THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention refers generally to a plate heat exchanger, in particular a plate heat exchanger in the form of an evaporator, i.e. a plate heat exchanger designed to cool a fluid through evaporation of a cooling medium in a cooling medium circuit for various, preferably industrial applications, such as air conditioning, cooling systems, heat pump systems, etc.

The present invention refers especially to a plate heat exchanger comprising a plate package, which comprises a number of heat exchanger plates that are provided beside each other in such a way that a first plate interspace for a cooling medium is formed between every second pair of adjacent heat exchanger plates, and a second plate interspace for a fluid between remaining pairs of adjacent heat exchanger plates, wherein the first plate interspaces and the second plate interspaces are separated from each other and provided beside each other in an alternating order in the plate package, wherein substantially each heat exchanger plate has at least a first porthole and a second porthole, wherein the first portholes enclose an inlet channel for the cooling medium to the first plate interspaces and the second portholes enclose an outlet channel for the cooling medium from the first plate interspaces, wherein the inlet channel is adapted to permit separation of the cooling medium to a substantially gaseous phase and a substantially liquid phase, wherein the plate heat exchanger includes at least a primary passage for conveying the gaseous phase from the inlet channel to the first plate interspaces and at least a secondary passage for conveying the liquid phase from the inlet channel to the first plate interspaces, and wherein the primary

passage and the secondary passage meet in an area for re¬ mixing of the liquid phase into the gaseous phase for transport of this mixture further into the first plate interspaces.

The invention also refers to a plate module for a plate package in a plate heat exchanger, wherein the plate module comprises two heat exchanger plates which are provided beside each other in such a way that a plate interspace for a cooling medium is formed between the heat exchanger plates, wherein substantially each heat exchanger plate has at least a first porthole and a second porthole, wherein the first portholes form an inlet channel for the cooling medium to the plate interspace and the second portholes form an outlet channel for the cooling medium from the plate interspace, wherein the inlet channel is designed to permit separation of the cooling medium into a substantially gaseous phase and a substantially liquid phase, wherein the plate module comprises at least a primary passage for conveying the gaseous phase from the inlet channel to the plate interspace and at least a secondary passage for conveying the liquid phase from the inner channel to the plate interspace, and wherein the primary passage and the secondary passage meet in an area for re-mixing of the liquid phase into the gaseous phase for transport of this mixture further into the plate interspace.

The cooling medium, which is supplied to the inlet channel of such a plate heat exchanger for evaporation of the cooling medium, is usually present in both a gaseous state and a liquid state. It is then difficult to provide an optimum distribution of the cooling medium to the different plate interspaces in the evaporator so that the same quantity of cooling medium is supplied and flows through each plate interspace intended for the cooling medium. If the cooling medium has a relatively high velocity into the inlet channel, the liquid phase is inclined to be transported to the inner end of the inlet channel. If the cooling medium has a relatively low velocity into the plate heat

exchanger, the liquid phase is inclined to reach only the plate interspaces located at the outer end of the inlet channel. It is difficult to achieve an optimum velocity in this respect, it is known that this problem with the distribution of the cooling medium at least partly may be solved through the provision of a throttling for the cooling medium at each plate interspace. In such a way a pressure drop for the cooling medium is achieved when it enters the respective plate interspace. This solution is however in the first place suitable for relatively small evaporators but not for large evaporators in industrial applications.

SUMMARY OF THE INVENTION

The object of the present invention is to provide an improved plate heat exchanger for evaporation of a cooling medium. A further object is to provide such a plate heat exchanger, which contributes to a proper distribution of the cooling medium to all plate interspaces for the cooling medium. A further object is to provide such a plate heat exchanger which is compact and can be manufactured in an easy manner.

This object is achieved by the plate heat exchanger initially defined, which is characterised in that the primary passage is designed to increase the velocity of the gaseous phase and to convey the gaseous phase to and past the liquid phase in said area in such a way that liquid is re-mixed into the gaseous phase by means of an ejector action.

By means of such a plate heat exchanger, the gaseous phase and the liquid phase of the incoming cooling medium will be separated from each other and thereafter re-mixed prior to the entry into the first plate interspaces. The separated gaseous phase may be used to bring a part of the liquid phase into each of the first plate interspaces in such a way that the liquid phase is distributed uniformly between all first plate interspaces of the

plate heat exchanger. Thanks to the created ejector action an efficient mixing of liquid in the gaseous phase is achieved substantially immediately before the cooling medium is distributed in the first plate interspaces.

According to an embodiment of the invention, the inlet channel is connected to at least an upper outlet which forms an inlet to the primary passage, and at least a lower outlet which forms an inlet to the secondary passage. The primary passage may then extend to the secondary passage.

According to a further embodiment of the invention, the plate heat exchanger is adapted to be provided in such a way that the lower outlet is located beneath the upper outlet, wherein the lower outlet is dimensioned in such a way that it permits liquid from the liquid phase to be collected upstream the lower outlet. The liquid in the liquid phase may then be collected in a lower part of the inlet channel, preferably along substantially the whole length of the inlet channel. In such a way, there will always be liquid to be brought, by the gaseous phase in the primary passage, into each of the first plate interspaces.

According to a further embodiment of the invention, the primary passage has a total minimum flow area and the secondary passage has a total minimum flow area, wherein the minimum flow area of the secondary passage is less than the minimum flow area of the primary passage. In such a way it is ensured that liquid is collected upstream the secondary passage and that the liquid successively is discharged from the inlet channel in a controlled manner.

According to a further embodiment of the invention, the heat exchanger plates are compression-moulded in such a way that a substantially closed channel, which extends around at least a part of the inlet channel is formed in substantially each of the first plate interspaces, wherein these closed channels are

comprised by the primary passage. In such a way, the arrangement with the separate primary and secondary passages for the gaseous phase and the liquid phase, respectively, may in an easy manner be provided during the compression-moulding of the heat exchanger plates. No further components than the heat exchanger plates are necessary for the achievement of the desired function. Advantageously, the heat exchanger plates may then be compression-moulded in such a way that the upper outlet is designed as a channel extending from the inlet channel to the substantially closed channel in substantially each of the first plate interspaces. Furthermore, the heat exchanger plates may also be compression-moulded in such a way that the lower outlet is designed as a channel, which extends from the inlet channel in substantially each of the first plate interspaces. Also these two channels, forming an outlet from the inlet channel, may thus in an easy manner be provided during the compression-moulding of the heat exchanger plates.

According to a further embodiment of the invention, the primary passage comprises two primary portions, which from an area at an upper part of the inlet channel extend in a respective direction around the inlet channel, wherein the two primary portions meet substantially immediately downstream the lower outlet. Consequently, the two upper outlets for each of the first plate interspaces may extend from the inlet channel. Alternatively, the primary passage may substantially immediately downstream the upper outlet be divided into the two primary portions.

According to another embodiment of the invention, each heat exchanger plate is designed in such a way that it comprises a lower aperture which is located beneath the first porthole and which is delimited from the first porthole by means of a first partitioning portion, wherein the first partitioning portion is designed to permit at least said liquid phase to pass the first partitioning portion and wherein the lower apertures form a

liquid channel which extends through the plate package substantially in parallel to the inlet channel. Also such a design may be provided in an easy manner during the compression- moulding and punching of the heat exchanger plates. No further components are required. Advantageously, the lower outlet may then extend from the liquid channel. According to this embodiment, liquid may thus be collected in the liquid channel, wherein the liquid is discharged successively from the liquid channel in a controlled manner through the lower outlet.

According to a further embodiment of the invention, each heat exchanger plate is designed in such a way that it comprises an upper aperture which is delimited from the first porthole by means of a second partitioning portion, wherein the upper apertures form a gas channel extending through the plate package in parallel to the inlet channel. Also such an aperture may be provided in connection with the compression-moulding and the punching of the heat exchanger plates. The upper outlet may then extend from the inlet channel to the gas channel and the closed channel may extend from the gas channel.

According to a further embodiment of the invention, the plate heat exchanger comprises a first pipe, which extends through the first portholes of substantially each heat exchanger plate and which forms the inlet channel. According to this embodiment, the plate heat exchanger may be produced by means of common heat exchanger plates, wherein the first pipe is introduced into the inlet channel for forming the primary passage and the secondary passage. Advantageously, the upper outlet and the lower outlet may then extend through the first pipe, wherein the primary passage extends around at least a part of the first pipe. The primary passage may thus extend in the relatively thin gap formed between the inlet channel and the outer side of the first pipe.

According to a further embodiment of the invention, the plate heat exchanger comprises a partitioning plate, which is provided with an angle of inclination in the first pipe and which extends along substantially the whole length of the inlet channel, wherein the upper outlet is located above the partitioning plate and the lower outlet is located beneath the partitioning plate and wherein the partitioning plate in a lower area has an aperture for the liquid phase. Liquid may thus be collected in a lower area of the first pipe, especially in an area beneath the partitioning plate.

According to a further embodiment of the invention, the plate heat exchanger comprises a second pipe which extends in the first pipe along substantially the whole length of the inlet channel, wherein the second pipe comprises at least an aperture for discharging the gaseous phase and the liquid phase into the first pipe.

According to a further embodiment of the invention, the plate heat exchanger comprises a first end plate and a second end plate, between which the heat exchanger plates are provided.

Furthermore, substantially each heat exchanger plate may comprise a third porthole and a fourth porthole, wherein the third portholes form an inlet channel for said fluid to the second interspaces, and the fourth portholes form an outlet channel for said fluid from the second plate interspaces. The inlet channels and the outlet channels may then extend through the first end plate. The heat exchanger plates may also be permanently connected to each other in pairs, wherein each pair encloses one of the first plate interspaces.

The object is also achieved by means of the initially defined plate module, which is characterised in that the primary passage is designed to increase the velocity of the gaseous phase and to convey the gaseous phase to and past the liquid phase in said

area in such a way that liquid is re-mixed into the gaseous phase by means of an ejector action.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained more closely by means of a description of various embodiments disclosed by way of example and with reference to the drawings attached hereto.

Fig. 1 discloses schematically a sideview of a plate heat exchanger according to a first embodiment of the invention.

Fig. 2 discloses schematically a front view of the plate heat exchanger in Fig. 1 .

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

Fig. 4 discloses schematically a plan view of an area around a porthole of the heat exchanger plate in Fig. 3.

Fig. 5 discloses schematically a sectional view through a number of heat exchanger plates along the line V-V in Fig. 4.

Fig. 6 discloses schematically a plan view of an area around a porthole of a heat exchanger plate according to a second embodiment of the invention. Fig. 7 discloses schematically a plan view of an area around a porthole of a heat exchanger plate according to a third embodiment of the invention.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

Figs. 1 to 5 disclose a first embodiment of the plate heat exchanger according to the invention. The plate heat exchanger comprises a plate package P, which comprises a number of

compression-moulded heat exchanger plates 1 that are provided beside each other. The heat exchanger plates 1 are provided in such a way that a first interspace 3 for a cooling medium is formed between every second pair of adjacent heat exchanger plates 1 , and a second plate interspace 4 for a fluid between the remaining pairs of adjacent heat exchanger plates 1. The first plate interspaces 3 and the second plate interspaces 4 are thus separated from each other and provided beside each other in an alternating order in the plate package P.

Furthermore, the plate heat exchanger comprises a first end plate 5 and a second end plate 6, between which the heat exchanger plates 1 are provided. In the first embodiment, which is disclosed in Figs. 1 and 2, the first end plate 5 is a so-called pressure plate and the second end plate 6 is a so-called frame plate. The plate package P is in the first embodiment kept together by means of a number of tie bolts 7, which extend outside the heat exchanger plates 1 but through the end plates 5 and 6. The plate package P is compressed by means of nuts 8 threaded on the tie bolts 7.

According to the first embodiment, the heat exchanger plates 1 are permanently connected to each other in pairs. The two heat exchanger plates 1 in each pair may thus be welded to each other by means of a weld joint 9, see Fig. 3. The heat exchanger plates 1 in one pair may also be brazed to each other, or permanently connected in any other way. Such a permanently connected pair forms a plate module 10, see Fig. 5. The two heat exchanger plates 1 in a plate module 10 encloses between themselves one of the first plate interspaces 3. In the plate package 3, the second plate interspaces 4 are enclosed between adjacent plate modules 10. The second plate interspaces 10 may be sealed by means of gaskets 11 in a manner known per se. It is to be noted, that the invention also is applicable to plate heat exchangers where every plate interspace 3, 4 is sealed by means of gaskets, or plate heat

exchangers where all heat exchanger plates 1 are brazed to a permanently connected plate package.

Substantially each heat exchanger plate 1 comprises a first porthole 12, a second porthole 12, a third porthole 12 and a fourth porthole 12, see Fig. 3. The first portholes 12 enclose an inlet channel 13 for the cooling medium to the first plate interspaces 3. The second portholes 12 enclose an outlet channel 14 for the cooling medium from the first plate interspaces 3. The third portholes 12 enclose an inlet channel 15 for said fluid to the second plate interspaces 4. The fourth portholes 12 enclose an outlet channel 16 for said fluid from the second plate interspaces 4. In a central area of each heat exchanger plate A, B between the portholes 12, there is an active heat transfer area 18, which is provided with a corrugation of ridges and valleys in a manner known per se. In the embodiment disclosed in Fig. 3, the corrugations extend in a herringbone-like pattern, wherein the corrugations of adjacent heat exchanger plates 1 points in opposite directions. The heat transfer area 18 may of course have other kinds of patterns, compare Fig. 4.

Each heat exchanger plate 1 has a longitudinal centre axis x, see Figs. 2 and 3. The heat exchanger plates 1 and the plate heat exchanger are in all embodiments disclosed adapted to be provided in such a way that the centre axis x extends substantially vertically. The inlet channel 13 for the cooling medium and the outlet channel 16 for the fluid will then be located in the proximity of a lower end of the plate heat exchanger, whereas the outlet channel 14 for the cooling medium and the inlet channel 15 for the fluid will be located in the proximity of an upper end of the plate heat exchanger. In an evaporator application, the cooling medium preferably flows upwardly through the plate heat exchanger. In the embodiments disclosed, the plate heat exchanger is designed as a counter

current configuration. The invention is however also applicable to a parallel flow configuration.

The cooling medium supplied to an evaporator is normally a mixture of a gas and a liquid. According to this invention, the gas is first to be separated from the liquid. To this end, the inlet channel 13 is arranged to permit separation of the cooling medium entering the inlet channel 13 to a substantially gaseous phase and a substantially liquid phase. Thereafter the gaseous phase and the liquid phase are to be conveyed separated from each other to an area 19 in each of the first plate interspaces 3. In the area 19, the liquid phase and the gaseous phase meet and are re-mixed with each other. In such a way, it is possible to control especially the supply of liquid to various parts of the inlet channel and consequently ensure that the liquid is uniformly distributed between each of the first plate interspaces 3. The plate heat exchanger comprises to this end at least a primary passage for conveying the gaseous phase from the inlet channel 13 to the first plate interspaces 3, and at least a secondary passage for conveying the liquid phase from the inlet channel 13 to the first plate interspaces 3. The primary passage and the secondary passage meet in said area 19 in the proximity of the first plate interspaces 3 for re-mixing of the liquid phase in the gaseous phase. The primary passage is designed to increase the velocity of the gaseous phase and to convey the gaseous phase to and past the liquid phase at a relatively high velocity in such a way that liquid is re-mixed in the gaseous phase by means of an ejector action in said area 19.

Especially with reference to in particular Figs. 4 and 5, the first embodiment is now to be described more closely. In these figures, the area around the inlet channel 13 is disclosed more closely. According to the first embodiment, the primary passage, the secondary passage and the lower area 19 have been produced during compression-moulding of the heat exchanger plates 1. The primary passage comprises in substantially each

of the first plate interspaces 3 an upper outlet 20 which is designed as a channel extending from the inlet channel 13. Furthermore, the primary passage comprises in each of the first plate interspaces 3 two substantially closed channels 21 , which extend from the upper ogtlet 20 around a respective half of the inlet channel 13 to said area 19 located beneath the inlet channel 13. The secondary passage comprises in substantially each of the first plate interspaces 3 a lower outlet 22, which is designed as a channel extending from the inlet channel 13 to said area 19 beneath the inlet channel 13. When the gaseous phase has been re-mixed with the liquid phase, wherein liquid is supplied to the gas passing by means of an ejector action, the mixture leaves the lower area 19 and is conveyed out in the heat transfer area 18 in the first plate interspaces 3 via an annular channel 24 extending around the inlet channel 13 and the two closed channels 21 in each of the first plate interspaces 3. The annular channel 24 has also been produced through compression-moulding of the heat exchanger plates 1. Each heat exchanger plate 1 forms on the side turned away from the annular channel 24 an receiving area for the gasket 1 1 mentioned above, see Fig. 5.

The lower outlet 22 is dimensioned in such a way that it permits liquid from the liquid phase to be collected in a lower area of the inlet channel 13 upstream the lower outlet 13. The secondary passage then has in the lower outlet 22 a minimum flow area which is relatively small and less than a minimum flow area of the primary passage.

As appears from above, the primary passage is in the first embodiment divided into two primary portions, which from an area at an upper part of the inlet channel 13 extend in a respective direction around the inlet channel 13. The two primary portions meet substantially immediately downstream the lower outlet 22. However, it is also possible to provide two upper outlets in the inlet channel 13, one for each such primary

portion. In this case, there are thus two primary passages in each of the first plate interspaces 3.

The second embodiment is now to be described more closely with reference to Fig. 6. According to the second embodiment, heat exchanger plates 1 , which are compression-moulded and punched in such a way that the primary passage and the secondary passage are produced, are also employed. Each heat exchanger plate 1 is then compression-moulded and punched in such a way that it has the first porthole 12. Also in the second embodiment, the first portholes 12 form the inlet channel 13. Each heat exchanger plate also has a lower aperture 30 which is located beneath the first porthole 12. The lower aperture 30 is delimited from the first porthole 12 by means of a first partitioning portion 31. The lower apertures 30 form a liquid channel 32 extending through substantially the whole plate package 1 1 substantially in parallel to the inlet channel 13. The first partitioning portion 31 is designed to permit that at least the liquid phase is conveyed from the inlet channel 13 over the partitioning portion 31 down to the liquid channel 32. The lower outlet 22 extends from the liquid channel 32 and in particular through a ridge 33 delimiting the liquid channel 32 downwards.

Each heat exchanger plate 1 is furthermore compression- moulded and punched in such a way that it has an upper aperture 34, which is delimited from the first porthole by means of a second partitioning portion 35. The upper apertures 35 form a gas channel 36 extending through substantially the whole plate package P substantially in parallel to the inlet channel 13. The upper outlet 20 extends from the inlet channel 13 to the upper aperture 35 and the gas channel 36 via the second partitioning portion 35 and in particular around an upper ridge

37 that delimits the inlet channel 13 upwardly and to gas channel 36. From the gas channel 36 and the upper outlet 20, the closed channel 21 extends up to the area 19 where the gaseous phase, which is transported through the closed channel

21 , meets the liquid phase from the lower outlet 22. The area 19 is, also according to the second embodiment, located beneath the lower outlet 22. The mixture of the gaseous phase and the liquid phase are then transported from the area 19 to the heat transfer area 18 via an outlet channel 38 in each of the first plate interspaces 3.

The third embodiment is now to be described more closely with reference to Fig. 7. According to the third embodiment, heat exchanger plates 1 are employed, which are provided for forming the first plate interspaces 3 between every second pair of adjacent plates 1 , and the second plate interspaces 4 between the remaining pairs of adjacent plates 1. The plates 1 may be connected to each other in all possible ways, for instance pressed against each other between two end plates 5 and 6, permanently connected to each other in pairs, or the whole plate package P may be brazed.

According to the third embodiment, the plate heat exchanger comprises a first pipe 40, which extends through the first portholes 12 of substantially each heat exchanger plate 1. The first pipe 40 form the inlet channel 13. The upper outlet 20 and the lower outlet 22 extend through the pipe 40, wherein the primary passage extends around at least a part of said pipe. Preferably, there is an upper outlet 20 in the form of a hole through the first pipe 40 for each of the first plate interspaces 3, and a lower outlet 22 in the form of a hole through the first pipe 40 for each of the first plate interspaces 3. Furthermore, a partitioning plate 41 is provided in the first pipe 40. The partitioning plate 41 has an angle of inclination in relation to the centre axis x. The partitioning plate 41 extends along substantially the whole length of the first pipe 40 and the inlet channel 13. The upper outlet 20 is located above the partitioning plate 41 , and the lower outlet 22 is located beneath the partitioning plate 41 . Furthermore, the partitioning plate 41 has

in a lower area an aperture 42 through which the liquid phase may pass.

According to the third embodiment, the plate heat exchanger also comprises a second pipe 43 for the supply of the cooling medium to the plate heat exchanger. The second pipe 43 extends in the first pipe 40 along substantially the whole length of the inlet channel 13. The second pipe 43 comprises at least one aperture 44 for discharging the cooling media, i. e. the gaseous phase and the liquid phase, into the first pipe 40 above the partitioning plate 41. The gaseous phase will thus be discharged through the upper outlets 20 and then pass through the primary passage along the outer side of the first pipe 40 down to said area 19 which is located beneath the lower outlets 22. From the area 19, the mixture is transported out into the heat transfer area in each of the first plate interspaces 3.

The invention is not limited to the embodiments disclosed but may be varied and modified within the scope of the following claims.