EP1026448B1 - Mixed boiler - Google Patents

Abstract

The gas heated water heater has a circulation pump with a gas burner (3) and a reheating duct (4) connected to the pump. The primary (15) of the direct heat exchanger (14) is fed with hot water from the recirculation duct. The auxiliary heat exchanger (E) has a reduced capacity envelope (10) and a direct counter current heat exchanger.

Description

The invention relates to domestic hot water generators and central heating water, using the combustion of a gas.

• un circuit d'eau fermé dit « de réchauffage sanitaire », comportant une pompe de circulation, une tubulure associée à un brûleur à gaz dans une chambre de combustion et formant avec ce brûleur un échangeur thermique principal, et le primaire d'un échangeur thermique auxiliaire,
• un circuit d'eau de puisage comprenant une arrivée d'eau froide, le secondaire de l'échangeur thermique auxiliaire et une sortie de puisage, l'échangeur thermique auxiliaire comprenant un ballon de capacité réduite et un échangeur direct à contre-courant monté en amont par rapport au ballon sur le circuit de puisage, et
• un circuit de chauffage central, monté en parallèle sur le tronçon du circuit de réchauffage sanitaire qui comprend la pompe et la tubulure, la connexion d'une extrémité dudit circuit de chauffage central avec ledit tronçon étant effectuée par une vanne à trois voies.

The invention relates more particularly to improvements made to devices of this type, called mixed, as described in FR-A-2742214 and EP-A-0778450, and comprising:

• a closed water circuit called "sanitary heating", comprising a circulation pump, a pipe associated with a gas burner in a combustion chamber and forming with this burner a main heat exchanger, and the primary of a heat exchanger auxiliary,
• a draw-off water circuit comprising a cold water inlet, the secondary of the auxiliary heat exchanger and a draw-off outlet, the auxiliary heat exchanger comprising a reduced capacity tank and a direct counter-current exchanger mounted in upstream with respect to the balloon on the drawing circuit, and
• a central heating circuit, mounted in parallel on the section of the domestic heating circuit which includes the pump and the pipe, the connection of one end of said central heating circuit with said section being effected by a three-way valve.

In FR-A-2742214 and EP-A-0778450, the balloon and the direct heat exchanger counter current of the auxiliary heat exchanger are in series, so that the direct exchanger is mounted downstream from the tank on the heating circuit domestic hot water from the main heat exchanger tubing passing through a primary loop of the auxiliary heat exchanger which is drowned in the balloon before reaching the primary of the direct exchanger against a current.

In addition, according to the aforementioned documents, the direct counter-current exchanger can be of a compact plate type, and can be embedded inside the ball.

But, in this case, the primary of the direct counter-current exchanger and with plates remains downstream, on the domestic heating circuit, of the loop supra, drowned in the balloon.

The problem underlying the invention is to perfect an apparatus hot water generator of the type presented above and known from the documents mentioned above, and in which the direct counter-current exchanger is a plate heat exchanger essentially arranged inside the tank, simplifying the design of the hydraulic assembly of such an apparatus for, on the one hand, facilitate the assembly and maintenance of this hydraulic assembly, and, on the other part, obtain that the functions of such a hydraulic assembly are fulfilled more economically.

To this end, the hot water generating device according to the invention, of the type presented above, is characterized in that the primary of the direct heat exchanger plates is supplied with hot water from the main exchanger tubing, that is to say without the intermediary of a loop embedded in the balloon and belonging in the primary of the auxiliary heat exchanger, and in that the primary of the direct plate heat exchanger comprises at least two lateral channels extreme, adjacent to two external and opposite side walls of the direct exchanger, at the lateral ends of all the demarcated channels between the substantially parallel plates of the direct exchanger, so that the water in the primary of the direct exchanger is in heat exchange relationship with the water from the drawing circuit, on the one hand, in the balloon and around the direct exchanger, by convection through said external walls of the direct exchanger which are in direct contact with the water in the drawing circuit in the tank, to perform the functions of reheating and maintaining temperature of the sanitary water in the tank, and, on the other hand, in at least one secondary channel of the direct exchanger, extending between said lateral channels, the secondary outlet of the direct exchanger leading directly in the tank, to ensure the direct heating function of the domestic cold water during drawing.

An advantage of the apparatus according to the invention is that excellent performance maintaining the temperature and reheating the domestic water balloon, when restarting after a complete stop of the device, can be obtained by the fact that the two extreme channels of the exchanger with plates, adjacent to the external and opposite lateral walls of this exchanger, belong to the primary of this exchanger and must be irrigated by hot water from the main exchanger tubing, possibly via the three-way valve, which ensures direct heat transfer through these two external walls of the exchanger at plates, by forced convection on the internal side of these walls, by circulation hot water from the domestic heating circuit when the circulation pump works, and by free convection on the side external to these walls, in the sanitary water contained in the tank.

This advantage is reinforced if, advantageously, the direct heat exchanger plates includes a set of plates provided with reliefs on their two lateral faces and which are joined and brazed to each other at least the along their periphery, and so as to delimit between the plates of the channels of the primary and secondary direct exchanger, each secondary channel extending between two primary channels and the two plates at the ends of the set of plates constituting the external side walls of the direct exchanger. To have a sufficient heat exchange surface at the level of the external walls, in order to obtain performance required in maintaining the temperature and heating of the water in the tank, under the circumstances mentioned above, it suffices then to give the plates of the direct exchanger of sufficient dimensions, in general slightly more larger than those of the plates used in the case of a direct heat exchanger plates outside the ball.

In three preferred embodiments, further use is made of one or more of the following.

In a first embodiment, the direct exchanger is supported in the flask at least by three rigid tubes sealingly crossing the wall of the tank, and a first tube of which connects the domestic heating circuit at the entry of the primary of the direct exchanger, in an end part of said direct exchanger in which the secondary outlet also opens of said direct exchanger, the second and third tubes connecting respectively the primary outlet and the secondary inlet of the direct exchanger, in the opposite end part of said direct exchanger, to the heating circuit and the draw-off water circuit respectively. This embodiment requires mounting the direct heat exchanger in the tank before closing the latter, so that the plate heat exchanger assembly is not easily removable or even non-removable.

In a second exemplary embodiment, with a balloon-exchanger assembly with removable plates, the direct plate exchanger is supported in the flask by at least two flanges each connected with tightness to one respectively of two opposite parts of the wall of the ball which are each pierced with an opening, each of the two flanges supporting one respectively of the two opposite end portions of said direct exchanger, a first flange also participating in the sealed connection between the circuit sanitary heating and the primary exchanger inlet of the direct exchanger, and putting in communication the secondary outlet of said direct exchanger with inside the balloon, and the second flange ensuring a tight connection between, on the one hand, the output of the primary of said direct exchanger and the heating circuit sanitary, and, on the other hand, the secondary entrance of said direct exchanger and the drawing water circuit.

Thus, the direct plate heat exchanger can be pre-mounted on two flanges at the ends of the exchanger, then the assembly can be introduced into the tank through one of the wall openings and fixed by the flanges on the wall of the ball.

However, to limit the size of one of the openings in the wall of the balloon, it is advantageous that the first flange substantially envelops the part corresponding end of the direct exchanger inside the tank, and includes a sealed connection tip at the inlet of the primary of said exchanger direct, said connecting end piece being engaged with sealing in a room support, supporting the first flange and attached with sealing around a opening in the wall of the balloon, this support piece having a nozzle tight connection to the domestic heating circuit.

In this second embodiment, it is advantageous that the second flange substantially envelops the corresponding end portion of the direct exchanger and is directly attached with sealing around a opening in the wall of the tank for the insertion of the direct exchanger in the balloon, and said second flange comprises two sealed connection ends, of which one ensures the connection between the primary outlet of the direct exchanger and the domestic heating circuit, and the other ensures the connection between the drawing water circuit and the secondary inlet of said direct exchanger.

In the first and second embodiments, to facilitate the connections hydraulic, primary and secondary inputs and outputs of the direct exchanger can lead into the same external side wall of the direct interchange, the entry of the primary and the exit of the secondary being provided in an end portion of said direct exchanger, while the inlet of the secondary and the outlet of the primary are provided in the end part opposite of said direct exchanger.

However, entry to primary and exit from secondary can be formed in an end portion and on an external side wall of the plate heat exchanger, while the primary outlet and the secondary inlet are provided in the opposite end part of the exchanger and on the other external side wall of the latter.

In the third preferred embodiment, the direct exchanger is supported in the balloon by at least one flange substantially enveloping a end part of the direct exchanger, and tightly connected to a part of the wall of the tank which has a direct heat exchanger insertion opening in the balloon, said flange comprising three sealed connection ends participating in the connections between the primary input and output and the input from the secondary of the direct exchanger to the heating circuits respectively sanitary and water supply, as well as a communication passage between the secondary exit from the direct heat exchanger and inside the tank.

The device thus has a removable direct balloon-exchanger assembly, the direct plate heat exchanger being pre-mounted on a flange at one end of the exchanger and the assembly can be introduced into the balloon by a insertion opening and fixed by the flange on the wall of the balloon, around the insertion opening.

To facilitate this mounting, the flange advantageously comprises at least two flange parts fixed to each other by enclosing said part between them end of the direct exchanger, a first flange part comprising two sealed connection ends respectively at the outlet of the primary and at the secondary heat exchanger entrance, and the second flange part comprising a sealed connection end piece at the inlet of the exchanger primary direct, and a communication end of the secondary output of the direct heat exchanger with the inside of the tank, the two ends of the first flange part and the end piece of the second flange part being engaged with sealing each in one respectively of three ends of a support piece, supporting said flange parts and attached with tightness to the wall of the tank around the insertion opening of the direct exchanger in the tank, the end pieces of the support piece ensuring the watertight connection with the domestic heating circuit for the two end pieces which receive the end pieces sealing connection of the flange parts to the inlet and outlet of the primary from the direct exchanger, and with the drawing-off water circuit for the receiving nozzle the sealed connection end piece of the second flange part at the entrance to the secondary from the direct heat exchanger.

In this way, the direct exchanger can be supported cantilever in the ball. However, advantageously the direct exchanger and the tank can be arranged substantially vertically, the first preferably at the bottom in the second, and so that the support piece constitutes a bottom of the balloon and includes means, such as a fourth tubular nozzle, for connection watertight with a partial domestic hot water collection tube high in the balloon, and with said drawing outlet.

This embodiment is advantageously combined with the use of a plate heat exchanger with primary and secondary inputs and outputs are provided in a single end portion of the direct exchanger, entering primary and leaving secondary advantageously leading in an external side wall of this direct exchanger, while the leaving primary and entering secondary advantageously lead into the opposite external side wall of this direct exchanger.

• la figure 1 représente schématiquement un appareil mixte de chauffage d'eau conforme à l'invention, ainsi que l'installation associée à cet appareil,
• les figures 2a et 2b sont des vues schématiques éclatées d'un premier exemple d'échangeur à plaques utilisable dans l'appareil de la figure 1, et représenté respectivement en mode de chauffage direct de l'eau sanitaire en cours de puisage et en mode de maintien en température et de réchauffage de l'eau sanitaire dans le ballon,
• la figure 2c est analogue à la figure 2a pour une variante de l'échangeur des figures 2a et 2b,
• la figure 3 représente schématiquement un premier ensemble ballon-échangeur à plaques comportant un échangeur selon les figures 2a à 2c, ou selon la figure 2c,
• les figures 4 et 5 représentent schématiquement un second exemple d'ensemble ballon-échangeur à plaques comportant un échangeur selon les figures 2a et 2b, respectivement au niveau de ses extrémités de droite et de gauche sur ces figures,
• les figures 6a et 6b sont des vues analogues aux figures 2a et 2b pour un exemple d'échangeur à plaques du type « à deux passes », dont les entrées et sorties du primaire et du secondaire sont ménagées dans une même extrémité de l'échangeur,
• les figures 7 et 8 sont des vues schématiques en partie en coupe et en partie en élévation latérale, respectivement d'un côté et de l'autre de l'extrémité de l'échangeur des figures 6a et 6b dans laquelle sont ménagées les entrées et sorties du primaire et du secondaire, à droite sur les figures 6a et 6b, et
• la figure 9 est une vue schématique d'un montage vertical de l'échangeur direct selon les figures 6a et 6b, et selon une variante du montage des figures 7 et 8.

Other advantages and characteristics of the invention will emerge from the description given below, without implied limitation, of embodiments described with reference to the appended drawings in which:

• FIG. 1 schematically represents a mixed water heating appliance according to the invention, as well as the installation associated with this appliance,
• FIGS. 2a and 2b are exploded schematic views of a first example of a plate heat exchanger usable in the device of FIG. 1, and shown respectively in direct heating mode of the domestic water being drawn and in mode maintaining the temperature and reheating the domestic water in the tank,
• FIG. 2c is similar to FIG. 2a for a variant of the exchanger of FIGS. 2a and 2b,
• FIG. 3 schematically represents a first balloon-plate exchanger assembly comprising an exchanger according to FIGS. 2a to 2c, or according to FIG. 2c,
• FIGS. 4 and 5 schematically represent a second example of a plate heat exchanger assembly comprising an exchanger according to FIGS. 2a and 2b, respectively at its right and left ends in these figures,
• FIGS. 6a and 6b are views similar to FIGS. 2a and 2b for an example of a plate exchanger of the “two pass” type, the inputs and outputs of the primary and secondary of which are provided in one and the same end of the exchanger ,
• FIGS. 7 and 8 are schematic views partly in section and partly in side elevation, respectively on one side and the other of the end of the exchanger of FIGS. 6a and 6b in which the inlets and primary and secondary education, on the right in Figures 6a and 6b, and
• FIG. 9 is a schematic view of a vertical mounting of the direct exchanger according to FIGS. 6a and 6b, and according to a variant of the mounting of FIGS. 7 and 8.

• un générateur de calories comportant, dans une chambre de combustion 2, un brûleur à gaz 3 et une tubulure 4 exposée aux flammes et/ou aux gaz chauds produits par le brûleur 3, la tubulure 4 étant destinée à être parcourue par de l'eau à chauffer et constituant avec le brûleur 3 un échangeur thermique principal,
• une pompe de circulation 5 raccordée à la tubulure 4,
• un tronçon de conduite 6 formant, avec la tubulure 4 et la pompe 5, un circuit fermé dit de réchauffage sanitaire, ce tronçon 6 constituant le primaire d'un échangeur thermique auxiliaire E, et
• un circuit de puisage comprenant, entre son arrivée d'eau froide 7 et une sortie d'eau chaude 8, un tronçon 9 appartenant au secondaire de l'échangeur thermique auxiliaire E.

In FIG. 1, the heating appliance considered comprises, inside a casing 1:

• a calorie generator comprising, in a combustion chamber 2, a gas burner 3 and a pipe 4 exposed to the flames and / or to the hot gases produced by the burner 3, the pipe 4 being intended to be traversed by water to be heated and constituting with the burner 3 a main heat exchanger,
• a circulation pump 5 connected to the pipe 4,
• a pipe section 6 forming, with the tubing 4 and the pump 5, a closed circuit called sanitary heating, this section 6 constituting the primary of an auxiliary heat exchanger E, and
• a drawing circuit comprising, between its cold water inlet 7 and a hot water outlet 8, a section 9 belonging to the secondary of the auxiliary heat exchanger E.

The invention relates essentially to this auxiliary heat exchanger E.

• d'une part, un ballon 10 destiné à contenir une réserve d'eau chaude sanitaire, de volume relativement réduit, immédiatement disponible pour le puisage, le volume intérieur du ballon 10, qui fait partie du tronçon 9 ou secondaire de l'échangeur E, étant raccordé en un point haut 13 dans le ballon 10 à la sortie d'eau chaude 8 par un tube rigide 11 pénétrant dans le ballon 10, et
• d'autre part, un échangeur thermique 14, qui est un échangeur direct à contre-courant et à plaques, pour présenter une forte capacité volumique d'échange thermique, comportant un primaire 15 et un secondaire 16, schématisés par deux portions de canalisation faisant partie respectivement des deux tronçons 6 et 9 ou primaire et secondaire de l'échangeur thermique auxiliaire E, et mises en contact thermique mutuel à contre-courant, cet échangeur à plaques 14 étant noyé dans le ballon 10.

The exchanger E includes:

• on the one hand, a tank 10 intended to contain a reserve of domestic hot water, of relatively reduced volume, immediately available for drawing, the interior volume of the tank 10, which is part of the section 9 or secondary of the exchanger E , being connected at a high point 13 in the tank 10 to the hot water outlet 8 by a rigid tube 11 entering the tank 10, and
• on the other hand, a heat exchanger 14, which is a direct counter-current and plate exchanger, for presenting a high volume heat exchange capacity, comprising a primary 15 and a secondary 16, shown diagrammatically by two portions of pipe making part respectively of the two sections 6 and 9 or primary and secondary of the auxiliary heat exchanger E, and brought into mutual thermal contact against the current, this plate exchanger 14 being embedded in the tank 10.

The tank 10 and the plate heat exchanger 14 are mounted as follows : the primary 15 of the plate heat exchanger 14, on the section 6 of the circuit DHW 4, 5, 6, is directly supplied by the tubing 4 of the main exchanger 2, through the three-way two-way valve 21 (the function of which is explained below), when the valve 21 is in the position shown in Figure 1. The primary of the heat exchanger auxiliary E is therefore essentially constituted by the primary 15 of the plate exchanger 14. Regarding the secondary 9 of the heat exchanger auxiliary E, it is made up in series, from upstream to downstream, i.e. the cold water inlet 7 to the hot water outlet 8, through the secondary 16 of the plate heat exchanger 14 and by the volume of water inside the tank 10 and around the plate exchanger 14, the secondary 16 outlet of the exchanger 14 emerging at a low point 12 directly in the balloon 10.

In other words, the plate exchanger 14 is mounted upstream by compared to balloon 10 on the drawing circuit 7, 9, 8.

Thus, when the burner 3 is lit, the hot water leaving the manifold 4 and driven by the pump 5 circulates in the sanitary heating circuit and passes through the primary 15 of the plate heat exchanger 14, then is recycled by the pump 5 to tubing 4. In the absence of domestic water drawing, domestic water present in the flask 10 is heated and maintained at temperature by heat exchange between the hot water circulating in the primary 15 of the exchanger 14 and the sanitary water in the tank 10, through the external walls of the exchanger 14, as more precisely described below with reference in Figures 2a, 2b, 6a and 6b. On the other hand, when drawing sanitary water, the water cold sanitary entering the drawing circuit by the inlet 7 cross first the secondary 16 of the exchanger 14 then the internal volume of the tank 10, so that it is heated by thermal transfer between the primary 15 and the secondary 16 of the plate heat exchanger 14, and this heated domestic water is mixture with that contained in the flask 10 and then flows through the tube 11 to outlet 8 for domestic hot water.

In FIG. 1, several bodies or assemblies outside the casing 1 and also connected to the circuits described above are also shown.

• d'une source d'eau froide sous pression 17, raccordée à l'arrivée d'eau froide 7,
• d'un robinet de puisage 18, raccordé à la sortie d'eau chaude 8, et
• d'un tronçon de circuit de chauffage central 19, comprenant des radiateurs 20 et monté en parallèle sur l'ensemble constitué par la tubulure 4 et la pompe 5, l'une des connexions du tronçon 19 avec cet ensemble 4, 5 étant réalisée au moyen de la vanne 21 à trois voies et deux positions, permettant de relier sélectivement l'ensemble 4, 5 soit au tronçon 6 de réchauffage sanitaire, soit au tronçon 19 de chauffage central.

It's about :

• a source of cold water under pressure 17, connected to the cold water inlet 7,
• a draw-off tap 18, connected to the hot water outlet 8, and
• a section of central heating circuit 19, comprising radiators 20 and mounted in parallel on the assembly constituted by the pipe 4 and the pump 5, one of the connections of the section 19 with this assembly 4, 5 being made at by means of the three-way, two-position valve 21, making it possible to selectively connect the assembly 4, 5 either to the section 6 of domestic heating, or to the section 19 of central heating.

FIG. 1 also shows a safety valve 22, connected to the hot water outlet 8, a flow meter 23, mounted on the water inlet cold 7, and a temperature probe 24 mounted in the tank 10.

Alternatively, the temperature probe 24 can be arranged in or at close to exit 12 of secondary 16 of the plate heat exchanger 14, and supported by the latter or by support and positioning parts of the exchanger 14 in the tank 10, and the probe 24 can be seconded by a another temperature sensor (not shown in Figure 1) in or near immediately from the entrance to secondary 16 of exchanger 14. The flow meter 23 and the probe (s) such as 24 are associated, as described in FR-A-2742214 and EP-A-0778450, has means for controlling the power calorific released by the boiler 2-3-4 with flow and temperature parameters detected, according to an advantageous mode of action described in the documents cited above, to which reference may be made for further details on this subject.

It suffices to recall that, when the probe 24 detects a temperature domestic water in the tank 10 below a threshold, the burner 3 is turned on operating at a maximum speed or at a reduced speed depending on whether the flow of water detected by the flow meter 23 is above or below a threshold of setpoint.

If there is no need for central heating (valve 21 in the position of Figure 1), and in the absence of domestic water drawing, the tap 18 is closed, the burner 3 is turned off and the pump 5 stopped, and the tank 10 contains a supply of sanitary water at a sufficient temperature, for example of the order of 60 °, to meet the needs for drawing domestic hot water.

From this initial state, if the temperature detected by the probe 24 becomes below a set point, the operation of pump 5 and the ignition of the burner 3 are controlled, at a reduced rate of the burner 3, by no draw, which circulates hot water in the heating circuit 4, 5, 6, and therefore in primary 15 of the plate heat exchanger 14, in heat exchange relation with the water in the balloon 10 through of the external walls of the plate heat exchanger 14, until the temperature of the water reserve in the tank 10 has again reached the desired value, which causes the pump 5 to stop and the burner 3 to go out.

If domestic hot water is drawn, the opening of tap 18 is of no consequence as long as the temperature of the water in the tank 10 remains above the set point. Hot water from tank 10 and drawn by the tube 11 is replaced by cold water coming from the inlet 7, so that the temperature of the water reserve in the tank 10 decreases gradually. When this temperature drops below the set point, the pump 5 is put into operation and the burner 3 lit, at a speed which depends on the drawing flow, detected by the flow meter 23, the power thermal released by the burner 3 being maximum or reduced depending on whether the threshold flow setpoint is exceeded or not by the drawing flow, the operation pump 5 and burner 3 as well as hot water circulation in the domestic heating circuit being maintained for the entire duration of the drawdown considered.

At the plate exchanger 14, during drawing, the water from drawing first crosses secondary 16 of exchanger 14 before reaching in the tank 10, and, due to the higher temperature of the heating water passing through the primary 15 of the exchanger 14, the drawing water is heated in secondary 16 of exchanger 14 before its introduction into the tank 10, which does not substantially cool the domestic hot water in reserve in this tank 10, and the temperature of the domestic hot water drawn can remain at a sufficient value during all the drawing, and even beyond a drawing time corresponding to a total volume distribution in reserve in the tank 10. The location of the secondary 16 of the exchanger 14 upstream of the tank 10 on the domestic water drawing circuit not only minimizes the introduction of cold water into the tank 10, which is harmful the temperature resistance of the water reserve contained in this tank 10, but also avoids the risks of overheating of the drawn water, since the sanitary water leaving secondary 16 of the plate exchanger 14 is mixed with the water in reserve in the tank 10 before reaching the tap 18.

The heating water circulating in the primary 15 of the exchanger 14 is never brought to a very high temperature, which avoids risks scaling of primary 15, because in the absence of drawing, the burner appearance 3 is moderate when in use, and calories from the main exchanger 2, 3, 4 are mainly distributed to sanitary water in the flask 10 by heat exchange with the heating water in the primary 15 of exchanger 14, through the external walls of this exchanger 14, while in drawing mode, the burner 3 has a moderate pace or maximum, the calories from the main heat exchanger 2, 3, 4 are mainly transmitted to sanitary water in the secondary of exchanger 14, by thermal transfer from the heating water in the primary 15 of this exchanger 14, a calorific contribution limited to the water in the remaining tank 10 provided through the external walls of the exchanger 14.

This very advantageous operating mode is obtained by using, in particular, plate exchangers 14 or 14 ', such as those schematically shown in Figures 2a to 2c and 6a and 6b.

The plate exchanger 14 of FIGS. 2a and 2b comprises an assembly of six plates 26a to 26f of the same rectangular external shape elongated at rounded corners made of a metal or alloy that is a good heat conductor, each plate having, on its two lateral faces, reliefs made up of ribs and V-shaped grooves alternately and in succession, so as to draw rafters. The six plates are placed next to each other so as to form five channels 27a to 27e, each of which is delimited between the two facing faces of two neighboring plates in the assembly. Channels 27a to 27e are easily visible in Figures 2a and 2b, showing the heat exchanger exploded perspective plates, with plates 26a to 26e slightly apart each other. The two longitudinal end portions 28 and 29 of each plate 26a to 26d are each pierced with an upper orifice 30 and a lower orifice 31, the two ends of the plate 26e not having each an upper orifice 30, and the plate 26f having no orifice. The plates of the assembly are joined and brazed to each other along their periphery to close the channels 27a to 27e vis-à-vis the outside of the exchanger, and so as to establish a watertight communication all the upper holes 30 between them and only with the lateral channels extremes 27a and 27e and the central channel 27c to form the primary of the plate heat exchanger 14, on the one hand, and, on the other hand, so as to connect from sealingly all the lower orifices 31 between them and with the two channels intermediate 27b and 27d, to form the secondary of the exchanger at plates 14, each secondary channel 27b or 27d thus extending between two channels 27a and 27c or 27c and 27e of the primary, including the lateral channels 27a and 27e, at the lateral ends of the exchanger 14, are directly adjacent each to one respectively of the plates 26a and 27f, at the ends side of the assembly, and constituting the external and opposite side walls of the exchanger 14.

Thus, the inputs and outputs of primary 15 and secondary 16 of the exchanger 14 are formed in the same external lateral wall 26a of the exchanger 14, the inlet of the primary 15 and the outlet of the corresponding secondary 16 respectively at the holes 30 and 31 in the end 28 of the plate 26a, and the output of primary 15 and the input of secondary 16 corresponding respectively to the holes 30 and 31 in the end 29 of this same plate 26a, since primary 15 and secondary 16 are against the tide, as indicated schematically by the arrows in Figure 2a.

This figure 2a represents the plate exchanger 14 in heating mode direct sanitary water circulating in secondary 16 (channels 27b and 27d) by the heating water coming from the tubing 4 and circulating in the primary 15 (channels 27a, 27c, 27e).

Figure 2b shows the plate heat exchanger 14 in holding mode in temperature and heating of domestic water in the tank 10 by circulation warming water from tubing 4 in primary 15 (channels 27a, 27c, 27e) in the absence of domestic water circulation in the secondary 16. There is a convective heat exchange through the walls lateral ends 26a and 26f towards the water in the tank 10. This heat exchange results from forced convection by circulation of heating water in the end channels 27a and 27e towards the side walls 26a and 26f, and a free convection, shown schematically by other arrows in Figure 2b, between these walls 26a and 26f and the water in the balloon 10, due to the direct contact of these external walls 26a and 26f with the water from the drawing circuit in the tank 10.

In the variant of Figure 2c, schematically showing another plate heat exchanger 14 in direct heating mode of the domestic water in the secondary 16 by heating water in primary 15, primary 15 always includes the two extreme lateral channels 27a and 27e as well as the central channel 27c, and the secondary still includes the intermediate channels 27b and 27d, but the upper 30 and lower 31 holes are distributed in the ends 28 and 29 of the plates 26a to 26f so that the entry of the primary 15 and the secondary 16 exit (communicating directly with the interior of the tank 10) correspond respectively to the holes 30 and 31 in the end 28 (on the left in FIG. 2c) of the end plate 26f (on the rear on the FIG. 2c), and no longer in the other end plate 26a (at the front in the figure), in which the exit of the primary 15 and the entry of the secondary 16, corresponding respectively to orifices 30 and 31 in the end 29 (of the right) of this end plate 26a.

A plate heat exchanger 14 according to Figures 2a and 2b, or according to the figure 2c, can be embedded in the balloon 10 as shown diagrammatically on Figure 3. The plate heat exchanger 14 is mounted in the tank 10 before closing of the latter, by welding or soldering on ends, internal to the balloon 10, of three rigid tubes 32, 33 and 34, thus rigidly connected to the exchanger 14 and passing through the walls of the tank 10 with a seal produced also by soldering. The tube 32 tightly connects the inlet primary 15 of exchanger 14, for example orifice 30 of end 28 of the plate 26a of the exchanger of Figures 2a and 2b, to a connecting pipe to the valve 21, while the tube 32 sealingly connects the outlet of the primary 15 of the exchanger 14, for example the orifice 30 of the end 29 of the plate 26a in Figures 2a and 2b, to a return line to the pump 5, and that the tube 34 tightly connects the inlet of the secondary 16 of the exchanger 14, for example the orifice 31 of the end 29 of the plate 26a on Figures 2a and 2b, to a pipe connected to the flow meter 23 and to the inlet of water 7.

The connections between the exchanger 14 and the tank 10 and the hydraulic connections between the outside of the tank 10 and the exchanger 14 inside the tank 10 are made rigidly by rigid tubes 32, 33 and 34 as well as by the solder or welds at their ends and at their crossing of the wall of the balloon 10. The disadvantage of this embodiment is that the balloon-exchanger assembly with plates obtained is difficult to dismantle.

To make such a removable assembly, a plate heat exchanger 14 such as that of FIGS. 2a and 2b or of FIG. 2c is advantageously mounted in the balloon 10 as shown in Figures 4 and 5.

In this example, the plate heat exchanger 14 is pre-mounted on two flanges, one of which 35 (Figure 4) surrounds the end part of the exchanger 14 constituted by the ends 29 of the adjoining plates 26a to 26f, and the other of which flange 36 (FIG. 5) encloses the opposite end part of the exchanger 14, constituted by the ends 28 of the adjoining plates 26a to 26f. The flange 35 has two integrated end pieces 37 and 38, with flat connection faces at their free end, on the opposite side to the exchanger 14, and which are each a nozzle tubular bent towards the inside of the flange 35 and towards the orifices 30 and 31 of the end 28 of the plate 26a of the exchanger 14, so that the end pieces tubular 37 and 38 are tightly connected respectively with the exit of primary 15 and entry of secondary 16 of exchanger 14, using seals 39 and 40 tablets between end caps 37 and 38 and the periphery plane of the corresponding holes 30 and 31.

Similarly, the flange 36 has a tubular end piece 41 also angled, tightly connected to the inlet of the primary 15 of the exchanger 14 by compression of a seal 42 between the tubular end piece 41 and the flat periphery of the orifice 30 of the end 28 of the plate 26a forming the primary entrance, while the flange 36 has, opposite the orifice 31 constituting the outlet of the secondary 16 at this same end of the exchanger 14, a short bent sleeve 43 opening towards the inside of the tank 10, when the exchanger 14 and its flanges 35 and 36 is disposed in the balloon 10 in the following manner. The sub-assembly consisting of the exchanger 14 and flanges 35 and 36 is introduced into the ball 10 in a direction of mounting going from right to left in Figures 4 and 5, through an orifice 44, formed in the wall of the tank 10 for the insertion of the exchanger 14. By this insertion, the flange 36 around the end of the exchanger 14 which is the first engaged in the balloon 10, is guided by its tubular endpiece 41 to the inside of a tubular end piece 46 of a support piece 47 fixed with sealing, through a seal 48, against the wall of the balloon 10, around a second opening in the part of the wall of the balloon 10 which is opposite to opening 44, this second opening thus being closed off by the support piece 47 around the end piece 41 of the flange 36, the seal between the tubular end piece 46 and the tubular end piece 41 fitted therein being provided by compression a seal 49 between the two end pieces.

After guiding, positioning and immobilizing the flange 36 and the corresponding end of the exchanger 14 in the support part 47, and therefore on the wall of the tank 10, the flange 35 at the other end of the exchanger 14 is also tightly fixed, by compression of a seal 50, on the wall of the tank 10, around the opening 44 for inserting the exchanger 14. It then suffices to make the watertight hydraulic connections of the end pieces 46 and 37 with the heating circuit, respectively on the side of the valve 21 and pump 5, and the sealed hydraulic connection of the nozzle 38 with the drawing-off water circuit, on the side of the flow meter 23 and of inlet 7, to obtain that the exchanger 14 is properly positioned and fixed on opposite parts of the wall of the balloon 10, with tight connections between the flanges 35 and 36 and the balloon 10 by compression of the seals 50, 49 and 48, and with sealed connections between the entry and exit of the primary 15 and the secondary 16 inlet of the exchanger 14 with the tubular ends 41, 37 and 38 of the flanges 36 and 35, by compression of the seals 42, 40 and 39, these same tubular end pieces allowing waterproof and external connections to the balloon 10 with the pipes of the heating and drawing circuits.

In addition, the flanges 35 and 36 and / or the support piece 47 can serve as support for temperature probes (not shown) detecting the temperature sanitary water respectively at the entry and exit of the secondary 16 of exchanger 14.

The flanges 35 and 36 as well as the support piece 47 can be molded of composite material, for example a matrix of synthetic resin and fibers glass or carbon reinforcement, which allows to directly obtain shapes bowl complexes, for receiving the corresponding ends of the exchanger 14, with bent tubular end pieces projecting towards inside the bowls, for tight connections to the two inlets and to an outlet from the exchanger 14. The molding of the flanges 35 and 36 and of the part support 47 allows, at low cost, arrangements for easy mounting of the temperature probe 24 of FIG. 1, avoiding adjustments specific on the wall of the balloon 10, such as a probe support brazed by example.

The plate heat exchanger 14 'of FIGS. 6a and 6b, which can be substituted for the plate exchanger 14 of Figures 1, 2a and 2b, and its variant according to the figure 2c, differs from the exchangers previously described and of the type known as "at one pass ", in that it is an exchanger of the so-called" two pass "type, the entries and exits of primary and secondary are arranged in the same end part of the exchanger 14 ', but open into the side walls opposite of the exchanger.

More specifically, in Figures 6a and 6b, the plate heat exchanger 14 ' includes a set of seven plates 26'a to 26'g, which are of the same shape and of the same structure as the plates 26a to 26f of the exchangers of FIGS. 2a to 2c, and joined and brazed together in the same way, so that delimit between them six channels 27'a to 27'f, including four 27'a, 27'c, 27'd and 27'f belong to primary 15 ', and the other two 27'b and 27'e belong to secondary 16 'of the exchanger 14', so that each of the two channels 27'b and 27 'e of secondary 16' extends between two channels 27 'and 27'c, or 27'd and 27'f, from primary 15 ', and that both channels simultaneously lateral ends 27'a and 27'f of all the channels delimited between the plates are directly adjacent each to one respectively of the two extreme side plates 26'a and 26'g which constitute the two side walls opposite the exchanger 14 '.

To this end, the upper 30 and lower 31 orifice openings in the end portions 28 and 29 of the plates 26'a to 26'g are distributed and connected selectively between them and at channels 27'a to 27'f so that the entry of the primary 15 'and secondary 16' exit correspond respectively to upper 30 and lower 31 holes in the end 29 (on the right in the figures 6a and 6b) of the end side plate 26'g, while the primary outlet 15 'and the secondary entrance 16' correspond to the respectively upper orifices 30 and lower 31 in the end 29 of the other side plate end 26'a.

In direct heating mode of domestic water in secondary 16 ' by the heating water in the primary 15 '(figure 6a), the heating water thus flows from right to left in Figure 6a in channels 27'f and 27'd, then from left to right in channels 27'c and 27'a, while that the sanitary water flows against the current from right to left in the channel 27'b then from left to right in channel 27'e.

In temperature maintenance and domestic water heating mode in the balloon 10 (FIG. 6b), the circulation in the primary 15 ′ remains the same, but a heat transfer takes place by convection between the heating water of the primary circuit 15 'and the sanitary water in the tank 10, through external side walls of the exchanger 14 'formed by the plates 26'a and 26'g, as shown by arrows.

Of course, the number of plates of the exchanger 14 '(FIGS. 6a and 6b) or 14 (Figures 2a to 2c) can be greater than 7, respectively 6, if necessary, insofar as the end channels are supplied by the heating water (primary circuit).

Such an exchanger 14 ′ can be mounted in the tank, for example by overhang, being tightly fixed to the wall of the balloon 10 and connected tightly to the heating and drawing circuits by the part end of the exchanger 14 'which presents the inputs and outputs of the primary 15 'and secondary 16' of this exchanger 14 ', for example using a flange, pre-mounted on this end of the exchanger, and which is supported so sealed by the wall of the tank and itself connected with sealing, of a share, at the entrances and exits of primary 15 'and secondary 16', with the exception of the secondary 16 ′ outlet which opens at a low point in the balloon 10, and, on the other hand, to the heating and drawing circuits.

Such an arrangement is shown schematically in Figures 7 and 8 showing the same end of the exchanger 14 'seen partly in section and in part in side elevation on two opposite sides. The end of the exchanger 14 'showing the inputs and. primary 15 'and secondary 16' outputs from this exchanger 14 'is enclosed in a flange 51, constituted by the assembly of two asymmetrical flange halves 52 and 53, rigidly fixed one against the other the other by screws or rivets 54, or by any other suitable fixing means such as that bonding and welding, and one of which 52 mainly covers the part end 29 of the outer side plate 26'a of the exchanger 14 ', while the other half flange 53 essentially covers the end 29 of the other plate lateral side 26'g of the exchanger 14 '.

The half flange 52, in the form of a bowl for substantially enveloping the half of the periphery of the corresponding end of the exchanger 14 ', comprises also two bent tubular ends 55 and 56, which ensure the connection waterproof by compression of a seal respectively 57 and 58 against the planar periphery of the corresponding orifices 30 and 31 respectively, in this end 29 of the plate 26'a, respectively at the outlet of the primary and at the entrance of the secondary of the exchanger 14 '. Likewise, the other half flange 53, also bowl-shaped to wrap half of the periphery of this end of the exchanger 14 ′, has a tubular end piece angled 59 connected with sealing to the inlet of the primary 15 'of the exchanger 14 'by compression of a seal 60 on the flat periphery of the orifice 30 in the end 29 of the other external side plate 26'g of the exchanger 14 ', this same half-flange 53 further comprising a small sleeve angled 61 connecting the secondary outlet 16 ', at the level of the lower orifice 31 in this same end 29 of the plate 26'g, inside the balloon 10.

The flange 51 is itself engaged and supported in a support piece 62, also in the general shape of a bowl, and which is fixed by its periphery to the wall of the balloon 10, around an opening 63 formed in this wall for the insertion of the exchanger 14 ', the connection between the support part 62 and the wall of the balloon 10 being sealed by compression of a seal 64 surrounding the opening 63. The support piece 62 also has three end caps tubular 65, 66 and 67, in which are fitted with sealing respectively the tubular ends 55 and 56 of the half-flange 52 and the end piece tubular 59 of the half-flange 53, the seal being ensured by compression of seals 68, 69 and 70, each compressed between two corresponding end caps fitted into each other. Thus, the support piece 62 ensures immobilization of the exchanger 14 ′ and of its flange 51 with respect to the balloon 10, by the fixing of the support piece 62 on the wall of the tank 10, as well as the connections sealed to the heating and drawing circuits by the nozzles 65, 66 and 67, tightly connected to the pipeline respectively of the heating circuit leading to pump 5 (Figure 1), to the pipe of the drawing circuit connected to the flow meter 23 and to the cold water inlet 7, and to the pipe of the heating circuit connected to valve 21.

In this example, the half-flanges 52 and 53 as well as the support part 62 can also be molded each in a single piece of material composite, like flanges 35 and 36 and support piece 47 of the example of Figures 4 and 5. As for the support part 47, the molding of the part support 62 allows low-cost arrangements for easy mounting of the temperature sensor 24 (see FIG. 1) without specific arrangement on the inner wall of the tank 10.

To avoid excessive cantilever mounting of the exchanger 14 ', a wedge can be placed in the balloon 10 to support the end of the exchanger 14 ′ which is opposite to that enclosed in the flange 51.

But another variant of mounting the exchanger 14 'using the half-flanges 52 and 53 and a support piece 62 ', variant of the support piece 62 Figures 7 and 8 avoids any overhang, as shown in the Figure 9. This arrangement assumes the preferred use of a balloon 10 of form substantially cylindrical and elongated, of smaller diameter than in previous examples, but longer to keep the volume of the reserve hot sanitary water, with a substantially vertical axis, and the exchanger 14 ' is held substantially vertically in the balloon 10. The support piece 62 ', which cooperates in the same way as the support piece 62 with the half-flanges 52 and 53 and with the wall of the balloon 10 and therefore has substantially the same structure, suitable for this purpose, as the support piece 62, constitutes one bottoms of the balloon 10, for example its bottom bottom, closed sealed on the wall of the tank 10 thanks to the seal 64. This arrangement allows a optimal functioning of the device, thanks to the exchanger 14 'at the bottom in the balloon 10. The support piece 62 'is different from the support piece 62 in what it presents arrangements allowing, in the balloon 10, the connection easy from tube 11 to draw hot sanitary water at the top in the tank 10, and, outside the tank 10, the connection sealed to the hot water outlet pipe 8 (see figure 1). To this end, in addition to three tubular ends such as 65, 67 and 66 of the support piece 62, for the watertight connections respectively to the outlet and inlet of the primary 15 'and at the entrance to the secondary 16 'of the exchanger 14', the support part 62 'may include a fourth tubular end piece 71, in which the tube 11 is fitted with sealing, and connecting itself with sealing to the pipe from the hot water outlet 8 at its end external to the tank 10.

This example presents the advantages of a simplicity of realization of the tank 10 and a simplification of the assembly operations of the exchanger 14 ' in balloon 10 and checking this assembly.

Claims (11)

1. Apparatus to produce domestic hot water and central heating water using the combustion of a gas and comprising a closed water circuit called a "domestic heating" circuit consisting of a circulating pump (5), a pipe manifold system (4) in conjunction with a gas burner (3) in a combustion chamber (2) and forming together with this burner (3) a main heat exchanger, and the primary (6) of an auxiliary heat exchanger (E); and a water offtake circuit comprising a cold water inlet (7), the secondary (9) of the auxiliary heat exchanger (E) and an offtake outlet (8), the auxiliary heat exchanger (E) comprising a vessel (10) with a limited capacity and a direct counter-current exchanger (14, 14') which is a plate exchanger arranged essentially inside the vessel (10) and arranged in such a way that the direct exchanger (14, 14') is installed upstream relative to the vessel (10) in the offtake circuit (9), and a central heating circuit (19) installed in parallel on the section of the domestic heating circuit which comprises the pump (5) and the pipe manifold system (4), the connection between one end of the said central heating circuit (19) and the said section (4, 5) being made by a three-way valve (21), characterized in that the primary (15, 15') of the direct exchanger (14, 14') is supplied with hot water from the said pipe manifold system (4) and comprises at least two lateral end channels (27a, 27e; 27'a, 27'f) adjacent to two external and opposite side walls (26a, 26f; 26'a, 26'g) of the direct exchanger (14, 14') at the lateral ends of the totality of the channels (27a-27c; 27'a-27'f) demarcated between the approximately parallel plates (26a-26f; 26'a-26'g) of the direct exchanger (14, 14') in such a way that the water in the primary (15, 15') of the direct exchanger (14, 14') is in a heat exchange relationship with the water of the offtake circuit, firstly in the vessel (10) and around the direct exchanger (14, 14') by convection across the said external walls (26a, 26f; 26'a, 26'g) of the direct exchanger (14, 14') that are in direct contact with the water of the offtake circuit in the vessel (10), and secondly in at least one channel (27b, 27d; 27'b, 27'e) of the secondary (16, 16') of the direct exchanger (14) extending between the said lateral channels (27a, 27c; 27'a, 27'f), the outlet (12) of the secondary (16, 16') of the direct exchanger (14, 14') opening directly into the vessel (10).
2. Apparatus according to Claim 1, characterized in that the direct exchanger (14) is supported in the vessel (10) at least by three rigid tubes (32, 33, 34) passing in a leak-tight manner through the wall of the vessel (10), of which a first tube (32) connects the domestic heating circuit to the inlet of the primary (15) of the direct exchanger (14) at an end portion of the said direct exchanger (14) into which the outlet (12) of the secondary (16) of the said direct exchanger (14) also opens, and of which the second and third tubes (33, 34) connect respectively the outlet of the primary (15) and the inlet of the secondary (16) of the direct exchanger (14) in the portion of the opposite end of the said direct exchanger (14) to the domestic heating circuit and to the water offtake circuit respectively.
3. Apparatus according to Claim 1, characterized in that the direct exchanger (14) is supported in the vessel (10) by at least two flanges (35, 36) each attached in a leak-tight manner (50, 48) respectively to one of two opposite parts of the wall of the vessel (10), each of which is perforated by an aperture (44), and each of the two flanges (35, 36) supporting respectively one of two parts (29, 28) of opposite ends of the said direct exchanger (14), the first flange (36) also taking part in the leak-tight attachment between the domestic heating circuit and the inlet of the primary (15) of the direct exchanger (14) and establishing a connection between the outlet of the secondary (16) of the said direct exchanger (14) and the inside of the vessel (10), and the second flange (35) ensuring a leak-tight connection firstly between the outlet of the primary (15) of the said direct exchanger (14) and the domestic heating circuit and secondly between the inlet of the secondary (16) of the said direct exchanger (14) and the water offtake circuit.
4. Apparatus according to Claim 3, characterized in that the first flange (36) more or less surrounds the corresponding end portion (28) of the direct exchanger (14) inside the vessel (10) and comprises a jointing piece (41) of a leak-tight attachment (42) at the inlet of the primary (15) of the said direct exchanger (14), the said attachment jointing piece (41) being in leak-tight engagement (49) in a supporting piece (47) supporting the first flange (36) and brought into leak-tight contact (48) around an opening in the wall of the vessel (10) and providing a jointing piece (46) for a leak-tight attachment to the domestic heating circuit.
5. Apparatus according to one of the Claims 3 and 4, characterized in that the second flange (35) more or less surrounds the corresponding end portion (29) of the direct exchanger (14) and is directly brought in to contact (50) in a leak-tight manner around an opening (44) in the wall of the vessel (10) in order to insert the direct exchanger (14) into the vessel (10), and in that the said second flange (35) comprises two jointing pieces (37, 38) forming a leak-tight connection, of which one (37) ensures the connection between the outlet of the primary (15) of the said direct exchanger (14) and the domestic heating circuit, and the other (38) ensures the connection between the water offtake circuit and the inlet of the secondary (16) of the said direct exchanger (14).
6. Apparatus according to any of the Claims 1 to 5, characterized in that the inlets and outlets of the primary (15) and of the secondary (16) of the direct exchanger (14) emerge in a same external side wall (26a) of the said direct exchanger (14), the inlet of the primary (15) and the outlet of the secondary (16) being arranged in one end portion (28) of the said direct exchanger (14), while the inlet of the secondary (16) and the outlet of the primary (15) are arranged in the opposite end portion (29) of the said direct exchanger (14).
7. Apparatus according to Claim 1, characterized in that the direct exchanger (14') is supported in the vessel (10) by at least one flange (51) more or less surrounding one end portion (29) of the direct exchanger (14') and attached in a leak-tight manner (64) to a part of the vessel wall (10) which provides an opening (63) to insert the direct exchanger (14') into the vessel (10), the said flange (51) comprising three jointing pieces (55, 56, 59) for leak-tight attachment taking part in the connections of the inlet and outlet of the primary (15') and of the inlet of the secondary (16') of the direct exchanger (14') to the respective circuits for domestic heating and for offtake water, as well as a connecting passage (61) between the outlet of the secondary (16') of the direct exchanger (14') and the interior of the vessel (10).
8. Apparatus according to Claim 7, characterized in that the said flange (51) comprises at least two flange portions (52, 53) attached to one another so as to enclose between them the said end portion (29) of the direct exchanger (14'), a first portion of the flange (52) comprising two jointing pieces (55, 56) to make a leak-tight joint (57, 58) respectively to the outlet of the primary (15') and to the inlet of the secondary (16') of the direct exchanger (14'), and the second portion of the flange (53) comprising a jointing piece (59) for a leak-tight connection to the inlet of the primary (15') of the direct exchanger (14') and a jointing piece (61) for a communication between the outlet of the secondary (16') of the direct exchanger (14') and the interior of the vessel (10), the two jointing pieces (55, 56) of the first portion of the flange (52) and the jointing piece (59) of the second portion of the flange (53) each being engaged in a leak-tight manner into respectively one of three jointing pieces (65, 66, 67) of a support piece (62, 62') supporting the said portions of the flange (52, 53) and brought into contact in a leak-tight manner (64) onto the wall of the vessel (10) around the opening (63) for the insertion of the direct exchanger (14') into the vessel (10), the jointing pieces (65, 66, 67) of the support piece (62, 62') ensuring the leak-tight connection to the domestic heating circuit for the two jointing pieces (65, 67) that receive the jointing pieces (55, 59) for leak-tight connection of the portions of the flange (52, 53) to the inlet and outlet of the primary (15') of the direct exchanger (14'), and to the offtake water circuit for the jointing piece (66) that receives the jointing piece (56) for leak-tight connection between the second portion of the flange (52) and the inlet of the secondary (16') of the direct exchanger (14').
9. Apparatus according to Claim 8, characterized in that the direct exchanger (14') and the vessel (10) are arranged approximately vertically, preferably the former being arranged in the lower portion of the latter and in such a way that the support piece (62') forms a base of the vessel (10) and comprises means, such as a fourth tubular jointing piece (71) for leak-tight connection to a tube (11) for withdrawing domestic hot water at the upper part of the vessel (10) and to the said offtake outlet (8).
10. Apparatus according to any of the Claims 7 to 9, characterized in that the inlets and outlets of the primary (15') and of the secondary (16') of the direct exchanger (14') are arranged in a same part of the end (29) of the said direct exchanger (14'), the inlet of the primary (15') and the outlet of the secondary (16') emerging in an external side wall (26'g) of the said direct exchanger (14'), while the outlet of the primary (15') and the inlet of the secondary (16') emerge in the opposite external side wall (26'a) of the said direct exchanger (14').
11. Apparatus according to any of the Claims 1 to 10, characterized in that the direct plate exchanger (14, 14') comprises a set of plates (26a-26f; 26'a-26'g) equipped with embossings on their two side faces, and placed side by side and welded to one another at least along their periphery in such a way as to demarcate, between the plates, channels (27a-27e; 27'a-27'f) of the primary (15, 15') and of the secondary (16, 16') of the direct exchanger (14, 14'), each channel (27b, 27d; 27'b, 27'e) of the secondary (16, 16') extending between two channels (27a, 27c, 27e; 27'a, 27'c, 27'd, 27'f) of the primary (15, 15'), and the two plates (26a, 26f; 26'a, 26'g) at the ends of the set of plates constituting the external side walls of the direct exchanger (14, 14').

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