GB2041190A - Heat exchanger - Google Patents

Abstract

A plate-type heat exchanger in which the plates 1,2,3,4 may be disassembled, the plates defining alternate channels for the exchange of heat between two or more fluids, the heat exchanger being rectangular in plan and having recessed corners accommodating a sealing strip 28. Each plate has complex flanges at two non-adjacent edge portions. The flanges each have a step shape with a riser 11 and tread 12 and, as shown, also comprise a lip 13. The corner recesses 24,25,26,27 extend directly into contact with the major portion of the plate (ie the portion which extends between the risers). At each recess, the major portion of the plate terminates in abutment to, and perpendicular to the length of, sealing material 28. Corrugated resilient strips 16,17,18 are positioned in channels formed by the flanges. The plates may have dimples or grooves (not shown). The heat exchanger is a modification of that described in British Patent Specification No 1 058 201. <IMAGE>

Description

SPECIFICATION Heat exchanger This invention relates to heat exchangers and has particular reference to plate-type heat exchangers.

In piate-type heat exchangers a plurality of plates are stacked in face-to-face relationship so as to provide flow channels for fluids. Each channel is separated from its adjacent channel by a plate through which heat transfer between the fluids occurs. To prevent mixing of the fluids in adjacent channels it is necessary to stop leakage at the side and corner edges of the stack of plates. One method of preventing leakage is to form a brazed plate-type heat exchanger. However, brazed units are expensive. Also, it is not possible to dismantle a brazed plate heat exchanger easily for cleaning purposes. This may be of particular importance if one of the fluids is dirty or polluted air which can eventually clog the heat exchanger flow paths.Bolted constructions for heat exchangers have been proposed and one particularly suitable bolted construction is described in British Patent Specification No 1 058 201, the disclosure of which is incorporated herein by way of reference. The present invention is in fact an improvement in the arrangement described and illustrated in British Patent Specification No 1 058 201 in that the present invention provides improved corner sealing arrangements to reduce the possibility of mixing of the fluids passing through the heat exchanger.

By the present invention there is provided a rectangular heat exchanger incorporating a plurality of plates stacked in face-to-face relationship in which each plate has at least two non-adjacent edge portions, each of which comprises a complex flange of step shape having a tread and riser, the treads of each plate being displaced by the risers in the same directional sense relative to the major portion of the plate which lies between the risers and adjacent plates being relatively located with the complex flanges of each plate in noncorresponding relationship with the complex flanges of the other plate and with all of the treads being displaced from their associated plates in the same directional sense with respect to the exchanger so that risers effect spacing of parts of each plate which lie between its risers from part or parts of the or each adjacent plate which lie between its risers, the corners of each of the plates being recessed and there being provided lengths of sealing material in the recess, characterised in that the recesses extend directly into contact with the major portion of the plate and the major portion of the plate terminates in abut ment to the length of sealing material perpen dicular to the length of sealing material.

The lengths of sealing material may comprise lengths of polymeric or ceramic based material or any other material to suit the conditions of a given application. The sealing material may be reinforced either homogeneously or alternatively backed with a metal or other reinforcing material. Alternatively, the length of sealing material may be a length of metal and the corners may be dipped if required in an adhesive and/or sealant solution to seal the edges of the plates to the lengths of sealing material. The adhesive may be sufficiently weak to be broken for disassembly purposes of the heat exchanger.

Adjacent surfaces of the treads of each plate, except for one plate at one end of the stack, may be spaced apart by their risers from an opposing surface of another adjacent plate and pressure distributing and transmitting means may be disposed between the spaced apart adjacent surfaces of the treads and plates, this means being an open structure so as to permit the passage of fluid therethrough.

The pressure distributing and transmitting means may be resilient and may be a corrugated metal strip.

The treads of the plates may be extended by lips which oppose the risers to form troughs between the risers and lips in which the pressure distributing and transmitting means are located.

The heat exchanger assembly may be held together by releasable holding means comprising end plates bolted together so as to clamp the heat exchanger plates between them.

By way of example embodiments of the present invention will now be described with reference to the accompanying drawings, of which: Figure 1 is an exploded view (not to scale) of a heat exchanger in accordance with the present invention; Figure 2 is a perspective view of a prior art corner arrangement; and Figure 3 is a view of the corner of Fig. 2 along the line of arrow Ill.

Refering to Fig. 1 this shows a series of rectangular plates 1, 2, 3, 4 which divide and form the sides of channels for gases which flow through the heat exchanger. The plate 1 has on opposite sides channels 5, 6 which are defined by risers 7 and treads 8 together with lips 9. Similarly, plate 2 has channels, one of which is shown at 10, formed by risers 11, treads 1 2 and lips 1 3. It can be seen that the channels on the plate 2 are at right angles to the channels on plate 1. Similarly, plate-3 is provided with channels as at 14 and plate 4 with channels as at 1 5.

Positioned within the channel 10 is a corrugated, resilient strip 1 6 which serves to support plate 1 relative to the channel 1 0. Simi larly, a corrugated strip is provided for each of the channels (apart from the upper channels 5 and 6) as is shown at 17 and 18.

Located within the channels 5 and 6 are spacer bars 19, 20 which abut an outer plate 21. A corresponding spacer bar 22 is provided at the bottom of the heat exchanger to abut lower plate 23.

The corners of each of the plates 1 to 4 are recessed as is shown at 24, 25, 26 and 27.

Located within the recesses are longitudinally extending sealing strips which in the present case are in the form of extruded lengths 28 which are rectangular insofar as they extend into the recesses. It will be seen that the recesses extend into the major portion of the plates 1 to 4 and the plates abut directly to and perpendicular to the lengths 28.

The feature of the perpendicular contact provides improved sealing when compared to the contact provided by the construction disclosed and described in British Patent Specification No 1 058 201. When the flanges are formed on the main body of the sheet by bending them over, thus forming the riser, the outer portions of the corner are inevitably radiussed. It is not possible, unless the corners are expensively machined, to provide a sharp corner. The radius, therefore, provides a small triangular cross-sectioned path for leakage between the top edge of the riser and the tread of the adjacent plate.

This is shown in more detail in Figs. 2 and 3 where the leakage paths 40, 41 and 42 are formed as small triangular cross-sectional paths between, for example, riser 43 and tread 44. By having the direct contact perpendicular to the corner bars as is provided by the present invention this small leakage path is considerably reduced or even, in the optimum circumstances, eliminated.

The whole heat exchanger is held together by means of long bolts 29, 30 which clamp, by means of nuts 31, 32, the assembled heat exchanger together. Suitable flanges 33, 34, 35, 36 are provided to enable the heat exchanger to be bolted into a suitable duct.

If required the corners of the heat exchanger can be dipped into a suitable sealing medium so as to enhance the seal between the corners of the plates and the longitudinally extending strips. It will be seen that the arrangement described differs from that of the prior art in that the recesses 24 extend into the major region of the plates and this enables improved sealing between the plates and the edge strips to be provided.

The material from which the heat exchanger is made can be any suitable metal such as aluminium, mild or stainless steel. The longitudinally extending lengths such as 28 can also be made from a metal or from a coated metal or from a plastics material or from a reinforced plastics material-the reinforcement may Itself be of a metal.

With the addition of partial or complete blanking plates or flow turn-round tanks on one or more of the matrix faces of the heat exchanger, it may be adapted to approximate to any required flow arrangement, eg counter, parallel, cross, cross-counter or cross-parallel.

The plates of the heat exchanger may also be plain or may be modified either by indentations formed in the plates or by the addition of material between them. Such modifications may be introduced in order to assist in spacing and support of the plates, to control the pressure drop through the channels, to alter the heat transfer characteristics, to provide flow guidance or to impart stiffness. The indentations may be dimples or grooves, for example, formed in the plates in such a pattern that the plates do not nest together when stacked together in their assembled sequence. Material added between the plates may take the form of washers, spacers, ribs, corrugations, flow splitters or guides.

Claims (9)

1. A rectangular heat exchanger incorporating a plurality of plates stacked in face-toface relationship in which each plate has at least two non-adjacent edge portions, each of which comprises a complex flange of step shape having a tread and riser, the treads of each plate being displaced by the risers in the same directional sense relative to the major portion of the plate which lies between the risers and adjacent plates being relatively located with the complex flanges of each plate in non-corresponding relationship with the complex flanges of the other plate and with all of the treads being displaced from their associated plates in the same directional sense with respect to the exchanger so that risers effect spacing of parts of each plate which lie between its risers from part or parts of the or each adjacent plate which lie between its risers, the corners of each of the plates being recessed and there being provided lengths of sealing material in the recess, characterised in that the recesses extend directly into contact with the major portion of the plate and the major portion of the plate terminates in abutment to the length of sealing material perpendicular to the length of sealing material.

2. A heat exchanger as claimed in Claim 1 in which the lengths of sealing material are formed from polymeric material or metal reinforced polymeric material.

3. A heat exchanger as claimed in Claim 1 in which the length of sealing material comprises a length of metal, the corners of the heat exchanger being coated with an adhesive solution to seal the edges of the plates to the lengths of metal.

4. A heat exchanger as claimed in Claim 3 in which the strength of the adhesive is so chosen that in use it may be broken for disassembly purposes of the heat exchanger.

5. A heat exchanger as claimed in any one of Claims 1 to 4 in which adjacent surfaces of the treads of each plate, except for one plate at one end of the stack, are spaced apart by their risers from an opposing surface of another adjacent plate and pressure distributing and transmitting means are disposed between the spaced apart adjacent surfaces of the treads and plates, the means being an open structure so as to permit the passage of fluid therethrough.

6. A heat exchanger as claimed in Claim 5 in which the pressure distributing and transmitting means are resilient and are formed of a corrugated metal strip.

7. A heat exchanger as claimed in any one of Claims 1 to 6 in which the treads of the plates are extended by lips which oppose the risers to form troughs between the risers and lips in which the pressure distributing and transmitting means are located.

8. A heat exchanger as claimed in any one of Claims 1 to 7 in which the assembly is held together by releasable holding means comprising end plates bolted together so as to clamp the heat exchanger plates between them.

9. A heat exchanger substantially as herein described with reference to and as illustrated by Figs. 1 and 2 of the accompanying drawings.