GB2142715A - Heat exchangers - Google Patents

Abstract

An annular heat exchanger has flat tubes extending from one header 9 to another header 10 with airways between each tube. The tubes each consist of a pair of annular plates 5 having two apertures for the headers and divider means between the headers equal to the internal thickness of the tubes. Between each tube spacer 11 is provided. The heat exchanger has a simple construction and can take compressive loads in the region the headers. The divider means may take the form of an edging strip 6 or a divider plate 24 (not shown). <IMAGE>

Description

SPECIFICATION Heat exchangers This invention relates to heat exchangers.

It is known for heat exchangers to be made in annular form. In this type of heat exchanger, the tubes extend between two headers which are parallel to the axis of the heat exchanger, the tubes extending in a circumferential direction.

The invention provides a heat exchanger comprising tubes extending between two headers and airways between the tubes, the heat exchanger being of annular form, the headers being parallel to the axis of the heat exchanger and the tubes extending between the headers around the circumference of the heat exchanger, the tubes being flat and the plane of the tubes being perpendicular to the axis of the heat exchanger, wherein at least some of the tubes are made of two annular plates having two apertures for the headers and divider means between the apertures equal to the internal thickness of the tubes for separating the headers and for providing support for compressive loads on the tubes.

Such a heat exchanger can be manufactured in a simple manner.

Advantageously there is provided a spacer between adjacent tubes to allow space for the airway, the spacer having an aperture which registers with holes in adjacent annular plates to form the header.

Advantageously there is provided a plurality of additional spacers spaced around the circuniference of the heat exchanger, each spacer having an aperture which registers with additional apertures in the annular plates, the additional spacers overlying washers positioned between the annular plates. This enables the heat exchanger to withstand compressive Ipads around its circumference.

Two heat exchangers constructed in accordance with the invention will now be described by way of example with reference to the accompanuing drawings, in which: Figure 1 is a plan view of the first heat exchanger;.

Figure 2 is an end view of the first heat exchanger; Figure 3 is a section through the lines x-x of Figure 1 but on an enlarged scale; Figure 4 is a section taken through the line a-a of Figure 1 but on an enlarged scale; Figure 5 is a plan view of the second heat exchanger; and Figure 6 is a section through one tube plate of the second heat exchanger on an enlarged scale.

The first heat exchanger is annular, that is, the tubes indicated generally by the reference nuneral 1 extend in a circumferential direction between two headers 2, 3. The tubes are flat in a plane perpendicular to the axis of the heat exchanger. Between adjacent tubes airways 4 are provided.

Heat exchangers of this general kind are known.

In accordance with the invention, each tube 1 is made up of two annular plates 5 of the order of twenty thousandths of an inch thick and an edging strip 6 (see Figures 3 and 4).

The edging strip extends around the entire inner and outer circumferences of the annular plates, except in the region of the headers, where the edging strip forms loops 7, 8 behind apertures 9, 10 which are formed in each annular plate. Thus the edging strip defines the sides of each tube and also the two ends of each tube. The apertures 9, 10 are obviously present to enable liquid to enter and leave the tubes.

Turning now to Figure 4, a spacer 11 is provided between each adjacent pair of tubes.

The spacer permits the usage of conventional airway material 4.

In addition, the spacer is provided two apertures 1 2, 1 3 which register with the holes 9, 10 in the annular plates 5. The spacers thus define the headers 2, 3f. The spacers also overlie the loops 7, 8 of the edging strip 6, and this enables compressive loads to be applied to the heat exchanger in the region of the spacers 11 and the headers 2, 3.

Turning to Figure 3, additional spacers 14 are provided, both at the location shown in Figure 1 and at six other locations around the circumference of the tubes. All these seven spacers are identical. The spacers 14 permit the insertion of airway material as before.

Each annular plate 5 has an aperture 1 5 which reqisters with the aperture in the centre of the spacers 14, and through these registering apertures extends a tube 1 6. In order to prevent leakage from the tubes at this point, a washer 1 7 is provided between adjacent pairs of annular plates. The washer 1 7 however serves an additional function of allowing a compressive load to be applied from the top of the heat exchanger to the bottom through the tube 16.

The tube plates have a further aperture, and a further washer in the region of the spacer 11, and a further tube passes through. This is indicated by the numeral 18 on Figure 1.

It will be noted that the edging strip 6 loops closely round the apertures 9, 10 in the annular plates, and this assists in the taking of compressive loads. The construction of the invention provides a simple construction which affords compressive loading of the heat exchanger.

The heat exchanger may be for cooling liquid, for example oil or water which enters through one header and leaves through the other, and air may be blown from the inside to the outside of the heat exchanger.

During assembly, the parts are all coated with alloy, the heat exchanger is built up by mounting an edging strip and washers 14 on a plate placing a further plate on top of it, then placing spacers 14 and 11 at appropriate positions and then assemblying a further tube. The whole assembly is then bonded together by any recognised technique, for example, salt bath, brazing, furnace brazing, vacuum or inert gas.

Various modifications are of course possible. For example, each tube may include a turbulator.

Referring to Figure 5 an alternative construction of heat exchanger dispenses with the need for an edging strip. Each of the annular plates 20 has a raised flange 21 which mates with the corresponding flange on the other annular tube plate of each pair. Each annular plate has apertures 22, 23 for the headers. In order to divide off the annular tube plate over this region a wine glass shaped plate 24 equal to the internal thickness of the tube plate is inserted between each pair of annular plates before they are joined together. The divider plate 24 extends from one rim of the annular plate to the other, and has arcuate recesses 25, 26 adjacent to the headers 22, 23. When the parts are secured together during brazing the divider plate provides a complete fluid-tight barrier radially across each annular plate. It also provides a platform for enabling compressive loads to be borne by the tube plate in the region of it.

A stiffener 27 is included between each of the annular plates and an aperture 28 is provided similar to the aperture 1 8 in Figure 1 for receiving a bolt to pass through the thickness of the heat exchanger. The spacers between adjacent tube plates may be as in the first heat exchanger, as may the tubes 16 spaced around the circumference of the heat exchanger as in Figures 1 and 3.

As compared with the first embodiment, it is now unnecessary to deform the edging strip into a closely controlled shape, the function of the edging strip being taken up by the raised rims on each annular plate.

Claims (9)

1 A heat exchanger comprising tubes extending between two headers and airways between the tubes, the heat exchanger being of annular form, the headers being parallel to the axis of the heat exchanger and the tubes extending between the headers around the clrclmfersnce of the heat exchanger, the tubes hPing flat and the plane of the tubes being nerpendicular to the axis of the heat exchanger, wherein at least some of the tubes are made of two annular plates having two apertures for the headers and divider means between the apertures equal to the internal thickness of the tubes for separating the headers and for providing support for compressive loads on the tubes.

2 A heat exchanger as claimed in claim 1 or claim 2, wherein the divider means has an arcuate surface adjacent to each aperture.

3 A heat exchanger as claimed in claim 1 or claim 2, wherein the annular plates are flanged around adjacent circumferences in order to enable them to be joined, and the divider means is a plate inserted between the tubes before joining.

4 A heat exchanger as claimed in claim 1 or claim 2, wherein the annular plates are joined at the circumferences by a continuous strip which forms a loop around each aperture to form the divider means.

5 A heat exchanger as claimed in any preceding claim, wherein there is provided a spacer between adjacent tubes to allow space for the airway, the spacer having an aperture which registers with holes in adjacent annular plates to form the header.

6 A heat exchanger as claimed in claim 5, wherein each spacer has two apertures in it registering with holes in adjacent annular plates, to form both headers.

7 A heat exchanger as claimed in claim 5, or claim 6, wherein the spacer overlies the divider means.

8 A heat exchanger as claimed in any one of claims 1 to 7, wherein there is provided a plurality of additional spacers spaced around the circumference of the heat exchanger, each spacer having an aperture which registers with additional apertures in the annular plates, the additional spacers overlying washers positioned between the annular plates.

9 A heat exchanger substantially as hereinbefore described with reference to the accompanying drawings.