A BRAZED PLATE HEAT EXCHANGER AND USE THEREOF
A brazed plate heat exchanger (100) includes a plurality of first and second heat exchanger plates (110, 120), wherein the first heat exchanger plates (110) are formed with a first pattern of ridges and grooves, and the second heat exchanger plates (120) are formed with a second pattern of ridges and grooves providing contact points between at least some crossing ridges and grooves of neighbouring plates under formation of interplate flow channels for fluids to exchange heat, said interplate flow channels being in selective fluid communication through port openings. The first pattern of ridges and grooves is different from the second pattern of ridges and grooves, so that an interplate flow channel volume on one side of the first heat exchanger plates (110) is different from an interplate flow channel volume on the opposite side of the first heat exchanger plates (110), and at least some of the ridges and grooves of the first pattern extend in a first angle (β1) and at least some of the ridges and grooves of the second pattern extend in a second angle (β2) different from the first angle (β1).
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The present invention relates to a brazed plate heat exchanger comprising a plurality of heat exchanger plates having a pattern of ridges and grooves providing contact points between at least some crossing ridges and grooves of neighbouring plates under formation of interplate flow channels for fluids to exchange heat. The present invention is also related to the use of such a heat exchanger.
PRIOR ARTHeat exchangers are used for exchanging heat between fluid media. They generally comprise a start plate, an end plate and a number of heat exchanger plates stacked onto one another in a manner forming flow channels between the heat exchanger plates. Usually, port openings are provided to allow selective fluid flow in and out from the flow channels in a way well known to persons skilled in the art.
A common way of manufacturing a plate heat exchanger is to braze the heat exchanger plates together to form the plate heat exchanger. Brazing a heat exchanger means that a number of heat exchanger plates are provided with a brazing material, after which the heat exchanger plates are 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, whereupon the heat exchanger plates will be joined to one another to form a compact and strong heat exchanger.
It is well known by persons skilled in the art that the flow channels between the heat exchanger plates of a plate heat exchanger are created by providing the heat exchanger plates with a pressed pattern of ridges and grooves. A number of heat exchanger plates are typically stacked on one another, wherein the plates can be identical to provide a symmetric plate heat exchanger or not identical to provide an asymmetric plate heat exchanger. When stacked, the ridges of a first heat exchanger plate contact the grooves of a neighboring heat exchanger plate and the plates are thus kept at a distance from each other through contact points. Hence, flow channels are formed. In these flow channels, fluid media, such as a first and second fluid media are lead so that heat transfer is obtained between such media.
A plurality of brazed plate heat exchangers with a pressed corrugated pattern having ridges and grooves in a herringbone pattern is known in the prior art. However, there is a need to improve such prior art heat exchangers.
It is the object of the present invention to provide a plate heat exchanger with favourable flow distribution, pressure drop and heat transfer between the fluid media.
SUMMARY OF THE INVENTIONAccording to the invention, the above object is achieved by a brazed plate heat exchanger (BPHE) comprising a plurality of first and second heat exchanger plates, wherein the first heat exchanger plates are formed with a first pattern of ridges and grooves, and the second heat exchanger plates are formed with a second pattern of ridges and grooves providing contact points between at least some crossing ridges and grooves of neighbouring plates under formation of interplate flow channels for fluids to exchange heat, said interplate flow channels being in selective fluid communication through port openings, characterised in that the first pattern of ridges and grooves is different from the second pattern of ridges and grooves, so that an interplate flow channel volume on one side of the first heat exchanger plates is different from an interplate flow channel volume on the opposite side of the first heat exchanger plates, and at least some of the ridges and grooves of the first pattern extend in a first angle and at least some of the ridges and grooves of the second pattern extend in a second angle different from the first angle. The combination of different interplate flow channel volumes on opposite sides of the plates and at least two different plate patterns having different angles result in a BPHE with favourable properties for fluid distribution, wherein the fluid flow distribution and pressure drop can be balanced to achieve efficient heat exchange. This makes it possible to achieve different properties in interplate flow channels on opposite sides of the same plate, wherein the flow and pressure drop on one side can be different from the opposite side. Also, the different flow channel volumes on opposite sides of the plates can be used for different types of medias, such as a liquid in one and a gas in the other.
When a refrigerant start to evaporate it is transferred from a liquid state to a vapour state. The liquid has a density that is much higher than the vapour density. For example R410A at Tdew=5° C. has 32 times higher density for the liquid than the vapour. This also mean that the vapour will move in a channel at velocities that are 32 times higher than the liquid. This will automatically lead to the dynamic pressure drop for the vapour being 32 times higher than for the liquid, i.e. vapour creates much higher pressure drop for all kind of refrigerants.
The performance (Temperature Approach, TA) of a heat exchanger is defined as the water outlet temperature (at the inlet of the heat exchanger channel) minus the evaporation temperature (Tdew) at the outlet of the heat exchanger channel. A high pressure drop along the heat exchanger surface results in different local saturation temperatures that will result in a relatively large total difference in refrigerant temperature between the inlet and outlet of the channel. The temperature will be higher at the inlet of the channel. This will have a direct, detrimental impact on the performance of the heat exchanger, since a higher inlet refrigerant temperature (due to too high channel pressure drop) makes it harder to cool the outlet water to the correct temperature. The only way for the system to compensate for the too high refrigerant inlet temperature is by lowering the evaporation temperature until correct water outlet temperature can be reached. By creating pattern for heat exchanger channels that have high heat transfer characteristics and at the same time have low pressure drop characteristics, a higher performance can be reached for the heat exchanger. A lower overall refrigerant pressure drop in the channel will not only improve the heat exchanger performance it will also have a positive impact on the total system performance and, hence, the energy consumption.
At least one of the first and second heat exchanger plates can be an asymmetric heat exchanger plate. Alternatively, the first heat exchanger plates are formed with another corrugation width than the second heat exchanger plates. The first heat exchanger plate can be a symmetric heat exchanger plate, wherein the second heat exchanger plate can be an asymmetric heat exchanger plate. Hence, first grooves of the second heat exchanger plates can be formed with a first depth, and second grooves of the second heat exchanger plates can be formed with a second depth different from the first depth. Through the combination of different angles and corrugation depth patterns, the fluid flow distribution and pressure drop can be customized for the application to achieve efficient heat exchange. The patterns of ridges and grooves can be herringbone patterns, wherein the angles of the pattern of ridges and grooves are chevron angles.
Furthermore, the depths of the first and second heat exchanger plates may differ from each other in a way that the interplate flow channels have different sizes seen in cross section, wherein the interplate flow channels have different volumes on opposite sides of the plates. Hence, the interplate flow channels can have different cross section areas on opposite sides of the plates. This provides an asymmetric plate heat exchanger that combines favourable heat transfer with low pressure drop to achieve a more efficient heat exchanger for various purposes, such as for heating, refrigeration or a reversible refrigeration system.
The first and second patterns can be herringbone patterns or patterns where the ridges and grooves extend in oblique straight lines over the heat exchanger plate. Hence, the angles are in a plane of the heat exchanger plates, e.g. towards a side of the heat exchanger plates. For example, the angle is between a short side of a rectangular heat exchanger plate and the extension of the ridges and grooves. The first and second angles, such as first and second chevron angles, can be 0-90°, 25-70° or 30-45°. Hence, the angles can be selected to achieve favourable fluid distribution. The difference between the first and second angles can be 2-35°. The first and second patterns can be in opposite directions, wherein the first and second angles are in opposite directions, such as towards opposite short sides of rectangular heat exchanger plates.
Disclosed is also the use of a brazed plate heat exchanger according to the present invention for evaporation or condensation of media.
Further characteristics and advantages of the present invention will become apparent from the description of the embodiments below, the appended drawings and the dependent claims.
In the following, the invention will be described with reference to appended drawings, wherein:
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The heat exchanger plates 110, 120 are made from sheet metal and are provided with a pressed pattern of ridges R1, R2a, R2b and grooves G1, G2a, G2b such that interplate flow channels for fluids to exchange heat are formed between the plates when the plates are stacked in a stack to form the heat exchanger 100 by providing contact points between at least some crossing ridges and grooves of neighbouring plates 110, 120 under formation of the interplate flow channels for fluids to exchange heat. The pressed pattern of
In the illustrated embodiment, each of the heat exchanger plates 110, 120 is surrounded by a skirt S, which extends generally perpendicular to a plane of the heat exchanger plate and is adapted to contact skirts of neighbouring plates in order to provide a seal along the circumference of the heat exchanger. Apart from the skirt S and ports O1-O4 practically the remaining part of the heat exchanger plates 110, 120 forms a heat exchanging surface 130, 140.
The heat exchanger plates 110, 120 are arranged with port openings O1-O4 for letting fluids to exchange heat into and out of the interplate flow channels. In the illustrated embodiment, the heat exchanger plates 110, 120 are arranged with a first port opening O1, a second port opening O2, a third port opening O3 and a fourth port opening O4. Areas surrounding the port openings O1 to O4 are provided at different heights such that selective communication between the port openings and the interplate flow channels is achieved. In the heat exchanger 100, the areas surrounding the port openings O1-O4 are arranged such that the first and second port openings O1 and O2 are in fluid communication with one another through some interplate flow channels, whereas the third and fourth port openings O3 and O4 are in fluid communication with one another by neighboring interplate flow channels. In the illustrated embodiment, the heat exchanger plates 110, 120 are rectangular with rounded corners, wherein the port openings O1-O4 are arranged near the corners. Alternatively, the heat exchanger plates 110, 120 are square, e.g. with rounded corners. Alternatively, the heat exchanger plates 110, 120 are circular, oval or arranged with other suitable shape, wherein the port openings O1-O4 are distributed in a suitable manner. In the illustrated embodiment, each of the heat exchanger plates 110, 120 is formed with four port openings O1-O4.
Please note that in other embodiments of the invention, the number of port openings may be larger than four, i.e. six, eight or ten. For example, the number of port openings is at least six, wherein the heat exchanger is configured for providing heat exchange between at least three fluids. Hence, according to one embodiment, the heat exchanger is a three circuit heat exchanger having at least six port openings and in addition being arranged with or without at least one integrated suction gas heat exchanger. Alternatively, the number of port openings is at least six, wherein the heat exchanger includes one or more integrated suction gas heat exchangers.
In the illustrated embodiment, the heat exchanger 100 comprises only the first and second heat exchanger plates 110, 120. Alternatively, the heat exchanger 100 comprises a third and optionally also a fourth heat exchanger plate, wherein the third and optional fourth heat exchanger plates are arranged with different pressed patterns than the first and second heat exchanger plates 110, 120, and wherein the heat exchanger plates are arranged in a suitable order.
In the illustrated embodiment, the heat exchanger 100 also comprises a start plate 150 and an end plate 160. The start plate 150 is formed with openings corresponding to the port openings O1-O4 for letting fluids into and out of the interplate flow channels formed by the first and second heat exchanger plates 110, 120. For example, the end plate 160 is a conventional end plate.
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Hence, the first and second heat exchanger plates 110, 120 are formed with different chevron angles β1, β2 and different pressed patterns resulting in different interplate volumes. For example, the first and second heat exchanger plates 110, 120 are provided with different corrugation depths. Alternatively or in addition, the first and second heat exchanger plates 110, 120 are provided with different corrugation frequencies. For example, the first and second heat exchanger plates 110, 120 are provided with the same corrugation depth but different corrugation frequencies. Hence, the first and second heat exchanger plates 110, 120 are provided with different corrugation depths and/or different corrugation frequencies. For example, one of the first and second heat exchanger plates 110, 120 is a symmetric heat exchanger plate, wherein the other is asymmetric. Alternatively, both the first and second heat exchanger plates 110, 120 are asymmetric. Alternatively, both the first and second heat exchanger plates 110, 120 are symmetric.
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According to one embodiment, the brazing joints 170 between the first and second heat exchanger plates 110, 120 are elongated, such as oval, wherein the brazing joints 170 are arranged in a first orientation in the interplate flow channels having bigger volume and in a second orientation in the interplate flow channels having smaller volume to provide a favourable pressure drop in the desired interplate flow channels. For example, the brazing joints 170 are arranged in a first angle in relation to a longitudinal direction of the plates 110, 120 in the interplate flow channels having bigger volume and in a second angle in the remaining interplate flow channels. According to one embodiment, the first angle is bigger than the second angle.
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The heat exchanger according to the present invention is, e.g. used for condensation or evaporation, wherein at least one media at some point is in gaseous phase. For example, the heat exchanger is used for heat exchange, wherein condensation or evaporation takes place in the interplate flow channels of bigger volume. For example, a liquid media, such as water or brine, is conducted through the interplate flow channels having smaller volume.
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Claims
1. A brazed plate heat exchanger comprising a plurality of first and second heat exchanger plates, wherein the first heat exchanger plates are formed with a first pattern of ridges and grooves, and the second heat exchanger plates are formed with a second pattern of ridges and grooves providing contact points between at least some crossing ridges and grooves of neighbouring plates under formation of interplate flow channels for fluids to exchange heat, said interplate flow channels being in selective fluid communication through port openings, wherein
- the first pattern of ridges and grooves is different from the second pattern of ridges and grooves, so that an interplate flow channel volume on one side of the first heat exchanger plates is different from the interplate flow channel volume on the opposite side of the first heat exchanger plates, and
- at least some of the ridges and grooves of the first pattern extend in a first angle and at least some of the ridges and grooves of the second pattern extend in a second angle different from the first angle.
2. The brazed plate heat exchanger of claim 1, wherein the interplate flow channels on one side of the first heat exchanger plates have a different cross section area than on the opposite side.
3. The brazed plate heat exchanger of claim 1, wherein at least a central main heat exchanging section of the first heat exchanger plates exhibits the first angle, wherein at least a central main heat exchanging section of the second heat exchanger plates exhibits the second angle.
4. The brazed plate heat exchanger of claim 1, wherein the first heat exchanger plates are symmetric.
5. The brazed plate heat exchanger of claim 1, wherein the grooves of the first heat exchanger plates are formed with identical corrugation depth, wherein first grooves of the second heat exchanger plates are formed with a first depth, and second grooves of the second heat exchanger plates are formed with a second depth different from the first depth.
6. The brazed plate heat exchanger of claim 1, wherein a depth of the grooves of the first heat exchanger plate is in the range of 0.6-2 mm.
7. The brazed plate heat exchanger of claim 1, wherein a first depth of the second heat exchanger plate is in the range of 0.6-3 mm, and a second depth of the second heat exchanger plate is in the range of 30-80% of the first depth.
8. The brazed plate heat exchanger of claim 1, wherein the first angle of the first pattern of ridges and grooves is in the range of 25-70°.
9. The brazed plate heat exchanger of claim 1, wherein the second angle of the second pattern of ridges and grooves is in the range of 25-70°.
10. The brazed plate heat exchanger of claim 1, wherein a difference between the first angle of the first pattern of ridges and grooves and the second angle of the second pattern of ridges and grooves is in the range of 2-35°.
11. The brazed plate heat exchanger of claim 1, wherein the first and second heat exchanger plates are provided with different corrugation depths.
12. The brazed plate heat exchanger of claim 1, wherein the heat exchanger plates are provided with different corrugation widths.
13. The brazed plate heat exchanger of claim 1, wherein the first pattern is a first herringbone pattern or a first pattern of obliquely extending straight lines and the second pattern is a second herringbone pattern or a second pattern of obliquely extending straight lines, and wherein ridges and grooves of the first and second patterns extend from one long side of the heat exchanger plates to the other, and wherein the first angle is towards one short side of the heat exchanger plates and the second angle is towards the opposite short side.
14. The brazed plate heat exchanger of claim 1, wherein the first and second heat exchanger plates are arranged alternatingly, wherein every other plate is a first heat exchanger plate and every other plate is a second heat exchanger plate throughout the heat exchanger.
15. The brazed plate heat exchanger of claim 1, wherein brazing points between the first and second heat exchanger plates are elongated and arranged in a first orientation in the interplate flow channels having bigger volume and in a second orientation in the interplate flow channels having smaller volume.
16. A method for exchanging heat by a brazed heat exchanger according to claim 1, wherein media is evaporated or condensed in the interplate flow channels of smaller volume, wherein liquid media is conducted to the interplate flow channels of bigger volume.
17. (canceled)
Type: Application
Filed: Jan 29, 2021
Publication Date: Feb 2, 2023
Applicant: SWEP International AB (Landskrona)
Inventors: Sven ANDERSSON (Hässleholm), Tomas DAHLBERG (Helsingborg)
Application Number: 17/789,255