SMOKE ROTATION SYSTEMS
TABLE OF CONTENTSFurnace chimneys (chimneys, channels) are, on the one hand, like a kind of channel, moving along which combustion products pass from the firebox to the chimney; on the other hand, they serve as the internal heat-absorbing surface of the furnace, which should absorb as much heat as possible from the gases passing through the smoke circuits, transfer this heat to the external surface of the furnace due to thermal conductivity and then transfer it to the room air and surrounding objects by radiation, as well as convection and conduction .
In this regard, furnace smoke circulation should:1) have a sufficiently developed inner heat-receiving surface and a corresponding outer heat-transfer surface;
2) to ensure uniform distribution of heat throughout the furnace mass, preferably with its predominant concentration in the lower zone of the furnace;
3) represent the smallest gas resistance for the passage of flue gases.
Let us consider in detail all the existing smoke circulation systems of the especially important role they play in the design of the furnace.
As noted earlier, despite all their apparent diversity, they can be reduced to the following four main types:
1) a multi-turn system with a sequential passage of flue gases through the channels;
2) a single-breasted system with one ascending and many descending channels;
3) channelless system;
4) system with predominant lower heating.
The system of multi-turn serial channels, in turn, consists of vertical and horizontal channels with a possibly significant extent in series and thereby take away more heat from the gases.
The system of multi-turn successive vertical channels (see Fig. 4 above) is characterized by the fact that flue gases form in the furnace space and rise upwards with one lifting channel; having reached the upper gas, they also go down along one channel; leaning to the surface of the roof above the firebox, the gases again rise up through the adjacent channel, etc., making a series of successive turns upwards into the pipe, the number of which in practice varies from 3 to 8. This is the device of the well-known "Dutch" furnace. which led the inventor of this system, was to make the flue gases come into contact with the walls of the furnace chimneys for as long as possible and thereby take more heat from the gases.
The main disadvantages of this system are the following:
1) The large length of the path traversed by flue gases presents a significant resistance to their movement, in addition to a significant number of turns. To overcome this resistance, it is necessary to have a strong draft in the chimney, which, as you know, is created, on the one hand, by the height of the chimney, and on the other hand, by the temperature difference between the flue gases and the outside air. The first condition - the height of the pipe - in most cases is determined by the height of the building and cannot be changed (5-6 m for one-story and 8-9 m for two-story buildings). To fulfill the second condition, it is necessary to have a high temperature of the exhaust gases. The latter circumstance is unfavorable, since it leads to an increase in the heat losses of the furnace, significantly reducing the efficiency.
2) The temperature of the flue gases gradually decreases as they move along the revolutions of the furnace. The most heated gases pass through the first flame channel, the less heated gases pass through the second, even cooler gases pass through the third, etc.) Accordingly, the outer heat-releasing surface of the furnace is heated in the same sequence. The parts closest to the furnace heat up unacceptably, while the most distant ones warm up weakly, that the heating of the furnace surfaces occurs very unevenly.
3) Uneven heating of the furnace mass usually entails yourself cracking of the masonry in the weakest parts (very often, due to the inevitable design features in multi-turn furnaces, the first most heated flame channel and the last chimney, the most poorly heated, are next to each other). Through the formed cracks, flue gases and flames are emitted, which leads to indoor air pollution and causes a fire hazard.
The system of multi-turn serial horizontal channels, as shown above in fig. 5, consists in the fact that the flue gases, having risen in one ascending channel to the very top of the furnace, then fall down to overlap the firebox with several horizontal channels interconnected by short vertical segments.
This smoke circulation system has all the disadvantages inherent in a system with vertical sequential smoke circulations, and moreover, it has its own: the horizontal sections of the chimneys, slowing down the speed of gases in them, contribute to the stratification of the gas flow and increased soot deposition in them up to their complete clogging. It is necessary to install cleaning doors in each horizontal stroke.
The gas resistance of furnaces with a multi-turn channel system is relatively high and varies depending on the number of revolutions from 1.2 to 2.5 mm water. Art.
b) Single turn system with one ascending and many parallel descending channels.
Compared with the considered multi-turn channel systems, this system (Fig. 6) has a number of advantages:
All downcomers are washed by gases of approximately the same temperature, which determines the uniformity of heating along the perimeter of the outer heat-releasing surface of the furnace.
Due to the presence of a more spacious path for gases (gases move through all downcomers at once), the resistance of the smoke circuits is negligible, and the furnace can operate with a lower temperature of the exhaust gases. In this case, heat losses are minimal.
If for the correct operation of a furnace with successive channels it is necessary to release gases into a chimney with a temperature of 200-250 °, then for the normal operation of a furnace with parallel downcomers, the temperature of the exhaust gases can be reduced to 120-130 °, i.e. almost twice. Hence, the losses with the exhaust gases become much smaller.
Uniform heating of the heat-releasing surface of the furnace in a system with parallel downcomers is ensured by the fact that gases pass through them at the same temperature. Overheating of one of the channels to the detriment of others cannot take place due to the self-regulating property that this system has.
It consists in the following: the lag in the heating of one of the channels can obviously be caused by the fact that the gases passing through this channel receive more cooling; but in this case, their specific gravity increases, as a result of which their fall begins to proceed at a greater speed, which in turn will cause an increased influx of a fresh portion of hot gases in this channel, which will restore the disturbed thermal equilibrium.
The same happens in channels that are accidentally overheated: due to a decrease in the specific gravity of flue gases, the influx of new gases automatically decreases and their heating decreases.
This is not what happens in a system consisting of several walking channels; accidental overheating of one of them causes an increased influx of hot gases here, which even more exceeds the temperature of the channel walls and leads to further intensification. influx of hot gases and, consequently, an increase in the temperature of the furnace surface.
The gas resistance of furnaces with one ascending and vhymn parallel descending channels is relatively large and ranges from 1.0 to 1.2 mm water. st
c) Channelless (non-circulating or hood) smoke circulation system.
The essence of this system lies in the fact that gases, upon exiting the firebox through a hail located in the ceiling of the firebox, enter the upper chamber-bell, equipped with either buttresses or a brick nozzle. Having reached the overlap of the chamber, the gases spread along the sides, come into contact with the walls or the nozzle, cool and, having become heavy, fall down, and then go into the chimney (Fig. 7).
The movement of gases occurs freely, without coercion: the most heated and light gases float up, and cooled as heavier ones fall down and go through the chimney into the atmosphere; there is no forced "dragging" of gases through smoke circulations, which is observed in duct systems.
It follows that the gas resistance of such a furnace is negligible, and the uniformity of heating of the walls along the perimeter of the furnace is almost ideal.
The best cross-sectional shape of a ductless furnace is round, as it most closely matches the natural shape of the gas flow. However, other oven shapes such as square and rectangular are also allowed in this system.
The disadvantage of this system, according to its author prof. Grum-Grzhimailo is a stronger heating of the top of the furnace.
The thermal profile of furnaces with top heating (which include channelless furnaces) is shown in fig. 30. It can be seen from it that the top of the furnace is subjected to predominant heating. This is a disadvantage of both this system and the single-turn system.
The chimney draft force sufficient for the successful operation of channelless furnaces is only 0.80-1.0 mm water. Art.
d) A system with predominant bottom heating is characterized by the fact that the bottom of the furnace warms up noticeably more .
This can be achieved in two ways:
I) In small furnaces, this is an inevitable constructive value, since the walls of the firebox, which are most strongly heated, are at the same time the outer walls of the furnace.
2) In large furnaces, this is achieved by passing the most heated flue gases directly from the firebox through channels located in the lower part of the furnace. In this case, the release of gases from the firebox is done either on one or on the bottom of the side.
An even greater effect in terms of heating the bottom of the furnace is obtained by passing hot gases through channels passing under the firebox and ash pan.
The thermal profile of the furnace with bottom heating is shown in fig. 32. It shows how much more the lower part of the furnace warms up compared to the top.
However, such a forced attraction of hot gases downwards at the moment when they, having the greatest inertia, tend upwards, does not pass without the expenditure of some energy; the gas resistance of furnaces increases at the same time to 1.8-2.0 mm water. Art. From this it should be concluded that furnaces with bottom heating may be recommended for installation only in cases where there is complete confidence in the presence of constant good traction, for example, in the lower floors of two-story and multi-story buildings or in one-story buildings, but with a pipe height of at least 6-7 m. In the absence of the necessary draft, such stoves often smoke during kindling, especially when the relatively high outside temperature does not provide adequate draft.
THE PROCESS OF HEAT RECEPTION, HEAT TRANSFER AND HEAT STORAGE IN HEATING FURNACES. MOVEMENT OF FLUE GASES IN THE CHANNELS
a) Te I left acceptance by the walls of the furnace. The duration of the furnace furnaces of large and medium heat capacity varies
usually within 1 to 2-2.5 hours. - when heating with wood, peat, husk, I from 2.5 to 5-6 hours. - for heating with coal and anthracite.
During this short period of time, the walls of the firebox and smoke circulations accumulate the entire amount of heat that the stove gives off to the room air in the next 24 or 12-14 hours.
To accomplish this task, the walls of the firebox of smoke circulations must have a sufficiently developed heat absorption surface. However, in this area we still do not have completely reliable and experimentally verified data.
Obviously, only one thing is that they are not equivalent in terms of the degree of heat absorption. Thus, the walls of the firebox, washed by gases of a higher temperature and exposed to the radiant heat of burning fuel (the so-called direct recoil), absorb heat more intensively than the walls of smoke circulations. , completely devoid of the influence of radiant heat and washed by gases of a lower temperature.
Thermal perception of the internal surfaces of the furnace
Dimensions sections smoke channels are usually accepted multiples ½ brick or 1 brick. Dimensions less than ½ brick unwanted for fear of contamination them soot or carryover from the firebox.
The thickness of brick partitions between individual channels is usually taken as 1/2 brick. The device of internal partitions in 1 / 4 bricks is not recommended due to their fragility, rapid heating during the heating of the furnace and the inability to accumulate the required amount of heat due to their low massiveness.
The most common flue sizes are:13x13 cm(1/2 x ½brick);13x19cm ( 1 / 2 X 3 / 4brick);13x25 cm (1/2 x 1brick). Only in large furnaces or as flame channels of conventional furnaces are channels of size25x25cm (1x1brick) and25x38cm (1 x 1 ½ bricks).
The speed of movement of flue gases in the channels, depending on the purpose of the latter, is usually taken as follows:
1st (heat channel) 5-7 m/s
2nd smoke channel and subsequent downcomers
vertical channels from 0.2 to 2.0 m/s
Horizontal channels 1.0 - 2.3
b) The nature of the movement of flue gases in the channels. In horizontal channels, the speed of movement of gases below the specified norm is not recommended, because at low speeds, soot is deposited to a large extent on the bottom of the channel. In addition, with a significant height of the channel and an insufficient amount of flowing gases, stratification of the hotter part of the channel, inflow, can occur, i.e., a phenomenon in which the hottest gases rise and stay at the top, while cold air can stagnate below; the temperature of the walls of such a channel will not be the same along the height.
To fully understand the picture of the movement of gases through the channels of the furnace, we present several comparisons. So, for example, when pouring water from one glass into another, the second glass is substituted under the first; when a gas lighter than air is poured, the second glass, filled with gas, is held upside down above the first glass.
When water flows through a channel, it first of all fills and stays in its lower part up to a certain level (Fig. 35); it is completely unnecessary to close the channel from above with a lid. The same, only in reverse order, is also observed when flue gases flow through a horizontal channel. If there is not much gas, then it fills only its upper part; the level of the gas flow is located below, under the gas.
Additional devices and accessories used in indoor ovens
Holes (windows) in the walls of the firebox (Fig. 53). Holes are small windows sized 3x7 or 7x7, arranged in the back or side walls. furnace fireboxes and communicating furnace space with side flues. They are additional passages of gases along with with main course through hailo or flame windows. Holes are used only in ovens with internal firebox surrounded by sinkhole system or channelless camera - cap.
Their purpose is to remove part of the combustion gases during the combustion of the furnace directly into the side chimneys and thereby increase the temperature of the bulk of the flue gases, which are already sufficiently cooled from contact with the walls of the furnace. This increases the heating of the outer walls of the furnace, falling against the holes, as it were, the zone of maximum heating of the furnace decreases and the latter approaches in its properties to furnaces with lower heating. At the same time, the places on the walls of the chimneys, which fall against the very holes, warm up especially well (Fig. 53, a). The deviation of parts of the gas flow from the main direction into the boreholes was verified and proved by the works of VTI, and the very idea of using them was proposed by Eng. Podgorodnik, the closest collaborator of prof. Groom-Grzhimailo.
In the channelless furnaces developed by Eng. Podgorodnik, boreholes simultaneously increase the temperature of excessively cooled flue gases to the required extent when they exit into the pipe and thereby contribute to increased draft (see Album of indoor stoves compiled by engineer Podgornik, ed. Selkhozproekt).
After closing the chimney, the boreholes perform a different purpose: during the cooling period of the furnace, the gases and air remaining in the furnace circulate through the boreholes (Fig. 53, (5), while the heat accumulated in the firebox and in the afterburner is transferred to the outer walls of the furnace. When When the valve is not tightly closed, the air sucked in the firebox overflows through the boreholes and goes into the chimney, without cooling either the firebox itself or its overlying parts.
b) Air (wind) chambers and retreats. In large furnaces, which are of considerable size in plan, their internal array, heated by the revolutions passing there, does not come into contact with the outside air, and therefore the heat accumulated by it does not have a direct exit to the room. In order to extract this heat, the furnace array is cut through by air channels and chambers that communicate with outside air and room air.
On fig. 54 shows a furnace with two through-air chambers in its upper part and two through-air (channels) at the bottom.
According to the normative data given earlier, the heat transfer of the walls of the air chambers decreases against the heat transfer of the open surfaces of the furnace by 25-50%, depending on the design.
Cameras as shown in fig. 54, open on both sides, completely before feet for inspection and dust removal. This is in full compliance with the existing sanitary and hygienic requirements, on the basis of which the installation of closed and inaccessible cameras is prohibited. If desired, these air chambers can be equipped with opening doors so that access to them is not compromised. The same applies to two small products.
The harmful effect of organic dust lies in the fact that, settling on highly heated brick surfaces of chimneys, this dust burns, releasing gaseous products of dry distillation into the air, irritating the mucous membranes of the eyelids, nostrils and oral cavity.
In order to be able to clean closed air channels and chambers in the outer walls of the furnace, cleaning holes provided with doors are left at the top and bottom of these chambers or against the channels.
It is also completely unacceptable to install “fire” air vents, that is, those that are embedded in smoke channels. Such a device is very dangerous in terms of waste. When the pipe is closed early, when the coals in the depths of the firebox have not yet completely burned out, with the furnace door closed, carbon monoxide (CO) is formed and stagnates in the upper part of the smoke circuits. When you open a ventilator placed in the upper part of the furnace chimneys, this gas enters the room and poisons the human body, which often leads to death.
According to the accepted custom, the furnace is almost always installed near the inner or outer wall of the room, it turns out that one, and sometimes two walls of the furnace are facing the walls of the building. In order to use the heat transfer of these walls, furnaces are built not close to the wall, but with some indentation, which is why the very space between the furnace wall and the wall of the room is called "indentation".
The retreat, in turn, is closed on both sides with walls a quarter or half a brick thick, and rejects are left in the lower and upper parts of the seal, closed by opening gratings. Room air circulates through these openings, while the room air, as colder, enters through the lower grate, and warmed in the indentation exits through the upper grate.
Since the recesses are the same air chambers as a heating wall, the requirement for the accessibility of inspection and cleaning from dust remains valid for them, as for the chambers.
c) Heads of chimneys and wind vanes. Wind under certain conditions can have a great influence on the draft in the chimneys of furnaces, in some cases contributing to its strengthening, and in others causing a weakening and even overturning of the draft.
A careful study of the nature of the effect of wind on draft in pipes has led to the invention of devices by which the harmful effects of wind can be transformed and used to increase draft.
Let us consider three possible cases of wind impact on a chimney ending at the top with a horizontal plane.
First case: the wind has a horizontal direction. In this case, the horizontal jets of air at the top of the pipe at point A meet with normal to them, deflected pipe walls and other upward air jets. Further movement of air above the plane of the pipe occurs along the resultant R of both of these directions. In this case, flue gases are sucked from the pipe, and the thrust consequently increases.
Second case: Wind blows at an angle to the horizon from bottom to top.
In this case, as can be seen from the drawing, the direction of the resultant R makes an even larger angle with the horizon than in the previous case, and the suction effect of the wind increases even more.
Thirdhappening. The wind moves at an angle to the horizon from top to bottom. Expanding the wind direction into horizontal and downward vertical, we see that the horizontal component of wind pressure L should have the same effect as in the first case.
The vertical term TO, acting in the direction opposite to the flow of flue gases, tends to weaken, stop or (depending on the strength and speed of the wind) overturn it.
The magnitude of the effect of wind on the draft in the pipe can be determined as follows:
Given: h- pipe height in m;f- section of the pipe in m;t°- flue gas temperature; t- outside air temperature.
It is required to determine at what wind speed X, blowing at an angle in to the horizon, the wind will be able to stop the draft in the pipe.
Such a wind is not uncommon in our country, and therefore it becomes obvious that in the practice of heating a furnace, especially in one-story buildings, where the height of the chimney does not exceed 8.0 m, the phenomenon of hampered traction and even overturning of the latter can occur quite often.
All draft devices installed above pipes must protect the latter from atmospheric precipitation and are divided into two groups: 1) stationary devices and 2) devices with rotating parts.
The first group includes caps, umbrellas and deflectors of various designs. To the second - weather vanes, turning on a vertical axis under the influence of the wind.
On fig. 61 shows the simplest pyramidal umbrella - a cap, which is a fairly reliable device for enhancing traction.
On fig. the Volpert deflector is shown, and in fig. Grigorovich, which is an improvement of the Volpert deflector. The upper branch pipe of the Grigorovich deflector has the shape of a truncated cone, and the umbrella consists of two cones connected by a base.
On fig. 64 shows a weather vane. Conical or cylindrical nozzle BUT, motionlessly reinforced by the upper section of the brick
pipes, ends with a second cylindrical branch pipe put on it, equipped with a socket FROM. The top nozzle can freely rotate 360°, being fixed on a movable vertical axis D, which can be lifted m and guide P hidden inside the device.
To install the bell in the desired direction, a sail-weather vane connected to it tightly is used. F, which is always installed downwind and at the same time sets the bell under vacuum.
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What the very first chimneys were, of course, one can only guess, but it is not difficult to judge them by the stoves that were used even before the middle of the last century. But even when installing a modern gas boiler, you can’t do without a chimney. However, it should be noted that assembling a chimney for a gas boiler is much easier than laying out this design for a traditional stove.
If it is more profitable for a gas boiler to install a metal chimney, then for a wood-burning stove the best option is a brick construction. If the brick pipe is strictly vertical, then most of the heat will go outside.
Many of you have probably heard the name horizontal chimney? No, we do not mean a chimney for a gas boiler "pipe in pipe", located horizontally and designed to remove combustion products from a gas boiler with forced draft. Such chimneys are called coaxial.
Verticality is not always justified
Today we will talk about the device of horizontal stove chimneys and the intricacies of their device.
If a solid fuel or gas boiler is designed to heat radiators, which, in turn, give off heat into the room, everything is clear with their chimneys, the more vertical, the better.
More doesn't mean better
On what principle does a conventional brick oven work? Heated bricks give off their heat inside the room. Accordingly, the greater the maximum length of the heated brickwork, the more heat enters the room.
But this does not mean at all that it is imperative to build a large oven. It is simply necessary to have such a device of the furnace, in which the heat received from the combustion of fuel will be used as much as possible.
Snake is an effective solution
This is how chimneys appeared, arranged according to the “snake” principle, or, more simply, multi-turn chimneys, the length of which is many times greater than the length of a straight pipe.
There are multi-turn chimneys vertical and horizontal. In vertical multi-turn chimneys, the location of the main channels is directed strictly vertically. The main disadvantage of such a chimney is uneven heating.
In contrast, a multi-turn horizontal chimney warms up much more efficiently. Since hot gases tend upwards, and the upper area of a horizontal chimney is much larger than that of a vertical chimney, respectively, heating is carried out much better using the same volume of fuel.
Three basic rules
Folding a multi-flue chimney for a furnace is much more difficult than assembling a modular flue system for a gas boiler. When performing work, you must follow strict rules:
- The cross section of the chimney must be strictly the same size throughout the chimney.
- Sharp corners inside the chimney must be minimized.
- Observe the smoothness of the inner surface.
At first glance, these are very simple rules, but how can you follow them in practice?
Brick and chimney - dimensions matter
Faced with the laying of a horizontal chimney for the first time (see), even an experienced craftsman can get stuck when following these rules.
But let's look at everything in order.
- Standard brick has a size 250×120×65 mm. What do we have in this case?
- It is clear that half of the brick will have a size of 1 25×120×65 mm. Since we are blocking the horizontal section of the chimney with bricks, we have decided on the size 125 mm.
- Since the height of the brick is 65 mm, it becomes clear that to create one channel, you will need to lay out two rows, 65+65=130 , add to this two solution layers.
Our chimney will have a section 125×125×140 mm. This is very important to remember, since when laying this kind of chimneys, many make a gross mistake.
If the horizontal part of the chimney they have a size 125×125×140 mm, then the maximum length of the vertical section of the smoke circulation is arranged completely arbitrarily, i.e. the way it works.
This should not be allowed if, when laying the last brick of the floor, the size of the vertical transition does not correspond to the above parameters, cut the brick to comply with the size. Again, this is very important.
Twists - Methods for Solving the Problem
The next question is the minimization of sharp corners. If we imagine the movement of combustion products inside the chimney as a water flow, it becomes clear that turbulences will occur at the sharp corners of the brickwork, preventing the normal movement of gases and, as a result, a deterioration in draft.
The only correct solution in this case will be to smooth out sharp corners inside the chimney.
Considering the transitions inside the chimney, it is clear that it is possible to smooth out sharp corners only on the very overlap of the smoke channel. This is done by simply chipping the sharp corners of the brick. This must be done very carefully and accurately.
Our advice: use an electric grinder to smooth out the sharp edges of the brick. So much faster, and the result will be much better.
There is a stove - there will be a chimney
The figure shows the part of the furnace for which it is necessary to arrange a horizontal chimney.
As mentioned earlier, we must comply with all the dimensions of the internal section. If experience in this kind of work is not enough, then you can build a pattern of the appropriate size. With it, it will be possible to successfully control the entire process of laying bricks.
As previously mentioned, the size of the section of the inside of our chimney will be 125 × 125 × 140 mm.
Setting up a horizontal channel
- To do this, we lay two rows of bricks in such a way that we get a horizontal chimney channel. The figure makes it clear how to do this. Bricks are laid in the usual way for brickwork.
- The only thing that is required is strict adherence to the thickness of the seams. Since a difference of a few millimeters does not play a big role in an ordinary brick wall, in a chimney this difference will lead to a change in the internal section of the chimney.
- Therefore, when laying each brick, carefully check and adjust the thickness of the seam and the horizontal laying. This can be done using the building level.
If necessary, the brick is knocked out with a rubber-tipped hammer or a conventional hammer with a wooden backing. We remind you that the thickness of the seam we have 3 mm.
Overlay preparation
The chimney channel is ready. Overlay needs to be done. To do this, we will prepare a channel. We lay another row according to the scheme shown in the figure.
Now everything is ready for laying the floor. What else is important to know. When laying bricks, carefully monitor the protruding mortar. All protruding solution must be carefully removed.
Internal seams should be completely filled with mortar whenever possible. The disadvantages of the solution form additional steps, on which soot will subsequently accumulate.
Floor brick - skill, skill, desire, training
How to lay floor bricks correctly? This requires some skill and knowledge. Getting Started:
- We apply a brick without mortar and determine the part that is inside the chimney channel at speed.
- With the help of a grinder, we round off sharp corners as shown in the early diagram.
Our advice: since not all bricks are rounded, you can prepare the required amount at once, according to the chimney diagram. If necessary, they can always be cut to size.
- As for the solution. When laying floor bricks, the mortar is applied to the brick being laid and in no case to the masonry bricks.
- Attach a brick and determine which parts it is in contact with the chimney masonry. As can be seen from the figure, it adjoins the masonry with one full bonder and spoon part and half of the pastel.
- Apply the solution to these parts and spread as evenly as possible. Please note that in order for the brick not to sink to the sides, there should be a little more mortar around the edges than in the center.
- The solution is applied to the brick upside down. When the solution is applied, we lay the brick and press it tightly with the spoon and bonder part.
Accuracy Matters
Then, using the level, we make the necessary measurement. If necessary, knock out the brick with a rubber mallet. In no case should you hit the part above the smoke channel.
You can support the brick from below with one hand and carry out the necessary manipulations. Thus, the entire row fits. In the end, you should get as shown in the picture.
Again, when laying the last floor brick, check the size of the vertical turn. If necessary, trim the brick just enough so that the vertical channel matches the size of the horizontal channel.
Reference: observance of the dimensions of the smoke channel is the key to a good and efficient operation of the chimney.
Now everything can be repeated in the opposite direction. This is how the entire chimney fits.
Soot: brick or doors
In such a chimney, a soot issue will necessarily arise. The main disadvantage of such a chimney is the need for a large number of cleaning doors ().
Doors greatly reduce the efficiency of the chimney. Uneven heating of brick walls and metal doors leads to large temperature differences inside the chimney and, as a result, to a deterioration in draft.
Our advice: instead of metal doors, install knockout bricks. Of course, this will complicate the maintenance of the chimney a little, but in any case, it will significantly improve its performance.
The work does not require haste. The main thing in the construction of this chimney is attentiveness and accuracy. Using the above tips and tricks, you can successfully build a horizontal chimney for your stove.
The largest amount of heat goes into the chimney with a vertical chimney design. You can make the heating unit more energy efficient with the help of a horizontal flue duct. In the furnace, it must simultaneously rise up, which is why the horizontal chimney is a snake. The upper walls of its horizontal sections are heated most strongly, and the vertical parts have a small height. Thus, this design leads to good heating of the walls and significantly increases the heat transfer of the stove or fireplace.
More about horizontal chimney
A horizontal channel has a surface area several times larger than a straight vertical one. Gases tend to rise, thanks to natural traction, but for this they have to overcome a long way: constantly turn left, right, go through horizontal sections. That is why this design is called multi-turn. It is arranged only in brick chimneys of stoves and fireplaces.
The work should be done by an experienced stove-maker, as it is necessary to correctly position the turns, roundings, and folds. It is these structural elements that create areas of high resistance due to the fact that the gases change direction. It should be remembered that these places sharply reduce traction, therefore turning the corners of the brick into rounds is very important. To do this, they are chipped off at the masonry stage, and it is better to clean them to a smooth oval surface with a grinder.
Standard Design Parameters
During the laying of the furnace and smoke ducts, the design parameters must be observed. For example, the horizontal section of the chimney must have a certain cross-sectional size, which is undesirable to change at one's own discretion. The cross section of the passages depends on the design and power of the heating unit, while the values \u200b\u200bare selected from the following standards:
- 260x260 mm (brick x brick size),
- 260x130 mm (brick x half brick),
- 130x130 (half brick x half brick).
Why is it impossible to take other parameters of the chimney channels? The cross section above the norm leads to a slowdown in the movement of gases, because of this it will be necessary to increase the size of the furnace and the entire furnace. Also, the slow movement of gases leads to the fact that they cool down even in the chimney. As a result, its walls do not heat up enough, the heat transfer of the unit decreases.
As a result, condensation appears on the walls of the chimney. It contains acid, which eventually destroys the masonry. In addition, condensate is moisture, and soot will begin to stick to it. The walls of the chimney become clogged, the diameter decreases and, ultimately, the draft decreases, which leads to the release of gases into the room.
The cross section of the flue passages below the norm leads to overheating of the chimney and the appearance of cracks in the masonry. The temperature of the gases rises to 300ºC with a maximum rate of 140ºC. Overheating will not increase the energy efficiency of the stove and will not heat up the room even more. At the same time, it can lead over time to destruction and the need to shift the pipe.
Equally important is the length of each horizontal channel. The speed and temperature of the gases leaving the furnace also depend on it. As a standard, in a chimney 8 bricks wide, the length of the channel is made in 3 masonry units. Wherein according to the norms, it should not exceed 0.5 m.
Requirements for cleaning horizontal channels
It should be noted that stoves with a horizontal chimney require regular and more frequent cleaning than other designs. To do this, cleaning doors are made in its side wall. Their number corresponds to the number of channels, since each door is located opposite one of them. Thus, this design is characterized by the largest number of cleanings. As a standard, 4 horizontal channels and 4 cleaning doors are made.
However, it should be understood that this number is not mandatory, since it depends on the parameters, dimensions of the furnace and chimney. Knockout bricks are an alternative to cleaning doors. It is believed that they retain heat better and increase the efficiency of the chimney. Also, the same structure of materials will lead to uniform heating of the surface. Metal doors have a different heating temperature with bricks. This leads to a temperature drop, a weakening of traction.
Masonry features
It is important that the thickness of the seams does not exceed 5 mm. It is better if the stove-maker can keep a thickness of no more than 3 mm. An increase in the parameter leads to a decrease in the internal dimensions of the pipe. During work, the horizontal position of the masonry is constantly monitored by the building level. A rubber mallet is used to knock out bricks. It is forbidden to knock bricks from top to bottom.
The overlap of the horizontal channel is done in the following sequence:
- One side of the channel should be one brick laying higher. This will ensure that it is positioned as a bed on the smaller side and end-to-end with the opposite side.
- The prepared brick is laid on the bottom wall so that it is docked flush with the opposite wall with its butt side. This is a fitting of a brick, which is mandatory.
- Then, on the bonding side of the brick and on the lower wall of the channel, put the solution in an even layer. The brick is pressed, and the mixture that has come out of the seams is immediately removed.
- It should be remembered that the last brick must have rounded and polished corners on the underside. It is better to process them directly during laying, and if this is done in advance, the exact number of such bricks should be calculated. The next channel is arranged in the opposite direction.
Requirements for horizontal chimneys
The angles inside the channel lead to turbulence of gases, and soot settles on its walls. Chimneys of this design are characterized by the highest degree of soot formation, so their inner surface should be as smooth as possible. The cross section of the channel should not change throughout. For masonry, only refractory bricks and mortar are used, the characteristics of which correspond to the following parameters:
- gas tight structure
- maintaining tightness,
- resistance to condensate and its acids.
The horizontal part of the chimney is equipped in heating and cooking furnaces, in which the design provides for a drying chamber. It is its location above the horizontal channels that provides optimal conditions for drying. Also, this type of chimney is the main one in the construction of drying ovens. It should be noted that heating units of this design are rarely laid, since the work is considered difficult and requires experience. The weight of such furnaces is the largest compared to other options.
Designs of smoke circulations and the movement of flue gases.
We will not dwell on the theory of the movement of flue gases in furnaces, but only briefly describe some useful information that a novice stove-maker needs to know about. After all, we are not going to lay out our own design of the furnace. This is fraught with many errors that can make your oven inoperable. But when using ready-made and time-tested oven drawings this information may be useful to you.
So, the firebox. What is important to know about it? The combustion of fuel takes place in the firebox and its walls take most of the heat load. All the heat that is released during combustion is distributed as follows: part of the heat is spent on draft formation, the other part is accumulated in the walls of the firebox itself, and part of the heat from the burnt fuel is accumulated in the walls of the channels through which flue gases pass. The more such channels, the more heat remains in kiln array, but, in fact, the less heat remains for the formation of the thrust itself.
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If you have to deal with the phrase "horizontal chimney" you should understand it correctly. The entire structure, from the firebox in the furnace to the outlet in the pipe on the roof, is a chimney-chimney. And since the difference in height between the firebox and the chimney on the roof is several meters, it is obvious that “horizontal chimney” is the name of the part of the structure located somewhere between the firebox and on the roof.
A horizontal section appears in such cases:
- When it is necessary to connect the furnace to a vertical pipe located at a distance. A typical case - the stove or fireplace is in the house, and the pipe is outside. A horizontal pipe from a stove or fireplace passes through the wall and connects to a vertical pipe from the outside, forming horizontal part of the chimney.
- When the goal is to increase the heat transfer of the furnace by using the heat of the furnace gases. In this case, the combustion products do not just fly out, but go through a winding path in a specially designed chimney. Since the surface accompanying such a path is much larger than in the vertical chimney connecting the furnace and the pipe on the roof, it is significantly more and heat dissipation of the stove.
How to make a "snake"
The benefit of increasing heat turns into a significant complication of the design and laboriousness of manufacturing a horizontal chimney, which is identical in appearance to the "coil" pipe, which is present in almost every bathroom in apartment buildings. Each change in direction in such a snake is called a “turn”, and the chimney itself, if there are several such changes in direction, is called a multi-turn.
Since the horizontal section leads to a deterioration in traction, it is not recommended to make this section longer than one meter. There are also other additional requirements:
- throughout the length cross-sectional area multi-turn chimney must be the same.
- Transitions from horizontal sections to vertical sections must be rounded.
- The inner surface should be maximum smooth and even.
The listed requirements are aimed at obtaining maximum draft in a multi-turn chimney.
In such a chimney, it is possible by increasing the temperature of the furnace gases in it. As a result, the characteristics of the stove as a whole will improve, especially the duration of burning wood. In this case, the chimney will be used as chamber for afterburning furnace gases. To do this, in the lowest horizontal part closer to the firebox, a separate overlapped tube should be installed, the other end of which should be located just below the furnace blower door. Air will flow through the tube, and the furnace gas will effectively burn out in the chimney.
Read also: Installation of a chimney on the roof
How to effectively remove blockages
But in addition to problems with the deterioration of traction, another most unpleasant problem is added. Such winding chimneys are difficult to clean from accumulated ash. Therefore, softwood firewood, which leads to a rapid clogging of the chimney, cannot be used in the stove. In order to gain access for cleaning, the following are installed at the turning points:
- special metal doors;
- removed bricks.
But the listed traditional solutions for cleaning the chimney are very time consuming and cause pollution of the room. Today you can solve the problem of cleaning differently. On the roof, on the pipe, install a smoke exhauster and use a chemical soot remover in the furnace of the stove. If you regularly produce in this way cleaning, the house will always be warm and clean.
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