GB2235040A

GB2235040A - Plate heat exchangers

Info

Publication number: GB2235040A
Application number: GB9011911A
Authority: GB
Inventors: Eberhard Krause
Original assignee: BAVARIA ANLAGENBAU GmbH
Current assignee: BAVARIA ANLAGENBAU GmbH
Priority date: 1989-07-25
Filing date: 1990-05-29
Publication date: 1991-02-20
Anticipated expiration: 2010-05-29
Also published as: BE1004093A5; JPH03221790A; DE3924581A1; GB2235040B; DE3924581C2; FR2650381A1; GB9011911D0

Abstract

A cross-flow plate heat exchanger comprises plates joined at first opposite edges to form plate pairs defining open-ended first passages for a first fluid, adjacent plate pairs being joined together at second opposite edges to define open-ended second passages for a second fluid, wherein for fluid separation of the first and second passages comb-like metal sheets 20 are provided with their teeth 25, whose mutual distance corresponds to the depth of a plate pair plus twice the sheet metal thickness of a plate, engaging between the individual plate pairs, and are rigidly joined to shell sheets 30 to form frames, the corners of the frames being rigidly joined via profile bars 40. <IMAGE>

Description

t -I- PLATE HEAT EXCHANGER MODULE

The invention relates to a plate heat exchanger according to the preamble of Patent Claim 1, such as has been described and shown, for example, in DE 3,710j823 Al.

In the plate heat exchanger forming the generic type, the flow paths for the two media participating in the heat exchange are separated from one another at the corners of the stack by corner welds running at rightangles to the seam welds and fillet welds.

The build-up of such corner welds involves difficult welding technology, in particular if the sheet metal thickness of the individual plate elements combined into a stack is small. for example equal to or smaller than 0.2 mm. A further aggravating factor is that these corner welds serve at the same time as elements for joining the stack to the casing surrounding it. Thus, these corner welds are weak points in the overall strength of such a plate heat exchanger whose plate pairs combined into stacks and consisting of plate elements form so-called modules which can be combined to give plate heat exchangers of any desired size.

Plate heat exchangers are also known in which the individual plate elements. for separating the flow paths for the two media participating in the heat exchange, are sealed by means of gaskets at their mutual junctions and are held firmly together by stay bolts which at the same time serve as elements for joining to the casing which encloses the stackcompare British Patent Specification 1,034.466. Although modules which can easily be mounted and readily handled and which can be assembled to give plate heat exchangers of any desired large capacity can be produced in this way, the multiplicity of the elastic seals between the individual plate elements has the result that the mechanical strength of the plate elements cannot be fully utilised, since the strength of such plate stacks is in that case determined above all by the pressure resistance and temperature resistance of the sealing materials which. in addition. have a relatively short service life under the applicable operating is conditions and must therefore be replaced f airly frequently. Moreover, the leak-tightness of such joints leaves a great deal to be desired, in particular in the case of heat-exchanging media having aggressive properties.

Protection of the environment and energy conservation measures increasingly require the use of heat exchangers even in process plants which run under extreme operating conditions, so that increasingly more stringent demands have to be met by such heat exchangers. In addition, there is the demand to achieve a high performance density, that is to say an optimum ratio between the constructional volume and the heat exchanger capacity, as well as a good performance/weight ratio. Apart from the media pressures and temperatures applying during operation, that is to say those which are permissible, the specific thermal output determines the performance density and hence also the performance/weight ratio; the sheet metal thickness of the individual plate elements here plays a significant role.

It is therefore the object of the invention to provide, for plate heat exchangers of relatively thin plate elements which are welded to one another to form the flow paths for the media participating in the heat exchange, a novel corner joint which at the same time serves as a connecting element for the casing and which is easy to produce and mount and statically fixes the individual plate elements in the stack and casing even over prolonged operating periods and also ensures reliable sealing under all operating conditions.

Claims

This object is achieved according to the invention by the characterizing

features of Patent Claim 1.

By means of the design,, according to the invention,, of the corner joint as a frame shell, end face frames are created on the tube side at the beginning and end of a stack of plate elements,, which frames serve equally well as seal and as connecting elements and are mutually joined via profile bars arranged at rightangles to the plane of the frame,, so that modules are f ormed which can easily be produced and handled, have a predetermined size and can be assembled to give heat exchangers of any desired capacity.

Due to the U-shaped design of the comb-type metal sheets and shell sheets, a high mechanical strength coupled with small material thickness is achieved, and the short legs of the frame sheets at the same time form stops for the outsides of the particular outer plate element of the stack.

When several such modules are assembled via the profile bars to give a plate heat exchanger, dents in the thin plate elements of the stack are reliably prevented between the individual stacks by the support elements covering the surfaces.

As a result of the silicone sealing strip located between the comb-type metal sheets and plate pairs of the stack, the requisite fluid-wise separation at the corners of the stack is reliably achieved over prolonged operating periods, since this sealing strip is not subject to any mechanical stresses, for example due to stay bolts which generate a sealing pressure. The mechanical fixing of the plate elements of the stack is effected solely by the teeth of the comb-type metal sheets, engaging from the tube side between the individual plate pairs.

The comb-type metal sheets formed as T-shaped profile bars according to a further embodiment of the invention have the advantage that, due to their teeth of reduced thickness, these can be welded to the plate pairs at the engagement points.

The invention is described below by reference to two illustrative examples represented more or less diagrammatically in the drawing in which:

Figure 1 shows a perspective view, partially in section, of a heat exchanger module according to the invention with a merely indicated second adjoining heat exchanger module; Figure 2 shows a view of the gap side of the heat exchanger module according to Figure 1 as viewed in the direction of the arrow 2; S t is Figure 3 shows a side view of the heat exchanger module according to Figure 1 as viewed in the direction of the arrow 3; Figure 4 shows a side view of the heat exchanger module according to Figure 1 as viewed from the tube side in the direction of the arrow 4; Figure 5 shows a perspective view of a comb-type metal sheet which is part of the end f ace frame of the heat exchanger module; Figure 6 shows a perspective view of a shell sheet which is part of the end face frame of the heat exchanger module; Figure 7 shows a perspective view, partially in section, of the incorporation of a comb-type metal sheet, formed from T-shaped profile bars, of a second embodiment of the invention; and Figure 8 shows a perspective illustration of the T-shaped comb-type metal sheet according to Figure 7.

A heat exchanger module WM suitable for the most diverse applications consists,, as shown especially by Figure 1,, of plate elements 10 assembled to give a stack and having regular embossings 11. In each case two embossed plate elements 10 are combined, in mirrorinverted superposition, to give plate pairs 14 by means of f irst welds 13 - seam welds - located on their opposite unembossed edge regions 12, the plate elements of the plate pairs f orming gap-like openings - gaps - 15 with their mutually f acing surf aces (compare Figures 2 and 7).

Each plate pair 14 is firmly joined to the adjacent plate pair 14 by mutually opposite second welds 16 - edge joint weld at the parallel joint - connecting the mutually adjacent edge end joints.

The mutually f acing surf aces of the individual plate pairs form tubular openings 18 - tubes (Figure 4).

The individual plate elements and the plate pairs formed from them are here arranged in such a way that the gap-side and tube-side openings for the heat-exchanging media are arranged at a mutual angle.

I The individual plate pairs 14 which are assembled with one another to give a stack St by means of the edge joint welds are held in their stacked position by four comb-type metal sheets 20 which extend, mutually opposite in each case, on both sides beyond the end-face edge length of the stack St, as shown especially in Figures 1 and 2.

The comb-type metal sheets 20 have a U-shaped cross-section - see Figure 5 - with legs 22 and 23 of unequal length, the legs 23 having teeth 25. The mutual distance a of the teeth 25 corresponds to the embossing depth t of a plate pair plus twice the sheet metal thickness s of a plate element (compare Figure 2). The comb-type metal sheets 20 are arranged in such a way that the teeth 25 engage from the tube side of the plate pairs between the individual plate pairs and thereby positively f ix the latter; compare Figures 1, 2 and 4. Sealing strips 37 of silicone are arranged between the comb-type metal sheets 20 and plate pairs 14 in order to obtain reliable fluid-wise separation at the corners of the stack St; compare Figures 2 and 3 (not shown in Figure 1 for the sake of clarity).

The comb-type metal sheets 20 at the top and bottom in relation to Figure 2 are welded at their ends to two likewise mutually opposite shell sheets 30 to give in each case a frame which represents the end face in relation to the stack St, that is to say they are firmly joined to one another. For this purpose, the comb-type metal sheets 20 each have at both ends in each case a projecting lug 26, the width of which corresponds to the width of the long leg 31 of the shell sheets 30 which likewise have a U- shaped cross-section - compare Figure 6. The short leg 33 of the shell sheets 30 serves as a contact surface for the welded connection of the f irst and last plate element of the stack St, as Figure 1 clearly shows.

The end-face frames formed by the comb-type and shell sheets are welded together, that is to say firmly joined-, via four profile bars 40 having an angle profile f is to give a stack framework SG which surrounds the stack St on all sides. In this way, a heat exchanger module which can easily be handled and has a predetermined capacity is formed, and a plurality of such modules WM, WM-2... WM-n can then be assembled to give a heat exchanger of any desired large capacity. In this case, it is advantageous to insert support elements 50, compare Figure 1, between two modules, which support elements can consist of different materials depending on the particular application; a foam glass enclosed by a silicone skin 51 has proved to be suitable.

A further illustrative example of the comb-type metal sheets described in conjunction with Figure 5 is shown in Figures 6 and. 7, identical parts carrying identical reference numbers.

As shown in Figures 6 and 7, comb-type metal sheets 70 are provided there, which are made of T-shaped profiles. one leg 72 of the profile bars has a reduced thickness of material in the region 71 as compared with the remainder, preferably down to about 2 mm, in order to allow welding to the edge regions 12 of the plate pairs 14. In this way, a completely welded heat exchanger is formed, so that the sealing strips 37 according to the first illustrative example - compare Figures 2 and 3 can be omitted.

The teeth 25 are worked into the reduced thickness region 71, for example by milling-out in accordance with the illustrative example already explained.

In this case too, shell sheets 74 are provided which, together with combtype metal sheets 71, form the end-face frames which in turn are joined via their surface extent to the stack framework SG which has already been described and which encloses a stack St of plate pairs 14 and, with the latter, forms the said heat exchanger module WM.

A 6 PATENT CLAIMS 1. Plate heat exchanger, consisting of plate elements which have regular embossings and are joined at their embossing-free edges to give plate pairs forming gap-side openings and by fillet welds mutually joining the plate pairs by the edge joints of the in each case mutually facing plate elements of two adjacent plate pairs to form tube-side openings, to give a stack whose gap-side and tube-side openings are arranged at a mutual angle, characterized in that, for fluid-wise separation of the gap-sides and tube-sides (15, 18) formed by the plate pairs (14), comb-type metal sheets (20) are provided which extend on both sides beyond the edge length of the end faces of the stack (St) and which, with their teeth (25) whose mutual distance (a) corresponds to the embossing depths (t) of a plate pair (14) plus twice the sheet metal thickness (s) of a plate element (10), engage f rom the tube side between the individual plate pairs (14) and are rigidly joined to shell sheets (30) extending along the gap sides likewise beyond the edge length of the stack (St) to give a frame located at each end face of the stack, the corners of the frame being rigidly joined via profile bars (40) enclosing the stack (St) on the longitudinal side in order to form a stack framework (SG).
2. Plate heat exchanger according to Claim 1, characterized in that the comb-type metal sheets (20) are formed with a U-shaped cross-section having legs (22, 23) of unequal length, of which one leg (23) is toothed (teeth 25).
3. Plate heat exchanger according to Claim 1, characterized in that the shell sheets (30) are likewise formed with a U-shaped cross-section having legs (31, 33) of unequal length and are each firmly joined by their short legs (33) to the outside of the particular outer plate element (10) of the stack (St). bearing against the comb-type metal sheets (20).
4. Plate heat exchanger according to Claim 1 f 1k characterized in that the comb-type metal sheets (20) have, at their ends, lugs (26) which correspond to the width of the long legs (31) of the shell sheets (30) and serve for joining to the shell sheets.
5. Plate heat exchanger according to Claims 1 to 4, characterized in that the comb-type and shell Bheets (20, 30) as well as the profile bars (40) are rigidly joined to one another by welded joints, and that a Bealing strip (37) Of Bilicone, which seals the gap Bides and tube sides (15, 18) from one another, is located between the comb-type metal sheets (20) and the plate pairs (14) of the Btack (St).
6. Plate heat exchanger according to Claim 4, characterized in that, when a plurality of stacks (St) is arranged in rows, a support element (50) which bears with its surface against the plate elements is provided in each case between the mutually facing plate elements of a stack (St), enclosed in each case by a stack framework (St), and that the support elements (50) consist of foam glass enclosed by a Bilicone skin (51).
7. Plate heat exchanger according to Claim 1, characterized in that the comb-type metal sheets are formed as T-shaped profile bars (70) whose legs (71) carrying the teeth (25) are reduced in their thickness to about 2 mm thickness in the region (72) of the teeth, and that the shell sheets are formed as rectangular bars (75) welded to the webs (74) of the profile bars (70).
8. Plate heat exchanger according to Claim 7. characterized in that the teeth (25) of the profile bars (70) are welded to the plate pairs (14) at the engagement points.
9. A plate heat exchanger substantially as herein described with reference to the accompanying illustrative drawings.

Published 1991 at '17he Patent Office. State House. 66/71 High Holborn. London WCIR 47?. Further copies may be obtained from Sales Branch, Unit 6. Nin- Mile Point. Cwmfelinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques lid, St May Cray. Kent.

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