Heating and supply ventilation systems must operate in buildings at average daily outside air temperatures tn.day from + 8C and below in areas with the design outside air temperature for heating design up to -30C and at tn.day from + 10C and below in areas with the design outside air temperature for the design of heating below -30C. The values ​​of the duration of the heating period Nо and the average outside air temperature tn.av are given in and for some cities of Russia in Appendix A. tn.day = + 10C.

Heat consumption in GJ or Gcal for heating and ventilation of buildings for a certain period (month or heating season) is determined by the following formulas

Qо. = 0.00124NQо.р (tвн - tн.ср) / (tвн - tн.р),

Qw. = 0.001ZwNQw.r (tvn - tn.w.) / (tvn - tn.r),

where N is the number of days in the billing period; for heating systems N is the duration heating season No from Appendix A or the number of days in a particular month Nmonth; for supply systems ventilation N is the number of working days of the enterprise or institution during the month Nm.w or the heating season Nw, for example, with a five-day work week Nm.w = Nm.5 / 7, and Nw = No5 / 7;

Qо.р, Qв.р - calculated heat load(maximum hourly consumption) in MJ / h or Mcal / h for heating or ventilation of the building, calculated by the formulas.

tvn - average temperature air in the building, given in Appendix B;

tн.ср - the average outside air temperature for the period under consideration (heating season or month), taken according to or according to Appendix B;

tн.р - the design temperature of the outside air for the design of heating (the temperature of the coldest five-day period with a security of 0.92);

Zв - the number of hours of operation of the supply ventilation systems and air-thermal curtains during the day; with one-shift work of a workshop or institution, Zw = 8 hours / day, with two-shift work - Zw = 16 hours / day, in the absence of data in general for the microdistrict Zw = 16 hours / day.

The annual heat consumption for hot water supply Qgw.year in GJ / year or Gcal / year is determined by the formula

Qgw.year = 0.001Qday (Nz + Nl Kl),

where Qday is the daily heat consumption for hot water supply of the building in MJ / day or Mcal / day, calculated by the formula;

Nз - number of days of consumption hot water in the building for the heating (winter) period; for residential buildings, hospitals, grocery stores and other buildings with daily operation of hot water supply systems, Nz is taken equal to the duration of the heating season Nо; for enterprises and institutions, Nz is the number of working days during the heating period, for example, with a five-day working week Nz = Nо5 / 7;

Nl is the number of days of hot water consumption in the building for summer period; for residential buildings, hospitals, grocery stores and other buildings with daily operation of hot water supply systems Nl = 350 - Nо, where 350 is the estimated number of days in a year of operation of hot water systems; for enterprises and institutions Nl is the number of working days during the summer period, for example, with a five-day working week Nl = (350 - Nо) 5/7;

Kl is a coefficient that takes into account a decrease in heat consumption for hot water due to a higher initial temperature of heated water, which in winter is equal to tx.z = 5 deg, and in summer, on average tx.l = 15 deg; in this case, the coefficient Kl will be equal to Kl = (tg - tx.l) / (tg - tx.z) = (55 - 15) / (55 - 5) = 0.8; when taking water from wells, it may turn out to be tx.l = tx.z and then Kl = 1.0;

Coefficient taking into account a possible decrease in the number of hot water consumers in summer time in connection with the departure of a part of residents from the city on vacation and taken for the housing and communal sector equal = 0.8 (for resort and southern cities = 1.5), and for enterprises = 1.0.

What is it - specific consumption of heat energy for heating a building? Is it possible to calculate the hourly heat consumption for heating in a cottage with your own hands? We will devote this article to terminology and general principles calculating the need for heat energy.

The basis of new building projects is energy efficiency.

Terminology

What is it - specific heat consumption for heating?

We are talking about the amount of thermal energy that must be supplied inside the building in terms of each square or cubic meter in order to maintain normalized parameters in it that are comfortable for work and living.

Usually, a preliminary calculation of heat losses is carried out using enlarged meters, that is, based on the average thermal resistance of the walls, the approximate temperature in the building and its total volume.

Factors

What affects the annual heat consumption for heating?

• Heating season duration (). It, in turn, is determined by the dates when the average daily temperature outside over the last five days will drop below (and rise above) 8 degrees Celsius.

Useful: in practice, the weather forecast is taken into account when planning the start and stop of heating. Long thaws also occur in winter, and frosts can hit as early as September.

• Average temperatures of the winter months. Usually, when designing a heating system, the average monthly temperature of the coldest month, January, is taken as a reference. It is clear that the colder it is outside, the more heat the building loses through the enclosing structures.

• The degree of thermal insulation of the building very strongly affects what will be the rate of heat output for it. The insulated facade is able to reduce the need for heat by half in relation to the wall made of concrete slabs or brick.
• Glazing coefficient of the building. Even when using multi-chamber double-glazed windows and energy-saving spraying, noticeably more heat is lost through the windows than through the walls. The larger part of the façade is glazed, the greater the need for heat.
• Illumination of the building. On a sunny day, a surface oriented perpendicular sunbeams, capable of absorbing up to a kilowatt of heat for square meter.

Clarification: In practice, it will be extremely difficult to accurately calculate the amount of absorbed solar heat. The same glass facades, which lose heat in cloudy weather, will serve as heating in sunny weather. The orientation of a building, the slope of the roof and even the color of the walls will all affect the ability to absorb solar heat.

Calculations

Theory is theory, but how heating costs are calculated in practice country house? Is it possible to estimate the estimated costs without plunging into the abyss of complex heat engineering formulas?

Consumption of the required amount of thermal energy

Instructions for calculating the approximate quantity necessary heat relatively simple. The key phrase is an approximate amount: for the sake of simplification of calculations, we sacrifice accuracy, ignoring a number of factors.

• The basic value of the amount of thermal energy is 40 watts per cubic meter of the volume of the cottage.
• The base value is added 100 watts for each window and 200 watts for each door in the outer walls.

• Further, the resulting value is multiplied by a coefficient, which is determined by the average amount of heat loss through the outer contour of the building. For apartments in the center apartment building a coefficient equal to one is taken: only losses through the facade are noticeable. Three of the four walls of the contour of the apartment are bordered by warm rooms.

For corner and end apartments, a coefficient of 1.2 - 1.3 is taken, depending on the material of the walls. The reasons are obvious: two or even three walls become external.

Finally, in a private house there is a street not only along the perimeter, but also below and above. In this case, a factor of 1.5 is applied.

Please note: for apartments on the outer floors, if the basement and attic are not insulated, it is also quite logical to use a coefficient of 1.3 in the middle of the house and 1.4 at the end.

• Finally, the resulting thermal power multiplied by the regional coefficient: 0.7 for Anapa or Krasnodar, 1.3 for St. Petersburg, 1.5 for Khabarovsk and 2.0 for Yakutia.

In the cold climatic zone- special heating requirements.

Let's calculate how much heat is needed for a 10x10x3 meter cottage in the city of Komsomolsk-on-Amur, Khabarovsk Territory.

The volume of the building is 10 * 10 * 3 = 300 m3.

Multiplying the volume by 40 watts / cube will give 300 * 40 = 12000 watts.

Six windows and one door is another 6 * 100 + 200 = 800 watts. 1200 + 800 = 12800.

Private house. The coefficient is 1.5. 12800 * 1.5 = 19200.

Khabarovsk region. We multiply the demand for heat by one and a half times: 19200 * 1.5 = 28800. Total - at the peak of frost, we need about a 30-kilowatt boiler.

Heating cost calculation

The easiest way is to calculate the electricity consumption for heating: when using an electric boiler, it is exactly equal to the cost of thermal power. With a continuous consumption of 30 kilowatts per hour, we will spend 30 * 4 rubles (the approximate current price of a kilowatt-hour of electricity) = 120 rubles.

Fortunately, the reality is not so nightmare: as practice shows, the average demand for heat is about half the calculated one.

• Firewood - 0.4 kg / kWh. Thus, the approximate rates of firewood consumption for heating will be in our case equal to 30/2 (the rated power, as we remember, can be divided in half) * 0.4 = 6 kilograms per hour.
• Consumption of brown coal per kilowatt of heat - 0.2 kg. Coal consumption rates for heating are calculated in our case as 30/2 * 0.2 = 3 kg / h.

Brown coal is a relatively inexpensive source of heat.

• For firewood - 3 rubles (cost per kilogram) * 720 (hours per month) * 6 (hourly consumption) = 12,960 rubles.
• For coal - 2 rubles * 720 * 3 = 4320 rubles (read others).

Conclusion

You can, as usual, find additional information about and methods of calculating costs in the video attached to the article. Warm winters!

What is a gigacalorie measuring unit? How does it relate to the traditional kilowatt-hours, in which it is calculated thermal energy? What information do you need to have in order to correctly calculate Gcal for heating? After all, what formula should you use during the calculation? This, as well as many other things, will be discussed in today's article.

What is Gcal?

You should start with a related definition. Calorie refers to the amount of energy required to heat one gram of water to one degree Celsius (under atmospheric pressure, of course). And in view of the fact that from the point of view of heating costs, say, at home, one calorie is a meager value, then in most cases gigacalories (or abbreviated Gcal) are used for calculations, corresponding to one billion calories. We have decided on this, we are moving on.

The use of this value is regulated by the relevant document of the Ministry of Fuel and Energy, issued back in 1995.

Note! On average, the consumption standard in Russia per square meter is 0.0342 Gcal per month. Of course, this figure may change for different regions since everything depends on climatic conditions.

So, what is a gigacalorie, if we "transform" it into values ​​that are more familiar to us? See for yourself.

1. One gigacalorie equals approximately 1,162.2 kilowatt-hours.

2. One gigacalorie of energy is enough to heat a thousand tons of water up to + 1 ° С.

What is all this for?

The problem should be considered from two points of view - from the point of view apartment buildings and private. Let's start with the first ones.

Apartment buildings

There is nothing complicated here: gigacalories are used in thermal calculations. And if you know how much heat energy remains in the house, then you can present the consumer with a specific bill. Let's make a small comparison: if centralized heating will function in the absence of a meter, then you have to pay according to the area of ​​the heated room. If there is a heat meter, this in itself implies a horizontal wiring (either collector or sequential): two risers are brought into the apartment (for "return" and supply), and the intra-apartment system (more precisely, its configuration) is determined by the residents. This kind of scheme is used in new buildings, thanks to which people regulate the consumption of thermal energy, making a choice between economy and comfort.

Let's find out how this adjustment is carried out.

1. Installation of a common thermostat on the "return" line. In this case, the flow rate of the working fluid is determined by the temperature inside the apartment: if it decreases, then the flow rate will accordingly increase, and if it rises, it will decrease.

2. Throttling of heating radiators. Thanks to the throttle passability heater is limited, the temperature decreases, which means that the consumption of thermal energy is reduced.

Private houses

We continue to talk about the calculation of Gcal for heating. Owners country houses they are primarily interested in the cost of a gigacalorie of thermal energy obtained from a particular type of fuel. The table below can help with this.

Table. Comparison of the cost of 1 Gcal (including transportation costs)

* - prices are approximate, since tariffs may differ depending on the region, moreover, they are also constantly growing.

Heat meters

Now let's find out what information is needed in order to calculate the heating. It is easy to guess what this information is.

1. Temperature of the working fluid at the outlet / inlet of a specific section of the line.

2. The flow rate of the working fluid that passes through the heating devices.

Consumption is determined by using heat metering devices, that is, meters. These can be of two types, let's get acquainted with them.

Vane meters

Such devices are intended not only for heating systems, but also for hot water supply. Their only difference from those counters that are used for cold water, is the material from which the impeller is made - in this case, it is more resistant to high temperatures.

As for the mechanism of operation, it is practically the same:

• due to the circulation of the working fluid, the impeller begins to rotate;
• the rotation of the impeller is transferred to the metering mechanism;
• transmission is carried out without direct interaction, but with the help of a permanent magnet.

Despite the fact that the design of such meters is extremely simple, their response threshold is quite low, moreover, there is also reliable protection from distortion of readings: the slightest attempts to brake the impeller by means of an external magnetic field are suppressed thanks to the anti-magnetic shield.

Devices with a differential recorder

Such devices operate on the basis of Bernoulli's law, which states that the speed of a gas or liquid flow is inversely proportional to its static movement. But how does this hydrodynamic property apply to the calculation of the flow rate of the working fluid? It's very simple - you just need to block her path with a retaining washer. In this case, the rate of pressure drop on this washer will be inversely proportional to the speed of the moving stream. And if the pressure is recorded by two sensors at once, then you can easily determine the flow rate, and in real time.

Note! The design of the meter implies the presence of electronics. The vast majority of such modern models provides not only dry information (temperature of the working fluid, its flow rate), but also determines the actual use of thermal energy. The control module here is equipped with a port for connecting to a PC and can be manually configured.

Many readers will probably have a logical question: what if we are talking not about a closed heating system, but about an open one, in which selection for hot water supply is possible? How, in this case, to calculate Gcal for heating? The answer is quite obvious: here the pressure sensors (as well as the retaining washers) are placed simultaneously on the supply and on the "return". And the difference in the flow rate of the working fluid will indicate the amount of heated water that was used for domestic needs.

How to calculate the consumed heat energy?

If a heat meter is absent for one reason or another, then the following formula must be used to calculate heat energy:

Vx (T1-T2) / 1000 = Q

Let's take a look at what these conventions mean.

1. V denotes the amount of hot water consumed, which can be calculated either in cubic meters or in tons.

2. T1 is the temperature indicator of the hottest water (traditionally measured in the usual degrees Celsius). In this case, it is preferable to use exactly the temperature that is observed at a certain operating pressure. By the way, the indicator even has a special name - this is enthalpy. But if desired sensor is absent, then as a basis you can take that temperature regime, which is extremely close to this enthalpy. In most cases, the average is about 60-65 degrees.

3. T2 in the above formula also denotes the temperature, but already of cold water. Due to the fact that to penetrate the highway with cold water- the matter is quite difficult, constant values ​​are used as this value, which can change depending on the climatic conditions on the street. So, in winter, when the heating season is in full swing, this indicator is 5 degrees, and in the summer, with the heating turned off, 15 degrees.

4. As for 1000, this is the standard coefficient used in the formula in order to get the result already in giga calories. It will be more accurate than using calories.

5. Finally, Q is the total heat energy.

As you can see, there is nothing complicated here, so we move on. If the heating circuit closed type(and this is more convenient from an operational point of view), then the calculations must be made in a slightly different way. Formula to be used for a building with a closed heating system, should look like this:

((V1x (T1-T) - (V2x (T2-T)) = Q

Now, respectively, to decryption.

1. V1 denotes the flow rate of the working fluid in the supply pipeline (not only water, but also steam can act as a source of thermal energy, which is typical).

2. V2 is the flow rate of the working fluid in the "return" line.

3. T is an indicator of the temperature of a cold liquid.

4. Т1 - water temperature in the supply pipeline.

5. T2 is the temperature indicator that is observed at the outlet.

6. And finally, Q is the same amount of heat energy.

It is also worth noting that the calculation of Gcal for heating in this case from several designations:

• thermal energy that entered the system (measured in calories);
• temperature indicator during the removal of the working fluid through the "return" pipeline.

Other ways to determine the amount of heat

We add that there are also other ways by which you can calculate the amount of heat that enters the heating system. In this case, the formula is not only slightly different from the ones below, but also has several variations.

((V1x (T1-T2) + (V1- V2) x (T2-T1)) / 1000 = Q

((V2x (T1-T2) + (V1- V2) x (T1-T) / 1000 = Q

As for the values ​​of the variables, they are the same here as in the previous paragraph of this article. Based on all this, we can confidently conclude that it is quite possible to calculate heat for heating on our own. However, at the same time, one should not forget about consulting with specialized organizations that are responsible for providing housing with heat, since their methods and principles for making calculations may differ, and significantly, and the procedure may consist of a different set of measures.

If you intend to equip a "warm floor" system, then prepare for the fact that the calculation process will be more complicated, since it takes into account not only the features of the heating circuit, but also the characteristics electrical network, which, in fact, will heat the floor. Moreover, the organizations that are engaged in the installation of this kind of equipment will also be different.

Note! People often face a problem when calories should be converted into kilowatts, which is explained by the use of a unit of measurement in many specialized manuals, which is called "C" in the international system.

In such cases, it must be remembered that the coefficient due to which kilocalories will be converted into kilowatts is 850. In simpler terms, one kilowatt is 850 kilocalories. This option the calculation is simpler than the ones given above, since it is possible to determine the value in gigacalories in a few seconds, since Gcal, as noted earlier, is a million calories.

To avoid possible mistakes, do not forget that almost all modern heat meters work with some error, albeit within the permissible limits. Such an error can also be calculated with your own hands, for which you need to use the following formula:

(V1- V2) / (V1 + V2) х100 = E

Traditionally, now we figure out what each of these variable values ​​means.

1. V1 is the flow rate of the working fluid in the supply line.

2. V2 - a similar indicator, but already in the "return" pipeline.

3. 100 is the number by which the value is converted to percent.

4. Finally, E is the error of the accounting device.

According to operational requirements and norms, the maximum permissible error should not exceed 2 percent, although in most meters it is somewhere around 1 percent.

As a result, we note that a correctly calculated Gcal for heating can significantly save money spent on heating the room. At first glance, this procedure is quite complicated, but - and you have seen it yourself - with good instructions, there is nothing difficult about it.

Video - How to calculate heating in a private house

Annual heat loss of the building Q ts , kWh, should be determined by the formula

where is the sum of heat losses through the enclosing structures of the premises, W;

t v- the weighted average by the volume of the building, the design temperature of the internal air, С;

t NS- the average temperature of the coldest five-day period with a security of 0.92, С, taken according to TKP / 1 /;

D- the number of degree-days of the heating period, Сdays.

8.5.4. Total annual consumption of heat energy for heating and ventilation of the building

Total annual consumption of heat energy for heating and ventilation of the building Q s, kWh, should be determined by the formula

Q s = Q ts  Q hs  1 , (7)

where Q ts- annual heat losses of the building, kWh;

Q hs- annual heat input from electrical appliances, lighting, technological equipment, communications, materials, people and other sources, kWh;

 1 - coefficient taken according to table 1 depending on the method of regulation of the building heating system.

Table 8.1

Q s = Q ts Q hs  1 = 150.54 - 69.05 0.4 = 122.92 kWh

8.5.5. Specific consumption of heat energy for heating and ventilation

Specific consumption of heat energy for heating and ventilation of buildings q A, Wh / (m 2  ° Сday), and q V, W · h / (m 3  ° Сday), should be determined by the formulas:

where Q s- total annual consumption of heat energy for heating and ventilation of the building, kWh;

F from - heated area of ​​the building, m 2, determined along the inner perimeter of the outer vertical enclosing structures;

V from- heated building volume, m 3;

D- the number of degree-days of the heating period, ° Сday.

8.5.6. Standard specific consumption of heat energy for heating and ventilation

The standard specific consumption of heat energy for heating and ventilation of residential and public buildings is shown in Table 8.2.

Table 8.2