EP4675212A1

EP4675212A1 - Plate set

Info

Publication number: EP4675212A1
Application number: EP24186240.8A
Authority: EP
Inventors: Magnus Hedberg
Original assignee: Alfa Laval Corporate AB
Current assignee: Alfa Laval Corporate AB
Priority date: 2024-07-03
Filing date: 2024-07-03
Publication date: 2026-01-07
Also published as: WO2026008423A1

Abstract

A plate set (2) comprising a first heat transfer plate (4), a second heat transfer plate (6) and a third heat transfer plate (7) is provided. The first, second and third heat transfer plates each has a heat transfer area (14) provided with a heat transfer pattern comprising elongate inclined corrugations (18). The corrugations of the second heat transfer plate cross the corrugations of the first and third heat transfer plates. The corrugations of the second heat transfer plate contact a sub-set of the corrugations of the first heat transfer plate and a sub-set of the corrugations of the third heat transfer plate in contact areas (20a, 20b). The plate set is characterized in that each of at least a plurality of the corrugations of the first, second and third heat transfer plates comprises a number ≥ 1 of plate recesses (22a, 22b). Further, each of at least a plurality of the contact areas is surrounded by a respective one of the plate recesses formed in one of the first, second and third heat transfer plates. Said respective one of the plate recesses extends at least on two opposite sides of the contact area.

Description

Technical Field

The invention relates to a plate set comprising aligned first, second and third heat transfer plates which are arranged in succession.

Background Art

Plate heat exchangers, PHEs, typically comprises 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 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. In other words, every second one of the heat transfer plates is rotated 180 degrees, around its normal, in relation to the rest of the 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. In other words, every second one of the heat transfer plates is rotated 180 degrees, around its transverse center axis, in relation to the rest of the plates. Typically, this is referred to as the heat transfer plates being "flipped" 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. In other words, every second one of the heat transfer plates is rotated 180 degrees, around its longitudinal center axis, in relation to the rest of the plates. Typically, this is referred to as the heat transfer plates being "turned" in relation to each other. Parallel flow channels are formed between the heat transfer plates, one channel between each pair of heat transfer plates. Two fluids of initially different temperatures can flow through every second channel for transferring heat from one fluid to the other, which fluids enter and exit the channels through inlet and outlet port holes in the heat transfer plates.
Typically, a heat transfer plate comprises two end parts and an intermediate center part. The end parts comprise the inlet and outlet port holes and a distribution area pressed with a distribution pattern of corrugations. Similarly, the center part comprises a heat transfer area pressed with a heat transfer pattern of corrugations. The corrugations of the distribution and heat transfer patterns of one heat transfer plate are arranged to contact, in contact areas, corrugations of distribution and heat transfer patterns of an upper and a lower adjacent heat transfer plate.
The main task of the distribution area of the heat transfer plates is to spread a fluid entering the channel across a width of the heat transfer plate before the fluid reaches the heat transfer area, and to collect the fluid and guide it out of the channel after it has passed the heat transfer area. On the contrary, the main task of the heat transfer area is heat transfer. Since the distribution area and the heat transfer area have different main tasks, the distribution pattern may differ from the heat transfer pattern. One common heat transfer pattern is the so-called herringbone pattern which comprises corrugations in the form of parallel elongate beams extending inclined in relation to a longitudinal center axis of the heat transfer plate. Typically, a herringbone pattern offers small, densely arranged contact areas between abutting heat transfer plates, i.e. areas in which the abutting heat transfer plates are arranged to contact each other.
The two fluids of initially different temperatures should flow on different sides of each heat transfer plate, from a respective one of the inlet portholes arranged at one of the end parts of the heat transfer plates to a respective one of the outlet portholes arranged at the other one of the end parts of the heat transfer plates. Behind the contact areas, as seen in a respective main flow direction of the fluids, wakes may be formed which may create stagnant zones of decreased fluid flow and, thus, impaired heat transfer. Also, a decreased fluid flow may increase the degree of fouling of the heat transfer plate, which may result in further impaired heat transfer.

Summary

An object of the present invention is to provide a plate set comprising heat transfer plates designed so as to overcome, or at least reduce, the above discussed problem of stagnant zones between the heat transfer plates. The basic concept of the invention is provide the heat transfer plates with bypasses at the contact areas to increase the fluid flow around these. The plate set is defined in the appended claims and discussed below.
A plate set according to the invention comprises a first heat transfer plate, a second heat transfer plate and a third heat transfer plate. The first, second and third heat transfer plates are aligned and arranged in succession. Each of them has a longitudinal center axis, a transverse center axis, an upper port hole pair, a lower port hole pair and a heat transfer area provided with a heat transfer pattern comprising elongate corrugations. Each of the corrugations has a longitudinal extension of an angle ≠ 0 degrees in relation to the respective longitudinal center axis. The elongate corrugations of the second heat transfer plate cross the elongate corrugations of the first heat transfer plate and the third heat transfer plate. For each of the first, second and third heat transfer plates, the upper port hole pair and the heat transfer area are arranged on opposite sides of an imaginary straight upper line extending parallel to the transverse center axis. Further, for each of the first, second and third heat transfer plates, the lower port hole pair and the heat transfer area are arranged on opposite sides of an imaginary straight lower line extending parallel to the transverse center axis. The elongate corrugations of the second heat transfer plate contact, in contact areas, a sub-set of the elongate corrugations of the first heat transfer plate and a sub-set of the elongate corrugations of the third heat transfer plate. The plate set is characterized in that each of at least a plurality of the elongate corrugations of the first heat transfer plate comprises a number ≥ 1 of plate recesses, each of at least a plurality of the elongate corrugations of the second heat transfer plate comprises a number ≥ 1 of plate recesses, and each of at least a plurality of the elongate corrugations of the third heat transfer plate comprises a number ≥ 1 of plate recesses. Further, each of at least a plurality, preferably at least half, possibly at least a majority, of the contact areas is surrounded by a respective one of the plate recesses formed in one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate. Said respective one of the plate recesses extends at least on two opposite sides of the contact area.
The first, second and third heat transfer plates may, or may not, be similar.
That the first, second and third heat transfer plates are aligned typically means that a longitudinal center axis of the first heat transfer plate is substantially parallel to a respective longitudinal center axis of the second and third heat transfer plates, that a transverse center axis of the first heat transfer plate is substantially parallel to a respective transverse center axis of the second and third heat transfer plates, and that a depth center axis of the first heat transfer plate substantially coincides with a respective depth center axis of the second and third heat transfer plates. The longitudinal, transverse and depth center axes are orthogonal to each other.
In that the first, second and third heat transfer plates are arranged in succession, the second heat transfer plate is arranged between the first and third heat transfer plates.
In that each of the corrugations has longitudinal extension of an angle ≠ 0 degrees in relation to the respective longitudinal center axis, the corrugations extend inclined in relation to the respective longitudinal center axis. The angle may vary between corrugations. The corrugations may have any suitable form, such as straight, bent, etc.
As said above, the corrugations of the heat transfer pattern of the second heat transfer plate cross the corrugations of the heat transfer pattern of the first and third heat transfer plates. This can be obtained by having the second heat transfer plate "rotated", "flipped" or "turned" in relation to the first and third heat transfer plates.
The corrugations may comprise alternately arranged projections and depressions and as seen from a respective front side of the first, second and third heat transfer plates. What is a projection as seen from the front side is a depression as seen from a back side of the first, second and third heat transfer plates, and vice versa. Said sub-set of the elongate corrugations of the heat transfer patterns of the first and third heat transfer plates may be either projections or depressions, as seen from the front side, depending on how the first, second and third heat transfer plates are orientated in relation to each other.
The contact areas are obtained when the second heat transfer plate engages with the first and third heat transfer plates and the contact areas are typically separated and scattered across the heat transfer areas of the first, second and third heat transfer plates. The location, size and shape of the contact areas are determined by the characteristics of the corrugations of the heat transfer patterns, and the orientation, of the first, second and third heat transfer plates.
The plate recesses are indentations as seen from a respective central extension plane of the first, second and third heat transfer plates and they are formed by a locally reduced pressing depth of the first, second and third heat transfer plates. Each of the plate recesses may be intermittent or continuous. There is at least one plate recess, formed in either the first heat transfer plate, the second heat transfer plate or the third heat transfer plate, for each one of said at least a plurality, preferably at least half, possibly at least a majority, of the contact areas.
When the contact area is round, possibly circular, the plate recess may extend at least on two diametrically opposite sides of it.
The plate recesses function as bypasses which guide fluid past the contact areas. Thereby, the plate recesses enable an increased fluid flow around the contact areas which results in less or no wakes behind the contact areas. In turn, this reduces the pressure drop with maintained thermal performance within the heat transfer areas, i.e. within a respective intermediate or center portion, of the first, second and third heat transfer plates. In that said respective one of the plate recesses extends at least on two opposite sides of the contact area, a bypass on both sides of the contact area is created which may optimize the fluid flow around the contact area.
As said above, there is at least one plate recess, formed in one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plates, i.e. formed in either the first heat transfer plate or the second heat transfer plate or the third heat transfer plate, for each one of said at least a plurality of the contact areas. The plate set may be such that each of said at least a plurality of the contact areas is surrounded by a respective one of the plate recesses formed in another one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate. Then, there is two plate recesses, one formed in the first heat transfer plate and the other one formed in the second heat transfer plate, or one formed in the third heat transfer plate and the other one formed in the second heat transfer plate, for each one of said at least a plurality of the contact areas. Said at least one of the plate recesses formed in said another one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate may extend at least on two opposite sides of the contact area. Two plate recesses for one contact area may further improve the fluid flow around the contact area and result in an even more improved heat transfer. Again, a bypass on both sides of the contact area may optimize the fluid flow around the contact area.
The plate set may be so designed that said respective one of the plate recesses formed in said one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate, and said respective one of the plate recesses formed in the said another one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate, are aligned. Such a design may maximize the fluid flow around, and minimize the stagnant zone behind, the respective contact area.
Said respective one of the plate recesses formed in said another one of first heat transfer plate, the second heat transfer plate and the third heat transfer plate may be a mirroring, as seen from the contact area, of said respective one of the plate recesses formed in said one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate. Such a configuration may maximize the fluid flow around, and minimize the stagnant zone behind, the respective contact area.
Said respective one of the plate recesses formed in said one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate may extend only partially around the respective one of the contact areas. Similarly, said respective one of the plate recesses formed in said another one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate may extend only partially around the respective one of the contact areas. Plate recesses extending only partially around the contact areas may increase the mechanical strength of said one and said another one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate.
Said respective one of the plate recesses formed in said one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate may comprise two separated sub-recesses arranged on opposite sides of the respective one of the contact areas. Such a plate recess is intermittent. Similarly, said respective one of the plate recesses formed in said another one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate may comprise two separated sub-recesses arranged on opposite sides of the respective one of the contact areas. Plate recesses comprising two separated sub-recesses may enable equal fluid and equal fluid pressure drop across said one and said another one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate, irrespective of fluid flow direction. The plate set may be so designed that each of at least a majority of the sub-recesses is elongate. An elongate sub-recess may guide the fluid close to the respective contact area where it is needed the most.
Each of at least a majority of the sub-recesses may comprises a straight portion. This may enable a relatively uncomplicated design of said one and said another one of the first heat transfer plate, the second heat transfer plate and the third heat transfer plate. The straight portion may extend substantially parallel to the longitudinal center axis, i.e. in the main flow direction across the heat transfer plate, so as to guide the fluid past the respective contact area as effectively as possible. Alternatively, the straight portion may extend substantially perpendicular to the longitudinal extension of the corresponding one of the corrugations. The straight portion may also extend in any other suitable direction deviating from the two directions mentioned above. Preferably, the straight portion extends in the desired flow direction.
Each of at least a majority of the sub-recesses may comprise a curved portion which is bent towards the other sub-recess of the corresponding one of the plate recesses. A bent or partly bent sub-recess may partly enclose the respective contact area so as to guide the fluid around, to, in turn, optimize the fluid flow. The curved portions of the sub-recesses of said corresponding one of the plate recesses may extend on opposite sides of a longitudinal center line, which is parallel to the longitudinal extension, of the corresponding one of the corrugations. This may enable an optimum fluid flow around the corresponding one of the contact areas.
Each of at least a majority of the sub-recesses may be essentially L-shaped.
The plate set may be such that a cross section perpendicular to the longitudinal extension of each of at least a majority of the corrugations is constant, along the longitudinal extension, outside the plate recesses. It should be stressed that this feature refers to the corrugations where they have a "full cross section", i.e not, for example, to obliquely cut end portions of the corrugations. Such a constant cross section enables a mechanically straight forward plate set.
The plate set may be such that each of the first, second and third heat transfer plates further comprises an upper distribution area extending between the upper port hole pair and the heat transfer area, and a lower distribution area extending between the lower port hole pair and the heat transfer area. The upper distribution area and the lower distribution area may be provided with an upper distribution pattern and a lower distribution pattern, respectively. The heat transfer pattern may differ from the upper distribution pattern and the lower distribution pattern. The upper distribution area, the heat transfer area and the lower distribution area may be arranged in succession along the respective longitudinal center axis. Such a design may enable a plate set which is optimized as regards fluid distribution as well as heat transfer.
At least one of the first, second and third heat transfer plates may further comprise a field gasket groove, an upper port hole gasket groove and a lower port hole gasket groove. The field gasket groove may extend around the heat transfer area, the lower and upper distribution areas, one port hole of the upper port hole pair and one port hole of the lower port hole pair. The upper port hole gasket groove may extend around another port hole of the upper port hole pair. The lower port hole gasket groove may extend around another port hole of the lower port hole pair. Such a configuration may enable arrangement of gasket between at least two of the first, second and third heat transfer plates and use of the plate set in a gasketed or semi-welded plate heat exchanger.
The plate set may be such that the elongate corrugations of the second heat transfer plate comprise alternately arranged ridges and valleys in relation to an imaginary intermediate plane defining a border between the ridges and the valleys. Some of said at least a plurality of the elongate corrugations of the second heat transfer plate comprising a number ≥ 1 of plate recesses may be ridges, and some of said at least a plurality of the elongate corrugations of the second heat transfer plate comprising a number ≥ 1 of plate recesses may be valleys. Ridges and valleys as seen from the front side of the second heat transfer plate are valleys and ridges, respectively, as seen from the back side of the second heat transfer plate. A second heat transfer plate having plate recesses in at least some of the ridges as well as in some of the valleys enable the creation of fluid bypasses on both the front side and the back side of the second heat transfer plate.
Similarly, the plate set may be such that the elongate corrugations of the first and third heat transfer plates comprise alternately arranged ridges and valleys in relation to a respective imaginary intermediate plane defining a border between the ridges and the valleys. Some of said at least a plurality of the elongate corrugations of the first and third heat transfer plates comprising a number ≥ 1 of plate recesses may be ridges, and some of said at least a plurality of the elongate corrugations of the first and third heat transfer plates comprising a number ≥ 1 of plate recesses may be valleys. Ridges and valleys as seen from the front side of the first and third heat transfer plates are valleys and ridges, respectively, as seen from the back side of the first and third heat transfer plates. First and third heat transfer plates having plate recesses in at least some of the ridges as well as in some of the valleys enable the creation of fluid bypasses on both the front side and the back side of the first and third heat transfer plates.
The plate set may be such that at least a majority of the plate recesses of the second heat transfer plate has a depth less than half a distance between two parallel imaginary extreme planes which define an extension of the second heat transfer plate along the depth center axis of the second heat transfer plate.
Similarly, at least a majority of the plate recesses of the first heat transfer plate may have a depth less than half a distance between two parallel imaginary extreme planes which define an extension of the first heat transfer plate along the depth center axis of the first heat transfer plate. Similarly, at least a majority of the plate recesses of the third heat transfer plate may have a depth less than half a distance between two parallel imaginary extreme planes which define an extension of the third heat transfer plate along the depth center axis of the third heat transfer plate.
As a general remark, herein, when it is said that some portion, part, section, etc., of the first, second and third heat transfer plates extends in a certain plane, angle or in some other way, it is the main extension of the portion, part, section, etc. that is referred to. Naturally, a portion, part, section, etc., may locally have an extension deviating from the main extension, for example at a transition to another adjacent portion, part, section, etc.
It should be stressed that the above discussed advantages of the different embodiments of the plate set according to the invention appears first when the plate set is arranged in a PHE together with other plate sets (which possibly also are designed according to the present invention) and other components needed in a properly functioning PHE.
Still other objectives, features, aspects and advantages of the invention will appear from the following detailed description as well as from the drawings.

Brief Description of the Drawings

The invention will now be described in more detail with reference to the appended schematic drawings, in which

Fig. 1 is a schematic side view of a plate set according to the invention,
Fig. 2 is schematic front view of the plate set in Fig. 1,
Fig. 3 is an enlargement of a portion of a first heat transfer plate of the plate set in Fig. 1,
Fig. 4 is an enlargement of a portion of the plate set in Figs. 1 and 2,
Fig. 5 is a schematic cross section of the plate set in Figs. 1 and 2 taken along line A-A in Fig. 4,
Fig. 6 is a schematic cross section of the plate set in Figs. 1 and 2 taken along line B-B in Fig. 4,
Fig. 7 schematically illustrates an enlargement of a portion of a plate set according to an alternative embodiment,
Fig. 8 schematically illustrates an enlargement of a portion of a plate set according to another alternative embodiment,
Fig. 9 schematically illustrates an enlargement of a portion of a plate set according to yet another alternative embodiment,
Fig. 10 schematically illustrates an enlargement of a portion of a plate set according to yet another alternative embodiment,
Fig. 11 is a schematic, simplified cross section of the plate set in Fig. 10,
Fig. 12 is a schematic, simplified cross section of the plate set in Fig. 10 with an alternative orientation of the plates in relation to each other, and
Fig. 13 corresponds to Fig. 10 but relates to the alternative plate orientation of Fig. 12.

Detailed description

Figs. 1 and 2 show a plate set 2 for use in a gasketed plate heat exchanger (not illustrated in its entirety herein) containing one type of heat transfer plates, only, which are "rotated" in relation to each other. The plate set 2 comprises a first heat transfer plate 4, a second heat transfer plate 6, and a third heat transfer plate 7, the second and third heat transfer plates 6 and 7 being visible only in Fig. 1. The second heat transfer plate 6 is arranged between the first and third heat transfer plates 6 and 7. The first, second and third heat transfer plates 4, 6 and 7 are all similar. Therefore, hereinafter, the description will be focused mainly on the first heat transfer plate 4 but it is equally applicable to the second and third heat transfer plates 6 and 7.
In the plate set 2, the first, second and third heat transfer plates 4, 6 and 7 are aligned. More particularly, a longitudinal center axis L and a transverse center axis T of the first heat transfer plate 4 are parallel to a longitudinal center axis L and a transverse center axis T, respectively, of the second and third heat transfer plates 6 and 7. Further, a depth center axis D of the first heat transfer plate 4 coincides with a depth center axis D of the second and third heat transfer plates 6 and 7.
The first heat transfer plate 4 comprises an upper port hole pair 8, which includes two upper port holes 8a and 8b, and a lower port hole pair 10, which includes two lower port holes 10a and 10b. In Fig. 2, the upper and lower port holes 8a, 8b, 10a and 10b are illustrated uncut. The first heat transfer plate 4 further comprises an upper distribution area 12, a heat transfer area 14 and a lower distribution area 16 arranged in succession along the longitudinal center axis L. The heat transfer area 14 and the upper port hole pair 8 are arranged on opposite sides of an imaginary straight upper line IU which extends parallel to the transverse center axis T. Similarly, the heat transfer area 14 and the lower port hole pair 10 are arranged on opposite sides of an imaginary straight lower line IL which extends parallel to the transverse center axis T. The upper distribution area 12 extends between the upper port hole pair 8 and the heat transfer area 14 and in between the upper port holes 8a and 8b. The lower distribution area 16 extends between the lower port hole pair 10 and the heat transfer area 14 and in between the lower port holes 10a and 10b. The heat transfer area 14 is provided with a heat transfer pattern. The heat transfer pattern is of so-called herringbone type but may be of other types in alternative embodiments of the invention. The upper and lower distribution areas 12 and 16 are provided with a distribution pattern. The distribution pattern is of so-called chocolate type but may be of other types in alternative embodiments of the invention.
The first heat transfer plate 4 further comprises a field gasket groove FG arranged to accommodate a field gasket not illustrated herein. The field gasket groove FG extends around the upper port hole 8a, the upper distribution area 12, the heat transfer area 14, the lower distribution area 16 and the lower port hole 10a. The first heat transfer plate 4 further comprises an upper ring gasket groove URG arranged to accommodate an upper ring gasket not illustrated herein. The upper ring gasket groove URG extends around the upper port hole 8b. The first heat transfer plate 4 further comprises a lower ring gasket groove LRG arranged to accommodate a lower ring gasket not illustrated herein. The lower ring gasket groove LRG extends around the lower port hole 10b.
The heat transfer pattern comprises elongate straight corrugations 18 longitudinally extending inclined, i.e. with an angle ≠ 0, in relation to the longitudinal center axis L. The corrugations 18 comprise, as seen from a front side F of the first heat transfer plate 4, alternately arranged ridges 18a and valleys 18b. The ridges 18a, just like the valleys 18b, form pairwise, downwards pointing arrows with arrow heads arranged along the longitudinal center axis L. An imaginary intermediate plane P, which is illustrated in Fig. 5, defines a border between the ridges 18a and the valleys 18b. The imaginary intermediate plane P is arranged halfway between two parallel imaginary extreme planes P1 and P2 which define an extension of the first heat transfer plate 4 along the depth center axis D.
In the plate set 2, the second heat transfer plate 6 is "rotated" in relation to the first and third heat transfer plate 4 and 7. This is illustrated in Figs. 5 and 6 which illustrate schematic cross sections of the plate set 2 along lines A-A and B-B, respectively, in Fig. 4. In that the second heat transfer plate 6 is "rotated" in relation to the first and third heat transfer plates 4 and 7, the corrugations 18 of the first and third heat transfer plates 4 and 7 cross the corrugations 18 of the second heat transfer plate 6. Further, a sub-set, more particularly the valleys 18b, of the elongate corrugations 18 of the first heat transfer plate 4, and a sub-set, more particularly the ridges 18a, of the elongate corrugations 18 of the second heat transfer plate 6, abut each other in contact areas 20b. The contact areas 20b are arranged at a back side B (Fig. 5) of the first heat transfer plate 4 but the location of them is indicated in Fig. 2. The contact areas 20b are separated from each other and scattered across the heat transfer areas 14 of the first and second heat transfer plates 4 and 6. Correspondingly, a sub-set, more particularly the ridges 18a, of the elongate corrugations 18 of the third heat transfer plate 7, and a sub-set, more particularly the valleys 18b, of the elongate corrugations 18 of the second heat transfer plate 6, abut each other in contact areas 20a. The contact areas 20a are arranged between the second and third heat transfer plates 6 and 7 but the location of them is indicated in Fig. 2. The contact areas 20a are separated from each other and scattered across the heat transfer areas 14 of the second and third heat transfer plates 6 and 7. In a similar way, although not illustrated herein, the ridges 18a of the first heat transfer plate 4 is arranged to contact another heat transfer plate in contact areas 20a (indicated in Fig. 5), while the valleys 18b of the third heat transfer area 7 is arranged to contact yet another heat transfer plate in contact areas 20b (indicated in Fig. 5).
Field and ring gaskets (which are not illustrated herein) are arranged between the first, second and third heat transfer plates 4, 6 and 7 to seal between these.
With reference to Figs. 2, 3, 4 and 5, almost all the ridges 18a of the first heat transfer plate 4 each comprises one or more plate recesses 22a as seen from the front side F of the first heat transfer plate 4. Here, each of the plate recesses 22a surrounds a respective one of the contact areas 20a. The plate recesses 22a are areas of locally reduced pressing depth of the first heat transfer plate 4, i.e. at the plate recesses 22a, a distance to the imaginary intermediate plane P is smaller than just outside the plate recesses 22a. A depth of the plate recesses 22a is such that they extend between the imaginary extreme plane P1 and the imaginary intermediate plane P. Thus, a cross section perpendicular to a longitudinal extension of the ridges 18a is constant except for at the plate recesses 22a, and at oblique ends of the ridges 18a. Similarly, almost all the valleys 18b of the first heat transfer plate 4 each comprises one or more plate recesses 22b. Here, each of the plate recesses 22b surrounds a respective one of the contact areas 20b. The plate recesses 22b are areas of locally reduced pressing depth of the first heat transfer plate 4, i.e. at the plate recesses 22b, a distance to the imaginary intermediate plane P is smaller than just outside the plate recesses 22b. A depth of the plate recesses 22b is such that they extend between the imaginary extreme plane P2 and the imaginary intermediate plane P. Thus, a cross section perpendicular to a longitudinal extension of the valleys 18b is constant except for at the plate recesses 22b, and at oblique ends of the valleys 18b. It should be stressed, again, that the valleys 18b as seen from the front side F of the first heat transfer plate 4 are ridges as seen from the back side B of the first heat transfer plate 4. However, the plate recesses 22b are plate recesses as seen from the back side B, and plate projections as seen from the front side F, of the first heat transfer plate 4.
Special reference is now made to Fig. 3 which schematically illustrates the location of one of the contact areas 20a and one of the plate recesses 22a surrounding it, and one of the contact areas 20b and one of the plate recesses 22b surrounding it. Each of the plate recesses 22a comprises two separated elongate sub-recesses 22a' and 22a". The sub-recesses 22a' and 22a" of each one of the plate recesses 22a extend on opposite sides of a respective one of the contact areas 20a so as to partly surround it. Similarly, each of the plate recesses 22b comprises two separated elongate sub-recesses 22b' and 22b". The sub-recesses 22b' and 22b" of each one of the plate recesses 22b extend on opposite sides of a respective one of the contact areas 20b so as to partly surround it.
As is clear from Fig. 3, each of the sub-recesses 22a', 22a", 22b' and 22b" of the plate recesses 22a and 22b comprises a straight portion s extending essentially parallel to the longitudinal center axis L (Fig. 2) of the first heat transfer plate 4. Further, each of the sub-recesses 22a', 22a", 22b' and 22b" of the plate recesses 22a and 22b comprises a curved portion c which is bent around the respective one of the contact areas 20a and 20b. Thus, the curved portions c of the two sub-recesses of each of the plate recesses are bent towards each other. They extend on opposite sides of a longitudinal center line I of the corresponding one of the corrugations 18, which longitudinal center line I is parallel to the longitudinal extension of the corresponding one of the corrugations 18. Despite from what it looks like in the figures, the plate recess 22b is a mirroring, in the imaginary intermediate plane P (Fig. 5), of the plate recess 22a. From the figures, it may seem as if the plate recesses 22a have a slightly different shape and size than the plate recesses 22b. This is because it is a tool for pressing the first, second and third heat transfer plates 4, 6 and 7 that is illustrated for reasons of clarity. On the actual first, second and third transfer plates 4, 6 and 7 obtained by the pressing tool, the plate recesses 22a and 22b will have the same shape and size. However, in alternative embodiments of the invention, the plate recesses 22a and 22b need not have the same size and/or shape.
In the plate set 2, the plate recesses 22b of the first heat transfer plate 4 will be aligned with a respective one of the plate recesses 22a of the second heat transfer plate 6, and most of the contact areas 20b will each be surrounded by one of the plate recesses 22b of the first heat transfer plate 4 and one of the plate recesses 22a of the second heat transfer plate 6. Thus, for each of these contact areas 20b, the sub-recess 22b' of the plate recess 22b of the first heat transfer plate 4 and the sub-recess 22a" of the plate recess 22a of the second heat transfer plate 6 will together form a fluid bypass on one side of the contact area, and the sub-recess 22b" of the plate recess 22b of the first heat transfer plate 4 and the sub-recess 22a' of the plate recess 22a of the second heat transfer plate 6 will together form a fluid bypass on another side of the contact area. These fluid bypasses are arranged to guide a fluid flowing between the first and second heat transfer plates 4 and 6 past the contact areas partly enclosed by the fluid bypasses so as to reduce the risk of having wakes or stagnant zones behind these contact areas as seen in the main fluid flow direction.
In a corresponding way, the plate recesses 22a of the third heat transfer plate 7 will be aligned with a respective one of the plate recesses 22b of the second heat transfer plate 6, and most of the contact areas 20a will each be surrounded by one of the plate recesses 22a of the third heat transfer plate 7 and one of the plate recesses 22b of the second heat transfer plate 6. Thus, for each of these contact areas 20a, the sub-recess 22a' of the plate recess 22a of the third heat transfer plate 7 and the sub-recess 22b" of the plate recess 22b of the second heat transfer plate will together form a fluid bypass on one side of the contact area, and the sub-recess 22a" of the plate recess 22a of the third heat transfer plate 7 and the sub-recess 22b' of the plate recesses 22b of the second heat transfer plate 6 will together form a fluid bypass on another side of the contact area. These fluid bypasses are arranged to guide a fluid flowing between the third and second heat transfer plates 7 and 6 past the contact areas partly enclosed by the fluid bypasses so as to reduce the risk of having wakes or stagnant zones behind these contact areas as seen in the main fluid flow direction.
The above described plate recesses are intermittent and each comprises two separated "banana-shaped" or "L-shaped" sub-recesses. According to alternative embodiments of the invention, the plate recesses may have different designs, for example any of the designs illustrated in Figs. 7-9.
Fig. 7 illustrates a plate recess 24a which is intermittent and comprises two separated elongate straight sub-recesses 24a' and 24a" which each has a straight portion s' extending essentially parallel to the longitudinal center axis L (Fig. 2) of the heat transfer plate.
Fig. 8 illustrates a plate recess 26a which is intermittent and comprises two separated elongate straight sub-recesses 26a' and 26a" which each has a straight portion s" extending essentially parallel to a longitudinal extension of the ridge in which they are formed.
Fig. 9 illustrates a plate recess 28a which is continuous and annular.
The above described first, second and third heat transfer plates 4, 6 and 7 are arranged to be "rotated" in relation to each other. According to alternative embodiments of the invention, the plate set may instead be so configured that it comprises first, second and third heat transfer plates "flipped" or "turned" in relation to each other. This may affect the location of the contact areas between the first and second heat transfer plates and, thus, necessitate a different positioning of the plate recesses.
Figs. 10 and 11 illustrate a plate set 2 comprising first, second and third heat transfer plates 4, 6 and 7 (only the first heat transfer plate 4 visible in Fig. 10) "rotated" in relation to each other. The first, second and third heat transfer plates in Figs. 10 and 11 are similar to each other but somewhat different from the first, second and third heat transfer plates illustrated in Figs. 1-6. Nevertheless, the plate set illustrated in Figs. 10 and 11 is, in many ways, similar to the plate set illustrated in Figs. 1-6 and described above. Consequently, the above description is, to a large extent, valid also for the plate set in Figs. 10 and 11. Therefore, to avoid undue repetition, in the below description of the plate set illustrated in Figs. 10 and 11, the differences of the plate set illustrated in Figs. 10 and 11 as compared to the plate set illustrated in Figs. 1-6 will be focused on.
The first heat transfer plate 4 (just like the second and third heat transfer plates 6 and 7) is so-called asymmetric in that its ridges 18a are more narrow than its valleys 18b. This is schematically illustrated in Fig. 11. This means that a volume v1 defined by an imaginary intermediate plane (like the imaginary intermediate plane P illustrated in Fig. 5) and the ridges 18a is smaller than a volume v2 defined by the imaginary intermediate plane and the valleys 18b. In turn, this means that different channel volumes may be formed between the first, second and third heat transfer plates 4, 6 and 7 depending on how they are orientated in relation to each other. If they are "rotated", i.e. arranged backside to frontside, like in Figs. 10 and 11, a channel volume CV1 is formed between the first and second heat transfer plates 4 and 6 and between the third and second heat transfer plates 7 and 6. If they instead are "flipped" and arranged backside to backside and frontside to frontside like in Fig. 12, a channel volume CV2 is formed between the first and second heat transfer plates 4 and 6, while a channel volume CV3 is formed between the third and second heat transfer plates 7 and 6. CV2 < CV1 < CV3. Thus, in a plate pack of multiple aligned heat transfer plates like the first, second and third heat transfer plates 4, 6 and 7, which are "rotated" in relation to each other, every channel will have a volume CV1. However, in a plate pack of multiple aligned heat transfer plates like the first, second and third heat transfer plates 4, 6 and 7, which are "flipped" in relation to each other, every other channel will have a volume CV2 while the rest of the channels will have a volume CV3. A larger channel volume is associated with a smaller pressure drop in an operating plate heat exchanger.
The orientation of the asymmetric heat transfer plates in relation to each other does not only effect the channel volume between the plates but also the location of the contact areas between plates.
The location of the contact areas 20b on the back side B (Fig. 11) of the first heat transfer plate 4, when the first and second heat transfer plates 4 and 6 are "rotated", and orientated as illustrated in Fig. 11, in relation to each other, is indicated in Fig. 10. The location of the contact areas 20a between the second and third heat transfer plates 6 and 7 when these are "rotated", and orientated as illustrated in Fig. 11, in relation to each other, is also indicated in Fig. 10. The contact areas 20a and 20b are alternately arranged and longitudinally aligned. With reference to Fig. 10, just like described above, almost all the ridges 18a each comprises one or more plate recesses 22a as seen from the front side F of the first heat transfer plate 4. Here, every second one of the plate recesses 22a surrounds a respective one of the contact areas 20a. Each one of the rest of the plate recesses 22a is arranged between two adjacent ones of the contact areas 20a. Further, almost all the valleys 18b each comprises one or more plate recesses 22b. However, here, each of the plate recesses 22b surrounds a respective one of the contact areas 20b. Here, as is indicated in Fig. 10, the plate recesses 22b are not mirrorings, in the imaginary intermediate plane P, of the plate recesses 22a.
In the plate set 2 illustrated in Fig. 10, the plate recesses 22b of the first heat transfer plate 4 will be aligned with a respective one of the plate recesses 22a of the second heat transfer plate 6, which will result in contact areas 20b surrounded by one of the plate recesses 22b of the first heat transfer plate 4 and one of the plate recesses 22a of the second heat transfer plate 6. The plate recesses of the first and second heat transfer plates 4 and 6 will together form fluid bypasses on opposite sides of the contact areas 20b. Further, the plate recesses 22a and 22b of the third and second heat transfer plates 7 and 6 surrounding the contact areas 20a will be aligned and together form fluid bypasses on opposite sides of the contact areas 20a.
The location of the contact areas 20b on the back side B (Fig. 12) of the first heat transfer plate 4, when the first and second heat transfer plates 4 and 6 are "flipped", and orientated as illustrated in Fig. 12, in relation to each other, is indicated by dashed circles in Fig. 13. The location of the contact areas 20a between the second and third heat transfer plates 6 and 7 when these are "flipped", and orientated as illustrated in Fig. 12, in relation to each other, is also indicated in Fig. 13. The contact areas 20a and 20b are alternately arranged and longitudinally aligned. As previously said, with reference to Fig. 13, almost all the ridges 18a each comprises one or more plate recesses 22a as seen from the front side F of the first heat transfer plate 4, with every second one of the plate recesses 22a surrounding a respective one of the contact areas 20a. Further, almost all the valleys 18b each comprises one or more plate recesses 22b. Here, each of the plate recesses 22b is arranged between two adjacent ones of the contact areas 20b.
In the plate set 2 illustrated in Fig. 13, the contact areas 20b are not surrounded by plate recesses like above, and no fluid bypasses for guiding a fluid flowing between the first and second heat transfer plates 4 and 6 around and past the contact areas 20b exist. However, the plate recesses 22a of the third and second heat transfer plates 7 and 6 surrounding the contact areas 20a will be aligned and together form fluid bypasses on opposite sides of the contact areas 20a. As described above, these fluid bypasses are arranged to guide a fluid flowing between the third heat transfer plate 7 and the second heat transfer plate 6 past the contact areas partly enclosed by the fluid bypasses so as to reduce the risk of having wakes or stagnant zones behind these contact areas as seen in the main fluid flow direction. The presence of fluid bypasses like these is associated with a decreased pressure drop and, thus, an even larger difference in pressure drop between the channel formed between the first and second heat transfer plates 4 and 6 and the channel formed between the third and second heat transfer plates 7 and 6.
Thus, with asymmetric heat transfer plates provided with plate recesses as illustrated in Figs. 10 and 13, different channel volumes and different sets of fluid bypasses, and thus different pressure drops, can be obtained depending on how the heat transfer plates are orientated in relation to each other in a plate pack.
It should be stressed that the plate recesses 22a and 22b are not illustrated in Figs. 11 and 12.
The above described embodiments of the present invention should only be seen examples. A person skilled in the art realizes that the embodiments discussed can be varied and combined in a number of ways without deviating from the inventive conception.
As an example, only the ridges, or only the valleys, of one or more of the first, second and third heat transfer plates may be provided with plate recesses, instead of both the ridges and the valleys. This may have different effects depending on how the first, second and third heat transfer plates are orientated in relation to each other in the plate set.
The present invention could be used in connection with other types of plate heat exchangers than gasketed ones, such as semi-welded, all-welded and brazed plate heat exchangers.
In the above described plate sets the first, second and third heat transfer plates are all similar which results in contact areas between the plates which are longitudinally aligned. In plate sets according to alternative embodiments, the contact areas may not be arranged in longitudinal lines, especially if the first, second and third heat transfer plates are different, for example, are provided with different heat transfer patterns.
In the above described plate set, the first, second and third heat transfer plates all have elongate corrugations comprising plate recesses. One or more of the first, second and third heat transfer plates could lack plate recesses. Further, a plate set could comprise only a first and a second heat transfer plate, one of which lacks plate recesses. However, this is outside the scope of the present invention.
It should be stressed that the attributes front, back, upper, lower, first, second, third, etc. is used herein just to distinguish between details and not to express any kind of orientation or mutual order between the details.
Further, 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. Some details in the figures may also be exaggerated for the sake of clarity. 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 on another figure.

Claims

A plate set (2) comprising a first heat transfer plate (4), a second heat transfer plate (6) and a third heat transfer plate (7) which are arranged aligned, in succession, and each has a longitudinal center axis (L), a transverse center axis (T), an upper port hole pair (8), a lower port hole pair (10) and a heat transfer area (14) provided with a heat transfer pattern comprising elongate corrugations (18) which each has a longitudinal extension of an angle ≠ 0 degrees in relation to the respective longitudinal center axis (L), the elongate corrugations (18) of the second heat transfer plate (6) crossing the elongate corrugations (18) of the first heat transfer plate (4) and the third heat transfer plate (7), wherein, for each of the first, second and third heat transfer plates (4, 6, 7), the upper port hole pair (8) and the heat transfer area (14) are arranged on opposite sides of an imaginary straight upper line (IU) extending parallel to the transverse center axis (T) and the lower port hole pair (10) and the heat transfer area (14) are arranged on opposite sides of an imaginary straight lower line (IL) extending parallel to the transverse center axis (T), the elongate corrugations (18) of the second heat transfer plate (6) contacting a sub-set of the elongate corrugations (18) of the first heat transfer plate (4) and a sub-set of the elongate corrugations (18) of the third heat transfer plate (7) in contact areas (20a, 20b), characterized in that each of at least a plurality of the elongate corrugations (18) of the first heat transfer plate (4) comprises a number ≥ 1 of plate recesses (22a, 22b), each of at least a plurality of the elongate corrugations (18) of the second heat transfer plate (6) comprises a number ≥ 1 of plate recesses (22a, 22b), each of at least a plurality of the elongate corrugations (18) of the third heat transfer plate (7) comprises a number ≥ 1 of plate recesses (22a, 22b), and each of at least a plurality of the contact areas (20a, 20b) is surrounded by a respective one of the plate recesses (22a, 22b) formed in one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7), said respective one of the plate recesses (22a, 22b) extending at least on two opposite sides of the contact area (20a, 20b).
A plate set (2) according to claim 1, wherein each of said at least a plurality of the contact areas (20a, 20b) is surrounded by a respective one of the plate recesses (22a, 22b) formed in another one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7), said at least one of the plate recesses (22a, 22b) formed in said another one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7) extending at least on two opposite sides of the contact area (20a, 20b).
A plate set (2) according to claim 2, wherein said respective one of the plate recesses (22a, 22b) formed in said one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7), and said respective one of the plate recesses (22a, 22b) formed in said another one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7), are aligned.
A plate set (2) according to any of claims 2-3, wherein said respective one of the plate recesses (22a, 22b) formed in said another one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7) is a mirroring, as seen from the contact area (20a, 20b), of said respective one of the plate recesses (22a, 22b) formed in said one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7).
A plate set (2) according to any of the preceding claims, wherein said respective one of the plate recesses (22a, 22b) formed in said one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7) extends only partially around the respective one of the contact areas (20a, 20b).
A plate set (2) according to any of the preceding claims, wherein said respective one of the plate recesses (22a, 22b) formed in said one of the first heat transfer plate (4), the second heat transfer plate (6) and the third heat transfer plate (7) comprises two separated sub-recesses (22a', 22a", 22b', 22b") arranged on opposite sides of the respective one of the contact areas (20a, 20b).
A plate set (2) according to claim 6, wherein each of at least a majority of the sub-recesses (22a', 22a", 22b', 22b") is elongate.
A plate set (2) according to any of claims 6-7, wherein each of at least a majority of the sub-recesses (22a, 22a", 22b', 22b") comprises a straight portion (s).
A plate set (2) according to claim 8, wherein the straight portion (s) extends parallel to the longitudinal center axis (L).
A plate set (2) according to claim 8, wherein the straight portion (s) extends perpendicular to the longitudinal extension of the corresponding one of the corrugations (18).
A plate set (2) according to any of claims 6-10, wherein each of at least a majority of the sub-recesses (22a', 22a", 22b', 22b") comprises a curved portion (c) which is bent towards the other sub-recess (22a', 22a", 22b', 22b") of the corresponding one of the plate recesses (22a, 22b).
A plate set (2) according to any of the preceding claims, wherein a cross section perpendicular to the longitudinal extension of each of at least a majority of the corrugations (18) is constant, along the longitudinal extension, outside the plate recesses (22a, 22b).
A plate set (2) according to any of the preceding claims, wherein each of the first, second and third heat transfer plates (4, 6, 7) further comprises an upper distribution area (12) extending between the upper port hole pair (8) and the heat transfer area (14), and a lower distribution area (16) extending between the lower port hole pair (10) and the heat transfer area (14), the upper distribution area (12) and the lower distribution area (16) being provided with an upper distribution pattern and a lower distribution pattern, respectively, the heat transfer pattern differing from the upper distribution pattern and the lower distribution pattern, the upper distribution area (12), the heat transfer area (14) and the lower distribution area (16) being arranged in succession along the respective longitudinal center axis (L).
A plate set (2) according to any of the preceding claims, wherein the elongate corrugations (18) of the second heat transfer plate (6) comprise alternately arranged ridges (18a) and valleys (18b) in relation to an imaginary intermediate plane (P) defining a border between the ridges (18a) and the valleys (18b), wherein some of said at least a plurality of the elongate corrugations (18) of the second heat transfer plate (6) comprising a number ≥ 1 of plate recesses (22a, 22b) are ridges (18a), and some of said at least a plurality of the elongate corrugations (18) of the second heat transfer plate (6) comprising a number ≥ 1 of plate recesses (22a, 22b) are valleys (18b).
A plate set (2) according to any of the preceding claims, wherein at least a majority of the plate recesses (22a, 22b) of the second heat transfer plate (6) has a depth less than half a distance between two parallel imaginary extreme planes (P1, P2) which define an extension of the second heat transfer plate (6) along a depth center axis (D) of the second heat transfer plate (6).