EP0164391B1

EP0164391B1 - Heat exchanger plate

Info

Publication number: EP0164391B1
Application number: EP85900237A
Authority: EP
Inventors: Jan-Ove Bergqvist; Nils Stadmark; Arthur Dahlgren
Original assignee: Alfa Laval Thermal AB
Current assignee: Alfa Laval Thermal AB
Priority date: 1983-12-08
Filing date: 1984-12-05
Publication date: 1987-07-22
Also published as: SE8306795D0; WO1985002670A1; DK359285A; DE3464961D1; DK359285D0; EP0164391A1; JPS61500626A; BR8407210A; NO853123L; ATE28511T1

Abstract

A heat exchanger plate has a primary heat exchange part (1b), two secondary heat exchange parts (2b, 3b) placed on each side of this one and four holes or ports (4b, 5b, 6b, 7b). Two of the ports are located at one of the secondary heat exchange parts in the same distance from but on each side of a centre line (M) of the plate. The two other ports are in a corresponding way located at the other secondary heat exchange part. The plate has in all heat exchange parts (1b, 2b, 3b) ridges and valleys embossed into it, which are so placed that when two plates are put against each other - one of them turned 180<o> relative to the other one - ridges in one plate intersectingly rest against ridges in the other plate. At least the ridges and the valleys in the secondary heat exchange parts (2b, 3b) are so embossed that they have a volume of essentially the same size on respective sides of the plate. In a plate of this kind each of the two secondary heat exchange parts is provided with ridges and valleys forming an angle with the centre line (M) of the plate. This angle (or these angles) differs from the angle (the angles) which the ridges and the valleys in the primary heat exchange part (1b) of the plate form with the centre line (M). Furthermore, the ridges and valleys of the plate form such angles with the centre line (M) that in a plate interspace they bring about less flow resistance in the areas of the secondary heat exchange parts (2b, 3b) of the plates - on both sides of the centre line (M) - than in the area of the primary heat exchange part (M) of the plates.

Description

This invention relates to plate heat exchangers, and in particular relates to a heat exchanger plate of the kind having a central primary heat exchange part, separating two secondary heat exchange parts, and four holes or ports located two in each secondary heat exchange part at equal distances from a centre line of the heat exchanger plate extending through the primary and secondary heat exchange parts.
In a plate heat exchanger, a great number of plates of this kind, manufactured of a relatively thin plate, can be clamped together under great pressure between two thicker end plates of a frame. Two heat exchange media are intended to flow through the interspaces defined between the plates, they are conducted to and from the interspaces through channels formed by the ports in the heat exchanger-plates, which ports are in line with each other. Adjacent plates are sealed together, e.g. by gaskets or other means, so that the flow passage between them is sealed from the surrounding environment.
In each plate interspace, the heat exchange medium which passes therethrough can flow either diagonally over the heat exchanger plates, or essentially parallel with the centre line and two sides of the plates. This invention concerns a plate for diagonal flow and which for this reason, in a known way, is adapted, e.g. by provision of a gasket or the like, to be sealed to an adjacent plate around a sealing line which surrounds all the heat exchange parts and two diagonally opposite ports.
It is known for heat exchanger plates to be given a corrugation pattern of ridges and intervening valleys pressed in the plate, so that when two substantially similar plates are put against each other - with one of them turned through 180° relative to the other one- the ridges of one plate rest against and intersect the ridges of the other plate. At least the ridges and valleys in the secondary heat exchange parts are so arranged that they have substantially equal volumes on the opposite sides of the plate.
A heat exchanger plate as described above is known from SE-B- 342.691. In one of the secondary heat exchange parts of this known plate the ridges and valleys form the same angles (60° and 120⁰) with the centre line of the plate as do the ridges and the valleys in the primary heat exchange part, while in the other secondary heat exchange part the ridges and the valleys extend parallel to the centre line.
The purpose of the special design of the ridges and the valleys in the other secondary heat exchange part is, according to the patent, to bring about a reduced flow resistance for a heat exchange medium streaming through a plate interspace formed by two equal plates of this form, in the area closest to the port through which it enters the plate interspace, i.e. where the through-flow area for the heat exchange medium is substantially less than it is at the primary heat exchange parts or the plates.
It is correctly stated in the patent that, in conventional heat exchanger plates, the flow resistance in the mentioned area closest to the inlet port is undesirably high and this area of the plates cannot be effectively utilized for the heat exchange itself. The same is true for the area on the downstream side of the primary heat exchange part, and closest to the outlet port.
The aim of the present invention is to provide a heat exchanger plate enabling improved efficiency.
In accordance with the invention there is provided a heat exchanger plate having a central primary heat exchange part located between two secondary heat exchange parts, and four ports located two in each secondary heat exchange part, the two ports in each secondary heat exchange part being at the same distance from but on opposite sides of the centre line of the heat exchanger plate extending through the primary and secondary heat exchange parts, - the primary heat exchange part and the secondary heat exchange parts having corrugation ridges and valleys so arranged that when the plate is positioned against another substantially similar plate turned through 180° relative to said plate, the ridges of the respective plates will intersect and rest against one another, and in at least the secondary heat exchange parts the corrugation valleys on one side of the plate being of substantially the same volume as the corrugation valleys on the other side of the plate, characterized in that the plate is adapted to be sealed to another similar plate positioned thereagainst around a sealing line surrounding all the heat exchange parts and two diagonally opposite ports of said plate, whereby to delimit a passage for flow of a heat exchange medium between the plates from one port to the diagonally oppositely positioned port, - that in each of the two secondary heat exchange parts, at least on one side of the said centre line of the plate, the ridges and valleys extend at an angle to the centre line, - that the ridges and valleys in the primary heat exchange part and each secondary heat exchange part extend at different angles to said centre line of the plate, and - that the ridges and valleys form such angles with the centre line of the plate that when the plate is positioned against another substantially similar plate turned through 180° relative to said plate, a plate interspace is formed having for the flow direction through the interspace a flow resistance per unit length which is lower over the whole areas of secondary heat exchange parts than is said resistance over the area of the primary heat exchange part.
Due to the different design of the two secondary heat exchange parts in a plate according to the invention compared with the design of the corresponding parts of the plate disclosed in SE-B- 342961 it has been found possible in a plate interspace to have a particularly favourable flow of entering heat exchange medium over the plates, with the result that the secondary heat exchange parts of the plates are utilized effectively for heat exchange, not only in close proximity to the port through which the heat exchange medium enters the plate interspace but also on the opposite side of the centre line of the plate. It has appeared that when the secondary heat exchange parts are designed in accordance with the prior Swedish patent, such a favourable flow does not come about due to the reduced flow resistance in the plate interspace is confined to the area closest to the actual inlet port.
Some embodiments of the invention are described in detail below with reference being made to the accompanying drawings, in which:

Figure 1 illustrates a so-called diagonal flow of two heat exchange media on respective sides of a heat exchanger plate;
Figure 2 shows two heat exchanger plates according to a first embodiment of the invention;
Figure 3 shows a cross-section along the line III-III in Figure 2;
Figure 4 and Figure 5 illustrate how ridges designed in different ways in two plates put against each other intersect each other in a plate interspace; and
Figure 6 shows two heat exchanger plates according to a second embodiment of the invention.

In Figure 1 is schematically shown a heat exchanger plate with a primary heat exchange part 1, two secondary heat exchange parts 2, 3 and four through holes or so-called ports 4, 5, 6 and 7. Two fulldrawn lines 8 and 9 illustrate how a first heat exchange medium is intended to stream on one side of the plate from the port 4 to the diagonally oppositely positioned port 6, while two broken lines 10 and 11 illustrate how a second heat exchange medium is intended to stream on the other side of the plate from the port 7 to the port 5.
The flow of two heat exchanging media as illustrated in Figure 1 is usually called diagonal flow.
In Figure 2 there are shown two heat exchanger plates 12 and 13 similarly pressed or embossed. One plate is turned through 180° in its own plane relative to the other one. Each plate 12 and 13, respectively, has a primary heat exchange part 1a, two secondary heat exchange parts 2a and 3a, respectively, and four ports 4a, 5a, 6a and 7a. On the side of the plate 12 visible in Figure 2 all three heat exchange parts 1a. 2a and 3a together with the ports 4a and 6a are surrounded by a gasket 14 arranged in a groove pressed in the plate. Separate gaskets (not shown in the drawing) surround the ports 5a and 7a, respectively. In the plate 13 all three heat exchange parts 1a, 2a and 3a and the ports 5a and 7a are similarly surrounded by a gasket 15.
The primary heat exchange part 1a a of each plate 12 and 13, has a corrugation pattern of ridges and valleys brought about by pressing. The pattern is symmetrical with respect to a centre line M of the plate and forms such angles relative to this centre line that in an interspace formed between two adjacent plates arranged together as shown in Figure 2, the ridges of one plate intersect with and may rest against the ridges of the other plate.
The secondary heat exchange parts 2a and 3a of the plates 12 and 13 also have ridges and valleys which are inclined to the centre line M so that in the interspace between two plates assenbled together as in Figure 2, ridges in the part 2a of one plate intersect and can rest against ridges in the part 3a of the other plate.
The ridges and valleys in the primary heat exchange parts la of the plates 12 and 13 form an angle of about 60° with the centre line M on one side of this line and an angle of about 120° with the centre line M on the other side of this line. In the secondary heat exchange parts 2a, the ridges and valleys form an angle of about 45° with the centre line M, while corresponding angle is about 135° in the other secondary heat exchange parts 3a.
As is apparent from Figure 1, one of the heat exchanging media streams essentially cross the flow direction for the second medium at each of the secondary heat exchange parts of the plate. If the same flow conditions are required for both heat exchange media it is necessary, with plates intended for diagonal flow that the ridges and the valleys in the secondary heat exchange parts are so designed that they have volumes of essentially the same size on opposite sides of the plate.
This is illustrated by Figure 3 which is a sectional view along the line III-III in Figure 2. In Figure 3 there are shown two planes 16 and 17 extending through the tops of the ridges formed on each side of a plate. The enclosed volume between the plane 16 and two adjacent ridges on one side of the plate is accordingly essentially equal to the volume between the plane 17 and two adjacent ridges on the other side of the plate.
Figure 4 illustrates how ridges in the secondary heat exchange part 2a or the plate 12 intersect ridges in the secondary heat exchange part 3a of the plate 13 when the plates 12 and 13 are arranged to form a plate interspace in accordance with Figure 2.
Figure 5 similarly illustrates the manner in which the ridges in the primary heat exchange parts 1a of the plates 12 and 13 intersect.
Different flow directions for a heat exchange medium have been indicated by means of arrows 18,19 and 20 in Figure 4 and by arrows 21, 22 and 23 in Figure 5.
It is generally known how the flow resistance for a heat exchange medium varies in a plate interspace depending on the arrangement of the ridges of the plates in relation to the flow direction of the heat exchange medium. When the ridges in two adjacent plates intersect each other essentially at right angles (90°), as is illustrated in Figure 4, there arises, of course, a resistance to flow in the direction 18 as large as the resistance to flow in the direction 20. Furthermore, for a flow in the direction 19, the flow resistance is essentially as large as for flows in the directions 18 and 20.
When the ridges in two adjacent plates intersect each other at angles as shown in Figure 5, the flow resistances are very different for different flow directions. For a flow in the direction 21, the flow resistance is several times greater than the resistance to flow in the direction 23. For a flow in the direction 22, the flow resistance is something therebetween. The flow resistance in a plate interspace according to Figure 5, for a flow with the direction 21, is also greater than the flow resistance in a plate interspace according to Figure 4 irrespective of the direction of the flow in the latter interspace.
Thus, it is possible, by choosing the directions of the ridges pressed in the plates in relation to the intended flow directions for the heat exchanging media, to obtain the required flow resistance for the media in the different parts of a plate interspace.
In the heat exchange plates 12 and 13 in Figure 2 choice of the ridge directions has the consequence that a heat exchange medium entering the interspace between the plates via the port 7a of the plate 13 (or via the port 5a of the plate 12) meets a relatively small flow resistance in whole that part of the plate interspace formed by the part 2a of the plate 12 and the part 3a of the plate 13.
This has the result that the different branch flows of the heat exchange medium reaching the primary heat exchange parts la of the plates, which parts 1 a produce a greater flow resistance than the secondary heat exchange parts 2a and 3a, are of essentially the same size. Consequently, the secondary heat exchange parts of the plates as well as the primary heat exchange parts in their entirety are utilized in an effective way, i.e. the total pressure drop that the heat exchange medium experiences during its passage through the plate interspace is utilized as far as possible for the heat exchange itself.
In Figure 6 there are shown two similar heat exchange plates 24 and 25 equally pressed or embossed. The only difference between these plates and the plates 12 and 13, respectively, in Figure 2 is the design of the secondary heat exchange parts of the plates. The heat exchange parts of the plates 24 and 25 have been denoted 1b, 2b and 3b in Figure 6. The ports in the plates have been denoted 4b, 5b, 6b and 7b, and the two gaskets have been denoted 26 and 27, respectively.
As is apparent, the ridges and the valleys in each of the secondary heat exchange parts 2b and 3b are symmetrical with regard to the centre line M of the plates. On one side of the centre line M the ridges form an angle of ahout 45° with the centre line both in the part 2b and in the part 3b, while on the other side of the centre line M the ridges in both parts 2b and 3b form an angle of about 135° with the centre line.
The different design of the secondary heat exchange parts of the plates 24 and 25 does not materially influence the flow resistance in a plate interspace formed by these plates, as compared with the flow resistance in a plate interspace formed by the plates 12 and 13 in Figure 2. On each side of the centre line M the ridges in the secondary heat exchange parts of the plates resting against cach other intersect at right angles, and in both cases the ridges of one plate form an angle of 45° and the ridges of the other plate an angle of 135° with the centre line of the plates.
An advantage with the design of the secondary heat exchange parts as they are shown in Figure 6 is that the above described advantageous flow can be brought about between the plates 24 and 25 even if the plate 25 is turned 180° about its centre line M, i.e. positioned with its reverse side against the reverse side of the plate 24. This can come into question if the sealing between the plates 24 and 25 is obtained by soldering or welding instead of a rubber gasket.
The division of the corrugation pattern, i.e. the pitch of the ridges and valleys, in the secondary heat exchange part is, in both embodiments according to Figures 2 and 6, essentially the same as that of the corrugation pattern in the primary heat exchange part.
The two different arrangements of the secondary heat exchange parts appearing from Figures 2 and 6 are not the only ones possible within the scope of the present invention as defined in the claims.
By way of an example, in each of the secondary heat exchange parts the ridges on one side of the centre line M can form an angle of 90° with this line, while the ridges on the other side of the centre line M form another angle or extend parallel with the centre line.

Claims

1. A heat exchanger plate having a central primary heat exchange part (1) located between two secondary heat exchange parts (2, 3), and four ports (4-7) located two in each secondary heat exchange part, the two ports in each secondary heat exchange part being at the same distance from but on opposite sides of the centre line (M) of the heat exchanger plate extending through the primary and secondary heat exchange parts, - the primary heat exchange part (1) and the secondary heat exchange parts (2, 3) having corrugation ridges and valleys so arranged that when the plate is positioned against another substantially similar plate turned through 180° relative to said plate, the ridges of the respective plates will intersect and rest against one another, and - in at least the secondary heat exchange parts (2, 3) the corrugation valleys on one side of the plate being of substantially the same volume as the corrugation valleys on the other side of the plate, characterized in that the plate is adapted to be sealed to another similar plate positioned thereagainst around a sealing line surrounding all the heat exchange parts (1-3) and two diagonally opposite ports (4, 6; 5, 7) of said plate, whereby to delimit a passage for flow of a heat exchange medium between the plates from one port (4, 7) to the diagonally oppositely positioned port (5, 6), - that in each of the two secondary heat exchange parts (2a, 3a; 2b, 3b), at least on one side of the said centre line (M) of the plate, the ridges and valleys extend at an angle to the centre line, - that ridges and valleys in the primary heat exchange part (1a; 1b) and each secondary heat exchange part (2a, 3a; 2b, 3b) extend at different angles to said centre line (M) of the plate, and - that the ridges and valleys form such angles with the centre line of the plate that when the plate is positioned against another substantially similar plate turned through 180° relative to said plate, a plate interspace is formed having for the flow direction through the interspace a flow resistance per unit length which is lower over the whole areas of secondary heat exchange parts (2a, 3a; 2b, 3b) than is said resistance over the area of the primary heat exchange part (1a; 1b).

2. A heat exchanger plate according to claim 1, wherein the ridges and valleys extend in such directions that when the plate is positioned against another substantially similar plate turned through 180° in relation to said plate, the ridges resting against each other intersect at different angles in the secondary heat exchange parts (2a, 3a; 2b, 3b) than in the primary heat exchange parts (1a; 1b).

3. A heat exchanger plate according to claim 2, wherein the ridges and valleys in the primary heat exchange part (1a; 1b) are at an angle in the order of 60° (1200) to the centre line (M) of the plate, and the ridges and valleys in the secondary heat exchange parts (2a, 3a; 2b, 3b) are at an angle in the order of 45° (135⁰) with the centre line (M) of the plate.

4. A heat exchanger plate according to any one of the preceding claims, wherein the ridges and valleys extend in one direction in the portions of the secondary heat exchange parts (2b, 3b) on one side of the centre line (M) of the plate, and in another direction in the portions of the secondary heat exchange parts (2b, 3b) on the other side of the centre line (M).

5. A heat exchanger plate according to claim 4, wherein the ridges and valleys in each secondary heat exchange part (2b, 3b) are symmetrical with regard to the centre line (M) of the plate.

6. A heat exchanger plate according to any one of the preceding claims, wherein the division of the corrugation pattern in the secondary heat exchange part is substantially the same as that of the corrugation pattern in the primary heat exchange part.