Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
  • F24H1/48—Water heaters for central heating incorporating heaters for domestic water
  • F24H1/52—Water heaters for central heating incorporating heaters for domestic water incorporating heat exchangers for domestic water
  • F24H1/523—Heat exchangers for sanitary water directly heated by the burner
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
  • F24H1/22—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating
  • F24H1/38—Water heaters other than continuous-flow or water-storage heaters, e.g. water heaters for central heating with water contained in separate elements, e.g. radiator-type element
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F24—HEATING; RANGES; VENTILATING
  • F24H—FLUID HEATERS, e.g. WATER OR AIR HEATERS, HAVING HEAT-GENERATING MEANS, e.g. HEAT PUMPS, IN GENERAL
  • F24H1/00—Water heaters, e.g. boilers, continuous-flow heaters or water-storage heaters
  • F24H1/48—Water heaters for central heating incorporating heaters for domestic water
  • F24H1/52—Water heaters for central heating incorporating heaters for domestic water incorporating heat exchangers for domestic water
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D1/00—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators
  • F28D1/02—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid
  • F28D1/03—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid with plate-like or laminated conduits
  • F28D1/0308—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid with plate-like or laminated conduits the conduits being formed by paired plates touching each other
  • F28D1/0325—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid with plate-like or laminated conduits the conduits being formed by paired plates touching each other the plates having lateral openings therein for circulation of the heat-exchange medium from one conduit to another
  • F28D1/0333—Heat-exchange apparatus having stationary conduit assemblies for one heat-exchange medium only, the media being in contact with different sides of the conduit wall, in which the other heat-exchange medium is a large body of fluid, e.g. domestic or motor car radiators with heat-exchange conduits immersed in the body of fluid with plate-like or laminated conduits the conduits being formed by paired plates touching each other the plates having lateral openings therein for circulation of the heat-exchange medium from one conduit to another the plates having integrated connecting members
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D9/00—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D9/0031—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by paired plates touching each other
  • F28D9/0043—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by paired plates touching each other the plates having openings therein for circulation of at least one heat-exchange medium from one conduit to another
  • F28D9/005—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits for one heat-exchange medium being formed by paired plates touching each other the plates having openings therein for circulation of at least one heat-exchange medium from one conduit to another the plates having openings therein for both heat-exchange media
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F28—HEAT EXCHANGE IN GENERAL
  • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
  • F28D9/00—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
  • F28D9/0093—Multi-circuit heat-exchangers, e.g. integrating different heat exchange sections in the same unit or heat-exchangers for more than two fluids

Definitions

• the present invention relates both to a plate heat exchanger according to the preamble of claim 1 and to a method of heat transfer in a plate heat exchanger according to the preamble of claim 10.
• a plate heat exchanger comprising cassettes normally has cassettes which are composed of a number of plates stacked on top of one another in a plate stack. In the plate stack, two or more plates are joined together and constitute cassettes. The joining together is normally effected by means of known joining methods, e.g. welding, brazing, bonding by adhesive etc.
• the cassettes In a plate heat exchanger as above, it is usual for the cassettes to be mechanically connected to one another. They are normally connected to one another by some form of direct contact, e.g. by the above-mentioned joining techniques. Another alternative is that the cassettes have between them some form of packing.
• a further common alternative for heat exchangers with cassettes is that the cassettes have no mutual contact between their heat-transferring parts. In this latter case, the cassettes usually form part of a heat exchanger whose cassettes are surrounded by, for example, a vessel containing a medium which fills the region between the cassettes.
• Plate heat exchangers comprising cassettes which are composed of two different plate types stacked on top of one another in a plate stack are known.
• the term "plate type" in this specification defines a plate which has a profiled shape obtained by plastic deformation by means of a specific shaping tool, i.e. each plate type is pressed in a different shaping tool. Plastic deformation is effected, for example, by pressing, rolling, forging or stamping. Two plates of the one plate type are permanently connected to each other in order to constitute a first cassette type. Two plates of the other plate type are permanently connected to one another in order to constitute a second cassette type.
• American patent specification US 4002201 refers to a plate heat exchanger for receiving various media which is composed of plates which constitute cassettes which are stacked on one another. Between the cassettes, which are identical, metal insert sheets are placed and are in mechanical contact with the respective two adjacent cassettes.
• a disadvantage of the invention according to US 4002201 is that the heat exchanger is designed to receive between the cassettes a medium in gaseous form, e.g. air, and is not suitable for other types of medium.
• the temperature of the medium in the cassettes cannot be regulated in a readily controllable manner. This temperature depends directly on the temperature of the gas in the intermediate insert sheets. Any change in the temperature of the gas directly affects the temperature of the media in the cassettes.
• 4002201 is that the fact that only one plate type is used for constructing the heat exchanger's cassettes means that only one cassette type is created, thereby making it impossible to create a heat exchanger with various cassette types.
• the Japanese patent application with publication number JP 2003-148881 refers to a heat exchanger for receiving three media whereby a medium emitting heat flows through a channel situated between two adjacent channels which are external to said channel.
• a disadvantage of the heat exchanger according to JP 2003-148881 is that its cassettes are composed of at least three different plate types which constitute the various channels. Having numerous different plate types makes the heat exchanger expensive to manufacture.
• a further disadvantage is its mode of operation in that the temperature of the media in the two channels situated externally depends directly on the temperature of the medium in the intermediate channel. Any change in the temperature of the intermediate medium directly affects the temperature of the media in the adjacent channels.
• a further disadvantage of the design according to JP 2003-148881 is that the cassettes have their ports with pipe connections on their respective tops and undersides, thereby making it impossible to stack two or more cassettes.
• British patent specification GB 2332508 describes a cast heat exchanger which can receive three different media and which comprises a centrally situated heat circuit.
• a disadvantage of the design according to GB 2332508 is that the heat exchanger is cast. This makes the heat exchanger expensive to manufacture and entails numerous operations which are difficult from the manufacturing point of view.
• a further disadvantage is that cast elements in a heat exchanger entail difficulties in repair and servicing, thereby making such operations more expensive.
• the Japanese patent specification with publication number JP 02-254291 describes a plate heat exchanger for receiving three media which is provided with packings.
• the plate heat exchanger is intended to be used for thermal sterilisation of liquid food, whereby the food is heated by a heated water circuit adjacent to the food.
• a disadvantage of the design is that it has no cassettes and has instead packings between the plates, thereby rendering the heat exchanger temperature-sensitive. Owing to their material, packings do not cope with excessive temperature changes or excessively high temperatures. Further disadvantages of heat exchangers provided with packings and used for foodstuffs is that precipitation from packings may lead to changes in the taste of foodstuffs processed in the heat exchanger.
• One object of the present invention is to provide a heat exchanger having cassettes whereby the above-mentioned problems are eliminated.
• a further object of the present invention is to provide a heat exchanger which effects indirect heat transfer and prevents large temperature changes in an outgoing medium from occurring at the time of switching a heat source on and off, e.g. a gas burner.
• a further object of the present invention is to provide a heat exchanger which performs the same function as two separate traditional heat exchangers when they are used with a so-called boiler, i.e. a unit provided with gas burner for production of domestic hot water and central heating water.
• a further object of the present invention is to provide a heat exchanger composed of two cassette types, for receiving three different media and with no possibility of the media becoming mixed with one another.
• a further object of the present invention is to provide a heat exchanger whose cost-effectiveness and performance are better than existing heat exchangers. Additional objects are that it should be easy to construct and that its production should entail savings of time.
• a further object of the present invention is to counteract and retard the occurrence in the heat exchanger of lime deposition caused by large and rapid changes in the temperature of the media flowing through the heat exchanger.
• the method according to the invention results in lime precipitation in the heat exchanger being retarded and counteracted because the indirect heat transfer results in slower temperature variations.
• Water normally contains varying amounts of lime which determine the hardness of the water. Hard water is rich in lime and the corresponding feature of soft water is that it contains little lime.
• temperature changes e.g. by heating
• the heat exchanger according to the invention comprises cassettes of a first type which surround other cassettes of a second type.
• the cassettes are arranged on top of one another and constitute a stack, also called a plate stack. Where necessary, the cassettes may be stacked to facilitate their forming part of a heat exchanger, e.g. a plate package.
• the heat exchanger according to the invention is composed of two plate types, whereby the first cassette type is composed of the first plate type and the second cassette type is composed of the second plate type.
• Each plate has a heat transfer surface and an edge which is defined as the portion which extends round the periphery of the plate, outside the heat transfer surface.
• the edge is constituted by a .first portion in the form of a rim and a second portion in the form of a web situated between the rim and the heat transfer surface.
• the web is angled from the plane in which the heat transfer surface is situated. This may be likened to an ordinary serving tray carrying coffee cups which has around its periphery an edge angled upwards. On the serving tray, this edge is angled from the plane which is used for placing the coffee cups on.
• the inside of the plate is defined as the side situated within the bent-up edge.
• the outside of the plate is thus defined as the side situated on the other side of the plate.
• first cassette type which surrounds a second cassette type makes it necessary to have two different plate types.
• the plates which constitute the first cassette type to be able to surround the second cassette type their configuration must be different from the plates which constitute the second cassette type.
• the edge of the first plate type has to be larger than for the second, since the sides of the first plates together surround the plates of the second type.
• their edges cannot be higher than the tops of the heat transfer configurations of these plates.
• the heat exchanger may be modified by the first cassette types being composed of first plate types with planar heat transfer surface.
• planar plate types minimises or eliminates the first channel between the first cassettes at assembly stage. The result will be that the first cassettes are adjacent without any real intermediate space.
• This solution may be adopted in cases involving heat transfer between two media but require reliable prevention of mixing of the media.
• An example of this is media which, when in contact with one another, may constitute explosion risk.
• the present invention adapted to receiving two media makes it possible to bring about safe heat transfer even between such media.
• heat is supplied via a heat source, e.g. a gas burner, situated in the immediate vicinity of the cassettes and delivering hot waste gases which are led into the heat exchanger.
• a heat source e.g. a gas burner
• the heat source may of course also take the form of other types of heat-producing units.
• the gas burner may for example be situated above the cassettes.
• the hot gas from the gas burner which has an approximate initial temperature of about 1200°C, is forced downwards into the defined first channels, which communicate with the heat source. In these first channels, the gas transfers its heat to the medium flowing on the other side of the plates of the cassettes, i.e. to the second channel inside the first cassettes. After passing through the cassettes, the gas is led away from the unit.
• a problem in using conventional heat exchangers is that the domestic hot water temperature is directly and immediately affected by the heat source. Cessation of heat from the heat source normally has an immediate effect on the temperature of the medium leaving the heat exchanger, which may for example be domestic hot water which must not become too hot and cause risk of scalding.
• a closed circuit may also be used as a central heating circuit.
• a medium flows which does not mix with other media in the heat exchanger. The medium in this second channel is heated by the medium in the aforesaid first channel.
• the temperature of the medium in the second channel is between 60°C and 90°C.
• this second channel is a closed circuit provided with one or more radiators, the simplest and most advantageous way of varying its temperature is by the medium being caused to circulate by means of a pump.
• the medium in this second circuit acts as a buffer in the form of stored thermal energy.
• From this second channel there is heat transfer to the third medium flowing through the third channel defined according to the preferred embodiment of the invention.
• the temperature level in the second channel is relatively stable. This means that heat transfer from the second channel to the medium in the third channel can take place in a stable and controlled manner. The result will be that the medium leaving the third channel will only exhibit small temperature differences and may have a temperature in the range 50° - 70°C.
• the advantage of the preferred embodiment is that the design described above causes indirect heat transfer from the first medium to the third medium via the second medium, thereby preventing large and rapid temperature fluctuations in the outgoing third medium at the time of switching the gas burner on and off. The occurrence of lime deposition in the heat exchanger can thus be retarded and counteracted.
• the preferred embodiment of the invention also helps the design of the cassettes to make it possible for heat exchanger manufacture to be customised.
• the number of cassettes in the heat exchanger can be greater or smaller according to customer requirements.
• Fig. 1 depicts a boiler as seen from in front, with a housing comprising a heat exchanger according to the invention and with a fan and a gas burner situated above the heat exchanger.
• Fig. 2 depicts a cassette which surrounds another cassette (broken line) in a heat exchanger according to the invention, with a first section line drawn through the heat exchanger's inlet ports and a second section line drawn through the heat exchanger's outlet ports.
• Fig. 3 depicts in cutaway section the boiler according to Fig. 1 with the heat exchanger in cutaway section along the section line III according to Fig. 2.
• Fig. 4 depicts in cutaway section the boiler according to Fig. 1 with the heat exchanger in cutaway section along the section line IV according to Fig. 2 with a gas burner and fan situated above the heat exchanger.
• Fig. 1 depicts a boiler (1) comprising a heat exchanger (2) according to a first embodiment of the invention.
• the boiler (1) is surrounded by a housing (3).
• a gas burner (4) is situated above the heat exchanger (2).
• a fan (5) is situated above the gas burner (4).
• Two inlet ports (7 and 8) intended for domestic hot water inlet (7) and central heating inlet (8) respectively are situated on the front (6) of the heat exchanger (2).
• In the housing (3) there are recesses for exhaust gas outlet (9) and condensate outlet (10).
• Two outlet ports (13 and 14) intended for domestic hot water outlet (13) and central heating outlet (14) respectively, represented by broken lines in Fig. 1 are situated on the rear of the heat exchanger (2).
• the heat exchanger (2) comprises two types of cassettes, a first cassette type (15) and a second cassette type (16).
• the first cassette type (15) surrounds the second cassette type (16).
• the second cassette type (16) is represented by broken lines because it is surrounded by the first cassette type (15).
• the cassettes in the heat exchanger (2) comprise two types of plates (17 and 18), viz. a first plate type (17) and a second plate type (18).
• Each plate in the heat exchanger (2) has, extending round its periphery, an edge (21 and 22) which is angled from the plane of the plate.
• the plate may be likened to a serving tray with an outside and an inside.
• the inside of the plate is represented by what is within the bent-up edge.
• the outside is thus what is on the other side of the plate.
• the first cassette type (15) surrounds the second cassette type (16).
• the first cassette type (15) is composed of two plates of the first plate type (17) with their respective insides (19) facing one another.
• the second cassette type constituted (16) is composed of two plates of the second plate type (18) with their respective insides (20) facing towards one another.
• the heat exchanger (2) comprises cassette types (15 and 16) as described above which are joined to one another.
• a first channel (X) is formed between each pair of mutually directly adjacent cassettes (15) of the first type.
• a second channel (Y) is formed between the different cassette types, i.e. within the walls of the first cassette type (15) but outside the walls of the second cassette type (16).
• a third channel (Z) is formed within the walls of each second cassette type (16).
• the first channel (X) communicates with the gas burner (4) in order to be able to receive heated gases from the gas burner (4) and lead them through the heat exchanger (2).
• the heat transfer surfaces of the plates are corrugated (not shown in the drawings).
• the corrugation configuration pressed into the plates is such that the ridges facing outwards of the first plate types (17) abut against one another when the first cassette types (15) are placed against one another.
• the corrugation configuration is in a known manner angled relative to the corrugation configuration of the adjacent plate so that the tops of the ridges constitute contact points.
• the valleys situated between the contact points of the corrugation configuration form the first channel (X) defined above.
• the second channel (Y), see Fig. 2, section line III, and Fig. 3, is defined by the space situated between the plates of the first cassette type (15) and the plates of the second cassette type (16) and is intended to receive central heating or radiator water.
• the second channel (Y) communicates with the central heating inlet (8), situated on the rear (6) of the heat exchanger (2), via a port channel (23) for the central heating inlet (8).
• the second channel (Y), see Fig. 2, section line IV, and Fig. 4 also communicates with the central heating outlet (14), situated on the rear of the heat exchanger, via a port channel (24) for the central heating outlet (14).
• the third channel (Z), see Fig. 2, section line III, and Fig. 3, is defined by the space formed inside the second cassette types (16) and is intended to receive domestic heating water.
• the third channel (Z) communicates with the domestic hot water inlet (7), situated on the rear (6) of the heat exchanger (2), via a port channel (25) for the domestic hot water inlet (7).
• the third channel (Z), see Fig. 2, section line IV, and Fig. 4 also communicates with the domestic hot water outlet (13), situated on the rear of the heat exchanger, via a port channel (26) for the domestic hot water outlet (13).
• the cassette types together constitute a stack of cassettes in which plates and cassettes are connected to one another by brazing.
• the invention is not limited merely to said joining method, as other joining methods may also be used, e.g. welding, brazing, bonding by adhesive etc.
• All the plates (17 and 18) and cassettes (15 and 16) in the heat exchanger (2) are brazed to one another via the contact points of the corrugation configuration of the plates which occur when the ridges of the plates are placed against one another.
• the following brazing is effected at these contact points in the heat exchanger:
• the second plate types (18), see Figs. 3 and 4, for the second cassette type (16) are brazed to one another round their peripheral edge (22) and round recesses in the plate for inlet and outlet of the second channel (Y).
• the first plate types (17) for the first cassette type (15) are brazed to the second cassette type (16) by a first plate type (17) being placed on each side of said second cassette type (16).
• the edge (21 ) of the first plate type (17) is brazed to the edge (22) of the second cassette type (16), round the recesses in the plate for inlet and outlet of the third channel (Z) for the second cassette type (16), round the recesses in the plate for inlet and outlet of the third channel (Z) to the first cassette type (15) and round the recesses in the plate for inlet and outlet of the second channel (Y) to the first cassette type (15).
• the heat exchanger (2) is mechanically connected to the housing (3) of the boiler (1).
• the exhaust gas outlet (9) and condensate outlet (10) belonging to the boiler (1) are connected to the housing (3) by brazing.
• the heat exchanger described above functions during operation of the boiler in the following manner.
• the gas burner (4) delivers hot gases which are led downwards through the first channels (X) of the heat exchanger (2) which are formed between the first cassette types (15).
• the hot gas is forced down into the first channels (X) by a fan (5) situated above the gas burner (4).
• the heated gas transfers its heat to the central heating water present in the second channel (Y) inside the first cassette type (15), but outside the walls constituting the second cassette type (16).
• the central heating water is led into the heat exchanger (2) via the central heating inlet (8), see Fig. 3, into the second channels (Y) of the first cassette types (15) and is thereafter led out from the heat exchanger (2) via the central heating outlet (14), see Fig. 4. Causing the central heating water to circulate in and out of the heat exchanger (2) in a closed circuit makes it possible for its temperature to be regulated in order to maintain it at a specified level.
• the central heating water transfers its heat to the domestic hot water present in the third channel (Z) in the second cassette type (16).
• the domestic hot water is led into the heat exchanger (2) via the domestic hot water inlet (7), see Fig. 3, and into the third channels (Z) of the second cassette types (16) and is thereafter led out from the heat exchanger (2) via the domestic hot water outlet (13), see Fig. 4, to, for example, a water tap which regulates the flow of heated domestic hot water from the heat exchanger (2).
• a further alternative for the configuration of the heat exchanger (2) is that the cassettes (15) of the first type are not permanently connected together. Instead, the cassettes have between them a packing so designed that heated gas is allowed to come in between the cassettes from above and is led out from below (not shown in the drawings). Depending on the positioning of the gas burner (4) and the fan (5), the gas may also be led upwards from below.
• the advantage of the embodiment described above comprising packings is that it becomes possible to separate the cassettes in order, for example, to carry out servicing or cleaning of the space between the cassettes (15).

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

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• 2004
  • 2004-01-23 SE SE0400138A patent/SE527450C2/sv not_active IP Right Cessation
• 2005
  • 2005-01-07 CN CN2005800026551A patent/CN1981175B/zh not_active Expired - Fee Related
  • 2005-01-07 EP EP05704682A patent/EP1706696A1/en not_active Withdrawn
  • 2005-01-07 WO PCT/SE2005/000008 patent/WO2005071343A1/en active Application Filing

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