GB2092691A

GB2092691A - Manufacturing a heat exchanger

Info

Publication number: GB2092691A
Application number: GB8200034A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-01-05
Filing date: 1982-01-04
Publication date: 1982-08-18
Also published as: FR2497567B1; NL8200006A; DE3200046A1; FR2497567A1

Abstract

A process for manufacturing a heat exchanger composed of bundles of parallel tubes made of plastics material, of which the end parts are engaged in opposite holes of two parallel perforated plates, is characterized in that a tubular insert 8 made of a material resistant to the aggression of the fluid passing therethrough and whose outer diameter corresponds substantially to the inner diameter of the tube 7, is introduced into the end part of each of the tubes intended to be fixed on a perforated plate 5. Thereafter the end part of the plastics tube containing said insert is engaged in a hole 14 whose diameter corresponds substantially to that of the tube. Finally, the insert is mechanically deformed inside the tube so as to cause diametrical expansion thereof and consequently the wall of the tube is gripped between the expanded insert and the lateral surface of the hole. <IMAGE>

Description

SPECIFICATION A process for manufacturing a heat exchanger The present invention relates to a process for making a heat exchanger and to a heat exchanger produced thereby.

Heat exchangers composed of bundles of parallel tubes generally comprise two parallel plates, perforated with suitably distributed holes, and a bundle of parallel tubes enabling each hole in one of the plates to communicate with a hole in the other plate. One of the two fluids participating in the heat exchange circulates inside the various tubes whilst the other fluid passes outside.

If it is desired to use such a heat exchanger for recovering calories coming from corrosive fluids, for example the fumes produced by dehydration of organic materials such as alfalfa, the exchange surfaces must be considerable and if the plates and the bundles of tubes are made of stainless steel of such quality that they are resistant to the aggressive action of the fumes, the weight and cost of manufacture are prohibitive and recovery of the calories is uneconomic.

To overcome this drawback, it has already been envisaged to produce heat exchangers in which the parallel tubes are made of a corrosion resistant plastics material. Such heat exchangers are described for example in French Patents Nos.

2 229 032 and 2 353 035. However, the use of tubes made of plastics material raises a problem as far as the fixing of their end parts to the perforated plates is concerned. To carry out this fixing, complex, expensive devices have been heretofore used, which often comprise a plurality of machined parts.

It is essentially an object of the present invention to remedy this drawback by providing a particularly simple process of fixing, enabling a heat exchanger of low cost price to be obtained.

To this end, this process for manufacturing a heat exchanger composed of bundles of parallel tubes made of plastics material, of which the end parts are engaged in opposite holes of two parallel perforated plates, is characterized in that a tubular insert made of a material resistant to the aggression of the fluid passing therethrough and whose outer diameter corresponds substantially to the inner diameter of the tube, is firstly introduced into the end part of each of the tubes intended to be fixed on a perforated plate, the end part of the plastic tube containing said insert is engaged in a hole whose diameter corresponds substantially to that of the tube, and finally, the insert is mechanically deformed inside the tube so as to provoke diametrical expansion thereof and consequently the crushing and gripping of the wall of the tube between the expanded insert and the lateral surface of the hole.

According to a further feature of the invention, the outer end part of the insert is widened outwardly so as to effect a complementary crimping of the end of the insert and that of the plastic tube.

The process according to the invention offers the advantage that the end part of a tube may be fixed very rapidly and very simply and that it may be carried out for several tubes simultaneously, this bringing about a considerable reduction in the cost price of the heat exchanger obtained.

The invention will be more readily understood on reading the following description with reference to the accompanying drawings, in which: Figure 1 is a view in vertical and longitudinal section of a heat exchanger composed of a bundle of parallel tubes, according to the invention.

Figures 2 and 3 are views in partial axial section illustrating a mode of fixing the end of a tube to a transverse plate, respectively before and after the diametrical expansion of the insert.

Figures 4 and 5, 6 and 7, 8 and 9 are views in axial section illustrating other variants of the modes of fixing the end of the tube, respectively before and after the diametrical expansion of the inner insert.

Figures 10, 1 1, 12 and 13 are views in axial section of various embodiments of the insert whioh may be used for fixing the tubes.

Referring now to the drawings, the heat eXchanger according to the invention, of which one non-limiting embodiment is shown in figure 1, comprises four similar modules 1, 2, 3, 4 each comprising an upper plate 5 and a lower plate 6 pierced with vertically aligned holes. These holes are connected in two's by vertical tubes 7, parallel to one another, made of a corrosion-resistant plastics material, for example of cross linked polyethylene. The heat exchange is effected between two fluids passing respectively inside the tubes 7 and outside same. following the path indicated by the arrows.

To connect the upper and lower ends of the plastic tubes 7 respectively to the horizontal upper and lower plates 5 and 6, cylindrical or slightly truncated inserts are used, whose outer diameter corresponds substantially to the inner diameter of the tubes 7. Figures 10 to 13 show, by way of example, several inserts which may be used for fixing the tubes 7, namely a cylindrical insert 8 (Figure 10), a slightly truncated insert 9 (Figure 11), a cylindrical insert 10 with an outer transverse annular flange 1 1 at one of its ends (Figure 12), or a slightly truncated insert 12 with an outer transverse annular flange at its large base (Figure 13).

The following description will be made with regard to the use of a cylindrical insert 8 without flange, but it is obvious that it is also applied to all the other types of inserts.

In the embodiment illustrated in Figures 2 and 3, the upper plate 5 is pierced with a hole 14 of which the diameter corresponds to the outer diameter of the tube 7 in which is engaged the upper end part of this tube in which the cylindrical insert 8 is housed. The outer edge of the insert 8 is flush with the corresponding edge of the tube 7.

The end part of the tube 7 and the insert 8 may project slightly above the plate 5 as illustrated in Figures 2 and 3 or be flush with the upper surface of the plate 5.

Once the tube 7 and the insert 8 are engaged in the hole 14 as indicated hereinabove, a diametrical expansion of the insert 8 is effected, to ensure the firm connection of the tube 7 with the plate 5, as illustrated in Figure 3. The expansion of the insert 8 therefore crushes the layer of plastics material gripped between this insert and the edge of the hole 14. This crushing ensures that the top end of the tube 7 is held. Such holding may be reinforced, if the insert 8 and the tube 7 project beyond the plate 5, due to the upper end part of the insert 8 being widened out, in its outer part 8a.

This flated or truncated form, with apex directed towards the inside of the tube 7, has for its effect to bend the upper end 7a of the tube 7 outwardly, thus forming a truncated flange. The crimping of the outer end 8a of the insert 8 thus contributes to reinforcing the hold of the tube 7 in the hole 14 in the plate 5.

The mode of fixation illustrated in Figure 2 and 3 is suitable whenever the plate 5 is thin or thick and when the field of use is that of low temperatures.

Figures 4 and 5 illustrate a mode of fixing the tube 7 in a hole 15 in a relatively thin plate 5, defined by a downwardly bent cylindrical edge 5a.

The upper end part of the tube 7 is fixed, as in the foregoing case, by diametrical expansion of the insert 8, level with the flange 5a, and the widening out of the outer end 8a of the insert 8.

Consequently, the upper end 7a of the tube 7 forms a flared truncated flange gripped between the flared end 8a of the insert 8 and the rounded part 5b by which the edge 5a is joined to the rest of the plate 5.

The mode of fixing which has just been described with reference to Figures 4 and 5 is suitable in all cases where there are considerable thermal stresses.

Figures 6 and 7 illustrate a mode of fixing which may be used in the case of a very thick plate 5. In this case, each hole 16 in the plate 15 presents, in its lateral wall, at least one annular groove 17 for example of V-shaped cross section.

The top end part of the tube 7 is fixed, as in the foregoing cases, by diametrical expansion of the insert 8, and also by forming on the lateral surface of this insert 8, level with the groove 17, an annular bead 18 which presses the plastics material thereopposite into the groove 17. The anchoring of the tube 7 in the plate 5 is thus strongly reinforced and this mode of fixing is suitable whenever there are mechanical stresses and hygienic standards to be respected.

In the embodiment illustrated in Figures 8 and 9, the plate 5, of very large thickness, is pierced with a hole 19 in the lateral wall of which are formed a plurality of annular transverse grooves 20, for example of V-section. There again, the diametrical expansion of the insert 8 causes the plastics material to be pressed in these grooves 20 and offers a firm anchorage of the tube 7 in the plate 5.

The plates 5 and 6, in the holes of which are fixed the ends of the tubes 7, may be made of a material varying according to the products to be treated, for example of steel, stainless steel, titanium, steel coated with a film protecting against corrosion, etc.... Similarly, the inserts 8, 9, 10, 12 may be made of any material presenting characteristics of both mechanical strength and resistance to deformation, such as brass, copper, aluminium, steel, stainless steel, titanium, etc....

The length of the inserts varies depending on the mechanical stresses to which the tubes are subjected.

Claims

1. Process for making a heat exchanger composed of a bundle of parallel tubes made of plastics material, of which the end parts are engaged in opposite holes in two parallel perforated plates, comprising the steps of: ~firstly introducing into the end part of each of the tube intended to be fixed to a perforated plate, a tubular insert made of a material resistant to the aggression of the fluid passing therethrough and whose outer diameter corresponds substantially to the inner diameter of the tube, ~engaging the end part of the tube made of plastics material, containing insert, in a hole of which the diameter corresponds substantially to that of the tube, and ~finally, mechanically deforming the insert inside the tube so as to cause diametrical expansion thereof and consequently crushing and gripping the wall of the tube between the expanded insert and the lateral surface of the hole.

2. The process of Claim 1, wherein the outer end part of the insert is outwardly widened out so as to effect a complementary crimping of the end of the insert and that of the tube made of plastics material.

3. The process of Claim 2, wherein a hole is previously made in the relatively thin plate, which hole is defined by a bent cylindrical edge, joined to the rest of the plate by a rounded part, and the end of the insert and the end of the tube are crimped on this rounded part.

4. The process of Claim 1, wherein a hole is previously made in the plate of considerable thickness, said hole presenting in its lateral wall at least one annular groove, and an annular bead is also formed on the lateral surface of the insert, level with the groove, upon diametrical expansion of the insert, which bead presses the plastics material thereopposite into the groove.

5. The process of Claim 1, wherein a hole is previously formed in the plate of very great thickness, and a plurality of annular transverse grooves are formed in the lateral wall of said hole.

6. The process of Claim 1, wherein a cylindrical insert is used.

7. The process of Claim 6, wherein the cylindrical insert presents an outer transverse annular flange at one of its ends.

8. The process of Claim 1, wherein a slightly truncated insert is used.

9. The process of Claim 8, wherein the truncated insert presents an outer transverse annular flange at its large base.

10. A heat exchanger composed of a bundle of parallel tubes made of plastics material, obtained by the process of any one of Claims 1 to 9.

11. A process for making a heat exchanger, substantially as herein described with reference to and as illustrated in the accompanying drawings.