TECHN ICAL FI ELD OF THE I NVENTION The present i nvention refers to a plate heat exchanger for evaporation according to the preamble of claim 1 .

BACKGROUN D OF THE I NVENTION AND PRIOR ART EP-2 730 878 discloses a plate package of a plate heat exchanger. The plate package comprises first heat exchanger plates and second heat exchanger plates, which are arranged side by side in such a way that a first plate interspace is formed between each pair of adjacent first heat exchanger plates and second heat exchanger plates, and a second plate i nterspace between each pair of adjacent second heat exchanger plates and first heat exchanger plates. The first plate interspaces and the second plate interspaces are separated from each other and provided side by side in an alternating order in the plate package. Each of the first and second heat exchanger plates has a first porthole, surrounded by a peripheral rim . The first heat exchanger plates and the second heat exchanger plates are joined to each other via joints of braze material between the first and second heat exchanger plates and arranged in such a way that the peripheral rims together define an i nlet channel extendi ng through the plate package.

A restriction hole is provided through the peripheral rim of the first and/or the second heat exchanger plates and forms a fluid passage allowing a communication between the i nlet channel and the first plate interspaces.

One problem related to the prior art plate heat exchanger is that the restriction hole is sensible to cracking . This sensibility is due to the relatively low height of the peripheral rim , which means that the restriction hole will be positioned relatively close to the edge of the peripheral rim . Consequently, there will be only a short distance between the restriction hole and the edge of the peripheral rim . This is in particular the case when the pressure depth of the heat exchanger plates is small .

SUMMARY OF THE I NVENTION

The object of the present invention is to remedy the problems discussed above. I n particular, it is aimed at a plate heat exchanger bei ng less susceptible to cracks at the inlet channel , in particularly in the peripheral rim forming the inlet channel .

This object is achieved by the plate heat exchanger i nitially defined , which is characterized in that each of the secondary pairs encloses an inlet chamber adjacent to the peripheral rim , and that the i nlet chamber is closed to the second plate interspaces, is open to the inlet channel and communicates with one of the first plate interspaces via at least one nozzle member, comprising one or more restrictions holes, thereby permitting a flow of the first fluid from the i nlet channel to the first plate interspaces.

By locating the nozzle for the first fluid in the i nlet chamber and not through the peripheral rim, cracking of the peripheral rim can be avoided . The nozzle member comprises one or more restriction holes. Such restriction hole may be made in advance, before the plate heat exchanger is assembled . The one or more restriction holes provide a restriction or throttling of the first fluid passing through the nozzle member. Such restriction or throttling ensures a proper distribution of the first fluid in the first plate interspace. The first fl uid may thus flow from the i nlet channel into the i nlet chamber and then through the nozzle into the first plate interspaces. Accordi ng to an embodiment of the invention , the nozzle member extends through the first heat exchanger plate between the inlet chamber and said one of the first plate interspaces. The nozzle may thus be located at a distance from the peripheral rim so that the risk for cracks is avoided . Accordi ng to an embodiment of the invention , the number of restriction holes through the first heat exchanger plate may be one, two, three, four or even more.

Accordi ng to an embodiment of the invention , the one or more restriction holes together have a flow area of 1 .5 - 2.5 mm ² .

Accordi ng to an embodiment of the invention , each of the inlet chambers is separated from the other inlet chambers of the plate heat exchanger.

Accordi ng to an embodiment of the invention , the i nlet chamber surrounds the inlet channel . The i nlet chamber may thus be annular. The inlet chamber may alternatively extend along a part of the circumference of the inlet channel .

Accordi ng to an embodiment of the invention , each of the first heat exchanger plates comprises an annular flat portion adjacent the peripheral rim . The annular flat portion and the peripheral rim may partly enclose the inlet chamber. The annular flat portion contributes to strengthen the region close to the peripheral rim.

Accordi ng to an embodiment of the invention , the annular flat portion extends su bstantially in parallel with the extension plane.

Accordi ng to an embodiment of the invention , the annular flat portion adjoins a corresponding annular flat portion of the second heat exchanger plate of an adjacent secondary pair. The joining of the annular flat portion to the corresponding annular flat portion secures a high strength of the plate heat exchanger around the inlet channel .

Accordi ng to an embodiment of the invention , the peripheral rim of the first heat exchanger plate of the secondary pairs comprises a depression forming a surface portion extending away from the inlet channel , wherein an aperture extends through the surface portion and permits said flow of the first fluid from the inlet channel to the first plate interspace.

By providing an aperture through such a surface portion , the aperture may be located at a greater distance from an edge of the peripheral rim than if it is located directly on the peripheral rim . The aperture is thus less suscepti ble to create cracks i n the peripheral rim. The first fluid may thus flow from the inlet channel into the depression and through the aperture through the surface, and then further into the first plate interspaces.

Accordi ng to an embodiment of the invention , the depression extends from the annular surface and from the peripheral rim.

Accordi ng to an embodiment of the invention , the surface portion is partly surrounded by a wall surface, which extends between and connects to the surface portion and the annular flat portion .

Accordi ng to an embodiment of the invention, the surface portion is substantially plane. Accordi ng to an embodiment of the invention , the surface portion extends su bstantially in parallel with the extension plane.

Accordi ng to an embodiment of the invention , the peripheral rim of the first heat exchanger plate of the secondary pairs comprises a recess extending from an edge of the peripheral rim , and permitting said flow of the first fluid from the inlet channel to the first plate interspaces.

Such a recess located at the edge of the peripheral rim is less susceptible to create cracks in the peripheral rim than a hole through the peripheral rim close to the edge. The first fluid may thus flow from the inlet channel through the recess into the inlet chamber and then further into the first plate interspace. Accordi ng to an embodiment of the invention , the peripheral rim has a rim height perpendicular to the extension plane from an edge to a root end of the peripheral rim , wherei n the peripheral rim passes the adjacent second heat exchanger plate before reaching the adjacent first heat exchanger plate. The edge of the peripheral rim may thus be joined to the root end of the peripheral rim of the first heat exchanger plate of the adjacent secondary pair.

Accordi ng to an embodiment of the invention , each of the first and second heat exchanger plates has a heat exchanger area comprising a corrugation of ridges and valleys, and wherein a pressure depth is defined between an upper point of the ridges and a lower point of the valleys on an upper side of the heat exchanger plate.

Accordi ng to an embodiment of the invention, the pressure depth is less than 3 mm, preferably less than 2 mm.

Accordi ng to an embodiment of the invention, each of the first and second heat exchanger plates comprises an edge area extendi ng around the heat exchanger area.

Accordi ng to any one of the preceding claims, wherein the first heat exchanger plates and the second heat exchanger plates are permanently joined to each other, preferably through brazing . BRI EF DESCRI PTI ON OF TH E DRAWI NGS

The present i nvention is now to be explained more closely through a description of various embodiments and with reference to the drawi ngs attached hereto.

Fig 1 discloses schematically a plan view of a plate heat exchanger according to a first embodiment of the i nvention .

Fig 2 discloses schematically a longitudinal sectional view along the line l l-l l in Fig 1 .

Fig 3 discloses schematically a plan view of a first heat exchanger plate of the plate heat exchanger in Fig 1 . Fig 4 discloses schematically a plan view of a second heat exchanger plate of the plate heat exchanger in Fig 1 .

Fig 5 discloses schematically a plan view of an inlet channel area of the first heat exchanger plate.

Fig 6 discloses schematically a plan view of an inlet channel area of the second heat exchanger plate.

Fig 7 discloses schematically a sectional view of the inlet channel area of some of the heat exchanger plates along the line VI I-VI I i n Fig 5.

Fig 8 discloses schematically a sectional view of the inlet channel area of some of the heat exchanger plates along the line VI M-VI M in Fig 5. Fig 9 discloses schematically a plan view of the inlet channel area of the first heat exchanger plate of a plate heat exchanger accordi ng to a second embodiment. Fig 10 discloses schematically a sectional view of an inlet channel area of the second heat exchanger plate.

Fig 1 1 discloses schematically a front view of a secondary pair of heat exchanger plates seen from the inlet channel in Fig 9.

Fig 12 discloses schematically a sectional view of the inlet channel area of some of the heat exchanger plates along the line XI I-XI I i n Fig 9. Fig 13 discloses schematically a sectional view of the inlet channel area of some of the heat exchanger plates along the line XI 11 -XI 11 in Fig 10.

DETAI LED DESCRI PTION OF VARIOUS EMBODI MENTS

Figs 1 and 2 disclose a plate heat exchanger comprising a plurality of heat exchanger plates 1 , 2. The heat exchanger plates 1 , 2 comprise first heat exchanger plates 1 and second heat exchanger plates 2 arranged beside each other i n an alternating order in the plate heat exchanger.

Each of the first heat exchanger plates 1 and the second heat exchanger plates 2 extends i n parallel with an extension plane

P -

The first and second heat exchanger plates 1 , 2 are arranged side by side in such in a way that first plate interspaces 3 for a first fluid and second plate interspaces 4 for a second medium are formed . The plate heat exchanger is configured to be operated as an evaporator, wherein the first plate interspaces 3 are configured to receive the first fluid to be evaporated therein . The first fluid may be any suitable refrigerant. The second plate interspaces 4 are configured to receive the second fluid for heati ng the first fluid to be evaporated in the first plate interspaces 3.

The plate heat exchanger may also be reversed , and is then configured to be operated as a condenser, wherein the first fluid , i .e. the refrigerant, is condensed in the first plate interspaces 3, and the second fl uid is conveyed through the second plate interspaces 4 for cooling the first fluid conveyed through the first plate interspaces 3. Each first plate interspace 3 is formed by a primary pair I , consisting of one of the second heat exchanger plates 2 and an adjacent one of the first heat exchanger plates 1 , see Figs 7 and 8. Each second plate interspace 4 is formed by a secondary pair I I , consisting of one of the first heat exchanger plates 1 and an adjacent one of the second heat exchanger plates 2, see Figs 7 and 8. The first plate interspaces 3 and the second plate interspaces 4 are provided side by side in an alternating order in the plate heat exchanger, as can be seen in Fig 2.

Each first and second heat exchanger plate 1 , 2 has a heat exchanger area 5, see Figs 3 and 4 , extending in parallel with the extension plane p, and an edge area 6 extending around the heat exchanger area 5. The edge area 6 thus surrounds the heat exchanger area 5 and forms a flange, which is inclined in relation to the extension plane p, see Fig 2. The flange of the edge area 6 of one of the heat exchanger plates 1 , 2 adjoins, and is joined to the corresponding flange of the edge area 6 of an adjacent one of the heat exchanger plates 1 , 2, i n a manner known per se.

The heat exchanger area 5 comprises a corrugation 7 of ridges and valleys, which is schematically indicated i n Figs 3 and 4, and in Figs 7 and 8. The corrugation 7 may form various patterns, for instance a diagonal pattern , a fish bone pattern , etc. as is known in the art of plate heat exchangers. A pressure depth 8 is defined between an upper point of the ridges and a lower point of the valleys on an upper side of the respective first and second heat exchanger plates 1 , 2, see Fig 7. The pressure depth 8 is less than 3 mm, preferably less than 2 mm. The pressure depth may preferably be equal to or larger than 1 mm.

Each of the first heat exchanger plates 1 and the second heat exchanger plates 2 also comprises four port holes 1 1 , 12, 13, 14.

A first port hole 1 1 of the port holes 1 1 - 14 of the first heat exchanger plates 1 is surrounded by a peripheral rim 15, see Figs 7 and 8. The peripheral rim 15 is annular and extends away from the heat exchanger area 5 transversally, or substantially transversally to the extension plane p.

The peripheral rim 15 has an edge 16 and a root end 1 7. The peripheral rim 15 has a rim height 18 perpendicular to the extension plane p from the edge 16 to the root end 1 7, see Fig 7. The rim height 18 is larger than or slightly larger than twice the pressure depth 8.

As can be seen in Figs 7 and 8, the peripheral rim 15 is tapering or conical , or slightly tapering or conical , and tapers towards the edge 16, especially from the root end 1 7 to the edge 16. The remaining three port holes 1 2- 14 are not provided with such a peripheral rim , but are defined by a porthole edge, as schematically indicated in Fig 2 for the portholes 13. In the embodiments disclosed , the first port hole 1 1 of the second heat exchanger plates 2 also lacks the peripheral rim. The first port hole 1 1 of the second heat exchanger plates 2 is defined by a porthole edge 19, see Figs 7 and 8. The first heat exchanger plates 1 and the second heat exchanger plates 2 are permanently joined to each other via joints of braze material , such as copper or a copper alloy, between the first and second heat exchanger plates 1 , 2. The first and second heat exchanger plates 1 , 2 may be made of a metal or a metal alloy, such as stainless steel , which extends to the outer surface of the heat exchanger plate 1 , 2. The outer surface of the metal or 5 metal alloy has such properties that it adheres to the braze material duri ng the brazi ng of the plate heat exchanger.

The heat exchanger plates 1 , 2 are arranged in such a way that the peripheral rim 15 of the first heat exchanger plates 1 defi ne an inlet channel 21 extending through the plate heat exchanger, as can be seen i n Figs 7 and 8. The peripheral rim 15 passes the adjacent second heat exchanger plate 2 before reachi ng the adjacent first heat exchanger plate 1 . The edge 16 of the peripheral rim of the first heat exchanger plate 1 of one secondary pair I I is thus joined to the root end 1 7 of the peripheral rim 15 of the first heat exchanger plate 1 of the adjacent secondary pair I I .

The second port holes 12 of the heat exchanger plates 1 , 2 define an outlet channel 22 for the first fluid , see Figs 1 and 2. The third port hole 13 of the heat exchanger plates 1 , 2 define an inlet channel 23 for the second fl uid . The fourth port hole 14 of the heat exchanger plates 1 , 2 define an outlet channel 24 for the second fluid .

The peripheral rim 15 has a convex side, and an opposite concave side. The concave side of the peripheral rim 15 faces the inlet channel 21 .

Each of the secondary pairs I I encloses a respective inlet chamber 30 adjacent to the peripheral rim 15. The convex side of the peripheral rim 15 faces the inlet chamber 30.

Each of the inlet chambers 30 is closed to the second plate interspaces 4, is open to the inlet channel 21 and communicates with one of the first plate interspaces 3 via a respective nozzle member 31 , see Figs 5 and 8.

Each of the inlet chambers 30 is thus separated from or closed to the other inlet chambers 30 of the plate heat exchanger. A flow of the first fluid from the inlet channel 21 to the first plate interspace 3 via the inlet chamber 30 is permitted .

The nozzle member 31 extends through the first heat exchanger plate 1 between the inlet chamber 30 and one of the first plate interspaces 3.

In the embodiments disclosed , the nozzle member 31 comprises or is formed by one restriction hole. It should be noted that the nozzle member 31 may comprise more than one restriction hole. The restriction hole provides a restriction or throttling of the first fluid passing through the nozzle member. Such restriction or throttling ensures a proper distribution of the first fluid in the first plate interspace. The restriction hole, or more than one restriction holes, together have a flow area of 1 .5 - 2.5 mm ² . The restriction hole, or restriction holes, may be circular.

In the embodiments disclosed , the inlet chamber 30 surrounds the inlet channel 21 . The i nlet chamber 30 is thus annular.

Each of the first heat exchanger plates 1 comprises an annular flat portion 32 adjacent the peripheral rim 15. The annular flat portion 32 extends from the peripheral rim 15 in parallel with , or substantially in parallel with , the extension plane p.

Each of the second heat exchanger plates 2 comprises a corresponding annular flat portion 33, which extends from the porthole edge 1 9 in parallel with , or substantially in parallel with the extension plane p, see Fig 6.

The annular flat portion 32 and the corresponding annular flat portion 33 extend i n parallel with each other and adjoins each other, see Figs 7 and 8. The annular flat portion 32, the peripheral rim 15, and the corresponding annular flat portion 33 enclose the inlet chamber 30.

As can be seen i n Fig 5, the annular flat portion 32 has a first projection 34 extending away from the peripheral rim 15 in parallel with the extension plane p. At the first projection 3, the annular flat portion 32 is wider.

As can be seen i n Fig 6, the corresponding annular flat portion 33 has a second projection 35. At the second projection 35, the corresponding annular flat portion 33 is wider, and thus extends further from the porthole edge 1 9. The second projection 35 has a longer peripheral length than the first projection 34.

Beside the first projection 34, the first heat exchanger plate 1 of each secondary pair I I has a flat area 36, see Fig 5, which extends in parallel with the extension plane p, see Fig 8. The flat area 36 is located adjacent to a concave part of the plate annular flat portion 32 and extend towards the peripheral rim 15.

The first projection 34 and the flat area 36 are located opposite to the second projection 35. The nozzle member 31 extends through the flat area 36 as can be seen in Figs 5 and 7. It should be noted that the annular chamber 30 alternatively may extend only along a part of the circumference of the inlet channel 21 . For instance, the inlet chamber 30 may have a circumferential length corresponding to the length of the second projection 35.

In the first embodiment, the peripheral rim 15 of the first heat exchanger plate 1 of the secondary pairs I I comprises a depression 40, which forms a surface portion 41 that extends away from the inlet channel 21 , see Figs 3, 5 and 7. The depression 40 extends from the annular flat portion 32 and from the peripheral rim 15. The surface portion 41 is partly surrounded by a wall surface 42 , which extends between and connects to the surface portion 41 and the annular flat portion 32.

The surface portion 41 is substantially plane and extends substantially in parallel with the extension plane p.

In the first embodiment, the i nlet chamber 30, is open to the inlet channel 21 via an aperture 43, see Figs 5 and 7. The aperture 43 extends through the surface portion 41 and permits a flow of the first fluid from the i nlet channel 21 to the first plate interspace 3 via the inlet chamber 30. Although only one aperture 43 is disclosed in the first embodiment, it should be noted that more than one apertures 43 may be provided . The aperture 43, or apertures, have a total flow area that is larger than the flow area of the nozzle member 31 , in particular larger than the total flow area of the one or more restriction holes of the nozzle member 31 .

The second embodiment, see Figs 9 to 13, differs from the first embodiment i n how the inlet channel 21 is open to the inlet chamber 30. It should be noted that the same reference signs has been used i n the different embodiments for corresponding elements.

In the second embodiment, the peripheral rim 1 5 of the first heat exchanger plate 1 of the secondary pairs I I comprises a recess 50. The recess 50 is open towards and extends from the edge 16 of the peripheral rim 15, see in particular Figs 1 1 and 12.

In the second embodiment, the inlet chamber 30, is thus open to the inlet channel 21 via the recess 50, which permits a flow of the first fluid from the inlet channel 21 to the first plate interspace 3 via the i nlet chamber 30 and the nozzle member 31 , which extends through the flat area 36 of the first heat exchanger plate 1 .

The recess 50 is located opposite to the first projection 34 of the annular flat portion 32, as can be seen in Fig 1 2.

Although only one recess 50 is disclosed in the second embodiment, it should be noted that more than one recesses 50 may be provided . The recess 50, or recesses, have a total flow area that is larger than the flow area of the nozzle member 31 , in particular larger than the total flow area of the one or more restriction holes of the nozzle member 31 .

In the second embodiment, peripheral rim 15 has no depression forming a surface portion . The invention is not limited to the embodiments disclosed , but may be varied and modified within the scope of the following claims.