HEAT EXCHANGER PLATE

The present invention relates to a heat exchanger plate in accordance with the preamble of claim 1.

Most of the known heat exchanger plates for plate heat exchangers are provided with a regular corrugated pattern, for instance the conventional chevron or fishbone pattern or the conventional washboard pattern. The purpose of providing these patterns on the heat exchanger plate is:

To provide flow channels for the heat exchanging fluid.

To give the heat exchanger constructions mechanical strength due to the numerous contact points .

To ensure a good heat transfer between the heat exchanging fluids .

By designing heat exchanger plates for plate heat exchangers it is for some applications desirable to obtain a high number of transfer units (NTU-VALUE) . In principle the NTU- VALUE of a plate heat exchanger can be increased by

reducing the plate gap, i.e. the distance between two adjacent plates and/or

reducing the angle of the regular pattern (pattern angle), i.e. the angle of the direction into which the ribs and grooves of the pattern are extending relatively to a direction being perpendicular to the main flow direction of the fluid.

The plate gap normally corresponds to the amplitude of the corrugation providing the pattern. The plate gap also defines the height of the gasket placed between two adjacent heat exchanger plates. The gaskets seal the fluids in the plate heat exchanger and separate them from each other.

If the plate gap is changed, normally the whole design and construction of the heat exchanger plate and the gasket has to be changed and also new gaskets, and therefore, new or modified gasket tools are necessary. Accordingly it will be expensive to improve the efficiency of existing plate heat exchangers by means of reducing the plate gap. Furthermore there are practical limits on the reduction of the plate gap, such as gasket sealing force and gasket life time.

A continual reduction of the pattern angle to less than about 30° will not result in a corresponding continual increase in the plate efficiency. Accordingly most plate heat exchangers for applications wherein a high NTU-VALUE is desirable, have a pattern angle of about 30°.

For some applications, where plate heat exchangers are used, limitations are given to the overall height of the plate heat exchangers by the available space and/or tooled parts. Therefore, it will not be possible to increase the size of the plate heat exchanger, if a higher NTU-VALUE is required.

Therefore, it is an object of the invention to provide heat exchanger plates having a pattern resulting in a higher NTU- VALUE compared to the known pattern having the same outer dimensions, the same plate gap and the same pattern angle.

The object of the invention is obtained by a heat exchanger plate with the features of claim 1. Preferred embodiments are disclosed in the dependent claims.

According to one aspect of the invention there is provided a heat exchanger plate for the use in a plate heat exchanger having a first contact side for contacting a primary heat exchanging fluid if the heat exchanger plate is assembled and used in a heat exchanger and a second contact side for contacting a secondary heat exchanging fluid if the heat exchanger plate is assembled and used in a heat exchanger, wherein the first contact side and the second contact side each comprise a pattern forming respective uneven surfaces on the first and second contact sides and providing respective contact points or contact areas for contacting a corresponding heat exchanger plate if assembled together in a plate heat exchanger, wherein a series of dents, indents, recesses, protrusions and/or additional corrugations are provided in the pattern on the first contact side and/or on the second contact side between or outside the contact points or contact areas.

According to this aspect of the invention additional turbulences can be induced into the fluids flowing through a plate heat exchanger having at least one of such heat exchanger plates. Such additional turbulences will result in a higher NTU-VALUE just by providing a series of dents, indents, recesses, protrusions and/or additional corrugations in the pattern on the first contact side and/or on the second contact side between or outside the contact points or contact areas.

Another advantage of this aspect of the invention is that the modifications of the pattern can provide a mechanical fixing of two adjacent heat exchanger plates if they are assembled into a plate heat exchanger. Because of the mechanical fixing, the assembling of the plate heat exchanger will be simplified.

In accordance with this aspect of the invention the NTU- VALUE of a plate heat exchanger having at least one of these heat exchanger plates installed can be adjusted to a desired level (increased or even decreased) without changing the general and especially the outer geometry of the plate, the plate gap and the pattern angle. Therefore, existing tools for making the plates and gaskets can be reused. Existing tools for making the gaskets can be used without any modification. Tools for making the plates can be provided by modifying the insert of an existing tool. This will save investment costs. This makes it possible to produce improved heat exchanger plates without additional costs to the manufacture .

According to the invention the modification of the conventional pattern design is preferably made such that there are provided more obstacles for the fluids whereby more turbulences are created. This will increase the NTU- VALUE .

In addition with the embodiments of the invention it will be possible to partially (depending from the geometry of the alternating plates) decrease the effective plate gap in the dominant fluid pathways without changing the actual plate gap defining the size of the gasket.

In the context of this application "heat exchanger plate plane" means the plane of the gasket receiving sections.

In the context of this application "contact point plane" or "contact area plane" means the plane where the contact points or contact areas are located.

The distance between two neighbouring contact point planes (contact area planes) minus the plate thickness (the thickness of the plate sheet material) corresponds to the plate gap.

In accordance with the invention the dents, indents, recesses, protrusions and/or additional corrugations can be designed such that at least one of them and preferably some of them are extending from the heat exchanger plate plane over the contact point plane (or contact area plane) . Preferably the dents, indents, recesses, protrusions and/or additional corrugations can be designed such that at least one of them and preferably some of them are extending from the heat exchanger plate plane over the contact point plane (or contact area plane) by about 100%, preferably by less than about 95%, more preferably by less than about 80%, more preferably by less than 70%, more preferably by less than about 60% and/or by more than 1%, preferably by more than 5%, more preferably by more than 10%, more preferably by more than 20%, more preferably by more than 30%, more preferably by more than 40%, and especially and especially by about 50% of the distance between these planes.

In accordance with the invention the dents, indents, recesses, protrusions and/or additional corrugations can be designed such that at least one of them and preferably some of them are located between the heat exchanger plate plane and the contact point plane (or contact area plane) . This can for instance achieved by modifying a conventional pattern (fishbone, chevron or washboard) with some indents extending from the ribs to the plane of the heat exchanger plate .

In accordance with the invention the dents, indents, recesses, protrusions and/or additional corrugations can be designed such that at least one of them and preferably some of them are having a distance from the contact point plane (or contact area plane) corresponding to about 100%, preferably by less than about 95%, more preferably by less than about 80%, more preferably by less than 70%, more preferably by less than about 60% and especially by about 50% of the distance between the heat exchanger plate plane and the contact point plane (or contact area plane) .

In accordance with the invention the dents, indents, recesses, protrusions and/or additional corrugations can be designed such that at least one of them and preferably some of them are having a distance from the heat exchanger plate plane corresponding to about 100%, preferably by less than about 95%, more preferably by less than about 80%, more preferably by less than 70%, more preferably by less than about 60% and especially by about 50% of the distance between the heat exchanger plate plane and the contact point plane (or contact area plane) .

In accordance with the invention a pattern groove (or the pattern grooves) on one of the contact sides of one plate can correspond to a pattern hill (or the pattern hills) on the other one of the contact sides of this plate and a pattern hill (or the pattern hills) on one of the contact sides of one plate can correspond to a pattern groove (or the pattern grooves) on the other one of the contact sides of this plate. These features are due to the conventional manufacturing heat exchanger plates by stamping sheet metal material (preferably stainless steal) .

In accordance with the invention the heat exchanger plate can comprise a corrugated pattern (known in the art for instance as a chevron or fishbone pattern) and preferably an

additional corrugated pattern located outside the contact points or contact areas.

In accordance with the invention the pattern is a fishbone pattern or a washboard pattern. According to the invention the pattern will be modified with obstacles as defined in the specification and especially claim 1.

In accordance with the invention the angle between a line being perpendicular to the flow direction of the fluids and the direction of the grooves of the fish bone or washboard pattern can be less than 65°, preferably less than 55°, preferably less than 45°, preferably less than 40°, more preferably less than 35° and most preferred about 30°. This angle is known as the chevron or washboard angle. A chevron of about 30° will provide by conventional washboard or fishbone pattern an optimal NTU-VALUE. Accordingly most of the known washboard or fishbone pattern have an chevron angle between about 65° and about 30° . The above mentioned features of the invention will provide a further increase of the NTU-VALUE without changing the plate gap or the overall dimensions of the plate heat exchanger.

In accordance with the invention the dents, indents, recesses, protrusions and/or additional corrugations can be provided between at least two and preferably between more of the contact points or contact areas and, if one wanted to maximise the NTU-VALUE, more preferably between all contact points or contact areas .

In accordance with the invention the dents, indents, recesses, protrusions and/or additional corrugations can be provided on lines essentially extending in the intended flow direction of the fluids if the heat exchanger plate is assembled and used in the plate heat exchanger. Most of the fluids will pass on these lines through the plate heat

exchanger. By providing obstacles for the passage of the fluids on these lines turbulences in the fluids will occur resulting in an increase of the NTU-VALUE of the plate heat exchanger .

In accordance with the invention the dents, indents, recesses, protrusions and/or additional corrugations can be designed such that they are reducing the distance to the adjacent heat exchanger plate in the area of the protrusion, recess, indent and/or additional corrugation if the heat exchanger plate is assembled in a plate heat exchanger by- more than 1%, preferably by more than 5%, more preferably by more than about 15%, more preferably by more than 30%, and most preferably by about 50%.

In accordance with the invention the dents, indents, recesses, protrusions and/or additional corrugations can be designed such that they are reducing the distance to the adjacent heat exchanger plate in the area of the protrusion, recess or indent if the heat exchanger plate is assembled in a plate heat exchanger by about 100%, preferably less than about 95%, more preferably less than about 80%, more preferably by less than 70%, more preferably by less than about 60% and most preferably by about 50%.

In accordance with the invention the dents, indents, recesses and/or protrusions can have a round, circular, linear, rectangular, cross-like or other shaped cross- section in the plane of the heat exchanger plate. Other suitable forms are possible as long as they provide obstacles for the passing fluids if desired.

In accordance with the invention the dents, indents, recesses and/or protrusions can have a corrugated cross- section as viewed from the side of the heat exchanger plate. Preferably they have a higher (or a lower) amplitude than

the corresponding cross-section of the common fishbone pattern or washboard pattern.

The invention relates also to a plate heat exchanger having a plurality of heat exchanger plates, where at least one, and preferably every tenth, more preferably every eighth, more preferably every sixth, more preferably every fourth, more preferably every second and most preferred every heat exchanger plate is in accordance with the present invention as laid down above to increase the NTU-VALUE. The number of heat exchanger plates in accordance with the invention to be installed into the plate heat exchanger will be chosen in order to optimize the resulting NTU-VALUE of the plate heat exchanger in accordance with the desired NTU-value. With other words, the NTU-VALUE of a plate heat exchanger will be dependent and therefore can be adjusted by the number of heat exchanger plates of the invention being installed into the plate heat exchanger.

According to one aspect of the invention there is provided a plate heat exchanger having at least two heat exchanger plates especially being in accordance with the present invention as laid down above, wherein the heat exchanger plates are installed alternately in opposite orientations and nesting each other in areas where protrusions are provided. This will result in an increase of the NTU-VALUE without changes of the plate gap or the overall dimensions of the plate heat exchanger.

According to one aspect of the invention there is provided a plate heat exchanger especially in accordance with the above mentioned having at least two heat exchanger plates especially being in accordance with the present invention as laid down above, wherein at least two adjacent heat exchanger plates are provided with dents, indents, recesses, protrusions and/or additional corrugations which are arranged such that the heat exchanger plates are

mechanically fixed relative to each other. The mechanically fixing will simplify the assembling of the plate heat exchanger because the heat exchanger plates will not be able to slip on each other significantly but stay more or less aligned.

Preferred embodiments of the invention are shown in the attached drawings .

Fig. 1 is a schematic top view of a heat exchanger plate in accordance with an embodiment of the invention.

Fig. 2 is a sketch illustrating the contact points if two plates as shown in Fig. 1 are assembled in a plate heat exchanger.

Fig. 3a) is a schematic sectional view of the heat exchanger plate of Fig. 1 without gasket along lines III-III.

Fig. 3b) is a schematic sectional view corresponding to the sectional view of Fig. 3a) but of a conventional heat exchanger plate.

Fig. 3c) is a schematic sectional view corresponding to the sectional view of Fig. 3a) showing the differences between the embodiment of the invention (bold line) and the conventional heat exchanger plate (dash-dotted line) .

Fig. 4a) is a schematic sectional view of the heat exchanger plate of Fig. 1 without gasket along lines IV-IV.

Fig. 4b) is a schematic sectional view corresponding to the sectional view of Fig. 4a) but showing a conventional heat exchanger plate.

Fig. 4c) is a schematic sectional view corresponding to the sectional view of Fig. 4a) showing the differences between the embodiment of the invention (bold line) and the conventional heat exchanger plate (dash-dotted line) .

Fig. 5a) is a schematic sectional view corresponding to

Fig. 3a) but with two heat exchanger plates placed on top of each other as assembled in a plate heat exchanger .

Fig. 5b) is a schematic sectional view corresponding to the sectional view of Fig. 5a) but showing conventional heat exchanger plates.

Fig. 5c) is a schematic sectional view corresponding to the sectional view of Fig. 5a) showing the differences between the embodiment of the invention (bold line) and the conventional heat exchanger plate (dash-dotted line) .

Fig. 6a) is a schematic sectional view corresponding to

Fig. 4a) but with two heat exchanger plates placed on top of each other as assembled in a plate heat exchanger.

Fig. 6b) is a schematic sectional view corresponding to the sectional view of Fig. 6a) but showing conventional heat exchanger plates .

Fig. 6c) is a schematic sectional view corresponding to the sectional view of Fig. 6a) showing the differences between the embodiment of the invention (bold line) and the conventional heat exchanger plate (dash-dotted line) .

Fig. 7a) is an enlarged schematic part view of the pattern of the heat exchanger plate of Fig . 1.

Fig. 7b) is an enlarged schematic part view corresponding to Fig. 7a) of the pattern of the heat exchanger plate in accordance with another embodiment of the invention .

Fig. 7c) is an enlarged schematic part view corresponding to Fig. 7a) of the pattern of the heat exchanger plate in accordance with another embodiment of the invention.

Fig. 7d) is an enlarged schematic part view corresponding to Fig. 7a) of the pattern of the heat exchanger plate in accordance with another embodiment of the invention.

Fig. 8a) is a schematic view showing a part of a modified washboard pattern for a heat exchanger plate in accordance with another embodiment of the invention wherein the modifications are shown as circles (protrusions if located on a line and recesses if located therebetween) and the contact points are indicated as bold crosses.

Fig. 8b) is a schematic view showing a part of a modified washboard pattern for a heat exchanger plate in accordance with another embodiment of the invention wherein the modifications are shown as circles (protrusions if located on a line and recesses if located therebetween) and the contact points are indicated as bold crosses.

The invention will be explained in further detail with reference to the drawings, wherein the following reference numbers are used (sometimes identical reference numbers are

used for similar or corresponding parts of other embodiments with added ' or added small letters a, b, c or d) :

1 heat exchanger plate

2 gasket

3 entrance orifice for the primary fluid

4 exit orifice for the primary fluid

5 entrance orifice for the secondary fluid

6 exit orifice for the secondary fluid

10 first contact side

11 gasket receiving portion

12 first portion of pattern

13 second portion of pattern

14 meeting point (meeting area)

15 contact point (contact area)

16 protrusion

17 recess (indent)

20 second contact side

21 gasket receiving portion

22 first portion of pattern

23 second portion of pattern

24 meeting point (meeting area)

25 contact point (contact area)

26 protrusion

27 recess (indent)

30 flow direction of primary fluid

40 flow direction of secondary fluid α pattern angle

An embodiment of the invention comprising a modified chevron pattern will be explained first with special reference to Figs. 1, 2, 3a), 4a), 5a), 6a) and 7a). Then the differences will be explained with special reference to Figs. 3b), 3c) 4b) , 4c) , 5b) , 5c) , and 6b) 6c) .

The heat exchanger plate 1 comprises a first contact side 10

for contacting a primary fluid (not shown) if the heat exchanger plate is assembled into and used in a heat exchanger. On the opposite side there is a second contact side 20 (see for instance Fig. 3a) for contacting a secondary fluid (not shown) if the heat exchanger plate is assembled into and used in a heat exchanger. A gasket 2 for sealing one heat exchanger plate against an adjacent heat exchanger plate is shown. The gasket 2 is preferably a separate part and normally manufactured separately. The gasket is received in a gasket receiving portion 21. If the heat exchanger plate is assembled into and used in a plate heat exchanger the primary fluid will flow essentially in the direction of arrow 30 from the entrance orifice 3 for the primary fluid over the first contact side (and a similar contact side of the adjacent heat exchanger plate 1' assembled next to plate 1) to the exit orifice 4 for the primary fluid. Therefore, as shown in Fig. 1 the gasket is not circumscribing orifices 3 and 4 at the first contact side 10 (but at the second contact side 20, not shown in Fig. 1). The secondary fluid will flow essentially in the direction of arrow 40 from the entrance orifice 5 for the secondary fluid over the second contact side 20 (and a similar contact side of the adjacent heat exchanger plate 1' assembled next to plate 1) to the exit orifice 6 for the secondary fluid. Accordingly the gasket is circumscribing orifices 5 and 6 at the first contact side 10 (but not at the second contact side 20, not shown in Fig. 1) .

Normally plate heat exchangers are operated counterflowwise, i.e. that for instance the primary fluid passes the plate heat exchanger in the direction of arrow 30 and the secondary fluid passes the plate heat exchanger in the opposite direction of arrow 40. It is to be understood that depending on the application the plate heat exchangers could be operated differently, for instance with perpendicular or parallel flow directions for the two or more heat exchanging fluids .

The embodiment comprises a pattern essentially based on the fishbone or chevron pattern. There is a first portion 12 of the pattern having a rib or protrusion extending in an angle α (Fig. 7a) of essentially 30° to a direction being perpendicular the flow direction 30, 30a of the fluid. A corresponding second portion 13 of the pattern is tilted by preferably the same angle, but in the other direction as best shown in Fig. 7a) . Both portions 12, 13 met in a meeting point or meeting area 14. Between the ribs or protrusions are corresponding grooves. This is corresponding to the conventional fishbone or chevron pattern.

This pattern is modified in that there is provided an overlying additional corrugations outside the plate contact points. The additional corrugations are extending essentially parallel to the main flow directions 30, 40. With other words the pattern comprises some protrusions 16 (shown as a bold circles respectively located on the lines schematically showing the tips of the respective ribs) protruding from the ribs (first and second portions of the patterns forming the fishbone pattern) and some corresponding recesses 17 (shown as bold circles located between the lines schematically showing the tips of the respective ribs) in the valleys between the ribs. These protrusions 16 and 17 are located between the contact points or contact areas 15 (shown as bold crosses) with an adjacent heat exchanger plate .

According to the invention less or more protrusions or irregularities can be provided in the conventional pattern in order to increase the NTU-VALUE of a plate heat exchanger having at least one of the inventive heat exchanger plates installed.

Tests made by the present owner of the invention have surprisingly showed, that the NTU-VALUE can be increased by

providing the modifications as shown in the Figs. 1 and 3a), 4a) etc. significant, for instance more than 5%.

The other side of the heat exchanger plate 1 is the second contact side 20 for contacting the secondary fluid if installed and used in a plate heat exchanger.

Normally the heat exchanger plate is a metal sheet manufactured with a stamp tool . However other methods for fabricating heat exchanger plates as known to the skilled person are considered to be encompassed by the present invention. Preferably and as embodied by the described embodiment of Fig. 1 the second contact side 20 will have a similar design as the first contact side 10. Accordingly there is a gasket receiving portion 21 and there are corresponding first portions 22 and second portions 23 of the pattern being joined in respective meeting points 24 (meeting areas 24) . It is clear that ribs or protrusions on the first side 10 will correspond to grooves or recesses on the second side. The second contact side has contact points 25 (contact areas) for making contact with an adjacent heat exchanger plate . Due to the manufacturing method of the embodiment there are also protrusion 26 and recesses (dents, indents) 27 on the second contact side 20.

It is clear that other conventional pattern can be modified with corresponding modifications. For instance the known washboard patterns can be modified with additional (superimposed) corrugations or regular or irregular distributed recesses (and/or dents, indents) and/or protrusions .

Fig. 3a) is a schematic sectional view of the heat exchanger plate 1 of Fig. 1 showed without the gasket along lines III- III. In Fig. 3a) the protrusions 16 and recesses 17 on the first contact side 10 as well as the protrusions 26 and recesses 27 provided on the second contact side 20 are

illustrated. If the heat exchanger plate is assembled in a plate heat exchanger one gasket is placed into the gasket receiving region 11 and another gasket is placed on the other side of the heat exchanger plate into the gasket receiving region 21.

Fig. 3b) is a schematic sectional view corresponding to the sectional view of Fig. 3a) but of a conventional heat exchanger plate. The differences can be seen from Fig. 3c) wherein the sectional views of Figs. 3a) and 3b) are shown superimposed. The embodiment of Fig. 1 and Fig. 3a) is shown as bold line and the corresponding sectional view of the conventional heat exchanger plate is shown as dash-dotted line which can only be seen in the areas where differences are provided. These are the protrusions and recesses as referenced in Fig. 3a) .

Fig. 4a) is a schematic sectional view of the heat exchanger plate of Fig. 1 without gasket along lines IV-IV, i.e. in the direction of arrow 30 (Fig. 1) along a line extending through the locations of the protrusions and recesses or with other words along a line between the contact points 14.

Figs. 4b) and Fig. 4c) are provided in order to show the difference between the embodiment of the invention and a conventional plate heat exchanger. Reference is made to the corresponding description of Figs. 3b) and 3b) .

Figs. 5a), 5b) and 5c) as well as Figs. 6a), 6b) and 6c) are similar to Figs. 3a), 3b) and 3c) as well as Figs. 4a), 4b) and 4c) but showing in addition a second heat exchanger plate 1' arranged adjacent to the one as shown in Figs. 3a) to 4c) .

The difference between conventional hest exchanger plates and the inventive heat exchanger plates can best be seen from these Figs, and especially from Fig. 6c) . As shown in

Fig. 6c) the fluid passing through the plate heat exchanger with heat exchanger plates in accordance with the invention has to change its flow direction much more than by flowing through a conventional plate heat exchanger. The fluid has to change its flow direction more than in the conventional plate heat exchangers due to the protrusions and recesses in adjacent heat exchanger plates (if installed in a plate heat exchanger) providing a nesting of adjacent plates. This nesting will take place in the main flow areas because the contact between adjacent heat exchanger plates provides other flow obstacles. Due to this, more turbulences will be created in the fluid which will increase the NTU-VALUE of the plate heat exchanger.

Figs. 7a) are showing some exemplary designs for the construction of the protrusions and recesses. Other designs are possible (as long as more turbulence is created, if an increased NTU-VALUE is desired) .

Fig. 7a) is an enlarged schematic part view of the pattern of the heat exchanger plate of Fig. 1 whereas Figs. 7b), 7c) and 7d) are showing alternative designs for the modifications. Alternatively the protrusions can be provided as recesses and the recesses as protrusions. In that case no nesting will be achieved but still an increased turbulence will be induced resulting in a higher NTU-VALUE of a plate heat exchanger equipped with such heat exchanger plates . This has been confirmed by tests made by the owner of the present invention.

According to Fig. 7b) other possible modifications are grooves provided in the ribs of the chevron pattern extending perpendicular to the flow direction 30b. With this design no nesting of the plates will be achieved but still an increased turbulence will be induced resulting in a higher NTU-VALUE of a plate heat exchanger equipped with

such heat exchanger plates. This has been confirmed by tests made by the owner of the present invention.

According to Fig. 7c) other possible modifications are shown. The modifications can have a regular of irregular shape .

According to Fig. 7d) other possible modifications are grooves provided in the ribs of the chevron pattern extending parallel to the flow direction 3Od. This will decrease the pressure drop created in the plate heat exchanger which will be desirable for some applications especially where a lower NTU-VALUE is desired.

The embodiments of the invention as shown in the Figs . and/or described above comprise a modified fishbone or chevron pattern. However it will be clear that similar modifications can be made to washboard or other prior art patterns especially if used for similar or same applications. The skilled person will have the skill to make similar modification in knowledge of the present disclosure of the invention. This applies especially to the modifications as shown in Figs. 7a) 7b) , 7c) and 7d) .

It is clear that the description of the specific embodiments of the invention is not to be intended to limit the scope of protection which is defined by the claims. It is also clear that obvious alternatives which the skilled person will notice by reading the specification are intended to be in the scope of protection as defined by the claims.