TECHNICAL FIELD

The present invention relates to a gasket for a plate heat exchanger and its design. The present invention also relates to an assembly for a plate heat exchanger comprising such a gasket.

BACKGROUND OF INVENTION

Plate heat exchangers typically consist of two end plates in between which a number of heat transfer plates are arranged in an aligned manner, i.e. in a stack or pack. The heat transfer plates of a PHE may be of the same or different types and they may be stacked in different ways. In some PHEs, the heat transfer plates are stacked with the front side and the back side of one heat transfer plate facing the back side and the front side, respectively, of other heat transfer plates, and every other heat transfer plate turned upside down in relation to the rest of the heat transfer plates. Typically, this is referred to as the heat transfer plates being “rotated” in relation to each other. In other PHEs, the heat transfer plates are stacked with the front side and the back side of one heat transfer plate facing the front side and back side, respectively, of other heat transfer plates, and every other heat transfer plate turned upside down in relation to the rest of the heat transfer plates. Typically, this is referred to as the heat transfer plates being “flipped” in relation to each other.

The heat transfer plates are typically corrugated so as to comprise ridges extending in an upper plane, and valleys extending in a lower plane. In one type of well-known PHEs, the so called gasketed plate heat exchangers, gaskets are arranged between the heat transfer plates, more particularly in gasket grooves extending along outer edges and around portholes of the heat transfer plates. The gasket grooves may extend in the lower plane and/or in an intermediate plane arranged between the upper and lower planes. The intermediate plane could extend halfway between the upper and lower planes, i.e. be a so-called as half-plane. The end plates, and therefore the heat transfer plates, are pressed towards each other whereby the gaskets seal between the heat transfer plates. The gaskets define parallel flow channels between the heat transfer plates, one channel between each pair of heat transfer plates. Two fluids or media of initially different temperatures can flow through every second channel for transferring heat from one fluid or medium to the other.

The fluids enter and exit the channels through inlet and outlet ports, respectively, which extend through the PHE and are formed by respective aligned portholes in the heat transfer plates and the gaskets sealing, completely or partly, around the portholes. The inlet and outlet ports communicate with inlets and outlets, respectively, of the PHE for feeding the fluids to and from the PHE.

For the plate heat exchanger not to leak, the gaskets must seal properly between the heat transfer plates. To achieve such proper sealing, the gaskets must have a suitable design. One type of known gaskets for plate heat exchangers comprises an elongate body and parallel longitudinal ribs projecting from an upper surface of the body. The purpose of the ribs is to increase the sealing capacity of the gasket. Despite the provision of the ribs, there is still a risk that the gasket will leak. If the gasket should leak there is a risk that the leaking fluid would end up between the ribs, which would make it difficult to detect the leak. Further, the fluid between the ribs could be a problem from a hygienic point of view.

SUMMARY

An object of the present invention is to provide a gasket for a plate heat exchanger which facilitates leak detection and is more hygienic, but which is still capable of effectively sealing between two adjacent heat transfer plates in a plate heat exchanger. The basic concept of the invention is to provide the gasket with at least one longitudinal rib or projection which is provided with draining means. The gasket and an assembly comprising such a gasket for achieving the object above are defined in the appended claims and discussed in further detail below. A gasket for a plate heat exchanger according to the present invention is arranged to seal between a first heat transfer plate of the plate heat exchanger and an adjacent second heat transfer plate of the plate heat exchanger. The gasket comprises an elongate body. A lower side of the gasket body is arranged to face the first heat transfer plate while an opposing upper side of the body is arranged to face the second heat transfer plate. The gasket further comprises a first number > 2 of elongate projections projecting from the upper side of the gasket body and extending along a longitudinal extension of the gasket. An inside of an annual part of the gasket is arranged to define a fluid flow channel between the first and second heat transfer plates. A first projection of the projections and a second projection of the projections extend along each other along at least a first portion and a second portion of the annular part of the gasket. The first projection is arranged closer to the inside of the annual part of the gasket than the second projection. The gasket is characterized in that the first projection has a constant height along said first and second portions of the annular part of the gasket. Further, the second projection comprises recesses, which each gives the second projection a locally reduced height, along said first and second portions of the annular part of the gasket. The second projection comprises full height projection parts separated by the recesses along the first and second portions of the annular part of the gasket.

The gasket may consist of said annual part only, or comprise further parts integrally or non-integrally formed with said annual part.

The first and second portions of the annular part of the gasket may, or may not, be directly connected to each other.

The inside of the annular part of the gasket extends between the lower and upper sides of the gasket body and is arranged to be in contact with the fluid or medium flowing through the channel between the first and second heat transfer plates.

By full height projection parts is meant projection parts having the maximum height of the second projection within the first and second portions of the annular part of the gasket. The projections may also be referred to as ribs, protrusions, edges, strips, etc.

The gasket may comprise two or more projections which may extend parallel to each other along part of their extensions. In case the gasket comprises more than two projections, a distance between each two adjacent ones of the projections may be the same along part of their extensions.

The projections may have any suitable cross section. Further, the projections may, or may not, have similar cross sections along part of their extensions. As an example, one or more of the projections may have a cross section which is symmetric with respect to a normal plane of the upper side of the gasket body extending through a top of the projection. As another example, one or more of the projections may have a cross section which is asymmetric with respect to a normal plane of the upper side of the gasket body extending through a top of the projection, such as a cross section according to EP19210337.2. The first projection may, or may not, have a constant cross section along its complete extension.

One or more of the projections is provided with recesses as draining means. Typically, all the projections but one, more particularly the first projection, which is arranged closest to the fluid and has a main sealing function, is provided with recesses. The rest of the projections are provided primarily to achieve a more uniform load on the gasket. Thereby, if the gasket should leak, fluid managing to pass the first projection, may be drained to the outside through the recesses of the rest of the projections, instead of being trapped between the projections of the gasket. Thereby, it may be easier to discover a leak and to maintain a good hygiene of the plate heat exchanger containing the gasket.

The gasket may be so designed that the second projection has a height equal to zero within the recesses. According to such a design the second projection may be regarded as being discontinuous, intermittent or disrupted, and comprising non-integrally formed projections parts separated by breaks or interruptions, along said first and second portions of the annular part of the gasket. Such a design may be the most beneficial one in view of leak detection and hygiene.

The first projection of the gasket may extend, and have a height ¹0, along the complete annual part of the gasket, which would make also the first projection annual. Such an embodiment may enable a straightforward and structurally uncomplicated design of the gasket.

The gasket may be such that the projection parts of the second projection are essentially aligned along more than half of said first and second portions of the annular part of the gasket. Such an embodiment may enable a relatively uniform load on the gasket when this is compressed between the first and second heat transfer plates.

The gasket may be such that the projection parts of the second projection are essentially equidistantly arranged, or evenly distributed, along more than half of said first and second portions of the annular part of the gasket. Such an embodiment may make the gasket suitable for use with first and second heat transfer plates conventionally designed with a corrugated outer edge portion, as will be further discussed below.

The gasket may be such that the projection parts of the second projection have essentially the same length along more than half of said first and second portions of the annular part of the gasket. Again, such an embodiment may make the gasket suitable for use with conventionally designed first and second heat transfer plates.

The length or longitudinal extension of the projection parts is measured parallel to the longitudinal extension of the gasket.

The gasket may be such that the projection parts of the second projection have essentially the same form along more than half of said first and second portions of the annular part of the gasket. Again, such an embodiment may enable a relatively uniform load on the gasket when this is compressed between the first and second heat transfer plates.

The gasket may be such that the length of the projection parts is essentially equal to the distance between each two adjacent ones of the projection parts, i.e. the length of the recesses, along more than half of said first and second portions of the annular part of the gasket. Again, such an embodiment may make the gasket suitable for use with conventionally designed first and second heat transfer plates.

According to one embodiment of the invention the first and second portions of the annular part of the gasket are arranged to extend along a respective one of two opposing long sides of the first and second heat transfer plates. At the long sides of the heat transfer plates the distance between the gasket and the outside is typically relatively small which may facilitate leak detection and leak drainage.

The annular part of the gasket may comprise a third portion arranged to partly enclose a respective porthole area of the first and second heat transfer plates and extending from one of the first and second portions, and a fourth portion arranged to partly enclose another respective porthole area of the first and second heat transfer plates and extending from one of the first and second portions. The annular part of the gasket may further comprise a fifth portion extending from one of the first and second portions to the third portion, and a sixth portion extending from one of the first and second portions to the fourth portion. The first and second projections may extend along each other along the fifth and sixth portions of the annular part of the gasket. Further, the first projection may have a constant height, and the second projection may comprise recesses, which each gives the second projection a locally reduced height, along said fifth and sixth portions of the annular part of the gasket. The second projection may comprise full height projection parts separated by the recesses along the fifth and sixth portions of the annular part of the gasket. According to this embodiment, not only the first and second portions, but also fifth and sixth portions of the annular part of the gasket, which fifth and sixth portions may correspond to the so-called diagonal portions of conventional gaskets, are provided with a projection of constant height and a projection provided with draining means in the form of recesses, which may further facilitate leak detection and the maintenance of a good hygiene of the plate heat exchanger containing the gasket. The gasket may be so designed that the second projection extends outside the third and fourth portions of the annular part of the gasket, i.e. such that the second projection does not extend within the third and fourth portions. The third and fourth portions of the annular part of the gasket often have a design which makes the provision of the second projection within these portions unnecessary.

An assembly for a plate heat exchanger according to the present invention comprises a gasket according to the present invention and as described above, as well as a first heat transfer plate. Said first heat transfer plate comprises opposing first and second sides and a groove for receiving the gasket on the first side of the first heat transfer plate. A first portion of the groove is arranged to receive the first portion of the annular part of the gasket and a second portion of the groove is arranged to receive the second portion of the annular part of the gasket. A corrugation of said first heat transfer plate comprising alternately arranged ridges and valleys extends along at least part of the first and second portions of the groove. A width of each of the valleys, which width is measured parallel to a longitudinal extension of the groove, is essentially equal to the length of the projection parts along more than half of said at least part of said first and second portions of the groove.

What is ridges and valleys of the first heat transfer plate as seen from the first side is, of course, valleys and ridges, respectively, as seen from the second side.

The width of the valleys of said corrugation may be equal to a width of the ridges of said corrugation along said at least part of said first and second portions of the groove.

This embodiment may enable that the projection parts and the ridges/valleys can be arranged directly opposite each other in pairs along more than half of said at least part of said first and second portions of the groove which may result in different advantages depending on the arrangement, as is further discussed below.

According to one embodiment of the assembly, the projection parts of the second projection of the gasket are arranged flush with, or directly opposite to, a respective one of the valleys of the first heat transfer plate along more than half of said at least part of said first and second portions of the groove. This arrangement may result in positioning of the recesses of the second projection flush with a respective one of the ridges of the first heat transfer plate along more than half of said at least part of said first and second portions of the groove. This embodiment may improve the support of the gasket at the recesses and give a more uniform sealing pressure along more than half of said at least part of said first and second portions of the groove.

According to an alternative embodiment of the assembly, the projection parts of the second projection of the gasket are arranged flush with, or directly opposite to, a respective one of the ridges of the first heat transfer plate along more than half of said at least part of said first and second portions of the groove. This arrangement may result in positioning of the recesses of the second projection flush with a respective one of the valleys of the first heat transfer plate along more than half of said at least part of said first and second portions of the groove. This embodiment may facilitate drainage of leaking fluid through the recesses.

The above described advantages of the different designs of the gasket according to the invention are transferable to the assembly for a plate heat exchanger according to the invention as this comprises the gasket.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages will appear from the following detailed description of embodiments of the invention with reference to the drawings, in which:

Fig. 1 is a schematic plan view of an assembly for a plate heat exchanger, which assembly comprises a gasket and a first heat transfer plate provided with a gasket groove,

Fig. 2 is a schematic plan view of the gasket of Fig. 1 ,

Fig. 3 is a schematic perspective view of a part, within a first or second portion of the gasket and the gasket groove, of the assembly of Fig. 1 , Fig. 4 is another schematic perspective view of the part of the assembly of Fig. 3,

Fig. 5 is a schematic cross section of the part of the assembly of Fig. 3,

Fig. 6 is another schematic cross section of the part of the assembly of

Fig. 3,

Fig. 7 schematically illustrates abutting outer edges of adjacent heat transfer plates in a plate pack, as seen from the outside of a long side of the plate pack, and

Fig. 8 is an enlargement of a part of the first or second portion of the gasket in Fig. 2.

DETAILED DESCRIPTION OF EMBODIMENTS

In Fig. 1 , 3, 4, 5 and 6 an assembly 1 for a plate heat exchanger (not shown) is illustrated, in whole or in part. The assembly 1 comprises an essentially rectangular first heat transfer plate 3 of stainless steel and a rubber gasket 5. In the plate heat exchanger, the first heat transfer plate 3 is arranged between a second heat transfer plate 2 (illustrated in Fig. 7) and a third heat transfer plate 4 (illustrated in Fig. 7), and the gasket 5 seals between the first heat transfer plate 3 and the second heat transfer plate 2. In the plate heat exchanger, the first, second and third heat transfer plates form part of a plate pack. The plates in the plate pack are all of the same type, but in alternative embodiments they could be of different types. Further, with reference to the section of the text describing the background of the invention, the heat transfer plates in the plate pack are “rotated” in relation to each other, but in alternative embodiments they could instead be “flipped” in relation to each other.

The first heat transfer plate 3 comprises (Figs. 1 , 5 and 6) a first side 7, an opposing second side 9 and four porthole areas 11a-d arranged in a respective corner of the first heat transfer plate 3. The porthole areas 11a-d are typically cut open so as to form portholes but in Fig. 1 the porthole areas are closed. The first heat transfer plate 3 further comprises a groove 13 on the first side 7 for receiving the gasket 5. With reference to Fig. 1 , first and second portions 13a and 13b, respectively, of the groove 13 extend along an outer edge 19 of the first heat transfer plate 3 and along first and second long sides 24 and 25, respectively, of the first heat transfer plate 3. Further, third and fourth portions 13c and 13d, respectively, of the groove 13 extend from a respective end of the first portion 13a and partly around a respective one of the porthole areas 11c and 11 d, respectively. Further, fifth and sixth portions 13e and 13f, respectively, of the groove 13 extend, diagonally from a respective end of the third and fourth portions 13c and 13d, respectively, to a respective end of the second portion 13b, on an inside of the porthole areas 11 a and 11 b, respectively. Further, seventh and eight portions 13g and 13h, respectively, of the groove 13 extend completely around the porthole areas 11a and 11b.

Different areas of the first heat transfer plate 3 are provided with different corrugation patterns, and the corrugation pattern within a specific plate area is adapted to the main function of this plate area. More particularly, the first heat transfer plate 3 comprises adiabatic areas 27 on an inside of the porthole areas 11 a-d, which adiabatic areas are provided with an adiabatic pattern. Further, the first heat transfer plate 3 comprises a first distribution area 29 provided with a distribution pattern, a heat transfer area 31 provided with a heat transfer pattern, and a second distribution area 33 provided with a distribution pattern, which areas are arranged in succession along a longitudinal center axis c of the first heat transfer plate 3. Further, an edge portion 35 of the first heat transfer plate 3 is provided with a corrugation 37 (Figs. 3, 5 and 6). This corrugation extends along most of the outer edge 19 of the first heat transfer plate 3 so as to give it a wave-shape. The corrugation 37, which comprises alternately arranged ridges 39 and valleys 41 as seen from the first side 7 of the heat transfer plate 3, and also corrugations within the adiabatic areas 27, the first and second distribution areas 29 and 33 and the heat transfer area 31 , extend between and in an imaginary first plane p1 and an imaginary second plane p2, which planes are illustrated in Figs. 5, 6 and 7. The corrugation 37 extends along, and defines an outside of the gasket groove 13 within the first, second, third, fourth, and outer sections of the seventh and eight portions thereof. A bottom 43 of the groove 13 extends in an imaginary intermediate plane pi arranged halfway between, and parallel to, the imaginary first and second planes p1 and p2. The intermediate plane pi defines the border between the ridges 39 and the valleys 41 of the corrugation 37.

Since the first, second and third heat transfer plates are all of the same kind, the above description of the first heat transfer plate 3 is valid also for the second and third heat transfer plates 2 and 4.

In the plate heat exchanger, the first side 7 of the first heat transfer plate 3 faces the second heat transfer plate 2 while the second opposing side 9 of the first heat transfer plate 3 faces the third heat transfer plate 4. Arranged like that, corrugations of the first heat transfer plate 3 abut corrugations of the second and third heat transfer plates. Simultaneously, the gasket 5, arranged in the groove 13 of the first heat transfer plate 3, is compressed between the first and second heat transfer plates. A similar gasket is correspondingly arranged, and compressed between, the second and third heat transfer plates.

To fit in the groove 13, the gasket 5 comprises, with reference to Fig. 2, first and second portions 5a and 5b, respectively, arranged to be received in the first and second portions 13a and 13b, respectively, of the groove 13, third and fourth portions 5c and 5d, respectively, arranged to be received in the third and fourth portions 13c and 13d, respectively, of the groove 13, and fifth and sixth portions 5e and 5f, respectively, arranged to be received in the fifth and sixth portions 13e and 13f, respectively, of the groove 13. The first, second, third, fourth, fifth and sixth portions 5a-f form an annular part 45 of the gasket 5, which annular part 45 has an inside 46 arranged to face a fluid or medium flowing between the first heat transfer plate 3 and the second heat transfer plate 2. The gasket 5 further comprises seventh and eight portions 5g and 5h, respectively, arranged to be received in the seventh and eight portions 13g and 13h, respectively, of the groove 13. The annular part 45 and the seventh and eight portions 5g and 5h of the gasket 5 are connected by non-sealing portions of the gasket having a reduced height.

With reference to Figs. 2-6, which illustrate the gasket 5 in an unloaded state, the gasket 5 comprises an elongate body 47 extending, in a height direction FI (Fig. 6), between parallel imaginary third and fourth planes p3 and p4. An upper side 49 of the body 47 is arranged to face the second heat transfer plate 2 while a lower side 51 of the body 47 is arranged to face the first heat transfer plate 3. The body 47 is symmetric with respect to an imaginary fifth plane p5 extending parallel to, and halfway between, the imaginary third and fourth planes p3 and p4. The gasket 5 further comprises an inner first projection 53 and an outer second projection 55 projecting from the upper side 49 of the body 47 to an imaginary sixth plane p6 which is parallel to the imaginary third and fourth planes p3 and p4. The first and second projections 53 and 55 are arranged on opposite sides of, and on the same distance from, a longitudinal center axis of the gasket 5, which is parallel to a longitudinal extension L of the gasket 5. The first and second projections 53 and 55 extend, separated from each other and in parallel, along the longitudinal extension L of the gasket 5, within the first, second, fifth and sixth portions 5a, 5b, 5e and 5f of the gasket 5. The first projection 53 also extends within the third and fourth portions 5c and 5d of the gasket 5 so as to extend along the complete annular part 45 thereof, and within the seventh and eight portions 5g and 5h of the gasket 5.

The first projection 53 is an elongate rib having, along its complete extension, an essentially constant cross section perpendicular to the longitudinal extension L of the gasket 5. Thus, along the complete extension of the annular part 45 of the gasket 5, the first projection 53 has an essentially constant height equal to a distance between the sixth and fourth planes p6 and p4, respectively. The second projection 55 has, along its complete extension, a varying cross section perpendicular to the longitudinal extension L of the gasket 5. More particularly, along the first, second, fifth and sixth portions 5a, 5b, 5e and 5f of the annular part 45 of the gasket 5, the second projection 55 has a varying height. With reference to Figs. 2 and 6, within the first and second portions 5a and 5b of the gasket 5, the second projection 55 comprises recesses 57a within which the height of the second projection is 0 and the second projection does not projection from the gasket body 47, and full height elongate projection parts or ribs 59a within which the height is equal to a distance between the sixth and fourth planes p6 and p4, respectively. Similarly, within the fifth and sixth portions 5e and 5f of the gasket 5, the second projection 55 comprises recesses 57b within which the height of the second projection is 0 and the second projection does not projection from the gasket body 47, and full height elongate projection parts or ribs 59b within which the height is equal to a distance between the sixth and fourth planes p6 and p4, respectively. The recesses and projection parts are aligned and alternately arranged along the longitudinal extension of the second projection 55.

Herein, when the height of the second projection 55 is discussed, it is the “nominal” height that is referred to, i.e. the height within center portions of the recesses and projection parts. The recesses and projection parts are typically slightly bevelled at their ends, as is clear from Figs. 3 and 4.

With reference to Figs. 1, 2 and 3, the longitudinal extension of the gasket body 47 corresponds to the longitudinal extension of the gasket groove 13, and the design of the first and second projections 53 and 55 is adapted to the longitudinal extension of the gasket body 47.

Accordingly, within the gasket portions 5a and 5b, the gasket body 47, the first projection 53 and the second projection 55 are all straight except for locally at the first long side 24 of the first heat transfer plate 3, at a transition between the first distribution area 29 and the most adjacent one of the adiabatic areas 27, at a transition between the second distribution area 33 and the most adjacent one of the adiabatic areas 27 and at transitions to the third and fourth gasket portions 5c and 5d, and except for locally at the second long side 25 of the first heat transfer plate 3, at transitions to the fifth and sixth gasket portions 5e and 5f. Fig. 8 illustrates what the first and second gasket portions 5a and 5b look like within the straight sections thereof. Within the straight sections, the recesses 57a have essentially the same form and length or longitudinal extension Ir, and the projection parts 59a have essentially the same form and length or longitudinal extension Ip. Further, within the straight sections, the length Ir of the recesses 57a, i.e. the distance between two adjacent ones of the projection parts 59a, is essentially equal to the length Ip of the projection parts 59a, i.e. Ir=lp. This means that the projection parts 59a are equidistantly distributed along the straight sections, i.e. along essentially the complete first and second gasket portions 5a and 5b. With reference to Figs. 1 and 7, along the first and second portions 13a and 13b of the gasket groove 13, the ridges 39 have a width wr equal to a width wv of the valleys 41 , i.e. wr=wv, wherein the widths are measured parallel to a longitudinal extension I of the gasket groove 13 (groove not illustrated in Fig. 7). To enable alignment of the ridges 39 and valleys 41 of the first heat transfer plate 3 and the recesses 57a and projection parts 59a of the gasket 5, wr=wv=lr=lp.

As can be seen in Fig. 1 , when the gasket 5 is properly arranged on the first heat transfer plate 3, along the first and second portions 13a and 13b of the groove 13 and the first and second portions 5a and 5b of the gasket 5, the valleys 41 of the edge portion 35 are arranged directly opposite the projection parts 59a of the gasket 5, while the ridges 39 of the edge portion 35 are arranged directly opposite the recesses 57a of the gasket 5.

Thus, along the first and second portions 5a and 5b of the gasket 5, the design of the second projection 55 is adapted to the design of the corrugation 37 along the first and second portions 13a and 13b of the gasket groove 13. In a corresponding way, along the fifth and sixth portions 5e and 5f of the gasket 5, the design of the second projection 55 is adapted to the design of the adiabatic areas 27 and the first and second distribution areas 29 and 33. More particularly, along the fifth and sixth portions 5e and 5f of the gasket 5, the form and length or longitudinal extension of the recesses 57b and the projection parts 59b are adapted to corrugations within the adiabatic areas 27 and the first and second distribution areas 29 and 33. As a result, the form and length or longitudinal extension of the recesses 57b and the projection parts 59b differs along the fifth and sixth portions 5e and 5f of the gasket 5.

As can be seen in Fig. 1, when the gasket 5 is properly arranged on the first heat transfer plate 3, along the fifth and sixth portions 13e and 13f of the groove 13 and the fifth and sixth portions 5e and 5f of the gasket 5, valleys of the corrugations within the adiabatic areas 27 and the first and second distribution areas 29 and 33 are arranged directly opposite the projection parts 59b of the gasket 5, while ridges of the corrugations within the adiabatic areas 27 and the first and second distribution areas 29 and 33 are arranged directly opposite the recesses 57b of the gasket 5. In the above described embodiment, the recesses 57a and 57b of the gasket 5 are arranged directly opposite ridges of the corrugations of the first heat transfer plate 3, while the projection parts 59a and 59b of the gasket 5 are arranged directly opposite valleys of the corrugations of the first heat transfer plate 3. In an alternative embodiment it could be the other way around such that the recesses 57a and 57b of the gasket 5 are arranged directly opposite valleys of the corrugations of the first heat transfer plate 3, while the projection parts 59a and 59b of the gasket 5 are arranged directly opposite ridges of the corrugations of the first heat transfer plate 3.

The above described embodiments of the present invention should only be seen as examples. A person skilled in the art realizes that the embodiments discussed can be combined and varied in a number of ways without deviating from the inventive conception.

As an example, the number of gasket projections need not be two, but could be more. Similarly, the number of projections provided with recesses and projection parts need not be one but could be more. In case of more than one projection provided with recesses and projection parts, these may or may not have the same design. Further, the recesses and projection parts of one such projection need not be aligned or arranged directly opposite to the recesses and projection parts of another such projection.

The design of the projections can be varied endlessly. Instead of having an unsymmetrical cross section as illustrated in the figures, the projections could have a symmetrical cross section with respect to a respective normal plane of the upper side of the gasket extending though a top of the projection. The projections need not all have the same cross section.

The gasket could also comprise projections projecting from the lower side of the gasket body. These projections could be designed like the projections projecting from the upper side of the gasket body.

The assembly illustrated in Fig. 1 is adapted for use in a plate heat exchanger of parallel flow type. Naturally, the present invention is equally applicable in connection with a plate heat exchanger of diagonal flow type.

Then, the third portion of the groove could extend from an end of the first portion and partly around an upper left porthole area, while the fourth portion of the groove could extend from an end of the second portion and partly around a lower right porthole area. Further, the fifth portion of the groove could extend diagonally from an end of the third portion to an end of the second portion, on an inside of an upper right porthole area, while the sixth portion of the groove could extend diagonally from an end of the fourth portion to an end of the first portion, on an inside of a lower left porthole area. Further, the seventh and eight portions, respectively, of the groove could extend completely around a respective one of the upper right and lower left porthole areas. The gasket could be designed in a corresponding way.

The projections need not all have the same full height. As an example, the first projection could have a larger full height than the second projection, or it could be the other way around. Further, the projections need not be arranged on the same distance from the longitudinal center axis of the gasket.

The gasket body need not be designed with the same maximum height and the same maximum width along its complete extension. As an example, the fifth and sixth gasket portions and/or inner sections of the seventh and eight gasket portions may have a larger maximum gasket body height, a smaller maximum gasket body width and/or a smaller distance between the first and second projections (where both are present) than the rest of the gasket.

The upper side of the body of the gasket need not extend in the imaginary fourth plane along its complete/part of its extension.

The portions of the gasket need not be integrally formed. For example, the seventh and eight portions can be separate from the rest of the gasket.

The second projection could extend along the complete annular part of the gasket, or along the complete longitudinal extension of the gasket just like the first projection.

Some or all of the recesses of the second projection could be less deep so as to give the second projection a height larger than zero also within the recesses. The intermediate plane need not extend halfway between the imaginary first and second planes but could be displaced upwards or downwards together with the bottom of the gasket groove.

The bottom of the gasket groove need not extend in so called half-plane but could extend in a lower plane of the plate, e.g. the imaginary first plane.

The gasket could be made of another material than rubber. Similarly, the heat transfer plates could be made of another material than stainless steel, such as titanium or aluminium.

The gaskets could be arranged to be fastened to the heat transfer plates in different ways, for example by glue, adhesive tape or some kind of fastening means, for example so called clip-on tabs, comprised in the gaskets and arranged to engage with the heat transfer plates.

It should be stressed that a description of details not relevant to the present invention has been omitted and that the figures are just schematic and not drawn according to scale. It should also be said that some of the figures have been more simplified than others. Therefore, some components may be illustrated in one figure but left out in another figure. Finally, as used herein, the prefixes “first”, “second”, “top”, “bottom”, “upper”, “lower”, “horizontal”, “vertical” etc. are used only to distinguish between different components and pose no requirements as regards relative positioning or orientation.