Patent Application
20190226771
The present invention relates to a heat exchanger plate, as well as to a heat exchanger comprising a plurality of such plates. In particular, the present invention is useful in a condenser-type plate heat exchanger.
Heat exchangers of different types are used in many different applications. A particular type of prior art heat exchanger is a plate heat exchanger, in which flow channels of different media to be heat exchanged are formed between adjacent heat exchanging plates in a stack of such plates, and in particular delimited by corresponding heat exchanging surfaces on such plates.
In particular, it has turned out that plate heat exchangers can advantageously be manufactured from relatively thin, stamped sheet metal pieces, which metal pieces can be joined to form the heat exchanger. Such heat exchangers can be made relatively efficient.
The prior art comprises, inter alia, WO2009112031A3, EP1630510B2 and EP1091185A3, describing heat exchangers with plates fishbone-shaped protrusion patterns.
Furthermore, EP0186592B1 describes a plate heat exchanger with dimple-provided plates.
However, there is a problem of achieving sufficient mechanical stability in such plate heat exchangers of the above described type while still achieving sufficient heat exchanging efficiency. In particular, this is a problem in larger heat exchangers.
A further problem is to achieve sufficient heat exchanging efficiency under a certain maximum acceptable pressure drop across the heat exchanger.
Furthermore, this problem is in specifically present in condenser-type heat exchangers, such as in heat pumping and in particular refrigeration applications. Moreover, in such applications it is also desirable to minimize the amount of used refrigerant, while maintaining a high heat exchanging power and efficient condensing of the refrigerant.
Specifically regarding the conventional fishbone-shaped protrusion patterns, these provide good thermal transfer due to large contact surfaces and media turbulence. However, they have turned out not to perform well in terms of efficiency in relation to pressure drop. Also, it is difficult to design a fishbone-type plate which provides sufficient efficiency in relation to pressure drop while also keeping the amount of heat medium to a minimum.
The present invention solves the above described problems, providing a highly efficient, mechanically stable heat exchanger. In particular, for condenser-type heat exchangers, the invention provides these advantages while maintaining efficient condensing, such as of a refrigerant, while keeping the necessary amount of refrigerant to a minimum.
Hence, the invention relates to a plate for a heat exchanger between a first medium and a second medium, the plate being associated with a main plane of extension and a main longitudinal direction and comprising a first heat transfer surface, extending substantially in parallel to said main plane and arranged to be in contact with the first medium, generally flowing along the first surface in a first flow direction; and a second heat transfer surface, extending substantially in parallel to said main plane and arranged to be in contact with the second medium, generally flowing along the second surface in a second flow direction; and is characterised in that the first surface comprises protruding ridges defining at least two parallel and open-ended channels extending in the first flow direction, and in that the second surface comprises a plurality of protruding dimples arranged in said channels between neighbouring respective pairs of said ridges.
In the following, the invention will be described in detail, with reference to exemplifying embodiments of the invention and to the enclosed drawings, wherein:
All Figures share a common set of reference numerals, denoting same parts. Moreover, for the two main exemplifying heat exchanging plates 100, 200 shown in the Figures, the respective two last digits in each reference numerals denote corresponding parts of these two plates, as applicable.
Hence,
The plate 100, 200 is associated with a main plane of extension, which is not indicated in the Figures but which lies in the plane of the paper in
The plate 100 comprises a first heat transfer surface 101, extending substantially in parallel to said main plane and arranged to be in contact with the first medium during heat exchanging, which first medium generally flows, during use of the plate 100 in said heat exchanger, along the first surface 101 in a first flow direction F1. The plate 100 furthermore comprises a second heat transfer surface 102, extending substantially in parallel to said main plane and arranged to be in contact with the second medium, generally flowing, during such use, along the second surface 102 in a second flow direction F2. Both flow directions F1 and F2 are preferably substantially parallel to the longitudinal direction L.
It is noted that the flow directions F1 and F2 illustrated in the figures are such that the plate 100 is for a counter-flow heat exchanger. It is, however, realized that the principles described herein are also applicable to parallel-flow heat exchangers, in which case F1 and F2 would be directed in the same direction, or at least in the same general direction.
The plate 100 comprises, in reverse order in the longitudinal direction L, a first region 110, a second region 120 and a third region 130. The first 110 and third 130 regions comprise media inlets and outlets, while the second region 120 is a transfer region across which the media are transported between regions 110, 130. Preferably, there are no media inlets or outlets along the transfer region 120, which preferably occupies at least half of the total length of the plate 100 in the longitudinal direction L.
The plate 100 furthermore comprises an inlet 131 for the first medium and an outlet 112 for the first medium, as well as an inlet 111 for the second medium and an outlet 132 for the second medium. These inlets 111, 131 and outlets 112, 132 may be in the form of through holes in the plate 100. In the Figures, the said through holes have circular shape. However, it is realized that any suitable shape can be used, such as quadratic shapes. Since the plates 100, 200 are preferably identical or substantially identical (apart from some being mirrored—see below regarding plates 100, 200 of first and second types), when the plates 100, 200 are stacked these through holes will align to form a tunnel with a cross-sectional shape being the same as the shape of the through holes in question. During use, when the plate 100 is mounted as one of a plurality of such plates 100 in a heat exchanger according to the invention, as described in further detail below, each of the inlets and outlets 131; 112; 111; 132 are connected to corresponding inlets/outlets of other plates in the same plate stack so as to form a general first medium inlet, first medium outlet, second medium inlet and second medium outlet port. Then, the inlet ports are arranged to distribute the first and second medium, respectively, to the inlets 131; 111 of each plate, and which outlet ports are arranged to convey the first and second medium, respectively, from the outlets 112; 132 and away from the heat exchanger.
Inlet 111 and outlet 112 are preferably completely arranged in said first region 110, while inlet 131 and outlet 132 preferably are completely arranged in the second region 130.
Along the flow direction F1, F2, the first and second medium, respectively, flow in channels formed by adjacent plates 100 in the same plate stack, between respective inlet 111, 131 and respective outlet 112, 132.
More particularly, a heat exchanger according to the present invention comprises a plurality of plates 100 of two types—a first type and a second type. Plates 100 of both said first 100a and said second 100b type are as such plates of the type described herein, where the plates of said second type have a shape which is substantially mirrored, in relation to the said main plane of the plate 100 in question, to the shape of the plates of said first type. All plates of the first type may be identical within the group of first type plates, while all plates of the second type may be identical within that group. Furthermore, the plates are arranged in a stack on top of each other (stacked in a direction perpendicular to the main plane of the plates, which main planes are arranged to be parallel), with plates of said first and second type arranged alternatingly. Since the plates of first and second type are mirrored, corresponding ones of dimples and ridges arranged on adjacent plates come and stay into direct contact with each other, so that corresponding first 101 and/or second surfaces 102 of adjacent plates directly abut each other and so that flow channels 103, 104 for said first and second media are formed between said surfaces 101, 102. This is illustrated in
It is realized that the plate 200 (see below) may preferably be stacked in a corresponding manner so as to constitute component parts of a corresponding heat exchanger according to the invention. As is clear from
In such a heat exchanger, suitably designed end plates may be used, sealing the last plate 100, 200 in the stack on either stack end and forming a sealed heat exchanger the only inlets/outlets of which are the above described inlet and outlet ports.
Hence, each plate 100 transfers heat between the said first and second media, as a result of the first medium being transported in a channel 103 (see
According to the invention, the first surface 101 comprises protruding ridges 121, defining at least two parallel and open-ended channels 122 extending in the first flow direction F1. Furthermore, the second surface 102 comprises a plurality of protruding dimples 123 arranged in said channels 122 between neighbouring respective pairs of said ridges 121.
Herein, a “ridge” refers to an elongated protruding geometric feature of the surface 101 in question on which the ridge is arranged. Preferably, such a ridge 121 in the first surface 101 is associated with a corresponding elongated indentation or recess in the opposite surface 102.
Similarly, a “dimple” refers herein to a point-like protruding geometric feature of the surface 102 in question on which the dimple in question is arranged. Preferably, such a dimple is associated with a corresponding point-like indentation or recess in the opposite surface 101. In the Figures, dimples are shown with a generally circular shape. It is, however, realized that any suitable shape, such as quadratic or octagonal, may be used, depending on application. Hence, the word “point-like” is intended to mean “with a shape, in the main plane of the plate in question, which is generally centred about a particular point rather than elongated”.
Both ridges and dimples are preferably arranged with a planar top surface, arranged to abut a corresponding planar top surface of a corresponding ridge or dimples, respectively, of an adjacently arranged, mirrored heat exchanger plate.
The plate 100 is preferably manufactured from sheet metal, with a material thickness which preferably is substantially equal across the whole plate 100 main plane, and in particular across ridges 121 and dimples 123, 113, 114, 133, 134 (see below). Advantageously, the plate 100 is manufactured from a piece of sheet metal which is stamped into the desired shape.
A heat exchanging plate 100 with such a pattern of channel-forming ridges 121 and dimples 123 arranged in the formed channels 122 has been found to provide very good mechanical stability when used as a component part in a heat exchanger of the type described herein, while still being able to very efficiently transfer heat between said first and second media, across a wide range of applications. Using such a plate 100 also makes it possible for the ridges and dimples to be designed with very small height (see below), so as to achieve a heat exchanger using only a very small volume of first and/or second medium. In particular, the ridge height can be made very small, whereby the amount of first medium can be reduced. Such miniaturizing can be made without jeopardizing efficiency and pressure drop requirements.
As illustrated in the Figures, said protruding ridges 121, 221 preferably define at least three, preferably at least five (in the exemplifying plate 100, there are six channels 122, while there are seven channels 222 in the exemplifying plate 200), parallel and open-ended channels 122 extending in the first flow direction F1. The inventors have found that, for small heat exchangers, substantial advantages can be achieved already with two, in some cases at least three, such channels, while, for larger heat exchangers, more channels will provide better distribution of the first medium.
It is preferred that the channels 122 extend along substantially the whole second region 120 of the plate 100, along the longitudinal direction L. In particular, at least three of the channels 122 preferably each extend along at least 50%, preferably at least 60%, of the entire length, in the longitudinal direction L, of the plate 100.
It is preferred that the dimples 123 are arranged along at least three of the channels 122, preferably along all channels 122. Preferably, the dimples 123 are distributed along substantially the entire length of each individual channel 122, preferably substantially equidistantly. Preferably, each channel having dimples 123 is arranged with at least three, preferably at least five, preferably at least ten, such dimples 123 along its respective length. The dimples 123 of adjacent parallel channels 122 are preferably arranged so that they are displaced somewhat in the longitudinal direction L in relation to each other, as disclosed in the Figures.
According to one preferred embodiment, the channels 122 are arranged with a shape permitting the channels 122, 103 (wherein channel 103 is formed by two opposed and mirrored open channel parts 122 as described above) to be completely emptied of the first medium, when the first medium is in liquid form and when the plate 100 is arranged in a mounted state for use, which mounted state is illustrated in
That the channels 122 can be emptied completely when the plate 100 is in the slightly slanted mounted orientation as illustrated in
Preferably, at least one, preferably at least two neighbouring ones, of said ridges 121 is or are interrupted in at least one location along said first flow direction F1, defining a respective mixing zone 124 for the first medium flowing through corresponding neighbouring ones of said channels 122. Further preferably, the said mixing zone 124 interconnects all, or at least a majority, of said parallel channels 122 being present in said at least one location along the first flow direction F1. This provides good heat transfer efficiency while maintaining structural robustness of the heat exchanger. By distributing the first medium evenly across the cross-direction, plate 100 tensions are also kept to a minimum since the heat transfer process will be even. According to an alternative embodiment, the mixing zones 124 does not interconnect all of said parallel channels 122 being present in said at least one location along the first flow direction F1.
In particular, it is preferred that several such mixing zones 124 are arranged at different locations along the longitudinal direction L, such as equidistantly arranged. It is also preferred, as illustrated in the Figures, that neighbouring mixing zones 124 are displaced in relation to each other in the cross direction C, so that at least one channel 122 extends uninterrupted past at least one mixing zone.
In
As mentioned above, the plate 100 preferably comprises, in reverse order along the main longitudinal direction L, regions 110,120 and 130. The region 130 may comprise, on the first surface 101, a first medium inlet region. The region 120 may comprise, on the first surface 101, a first medium transfer region. The region 110 may comprise, on the first surface 101, a first medium outlet region.
In a preferred embodiment, the first surface 101 comprises at least three mixing zones 124 of the above described type, arranged at different locations in the first flow direction F1, and wherein the said mixing zones 124 are more densely or closer arranged, as seen in the first flow direction F1, closer to the first medium inlet region 130 than further from the first medium inlet region 130. Note that such varying mixing region 124 density is not illustrated in the Figures.
Further in the preferred case with first medium inlet, transfer and outlet regions, the plate 100 preferably further comprises, on its opposite second surface 102, a second medium inlet region, overlapping with the first medium outlet region, and a second medium outlet region, overlapping with the first medium inlet region. This then defines a plate for use in a counter-flow heat exchanger. Alternatively, fora parallel-flow heat exchanger, the plate 100 may comprise, on the second surface 102, a second medium outlet region, overlapping with the first medium outlet region, and a second medium inlet region, overlapping with the first medium inlet region. For both heat exchanger types, the plate 100 preferably comprises, on the second surface 102, a second medium transfer region, overlapping with the first medium transfer region.
In particular, it is preferred that the said first medium inlet region comprises the first medium inlet 131, whereas the first medium outlet region comprises the first medium outlet 112. Then, it is preferred, in particular in case the heat exchanger is a condenser type heat exchanger, that the first medium inlet 131 has a larger, preferably at least two times the size, cross-section, in the main plane, than the first medium outlet 112. This cross-section size is hence the hole size in the preferred case in which the inlet 131 and the outlet 112 are through holes. Such configuration caters for an efficient construction when using a first medium which is condensed from gas phase to liquid phase as a result of the heat exchange.
Furthermore, it is preferred that the first medium inlet region comprises a pattern of protrusions 235 (see
As to the first medium outlet region, it is preferred, as illustrated in
According to a very preferred embodiment, apart from the above described ridges 121, 221 and dimples 123, 223 arranged in the channels 122, 222, at least one of the first 101 and second 102 surfaces, preferably both, comprises a respective plurality of additional protruding dimples. In the Figures, these additional dimples are illustrated as first surface 101, 201 dimples 113, 213 in the first region 110, 210; first surface 101, 201 dimples 133, 233 in the third region 130, 230; second surface 102, 202 dimples 114, 214 in the first region 110, 210; and second surface 102, 202 dimples 134, 234 in the third region 130, 230. It is preferred that the plate 100, 200 comprises all four or these types of dimples 113, 133, 114, 134; 213, 233, 214, 234.
These dimples share the joint purpose of distributing the respective medium across the plate 100; 200 respective surface 101, 102; 201, 202, increasing heat transfer efficiency; as well as providing mechanical stability to the heat exchanger.
In particular, it is preferred that the first surface 101, 201 comprises more, preferably at least twice as many, preferably at least three times as many, of said additional dimples 113, 133; 213, 233 as compared to the number of second surface 102, 202 additional dimples 114, 134; 214, 234. This has proven to achieve very efficient heat transfer, in particular in the case of a condenser-type heat exchanger, without jeopardizing its mechanical stability. Also, this achieves the possibility of handling larger medium pressure resistance to the heat exchanger.
As is clear from
In particular, it is preferred that the respective height, perpendicular to the said main plane, of the above described dimples and ridges define a first flow height for the first medium, in said first medium channel 103, and a second flow height for the second medium, in said second channel 104. Then, it is preferred that the second flow height is at least 2 times, preferably at least 5 times, larger than the first flow height.
In order for all corresponding dimples and ridges to abut between adjacent, mirrored plates, it is realized that all dimples and ridges on either surface 101, 102; 201, 202 are preferably of the same height as measured from the said main plane.
In a particularly preferred embodiment, the first flow height, of the first medium channel 103, is at the most 1.5 mm, preferably at the most 1 mm, preferably at least 0.4 mm. This means that the height, including any additional material used to join the plates together, such as brazing material between abuting dimpels and ridges, of individual dimples and ridges is at the most 0.75 mm, preferably 0.50 mm, preferably at least 0.20 mm. In the preferred case of a brazed together structure (see below), it is preferred that the brazing material used, preferably in the form of a foil, such as a copper foil, before heating, is 0.01 mm to 0.08 mm thick.
As regards the parallel channels 122, 222, they are preferably between 5 and 20 mm, preferably between 8 and 15 mm, wide, in the cross direction C.
According to a very preferred embodiment, the plates 100, 200 together forming a heat exchanger by being brazed together in the stack structure described above, so that corresponding ones of said dimples and ridges of adjacent, mirrored plates 100, 200 are brazed together, top face against top face. This forms a very sturdy construction, without risking the integrity of the complicated channels formed between said ridges and dimples. In particular, the plates 100, 200 are preferably manufactured from stainless steel, and are brazed together using copper or nickel; or alternatively the plates 100, 200 may be manufactured from aluminium, and brazed together using aluminium. In practise, plates 100, 200 are arranged in the said stack structure, with brazing foil material in between. Then, the whole stack is subjected to heat in a furnace, causing the brazing material to melt and permanently join the plates 100, 200 together via the above described dimples and ridges.
In particular, such a heat exchanger according to the invention may preferably be a closed counter- or parallel flow heat exchanger, comprising a first medium inlet port 353 arranged to distribute the first medium to the respective first medium channels 103 in contact with said first surfaces 101 of said plates 100; a first medium outlet port 351 arranged to lead the first medium from said first channels 103 in contact with said first surfaces 101 and out from the heat exchanger; a second medium inlet port 350 arranged to distribute the second medium to the respective second medium channels 104 in contact with the second surfaces 102 of said plates; and a second medium outlet port 352 arranged to lead the second medium from said second medium channels 104 in contact with the second surfaces 102 and out from the heat exchanger. The corresponding is true regarding a heat exchanger using plates 200 as shown in
In particular, and as mentioned above, the heat exchanger is a condenser-type heat exchanger, arranged to heat exchange the first medium in gas phase to the second medium, so that the first medium condenses into liquid form. In this case, it is preferred that the heat exchanger is arranged so that the condensed, liquid first medium thereafter flows out from the first medium outlet port 351.
In particular, the present invention is useful in the specific case in which the first medium is a refrigerant, preferably a hydrocarbon, preferably propane. Similarly, the second medium may preferably be a liquid, preferably water.
Preferred uses of such a heat exchanger comprise use as a heat exchanger in a cooling apparatus, such as a freezer or refrigerator; in a heat pump for heating indoors air, water or similar in a property; for industrial heat exchanging and refrigeration purposes, such as within the food industry; and so on.
Preferably, a heat exchanger according to the invention is maximally 1 meter in its longest dimension.
The first medium enters the heat exchanger 300 via a first medium inlet port 353, in communication with all the channels formed between respective adjacent pairs of plates 200, and delimited by their respective first surfaces 201. Preferably, these channels are parallel, so that the first medium flows in parallel flows along the first flow direction F1. The first medium is then collected from these channels and exit via a first medium outlet port 351.
The second medium enters the heat exchanger 300 via a second medium inlet port 350, in communication with all the channels formed between respective adjacent pairs of plates 200, and delimited by their respective second surfaces 202. Preferably, these channels are parallel, so that the second medium flows in parallel flows along the second flow direction F2. The second medium is then collected from these channels and exit via a second medium outlet port 352.
It is hence realized that the flow of both the first and second media flow in a parallel-flow manner, through a plurality of channels of said type, between pairs of individual plates 200 in said stack, between respective inlet and outlet ports.
As best seen in
Above, preferred embodiments have been described. However, it is apparent to the skilled person that many modifications can be made to the disclosed embodiments without departing from the basic idea of the invention.
In general, the above described features of the plates 100, 200 and heat exchangers are freely combinable, as applicable.
Everything which has been said regarding plate 100 is equally relevant to plate 200 and vice versa, as applicable. Hence, the plate 200 may for instance also be arranged with a pattern of slanted ridges 115 as shown in plate 100, and so on.
The specific patterns of dimples and ridges illustrated in the Figures may vary, as long as the above-described design principles are respected.
Hence, the invention is not limited to the described embodiments, but can be varied within the scope of the enclosed claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 16192854.4 | Oct 2016 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2017/053537 | 2/16/2017 | WO | 00 |
