EP0775876A1 - 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 boiler heating bodies, in particular gas central heating. These boilers for domestic or industrial use must provide the user with both domestic hot water, the temperature of which must not exceed 65 ° C, and hot heating water which is circulated in a closed circuit within the central heating network of the house.

These heating bodies are commonly called mixed heating bodies because they have two separate water circuits, one for domestic water, the other for heating water, which are made integral so 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, or separate tubular circuits but flattened and joined one against each other. These heating bodies also have a bundle of fins responsible for transmitting to the tubular circuits, the heat flux conveyed by the fumes resulting from combustion within a burner placed in the 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 transporting a heat transfer fluid and containing at least one internal tube of smaller diameter transporting a second heat transfer fluid in heat exchange with the first, as well as means for ensuring a playless support of the inner tube against the outer tube.

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

At present, normative regulations impose temperature thresholds not to be exceeded, mainly on the domestic water heating circuit, this barrier being very difficult to observe with the type of mixed heating body known to the prior art.

In order to meet these standards, however, the designers of the mixed heating body solve this problem by incorporating clipping devices in the installation, which considerably complicate the structure of the exchanger. Another way to solve this problem is to impose on the heating water circuit recirculations in closed loop within the boiler during the drawing of sanitary water. This solution requires that there is a three-way valve and a connecting pipe on the heating circuit, which increases the cost of manufacture and maintenance.

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

According to another characteristic of the invention, it relates to a process for the preparation of this type of mixed heating body.

To this end, the invention provides a mixed heating body, comprising a domestic heating circuit and a central heating circuit, the latter being arranged one inside the other, characterized in that it comprises a plurality of first elements for the central heating circuit, connected at their ends to feeders and within which meanders a plurality of second elements with complex cross-section, intended for the domestic heating circuit, these second elements also opening into said feeders, mounting the second element in the first element further delimiting a plurality of generators of contact between said second elements and said first elements in order to produce thermal bridges at these generators, the heating water circulating in the sections delimited between the outer walls of the tube forming the second elements and the inner wall of the first elements elements.

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

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

The second element 3 constitutes the sanitary heating circuit, the sanitary water travels 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 of complex cross section 3 and the external tube 2; these contact generators 6 are made integral at the level of the first 2 and second elements 3 by means of known means such as in particular by a soldering or welding operation, in order to produce thermal bridges at the level of these generators.

Thanks to this arrangement between these two elements 2, 3, during sanitary operation, the heat flow travels in for the most part directly by conduction between sanitary water and the material in contact with the fumes, without excessively using the heating water circuit as heat transfer fluid.

According to another advantageous characteristic of the invention, the complex profile of the second element 3 guarantees that it has a sufficient exchange surface 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 wall temperature of the peripheral channels 8 - these being delimited by the first element and the connection zones of the second element - reaches a homogeneous temperature at their wet section very close to that of the first element, which makes it possible to reach, thanks to the high exchange coefficient and the large developed surface, the level of efficiency on the heating side required by the standards.

The industrialization and manufacturing constraints of a central heating boiler equipped with a mixed heating body 1 according to the invention require that the circulator or the accelerator mounted on the heating circuit be dimensioned as accurately as possible. The power of the latter is calculated so as to compensate for the hydraulic head losses of the entire circuit. With regard to the pressure drops, these are noted at the level of the piping and the radiators constituting the central heating installation, but also at the level of the boiler and very 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, the hydraulic diameter of which is optimized so as 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 elements 2 of the central heating circuit are connected to manifolds 9, 10 arranged on either side of the exchanger.

The circulation of the central heating water takes place in parallel within these manifolds, so as to guarantee an identical flow rate 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 manifold 9, 10. These various elements are produced as appropriate, in copper or stainless steel.

According to a first method of obtaining, these half-shells 11, 12 are produced directly by stamping a metal sheet, it being understood that there are two different dies respectively depending on the obtaining of an upper half-shell and of a lower half-shell.

According to a second embodiment, the various elements (the first semi-cylindrical or semi-oval elements 2, the side half-nurses 9, 10) are produced separately, in particular by stamping, and are made integral 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, the cross section of which is complex, in particular of cruciform profile, are obtained from cylindrical tubes delivered in a crown, by a cycle of either cross profiling then bending of the latter so as to conform a succession of pins forming a coil, or bending a cylindrical tube followed by a hydroforming step.

These processes for developing the second elements 3 make it possible to obtain a constant thickness all along the coil, which guarantees the absence of weak points at the level of 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 heating circuit of the domestic water and the heating circuit of the central heating water.

• 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 comprises 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 furnace, the exchangers are ready to supply the assembly line of the boilers without resorting to subsequent steps for the assembly of 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, essentially consisting of a tinning phase by soaking. The entire heating body 1 is soaked in a tin bath so as to have, on the one hand a tin film which protects the exchanger against corrosion and on the other hand, keeping the building material from the together, like copper, its work hardened, to avoid to the fins 16 to deform easily during handling.

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

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

Furthermore, the absence of added bends on each of the circuits, the changes of direction being obtained by bending the tubes of the different circuits, simplifies the method of manufacturing the exchanger, no more soldering or soldering, which avoids the risks of leaks.

Claims (11)

Mixed heating body (1), comprising a sanitary heating circuit and a central heating circuit, the latter being arranged one inside the other, characterized in that it comprises a plurality of first elements ( 2) for the central heating circuit, connected by their ends to manifolds (9, 10) and within which meanders a plurality of second elements (3) with complex cross section, intended for the sanitary heating circuit, these second elements ( 3) also opening into said nurses (9, 10), the mounting of the second element (3) in the first element (2) further delimiting a plurality of contact generators (6) between said second elements (3) and said first elements (2) in order to produce thermal bridges at the level of these generators, the heating water circulating in the sections delimited between the external walls (4) of the tube forming the second elements (3) and the internal wall first (5) of the first elements (2). Mixed heating element according to claim 1, characterized in that the first elements (2) are produced in the form of a tube of circular or oval cross section, into which are incorporated a plurality of second elements (3) having in the form of a complex cross-section tube, such as in particular cross, X, Y. Mixed heating element according to one of claims 1 or 2, characterized in that the complex profile of the second element (3) guarantees that it has a sufficient exchange surface to allow all of the thermal power delivered by the burner (7), positioned in its lower part. Mixed heating element according to any one of the preceding claims, characterized in that the central heating water circulation takes place in parallel within the manifolds (9, 10), so as to guarantee an identical flow in each of the channels (8), the circulation of the sanitary water being carried out in series and successively within the plurality of second elements (3). Heating element according to any one of the preceding claims, characterized in that the lower and upper half-shells (11, 12) differ from each other mainly in that one of them is arranged on the wall external side housings (9, 10), orifices (13) allowing connection to the various domestic and central heating circuits. Process for the preparation of a mixed heating body according to any one of the preceding claims, characterized in that it comprises: - A first step consisting in producing two half-shells (11, 12), each half-shell (11, 12) essentially comprising a plurality of first elements (2) extending in the form of semi-cylindrical or semi-tubular tubes ovals, preferably five to eight in number, arranged in parallel and connected at each of their ends to a manifold (9, 10), these various elements being produced as appropriate, from copper or stainless steel. - A second step consisting in the manufacture of the second elements (3) intended for the circulation of the water of the sanitary heating circuit. - A third step consisting in placing, within the half-shells (11, 12) essentially consisting of first elements (2) connected at their ends to nurses (9, 10) the coil of second elements (3). - A fourth step consisting in interposing between the joint planes (14) delimited by the lower and upper half-shells (11, 12), brazing rods (15) and 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 consisting in positioning at the base of the fins (16) and in contact with the first elements (2) forming the heating body, brazing rods and placing the assembly in a brazing furnace operating advantageously in a neutral atmosphere or reductive. Process for the preparation of a mixed heating element according to any one of Claims 1 to 5, characterized in that the so-called "strong" brazing step is replaced by a so-called "soft" brazing step, consisting essentially of a tinning phase by soaking. Production method according to either of Claims 6 and 7, characterized in that the separate fins (16) are replaced by fins in the form of an accordion. Production method according to any one of Claims 6 to 8, characterized in that the half-shells (11, 12) are produced directly by stamping a metal sheet. Production method according to any one of Claims 6 to 8, characterized in that the various elements (the first semi-cylindrical or semi-oval elements (2), the lateral half-nurses (9, 10) are produced separately , especially by stamping, and are joined together by a second operation consisting for example of a welding or brazing phase. Process for the production of a heating body according to any one of Claims 6 to 8, characterized in that the second elements (3), the cross section of which is complex, in particular of cruciform profile, are obtained from tubes cylindrical delivered in a crown, by a cycle either of cross profiling then bending of the latter so as to conform a succession of pins forming a serpentine, or of bending of cylindrical tube followed by a hydroforming step.

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