PLATE HEAT EXCHANGER AND METHOD FOR MANUFACTURING A PLATE HEAT EXCHANGER

Abstract

The plate heat exchanger and method for manufacturing a plate heat exchanger comprise a stack of heat transfer plates, with first and second flow channels arranged between the plates. Pairs of heat transfer plates form cells. A cell comprises inner spacing elements arranged between the heat transfer plates leaving open a first inlet opening and a first outlet opening for the one of the fluids. The cell also comprises outer spacing elements welded to the heat transfer plates on the sides of the heat transfer plates facing away from each other. The cells are stacked against each other and joined together by welding via the outer spacing elements. The plate heat exchanger further comprises cover plates for covering sides of the stack of heat transfer plates with interruption for an inlet port section formed by the first inlet openings and an outlet port section formed by the first outlet openings. The two first sides of the cell comprising the first inlet opening or the first outlet opening comprise leakage passageways provided between the heat transfer plates for the one of the fluids, in addition to the passages provided by the first inlet opening and the first outlet opening.

Claims

1. Plate heat exchanger comprising a stack of heat transfer plates, each heat transfer plate extending in a general plane and comprising four edge parts, wherein first and second flow channels are arranged between the plates, with every first flow channel for a through-flow of a first fluid and every second flow channel for a through-flow of a second fluid, the first flow channels for one of the fluids are via first inlet openings and first outlet openings connectable to an inlet port and an outlet port, wherein pairs of heat transfer plates form cells, a cell comprising inner spacing elements arranged between the heat transfer plates, the inner spacing elements extending along the four edge parts leaving open a first inlet opening and a first outlet opening for the one of the fluids, outer spacing elements welded to at least one of the heat transfer plates on at least one of the sides of the heat transfer plates facing away from each other, along at least two of the four edge parts, wherein the cells are stacked against each other and joined together by welding via the outer spacing elements; the plate heat exchanger further comprising cover plates for covering sides of the stack of heat transfer plates, the cover plates covering first two sides of the stack of heat transfer plates with interruption for an inlet port section formed by the first inlet openings and for an outlet port section formed by the first outlet openings, wherein first two sides of the cell comprising the first inlet opening or the first outlet opening comprise leakage passageways provided between the heat transfer plates for the one of the fluids, the leakage passageways being provided in addition to the passages provided by the first inlet opening and the first outlet opening.

2. Plate heat exchanger according to claim 1, wherein the leakage passageways are arranged between the heat transfer plates and the inner spacing elements along the two edge parts of the heat transfer plates of the first two sides of the cell comprising the first inlet opening or first outlet opening.

3. Plate heat exchanger according to claim 1, wherein the leakage passageways in the first two sides of the cell each have a size such that in combination with the cover plates covering said first two sides of the cell, a leakage amount through the leakage passageways of each of the first two sides has a maximum of 1 percent of a flow volume of the one of the fluids through the corresponding first inlet opening or first outlet opening arranged in said first two sides of the cell.

4. Plate heat exchanger according to claim 1, wherein the outer spacing elements are welded to the at least one heat transfer plate by welding energy supplied in a direction parallel to the general plane, the plate heat exchanger comprising weld joints between the at least one heat transfer plate along the edge parts and the outer spacing elements.

5. Plate heat exchanger according to claim 1, wherein the outer spacing elements are welded to each other by supplying welding energy in a direction parallel to the general plane comprising weld joints between the outer spacing elements along edge parts of the outer spacing elements.

6. Plate heat exchanger according to claim 1, wherein the heat transfer plates have a thickness in a range between 50 micrometer and 300 micrometer.

7. Plate heat exchanger according to claim 1, wherein the outer spacing elements have a thickness in a range between 0.3 millimeter and 3 millimeter.

8. Plate heat exchanger according to claim 1, wherein the inner spacing elements arranged between the heat transfer plates on the first two sides of the cell comprising the first inlet opening or first outlet opening comprise a predefined flexibility in a direction perpendicular to the direction of the general plane.

9. Plate heat exchanger according to claim 1, wherein the inner spacing elements are corrugated sheets.

10. Plate heat exchanger according to claim 8, wherein the inner spacing elements arranged between the heat transfer plates on the first two sides of the cell comprising the first inlet opening or first outlet opening have a height, which is larger than the height of the inner spacing elements arranged on second two sides of the cell not comprising the first inlet opening or the first outlet opening.

11. Method for manufacturing a plate heat exchanger comprising a stack of heat transfer plates, comprising the steps of: arranging heat transfer plates in a stack, each heat transfer plate extending in a general plane and comprising four edge parts, providing first flow channels and second flow channels between the heat transfer plates, with every first flow channel for a through-flow of a first fluid and every second flow channel for a through-flow of a second fluid, forming cells by pairs of heat transfer plates, and by arranging inner spacing elements between the heat transfer plates of a cell, the inner spacing elements extending along the four edge parts of the heat transfer plates leaving open a first inlet opening and a first outlet opening for the one of the fluids, and further by providing outer spacing elements and welding the outer spacing elements to at least one of the heat transfer plates on at least one of the sides of the heat transfer plates facing away from each other, along at least two of the edge parts; stacking the cells against each other and joining the cells by welding the outer spacing elements; providing cover plates and covering sides of the stack of heat transfer plates, thereby covering first two sides of the stack of heat transfer plates with interruption for an inlet port section formed by the first inlet openings and for an outlet port section formed by the first outlet openings, welding together the heat transfer plates and the inner spacing elements on second two sides of the cell not comprising the first inlet opening or first outlet opening, and providing leakage passageways between the heat transfer plates in the first two sides of the cell for the one of the fluids in addition to the passages of the first inlet opening and the first outlet opening by not welding together the heat transfer plates and the inner spacing elements on the first two sides of the cell comprising the first inlet opening or first outlet opening.

12. Method according to claim 11, wherein the step of welding together the heat transfer plates and the inner spacing elements on second two sides of the cell not comprising the first inlet opening or first outlet opening comprises supplying welding energy in a direction parallel to the general plane to produce weld joints between two edge parts of the heat transfer plates and the inner spacing elements.

13. Method according to claim 11, further comprising the step of welding together the heat transfer plates and the outer spacing elements by supplying welding energy in a direction parallel to the general plane to produce weld joints between edge parts of the heat transfer plates and the outer spacing elements.

14. Method according to claim 11, further comprising the step of providing a pressing force onto edge parts of the heat transfer plates, thereby pressing inner spacing elements, heat transfer plates and outer spacing elements against each other.

15. Method according to claim 14, wherein the step of providing a pressing force onto edge parts of the heat transfer plates comprises providing flexible inner spacing elements.

16. Method according to claim 12, further comprising the step of welding together the heat transfer plates and the outer spacing elements by supplying welding energy in a direction parallel to the general plane to produce weld joints between edge parts of the heat transfer plates and the outer spacing elements.

17. Method according to claim 12, further comprising the step of providing a pressing force onto edge parts of the heat transfer plates, thereby pressing inner spacing elements, heat transfer plates and outer spacing elements against each other.

18. Plate heat exchanger according to claim 4, wherein the outer spacing elements are welded to each other by supplying welding energy in a direction parallel to the general plane comprising weld joints between the outer spacing elements along edge parts of the outer spacing elements.

19. Plate heat exchanger according to claim 2, wherein the inner spacing elements arranged between the heat transfer plates on the first two sides of the cell comprising the first inlet opening or first outlet opening comprise a predefined flexibility in a direction perpendicular to the direction of the general plane.

20. Plate heat exchanger according to claim 4, wherein the inner spacing elements arranged between the heat transfer plates on the first two sides of the cell comprising the first inlet opening or first outlet opening comprise a predefined flexibility in a direction perpendicular to the direction of the general plane.

Description

[0077] The invention is further described with regard to embodiments, which are illustrated by means of the following drawings, wherein:

[0078] FIG. 1 shows a schematic arrangement of a plate heat exchanger;

[0079] FIG. 2 shows elements of a cell of a plate heat exchanger;

[0080] FIG. 3 schematically illustrates an arrangement of elements of a plate heat exchanger;

[0081] FIG. 4 is an excerpt of the arrangement of FIG. 3;

[0082] FIG. 5 illustrates a cross-section through an embodiment of a heat exchanger set-up with welding details;

[0083] FIG. 6 illustrates a cross-section through another embodiment of a heat exchanger set-up with welding details.

[0084] FIG. 1 shows a plate heat exchanger 1 comprising a stack of rectangular heat transfer plates 4 divided by spacing elements to form channels in between the heat transfer plates 4. In the stack of the heat exchanger shown in FIG. 1, the rectangular plates are arranged vertically. For example, 20 to 30 plates may be arranged above or next to each other to form a stack.

[0085] A first fluid, preferably a cooling gas, may enter the stack 53 at a first inlet port section 18 on a first one of two first sides of the stack. After having passed the stack by flowing through first channels, the first fluid 11 may leave the heat exchanger at the opposite second one of the two first sides (in the figure to the back).

[0086] A second fluid 12, preferably a hot gas, may enter the stack at a second inlet port section 13 on a first one of two second sides of the stack. After having passed the stack by flowing through second channels, the second fluid 12 may leave the heat exchanger at the opposite second one of the two second sides or a bottom side in FIG. 1.

[0087] A first cover plate 16 covers the first one of the two first sides of the heat exchanger but for the inlet port section 18 arranged versus a first top end of the heat exchanger. The first outlet port section (not shown) is constructed likewise but on the opposite side of the heat exchanger versus a bottom end of the stack. This cover plate set-up may be used for embodiments of a heat exchanger, where an open inner spacing element, such as a corrugated sheet, is arranged along entire first sides of the heat exchanger. The sizes of the inlet and outlet port sections are then mainly defined by the arrangement of the cover plate. This cover plate set-up may be also be used for embodiments of the heat exchanger, where no spacing element or an open inner spacing element, such as a corrugated sheet, is solely arranged in the inlet or outlet openings, that is, along a portion of the first sides of the heat exchanger only. The inlet and outlet port sections are then mainly defined by the inlet and outlet openings. The first cover plate 16 (and opposite side of the stack accordingly) covers about ⅔ or ⅘ of the first one side of the stack.

[0088] The second inlet port section 13 extends over the entire top of the heat exchanger 1 and the second outlet port section (not shown) extends over the entire bottom of the heat exchanger 1. The first and the second fluid are guided in alternating first and second channels through the stack and in the application described essentially parallel to each other.

[0089] Cover plates 15 entirely cover two third sides of the stack. The bottom and top of the stack may be provided with collars 17 for application of corresponding collectors.

[0090] Preferably, the cover plates 15,16 are welded together and to the stack along edge or corner parts 14. The cover plates 15 on the two third sides are welded along their four edge parts 14. The cover plates 16 on the two first sides are welded along three edge parts 14 but preferably not along the edge part forming the first inlet or outlet port sections 18.

[0091] In the exploded view of FIG. 2 a simplified cell is shown, which cell may be used to form a plate heat exchanger by stacking several cells above or next to each other if provided by a further heat transfer plate (which has been omitted from the drawing).

[0092] Spacing elements in the form of straight rectangular spacers 31, for example stainless steel spacers in particular austenitic high temperature steel spacers, are arranged on a top side of a heat transfer plate 4 and along the entire edges of two opposite first sides 110 of the heat transfer plate 4. The two opposite second sides 111 on the top of the heat transfer plate 4 are not provided with spacing elements and form corresponding inlet and outlet openings 13 for a second fluid to be guided along the top side of the heat transfer plate 4. The spacers have a height of, for example, 0.5 millimeter and are a half of a double-spacer.

[0093] L-shaped rectangular spacing elements 21, for example L-shaped stainless steel spacers in particular austenitic high temperature steel spacers are arranged along the entire two opposite second sides 111 on the bottom of the heat transfer plate 4, as well as along a portion of the two opposite first sides 110 on the bottom of the heat transfer plate 4. The remaining portions along the edges of the first two sides form a first inlet opening section 18 and a first outlet opening section (not shown) for a first fluid to be guided into and out of the first channel formed along the bottom side of the heat transfer plate 4. Heat transfer between the first and the second fluids occurs through the heat transfer plate 4, preferably a high corrosion resistant material, for example a nickel-based high corrosion resistant material, for example Inconel® 617, 602 or 693. Preferably, the thickness of the heat transfer plate is below 250 micrometer. The thickness of the heat transfer plates is preferably about 150 micrometer.

[0094] In the first inlet opening 180 and the first outlet opening an open spacing element in the form of a corrugated sheet 20 is arranged. The corrugated sheet 20 and the L-shaped spacing element 21 may be integrally formed, formed in one piece or may be separate spacing elements. The corrugated sheet 20 provides sufficient openings for a fluid flow to pass through without causing inacceptable high back pressure. The corrugated sheet serves as spacer also in the inlet and outlet opening section. In addition, the corrugated sheet comprises a certain flexibility and compressibility such that upon applying a force from above and below onto the cell, the corrugated sheet applies a corresponding compressing force onto above and below lying edge portions of the cell or of a stack. The close positioning of the elements guarantee a secure welding and allow application of a minimum and very localized welding energy. Preferably, also the L-shaped spacing element 21 on the two sides comprising the first inlet or outlet opening 180 may apply a force onto above and below lying edge portions of the cell. By this, a pressing force may be applied along the entire two opposite edge parts of the heat transfer plate 4.

[0095] The L-shaped spacing element 21 on the two sides comprising the first inlet or outlet opening 180 may, for example be made of a slightly compressible material.

[0096] Preferably, the height of the corrugated sheet 20 and the L-shaped spacing element 21 on the two sides comprising the first inlet or outlet opening 180 are preferably about 5 percent higher than the L-shaped spacing element 21 on the two sides not comprising the first inlet and outlet opening. By this an about 5 percent compression of the spacing elements on the two sides comprising the first inlet and outlet opening 180 may be achieved.

[0097] The corrugated sheet 20 as well as the L-shaped spacing element 21 are not welded to the heat transfer plate 4 on the two first sides 110 comprising the inlet or outlet opening 180. On the two second sides 111 (not comprising the inlet and outlet opening 180) the spacing element 21 is welded in a fluid-tight, preferably gas-tight manner to the heat transfer plate 4. Also the spacing element 31 on the top of the heat transfer plate is welded to the heat transfer plate in a fluid-tight, preferable gas-tight manner.

[0098] The welding is performed in the plane of the heat transfer plate, providing very narrow welds along the edge parts of the heat transfer plates and the respective spacing elements.

[0099] The first and second fluid may be at atmospheric pressure or may be pressurized. Preferably, both fluids are at atmospheric pressure. However, one fluid may be at atmospheric pressure and the other fluid may be pressurised, for example with 2, 3 or 4 bar. Experiments have shown that a pressure in this range or pressure differences between fluids in this range has no or no noticeable influence on the amount of leakage fluid passing through the leakage passageways created by the non-welding of some elements and thus has no or no significant negative influence onto a performance of the plate heat exchanger.

[0100] In FIG. 3 an exemplary small stack, basically a double cell, is shown, wherein the same or similar elements are provided with the same reference numbers as in FIG. 2. In the embodiment of FIG. 3 the inlet opening 190 and outlet opening 191 for the second fluid 12 as well as the inlet opening 180 and outlet opening 181 for the first fluid 11 is provided with a spacing element in the form of a corrugated sheet 30, 20. The corrugated sheets 20 forming the first inlet 180 and first outlet 181 extend only along a portion of the edge parts of the heat transfer plate on the two opposite first sides 110. The corrugated sheets 30 forming the second inlet 190 and second outlet 191 extend along the entire edge parts of the heat transfer plate on the two opposite second sides 111 of the heat transfer plate 4. The ‘entire’ edge part of the plate is herein understood to also include the entire edge part minus the width of spacing elements arranged along the other two opposite sides of the heat transfer plate 4.

[0101] Exemplary dimensions of a heat transfer plate are preferably between 100 millimeter and 300 millimeter parallel to a flow direction and between 100 millimeter and 400 millimeter perpendicular to the flow direction.

[0102] In FIG. 4 an edge portion of the stack of FIG. 3 is shown in an enlarged view. Again the same reference numbers are used for the same or similar elements. The cover plate 15 forms the one side of the stack. A heat transfer plate 4 is arranged next to the cover plate 15. On the next level, a second side 111 is closed by a spacer 21 welded through horizontal welding to the heat transfer plate 4 above and below the spacer 21. The first side 110 is open and provided with a corrugated sheet 20, which may extend over the inlet opening 180 (or outlet opening 181) only as in the example of FIG. 3, or may also extend along the entire first side 110. This first channel is closed by the next heat transfer plate. In a further layer the first side 110 is closed by a spacer 31, while the second side 111 is open and provided with a corrugated sheet 30. This second channel is closed again by a further heat transfer plate 4. The spacer 31 of the further layer is welded in a horizontal manner to this further heat transfer plate 4.

[0103] The next level is a repetition of the first channel and formed accordingly, while the level after the next is a repetition of the second channel.

[0104] Between the spacers 31 and the heat transfer plates 4 weld joints are provided along the edge parts along an entire side of the heat transfer plate. Weld joints are also provided between spacers 21 and the heat transfer plate 4 on the second sides 111 of the stack not comprising the first inlet or outlet opening 180, 181.

[0105] No weld joints are provided between the corrugated sheets 20, 30 and the heat transfer plates 4. Also no weld joints are provided between the heat transfer plates 4 and the spacers (see FIG. 3) on the first sides 110 of the stack comprising the first inlet or first outlet opening 180, 181 such that leakages passageways are formed between said non-welded corrugated sheets 20, 30 or spacers 21 and heat transfer plates 4.

[0106] In FIG. 4 the spacers 31 of the second fluid channel are part of a double spacer defining the distance 300 of two heat transfer plates 4 and the height of the second channel. Preferably, the double spacer is formed upon stacking cells to each other each cell having a spacer 31 arranged on its outside.

[0107] In the cross-sectional view of FIG. 5 an alternating arrangement of spacing elements 22, 32 and heat transfer plates 4 is shown. The inner spacing element 22 is not welded to the heat transfer plates 4 arranged adjacent to the inner spacing element 22. Thus between the inner spacing element 22 and the heat transfer plate 4 a leakage passageway 101 is formed, where a small leakage flow 100 may exit the flow channel 25.

[0108] The outer spacing elements 32 are welded to and along the edges of the heat transfer plates 4 as is indicated by weld joints 50. These weld joints 50 are created by supplying welding energy in a direction parallel to the plane of the heat transfer plates 4, and preferably at the position of the interface between outer spacing element 32 and heat transfer plate 4.

[0109] The cover plate 16 covers the side of the stack and hinders the leakage flow 100 to leave the heat exchanger. Due to the gas-tight welding between outer spacing elements 32 and heat transfer plates 4 no communicating path exists between first flow channel 25 and second flow channel 26 or between a respective first fluid flow and a second fluid flow. Thus, the amount of leakage flow 100 leaving a first channel 25 may only enter back into the same or another first channel or possibly leave the stack through a first outlet opening provided for the first fluid to leave the stack.

[0110] The inner spacing element 22 has, for example, by its shape or material a certain elasticity. This elasticity allows to slightly compress the inner spacing element 22 when a force is applied onto the spacing element 22 in a direction perpendicular to the stack (from above and below in the drawing). By compressing the inner spacing element 22 the same amount of compressing force 220 is applied to the heat transfer plates 4 above and below the inner spacing element 22. By this, the heat transfer plates 4 are pushed against the outer spacing elements 32, forming a tight contact between them, which supports a proper welding.

[0111] In the embodiment of FIG. 5, first and second channels 25, 26 have about a same height, which height is defined by the thickness of the spacing elements 22, 32. Preferably, such a thickness is about 1 millimeter, while the thickness of the heat transfer plates 4 is preferably about 150 micrometer. To weld the heat transfer plates 4 to the outer spacing elements 32, preferably laser welding is used, with a laser spot diameter of about 40 to 50 micrometer.

[0112] In the cross-sectional view of FIG. 6 an arrangement of an inner spacing element 22, two outer spacing elements 31 with heat transfer plates 4 is shown. The inner spacing element 22 may be the same as in FIG. 5 and is not welded to the heat transfer plates 4 arranged next to the inner spacing element 22. Again, between inner spacing element 22 and the heat transfer plates 4 a leakage passageway 101 forms, where a small leakage flow 100 may exit the flow channel 25. For simplicity reasons the cover plate is not shown.

[0113] The outer spacing elements 31 are again welded by horizontal welding to and along the edge parts of the heat transfer plates 4 as indicated by weld joint 50.

[0114] In the embodiment of FIG. 6, first and second channels 25, 26 have about a same height, which height is defined by the thickness of the spacing element 22 and the two spacing elements 31. Preferably, such a thickness is about 1 millimeter, while the thickness of the heat transfer plate is preferably about 150 micrometer. However, the height of the second channel 26 is formed by a double spacer formed by two outer spacing elements 31 welded together as indicated by weld joint 51. Preferably, the outer spacing elements 31 are identical spacers having a same height. Such an embodiment may facilitate manufacturing of a plate heat exchanger. Individual cells 2 comprising an inner spacing element 22 between two heat transfer plates 4, as well as one outer spacer 31 welded to opposite sides of each of the heat transfer plates 4 may be pre-manufactured. A desired plurality of such cells 2 may then be stacked and welded to each other by welding the outer spacing elements 31. Only one kind of cell may be pre-manufactured, not requiring changes in a production process or selection upon stacking cells.

[0115] By the pre-manufacturing, the welding between thin heat transfer plates 4 and thick spacing elements 22, 31 requiring precise alignment and welding may be performed in advance. A single cell 2 only comprises few components that need to be aligned and kept in position during welding.

[0116] The welding between two thicker outer spacing elements 31 may then also be performed using other welding techniques or using laser welding but possibly using larger focus diameters.

[0117] As may well be seen in FIGS. 5 and 6, the horizontal welding or welding in a direction of the general plane of a heat transfer plate does not or only to a very limited extent cause bulging or deformation of the welded elements and causes no undesired weld material in between to be welded elements. Additional weld material due to the melting of the materials of the plate and spacing elements—if produced at all—extends to the side of the stack, extending into a gap between cells 2 and cover plate 16.

[0118] Preferably, the inner spacing element 22 also has a certain elasticity in the direction perpendicular to the plane of the heat transfer plate 4 for applying a certain pressing force 220 onto the heat transfer plates 4 and outer spacing elements 31 to support welding between the outer spacing elements 31 and the heat transfer plates 4.

[0119] Before horizontal welding is applied along parts of an edge or along an entire edge, small weld spots may be applied between a heat transfer plate and an inner or outer spacing element. Such small weld spots may prevent misalignment of the elements of a cell or of a stack before being fixed to each other.