Method of making a plate package for a plate heat exchanger

Abstract

A plate package made according to the method includes first heat exchanger plates and second heat exchanger plates. Each heat exchanger plate has a first porthole, and the port hole of at least one of the heat exchanger plates is surrounded by a peripheral rim. The first heat exchanger plates and the second heat exchanger plates, are joined to each other and arranged side by side in such a way that the peripheral rims together define an inlet channel extending through the plate package. The peripheral rim of the first and/or the second heat exchanger plates has at least one through hole, forming a fluid passage allowing a communication between the inlet channel and the first plate interspaces. The at least one through hole is made in a condition in which the first and the second heat exchanger plates have been joined to each other to form the plate package.

Claims

1. A method of making a plate package for a plate heat exchanger, the method comprising; providing a number of first heat exchanger plates and a number of second heat exchanger plates, each heat exchanger plate having a first porthole, wherein said port hole of at least one of the heat exchanger plates is surrounded by a peripheral rim, arranging the first heat exchanger plates and the second heat exchanger plates side by side in an alternating order in which, the peripheral rims together define an inlet channel extending through the first and the second heat exchanger plates, joining said first and second heat exchanger plates with each other to form the plate package, and making, in a condition in which the first and the second heat exchanger plates have been joined to each other, at least one through hole in the peripheral rim of at least one of the first heat exchanger plate and the second heat exchanger plate.

2. A method of making a plate package according to claim 1, wherein the at least one through hole is made by a thermal process using a laser beam process, an electron beam process or a plasma process.

3. A method of making a plate package according to claim 1, wherein the at least one through hole is made by a mechanical process using a punching process or a drilling process.

4. A method of making a plate package for a plate heat exchanger, the method comprising: arranging a plurality of first heat exchanger plates and a plurality of second heat exchanger plates side by side in an alternating order, each heat exchanger plate including a first porthole surrounded by a flanged portion of the respective heat exchanger plate to form a peripheral rim, the arranging of the plurality of first and second heat exchanger plates comprising arranging the first and second heat exchanger plates so that the peripheral rims together define an inlet channel extending through the first and the second heat exchanger plates; joining the first and second heat exchanger plates with each other to produce the plate package in which first and second plate interspaces are formed in an alternating order between adjacent pairs of the first and second heat exchanger plates; and forming a through hole in the peripheral rim of several of the first heat exchanger plates to form a fluid passage in the peripheral rim of each of the several first heat exchanger plates that allows communication between the inlet channel and the first plate interspaces, the forming of the through hole in the peripheral rim of several of the first heat exchanger plates occurring after the first and the second heat exchanger plates have been joined to each other.

5. A method of making a plate package according to claim 4, wherein the through holes are made by a thermal process using a laser beam process, an electron beam process or a plasma process.

6. A method of making a plate package according to claim 4, wherein the through holes are made by a mechanical process using a punching process or a drilling process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example, with reference to the accompanying schematic drawings, in which

(2) FIG. 1 discloses schematically a side view of a typical plate heat exchanger.

(3) FIG. 2 discloses schematically a front view of the plate heat exchanger in FIG. 1.

(4) FIG. 3 discloses schematically a cross section of an inlet or outlet channel of a plate heat exchanger.

(5) FIG. 4 discloses highly schematically the front side of a typical first heat exchanger plate.

(6) FIG. 5 discloses highly schematically the front side of a typical second heat exchanger plate.

(7) FIG. 6-9 disclose four different embodiments of a cross section of the inlet channel of a plate package according to the invention.

(8) FIG. 10-11 disclose highly schematically two additional embodiments of a part of a cross section of the inlet channel of a plate package according to the invention.

(9) FIG. 12 discloses highly schematically the invention applied to a so called semi-welded or semi-bonded plate package.

DETAILED DESCRIPTION

(10) FIGS. 1 to 3 disclose a typical example of a plate heat exchanger 1. The plate heat exchanger 1 includes a plate package P, which is formed by a number of heat exchanger plates A, B, which are provided side by side of each other. The plate heat exchanger 1 comprises two different types of heat exchanger plates, which in the following are called the first heat exchanger plates A, see FIGS. 3 and 4, and the second heat exchanger plate B, see FIGS. 3 and 5. The plate package P includes substantially the same number of first heat exchanger plates A and second heat exchanger plates B. As is clear from FIG. 3, the heat exchanger plates A, B are provided side by side in such a way that a first plate interspace 3 is formed between each pair of adjacent first heat exchanger plates A and second heat exchanger plates B, and a second plate interspace 4 between each pair of adjacent second heat exchanger plates B and first heat exchanger plates A.

(11) Every second plate interspace thus forms a respective first plate interspace 3 and the remaining plate interspaces form a respective second plate interspace 4, i.e. the first and second plate interspaces 3, 4 are provided in an alternating order in the plate package P. Furthermore, the first and second plate interspaces 3 and 4 are substantially completely separated from each other.

(12) A plate heat exchanger 1 may advantageously be adapted to operate as an evaporator in a cooling agent circuit, not disclosed. In such an evaporator application, the first plate interspaces 3 may form first passages for a first fluid being a refrigerant whereas the second plate interspaces 4 may form second passages for a second fluid, which is adapted to cooled by the first fluid.

(13) The disclosed plate package P is provided with an upper end plate 6 and a lower end plate 7, which are provided on a respective side of the plate package P.

(14) In the embodiment disclosed, the heat exchanger plates A, B and the end plates 6, 7 are permanently joined to each other. Such a permanent joining may advantageously be performed through brazing, welding, adhesive or bonding. During joining by means of brazing a suitable number of heat exchanger plates are typically stacked on each other with a solder (not shown) in the shape of a thin sheet, disc or paste located between adjacent heat exchanger plates A, B, and subsequently the whole plate package P is heated in an oven until said solder melts. This will result in a permanent joint between bearing contact surfaces.

(15) As appears from especially FIGS. 2, 4 and 5, substantially each heat exchanger plate A, B has four portholes 8. The first portholes 8 form a first inlet channel 9 to the first plate interspaces 3, which extends through substantially the whole plate package P, i.e. all plates A, B and the upper end plate 6. The second portholes 8 form a first outlet channel 10 from the first plate interspaces 3, which also extends through substantially the whole plate package P, i.e. all plates A, B and the upper end plate 6. The third portholes 8 form a second inlet channel 11 to the second plate interspaces 4, and the fourth portholes 8 form a second outlet channel 12 from the second plate interspaces 4. Also these two channels 11 and 12 extend through substantially the whole plate package P, i.e. all plates A, B and the upper end plate 6. The four portholes 8 are in the disclosed embodiment provided in the proximity of a respective corner of the substantially rectangular heat exchanger plates A, B. It is however to be understood that other positions are possible, and the invention should not be limited to the illustrated and disclosed positions.

(16) In a central area of each heat exchanger plate A, B there is an active heat transfer area 18, which is provided with a corrugation 19 of ridges and valleys in a manner known per se. The heat transfer area 18 may of course have other kinds of patterns or even no pattern at all.

(17) Now turning to FIG. 6, a first embodiment of a plate package P according to the invention will be discussed. More precisely, FIG. 6 discloses a portion in and around the first inlet channel 9. In line with the prior art plate heat exchanger discussed above, a plurality of heat exchanger plates A, B are provided side by side in such a way that a first plate interspace 3 is formed between each pair of adjacent first heat exchanger plates A and second heat exchanger plates B, and a second plate interspace 4 between each pair of adjacent second heat exchanger plates B and first heat exchanger plates A. Every second plate interspace thus forms a respective first plate interspace 3 and the remaining plate interspaces form a respective second plate interspace 4. Thus, the first and second plate interspaces 3, 4 are provided in an alternating order in the plate package P. Furthermore, the first and second plate interspaces 3 and 4 are substantially completely separated from each other.

(18) Each first porthole 8 of each heat exchanger plate A, B may be surrounded by a peripheral rim 20 in the form of a flanged portion 21 integrally formed with the respective heat exchanger plate A, B. Thus, the peripheral rim 20 is formed while forming the heat exchanger plate as such. It is to be understood that the peripheral rim 20 equally well may be a rim shaped item which is permanently joined with the heat exchanger plate. Such joining may be made while joining the heat exchanger plates A, B to form the plate package P. The joining may also be made as a separate step before stacking the heat exchanger plates A, B.

(19) The first and second heat exchanger plates A, B are so stacked that the peripheral rim 20 of a the first heat exchanger plate A in a first pair P1 of first and second heat exchanger plates A, B is arranged in an at least partly overlapping condition with the peripheral rim 20 of the second heat exchanger plate B in the first pair P1 of first and second heat exchanger plates A, B. The peripheral rim 20 of the second heat exchanger plate B in the first pair P1 of first and second heat exchanger plates A, B is arranged to at least partly overlap the peripheral rim 20 of a first heat exchanger plate A in a second, adjacent pair P2 of first and second heat exchanger plates A, B. Thereby the overlapping relationship form lap joints 22 extending in the circumferential direction of the inlet channel 9. Further, the lap joints 22 have a longitudinal extension essentially corresponding to the longitudinal extension L of the first inlet channel 9. Further, the free edges 23 of the peripheral rims 20 are all directed essentially in the same direction in parallel with the longitudinal extension L of the first inlet channel 9. Thereby an essentially smooth envelope surface 24 of the inlet channel 9 is created. The free edges may be oriented to face an intended downstream flow or an intended upstream flow through the inlet channel 9.

(20) It is to be understood that to allow this kind of overlapping, the flanged portion 21 of the peripheral rim 20 forms a small angle in view of the longitudinal extension L of the first inlet channel 9. The angle may by way of a non limiting example be within the range of 5-25 degrees and more preferred within the range of 7-12 degrees. The suitable angle is depending on parameters such as pressing depth, which in turn depends on base material and design of a pre-cut hole (not shown) which is used to form the inlet channel 9. It goes without saying that in case of the peripheral rim being a separate item joined with the heat exchanger plate the angle may be as low as 0 to 10 degrees.

(21) The overlapping distance in the lap joint 22 as seen in the longitudinal extension L of the inlet channel 9 should preferably be large enough to provide for a tight joint. By a tight joint is meant that no fluid flow should be allowed through the envelope surface 24 of the inlet channel via the joints. Typically, as a non-limiting example the overlapping distance of the joint may be in the range of 1-3 mm. Influencing parameters are by way of example tolerances during the pressing, any spring back, type of material in the base material, type of joining method etc.

(22) The lap joint 22 is formed while forming and joining the plate package P as such. Preferably it is made by using the same joining method, i.e. brazing, welding, adhesive or bonding as used when joining the plate package P. Thus, the lap joint 22 is to be regarded as a permanent joint. It should be stressed that the joining material, such as the solder, is not illustrated in FIG. 6.

(23) A number of through holes 25 are arranged in the flanged portion 21 of the peripheral rim 20 of the first or the second heat exchanger plates A, B. The through holes 25 do each form a fluid passage 26 allowing a communication between the inlet channel 9 and the first plate interspaces 3.

(24) The through holes 25 may be made in a portion of the peripheral rim 20 and its flanged portion 21 having a thickness of material corresponding to the thickness of material of one single heat exchanger plate A, B. It is also to the understood that the through holes 25 may be made to extend through a double thickness of material, which is the case if the through hole is made in the overlapping area of the lap joint 22. Even a triple thickness of material may in some circumstances be possible. It is to be understood that a single thickness material is preferred in terms of the energy required to penetrate the material during the hole making process. Also, the thinner material of thickness, the more uniform cross section along the longitudinal extension of the through hole 25 is provided for. Although the through holes 25 are illustrated as circular holes, it is to be understood that virtually any cross section is possible. In case of a circular hole, a typical diameter is within the range of 0.2-3 mm. This is however to be regarded as a non-limiting example.

(25) The at least one through hole 25 is made in a condition in which the first and the second heat exchanger plates A, B have been joined to each other to form the plate package P. Thus, the individual heat exchanger plates A, B are stacked and joined to form a plate package P, and then the through holes 25 are made. This allows a great degree of freedom when it comes to the number of through holes 25, their positions as seen in the circumferential and longitudinal extension L of the inlet channel 9 and also, their positions in view of the overlapping area of the lap joint 22. The latter is essential in terms of the thickness of material to penetrate.

(26) Accordingly, the individual heat exchanger plates A, B as such must not be custom made in terms of the number and the position of the through holes 25. Rather, the heat exchanger plates A, B may be off the shelf products. Further, there is no risk that any pre-made through holes are blocked by solder, adhesive, welding material or the like during the joining process.

(27) The through holes 25 are preferably made by a thermal process using a laser beam process, an electron beam process or a plasma method. Alternatively, the through holes 25 are made by a mechanical process using a punching process or a drilling process. These processes will be discussed separately below.

(28) Now turning to FIG. 7, a second embodiment is disclosed. FIG. 7 discloses a portion in and around the first inlet channel 9 of a plate package P. The overall design of the plate package P as such has previously been discussed above, and to avoid undue repetition reference is made to the previous discussion.

(29) The first and second heat exchanger plates A, B are so stacked that the peripheral rim 20 of a first heat exchanger plate A in a first pair P1 of first and second heat exchanger plates A, B is arranged in an at least partly overlapping condition with the peripheral rim 20 of the second heat exchanger plate B in the same first pair P1 of heat exchanger plates A, B. The overlapping condition thus forms a lap joint 22 extending in the circumferential direction of the inlet channel 9. Further, the lap joint 22 has a longitudinal extension essentially corresponding to the longitudinal extension L of the inlet channel 9. The free edges 23 of the peripheral rims 20 are directed essentially in the same direction in parallel with the longitudinal extension L of the first inlet channel 9.

(30) There is no connection between the lap joint 22 of the first pair P1 of heat exchanger plates A, B and the lap joint 22 of the second, adjacent pair P2 of heat exchanger plates A, B. Thus, a small chamber 27 is defined between each pair of heat exchanger plates A, B, which chamber 27 has one open end facing the inlet channel 9. However, by a rear joint portion 28 between the adjacent first and second pairs P1, P2 of heat exchanger plates A, B, there is no communication between the chamber 27 and the first and second rearwards arranged plate interspaces 3, 4.

(31) Accordingly, in this embodiment, the inlet channel 9 does not have an essentially smooth envelope surface 24.

(32) A number of through holes 25 are arranged in the flanged portion 21 of the first heat exchanger plates A. The through holes 25 do each form a fluid passage 26 allowing a communication between the inlet channel 9 and the first plate interspaces 3. The at least one through hole 25 is made in a condition in which the first and the second heat exchanger plates A, B have been joined to each other to form the plate package P.

(33) The through holes 25 may be made in a portion of the flanged portion 21 of the peripheral rim 20 having a thickness of material corresponding to the thickness of material of one single heat exchanger plate.

(34) The through holes 25 are preferably made by a thermal process using a laser beam process or an electron beam process. Alternatively, the through holes 25 are made by a mechanical process using a punching process or a drilling process. These processes will be discussed separately below.

(35) Now turning to FIG. 8, a third embodiment is disclosed. FIG. 8 discloses a portion in and around the first inlet channel 9 of a plate package P. The overall design of the plate package P as such has previously been discussed above, and to avoid undue repetition reference is made to the previous discussion.

(36) The peripheral rim 20 of the first heat exchanger plate A has a flanged portion 21 extending essentially in parallel with the longitudinal extension L of the inlet channel 9. The peripheral rim 20 of the second heat exchanger plate B has a flanged portion 21 extending essentially perpendicular to the longitudinal extension L of the inlet channel 9.

(37) The first and second heat exchanger plates A, B are so stacked that the flanged portion 21 of the first heat exchanger plate A in a first pair P1 of first and second heat exchanger plates A, B is arranged in an at least partly overlapping condition with the corresponding flanged portion 21 of the first heat exchanger plate A in the second adjacent pair P2 of first and second heat exchanger plates A, B. Thus, the flanged portions 21 of two successive first heat exchanger plates A, B form a lap joint 22 extending essentially in parallel with the longitudinal extension L of the first inlet channel 9. Further, the lap joint 22 extends in the circumferential direction of the inlet channel 9. This results in an essentially smooth envelope surface 24 of the first inlet channel 9.

(38) Further, the flanged portion 21 of the second heat exchanger plate B in a first pair P1 of first and second heat exchanger plates A, B is arranged to abut and join with a portion 28 of the peripheral rim 20 of the first heat exchanger plate A in a second adjacent pair P2 of first and second heat exchanger plates A, B. The portion 28 is arranged essentially perpendicular to the longitudinal extension L of the inlet channel 9. The portion 28 together with the lap joint 22 do both provide tight joints defining the first plate interspace 3.

(39) A number of through holes 25 are arranged in the flanged portion 21 of the peripheral rim 20 of the first heat exchanger plates A. The through holes 25 do each form a fluid passage 26 allowing a communication between the inlet channel 9 and the first plate interspaces 3. The at least one through hole 25 is made in a condition in which the first and the second heat exchanger plates A, B have been joined to each other to form the plate package P.

(40) In this embodiment, the through holes 25 are made in a portion of the flanged portion 21 of the peripheral rim 20 having a thickness of material corresponding to the thickness of material of one single heat exchanger plate A, B.

(41) The through holes 25 are preferably made by a thermal process using a laser beam process or an electron beam process. Alternatively, the through holes 25 are made by a mechanical process using a punching process or a drilling process. These processes will be discussed separately below.

(42) Now turning to FIG. 9, a fourth embodiment is disclosed. FIG. 9 discloses a portion in and around the first inlet channel 9 of a plate package P. Further, FIG. 9 only discloses a portion of the first plate interspace 3. The overall design of the plate package P as such has previously been discussed above, and to avoid undue repetition, reference is made to the previous discussion.

(43) The peripheral rims 20 of the first and the second heat exchanger plates A; B have each a flanged portion 21 extending in a plane essentially perpendicular to the longitudinal extension L of the inlet channel 9. The two flanged portions 21 are arranged to abut and join each other and form a lap joint 22.

(44) The first and second heat exchanger plates A, B are so stacked that the flanged portion 21 of the peripheral rim 20 of the first heat exchanger plate A in a first pair P1 of first and second heat exchanger plates A, B is arranged in an at least partly overlapping condition with the corresponding flanged portion 21 of the peripheral rim 20 of the second heat exchanger plate B in the first pair P1 of first and second heat exchanger plates A, B. Thus, the flanged portions 21 of the first and second heat exchanger plates A, B forming a pair P1 form a lap joint 22 extending essentially perpendicular to the longitudinal extension L of the first inlet channel 9. Further, the lap joint 22 extends in the circumferential direction of the inlet channel 9. This results in an uneven, flanged envelope surface 24 of the first inlet channel 9.

(45) A number of through holes 25 are arranged in the flanged portion 21 of the peripheral rim 20 of the first or the second heat exchanger plates A, B. The through holes 25 do each form a fluid passage 26 allowing a communication between the inlet channel 9 and the first plate interspaces 3.

(46) In this embodiment, the through holes 25 may be made in either the first or the second heat exchanger plates A, B. Further, the through holes 25 are arranged in the flanged portion having a thickness of material corresponding to the thickness of material of one single heat exchanger plate A, B.

(47) The at least one through hole 25 is made in a condition after in which the first and the second heat exchanger plates A, B have been joined to each other to form the plate package P.

(48) The through holes 25 are preferably made by a thermal process using a laser beam process or an electron beam process. Alternatively, the through holes 25 are made by a mechanical process using a punching process or a drilling process. These processes will be discussed separately below.

(49) Now referring to FIGS. 10 and 11, two additional embodiments of a plate package P of the invention will be discussed. FIGS. 10 and 11 only disclose a portion of the inlet channel and are highly schematic. By way of example, they do not illustrate the first and second plate interspaces. The overall design of the plate package P as such has previously been discussed above, and to avoid undue repetition reference is made to the previous discussion.

(50) In the disclosed embodiments, the peripheral rims 20 of the first and the second heat exchanger plates A, B have each a flanged portion 21 extending in a plane essentially in parallel with the longitudinal extension L of the inlet channel 9. In FIG. 10, the free edges 23 of the flanged portions 21 are arranged in opposite directions facing each other and also joined with each other in an at least partial overlapping condition, forming a lap joint 22. In FIG. 11, the free edges 23 of the flanged portions 21 are arranged in opposite directions facing each other and joined with each other in an abutting relationship, edge to edge. Thus, they form a butt joint.

(51) In line with the embodiments discussed above, a number of through holes 25 are arranged in the flanged portion 21 of the peripheral rim 20 of the first or the second heat exchanger plates A, B. The through holes 25 do each form a fluid passage 26 allowing a communication between the inlet channel 9 and the first plate interspaces 3. The at least one through hole 25 is made in a condition in which the first and the second heat exchanger plates A, B have been joined to each other to form the plate package P. The through holes 25 are preferably made be by a thermal process using a laser beam process or an electron beam process. Alternatively, the through holes 25 are made by a mechanical process using a punching process or a drilling process. These processes will be discussed separately below.

(52) Now referring to FIG. 12, the invention is disclosed as applied to a so called semi-welded or semi-bonded plate package. The disclosed embodiment is based on a plate package P having an overall design corresponding to that previously disclosed in FIG. 9. The difference lies in that the heat exchanger plates A, B included in the plate package are pair-wise permanently joined, wherein each pair P1, P2 forms a cassette 30. Further, a gasket 29 is arranged between each cassette 30.

(53) In the following the hole making processes mentioned will be discussed. As given above, the through holes 25 are preferably made by a thermal process using a laser beam process or an electron beam process. Alternatively, the through holes 25 are made by a mechanical process using a punching process or a drilling process.

(54) Starting with the laser, a laser beam process, also known as laser beam machining (LBM) is a machining process in which a beam of highly coherent light, called a laser beam, is directed towards the work piece. Since the rays of a laser beam are monochromatic and parallel, the beam it may be focused to a very small diameter and produce a very high energy content at a strictly limited area. There are a number of lasers available, well known to the skilled person, such as CO2-laser, neodymium laser (Nd-laser) and neodymium yttrium-aluminium-garnet (Nd-YAG)-lasers.

(55) During the hole making process, a numerically controlled head 100 (see FIG. 3) comprising optics and mirrors (not shown) is inserted into and moved along the interior of the inlet channel, whereby a plurality of through holes may be made by directing the laser beam to an intended position of the hole to be made. The hole making may be seen as a drilling or cutting operation. It is possible to use a so called pulsed laser, in which a high-power burst of energy is provided for a short period. Provided any cooling is required, this may be provided.

(56) Laser drilling of cylindrical holes generally occurs through melting and/or vaporization (also referred to as ablation) of the work piece material through absorption of energy from the laser beam. Thus, the laser beam process offers a hole making process essentially free of chips formation and there is accordingly no risk that that chips are collected inside the plate package risking future operation problems.

(57) As an alternative method, it is possible to use electron beam machining (EBM). EBM is a process where high-velocity electrons concentrated into a narrow beam are directed towards the work piece, creating heat which melts and/or vaporizes the material. EBM may be used for very accurate cutting or drilling. As the electrons transfer their kinetic energy into heat in a very small volume, the material impacted by the beam is evaporated in very short time. During the hole making process, a numerically controlled head 100 (see FIG. 3) comprising the required nozzle (not shown) is inserted into and moved along the interior of the inlet channel of the plate package, whereby a plurality of through holes may be made with very high accuracy.

(58) Plasma cutting or plasma drilling is a method using a plasma torch. In the process, an inert gas, in some units compressed air, is blown at high speed out of a nozzle. At the same time an electrical arc is formed through the gas from the nozzle to the surface being cut. This turns some of the gas into plasma. The plasma is sufficiently hot to melt the metal being cut and also it moves sufficiently fast to blow molten metal away from the cut. During the hole making process, a numerically controlled head 100 (see FIG. 3) comprising the required nozzle (not shown) is inserted into and moved along the interior of the inlet channel of the plate package, whereby a plurality of through holes may be made with very high accuracy.

(59) In the embodiments given above, the number, the size, the geometry and the position of the through holes 25 have been illustrated highly schematically. The through holes 25 have been illustrated as circular holes, but it is to be understood that other geometries are possible.

(60) Since the at least one through hole 25 is made in a condition in which the first and the second heat exchanger plates A, B have been joined to each other to form the plate package P, a great flexibility is offered. Heat exchanger plates off the shelf may be used to form the plate package P, and then the resulting plate package P may be custom made in terms of number, size, geometry and position of the through holes 25 distributing the fluid from the inlet channel 9 to the individual first plate interspaces 3.

(61) This offers new possibilities allowing a very high flexibility. By way of example, the plate package P may be dimensioned in terms of the number of heat exchanger plates A, B and the type of heat exchanger plates depending on the intended use of the heat exchanger and depending on the dimensioned efficiency. Throughout this process, off the shelf heat exchanger plates may be used. Then, the plate package P may be put together and be joined by any desired method such as brazing, welding, adhesive or bonding. The resulting plate package P is then subjected to the thermal process using a laser beam process, an electron beam process or a plasma process wherein a custom specific pattern of through holes 25 is made. The hole pattern may be made with high accuracy by using numerically controlled operation. The hole pattern may be based on calculations or simulations of the flow of fluid based on the specific custom needs.

(62) One of the problems to be solved when designing a plate heat exchanger is the provision of an even distribution of the fluid inside the inlet channel and into the individual first plate interspaces, and also to allow an even distribution within the individual plate interspaces in order to use the available heat transfer surface of the heat exchanger plates as effective as possible. The distribution into the first plate interspaces is provided by the through holes and it is to be understood that the distribution of the through holes around and along the circumferential envelope surface of the inlet channel may vary from one heat exchanger to another depending on the customer's needs. It is also to be understood that the distribution may even vary within one and the same plate package as seen along the longitudinal direction of the inlet channel.

(63) Thus, following the complexity of the position and distribution of the through holes, the fact that the through holes now, by the invention, are made once the plate package has been formed and joined, offers completely new possibilities in the design of a plate heat exchanger based on custom specific needs and optimization of the efficiency.

(64) The invention has been illustrated and disclosed throughout this document with the port holes 8 and thereby also the first inlet channel 9 arranged in the corners of rectangular heat exchanger plates A, B. It is however to be understood that also other geometries and positions are possible within the scope of protection. Also, the port holes 8 have been illustrated and disclosed as circular holes. It is to be understood that other geometries are possible within the scope of the protection.

(65) It is to be understood that the invention is applicable also to plate heat exchangers of the type (not disclosed) where a plate package is kept together by tie-bolts extending through the heat exchanger plates and the upper and lower end plates. In the latter case gaskets may be used between the heat exchanger plates.

(66) The plate heat exchanger may be provided with several inlet and outlet channels, whereas the shape and location of the channels may be freely chosen. For instance, the plate heat exchanger may be a dual circuit heat exchanger for three different fluids having six ports. In the latter case not every heat exchanger plate or every second heat exchanger plate and its related rim is provided with at least one through hole but rather each fourth heat exchanger plate,

(67) Accordingly, although the invention has been exemplified above as each individual heat exchanger plate or every second heat exchanger plate and their related rims are provided with at least one through hole, it is to be understood that this must not be the case. Rather, it is to be understood that the trough holes should be arranged in a rim providing access to a plate interspace intended to receive the fluid to be fed through the actual inlet channel being formed by the rims of a plurality of mutually joined heat exchanger plates.

(68) Although the hole making process has been described as a thermal process using laser, electron beam or plasma, it is to be understood that it is possible to use also a water jet method, with or without abrasives or even a mechanical hole making process such as punching or drilling.

(69) In the disclosed embodiments, the plate packages exhibits one and the same joint type along the full extent of the inlet channel. It is to be understood that an inlet channel of a plate package may exhibit a combination of different joint types, i.e. a mixture of lap joints and butt joints.

(70) From the description above follows that, although various embodiments of the invention have been described and shown, the invention is not restricted thereto, but may also be embodied in other ways within the scope of the subject-matter defined in the following claims.