DISPOSITIF D'EXTRACTION DE LA CHALEUR D'UN FOYER A FEU NU

CONSTRUCTION FOR RECOVERING THE HEAT IN OPEN FIREPLACES

Abrégé anglais

ABSTRACT

A structure for recovering the heat in open
fireplaces comprising a space having one wall serving as the
hearth plate for the fire and one vertical wall serving as the
back plate over which the air to be heated circulates. Within
the space a plurality of tubes are disposed open at the bottom
transversely of the back plate at the level of the wood and/or
the burning embers, and at the top opening into the flue.

Revendications

The embodiments of the invention in which an exclusive
property or privilege is claimed are defined as follows,


1. A construction for recovering the heat in open
fireplaces comprising a space having one wall serving as a hearth
plate for the fire and one vertical wall serving as a back plate
over which air to be heated circulates, a plurality of tubes
within said space opening at the bottom transversely of the back
plate at the level of wood and/or burning embers of said fire,
and at the top opening into a flue.


2. A construction according to claim 1, in which the
tubes have a restricted cross-section to exclude surplus air not
participating in the combustion.


3. A construction according to claim 1 or 2, in which
lower open ends of the tubes are disposed at different heights.


4. A construction according to claims 1 or 2,
including shutter means associated with at least certain of said
tubes for the selective closure of certain tubes as desired.


5. A construction according to claim 1 or 2, in which
lower open ends of the tubes are disposed at different heights
and including shutter means associated with at least certain of
said tubes for the selective closure of certain tubes as desired.



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Description

the hot
The present invention concerns a construction for heatin~ air
assoeiated ~Jith the flue of an open fire.
Arrangements for recovering the heat in the flues of open fires
by heating air or water are already known. For example, among known
constructions for heating air may be mentioned those which are
described in French Patents published under Nos: 22 70 527, 22 73 238
and 23 4l ~2l. These constructions all comprise an enclosed space
which extends around the fire and in which the air to be heated
circulates, the wall of the space adjacent to the fire being heated
by the flames and smoke and serving to heat the air circulating in
the space. Now it is known that the temperature of the flames
decreases very quickly on leaving the surface of the fuel and that
the temperature of the smoke also decreases rapidl~y as it mixes with
excess air passing into the flue without participating in the combustion.
In particular, the height ~f the back plate of the flue does not enable
air to be re-heated above about 60.
One object of the present invention is to provide a construction
which enables the delivery of hot air at temperatures substantially
more elevated~
According to one feature of the invention a construction is
provided comprising a space having one surface serving as the hearth
plate and one surface serving as a back plate over which the air to be
heated circulates, the arrangement also comprising, within said space,
a plurality of tubes open at the bottom, extending over the surface

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o~ the back plate from the height of the wood and/or embers, and
opening at the top into the flue passage.
Accordjng to another feature of the invention, the tubes are of
relatively restricted cross-section so as not to permit the passage
of air not taking part in the combustion.
According to a further feature the lower outlets of the pipes
are located at different levels.
According to yet another -Feat~re enclosure means are provided to
enable the outlets of selected pipes to be closed as desired.
The features of the invention mentioned above, as well as others
will be more clearly apparent from the followins description with
reference to the accompanying drawings of a practical example, wherein
Figure 1 is a sectional elevation of an open fireplace
incorporating an arrangement for heating air according to the inventlon,

Figure 2 is a front elevation of the fireplace of Figure 1,
Figure 3 is a sectional plan of line III-III showing the arrange-
ment for heating, and
Figure 4 is a front elevation of an arrangement for selection of
the tubes to be opened.
The open fireplace shown in Figure 1 comprises, as is customary,
a hearth plate 1 on which stands the grate 2 supporting the burning
firelogs 3, a back plate 4, jambs 5, a lintel 6, a hood
7 and a flue pipe 8.
The back plate 4 is actually a wall in front of a space 9 which has
the form o~ a chamber L-shaped in vertical section, the bottom limb
of the L extend;ng under at least part of the hearthl and the upright
limb of the L rising as far as the hood 7. The space 9 has at the
bottom an air intake passage 10 to allow the entry of cold air from


outside of the room in which the fireplace is located, and at the
top the air outlets 11 which deliver the hot air either into the same
room, for example through the hood, or into another room. For this
purpose, in the embodiment shown, the top place 12 of the space 9 is
pierced by two apertures 11 to which are connected branch pipes 13
opening on the 5i des of the hood 7.
Also there are provided in the upright leg of the L-shaped space 9,
tubes 14 which run in general vertical, the lower ends being welded to
the back plate 4 and their upper ends welded to the plate 12. The
plates 4 and 12 are pierced correspondingly by the tubes 14. The
tubes are advantageously about 3 mm in diameter.
The tubes 14 serve as bye-pass outlets of restricted cross-section
in relation to the principal fire. The direct result is that the burning
cornbustion gases emitted by the wood are able to rise also while
burning in the tubes 14. In fact though not seen, they proceed, as
indicated by the flames 15, into the apertures at the bottom of the
back plate ~. As the quantity of air admitted into each tube 4 is
limited by the narrow section of the tubes, the hot gases rising in
each tube are not mixed with an excess of cold air n~t participating
in the combustion. Thus the temperature in the tubes 14 is, at the
same ~evel, much greater than that of the plate 4. 0~ course, the
plate 4 transfers the heat of the fire to the interior of the
space 9, as in the known constructions.
Moreover, the-ratio of the surface of a tube to its volume is
maximal with the result that the transfer of heat to the air passing
through the space 9 is clearly much more effective than w;th a con-
struction having only as the heat transfer surface the plate 4 and
the part extending below the hearth.
Experience.has shown that, of the tubes 14~ those which conduct


most of the -flames are those which open at the level where the flames
originate. This is the reason why, as shown in Figure 2, the inlets
of the tubes 14 are located at different heights, and as shown in
Figure 4, the sliding obturating plate 16 having appropriately disposed
apertures 17 enables the apertures which are open to be selected.

This device permits adjustment according to the height of the heat
of burning logs so as to obtain the best results.
The section of the space may be rela~ively flat in order
to obtain a sufficient supply of hot air.

In its upper part the space 9 ma~ be inclined towards the lintel
6 so as to create a constriction which improves the draught to the
flue.