WO2012123301A1

WO2012123301A1 - Heating apparatus using gas condensate

Info

Publication number: WO2012123301A1
Application number: PCT/EP2012/053864
Authority: WO
Inventors: Joseph Le Mer
Original assignee: Giannoni France
Priority date: 2011-03-14
Filing date: 2012-03-07
Publication date: 2012-09-20
Also published as: FR2972789A1; FR2972789B1

Abstract

The invention relates to a heating apparatus (1) including a condensation heat exchanger (2), a gas burner (3), a sleeve (40) for conveying an air/gas mixture to the burner (3), a means (42) for circulating said mixture in the apparatus, and a pipe (430) for feeding said gas into the intake sleeve (40). The heat exchanger (2) includes a tube (21) mounted inside an enclosure (200) defined by a housing (20), wherein a fluid to be heated flows through the tube (21) and the tube is exposed to hot gases generated by said burner (3), said housing (20) including a sleeve (205) for discharging the burnt gases. The invention is characterized in that at least one Venturi tube (70) is provided in said supply sleeve (40) downstream from the gas-feeding pipe (430), and the partial-vacuum chamber (76) of the Venturi tube (70) is in fluid communication with the collar (71) of the Venturi tube, said collar having a hole (710) extending therethrough, and in that at least one tubular junction part (8) connects the inside of the enclosure (200) with the partial-vacuum chamber (76) in order to collect a portion of the burnt gases and mix the latter with the air/gas mixture fed into the burner.

Description

Condensing gas heater.

The present invention relates to a condensing gas heater for reducing emissions of air pollutants.

It is intended in particular to equip a gas boiler for domestic or industrial applications, for example to supply a central heating circuit and / or to provide water for sanitary purposes.

This heater is of the type comprising a condensing heat exchanger, associated with a gas burner and means for supplying up to this burner an air (oxidizer) / gas (fuel) mixture.

The heat exchanger is capable of providing a very efficient heat exchange between, on the one hand, very hot gases generated by the burner, and on the other hand, a fluid to be heated, such as water , which circulates inside a tube of thermally good conductor material.

In the past, traditional gas heaters were equipped with so-called "atmospheric" burners. In these burners, the air flow required for combustion was induced by the flow rate of the gas under pressure. However, the respective ratios of gas and air supplied to the burner were not controlled and therefore very approximate.

As a result, the emissions of flue gases (fumes) into the atmosphere at the outlet of the heater were of the order of 100 ppm (parts per million) of carbon monoxide (CO) and 150 ppm of nitrogen oxides (NOx).

More recently appeared on the market, condensing heaters, equipped with burners known under the trade name "Premix". In these devices, a feeding system allows the creation of the air-gas mixture with optimal proportions, before sending it to a surface combustion burner.

In this case, the air flow is produced by a fan whose speed is variable and the gas flow rate is adjusted by a supply valve, pneumatically or electronically controlled, the operation of the fan and that of the valve being controlled by a control box. This makes it possible to maintain an air flow rate / gas flow rate ratio, which is appropriate for all the speeds of variation of fan speed and therefore of burner power. These devices made it possible to very significantly reduce pollutant discharges into the atmosphere at levels of the order of 30 ppm CO and 22 ppm NOx.

Those skilled in the art also know that it is possible to further reduce these CO and NOx emissions, by adding in the air / gas mixture supplied to the burner, about 6 to 12% by volume, preferably 8 to 10% by volume. % by volume of the flue gases resulting from the combustion of this mixture.

This principle of recirculation of part of the fumes attenuates the oxygen content in the chemical reaction of the combustion. This results in a decrease in the combustion temperature conducive to a reduction of NOx and CO emissions.

The object of the present invention is to provide a condensing gas heating appliance which not only makes it possible to carry out this recirculation of flue gases, but to do so by further reducing these polluting discharges, of the order of 40% for CO and 50% for NOx.

Another object of the invention is to provide such a reliable, secure heating appliance with a very small additional cost compared with existing appliances.

The invention also aims to provide an additional safety device that allows the detection of the overflow of condensates.

For this purpose, the invention relates to a condensing gas heater, of the type comprising a condensing heat exchanger, associated with a gas burner and means for supplying the burner with an air / gas mixture. , the condensing heat exchanger comprising at least one bundle of tubes, made of thermally good conducting material, mounted inside an enclosure delimited by a gas-tight envelope, this tube bundle being traversed by at least one fluid to be heated, such as cold water, and being exposed to hot gases generated by said gas burner, said envelope comprising a flue gas exhaust duct and fumes, means for supplying the air / gas mixture comprising an intake sleeve of said air / gas mixture, the outlet orifice of which is connected to the burner, means for circulating the air / gas mixture inside the heating apparatus, a pipe for introducing the gas at l inlet of said intake sleeve, equipped with an intake valve.

According to the invention, at least one Venturi tube is disposed inside said intake sleeve, downstream of said gas introduction pipe, the space provided between the inner wall of said intake sleeve and the outer wall of said Venturi tube defining a so-called chamber "Depression", in fluid communication with the neck of said Venturi tube via at least one hole drilled in the wall thereof and in that at least one tubular junction piece connects the interior of the enclosure of the exchanger with said vacuum chamber, so as to take a portion of the burnt gases present in said chamber and to incorporate them into the air / gas mixture introduced into the burner.

According to other advantageous and nonlimiting features of the invention, taken alone or in combination:

said means for circulating the air / gas mixture inside the heating apparatus comprise a fan whose output is connected to the inlet orifice of said intake sleeve, upstream of said Venturi tube; and whose air inlet is connected to the outlet of said gas introduction pipe;

the means for circulating the air / gas mixture inside the heating apparatus comprise a gas extractor connected to the outlet of the exhaust duct and in that said gas introduction duct is connected at the inlet of the inlet sleeve upstream of said Venturi tube;

the condensing heat exchanger comprises two bundles of helical tubes, acting respectively as primary exchanger and secondary exchanger, coaxially mounted inside said casing, separated by at least one deflector plate made of insulating material, envelope being closed by a front plate in the center of which is mounted a removable door which supports said burner, said heater being arranged so that the hot gases generated by the burner first pass through the primary heat exchanger, crossing the interstices separating its turns from the inside outwards, then the secondary exchanger, through the interstices separating its turns from the outside to the inside, after which they are evacuated to the outside via said sleeve of evacuation, and in that said tubular connecting piece is connected to the inside of the enclosure by an orifice in said pla front facing a zone of the enclosure located outside said primary exchanger, so as to collect the burnt gases after they have passed through the turns of said primary heat exchanger;

the apparatus comprises several, for example four, Venturi tubes which are mounted in parallel inside the intake sleeve and have a common depression chamber;

said tubular junction piece comprises two tubes mounted in parallel; the area of the section of the tubular junction piece and the dimensions of the Venturi tube (s) are calculated to ensure the recirculation of a fraction of the order of 6 to 12% by volume, preferably of the order of 8 to 10% by volume of the flue gases;

the bottom wall of the envelope comprises an outlet orifice for the condensates (C) resulting from the combustion of the air / gas mixture and the apparatus comprises a safety device detecting the closure of this orifice and the overflow of the condensates .

the above-mentioned heating apparatus comprises an ionization electrode electrically connected to an electronic control unit controlling the operation of the gas supply valve and means for circulating the air / gas mixture inside the heating apparatus, and said safety device comprises a detection electrode electrically connected to said ionization electrode, this detection electrode opening into the lower part of the enclosure, so that when the condensates (C) come into contact both with said sensing electrode and a metal part located inside the shell and connected to ground, such as the facade, as a result of the electrical conductivity of the condensates, a voltage drop occurs at the level of the ionization electrode, which generates a signal addressed to the electronic control unit which stops the operation of said valve and said means of circulation;

the detection electrode opens inside the tube of the tubular junction piece;

the detection electrode opens inside the outlet orifice of the condensates or in the vicinity of the latter.

Other features and advantages of the invention will appear from the description which will now be made, with reference to the accompanying drawings, which show, by way of indication but not limitation, several possible embodiments.

On these drawings:

FIG. 1 is a diagrammatic front view, in axial section, of an exemplary embodiment of a heating apparatus according to the prior art,

FIG. 2 is a diagrammatic front view, in axial section, of a first embodiment of a heating apparatus according to the invention,

FIG. 3 is a sectional view of the apparatus of FIG. 2 along section plane III-III; FIG. 4 is a perspective view of a one-piece piece associating four Venturi tubes,

FIG. 5 is a sectional view of the part of FIG. 4, taken along the sectional plane V-V,

FIGS. 6 and 8 are views in perspective and in elevation of a tubular connecting piece, established according to two different angles of observation,

- Figure 7 and a sectional view of the part of Figure 6, according to the sectional plane VII-VII,

FIG. 9 is a diagrammatic view similar to FIG. 2, in which a condensate overflow situation has been represented,

Figure 10 is a schematic view similar to Figure 9, but showing a second embodiment of the heater, wherein the condensate overflow detection system is different.

An exemplary embodiment of a heater belonging to the state of the art will now be described with reference to FIG.

On it, there can be seen a heater A which comprises a condensing heat exchanger 2, associated with a gas burner 3 and means 4 for supplying an air / gas mixture to this burner.

The heat exchanger 2 comprises a gas-tight shell or envelope 20 which delimits an enclosure 200 within which a tubular bundle 21 is fixedly mounted, which consists of two bundles of coaxial tubes placed end to end, of which the one 21 serves as primary exchanger and the other 21B secondary exchanger.

This enclosure has approximately a generally cylindrical shape, of horizontal axis X-X '.

The beams 21A and 21B consist of several tubes, made of a thermally good conductive material, helically wound around the X-X axis, arranged end to end and connected in series. The gap between the turns is calibrated and of small width. These tubes have a flattened cross section whose long sides are perpendicular to the axis X-X '.

A baffle plate 22 made of insulating and heat-resistant material is interposed between the two primary and secondary 21A and 21B beams.

The tubular bundle 21 is intended to be traversed internally by at least one fluid to be heated, which is, for example, water, this fluid flowing from the left to the right of FIG. Lateral collectors (not shown in Figure 1 but visible on the left side of Figure 3) are attached to the casing 20, they allow the connection of the apparatus, conventionally, on a fluid supply duct cold that needs to be warmed up, and venting the heated fluid.

These collectors also transfer the circulating fluid from a tubular winding to the neighboring winding.

Advantageously, the envelope 20 is made of plastic. In this case, it is preferably furnished with a heat shield (not shown), which may consist of a metal ferrule which covers with a slight spacing, the inner face of the envelope.

It is open on one of its sides, in this case the side on the right, if we consider Figure 1.

During use of the apparatus, part of the water vapor contained in the flue gases condenses in contact with the walls of the tubes 21.

The reference 201 designates the bottom wall of the enclosure. In known manner, this bottom is sloped, which allows the evacuation of the condensate through an outlet port 202.

Also known, the casing 20 comprises a vertical rear wall 203, an upper wall 204 and a discharge sleeve 205 of the flue gases and fumes.

The outlet orifice 202 is connected to a condensate outlet duct, while the sleeve 205 is connected to a flue gas discharge duct, for example a flue. These ducts are not shown in FIG.

This type of heat exchanger, well known, will not be described in more detail below in order not to unnecessarily burden this description.

However, if necessary, the reader can refer to the following patent documents, which relate to an exchanger of this type: EP-B-0678186 (see in particular FIG. 18), WO 2004/036121 A1 (FIGS. 1 and 5) and WO 2004/097311 A1 (see Figures 1-2).

Figures 13 and 14 of WO 2004/036121 A1 represent the aforementioned ferrule forming heat shield (reference 100).

The open side of the casing 20 is closed by a front plate 23, made for example in a stainless steel sheet. It has a generally annular shape and its central orifice is normally closed by a removable door 5. In the example shown in Figure 1, it is a so-called "cold" door, which reduces the heat loss of the heater to the outside.

The door 5 has a generally circular shape. It comprises, in a manner known per se, an outer wall 50 and an inner wall 51 between which is mounted a discoidal deflector plate 52. These walls are made of metal, for example made of stainless steel sheet.

The reader will be able to refer to a more complete description of this door in the document WO 2010/100004.

The door 5 comprises, on the inside, an annular lining 53 made of thermally insulating and heat-resistant material, such as ceramic.

The inner plate 51 has a central zone pierced with a circular opening 510 centered on the axis X-X ', at which the cylindrical burner 3 is fixed. The burner could also have another shape. It is made of metal.

The outer sheet 50 is pierced with a circular opening 500 centered on the axis X-X 'and on which is fixed a sleeve 40 for admission of the air / gas mixture.

The inlet orifice 41 of the sleeve 40 is connected to the outlet 420 of a fan 42.

Furthermore, an intake valve 43 is mounted on a pipe 430 connecting an external gas supply source G, to the air inlet 421 of the fan 42.

The operation of the fan 42 and the opening or closing of the valve 43 are controlled from an electronic control unit 6, via the connections shown in broken lines 61 and 62.

The intake sleeve 40, the fan 42 and the valve 43 constitute means 4 for supplying the air / gas mixture to the burner.

According to an alternative embodiment not shown in the figures, the fan 42 could be removed and replaced by a gas extractor, connected to the exhaust sleeve 205. In this case, the gas introduction conduit 430 is connected directly to the intake port 41 of the intake sleeve, in a manner which allows, however, the admission of outside air into the sleeve 40.

The depression generated by this extractor in the outlet sleeve 205 causes, at the same time, the evacuation of the flue gases and fumes by this cuff, and the path of aspiration of gases before and after combustion through the apparatus.

An ionization electrode 31 is disposed a few millimeters from the combustion surface of the burner 3. It is mounted through the door 5 and the seal 53, via an electrically insulating sleeve 310. It is connected by an electric wire 63 to the electronic control unit 6.

An electrical wire 64 further connects the electronic control unit 6 to the metal front plate 23, which thus acts as a mass.

The ionization electrode 31 ensures ignition of the burner 3 and the safety control of the presence of the flame around the burner. This electrode measures, via the electronics of the control unit 6, an ionization current produced by the presence of the flame. This voltage measurement of a few millivolts is taken between the mass of the burner and the electrode 31.

If the flame goes out, the corresponding voltage drop is detected by the control box 6, which then sends a signal controlling the closing of the valve 43 and the shutdown of the fan 42.

When the fan 42 is running (the valve 43 being open), it induces a gas flow at its inlet 421 from the gas source G. The air / gas pre-mixture thus formed arrives at the inlet of the cold door 5, via the intake sleeve 4, before reaching the burner 3.

The hot gases generated in the combustion chamber 24 first pass through the primary tubular bundle 21A passing radially between the interstices of said tubes, from the inside to the outside; they can not escape axially due to the presence of the deflector disk 22 (arrows i).

They are then channeled in an annular space 25 formed between the tubular bundle 21 and the walls 201 and 204 and called "intermediate chamber". The hot burned gases then pass through the secondary exchanger 21B through the interstices of the turns, this time from the outside towards the inside of the exchanger (arrows ii) in the space 26 located behind the deflector plate 22.

Finally, these flue gases exit the exchanger through the exhaust sleeve 205 (arrow iii).

The water circulating inside the bundle of the tube 21 - against the current of the gases - is thus reheated, its preheating being ensured in the secondary bundle 21 A, and its heating itself in the main beam 21 A. Moreover the condensates escape through the outlet orifice 202 located at the bottom of the exchanger. The heating apparatus 1 according to the invention will now be described in connection with FIG. 2. The elements common to the heating apparatus A of the prior art previously described bear the same numerical references and will not be described again.

As a preliminary, it will be noted that the arrangement of the heat exchanger could be different without departing from the scope of the invention.

According to the invention, at least one Venturi tube 70 is disposed inside the sleeve 4, downstream of the fan 42.

This Venturi tube is a nozzle conventionally comprising a neck 71, preceded by a converging 72 and extending by a diverging 73. The converging 72 and the diverging 73 are both of approximately frustoconical sections, but the angle of conicity the convergent is greater than that of the divergent.

Preferably, several Venturi tubes 70 are arranged in parallel inside the sleeve 4, so as to improve the efficiency of the device and reduce its bulk. More preferably, these tubes are four in number.

FIG. 4 represents a one-piece piece 7 which associates four Venturi tubes 70, arranged side by side so that their respective longitudinal axes Y-Y 'are parallel or substantially parallel.

This part 7 is preferably made of heat-resistant plastic material and manufactured for example injection molding.

The four Venturi tubes 70 are secured at their lower ends to a substantially rectangular plate 74 and at their upper ends to a similar plate 75.

Thus, the inlet orifices 720 of the convergents 72 open through the bottom plate 74, while the outlet orifices 730 of the divergents 73 open through the upper plate 75.

The neck 71 is pierced radially with at least one hole 710, preferably several, for example four, distributed angularly in a regular manner.

The bottom plate 74 and the upper plate 75 are each bordered by a peripheral groove 740, respectively 750, inside which is disposed a seal not shown in the figures.

Advantageously, a stiffening rib 77 of substantially rectangular shape extends around the four diverging portions 73 of the Venturi tubes 7. The sleeve 40 consists for example of two parts which are assembled to one another, after the part 7 grouping the four Venturi tubes has been mounted inside one of them.

As best shown in FIG. 3, the part 7 is disposed in the sleeve 40, so that the longitudinal axes YY 'of the Venturi tubes 70 are parallel to the longitudinal axis of the sleeve and the housed gaskets in the grooves 740 and 750 are pressed against the inner walls of the intake sleeve 40.

The space provided between the inner wall of the sleeve 40 and the outer wall (s) of the Venturi tube (s) 70 constitutes a chamber 76 (see FIG. 2).

The seals housed in the grooves 740 and 750 provide gastightness of this chamber 76 in its lower and upper part. The hole (s) 710 ensures (s) the communication of fluids between the chamber 76 and each of the necks 71.

The air / gas pre-mixture enters the Venturi tubes 70 under a pressure P 1 which corresponds to the delivery pressure of the fan 42 in the sleeve 40. This air / gas pre-mixture leaves the Venturi tube 70 under a pressure P2 , slightly lower than PI, taking into account the pressure drop in the Venturi tube 70. This pressure drop causes a depression at the neck 71 and consequently in the chamber 76, hereinafter referred to as "depression chamber" .

It will be noted that for a given geometry of Venturi tubes 7, the depression prevailing in the vacuum chamber 76 is substantially proportional to the pressure P1 prevailing upstream in the sleeve 4, this pressure P 1 being itself defined by the speed of rotation. fan 42.

A tubular connecting piece 8 connects an orifice 231 formed in the lower part of the facade 23 to an orifice 44 formed in the sleeve 4, facing the lower part of the vacuum chamber 76. The chamber 200 of the exchanger of heat is thus in fluid communication with the vacuum chamber 76.

FIG. 6 represents an exemplary embodiment of the tubular junction piece 8.

Advantageously, the piece 8 is monobloc and made of heat resistant plastic material; it is manufactured for example by injection molding. The part 8 comprises two sections of tube 80, 80 'of oblong cross section, arranged side by side, and connected by their short sides by a tongue of material 81.

The respective outlet mouths 82, 82 'of the tubes 80, 80' are bordered by an axial peripheral annular groove 820, 820 ', adapted to receive a seal not shown in the figures.

Similarly, and as it appears better in FIG. 8, the inlet mouths 83 and 83 'of the tubes 80, 80' are also bordered, on at least a part of their periphery, by grooves 830, respectively 830 ' , able to receive seals.

A stiffening rib 84 provides the connection between the upper parts of the tubes 80 and 80 '. It extends posteriorly by a perpendicular wing 85, which extends itself perpendicularly to the tongue of material 81.

The rib 84 has on its front face, that is to say the one facing the front 23, one or more lugs 840 '. These allow the attachment, for example by snapping, of the part 8 on the facade 23.

The section, shape and layout of the entrance mouths 83,

83 'correspond to those of the orifices 231 arranged opposite in the facade 23. Similarly, the section, the shape and the arrangement of the outlet mouths

82, 82 'correspond to those of the orifices 44 formed in the sleeve 40.

In FIG. 3, it can be seen that each orifice 44 opens at the base of two Venturi tubes 70, the vacuum chamber 76 being common to the four tubes.

In the exemplary embodiment shown in FIG. 5, the connecting piece 8 has two tubes 80, 80 'rather than just one, which makes it possible to avoid drilling an orifice of too large dimensions both in the sleeve 4 and in the facade 23, which could weaken these parts. However, the joining piece 8 could comprise only one tube or, conversely, more than two, without departing from the scope of the invention.

The Venturi part 7 and the tubular junction piece 8 constitute a device which makes it possible to recirculate part of the flue gases towards the burner 3.

The areas of the sections of the tubes 80 and 80 'and the dimensions of the Venturi tube (s) 7 are calculated, so as to ensure the recirculation of 6 to 12% by volume of the flue gases, preferably of the order of 8 to 10% by volume. The burnt gases generated by the burner 3 arrive in the combustion chamber 24 at a pressure P3 less than P2. After the flue gases have passed through the interstices between the tubes of the main exchanger 21 A, they are found at a pressure P4, itself lower than P3, in the intermediate chamber 25.

These burnt gases are at a much lower temperature than in the combustion chamber 24 because of the heat transfer that took place during this passage in the main heat exchanger 21 A, to heat the water flowing in it. beam.

Part of the flue gases, which are at a pressure P4, are then sucked into the vacuum chamber 76 via the junction piece 8, then via the holes 710 are recirculated in the sleeve 40 where they are mixed with the air / mixture. incoming gas. It will be noted that the gases taken after passing through the main heat exchanger 21 A are at a temperature of the order of 100 ° C. to 140 ° C. which is not harmful to the plastics used to manufacture the parts 7 and 8.

As a guide, it should be noted that the temperature of the flue gases inside the combustion chamber is generally of the order of 1000 ° C.

Finally, the combustion products that are not recycled pass through the interstices between the tubes of the secondary heat exchanger 21B, arrive in the outlet space 26, at a further lowered temperature, to be finally discharged via the sleeve 205 at a pressure P5, less than P4.

By way of purely illustrative example, if the pressure P1 is between 110 Pa and 120 Pa, the pressures P2, P3, P4 and P5 are respectively of the order of 45 Pa, 15 Pa, 12 Pa and 8 Pa, for average fan power of 27 kW.

It should be noted that plastic parts 7 and 8 are likely to be produced at very low cost and are simple to install in the heater.

As indicated above, by recycling a fraction of the flue gas into the gas / air mixture feed to the burner, a significant reduction of the releases into the atmosphere of CO and NOx is obtained.

Indeed, the heating apparatus according to the invention makes it possible to obtain CO emissions of the order of 18 ppm and NOx of the order of 10 ppm, which is much lower than the values observed with the devices. of the prior art. In addition, because the fraction of burnt gases incorporated in the gas / air mixture stream feeding the burner is hot (at a temperature of the order of 100 ° C. to 140 ° C., as already stated), a preheating of this stream, which is favorable to good combustion and beneficial in terms of the overall energy balance of the device.

It should be noted that a recycling of a portion of the flue gases would theoretically be possible via the fan in which the air / gas mixture is formed. This solution is however not satisfactory because it would lead to rapid clogging and malfunction of the fan.

The Applicant has found that, if the condensate discharge orifice 202 was accidentally clogged, the level of the condensates C could rise inside the casing 20 until it reaches the tubular connecting element 8 and even the Venturi tube 7.

If no device for detecting this rise in the level of the condensates C is provided, they will rise until reaching the level of the ionization electrode 31. The condensates C which form an electrically conductive liquid being then in contact both with the electrode 31 and with any metal part of the heat exchanger, for example the facade 23, it follows a short circuit and the immediate safety of the burner 3 via the electronic control unit 6, with closure of the gas admission valve 43 and the shutdown of the fan 42.

However, before reaching the level of the ionization electrode 31, the condensates C could have flowed via the Venturi 7 and the holes 710, towards the fan 42, causing irreparable damage thereof. They could also be sucked up and returned to the burner 3, which is detrimental to the reduction of polluting emissions.

The Applicant has therefore developed a safety device for detecting early overflow of condensate due to a closure of the discharge port 202.

Two different exemplary embodiments of this security device will now be described, with reference to FIGS. 9 and 10.

According to a first embodiment of the invention shown in FIG. 9, this device comprises a so-called "detection" electrode 90, made of stainless steel, disposed through one of the tubes of the tubular connecting piece 8, for example the tube 80, as it appears better in FIG. One of the ends 91 of the electrode 90 opens inside the tube 80, while its opposite end 92 is connected, for example via a connecting lug 920, to an electrical wire 65. The latter is in turn connected to the electrical wire 63 providing the connection between the ionization electrode 31 and the control box 6.

As shown in FIG. 9, when the evacuation of the condensates C no longer takes place correctly through the orifice 202, the level of the liquid condensates rises in the bottom of the exchanger until, at first, it reaches , the lower part of the metal facade 23 (which serves as mass) and, in a second step, the end 91 of the electrode 90.

The liquid condensates being electrically conductive, this electrode 90 is therefore found at a zero voltage (corresponding to the mass). It is the same for the lead 65 to which this electrode 90 is connected.

The electrode 31 which is itself connected to the conductor wire 65 by the lead wire 63 is therefore also at zero voltage - at the same voltage as that of the burner - in a situation similar to a lack of ionization current. produced by the presence of the flame.

This therefore has the effect of canceling the reading of the ionisation voltage perceived by the electrode 31. As explained above, it ensues an immediate security of the device by cutting the valve 43 and the fan 42.

At no time did the condensate level reach the Venturi 7.

According to an alternative embodiment shown in FIG. 10, a detection electrode 94 is disposed in the vicinity of the outlet orifice 202 of the condensates, for example on the condensation outlet duct 206.

Similarly to what has been described for the first embodiment, it is connected to the electrical wire 63 connecting the ionization electrode 31 to the housing 6. Its operating principle is the same as that described previously for the electrode 91.

The main difference with the previous embodiment is that the contacting of the condensate C with the electrode 94 is performed before they come into contact with the lower part of the metal front 23.

What is important is that this double contact occurs before the condensate reaches the level of the connecting tube 8.

Finally, it will be noted that if the envelope 20 was made of metal, and therefore of a good electrical conductor material, the detection of the recovery of the condensates would take place as soon as the level of the condensates C would affect both the detection electrode 94 and the tubing constituting the outlet orifice 202.

Note that the anti-overflow safety device in which the sensing electrode 94, located at the outlet of the condensates 202, is used could also be used in a condensing heater not including the device. recycling described previously.

Indeed, as mentioned above in the absence of such a detection electrode, it is necessary to wait until the condensates have reached the ionization electrode 31 to obtain the safety of the device. At this stage, the baffle plate 22 ceramic and the ceramic lining 53 are, however, strongly soaked with water condensates and must be changed.

Claims

Condensation gas heating apparatus (1), of the type comprising a condensing heat exchanger (2), associated with a gas burner (3) and means (4) for supplying said burner with an air / gas mixture, the condensing heat exchanger (2) comprising at least one bundle of tubes (21), made of a thermally good conducting material, mounted inside an enclosure (200) delimited by an envelope ( 20) gastight, this tube bundle (21) being traversed by at least one fluid to be heated, such as cold water, and being exposed to hot gases generated by said gas burner (3), said envelope (20) comprising a sleeve (205) for evacuation of the flue gases and fumes, the means (4) for supplying the air / gas mixture comprising a sleeve (40) for admitting said air / gas mixture whose orifice outlet is connected to the burner (3), means (42) for circulating the air / gas mixture inside the heating apparatus (1) and a pipe (430) for introducing gas into the inlet of said intake sleeve (40), equipped with an inlet valve (43), characterized in that at least one tube of the Venturi (70) is disposed inside said intake sleeve (40), downstream of said gas introduction pipe (430), the space provided between the inner wall of said intake sleeve ( 40) and the outer wall of said Venturi tube (70) defining a so-called "depression" chamber (76) in fluid communication with the neck (71) of said Venturi tube via at least one hole (710) pierced in the wall of the latter and in that at least one tubular connecting piece (8) connects the inside of the enclosure (200) of the exchanger (2) with said vacuum chamber (76), so that removing a portion of the burnt gases present in said enclosure (200) and incorporating them into the air / gas mixture introduced into the burner.

2. Heating apparatus (1) according to claim 1, characterized in that said means for circulating the air / gas mixture inside the heating apparatus (1) comprises a fan (42) whose outlet (420) is connected to the inlet port (41) of said intake sleeve, upstream of said Venturi tube (7) and whose air inlet (421) is connected to the air inlet output of said gas introduction pipe (430).

3. Heating apparatus (1) according to claim 1, characterized in that the means for circulating the air / gas mixture inside the heating apparatus (1) comprises a gas extractor connected to the Release the discharge sleeve (205) and that said gas introduction line (430) is connected to the inlet of the intake sleeve (40) upstream of said Venturi tube (70).

4. Heating apparatus (1) according to one of the preceding claims, characterized in that the condensing heat exchanger (2) comprises two helical tube bundles, acting respectively as a primary heat exchanger (21 A). and secondary exchanger (21B), coaxially mounted inside said casing (20), separated by at least one baffle plate (22) made of insulating material, the casing (20) being closed by a faceplate ( 23) in the center of which is mounted a removable door (5) which supports said burner (3), said heating apparatus (1) being arranged so that the hot gases generated by the burner (3) pass first through the burner (3). primary exchanger (21 A), crossing the interstices separating its turns from the inside to the outside, then the secondary exchanger (21B), crossing the interstices separating its turns from the outside to the inside, after which they are evacuated to the outside vi said discharge sleeve (205), and in that said tubular connecting piece (8) is connected inside the enclosure (200) through an orifice (231) in said front plate (23). ) facing an area of the chamber (200) located outside said primary heat exchanger (21 A), so as to collect the flue gases after they have passed through the turns of said primary heat exchanger (21A).

5. Heating apparatus (1) according to one of the preceding claims, characterized in that it comprises several, for example four, Venturi tubes which are mounted in parallel inside the intake sleeve (40). ) and have a common vacuum chamber (76).

6. Heating apparatus (1) according to one of the preceding claims, characterized in that said tubular connecting piece (8) comprises two tubes (80, 80 ') connected in parallel.

7. Heating apparatus (1) according to one of the preceding claims, characterized in that the area of the section of the tubular junction piece (8) and the dimensions of the Venturi tube (s) are calculated to ensure the recirculation of a fraction of the order of 6 to 12% by volume, preferably of the order of 8 to 10% by volume of the flue gases.

8. Heating apparatus (1) according to one of the preceding claims, characterized in that the bottom wall (201) of the casing (20) comprises an orifice (202) for the exit of condensates (C) from the combustion of air / gas mixture and in that it comprises a safety device detecting the closure of this orifice (202) and the overflow of the condensates.

The heating apparatus (1) according to claim 8, which comprises an ionization electrode (31) electrically connected to an electronic control unit (6) controlling the operation of the gas supply valve (43) and means (42) for circulating the air / gas mixture inside the heating apparatus (1), characterized in that said safety device comprises a detection electrode (90, 94) electrically connected to said ionization electrode (31), said detection electrode (90, 94) opening into the lower part of the enclosure (200), so that when the condensates (C) come into contact with both said detection electrode (90, 94) and a metal piece located inside the casing (20) and connected to the ground, such as the facade (23), there results, as a result of the electrical conductivity of the condensates, a fall voltage at the ionisation electrode (31), this which generates a signal addressed to the electronic control unit (6) which stops the operation of said valve (43) and said means (42) for circulation.

10. Heating apparatus (1) according to claim 9, characterized in that the detection electrode (90) opens into the tube (80) of the tubular connecting piece (8).

11. Heating device (1) according to claim 9, characterized in that the detection electrode (94) opens inside the outlet (202) of the condensate or in the vicinity thereof.