GB2197450A

GB2197450A - Heat exchangers

Info

Publication number: GB2197450A
Application number: GB08626723A
Authority: GB
Inventors: Eric Smith
Original assignee: PENTAGON RADIATOR
Current assignee: PENTAGON RADIATOR
Priority date: 1986-11-08
Filing date: 1986-11-08
Publication date: 1988-05-18
Also published as: GB8626723D0

Abstract

A heat exchanger made of thin sheet or foil e.g. aluminium alloy comprises a stack of tubes 10, 12 alternating with fin plates 30, each tube being made of a pair of channel section pressings and containing a sinuous insert 20 in contact with both flat faces of the tube to increase the heat exchange surface area within the tube, the corrugations of the insert 20 being transverse to the length of the tube and being perforated. <IMAGE>

Description

SPECIFICATION Prefabricated tubes This invention relates to heat exchangers of the kind comprising a plurality of parallel tubes alternating with fin plates to make a stack. A first fluid of the heat exchange pair flows through the tubes, for example between manifolds or header tanks, and a second fluid of the heat exchange pair flows between the tubes and across their length, through the fins.

The object of the present invention is to provide a particularly lightweight and economical construction.

According to the invention, a heat exchanger of the kind referred to comprises tubes each made of a pair of metal pressings assembled together with sealed joints, and with a longitudinally extending sinuous insert in the tube, which insert contacts alternate faces of the tube along its length, the insert being perforated to allow the first fluid of the pair to flow through it.

The two components of the tube may be made as metal pressings or by profile rolling from strip for example.

The inserts may be made by feeding strip through a pair of meshed gears to produce a zig-zag configuration. The corrugations so produced may extend transversely, or may be inclined, that is to say at an angle other than 90 degrees to the edges of the strip. Two or more like inserts may be employed with inclined corrugations oppositely extending.

Particularly thin sheet metal may be employed for all of the components, for example metal foil.

preferably the height of the corrugations is equal to or in excess of the internal height of the two assembled components of the tube, so as to get good insert/tube contact, e.g. by locating the insert in one of the components, and then assembling the second component, and applying pressure to the two components before the seal is effected, particularly good heat conducting contact can be achieved between the insert and the tube walls.

The fin plates may comprise corrugated foil generally similar to the tube inserts, but sandwiched between adjacent tubes. By using inclined corrugations, two or more fin plates may be located in opposite relationship or alternate relationship between each two tubes, in the same way as multiple inserts without nesting and without needing any intervening plates.

Preferably, where only a single fin plate is used between two tubes, the inserts are inclinedly corrugated in one direction and the fin plates also have inclined corrugations which are arranged in the opposite direction in the assembly, thus contributing to the strength of the structure.

The whole heat exchanger may be fabricated from clad aluminium or light alloy foil so that the assembly can be held together under pressure and pass through a brazing furnace to make all of the joints and seals between the parts.

Alternatively, all of the joints and seals may be made by appropriate adhesives such as epoxy resins, with suitable post-assembly curing again whilst held assembled under pressure.

One presently preferred embodiment of the invention is more particularly described with reference to the accompanying drawing in which Figure 1 is a fragmentary exploded perspective view showing components of a heat exchanger; and Figure 2 is a fragmentary sectional elevation of an assembly.

Turning now to Fig. 1, each tube comprises a pair of plain channel section components 10 12 which may be identical, or preferably component 10 is slightly narrower than the component 12 so that its side flanges 14 fit between the side flanges 16 of the part 12 when the two are assembled together. The depth D of the side flanges may be chosen so that the assembly is of complete rectangular section. These parts can be made by profile rolling or pressing a suitable thin sheet metal or metal foil. Where the assembly is held together and sealed by an adhesive, it may be the outer faces of the flanges 14 which are coated with epoxy resin prior to assembly.

Each tube contains an insert 20 in the form of a length of metal foil of slightly less width than the internal transverse dimension of the smaller of the components 10 12, and which is, in this instance, generally transversely corrugated, but with the corrugations inclined at an angle A of about 60-70 degrees to the side edges. The strip is essentially perforated with a multitude of perforations 22 which may be randomly distributed with respect to the corrugations but at such frequency that every corrugation includes at least one and preferably a plurality of such perforations, the total perforation area in each corrugation depending upon the desired resistance to flow in the tubes.

The thickness T of the corrugated strip is similar to the depth D of the side flanges.

Hence, when the strip is inserted in one of the channels, and the second of the channels is fitted as a lid to complete the tube. There is intimate contact between the apices of the corrugations and the internal faces of the'two tube parts 10 12. It is preferred to fix the inserts in the tubes by use of adhesive or brazing but this could be omitted if desired.

A plurality of tubes so formed are assembled into the heat exchange stack shown in Fig. 2, interleaved by fin plates 30. These are, or may be, generally similar to the inserts 20, with or without the perforations in this instance, but they may be assembled so that the corrugations are inclined in the opposite direction to those of the inserts 20.

Where adhesive is employed in the construction, this may be applied in bands in the tube components so as, for example to contact the inserts along the lines B in Fig. 1.

The complete stack can be assembled with end plates, header tanks and the like, held together in a jig, pressurised, and passed through a curing chamber at an elevated temperature according to the nature of the adhesive used.

If the invention is employed using brazing, preferably using pre-clad aluminium alloy sheet, a similar technique of assembly is a jig and pressurisation can be employed before the assembly is passed through a furnace at an appropriate elevated temperature to effect the brazing operation.

Claims

1. A heat exchanger comprising a plurality of parallel tubes alternating with fin plates in a stack, in which at least one tube is made of a pair of metal pressings assembled together with sealed joints, and with a longitudinally extending sinuous insert in the tube along its length, the insert being perforated to allow fluid flow through it.

2. A heat exchanger as claimed in Claim 1 wherein the metal pressings are made by profile rolling from strip.

3. A heat exchanger as claimed in Claim 1 wherein the inserts are made by feeding strip through a pair of meshed gears to produce a zig-zag configuration.

4. A heat exchanger as claimed in Claim 3 wherein the corrugations are inclined at an angle other than 90" to the edges of the strip.

5. A heat exchanger as claimed in Claim 4 wherein two or more inserts are employed in the tube with inclined corrugations oppositely extending.

6. A heat exchanger as claimed in any preceding claim wherein the height of the corrugations, prior to assembly is in excess of the internal height of the two assembled tube components.

7. A heat exchanger as claimed in any preceding claim wherein the fin plates are made by feeding strip through a pair of meshed gears to produce a zig-zag configuration.

8. A heat exchanger as claimed in Claim 7 wherein the fin plate corrugations are inclined at a angle other than 90" to the edges of the strip.

9. A heat exchanger as claimed in Claim 7 wherein two or more fin plates are employed between two adjacent tubes, with the corrugations of the fin plates oppositely inclined.

10. A heat exchanger as claimed in Claim 6 and any other preceding claim made by assembling the stack of said tubes and plates with joints and seals made by adhesive and holding the stack under pressure whilst post assembly curing of the adhesive takes place.

11. A heat exchanger as claimed in Claim 6 and any other preceding claim made by fabricating from clad aluminium or light alloy foil, assembling the stack of said tubes and fin plates together, and holding the assembly together whilst passing the stack through a brazing furnace.

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