WO2002061357A1

WO2002061357A1 - A plate heat exchanger

Info

Publication number: WO2002061357A1
Application number: PCT/SE2002/000169
Authority: WO
Inventors: Ingvar Lindholm; Anders Knutsson
Original assignee: Alfa Laval Corporate Ab
Priority date: 2001-01-31
Filing date: 2002-01-30
Publication date: 2002-08-08
Also published as: SE518248C2; FI118140B; SE0100286D0; DE10295888T5; SE0100286L; FI20031115A; WO2002061357A8

Abstract

The present invention relates to a plate heat exchanger for transferring of heat between at least a first and a second medium. The plate heat exchanger comprises a first end plate (1), a plurality of intermediate plates (3) and a second end plate (2). The plates (1, 2, 3) are stacked on each other and designed such that they form a plat package, which comprises a first flow channel (5) with inlet and outlet openings (4) for the first medium and a second flow channel (6) with inlet and outlet openings (4) for the second medium. At least the first end plate (1) comprises a collar-shaped portion with an internal surface, which defines such an inlet or outlet opening (4) and may comprise a connection with a connection member (13). The internal surface of the collar-shaped portion (9) has an extension between a curved portion (11) and an ending edge portion (12) and the ending edge portion (12) is located at a shorter perpendicular distance from the second end plate (2) than the curved portion (11).

Description

A plate heat exchanger

BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates to a plate heat exchanger for transferring of heat between at least a first medium and a second medium, wherein the plate heat exchanger comprises a first end plate, a plurality of intermediate plates and a second end plate, which plates are stacked on each other and designed in such a way that they form a plate package comprising a first flow channel with inlet and outlet openings for the first medium and a second flow channel with inlet and outlet openings for the second medium and wherein at least the first end plate comprises a collar-shaped portion with an internal surface, which defines such an inlet or outlet opening.

Usually, such plate heat exchangers are used in different connections where there is desired to cool a liquid medium by another liquid medium. A connection member in the form of a con- nection conduit is usually connected to the inlet and the outlet openings in the end plates of the plate heat exchanger. Generally, the surfaces of the connection conduit has to be worked to a suitable design, for example by turning, for the achievement of a reliable connection between the connection conduit and a connection surface of the end plate. Such a connection is usually accomplished by brazing. Since the connection conduit has to be worked before it could be connected to the end plate, the cost for such a connection conduit is relatively high, which increases the cost for the plate heat exchanger.

Conventional openings in the end plates for receiving of connection conduits also have such a construction that molten solder, during the process for brazing the plates together, relatively easy may flow out. The solder, which flows out from the plate package, will usually come into contact with and solidifies on brazing fixtures, which lie between plate packages during the brazing process.

From SE 127 970, JP 6265289, GB 2 270 971 and WO 9859208 plate heat exchangers are known, which are provided with end plates with an outwardly directed collar-shaped portion, which defines an opening and comprises a connection surface to a connection conduit. By such an outwardly directed collar-shaped portion, no special treatment needs to be made of the connec- tion surfaces of the connection conduit for establishment of an acceptable connection between the connection conduit and the end plate. Connection conduits with substantially untreated connection surfaces may be used.

However, such outwardly directed collar-shaped parts of end plates result in certain disadvantages. During the brazing of the plates, molten solder located internally in the plate package may flow out through such an opening and solidify on the inside of the collar-shaped portion, which is intended to form a connec- tion surface to the connection conduit. Thereby, the opening risks to be obstructed such that a connection conduit can not be inserted through the opening. Furthermore, the collar-shaped portion forms a portion, which protrudes from the end plate, which results in that a fixture, which adjoins the end plate, dur- ing a brazing process, has to be provided with corresponding holes or stops. It is also difficult to pressure test the created brazed plate package since it is not easy to keep the end surface of the protruding collar-shaped portion in a perfectly plane position.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a plate heat exchanger, which has such a construction that it may be manu- factured with a high capacity but to a lower cost than conventional plate heat exchangers. This object is achieved by the plate heat exchanger of the initially mentioned kind, which is characterised in that the internal surface of the collar-shaped portion has an extension between a curved portion and an ending edge portion and that the ending edge portion is located at a shorter perpendicular distance from the second end plate than the first curved portion. Consequently, the plate heat exchanger is provided with an inwardly directed collar-shaped portion. By an inwardly directed collar- shaped portion, an upwardly directed barrier is obtained preventing possibly downwards flowing solder from reaching the opening during the process of brazing the plates together. Thereby, the risk is eliminated that such solder obstructs the opening. By such an inwardly directed collar-shaped portion, no portion protruding from the external surface of the end plate is neither obtained. Thereby, uncomplicated fixtures with plane surfaces may be used when said plate packages are to be brazed together. Thus, the fixtures do not need to be provided with holes or stops adapted to portions protruding from the plate package. Furthermore, by an inwardly directed collar-shaped portion, the following pressure test of the plate package is facilitated since the whole surface of the end plate up to the opening may be used to accomplish a tight surface with a pressure test member.

According to a preferred embodiment of the present invention, said connection is accomplished along substantially the whole internal surface of the collar-shaped portion. Thereby, a relatively large connection surface and a strong connection between the collar-shaped portion and a connection member may be accomplished. Advantageously, the connection member is a connection conduit but may also be a coupling member in which a connection conduit is attachable. Advantageously, the internal surface of the collar-shaped portion forms an angle of about 90° to the main extension plane of the first end plate. Thereby, a connection member in the form of a connection conduit may easy be applied in the collar-shaped portion. The internal surface of the collar-shaped portion may have an extension from 2 to 10 mm from the curved portion to the ending edge portion. By such a collar length, a sufficient surface is usually obtained in order to accomplish a safe and strong connection between the connection member and the collar-shaped portion.

According to another preferred embodiment of the present invention, said connection is accomplished by the supply of an additional material. By a suitable such additional material, a strong connection may, in a relatively simple manner, be accomplished between the connection member and the collar- shaped portion. Preferably, said connection is accomplished by brazing. After the connection member has been applied in the opening, a ring of solder is preferably applied to the end plate around the connection member. Thereafter, the plate heat exchanger is heated to such a temperature that the solder melts and flows out and connects the connection member and the collar-shaped portion. Alternatively, said connection may be ac- complished by welding or a suitable glue. Advantageously, said additional material is arranged to fill up a thin gap between the collar-shaped portion and the connection member. Advantageously, such a gap is about 0, 1 mm wide. Thereby, the filling material may obtain a substantially optimal distribution in the gap by the capillary effects.

According to another preferred embodiment of the present invention, said curved portion comprises a rounded surface. By such a rounded surface, a recess is formed in the end plate, which extends around the connection member. Such a recess constitutes a suitable application surface for the solder. Preferably, the rounded surface has such a curvature that said recess obtains a continuously increasing depth in the direction towards the connection member. The solder applied in the recess thereby flows along an inclined path in the direction towards the connection member. Thereby, substantially all solder may be used and applied at the intended place between the connection member and the inwards directed collar-shaped portion.

According to another preferred embodiment of the present in- vention, the collar-shaped portion has a thinner material thickness than the material in the rest of the end plate. Preferably, the collar-shaped portion is manufactured by pressing. For being able to obtain an acceptable collar length with a maintained surface quality, it is suitable if the collar-shaped portion has a relatively thin material thickness. Therefore, the collar-shaped portion of the end plate suitably has a 20-50% thinner material thickness than the material in the rest of the end plate.

According to another preferred embodiment of the present in- vention, at least one of the end plates is formed by two plates joined together, which each has a sheet thickness corresponding to the sheet thickness of the intermediate plates. For reasons of strength, the end plates must have a relatively rigid construction. Likewise, the collar-shaped portion ought not to be too thin. The design of end plates with inwardly directed collar- shaped portions of a sheet material having a similar thickness as the intermediate plates results in production technical savings. Advantageously, at least one of the end plates comprises the same material as the intermediate plates. Thereby, all plates in the plate package may be manufactured of the same original sheet material.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, preferred embodiments of the invention is described as examples with reference to the attached drawings, in which:

Fig 1 shows a perspective view of a plate heat exchanger according to a first embodiment, Fig 2 shows a cross-section through the plate heat exchanger in Fig 1 ,

Fig 3 shows a cross-section through a plate heat exchanger according to a second embodiment provided with con- nection conduits,

Fig 4 shows a cross-section through two plate heat exchangers according to a third embodiment during a brazing process,

Fig 5 shows a cross-section through a fourth embodiment of a plate heat exchanger and

Fig 6 shows a cross-section through a fifth embodiment of a plate heat exchanger.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

Fig 1 shows a plate heat exchanger according to the present invention. The plate heat exchanger comprises a first end plate 1 and a second end plate 2. A plurality of intermediate plates 3 are provided between the end plates 1 , 2. The plates 1 , 2, 3 are permanently joined together and stacked on each other such that they form a plate package. The first end plate 1 is provided with openings 4 for an inlet and an outlet, respectively, for a first medium. In a corresponding manner, the second end plate 2 is provided with openings 4, which are not visible in Fig 1 , for an inlet and an outlet, respectively, for a second medium.

Fig 2 shows a cross-section through the plate heat exchanger in Fig 1. The cross-section extends through openings 4 in each of the end plates 1 , 2. The end plates 1 , 2 and the intermediate plates 3 are stacked on each other and designed so that they form a plate package with an inner space, which comprises a first flow channel 5 for the first medium and a second flow channel 6 for the second medium. The first flow channel 5 extends between the openings 4 of the inlet and the outlet, respectively, for the first medium and the second flow channel 6 extends be- tween the openings 4 of the inlet and the outlet, respectively, for the second medium. The intermediate plates 3 are manufactured of a material having a high thermal conductivity such that an effective heat exchange between the flowing first and second mediums In the respective flow channels 5, 6 Is provided. Each of the intermediate plates 3 is provided with one or several corrugations extending vertically within an area restricted by two parallel first and second planes, respectively, which are located at a distance from each other and which both are substantially parallel with all the intermediate plates 3 as well as with the end plates 1 , 2 of the plate heat exchanger. The first plane is located nearer a first end plate in one end of the heat exchanger than the second plane and the second plane is located nearer a second end plate 2 in the other end of the heat exchanger than the first plane.

For reasons of strength, the end plates 1 and 2 usually comprise a larger material thickness than the intermediate plates 3. The openings 4 in the end plates 1 , 2 comprise an inwardly directed collar-shaped portion 9. The collar-shaped portion 9 comprises an internal surface 10, which defines an opening 4. The internal surface 10 has an extension between a curved portion 1 1 and an ending edge portion 12. Since the collar-shaped portion 9 is directed inwardly, the second edge portion 12 is thus located at a shorter perpendicular distance from the second end plate 2 than the curved portion 1 1. The internal surface 10 of the collar- shaped portion 9 forms an angle of about 90° to the main extension plane of the first end plate 1. In order to design, for example by pressing, a collar-shaped portion 9 with a satisfactory surface smoothness and collar length, the collar-shaped portion 9 comprises a thinner material thickness than the material in the rest of the end plate 1 , 2. The collar-shaped portion 9 of the end plates 1 , 2 has suitably a 20-50% thinner material thickness than the material in the rest of the end plates 1 , 2. Generally, a suitable collar length is within the range of 2 to 10 mm in order to accomplish a strong connection with a connection member. Fig 3 shows a plate heat exchanger according to a second embodiment. In this embodiment, the end plates 1 , 2 have a somewhat outwardly bulging shape. By such a bulging shape, an im- proved sealing is obtained especially when the first and the second media have a positive pressure in relation to the surroundings. The plate heat exchanger has here been provided with connection members in the form of connection conduits 13 for conveying the respective medium to and from the flow channels 5, 6 in the plate package. The collar-shaped portion 9 and the connection conduit 13 are dimensioned so that a thin gap is created therebetween in an assembled state. The gap has a size of about 0, 1 mm. Thereby, an additional material as molten solder obtains a good dispersion in the gap by the capillary effects. The curved portion 1 1 comprises a rounded surface. Thereby, an annular recess is formed extending around the connection conduit 13. The recess comprises a depth, which increases continuously in the direction towards the connection conduit 13.

After a connection conduit 13 has been placed in a collar- shaped portion 9, an additional material is applied, preferably, in the form of a ring of solder in the recess. Thereafter, the solder is heated such that it melts and flows down in the thin gap between the connection conduit and the collar-shaped portion 9. Consequently, the solder is distributed by the capillary effects in the thin gap between the connection conduit 13 and the collar- shaped portion 9. The remaining solder is retained and solidifies in the annular recess, which extends around the connection conduit 13. Hereby, a strong connection between relatively large surfaces of the connection conduit 13 and the collar-shaped portion 9 is obtained. By such a recess, it is also easy to apply the solder at the intended place at the same time as the molten solder is prevented to flow in the wrong direction out over the end plates 1 , 2. Fig 4 shows a manufacturing step where the end plates 1 , 2 and the intermediate plates 3 are joined together to a plate package. In this embodiment, the end plates 1 , 2 have a substantially plane external surface and the intermediate plates 3 have a de- sign adapted thereto. In order to join the end plates 1 , 2 and the intermediate plates 3 together to a plate package, they are stacked on each other. Solders are applied at suitable connection places between the plates 1 , 2, 3. A fixture 14 is provided between each stacked plate package. Fig 4 shows two stacked plate packages with an intermediate fixture 14. However, in practice a considerably larger number of plate packages and fixtures 14 are stacked on each other. Thereafter, the plate packages are introduced into an oven to be heated at least to a temperature at which the solder melts. The molten solder joins the abutting plates 1 , 2, 3 together to each other such that plate packages joined together in one piece are created.

It is from a plurality of aspects an advantage to use inwardly directed collar-shaped portions 9 instead of outwardly directed such ones during the brazing operation. With inwardly directed collar-shaped portions 9, no portion protruding from the end plates 1 , 2 is obtained. The fixtures 14, which are provided between two adjacent plate packages, may thereby have an uncomplicated construction with plane surfaces without recesses or stops. Furthermore, the inwardly directed collar-shaped portions 9 facilitate a following pressure test of the plate packages when the pressure test members tightly may be applied to substantially the whole surface of the end plates up to the openings 4. Finally, the inwardly directed collar-shaped portions 9 prevent a downwards flowing solder in the plate package from flowing out through the lower openings 4. The inwardly directed collar- shaped portion 9 forms a stop surface for the solder. In other cases, such flowing solder through the opening 4 may come into contact with and solidify on the underlying fixture 14. If the lower end plate 2 instead comprises an outwardly directed collar-shaped portion, such flowing solder will solidify on the inside of the collar and thereby prevent the insertion of a connection conduit.

Fig 5 shows a further embodiment of a plate heat exchanger. In this embodiment, the end plates 1 , 2 are formed by two thin plates 1 a, b, 2a, b, joined together, which each has a material thickness corresponding to the material thickness of the intermediate plates 3. The plates 1 a, b, 2a, b are manufactured of the same material as the intermediate plates 3. Thereby, the end plates 1 , 2 may be manufactured from one and the same sheet material as the intermediate plates 3. Thereby, the manufacturing process of the end plates 1 , 2 is simplified. The plates 1 a, b, 2a, b may during an initial manufacturing period go through one and the same pressing operation as the intermedi- ate plates 3. Thereafter, the intermediate plates 3 go through a hole providing operation in order to form holes for the first 5 and the second 6 flow channel. The plates 1 a, b, 2a, 2b included in the end plates 1 , 2 thereafter go through a hole providing operation in order to form said openings 4 whereafter the edges 4 of the openings go through a pressing operation such that the inwardly directed collar-shaped portions 9 are formed. An end plate, which comprise two such plates 1 a, b, 2a, b joined together, is less expensive to manufacture than a homogenous end plate 1 , 2 and may with a suitable dimensioning fulfil neces- sary requirements of strong. The collar-shaped portion 9 also comprises two such plates 1 a, b, 2a, b joined together and obtains thereby a sufficient strong for the connection of a connection conduit 13.

Fig 6 shows a further embodiment of a -plate heat exchanger with end plates 1 , 2, which comprise two thin plates 1 a, b, 2a, b joined together. The plates 1 a, b, 2a, b are manufactured from the same sheet material as the intermediate plates 3. In this case, the plate heat exchanger comprises three flow channels 5, 6, 15 for three different mediums. The collar-shaped parts 9 of the openings 4 of the flow channels 5, 6 are directed inwardly while the collar-shaped portions 16 of the opening 4 of the flow channel 15 is directed outwardly. In this case, it has been considered that the possibility to use substantially the same kind of end plates 1 a, b, 2a, b in the both ends has outweighed the disadvantage of an outwardly directed collar-shaped portion 16. By directing the outwardly directed collar-shaped portion 16 upwardly during the brazing process for the plate package, the risk is avoided that downwards flowing solder flows out through the corresponding opening 4.

The present invention is not in any way restricted to the above- described embodiments but may be modified freely within the scope of the claims. For example, the plate heat exchanger may only comprise one inwardly directed collar-shaped portion 9.

Claims

1. A plate heat exchanger for transferring of heat between at least a first medium and a second medium, wherein the plate heat exchanger comprises a first end plate (1 ), a plurality of intermediate plates (3) and a second end plate (2), which plates (1 , 2, 3) are stacked on each other and designed in such a way that they form a plate package comprising a first flow channel (5) with inlet and outlet openings (4) for the first medium and a second flow channel (6) with inlet and outlet openings (4) for the second medium and wherein at least the first end plate (1 ) comprises a collar-shaped portion (9) with an internal surface (10), which defines such an inlet or outlet opening (4), characterised in that the internal surface (10) of the collar-shaped portion (9) has an extension between a curved portion (1 1 ) and an ending edge portion (12) and that the ending edge portion (12) is located at a shorter perpendicular distance from the second end plate (2) than the first curved portion (1 1 ).

2. A plate heat exchanger according to claim 1 , characterised in that the internal surface of the collar-shaped portion (9) forms an angle of about 90° to the main extension plane of the first end plate (1 ).

3. A plate heat exchanger according to any one of the preceding claims, characterised in that the internal surface of the collar- shaped portion (9) has an extension from 2 to 10 mm from the curved portion (1 1 ) to the ending edge portion (12).

4. A plate heat exchanger according to any one of the preceding claims, characterised in that the internal surface (10) of the collar-shaped portion (9) comprises a connection with a connection member (13).

5. A plate heat exchanger according to claim 4, characterised in that said connection is provided along substantially the whole internal surface (10) of the collar-shaped portion (9).

6. A plate heat exchanger according to claim 4 or 5, characterised in that said connection is provided by the supply of an additional material.

7. A plate heat exchanger according to claim 6, characterised in that said connection is provided by brazing.

8. A plate heat exchanger according to claim 6, characterised in that said connection is provided by welding.

9. A plate heat exchanger according to any one of the preceding claims 6-8, characterised in that the additional material is arranged to fill up a thin gap between the collar-shaped portion (9) and the connection member (13).

10. A plate heat exchanger according to any one of the preceding claims, characterised in that said curved portion (11 ) comprises a rounded surface.

1 1. A plate heat exchanger according to any one of the preced- ing claims, characterised in that the collar-shaped portion (9) has a thinner material thickness than the material in the rest of the end plate (1 ).

12. A plate heat exchanger according to claim 1 1 , characterised injhat the collar-shaped portion (9) has a 20-50% thinner material thickness than the material in the rest of the end plate (1 ).

13. A plate heat exchanger according to any one of the preceding claims, characterised in that at least one of the end plates (1 , 2) is formed of two plate-shaped pieces joined together, which each has a sheet thickness corresponding to the sheet thickness of the intermediate plates (3).

14. A plate heat exchanger according to any one of the preceding claims, characterised in that at least one of the end plates (1 , 2) is made of the same material as the intermediate plates (3).