EP0775876B1 - Mixed heat exchanger coil with complex straight section - Google Patents

Abstract

The combination heater consists of a hot water circuit and a central heating circuit. The circuit consists of pipes made from outer (2) and inner (3) elements, connected at their ends to manifolds. The inner elements, which have a complex cross-section, create a series of contact surfaces (6) between the two elements of the pipe which form thermal bridges. The central heating water circulates through the spaces between the outer and inner elements. The outer elements of the pipes are round or oval in section. The inner elements have a complex cross-section, e.g. cross-shaped, X-shaped or Y-shaped, and provide a heat exchange surface which is sufficient to disperse the whole of the thermal power produced by the burner. The outer elements are made from sheet metal with brazed or welded seams, and the inner ones from shaped tubing.

Description

The present invention relates to improvements made to the heating bodies of boilers, especially gas central heating. These boilers for domestic or industrial use must provide the user with both hot water sanitary whose temperature must not exceed 65 ° C, that the heating hot water which is circulated in a closed circuit within the central heating network of the house.

These heaters are commonly called mixed heaters because they have two water circuits separate, one for domestic water, the other for domestic water heating, which are joined together so that that there is an intimate thermal contact between them. Generally, these are tubular circuits arranged one inside the other, and comprising either means for making the thermal bridges between the two circuits, either separate tubular circuits but flattened and pushed together. These bodies of heaters also have a bundle of fins responsible for transmitting to the tubular circuits, the flow thermal transported by the fumes resulting from the combustion within a partially placed burner lower part of the heating body.

EP-A-0 401 543 describes a heat exchanger, in particular for water heaters with liquid or gaseous fuel, comprising at least one external tube carrying a heat transfer fluid and containing at least one internal tube smaller diameter carrying a second fluid heat exchanger in heat exchange with the first, as well only means for ensuring a play-free support of the tube internal against the external tube.

A main constraint that acts on this type of exchanger mainly lies in the fact that the different water circuits circulate alternately. Each of the circuits in circulation must be capable to evacuate all the calories present in the smoke, without the other stagnant circuit rising excessively in temperature or pressure.

Currently, normative regulations impose temperature thresholds not to be exceeded, mainly on the water heating circuit sanitary, this barrier being very difficult to observe with the type of mixed heater known in the art prior.

In order to meet these standards, however, the designers of the mixed heater solve this problem by incorporating clipping devices into the installation which significantly complicate the structure of the exchanger. Another way to solve this problem is to impose on the recirculation heating water circuit in closed loop within the boiler when drawing sanitary water. This solution requires that it exists on the heating circuit a three-way valve and a connection piping, which increases the cost of manufacturing and maintenance.

The present invention therefore aims to overcome these disadvantages, by proposing a heating body which has both a water heating circuit sanitary and a central heating water circuit, these circuits being nested one inside the other but having optimization of flows and heat exchanges within the exchanger.

• Une première étape consistant à réaliser deux demi-coquilles, chaque demi-coquille comportant essentiellement une pluralité de premiers éléments s'étendant sous la forme de tubes semi-cylindriques ou semi-ovales, préférentiellement au nombre de cinq à huit, disposés en parallèle et reliés à chacune de leurs extrémités à une nourrice, ces divers éléments étant réalisés selon le cas, en cuivre ou en acier inoxydable.
• Une deuxième étape consistant en la fabrication des seconds éléments destinés à la circulation de l'eau du circuit de chauffage sanitaire.
• Une troisième étape consistant à disposer, au sein des demi-coquilles constituées essentiellement de premiers éléments reliés à leurs extrémités à des nourrices le serpentin de seconds éléments.
• Une quatrième étape consistant à interposer entre les plans de joints délimités par les demi-coquilles inférieure et supérieure, des baguettes de brasure et à placer au-dessus des tubes cylindriques ou ovales des premiers éléments, une pluralité d'ailettes, et à ramener les bords rabattus des ailettes initialement perpendiculaires au-dessus des tubes de manière à conformer un corps de chauffe mixte manipulable, mécaniquement solidaire.
• Une cinquième étape consistant à positionner à la base des ailettes et au contact des premiers éléments formant le corps de chauffe, des baguettes de brasure et à disposer l'ensemble dans un four de brasage fonctionnant avantageusement sous atmosphère neutre ou réductrice.

The invention is aimed firstly at a method for producing this type of mixed heating body, characterized in that it comprises:

• A first step consisting in producing two half-shells, each half-shell essentially comprising a plurality of first elements extending in the form of semi-cylindrical or semi-oval tubes, preferably five to eight in number, arranged in parallel and connected at each of their ends to a manifold, these various elements being made as appropriate, in copper or stainless steel.
• A second step consisting in the manufacture of the second elements intended for the circulation of the water of the sanitary heating circuit.
• A third step consisting in placing, within the half-shells essentially consisting of first elements connected at their ends to nurse pipes, the coil of second elements.
• A fourth step consisting in interposing between the joint planes delimited by the lower and upper half-shells, brazing rods and in placing above the cylindrical or oval tubes of the first elements, a plurality of fins, and in bringing the folded edges of the fins initially perpendicular above the tubes so as to conform a manipulative mixed heating body, mechanically integral.
• A fifth step consisting in positioning the brazing rods at the base of the fins and in contact with the first elements forming the heating body, and in placing the assembly in a brazing oven advantageously operating in a neutral or reducing atmosphere.

The invention is secondly aimed at a mixed heating body obtained by implementing the process specified above and having the characteristics defined in claim 7.

• La figure 1 est une vue en perspective et en écorché, illustrant le montage dans une chaudière murale d'un corps de chauffe mixte selon l'invention ;
• La figure 2 est une vue en perspective d'un corps de chauffe mixte selon l'invention ;
• la figure 3 est une vue en coupe, en élévation latérale, d'un corps de chauffe mixte selon l'invention ;
• la figure 4 est une vue en coupe, en élévation frontale, de la figure 3.

Other characteristics and advantages of the present invention will emerge from the description given below, with reference to the appended drawings which illustrate an embodiment thereof devoid of any limiting character. In the figures:

• Figure 1 is a perspective view in cutaway, illustrating the mounting in a wall-mounted boiler of a mixed heating body according to the invention;
• Figure 2 is a perspective view of a combination heater according to the invention;
• Figure 3 is a sectional view, in side elevation, of a combination heater according to the invention;
• FIG. 4 is a sectional view, in front elevation, of FIG. 3.

According to a preferred embodiment of the heating body mixed 1, object of the invention, it comprises a plurality first elements 2 produced in the form of a tube of circular or oval cross section, within which a plurality of second elements 3 are incorporated in the form of a cross-section tube complex, such as in particular in cross, in X, in Y.

The first element 2 constitutes the heating circuit, the heating water circulates in the delimited sections between the outer walls 4 of the cross section tube complex and the inner wall 5 of the first element 2.

The second element 3 constitutes the heating circuit sanitary, sanitary water flows inside the complex cross section.

According to an advantageous characteristic, the mounting of the second element 3 in the first element 2 delimits a plurality of contact generators 6 between the tube complex cross section 3 and the outer tube 2; these contact generators 6 are made integral with the level of the first 2 and second elements 3 by through known means such as in particular by a brazing or welding operation, in order to carry out at the level of these generators thermal bridges.

Thanks to this mounting between these two elements 2, 3, during the sanitary operation, the heat flow travels in largely directly by conduction between water and the material in contact with the fumes, without overuse the heating water circuit as coolant.

According to another advantageous characteristic of the invention, the complex profile of the second element 3 guarantees that it has an exchange surface sufficient to allow all of the thermal power delivered by the burner 7, positioned in its lower part.

On the other hand, the particular arrangement between the first 2 and second 3 elements ensures that during operation in central heating, the channel wall temperature peripherals 8 - these being delimited by the first element and the connection zones of the second element - reached at the level of their wet section a homogeneous temperature and very close to that of the first element, which achieves, thanks to the coefficient of high exchange and with a large developed surface, the level of efficiency on the heating side required by standards.

Industrialization and manufacturing constraints a central heating boiler fitted with a body of mixed heater 1 according to the invention require size the circulator as accurately as possible or the accelerator mounted on the heating circuit. The power of the latter is calculated so as to compensate for the hydraulic head losses of the assembly of the circuit. Regarding pressure losses, we notes these at the piping and radiators constituting the heating installation central, but also at the boiler and all particularly at the level of the heating body, mainly on the pipes forming the first 2 and second 3 elements.

These first 2 and second 3 elements, whose diameter hydraulics is optimized to reduce the size of the heating body 1, generate the major part of the hydraulic head losses and, in order to minimize the installed power of the circulator, the first 2 elements of the central heating circuit are connected to nurses 9, 10 arranged on the side and on the other side of the exchanger.

Central heating water circulation takes place in parallel within these nurses, so that guarantee an identical flow in each of the channels 8.

On the other hand, the circulation of sanitary water is carried out in series and successively within the plurality of second elements 3.

• Une première étape qui consiste à réaliser deux demi-coquilles 11, 12. Chaque demi-coquille 11, 12 comporte essentiellement une pluralité de premiers éléments 2 s'étendant sous la forme de tubes semi-cylindriques ou semi-ovales, préférentiellement au nombre de cinq à huit, disposés en parallèle et reliés à chacune de leurs extrémités à une nourrice 9, 10. Ces divers éléments sont réalisés selon le cas, en cuivre ou en acier inoxydable.

According to a process for developing a heating body 1 according to the invention, it comprises a succession of simple steps, broken down into:

• A first step which consists in producing two half-shells 11, 12. Each half-shell 11, 12 essentially comprises a plurality of first elements 2 extending in the form of semi-cylindrical or semi-oval tubes, preferably the number of five to eight, arranged in parallel and connected at each of their ends to a nurse 9, 10. These various elements are made as appropriate, in copper or stainless steel.

According to a first mode of production, these half-shells 11, 12 are produced directly by stamping a metallic foil, it being understood that there are two different matrices respectively depending on obtaining an upper half-shell and a half-shell lower.

According to a second embodiment, the various elements (the first elements 2 semi-cylindrical or semi-oval, the side half-nurses 9, 10) are produced separately, in particular by stamping, and are rendered united by a second operation consisting of example in a welding or brazing phase.

• Une deuxième étape consistant en la fabrication des seconds éléments 3 destinés à la circulation de l'eau du circuit de chauffage sanitaire.

The lower and upper half-shells 11, 12 differ from each other mainly in that one of them has on the external wall of the side housings 9, 10, orifices 13 allowing connection to the various circuits domestic and central heating.

• A second step consisting in the manufacture of the second elements 3 intended for the circulation of the water of the sanitary heating circuit.

These second elements 3, of which. the right section is complex, especially cruciform, are obtained at from cylindrical tubes delivered in a crown, by a cycle either of cross profiling then bending of these last so as to conform a succession of pins forming a coil, or tube bending cylindrical followed by a hydroforming step.

These processes for developing the second elements 3 allow constant thickness to be obtained throughout of the coil, which guarantees the absence of weak points corrosion.

• Une troisième étape consiste à disposer, au sein des demi-coquilles 11, 12 constituées essentiellement de premiers éléments 2 reliés à leurs extrémités à des nourrices 9, 10, le serpentin de seconds éléments 3.

It can also be noted that the use of a one-piece coil eliminates any brazed connection between the domestic water heating circuit and the central heating water heating circuit.

• A third step consists in placing, within the half-shells 11, 12 essentially consisting of first elements 2 connected at their ends to manifolds 9, 10, the coil of second elements 3.

• Une quatrième étape consiste à interposer entre les plans de joints 14 délimités par les demi-coquilles 11, 12 inférieure et supérieure, des baguettes de brasure 15 et à placer au-dessus des tubes cylindriques ou ovales des premiers éléments 1, une pluralité d'ailettes 16, et à ramener les bords rabattus des ailettes initialement perpendiculaires au-dessus des tubes de manière à conformer un corps de chauffe mixte 1 manipulable, mécaniquement solidaire.
• Une cinquième étape consiste à positionner à la base des ailettes 16 et au contact des premiers éléments 2 formant le corps de chauffe, des baguettes de brasure et à disposer l'ensemble dans un four de brasage fonctionnant avantageusement sous atmosphère neutre ou réductrice.

Advantageously, the coil is arranged in the lower half-shell 12 because the latter has the orifices 13 for connection to the various circuits.

• A fourth step consists in interposing between the joint planes 14 delimited by the lower and upper half-shells 11, 12, brazing rods 15 and in placing above the cylindrical or oval tubes of the first elements 1, a plurality of fins 16, and to bring the folded edges of the fins initially perpendicular above the tubes so as to conform a mixed heating body 1 manipulable, mechanically integral.
• A fifth step consists in positioning the brazing rods at the base of the fins 16 and in contact with the first elements 2 forming the heating body, and in placing the assembly in a brazing oven operating advantageously under a neutral or reducing atmosphere.

At the outlet of this oven, the exchangers are ready to supply the boiler assembly line without use of subsequent steps to assemble fittings, various elbows, manifolds ...

According to another method of assembling the heating body, object of the invention, the so-called "strong" brazing step is replaced by a so-called "soft" brazing step, consisting essentially in a tinning phase by soaking. The 1 whole heating element is soaked in a tin bath so as to have, on the one hand a tin film which protects the heat exchanger against corrosion and other share, keeping the building material from the whole, like copper, its work hardened, to avoid to the fins 16 to deform easily during manipulations.

According to another method of obtaining the fins, these instead of being in the form of separate fins, present in the form of an accordion.

The heating body as described above allows a perfect heat exchange between the fluids contained in the two circuits, via a surface significant exchange between the conduits, obtained thanks to their relative provision.

Furthermore, the absence of elbows reported on each circuits, changes of direction being obtained by bending the tubes of the different circuits, simplifies the heat exchanger manufacturing method, no more solder or welding, which avoids the risk of leaks.

Claims (10)

1. Process for producing a mixed heat exchanger characterised in that it comprises:

   A first stage consisting of producing two half-shells (11, 12), each half-shell (11, 12) substantially comprising a plurality of first elements (2) extending in the form of semi-cylindrical or semi-oval tubes, preferably in a quantity of five to eight, disposed in parallel and connected at each of their ends to a feed-pipe (9, 10), these various elements being produced from copper or stainless steel, depending on the individual case.

   A second stage consisting of producing second elements (3) intended for circulating the water from the domestic heating circuit.

   A third stage consisting of placing the coil of second elements (3) in the half-shells (11, 12) substantially comprising first elements (2) connected at their ends to feed-pipes (9, 10).

   A fourth stage consisting of interposing brazing solder rods (15) between the joint planes (14) defined by the lower and upper half-shells (11, 12) and of placing a plurality of fins (16) above cylindrical or oval tubes of the first elements (2), and bringing the turned-back edges of the initially perpendicular fins above the tubes so as to form an easy-to-handle mechanically integral, mixed heat exchanger.

   A fifth stage consisting of positioning brazing solder rods at the base of the fins (16) and in contact with the first elements (2) forming the heat exchanger, and of placing the assembly in a brazing furnace advantageously operating in a neutral or reducing atmosphere.
2. Process for producing a mixed heat exchanger according to claim 1, characterised in that the brazing phase called "strong" is replaced by a brazing stage called "gentle" substantially consisting of a stage of tinning by dip soldering.
3. Production process according to either of claims 1 or 2, characterised in that the separated fins (16) are replaced by concertina-type fins.
4. Production process according to any of claims 1 to 3, characterised in that the half-shells (11, 12) are produced directly by stamping a metal sheet.
5. Production process according to any of claims 1 to 4, characterised in that the semi-cylindrical or semi-oval first elements (2) and the lateral half-feed-pipes (9, 10) are produced separately, in particular by stamping, and are joined together by a second operation consisting of a soldering or brazing phase.
6. Process for producing a heat exchanger according to any of claims 1 to 5, characterised in that the second elements (3), the cross-section of which is complex, in particular cross-shaped, are obtained from cylindrical tubes supplied as a coil, either by a cycle of shaping into a cross-shape then bending these tubes to shape a succession of pins forming a coil, or bending the cylindrical tube followed by a hydroforming stage.
7. Mixed heat exchanger (1) obtained by implementation according to any of claims 1 to 6 comprising a domestic heating circuit and a central heating circuit, these circuits being disposed one inside the other, comprising upper and lower half-shells (11, 12) each comprising a plurality of first elements (2) for the central heating circuit connected by their ends to feed-pipes (9, 10) and in which there coil a plurality of second elements (3) intended for the domestic heating circuit, said second elements (3) also discharging into said feed-pipes (9, 10), the heating water circulating in the defined sections between the external walls (4) of the tube forming the second elements (3) and the internal wall (5) of the first elements (2), characterised in that the lower and upper half-shells forming the first elements (2), which extend in the form of semi-cylindrical or semi-oval tubes, differ from one another principally in that one of them has lateral feed-pipes (9, 10) disposed on the external wall and orifices (13) allowing connection to various domestic heating and central heating circuits.
8. Mixed heat exchanger according to claim 7, characterised in that the second elements (3) are in the form of tubes with a complicated cross-section, such as, in particular, a cross, an X or a Y.
9. Mixed heat exchanger according to one of claims 7 or 8, characterised in that the complex profile of the second elements (3) guarantees that they have an exchange surface which is adequate for discharging all the thermal power provided by the burner (7) located in its lower part.
10. Mixed heat exchanger according to any of claims 7 to 9, characterised in that the central heating water is circulated in parallel in the feed-pipes (9, 10) so as to ensure an identical flow rate in each of the ducts (8), circulation of the domestic water being carried out in series and in succession in the plurality of second elements (3).

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