FR2543266A1 - Heat recuperator with sealed outside-air supply - Google Patents

Abstract

This recuperator is characterised essentially by an outside-air intake which is connected in a sealed manner (pipe: see 2) to the furnace. This adjustable intake for oxidant air forms, with the gases and fumes, the first circuit of the system. The second circuit is operated by a tangential fan (see 9) which is placed under the furnace plate and pulses air into three exchangers placed in series which yield the calories of the coals, the flames and the fumes respectively. The oblique arrangement of the tubes (see 8) in the third exchanger makes possible circulation by natural convection when the fan is stopped. The pulsing mouths (see 19) are equipped with a shutter, which makes it possible to modulate the heating in the rooms to be served. The construction of the recuperator in three exchangers to be assembled reduces the weight of the pieces to be handled and makes it possible for expansions to take place without the risk of causing disorders which are sometimes encountered with monobloc exchangers (see 13 for the assembly joints of the three parts).

Description

CALORIE RECOVERY FOR FIREPLACES WITH
WATERPROOF EXTERIOR AIR SUPPLY
The present invention relates to a recuperator with double air circuit for decorative chimney.

 This device is a heat exchanger which recovers them at the level of embers, at the level of the flames and at the level of the fumes, which makes it possible to reach in the room or rooms to be heated a given temperature with less consumption of fuel. . Indeed, ordinary fireplaces produce heating only by radiation from the ignited parts and elements which, heated by conduction or radiation from the hearth, in turn return calories to the room to be heated.

Certain methods of recovering calories are based on natural convection (according to the physics principle that a hot gas is lighter than a cold gas). Other processes use forced circulation, but by removing cold outside air, which considerably reduces the yield and bringing the room to be heated to the desired temperature. Another method uses the ambient air which is pulsed through an exchanger, but it has the following drawbacks a) the combustion air taken from the outside is not connected directly
home. A simple opening towards the crawl space, the cellar
or the outside of the house avoids putting the room in depression. By
high wind, there can be an overabundant amount of room
outside air, which cools it.

b) there is no device for adjusting the supply of fresh air, which, in
external air overpressure, may cause projection of
hearth ashes in the ambient air.

c) the horizontal arrangement of the pipes where the hot air circulates in the drain
does not facilitate air circulation by natural convection when the
tangential fan is stopped.

d) the outlets, by their rectangular shape, make it difficult
the supply of hot air some distance from the chimney.

e) these mouths do not have a shutter, which prevents flow adjustment
hot air to certain places that we want to favor.

The invention presented here overcomes these drawbacks as follows: - The fresh combustion air taken from outside the room to be heated is brought
to the hearth by a pipe which, on the one hand, is sealed in the wall
that it crosses, thus preventing any propagation of fresh outside air
in the room and on the other hand is tightly connected to the fireplace.

- the air supply to the fireplace is regulated by a butterfly controlled by a
external linkage.

- the steel pipes forming the upper exchanger in the drain are arranged
oblique to facilitate air circulation by natural conection.

- the connection sockets on the third exchanger (drain) are cylindrical,
which allows easy connection of pipes to conduct air
warm at the mouths of drive.

- the air outlets are fitted with a shutter valve
An embodiment is given, by way of example; the description below referring to the attached drawings, the nomenclature of which is as follows, this embodiment being non-limiting - Figure 1: HORIZONTAL CUT THROUGH THE HEART - Figure 2: ELEVATION VIEW OF THE HEART - Figure 3: CUT IN THE INDOOR EXCHANGER - Figure 4: CROSS-SECTIONAL COIJPE IN THE LOWER EXCHANGER
AND THE HEART - Figure 5: DOWNSTREAM (UPPER EXCHANGER) SEEN FROM ABOVE - Figure 6: FRONT VIEW OF THE DOWNHOUSE - Figure 7: CROSS SECTION IN THE DOWNHOUSE - Figure 8: CROSS SECTION SHOWING THE ASSEMBLY
The chimney fitted with its recuperator works as follows
The first circuit is formed by the combustion air which, coming from the crawl space, or from the cellar, (see 1), is channeled by a sheath (see 2) which is tightly fixed to the arrival shell (see 3) fitted with an adjustment throttle (see 4) controlled by an external linkage (see 5). From the ferrule (see 3) the air is distributed to the two vents (see 6) placed on either side of the fireplace. The combustion air accompanied by the gases and fumes escapes through the duct after having crossed the drain where they transfer part of the calories they contain to the upper exchanger (internal walls of the drain - see 7 - and tubes - see 8-).

 The second circuit consists essentially of the tangential fan (see 9) with a power of about 20 watts, placed under the hearth plate, therefore a short distance from the ground, there where the air in the room is the least warm.

This air is successively pulsed: a) in a trapezoidal section box (see 10) whose upper plate
supports the embers of the hearth. This box is entirely made in
sheets assembled by welding.

b) in the heart of the hearth (see 11) in which steel tubes are embedded
(see 12).

c) in the trough in the shape of a truncated pyramid from which the air is forced into
the room to be heated (see plate 2/3).

The advantages of this system are a) the air from the secondary circuit being taken up in the room itself, its temperature
rises more and more, which is not the case with systems taking
outside air to be heated
b) there is no possible mixing between the hot pulsed air and the fumes,
the air circuit being put under overpressure, thanks to the tangential fan,
in relation to the smoke circuit; this is important in case a
assembly fault would cause a lack of tightness
c) the thermal inertia of the heart makes it play the role of recuperator of
heat, even after the fire has gone out
d) it is possible to shut off the fresh air supply when not in use
the chimney, and the tightness of the fresh air intake prevents the spread
this in the room e) the exchanger consists of three separate parts to be assembled on site
without special tools, which reduces the weight of the items to be handled
and gives them a certain flexibility allowing thermal expansions
to manifest without disturbing either the cohesion or the tightness of the circuits.

 The three main parts mentioned above are assembled together by asbestos and plaster joints made on site (see 13).

The lower exchanger is constructed, for the plate (see 14) in contact with the embers, of special steel alloyed mainly with silicon, copper, chromium, nickel and manganese, which gives it good resistance to corrosion due to the aggressiveness of wood combustion residues. Under this plate are welded over their entire length sheet metal elements folded in the shape of waves (see 15) and whose role is twofold: a) bring the heat of the hearth plate by thermal conduction into contact
forced air and increase the contact surface between it and
hottest parts b) play the role of stiffeners of the hearth plate.

 The tangential fan is fixed on the widest part of the trapezoidal box and its discharge oule adapts perfectly to the box.

The other end of it opens into a distribution ramp (see 16) from which air is distributed to the steel tubes forming the second exchanger (see 12). These pass the air from the first to the third exchanger, and allow the air to heat up again in contact with the bricks heated mainly by the radiation of the flames, At each end of the distribution ramp are placed the inlets fresh air which, via a welded steel manifold (see 17), is connected to the shell fitted with an adjusting butterfly (see 4); the spiral hose is connected to this ferrule
spiral connecting the hearth to the outside air.

 The steel pipes embedded in the core protrude into the lower and upper edges of the core; they fit into a slot on the one hand in the distribution ramp for the lower edge and in the rear part of the hood (see 18) for the upper edge.

 The drain consists of an internal corrosion-resistant steel envelope. In the anterior and posterior walls are welded steel tubes (see 8) forming a parallel network making an angle of approximately 300 with the horizontal, leading the air arriving through the posterior part obliquely and rising towards the part anterior. A second sheet steel casing forms a perfectly watertight covering on which the ferrules are placed (see 19) where the spiral aluminum hoses can be connected leading the heated air to the air outlets fitted with an adjustment valve (see 20). There are four of these ferrules, two on the front side and one on each side.

 The downstream bases rest on the core (rear part), on a brick frieze (see 21) for the front part and on the reluctant or frieze returns for the sides.

The drain is surmounted by a rectangular collar penetrating 3 cm inside the first bushel forming the flue. This flange serves as a bearing surface for a tilting hatch (see 22) rotating around a transverse axis. The hatch is operated by a chain which, when released, causes the hatch to close. For the rest of the chimney, the constituent elements are those that are encountered in a traditional construction, except that the different parts are prefabricated and delivered ready to be assembled. They are essentially: - the hearth plate (see 23) in refractory bricks assembled on a
a concrete based on molten cement. It is necessary that the hearth plate
is at least 25 cm from the ground to allow access to the fan
tangential (secondary air circuit and maintenance).

- one or two cross-hearts, possibly with jambs and crows.

- a wooden or stone beam, a hood, as well as possibly
benches finish the construction of the chimney.

 As for the tangential fan, it is controlled by a 3-position switch (off, low speed, high speed), normally placed near the chimney. It is connected to the 220 volt network and to the earth connection.

 It should be noted that the tangential fan can be coupled to a room thermostat which allows the fan to be stopped or switched on according to the set temperature. In addition, when the tangential fan is stopped, a natural convection occurs through the fan itself, the trapezoidal box forming the lower exchanger, the network of vertical tubes forming the intermediate exchanger, the oblique tubes of the outlet, to finally reach the air intake vents.

 It should be added that by a flexible sheath connection connected to one of the outlets of the drain, it is possible to heat a neighboring room either on the same floor or on the upper floor. The only precaution to be observed is to provide a return of the forced air to the room where the chimney is located so as not to overpress the neighboring room. This would obviously result in considerably braking the hot air impulse therein.

 The fireplace fitted with its heat recovery unit can be either leaned against a wall or placed in the corner. If the wall against which the chimney is leaned is of combustible or easily flammable material, thermal insulation is provided automatically, and the covering of the chimney (jambs, crows, cores etc ...), would be fitted out with so as to hide this insulation on the sides.

 The process which is the subject of this patent does not only apply to a chimney with a traditional look, but can also be used for a modern chimney for example, the hood of which would be completely suspended. In this case, we could either embed the heart in such a way that it touches the surface of the wall or lean it against the wall and provide edges on the sides of the heart.

Claims (5)

i REVERDICATIONS  1.- Heat recovery unit intended to equip a chimney (hearth) for inhabited premises operating normally using wood as fuel and based essentially on a double air circuit. It is characterized in that the first is an open circuit which is tightly connected to the hearth to bring there, at its base coming from outside the room, Combustion air. Impregnation of the external surface of the embedded tubes  in refractory concrete, material with a low melting point allows them to expand, thus avoiding any cracking of the core due to differential expansions between the steel tubes and the concrete. At the outlet of the second exchanger, the air passes through a bundle of parallel steel tubes arranged obliquely in the upward direction.  2. A heat exchanger according to claim 1 characterized in that the air of the primary circuit coming from the outside is tightly connected to the hearth, by means of a spiral duct.  3. A heat exchanger according to claim 1, characterized by corrugated sheet elements immersed in the air circuit blown by the tangential fan and bringing there by thermal conduction the heat of the hearth plate.  4. A heat exchanger according to claim l, characterized in that the core forming a thermal accumulator can, as a variant, be replaced by a special sheet metal box, with low thermal inertia, the first and the third exchanger remaining unchanged. This variant has the advantage, upon ignition, of obtaining warmer air more quickly at the outlet vents. This box can either be visible in the heart of the chimney or be covered by a prefabricated element. in refractory bricks.  5.- heat exchanger according to claim I, characterized in that the faces of the exchangers not in contact with the elements yielding heat (embers, flames, fumes), is thermally insulated to improve the efficiency of the 'apparatus.