Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
- l ~ 31 93~3
"Hearth comprising a device for heat ~ecuperation".
The present invention relates to a hearth comprising
a device for recuperation of heat contained in flue gas generated
by combustion of a fuel such as for example, but non-exclusively,
wood, said recuperation device being disposed inside an enclosure
formed i._. of two side walls, a back wall and a front wall comprising
an entrance for inputting said fuel.
Several attempts have already been made for recu-
perating heat comprised in the flue gas generated by a hearth. So
primitive concep ts and highly sophisticated solutions have been elabo-
rated which unfortunately did not provide a satisfactory solution.
The old stoves are for example known, of which
the exhaust pipe crossed, nearly horizontally, the room to be heated.
This allows a good dispersion, by simple convection, of the calories
contairled in the flue gas. It is good to mention that this use has
disappeared for aesthetical and security reasons. The use of wood,
as such, for fuel presented a certain danger due to the fact of a
tarry creosote settling in the conduct or exhaust pipe. That tarry
creasote settling is nowadays still the reason of a lot of chimney
fires and results from two well known situations: on the one hand
2 0 an insufficiently high input temperature of the flue gas into the
chimney (the ideal temperature would be approximately 200C), and
on the other hand, a flue gas which is to much charged with creosote
resulting from an insufficient combustion due to a lack of primary
air necessary to the combustion. In the latest case, where those two
2 5 phenomenons are combined, there is a condensation in the chimney
conducts and thus a settling of tarry creosote in the conducts.
An improved realization wherein an attempt is
made in order to recover the caloriesj is provided by the so-called
stoves with a recuperator which comprise, above the heating body,
~'
13193~3
-- 2 --
closed spaces, with diminishing dimensions or not, in such a manner
that the flue gas is brought to travel through the longest possible
way in order to abandon the calories it comprises into the room to
be heated. The drawback of that system, beside the cumbersomeness
it supposes, is that the draught (or suction of the smoke) is often
insufficient and that the slip-stream created into chose "calories
recuperation boxes" leads to the same drawbacks caused by said tarry
creosote settlings which have already been mentioned hereabove.
A lot of other systems, called "turbo" or "catalytic"
are also known. Another already tested out solution consists of the
mounting at the back side of the heating body of a combustion stage
provided for burning the combustion elements still contained in the
flue gas, by bringing them into contact with oxygen heated before
and to which a chemical catalytic agent has been added. The combus-
tion realised at such a place has for consequence that the flue gas
which are rid of of most of their creosote, travels a way of some
then centimeters (in function of the circumstances) before they flow
into the chimney. That recuperation principle has to be considered
as being more saEely and as being the most performant at the present
2 0 time.
An object of the invention is to cope with the draw-
backs of which the principles have been mentioned hereabove and
to provide a perfectly acceptable solution to the problems caused
by the recuperation of flue gas in hearths of the considered type.
2 5 According to the invention that object is achieved
in that said recuperation device comprises a se t of pipes collecting
the flue gas in the neighbourhood of the back wall and in an upper-
part of said enclosure in order to lead the flue gas to said front
wall and to lead it thereafter to an upperpart of said enclosure in
order to penetrate into a hori~ontal chamber situated in the upper-
part of the enclosure from which the flue ~as is evacuated by means
of a socket coupling to a chimney.
In a first embodiment, said set of pipes consists
of two pipes each having an input aperture for inputting said flue
gas and wherein each pipe comprises at an upperpart a first pipe,
l31.~3~
-- 3 --
said first pipe being thereafter extended by a second pipe which cross
said enclosure starting from the back wall and extending towards
the front wall for extending thereafter towards the upper part by
means of a third pipe and penetrating into said horizontal chamber.
In another embodiment which can be considered
as an alternatiE solution, said set of pipes consists of a set of deflec-
tors which direct the flue gas between two lateral walls starting
from an input aperture of the flue gas, which aperture is disposed
at the upper part of said pipes, said deflectors issue forth at their
upper part in said horizontal chamber.
According to a remarkable characteristic of the
invention, said enclosure which is provided for receiving said device
comprises at its under part a first aperture for inputting ambient
air and, at its upper part, a second aperture, provided in a further
horizontal chamber of said hearth and through which the air heated
between the walls of the enclosure and the back wall of said device
is returned outside said hearth.
Other details and advantages of the invention will
become clear Irom the description which will be given hereafter
2 0 and which relates to a hearth comprising a recuperation device for
recuperating the heat contained in the flue gas.
The description is only given by way of an example
and does not limit the invention. The references relates to the accom-
pagning drawings.
Figure I is a perspective view oE a hearth according
to the invention, showing partially the recuperation device according
to the invention.
Figure 2 is an analogous view to the one given
in figure 1, but showing only the device for recuperating the heat
comprised in the flue gas generated by the combustion of a fuel.
Figure 1 shows a hearth, given by way of example
only, which comprises side walls 1, a back wall, which can not be
seen in the drawing, and a front wall 2 having an entrance 3 for
inputting a fuel. Beside the fact that the hearth according to the
invention comprises also importan t details which will be considered
hereafter, it has to be considered that the main improvements tending
to obtain an as total as possible recuperation of the heat comprised
in the flue gas, consist in providing a set of pipes which collect the
flue gas in the neighbourhood of the back wall of the hearth. In fact,
the device comprises two pipes 4', 5' each having a flue gas input
aperture 6, 7 which is situated at the upper and back side of the
enclosure of the hearth. Both pipes comprise a first part 4', 5' exten-
ding towards the under side and show then a horizontal second part
4", 5" which is directed towards the front of the hearth and commu-
nicates with a third part 4"', 5"' which is vertically disposed and
which issues forth at its top in a horizontal chamber 8 extending
nearly over the whole upper surface of the enclosure. That chamber
8 communicates with a chimney 9.
It can thus be seen that the flue gas exhausted
by the combustion inside the enclosure is forced to circulate along
the longest possible track inside that enclosure.
The object of the device is to take away the largest
possible part of the calories which are produced by any kind of combus-
tion and by conserving the minimal temperature for the flue gas,
either or not filtered, at its entry into the chimney thus avoiding
the well known condensation phenomenon.
In an embocliment which is formally claimed, the
set of pipes 4, 5 can be replaced by a set of deflectors which lead
the flue gas starting from an input towarcls an output which puts
that set of deflectors into communication whith the horizontal chamber
8. In that case, the hot gas circulates lateraly over large surfaces,
which is an object of the invention.
In figure 2 i t can be seen that the vertical pipes
4', 5' are fixed at a wall 10 which is part of the device and which
extends until a sole 11 which can be constituted of a refractory
material or of a metal sheet.
The hearth according to the invention comprises
at its under and front part an input aperture 12 through which the
ambient air penetrates. That aperture 12 creates, under the sole
11, a space 13 which comrnunicates, by means of the vertical space
~3~o~
situated beyond the wall 10, with a second horizon tal chamber 14
situated at the upper part of the device. That second horizontal chamber
14 comprises an aperture 15 through which the heated air escapes.
It will be evident that the ambient air circulation in that second
circuit can be realised by a f an sucking or driving back the air des-
tinated to circulate in that circuit.
From the description of a hearth comprising a recu-
peration device according to the invention clearly results that the
set of pipes 4, 5 constitu tes the longest possible way that can be
imposed on the flue gas of which the calories has to be recuperated.
A very big advantage has to be seen in the fact that the parts which
are the most exposed to a high heating are situated at the back of
the hearth in such a manner that one has no longer to be afraid from
an excessif heating of the front wall and of the loadin~ input of
the hearth. This is indeed a very important object of the invention.
It will also be clear that all other modifications
of the profile of the pipes can be provided in order to give them
a path which is as long as possible and in order to recuperate a
maximum of calories thereof.
2 0 It is of course also possible to modify the path
to which the ambient air is subjected when it is passing through the
hearth, but it also clear that the choice of the components as des-
cribed in the present application constitu tes an optimal solution to
the problems mentioned in the preamble.
