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(11) | EP 3 045 814 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | COLLECTIVE CONCENTRIC FLUE DUCT |
| (57) Collective concentric flue duct (CLV) for connecting a plurality of stoves (1, 1'),
wherein the CLV (14) comprises an inner pipe (15) for the discharge of flue gases
and an outer pipe (16) for the supply of combustion air, wherein the inner pipe extends
further at the top than the outer pipe, wherein the outer pipe is closed at the bottom,
and wherein the inner pipe is provided at the bottom with a water outlet (19), wherein
a flue gas connecting element and a combustion air connecting element are provided
for each of the plurality of stoves for connecting respectively a flue gas outlet
and a combustion air inlet of the stove to respectively the inner pipe and the outer
pipe, wherein each flue gas connecting element is formed to guide moisture droplets
from the flue gas outlet against the inner wall of the inner pipe.
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[0001] The present invention relates to a collective concentric flue duct, also referred to as a CLV.
[0002] Collective concentric flue ducts (CLVs) are known and are applied mainly in buildings with multiple residential units, such as apartment buildings. In a building with multiple residential units, such as an apartment building, each residential unit typically has its own heating device. Frequently opted for in recent years as heating device is a gas heating device with condensation function. These devices are then connected to a collective concentric flue duct such that the devices can discharge flue gases via the inner pipe of the CLV for discharge of flue gases and can draw in combustion air via the outer pipe for the supply of combustion air. The combustion device can in this way operate at a high efficiency and the chance of contamination of the area surrounding the combustion device is minimal since both supplied air and discharged air flow via the collective concentric flue duct, whereby in theory there is no interference with air in the room in which the heating device is placed.
[0003] Efforts have already been made to connect stoves such as gas stoves or pellet stoves to existing CLVs. Tests have however indicated that such a stove disrupts proper operation of the CLV. It is therefore an object of the invention to provide a CLV which is adapted for the connection of stoves.
[0004] The invention provides for this purpose a collective concentric flue duct CLV for connecting a plurality of stoves, wherein the CLV comprises an inner pipe for the discharge of flue gases and an outer pipe for the supply of combustion air, wherein the inner pipe extends further at the top than the outer pipe, wherein the outer pipe is closed at the bottom, and wherein the inner pipe is provided at the bottom with a water outlet, wherein a flue gas connecting element and a combustion air connecting element are provided for each of the plurality of stoves for connecting respectively a flue gas outlet and a combustion air inlet of the stove to respectively the inner pipe and the outer pipe of the CLV, wherein each flue gas connecting element is formed to guide moisture droplets from the flue gas outlet against the inner wall of the inner pipe.
[0005] The invention is based on the insight that a collective concentric flue duct (CLV) reacts wholly differently to condensation combustion devices and to stoves. Particularly the moisture content in the flue gases coming from the stove has a considerable influence on the operation of the CLV. In condensation combustion devices typically connected to a CLV the flue gases are relatively dry and no or hardly any condensation will occur in the CLV. The CLV can hereby be constructed on natural draught basis, i.e. in the case of such a CLV the inner pipe and outer pipe are typically open toward each other at the bottom of the CLV such that a natural draught occurs from outer pipe to inner pipe. This natural draught occurs on the one hand because of the height difference at the top of the CLV between inner pipe and outer pipe, because of the heat of the flue gases, and can be further affected by wind influences. The flue gases which enter the inner pipe of such a CLV, and which are typically dry, will be carried upward via the natural draught and thus leave the CLV via the top side of the central pipe part. The heat of the flue gases reinforces the effect of the drawing of the CLV.
[0006] When a stove is connected to such a CLV, wherein the stove is typically not a condensation combustion device and therefore sends relatively wet flue gases in the direction of the CLV, condensation will typically occur in the flue gas outlet and in the inner pipe of the CLV. Because moist air is heavier, the relatively wet flue gases will counteract the natural draught in the CLV, so that the CLV, which is conventionally open at the bottom, would cease drawing. A considerable quantity of condensate will further occur in the inner pipe of the CLV which, in a conventional CLV, has no way out. Tests have further indicated that when a flue gas outlet is connected in conventional manner via a flue gas connecting element to the inner pipe of the CLV, droplets of moisture drop downward in the inner pipe of the CLV and thus cause a ticking or tapping sound. Because the CLV typically extends through the whole building with multiple residential units, this ticking or tapping sound will also be audible in the whole building, this being unacceptable in respect of the comfort of the residents.
[0007] The CLV according to the invention is for the above reasons embodied wholly differently, wherein specific technical choices have been made to optimize operation of the CLV with stoves. The outer pipe of the CLV is for this purpose closed at the bottom. A natural draught will as a result not occur in the CLV per se. All air flowing through the CLV will also flow through the combustion device, in this case the stoves. In a conventional CLV heavy air could result in air sinking in the inner pipe of the CLV whereby, because of the connection of inner pipe and outer pipe at the bottom of the CLV, air rises in the outer pipe. However, because the outer pipe is closed at the bottom in the CLV according to the invention, this effect cannot occur in the CLV according to the invention and the heavy, relatively wet air from the stoves cannot disrupt proper operation of the CLV. The flue gas connecting element is further provided to guide moisture droplets from the flue gas outlet against the inner wall of the inner pipe. When moisture droplets are present against the inner wall of the inner pipe, they will roll downward along the inner wall. In contrast to droplets dropping downward in the inner pipe, the rolling of droplets against the wall will be scarcely audible and thus not cause any noise nuisance. The inner pipe is provided at the bottom with a water outlet such that condensed water can be discharged. All these technical choices allow for optimal operation of a CLV for stoves.
[0008] The flue gas outlet preferably drains in the direction of the CLV. Because a stove is not a condensation heating device, the flue gases will typically condense at least partially in the flue gas outlet and in the inner pipe of the CLV. By draining the flue gas outlet in the direction of the CLV it will be possible to discharge condensate from the flue gas outlet via the CLV. The CLV is optimized here to discharge condensed water from the flue gas outlet because the flue gas outlet is connected via a flue gas connecting element to the inner pipe, which flue gas connecting element is formed so as to guide moisture droplets from the flue gas outlet against the inner wall of the inner pipe. Condensate can hereby be discharged in an optimal and comfortable manner via the CLV. An indirect consequence hereof is that the stove can perform optimally, does not have to be provided with a condensed water discharge system and there is hardly any problem of condensate in the combustion chamber. It is noted in this context that condensate in the combustion chamber often has destructive consequences, and results for instance in paint layers or lacquer layers breaking off the metal from which the combustion chamber has been formed.
[0009] Each flue gas connecting element preferably has at least one convex surface at least on an underside of the connection between flue gas outlet and inner pipe. In contrast to sharp edges, convex surfaces tend to allow moisture droplets to roll over the surface instead of the moisture droplets dripping off. Moisture droplets can hereby be guided against the inner wall of the inner pipe in a technically simple manner by means of a convex surface extending between the inner side of the flue gas outlet and the inner side of the inner wall of the CLV.
[0010] The water outlet is preferably provided with a neutralizer for neutralizing a pH of condensed water before discharging the condensed water. Because of byproducts of the combustion process condensed water is typically acidic such that neutralization is desirable. Because of pH neutralization of the condensed water the condensed water can be discharged via public disposal systems such as sewers without adversely affecting the pipes.
[0011] The water outlet is preferably connected to a water discharge conduit. The water can be discharged automatically and continuously by the CLV via a water discharge conduit.
[0012] Each flue gas outlet preferably comprises an active flue gas extractor. Flue gases can be blown actively to the outside through the inner pipe of the CLV by the flue gas extractor. A further advantage of the flue gas extractor is that the flue gas extractor draws air through the stove. The result hereof is that the stove with combustion chamber is subjected to an underpressure. Because a combustion chamber and elements mounted thereon, such as flue gas outlet and combustion air inlet, can never be manufactured so as to be 100% airtight, it is an advantage to have an underpressure in the stove. This is because the underpressure ensures that possible soot, CO or other harmful byproducts of the combustion will not leak out of the stove into the surrounding spaces, or hardly so.
[0013] The flue gas extractor preferably comprises a fan and a valve, wherein the valve has a closed position and at least one extraction position. An advantage of having a valve in the flue gas outlet is that the valve can be closed, for instance when the stove is not in use. This will ensure that flue gases are from the inner pipe of the CLV, which come for instance from another stove connected to the CLV, cannot flow via the flue gas outlet into the stove which is not in use. The valve hereby ensures, in the closed position, that a first operating stove cannot affect a second non-operational stove. An optimal collective concentric flue duct for connecting a plurality of stoves can hereby be obtained.
[0014] Each flue gas extractor preferably has at least five extraction positions formed respectively by at least five different openings of the valve, wherein the flue gas extractor is controllable by a controller. Providing a plurality of flue gas extraction positions enables any extraction of flue gases from the stove to be controlled subject to the energy output of the stove and the operating characteristics of the CLV. It is noted here that in some situations a stove operates at a first energy output while other stoves in the building which are connected to the same CLV are not operating. The one operational stove will hereby have to take up a different flue gas extraction position than if the same stove were operating at the same energy output while all other stoves in the building are in operation.
[0015] Each stove preferably has infeed means for introducing a predetermined quantity of fuel into the combustion chamber, wherein the fuel is chosen from gas or pellets and wherein the controller controls the flue gas extractor on the basis of an input value related to the predetermined quantity of fuel or on the basis of a measurement from a sensor in the stove. The efficiency of the stove can in this way be optimized by controlling the flue gas extractor on the basis of an input value.
[0016] The invention further relates to a building with multiple residential units, which building has a collective concentric flue duct CLV for connecting a plurality of stoves according to the invention and a further collective concentric flue duct CLV for connecting a plurality of condensation heating devices. The building hereby has two CLVs, wherein a first CLV is optimized for the discharge of flue gases coming from a condensation combustion device, these typically being dry flue gases. The building has a second CLV which is constructed according to the invention and which is thereby optimized for the discharge of flue gases from a stove, this typically being a non-condensation combustion device with relatively wet flue gases.
[0017] The CLV is preferably placed, at least on the upper side, at a horizontal distance of at least 2 metres from the further CLV. This has the result that flue gases from the one CLV are not drawn in as combustion air by the other CLV, or hardly so. The two CLVs can hereby operate optimally and independently of each other.
[0018] The invention will now be further described with reference to an exemplary embodiment shown in the drawing.
[0019] In the drawing:
figure 1 shows a CLV according to an embodiment of the invention in which a stove is connected; and
figure 2 shows a flue gas extractor which can be applied in the invention.
[0021] Figure 1 shows a stove 1 with a combustion chamber 2 for a fuel. A stove is hereby defined as a heating device wherein the primary object is direct heating of the immediate area around stove 1. A stove is more preferably defined as a heating device wherein the secondary object is to achieve an aesthetically appealing combustion in stove 1. Combustion chamber 2 is for this purpose typically formed as a casing in which the combustion can take place and wherein at least a segment of the casing is formed by a transparent material, for instance glass. The transparent material has the function here of simultaneously allowing several people in the surrounding area to see the flames created during the combustion process.
[0022] Combustion chamber 2 further comprises a flue gas outlet 3 which is provided for discharge of the flue gases which are the consequence of the process of the combustion of the fuel. Combustion chamber 2 further comprises a combustion air inlet 4 for supplying air with which the combustion process is performed. In the embodiment as shown in figure 1 flue gas outlet 3 and combustion air inlet 4 are formed via a concentric pipe 5 such that a heat exchange takes place between the relatively cold supplied air and the relatively hot flue gases. The supplied air, which is supplied via combustion air inlet 4, is hereby preheated whereby the energy efficiency of stove 1 is increased. It is however noted in this context that it is not essential for flue gas outlet 3 and combustion gas inlet 4 to be formed concentrically. In residential environments for instance combustion air can be supplied from a location other than that where the flue gases are discharged. When CLVs are applied as shown in figure 1, it is also an option to provide flue gas outlet 3 and combustion air inlet 4 via separate pipes.
[0023] Shown in figure 1 is a stove which is provided for combustion of gas as fuel. Stove 1 is provided for this purpose with at least one gas injector 10. Stove 1 can alternatively be provided so as to burn pellets or wood. The advantage of gas or pellet stoves compared to wood stoves is that the supply of fuel, being respectively gas or pellets, is mechanically dosable in simple manner such that the energy value of the fuel introduced into the combustion chamber is controllable over time. This mechanical control of the fuel supply forms a good basis for also controlling, and preferably automating, the other parameters of the stove, such as energy output and efficiency. It will be apparent to the skilled person that the stated fuels are not limitative and that different types of stove can be designed to burn different types of fuel.
[0024] Several airflows, passive or active, are conventionally created in stoves which affect and seek to optimize the operation of the stove. Fuel is typically introduced into a lowest zone of combustion chamber 2. Primary air 6 is air which is introduced into the combustion chamber at, below or at least close to the fuel 7. Primary air 6 is in other words introduced into said lowest zone. Secondary air 8 is combustion air which is introduced into combustion chamber 2 at a height above the fuel. Secondary air 8 is in other words introduced above said lowest zone. Secondary air 8 is typically introduced along the sides of the combustion chamber or along the upper side of the combustion chamber into an upper zone of combustion chamber 2.
[0025] Tertiary air 9 is ambient air which is blown over an outer surface of combustion chamber 2 so as to be heated by the casing of combustion chamber 2, which heated air is then typically blown back into the surrounding area so as to thus heat the surrounding area. Tertiary air 9 does not enter combustion chamber 2 and does not therefore comprise any harmful substances which can be created by the combustion process. The ratio of primary air 6 and secondary air 8 is substantially fixed. The primary air 6 and the secondary air 8, together with the residual products of the combustion process, form the flue gases 12.
[0026] During the combustion process the quantity of primary and secondary air is preferably held in balance with the quantity of fuel introduced into the combustion chamber. Fuel typically comprises an amount of hydrocarbons which are converted during combustion substantially to water and carbon dioxide and, to limited extent, also possibly harmful byproducts. Necessary for the conversion of hydrocarbons to water and carbon dioxide is oxygen which is taken from the primary and secondary air. In this context excess air is used in the art. Excess air is defined as the effective ratio of oxygen/fuel divided by the stoichiometric ratio of oxygen/fuel. The excess air hereby denotes a surplus (or deficiency) of oxygen in the primary and secondary air after all hydrocarbons of the fuel have been converted to water and carbon dioxide. An excess of air of 1 means that all oxygen from the primary and secondary air has been used up in the conversion of the fuel to CO2 and H2O. This is a theoretical situation which can never be realized in practice. An excess of air greater than 1 will always have to be available in practice to allow the chemical reaction of hydrocarbons from the fuel to take place. The excess air can become too large, whereby too much oxygen is present in the primary and secondary air for converting the hydrocarbons. The volume of flue gases will hereby be greater than in the case of a lower excess of air. Because the quantity of flue gases is greater, the amount of energy discharged by means of the flue gases will also be greater. It is assumed here that a predetermined quantity of flue gases can transport a substantially fixed predetermined amount of energy. More incoming air will also have to be heated, so that more energy is lost. In addition, this also causes waste of fan energy when the airflow is actively driven. When the excess air is lower than 1, i.e. there are more hydrocarbons to be converted than there is oxygen to allow the reaction to take place, harmful byproducts such as soot will be formed because the combustion is then incomplete. This can also result in problems in start-up of the stove. An excess of air lower than 1 is therefore to be avoided. In order to maximize the energy efficiency of the stove and to optimize the combustion the goal is to achieve a minimal excess air greater than 1. A preferable goal is an excess of air greater than 1.05, preferably greater than 1.1, most preferably greater than 1.2. A more preferable goal is an excess of air of less than 1.9, preferably less than 1.7, more preferably less than 1.5. Excess air can conventionally be measured using a lambda probe at the location of the flue gas outlet for the purpose of measuring the remaining content of oxygen in the flue gases.
[0027] Figure 1 shows a flue gas extractor 11 in principle. Flue gas extractor 11 is provided for the purpose of active discharge of the flue gases 12. Via the flue gas extractor the flow rate of the discharged flue gases 12 can be determined, and the flow rate of the primary air 6 and the secondary air 8 can hereby also be determined, i.e. the primary air and secondary air together with the combustion products form the flue gases 12. Flue gas extractor 11 is placed at a distance from combustion chamber 2, this distance preferably being greater than 1 metre, more preferably greater than 2 metres and most preferably greater than 3 metres. Because flue gas extractor 11 is placed at a distance from the combustion chamber, the flue gases coming from combustion chamber 2 have the chance to cool at least partially before they pass through flue gas extractor 11. The temperature of the flue gas extractor will hereby not exceed a predetermined maximum operating temperature of the flue gas extractor. This cooling of the flue gases is further enhanced in the embodiment of figure 1 by the concentric pipe 5 which ensures that the heat of the flue gases is exchanged with the supplied combustion air, whereby the temperature of the flue gases in flue gas outlet 3 falls sharply. Flue gas extractor 11 is further set to control the combustion process in combustion chamber 2 in accordance with optimal excess air. An optimal excess air is defined here as an excess of air which is greater than 1 and which is minimal. The combustion of the fuel is hereby complete because the excess air is greater than 1, and the total quantity of flue gases is minimal because the excess air is minimal. As a result of the minimal quantity of flue gases the energy from combustion chamber 2 carried by the flue gases to flue gas outlet 3 is also minimal, whereby the temperature at the location of flue gas extractor 11 remains within predetermined limits.
[0028] The advantage of using a flue gas extractor 11 which is placed in flue gas outlet 3 is that the flue gas extractor draws the air out of combustion chamber 2 and pushes it to the chimney (not shown; the location where the flue gases are blown into the ambient air). Because flue gas extractor 11 draws air out of the combustion chamber, an underpressure will be created in the combustion chamber. It is noted in this context that it will never be possible to manufacture 100% airtight combustion chambers 2 and associated connections of flue gas outlet 3 and combustion air inlet 4. Because combustion chamber 2, and hereby also the flue gas outlet and combustion air inlet connected thereto, are subjected to an underpressure by flue gas extractor 11, flue gases cannot leak to the surrounding area. A considerable safety advantage is hereby achieved.
[0029] Shown in figure 1 is how flue gas outlet 3 and combustion air inlet 4 are connected to a CLV 14. A CLV is a collective feed of air and discharge of combustion gases which is typically applied in buildings with multiple residential units in order to allow a plurality of combustion devices to be connected to one chimney. CLV 14 comprises an inner pipe 15 and an outer pipe 16. Inner pipe 15 is provided for the purpose of upward discharge of flue gases 12. The inner pipe is open for this purpose at the top of the CLV. Inner pipe 15 preferably extends higher at the top than outer pipe 16 in order to prevent flue gases 12 blown out of the inner pipe being drawn in by the outer pipe as combustion air 13. Inner pipe 15 is provided at the bottom with a water outlet 19. A water outlet 19 is optionally provided with a pH neutralizer 20. Water outlet 19 is provided so as to be connected to sewer 21, optionally with a pH neutralizer 20 between outlet 19 and sewer 21. Inner pipe 15 is closed off from air at the bottom such that flue gases 12 cannot leave the inner pipe at the bottom. The skilled person will be familiar with different principles for closing a pipe off from air such that water can however be discharged, such principles being generally applied in water outlets for washbasins and toilets.
[0030] CLV 14 further comprises an outer pipe 16 which is closed 17 at the bottom. Because outer pipe 16 is closed 17 at the bottom, air cannot flow directly from outer pipe 16 to inner pipe 15. CLV 14 as shown in figure 1 will hereby not display any natural draught when the combustion devices connected thereto are not in operation.
[0031] A moisture guide 18 is placed at the position of the connection of flue gas outlet 3 to inner pipe 15 of CLV 14. Moisture guide 18 is provided so as to guide moisture droplets from flue gas outlet 3 to the inner side of inner pipe 15. In a first embodiment moisture guide 18 has for this purpose a convex surface on which extends between the wall of flue gas outlet 3 and the inner side of inner pipe 15 of the CLV. Because of the convex surface moisture will not have the chance to drip off and drop downward in inner pipe 15 of the CLV. Downward falling droplets would cause an unacceptable noise nuisance in the building in which CLV 14 is placed. Having the droplets roll downward along the inner side of inner wall 15 prevents this noise nuisance. The skilled person will appreciate that different moisture guides 18 can be designed to prevent droplets forming and dropping downward in inner pipe 15. According to a further embodiment a moisture guide 18 can thus be formed by a succession of surfaces having an obtuse angle relative to each other so that droplets can roll from the one surface to the other without dripping off the edge between the surfaces. On the basis of the described effect, i.e. guiding moisture droplets from flue gas outlet 3 to the inner wall of inner pipe 15, it will be apparent to the skilled person which connections will suffice here and which will not. This result can also be tested in simple manner by introducing a minimal flow of water into the flue gas outlet and then testing whether the minimal flow of water drips in inner pipe 15 or runs off against the inner side. The minimal flow of water is selected here such that it is representative of the amount of condensed water present in the flue gases from the stove at maximum energy output.
[0032] In order to optimize discharge of condensate out of flue gas outlet 3 the flue gas outlet 3 is preferably placed in draining manner. This means that the horizontal distance between stove 1 and CLV 14 spanned by flue gas outlet 3 is placed in draining manner. Flue gas outlet 3 will specifically have to have a gradient of at least 1% over at least 70% of the horizontal distance between stove 1 and CLV 14. The skilled person will appreciate how flue gas outlet 3 can be formed in draining manner in order to guide condensate occurring in flue gas outlet 3 away from stove 1 and to inner pipe 15 of the CLV.
[0033] Figure 2 shows a possible embodiment of flue gas extractor 11. Figure 2 shows here how flue gas outlet 3, which is the inner pipe of concentric pipe 5, is separated at the position of flue gas outlet 11 from the combustion air inlet 4 formed by the outer pipe. This allows a module to be placed in the flue gas outlet which comprises a fan 22 and a valve 23, preferably a throttle valve 23. Valve 23 preferably has a closed position and a plurality of open positions. The closed position is preferably used when the stove is not in operation such that flue gases which are present in inner pipe 15 of the CLV, and which come for instance from other stoves connected to CLV 14, cannot be blown through the flue gas outlet to combustion chamber 2 of the non-operational stove. The valve with closed position hereby allows a plurality of stoves to be connected to one CLV. The plurality of open positions of valve 23, in co-action with the active fan 22, will result in a plurality of corresponding flow rates of flue gases flowing through the flue gas extractor. The flow rate of the flue gases can be controlled by adjusting the open position of valve 23. The skilled person will be familiar with the general principle of controlling and adjusting airflows by means of a combination of a fan and a valve. This will not therefore be explained in further detail in this description.
[0034] Valve 23 and fan 22 placed in flue gas outlet 3 together form flue gas extractor 11. Fan 22 and valve 23 are preferably connected operatively to a controller of stove 1. Fan 22 and valve 23 are placed in a position on the basis of input parameters of stove 1 or on the basis of measurement data from sensors in or on stove 1. A lambda probe can for instance be used to control flue gas extractor 11. It will be apparent to the skilled person that this control of valve 23 and fan 24 by the controller (not shown) can be implemented in different ways, for instance on the basis of a table wherein respective positions of valve 23 are related to corresponding settings or input parameters or sensor values of stove 1. Valve 23 can alternatively be controlled on the basis of an algorithm in which one or more of the following values serve as basis for calculating the valve position: input parameters of the valve position, measurement values of sensors in the stove.
[0035] Shown in figure 1 is a simple mechanism for indirect measurement of an excess of air in combustion chamber 2. The excess air is determined on the basis of temperature measurement performed by a temperature sensor 24 on gas injector 10. This measurement principle is based on the insight that the temperature of gas injector 10 is related to the excess air. Tests and studies have shown that this is the result of the substantially fixed ratio of primary air 6 and secondary air 8. This operation of the temperature sensor will be elucidated on the basis of several examples. The airflow through stove 1 can be optimized on the basis of the temperature sensor. This is possible by means of controlling a flue gas extractor 11 in the embodiment of stove 1 of figure 1. This is also possible however in other embodiments of stoves wherein the airflows through stove 1 are controlled in other ways. There are therefore stoves which have a blower at the position of the air inlet to blow air through the stove, which blower can be controlled on the basis of temperature sensor 24. Stoves also exist which influence a passive airflow, for instance on the basis of natural draught of the chimney, by opening and closing a valve, which valve can then be controlled on the basis of temperature sensor 24.
[0036] In a first example illustrating the operation of temperature sensor 24 a lean gas on the one hand and a rich gas on the other are introduced into combustion chamber 2 as fuel. A lean gas has considerably fewer hydrocarbons than a rich gas, whereby the lean gas also requires less air 6, 8 for combustion compared to the rich gas. When a first predetermined quantity of air is introduced into combustion chamber 2 for combustion of the lean gas, a first gas mixture will result from mixing the lean gas with the first quantity of primary air 6. This first gas mixture will have a ratio of hydrocarbons - oxygen lying very close to the ignitable ratio because relatively few hydrocarbons are present in the lean gas. As a result the first gas mixture will ignite very closely to injectors 10 in combustion chamber 2, whereby the injectors become warmer because the flame comes close to the injectors. When a rich gas is mixed with the same quantity of primary air 6 a second gas mixture will result from mixing the first quantity of primary air 6 and the rich gas. This second gas mixture will however have a ratio of hydrocarbons - oxygen which is still some way from the ignitable ratio because a relatively large amount of hydrocarbons are present in the rich gas. A considerable amount of secondary air 8 will hereby have to be added to the second gas mixture in order to combust the mixture. As a result the second gas mixture will only ignite at an appreciable distance from the injectors, whereby the injectors become less warm.
[0037] By adjusting the flue gas extractor in the case of the lean gas to a lower setting, at which fewer flue gases are discharged, less air will be supplied and, because the ratio of primary air 6 and secondary air 8 is substantially constant, less primary air 6 will therefore be added to the lean gas upon injection 10 thereof. Because less primary air 6 is added, the first gas mixture will be further from the ignitable ratio of hydrocarbons - oxygen, whereby the mixture ignites higher in combustion chamber 2. The temperature of injector 10 will hereby fall because the flames occur further away from injector 10. This first example shows how the airflow through combustion chamber 2 can be controlled on the basis of temperature sensor 24 in order to optimize the excess air in accordance with the type of gas introduced into the combustion chamber as fuel.
[0038] A further example shows how the airflow through combustion chamber 2 can be controlled on the basis of temperature sensor 24 in order to compensate external effects on the airflow. The maximum airflow will thus depend in the case of a self-drawing chimney on weather conditions and other factors. A resistance in flue gas outlet 12 will also occur in the case of a CLV system when multiple devices are operating simultaneously, whereby a flue gas extractor 11 will have to overcome a higher pressure on the side of CLV 14. Use is made in this second example of a flue gas extractor 11 which is in a first position and wherein the chimney draught is such that the airflow through combustion chamber 2 is relatively large. In a similar situation the same flue gas extractor 11 is placed in the same position but flue gas extractor 11 is connected to a CLV 14 to which other stoves are connected and are in operation such that the pressure in the inner pipe of the CLV is also high. A relatively low quantity of air will hereby flow through combustion chamber 2.
[0039] In the case of the self-drawing chimney the relatively high quantity of air will flow through combustion chamber 2, whereby a relatively large quantity of primary air 6 is also mixed with the gas. Because a relatively large quantity of primary air 6 is mixed with the gas, the ratio of hydrocarbons - oxygen in the mixture lies close to the ignitable range. The mixture will hereby ignite close to the injector and the temperature measured by temperature sensor 24 will be high. Flue gas extractor 11 can hereby be set to a lower position whereby less air will flow through combustion chamber 2.
[0040] In the case of the CLV with high pressure in the inner pipe relatively little air will flow through combustion chamber 2 and less primary air 6 will also be mixed with the gas. The mixture of primary air and gas will hereby have a ratio of hydrocarbons - oxygen which is still some way from the ignitable ratio. As a result a further considerable quantity of secondary air 8 will have to be mixed with the mixture before the mixture can ignite or combust. The mixture will hereby ignite higher in the combustion chamber, whereby the temperature measured by temperature sensor 24 will be relatively low. In such a case the flue gas extractor 11 can be adjusted to a higher setting in order to draw more air through combustion chamber 2, whereby the resistance in inner pipe 15 is compensated.
[0041] Both examples are based on a gas stove. It will however be apparent to the skilled person that other types of stove, such as wood stoves and pellet stoves, also facilitate a combustion process wherein a ratio of hydrocarbons and oxygen must come within an ignitable range before flames are formed. The quantity of primary air and the energy density of the fuel will also influence this ratio in other types of stove. It will therefore also be possible to control an excess of air on the basis of a temperature sensor placed in a lowest zone of another type of stove. The use of temperature sensor 24 to determine the excess air is therefore not limited to gas stoves.
[0042] The above described examples show that a good indication can be obtained of an excess of air in combustion chamber 2 on the basis of a temperature sensor 24 in a lowest zone of combustion chamber 2. The excess air may then be influenced here by the operation of the chimney and/or flue gas outlet and/or combustion air inlet, or the excess air can be influenced by the energy properties of the fuel, and a good control of the excess air can always be obtained on the basis of temperature sensor 24. It is noted here that a temperature sensor can be provided easily and inexpensively in stove 1.
[0043] Figure 1 shows two embodiments of temperature sensors 24. A first temperature sensor 24 is shown on an underside of injector 10. A second embodiment of the temperature sensor is indicated with reference numeral 24' and is placed on an upper side of injector 10. The controller (not shown) is preferably connected to temperature sensor 24 and/or 24' and provided with a control mechanism for controlling the airflow through combustion chamber 2 to a lower flow rate when the temperature of temperature sensor 24 rises above a predetermined value or above a predetermined temperature range. The controller is also provided with a control mechanism for controlling the airflow through combustion chamber 2 to a higher flow rate when temperature sensor 24 measures a temperature lying below a predetermined value or below a predetermined temperature range. The temperature value and/or the temperature range will preferably be determined here by the manufacturer of the stove, for instance on the basis of tests, taking into account the exact position of the temperature sensor or temperature sensors 24, taking account of the structural properties of stove 1 and taking account of the type of fuel for which the stove is designed.
[0044] The description and the figures serve only to illustrate the principles of the invention. It will therefore be appreciated that a skilled person can deviate from the different setups which may or may not have been explicitly shown and described above and which comprise the principles of the invention. All examples described herein are further intended solely for the purpose of illustrating the invention and aiding the reader in properly understanding the principles of the invention. The examples will not be limitative here to the scope of protection. All statements describing principles, aspects and embodiments of the invention and specific examples thereof are here also understood to comprise equivalents thereof. The scope of protection of the present invention will therefore be defined solely by the following claims.
1. Collective concentric flue duct (CLV) for connecting a plurality of stoves, wherein
the CLV comprises an inner pipe for the discharge of flue gases and an outer pipe
for the supply of combustion air, wherein the inner pipe extends further at the top
than the outer pipe, wherein the outer pipe is closed at the bottom, and wherein the
inner pipe is provided at the bottom with a water outlet, wherein a flue gas connecting
element and a combustion air connecting element are provided for each of the plurality
of stoves for connecting respectively a flue gas outlet and a combustion air inlet
of the stove to respectively the inner pipe and the outer pipe, wherein each flue
gas connecting element is formed to guide moisture droplets from the flue gas outlet
against the inner wall of the inner pipe.
2. Collective concentric flue duct (CLV) as claimed in claim 1, wherein the flue gas
outlet drains in the direction of the CLV.
3. Collective concentric flue duct (CLV) as claimed in any of the foregoing claims, wherein
each flue gas connecting element has at least one convex surface at least on an underside
of the connection between flue gas outlet and inner pipe.
4. Collective concentric flue duct (CLV) as claimed in any of the foregoing claims, wherein
the water outlet is provided with a neutralizer for neutralizing a pH of condensed
water before discharging the condensed water.
5. Collective concentric flue duct (CLV) as claimed in any of the foregoing claims, wherein
the water outlet is connected to a water discharge conduit.
6. Collective concentric flue duct (CLV) as claimed in any of the foregoing claims, wherein
each flue gas outlet comprises an active flue gas extractor.
7. Collective concentric flue duct (CLV) as claimed in claim 6, wherein each flue gas
extractor comprises a fan and a valve, wherein the valve has a closed position and
at least one extraction position.
8. Collective concentric flue duct (CLV) as claimed in claim 7, wherein each flue gas
extractor has at least five extraction positions formed respectively by at least five
different openings of the valve, wherein the flue gas extractor is controllable by
a controller.
9. Collective concentric flue duct (CLV) as claimed in claim 8, wherein each stove has
infeed means for introducing a predetermined quantity of fuel into the combustion
chamber, wherein the fuel is chosen from gas or pellets and wherein the controller
controls the flue gas extractor on the basis of an input value related to the predetermined
quantity of fuel or on the basis of a measurement from a sensor in the stove.
10. Building with multiple residential units, which building has a collective concentric
flue duct (CLV) for connecting a plurality of stoves as claimed in any of the foregoing
claims and a further collective concentric flue duct (CLV) for connecting a plurality
of condensation heating devices.
11. Building as claimed in claim 10, wherein the CLV is placed, at least on its upper
side, at a horizontal distance of at least 2 metres in relation to the further CLV.