Heat exchanger plate, a plate package using such heat exchanger plate and a heat exchanger using such heat exchanger plate

A heat exchanger plate for use in a plate package for a heat exchanger device is disclosed. The plate has a geometrical main extension plane (q) and a circumferential edge portion, the circumferential edge portion having a curved upper portion, a substantially straight lower portion and two opposing side portions interconnecting the upper and the lower portions. An upper porthole is arranged in an upper section of the heat exchanger plate and located at a distance from the upper portion of the circumferential edge portion thereby defining an upper intermediate portion. The upper intermediate portion includes the shortest distance (d2) between a centre of the upper porthole and the upper portion of the circumferential edge portion. The heat exchanger plate further comprises an upper flange having an extension along the upper portion of the circumferential edge portion. The upper flange has a length (L2) as seen in a direction transverse the shortest distance (d2), being 200-80% of the diameter (D2) of the upper porthole and more preferred 180-120% of the diameter (D2) of the upper porthole. Further, a plate package is disclosed and also a heat exchanger device using such heat exchanger plate/plate package.

FIELD OF INVENTION

The invention relates to a heat exchanger plate, a plate package using such heat exchanger plate, the use of a heat exchanger plate of such type in a heat exchanger device and also a heat exchanger device as such.

TECHNICAL BACKGROUND

A typical plate package to be used in a plate heat exchanger device comprises a plurality of heat exchanger plates, alternatingly arranged one on top of the other together with an intermediate bonding material. Each heat exchanger plate is typically provided with a complex pattern of ridges and valleys to thereby form a pattern of flow channels in the resulting plate interspaces between adjacent heat exchanger plates. The resulting stack is arranged in an oven where the heat exchanger plates are subjected to heat and thereby are bonded to each other along their contact surfaces. As a result, a plate package is provided.

To allow a fluid flow through the plate interspaces of the plate package, each heat exchanger plate is provided with an inlet porthole and an outlet porthole. The portholes are typically arranged in the proximity of a circumferential edge of the heat exchanger plate. The proximity to a circumferential edge is advantageous since the available heat transferring surface in the plate package thereby is affected to a low extent. Also, it is a well-known truth that it is difficult to distribute the fluid into the intermediate area between the porthole and the circumferential edge whereby the efficiency provided by the intermediate area typically is lower as compared to the remainder of the area of the heat exchanger plate. It is also a matter of reducing material consumption and thereby cost and weight of the plate package.

Still, the proximity must not be too small since that also induces an overall weakness to the heat exchanger plate and the plate package. A reduced weakness becomes obvious when handling the individual heat exchanger plates during stacking since the plates may be experienced as being flabby. This is especially the case of larger heat exchanger plates.

The proximity may also cause quality problems to the plate package during manufacturing. If a porthole is arranged too close to the circumferential edge, the heat transfer across the main extension plane during the step of bonding the stacked heat exchanger plates in an oven becomes uneven. This results in buckling which is due to an uneven thermal expansion across the surface of the heat exchanger plates and especially in the intermediate area that is formed between the circumferential edge of the heat exchanger plate and the porthole as compared to the overall area of the heat exchanger plate. Buckling causes the risk of insufficient bonding along the intended contact surfaces between adjacent heat exchanger plates. Insufficient bonding may cause leakage of fluid between the intended flow channels that are to be formed by bonding between two adjacent heat exchanger plates. Insufficient bonding may also cause leakage of fluid to the ambience along the perimeter of the plate package. The latter is a non-acceptable defect.

Accordingly, the positioning of the portholes requires a lot of considerations.

SUMMARY OF INVENTION

It is an object of the invention to provide a heat exchanger plate in which the portholes may be arranged in the proximity to a circumferential edge portion of the heat exchanger plate while at the same time allowing an even heat distribution during bonding and thereby an improved joint quality.

It is also an object of the invention to provide an overall stiffer heat exchanger plate, which as such facilitates handling and stacking of the heat exchanger plate.

As yet another object, a heat exchanger plate should be provided which is allows more simple fixtures to be used during stacking of the heat exchanger plates.

These objects are met by a heat exchanger plate for use in a plate package for a heat exchanger device, the heat exchanger plate having a geometrical main extension plane and a circumferential edge portion, the circumferential edge portion having a curved upper portion, a substantially straight lower portion and two opposing side portions interconnecting the upper and the lower portions, and

an upper porthole arranged in an upper section of the heat exchanger plate and located at a distance from the upper portion of the circumferential edge portion thereby defining an upper intermediate portion located between the upper portion of the circumferential edge portion and a circumferential edge of the upper porthole, the upper intermediate portion including the shortest distance between a centre of the upper porthole and the upper portion of the circumferential edge portion,

wherein the heat exchanger plate, along at least a section of the upper intermediate portion, further comprises an upper flange having an extension along the upper portion of the circumferential edge portion and extending from the circumferential edge portion in direction from the geometrical main extension plane,

wherein the upper flange has a length as seen in a direction transverse the shortest distance, being 200-80% of the diameter of the upper porthole and more preferred 180-120% of the diameter of the upper porthole.

When subjecting the heat exchanger plate to heat during bonding of a stack of heat exchanger plates in an oven, the heat will transfer from the periphery of the heat exchanger plate towards the centre thereof. The time to achieve an even temperature gradient across the heat exchanger plate will depend on the amount of material that must be heated. In a prior art heat exchanger plate without a flange, the intermediate portion will be heated faster than the remainder of the heat exchanger plate. Such uneven temperature gradient in combination with the fact that the intermediate portion is weaker than the remainder of the heat exchanger plate results in the risk of a thermal buckling of the intermediate portion. The buckling jeopardizes the intended contact surfaces between adjacent heat exchanger plates, which in turn results in insufficient bonding and leaking joints. In the worst case scenario, the resulting plate package will leak fluid to the medium, which is a non-acceptable defect.

The invention resides in the idea of arranging a flange along at least an extension of the intermediate portion in the proximity to the porthole. Thereby a heat shielding effect is provided for. The heat shielding effect is caused by the locally added material that must be heated prior to the intermediate portion. By providing the locally added material as a flange, the added material will not form part of the available heat transferring area/foot print of the heat exchanger plate but rather extend along the circumferential side walls of the plate package to be formed. Accordingly, a more even temperature gradient may be provided. The improved heat distribution allows for an overall higher joint quality and thereby a lower risk of leakage.

The flange will not only act as a heat shield, but also provide the heat exchanger plate with an overall improved stiffness that makes the heat exchanger plate less flabby during handling. The latter is especially the case for larger heat exchanger plates. Further, the flange will contribute to the guiding of heat exchanger plates during stacking and handling of the stack until bonding. Thereby fixtures can be made less complex.

The extension of the flange depends on parameters such as the curvature of the portion of the circumferential edge portion along which the porthole is arranged, the shortest distance between the center of the porthole and the circumferential edge, the diameter of the porthole and the thickness of the material of the heat exchanger plate.

In the present case the upper porthole is arranged in the upper section of the heat exchanger plate and located at a distance from the upper curved edge portion. The curved edge results in that the area of the intermediate portion is smaller than if the upper portion instead should be straight. Simulations and trials have shown that provided the upper edge portion is curved, the flange may have a length, that as seen in a direction transverse the shortest distance between the upper portion of the circumferential edge portion and the centre of the upper porthole, is 200-80% of the diameter of the upper porthole and more preferred 180-120% of the diameter of the upper porthole.

As an alternative or a supplement to the formulation that the upper flange extends from the circumferential edge portion in direction from the geometrical main extension plane, the upper flange may extend from the circumferential edge portion at an angle α to the normal of the geometrical main extension plane.

The heat exchanger plate may further comprise a lower porthole arranged in a lower section of the heat exchanger plate and located at a distance from the lower portion of the circumferential edge portion thereby defining a lower intermediate portion located between the lower portion of the circumferential edge portion and a circumferential edge of the lower porthole, the lower intermediate portion including the shortest distance between a centre of the lower porthole and the lower portion of the circumferential edge portion, wherein the heat exchanger plate, along at least a section of the lower intermediate portion, further comprises a lower flange having an extension along the lower portion of the circumferential edge portion and extending from the circumferential edge portion in direction from the geometrical main extension plane, wherein the lower flange has a length as seen in a direction transverse the shortest distance, being smaller than the diameter of the lower porthole and more preferred smaller than 80% of the diameter of the lower porthole.

The lower flange serves the same purpose as the upper flange discussed above and to avoid undue repetition reference is made to the above. As a difference to the upper intermediate portion discussed above, the lower intermediate portion is arranged between the straight lower portion of the circumferential edge portion and the lower porthole. Provided the shortest distances in the two situations are the same and also the diameters of the lower and upper portholes are the same, the area of the upper intermediate portion will be smaller than the lower intermediate portion. To allow a corresponding heat shielding effect, the upper flange should thus be made longer than the lower flange. Simulations and trials have shown that the lower flange may have a length as seen in a direction transverse the shortest distance, that is being smaller than the diameter of the lower porthole and more preferred smaller than 80% of the diameter of the lower porthole.

As an alternative or a supplement to the formulation that the lower flange extends from the circumferential edge portion in direction from the geometrical main extension plane, the lower flange may extend from the circumferential edge portion at an angle α to the normal of the geometrical main extension plane.

The lower and/or upper flanges may have an extension with a component along a normal to the main extension plane of the heat exchanger plate, and wherein the angle α formed by the lower and/or upper flanges to the geometrical main extension plane is smaller than 20 degrees to the normal. The angle α depends on if both of the two subsequent heat exchanger plates of a plate pair to be joined are provided with flanges or if only one of the heat exchanger plates have a flange. In case of only one of the plates having a flange, the angle α can be made smaller, such as smaller than 10 degrees.

According to another aspect, the invention refers to a plate package comprising a plurality of heat exchanger plates of a first type and a plurality of heat exchanger plates of a second type arranged alternatingly in the plate package one on top of the other, wherein at least the heat exchanger plates of the first type correspond to the heat exchanger plate as previously described.

Reference is made to the previous discussion with the essence that the provision of flanges having a local and limited longitudinal extension along the intermediate portions that are formed between the portholes and the upper and lower portions of the circumferential edge portions, a heat shielding effect is provided for during the manufacturing of the plate package. This allows for a more even temperature gradient. The resulting improved heat distribution allows for an overall higher joint quality and thereby a lower risk of leakage.

The heat exchanger plates of the first type may be identical with the heat exchanger plates of the second type, or alternatively, the heat exchanger plates of the first type may be identical with the heat exchanger plates of the second type, with the exception that the lower and/or the upper flanges are cut-off. Thereby one and the same press-tool can be used.

The flanges of the heat exchanger plates of the first type may be oriented in one and the same direction, and have an extension with a component along a normal to the main extension plane such that a flange of a heat exchanger plate of the first type abuts or overlaps a flange of a second subsequent heat exchanger plate of the first type.

From a heat shielding aspect, the overlap provides for a facilitated and enhanced heat distribution across the edge of the plate package during the bonding operation. This due to the locally added material (twice the material thickness). Also, an overall improved stiffening of the heat exchanger plates is provided which reduces the risk of buckling in the intermediate portions during the heat treatment. The reduced risk of buckling reduces the risk of insufficient bonding along the contact surfaces between adjacent heat exchanger plates and thereby leakage. Further, the overlap provides for a guiding effect during stacking of the heat exchanger plates, thereby reducing the requirements put on fixtures.

The flanges of the heat exchanger plates may be oriented in one and the same direction, and have an extension with a component along a normal to the main extension plane such that a flange of a first heat exchanger plate of the first type abuts or overlaps a flange of a subsequent heat exchanger plate, said subsequent heat exchanger plate being a heat exchanger plate of the second type.

The overlap between two subsequent flanges may form a sealed joint. Thus, it is preferred that a bonding material is arranged not only between the intended contact and bonding points across the heat transferring surfaces of the heat exchanger plates but also along the flanges during stacking of the heat exchanger plates.

The alternatingly arranged heat exchanger plates may form first plate interspaces which are substantially open and arranged to permit a flow of a medium to be evaporated there through, and second plate interspaces, which are closed and arranged to permit a flow of a fluid for evaporating the medium,

wherein the heat exchanger plates of the first type and of the second type further comprise, along at least a section of the opposing side portions, mating abutment portions extending along and at a distance from the circumferential edge portion, thereby separating the respective first plate interspaces into an inner heat transferring portion and two outer draining portions,

wherein at least the heat exchanger plates of the first type further comprise, along at least a section of the opposing side portions, a draining channel flange extending from the circumferential edge portion in direction from the geometrical main extension plane,

wherein the draining channel flanges of the respective heat exchanger plates are oriented in one and the same direction, and have an extension with a component along a normal to the main extension plane such that a draining channel flange of a first heat exchanger plate of the first type abuts or overlaps a draining channel flange of a subsequent heat exchanger plate, said subsequent heat exchanger plate being either a heat exchanger plate of the first type or a heat exchanger plate of the second type,

whereby the draining channel flanges form outer walls to the outer draining portions thereby transforming the outer draining portions into draining channels.

As an alternative or a supplement to the formulation that the draining channel flange extends from the circumferential edge portion in direction from the geometrical main extension plane, the draining channel flange may extend from the circumferential edge portion at an angle β to the normal of the geometrical main extension plane.

Heat exchanger devices are well known for evaporating various types of cooling medium such as ammonia in applications for generating e.g. cold. The evaporated medium is conveyed from the heat exchanger device to a compressor and the compressed gaseous medium is thereafter condensed in a condenser. Thereafter the medium is permitted to expand and is recirculated to the heat exchanger device. One example of such heat exchanger device is a heat exchanger of the plate-and-shell type, see e.g. WO2004/111564 which discloses a plate package composed of substantially half-circular heat exchanger plates. The use of half-circular heat exchanger plates is advantageous since it provides a large volume inside the shell in the area above the plate package, which volume improves separation of liquid and gas. The separated liquid is transferred from the upper part of the inner space to a collection space in the lower part of the inner space via an interspace. The interspace is formed between the inner wall of the shell and the outer wall of the plate package. The interspace is part of a thermo-syphon loop which sucks the liquid towards the collection space of the shell.

Accordingly, by a plate package design of the above type, cooling medium in liquid form that is present in the upper part of the shell may be guided inside and along a plurality of draining channels that extend along opposing side portions of the inner wall of the shell but at a distance therefrom, and also at a distance from the first plate interspaces that are formed between opposing major surfaces of the heat exchanger plates. The distance is provided, depending on the design of the walls and the joints respectively defining the cross section of the draining channel, by at least the material thickness of the sheet material making up the heat exchanger plates. The distance formed can be seen as an insulation which reduces heat transfer from the inner wall of the shell and from the plate interspaces in the plate package towards the draining channel and which thereby reduces the risk of the liquid medium evaporating inside the draining channel and thereby disturbance or stopping of the thermo-syphon loop. Thereby a more stable liquid flow is promoted.

Also, the draining channels prevents compressor oil, which typically, due to its stronger affinity to carbon steel than stainless steel, is prone to follow the curvature of the inner wall of the shell, from transferring into the first interspaces of the plate package. By the presence of the draining channels, compressor oil that is present inside the interspace between the inner wall of the shell and the outer boundary of the plate package is prevented, from transferring in a direction transverse the longitudinal extension of the draining channel and into the first plate interspaces. Instead, the inflow of compressor oil into the first plate interspaces is now restricted to the longitudinal gaps facing the upper portion of the shell and which forms openings towards to the first interspaces.

By reducing the amount of compressor oil that will come into contact with the first plate interspaces, the risk of formation of thermally insulating deposits on the heat transferring surfaces is reduced. This allows the plate package to be made smaller in terms of foot print or in terms of the number of heat exchanger plates included in the plate package while remaining the efficiency. Thereby the overall cost may be reduced.

According to a further aspect, the invention relates to the use of the heat exchanger plate with the features given above in a heat exchanger device. Advantages of the inventive heat exchanger plate as such have been discussed above, and to avoid undue repetition, reference is made to the sections given above.

According to another aspect, the invention refers to a heat exchanger device including a shell which forms a substantially closed inner space and which includes an inner wall surface facing the inner space, said heat exchanger device being arranged to include a plate package comprising a plurality of heat exchanger plates of the type discussed above. Advantages of the inventive heat exchanger plate as such have been discussed above, and to avoid undue repetition, reference is made to the sections given above.

According to another aspect, the invention refers to a heat exchanger device including a shell which forms a substantially closed inner space and which includes an inner wall surface facing the inner space, said heat exchanger device being arranged to include a plate package of the type discussed above. Advantages of the inventive heat exchanger plate as such have been discussed above, and to avoid undue repetition, reference is made to the sections given above.

According to yet another aspect, the invention refers to a heat exchanger device including a shell which forms a substantially closed inner space and which includes an inner wall surface facing the inner space, said heat exchanger device being arranged to include a plate package, said plate package including

a plurality of heat exchanger plates of a first type and a plurality of heat exchanger plates of a second type arranged alternatingly in the plate package one on top of the other, wherein each heat exchanger plate has a geometrical main extension plane and is provided in such a way that the main extension plane is substantially vertical, wherein the alternatingly arranged heat exchanger plates form first plate interspaces which are substantially open towards the inner space and arranged to permit circulation of a medium to be evaporated from a lower part of the inner space upwardly to an upper part of the inner space, and second plate interspaces which are closed to the inner space and arranged to permit flow of a fluid for evaporating the medium,

wherein each of the heat exchanger plates of the first type and of the second type has a circumferential edge portion, the circumferential edge portion having a curved upper portion, a substantially straight lower portion and two opposing side portions interconnecting the upper and the lower portions,

wherein each of the heat exchanger plates of the first type and of the second type has an upper porthole arranged in an upper section of the heat exchanger plate and located at a distance from the upper portion of the circumferential edge portion thereby defining an upper intermediate portion located between the upper portion of the circumferential edge portion and a circumferential edge of the upper porthole, the upper intermediate portion including the shortest distance between a centre of the upper porthole and the upper portion of the circumferential edge portion,

wherein the heat exchanger plate, along at least a section of the upper intermediate portion, further comprises an upper flange having an extension along the upper portion of the circumferential edge portion and extending from the circumferential edge portion in direction from the geometrical main extension plane,

wherein the upper flange has a length as seen in a direction transverse the shortest distance, being 200-80% of the diameter of the upper porthole and more preferred 180-120% of the diameter of the upper porthole,

wherein each of the heat exchanger plates of the first type and of the second type has a lower porthole arranged in a lower section of the heat exchanger plate and located at a distance from the lower portion of the circumferential edge portion thereby defining a lower intermediate portion located between the lower portion of the circumferential edge portion and a circumferential edge of the lower porthole, the lower intermediate portion including the shortest distance between a centre of the lower porthole and the lower portion of the circumferential edge portion,

wherein the heat exchanger plate, along at least a section of the lower intermediate portion, further comprises a lower flange having an extension along the lower portion of the circumferential edge portion and extending from the circumferential edge portion indirection from the geometrical main extension plane,

wherein the lower flange has a length as seen in a direction transverse the shortest distance being smaller than the diameter of the lower porthole and more preferred smaller than 80% of the diameter of the lower porthole, and

wherein the lower and the upper flanges of the respective heat exchanger plates are oriented in one and the same direction, and have an extension with a component along a normal to the main extension plane such that a flange of a first heat exchanger plate of the first type abuts or overlaps a flange of a subsequent heat exchanger plate, said subsequent heat exchanger plate being either a heat exchanger plate of the first type or a heat exchanger plate of the second type.

Advantages of the inventive heat exchanger plate and the inventive plate package as such have been discussed above, and to avoid undue repetition, reference is made to the sections given above.

At least the heat exchanger plates of the first type may further comprise, along at least a section of the opposing side portions, a draining channel flange extending from the circumferential edge portion in direction from the geometrical main extension plane, wherein the draining channel flanges of the respective heat exchanger plates are oriented in one and the same direction, and have an extension with a component along a normal to the main extension plane such that a draining channel flange of a first heat exchanger plate of the first type abuts or overlaps a draining channel flange of a subsequent heat exchanger plate, said subsequent heat exchanger plate being either a heat exchanger plate of the first type or a heat exchanger plate of the second type, whereby the draining channel flanges form outer walls to the outer draining portions thereby transforming the outer draining portions into draining channels.

Preferred embodiments appear in the dependent claims and in the description.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring toFIGS. 1 and 2, a schematic cross section of a typical heat exchanger device of the plate-and-shell type is disclosed. The heat exchanger device includes a shell1, which forms a substantially closed inner space2. In the embodiment disclosed, the shell1has a substantially cylindrical shape with a substantially cylindrical shell wall3, seeFIG. 1, and two substantially plane end walls (as shown inFIG. 2). The end walls may also have a semi-spherical shape, for instance. Also other shapes of the shell1are possible. The shell1comprises a cylindrical inner wall surface3facing the inner space2. A sectional plane p extends through the shell1and the inner space2. The shell1is arranged to be provided in such a way that the sectional plane p is substantially vertical. The shell1may by way of example be of carbon steel.

The shell1includes an inlet5for the supply of a two-phase medium in a liquid state to the inner space2, and an outlet6for the discharge of the medium in a gaseous state from the inner space2. The inlet5includes an inlet conduit which ends in a lower part space2′ of the inner space2. The outlet6includes an outlet conduit, which extends from an upper part space2″ of the inner space2. In applications for generation of cold, the medium may by way of example be ammonia.

The heat exchanger device includes a plate package200, which is provided in the inner space2and includes a plurality of heat exchanger plates100provided adjacent to each other. The heat exchanger plates100are discussed in more detail in the following with reference inFIG. 3. The heat exchanger plates100are permanently connected to each other in the plate package200, for instance through welding, brazing such as copper brazing, fusion bonding, or gluing. Welding, brazing and gluing are well-known techniques and fusion bonding can be performed as described in WO 2013/144251 A1. The heat exchanger plates100may be made of a metallic material, such as a iron, nickel, titanium, aluminum, copper or cobalt based material, i.e. a metallic material (e.g. alloy) having iron, nickel, titanium, aluminum, copper or cobalt as the main constituent. Iron, nickel, titanium, aluminum, copper or cobalt may be the main constituent and thus be the constituent with the greatest percentage by weight. The metallic material may have a content of iron, nickel, titanium, aluminum, copper or cobalt of at least 30% by weight, such as at least 50% by weight, such as at least 70% by weight. The heat exchanger plates100are preferably manufactured in a corrosion resistant material, for instance stainless steel or titanium.

Each heat exchanger plate100has a main extension plane q and is provided in such a way in the plate package200and in the shell1that the extension plane q is substantially vertical and substantially perpendicular to the sectional plane p. The sectional plane p also extends transversally through each heat exchanger plate100. In the embodiment is disclosed, the sectional plane p also thus forms a vertical centre plane through each individual heat exchanger plate100.

The heat exchanger plates100form in the plate package200first interspaces12, which are open towards inner space2, and second plate interspaces13, which are closed towards the inner space2. The medium mentioned above, which is supplied to the shell1via the inlet5, thus pass into the plate package200and into the first plate interspaces12.

Each heat exchanger plate100includes a lower porthole107and an upper porthole108. The lower portholes107form an inlet channel connected to an inlet conduit16. The upper portholes108form an outlet channel connected to an outlet conduit17. It may be noted that in an alternative configuration, the lower portholes107form an outlet channel and the upper portholes108form an inlet channel. The sectional plane p extends through both the lower portholes107and the upper portholes108. The heat exchanger plates100are connected to each other around the portholes107and108in such a way that the inlet channel and the outlet channel are closed in relation to the first plate interspaces12but open in relation to the second plate interspaces13. A fluid may thus be supplied to the second plate interspaces13via the inlet conduit16and the associated inlet channel formed by the lower portholes107, and discharged from the second plate interspaces13via the outlet channel formed by the upper portholes107and the outlet conduit17.

As is shown inFIG. 1, the plate package200has an upper side and a lower side, and two opposite transverse sides. The plate package200is provided in the inner space2in such a way that it substantially is located in the lower part space2′ and that a collection space18is formed beneath the plate package200between the lower side of the plate package and the bottom portion of the inner wall surface3.

Furthermore, recirculation channels19are formed at each side of the plate package200. These may be formed by gaps between the inner wall surface3and the respective transverse side or as internal recirculation channels formed within the plate package200.

Each heat exchanger plate100includes a circumferential edge portion20which extends around substantially the whole heat exchanger plate100and which permits said permanent connection of the heat exchanger plates100to each other. These circumferential edge portions20will along the transverse sides abut the inner cylindrical wall surface3of the shell1. The recirculation channels19are formed by internal or external gaps extending along the transverse sides between each pair of heat exchanger plates100. It is also to be noted that the heat exchanger plates100are connected to each other in such a way that the first plate interspaces12are closed along the transverse sides, i.e. towards the recirculation channels19of the inner space2.

The embodiment of the heat exchanger device disclosed in this application may be used for evaporating a two-phase medium supplied in a liquid state via the inlet5and discharged in a gaseous state via the outlet6. The heat necessary for the evaporation is supplied by the plate package200, which via the inlet conduit16is fed with a fluid for instance water that is circulated through the second plate interspaces13and discharged via the outlet conduit17. The medium, which is evaporated, is thus at least partly present in a liquid state in the inner space2. The liquid level may extend to the level22indicated inFIG. 1. Consequently, substantially the whole lower part space2′ is filled by medium in a liquid state, whereas the upper part space2″ contains the medium in mainly the gaseous state.

Now turning toFIG. 3, a first embodiment of a heat exchanger plate100according to the invention is disclosed. The heat exchanger plate100is intended to form part of the plate package according to the invention. The heat exchanger plate100may easily be converted into a first type A or a second type B in a manner to be described below.

The heat exchanger plate100is provided by a pressed thin walled sheet metal plate. The heat exchanger plate100may by way of example be made of stainless steel. The heat exchanger plate100has a geometrical main extension plane q and a circumferential edge portion101. The circumferential edge portion101delimits a heat transferring surface102extending essentially across the geometrical main plane q.

The circumferential edge portion101comprises a curved upper portion103, a substantially straight lower portion104and two opposing side portions105interconnecting the upper and the lower portions103,104. The two opposing side portions105do each have a curvature corresponding to the curvature of the inner wall3of the shell1of the heat exchanger device300.

The heat transferring surface102comprises a corrugated pattern106of ridges and valleys. To facilitate the understanding of the invention the corrugation in and around the upper and lower portholes107,108(to be discussed below) have been removed. The corrugated pattern106extends in different directions at different parts of the heat exchanger plate100. When a plurality of heat exchanger plates100are stacked, one on top of the other, to thereby form the plate package200, every second heat exchanger plate100(heat exchanger plate of the first type A) is turned in the manner disclosed inFIG. 3, whereas every other plate (heat exchanger of the second type B) is rotated 180 degrees about a substantially vertical rotary axes coinciding with the sectional plane p. Thereby the corrugations106of adjacent heat exchanger plates100will cross each other. Also, a plurality of contact points will be formed where the ridges of the adjacent heat exchanger plates100abut each other. A layer of bonding material (not disclosed) may be arranged between the heat exchanger plates100during stacking. As the stack later is subjected to heat in an oven, the heat exchanger plates100will bond to each other along the contact points and thereby form a complex pattern of fluid channels. In such a way, an efficient heat transfer from the fluid to the medium is ensured at the same time as the plates included in the plate package are given the required mechanical support.

The bonding of the heat exchanger plates100to provide the plate package200may be made by brazing or by fusion bonding as discussed above. Fusion bonding is especially suitable when the heat exchanger plates100are made by stainless steel.

Depending on how the heat exchanger plate100is oriented in the plate package200, one side of the heat exchanger plate100will, during operation of the plate package200in a heat exchanger device300, face the first plate interspace12and hence be in contact with the two-phase medium, whereas the opposite side of the heat exchanger plate100will face the second plate interspace13and hence be in contact with the fluid.

The heat exchanger plate100comprises a lower porthole107intended to form an inlet port and an upper porthole108intended to form an outlet port. In the disclosed embodiment, the lower porthole107is located in the proximity of the lower portion104and the upper porthole108is located in the proximity of the upper portion103. When the heat exchanger plate100is arranged to form part of a plate package200, the fluid will hence during operation, flow upwardly through the second plate interspaces13in the plate package200. It is to be understood that it is possible to provide the portholes107,108in other positions on the heat exchanger plate100.

The lower porthole107is arranged in a lower section of the heat exchanger plate100and located at a distance from the lower portion104of the circumferential edge portion101. Thereby a lower intermediate portion117is defined which is located between the circumferential edge portion101and a circumferential edge118of the lower porthole107. The lower intermediate portion117includes the shortest distance d1 between a centre of the lower porthole107and the lower portion104of the circumferential edge portion101. Also, the lower intermediate portion117has a height Y1 along the shortest distance and a width X1 transverse to the shortest distance d1.

A lower flange119is arranged to have an extension along the lower portion104of the circumferential edge portion101. The lower flange119is arranged to extend along at least a section of the lower intermediate portion117. The lower flange119extends towards the surface of the heat exchanger plate100that is intended to be in contact with the fluid, i.e. the surface that is intended to face the second plate interspace13. The lower flange119extends from the circumferential edge portion101in direction from the geometrical main extension plane q. The lower flange109extends from the circumferential edge portion101at an angle α to the normal of the geometrical main extension plane q.

The lower flange119has a length L1 as seen in a direction transverse the shortest distance d1, being smaller than the diameter D1 of the lower porthole107and more preferred smaller than 80% of the diameter D1 of the lower porthole107.

The upper porthole108is arranged in an upper section of the heat exchanger plate100and located at a distance from the upper portion103of the circumferential edge portion101. Thereby an upper intermediate portion120is defined which is located between the circumferential edge portion101and a circumferential edge121of the upper porthole108. The upper intermediate portion120includes the shortest distance d2 between a centre of the upper porthole108and the upper portion103of the circumferential edge portion101. Also, the upper intermediate portion120has a height Y2 along the shortest distance d2 and a width X2 transverse to the shortest distance d2.

An upper flange122is arranged to have an extension along the upper portion103of the circumferential edge portion101. The upper flange122is arranged to extend along at least a section of the upper intermediate portion120. The upper flange122extends towards the surface of the heat exchanger plate100that is intended to be in contact with the fluid, i.e. the surface that is intended to face the second plate interspace13. The upper flange122extends from the circumferential edge portion101in direction from the geometrical main extension plane q. The upper flange109extends from the circumferential edge portion101at an angle α to the normal of the geometrical main extension plane q.

The upper flange122has a length L2 as seen in a direction transverse the shortest distance d2, being 200-80% of the diameter D2 of the upper porthole108and more preferred 180-120% of the diameter D2 of the upper porthole108.

As is best seen inFIGS. 3 and 6, the curvature of the upper portion103of the circumferential edge portion101of the heat exchanger plate100differs from the curvature of the lower portion104of the heat exchanger plate100. When the heat exchanger plate100is included in a plate package200and used in a heat exchanger device300, the lower portion104is intended to face the collection space18that is formed in the shell1beneath the plate package200. To allow the collection space18to have a certain volume, the lower portion104is in the disclosed embodiment more or less straight, whereas the upper portion103which is intended to face the upper part space2″ of the shell1has a convex curvature. Accordingly, the extension of the circumferential edge portion101adjacent a porthole107,108affects the area of the available intermediate portion117,120.

In the case where the lower portion104is essentially straight, the height Y1 of the lower intermediate portion117between the lower portion104and the circumferential edge101of the lower porthole107will increase rather rapidly with the distance X1 from the sectional plane p.

This can be compared to the upper porthole108adjacent the upper curved portion103, where the height Y2 of the upper intermediate portion120between the curved upper portion103and the circumferential edge101of the upper porthole108will increase more slowly with the distance X2 from the sectional plane p. The decisive factor in this case is the radius of the curved edge portion.

The impact from this difference can be seen by studying the temperature gradient when subjecting a stack of heat exchanger plates100to heat in an oven for bonding purposes. The upper intermediate portion120with the curved upper portion103will heat more rapidly than the lower intermediate portion117with the straight edge portion104. By introducing the lower and the upper flanges119,122and adjusting their lengths L1, L2 to the diameter D1, D2 of the respective portholes107,108, the difference in heating may be compensated for. Thereby the risk of buckling due to uneven thermal expansion and thereby insufficient bonding may be dealt with.

Now turning toFIGS. 3 and 5, the heat exchanger plate100may comprise, along at least a section of the opposing side portions105, a ridge110extending along and at a distance from the two opposing side portions105of the circumferential edge portion101. When the heat exchanger plates100are stacked, the ridge110of a heat exchanger plate100of the first type A is arranged to abut the ridge110of an adjacent heat exchanger plate100of the second type B. Thereby, the respective second plate interspaces13are separated into an inner heat transferring portion HTP and two outer draining portions DP. The respective draining portion DP will have an extension along the respective side portion105of the heat exchanger plate100.

The ridges110may have an extension that extends past the transition between the upper portion103and the respective side portions105. The ridges110may also have an extension that extends past the transition between the respective opposing side portions105and the lower portion104.

The heat exchanger plate100further comprises a draining channel flange109along at least a section of the two opposing side portions103. The draining channel flanges109extend towards the surface of the heat exchanger plate100that is intended to be in contact with the fluid, i.e. the surface that is intended to face the second plate interspace13. The draining channel flange109extends from the circumferential edge portion101in direction from the geometrical main extension plane q. The draining channel flange109extends from the circumferential edge portion101at an angle β to the normal of the geometrical main extension plane q.

Now turning toFIGS. 4 and 5, two schematic cross sections of a plate package200which is composed of a plurality of heat exchanger plates100of the above type is disclosed. The cross section inFIG. 4is taken transverse the lower flange119. For the record, a corresponding cross section taken transverse the upper flange122may look the same. The cross section inFIG. 5is taken transverse the draining channel flange109. InFIG. 5also the wall3of the shell1of a heat exchanger device300is shown.

As given above, the heat exchanger plate100according to the invention can easily be converted into either a heat exchanger plate100of a first type A or into a heat exchanger plate100of a second type B by simply cutting off the lower and upper flanges110,122and the draining channel flanges109after pressing.

When stacking the heat exchanger plates100to a form a plate package200, one on top of the other, every second heat exchanger plate100is turned in the manner disclosed inFIG. 3, whereas every other heat exchanger plate100is rotated 180 degrees about a substantially vertical rotary axes coinciding with the sectional plane p. Thereby the corrugated pattern106of adjacent plates11will cross each other. Also, a plurality of contact points will be formed where the ridges110of the adjacent heat exchanger plates100abut each other. A layer of bonding material (not disclosed) may be arranged between the heat exchanger plates100during stacking. As the stack later is subjected to heat in an oven, the heat exchanger plates100will bond to each other along the contact points and thereby form a complex pattern of fluid channels. It is to be understood that the width of the joint depends of the cross section of the corrugations.

As is seen in the embodiments ofFIGS. 4 and 5, the flanges of every second heat exchanger plate100, i.e. the heat exchanger plate100of the second type B have been cut off. Also, the flanges119,122,109of the respective heat exchanger plates100of the first type are oriented in one and the same direction, and have an extension with a component along a normal to the main extension plane q such that a flange119,122,109of a heat exchanger plate100of the first type A abuts or overlaps a flange119,122,109of a second subsequent heat exchanger plate100of the first type A. The thus formed overlap between two subsequent flanges119,122,109has a length e as seen in a direction corresponding to the normal of the geometrical main extension plane q corresponding to 5-90% of the height f of the flange119,122,109.

It is to be understood that it may be sufficient if the flange119,122,109of a heat exchanger plate100of the first type A abuts a flange119,122,109of a subsequent heat exchanger plate100.

The flanges119,122,109are disclosed as having an extension along the lower portion104of the circumferential edge portion101and extending from the circumferential edge portion101at an angle α, β to the normal of the geometrical main extension plane q. The angle α, β is preferably smaller than 20 degrees to the normal and more preferred smaller than 15 degrees to the normal. The angle α, β depends on if both of two subsequent heat exchanger plates100of a plate pair to be joined are provided with flanges119,122,109or if only one of the heat exchanger plates100have a flange. In case of only one of the plates having a flange119,122,109, the angle α, β can be made smaller, such as smaller than 10 degrees, such as smaller than 8 degrees and typically about 6-7 degrees. It is also to be understood that the angle α, β can be even 0 degrees. The angles α, β may be the same or be different from each other.

It is to be understood that the presence of the lower and upper flanges119,122and also the draining channel flanges109contributes to guidance of the heat exchanger plates during stacking. Thereby fixtures can be made simpler.

Now turning toFIG. 6one embodiment of the plate package200according to the invention is schematically disclosed as being contained in a heat exchanger device300. From this view it can clearly be seen how the lower and upper flanges119,122and also the two opposing draining channel flanges109form sealed circumferential side walls of the plate package200. By the limited length of the lower and upper flanges119,122, the communication between the upper part space2″ of the shell1and the first plate interspace12is not influenced to any substantial effect.

Medium in liquid form that is present in the upper part space2″ of the shell1may be guided inside and along the plurality of draining channels111that extend along opposing side portions of the inner wall surface3of the shell1but at a distance therefrom, and also at a distance from the first plate interspaces12that are formed between opposing major surfaces of the heat exchanger plates100. The distance is provided, depending on the design of the walls and the joints respectively defining the cross section of the draining channel111by at least the material thickness of the sheet material making up the heat exchanger plates100. The distance formed can be seen as an insulation which reduces heat transfer from the inner wall surface3of the shell1and from the first plate interspaces12in the plate package200towards the draining channel111and which thereby reduces the risk of the liquid medium evaporating inside the draining channel111and thereby disturbance or stopping of the thermo-syphon loop. Thereby a more stable liquid flow is promoted.

Also, the draining channels111prevents compressor oil, which typically, due to its stronger affinity to carbon steel than stainless steel, is prone to follow the curvature of the inner wall surface3of the shell1, from transferring into the first interspaces12of the plate package200. By the presence of the draining channels111, the compressor oil that is present inside the interspace between the inner wall surface3of the shell1and the outer boundary of the plate package200is prevented from transferring in a direction transverse the longitudinal extension of the draining channel111and into the first plate interspaces12. Instead, the inflow of compressor oil into the first plate interspaces12is now restricted to longitudinal gaps116facing the upper part space2″ of the shell1and which forms openings towards to the first interspaces12.

It is contemplated that there are numerous modifications of the embodiments described herein, which are still within the scope of the invention as defined by the appended claims.

By way of example, the heat exchanger plates100of the first and second types A; B may be identical with the only exception that the lower and upper flanges119,122and the draining channel flanges109on every second heat exchanger plate100are cut-off to thereby convert them into heat exchanger plates100of the first and the second type A, B. Thereby, one and the same press tool may be used.

It is to be understood that also the heat exchanger plates100of the second type B may be provided with flanges119,122,109of the type described above and that these flanges are not cut-off. This allows for the flanges119,122,109of heat exchanger plates100of the first type A to sealingly abut flanges of heat exchanger plates A of the second type B.