Brazed Plate Heat Exchanger

The present invention refers in general to a plate heat exchanger and, more specifically, to a brazed plate heat exchanger wherein the heat exchanger plates are provided with an improved corrugation pattern of ridges and grooves which facilitates the liquid condensate drainage.

Heat exchangers are devices used to transfer heat between two or more fluids. A plate heat exchanger is a specific type of heat exchanger wherein metal plates are used to transfer heat between two fluids. Plate-type heat exchangers generally comprise a start plate, an end plate and a plurality of intermediate plates stacked onto one another, so as to form flow channels between them. In a plate-type heat exchanger, the two fluids at different temperatures (one of which is usually identified as the refrigerant fluid) respectively flow through plate channels obtained between opposite surfaces of pairs of adjacent heat exchanger plates: in this way the two fluids exchange their thermal content. These fluids can flow counter-current or co-current and their leak-free circulation is ensured by gaskets or by the junctions between the heat exchanger plates.

The flow channels between the heat exchanger plates are commonly obtained by providing both plate surfaces with a corrugated pattern. In other words, both plate surfaces are provided with a pressed pattern of ridges and grooves. When the heat exchanger plates are stacked onto one another, the ridges of a first heat exchanger plate contact the grooves of an adjacent heat exchanger plate and these plates are thus kept at a distance from each other through spacer elements. In this way the flow channels are formed.

A common way of manufacturing a plate-type heat exchanger is to braze the heat exchanger plates together. This way of manufacturing requires that the heat exchanger plates are provided with a brazing material. During manufacturing, the heat exchanger plates stacked onto one another and placed in a furnace having a temperature sufficiently hot to at least partially melt the brazing material. After the temperature of the furnace has been lowered, the brazing material will solidify, allowing the heat exchanger plates to become joined to one another to form a compact and strong heat exchanger.

Brazed plate heat exchangers, also known by the acronym “BHE”, can be used as condensers in various applications (e.g., air conditioners, heat pumps, etc.). The condensing process usually occurs in vertical flow channels of the heat exchanger plates, with the refrigerant vapor generally flowing from the top to the bottom of the channels according to gravity. This facilitates the liquid condensate drainage by gravity, reducing the liquid film thickness on the surface of the plates, and its related thermal resistance.

Normally, BHE units used as condensers are installed in vertical position. This means that, since the heat exchanger plates usually have a substantially rectangular shape, the short sides of these plates are arranged horizontally, while the long sides of these plates are arranged vertically. Several corrugation patterns of BHE plates are known in the prior art. For example, a known corrugation pattern provides a plurality of channels in the shape of a single or multiple chevrons, with one or more vertical spines extending between the short sides of each heat exchanger plate. Further known corrugation patterns are disclosed, for example, in prior art documents WO 2021/154152, EP 3832243, U.S. Pat. No. 7,669,643, US 2011/0083833, CN 102519281 and JP 11037677.

The Applicant found that, by tilting a BHE provided with plates having a known corrugation pattern at a predefined angle with respect to a vertical axis, the BHE condenser performances were improved for certain inclination angles (see attached). A possible explanation was that an inclined BHE unit, at certain angles related likely to the cross-corrugation angle and the direction of gravity, could make it easier for the liquid condensate to be drained to the bottom of the heat exchanger plates (where subcooled liquid is built up), thinning the liquid film and so reducing its thermal resistance, with a final improvement of the condensing process (lower condensing temperature or lower temperature approach). Therefore, there is a need to improve such prior art BHE units, since it is not convenient to install these BHE units in arrangements other than the vertical one.

One object of the present invention is therefore to provide a brazed plate heat exchanger which is capable of resolving the drawbacks of the prior art in a simple, inexpensive and particularly functional manner.

In detail, one object of the present invention is to provide a brazed plate heat exchanger wherein the liquid condensate can be drained to the bottom of the heat exchanger plates in a simpler and faster way with respect to brazed plate heat exchangers according to the prior art, assuring a good heat transfer by a proper special selection of the corrugation angles of the plates.

Another object of the present invention is to provide a brazed plate heat exchanger wherein the corrugation pattern of the heat exchanger plates is easier to manufacture with respect to brazed plate heat exchangers according to the prior art.

These objects are achieved according to the present invention by providing a brazed plate heat exchanger as set forth in the attached claims.

Further features of the invention are underlined by the dependent claims, which are an integral part of the present description.

The brazed plate heat exchanger according to the present invention comprises a plurality of heat exchanger plates which are stacked onto one another. The heat exchanger plates are obtained by forming from respective metal sheets. The heat exchanger plates are permanently joined to each other through brazing by means of a braze material, so as to form a plate package provided with first plate interspaces for a first fluid and second plate interspaces for a second fluid. The plate package comprises an alternation between a first heat exchanger plate and a second heat exchanger plate. Each between the first heat exchanger plate and the second heat exchanger plate is provided with a plurality of portholes and has a substantially rectangular shape, with two long side edges, two short side edges and a longitudinal axis extending parallel to the two long side edges and transversely to the two short side edges. Each between the first heat exchanger plate and the second heat exchanger plate has a corrugation pattern which forms at least one heat transfer area that extends along the longitudinal axis. Each heat transfer area comprises mutually parallel ridges and grooves arranged in such a manner that the ridges of one of the first heat exchanger plates abut the grooves of an adjoining one of the second heat exchanger plates, so as to form a plurality of joining areas.

Each ridge and each groove of at least one first heat transfer area of each first heat exchanger plate are inclined with respect of the longitudinal axis by a first angle comprised between 0° and 30°. Additionally, each ridge and each groove of at least one heat transfer area of each second heat exchanger plate are inclined with respect of the longitudinal axis by a second angle comprised between 90° and 45°. Finally, at least part of the ridges and at least part of the grooves of at least a first heat transfer area of each first heat exchanger plate extend without discontinuities between the opposite edges of the respective heat transfer area, wherein these opposite edges are parallel to the short side edges.

Preferably, the first angle is of 20°, whereas the second angle is of 70°.

Also preferably, the amount of the ridges, and thus of the grooves, of the first heat transfer area of each first heat exchanger plate that extend without discontinuities between the opposite edges of the respective heat transfer area is equal to at least 30% of the total amount of the ridges, and thus of the grooves, of the first heat transfer area of each first heat exchanger plate.

According to a preferred aspect of the present invention, each of the first heat exchanger plates is provided with at least one second heat transfer area which is adjacent to the first heat transfer area. Each ridge and each groove of the second heat transfer area are preferably inclined with respect of the longitudinal axis by a third angle comprised between 45° and 90°. More preferably, this third angle is of 65°.

Also preferably, at least part of the ridges and at least part of the grooves of the second heat transfer area extend seamlessly, i.e., without discontinuities, between the opposite edges of the respective second heat transfer area, wherein these opposite edges are parallel to the short side edges. Still preferably, the second heat transfer area has a longitudinal extension, measured along the longitudinal axis, that is equal to about ⅓ of the longitudinal extension of the first heat transfer area.

Each ridge and each groove of each heat transfer area of both the first heat exchanger plates and the second heat exchanger plates are preferably straight and continuous along the respective heat transfer area. The longitudinal axis is preferably a vertical axis.

According to a preferred embodiment, each between the first heat exchanger plate and the second heat exchanger plate is provided with four portholes. Each porthole is then placed at a respective corner of the respective heat exchanger plate, that is, at the contact point between a long side edge and a short side edge of the respective heat exchanger plate.

Preferably, at least one of the portholes can be placed at a distance from its closest long side edge which is different from the distances from the respective closest long side edge of the remaining portholes. More preferably, said distance of the at least one porthole is greater than said distances of the remaining portholes. Still preferably, each corner of each heat exchanger plate is a rounded corner.

With reference to, a brazed plate heat exchangeris shown. The heat exchangercomprises, in a per se known manner, a plurality of heat exchanger platesA,B stacked onto one another. Typically, the heat exchanger platesA,B are stacked onto one another between a first end plateand a second end plateof the heat exchanger. Each heat exchanger plateA,B is obtained by forming from a respective metal sheet. The first end plate, the second end plateand the heat exchanger platesA,B are permanently joined to each other through brazing by means of a braze material, so as to form a plate package. The plate packageis thus provided with first plate interspaces for a first fluid and second plate interspaces for a second fluid. The first fluid and the second fluid may be any suitable heat transfer fluid.

The plate packageof the heat exchangercomprises an alternation between a first heat exchanger plateA and a second heat exchanger plateB. In other words, starting from the first end plateand up to the second end plate, a first heat exchanger plateA is joined to a second heat exchanger plateB, while this second heat exchanger plateB is joined to another first heat exchanger plateA, and so on. Plate interspaces are thus obtained between heat exchanger platesA,B of different type, that is, a first heat exchanger plateA and a second heat exchanger plateB.

Each between the first heat exchanger plateA and the second heat exchanger plateB, as well as the first end plateand the second end plate, is provided with a plurality of portholes, preferably four portholes P, P, Pand P. A first porthole Pis connected to a first connection pipeand communicates with the first plate interspaces. A second porthole Pis connected to a second connection pipeand communicates with the first plate interspaces. A third porthole Pis connected to a third connection pipeand communicates with the second plate interspaces. Finally, a fourth porthole Pis connected to a fourth connection pipeand communicates with the second plate interspaces. Connection pipes,,andmay be provided extending from the first end plate, as shown in, and/or from the second end plate.

Each between the first heat exchanger plateA and the second heat exchanger plateB, as well as the first end plateand the second end plate, has a substantially rectangular shape, with two long side edgesand two short side edges, as shown in. A longitudinal axis X extends parallel to the two long side edgesand transversely to the two short side edges.

Each between the first heat exchanger plateA and the second heat exchanger plateB has a corrugation pattern forming at least one heat transfer area,,that extends along the longitudinal axis X. Each heat transfer area,,comprises mutually parallel ridgesand groovesarranged in such a manner that the ridgesof one of the first heat exchanger platesA abut the groovesof an adjoining one of the second heat exchanger platesB, so as to form a plurality of small joining areas (called brazing joints).

According to the invention, each ridge, and thus each groove, of at least one first heat transfer areaof each first heat exchanger plateA are inclined with respect of the longitudinal axis X by a first angle α comprised between 0° and 30°, as shown in. Each ridge, and thus each groove, of the heat transfer areaof each second heat exchanger plateB are instead inclined with respect of the longitudinal axis X by a second angle β comprised between 90° and 45°, as shown in. Preferably, the first angle α is of 20°, while the second angle β is of 70°.

Additionally, at least part of the ridges, and thus at least part of the grooves, of the first heat transfer areaof each first heat exchanger plateA extend without discontinuities between the opposite edges of the respective heat transfer area, i.e., the opposite edges parallel to the short side edgesof the respective first heat exchanger plateA. In other words, since the longitudinal axis X is preferably a vertical axis, as shown in the figures, at least part of the ridges, and thus at least part of the grooves, of the first heat transfer areaof each first heat exchanger plateA extend seamlessly, i.e., without discontinuities, from top to bottom of the respective heat transfer area.

Preferably, the amount of the ridges, and thus of the grooves, of the first heat transfer areaof each first heat exchanger plateA that extend without discontinuities between the opposite edges of the respective heat transfer areais equal to at least 30% of the total amount of the ridges, and thus of the grooves, of the first heat transfer areaof each first heat exchanger plateA. For example, the preferred first angle α of 20° of each first heat exchanger plateA ensures that at least 40% of the respective ridges, and thus the respective grooves, extend seamlessly from top to bottom of the first heat transfer areaof each first heat exchanger plateA.

The second angle β of the second heat exchanger plateB, which is comprised between 90° and 60° and is preferably equal to 70°, is selected in such a way to obtain good thermal exchange coefficients. In fact, in a heat exchanger plate according to the prior art, with a standard pattern, i.e., with small corrugation angles (e.g.,) 20°, two drawbacks arise on pairs of adjacent heat exchanger plates: low thermal exchange coefficients and incorrect distribution of fluids within the respective channels.

Preferably, as shown in, each first heat exchanger plateA is provided with at least one second heat transfer areawhich is adjacent to the first heat transfer area. More specifically, in case of the longitudinal axis X is a vertical axis, the second heat transfer areais arranged below the first heat transfer area. Each ridge, and thus each groove, of this second heat transfer areaare inclined with respect of the longitudinal axis X by a third angle γ comprised between 45° and 90°. Preferably, the third angle γ is of 65°.

Similarly to the first heat transfer area, at least part of the ridges, and thus at least part of the grooves, of the second heat transfer areapreferably extend without discontinuities between the opposite edges of the respective second heat transfer area, i.e., the opposite edges parallel to the short side edgesof the respective first heat exchanger plateA. Preferably, as shown in, the second heat transfer areaof each first heat exchanger plateA has a longitudinal extension, measured along the longitudinal axis X, that is equal to about ⅓ of the longitudinal extension of the first heat transfer areaof the respective first heat exchanger plateA.

The corrugation pattern described above of both the first heat exchanger platesA and the second heat exchanger platesB is schematically shown in. This corrugation pattern allows one of the fluids processed by the heat exchanger, for example the liquid condensate in the case of said heat exchangeris used as a condenser, to move along almost vertical interspaces, so as to reach more easily the bottom zone of the heat exchanger platesA,B. Additionally, this advantageous feature is enhanced by the fact that each ridgeand each grooveof each heat transfer area,,of both the first heat exchanger platesA and the second heat exchanger platesB are straight and continuous along the respective heat transfer area,,. In other words, the heat exchanger platesA,B are not provided with any vertical spine or other discontinuities in the respective heat transfer areas,,, thus improving the capability of the liquid condensate to reach more easily the bottom zone of the heat exchanger platesA,B.

Preferably, each of the four portholes P, P, P, Pof the heat exchanger platesA,B is placed at a respective corner of the respective heat exchanger plateA,B. In other words, as shown in the figures, each of the four portholes P, P, P, Pof the heat exchanger platesA,B is placed at the contact point between a long side edgeand a short side edgeof the respective heat exchanger plateA,B. More preferably, each corner of each heat exchanger plateA,B is a rounded corner.

According to a preferred aspect of the invention, at least one of the portholes Pof each heat exchanger plateA,B, that is, the porthole Pin the upper left in, is placed at a distance Dfrom its closest long side edgewhich is different from the distances D, Dfrom the respective closest long side edgeof the remaining portholes P, P, P. Preferably but not exclusively, the distance Dof said at least one porthole Pis greater than the distances D, Dof the remaining portholes P, P, P. This preferred technical feature is due the fact that the specific and innovative combination of corrugation angles α and β requires an equally specific fluid port arrangement in order to have an even fluid distribution along the width of the heat exchanger platesA,B (so to maximize heat transfer).

It is thus seen that the brazed plate heat exchanger according to the present invention achieve the previously outlined objects.

The brazed plate heat exchanger of the present invention thus conceived is susceptible in any case of numerous modifications and variants, all falling within the same inventive concept; in addition, all the details can be substituted by technically equivalent elements. In practice, the materials used, as well as the shapes and size, can be of any type according to the technical requirements.

The scope of protection of the invention is therefore defined by the enclosed claims.