EP0302782A1 - Heat-transfer fluid heat exchanger - Google Patents

Abstract

The invention relates to a heat-transfer fluid heating boiler body which is intended to receive at least one burner and is surrounded at least partially by a jacket (3) for circulation of said fluid, said jacket (3) comprising an outlet (5) for the heated fluid, which is arranged in the bottom part of the latter, and an inlet (4) for the cooled return fluid, which is arranged in the top part of said water jacket (3). The body of the boiler according to the invention is characterised in that the inlet (4, 4', 4'') of the return fluid is arranged in such a manner that the fluid is distributed into said jacket in a number of places at the same time. <IMAGE>

Description

The invention relates to a heating fluid heating boiler body, intended to receive at least one burner and which is at least partially enveloped by a jacket for circulation of said fluid, which constitutes the heat exchanger of the boiler.

In a conventional boiler provided with a body of the aforementioned type, the fluid used is generally water. When the boiler is in operation, due to differences in density, the water is distributed from top to bottom according to its temperature, the water in the upper zone having a temperature significantly higher than the water in the zone bottom.

It is then conventional to arrange a departure of the heated water, towards radiators or tubes embedded in a ground for example, in the top of the jacket, and an arrival of the cooled water of return, in the bottom of said shirt, that is to say in the coldest area. In this way there is a very large temperature gradient between the top and the bottom which has the major drawbacks of increasing the risks of boiling at the top and of condensation at the bottom.

It is clear, in fact, that the internal wall of the water jacket serves as a heat exchange surface between the combustion gases coming from the burner and the water which circulates in the jacket. However, it is known that the combustion gases in contact with a relatively cold surface undergo the phenomenon of condensation also known as the dew phenomenon.

It is also known that such condensation of the combustion gases results in the formation of sulfuric acid which is particularly corrosive to the appliance, especially when the fuel used is domestic fuel oil or heavy fuel oil, due to their high percentage of sulfur.

Condensation occurs when the temperature drops below around 55 degrees C, but it is common for the temperature of the return water from radiators or heated floors to be around 20 degrees C.

Up to now, the risks of condensation and therefore of corrosion have been limited due to the large volume of conventional water jackets, in which the cold return water mixes with hot water before encountering their internal wall.

However, for a reduced volume water jacket, which is more and more sought after in order to reduce the bulk, the above-mentioned phenomena are of great importance, especially at the location chosen for the return of the cooled water. , with regard to condensation and therefore corrosion.

In addition, when the vertically arranged water jacket has a small thickness (for the aforementioned reasons), a phenomenon of stratification appears, that is to say that the temperature of the water varies from one end to the other. of the boiler in insulated slices or layers.

To solve the problems of condensation it is obviously possible to use materials such as stainless steel or cast iron ... However, the inventor solved the problem by means of several original solutions.

British Patent 894691 describes and relates to a heat exchanger which can, in particular, be arranged in the body of a heating appliance. In this patent, to allow a counter-current exchange between combustion gases and water, it has been envisaged to arrange the inlet of the water to be heated opposite the burner and the outlet of the water on the burner side, so that for a burner provided in the lower part of the boiler, the inlet is arranged in the upper part.

For different reasons, the inventor has adopted a similar arrangement (arrival in the upper part and departure in the lower part) so that the cooled water arrives in the hottest zone. In this way, on the one hand, the phenomenon of condensation is at least partly resolved and, on the other hand, this arrangement makes it possible to obtain a homogenization of the temperature by natural convection avoiding the use of a pump intended for circulate the water between the bottom and the top of the water jacket.

To further reduce the harmful effects of condensation and in particular to remove the "cold spot" traditional (place of arrival of the return water), while promoting the homogenization of the temperature, the boiler body according to the invention is remarkable in that the inlet is arranged in such a way that the fluid is distributed in the shirt in several places at the same time.

According to one embodiment, the inlet comprises a pipe which ends in a geometrically open ring, the latter being provided with a plurality of orifices through which the fluid is dispensed.

In order, on the one hand, to preheat the return water before feeding it into the jacket and, on the other hand, to provide an arrival in the lower or middle zone to avoid connection errors due to the force of the the habit of installers, the inventor proposes an embodiment which is remarkable in that the inlet comprises a pipe which is connected in the lower or middle part of the shirt and which rises therein towards its upper part.

For similar reasons of usual connection, the departure advantageously comprises a pipe which originates in the lower part of the shirt and which rises therein to exit therefrom in its upper part.

• - la figure 1 montre en perspective avec arrachement partiel , le corps d'une chaudière, selon l'invention.
• - la figure 2 est une coupe longitudinale du corps de la figure 1.
• - la figure 3 est une coupe selon III-III de la figure 2.

The invention will be clearly understood on reading the description which follows and which refers to the appended drawings in which:

• - Figure 1 shows in perspective with partial cutaway, the body of a boiler, according to the invention.
• - Figure 2 is a longitudinal section of the body of Figure 1.
• - Figure 3 is a section on III-III of Figure 2.

In the drawings we can see a body 1 formed at least in part by a cylinder arranged vertically and intended to receive, generally in the lower part, a burner (not shown), fuel oil for example.

The body 1 is surrounded by another coaxial cylinder 2 with a diameter greater than that which forms said body and which is closed so that a volume is formed between the walls of said cylinders, in which water circulates. This volume thus comprised between the body 1 and the cylinder 2 constitutes a jacket 3 for the circulation of water which envelops the major part of said body 1. The jacket 3 has here a relatively small volume, the height being quite large for a particularly reduced thickness. .

The water jacket 3 is provided with an inlet pipe 4 for the return water coming from the heating apparatus of the installation (radiators or the like) and with a departure pipe 5 for the heated water which is sent to said heaters.

As FIGS. 1 and 2 clearly show, the inlet pipe 4 is connected in the jacket 3 substantially below its horizontal median plane, and rises in the said jacket by a vertical part 4 ′ to end in the form of a geometrically open ring 4 ˝ (Figures 1 to 3).

The ring 4˝ is arranged in a substantially horizontal plane and has a plurality of orifices such as 6 intended to distribute the return water in the upper part of the jacket 3.

The starting pipe 5 originates in the lower part of the jacket 3, and rises by a vertical part 5 ′ in said jacket 3 to exit in the upper part thereof.

If Figures 2 and 3 show pipes 4 and 5 arranged diametrically opposite, unlike Figure 1, it is clear that it is for the sake of clarity of the drawings, the connection of pipe 4 relative to the outlet of the line 5 can of course be located in other places than that shown.

The drawings clearly show how the inlet pipe 4 which seems connected downwards, distributes the water in fact at the top of the jacket after having bathed by 4 ′ in said jacket so as to allow the water to be preheated. return. The latter is uniformly distributed over the circumference of said shirt 3 through the orifices 6 formed in the ring portion 4˝.

Given the high position of the return water distribution, the natural circulation of the latter by convection from bottom to top is hampered by the forced circulation which is imposed on it from top to bottom so that it ensuing stirring resulting in mixing and homogenization of the temperature (the forced circulation is obviously increased by the use of an external pump provided, for example, in the supply circuit). Temperature measurements have shown that it is fairly uniform throughout the jacket, so much so that it is possible to place the measurement probe of the burner control aquastat, substantially in the middle of said jacket ( aquastat generally set to maintain a temperature above 60 degrees). Furthermore, this is why the departure of hot water can then advantageously be provided as shown in the drawings at the bottom of the shirt.

It is interesting to underline again the role of the position reversals between the connection of the arrival pipe 4 downwards (while it goes up in a hidden way upwards) and the exit of departure pipe 5 upwards (while it originates at the bottom).

Apart from the aforementioned advantages, these non-mandatory provisions make it possible to avoid connection errors, because if it is customary to differentiate by marking the departure and arrival pipes, there could be a risk of reverse connection out of habit, during installation, if said inlet pipes 4 and outlet 5 were arranged in the upper and lower parts respectively, which clearly shows, if necessary, the prejudice that had to be overcome in order to adopt such a provision.

It is clear that the general shape of the body of the boiler shown in the drawings can be arbitrary. Indeed, if it is advantageous to produce said body and the outer envelope by means of cylinders of revolution, this is not compulsory, and it is possible to imagine other shapes, polygonal for example.

Claims (4)

1) Heating fluid heating boiler body, intended to receive at least one burner and which is at least partially enveloped by a jacket (3) for circulation of said fluid, which jacket (3) has a flow (5) for the fluid heated, which is arranged in the lower part of the latter, and an inlet (4) for the cooled return fluid, which is arranged in the upper part of said water jacket (3), boiler body characterized in that l 'arrival (4,4 ′, 4˝) of the return fluid is arranged in such a way that the fluid is distributed in said jacket in several places at the same time. 2) Boiler body according to claim 1, characterized in that the inlet comprises a pipe (4,4 ′) which ends in a ring (4˝) geometrically open, the latter being provided with a plurality of orifices (6) by which the fluid is dispensed. 3) Boiler body according to one of claims 1 and 2 characterized in that the inlet comprises a pipe (4) which is connected in the lower or middle part of the jacket (3) and which rises (4 ′) in this one towards its upper part. 4) Boiler body according to one of claims 1 to 3 characterized in that the flow comprises a pipe (5) which originates in the lower part of the jacket (3) and which rises (5 ′) therein to get out in its upper part.

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