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Thermophysical properties Gaseous combustion products needed to calculate the dependence of various parameters from the temperature of this gas environment can be set based on the values \u200b\u200bgiven in the table. In particular, the specified dependences for heat capacity were obtained in the form:

C PSM \u003d A -1/ D.,

where a. = 1,3615803; b. = 7,0065648; c. = 0,0053034712; d. = 20,761095;

C PSM \u003d A + bT SM. + ct. 2 SM.,

where a. = 0,94426057; b. = 0,00035133267; c. = -0,0000000539.

The first dependence is preferred by the accuracy of the approximation, the second dependence can be adopted for calculating less accuracy.

Physical parameters flue gases
(for P \u003d. 0.0981 MPa; r CO2 \u003d 0.13; p. H2O \u003d 0.11; r N2 \u003d 0.76)

Appendix 3.

(reference)

Air and smoke permeability of air ducts and valves

1. To determine the leaks or drowshes of air, the following formulas obtained by approximation of tabular data can be used in relation to the ventilation channels of the scene systems:

for class H air ducts (in the pressure range of 0.2 - 1.4 kPa): ΔL. = but(R - b.) fromwhere ΔL. - Sumps (leaks) of air, m 3 / m 2 · h; R - pressure, kPa; but = 10,752331; b. = 0,0069397038; from = 0,66419906;

for air ducts class P (in the pressure range of 0.2 - 5.0 kPa): where a \u003d. 0,00913545; b \u003d. -3,1647682 · 10 8; c \u003d. -1.2724412 · 10 9; d \u003d 0,68424233.

2. For fire-fighting normally closed valves, the number values \u200b\u200bof the specific characteristic of the resistance to smoke-permeation depending on the temperature of the gas correspond to the data obtained during the standing firing tests of various products on the experimental base of VNIIPO:

Heat combustion. The lowest heat combustion of dry gaseous fuel QF varies widely from 4 to 47 mJ / m3 and depends on its composition - the ratio and quality of combustible and non-combustible

Components. The smallest value of QF in the domain gas, the average composition of which is about 30% composed of combustible gases (mainly carbon oxide CO) and approximately 60% of non-combustible nitrogen N2. Most

The value of QF in associated gases, which is characterized by an increased content of heavy hydrocarbons. The heat of the combustion of natural gases varies in the narrow range QF \u003d 35.5 ... 37.5 MJ / M3.

The lower heat of the combustion of individual gases included in the composition of gaseous fuels is given in Table. 3.2. On methods for determining the heat of combustion of gaseous fuel, see section 3.

Density. There are absolute and relative gas density.

The absolute density of the RG gas, kg / m3, is the mass of gas, which comes on 1 m3 of this gas in this gas. When calculating the density of a separate gas, the volume of its kilometer is taken equal to 22.41 m3 (as for the perfect gas).

The relative gas density Rott is the ratio of the absolute gas density under normal conditions and similar air density:

Rott \u003d Rg / PV \u003d RG / 1,293, (6.1)

Where Rg, re - respectively, the absolute density of gas and air under normal conditions, kg / m3. The relative density of gases is usually used to compare various gases among themselves.

Values \u200b\u200bof absolute and relative density simple gases Led in Table. 6.1.

The density of the PJM gas mixture, kg / m3 is determined on the basis of the additivity rule, according to which the properties of gases are summed up by their volume fraction in the mixture:

Where xj is the volumetric content of the 7th gas in the fuel,%; (RG); - the density of the j-th gas included in the fuel, kg / m3; The number of individual gases in the fuel.

The values \u200b\u200bof the density of gaseous fuels are shown in Table. P.5.

The density of gases p, kg / m3, depending on temperature and pressure, can be calculated by the formula

Where P0 is the gas density under normal conditions (T0 \u003d 273 K and P0 \u003d 101.3 kPa), kg / m3; P and T-, respectively, valid pressure, kPa, and absolute gas temperature, K.

Almost all kinds of gaseous fuel are lighter than air, so when leakage, the gas accumulates under the floors. For security reasons before starting the boiler, the absence of gas is checked in the most likely places of its cluster.

Gas viscosity increases with increasing temperature. The values \u200b\u200bof the dynamic viscosity of the r, PA-C, can be calculated by the Siezer Empirical Equation - Lend

Table 6.1

Characteristics of gas fuel components (at T - O ° C CHR \u003d 101.3 kPa)

Where P0 is the coefficient of the dynamic viscosity of the gas under normal conditions (g0 \u003d 273 K and P0 - 101.3 kPa), PA-C; T - absolute gas temperature, K; C is a coefficient depending on the type of gas, K, is accepted in Table. 6.2.

For a mixture of gases, the dynamic viscosity coefficient can be approximately determined by the viscosity values \u200b\u200bof individual components:

Where the GJ is a mass fraction of the j-th gas in fuel,%; The dynamic viscosity of the j-th component, PA-C; P is the number of individual gases in the fuel.

In practice, the coefficient of kinematic viscosity V, M2 / C, which
ry associated with dynamic viscosity p through the density p dependence

V \u003d p / p. (6.6)

Taking into account (6.4) and (6.6), the coefficient of kinematic viscosity V, m2 / s, depending on pressure and temperature, can be calculated by the formula

Where V0 is the coefficient of the kinematic viscosity of the gas under normal conditions (th \u003d 273 K and P0 \u003d 101.3 kPa), m2 / s; p and g-respectively valid pressure, kPa, and absolute gas temperature, k; C is a coefficient depending on the type of gas, K, is accepted in Table. 6.2.

The values \u200b\u200bof kinematic viscosity coefficients for gaseous fuels are shown in Table. P.9.

Table 6.2.

The viscosity and thermal conductivity coefficients of gas fuel components

(at t \u003d 0 ° С Ir \u003d 101.3 kPa)

Thermal conductivity. Molecular power transfer in gases is characterized by the thermal conductivity coefficient 'K, W / (M-K). The thermal conductivity coefficient is inversely proportional to the pressure and increases with increasing temperature. The values \u200b\u200bof the X coefficient can be calculated by the Formula of the Seorerand

Where X, 0 is the coefficient of thermal conductivity of the gas under normal conditions (g0 \u003d 273 K and PO \u003d 101.3 kPa), W / (M-K); P and T-, respectively, the valid pressure, kPa, and the absolute temperature of the gas, K; C is a coefficient depending on the type of gas, K, is accepted in Table. 6.2.

The values \u200b\u200bof thermal conductivity coefficients for gaseous fuels are shown in Table. P.9.

The heat capacity of the gaseous fuel classified by 1 m3 of dry gas depends on its composition and in general defined as

4l \u003d 0. , 01 (CH2N2 + SS0 +

SSN4SH4 + CSO2Cog + - + Cx. X;), (6.9) where CH2, CRs0, schsch, ss02, ..., cx. - heat capacity of components of fuel components, respectively hydrogen, carbon monoxide, methane, carbon dioxide and / th component, KJ / (M3-K); H2, CO, CH4, C02, ..., xG--

The heat capacity of the combustible components of gaseous fuels is shown in Table. P.6, non-combustible - in table. P.7.

The heat capacity of wet gaseous fuel

SGGTL, KJ / (M3-K) is defined as

<тл = ctrn + 0,00124cHzq йтля, (6.10) где drTn- влагосодержание газообразного топлива,

Explosion. A mixture of combustible gas with air in certain proportions in the presence of fire or even sparks can explode, i.e., the process of its ignition and combustion at a speed close to the speed of sound propagation occurs. Explosive combustible gas concentrations in air depend on the chemical composition and gas properties. Volumetric concentration limits of ignition for individual combustible gases in the mixture with air are previously shown in Table. 6.1. Hydrogen has the widest limits of ignition (4 .. .74% by volume) and carbon oxide (12.5 ... 74%). For natural gas, the averaged lower and upper limits of ignition are 4.5 and 17%, respectively; for coke - 5.6 and 31%; For domain - 35 and 74%.

Toxicity. Under toxicity, the ability of gas to cause poisoning of living organisms. The degree of toxicity depends on the type of gas and its concentration. Most dangerous gas components in this respect are carbon monoxide and hydrogen sulfide H2S.

The toxicity of gas mixtures is mainly determined by the concentration of the most toxic component present in the mixture, with its harmful effect, as a rule, is noticeably enhanced in the presence of other harmful gases.

The presence and concentration in the air of harmful gases can be determined by a special instrument - a gas analyzer.

Almost all natural gases do not smell. To detect gas leakage and safety measures, natural gas before admission to the highway is odds, that is, is saturated with a substance having a sharp smell (for example, mercaptans).

The heat of combustion of various fuels fluctuates widely. For fuel oil, for example, it is over 40 mJ / kg, and for domain gas and some fuel flask brands - about 4 MJ / kg. The composition of energy fuels also varies widely. Thus, the same qualitative characteristics depending on the type and fuel brand can be sharply different between themselves quantitatively.

Specified fuel characteristics. For comparative analysis in the role of characteristics, generalizing the quality of fuel, the given fuel characteristics,% -KG / MJ, are used, which are generally calculated by the formula

Where hg is an indicator of the quality of work fuel,%; Q [- Specific heat combustion (lower), MJ / kg.

So, for example, to calculate the above

Humidity of sulfur sulfur s "p and

Nitrogen N ^ p (for the working condition of the fuel)

Formula (7.1) acquires the following form,% -KG / MJ:

Toc O "1-3" h z kp \u003d kl gt; (7.2)

4F \u003d l7e [; (7.3)

SNP. \u003d S '/ ї; (7.4)

^ p \u003d n7 q [. (7.5)

As a visual example, the following comparison is indicative of the incineration of various fuels in the boilers of the same thermal power. So, a comparison of the reduced humidity of the coal

Brands 2B (WјP \u003d 3.72% -KG / MJ) and Nazarov

2b coal (W ^ p \u003d 3.04% -KG / MJ) shows that in the first case the amount of moisture entered into the fuel boiler firebox will be about 1.2 times more than in the second, despite the fact that the working humidity in the coal near Moscow (W [\u003d 31%) is less than that

Nazarovsky coal (WF \u003d 39%).

Conditional fuel. In the energy sector to compare the efficiency of fuel use in various boiler installations, the concept of conditional fuel is introduced to plan the production and consumption of fuel in economic calculations. This fuel is accepted as a conditional fuel, the specific heat of the combustion (lower) of which in the operating state is equal to qy t \u003d 29300 kJ / kg (or

7000 kcal / kg).

For each natural fuel, there is a so-called dimensionless thermal equivalent E, which may be greater or less than one:

Wet air is a mixture of dry air and water vapor. In the unsaturated air, the moisture is in a state of overheated steam, and therefore the properties of wet air can approximately be described by the laws of ideal gases.

The main characteristics of wet air are:

1. Absolute humidity g.determining the amount of water vapor contained in 1 m 3 wet air. Water steam occupies the entire volume of the mixture, so the absolute humidity of the air is equal to mass 1 m 3 of water vapor or density of steam, kg / m 3

2. The relative humidity of the air j is expressed by the ratio of absolute humidity of the air to the maximum possible moisture content at the same pressure and temperature or the ratio of the mass of the water vapor concluded in 1 m 3 of wet air, to the mass of the water vapor required for the total saturation of 1 m 3 wet air Under the same pressure and temperature.

Relative humidity determines the degree of air saturation in moisture:

, (1.2)

where - the partial pressure of the water vapor, corresponding to its density of PA; - the pressure of a saturated pair at the same temperature, PA; - the maximum possible amount of steam in 1 m 3 saturated wet air, kg / m 3; - pair density during its partial pressure and humid air temperature, kg / m 3.

The ratio (1.2) is valid only when it can be assumed that the pairs of liquid is the perfect gas up to saturation state.

The density of wet air R is the amount of densities of water vapor and dry air in partial pressures in 1 m 3 of wet air at a humid air temperature T.To:

(1.3)

where is the density of dry air during its partial pressure in 1 m 3 of wet air, kg / m 3; - partial pressure of dry air, PA; - Gas constant of dry air, J / (kg × k).

Expressing both the equation for the condition for air and water vapor, we get

, (1.5)

where is the mass flow of air and water vapor, kg / s.

These equalities are valid for the same volume V. Wet air and the same temperature. Sharing the second equality on the first, we get another expression for moisture content

. (1.6)

Substituting the values \u200b\u200bof gas constant for air J / (kg × K) and for water vapor J / (kg × K), we obtain the value of moisture content, expressed in water vapor kilograms per 1 kg of dry air

. (1.7)

Replacing the partial air pressure of the magnitude, where from the previous one and IN - barometric air pressure in the same units as r, I get for wet air under barometric pressure

. (1.8)

Thus, at a given barometric pressure, the moisture content of air depends only on the partial pressure of the water vapor. Maximum possible moisture content in the air, from where

. (1.9)

Since saturation pressure grows with a temperature, then the maximum possible amount of moisture, which may be contained in the air depends on its temperature, the greater the higher the temperature. If equations (1.7) and (1.8) solve relatively and, then we get

(1.10)

. (1.11)

The volume of wet air in cubic meters per 1 kg of dry air is calculated by the formula

(1.12)

Specific volume of wet air v., m 3 / kg is determined by dividing the volume of wet air on a mass of a mixture per 1 kg of dry air:

Wet air as a coolant is characterized by enthalpy (in kilodzhoules per 1 kg of dry air), equal to the amount of dry air enthalpy and water vapor

(1.14)

where is the specific heat capacity of dry air, KJ / (kg × K); t. - air temperature, ° C; i. - Enthalpy of superheated steam, KJ / kg.

Enthalpy 1 kg of dry saturated water vapor at low pressures is determined by the empirical formula, KJ / kg:

where - a permanent coefficient, approximately equal to the enthalpy of the pair at 0 ° C; \u003d 1.97 kJ / (kg × K) - specific steam heat capacity.

Substituting meanings i. In the expression (1.14) and taking the specific heat capacity of dry air permanent and equal to 1.0036 kJ / (kg × K), we will find the enthalpy of wet air in kilodzhoules per 1 kg of dry air:

To determine the parameters of wet gas, similar to the equation discussed above are used.

, (1.17)

where is the gas constant for the gas under study; R - Gas pressure.

Entalpy Gas, KJ / kg,

where is the specific heat capacity of the gas, KJ / (kg × K).

Absolute moisture content of gas:

. (1.19)

When calculating contact heat exchangers for coolants of air-water, you can use the data Table. 1.1-1.2 or calculated dependencies to determine the physicochemical parameters of air (1.24-1.34) and water (1.35). For flue gases, data Table can be used. 1.3.

Waste gas density, kg / m 3:

, (1.20)

where - the density of dry gas at 0 ° C, kg / m 3; MG, M P is molecular weights of gas and steam.

The dynamic viscosity coefficient of wet gas, PA × C:

, (1.21)

where is the dynamic viscosity coefficient of water vapor, PA × C; - coefficient of dynamic viscosity of dry gas, PA × C; - mass concentration of steam, kg / kg.

Specific heat capacity of wet gas, KJ / (kg × K):

The coefficient of thermal conductivity of wet gas, W / (M × K):

, (1.23)

where k. - Indicator adiabat; IN - coefficient (for monatomic gases IN \u003d 2.5; For diatomic gases IN \u003d 1.9; For trochatomic gases IN = 1,72).

Table 1.1. Physical properties of dry air ( r \u003d 0,101 MPa)

The thermophysical properties of dry air can be approximated by the following equations.

Kinematic viscosity of dry air at a temperature from -20 to +140 ° C, m 2 / s:

PA; (1.24)

and from 140 to 400 ° C, m 2 / s:

. (1.25)

Table 1.2. Physical properties of water in saturation state

Density of wet gas, kg / m 3.

When the furnace device ideally, I want to have a design that automatically gave so much air as it is necessary for burning. At first glance, this can be done using a chimney. Indeed, the more intense firewood burns, the more hot flue gases should be, the greater should be the thrust (model of the carburetor). But it is not. The thrust does not depend on the amount of hot flue gases formed. The thrust is the pressure drop in the pipe from the tube's tank before the fuel. It is determined by the height of the pipe and the temperature of the flue gases, or rather, their density.

The thrust is determined by the formula:

F \u003d A (P B - P D) H

where F is the traction, and the coefficient, P B is the density of the outer air, P d - the density of flue gases, H is the height of the pipe

The density of flue gases is calculated by the formula:

p d \u003d p in (273 + t c) / (273 + t)

where T B and T D is the temperature in degrees Celsius of external atmospheric air outside the pipe and flue gases in the pipe.

The speed of movement of flue gases in the pipe (volume consumption, that is, the suction capacity of the pipe) G. It does not depend on the height of the pipe and is determined by the difference between the temperature of the flue gases and the outer air, as well as the cross-sectional cross section of the chimney. Hence the number of practical conclusions.

FirstlyThe flue pipes are made high at all in order to increase the air flow through the fifthly, but only to increase the thrust (that is, the pressure drop in the pipe). It is very important to prevent overturning of the thrust (muffling of the furnace) with a winddrop (the magnitude of the thrust should always exceed the possible wind backup).

Secondly, adjust the air flow is conveniently using devices that change the area of \u200b\u200bthe live cross section of the pipe, that is, with the help of valves. With an increase in the cross-sectional area of \u200b\u200bthe chimney channel, for example, twice - you can expect a roughly twofold increase in the volumetric air flow through the fuel.

Let us explain it a simple and visual example. We have two identical ovens. We combine them in one. We obtain a double furnace with a twin-lasting firewood, with two-time air consumption and cross-sectional pipe. Or (which is the same) if more than a firewood flare up in the fifuel, then you need to open the valves on the pipe more and more.

ThirdlyIf the stove burns normally in the steady mode, and we will add cold air stream by the burning firewood in the fifthly, the flue gases will come immediately, and air flow through the oven will be reduced. At the same time, burning firewood will begin to fade. That is, we seem to directly on firewood do not affect and send an additional flow by firewood, and it turns out that the pipe can skip less flue gases than before, when this additional air flow was absent. The pipe itself will reduce the flow of air on firewood, which was previously, and besides, it does not allow the additional flow of cold air. In other words, the smoke tube is running.

That is why it is so harmful to cold air superstar through the slots in the flue pipes, unnecessary air flows in the fuel cell and indeed any heat luminosity in the chimney, leading to a decrease in the temperature of the flue gases.

FourthThe greater the coefficient of gas-dynamic resistance of the chimney, the less air flow. That is, the walls of the chimney are preferably carried out as smooth, without twist and without turns.

FifthThe smaller the temperature of the flue gases, the more sharply changes the air flow during fluctuations in the temperature of the flue gases, which explains the situation of the stripping of the pipe under the ignition of the furnace.

At sixth, at high flue gas temperatures, air flow depends on the temperature of the flue gases. That is, with a strong overest of the furnace, the air flow ceases to increase and begins to depend only on the cross section of the pipe.

Issues of instability arise not only when analyzing the thermal characteristics of the pipe, but also when considering the dynamics of gas flows in the pipe. Indeed, the chimney is a well filled with light chimneys. If this light flue gas rises up not very fast, then the likelihood is not excluded that heavy outer air can simply drown in the light gas and create a falling downstream in the pipe. This is especially likely to such a situation with the cold walls of the chimney, that is, during the overseas oven.

Fig. 1. Gas movement scheme in a cold chimney: 1 - a fuel; 2 - air supply through pissed; 3-smoke trumpet; 4 - catch; 5 - Fireplace tooth; 6-smoke gases; 7-failing cold air; 8 - Air flow, causing tipping thrust.

a) smooth open vertical pipe
b) tube with a valve and tooth
c) pipe with top valve

Solid arrows - directions of movement of light hot flue gases. Dotted arrows - direction of movement of downward flows of cold heavy air from the atmosphere.

On the fig. 1A. The oven is schematically depicted in which the flue gases are supplied. 6. If the cross section of the pipe is large (or the flux gas speed of the flue gases), as a result of any fluctuation to the pipe begins to penetrate the cold heavy air 7, reaching Even a fuel. This incident flow can replace the "regular" air flow through confused 2. Even if the furnace is locked to all the doors and all the flaps of the air intake holes will be closed, then the oven can burn due to the air from above. By the way, it is as often as it happens when driving coal with the door closed furnaces. It may even happen complete tipping of thrust: the air will come on top through the pipe, and the flue gases - go out through the door.

In fact, on the inner wall of the chimney, there are always irregularities, thickening, roughness, with whose flue gases and counter-downward cold air flows are placed and mixed with each other. A cold downstream air flow is pushed out or, heating, begins to rise up a mixed-up with hot gases.

The effect of deploying downstream cold air fluxes is enhanced in the presence of partially open valves, as well as the so-called tooth, widely used in the manufacture of fireplaces. fig. 1B). The tooth prevents the flow of cold air from the pipe into the fireplace space and thereby prevents the smelting of the fireplace.

The downstream air flows in the pipe are especially dangerous in foggy weather: the flue gases are not able to evaporate the smallest droplets of water, cooled, the thrust is reduced and can even tilt. The oven is very smoking, it does not flare up.

For the same reason, stoves with raw smoky pipes strongly smoke. To prevent the occurrence of downlinks, top valves are particularly effective ( fig. 1V.), regulated depending on the speed of flue gases in the chimney. However, the operation of such valves is inconvenient.

Fig. 2. The dependence of the excess air coefficient is from the time of the furnace protest (solid curve). The dotted curve is the required air flow rate G of the Potch for the complete oxidation of firewood products (including soot and volatile substances) in flue gases (in relative units). Barcode-dotted curve - the real air consumption of the pipe provided by the tube (in relative units). The excess air coefficient is a private compartment G pipe on G Potch

Stable and sufficiently strong thrust occurs only after heating the walls of the smoke tube, which requires considerable time, so that at the beginning of the air protesting is always missing. The coefficient of excess air at the same time less than one, and the smoke furnace ( fig. 2.). Conversely: At the end of the protood, the smoke tube remains hot, the thrust is preserved for a long time, although the firewood has already been almost burned (excess air coefficient is more than one). Metal furnaces with metal warmed flue pipes are faster to regime due to low heat capacity compared to brick trumpets.

Analysis of the processes in the chimney can be continued, but it is already so clear that no matter how good the furnace itself, all its advantages can be reduced to zero by a bad chimney. Of course, in the ideal embodiment, the smoke pipe would have to be replaced with a modern system of forced flushing with flue gases using an electric fan with adjustable flow rate and with pre-condensation of moisture from flue gases. Such a system, among other things, could clean the flue gases from soot, carbon monoxide and other harmful impurities, as well as cooling discharged flue gases and ensure heat recovery.

But all this is in a distant perspective. For a dacket and gardener, the smoke trumpet sometimes can become much more expensive than the oven itself, especially in the case of heating a multi-level house. Banned flue pipes are usually simpler and shorter, but the level of thermal power of the furnace can be very large. Such pipes, as a rule, are strongly launched along the entire length, they often fly out sparks and ashes, but condensate and soot falling insignificantly.

If you plan to use a bath building only as a bath, then the pipe can be made and tight. If the bath is thinking by you and as a place of possible stay (temporary residence, overnight), especially in winter, then it is more expedient to immediately do the insulated, and qualitatively, "for life." The stoves can be changed at least every day, pick up the design of the dirty and in more detail, and the pipe will be the same.

At least, if the stove works in long-burning mode (fling), then the insulation of the pipe is absolutely necessary, since at low facilities (1 - 5 kW), the tight metal pipe will become completely cold, will be abundantly flowing condensate, which in the strongest frosts can Even climb and overlap the pipe. This is especially dangerous in the presence of sparking mesh and umbrellas with small passing gaps. Incrochovers are suitable for intense proturtes in the summer and are extremely dangerous for weak burning modes of firewood in winter. Due to the possible clogging of ice pipes, the installation of deflectors and umbrellas on chimneys was prohibited in 1991 (and in chimneys of gas stoves even earlier).

According to the same considerations, it is not necessary to get involved in the pipe height - the level of thrust is not so important for a non-free bath oven. If it will simulate, you can always quickly ventilate the room. But the height above the ridge of the roof (not less than 0.5 m) should be observed to prevent tipping thrust during wind gusts. On the gentle roofs, the pipe should perform over the snow cover. In any case, it is better to have a pipe down, but warmer (what is higher, but colder). High pipes in winter are always cold and dangerous in operation.

Cold flue pipes have a lot of flaws. At the same time, tangled, but not very long pipes on metal furnaces during extractors heated quickly (much faster than brick pipes), remain hot with an energetic protest and therefore in the baths (and not only in the baths) are used very widely, especially since They are relatively cheap. Asbic cement pipes on metal furnaces are not used, as they have a lot of weight, and also destroy when overheating with the sprout of fragments.

Fig. 3. The simplest designs of metal flue pipes: 1 - metal round chimney; 2 - sparkling; 3 - cap to protect the pipe from atmospheric precipitation; 4 - rafters; 5 - Roof lambers; 6-shaped bars between rafters (or beams) for registration of firefire (cutting) in the roof or overlap (if necessary); 7 - roof rustle; 8 - soft roof (rubberoid, hydrohotelloisol, soft tiles, corrugated cardboard-bitumen sheets, etc.); 9 - Metal sheet for roof flooring and overlap of the outlet (it is allowed to use a flat sheet of an aceida - an asbo-cement electrical insulating board); 10 - metal drainage lining; 11 - asbestos sealing of the gap (joint); 12 - metal cap-otter; 13 - ceiling beams (with the filling of space by insulation); 14 - ceiling cover; 15 - the sex of the attic (if necessary); 16 - metal sheet ceiling cutting; 17 - metal reinforcing corners; 18 - metal cover of the ceiling cutting (if necessary); 19 - insulation non-combustible heat-resistant (ceramzit, sand, perlite, minvat); 20 - protective pad (metal sheet on a layer of asbestos cardboard with a thickness of 8 mm); 21 - Metal screen pipe.

a) non-flagged tube;
b) the heat-insulated shielded pipe with heat transfer resistance of at least 0.3 m 2 -Grad / W (which is equivalent to the brick thickness of 130 mm or the thickness of the insulation of the MINVATA type 20 mm).

On the fig. 3. Presented typical assembly schemes of tangled metal pipes. The pipe itself should be purchased from stainless steel with a thickness of at least 0.7 mm. The most undercarriage diameter of the Russian pipe is 120 mm, Finnish - 115 mm.

According to GOST 9817-95, the cross-sectional area of \u200b\u200bthe multi-turn chimney should be at least 8 cm 2 per 1 kW of the nominal thermal power released in the firebox when burning firewood. This power should not be confused with the heat power of the oven, released from the outer brick surface of the furnace to the room by SNiP 2.04.05-91. This is one of the numerous misunderstandings of our regulatory documents. Since heat-drying furnaces are usually littered only 2-3 hours a day, then the power in the furnace is about ten times the power of heat release from the surface of the brick furnace.

Next time we will talk about the features of the flood pipe mounting.