FIELD OF THE INVENTION

The present invention relates to a brazed plate heat exchanger. More specifically, the present invention relates to a brazed plate heat exchanger comprising a stack of heat exchanger plates provided with a pattern of ridges and grooves forming plate interspaces for fluids to exchange heat, wherein the heat exchanger plates are provided with port openings and a skirt extending at least partially around one port opening of at least some of the plates. Such plate heat exchangers are used for exchanging heat between fluids for various purposes. For example, heat exchangers of this type are used for heating or cooling purposes, such as in a heat pump or refrigeration system. For example, heat exchangers of this type are used as an evaporator or a condenser.

PRIOR ART

A plurality of plate heat exchangers is known in the prior art. Such known plate heat exchangers comprise port openings and plate interspaces for fluids to exchange heat. Port opening areas are provided around the port openings, such that selective communication between said port openings and the plate interspaces is achieved. Such port opening areas are often flat and arranged to alternatingly contacting each other to provide selective communication with the plate interspaces. The port opening areas are often annular, surrounding the port openings and arranged for selectively sealing against a port opening area of an adjacent heat exchanger plate, for example by a brazing joint.

It is known to arrange skirts around port openings to provide an inlet channel for one of the fluids. Chambers are formed between skirts and the plate interspaces. The inlet channel communicates with the chambers and selected plate interspaces through holes in the skirts and holes in the plates.

For some applications, such as in a heat pump application using a refrigerant as one of the fluids, the heat exchanger must be able to withstand relatively high pressures. The port opening areas of brazed plate heat exchangers tend to break if subjected to high pressures.

Hence, one problem of prior art heat exchangers is that they are weak and cannot withstand high pressure. Another problem of the prior art heat exchangers is that they are inefficient.

Another problem of the prior art heat exchangers is that they may beexpensive to produce.

SUMMARY OF THE INVENTION It is an object of the present invention to mitigate problems of prior art heat exchangers and provide a brazed plate heat exchanger with favourable distribution of fluids which may result in a strong and efficient brazed plate heat exchanger which, according to some aspects, is relatively easy and cost effective to produce. According to further some aspects of the present invention, a brazed plate heat exchanger is provided with favourable distribution of media in various conditions, such as in low fluid flow conditions.

The present invention is related to a brazed plate heat exchanger comprising a stack of at least first and second heat exchanger plates each provided with a pattern comprising ridges and grooves adapted to form contact points between neighbouring heat exchanger plates such that plate pairs of the heat exchanger plates form alternating first and second plate interspaces for first and second fluids to exchange heat over the heat exchanger plates, wherein the heat exchanger plates are provided with port openings forming inlet and outlet channels for the first and second fluids, wherein at least one of the first and second heat exchanger plates in a plate pair is arranged with a skirt extending at least partially around its first port opening to form a chamber between the skirt and plate interspaces, and wherein the chamber communicates with the first or second plate interspaces through a hole in one of the first and second heat exchanger plates of said plate pair, characterised in that the chamber is open to the channel through a gap between at least a free end portion of the skirt and an adjacent heat exchanger plate, and the gap varies along the circumference of the channel and/or a cross section area of the chamber varies along the circumference of the channel. The variation of the gap between the free end portion or the free end of the skirt and the adjacent heat exchanger plate and/or the variation of the cross section area of the chamber result(s) in favourable pressure drop and distribution of the fluid to distribute the pressure and the stress around the port openings and achieve an even and efficient flow of the fluid from an inlet channel and into the plate interspaces. The possibility to control the pressure drop and distribution of fluid into the chamber and further to the hole and hence into the plate interspace result in the possibility to achieve a stronger heat exchanger that can withstand high pressure. The invention provides for a more even flow of the fluid in the inlet channel and improved distribution of the fluid therein, wherein the possibility for the heat exchanger to withstand pressure increases as the pressure on the heat exchanger plates at the skirt is distributed around its circumference to a greater extent. The heat exchanger can comprise a radial gap and/or an axial gap at the skirt for fluid to flow from the inlet channel to the chamber. The skirt extends in an angle offset from a plane of the heat exchanger plate, such as generally perpendicular to the plane of the heat exchanger plate, to form the inlet channel and also to form the chamber between the skirt and the plate interspaces. The heat exchanger plates are arranged with their planes in parallel. The plane of each heat exchanger plate extends in a radial direction. The gap can be smaller closer to the hole and bigger more remote from the hole, so that the fluid is distributed in a more favorable way. Hence, the variation of the gap can balance the distribution of fluid in the inlet channel and into the chamber. For example, there is no gap in front of the hole. Similarly, the cross section of the chamber can be smaller in a position closer to the hole and larger in a position remote from the hole in a direction around the inlet channel to balance the distribution of fluid to the chamber. Hence, the volume of the chamber decreases around the inlet channel towards the hole or a section comprising a plurality of holes, e.g., so that the volume of the chamber is smallest between the hole(s) and the portion of the skirt closest to the hole(s). For example, the chamber is bigger in a portion across the inlet channel seen from the hole or section of holes. The cross section of the chamber is a section in the axial direction, i.e. perpendicular to the plane of the plates. In the following a single hole is usually referred to as an example. However, a section of the heat exchanger plate comprising a plurality of holes may be used. The hole can be a restriction hole. For example, the area of the hole, or the total area of the holes if a plurality of holes is used, may be substantially smaller than the total area of the opening between the inlet channel and the chamber, so that a restriction of the flow is provided.

The first heat exchanger plate in a plate pair can be provided with a first skirt at least partly surrounding the first port opening of the first heat exchanger plate, and the second heat exchanger plate in the same plate pair can be provided with a second skirt at least partly surrounding the first port opening of the second heat exchanger plate. A radial gap can be arranged between the second skirt and the free end of the first skirt.

The first and second skirts can extend substantially in opposite directions. Hence, the first skirt can provide for a smooth inlet channel, wherein the second skirt can prevent mal-distribution of fluid and the first and second skirts can together provide the chamber with the varying gap into the chamber and/or the varying cross section area of the chamber.

The first port opening of the first heat exchanger plate can be smaller than the first port opening of the second heat exchanger plate. Hence, when the first heat exchanger plate comprises the first skirt it is arranged radially inside the first port opening of the second heat exchanger plate to provide a smooth inlet and favourable distribution of the fluid. The first port openings of the first and second heat exchanger plates can have a centre axis, which, e.g., may be aligned with the centre axis of the inlet channel or may be radially offset, i.e. eccentric, in relation to it. The first port openings of the second heat exchanger plates can be arranged eccentrically, i.e. radially offset, in relation to the first port openings of the first heat exchanger plates, so that the first port openings of the first heat exchanger plates are non-aligned with the first port openings of the second heat exchanger plates in the axial direction. Alternatively, the first and second port openings are of similar size and/or aligned with each other. Hence, the varying gap and/or varying cross section area of the chamber can be achieved in an efficient way. The first heat exchanger plates are arranged with a radially extending first port opening area surrounding the first port opening, and the second heat exchanger plates are arranged with a radially extending second port opening area surrounding the first port opening and contacting the first port opening area of an adjacent heat exchanger plate, wherein the second port opening area can be arranged with a different size than the first port openings area. Hence, the varying gap and/or varying cross section area of the chamber can be achieved in an efficient way. For example, the first port opening area is bigger than the second port opening area and/or the first and second port opening areas are arranged eccentrically in relation to each other, i.e. radially displaced in relation to each other and non-aligned in the axial direction.

The first and/or second skirts can be arranged with varying length, angle and/or shape to provide the varying gap and/or varying chamber cross section area.

Further characteristics and advantages of the present invention will become apparent from the description of the embodiments below, the appended drawings and the dependent claims.

BREF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described with reference to appended drawings, wherein: Fig. l is a schematic exploded view of a heat exchanger according to a first embodiment of the present invention,

Fig. 2 is a schematic front view of a first heat exchanger plate of the heat exchanger according to Fig. 1,

Fig. 3 is a schematic section view at line A-A of the first heat exchanger plate of Fig. 2, illustrating a port opening area and a skirt of the first port opening of the first heat exchanger plate according to one embodiment,

Fig. 4 is a schematic front view of a heat exchanger according to Fig. 1,

Fig. 5 is a schematic and simplified section view at line A-A of the heat exchanger of Fig. 4, illustrating chambers formed by port opening areas and skirts at the first port opening of the first and second heat exchanger plates according to the first embodiment,

Fig. 6 is a schematic and simplified section view of a heat exchanger according to a second embodiment, illustrating chambers communicating with plate interspaces according to the second embodiment,

Fig. 7 is a schematic view of a part of Fig. 5, illustrating an axial gap and a radial gap for a fluid to flow from an inlet channel to the chamber according to the first embodiment,

Fig. 8 is a schematic exploded view of a heat exchanger according to a third embodiment of the present invention,

Fig. 9 is a schematic and simplified section view of the heat exchanger of Fig. 8, illustrating chambers formed by port opening areas and a skirt at the first port opening of the first heat exchanger plates according to the third embodiment,

Fig. 10 is a schematic view of a part of Fig. 9, illustrating a varying gap from the inlet channel to the chamber according to the third embodiment,

Fig. 11 is a schematic and simplified section view of a heat exchanger according to a fourth embodiment, illustrating chambers formed by port opening areas and a skirt at the first port opening of the first heat exchanger plates according to the fourth embodiment, Fig. 12 is a schematic view of a part of Fig. 11, illustrating the skirt and the varying gap from the inlet channel to the chamber according to the fourth embodiment Fig. 13 is a schematic exploded view of a heat exchanger according to a fifth embodiment of the present invention,

Fig. 14 is a schematic and simplified section view of the heat exchanger according to the fifth embodiment, illustrating heat exchanger plates with skirts forming chambers communicating with plate interspaces according to the fifth embodiment,

Fig. 15 is a schematic view of a part of Fig. 14, illustrating an axial gap between the skirts of adjacent heat exchanger plates for a fluid to flow from the inlet channel to the chamber according to the fifth embodiment, Fig. 16 is a schematic exploded view of a heat exchanger according to a sixth embodiment of the present invention, Fig. 17 is a schematic section view of the heat exchanger according to the sixth embodiment, illustrating heat exchanger plates with skirts forming chambers communicating with plate interspaces according to the fifth embodiment,

Fig. 18 is a schematic view of a part of Fig. 17, illustrating the gap between the skirts of adjacent heat exchanger plates for a fluid to flow from the inlet channel to the chamber according to the sixth embodiment,

Fig. 19 is a schematic perspective view of as stack of heat exchanger plates according to the sixth embodiment,

Fig. 20 is a view of a part of Fig. 19, illustrating the configuration of the skirts of the first and second heat exchanger plates according to the sixth embodiment,

Fig. 21 is a schematic front view of as stack of heat exchanger plates according to the sixth embodiment, and

Fig. 22 is a view of a part of Fig. 21, illustrating the configuration of the skirts of the first and second heat exchanger plates according to the sixth embodiment.

DESCRIPTION OF EMBODIMENTS

With reference to Fig. 1, a heat exchanger 10 according to one embodiment of the present invention is illustrated schematically. The heat exchanger 10 comprises first and second end plates 11a. lib and a plurality of first and second heat exchanger plates 12a, 12b stacked in a stack to form the heat exchanger 10. The heat exchanger 10 is a brazed plate heat exchanger. For example, the heat exchanger 10 is configured to be used as an evaporator or a condenser, e.g. in a heat pump or refrigeration system. The heat exchanger 10 is configured to exchange heat between at least a first fluid and a second fluid. For example, one of the fluids is a refrigerant, such as R32, R290 or a similar refrigerant.

The heat exchanger plates 12a, 12b are provided with a pattern of ridges R and grooves G such that alternating first and second plate interspaces 13a, 13b for fluids to exchange heat are formed between the heat exchanger plates 12a, 12b when the plates are stacked in a stack to form the heat exchanger 10 by providing contact points between at least some crossing ridges R and grooves G of neighbouring heat exchanger plates 12a, 12b under formation of the plate interspaces 13 a, 13b for fluids to exchange heat, which will be described more in detail below. The pattern according to the illustrated embodiments is a herringbone pattern. However, the pattern may also be in the form of obliquely extending straight lines or other suitable patterns. The pattern of ridges R and grooves G is a corrugated pattern having a corrugation depth. The pattern is a pressed pattern. The pattern is adapted to keep the plates 12a, 12b on a distance from one another, except from the contact points, to form the plate interspaces 13a, 13b between adjacent heat exchanger plates 12a, 12b for the fluids to exchange heat. For example, the heat exchanger plates 12a, 12b are made from sheet metal, such as stainless steel, copper or other suitable metals or alloys. For example, the press depth of the heat exchanger plates 12a, 12b is 1-3 mm, such as 1-2 mm or 1-1.7 mm.

In the illustrated embodiment, each of the heat exchanger plates 12a, 12b are surrounded by a skirt S, which extends generally perpendicular to a plane of the heat exchanger plates 12a, 12b and is adapted to contact skirts S of neighbouring heat exchanger plates 12a, 12b in order to provide a seal along the circumference of the heat exchanger 10.

The heat exchanger plates 12a, 12b are arranged with port openings 01, 02,

03 and 04 forming inlet and outlet channels for fluids to exchange heat into and out of the plate interspaces 13a, 13b. In the illustrated embodiment, the first end plate 11a and the heat exchanger plates 12a. 12b are arranged with four port openings. Alternatively, the heat exchanger plates 12a, 12b are arranged with another number of port openings, such as six or eight or even more. In various illustrated embodiments, the first heat exchanger plates 12a are arranged with a first port opening Ola, wherein the second heat exchanger plates 12b are formed with a first port opening Olb. The first port openings Olb of the second heat exchanger plates 12b is, e.g., different from the first port openings Ola of the first heat exchanger plate 12a. In the illustrated first embodiment, the first port opening Ola of the first heat exchanger plate 12a is smaller than the first port opening Olb of the second heat exchanger plates 12b, which will be described more in detail below. Alternatively, the first port openings Ola, Olb of the first and second heat exchanger plates 12a, 12b are similar in size. For example, second, third and fourth port openings 02-04 are provided. Port opening areas 15 surrounding the port openings 01-04 are provided. The port opening areas 15 are provided, such that selective communication between said port openings 01-04 and the plate interspaces 13a, 13b is achieved. For example, the port opening areas 15 are flat and altematingly contacting each other to provide selective communication. The port opening areas 15 are arranged for sealing against a corresponding port opening area 15 of an adjacent heat exchanger plate 12a, 12b. For example, the port opening areas 15 are substantially flat and joined to each other by brazing joints. For example, the port opening areas 15 extend in the plane of the heat exchanger plates 12a, 12b or in parallel therewith. For example, the port opening areas 15 are annular and have a circular outer periphery. Alternatively, the port opening areas 15 have an oval outer periphery or is formed in another suitable manner.

In the illustrated embodiment, the heat exchanger plates 12a, 12b are rectangular with rounded corners, wherein the port openings Ola, 01b, 02, 03, 04 are arranged near the corners. Alternatively, the heat exchanger plates 12a, 12b are square, e.g. with rounded comers. Alternatively, the heat exchanger plates 12a, 12b are circular, oval or arranged with other suitable shape, wherein the port openings are distributed in a suitable manner. In the illustrated embodiments, the heat exchanger plates 12a, 12b are provided with a herringbone pattern, wherein the herringbone pattern of the first heat exchanger plates 12a is arranged in one direction and the herringbone pattern of the second heat exchanger plates is arranged in the opposite direction.

The first heat exchanger plates 12a are provided with a first skirt 16a at least partly surrounding the first port opening Ola of the first heat exchanger plate 12a. The first skirt 16a is, e.g. a folded portion of the first heat exchanger plate 12a, which folded portion entirely or partly surrounds the first port openings Ola. In the illustrated embodiments, the second heat exchanger plate 12b is provided with a second skirt 16b at least partly surrounding the first port opening 01b of the second heat exchanger plate 12b. The second skirt 16a may be a folded portion of the second heat exchanger plate 12b. For example, the first and/or second port skirts 16a, 16b is/are annular. With reference also to Figs. 2-7 the first and second skirts 16a, 16b form a chamber 17 around or at least partially around the first port openings Ola, Olb of a pair of heat exchanger plates 12a, 12b. The chambers 17 are illustrated in Figs. 5-7. The chambers 17 formed by the heat exchanger plates 12a, 12b extend around the inlet channel 14 formed by the first port openings Ola, Olb. In the illustrated embodiment, the chambers 17 are annular and surround an inlet channel 14. For example, the chamber 17 is formed by the skirts 16a, 16b and a port opening area 15a around the first port opening Ola of the first heat exchanger plate 12a and the port opening area 15b around the first port opening Olb of the second heat exchanger plate 12b. Said port openings areas 15a, 15b are alternatingly arranged on a higher and lower level and engage each other around the first port openings Ola, Olb. The port opening areas 15a, 15b engage an adjacent port opening area 15a, 15b of a heat exchanger plate 12a, 12b of an adjacent plate pair. Each chamber 17 communicates with the first or second plate interspaces 13 a, 13b through a hole 18 in one of the first and second heat exchanger plates 12a, 12b. In the embodiment of Fig. 5, the chamber 17 communicates with the second plate interspaces 13b through a hole 18 in the first heat exchanger plate 12a. In a second embodiment as illustrated in Fig. 6, the chamber 17 communicates with the second plate interspaces 13b through a hole 18 in the second heat exchanger plate 12b. For example, one of the first and second heat exchanger plates 12a, 12b is provided with a single hole 18. Alternatively, one of the first and second heat exchanger plates 12a, 12b is provided with a plurality of holes, e.g. in the same area or distributed around less than half or less than a third of the chamber circumference. According to one embodiment, the hole has a diameter of at least 0.5 mm, such as 0.5-2 mm or 0.5-1.5 mm or 0.5-1 mm.

The inlet channel 14 extends, at least partially, in an axial direction, as illustrated by a centre axis A in Fig. 5. The axial direction is perpendicular to the planes of the heat exchanger plates. The first skirt 16a extends in an angle offset from the plane of the heat exchanger plate and thus at least partially in the axial direction. The first skirt 16a has a base and at least a free end portion. The first skirt 16a extends in an angle offset from the plane of the heat exchanger plate from the base and towards the free end. The distance between the base and the free end of the first skirt 16a is the length thereof. For example, the entire length of first skirt is arranged at an angle offset from the plane of the heat exchanger plate, such as perpendicular or substantially perpendicular. For example, the first skirt 16a extends in the same direction throughout its length. In the illustrated embodiment, the entire first skirt 16a has a free end and is not contacting any other skirts or plates. The first skirt 16a extends in a direction towards its free end. The first skirt 16a extends in a direction substantially along the inlet channel 14 and in parallel to the centre axis A, e.g. in a direction along a fluid flowing axially into the heat exchanger 10 through the inlet channel 14, which is illustrated schematically by means of the arrow B in Fig. 5. In the illustrated embodiments, the axial direction is perpendicular to the planes of the heat exchanger plates. For example, the first skirt 16a extends, in a direction towards its free end, substantially axially and is inclined radially inward towards the centre axis A of the channel 14 formed by the first port openings

Ola, Olb. An axial gap 19 is arranged between the free end of the first skirt 16a and the first skirt 16a of the next first heat exchanger plate 12a in the adjacent plate pair. Alternatively, the axial gap 19 extends in the axial direction or substantially in the axial direction between the free end of the first skirt 16a and the port opening area 15b of the second heat exchanger plate 12b. For example, the axial gap 19 extends in the axial direction or substantially in the axial direction between the free end of the first skirt 16a and the base of the next first skirt 16a, which is illustrated schematically by means of the double arrow y in Fig. 7. Hence, the chamber 17 is open to the inlet channel 14 through the axial gap 19, so that fluid can pass from the inlet channel 14 to the chamber 17 through the axial gap 19. The first skirt 16a forms a smooth inlet for the fluid.

Except from the hole 18 or a plurality of holes, the chamber 17 is closed off from the plate interspaces 13a, 13b through a sealing area 20 surrounding the chamber 17. In the illustrated embodiment, the sealing area 20 is formed by flat areas of the first and second heat exchanger plates 12a, 12b in a plate pair engaging each other. For example, the sealing area 20 is formed by a depression in the first heat exchanger plate 12a and/or an elevation in the second heat exchanger plate 12b. For example, the first and second heat exchanger plates 12a, 12b are connected to each other in the sealing area 20 by a brazing joint, e.g. surrounding the chamber 17. For example, the sealing areas 20 are annular. In the illustrated embodiment, the second heat exchanger plate 12b is arranged with the second skirt 16b extending substantially in the opposite direction as the first skirt 16a. For example, the second skirt 16b extends in a direction against the intended axial fluid flow in the inlet channel 14 as illustrated by means of the arrow B. The second skirt 16b has a base and a free end, e.g. similar to the first skirt 16a. In the illustrated embodiment, the free end of the second skirt 16b is not aligned with the free end of the first skirt 16a. Hence, the first skirt 16a is radially displaced in relation to the second skirt 16b, wherein a radial gap 21 between the first skirt 16a and the second skirt 16b is formed. The radial gap 21 is illustrated schematically by means of the double arrow x in Fig. 7.

As can be seen in Fig. 5, the first and second skirts 16a, 16b overlap, i.e. they have a total length exceeding the distance between port opening areas 15a, 15b adjacent the skirts 16a, 16b in the same plate pair. Hence, the radial gap 21 extends substantially between the free end of the first skirt 16a and the free end of the second skirt 16b in the radial direction. The second skirt 16b is arranged radially outside the first skirt 16a. Hence, the first skirt 16a is arranged with a smaller diameter than the second skirt 16b, at least at the free end thereof. The second skirt 16b forms a flow shield to prevent mal distribution of the fluid. For example, the second skirt 16b forms a shield against gas bubbles. According to the illustrated embodiment of the present invention the radial gap

21 varies. Hence, the radial gap 21 varies between the free end of the first skirt 16a and the second skirt 16b around the circumference of the inlet channel 14. Hence, the radial gap 21 is smaller in one or more positions than in the other(s). For example, the radial gap 21 is smaller in a position closer to the hole 18 and larger in a position more remote from the hole 18. According to the illustrated embodiment, the radial gap 21 is biggest in a position opposite the hole 18, i.e. in a position across the first port opening Ola from the hole 18, and smallest into the chamber 17 in the vicinity of the hole 18. Hence, the radial gap 21 is tapering towards the hole 18.

In the illustrated embodiment, the port opening area 15a around the first port opening Ola of the first heat exchanger plates 12a is bigger than the port opening area 15b around the first port opening Olb of the second heat exchanger plates 12b. For example, the port opening area 15a around the first port opening Ola of the first heat exchanger plates 12a varies in size around the first port opening Ola of the first heat exchanger plates 12a. In the illustrated embodiment, the first port opening Ola of the first heat exchanger plate 12a is arranged eccentric in the port opening area 15a. Hence, the said port opening area 15a is tapering towards the hole 18.

In the embodiment of Figs. 5-7 the cross section area of the chamber 17 is substantially constant around the inlet channel 14. Alternatively, the cross section area of the chamber 17 varies, e.g. so that the cross section area is bigger in an area opposite the hole 18 and smaller in the vicinity of the hole 18. For example, the cross section area of the chamber 17 is tapering in a direction towards the hole 18.

In the illustrated embodiments, the skirts 16a, 16b are arranged with constant lengths around the first port opening Ola, Olb. Alternatively, the length of the first skirt and/or second skirt 16b varies around the circumference of the first port opening Ola, Olb. For example, the first skirt 16a is longer close to the hole 18, wherein the length thereof is reduced in a direction away from the hole 18. Hence, the axial gap 19 may be tapering in a direction towards the hole 18. The length of the second skirt 16b may be varied to provide a greater flow into the chamber 17 remote from the hole and restrict the flow of fluid into the chamber closer to the hole 18. In the illustrated embodiments, the first port openings Ola, Olb are circular, arranged with different diameters and eccentric to each other. Alternatively, the first and/or second first port opening Ola, Olb is/are elliptic, wherein the radial gap 21 varies.

In the illustrated embodiments, the first and second skirts 16a, 16b extend substantially in the axial direction and are inclined inward in an angle that is constant around the circumference of the first port opening Ola, Olb. Alternatively, the first and/or second skirt 16a, 16b is/are arranged with varying inclination angle to provide a varying radial gap 21. With reference to Figs. 8-10 a third embodiment of the present invention is illustrated schematically. The heat exchanger 10 of the third embodiment comprises alternatingly arranged first and second heat exchanger plates 12a, 12b with a pressed pattern, port openings 01-04, port opening areas 15a, 15b and plate interspaces 13a, 13b arranged such that selective communication between the port openings 01-04 and the plate interspaces 13a, 13b is achieved as described above.

In the third embodiment, the first heat exchanger plates 12a are arranged with a skirt 16 extending partly around the first port opening Ola of the first heat exchanger plates 12a, whereas the second heat exchanger plates 12b may or may not be provided with any skirt. Alternatively, the skirt 16 extends around the entire circumference of the first port opening Ola.

With reference particularly to Figs. 9 and 10, the skirts 16 extend in a direction substantially along the inlet channel 14 and is optionally inclined somewhat inward. The skirts 16 have at least a free end portion and a base connected to a port openings area 15a of the first heat exchanger plates 12a. In Figs. 9 and 10 the skirts 16 have a free end along its entire circumferential extension around the inlet channel 14. An axial gap 19 is arranged between the free end of the skirt 16 and the next heat exchanger plate. For example, the axial gap 19 extends in the axial direction or substantially in the axial direction between the free end of the skirt 16 and the port opening area 15b of the second heat exchanger plate 12b, as illustrated by the double arrow y in Fig. 10.

Alternatively, the gap 19 may extend between the free end of the skirt 16 and the next skirt 16, such as substantially at the base of the next skirt 16.

In the embodiment of Figs. 9 and 10, the skirts 16 form the chambers 17 partially around the inlet channel 14. Hence, the skirt 16 extend only along a part of the circumference of the inlet channel 14 to form the chamber 17 only partially around the inlet channel 14. The skirt 16 is formed by a folded portion of the first heat exchanger plate 12a around the first port openings Ola. The skirt 16 is arranged to shield the hole 18 from fluid flowing from the inlet channel 14 and into the plate interspaces 13a, 13b. Hence, the skirt 16 is arranged between the inlet channel 14 and the hole 18, wherein the chamber 17 is arranged between the inlet channel 14 and the hole 18. For example, the skirt 16 extends around at least half of the circumference of the first port opening Ola, such as around 30-90%, 40-80% or 50-80% thereof.

In the third embodiment, the skirt 16 is arranged with a varying length and tapering in a direction away from the hole 18, so that the axial gap 19 is varying correspondingly. Hence, the skirt 16 is bigger close to the hole 18 and decreases in length further away from the hole 18, wherein the axial gap 19 is smallest close to the hole 18 and bigger further away from it, so that the shielding effect of the skirt 16 is biggest in front of the hole 18. The skirt 16, or the combination of the first skirt 16a and the second skirt 16b, may form a shield in the area in front of the hole 18, which shield may decrease in a direction away from the hole 18, to distribute the fluid flowing in the channel 14 and provide a more even and favorable flow of the fluid from said channel 14 and into the selected plate interspaces. Hence, according to an alternative embodiment (not illustrated), the second heat exchanger plate 12b is provided with the second skirt 16b, which second skirt 16b may be arranged with a constant length and may vary in length, such as tapering in a direction away from the hole 18.

In Figs. 8-10, the second heat exchanger plates 12b are provided with the hole 18 between the port openings area 15b and the sealing area 20 but the hole 18 may alternatively be provided in the first heat exchanger plates 12a as described above.

With reference to Figs. 11 and 12 a fourth embodiment of the present invention is illustrated schematically. The fourth embodiment is similar to the third embodiment, except that a portion of the skirts 16 engages the adjacent heat exchanger plate and/or the skirt 16 of the next first heat exchanger plate 12a. For example, the skirts 16 are in contact with the adjacent heat exchanger plate and/or the next skirt 16 in front of the hole 18, so that the hole 18 is fully shielded in the radial direction between the inlet channel 14 and the hole 18. The chamber 17 is arranged between the inlet channel 14 and the hole 18.

In the embodiment of Figs. 11 and 12 the skirts 16 have at least one free end portion and an end portion not being free. For example, the skirt 16 has free end portions on both sides of the end portion being in contact with the adjacent plate or skirt. A gap 19 is arranged between the free end portion(s) and the adjacent plate or skirt as described above. For example, the gap 19 is an axial gap or at least extending partly in the axial direction. The gap 19 is illustrated in Fig. 12 by means of the double arrow y. Hence, the fluid must flow from the inlet channel 14 and into the chamber 17 around the portion of the skirt 16 in front of the hole 18. Fluid can, e.g. flow into the chamber 17 through the gap 19. Also in the embodiment of Figs. 11 and 12, the skirt 16 is arranged with a varying length and tapering in a direction away from the hole 18, so that the axial gap 19 is varying correspondingly. Hence, the skirt 16 is bigger close to the hole 18 and decreases in length further away from the hole 18, wherein there is no axial gap in front of the hole 18 and a growing gap 19 further away from the hole 18. The skirt 16, or the combination of the first skirt 16a and the second skirt 16b, may form a shield in the area in front of the hole 18 to distribute the fluid flowing in the channel 14 and provide a more even and favorable flow of the fluid from said channel 14 and into the selected plate interspaces. According to one embodiment (not illustrated), the first and second skirts 16a, 16b engage each other in front of the hole 18, wherein there is a growing gap between them further away from the hole 18.

With reference to Figs. 13-15 a fifth embodiment of the present invention is illustrated schematically. According to the fifth embodiment the first and second skirts 16a, 16b are arranged around the first port openings Ola, Olb of the first and second plates 12a, 12b and opposite each other to form the axial gap 19 between free ends of the first and second skirts 16a, 16b for fluid to flow from the inlet channel 14 and into the chamber 17. The first and second skirts 16a, 16b extend at an angle offset from the planes of the plates 12a, 12b and from the planes of the port opening areas 15a, 15b, such as 90-120 degrees from the port opening areas 15a, 15b. For example, the first and second skirts 16a, 16b extend substantially in opposite axial directions, e.g. somewhat inclined inward toward a centre of the inlet channel 14. For example, the first and second skirts 16a, 16b are arranged with similar lengths, which are constant around the entire port opening. For example, the first and second skirts 16a, 16b mirror each other to provide a similar flow in both directions through the inlet channel 14. In the fifth embodiment, the free end of the first skirt 16a substantially faces the free end of the second skirt 16b and the gap 19 between them is constant around the entire circumference of the inlet channel 14. For example, the first and second skirts 16a, 16b extend around the entire circumference of the port openings Ola, Olb and the inlet channel 14 and are formed as annular closed loops.

In the fifth embodiment, the port openings areas 15a, 15b of the first and second plates 12a, 12b are similar, aligned with each other and formed with a smaller width closer to the hole 18. The port opening areas 15a, 15b are flat and extend in the radial direction, such as in the plane of the plates 12a, 12b or in parallel therewith. The first port openings Ola, Olb of the first and second plates 12a, 12b are aligned with each other and are arranged eccentric in the port opening areas 15a, 15b, so that the chambers 17 are tapering toward the holes 18 into one of the first and second plate interspaces 13a, 13b. Except for the holes 18, the chambers 17 are closed off from the other of the first and second plate interspaces 13 a, 13b by means of the sealing area 20 as described above. The chambers 17 have a smaller cross section area closer to the holes 18 and a bigger cross section area further away from the holes 18. For example, the first port openings Ola, Olb are arranged eccentric in the port opening areas 15a, 15b, so that the chambers 17 are tapering in a direction toward the holes 18. For example, the port opening areas 15a, 15b of the plates 12a, 12b are circular or elliptic, wherein the first port openings Ola, Olb are circular or elliptic and arranged eccentric in the port opening areas 15 a, 15b. With reference to Figs. 16-22 a sixth embodiment of the present invention is illustrated schematically. According to the sixth embodiment the first port openings Ola, Olb of the first and second plates 12a, 12b are non-circular and form radially extending projections 22a, 22b and depressions 23a, 23b in relation to each other. The first and second skirts 16a, 16b are formed correspondingly to substantially follow the shape of the first port opening Ola, Olb. Hence, the first port openings Ola and the first skirts 16a are formed with the projections 22a and the depressions 23a, wherein the second port openings Olb and the second skirts 16b are formed with the projections 22b and the depressions 23b. As described above, the skirts 16a, 16b extend substantially axially in opposite directions and may be inclined inward. The projections 22a, 22b and depressions 23 a, 23b are arranged alternatingly around the circumference of the inlet channel 14. The projections 22a, 22b and depressions 23a, 23b are curved and may be wave-shaped in a polygonal fashion, wherein each corner of the polygon corresponds to a depression 23a, 23b with a projection 22a, 22b between each depression 23a, 23b. For example, such a polygonal-resembling shape may, e.g. have four to ten corners, such as the illustrated hexagonal shape having six projections 22a, 22b and six depressions 23a, 23b. For example, the projections 22a, 22b and the depressions 23a, 23b are distributed evenly around the circumference of the port openings Ola, Olb and skirts 16a, 16b. Hence, the first and second skirts 16a, 16b are arranged as circumferentially wave shaped tube portions.

The projections 22a of the first plate 12a are positioned at the depressions 23b of the second plate 12b and vice versa. Hence, the projections 22a, 22b and the depressions 23a, 23b are alternating also in the axial direction. The projections 22a of the first plates 12a are aligned with each other in the axial direction, wherein the depressions 23 a of the first plates 12a are aligned with each other. Similarly, the projections 22b of the second plates 12b are aligned with each other in the axial direction, wherein the depressions 23b thereof are aligned with each other. For example, the frequency of projections 22a, 22b and depressions 23a, 23b are similar for both the first and second plates 12a, 12b, but displaced around the circumference in relation to each other. Hence, the pattern of projections 22a, 22b and depressions 23a, 23b are displaced in relation to each other around the axis A through the inlet channel 14, so that projections 22a of the first plates 12a are arranged on both sides of a depression 23b of the second plates 12b in the axial direction. Similarly, the projections 22b of the second plates 12b are arranged on both sides of a depression 23 a of the first plates 12a in the axial direction. Hence, the projections 22a, 22b project radially into the inlet channel 14 to guide the flow of fluid into the chambers 17. For example, the projections and depressions are distributed evenly along the skirts, such as along the entire circumference thereof.

For example, in the sixth embodiment, the radial gap 21 between the inlet channel 14 and the chambers 17 vary around the circumference of the inlet channel 14 due to the altematingly overlapping projections 22a, 22b and depressions 23a, 23b of adjacent plates 12a, 12b. The distance between the free ends of the skirts 16a, 16b may be constant in the axial direction and varies in the radial direction, wherein the radial gap 21 altematingly varies from being smaller where the free ends of opposite skirts 16a, 16b are closer to each other to being bigger where they are more remote from each other. The radial gap 21 altematingly varies from zero in positions where the free ends of the skirts 16a, 16b face each other to a maximum size where a centre point of a projection 22a, 22b is aligned with a centre point of a depression 23a, 23b of an adjacent plate 12a, 12b. For example, the axial gap 19 is constant and may be very small.