Determination of heat consumption for heating a residential building. Calculation of the heat load on the heating of a building: formula, examples. Calculation of heat loads

What it is - specific consumption thermal energy to heat the building? Is it possible to calculate the hourly heat consumption for heating in a cottage with your own hands? This article will be devoted to terminology and general principles calculation of the need for thermal energy.

The basis of new building projects is energy efficiency.

Terminology

What is specific heat consumption for heating?

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

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

Factors

What influences annual consumption heat for heating?

Duration heating season (). It, in turn, is determined by the dates when the average daily temperature in the street for the last five days falls below (and rises above) 8 degrees Celsius.

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

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

The degree of thermal insulation of the building greatly affects what will be the rate of thermal power for him. An insulated facade can reduce the need for heat by half relative to a wall made of concrete slabs or brick.
building glazing factor. Even when using multi-chamber double-glazed windows and energy-saving spraying, noticeably more heat is lost through windows than through walls. The greater part of the facade is glazed, the greater the need for heat.
The degree of illumination of the building. On a sunny day, a surface oriented perpendicular sunbeams, capable of absorbing up to a kilowatt of heat per square meter.

Clarification: in practice, an accurate calculation of the amount of absorbed solar heat will be extremely difficult. Those same glass facades, which lose heat in cloudy weather, will serve as heating in sunny weather. The orientation of the 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 diving into the abyss complex formulas heat engineering?

Consumption of the required amount of thermal energy

The instruction for calculating the approximate amount of heat required is relatively simple. The key phrase is an approximate amount: for the sake of simplifying calculations, we sacrifice accuracy, ignoring a number of factors.

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

Further, the obtained 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 border on 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, the street is not only along the perimeter, but also from below and above. In this case, a coefficient of 1.5 is applied.

Please note: for apartments on the extreme 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 received thermal power is multiplied by a 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 climate zone- special heating requirements.

Let's calculate how much heat is needed for a cottage measuring 10x10x3 meters 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. Coefficient 1.5. 12800*1.5=19200.

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

Calculation of heating costs

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

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

Firewood - 0.4 kg / kW / h. Thus, the approximate norms for the consumption of firewood for heating in our case will be equal to 30/2 (the rated power, as we remember, can be divided in half) * 0.4 \u003d 6 kilograms per hour.
Consumption brown coal in terms of kilowatt of heat - 0.2 kg. The consumption rates of coal for heating are calculated in our case as 30/2*0.2=3 kg/h.

Brown coal is a relatively inexpensive heat source.

For firewood - 3 rubles (the cost of a kilogram) * 720 (hours in a month) * 6 (hourly consumption) \u003d 12960 rubles.
For coal - 2 rubles * 720 * 3 = 4320 rubles (read others).

Conclusion

You can, as usual, find additional information on cost calculation methods in the video attached to the article. Warm winters!

The procedure for calculating heating in the housing stock depends on the availability of metering devices and on how the house is equipped with them. There are several options for completing multi-apartment residential buildings with meters, and according to which, heat energy is calculated:

the presence of a common house meter, while apartments and non-residential premises are not equipped with metering devices.
heating costs are controlled by a common house device, and all or some rooms are equipped with metering devices.
there is no general house device for fixing the consumption and consumption of thermal energy.

Before calculating the number of gigacalories spent, it is necessary to find out the presence or absence of controllers in the house and in each individual room, including non-residential ones. Let's consider all three options for calculating thermal energy, for each of which a specific formula has been developed (posted on the website of state authorized bodies).

Option 1

So the house is equipped control device, and some rooms were left without it. Here it is necessary to take into account two positions: the calculation of Gcal for heating an apartment, the cost of thermal energy for general house needs (ODN).

In this case, formula No. 3 is used, which is based on the readings of the general meter, the area of \u200b\u200bthe house and the footage of the apartment.

Calculation example

We will assume that the controller recorded the heating costs of the house at 300 Gcal / month (this information can be obtained from the receipt or by contacting management company). For example, total area house, which consists of the sum of the areas of all premises (residential and non-residential), is 8000 m² (you can also find out this figure from the receipt or from the management company).

Let's take the area of an apartment of 70 m² (indicated in the data sheet, rental agreement or registration certificate). The last figure, on which the calculation of payment for consumed heat energy depends, is the tariff established by the authorized bodies of the Russian Federation (indicated on the receipt or found out in the house management company). Today, the heating tariff is 1,400 rubles/gcal.

Substituting the data in formula No. 3, we get the following result: 300 x 70 / 8,000 x 1,400 \u003d 1875 rubles.

Now you can proceed to the second stage of accounting for heating costs spent on the general needs of the house. Two formulas are required here: the search for the volume of services (No. 14) and the payment for the consumption of gigacalories in rubles (No. 10).

In order to correctly determine the volume of heating in this case, it will be necessary to sum up the area of \u200b\u200ball apartments and premises provided for common use(information provided by the management company).

For example, we have a total footage of 7000 m² (including apartments, offices, retail premises.).

Let's start calculating the payment for the consumption of thermal energy according to formula No. 14: 300 x (1 - 7,000 / 8,000) x 70 / 7,000 \u003d 0.375 Gcal.

Using formula No. 10, we get: 0.375 x 1,400 = 525, where:

0.375 - volume of service for heat supply;
1400 r. – tariff;
525 rubles - amount of payment.

We summarize the results (1875 + 525) and find out that the payment for heat consumption will be 2350 rubles.

Option 2

Now we will calculate payments in those conditions when the house is equipped with a common meter for heating, as well as some apartments are equipped with individual meters. As in the previous case, the calculation will be carried out in two positions (thermal energy consumption for housing and ONE).

We will need formulas No. 1 and No. 2 (accrual rules according to the testimony of the controller or taking into account the norms for heat consumption for residential premises in gcal). Calculations will be carried out in relation to the area of a residential building and an apartment from the previous version.

1.3 gigacalories - readings of an individual counter;
1 1820 r. - approved rate.

0.025 gcal - standard indicator of heat consumption per 1 m² of area in an apartment;
70 m² - area of the apartment;
1 400 rubles - tariff for thermal energy.

As it becomes clear, with this option, the payment amount will depend on the availability of a metering device in your apartment.

Formula No. 13: (300 - 12 - 7,000 x 0.025 - 9 - 30) x 75 / 8,000 \u003d 1.425 gcal, where:

300 gcal - indications of a common house meter;
12 gcal - the amount of thermal energy used for heating non-residential premises;
6,000 m² - the sum of the area of all residential premises;
0.025 - standard (thermal energy consumption for apartments);
9 gcal - the sum of indicators from the meters of all apartments that are equipped with metering devices;
35 gcal - the amount of heat spent on supply hot water in the absence of its centralized supply;
70 m² - area of the apartment;
8,000 m² - total area (all residential and non-residential premises in the house).

Please note that this option only includes real amounts of energy consumed, and if your house is equipped with a centralized hot water supply, then the amount of heat spent on hot water needs is not taken into account. The same applies to non-residential premises: if they are not in the house, then they will not be included in the calculation.

1.425 gcal - the amount of heat (ONE);

1820 + 1995 = 3,815 rubles - with individual counter.
2 450 + 1995 = 4445 rubles. - without individual device.

Option 3

We have left last option, during which we will consider the situation when there is no heat energy meter on the house. The calculation, as in previous cases, will be carried out in two categories (thermal energy consumption for an apartment and ONE).

We will derive the amount for heating using formulas No. 1 and No. 2 (rules on the procedure for calculating thermal energy, taking into account the readings of individual meters or in accordance with the established standards for residential premises in gcal).

Formula No. 1: 1.3 x 1,400 \u003d 1820 rubles, where:

1.3 gcal - readings of an individual meter;
1 400 rubles - approved rate.

Formula No. 2: 0.025 x 70 x 1,400 = 2,450 rubles, where:

1 400 rubles - approved rate.

As in the second option, the payment will depend on whether your housing is equipped with an individual heat meter. Now it is necessary to find out the amount of heat energy that was spent on general house needs, and this must be done according to formula No. 15 (volume of service for one unit) and No. 10 (amount for heating).

Formula No. 15: 0.025 x 150 x 70 / 7000 \u003d 0.0375 gcal, where:

0.025 gcal - standard indicator of heat consumption per 1 m² of living space;
100 m² - the sum of the area of \u200b\u200bthe premises intended for general house needs;
70 m² - the total area of the apartment;
7,000 m² - total area (all residential and non-residential premises).

Formula No. 10: 0.0375 x 1,400 = 52.5 rubles, where:

0.0375 - volume of heat (ONE);
1400 r. - approved rate.

As a result of the calculations, we found out that the full payment for heating will be:

1820 + 52.5 \u003d 1872.5 rubles. - with individual counter.
2450 + 52.5 \u003d 2,502.5 rubles. – without individual counter.

In the above calculations of payments for heating, data on the footage of the apartment, house, as well as on the meter indicators, which may differ significantly from those that you have, were used. All you need to do is plug your values into the formula and make the final calculation.

A private house can be considered as a thermodynamic system with internal energy and leading heat exchange with environment. The energy that a house receives or loses during heat exchange is called heat. The source of heat in a private house is a heat generator: boiler, convector, stove, a heating element etc.

The more intense the heat exchange between the house and the environment, the faster the heat of the house “leaves” and the more intensively the source of thermal energy must work to compensate for the losses. It is clear that the intensive operation of the boiler is associated with high fuel consumption, which leads to an increase in heating costs.

But this is not the main thing: the concept of comfort in a home during the cold season is inextricably linked with the heat in the house, which is possible only if there is a balance between the loss of thermal energy and its production.

However, the capabilities of any heat generator are limited by its design features. This means that in order to provide warmth and comfort in the house, a boiler or other source of thermal energy must be selected in accordance with the heat losses of the building, while making some margin (usually 20%) in case of windy weather or severe frosts.

So, we have decided: before choosing a boiler for heating a house, you need to determine it (at home) heat loss.

Determine heat loss

The heat loss of a building can be calculated separately for each room that has an external part in contact with the environment. Then the received data are summarized. For a private house, it is more convenient to determine the heat loss of the entire building as a whole, considering the heat loss separately through the walls, roof, and floor surface.

It should be noted that the calculation of heat losses at home is sufficient difficult process requiring specialized knowledge. Less accurate, but still reliable result can be obtained based on online calculator calculation of heat losses.

When choosing an online calculator, it is better to give preference to models that take into account all possible options heat loss. Here is their list:

outer wall surface

roof surface

floor surface

ventilation system

Having decided to use the calculator, you need to know the geometric dimensions of the building, the characteristics of the materials from which the house is made, as well as their thickness. The presence of a heat-insulating layer and its thickness are taken into account separately.

Based on the listed initial data, the online calculator issues general meaning heat loss at home. To determine how accurate the results obtained can be by dividing the result obtained by the total volume of the building and thus obtaining specific heat losses, the value of which should be in the range from 30 to 100 W.

If the numbers obtained using the online calculator go far beyond the specified values, it can be assumed that an error has crept into the calculation. Most often, the cause of errors in calculations is a mismatch in the dimensions of the quantities used in the calculation.

An important fact: the online calculator data is relevant only for houses and buildings with high-quality windows and a well-functioning ventilation system, in which there is no place for drafts and other heat losses.

To reduce heat loss, additional thermal insulation buildings, as well as use the heating of the air entering the room.

Heat loss know what's next?

The next step is to select heating unit(boiler). Its thermal power must exceed the value of thermal losses by at least 20%. If the boiler is also used for hot water supply, a thermal unit with an additional power reserve is selected. To do this, it is necessary to make an additional calculation, taking into account the needs for hot water supply.

Then get picked up heating appliances, the total power of which must correspond to the power of the heating boiler, excluding hot water supply.

Hydraulic calculation of the heating system

Having picked up the equipment, it is necessary to ensure its operation. This requires pipes circulation pump and expansion tank heating.

If the owner of the house decides to select the heating pipes on his own, you can use the reference literature and select the required diameter from the tables. The length of the pipes is calculated from project documentation. To do this, an additional wiring diagram for the heating system is simply laid on the building diagram and the length of the pipeline is calculated.

If for some reason there is no diagram of the house, you will have to draw it yourself, and then, with its help, calculate the length of the pipeline.

Knowing the length of the pipeline, the diameter of the pipes and having the technical data of the heating devices, the internal volume of the heating system is calculated, according to which the expansion tank and the circulation pump are selected.

Correct hydraulic calculation is also necessary so that all the heat generated by the boiler is evenly distributed throughout the house and reaches in full to the consumer.

Summing up

The amount of heat needed to heat a house directly depends on its heat loss. It is possible to reduce heat losses with the help of additional thermal insulation, installation quality windows and insulated doors, as well as when using recuperation in the ventilation system.

The amount of heat loss determines the power of the heating boiler. The total power of heating devices must be equal to the power of the boiler. To ensure the high-quality operation of the boiler and radiators, a hydraulic calculation of heating is carried out, during which the diameter of the pipes, their length, and the internal volume of heating are determined. According to these data, a circulation pump and an expansion heating tank are selected.

In case of severe frost the boiler is bought with a power reserve of at least 20%.

Heat loss is due to:

penetration of cold temperature from the outer walls of the room, through window slots,
poor sealing of window frames.

When installing heating systems, it is necessary to take into account the regional peculiarity of the temperature outside the window and, based on the parameters obtained, choose one or another type of heating equipment. But even the most efficient heating technique will not give the desired result if you do not get rid of the so-called "heat leakage points". When installing window frames, you should once spend money on high-quality ones that have a high coefficient of heat retention. To effectively carry out insulation work walls, the market for thermal insulation materials presents a large selection.

The heat consumption for heating will decrease several times if the work on sealing the premises is carried out efficiently. Any modern heating equipment can be regulated by controlling the flow of warm air masses into the room. Power heating appliances increases as the cold air supply decreases.

For complete comfort, two conditions must be met:

ensure the optimum temperature in the room at 20-22 degrees;
difference between the indoor air temperature and outer wall should be no more than 4 degrees, while the temperature of the wall should be above the dew point temperature.

The dew point is the cooling of the outside air before condensation begins and its vapors turn into dew. This is easy to achieve with a powerful boiler. But it is important to reduce heating costs.

The heat consumption for heating has two options for the consumption rate:

First - established norm on the heat transfer resistance of external walls, window frames, etc.
The second - the standard of energy consumption for heating the house is determined. The second method allows to reduce the resistance to heat supply of enclosing structures. Thus, one can choose optimal thickness walls of the room.

Professional builders often use the first option. Raising up concrete walls, to them they perform work on additional insulation various thermal insulation materials. This method significantly complicates the process and increases the cost of work.

When building private houses, it is not necessary to insulate the outer walls, it is enough to create a more insulated layer in the attic and underground. You should also give the house a shape that is energy efficient, given the compactness of the structure. For greater insulation, verandas, loggias are attached to the house, window frames make smaller sizes, etc. Thus, the heat consumption for heating is reduced many times over.

Having eliminated all the shortcomings, you can proceed to the choice heating equipment. It is worth paying attention to the parameters of the heating system that will be installed in the room. The temperature in the house also depends on the quality of the materials from which heat carriers, radiators and boilers of heating equipment will be made. Modern systems heating are in reserve big list new technologically equipped devices for saving heat. Automatic controllers to maintain optimal temperature in the room will be the main assistants in terms of heat energy consumption for heating.

When building an energy-saving house or ordering already finished project It is worth considering carefully the issues of building insulation with the involvement of experienced specialists. Job requires integrated approach and only in this case it is possible to build a comfortable, warm and cozy home.

Heating radiators and thermostats

In radiators, the coolant temperature should not exceed 90 degrees. When choosing powerful and resistant radiators, this temperature is quite suitable for cold winters. In order for the atmosphere in the room to be acceptable to everyone, you need to install thermostats. There are two types - mechanical and automatic. Mechanical must be constantly adjusted manually, not missing the moment of changing thermal values. The open position of the regulator provides the maximum mode, the closed position provides the minimum. If the hot water supply is lost, the battery cools down quickly.

The automatic thermostat, in turn, requires less attention. It is enough to fix the required mark on the scale, and the machine itself adjusts the temperature level. The use of a thermostat is possible only if the pipes are parallel, the use of regulators installed one after another blocks the circulation of the coolant in the pipes.

The consumption of thermal energy for heating carries considerable costs if the heating system is installed without taking into account other costs, such as a boiler, kitchen, bathroom.

Find a "leak"

To save more, when summing up the heating system, you need to take into account all the “sick” places of heat leakage. It will not be superfluous to say that the windows must be sealed. The thickness of the walls allows you to keep the heat, warm floors keep the temperature background at a positive level. The consumption of thermal energy for heating the room depends on the height of the ceilings, such as ventilation system, building materials when building a building.

After deducting all heat losses, you need to seriously approach the choice of a heating boiler. The main thing here is the budget part of the issue. Depending on the power and versatility, the price of the device also varies. If there is already gas in the house, then there is savings on electricity (the cost of which is considerable), and along with preparing, for example, dinner, the system warms up at the same time.

Another point in preserving heat is the type of heater - convector, radiator, battery, etc. Most suitable solution question - radiator, the number of sections of which is calculated using a simple formula. One section (rib) of the radiator has a power of 150 watts, for a room of 10 meters 1700 watts is enough. By dividing, we get 13 sections necessary for comfortable space heating.

Installing underfloor heating will half solve the problem of energy savings. According to experts, the amount of consumed heat energy is reduced by 2-3 times. The economical consumption of thermal energy for heating is obvious.

When installing the heating system by placing radiators, you can immediately connect the underfloor heating system. Constant circulation of the coolant creates a uniform temperature throughout the room.

When determining the heat load of the heating system, the features are taken into account thermal regime premises. In premises with a constant thermal regime, which include industrial buildings with a continuous technological process, agricultural premises and public buildings, the heat load of the heating system is determined from heat balance premises. The heat balance establishes a balance between the heat losses of the building and the heat gain, from where the heat consumption for heating will be equal to

Q o \u003d Q t + Q m - Q ext (1.1)

where Q o - heat consumption for heating, kW;

Q t - heat loss of the building by heat transfer through the external enclosing structures and infiltration due to the entry of cold air into the room through leaks, kW

Q m - heat consumption for heating materials entering the room, kW;

Q vn - internal heat generation, kW.

The calculated (maximum) heat losses of industrial buildings through external fences and infiltration are determined by the formula

Q t max \u003d (1 + μ) (t in - t but) q o V 10 -3 (1.2)

where μ is the infiltration coefficient;

t but - the design temperature of the outside air for calculating heating, is taken depending on the climatic region (Appendix B), ° С;

t in - average temperature of internal air individual rooms buildings, is accepted depending on the purpose of the premises (Appendix D), C;

q o - specific heating characteristic building, depending on the construction volume of the building and its purpose (Appendix D), J / (s.m 3 .K);

V - construction volume of a separate building according to the external measurement, m 3.

When choosing the indoor air temperature for industrial buildings, labor intensity should be taken into account. According to the intensity of labor, all types of work are divided into three categories: light, moderate and heavy. Light work includes work performed while sitting and standing, which do not require systematic physical stress (precision instrumentation processes, office work, etc.) The category of moderate work includes work associated with constant walking, carrying loads up to 10 kg (mechanical assembly shops, wood processing , textile industry, etc.). Category heavy work include work with systematic physical stress (forges, foundries, etc.).

The infiltration coefficient is determined by the expression

where b is the infiltration constant, for stand-alone industrial buildings b = 0.035 - 0.040 c/m is taken,

g - free fall acceleration, m/s;

L is the free height of the building, m. For public and administrative buildings, it is assumed to be equal to the floor height. For industrial buildings, you can take the values L = 5-25 m.

w in - the average wind speed for the coldest month (Appendix B), m/s.

Heat consumption for heating dissimilar materials entering the production facility during the cold season, kW

Q m max \u003d ∑ G m i c i (t in - t m), (1.4)

where i is the number of items of materials;

c i - specific heat capacity of the material (table I), kJ / (kg.deg)

t m - temperature of the material, about C. Tentatively accepted; for metals and metal products t m \u003d t but, for other non-bulk materials t m \u003d t but +10 o C for bulk materials t m \u003d t but +20 o C

G mi - mass of homogeneous material entering the shop, kg/s.

The total consumption of material by an industrial enterprise, tasks in Appendix B, must be distributed among the shops, in accordance with the purpose of the shops. A list of recommended materials is given in Table I.

Table 1 - Specific heat capacity of some materials

Internal heat dissipation industrial enterprises are quite stable and make up a significant proportion of the calculated heating load, so they must be taken into account when developing the heat supply mode. Sources of internal heat releases in industrial premises are; mechanical and electrical equipment, heated surfaces of apparatus, installations and pipelines, surfaces of heated baths, electric lighting, working people, cooling materials and combustion products, etc. Below is the methodology indicative calculation heat releases from technological equipment, electric lighting and working people.

The total amount of internal heat generation in individual industrial buildings, kW

In the event that actual data or projects are missing technological processes, internal heat dissipation from the equipment is calculated by analogues. For hot shops heat dissipation from production equipment and technological processes, kW

where q n is the specific heat density of the room (table 2), kW / m 3;

V - building volume of the room, m 3.

Table 2 - Specific heat density of hot shops / 18 /, kW / m 3

In non-hot shops, one of the main types of internal heat generation will be heat from technological equipment equipped with electric drive. Heat input from electric motors of mechanical equipment and machines driven by them, kW.

where k cn is the coefficient of demand for electricity (table 3);

k p - coefficient taking into account the completeness of the load of electric motors k p =0.9-1;

k T - coefficient of heat transfer to the room, For metal-cutting machines k T \u003d 0.9-1; for fans and pumps

η - efficiency of the electric motor when it is fully loaded η=0.85-0.9;

q el - specific gravity electrical power load(table 4), kW / m 2;

F - floor area of the shop premises, m 2.

Table 3 - Coefficient of demand for electricity

Table 4 - Specific densities of electrical loads per 1m 2 usable area industrial buildings

The amount of heat entering the room from sources artificial lighting, calculated by specific indicators

where F is the floor area of the room, m 2;

q os - specific density of electric lighting load (table 4), kW / m 2.
Heat emissions from people are determined depending on their energy consumption and the air temperature in the room. Total amount of heat, kW

where m" is the number of people in the room;

q l is the specific amount of total heat generated by one worker (table 5), kW.

Table 5 - Specific total amount of heat released by adults /1/, kW

Approximate formulas can be used to calculate the number of employees in a building. For production shops the number of workers in one shift is approximately equal to

for administrative buildings

where V is the construction volume of a workshop or building, m 3.

Estimated consumption heat for heating a residential area, in the absence of data on the type of development and the external volume of residential and public buildings, according to SNiP P-Z6-73, it is recommended to determine by the formula

where q w is an aggregated indicator of the maximum heat consumption for heating 1 m 2 of living space (table 6), kJ / (s.m 2);

F W - living area, determined on the basis of 12 m 2 per inhabitant of the area, m 2;

k 0 - coefficient taking into account the heat consumption for heating public buildings, in the absence of actual data, it is recommended to take k 0 \u003d 0.25

Table 6 - Aggregated indicator of the maximum heat consumption for heating residential buildings

INTRODUCTION

The consumption of thermal energy in Russia, as well as throughout the world, is steadily increasing to ensure engineering systems buildings and structures.

In this course project, the development plan of the microdistrict of the city is calculated, where the consumers of thermal energy are four residential buildings and one public - a hostel. This heating network must provide the flow required for heating and hot water supply of all buildings. Building 2 - a residential three-story building (it can accommodate 135 people), building 3.4 - a residential five-story building (it can accommodate 300 people), building 5 - a public building - a kindergarten (it can accommodate 150 people), building 1 - a residential four-story building (it accommodates 180 people).

The source of thermal energy is the central heating point. In connection with mass housing construction, it became necessary to build enlarged, central heating points, for which special land, as a rule, in the center of residential microdistricts. In closed heating systems thermal power such a central heating point for a microdistrict or a group of buildings it is recommended to take from 12 to 35 MW(according to the sum of the heat flow for heating and the average hourly flow for hot water supply). Hot water systems for closed system heat supply is connected through high-speed sectional water heaters. Each of them consists of several sections connected in series, in which there is a counterflow of network and tap water. To be able to clean the tubes from scale and dirt, heated tap water is fed into the tubes, and the network flows in the annulus.

This heat network can be characterized as follows. Heating network includes the supply of thermal energy for heating and hot water supply of buildings.

The heating main of the network has a closed independent four-pipe system, which consists of heating pipelines: return and supply, as well as hot and circulation water supply pipelines.

Water temperature in the heating supply pipe: 130 about C, reverse - 70 about C.

Water temperature in pipelines of hot and cold water supply 65 about C and 5 about S. The heating network provides five buildings with thermal energy for their heating and hot water supply.

The route of the heating network is laid in the area of the city of Izhevsk, the relief of which rises in the direction from the source of thermal energy to the last consumer. The source of thermal energy of the heating network is the central heating point (CHP). The route has a four-pipe system, which consists of heating pipelines (supply and return) and water supply pipelines (hot and circulation)

The heating network provides five buildings with thermal energy for their heating, ventilation and hot water supply.

Calculation scheme of the heat network

Initial parameters of buildings

CALCULATION OF HEAT EXPENSES

To calculate heat supply networks, it is necessary to develop design schemes. Separate calculation schemes are being developed for hot water supply and heating, since the number of nodal points in these networks does not always coincide. I begin the development of design schemes with determining the number of sectional units of the hot water supply system and local heating points of the heating system.

The number of sectional hot water supply units in the building, either according to the number of sections in the building, or at the rate of 36 apartments (approximately) per one sectional unit, each sectional unit and each heat point is numbered. All sectional nodes will be interconnected by distribution pipelines. Nodal points are placed on the resulting network, at which the coolant flow bifurcates. All nodes are numbered. The sections between the nodal points are the calculated sections. The costs in the sections between sectional nodes in buildings and at the entrances to buildings are determined by calculation. The flow rates in the distribution pipeline sections are determined by summing up the water flow rates in the sections suitable for the flow branching node.

Heat consumption for heating

In the course project, it is best to use the method of approximate determination of heat costs for heating and ventilation of residential and public buildings according to their thermal characteristics.
The approximate heat consumption for heating residential and public buildings is determined by the formula for the maximum hourly heat consumption:

where is the maximum hourly heat consumption for heating the building, W;

Thermal characteristic of the building, W/(); taken according to the table in the methodological manual;

a - coefficient that takes into account the heat consumption for heating outdoor air entering buildings by infiltration through leaks in the fences; taken into account a=(1.05…1.1);

K is a correction factor that takes into account the change in the calculated outdoor temperature; taken according to the table in the methodological manual;

The volume of the building by external measurement, ;

average temperature air in the building, ; accepted according to the standards;

- estimated outdoor air temperature for heating design, ; for Udmurtia.

For a 3-storey building:

For a 4-storey building:

For a 5-storey building:

Kindergarten 2 floors:

1.2 Heat consumption for ventilation
The values of heat consumption for ventilation for public buildings are determined by the formula:
(1.2)

where is the heat consumption for ventilation of public buildings, W;

- ventilation specific thermal characteristic, W/( ); taken according to the tables;

The volume of the building according to the external measurement,

- the temperature of the indoor air in the building, ; accepted for a specific building according to the standards;

Estimated outdoor air temperature for ventilation design, ; for Udmurtia is accepted ;

- correction for design temperature outside air, is taken according to the table of methodological material.

For a public building:

1.3 Heat consumption for hot water supply
Heat consumption for hot water for hot water supply of residential and public buildings is determined by the change in the enthalpy of water:

where - maximum flow heat for hot water supply, W;

with- heat capacity of water; with= 4.187 kJ/ (kg x; );

- density of water; - 983.2 kg / m3:

- second consumption of hot water, l/s;

- hot water temperature;

- temperature cold water, .

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