between the rollers 20, 23 and the required spot welding pressure is applied. The panel 13 and tube 10 are then fed between the rollers 20, 23 which are energised intermittently to form spot welds 14 at the required intervals along each run 11 of tube 10.

Various modifications may be made to the method described above without departing from the invention. For example, while a pair of roller electrodes are arranged to weld all four runs of the tubular element simultaneously, this may be done using individual pairs of rollers for each run or the runs may be welded sequentially, using one pair of rollers.

Claims

1. A method of forming a heat exchanger having a tubular element in thermal engagement with a heat collecting or emitting panel comprising; superimposing the tubular element onto the heat collecting or emitting panel so that said tubular element engages the panel along a substantial continuous part of its length; clamping the tubular element and the panel between a pair of welding electrodes, one electrode engaging about a substantial part of the circumference of the tubular element over a short length thereof and the other engaging a small area of the panel; applying a current between the electrodes to form a spot weld between the tubular element and the panel; and advancing the superimposed tubular element and panel between the welding electrodes, so that a series of spot welds are produced along the interengaging length of the tubular element and panel.

2. A method according to Claim 1 in which the tubular element comprises a plurality of parallel runs, the pair of electrodes or several pairs of electrodes being arranged transversely of these runs so that they may be welded simultaneously.

3. A method according to Claim 1 or 2 in which the electrodes engage the tubular element and panel continuously as they are advanced therebetween, the electrodes being energised intermittently to produce a spot weld at spaced locations along the length of the tubular element.

4. A method according to Claim 1 or 2 in which at least one of the electrodes is arranged to engage the tubular element or panel intermittently, as they are advanced therebetween.

5. A method according to Claim 4 in which the electrodes are energised continuously.

6. An apparatus for forming heat exchangers having a tubular element spot welded to a heat collecting or emitting panel comprising; a pair of electrodes arranged to engage opposite sides of the superimposed tubular element and panel and clamp them together, one electrode engaging the tubular element, the other the panel; the portion of the electrode engaging the tubular element being grooved so that it engages a substantial part of the circumference of the tubular element over a short length thereof.

7. An apparatus according to Claim 6 in which the groove is semi-circular, having a diameter of the order of 0.05 mm greater than the maximum outside diameter of the tubular element.

8. An apparatus according to Claim 7 in which the groove has a parallel sided lead-in portion.

9. An apparatus according to any one of Claims 6 to 8 in which the electrode is provided with a plurality of grooves, so that parallel runs of the tubular element may be welded simultaneously.

10. An apparatus according to any one of the preceding claims in which the electrodes are in the form of rollers.

11. An apparatus according to Claim 10 in which the electrodes are arranged to engage the tubular element and panel continuously and clamp them together as they are fed therebetween, means being provided to energise the electrodes intermittently to produce spot welds at spaced locations along the length of the superimposed portions of the tubular element and panel.

12. An apparatus according to Claim 11 in which the electrode engaging the panel is a plain roller.

13. An apparatus according to Claim 10 in which the electrode engaging the panel is arranged to make intermittent contact therewith.

14. An apparatus according to Claim 13 in which the electrodes are energised continuously so that a spot weld is produced every time the roller comes into contact with the panel.

15. An apparatus according to Claim 13 or 14 in which the roller engaging the panel is provided with radial projections.

16. An method of forming a heat exchanger having a tubular element in thermal engagement with a heat collecting or emitting panel substantially as described herein with reference to the accompanying drawings.

17. An apparatus for forming heat exchangers having a tubular element spot welded to a heat collecting or emitting panel substantially as described herein with reference to, and as shown in Figures 2 and 3.

18. A heat exchanger having a tubular element in thermal engagement with a heat collecting or emitting panel formed in accordance with the method claimed in any one of Claims 1 to 6 or 16.