EP2439459B1 - Parallelepipedal water heater with pierced longitudinal partitions - Google Patents

Description

The present invention relates to a water heater and in particular to such a device, the tank receiving the water to be heated has a generally parallelepiped shape and advantageously parallelepiped rectangle.

The water heaters on the market are currently circular in section and their size is a penalizing factor during their installation: they occupy a large space, are unattractive, generate a very high dead volume.

Document is known GB-A-731 769 a water heater of substantially rectangular section and flattened which is understood that one advantage is to facilitate the implementation relative to cylindrical water heater. However, this technique is currently not available on the market, which can be explained by the inability of water heaters of known rectangular section to ensure, on the one hand a satisfactory resistance and on the other hand, a performance suitable energy.

Mechanical strength is a fundamental point of reliability and safety of the water heater. The heated water induces high pressures inside the tank and it is easily understood that the circular section provides a better distribution of the forces applied to the tank, in particular by avoiding stress concentrations in corners.

At the same time, it is necessary to ensure the fastest possible heating of the water and a fine regulation of the temperature without affecting the energy consumption.

The water heater proposed by GB-A-731 769 appears unable to meet the requirements indicated above.

The document WO 00/43716 A1 discloses a water heater according to the preamble of the present claim 1.

The present invention aims to overcome all or part of the disadvantages of known techniques on substantially parallelepiped water heaters. For this purpose, the device of the invention according to claim 1 associates with a tank resistive heating means placed in a particular way in a conduit among a series of ducts, as well as partitions with holes between the ducts. The holes are also of selected format.

While the problem of mechanical strength of the tanks would normally lead to stiffening their components, the invention departs from this prejudice by using perforated partitions to separate the ducts. The surprising result is an increased resistance, particularly in fatigue, which can be explained by a better capacity of elastic deformation and therefore reversible response to the stress variations imposed by the pressure variations in the tank. The holes act as deformable elements of absorption of the stresses. At the same time, despite the perforated partitions according to the invention, the experiment shows with surprise that the convection remains oriented along the longitudinal direction of the ducts, that is to say the vertical in the usual operating conditions, in the same way that with solid partitions. This is advantageous for providing a stratification effect of the water, with a preferential placement of the heated water towards the top of the device where the collection of the heated water takes place.

Other objects and advantages will emerge from the description which follows and which shows, with reference to the drawings, a preferred but non-limiting embodiment of the invention.

Previously, it is stated that the present invention relates to a water heater according to claim 1.

The total area of the holes is between 10% and 40%, even more precisely of the order of 15% of the area of the partition.

Thus dimensioned the holes operate in a combined way an improvement of the mechanical strength and promotes the longitudinal flow of the water flow.

In the case of substantially flat partitions, the surface of the partition corresponds to the area of the partition. The percentage of holes refers to the proportion of holes relative to the area of the partition.

In the case of non-planar partitions, the surface ratio is preferably based on the surface of the orthogonal projection of the partition in a plane along the width of the partitions.

Advantageously, the width of the holes in a direction perpendicular to the longitudinal direction being such that the width occupied by the holes is less than half the width of the partition.

According to another possibility, each partition has a row of aligned and symmetrical holes along an axis located in the middle of the width of the partition. This symmetrical centered formation is particularly positive on the mechanical resistance.

The holes are regularly spaced in the longitudinal direction, the space between the holes being substantially equivalent to half the width of the partitions. They are also of advantageously identical shape and can be of circular or elliptical section.

One option is that the resistive heating means are located in a lower part of the tank at which, for example, the partitions defining the central duct do not comprise a hole. This configuration promotes longitudinal convection.

It is advantageous if the length of the rows of holes is greater than or equal to two-thirds of the length of the partitions. In combination with the previous option, this forms two zones along the tank: a first zone with the heating of the stream and a second zone with the parts of perforated partitions.

It can be ensured that the partitions cover the entire length of the tank, in particular to avoid the stress concentrations and therefore the weak areas at the lateral ends of the partitions. The holes of the partitions avoid having high and low ends of the partitions not connected to the periphery of the tank while ensuring the circulation of the water.

The partitions are advantageously connected at their upper and lower ends to the tank.

The tank advantageously comprises two flanges arranged at the longitudinal ends of the ducts so as to close the volume of the tank.

The two flanges can be configured to cooperate with the longitudinal ends of the partitions.

Preferably, the spacing between the resistive heating means and the partitions, and possibly also or alternatively the inner walls of the vessel which surround it, does not exceed 17% of the width of the tank 1. As a for example, of the order of 10% to 15% or about 50 to 55 mm wide for a tank width 1 of 500 mm. It has been found that this spacing makes it possible to optimize the convective effect of longitudinal direction. In particular, the proximity of the heating means with respect to the parietal boundaries of the ducts provides a strong convection around the resistive means. This convective intensity has the effect of strongly stirring the water around the (or) resistance (s) and limits bubbling problems that may scale the (or) resistance (s). This result is all the more surprising as one would think that the narrowness of the duct receiving the heating means would generate too much local heating.

According to another possibility, the ducts are of rectangular section.

To further improve the mechanical strength, the tank may also comprise two lateral profiles and at least one set of intermediate profiles connecting the space between the two lateral profiles, the profiles being assembled in pairs and with a longitudinal edge of a partition by a weld bead formed on the face of the profiles opposite to the inside of the tank. Preferably, the number of sets of intermediate profiles is odd. No welding element is thus made on the side of the tank receiving the water. In addition, the weld beads effectively take up the forces transmitted by the partitions.

Advantageously, the two flanges are configured additionally or alternatively to cooperate with the ends of the profiles. For example, the two flanges have a continuous groove at their periphery for receiving the ends of the profiles.

According to one possibility, each partition has a plurality of holes distributed over the width of the partition and over at least two thirds of the length of the partition, preferably over its entire length.

The total area of the holes is between 10 to 40%, more precisely of the order of 15% of the area of the partition.

• l'aire de la section longitudinale de la cuve est au moins 10 fois plus grande que celle de la section de la cuve suivant un plan perpendiculaire à la direction longitudinale.
• Il comprend selon une possibilité:
  • une série de cinq conduits,
  • une embouchure de raccordement fluidique configurée pour admettre de l'eau non chauffée dans la cuve et débouchant dans la partie basse suivant la direction longitudinale d'un conduit périphérique situé à une extrémité latérale de la série de conduits,
  • une embouchure de raccordement fluidique configurée pour évacuer de l'eau chauffée hors de la cuve et débouchant dans la partie haute suivant la direction longitudinale d'un conduit intermédiaire situé entre le conduit central et le conduit périphérique situé à une extrémité latérale de la série de conduits ne comportant pas l'embouchure de raccordement fluidique configurée pour admettre de l'eau non chauffée.

Other optional features of the invention that can be used in combination or alternatively are indicated below:

• the area of the longitudinal section of the tank is at least 10 times larger than that of the section of the tank in a plane perpendicular to the longitudinal direction.
• It understands according to a possibility:
  • a series of five ducts,
  • a fluidic connection mouth configured to admit unheated water into the vessel and opening into the bottom portion in the longitudinal direction of a peripheral conduit at a lateral end of the series of conduits,
  • a fluidic connection mouth configured to discharge heated water out of the tank and opening in the upper part in the longitudinal direction of an intermediate duct located between the central duct and the peripheral duct located at a lateral end of the series of ducts. conduits not having the fluidic connection mouth configured to admit unheated water.

• La figure 1 est une vue de l'arrière de la cuve selon un premier mode de réalisation de l'invention.
• La figure 2 est une vue d'un côté latéral de la cuve.
• La figure 3 est une vue de la cuve selon la coupe E-E de la figure 2.
• La figure 4 est une vue de la cuve selon la coupe F-F de la figure 2.
• La figure 5 est une vue de la cuve selon la coupe D-D de la figure 4.
• La figure 6 est une vue éclatée de la cuve selon l'invention.
• La figure 7 est une simulation de la déformation de la cuve selon l'invention sous pression de 7 bars.
• La figure 8 est une représentation de la stratification des températures dans une cuve selon l'invention.
• La figure 9 est une vue en coupe transversale de la cuve selon un deuxième mode de réalisation.

The accompanying drawings are given by way of example and are not limiting of the invention. They represent only one embodiment of the invention and will make it easy to understand.

• The figure 1 is a view from the rear of the tank according to a first embodiment of the invention.
• The figure 2 is a view of a lateral side of the tank.
• The figure 3 is a view of the tank according to section EE of the figure 2 .
• The figure 4 is a view of the tank according to the FF section of the figure 2 .
• The figure 5 is a view of the tank according to section DD of the figure 4 .
• The figure 6 is an exploded view of the tank according to the invention.
• The figure 7 is a simulation of the deformation of the tank according to the invention under pressure of 7 bar.
• The figure 8 is a representation of the stratification of temperatures in a tank according to the invention.
• The figure 9 is a cross-sectional view of the vessel according to a second embodiment.

The present invention relates to a water heater comprising a tank 1 receiving water to be heated. The tank 1 and advantageously also the water heater, have a parallelepipedic shape and advantageously parallelepiped rectangle. The edges of the tank and / or the outer shell of the water heater may be rounded.

The tank 1 comprises a first main wall 2, a second main wall 3, two side walls 4 and 5, a bottom wall 6 and an upper wall 7.

Preferably, the vessel 1 is used so that its largest dimension, the length, is oriented vertically.

The tank 1 is fixed to a wall such as a wall by fastening means 21 such as hooks. As a preference, the tank 1 is fixed with its second main wall 3 facing the wall.

The tank 1 according to the invention is divided into a plurality of preferably odd numbered conduits. The ducts are parallel to each other and juxtaposed in the direction perpendicular to the longitudinal axis of the tank, the width of the tank 1. The ducts extend in the longitudinal direction of the vessel 1. In general , all or part of the constituents of the tank, may be steel, from profiles or sheets of steel, especially stainless.

The ducts 8, 9, 10 are separated by partitions 11a, b, c, d. One of the ducts 8 receives resistive heating means 15. Resistive heating means 15 means at least one resistor intended to heat the water of the tank 1. The resistive heating means 15 are placed in at least one duct 8 and are oriented in the longitudinal direction of the vessel 1.

As a preference, the resistive heating means 15 are placed in a central duct 8, advantageously in a lower portion of the vessel 1.

The resistive heating means 15 are arranged in the center of the central duct 8 so as to generate a homogeneous heating in said duct 8.

The partitions 11 separating the ducts 8, 9, 10 are preferably flat plies such as steel sheets oriented in the longitudinal direction of the vessel 1 and transversely depending on the thickness of the vessel 1.

To improve the mechanical strength of the tank, it may be provided to lengthen the free length of the partitions 11 acting as a spring between the first main wall 2 and the second main wall 3 of the tank 1. For this purpose, several forms partitions 11 can be envisaged. For example, partitions 11 of sinusoidal section or slot or omega may be used. That is to say non-planar section plies identical in the longitudinal direction. By an omega shape is meant a U with two lateral wings 27 extending the sides of the U horizontally outwards. By way of preference, the sides 26 of the U have a minimum length of 12 mm. Advantageously, the base 25 of the U and the two wings 27 are of length substantially equal to one third of the width of the partition 11. The partitions 11 are arranged substantially parallel to each other. Advantageously, the partitions 11 of the central duct 8 are disposed on either side of the resistive heating means 15 of the partition 11 so as to be symmetrical with respect to a longitudinal plane 28 passing through the middle of the central duct 8 or by the resistive heating means 15 and oriented transversely according to the thickness of the vessel 1. This plane separates the vessel 1 into two half-tanks. This shape improves the fatigue resistance of the tank 1 and the heating performance.

According to an advantageous characteristic of the invention, the partitions 11 comprise holes 20. The holes 20 are arranged on at least two thirds of the length of the partition 11 and advantageously on two-thirds of the length of the partition which are not located opposite the resistive heating means 15. To improve the mechanical strength, the holes 20 are preferably present over the entire length of the partition 11.

The presence of the holes 20 on the partitions 11 allows fluid communication between the ducts 8, 9 without having the need to provide a fluid flow at one or both ends of the ducts by the upper and / or lower ends distant from the periphery of the tank 1.

The presence of this fluid flow by the absence of connection to the ends of the ducts leads to stress concentrations in the upper and lower portions of the tank 1 which are undesirable.

The holes 20 also have the role of improving the resistance of the tank 1 in particular in fatigue. As we can see in figure 7 the holes 20 are zones of elastic deformation. The lightest areas are those where the stresses are highest.

When the holes are only two-thirds of the length of the partitions 11, they are preferably placed on the upper part of the partitions 11 above the resistive heating means 15. This gives a zone without holes in the resistive heating means With substantial heating of the central duct 8 and an area with holes where there is fluid flow between the ducts.

It may also be provided a variation of the distribution of the holes 20 along the height of the partitions 11. This variation may follow for example a Gaussian function. The holes 20 will be further apart from each other at the ends of the partition 11 than in its central portion.

The presence of the holes 20 along the entire length of the partitions 11 makes it possible to reduce the stresses while maintaining a convection in the longitudinal direction causing a stratification of the water as a function of its temperature, as represented in FIG. figure 8 . The very dark zone in the lower part corresponds to the water with the lowest temperature and the dark zones located in the central pipe 8 and around the resistive heating means 15 corresponds to the water heated with the highest temperature. Between the two, stratification of the water is observed as a function of its temperature from the highest in the upper part and in the center of the tank to the coldest in the lower part and in the peripheral ducts 9a, 9b. Conventionally, the unheated water is introduced into the tank 1 by a lower fluid connection 16 and the heated water is captured by an upper fluid connection 17. The inlet of the unheated water at the lower fluidic connection 16 is deflected by the presence of a jet blocking the movement of the unheated water in a vertical component preventing its inadvertent mixing with the heated water.

The movement of water in a tank according to the invention is such that unheated water is introduced through the lower fluid connection 16 located in the lower part of the tank 1 and preferably in one of the two peripheral ducts 10a, 10b. This unheated water is distributed in the lower part of the tank 1 in particular through the holes 20.

The resistive heating means 15 heat the water in the central duct 8. The combination of a longitudinal position of the resistive heating means 15 and the longitudinal orientation of the ducts 11 generate a local heating allowing the water to rise in temperature while facilitating longitudinal convection sufficient not to create bubbling and scaling. The heated water rises along the central duct 8 substantially to the upper two-thirds with fluid communication with the confined ducts very limited. In the upper two-thirds of the tank 1, the heated water of the central duct 8 disperses to the peripheral ducts 9a, 9b gradually taking a cone-shaped shape. The water thus heated and moving away from the central duct 8 homogenizes the temperature of the surrounding water and thus descends into the tank 1 forming layers of water degressive temperature from top to bottom. Advantageously, it has been noted the formation of two loops of water circulation, a right, a left, on either side of the central duct 8 receiving the resistive heating means 15.

According to a first possibility, the holes 20 are distributed over at least two thirds of the length of the partition and advantageously over the entire length.

The holes 20 represent 10 to 40%, preferably 15% of the area of the partition 11. The holes 20 are preferably evenly distributed over the surface of the partitions.

According to a second preferred possibility and shown in the figures, the holes 20 are aligned in at least one row oriented in the longitudinal direction of the ducts 11. The holes 20, to play their role of deformable elements, are preferably aligned and symmetrical relative to an axis located in the middle of the width of the partition 11. The holes 20 may be of variable dimensions.

According to one possibility, the holes 20 are circular.

According to another possibility, the holes 20 have an ellipse shape. Advantageously, the ratio of the major axis and the minor axis of the ellipse may vary along the partition 11. For example, the major axis of the holes 20 formed in the central part of the partition is oriented according to the width of the the partition 11 while at the high and low ends of the partitions, the major axis is oriented along the longitudinal axis of the partition 11. For example for a width of 116 mm, in the center, the ellipse has a major axis oriented according to the width of the partitions, that is to say perpendicular to the longitudinal axis, a length of 70 mm and a small axis oriented along the longitudinal axis of a length of 20 mm. At the longitudinal ends of the partition 11, the ellipse has a major axis oriented along the longitudinal axis of a length of 70 mm and a small axis oriented perpendicular to the longitudinal axis of a length of 20 mm.

The variation in the ratio of the lengths of the major axis and the minor axis of the ellipse is such that, at no time, the holes are circular.

The holes 20 are for example regularly spaced from each other. They are preferably all identical and for example circular with a diameter less than or equal to half the width of the partition 11. For example, the diameter of the holes 20 is of the order of 50 mm and the width of a partition is 116 mm. According to one possibility, the partition 11 comprises between ten to twenty holes 20, preferably fifteen holes 20, for a wall length of 1672 mm.

The space between the holes 20 is substantially equivalent to half the width of the partitions 11. The space between the holes 20 is measured edge to edge by two successive holes 20 along an axis passing through the center of the holes 20.

According to another possibility, the holes 20 are aligned in two rows parallel to one another. The holes 20 of the two rows may be aligned according to the width of the partitions or staggered. According to this possibility, the two rows are arranged substantially symmetrical to each other with respect to the axis located in the middle of the width of the partition 11. The width of each hole is less than or equal to one quarter of the width of the partition 11.

According to one embodiment providing increased mechanical resistance to the tank 1, it comprises two lateral sections 12a and 12b and n sets of two intermediate sections. The number of profile sets is a function of the number of conduits. Preferably, the number n is odd and the number of ducts is odd.

Preferably, at least one set of intermediate profiles is used. In the figures, three games are used. The intermediate ducts 10a, 10b are arranged between the lateral sections 12a, 12b so as to connect them and to close the space between them. The profiles are assembled in pairs and with a longitudinal edge of a partition 11 by a weld bead 14 formed on the face of the opposite sections inside the vessel 1. More specifically, the longitudinal edge of the partitions 11 is configured to slightly exceed the thickness of the vessel 1. The slices of the lateral sections 12a, 12b and intermediate 10a, 10b can be applied to the edge of the partitions and the welding is performed at this location. The lateral sections 12a, 12b form the two lateral ends of the vessel 1.

The formation of weld seams 14 outside of the tank 1 makes it possible to limit the risks as to the potability of the water. In addition, the stress concentrations are reduced at the level of the partitions inside the vessel 1. Partitions with a thickness of the order of 1 to 2 mm are sufficient.

In addition, the use of identical elements makes it possible to design tanks 1 of various dimensions with always the same basic elements. The modularity of the tank 1 is particularly advantageous.

The welding beads 14 are preferably made over the entire height of the profiles 12, 13 and substantially over the entire height of the partition 11.

In the upper part and in the lower part of the tank 1, that is to say at the longitudinal ends of the ducts 8, 9, 10, the tank 1 comprises two flanges forming respectively the upper wall 7 and the lower wall 6. These two flanges are configured to cooperate with the profiles and the partitions 11.

Regarding the profiles, according to one configuration, the two flanges comprise at their periphery a groove in which are inserted the edges of the profiles. The flanges are therefore of dimensions slightly greater than those formed by the profiles. The welding of the flanges to the rest of the tank 1 is done by the outside of the tank 1 on the face of the profiles opposite to the inside of the tank 1. In this way, there is still no weld in the volume inside the tank 1 may be in contact with water.

According to another preferred configuration, the two flanges are slightly smaller than the section of the tank 1. In this way, the two flanges cooperate by their edges with the profiles of the tank 1. The two flanges are welded to the profiles by their periphery.

The two flanges comprise, according to one possibility, embossings 23 forming projections towards the inside of the vessel 1. The embossings 23 have a role of reinforcement. According to this possibility, it is at the level of these embossings 23 that will come to position the partitions 11, by their edge.

According to one variant, the embossings 23 may take the form of a groove receiving the lateral ends of the partitions 11 which are then held without requiring welding.

Preferably, the partitions 11 are welded to the inner faces of the flanges, preferably between the embossings 23.

It is well understood that the flanges, in particular that forming the bottom wall 6, advantageously comprise openings for the passage of lower fluid connections 16 and higher 17.

The capture of the heated water is advantageously in the upper part of the tank 1, the opposite of the introduction of unheated water. Preferably, the upper fluidic connection 17 for the collection of hot water is located in an intermediate duct 10a, 10b closest to the central duct 8 and opposite to the duct comprising the lower fluidic connection 16 for the introduction of non-water. heated.

The management of water is carried out in a conventional manner by an inlet and outlet system 19 of the water.

Similarly, the tank 1 is surrounded by insulating material, for example in the form of insulating blocks 22. It should be noted that the insulating blocks 22 or other insulating materials applied to the outside of the tank 1 are configured to cooperate with it and in particular with the weld beads 14. For this purpose, the insulating blocks advantageously comprise grooves receiving with or without contact the weld beads 14.

The ducts 8, 9, 10 are preferably of the same surface and preferably of the same size and as an example of a width of the order of 100 mm. The central duct 8 may be larger than the intermediate and peripheral ducts 9 as a function of the resistive heating means 15.

It is important to correlate the power of the resistive heating means with the size of the central duct 8 and the volume of the tank 1. For example, Resistive heating equipment with a power of 2 kilowatts can be used for tank volumes ranging from 50 to 100 liters.

The fact that the ducts 11 are of small section of the order of 10 times less than the length of the ducts 11 promotes the vertical convection of water and therefore a good distribution of hot water without risk of damaging the means of resistive heating 15.

With regard to the method of mounting a vessel 1 according to the invention, according to a preferred embodiment, the partitions 11 are welded at their longitudinal ends to the upper and lower flanges, preferably by weld beads over the entire width 11. The welds are advantageously cleaned.

The lateral sections 12 and the intermediate sections 13 are arranged between two partitions 11 and welded by their side edges to the partitions 11 by a weld bead 14 outside the vessel 1 and preferably present over the entire height of the profiles.

REFERENCES

1.

Tank

2.

First main wall

3.

Second main wall

4.

Side wall

5.

Side wall

6.

Bottom wall

7.

Upper wall

8.

Central duct

9a, 9b.

Peripheral conduit

10a, 10b.

Intermediate conduit

11a, b, c, d.

Partition

12a, 12b.

Lateral profile

13a, b, c, d, e, f.

Intermediate profile

14a, b, c, d, e, f.

Welding cord

15.

Resistive heating means

16.

Lower fluidic connection

17.

Superior fluidic connection

18.

Tube

19.

Entry / exit system

20.

Hole

21.

Means of fixation

22.

Insulation blocks

23.

embossing

24.

Purge hose

25.

U base

26.

Side of the U

27.

Wings of U

28.

Plan of symmetry of the tank

Claims (13)

1. A water heater comprising a tank (1) having a parallelepiped shape and comprising an odd number of juxtaposed parallel pipes separated by partitions (11), and in one of which resistive heating means (15) intended to heat an amount of water contained in the tank (1) extend in the longitudinal direction of the pipes (8, 9, 10), the resistive heating means (15) being positioned at the centre of a pipe (8) that is centrally arranged relative to the other pipes (9, 10), with each partition wall (11) comprising at least one row of holes (20) aligned in the longitudinal direction of the pipes, characterized in that the total surface area of the holes (20) occupies between 10 and 40% of the total surface area of the partition (11), and the holes (20) being regularly spaced in the longitudinal direction of the pipes, the space between the holes (20) being substantially equivalent to half the width of the partitions (11), the space being measured from edge to edge of two successive holes along an axis going through the centres of the holes.
2. A water heater according to claim 1, wherein the width of the holes in a direction perpendicular to the longitudinal direction of the pipes is such that the width occupied by the holes (20) is smaller than half the width of the partition (11).
3. A water heater according to any one of the preceding claims, wherein each partition (11) comprises a row of symmetrical holes (20) aligned along an axis located in the middle of the width of the partition (11).
4. A water heater according to one of the preceding claims, wherein the holes (20) have circular or elliptical sections.
5. A water heater according to one of the preceding claims, wherein the resistive heating means (15) are located in a lower portion of the tank (1) at which the partitions (11) defining the central pipe (8) include no hole (20).
6. A water heater according to one of the preceding claims, wherein the length of the rows of holes (20) is greater than or equal to two thirds of the length of the partitions (11).
7. A water heater according to one of the preceding claims, wherein the partitions (11) cover the whole length of the tank (1).
8. A water heater according to one of the preceding claims, wherein the spacing between the resistive heating means (15) and the partitions (11) surrounding these does not exceed 17% of the width of the tank (1).
9. A water heater according to one of the preceding claims, wherein the pipes have rectangular sections.
10. A water heater according to one of the preceding claims, wherein the tank (1) comprises two lateral sections (12) and at least one set of intermediate sections (13) closing the space between the two lateral sections, with the sections being assembled two by two and being interleaved with a longitudinal edge of a partition (11) by a weld bead (14) formed on the face of the runner opposite the inside of the tank (1).
11. A water heater according to any one of the preceding claims, wherein the tank (1) comprises at least two flanges respectively positioned at the longitudinal ends of the pipes, and intended to cooperate with the longitudinal ends of the partitions (11).
12. A water heater according to one of the preceding claims, wherein the surface area of the longitudinal section of the tank (1) is at least ten times greater than that of the section of the tank (1) along a plane perpendicular to the longitudinal direction.
13. A water heater according to one of the preceding claims, comprising:

    - a series of five pipes,

    - a fluid coupling outlet (16) so configured as to let unheated water into the tank (1) and opening into the lower part in the longitudinal direction of a peripheral pipe (9a, 9b) located at a side end of the series of pipes,

    - a fluid coupling outlet (17) so configured as to discharge heated water out of the tank and opening into the upper part in the longitudinal direction of an intermediate pipe (10a, 10b) located between the central pipe (8) and the peripheral pipe (9a, 9b) located at a side end of the series of pipes opposite the peripheral duct (9a, 9b) comprising the fluid coupling inlet so configured as to let unheated water in.

Images