SE527450C2 - Heat - Google Patents

Abstract

A permanently connected heat exchanger for receiving three media and composed of two plate types is intended to be used in a boiler. The heat exchanger is designed to counteract and prevent the occurrence of lime deposition (scaling) during the production of hot domestic hot water. The plates of the heat exchanger together constitute cassettes which are stacked on one another. The first plate type constitutes a first cassette which surrounds a second cassette composed of the second plate type. A first channel for receiving hot exhaust gas is formed between the cassettes of the first type. A second channel for receiving central heating water is formed in the space between the plates which constitute the first and second cassettes. A third channel for receiving domestic hot water is formed inside the second cassette. The fact that the heat transfer from the heated exhaust gas in the first channel to the domestic hot water in the third channel takes place via the central heating water in the second channel prevents sudden temperature changes in the domestic hot water, e.g. due to uneven heating cycles of the exhaust gas.

Description

20 25 30 527 450 i.e. each plate type is pressed separately in its own mold tool. Plastic deformation occurs e.g. by pressing, sizing, forging or punching.

Two plates of one type of plate are permanently connected to each other to form a first type of cassette. Two plates of the second type of plate are permanently connected to each other to form a second type of cassette.

US patent specification US 4002201 discloses a plate heat exchanger for receiving various media made up of plates which form cassettes which are stacked on top of each other. Between the cassettes, which are identical, metal insert plates are placed and in mechanical contact with the two adjacent cassettes. The disadvantage of the invention according to US 4002201 is that the heat exchanger is designed to receive medium in gaseous medium between the cassettes, e.g. air and is not suitable for other types of medium. A further disadvantage is that the temperature of the medium in the cassettes can not be regulated in a simple controllable manner. Its temperature is directly dependent on the temperature of the gas in the intermediate insert plates. If the temperature of the gas changes, this directly affects the temperature of the media in the cassettes. A further disadvantage of the invention according to US 4002201 is that since only one plate type is used for building the cassettes of the heat exchanger, only one type of cassette can be created, which makes it impossible to create a heat exchanger with different cassette types.

Japanese Patent Application Publication No. JP 2003-148881 discloses a heat exchanger for receiving three media in which a heat emitting medium flows in a channel located between two adjacent and surface channels. The disadvantage of the heat exchanger according to JP 2003-148881 is that its cassette is built up of * at least three different plate types that form the different channels. Having many different plate types means that the heat exchanger becomes expensive to manufacture. A further disadvantage is its function due to that the temperature of the media in the two surface channels is directly dependent on the temperature in the medium of the intermediate channel. If the temperature of the intermediate medium changes, it directly affects the temperature of the media in the adjacent channels. A further disadvantage of the construction according to JP 2003-148881 is that the cassette has its ports with pipe connections on their respective upper and lower sides, which makes it impossible to stack several cassettes.

British patent application GB 2332508 describes a molded heat exchanger which can receive three different media and which comprises a centrally located heating circuit. The disadvantage of the construction according to GB 2332508 is that the heat exchanger is cast. This means that the heat exchanger is expensive to manufacture and requires many difficult operations in terms of manufacturing. A further disadvantage is that cast elements in a heat exchanger cause difficulties in repair and service, which contributes to the cost of such interventions.

Japanese Patent Publication No. JP 02-254291 discloses a packaged plate heat exchanger for receiving three media. The plate heat exchanger is intended to be used for heat sterilization of liquid food, where the food is heated by a heated water circuit adjacent to the food. The disadvantage of the construction is that it lacks cassettes and instead has gaskets between the plates, which makes the heat exchanger temperature sensitive. Due to their material, gaskets cannot withstand excessive temperature changes or too high temperatures. Additional disadvantages of heat exchangers which are packaged and used for food are that precipitates from the packages can contribute to taste changes in the food which is processed in the heat exchanger. An object of the present invention is to provide a heat exchanger with cassettes where the above-mentioned problems are eliminated.

A further object of the present invention is to create a heat exchanger which provides indirect heat transfer and which prevents large temperature changes of an outgoing medium from occurring during switching on and on of a heat source, e.g. a gas burner.

A further object of the present invention is to create a heat exchanger which fulfills the same function as two individual, traditional heat exchangers when these are used in a so-called boiler, i.e. a unit equipped with a gas burner for the production of hot tap and radiator water.

A further object of the present invention is to create a heat exchanger built up of two types of boxes, for receiving three different media and where the media cannot be mixed with each other.

A further object of the present invention is to create a heat exchanger which is cost-effective and better in performance than existing heat exchangers. The purpose is also that it should be simple to design and lead to time savings in its production.

The above-mentioned and other objects are achieved according to the invention in that the plate heat exchanger initially described has been given the features stated in claim 1.

Advantages obtained with a heat exchanger according to the characterizing part of claim 1 are that only two plate types are needed to construct a heat exchanger according to the invention which can receive three media separated from each other.

A further advantage which is achieved with a heat exchanger according to the characterizing part of claim 1 is that there is a "soft" temperature effect for the medium emanating from the heat exchanger, e.g. tap water. Because the cassettes enclose each other, a buffer of hot medium is formed in the enclosing cassette, which encloses and has heat transfer to the outgoing medium. In addition to the fact that the outgoing medium is not exposed to large temperature changes, the formation of limescale coating in the enclosed cassette is also counteracted.

A further object of the present invention is to counteract and slow down the formation of limescale coating in the heat exchanger, which coating is caused by large and rapid temperature changes of the media flowing through the heat exchanger.

The above-mentioned and other objects are achieved according to the invention in that the initially described method for the heat transfer has been given the features stated in claim 7.

The method according to the invention means that the precipitation of lime is slowed down and counteracted in the heat exchanger because the indirect temperature transfer slows down the temperature variations. Normal water contains lime in varying amounts. The lime determines the hardness of the water. Hard water is rich in lime and the equivalent of soft water is that it contains a small amount of lime. In case of temperature changes, e.g. heating, of water the lime of the water precipitates. If the water is exposed to strong and rapid heating, the lime precipitates faster than with the corresponding slow heating. Preferred embodiments of the device according to the invention have furthermore been given the features set out in subclaims 2 to 6.

The heat exchanger according to the invention comprises cassettes of a first type which enclose second cassettes of a second type. The cassettes are arranged on top of each other and form a stack, also called a flat stack. If necessary, the cassettes can be stacked to form only a part of a heat exchanger, e.g. a flat package.

The heat exchanger according to the invention is built up of two plate types, where the first cassette type is built up of the first plate type and where the second cassette type is built up of the second plate type. Each plate has a heat transfer surface and a flank which is defined as the portion extending around the circumference of the plate, outside the heat transfer surface.

The flank consists of a first portion in the form of a board and a second portion in the form of a web, placed between the board and the heat transfer surface. Life is angled from the plane where the heat transfer surface is located. This can be compared to an ordinary serving tray which carries coffee cups and which has an upturned edge around its periphery. On the serving tray, this edge is angled from the plane used to place the coffee cups on.

The inside of the plate is defined as the side that is inside the curved flank. The outside of the plate is thus defined as the side located on the other side of the plate.

The invention creates the respective cassette type by taking two plates of the same type and joining them with their respective insides facing each other. The flanks come into contact with each other and can be associated with each other. 10 15 20 25 30 527 450 P.g.a. that in the preferred embodiment one has a first cassette type enclosing a second cassette type, it is necessary to have two different plate types. In order to be able to enclose the second type of cassette, the plates forming the first type of cassette must have a different design than the plates forming the second type of cassette. Bl.a. the flank of the first type of plate must be larger than that of the second because the first plates, with their flanks, together enclose the plates of the second type. In order for the plates of the second type to be able to abut each other with their respective insides and form the other box types, their flanks cannot be higher than the tops in the heat transfer pattern of these plates.

Should the need arise for a heat exchanger adapted to be able to receive only two media, the heat exchanger can be modified in that the first box types are built up of first plate types with a flat heat transfer surface. By using flat plate types, the first channel between the first cassettes during assembly is minimized or eliminated.

The result is that the first cassettes border on each other without any real space. This is a solution that can be chosen when it is necessary with heat transfer between two media, but when mixing of the media must certainly not occur. An example of this is media that in contact with each other can pose a risk of explosion. With the present invention adapted for receiving two media, it is possible to achieve a secure heat transfer also between such media. .

In a preferred embodiment of a heat exchanger according to the invention in a so-called boiler is supplied with heat via a heat source, e.g. a gas burner, which is located in the immediate vicinity of the cassettes and emits hot exhaust gases which are led into the heat exchanger. The heat source can of course also consist of other types of heat-producing units. The gas burner can e.g. be placed above the cassettes. The hot gas from the gas burner, which has an approximate outlet temperature of about 1200 ° C, is forced down into the defined first channels which are connected to the heat source. In these first channels, the gas transfers its heat to the medium flowing on the other side of the cassette plates, 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 with the use of conventional heat exchangers is that the temperature of the tap water is directly and immediately affected by the heat source.

If the heat source disappears, this normally has an immediate effect on the temperature of the output medium from the heat exchanger, which e.g. may be tap water which must not become too hot and carry the risk of scalding.

By having, according to the preferred embodiment of the invention, a closed circuit in the heat exchanger, which in the invention is defined as the second channel, this direct dependence on the heat source is eliminated. A closed circuit can also be used as a radiator circuit. In this second channel a medium flows which is not mixed with other media in the heat exchanger.

The medium in this second channel is heated by the medium in the above-mentioned first channel. The temperature of the medium in the second channel is between 60 ° C - 90 ° C. Since this second channel is a closed, radiator-equipped circuit, its temperature can be most easily and advantageously varied by forcing the medium to circulate by means of a pump. The means in this second circuit acts as a buffer in the form of stored heat energy. From this second channel temperature transfer takes place to the third medium which flows in the third channel defined according to the preferred embodiment of the invention. As mentioned earlier, the temperature level in the second channel is relatively stable. This means that the heat transfer from the second channel to the medium in the third channel can take place in a stable and controlled manner. The result is that the outgoing means from the third - 10 15 20 25 30 527 450 š ": i I IQ Ü .'É .. ° '° .. tx EE ... cnn D: S o: now the channel will only show small temperature differences and may have a temperature in the range 50 ° C - 70 ° C.

The advantage of the preferred invention is that p.g.a. construction described above, an indirect temperature transfer takes place from the first medium to the third medium via the second medium. P.g.a. this is prevented large. and rapid temperature fluctuations in the third output medium when the gas burner is turned on and off. This has the consequence that the formation of limescale in the heat exchanger can be slowed down and counteracted.

The preferred design for the invention also contributes to the design of the cassettes enabling the heat exchanger to be customized during manufacture. Depending on the customer's requirements, the number of cassettes can either be increased or decreased in the heat exchanger.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the device and method according to the invention will now be described in more detail with reference to the accompanying schematic drawings, which show only the details necessary for understanding the invention.

Fig. 1 shows a boiler from the front with a housing comprising a heat exchanger according to the invention where a fan and a gas burner are located above the heat exchanger.

Fig. 2 shows a cassette enclosing another cassette (dashed line) at a heat exchanger according to the invention where a first section line is drawn through the inlet ports of the heat exchanger and a second section line is drawn through the outlet ports of the heat exchanger.

Fig. 3 shows in section the boiler according to Fig. 1 with the heat exchanger in section along section line lll according to Fig. 2. 00 I 000: nu oob I 0 10 15 20 25 30 527 450 1åu ': HE 1: -' .az u: shows in cross-section the boiler according to Fig. 1 with the heat exchanger In cross-section along section line IV according to Fig. 2 with a gas burner and fan placed above the heat exchanger.

Fig. 4 DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION Fig. 1 shows 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).

Above the heat exchanger (2) is a gas burner (4) located. Above the gas burner (4) a fan (5) is placed. On the front side (6) of the heat exchanger (2), two inlet ports (7 and 8) are intended for tap water inlets (7) resp. central vatfenin inlet (8) located. In the housing (3) there are outlets for flue gas emissions (9) and condensate emissions (10). On the back of the heat exchanger (2), two outlet ports (13 and 14) are located intended for tap water outlets (13) resp. central water outlets (14), which are drawn with dashed lines in Fig. 1.

The heat exchanger (2), see Figs. 1 and 2, comprises two types of cassettes, a first cassette type (15) and a second cassette type (16). The first cassette type (15) encloses the second cassette type (16). In Figs. 1 and 2, the second cassette type (16) is torn with dashed lines because it is enclosed by the first cassette type (15).

The cassettes in the heat exchanger (2), see Figs. 3 and 4, are formed by two types of plates (17 and 18), namely a first plate type (17) and a second plate type (1 s). Each plate in the heat exchanger (2) has a flank (21 and 22) extending around its circumference »which is angled from the plane of the plate. As previously explained, the plate can be likened to a serving tray with one outside and one. 10 15 (20 25 527 450; §: .§ .. ;; g. Inside. The inside of the plate is represented by what is inside the raised flank. The outside is thus what is on the other side of the plate.

As previously mentioned, the first cassette type (15) encloses the second cassette type (16). The first cassette type (15) is made up of two plates of the first plate type (17) with their respective insides (19) facing each other. The second formed cassette type (16) is made up of two plates of the second plate type (18) with their respective insides (20) facing each other.

The heat exchanger (2), see Figs. 3 and 4, consists of box types (15 and 16) as described above, which are associated with each other. Between each pair of directly adjacent cassettes (15) of the first type, a first channel (X) is formed. Between the different box types, i.e. inside the walls of the first cassette type (15) but outside the walls of the second cassette type (16) a second channel (Y) is formed. Inside the walls of each second cassette type (16), a third channel (Z) is formed.

The first channel (X) is connected to the gas burner (4) in order to be able to receive the heated gases from the gas burner (4) and pass them through the heat exchanger (2). To obtain a larger and more efficient heat transfer, the heat transfer surfaces of the plates are corrugated (not shown in the figures). The corrugation pattern, which is pressed into the plates, is designed so that the outwardly facing axes of the first plate types (17) abut each other when the first box types (15) are abutted against each other.

The corrugation pattern is angled in a known manner in relation to the corrugation pattern of the adjacent plate so that the tops of the axes create contact points. Between the contact points of the corrugation pattern, valleys are formed which create the first channel (X) defined above. IQ ICO 0 1 win 1 0 10 15 '20 25 30 527 450 s ° = a' ° = ° -._.- '12 32%' The second channel (Y), see Fig. 2, section line lll, and Fig. 3, is defined by the space formed between the plates of the first cassette type (15) and the plates of the second cassette type (16) and is intended to receive central water, or radiator water. The second channel (Y) is connected to the central water inlet (8), located on the front side (6) of the heat exchanger (2), via a port channel (23) for the central water inlet (8). The second channel (Y), see Fig. 2, section line 1V, and Fig. 4, is also connected to the central water outlet (14), located on the back of the heat exchanger, via a port channel (24) for the central water outlet (14).

The third channel (Z), see Fig. 2, section line III, and Fig. 3, is defined by the space formed inside the other box types (16) and is intended to receive tap water. The third channel (Z) is connected to the tap water inlet (7), located on the front side (6) of the heat exchanger (2), via a port channel (25) for the tap water inlet (7). The third channel (Z), see Fig. 2, section line 1V, and Fig. 4, is also connected to the tap water outlet (13), located on the back of the heat exchanger, via a port channel (26) for the tap water outlet (13).

Together, the cassette types form a stack of cassettes where plates and cassettes are connected to each other by soldering. The invention is not limited only to said joining method, but also other joining methods can be used, e.g. welding, soldering, gluing etc ..

All plates (17 and 18) and cassettes (15 and 16) in the heat exchanger (2) are soldered together via the contact points in the corrugation pattern of the plates which occur when the axes of the plates are laid against each other. In addition to these contact points, the following soldering takes place in the heat exchanger: n ICO 0 10 15 20 25 30 527 450 1 -z '-.-' 2 za The other plate types (18), see Figs. 3 and 4, for the second cassette type (16 ) soldered together around their peripheral flank (22) and around recesses in the plate for inlet and outlet - to the second channel (Y).

The first plate types (17) for the first cassette type (15) are soldered together with the second cassette type (16) by placing a first plate type (17) on each side of said second cassette type (16). The flank (21) of the first plate type (17) is soldered to the flank (22) of the second cassette type (16), around the recesses in the plate for inlet and outlet to the third channel (Z) of the second cassette type (16), around the recesses in the plate for inlet and outlet to the third channel (Z) against the first cassette type (15) and around the recesses in the plate _ for inlet and outlet for the second channel (Y) against the first cassette type (15). the heat exchanger (2) is mechanically connected to the housing (3) of the boiler (1).

The associated flue gas emissions (9) and condensate emissions (10) of the boiler (1) are connected to the housing (3) by soldering.

The heat exchanger described above operates during operation of the boiler in the following manner.

The gas burner (4), see Figs. 3 and 4, emits hot exhaust gases which are led from the top down through the first channels (X) of the heat exchanger (2) which are formed between the first box types (15). Placed by a fan (5). above the gas burner (4) the hot gas is forced down into the first channels (X). In the first channels (X), the heated gas transfers its heat to the radiator water, which is located in the second channel (Y) inside the first cassette type (15), but outside the walls the second, cassette type (16) is formed.

The liquid water is led into the heat exchanger (2) via the central water inlet (8), see Fig. 3, into the second channels (Y) of the first box types (15) and is led 00000 10 15 '20 25 30 527 450' ° ..:: '' '' '' then out of the heat exchanger (2) through the central water outlet (14), see Fig. 4. By letting the radiator water circulate in and out of the heat exchanger (2) in a closed circuit, its temperature can be regulated to be kept at a certain level.

In the heat exchanger (2), the heated radiator water transfers its heat to the tap water, which is located in the third channel (Z) in the second cassette type (16).

The tap water is led into the heat exchanger (2) via the tap water inlet (7), see Fig. 3, and into the third channels (Z) of the other cassette types (16) and then led out of the heat exchanger (2) via the tap water outlet (13), see Fig. 4, to e.g. a water tap that regulates the flow of heated tap water from the heat exchanger (2).

Through the function described above, where the heat from a heating medium to the tap water goes via an additional medium, a stable and controlled temperature can be ensured for the outgoing tap water at the same time as the occurrence of limescale coating in the heat exchanger is counteracted and prevented.

An alternative to the placement of the gas burner (4) and the fan (5) in the boiler (1) is that these are placed under the cassettes instead of above as in the preferred embodiment. The heated gas is then instead led up through the first channels (X) (not shown in the figures). The fan (5) can possibly be dispensed with in this way. A further alternative to the design of the heat exchanger (2) is that the cassettes (15) of the first type are not permanently connected to each other. instead, the cassettes have a gasket between them designed in such a way that heated gas is allowed to enter between the cassettes from above and be led out from below (not shown in the figures). Depending on 10 (TI KO w .Pa 0 "! C) .lš-Jân: ä ...: åâå-.š EE the location of the gas burner (4) and the fan (5), the gas can also be conducted from the bottom up. the above-described embodiment comprising gaskets is that it becomes possible to separate the cassettes in order to, for example, perform service or cleaning of the space between the cassettes (15).

The invention is not limited to the embodiment shown but can be varied and modified within the scope of the appended claims, which has been partly described above.

Claims (1)

10 15 20 25 30 527 450 16 PATENT REQUIREMENTS Plate heat exchanger (2) preferably for a boiler comprising a stack of cassettes (15 and 16), formed of permanently connected plates of a first and a second type (17 and 18), which cassettes (15 and 16) are of a first cassette type (15) and a second cassette type (16), the first cassette type (15) consisting of the plates of the first plate type (17) and the second cassette type (16) consisting of plates of the second plate type (18), characterized therefrom, that each cassette (16) of the second type is enclosed by a cassette (15) of the first type. . Plate heat exchanger (2) according to claim 1, characterized in that the first box types (15) adjoin a first channel (X). . Plate heat exchanger (2) according to claim 1, characterized in that the first box types (15) create a channel (X, Y and Z) between them. . Plate heat exchanger (2) according to claim 1, characterized in that the cassettes (15 and 16) are formed by two plates of the same type (17 and 18), which are interconnected with their respective insides (19 and 20) directed towards each other. . Plate heat exchanger (2) according to claim 2, characterized in that a number of first box types (15) together define a second channel (Y), that a number of second box types (16) together define a third channel (Z) , the channels (Y and Z) forming flow paths for different media. Plate heat exchanger (2) according to claim 5, characterized in that the first channel (X) is connected to a heat source (4), the second channel (Y) is a closed circuit and that the third channel (Z) contains tap water. . Method for heat transfer in a permanently connected plate heat exchanger (2) in a boiler, wherein the heat exchanger (2) comprises cassettes (15 and 16) of a first and a second cassette type (15 and 16), the first cassette type (15) consisting of a first plate type (17), the second cassette type (16) consisting of a second plate type (18), which cassettes (15 and 16) between and in themselves form different channels (X, Y and Z) for receiving different media, characterized thereby, that the heat transfer from a first medium in a first channel (X) to a third medium in a third channel (Z) takes place via a second medium in a second channel (Y).