Heat transfer plate and plate heat exchanger comprising such a heat transfer plate

Abstract

A heat transfer plate comprises a first end area, a heat transfer area and a second end area along a longitudinal center axis of the plate which divides the plate into first and second halves delimited by first and second long sides respectively. The first end area comprises an inlet port hole, a distribution area and a transition area. The transition area adjoins the distribution area and the heat transfer area. The distribution area has a distribution pattern of projections and depressions, the transition area has a transition pattern of projections and depressions, and the heat transfer area has a heat transfer pattern of projections and depressions. An imaginary straight line extends between two end points of each transition projection with an angle relative to the longitudinal center axis. The angle varies between the transition projections and increases from the first long side to the second long side.

Claims

1. A heat transfer plate having a central extension plane and comprising a first end area, a heat transfer area and a second end area arranged in succession along a longitudinal center axis of the heat transfer plate, which longitudinal center axis divides the heat transfer plate into a first and a second half delimited by a first and second long side, respectively, the first end area comprising an inlet port hole arranged within the first half of the heat transfer plate, a distribution area and a transition area, the transition area adjoining the distribution area along a first borderline and the transition area adjoining the heat transfer area along a second borderline, the distribution area having a distribution pattern of distribution projections and distribution depressions in relation to the central extension plane, the transition area having a transition pattern of transition projections and transition depressions in relation to the central extension plane and the heat transfer area having a heat transfer pattern of heat transfer projections and heat transfer depressions in relation to the central extension plane, the transition pattern differing from the distribution pattern and the heat transfer pattern, the transition projections comprising transition contact areas arranged for contact with another heat transfer plate, and an imaginary straight line extending between two end points of each transition projection with an angle in relation to the longitudinal center axis, wherein the angle is varying between the transition projections and increasing in a direction from the first long side to the second long side.

2. A heat transfer plate according to claim 1, wherein the first borderline is non-linear.

3. A heat transfer plate according to claim 1, wherein the first borderline is arched and convex seen from the heat transfer area.

4. A heat transfer plate according to claim 1, wherein the distribution projections are arranged in projection sets and the distribution depressions are arranged in depression sets, the distribution projections of each projection set being arranged along a respective imaginary projection line extending from a respective first distribution projection to the first borderline, and the distribution depressions of each depression set being arranged along a respective imaginary depression line extending from a respective first distribution depression to the first borderline, a front side main flow path across the distribution area being defined by two adjacent projection lines and a back side main flow path across the distribution area being defined by two adjacent depression lines.

5. A heat transfer plate according to claim 4, wherein the projection lines cross the depression lines in crossing points to form a grid.

6. A heat transfer plate according to claim 5, wherein the crossing point of each projection line that is closest to the first borderline is arranged on an imaginary connection line, which connection line is parallel to the first borderline.

7. A heat transfer plate according to claim 6, wherein the imaginary connection line coincides with the first borderline.

8. A heat transfer plate according to claim 4, wherein an imaginary extension line extending along each transition projection is similar to a respective part of a third borderline delimiting the distribution area and the transition area and extending parallel to a longest one of the projection lines and further through a respective end point of the first and second borderlines.

9. A heat transfer plate according to claim 8, wherein each of the rest of the projection lines is similar to a respective part of said longest one of the projection lines.

10. A heat transfer plate according to claim 4, wherein a first distance between two adjacent ones of the transition projections is smaller than a second distance between two adjacent ones of the projection lines of the distribution area.

11. A heat transfer plate according to claim 1, wherein the transition contact area of each transition projection that is closest to the first borderline is arranged on an imaginary contact line, which imaginary contact line is parallel to the first borderline.

12. A heat transfer plate according to claim 1, wherein the second borderline is non-linear.

13. A heat transfer plate according to claim 1, wherein the second borderline is arched and convex seen from the heat transfer area.

14. A plate heat exchanger comprising a heat transfer plate according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1a-1c illustrate contact areas between different pairs of heat transfer plate patterns,

(3) FIG. 2 is a front view of a plate heat exchanger,

(4) FIG. 3 is a side view of the plate heat exchanger of FIG. 2,

(5) FIG. 4 is a plan view of a heat transfer plate,

(6) FIG. 5 is an enlargement of a part of the heat transfer plate of FIG. 4,

(7) FIG. 6 comprises an enlargement of a portion of the heat transfer plate part of FIG. 5 and illustrates schematically contact areas of a section of the heat transfer plate,

(8) FIG. 7 is a schematic cross section of distribution projections of a distribution pattern of the heat transfer plate,

(9) FIG. 8 is a schematic cross section of distribution depressions of the distribution pattern of the heat transfer plate,

(10) FIG. 9 is a schematic cross section of transition projections and transition depressions of a transition pattern of the heat transfer plate, and

(11) FIG. 10 is a schematic cross section of heat transfer projections and heat transfer depressions of a heat transfer pattern of the heat transfer plate.

DETAILED DESCRIPTION

(12) With reference to FIGS. 2 and 3, a gasketed plate heat exchanger 2 is shown. It comprises a first end plate 4, a second end plate 6 and a number of heat transfer plates arranged between the first and second end plates 4 and 6, respectively. The heat transfer plates are of two different types. One type has a medium-theta heat transfer pattern, while the other one has a high-theta heat transfer pattern, the types otherwise being essentially similar. One of the heat transfer plates with medium-theta heat transfer pattern, denoted 8, is illustrated in further detail in FIG. 4. The different heat transfer plates are alternately arranged in a plate pack 9 with a front side (illustrated in FIG. 4) of one heat transfer plate facing the back side of a neighboring heat transfer plate. Every second heat transfer plate is rotated 180 degrees, in relation to a reference orientation (illustrated in FIG. 4), around a normal direction of the figure plane of FIG. 4.

(13) The heat transfer plates are separated from each other by gaskets (not shown). The heat transfer plates together with the gaskets form parallel channels arranged to receive two fluids for transferring heat from one fluid to the other. To this end, a first fluid is arranged to flow in every second channel and a second fluid is arranged to flow in the remaining channels. The first fluid enters and exits the plate heat exchanger 2 through inlet 10 and outlet 12, respectively. Similarly, the second fluid enters and exits the plate heat exchanger 2 through inlet 14 and outlet 16, respectively. The above inlets and outlets will not be described in detail herein. Instead, reference is made to applicant's co-pending patent application “Heat exchanger plate and plate heat exchanger comprising such a heat exchanger plate”, filed on the same date as the present application and hereby incorporated herein. For the channels to be leak proof, the heat transfer plates must be pressed against each other whereby the gaskets seal between the heat transfer plates. To this end, the plate heat exchanger 2 comprises a number of tightening means 18 arranged to press the first and second end plates 4 and 6, respectively, towards each other.

(14) The heat transfer plate 8 will now be further described with reference to FIGS. 4, 5 and 6 which illustrate the complete heat transfer plate, a part A of the heat transfer plate and a portion C of the heat transfer plate part A, respectively, and FIGS. 7, 8, 9 and 10 which illustrate cross sections of projections and depressions of the heat transfer plate. The heat transfer plate 8 is an essentially rectangular sheet of stainless steel. It has a central extension plane c-c (see FIG. 3) parallel to the figure plane of FIGS. 4, 5 and 6, and to a longitudinal center axis y of the heat transfer plate 8. The longitudinal center axis y divides the heat transfer plate 8 into a first half 20 and a second half 22 having first long side 24 and a second long side 26, respectively. The heat transfer plate 8 comprises a first end area 28, a second end area 30 and a heat transfer area 32 arranged there between. In turn, the first end area 28 comprises an inlet port hole 34 for the first fluid and an outlet port hole 36 for the second fluid arranged for communication with the inlet 10 and the outlet 16, respectively, of the plate heat exchanger 2. Similarly, in turn, the second end area 30 comprises an inlet port hole 38 for the second fluid and an outlet port hole 40 for the first fluid arranged for communication with the inlet 14 and the outlet 12, respectively, of the plate heat exchanger 2. Hereinafter, only the first one of the first and second end areas will be described since the structures of the first and second end areas are the same but mirror inverted with respect to a transverse center axis x.

(15) The first end area 28 comprises a distribution area 42 and a transition area 44. A first borderline 46 separates the distribution and transition areas and the transition area 44 borders on the heat transfer area 32 along a second borderline 48. Third and fourth borderlines 50 and 52, respectively, which extend from a connection point 54 to a respective end point 56 and 58 of the second borderline 48 via a respective end point 60 and 62 of the first borderline 46, delimit the distribution area 42 and the transition area 44 from the rest of the first end area 28. The distribution area extends from the first borderline 46 in between the inlet and outlet port holes 34 and 36, respectively. The first and second borderlines 46 and 48, respectively, are both concave seen from the distribution area 42. However, the first borderline 46 has a sharper curvature than the second borderline 48 resulting in a transition area 44 with a varying width.

(16) The distribution area 42 is pressed with a distribution pattern of elongate distribution projections 64 (solid quadrangles) and distribution depressions 66 (dashed quadrangles) in relation to the central extension plane c-c, see FIG. 6. Only a few of these distribution projections and depressions are illustrated in the figures. The distribution projections 64 are divided into a number of projection sets, and the distribution projections of each projection set are arranged along a respective imaginary projection line 68 extending from the first distribution projection 70 of the projection set to the first borderline 46. FIG. 7 illustrates the cross section of the distribution projections 64 taken essentially perpendicular to the respective imaginary projection lines 68. The longest one of the projection lines 68 is the one closest to the outlet port hole 36 and it is denoted 72. The rest of the projection lines are all similar to a respective part of the longest projection line 72, which part extends from an end point 74 of the longest projection line. Thus, all the projection lines 68 are parallel. Also the third borderline 50 is parallel to the projection lines 68.

(17) Similarly, the distribution depressions 66 are divided into a number of depression sets, and the distribution depressions of each depression set are arranged along a respective imaginary depression line 76 extending from the first distribution depression 78 of the depression set to the first borderline 46. FIG. 8 illustrates the cross section of the distribution depressions 66 taken essentially perpendicular to the respective imaginary depression line 76. The longest one of the depression lines 76 is the one closest to the inlet port hole 34 and it is denoted 80. The rest of the depression lines are all similar to a respective part of the longest depression line 80, which part extends from an end point 82 of the longest depression line. Thus, all the depression lines 76 are parallel. Also the fourth borderline 52 is parallel to the depression lines 76. The longest depression line 80 and the longest projection line 72 are similar but mirror inverted with respect to the longitudinal center axis y.

(18) The imaginary projection lines 68 of the distribution projections 64 cross the imaginary depression lines 76 of the distribution depressions 66 in crossing points 71 to form a grid 73. The crossing point of each projection line 68 that is closest to the first borderline 46 is denoted 75 and arranged on an imaginary connection line 77 (illustrated dashed only in FIG. 6). The connection line 77 is parallel to the first borderline 46. As previously discussed, this contributes to a high strength of the heat transfer plate 8 at the transition between the distribution and transition areas 42 and 44, respectively. The distribution projections 64 of the heat transfer plate 8 are arranged to contact, along their complete extension, respective distribution depressions within the second end area of an overhead heat transfer plate while the distribution depressions 66 are arranged to contact, along their complete extension, respective distribution projections within the second end area of an underlying heat transfer plate. The distribution pattern is a so-called chocolate pattern.

(19) The transition area 44 is pressed with a transition pattern of alternately arranged transition projections 84 and transition depressions 86 (FIG. 9) in the form of ridges and valleys, respectively, in relation to the central extension plane c-c, which ridges and valleys all extend from the second borderline 48. In FIG. 4, the tops of these ridges are illustrated with imaginary extension lines 88 while the bottoms of these valleys (but just a few of them) are illustrated with imaginary extension lines 90. In FIGS. 5 and 6, for the sake of clarity, only the imaginary extension lines 88 of the ridges or transition projections 84 are illustrated. FIG. 9 illustrates the cross section of the transition projections 84 and the transition depressions 86 taken essentially perpendicular to the respective imaginary extension lines 88 and 90. Each of the extension lines 88 and 90 is similar to a respective part of the third borderline 50. More particularly, an extension line close to the first long side 24 of the heat transfer plate 8 is similar to an upper portion of the third borderline 50 while an extension line close to the second long side 26 is similar to a lower portion of the third borderline, and an extension line in the center of the heat transfer plate is similar to a center portion of the third borderline. Thus, the transition pattern is adapted to the distribution pattern which results in a relatively smooth transition between the distribution area 42 and the transition area 44 which in turn is beneficial to the fluid distribution across the heat transfer plate.

(20) The third borderline 50 comprises straight as well as curved portions which means that also the extension lines 88 and 90, and thus the transition projections 84 and the transition depressions 86, will comprise straight as well as curved portions. Further, the transition pattern is “divergent” meaning that the transition projections 84, and also the transition depressions 86, are non-parallel. More particularly, an angle α between the longitudinal center axis y and an imaginary straight line 92, which extends between two end points 94 and 96 of each transition projection 84 and transition depression 86 (illustrated for two of the transition projections in FIG. 4), varies between the transition projections and depressions and increases in a direction from the first long side 24 to a second long side 26 of the heat transfer plate 8. In other words, the transition projections 84 and transition depressions 86 are steeper close to the first long side than close to the second long side. As previously explained, this is beneficial to the fluid distribution across the heat transfer plate.

(21) The transition projections 84 comprise essentially point shaped transition contact areas 98 arranged for engagement with respective point shaped transition contact areas of the transition depressions within the second end area of an overhead heat transfer plate. This is illustrated in FIG. 6 where the bottom of these overhead transition depressions have been illustrated with imaginary extension lines 100. It should be stressed that FIG. 6 does not illustrate the engagement with the overhead heat transfer plate outside the transition and heat transfer areas. Similarly, the transition depressions 86 comprise essentially point shaped transition contact areas arranged for engagement with respective point shaped transition contact areas of the transition projections within the second end area of an underlying heat transfer plate (not illustrated). The transition pattern is a so-called herringbone pattern.

(22) The transition contact area of each transition projection 84 that is closest to the first borderline 46 is denoted 102 and arranged on an imaginary contact line 104 (illustrated dashed-dotted only in FIG. 6) which is parallel to the first borderline 46. As previously discussed, this contributes to a high strength of the heat transfer plate 8 at the transition between the distribution and transition areas 42 and 44, respectively.

(23) The heat transfer area 32 is divided into a number of heat transfer sub areas arranged in succession along the longitudinal center axis y of the heat transfer plate 8. A heat transfer sub area 106 adjoins the transition area 44 along the second borderline 48 and a heat transfer sub area 108 along a fifth borderline 110. The second and fifth borderlines are similar but mirror inverted with respect to an axis parallel to the transverse center axis x. Thus, the fifth borderline 110 is convex seen from the transition area 44. In line with what has been previously discussed, this contributes to a high strength of the heat transfer plate 8 at the transition between the heat transfer sub areas 106 and 108, respectively. As seen in FIG. 4, similar arched borderlines can be found also between the other heat transfer sub areas.

(24) The heat transfer sub areas are of two different types which are alternately arranged. Hereinafter, the heat transfer sub area 106 will be described with reference to FIGS. 4, 5, 6 and 10. It is pressed with a heat transfer pattern of alternately arranged essentially straight heat transfer projections 112 and heat transfer depressions 114 in the form of ridges and valleys, respectively, in relation to the central extension plane c-c. The heat transfer pattern of the first half 20 of the heat transfer plate and the heat transfer pattern of the second half 22 of the heat transfer plate 8 are similar but mirror inverted with respect to the longitudinal center axis y. Further, the heat transfer projections and depressions within the first half 20 are parallel meaning that also the heat transfer projections and depressions within the second half 22 are parallel. In FIGS. 4, 5 and 6 the tops of the heat transfer projections 112 are illustrated (bottoms not illustrated) with imaginary extension lines 117. FIG. 10 illustrates the cross section of the heat transfer projections 112 and the heat transfer depressions 114 taken perpendicular to the respective extension lines 117.

(25) The heat transfer projections 112 comprise essentially point shaped heat transfer contact areas 118 arranged for engagement with respective point shaped heat transfer contact areas of heat transfer depressions of an overhead heat transfer plate. This is illustrated in FIG. 6 where the bottom of these overhead heat transfer depressions have been illustrated with imaginary extension lines 120. As explained by way of introduction, since the heat transfer plate 8 has a medium-theta heat transfer pattern while the overhead heat transfer plate has a high-theta heat transfer pattern, the contact areas between the two heat transfer plates will be arranged along imaginary parallel straight lines 122 that are non-perpendicular to the longitudinal center axis y of the heat transfer plate 8. Thus, if the heat transfer plates had not been provided with transition areas, the strength of the heat transfer plates at the transition to the distribution area would have been relatively low. Similarly, the heat transfer depressions 114 comprise essentially point shaped heat transfer contact areas arranged for engagement with respective point shaped heat transfer contact areas of heat transfer projections of an underlying heat transfer plate (not illustrated). The heat transfer pattern is a so-called herringbone pattern.

(26) As apparent from the figures and especially FIG. 6, a first distance d1 between two adjacent ones of the transition projections 84 (or transition depressions 86) within the transition area 44 is smaller than a second distance d2 between two adjacent ones of the projection lines 68 (or depression lines 76) within the distribution area 42. As previously said, this means that the heat transfer capacity is larger within the transition area 44 than within the distribution area 42.

(27) As explained above, the plate heat exchanger 2 is arranged to receive two fluids for transferring heat from one fluid to the other. With reference to FIG. 4 and the heat transfer plate 8, the first fluid flows through the inlet port hole 34 to the back side (not visible) of the heat transfer plate 8, along a back side flow path through the distribution and transition areas of the first end area, the heat transfer area and the transition and distribution areas of the second end area and back through the outlet port hole 40. A back side main flow path through the distribution areas is defined by two adjacent imaginary depression lines. Similarly, the second fluid flows through an inlet port hole of an overhead heat transfer plate, which inlet port hole is aligned with the inlet port hole 38 of the heat transfer plate 8, to the front side of the heat transfer plate 8. Then, the second fluid flows along a front side flow path through the distribution and transition areas of the second end area, the heat transfer area and the transition and distribution areas of the first end area and back through an outlet port hole of the overhead heat transfer plate, which outlet port hole is aligned with the outlet port hole 36 of the heat transfer plate 8. A front side main flow path through the distribution areas is defined by two adjacent imaginary projection lines.

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

(29) As an example, the above specified distribution, transition and heat transfer patterns are just exemplary. Naturally, the invention is applicable in connection with other types of patterns. As an example, the projection lines, just like the depressions lines, of the distribution pattern need not be parallel but may diverge from each other. Moreover, the third and fourth borderlines delimiting the distribution and transition areas need not be similar to each other nor parallel to the projection and depression lines, respectively. Further, the first borderline between the distribution area and the transition area could coincide with the connection line on which the outermost crossing points of the distribution pattern are arranged.

(30) In the above described embodiment the curvature of the first borderline is determined by the locations of the imaginary crossing points of the distribution pattern. On the contrary, the curvature of the second borderline is determined by the borderlines between the heat transfer sub areas. The latter is to enable pressing of the heat transfer plate with a modular tool which is used to manufacture heat transfer plates of different sizes containing different numbers of heat transfer sub areas by addition/removal of heat transfer sub areas adjacent to the transition areas. Naturally, according to an alternative embodiment, the first and second borderlines could instead be parallel. Further, also the second borderline could be adapted to the locations of the contact areas within the transition and/or heat transfer patterns for increased strength of the heat transfer plate.

(31) Further, all or some of the first and second borderlines and the borderlines separating the heat transfer sub areas can have another form than a curved one, such as a wave form, a saw tooth form or a straight form.

(32) The above described plate heat exchanger is of parallel counter flow type, i.e. the inlet and the outlet for each fluid are arranged on the same half of the plate heat exchanger and the fluids flow in opposite directions through the channels between the heat transfer plates. Naturally, the plate heat exchanger could instead be of diagonal flow type and/or a co-flow type.

(33) Two different types of heat transfer plates are comprised in the plate heat exchanger above. Naturally, the plate heat exchanger could alternatively comprise only one plate type or more than two different plate types. Further, the heat transfer plates could be made of other materials than stainless steel. Finally, the present invention could be used in connection with other types of plate heat exchangers than gasketed ones, such as plate heat exchangers comprising permanently joined heat transfer plates.

(34) It should be stressed that the term “contact area” is used herein both to specify the areas of a single heat transfer plate that engage with another heat transfer plate, and the areas of mutual engagement between two adjacent heat transfer plates.

(35) 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 on another figure.