EP0443931A1 - Heat recovery device for a chimney stove - Google Patents

Abstract

The invention relates to improvements to the heat recovery device for a chimney functioning with an open or closed hearth, intended to be placed in the region of the flue to recover the calories present in the combustion smoke, the subject of main patent FR-88.17150. According to the invention, the recovery device is formed from at least two shells (1 and 2) separated by a panel (3) with a direct evacuation flap (4), one at least of the shells (1 or 2) comprising at least one lateral corridor (5, 6) for circulation of the combustion smoke. The external walls of the lateral corridors have a sawtooth shape to increase the exchange surface area. Moreover, inside each of the corridors, there are placed baffles in the form of grilles inserted into the recovery device like drawers, which facilitates maintenance. The invention is of interest to manufacturers of heating equipment. <IMAGE>

Description

The invention relates to improvements made to the heat recuperator for fireplaces operating with an open or closed hearth, intended to be placed at the level of the chimney flue to recover the calories present in the combustion fumes, subject of the main patent (FR- 88.17150).

It will find its application in particular in the manufacturers of heating equipment.

The mission of heat recovery units is to improve the heating efficiency of thermal installations.

In the case of closed fireplaces, when it is desired to have a high calorific output, it is necessary to install a heat recovery unit or heat exchanger, arranged for example in the chimney flue, to remove the calories abundant present in the fumes in order to heat a heat-transfer fluid which will ensure the distribution of heating.

Although the choice of heat transfer fluid is free, in most cases, air is used because it is a convenient, efficient and economical solution.

A particular problem arises when the chimney to be fitted with a heat recovery unit operates according to several heating regimes, for example with an open or closed hearth.

Indeed, during open hearth operation, it is essential to have an excellent draft to avoid any backdraft of smoke through the opening of the hearth.

Also, the heat exchanger placed in the chimney flue must be completely excluded to have sufficient draft.

On the other hand, during closed hearth operation, the chimney has good control of the heating rate by adjusting the air intake, the draft is more efficient and the problems of discharge are eliminated.

Under these conditions, it is possible to use a heat exchanger in the flue for example to efficiently recover calories.

The situation is therefore paradoxical since, depending on the operating mode with open or closed hearth of the chimney, this one supports or not the presence of a heat recuperator.

A truly effective solution has been exposed in the main French patent (FR-88.17150) where a heat recovery device is mentioned which offers the particularity of having a heat exchanger capable of being used or not.

Using a bypass, the combustion fumes can either pass directly from the inlet to the outlet of the exchanger, without circulating in the corridors of the heat exchanger, or run through the said corridors of the 'heat exchanger, in which case there is heat exchange and heat recovery using a heat transfer fluid.

When the combustion fumes pass without passing through the heat exchanger, there is no pressure drop and the chimney draft is absolutely not influenced by the presence of the heat recovery unit, which makes the latter compatible with operation according to the open fire pattern.

On the other hand, when the heat exchanger is in operation, that is to say that the direct communication flap between the inlet and the outlet of the heat recovery device is closed, then the calories of the fumes are largely recovered and transferred to the heat transfer fluid.

The heat recovery device described in the main patent (FR-88.17150) shows a feasible construction in mechanically welded sheet.

However, it is often preferred to implement using the foundry rather than the sheet metal.

Another important imperative is the possibility of cleaning the interior of the heat recovery device.

Particulate fumes clog the walls of the heat exchanger and for safety purposes and for the latter to maintain good efficiency, it is necessary to ensure regular cleaning of its internal volume.

The realization of the heat recovery device given in the main patent (FR-88.17150) does not allow an easy cleaning of the walls.

It should also be noted in this regard that the heat recovery unit is generally integrated in a chimney flue and that its housing is cramped.

We must therefore imagine a cleaning method compatible with the environment.

The main purpose of the present invention is to provide improvements to the heat recovery unit for fireplaces operating with an open or closed hearth according to the main patent (FR-88.17150), which has the same advantages, namely in particular the possibility of open hearth operation without that the recuperator does not create a pressure drop to maintain an excellent draft at the chimney but whose structure is compatible with molding techniques, which are interesting in this field.

In addition, the heat recuperator of the present invention is removable to ensure effective cleaning of its internal walls and according to a preferred embodiment of the invention, it also offers ease of cleaning of the places where the dirt is located.

Thus, routine maintenance of the heat exchanger is within the reach of the user, who will be able to clean the heat recovery unit on a regular basis while maintaining its efficiency.

Other objects and advantages of the present invention will appear during the description which follows which is however given only for information and which is not intended to limit it.

According to the present invention, the heat recovery unit for a chimney operating with an open or closed hearth, intended to be placed at the connection on the chimney flue to recover the calories present in the combustion fumes, according to claim 1 of the patent main (FR-88.17150), is characterized by the fact that it is formed of at least two shells separated by a plate with a direct discharge hatch, at least one of the shells comprising at least one lateral passage for circulation of fumes.

• la figure 1 schématise en vue éclatée les principales parties composant le récupérateur de chaleur selon l'invention,
• la figure 2 montre en vue de dessus avec coupe partielle et schématise la circulation des fumées à l'intérieur du récupérateur de l'invention,
• la figure 3 représente un mode avantageux de réalisation des chicanes du récupérateur de chaleur de l'invention,
• la figure 4 montre une vue en coupe selon l'axe IV-IV de la figure 2.

The invention will be better understood on reading the following description accompanied by attached drawings, among which:

• FIG. 1 shows schematically in exploded view the main parts making up the heat recovery unit according to the invention,
• FIG. 2 shows a top view with partial section and diagrams the circulation of the fumes inside the recuperator of the invention,
• FIG. 3 represents an advantageous embodiment of the baffles of the heat recovery unit of the invention,
• FIG. 4 shows a sectional view along the axis IV-IV of FIG. 2.

The present invention relates to improvements made to the heat recovery unit for a chimney operating with an open or closed hearth, intended to be placed at the level of the chimney flue to recover the calories present in the combustion fumes, subject of the main patent (FR-88.17150) .

The invention relates to manufacturers of heating equipment.

The presence of a heat recovery unit makes it possible to significantly improve the overall thermal efficiency of combustion by transferring the calories present in the combustion fumes to a heat transfer fluid.

The present invention relates particularly to a heat recovery unit which offers the same advantages in terms of principle as the heat recovery unit device described in the main patent (FR-88.17150), that is to say in particular the possibility of directly evacuating the fumes of combustion during operation of the fireplace with the door open or retracted while benefiting from a method of construction by molding, at least in part, and which, in addition, has ease of maintenance, in particular with regard to the cleaning of dirty parts .

The heat recuperator of the present invention mainly consists of three parts, as illustrated in FIG. 1.

These are at least two shells, one upper 1, the other lower 2, separated by a plate 3 provided with a hatch 4 for direct discharge of the combustion fumes.

The outlet of the device is connected to the lower shell 2, which corresponds to the inlet 21 of the combustion fumes in the heat recovery unit.

The upper shell 1 also has a connector 20 to the chimney flue to ensure the evacuation of combustion fumes.

When the hatch 4 is open, the fumes, present in the interior volume of the lower shell 2, pass through the opening released by the hatch 4 and communicate directly with the conduit 20 for discharging the fumes.

In this case, the hatch 4 constitutes a bypass and the combustion fumes simply pass through the heat recovery unit, as shown in particular in arrow 22 in FIG. 4, without pressure loss but also without recovering a maximum of heat energy.

This operating mode of the heat recuperator corresponds to the open hearth appearance of the chimney.

At least one of the two shells 1 or 2 comprises at least one side passage 5, 6 for circulation of the combustion fumes.

Figure 2 shows schematically the interior space defined by the upper 1 and lower 2 shells.

When the hatch 4 is closed, the fumes introduced into the lower shell 2 must, to exit, pass through the plate 3 at the level of orifices 7 and 8.

The fumes as shown diagrammatically by the arrows 9 in FIGS. 1 and 2, emerge at the level of the upper shell 1.

The orifices 7 and 8 are separated from the smoke evacuation duct 20 by a transverse partition 10.

The smoke must therefore pass through the lateral corridors 5 and 6 delimited on the one hand by the external walls 11 and 12 of the heat recovery unit and by internal longitudinal walls 13 and 14.

These inner walls 13 and 14 do not extend over the entire length of the shell 1 so that there remains at each end of the passages 7, 8, 23, 24 through which the fumes respectively enter and exit in the lateral corridors 5 and 6.

It should be noted that the upper 1 and lower 2 shells can perfectly come from foundry, which is precisely one of the objectives of the present invention.

Likewise, with regard to the intermediate plate 3 and the hatch 4, these can also be produced in a foundry.

The lateral corridors 5 and 6 preferably have a circulation path for the winding fumes.

This characteristic promotes the exchange of heat between the combustion fumes and the heat transfer fluid present outside the heat recovery unit.

The transfer of calories takes place through the outer walls 11 and 12.

The sinuous path of the combustion fumes inside the lateral corridors 5 and 6 is shown diagrammatically by the arrows 15 as shown in FIGS. 2 and 4.

This route in lanes 5 and 6 is therefore artificially lengthened, which increases the exchange time and this is also favorable to turbulence, also conducive to heat transfer.

To create this winding circulation path, in the lateral corridors 5 and 6, the latter have an outer wall 11 and 12 in the shape of a sawtooth.

The surface of the outer walls of the corridors 5 and 6 is therefore large in size to perfect the heat exchange.

In addition, the walls of the interior partitions 13 and 14 are provided planar; thus, it is advisable to set up in each lane 5, 6 baffles 16 and 17 whose role is to inflect the direction of flow of the fumes in each lane in order to have a winding path with maximum turbulence.

An identical effect could of course have been obtained by adopting a corrugated surface for the production of the interior walls 13 and 14.

However, this choice is not recommended because the lateral corridors 5 and 6 constitute the preferred fouling zones and the maintenance of the heat recovery unit would in this case require dismantling of the shells 1 and 2 to access the lateral corridors 5 and 6 and proceed to the cleaning of said corridors 5 and 6.

According to the invention, the use of removable internal baffles 16 and 17 is recommended, which facilitates maintenance.

Preferably, the baffles of a corridor are in the form of a grid, as illustrated in FIG. 3, threaded like a drawer into the shell 1.

• il faut bien entendu prévoir sur l'une des faces du récupérateur au moins une ouverture garnie d'une plaque 30 fixée de manière amovible et,
• de préférence, la coquille 1 est munie de moyens de guidage tels des fentes par lesquelles on engage avec jeu des grilles 16 et 17 dans les couloirs latéraux 5 et 6.

For that :

• it is of course necessary to provide on one of the faces of the recuperator at least one opening provided with a plate 30 removably fixed and,
• preferably, the shell 1 is provided with guide means such as slots through which the grids 16 and 17 are engaged with play in the lateral passages 5 and 6.

The bars 18 of the grid 16 have the same pitch as the saw teeth of the outer wall 11 and 12 of the shell 1.

However, when the grid 16 or 17 is in place, each of its bars 18 falls opposite one of the vertices of the saw teeth of the outer wall 11 and 12 to constitute the baffles.

In addition, it should be noted that the hottest gases present in the combustion fumes tend to circulate in the upper part of the side passages 5 and 6 while the less hot gases circulate in the lower part.

This phenomenon linked to differences in density is detrimental to the proper functioning of the heat exchange and this is why the grids 16 and 17 have in their upper part a smoke deflector 19, such as a fraction of a bar as illustrated in FIG. 3, which closes in particular the upper passaae of the lateral corridors 5 and 6 to create a mixing of the fumes and homogenize the temperatures.

The maintenance of a heat recovery unit, as described, is extremely easy since it is necessary to periodically remove the grids 16 and 17 to clean them and to clean the side aisles 5 and 6.

This manipulation is very fast, it does not require any disassembly of the recuperator since it suffices to slide the baffles through a slot.

Other implementations of the present invention, within the reach of those skilled in the art, could also have been envisaged without departing from the scope thereof.

Claims (8)

Heat recovery unit for chimneys operating with open or closed hearths, intended to be placed at the level of the connection on the chimney flue to recover the calories present in the fumes, according to claim 1 of the main patent FR-88.17150 CHARACTERIZED in that it is formed by at least two shells (1 and 2) separated by a plate (3) with a hatch (4) for direct discharge, at least one of the shells (1 or 2) comprising at least one lateral passage (5 , 6) circulation of combustion fumes. Heat recovery unit according to claim 1, characterized in that each lateral passage (5, 6) has a circulation path for the winding smoke (15). Heat recovery unit according to Claim 2, characterized in that the passage (5, 6) has an outer wall (12) in the form of a sawtooth. Heat recovery unit according to claim 3 characterized in that the corridor (5, 6) has removable internal baffles (16 and 17). Heat recovery unit according to claim 4 characterized in that the baffles (16 and 17) of a corridor are in the form of a grid of bars threaded like a drawer in the recovery unit (1 and 2). Heat recovery unit according to claim 5 characterized in that the bars (18) of the grid (16, 17) have the same pitch as the saw teeth of the outer wall (12) of the lateral passage (5, 6). Heat recovery unit according to claim 6 characterized in that the bars (18) of the grid (16, 17) fall opposite the tops of the saw teeth of the outer walls (12) of each of the lateral corridors (5 and 6 ). Heat recovery unit according to claim 5 characterized in that the grid (16 and 17) has in its central part a smoke deflector (19).

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