Thermal power - calculation formula and scope. Calculation of heating by area of ​​​​the room

Owners of private houses, apartments or any other objects have to deal with heat engineering calculations. This is the foundation of building design.

Understanding the essence of these calculations in official papers is not as difficult as it seems.

For yourself, you can also learn how to perform calculations in order to decide which insulation to use, how thick it should be, how much power the boiler should acquire, and whether there are enough existing radiators for a given area.

The answers to these and many other questions can be found if you understand what is thermal power. Formula, definition and scope - read the article.

Simply put, a thermal calculation helps you know exactly how much heat a building stores and loses, and how much energy heating needs to generate to keep a home comfortable.

When evaluating heat loss and the degree of heat supply, the following factors are taken into account:

1. What kind of object is it: how many floors it has, availability corner rooms, whether it is residential or industrial, etc.
2. How many people will "live" in the building.
3. An important detail is the area of ​​​​glazing. And the dimensions of the roof, walls, floor, doors, ceiling height, etc.
4. What is the duration heating season, climatic characteristics of the region.
5. According to SNiPs, the temperature standards that should be in the premises are determined.
6. The thickness of walls, ceilings, selected heat insulators and their properties.

Other conditions and features can be taken into account, for example, for production facilities, working days and weekends, the power and type of ventilation, the orientation of housing to the cardinal points, etc. are considered.

What is a thermal calculation for?

How did the builders of the past manage to do without thermal calculations?

The surviving merchant houses show that everything was done simply with a margin: the windows are smaller, the walls are thicker. It turned out warm, but economically unprofitable.

Thermal engineering calculation allows you to build the most optimal. Materials are taken no more - no less, but exactly as much as needed. The dimensions of the building and the cost of its construction are reduced.

The calculation of the dew point allows you to build so that the materials do not deteriorate for as long as possible.

To determine the required power of the boiler, one cannot do without calculations. Its total power is the sum of the energy costs for heating rooms, heating hot water for economic needs, and the ability to block heat losses from ventilation and air conditioning. The power reserve is added for the period of peak cold weather.

When gasifying an object, coordination with the services is required. The annual gas consumption for heating is calculated and general power heat sources in gigacalories.

Calculations are needed when selecting elements of the heating system. The system of pipes and radiators is calculated - you can find out what their length, surface area should be. The power loss is taken into account when the pipeline turns, at the joints and the passage of valves.

Did you know that the number of sections of heating radiators is not taken “from the ceiling”? Too little of them will lead to the fact that the house will be cold, and too much of them will create heat and lead to excessive dryness of the air. The link provides examples of the correct calculation of radiators.

Thermal power calculation: formula

Consider the formula and give examples of how to calculate for buildings with different coefficient scattering.

Vx(delta)TxK= kcal/h (heat output), where:

• The first indicator "V" is the volume of the calculated room;
• Delta "T" - the temperature difference - this is the value that shows how many degrees inside the room are warmer than outside;
• "K" is the dissipation coefficient (it is also called the "heat transmission coefficient"). The value is taken from the table. Usually the figure ranges from 4 to 0.6.

Approximate values ​​of the dissipation factor for a simplified calculation

• If it is an uninsulated metal profile or a board, then “K” will be = 3 - 4 units.
• Single brickwork and minimum insulation - "K" \u003d from 2 to 3-ex.
• Two brick wall standard overlap, windows and
• doors - "K" \u003d from 1 to 2.
• Most warm option. Double-glazed windows, brick walls with double insulation, etc. - "K" \u003d 0.6 - 0.9.

A more accurate calculation can be made by calculating the exact dimensions of the surfaces of the house that differ in properties in m 2 (windows, doors, etc.), making a calculation for them separately and adding up the resulting indicators.

Example of heat output calculation

Let's take a certain room of 80 m 2 with a ceiling height of 2.5 m and calculate how much boiler power we need to heat it.

First, we calculate the cubic capacity: 80 x 2.5 \u003d 200 m 3. Our house is insulated, but not enough - the dispersion coefficient is 1.2.

Frosts are up to -40 ° C, and in the room you want to have a comfortable +22 degrees, the temperature difference (delta "T") is 62 ° C.

We substitute the numbers in the formula for the power of heat losses and multiply:

200 x 62 x 1.2 \u003d 14880 kcal / h.

The resulting kilocalories are converted to kilowatts using the converter:

• 1 kW = 860 kcal;
• 14880 kcal = 17302.3 W.

We round up with a margin, and we understand that in the most severe frost of -40 degrees, we will need 18 kW of energy per hour.

Multiply the perimeter of the house by the height of the walls:

(8 + 10) x 2 x 2.5 \u003d 90 m 2 of wall surface + 80 m 2 ceiling = 170 m 2 of surface in contact with cold. The heat loss calculated by us above amounted to 18 kW / h, dividing the surface of the house by the calculated energy consumed, we get that 1 m 2 loses about 0.1 kW or 100 W hourly at an outdoor temperature of -40 ° C, and +22 ° C indoors WITH.

These data can become the basis for calculating the required thickness of insulation on the walls.

Let's give another example of calculation, it is more complicated in some moments, but more accurate.

Formula:

Q = S x (delta)T/R:

• Q is the desired value of heat loss at home in W;
• S is the area of ​​cooling surfaces in m 2 ;
• T is the temperature difference in degrees Celsius;
• R is the thermal resistance of the material (m 2 x K / W) (Square meters multiplied by Kelvin and divided by Watt).

So, to find "Q" of the same house as in the example above, let's calculate the area of ​​its surfaces "S" (we will not count the floor and windows).

• "S" in our case \u003d 170 m 2, of which 80 m 2 are the ceiling and 90 m 2 are the walls;
• T = 62 °С;
• R is thermal resistance.

We are looking for "R" according to the table of thermal resistances or according to the formula. The formula for calculating the thermal conductivity coefficient is as follows:

R= H/ K.T.(H is the thickness of the material in meters, K.T. is the coefficient of thermal conductivity).

In this case, our house has walls in two bricks sheathed with foam plastic 10 cm thick. The ceiling is covered with sawdust 30 cm thick.

The heating system of a private house must be arranged taking into account the savings in energy costs. , as well as recommendations for choosing boilers and radiators - read carefully.

How and how to insulate a wooden house from the inside, you will learn by reading. The choice of insulation and insulation technology.

From the table of thermal conductivity coefficients (measured W / (m 2 x K) Watt divided by the product of a square meter per Kelvin). We find the values ​​for each material, they will be:

• brick - 0.67;
• polystyrene - 0.037;
• sawdust - 0.065.

• R (ceiling 30 cm thick) \u003d 0.3 / 0.065 \u003d 4.6 (m 2 x K) / W;
• R( brick wall 50 cm) \u003d 0.5 / 0.67 \u003d 0.7 (m 2 x K) / W;
• R (foam 10 cm) \u003d 0.1 / 0.037 \u003d 2.7 (m 2 x K) / W;
• R (wall) \u003d R (brick) + R (polystyrene) \u003d 0.7 + 2.7 \u003d 3.4 (m 2 x K) / W.

Now we can proceed to the calculation of heat loss "Q":

• Q for the ceiling \u003d 80 x 62 / 4.6 \u003d 1078.2 watts.
• Q walls \u003d 90 x 62 / 3.4 \u003d 1641.1 watts.
• It remains to add 1078.2 + 1641.1 and convert to kW, it turns out (if rounded up immediately) 2.7 kW of energy in 1 hour.

You can pay attention to how big the difference turned out in the first and second cases, although the volume of houses and the temperature outside the window in the first and second cases were exactly the same.

It's all about the degree of fatigue of the houses (although, of course, the data could be different if we calculated the floor and windows).

Conclusion

The above formulas and examples show that in heat engineering calculations it is very important to take into account as many factors as possible that affect heat loss. This includes ventilation, and the area of ​​​​the windows, the degree of their fatigue, etc.

And the approach, when 1 kW of boiler power is taken for 10 m 2 of a house, is too approximate to seriously rely on it.

Related video

Creating a heating system in your own home or even in a city apartment is an extremely responsible task. It would be completely unwise to acquire boiler equipment, as they say, "by eye", that is, without taking into account all the features of housing. In this, it is quite possible to fall into two extremes: either the power of the boiler will not be enough - the equipment will work “to its fullest”, without pauses, but will not give the expected result, or, conversely, an overly expensive device will be purchased, the capabilities of which will remain completely unclaimed.

But that's not all. It is not enough to purchase the necessary heating boiler correctly - it is very important to optimally select and correctly place heat exchange devices in the premises - radiators, convectors or "warm floors". And again, relying only on your intuition or the "good advice" of your neighbors is not the most reasonable option. In a word, certain calculations are indispensable.

Of course, ideally, such heat engineering calculations should be carried out by appropriate specialists, but this often costs a lot of money. Isn't it interesting to try to do it yourself? This publication will show in detail how heating is calculated by the area of ​​\u200b\u200bthe room, taking into account many important nuances. By analogy, it will be possible to perform, built into this page, will help you perform the necessary calculations. The technique cannot be called completely “sinless”, however, it still allows you to get a result with a completely acceptable degree of accuracy.

The simplest methods of calculation

In order for the heating system to create comfortable living conditions during the cold season, it must cope with two main tasks. These functions are closely related, and their separation is very conditional.

• The first is maintaining optimal level air temperature in the entire volume of the heated room. Of course, the temperature level may vary slightly with altitude, but this difference should not be significant. Quite comfortable conditions are considered to be an average of +20 ° C - it is this temperature that, as a rule, is taken as the initial temperature in thermal calculations.

In other words, the heating system must be able to heat a certain volume of air.

If we approach with complete accuracy, then for individual rooms in residential buildings the standards for the required microclimate have been established - they are defined by GOST 30494-96. An excerpt from this document is in the table below:

• The second is the compensation of heat losses through the structural elements of the building.

The main "enemy" of the heating system is heat loss through building structures.

Alas, heat loss is the most serious "rival" of any heating system. They can be reduced to a certain minimum, but even with the highest quality thermal insulation, it is not yet possible to completely get rid of them. Thermal energy leaks go in all directions - their approximate distribution is shown in the table:

Naturally, in order to cope with such tasks, the heating system must have a certain thermal power, and this potential must not only meet the general needs of the building (apartment), but also be correctly distributed over the premises, in accordance with their area and a number of other important factors.

Usually the calculation is carried out in the direction "from small to large". Simply put, the required amount of thermal energy for each heated room is calculated, the obtained values ​​​​are summed up, approximately 10% of the reserve is added (so that the equipment does not work at the limit of its capabilities) - and the result will show how much power the heating boiler needs. And the values ​​​​for each room will be the starting point for the calculation required amount radiators.

The most simplified and most commonly used method in a non-professional environment is to accept a norm of 100 watts of thermal energy for each square meter area:

The most primitive way of counting is the ratio of 100 W / m²

Q = S× 100

Q- the required thermal power for the room;

S– area of ​​the room (m²);

100 — specific power per unit area (W/m²).

For example, room 3.2 × 5.5 m

S= 3.2 × 5.5 = 17.6 m²

Q= 17.6 × 100 = 1760 W ≈ 1.8 kW

The method is obviously very simple, but very imperfect. It is worth mentioning right away that it is conditionally applicable only with a standard ceiling height - approximately 2.7 m (permissible - in the range from 2.5 to 3.0 m). From this point of view, the calculation will be more accurate not from the area, but from the volume of the room.

It is clear that in this case the value of specific power is calculated per cubic meter. It is taken equal to 41 W / m³ for reinforced concrete panel house, or 34 W / m³ - in brick or made of other materials.

Q = S × h× 41 (or 34)

h- ceiling height (m);

41 or 34 - specific power per unit volume (W / m³).

For example, the same room panel house, with a ceiling height of 3.2 m:

Q= 17.6 × 3.2 × 41 = 2309 W ≈ 2.3 kW

The result is more accurate, since it already takes into account not only all linear dimensions rooms, but even, to a certain extent, the features of the walls.

But still, it is still far from real accuracy - many nuances are “outside the brackets”. How to perform calculations closer to real conditions - in the next section of the publication.

You may be interested in information about what they are

Carrying out calculations of the required thermal power, taking into account the characteristics of the premises

The calculation algorithms discussed above are useful for the initial “estimate”, but you should still rely on them completely with very great care. Even to a person who does not understand anything in building heat engineering, the indicated average values ​​\u200b\u200bmay certainly seem doubtful - they cannot be equal, say, for Krasnodar Territory and for the Arkhangelsk region. In addition, the room - the room is different: one is located on the corner of the house, that is, it has two external walls ki, and the other on three sides is protected from heat loss by other rooms. In addition, the room may have one or more windows, both small and very large, sometimes even panoramic. And the windows themselves may differ in the material of manufacture and other design features. And this is not a complete list - just such features are visible even to the "naked eye".

In a word, there are a lot of nuances that affect the heat loss of each particular room, and it is better not to be too lazy, but to carry out a more thorough calculation. Believe me, according to the method proposed in the article, this will not be so difficult to do.

General principles and calculation formula

The calculations will be based on the same ratio: 100 W per 1 square meter. But that's just the formula itself "overgrown" with a considerable number of various correction factors.

Q = (S × 100) × a × b × c × d × e × f × g × h × i × j × k × l × m

The Latin letters denoting the coefficients are taken quite arbitrarily, in alphabetical order, and are not related to any standard quantities accepted in physics. The meaning of each coefficient will be discussed separately.

• "a" - a coefficient that takes into account the number of external walls in a particular room.

Obviously, the more external walls in the room, the more area, through which heat loss. In addition, the presence of two or more external walls also means corners - extremely vulnerable places in terms of the formation of "cold bridges". The coefficient "a" will correct for this specific feature of the room.

The coefficient is taken equal to:

- external walls No (interior): a = 0.8;

- outer wall one: a = 1.0;

- external walls two: a = 1.2;

- external walls three: a = 1.4.

• "b" - coefficient taking into account the location of the external walls of the room relative to the cardinal points.

You may be interested in information about what are

Even on the coldest winter days solar energy still affects the temperature balance in the building. It is quite natural that the side of the house that is facing south receives some heating from the sun's rays, and heat loss through it is lower.

But the walls and windows facing north never “see” the Sun. The eastern part of the house, although it "grabs" the morning sun's rays, still does not receive any effective heating from them.

Based on this, we introduce the coefficient "b":

- the outer walls of the room look at North or East: b = 1.1;

- the outer walls of the room are oriented towards South or West: b = 1.0.

• "c" - coefficient taking into account the location of the room relative to the winter "wind rose"

Perhaps this amendment is not so necessary for houses located in areas protected from the winds. But sometimes the prevailing winter winds can make their own “hard adjustments” to the thermal balance of the building. Naturally, the windward side, that is, "substituted" for the wind, will lose significantly more body, compared to the leeward, opposite.

Based on the results of long-term meteorological observations in any region, the so-called "wind rose" is compiled - a graphic diagram showing the prevailing wind directions in winter and summer. This information can be obtained from the local hydrometeorological service. However, many residents themselves, without meteorologists, know perfectly well where the winds mainly blow from in winter, and from which side of the house the deepest snowdrifts usually sweep.

If there is a desire to carry out calculations with higher accuracy, then the correction factor “c” can also be included in the formula, taking it equal to:

- windward side of the house: c = 1.2;

- leeward walls of the house: c = 1.0;

- wall located parallel to the direction of the wind: c = 1.1.

• "d" - a correction factor that takes into account the peculiarities of the climatic conditions of the region where the house was built

Naturally, the amount of heat loss through all the building structures of the building will greatly depend on the level of winter temperatures. It is quite clear that during the winter the thermometer indicators “dance” in a certain range, but for each region there is an average indicator of the lowest temperatures characteristic of the coldest five-day period of the year (usually this is characteristic of January). For example, below is a map-scheme of the territory of Russia, on which colors show approximate values.

Usually this value is easy to check with the regional meteorological service, but you can, in principle, rely on your own observations.

So, the coefficient "d", taking into account the peculiarities of the climate of the region, for our calculations in we take equal to:

— from – 35 °С and below: d=1.5;

— from – 30 °С to – 34 °С: d=1.3;

— from – 25 °С to – 29 °С: d=1.2;

— from – 20 °С to – 24 °С: d=1.1;

— from – 15 °С to – 19 °С: d=1.0;

— from – 10 °С to – 14 °С: d=0.9;

- not colder - 10 ° С: d=0.7.

• "e" - coefficient taking into account the degree of insulation of external walls.

The total value of the heat loss of the building is directly related to the degree of insulation of all building structures. One of the "leaders" in terms of heat loss are walls. Therefore, the value of thermal power required to maintain comfortable conditions living indoors depends on the quality of their thermal insulation.

The value of the coefficient for our calculations can be taken as follows:

- external walls are not insulated: e = 1.27;

- medium degree of insulation - walls in two bricks or their surface thermal insulation with other heaters is provided: e = 1.0;

– insulation was carried out qualitatively, on the basis of heat engineering calculations: e = 0.85.

Later in the course of this publication, recommendations will be given on how to determine the degree of insulation of walls and other building structures.

• coefficient "f" - correction for ceiling height

Ceilings, especially in private homes, can have different heights. Therefore, the thermal power for heating one or another room of the same area will also differ in this parameter.

It will not be a big mistake to accept the following values ​​​​of the correction factor "f":

– ceiling height up to 2.7 m: f = 1.0;

— flow height from 2.8 to 3.0 m: f = 1.05;

– ceiling height from 3.1 to 3.5 m: f = 1.1;

– ceiling height from 3.6 to 4.0 m: f = 1.15;

– ceiling height over 4.1 m: f = 1.2.

• « g "- coefficient taking into account the type of floor or room located under the ceiling.

As shown above, the floor is one of the significant sources of heat loss. So, it is necessary to make some adjustments in the calculation of this feature of a particular room. The correction factor "g" can be taken equal to:

- cold floor on the ground or above unheated room(for example, basement or basement): g= 1,4 ;

- insulated floor on the ground or over an unheated room: g= 1,2 ;

- a heated room is located below: g= 1,0 .

• « h "- coefficient taking into account the type of room located above.

The air heated by the heating system always rises, and if the ceiling in the room is cold, then increased heat losses are inevitable, which will require an increase in the required heat output. We introduce the coefficient "h", which takes into account this feature of the calculated room:

- a "cold" attic is located on top: h = 1,0 ;

- an insulated attic or other insulated room is located on top: h = 0,9 ;

- any heated room is located above: h = 0,8 .

• « i "- coefficient taking into account the design features of windows

Windows are one of the "main routes" of heat leaks. Naturally, much in this matter depends on the quality of the window construction. Old wooden frames, which were previously installed everywhere in all houses, are significantly inferior to modern multi-chamber systems with double-glazed windows in terms of their thermal insulation.

Without words, it is clear that the thermal insulation qualities of these windows are significantly different.

But even between PVC-windows there is no complete uniformity. For example, a two-chamber double-glazed window (with three glasses) will be much warmer than a single-chamber one.

This means that it is necessary to enter a certain coefficient "i", taking into account the type of windows installed in the room:

— standard wooden windows with conventional double glazing: i = 1,27 ;

– modern window systems with single pane glass: i = 1,0 ;

– modern window systems with two-chamber or three-chamber double-glazed windows, including those with argon filling: i = 0,85 .

• « j» - correction factor for total area room glazing

Whatever quality windows however they were, it will still not be possible to completely avoid heat loss through them. But it is quite clear that it is impossible to compare a small window with panoramic glazing almost on the entire wall.

First you need to find the ratio of the areas of all the windows in the room and the room itself:

x = ∑SOK /SP

∑ SOK- the total area of ​​windows in the room;

SP- area of ​​the room.

Depending on the value obtained and the correction factor "j" is determined:

- x \u003d 0 ÷ 0.1 →j = 0,8 ;

- x \u003d 0.11 ÷ 0.2 →j = 0,9 ;

- x \u003d 0.21 ÷ 0.3 →j = 1,0 ;

- x \u003d 0.31 ÷ 0.4 →j = 1,1 ;

- x \u003d 0.41 ÷ 0.5 →j = 1,2 ;

• « k" - coefficient that corrects for the presence of an entrance door

The door to the street or to an unheated balcony is always an additional "loophole" for the cold

door to the street or outdoor balcony is able to make its own adjustments to the heat balance of the room - each of its opening is accompanied by the penetration of a considerable amount of cold air into the room. Therefore, it makes sense to take into account its presence - for this we introduce the coefficient "k", which we take equal to:

- no door k = 1,0 ;

- one door to the street or balcony: k = 1,3 ;

- two doors to the street or to the balcony: k = 1,7 .

• « l "- possible amendments to the connection diagram of heating radiators

Perhaps this will seem like an insignificant trifle to some, but still - why not immediately take into account the planned scheme for connecting heating radiators. The fact is that their heat transfer, and hence their participation in maintaining a certain temperature balance in the room, changes quite noticeably when different types tie-in supply and return pipes.

Illustration	Radiator insert type	The value of the coefficient "l"
	Diagonal connection: supply from above, "return" from below	l = 1.0
	Connection on one side: supply from above, "return" from below	l = 1.03
	Two-way connection: both supply and return from the bottom	l = 1.13
	Diagonal connection: supply from below, "return" from above	l = 1.25
	Connection on one side: supply from below, "return" from above	l = 1.28
	One-way connection, both supply and return from below	l = 1.28

• « m "- correction factor for the features of the installation site of heating radiators

And finally, the last coefficient, which is also associated with the features of connecting heating radiators. It is probably clear that if the battery is installed openly, is not obstructed by anything from above and from the front part, then it will give maximum heat transfer. However, such an installation is far from always possible - more often, radiators are partially hidden by window sills. Other options are also possible. In addition, some owners, trying to fit heating priors into the created interior ensemble, hide them completely or partially with decorative screens - this also significantly affects the heat output.

If there are certain “baskets” on how and where the radiators will be mounted, this can also be taken into account when making calculations by entering a special coefficient “m”:

So, there is clarity with the calculation formula. Surely, some of the readers will immediately take up their heads - they say, it's too complicated and cumbersome. However, if the matter is approached systematically, in an orderly manner, then there is no difficulty at all.

Any good landlord must have a detailed graphic plan of their "possessions" with affixed dimensions, and usually oriented to the cardinal points. It is not difficult to specify the climatic features of the region. It remains only to walk through all the rooms with a tape measure, to clarify some of the nuances for each room. Features of housing - "neighborhood vertically" from above and below, location entrance doors, the proposed or already existing scheme for installing heating radiators - no one except the owners knows better.

It is recommended to immediately draw up a worksheet, where you enter all the necessary data for each room. The result of the calculations will also be entered into it. Well, the calculations themselves will help to carry out the built-in calculator, in which all the coefficients and ratios mentioned above are already “laid”.

If some data could not be obtained, then, of course, they can not be taken into account, but in this case, the “default” calculator will calculate the result, taking into account the least favorable conditions.

It can be seen with an example. We have a house plan (taken completely arbitrary).

Region with level minimum temperatures within -20 ÷ 25 °С. Predominance of winter winds = northeasterly. The house is one-story, with an insulated attic. Insulated floors on the ground. The optimal diagonal connection radiators that will be installed under the window sills.

Let's create a table like this:

Then, using the calculator below, we make a calculation for each room (already taking into account a 10% reserve). With the recommended app, it won't take long. After that, it remains to sum up the obtained values ​​​​for each room - this will be the required total power of the heating system.

The result for each room, by the way, will help you choose the right number of heating radiators - it remains only to divide by the specific heat output of one section and round up.

where - estimated heat losses of the building, kW;

- coefficient for taking into account the additional heat flow of installed heating devices due to rounding over calculated value, taken according to the table. one.

Table 1

- coefficient for accounting for additional heat losses by heating devices located at external fences in the absence of heat shields, taken according to Table. 2.

table 2

- heat loss, kW, pipelines passing in unheated premises;

- heat flow, kW, regularly supplied from lighting, equipment and people, which should be taken into account as a whole for the heating system of the building. For reaped houses should be taken into account at the rate of 0.01 kW per 1 m "of the total area.

When calculating the thermal power of heating systems for industrial buildings, one should additionally take into account the heat consumption for heating materials, equipment and vehicles.

2. Estimated heat loss , kW, should be calculated by the formula:

(2)

where: - heat flow, kW, through the enclosing structures;

- heat loss, kW, for heating the ventilation air.

Quantities and calculated for each heated room.

3. Heat flow , kW, is calculated for each element of the building envelope according to the formula:

(3)

where A is the estimated area of ​​the building envelope, m 2;

R is the heat transfer resistance of the building envelope. m 2 °C / W, which should be determined according to SNiP II-3-79 ** (except for floors on the ground), taking into account the established standards for the minimum thermal resistance of fences. For floors on the ground and walls located below ground level, the resistance to heat transfer should be determined in zones 2 m wide parallel to the outer walls, according to the formula:

(4)

where - heat transfer resistance, m 2 ° C / W, taken equal to 2.1 for zone I, 4.3 for the second, 8.6 for the third zone and 14.2 for the remaining floor area;

- thickness of the insulating layer, m, taken into account when the coefficient of thermal conductivity of the insulation <1,2Вт/м 2 °С;

- design indoor air temperature, °C, adopted in accordance with the requirements of the design standards for buildings for various purposes, taking into account its increase depending on the height of the room;

- calculated outdoor air temperature, °C, taken according to Appendix 8, or the air temperature of an adjacent room, if its temperature differs by more than 3 °C from the temperature of the room for which heat losses are calculated;

- coefficient taken depending on the position of the outer surface of the building envelope in relation to the outside air and determined according to SNNP P-3-79 **

- additional heat losses in shares of the main losses, taken into account:

a) for outdoor vertical and inclined fences oriented to directions from which in January the wind blows at a speed exceeding 4.5 m/s with a frequency of at least 15% according to SNiP 2.01.01-82, in the amount of 0.05 at wind speed up to 5 m/s and in the amount of 0.10 at a speed of 5 m/s or more; in a typical design, additional losses should be taken into account in the amount of 0.05 for all rooms;

b) for external vertical and inclined fences of multi-storey buildings in the amount of 0.20 for the first and second floors; 0.15 - for the third; 0.10 - for the fourth floor of a building with 16 or more floors; for 10-15-storey buildings, additional losses should be taken into account in the amount of 0.10 for the first and second floors and 0.05 for the third floor.

4. Heat loss , kW, are calculated for each heated room with one or more windows or balcony doors in the outer walls, based on the need to provide heating of outdoor air with heaters in the amount of a single air exchange per hour according to the formula:

where - floor area of ​​the room, m 2;

- height of the room from floor to ceiling, m, but not more than 3.5.

Premises from which exhaust ventilation is organized with an exhaust volume exceeding a single air exchange per hour should, as a rule, be designed with supply ventilation with heated air. When justified, it is allowed to provide heating of the outside air with heating devices in separate rooms with a ventilation air volume not exceeding two exchanges per hour.

In rooms for which building design standards establish an exhaust volume of less than a single air exchange per hour, the value should be calculated as the heat consumption for heating the air in the volume of normalized air exchange from temperature up to temperature °C.

Heat loss kW, for heating the outside air that enters the entrance lobbies (halls) and stairwells through the external doors that open in the cold season in the absence of air-thermal curtains should be calculated using the formula:

where
- building height, m:

P is the number of people in the building;

B - coefficient taking into account the number of entrance vestibules. With one vestibule (two doors) in - 1.0; with two vestibules (three doors) v = 0.6.

Calculation of heat for heating outdoor air penetrating through the doors of heated smoke-free staircases with floor exits to the loggia should be carried out according to the formula (6) at
, taking for each floor the value
, different distance, m. from the middle of the door of the calculated floor to the ceiling of the staircase.

When calculating the heat loss of entrance lobbies, stairwells and workshops with air-thermal curtains: rooms equipped with forced ventilation with air overpressure operating constantly during working hours, as well as when calculating heat loss through summer and emergency external doors and gates, the value should not be taken into account.

Heat loss , kW, for heating the air rushing in through external gates not equipped with air-thermal curtains, should be calculated taking into account the wind speed, taken according to mandatory Appendix 8, and the gate opening time.

Calculation of the loss of warming: it is not required to perform heating of the air infiltrating through the leaks of the enclosing structures.

5. Heat loss , kW, pipelines passing in unheated premises should be determined by the formula:

(7)

where: - lengths of sections of heat-insulated pipelines of various diameters laid in unheated premises;

- normalized linear heat flux density of a heat-insulated pipeline, taken according to clause 3.23. At the same time, the thickness of the heat-insulating layer , m pipelines should. calculated by the formulas:

(8)

where - outer dimension of the pipeline, m;

- thermal conductivity of the heat-insulating layer, W/(m °C);

- the average temperature difference between the coolant and the ambient air for the heating season.

6. The value of the estimated annual heat consumption of the heating system of the building
, GJ. should be calculated using the formula:

where - the number of degree-days of the heating period, taken according to Appendix 8;

a - coefficient equal to 0.8. which must be taken into account if the heating system is equipped with devices for automatically reducing heat output during non-working hours;

- a coefficient different from 0.9, which must be taken into account if more than 75% of heating appliances are equipped with automatic temperature controllers;

with - a coefficient different from 0.95, which must be taken into account if automatic front-facing control devices are installed at the subscriber input of the heating system.

7. Thermal power values ​​determined by calculation and maximum annual heat consumption
, referred to 1 m 2 of total (for residential buildings) or usable (for public buildings) area, should not exceed the regulatory control values ​​\u200b\u200bgiven in mandatory Appendix 25.

8. Coolant consumption ,.kg/h. and the heating system should be determined by the formula:

(11)

where with - specific heat capacity of water, taken equal to 4.2 kJ / (kg 0 С);

- temperature difference. °C, coolant at the system inlet and outlet;

- thermal power of the system, kW. determined by formula (1) taking into account household heat emissions .

9. Estimated heat output
, kW, each heater should be determined by the formula:

where
should be calculated in accordance with 2-4 of this appendix;

- heat losses, kW, through the internal walls separating the room for which the heat output of the heater is calculated from the adjacent room, in which an operational temperature decrease is possible during regulation. the value
should be taken into account only when calculating the thermal power of heating appliances, on the connections to which automatic temperature controllers are designed. At the same time, heat losses should be calculated for each room.
only through one inner wall at a temperature difference between the inner rooms of 8 0 С;

- heat flow. kW, from uninsulated heating pipelines laid indoors;

- heat flux, kW, regularly supplied to the premises from electrical appliances, lighting, process equipment, communications, materials and other sources. When calculating the thermal power of heating appliances in residential, public and administrative buildings, the value
should not be taken into account.

The amount of domestic heat release is taken into account for the entire building as a whole when calculating the heat output of the heating system and the total flow of the coolant.

2.3. SPECIFIC THERMAL CHARACTERISTICS

The total heat loss of the building Q zd is usually attributed to 1 m 3 of its external volume and 1 ° C of the calculated temperature difference. The resulting indicator q 0, W / (m 3 K), is called the specific thermal characteristic of the building:

(2.11)

where V n - the volume of the heated part of the building according to the external measurement, m 3;

(t in -t n.5) - the estimated temperature difference for the main premises of the building.

The specific thermal characteristic, calculated after calculating the heat loss, is used for the thermal assessment of the design and planning solutions of the building, comparing it with the average values ​​for similar buildings. For residential and public buildings, the assessment is made according to the heat consumption related to I m 2 of the total area.

The value of the specific thermal characteristic is determined primarily by the size of the light openings in relation to the total area of ​​the external fences, since the heat transfer coefficient of filling the light openings is much higher than the heat transfer coefficient of other fences. In addition, it depends on the volume and shape of buildings. Buildings of small volume have an increased characteristic, as well as narrow buildings of a complex configuration with an enlarged perimeter.

Reduced heat loss and, consequently, the thermal characteristic are buildings, the shape of which is close to a cube. There is even less heat loss from spherical structures of the same volume due to a reduction in the area of ​​the outer surface.

The specific thermal characteristic also depends on the construction area of ​​the building due to changes in the heat-shielding properties of the fence. In the northern regions, with a relative decrease in the heat transfer coefficient of the fences, this figure is lower than in the southern ones.

The values ​​of specific thermal characteristics are given in the reference literature.

Applying it, determine the heat loss of the building according to the aggregated indicators:

where β t is a correction factor that takes into account the change in specific thermal characteristics when the actual calculated temperature difference deviates from 48 °:

(2.13)

Such calculations of heat losses make it possible to establish the approximate need for thermal energy in the long-term planning of thermal networks and stations.

3.1 CLASSIFICATION OF HEATING SYSTEMS

Heating installations are designed and installed during the construction of the building, linking their elements with building structures and the layout of the premises. Therefore, heating is considered a branch of construction equipment. Then heating installations operate during the entire service life of the structure, being one of the types of engineering equipment of buildings. The following requirements are imposed on heating installations:

1 - sanitary and hygienic: maintaining a uniform temperature of the premises; limiting the surface temperature of heating devices, the possibility of their cleaning.

2 - economic: low capital investments and operating costs, as well as low metal consumption.

3 - architectural and construction: compliance with the layout of the premises, compactness, coordination with building structures, coordination with the construction time of buildings.

4 - production and installation: mechanization of the manufacture of parts and assemblies, the minimum number of elements, reducing labor costs and increasing productivity during installation.

5 - operational: reliability and durability, simplicity and convenience of management and repair, noiselessness and safety of operation.

Each of these requirements should be taken into account when choosing a heating installation. However, sanitary and hygienic and operational requirements are considered basic. The installation must be able to transfer to the room the amount of heat that changes in accordance with the heat loss.

Heating system - a set of structural elements designed to receive, transfer and transfer the required amount of thermal energy to all heated rooms.

The heating system consists of the following main structural elements (Fig. 3.1).

Rice. 3.1. Schematic diagram of the heating system

1- heat exchanger; 2 and 4 - supply and return heat pipes; 3- heater.

heat exchanger 1 for obtaining thermal energy by burning fuel or from another source; heating devices 3 for heat transfer to the room; heat pipes 2 and 4 - a network of pipes or channels for heat transfer from the heat exchanger to the heaters. Heat transfer is carried out by a heat carrier - liquid (water) or gaseous (steam, air, gas).

1. Depending on the type of system, they are divided into:

Water;

Steam;

Air or gas;

Electrical.

2. Depending on the location of the heat source and the heated room:

Local;

Central;

Centralized.

3. According to the circulation method:

With natural circulation;

With mechanical circulation.

4. Water according to the parameters of the coolant:

Low temperature TI ≤ 105°C;

High temperature Tl>l05 0 C .

5. Water and steam in the direction of movement of the coolant in the mains:

dead ends;

With passing traffic.

6. Water and steam according to the connection scheme of heating devices with pipes:

Single-pipe;

Two-pipe.

7. Water at the place of laying the supply and return lines:

With top wiring;

With bottom wiring;

Inverted circulation.

8. Steam by steam pressure:

Vacuum steam R a<0.1 МПа;

Low pressure Pa =0.1 - 0.47 MPa;

High pressure Pa > 0.47 MPa.

3.2. HEAT CARRIERS

The heat carrier for the heating system can be any medium that has a good ability to accumulate thermal energy and change thermal properties, is mobile, cheap, does not worsen sanitary conditions in the room, and allows you to control the release of heat, including automatically. In addition, the coolant must contribute to the fulfillment of the requirements for heating systems.

The most widely used in heating systems are water, water vapor and air, since these heat carriers meet the listed requirements to the greatest extent. Consider the basic physical properties of each of the coolants that affect the design and operation of the heating system.

Properties water: high heat capacity, high density, incompressibility, expansion when heated with decreasing density, increase in boiling point with increasing pressure, release of absorbed gases with increasing temperature and decreasing pressure.

Properties pair: low density, high mobility, high enthalpy due to the latent heat of phase transformation (Table 3.1), increase in temperature and density with increasing pressure.

Properties air: low heat capacity and density, high mobility, decrease in density when heated.

A brief description of the parameters of heat carriers for the heating system is given in Table. 3.1.

Table 3.1. Parameters of the main coolants.

*Latent heat of phase transformation.

4.1. MAIN TYPES, CHARACTERISTICS AND APPLICATION OF HEATING SYSTEMS

Water heating due to a number of advantages over other systems is currently the most widespread. To understand the device and the principle of operation of the water heating system, consider the system diagram shown in Fig. 4.1.

Fig.4.1. Scheme two-pipe system water heating with top wiring and natural circulation.

The water heated in the heat generator K to a temperature T1 enters the heat pipeline - the main riser I into the supply main heat pipelines 2. Through the supply main heat pipelines, hot water enters the supply risers 9. Then, through the supply lines 13, hot water enters the heating devices 10, through the walls which heat is transferred to the room air. From the heaters, chilled water with a temperature of T2 through return pipes 14, return risers II and return main heat pipes 15 returns to the heat generator K, where it is again heated to a temperature T1 and then circulation occurs in a closed ring.

The water heating system is hydraulically closed and has a certain capacity of heating devices, heat pipes, fittings, i.e. constant volume of water filling it. With an increase in water temperature, it expands and in a closed, water-filled heating system, the internal hydraulic pressure can exceed the mechanical strength of its elements. To prevent this from happening, the water heating system has an expansion tank 4, designed to accommodate the increase in the volume of water when it is heated, as well as to remove air through it into the atmosphere, both when filling the system with water and during its operation. To regulate the heat transfer of heating devices, control valves 12 are installed on the connections to them.

Before commissioning, each system is filled with water from the water supply 17 through the return line to the signal pipe 3 into the expansion tank 4 . When the water level in the system rises to the level of the overflow pipe and water flows into the sink located in the boiler room, the valve on the signal pipe is closed and the filling of the system with water is stopped.

In case of insufficient heating of the devices due to clogging of pipelines or fittings, as well as in the event of a leak, water from individual risers can be drained without emptying and stopping the operation of other sections of the system. To do this, close the valves or taps 7 on the risers. A plug is unscrewed from the tee 8, installed at the bottom of the riser, and a flexible hose is attached to the riser fitting, through which water from the heat pipes and appliances flows into the sewer. In order for the water to drain faster and the glass completely, a cork is unscrewed from the upper tee 8. Presented in fig. 4.1-4.3 heating systems are called systems with natural circulation. In them, the movement of water is carried out under the action of the density difference between the chilled water after the heating devices and the hot water entering the heating system.

Vertical two-pipe systems with top wiring are mainly used for natural water circulation in heating systems for buildings up to 3 floors inclusive. These systems, in comparison with systems with a lower distribution of the supply line (Fig. 4.2), have a higher natural circulation pressure, it is easier to remove air from the system (through an expansion tank).

Rice. 7.14. Scheme of a two-pipe water heating system with bottom wiring and natural circulation

K-boiler; 1-main riser; 2, 3, 5-connecting, overflow, signal pipes of the expansion tank; 4 - expansion tank; 6-air line; 7 - air collector; 8 - supply lines; 9 - control valves for heating appliances; 10-heating devices; 11-reverse eyeliners; 12-return risers (chilled water); 13-feeding riser (hot water); 14-tee with a drain plug; 15- taps or valves on risers; 16, 17 - supply and return main heat pipelines; 18-stop valves or gate valves on main heat pipelines for regulating and shutting down individual branches; 19 - air taps.

Fig. 4.3. Scheme of a single-pipe water heating system with upper wiring and natural circulation

A two-pipe system with a lower location of both mains and natural circulation (Fig. 4.3) has an advantage over a system with an upper wiring: installation and start-up of systems can be carried out floor by floor as the building is erected: it is more convenient to operate the system, because valves and taps on the supply and return risers are located below and in one place. Two-pipe vertical systems with bottom wiring are used in low-rise buildings with double adjustment taps for heating appliances, which is explained by high hydraulic and thermal stability compared to systems with top wiring.

Removal of air from these systems is carried out by air valves 19 (Fig. 4.3).

The main advantage of two-pipe systems, regardless of the method of circulation of the heat carrier, is the supply of water with the highest temperature TI to each radiator, which ensures the maximum temperature difference TI-T2 and, consequently, the minimum surface area of ​​​​the devices. However, in a two-pipe system, especially with top wiring, there is a significant consumption of pipes and installation is complicated.

Compared to two-pipe heating systems, vertical one-pipe systems with closing sections (Fig. 4.3, left side) have a number of advantages: less initial cost, easier installation and shorter heat pipes, more beautiful appearance. If the devices located in the same room are connected according to the flow circuit to the riser on both sides, then one of them (the right riser in Fig. 4.3) is equipped with an adjusting valve. Such systems are used in low-rise industrial buildings.

On fig. 4.5 shows a diagram of single-pipe horizontal heating systems. Hot water in such systems enters the heating devices of the same floor from a heat pipe laid horizontally. Adjustment and inclusion of individual devices in horizontal systems with trailing sections (Fig. 4.5 b) is achieved as easily as in vertical systems. In horizontal flow systems (Fig. 4.5 a, c), adjustment can only be floor-by-floor, which is their significant drawback.

Rice. 4.5. Scheme of single-pipe horizontal water heating systems

a, c - flowing; b- with trailing sections.

Rice. 4.6 Water heating systems with artificial circulation

1 - expansion tank; 2 - air network; 3 - circulation pump; 4 - heat exchanger

The main advantages of single-pipe horizontal systems include less pipe consumption than in vertical systems, the possibility of switching the system on by floors and the standardity of nodes. Besides, horizontal systems do not require punching holes in the ceilings, and their installation in comparison with vertical systems is much easier. They are quite widely used in industrial and public buildings.

The general advantages of systems with natural circulation of water, which in some cases predetermine their choice, are the relative simplicity of the device and operation; lack of a pump and the need for an electric drive, noiseless operation; comparative durability with proper operation (up to 30-40 years) and ensuring a uniform air temperature in the room during heating period. However, in water heating systems with natural circulation, the natural pressure is very high. Therefore, with a large length of the circulation rings (> 30m), and, consequently, with significant resistance to the movement of water in them, the diameters of the pipelines, according to the calculation, are very large and the heating system is called economically unprofitable both in terms of initial costs and during operation.

In connection with the above, the scope of systems with natural circulation is limited to isolated civil buildings, where noise and vibration are unacceptable, apartment heating, upper (technical) floors of tall buildings.

Heating systems with artificial circulation (Fig. 4.6-4.8) are fundamentally different from water heating systems with natural circulation in that in them, in addition to the natural pressure resulting from the cooling of water in appliances and pipes, much more pressure is created by a circulation pump, which is installed on the return main pipeline near the boiler, and the expansion tank is connected not to the supply, but to the return heat pipe near the suction pipe of the pump. With this connection expansion tank air cannot be vented from the system through it; therefore, air lines, air collectors and air valves are used to remove air from the network of heat pipes and heating appliances.

Consider the schemes of vertical two-pipe heating systems with artificial circulation (Fig. 4.6). On the left is a system with an upper supply line, and on the right a system with a bottom position of both lines. Both heating systems belong to the so-called dead-end systems, in which there is often a large difference in pressure loss in the individual circulation rings, because. their lengths are different: the farther the device is located from the boiler, the greater the length of the ring of this device. Therefore, in systems with artificial circulation, especially with a large length of heat pipelines, it is advisable to use the associated movement of water in the supply and cooled mains according to the scheme proposed by prof. V. M. Chaplin. According to this scheme (Fig. 4.7), the length of all circulation rings is almost the same, as a result of which it is easy to obtain an equal pressure loss in them and uniform heating of all devices. SNiP recommends that such systems be installed with more than 6 risers in a branch. The disadvantage of this system compared to a dead-end one is a slightly longer total length of heat pipes, and, as a result, a 3-5% higher initial cost of the system.

Fig.4.7. Scheme of a two-pipe water heating system with upper wiring and associated movement of water in the supply and return lines and artificial circulation

1 - heat exchanger; 2, 3, 4, 5 - circulation, connecting, signal , overflow pipe expansion tank; 6 - expansion tank; 7- supply main heat pipeline; 8 - air collector; 9 - heater; 10 - double adjustment valve; 11 - return heat pipe; 12 - pump.

AT last years widely used single-pipe heating systems with bottom laying of hot and chilled water lines (Fig. 4.8) with artificial circulation of water.

The risers of the systems according to schemes b are divided into lifting and lowering. Riser systems according to the schemes a,in and G consist of lifting and lowering sections, along the upper part, usually under the floor of the upper floor, they are connected by a horizontal section. Risers are laid at a distance of 150 mm from the edge of the window opening. The length of the connections to the heating devices is taken as standard - 350 mm; heaters are shifted from the axis of the window towards the riser.

Fig 4.8. Varieties ( c, b, c, e) single-pipe water heating systems with bottom wiring

To regulate the heat transfer of heating devices, three-way valves of the KRTP type are installed, and in case of displaced closing sections, gate valves of reduced hydraulic resistance of the KRPSH type are installed.

A single-pipe system with bottom wiring is convenient for buildings with a non-attic floor, it has increased hydraulic and thermal stability. The advantages of single-pipe heating systems are the smaller diameter of the pipes, due to the greater pressure created by the pump; greater range; easier installation, and a greater possibility of unifying parts of heat pipes, instrument assemblies.

The disadvantages of the systems include the overrun of heating devices in comparison with two-pipe heating systems.

The scope of single-pipe heating systems is diverse: residential and public buildings with more than three floors, manufacturing enterprises, etc.

4.2. SELECTION OF THE HEATING SYSTEM

The heating system is chosen depending on the purpose and mode of operation of the building. Take into account the requirements for the system. The categories of fire and explosion hazard of the premises are taken into account.

The main factor determining the choice of a heating system is the thermal regime of the main premises of the building.

Considering the economic, procurement and installation and some operational advantages, SNiP 2.04.05-86, p.3.13 recommends designing, as a rule, single-pipe water heating systems from unified components and parts; when justified, the use of two-pipe systems is allowed.

The thermal regime of the premises of some buildings must be maintained unchanged throughout the entire heating season, while other buildings can be changed to reduce labor costs on a daily and weekly basis, during holidays, adjustment, repair and other work.

Civil, industrial and agricultural buildings with a constant thermal regime can be divided into 4 groups:

1) buildings of hospitals, maternity hospitals and similar medical and preventive institutions for round-the-clock use (except for psychiatric hospitals), the premises of which are subject to increased sanitary and hygienic requirements;

2) buildings of children's institutions, residential buildings, hostels, hotels, rest houses, sanatoriums, boarding houses, polyclinics, outpatient clinics, pharmacies, psychiatric hospitals, museums, exhibitions, libraries, baths, book depositories;

3) buildings of swimming pools, railway stations, airports;

4) industrial and agricultural buildings with a continuous technological process.

For example, in buildings of the second group, water heating with radiators and convectors (except for hospitals and baths). The limiting temperature of the water coolant is taken in two-pipe systems equal to 95 ° C, in one-pipe systems of buildings (except for baths, hospitals and children's institutions) -105 ° C (for convectors with a casing up to 130 ° C). For heating stairwells, it is possible to increase the design temperature up to 150°C. In buildings with round-the-clock operating supply ventilation, primarily in the buildings of museums, art galleries, book depositories, archives (except for hospitals and children's institutions), central air heating is arranged.

Heating systems should be designed with pump circulation, lower wiring, dead-end with open laying of risers in the first place.

The remaining systems are adopted depending on local conditions: architectural and planning solution, required thermal regime, type and parameters of the coolant in the external heating network, etc.

The heating system in a private house is, most often, a set stand-alone equipment, which uses the most appropriate substances for a particular region as an energy and heat carrier. Therefore, for each specific heating scheme, an individual calculation of the heat output of the heating system is required, which takes into account many factors, such as minimum flow heat energy for the home, heat consumption for rooms - for everyone, helps to determine the energy consumption per day and during the heating season, etc.

Formulas and coefficients for thermal calculation

The rated thermal power of the heating system for a private facility is determined by the formula (all results are expressed in kW):

• Q \u003d Q 1 x b 1 x b 2 + Q 2 - Q 3; where:
• Q 1 - total losses heat in the building according to calculations, kW;
• b 1 - coefficient of additional thermal energy from radiators in excess of what the calculation showed. The coefficient values ​​are shown in the table below:

• b 2 - coefficient of additional heat loss by radiators installed near external walls without shielding casings. The coefficient indicators are reflected in the table below:

• Q 2 - heat loss in pipelines laid in an unheated space;
• Q 3 - additional heat from lighting fixtures, household appliances and appliances, residents, etc. For residential buildings, Q 3 is taken as 0.01 kW / 1 m 2.

Q a - thermal energy passing through fences and external walls;

Q b - heat loss during heating of the air of the ventilation system.

The value of Q a and Q b is calculated for each individual room with connected heating.

Thermal energy Q a is determined by the formula:

• Q a \u003d 1 / R x A x (t b - t n) x (1 + Ʃß), where:
• A - the area of ​​\u200b\u200bthe fence (outer wall) in m 2;
• R is the heat transfer of the fence in m 2 ° С / W ( reference Information in SNiP II-3-79).

The need for thermal calculations for the whole house and individual heated rooms is justified by energy savings and family budget. In what cases such calculations are carried out:

1. To accurately calculate the power of boiler equipment for the most efficient heating all premises connected to heating. By purchasing a boiler without preliminary calculations you can install equipment that is completely inappropriate in terms of parameters, which will not cope with its task, and the money will be wasted. The thermal parameters of the entire heating system are determined as a result of adding up all the heat energy consumption in the premises connected and not connected to the heating boiler, if the pipeline passes through them. A power reserve is also needed for heat consumption to reduce wear. heating equipment and minimize the occurrence emergencies at high loads in cold weather;
2. Calculations of the thermal parameters of the heating system are necessary to obtain a technical certificate (TU), without which it will not be possible to agree on a project for gasification of a private house, since in 80% of installation cases autonomous heating install a gas boiler and related equipment. For other types of heating units specifications and connection documentation is not needed. For gas equipment it is necessary to know the annual gas consumption, and without appropriate calculations it will not be possible to obtain an exact figure;
3. Get the thermal parameters of the heating system is also necessary for the purchase the right equipment– pipes, radiators, fittings, filters, etc.

Accurate calculations of power and heat consumption for residential premises

The level and quality of insulation depends on the quality of work and architectural features rooms of the whole house. Most of the heat loss (up to 40%) when heating a building occurs through the surface of the outer walls, through windows and doors (up to 20%), as well as through the roof and floor (up to 10%). The remaining 30% of the heat can leave the house through vents and ducts.

To obtain refined results, the following reference coefficients are used:

1. Q 1 - used in calculations for rooms with windows. For PVC windows with double-glazed windows Q 1 \u003d 1, for windows with single-chamber glazing Q 1 \u003d 1.27, for a three-chamber window Q 1 \u003d 0.85;
2. Q 2 - used in the calculation of the coefficient of insulation internal walls. For foam concrete Q 2 \u003d 1, for concrete Q 2 - 1.2, for brick Q 2 \u003d 1.5;
3. Q 3 is used in calculating the ratio of floor areas and window openings. For 20% of the wall glazing area, the coefficient Q3 = 1, for 50% glazing, Q3 is taken as 1.5;
4. The value of the coefficient Q 4 varies depending on the minimum outdoor temperature for the entire annual heating period. At outdoor temperature-20 0 C Q 4 \u003d 1, then - for every 5 0 C, 0.1 is added or subtracted in one direction or another;
5. Coefficient Q 5 is used in calculations that take into account the total number of walls of the building. With one wall in the calculations Q 5 = 1, with 12 and 3 walls Q 5 = 1.2, for 4 walls Q 5 = 1.33;
6. Q 6 is used if the functional purpose of the room under the room for which the calculations are made is taken into account when calculating heat losses. If there is a residential floor at the top, then the coefficient Q 6 \u003d 0.82, if a heated or insulated attic, then Q 6 - 0.91, for a cold attic space Q6 = 1;
7. Parameter Q 7 fluctuates depending on the height of the ceilings of the examined room. With a ceiling height ≤ 2.5 m, the coefficient Q 7 \u003d 1.0, if the ceiling is higher than 3 m, then Q 7 is taken as 1.05.

After determining all the necessary amendments, the calculation of the heat power and heat losses in heating system for each individual room according to the following formula:

• Q i \u003d q x Si x Q 1 x Q 2 x Q 3 x Q 4 x Q 5 x Q 6 x Q 7, where:
• q \u003d 100 W / m²;
• Si is the area of ​​the examined premises.

Parameter results will increase when applying coefficients ≥ 1, and decrease if Q 1-Q 7 ≤1. After calculating the specific value of the calculation results for a specific room, you can calculate the total heat output of private autonomous heating using the following formula:

Q = Σ x Qi, (i = 1…N), where: N is the total number of rooms in the building.

To create comfort in residential and industrial premises carry out the preparation of the heat balance and determine the coefficient of performance (COP) of heaters. In all calculations, an energy characteristic is used, which makes it possible to link the loads of heating sources with the consumption indicators of consumers - thermal power. calculation physical quantity produced by formulas.

To calculate the thermal power, special formulas are used

Heater efficiency

Power is the physical definition of the rate of transmission or power consumption. It is equal to the ratio of the amount of work for a certain period of time to this period. Heating devices are characterized by the consumption of electricity in kilowatts.

To compare energies various kinds heat power formula introduced: N = Q / Δt, where:

1. Q is the amount of heat in joules;
2. Δ t is the time interval for energy release in seconds;
3. the dimension of the obtained value is J / s \u003d W.

To assess the efficiency of the heaters, a coefficient is used that indicates the amount of heat used for its intended purpose - efficiency. The indicator is determined by dividing the useful energy by the spent energy, it is a dimensionless unit and is expressed as a percentage. Towards different parts, constituting environment, the efficiency of the heater has unequal values. If we evaluate the kettle as a water heater, its efficiency will be 90%, and when used as a room heater, the coefficient rises to 99%.

The explanation for this is simple.: due to heat exchange with the surroundings, part of the temperature is dissipated and lost. The amount of energy lost depends on the conductivity of the materials and other factors. It is possible to theoretically calculate the heat loss power using the formula P = λ × S Δ T / h. Here λ is the thermal conductivity coefficient, W/(m × K); S - heat exchange area area, m²; Δ T - temperature difference on the controlled surface, deg. WITH; h is the thickness of the insulating layer, m.

It is clear from the formula that in order to increase power, it is necessary to increase the number of heating radiators and the heat transfer area. By reducing the contact surface with external environment minimizing room temperature losses. The more massive the wall of the building, the less heat leakage will be.

Space heating balance

The preparation of a project for any object begins with a heat engineering calculation designed to solve the problem of providing the building with heating, taking into account losses from each room. Balancing helps to find out what part of the heat is stored in the walls of the building, how much goes outside, the amount of energy required to generate a comfortable climate in the rooms.

Determination of thermal power is necessary to solve the following issues:

1. calculate the load of the heating boiler, which will provide heating, hot water supply, air conditioning and the functioning of the ventilation system;
2. agree on the gasification of the building and obtain technical conditions for connection to distribution network. This will require the volume annual expense fuel and the need for power (Gcal / h) of heat sources;
3. choose the equipment necessary for space heating.

Do not forget about the corresponding formula

It follows from the law of conservation of energy that confined space with constant temperature regime the heat balance must be observed: Q inflows - Q losses = 0 or Q excess = 0, or Σ Q = 0. A constant microclimate is maintained at the same level during the heating period in buildings of socially significant objects: residential, children's and medical institutions, as well as in production with a continuous mode of operation. If the heat loss exceeds the incoming, it is required to heat the premises.

Technical calculation helps to optimize the consumption of materials during construction, reduce the cost of building construction. The total thermal power of the boiler is determined by adding up the energy for heating apartments, heating hot water, compensation for ventilation and air conditioning losses, and a reserve for peak cold.

Thermal power calculation

It is difficult for a non-specialist to perform accurate calculations on a heating system, but simplified methods allow an unprepared person to calculate indicators. If you make calculations "by eye", it may turn out that the power of the boiler or heater is not enough. Or, on the contrary, due to the excess of generated energy, you will have to let the heat “downwind”.

Methods for self-assessment of heating characteristics:

1. Using the standard from the project documentation. For the Moscow region, a value of 100-150 watts per 1 m² is applied. The area to be heated is multiplied by the rate - this will be the desired parameter.
2. Application of the formula for calculating the thermal power: N = V × Δ T × K, kcal / hour. Symbol designations: V - room volume, Δ T - temperature difference inside and outside the room, K - heat transmission or dissipation coefficient.
3. Reliance on aggregated indicators. The method is similar to the previous method, but is used to determine the heat load of multi-apartment buildings.

The values ​​of the dispersion coefficient are taken from the tables, the limits of the change in the characteristic are from 0.6 to 4. Approximate values ​​for a simplified calculation:

An example of calculating the heat output of a boiler for a room of 80 m² with a ceiling of 2.5 m. Volume 80 × 2.5 = 200 m³. The dispersion coefficient for a typical house is 1.5. The difference between room (22°C) and outdoor (minus 40°C) temperatures is 62°C. We apply the formula: N \u003d 200 × 62 × 1.5 \u003d 18600 kcal / hour. The conversion to kilowatts is done by dividing by 860. Result = 21.6 kW.

The resulting power value is increased by 10% if there is a possibility of frost below 40 ° C / 21.6 × 1.1 = 23.8. For further calculations, the result is rounded up to 24 kW.