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Energy consumption in Russia, as well as throughout the world, is steadily increasing and, above all, to provide heat engineering systems buildings and structures. It is known that more than one third of all fossil fuel produced in our country is spent on heat supply of civil and industrial buildings.
The main heat consumption for household needs in buildings (heating, ventilation, air conditioning, hot water supply) is the cost of heating. This is due to the operating conditions of buildings during the heating season in most of the territory of Russia. At this time, heat loss through the external enclosing structures significantly exceeds the internal heat release (from people, lighting fixtures, equipment). Therefore, in order to maintain a microclimate and temperature normal for life in residential and public buildings, it is necessary to equip them heating installations and systems.
Thus, heating is called artificial, with the help of a special installation or system, heating the premises of a building to compensate for heat losses and maintain temperature parameters in them at a level determined by the conditions of thermal comfort for people in the room.
V last decade there is also a constant increase in the cost of all types of fuel. It is connected as with the transition to the conditions market economy and with the complication of fuel extraction during the development of deep deposits in certain regions of Russia. In this regard, it becomes more and more urgent to solve the problems of energy saving by increasing the heat resistance of the external enveloping structures of the building, and saving the consumption of thermal energy at different periods of time and at different conditions the environment by regulating with automatic devices.
Important in modern conditions is the problem of metering actually consumed heat energy. This question is fundamental in the relationship between the energy supplying organization and the consumer. And the more efficiently it is solved within the framework of a separate heat supply system of the building, the more expedient and noticeable the effectiveness of the application of energy saving measures.
Summarizing the above, we can say that modern system heat supply of a building, especially public or administrative, must meet the following requirements:
Providing the required thermal conditions in the room. Moreover, it is important that there is no subcooling or excess of the air temperature in the room, since both facts lead to a lack of comfort. This, in turn, can lead to a decrease in labor productivity and deterioration in the health of people arriving at the premises;
The ability to regulate the parameters of the heat supply system and, as a result, the parameters of the temperature inside the premises, depending on the desires of consumers, the time and characteristics of work administrative building and outside air temperature;
Maximum independence from the parameters of the coolant in district heating networks and district heating modes;
Accurate accounting of actually consumed heat for the needs of heat supply, ventilation and hot water supply.
The purpose of this diploma project is to design a heating system for a school building located at the address: Vologda Oblast, s. Koskovo, Kichmengsko-Gorodetsky district.
The school building is two-story with axial dimensions 49.5x42.0, the height of the floor is 3.6 m.
On the ground floor of the building there are classrooms, sanitary facilities, an electrical room, a canteen, a gym, a nurse's office, a director's office, a workshop, a cloakroom, a hall and corridors.
On the second floor there is an assembly hall, a teachers' room, a library, classrooms for girls, classrooms, dignity. nodes, laboratory, recreation.
Structural scheme of the building - load-bearing metal carcass from columns and trusses covering with cladding with wall sandwich panels Petropanel 120 mm thick and galvanized sheet along metal purlins.
Centralized heat supply from the boiler room. Connection point: single-pipe aboveground heating network. Connection of the heating system is provided according to the dependent scheme. The temperature of the heating medium in the system is 95-70 0 С. The temperature of the water in the heating system is 80-60 0 С.
1. ARCHITECTURAL AND DESIGN SECTION
The projected school building is located in the village of Koskovo, Kichmengsko-Gorodetsky district, Vologda region. The architectural solution of the facade of the building is dictated by the existing development, taking into account new technologies, using modern finishing materials... The planning solution of the building was made based on the design assignment and the requirements of regulatory documents.
On the ground floor there are: a hall, a cloakroom, a director's office, a nurse's office, grade 1 education classes, a combined workshop, toilets for men and women, as well as a separate one for people with limited mobility, recreation, a dining room, a gym, dressing rooms and showers, an electrical room.
A ramp is provided for access to the first floor.
On the second floor there are: laboratory assistants, high school students 'offices, recreation, library, teachers' room, an assembly hall with rooms for decorations, toilets for men and women, as well as a separate one for groups with limited mobility.
Number of students - 150 people, including:
Primary school - 40 people;
Secondary school - 110 people.
There are 18 teachers.
Canteen employees - 6 people.
Administration - 3 people.
Other specialists - 3 people.
Service staff - 3 people.
Construction area - the village of Koskovo, Kichmengsko-Gorodetsky district, Vologda region. We take climatic characteristics in accordance with the nearest settlement - the city of Nikolsk.
The land plot provided for capital construction is located in meteorological and climatic conditions:
Outside air temperature of the coldest five-day period with a security of 0.92 - t n = - 34 0 С
Temperature of the coldest day with a security of 0.92
Average temperature of the period with average daily air temperature<8 0 C (средняя температура отопительного периода) t от = - 4,9 0 С .
Duration of the period with the average daily outdoor temperature<8 0 С (продолжительность отопительного периода) z от = 236 сут.
Normative high-speed wind pressure - 23kgf / m2
The design temperature of the indoor air is taken depending on the functional purpose of each room in the building according to the requirements.
By determining the operating conditions of the enclosing structures, depending on the humidity conditions of the premises and humidity zones. Accordingly, we accept the operating conditions of external enclosing structures as "B".
The school building is two-storeyed with axial dimensions 42.0x49.5; the height of the floor is 3.6m.
There is a heating unit in the basement.
On the ground floor of the building there are classrooms, a canteen, a gym, corridors and recreation, a nurse's office, and toilets.
On the second floor there are classrooms, laboratory rooms, a library, a teachers' room, and an assembly hall.
Space-planning solutions are shown in Table 1.1.
Table 1.1
Space-planning solutions of the building
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The name of indicators |
unit of measurement |
Indicators |
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Number of floors |
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Basement height |
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1st floor height |
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2nd floor height |
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The total area of the building, including: |
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Building volume including |
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Underground part Aboveground part |
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Built-up area |
Structural scheme of the building: supporting metal frame from columns and roof trusses.
Foundations: the project adopted monolithic reinforced concrete columnar foundations for the columns of the building. The foundations are made of concrete class. B15, W4, F75. Under the foundations, concrete preparation t = 100 mm made of concrete, class В15 performed on compacted sand preparation t = 100 mm from coarse sand.
In the decoration of the premises related to the dining room, the following are used:
Walls: grouting and plaster, the bottom and top of the walls are painted with water-dispersion moisture-resistant paint, ceramic tiles;
Floors: porcelain stoneware tiles.
In the decoration of the premises related to the gym, the following are used:
Walls: grouting;
Ceilings: 2 layers of gypsum fiber board painted with water-based paint;
Floor: plank floor, porcelain stoneware tiles, linoleum.
In the decoration of the nurse's office, bathrooms and showers, the following are used:
Walls: ceramic tiles;
Ceilings: 2 layers of gypsum fiber board painted with water-based paint;
Floor: linoleum.
In the workshop, hall, recreation, wardrobe, the following are used:
Ceilings: 2 layers of gypsum fiber board painted with water-based paint;
Floor: linoleum.
In the decoration of premises related to the assembly hall, offices, corridors, libraries, laboratory assistants are used:
Walls: grouting, plaster, washable acrylic paint for interior work VD-AK-1180;
Ceilings: 2 layers of gypsum fiber board painted with water-based paint;
Floor: linoleum.
In the decoration of the director's office, the teacher's room, the following are used:
Walls: grouting, painting with water-based paint, wallpaper for painting;
Ceilings: 2 layers of gypsum fiber board painted with water-based paint;
Floor: laminate.
In the decoration of a book depository, a storage room for inventory, a utility room, they are used
Walls: grouting, plastering, oil painting.
Ceilings: 2 layers of gypsum fiber board painted with water-based paint.
Floor: linoleum.
The roof on the building is gable with a slope of 15 °, covered with galvanized steel on metal purlins.
The partitions in the building are made of tongue-and-groove slabs, and the wall cladding is made of plasterboard sheets.
The following measures have been taken to protect building structures from destruction:
- anti-corrosion protection of metal structures is provided in accordance with .
Space-planning and design solutions of the substation must meet the requirements.
To protect building structures from corrosion, anti-corrosion materials must be used in accordance with the requirements. The decoration of the fences of the heating points is provided from durable moisture-resistant materials that can be easily cleaned, while doing the following:
Plastering of the ground part of brick walls,
Whitewashing ceilings,
Concrete or tile flooring.
The walls of the substation are covered with tiles or painted to a height of 1.5 m from the floor with oil or other paint, above 1.5 m from the floor - with glue or other similar paint.
The floors, for water drainage, are made with a slope of 0.01 towards the ladder or catchment pit.
Individual heating points should be built into the buildings they serve and be located in separate rooms on the ground floor near the outer walls of the building at a distance of no more than 12 m from the entrance to the building. It is allowed to place IHP in technical undergrounds or basements of buildings or structures.
Doors from the substation must open from the premises of the substation away from you. It is not required to provide openings for natural lighting of the substation.
The minimum clear distance from building structures to pipelines, fittings, equipment, between the surfaces of heat-insulating structures of adjacent pipelines, as well as the width of the passage between building structures and equipment (in the light) are taken according to app. 1 . The distance from the surface of the thermal insulation structure of the pipeline to the building structures of the building or to the surface of the thermal insulation structure of another pipeline must be at least 30 mm clear.
The heating project was developed in accordance with the terms of reference issued by the customer and in accordance with the requirements. Heat carrier parameters in the heating system T 1 -80; T 2 -60 ° C.
The heating medium in the heating system is water with parameters 80-60 ° С.
The heat carrier in the ventilation system is water with parameters 90-70 ° С.
The connection of the heating system to the heating network is carried out at the heating point according to a dependent scheme.
The heating system is single-pipe vertical, with distribution of highways on the floor of the first floor.
Bimetallic radiators "Rifar Base" with built-in thermostats are used as heating devices.
Air removal from the heating system is carried out through the built-in plugs of devices, taps of the Mayevsky type.
To drain the heating system, drain taps are provided at the lowest points of the system. The slope of the pipelines is 0.003 towards the heating unit.
Heating systems are an integral part of the building. Therefore, they must meet the following requirements:
Heating devices must provide the temperature established by the norms, regardless of the outside temperature and the number of people in the room;
The room temperature must be uniform both horizontally and vertically.
Daily temperature fluctuations should not exceed 2-3 ° C for central heating.
The temperature of the internal surfaces of the enclosing structures (walls, ceilings, floors) should approach the air temperature of the premises, the temperature difference should not exceed 4-5 ° С;
Heating of premises should be continuous during the heating season and provide for qualitative and quantitative regulation of heat transfer;
The average temperature of heating devices should not exceed 80 ° C (higher temperatures lead to excessive heat radiation, burning and dust sublimation);
Technical and economic (means that the costs of building and operating the heating system are minimal);
architectural and construction (provide for the mutual coordination of all elements of the heating system with the construction architectural and planning solutions of premises, ensuring the safety of building structures throughout the entire life of the building);
installation and operational (the heating system must comply with the modern level of mechanization and industrialization of procurement installation works, ensure the reliability of operation during the entire period of their operation, be fairly easy to maintain).
The heating system includes three main elements: a heat source, heat pipes and heating devices. It is classified according to the type of heat carrier used and the location of the heat source.
The design of a heating system is an important part of the design process. In the graduation project, the following heating system is designed:
by type of coolant - water;
by the method of moving the coolant - with forced induction;
at the location of the heat source - central (rural boiler house);
by location of heat consumers - vertical;
by the type of connection of heating devices in risers - one-pipe;
in the direction of water movement in the highways - dead-end.
Today, a one-pipe heating system is one of the most common systems.
A big plus of such a system, of course, is the saving of materials. Connecting pipes, return risers, lintels and inlets to heating radiators - all this together gives a sufficient length of the pipeline, which costs a lot of money. A single-pipe heating system allows you to avoid the installation of unnecessary pipes, significantly saving money. Secondly, it looks much more aesthetically pleasing.
There are also many technological solutions that eliminate the problems that existed with such systems literally ten years ago. Modern one-pipe heating systems are equipped with thermostatic valves, radiator regulators, special air vents, balancing valves, and convenient ball valves. In modern heating systems that use a sequential supply of coolant, it is already possible to achieve a decrease in temperature in the previous radiator without lowering it in subsequent ones.
The task of the hydraulic calculation of the heating network pipeline is to select the optimal pipe sections for passing a given amount of water in individual sections. At the same time, the established technical and economic level of operational energy consumption for water movement, the sanitary and hygienic requirement for the level of hydraulic noise should not be exceeded, and the required metal consumption of the projected heating system should not be exceeded. In addition, a well-calculated and hydraulically linked pipeline network provides more reliable and thermal stability during off-design operation of the heating system at different periods of the heating season. The calculation is performed after determining the heat loss of the building room. But first, to obtain the required values, a heat engineering calculation of the external fences is performed.
The initial stage of designing a heating system is a heat engineering calculation of external enclosing structures. The enclosing structures include external walls, windows, balcony doors, stained glass windows, entrance doors, gates, etc. The purpose of the calculation is to determine the heat engineering indicators, the main of which are the values of the reduced heat transfer resistances of external fences. Thanks to them, they calculate the calculated heat loss for all rooms of the building and draw up a heat energy passport.
Outdoor meteorological parameters:
city - Nikolsk. Climatic region -;
temperature of the coldest five-day week (with security) -34;
temperature of the coldest day (with security) -;
average temperature of the heating season -;
heating period -.
Architectural and construction solutions for the enclosing structures of the designed building should be such that the total thermal resistance of heat transfer of these structures is equal to the economically feasible resistance to heat transfer, determined from the conditions for ensuring the lowest reduced costs, as well as not less than the required resistance to heat transfer, according to sanitary and hygienic conditions.
For the calculation of the required heat transfer resistance for the enclosing structures, with the exception of light openings (windows, balcony doors and lanterns), use the formula (2.1):
where is the coefficient taking into account the position of the enclosing structures in relation to the outside air;
Indoor air temperature, for a residential building,;
Estimated winter outdoor temperature, value given above;
Standard temperature difference between the temperature of the internal air and the temperature of the internal surface of the enclosing structure,;
Heat transfer coefficient of the inner surface of the enclosing structure,:
where: t vn is the design temperature of the internal air, C, taken according to;
t o.p. , n о. p. is the average temperature, C, and the duration, days, of the period with the average daily air temperature below or equal to 8C, according to.
According to the air temperature in rooms for outdoor sports, and in rooms in which people are in half-naked form (locker rooms, treatment rooms, doctors' offices) in the cold season should be within 17-19 C.
Heat transfer resistance R o for a homogeneous single-layer or multi-layer enclosing structure with homogeneous layers according to should be determined by the formula (2.3)
R 0 = 1 / a n + d 1 / l 1 - + --...-- + - d n / l n + 1 / a in, m 2 * 0 С / W (2.3)
A in - is taken according to table 7 a in = 8.7 W / m 2 * 0 С
A n - taken according to table 8 - a n = 23 W / m 2 * 0 С
The outer wall consists of Petropanel sandwich panels with a thickness of d = 0.12 m;
We substitute all the data in the formula (2.3).
According to the conditions of energy saving, the required heat transfer resistance is determined according to the table, depending on the degree-day of the heating period (GSOP).
GSNP is determined by the following formula:
where: t in - the estimated temperature of the internal air, C, taken according to;
t from.trans. , z from. per. - the average temperature, C, and the duration, days, of the period with the average daily air temperature below or equal to 8C, according to.
Degree-day for each type of premises is determined separately, since indoor temperature ranges from 16 to 25C.
According to the data for s. Koskovo:
t from.trans. = -4.9 C;
z from. per. = 236 days
Substituting the values into the formula.
Heat transfer resistance R o for a homogeneous single-layer or multi-layer enclosing structure with homogeneous layers according to should be determined by the formula:
R 0 = 1 / a n + d 1 / l 1 - + --...-- + - d n / l n + 1 / a in, m 2 * 0 С / W (2.5)
where: d ----- thickness of the insulation layer, m.
l ----- coefficient of thermal conductivity, W / m * 0 С
a n, a in --- heat transfer coefficients of the outer and inner surfaces of the walls, W / m 2 * 0 С
a b - taken according to table 7 a b = 8.7 W / m 2 * 0 С
a n - taken according to table 8 a n = 23 W / m 2 * 0 С
Roofing material galvanized sheet on metal purlins.
In this case, the attic floor is insulated.
For insulated floors, we calculate the value of the heat transfer resistance using the following formula:
R c.p. = R n.p. +? - d flat / - l st. (2.6)
where: R n.p. - heat transfer resistance for each zone of the non-insulated floor, m 2о С / W
D ut.sl - thickness of the insulating layer, mm
L ut.sl. - coefficient of thermal conductivity of the insulation layer, W / m * 0 С
The first floor floor structure consists of the following layers:
1st layer PVC linoleum on a heat-insulating basis GOST 18108-80 * on adhesive mastic d - = 0.005 m and thermal conductivity coefficient l - = 0.33 W / m * 0 С.
2nd layer screed made of cement-sand mortar М150 d - = 0.035 m and thermal conductivity coefficient l - = 0.93 W / m * 0 С.
3rd layer linocrome TPP d - = 0.0027 m
4th layer, underlying layer of concrete B7.5 d = 0.08 m and thermal conductivity coefficient l - = 0.7 W / m * 0 С.
For triple-glazed windows made of ordinary glass in separate bindings, the heat transfer resistance is assumed
R ok = 0.61m 2o C / W.
To ensure the air parameters in the premises within the permissible limits, when calculating the thermal power of the heating system, it is necessary to take into account:
heat loss through the enclosing structures of buildings and premises;
heat consumption for heating the outside air infiltrating in the room;
heat consumption for heating materials and vehicles entering the room;
the flow of heat regularly supplied to the premises from electrical appliances, lighting, technological equipment and other sources.
Estimated heat loss in the premises is calculated by the equation:
where: - the main heat loss of the room fences,;
A correction factor that takes into account the orientation of the outer fences along the sectors of the horizon, for example, for the north, and for the south -;
Estimated heat loss for heating ventilation air and heat loss for infiltration of outside air -,;
Household heat surpluses in the room,.
The main heat losses of the room fences are calculated according to the heat transfer equation:
where: - coefficient of heat transfer of external fences,;
The surface area of the fence,. The rules for measuring the premises are taken from.
The heat consumption for heating the air removed from the premises of residential and public buildings with natural exhaust ventilation, which is not compensated by the heated supply air, is determined by the formula:
where: - the minimum standard air exchange, which for a residential building is in the living area;
Air density,;
k is the coefficient that takes into account the counter heat flow, 0.8 for split-book balcony doors and windows is taken, for single and double-book windows - 1.0.
Under normal conditions, the air density is determined by the formula:
where is the air temperature,.
The heat consumption for heating the air that enters the room through various leaks in protective structures (fences) as a result of wind and thermal pressures is determined according to the formula:
where k is the coefficient taking into account the counter heat flow, 0.8 is taken for split-book balcony doors and windows, and 1.0 for single and double-book windows;
G i - flow rate of air penetrating (infiltrating) through protective structures (enclosing structures), kg / h;
Specific mass heat capacity of air,;
The largest of, is taken in the calculations.
Household heat surpluses are determined by the approximate formula:
The calculation of the heat losses of the building was carried out in the VALTEC program. The calculation result is in Appendices 1 and 2.
We accept Rifar radiators for installation.
The Russian company RIFAR is a domestic manufacturer of the latest series of high-quality bimetallic and aluminum sectional radiators.
The RIFAR company manufactures radiators designed to operate in heating systems with a maximum coolant temperature of up to 135 ° C, an operating pressure of up to 2.1 MPa (20 atm.); and are tested at maximum pressures of 3.1 MPa (30 atm.).
The RIFAR company uses the most modern technologies for painting and testing radiators. High heat transfer and low inertia of RIFAR radiators are achieved due to efficient supply and regulation of the coolant volume and the use of special flat-frame aluminum fins with high thermal conductivity and heat transfer from the radiating surface. This ensures fast and high-quality air heating, effective temperature control and comfortable temperature conditions in the room.
RIFAR bimetallic radiators have become very popular for installation in central heating systems throughout Russia. They take into account the features and requirements of the operation of Russian heating systems. Among other design advantages inherent in bimetallic radiators, it should be noted the method of sealing the intersection connection, which significantly increases the reliability of the heater assembly.
Its device is based on the special design of the parts of the connected sections and the parameters of the silicone gasket.
RIFAR Base radiators are presented in three models with a center distance of 500, 350 and 200 mm.
The RIFAR Base 500 model with a center distance of 500 mm is one of the most powerful bimetallic radiators, which makes it a priority when choosing radiators for heating large and low-temperature rooms. The RIFAR radiator section consists of a steel pipe cast under high pressure with an aluminum alloy with high strength and excellent casting properties. The resulting monolithic thin finned product provides efficient heat dissipation with maximum safety margin.
As a heat carrier for Base 500/350/200 models, only specially prepared water may be used, in accordance with clause 4.8. SO 153-34.20.501-2003 "Rules for the technical operation of power plants and networks of the Russian Federation".
The preliminary selection of heating devices is carried out according to the catalog of heating equipment "Rifar", given in Appendix 11.
The heating system consists of four main components: pipelines, heating devices, a heat generator, control and shut-off valves. All elements of the system have their own characteristics of hydraulic resistance and must be taken into account in the calculation. At the same time, as mentioned above, the hydraulic characteristics are not constant. Manufacturers of heating equipment and materials usually provide data on hydraulic characteristics (specific pressure loss) for the materials or equipment they produce.
The task of the hydraulic calculation is to select economical pipe diameters, taking into account the accepted pressure drops and coolant flow rates. At the same time, its supply to all parts of the heating system must be guaranteed to ensure the calculated thermal loads of heating devices. The correct choice of pipe diameters also leads to savings in metal.
Hydraulic calculation is performed in the following order:
1) The heat loads on the individual risers of the heating system are determined.
2) The main circulation ring is selected. In one-pipe heating systems, this ring is selected through the riser most loaded and most distant from the heating point with a dead-end movement of water or the most loaded riser, but from middle risers - with the passing movement of water in the mains. In a two-pipe system, this ring is selected through the lower heater in the same way as the selected risers.
3) The selected circulation ring is divided into sections along the direction of movement of the coolant, starting from the heating point.
A section of a pipeline with a constant flow rate of the coolant is taken as the calculated section. For each calculated section, it is necessary to indicate the serial number, length L, heat load Q uch and diameter d.
Heating agent consumption
The flow rate of the heat carrier directly depends on the heat load, which the heat carrier must move from the heat generator to the heating device.
Specifically, for the hydraulic calculation, it is required to determine the flow rate of the coolant in a given design section. What is the settlement area. The calculated section of the pipeline is a section of constant diameter with a constant flow rate of the coolant. For example, if a branch includes ten radiators (conventionally, each device with a power of 1 kW) and the total flow rate of the coolant is designed to transfer thermal energy equal to 10 kW by the coolant. Then the first section will be the section from the heat generator to the first in the radiator branch (provided that there is a constant diameter throughout the section) with a coolant flow rate for transfer of 10 kW. The second section will be located between the first and second radiators with a heat energy transfer rate of 9 kW, and so on up to the last radiator. The hydraulic resistance of both the supply pipeline and the return pipeline is calculated.
The coolant consumption (kg / h) for the site is calculated by the formula:
G uch = (3.6 * Q uch) / (s * (t g - t o)), (2.13)
where: Q uch - heat load of the section W., for example, for the above example, the heat load of the first section is 10 kW or 1000 W.
s = 4.2 kJ / (kg ° C) - specific heat capacity of water;
t g - design temperature of the hot coolant in the heating system, ° С;
t о - design temperature of the cooled heat carrier in the heating system, ° С.
Coolant flow rate
The minimum threshold for the speed of the coolant is recommended to be taken in the range of 0.2-0.25 m / s. At lower speeds, the process of release of excess air contained in the coolant begins, which can lead to the formation of air jams and, as a result, a complete or partial failure of the heating system. The upper threshold of the coolant velocity is in the range of 0.6-1.5 m / s. Compliance with the upper speed threshold avoids the occurrence of hydraulic noise in the pipelines. In practice, the optimal speed range of 0.3-0.7 m / s was determined.
A more accurate range of the recommended speed of the coolant depends on the material of the pipelines used in the heating system, and more precisely on the roughness coefficient of the inner surface of the pipelines. For example, for steel pipelines, it is better to adhere to the coolant speed from 0.25 to 0.5 m / s, for copper and polymer (polypropylene, polyethylene, metal-plastic pipelines) from 0.25 to 0.7 m / s, or use the manufacturer's recommendations if available ...
Full hydraulic resistance or pressure loss at the site.
Full hydraulic resistance or pressure loss in the section is the sum of pressure losses due to hydraulic friction and pressure losses in local resistances:
DP uch = R * l + ((s * n2) / 2) * Uzh, Pa (2.14)
where: n is the speed of the coolant, m / s;
с - density of the transported coolant, kg / m3;
R is the specific pressure loss of the pipeline, Pa / m;
l is the length of the pipeline at the calculated section of the system, m;
Already - the sum of the coefficients of local resistances installed on the site of shut-off and control valves and equipment.
The total hydraulic resistance of the calculated branch of the heating system is the sum of the hydraulic resistance of the sections.
Selection of the main design ring (branch) of the heating system.
In systems with a passing movement of the coolant in pipelines:
for one-pipe heating systems - a ring through the most loaded riser.
In systems with dead-end movement of the coolant:
for one-pipe heating systems - a ring through the most loaded of the most distant risers;
Load refers to the heat load.
The hydraulic calculation of the water heating system was carried out in the Valtec program. The calculation result is in Appendices 3 and 4.
Purpose and scope: VALTEC.PRG.3.1.3 program. is intended for performing thermohydraulic and hydraulic calculations. The program is in the public domain and makes it possible to calculate water radiator, floor and wall heating, determine the heat demand of the premises, the required consumption of cold and hot water, the volume of sewage, obtain hydraulic calculations of the internal heat and water supply networks of the facility. In addition, a user-friendly collection of reference materials is available to the user. Thanks to the intuitive interface, you can master the program without having the qualifications of a design engineer.
All calculations performed in the program can be output in MS Excel and in pdf format.
The program includes all types of devices, shut-off and control valves, fittings provided by VALTEC
Additional functions
The program can calculate:
a) Warm floors;
b) Warm walls;
c) Heating sites;
d) Heating:
e) Water supply and sewerage;
f) Aerodynamic calculation of chimneys.
Work in the program:
We begin the calculation of the heating system with information about the projected facility. Construction area, building type. Then we turn to the calculation of heat loss. To do this, you need to determine the temperature of the internal air and the thermal resistance of the enclosing structures. To determine the heat transfer coefficients of structures, we add the composition of the external enclosing structures to the program. After that, we move on to determining the heat loss for each room.
After calculating the heat loss, we proceed to the calculation of heating devices. This calculation allows you to determine the load on each riser and calculate the required number of radiator sections.
The next step is the hydraulic calculation of the heating system. We select the type of system: heating or water supply, the type of connection to the heating network: dependent, independent and the type of transported medium: water or glycol solution. Then we proceed to the calculation of the branches. We divide each branch into sections and calculate the pipeline at each section. To determine the CMC on the site, the program contains all the necessary types of fittings, fittings, devices and nodes for connecting risers.
The reference and technical information necessary for solving the problem includes a range of pipes, reference books on climatology, Kms and many others.
The program also has a calculator, converter, etc.
Output:
All design characteristics of the system are formed in tabular form in the MS Excel software environment and in pdf /
Heat points are heat supply facilities for buildings intended for connection to heating networks of heating, ventilation, air conditioning, hot water supply and technological heat-using installations of industrial and agricultural enterprises, residential and public buildings.
Technological schemes of heat points differ depending on:
the type and number of heat consumers connected to them at the same time - heating systems, hot water supply (hereinafter referred to as DHW), ventilation and air conditioning (hereinafter referred to as ventilation);
method of connection to the heating network of the hot water supply system - open or closed heat supply system;
the principle of heating water for hot water supply with a closed heat supply system - a one-stage or two-stage scheme;
the method of connecting heating and ventilation systems to the heating network - dependent, with the supply of the coolant to the heat consumption system directly from the heating networks, or independent - through water heaters;
coolant temperatures in the heating network and in heat consumption systems (heating and ventilation) - the same or different (for example, or);
piezometric graph of the heat supply system and its relationship to the elevation and height of the building;
requirements for the level of automation;
private instructions of the heat supply organization and additional requirements of the customer.
According to the functional purpose, the heat point can be divided into separate nodes, interconnected by pipelines and having separate or, in some cases, general automatic control means:
heating network input unit (steel shut-off flange or welded fittings at the entrance and exit from the building, strainers, mud collectors);
heat consumption metering unit (heat meter designed to calculate the consumed heat energy);
pressure matching unit in the heating network and heat consumption systems (pressure regulator designed to ensure the operation of all elements of a heating point, heat consumption systems, as well as heating networks in a stable and trouble-free hydraulic mode);
ventilation system connection unit;
hot water supply system connection unit;
heating system connection unit;
make-up unit (to compensate for heat carrier losses in heating and hot water supply systems).
Thermal points provide for the placement of equipment, fittings, control, management and automation devices, through which the following is carried out:
transformation of the type of coolant and its parameters;
control of coolant parameters;
regulation of the flow rate of the heat carrier and its distribution among the systems of heat consumption;
shutdown of heat consumption systems;
protection of local systems from an emergency increase in the parameters of the coolant;
filling and replenishment of heat consumption systems;
accounting of heat flows and consumption of coolant and condensate;
collection, cooling, return of condensate and control of its quality;
accumulation of heat;
water treatment for hot water systems.
In a heat point, depending on its purpose and specific conditions for connecting consumers, all of the listed functions or only a part of them can be performed.
The specification of the substation equipment is given in Appendix 13.
The name of the building is a public two-storey building.
Heat carrier temperature in the heating network -.
Heat carrier temperature in the heating system -.
The scheme for connecting heating systems to the heating network is dependent.
Thermal control unit - automated.
3.4 Selection of heat exchange equipment
The choice of the optimal design of the heat exchanger is a task that can be solved by a technical and economic comparison of several standard sizes of devices in relation to the given conditions or on the basis of an optimization criterion.
The heat exchange surface and its share of capital costs, as well as operating costs, are affected by heat underrecovery. The smaller the amount of heat underrecovery, i.e. the smaller the temperature difference between the heating medium at the inlet and the heated coolant at the outlet with counterflow, the larger the heat exchange surface, the higher the cost of the apparatus, but the lower the operating costs.
It is also known that with an increase in the number and length of pipes in a bundle and a decrease in the diameter of the pipes, the relative cost of one square meter of the shell-and-tube heat exchanger surface decreases, since this reduces the total metal consumption for the apparatus per unit heat exchange surface.
When choosing the type of heat exchanger, you can be guided by the following recommendations.
1. When exchanging heat of two liquids or two gases, it is advisable to choose sectional (element) heat exchangers; if, due to the large surface of the heat exchanger, the structure turns out to be cumbersome, a multi-pass shell-and-tube heat exchanger can be adopted for installation.
3. For chemically aggressive media and at low thermal capacities, jacket, irrigation and immersion heat exchangers are economically feasible.
4. If the heat transfer conditions on both sides of the heat transfer surface are sharply different (gas and liquid), tubular finned or finned heat exchangers should be recommended.
5. For mobile and transport thermal installations, aircraft engines and cryogenic systems, where high efficiency of the process requires compactness and low weight, plate finned and stamped heat exchangers are widely used.
In the diploma project, a plate heat exchanger FP P-012-10-43 was selected. Appendix 12.
Heating system pipelines are laid openly, with the exception of hot water heating pipelines with heating elements and risers built into the structure of buildings. Concealed laying of pipelines is allowed to be used if technological, hygienic, structural or architectural requirements are justified. In case of hidden laying of pipelines at the locations of prefabricated joints and fittings, hatches should be provided.
The main pipelines of water, steam and condensate are laid with a slope of at least 0.002, and steam pipelines - against the movement of steam with a slope of at least 0.006.
Leads to heating devices are made with a slope in the direction of movement of the coolant. The slope is taken from 5 to 10 mm for the entire length of the liner. With a liner length of up to 500 mm, it is laid without a slope.
Risers between floors are connected by squeezing and welding. The squeegees are installed at a height of 300 mm from the supply line. After assembling the riser and the connections, you need to carefully check the verticality of the risers, the correct slopes of the connections to the radiators, the strength of the fastening of pipes and radiators, the accuracy of the assembly - the thoroughness of stripping the flax at the threaded connections, the correct fastening of the pipes, cleaning the cement mortar on the surface of the walls at the clamps.
Pipes in clamps, ceilings and walls must be laid so that they can be freely moved. This is achieved by the fact that the clamps are made with a slightly larger diameter than the pipes.
Pipe sleeves are installed in the walls and ceilings. Sleeves, which are made from pipe cuttings or from roofing steel, should be slightly larger than the pipe diameter, which ensures free extension of the pipes when temperature conditions change. In addition, the sleeves should protrude 20-30 mm from the floor. At a coolant temperature above 100 ° C, pipes, in addition, must be wrapped with asbestos. If there is no insulation, then the distance from the pipe to wood and other combustible structures must be at least 100 mm. At a coolant temperature below 100 ° C, the sleeves can be made of sheet asbestos or cardboard. It is impossible to wrap the pipes with roofing tar, as spots will appear on the ceiling at the place where the pipe passes.
When installing devices in a niche and with an open laying of risers, the connections are made directly. When installing devices in deep niches and hidden laying of pipelines, as well as when installing devices near walls without niches and open laying of risers, the liners are placed with ducks. If the pipelines of two-pipe heating systems are laid openly, the brackets when bypassing the pipes are bent on the risers, and the bend should be directed towards the room. With the hidden laying of pipelines of two-pipe heating systems, the brackets are not made, and at the intersection of the pipes, the risers are somewhat displaced in the furrow.
When installing fittings and fittings, in order to give them the correct position, do not loosen the thread in the opposite direction (unscrew); otherwise, leakage may occur. With a cylindrical thread, unscrew the fittings or fittings, wind up the flax and screw it back on.
On the liners, the mount is installed only if their length is more than 1.5 m.
The main pipelines in the basement and in the attic are mounted on threads and welded in the following sequence: first, they are laid out on the installed supports of the return pipe, one half of the main line is adjusted along a given slope and the pipeline is connected by thread or welding. Then, with the help of squeegees, the risers are connected to the main line, first dry, and then on flax and red lead, and the pipeline is strengthened on the supports.
When installing main pipelines in the attic, first mark the axes of the main line on the surface of building structures and install suspensions or wall supports along the intended axes. After that, the main pipeline is assembled and fixed on hangers or supports, the lines are verified and the pipeline is connected by thread or welding; then the risers are connected to the main line.
When laying main pipelines, it is necessary to observe the design slopes, straightness of pipelines, install air collectors and descents in the places indicated in the project. If the project does not contain instructions on the slope of the pipes, then it is taken at least 0.002 with an ascent towards the air collectors. The slope of pipelines in attics, canals and basements is marked with a rail, a level and a cord. At the installation site, according to the project, the position of any point on the pipeline axis is determined. A horizontal line is laid from this point and a cord is pulled along it. Then, along a given slope at some distance from the first point, the second point of the pipeline axis is found. A cord is pulled along the two points found, which will determine the axis of the pipeline. It is not allowed to connect pipes in the thickness of walls and ceilings, since they cannot be inspected and repaired.
Heat engineering calculation of the building's external fencing. Description of the adopted heating and water supply system. Selection of a water meter and determination of the head loss in it. Drawing up a local estimate, technical and economic indicators of construction and installation works.
thesis, added 02/07/2016
Thermal calculation of the outer multilayer wall of the building. Calculation of heat consumption for heating the infiltrating air through the barriers. Determination of the specific thermal characteristics of the building. Calculation and selection of radiators of the building heating system.
thesis, added 02/15/2017
Heat engineering calculation of external wall fencing, floor structures above the basement and underground, skylights, external doors. Heating system design and selection. Selection of equipment for an individual heating point of a residential building.
term paper, added 12/02/2010
Heat engineering calculation of external enclosing structures, heat loss of a building, heating devices. Hydraulic calculation of the building heating system. Calculation of the thermal loads of a residential building. Requirements for heating systems and their operation.
practice report, added 04/26/2014
Requirements for an autonomous heating system. Heat engineering calculation of external enclosing structures. Hydraulic calculation of the heating system, equipment for it. Organization and safe working conditions in the workplace. Heating system costs.
thesis, added 03/17/2012
Structural features of the building. Calculation of enclosing structures and heat loss. Characteristics of the evolved hazards. Calculation of air exchange for three periods of the year, mechanical ventilation system. Drawing up a heat balance and choosing a heating system.
term paper added 06/02/2013
Determination of heat transfer resistance of external enclosing structures. Calculation of heat losses of the building envelope. Hydraulic calculation of the heating system. Calculation of heating devices. Automation of an individual heating point.
thesis, added 03/20/2017
Calculation of heat transfer of the outer wall, floor and floor of the building, heat output of the heating system, heat loss and heat release. Selection and calculation of heating devices for the heating system, heating point equipment. Hydraulic calculation methods.
term paper, added 03/08/2011
Thermal calculation of external fences. Determination of the thermal performance of the building. Local budgeting. The main technical and economic indicators of construction and installation work. Analysis of working conditions when performing plumbing work.
thesis, added 07/11/2014
Thermal calculation of external fences: selection of design parameters, determination of heat transfer resistance. Heat output and losses, heating system design. Hydraulic calculation of the heating system. Calculation of heating devices.
For educational institutions in areas with an estimated outdoor air temperature of –40 ° C and below, it is allowed to use water with additives that prevent it from freezing (as additives, harmful substances of the 1st and 2nd hazard classes according to GOST 12.1.005 should not be used), and in the buildings of preschool institutions it is not allowed to use a coolant with additives of hazardous substances of the 1st to 4th hazard classes.
The heating system of schools, kindergartens and other children's and educational institutions (universities, vocational schools, colleges) in cities is connected to the central heating and hot system, which is powered by the city CHP or its own boiler house. In rural areas, they use an autonomous scheme, placing their own boiler room in a special room. In the case of a gasified area, the boiler runs on natural gas; in small schools and preschool institutions, low-power boilers are used that run on solid or liquid fuels or electricity.
When designing an internal heating system, it is necessary to take into account the microclimatic standards for the air temperature in classrooms, classrooms, canteens, gyms, swimming pools and other premises. Zones of buildings that are different in terms of technical purpose must have their own heating networks with water and heat metering devices.
To heat the gyms, along with the water system, an air heating system is used, combined with forced ventilation and operating from the same boiler room. The device for water floor heating can be present in changing rooms, bathrooms, showers, swimming pools and other rooms, if available. Thermal curtains are installed at the entrance groups in large educational institutions.
For heating devices and pipelines in kindergartens, staircases and lobbies, it is necessary to provide for protective fences and thermal insulation of pipelines.
Introduction
a common part
Characteristics of the object
Determination of the number of heat consumers. Annual heat consumption graph
Heat supply system and schematic diagram
Calculation of the heating scheme of the boiler room
Boiler room equipment selection
Selection and placement of main and auxiliary equipment
Thermal calculation of the boiler unit
Aerodynamic calculation of the heat-blowing path
Special unit.
2. Development of a block heater system.
2.1 Water supply baseline data
2.2 Choosing a water preparation scheme
2.3 Calculation of equipment for a water heating installation
2.4 Calculating the network installation
3. Technical and economic part
3.1 Initial data
3.2 Calculation of the contractual cost of construction and installation work
3.3 Determination of annual operating costs
3.4 Determination of the annual economic effect
Installation of sectional water heaters
5. Automation
Automatic regulation and heat engineering control of the boiler unit KE-25-14s
6. Labor protection in construction
6.1 Labor protection during the installation of power and technological equipment in the boiler room
6.2 Analysis and prevention of potential hazards
6.3 Calculation of slings
7. Organization, planning and construction management
7.1 Boiler installation
7.2 Conditions for starting work
7.3 Production costing of labor and wages
7.4 Calculation of schedule parameters
7.5 Organization of the building plan
7.6 Calculation of technical and economic indicators
8. Organization of operation and energy saving
List of used literature
Introduction.
In our difficult time, with a sickly crisis economy, the construction of new industrial facilities is fraught with great difficulties, if at all construction is possible. But at any time, in any economic situation, there is a number of industries without the development of which the normal functioning of the national economy is impossible, it is impossible to ensure the necessary sanitary and hygienic conditions for the population. Such industries include energy, which provides comfortable living conditions for the population both in everyday life and at work.
Recent studies have shown the economic feasibility of maintaining a significant share of the participation of large heating boiler plants in covering the total consumption of thermal energy.
Along with large production, production and heating boiler houses with a capacity of hundreds of tons of steam per hour or hundreds of MW of heat load, a large number of boiler units up to 1 MW and operating on almost all types of fuel have been installed.
However, it is with fuel that the biggest problem exists. For liquid and gaseous fuels, consumers often do not have enough funds to pay. Therefore, it is necessary to use local resources.
In this diploma project, the reconstruction of the production and heating boiler plant of RSC Energia is being developed, which uses local mined coal as fuel. In the future, it is planned to transfer boiler units to gas combustion from degassing gas emissions from the mine, which is located on the territory of the processing plant. The existing boiler house has two steam boilers KE-25-14, which were used to supply steam to the RSC Energia plant, and hot water boilers TVG-8 (2 boilers) for heating, ventilation and hot water supply of administrative buildings and a residential village.
Due to the reduction in coal production, the production capacity of the coal mining enterprise decreased, which led to a decrease in the demand for steam. This caused the reconstruction of the boiler house, which consists in using steam boilers KE-25 not only for production purposes, but also for the production of hot water for heating, ventilation and hot water supply in special heat exchangers.
1. GENERAL PART
1.1. OBJECT CHARACTERISTICS
The projected boiler house is located on the territory of the RSC Energia plant
The planning, placement of buildings and structures at the industrial site of the processing plant are made in accordance with the requirements of SNiP.
The size of the territory of the industrial site within the boundaries of the fences is 12.66 hectares, the building area is 52194 m 2.
The transport network of the construction area is represented by public railways and local roads.
The terrain is flat, with slight rises; loam predominates in the soil.
The source of water supply is the filtration station and the Seversky Donets-Donbass canal. Duplication of the water conduit is provided.
1.3. Determination of the amount of heat consumed. Annual heat consumption graph.
Estimated heat consumption by industrial enterprises is determined according to specific heat consumption rates per unit of output or per one heat carrier operating by type of m (water, steam). Heat consumption for heating, ventilation and technological needs are shown in Table 1.2. thermal loads.
The annual schedule of heat consumption is built depending on the duration of the standing outside temperatures, which is reflected in table 1.2. of this graduation project.
The maximum ordinate of the annual heat consumption graph corresponds to the heat consumption at an outdoor air temperature of –23 С.
The area bounded by the curve and the ordinate axes gives the total heat consumption for the heating period, and the rectangle on the right side of the graph - the heat consumption for hot water supply in summer.
Based on the data in Table 1.2. we calculate the heat consumption by consumers for 4 modes: maximum winter (t p. o. = -23C;); at an average outside temperature during the heating period; at an outside air temperature of + 8C; in the summer.
The calculation is carried out in table 1.3. by the formulas:
Heat load for heating and ventilation, MW
Q ОВ = Q Р ОВ * (t int -t n) / (t int -t r.o.)
Heat load for hot water supply in summer, MW
Q Л ГВ = Q Р ГВ * (t г -t хл) / (t г -t хз) *
where: Q Р ОВ - design winter heat load for heating and ventilation at design outside air temperature for designing a heating system. We accept according to the table. 1.2.
t VN - internal air temperature in the heated room, t VN = 18С
Q Р ГВ - calculated winter heat load on hot water supply (Table 1.2);
t n - current outside air temperature, ° С;
t p.o. - the estimated heating temperature of the outside air,
t g - temperature of hot water in the hot water supply system, t g = 65 ° C
t chl, t xs - cold water temperature in summer and winter, t chl = 15 ° С, t хз = 5 ° С;
- correction factor for the summer period, = 0.85
Table 1.2
Thermal loads
|
Thermal type |
Heat load consumption, MW |
Characteristic |
|
|
Loads |
Heat carrier |
||
|
1.Heating and ventilation |
Water 150/70 С Steam P = 1.4 MPa |
||
|
2.Hot water supply |
By calculation | ||
|
3.Technological needs |
Steam P = 1.44MPa |
||
Table 1.3.
Calculation of annual heat loads
|
Load type |
Designation |
Heat load value at temperature MW |
||||
|
t p.o = -23 С |
t c.p. = -1.8С | |||||
|
Heating and ventilation | ||||||
|
Hot water supply | ||||||
|
Technology | ||||||
According to the table. 1.1. and 1.3. we build a graph of annual heat load costs, presented in Figure 1.1.
1.4. SYSTEM AND SCHEME OF HEAT SUPPLY
The source of heat supply is the reconstructed boiler house of the mine. The heat carrier is steam and superheated water. Drinking water is used only for hot water systems. For technological needs, steam P = 0.6 MPa is used. For the preparation of superheated water with a temperature of 150-70С, a network installation is provided, for the preparation of water with t = 65 ° С - a hot water supply installation.
The heat supply system is closed. Due to the lack of direct water intake and insignificant leakage of the coolant through leaks in the connections of pipes and equipment, closed systems are distinguished by a high constancy of the quantity and quality of the network water circulated in it.
In closed water heat supply systems, water from heating networks is used only as a heating medium for heating tap water in surface-type heaters, which then enters the local hot water supply system. In open water heat supply systems, hot water is supplied to the water-folding devices of the local hot water supply system directly from the heating networks.
At the industrial site, heat supply pipelines are laid along bridges and galleries and partially in non-passable trough channels of the Cl type. The pipelines are laid with a compensation device due to the angles of turns of the route and U-shaped expansion joints.
The pipelines are made of electric-welded steel pipes with a thermal insulation device.
On sheet 1 of the graphic part of the diploma project, the general plan of the industrial site with the distribution of heating networks to consumer objects is shown.
1.5. CALCULATION OF THE BOILER ROOM HEATING DIAGRAM
The basic thermal diagram characterizes the essence of the main technological process of energy conversion and the use of the heat of the working fluid in the installation. It is a conditional graphic representation of the main and auxiliary equipment, united by lines of pipelines of the working fluid in accordance with the sequence of its movement in the installation.
The main purpose of calculating the heating scheme of the boiler room is:
Determination of the total heat loads, consisting of external loads and heat consumption for auxiliary needs, and the distribution of these loads between the hot-water and steam parts of the boiler house to justify the choice of the main equipment;
Determination of all heat and mass flows required for the selection of auxiliary equipment and determination of the diameters of pipelines and fittings;
Determination of the initial data for further technical and economic calculations (annual heat production, annual fuel consumption, etc.).
The calculation of the thermal circuit allows you to determine the total heat output of the boiler plant in several modes of its operation.
The thermal diagram of the boiler room is shown on sheet 2 of the graphic part of the diploma project.
The initial data for calculating the heating scheme of the boiler house are given in Table 1.4, and the calculation of the heating scheme itself is given in Table 1.5.
Table 1.4
Initial data for calculating the thermal diagram of a heating and industrial boiler house with steam boilers KE-25-14s for a closed heat supply system.
|
Name |
Design modes |
Note |
||||||
|
pos. Exodus. data |
Maximum winter |
At the outside temperature at the break point of the temperature graph | ||||||
|
Outdoor temperature | ||||||||
|
Air temperature inside heated buildings | ||||||||
|
Maximum temperature of direct supply water | ||||||||
|
The minimum temperature of the direct supply water at the break point of the temperature graph | ||||||||
|
Maximum temperature of the return water supply | ||||||||
|
Deaerated water temperature after deaerator | ||||||||
|
Enthalpy of deaerated water |
From tables of saturated steam and water at a pressure of 1.2MPa |
|||||||
|
Raw water temperature at the boiler room inlet | ||||||||
|
Raw water temperature before chemical water treatment | ||||||||
|
Specific volume of water in the heat water supply system, including 1 MW of total heat supply for heating, ventilation and hot water supply |
For industrial enterprises |
|||||||
|
Parameters of steam generated by boilers (before the reduction unit) | ||||||||
|
Pressure |
From saturation tables |
|||||||
|
Temperature |
puppy couple and |
|||||||
|
Enthalpy |
water at a pressure of 1.4 MPa |
|||||||
|
Steam parameters after the reduction unit: | ||||||||
|
Pressure |
From saturation tables |
|||||||
|
Temperature |
puppy couple and |
|||||||
|
Enthalpy |
water at a pressure of 0.7 MPa |
|||||||
|
Parameters of steam generated in a continuous product separator: | ||||||||
|
Pressure |
From saturation tables |
|||||||
|
Temperature |
puppy couple and |
|||||||
|
Enthalpy |
water at a pressure of 0.17 MPa |
|||||||
|
Parameters of steam entering the vapor cooler from the deaerator: | ||||||||
|
Pressure |
From saturation tables |
|||||||
|
Temperature |
puppy couple and |
|||||||
|
Enthalpy |
water at a pressure of 0.12 MPa |
|||||||
|
Condenser parameters after vapor cooler: | ||||||||
|
Pressure |
From saturation tables |
|||||||
|
Temperature |
puppy couple and |
|||||||
|
Enthalpy |
water at a pressure of 0.12 MPa |
|||||||
|
Blowdown water parameters at the inlet to the continuous blowdown separator: | ||||||||
|
Pressure |
From saturation tables |
|||||||
|
Temperature |
puppy couple and |
|||||||
|
Enthalpy |
water at a pressure of 1.4 MPa |
|||||||
|
Blowdown water parameters at the outlet of the continuous blowdown separator: | ||||||||
|
Pressure |
From saturation tables |
|||||||
|
Temperature |
puppy couple and |
|||||||
|
Enthalpy |
water at a pressure of 0.17 MPa |
|||||||
|
Purge water temperature after purge water cooling | ||||||||
|
Condensate temperature from the network water heater unit |
Is accepted |
|||||||
|
Condensate temperature after a steam-water heater for raw water |
Is accepted |
|||||||
|
Enthalpy of condensate after a steam-water heater for raw water |
From tables of saturated steam and water at a pressure of 0.7 MPa |
|||||||
|
Condensate temperature returned from production | ||||||||
|
Continuous blowdown rate |
Taken on the basis of chemical water treatment |
|||||||
|
Specific losses of steam with vapor from the feed water deaerator in tons per 1 ton of deaerated water | ||||||||
|
Coefficient of internal needs of chemical water treatment | ||||||||
|
Intra-boiler steam loss coefficient |
Is accepted |
|||||||
|
Estimated heat supply from the boiler room for heating and ventilation | ||||||||
|
Estimated heat supply for hot water supply per day of highest water consumption | ||||||||
|
Heat supply to industrial consumers in the form of steam | ||||||||
|
Condensate return from industrial consumers (80%) | ||||||||
Table 1.5
Calculation of the thermal diagram of a heating and industrial boiler room with steam boilers KE-25-14s for a closed heat supply system.
|
Name |
Estimated |
Design modes |
||||||
|
pos. Exodus. data |
Maximum winter |
At the average temperature of the coldest period |
At the outside air temperature at the break point of the temperature graph of the supply water. | |||||
|
Outside air temperature at the break point of the network water temperature graph |
t int -0.354 (t int - t r.o.) |
18-0,354* *(18+24)= =3,486 | ||||||
|
Coefficient of reduction of heat consumption for heating and ventilation depending on the outdoor temperature |
(t int - t "n) / (t int - t p.o) |
(18-(-10))/(18-(-23))=0,67 |
(18-0,486)/ /(18-(-24))= =0,354 | |||||
|
Estimated heat supply for heating and ventilation |
Q max s * K s |
15,86*0,67= 10,62 | ||||||
|
The value of the coefficient K ov to the power of 0.8 | ||||||||
|
The temperature of the direct supply water at the outlet of the boiler room |
18 + 64.5 * * K 0.8 s + 64.5 * K s |
18+64,5*0,73+67,5*0,67= 110,3 | ||||||
|
Return water temperature | ||||||||
|
Total heat supply for heating, ventilation and hot water supply in winter modes |
Q ov + Q avg gv | |||||||
|
Estimated flow rate of network water in winter modes |
Q ov + gv * 10 3 / (t 1 -t 2) * C | |||||||
|
Heat release for hot water supply in summer mode | ||||||||
|
Estimated flow of network water in summer mode |
Q l gv * 10 3 / (t 1 -t 2) * C | |||||||
|
The volume of network water in the water supply system |
q sys * Q d max | |||||||
|
Make-up water consumption for replenishing leaks in the heating network |
0.005 * G syst * 1 / 3.60 | |||||||
|
Return water quantity |
G net. |
G set - G ut | ||||||
|
Return water temperature in front of the mains pumps |
t 2 * G set.obr + T * G ut / G set | |||||||
|
Steam consumption for heating water heaters |
G set * (t 1 -t 3) / (i 2 / 4.19-t kb) * 0.98 | |||||||
|
The amount of condensate from heating water heaters | ||||||||
|
Steam load on the boiler room minus the steam consumption for deaeration and for heating raw water softened to feed the boilers, as well as without taking into account intra-boiler losses |
D potr + D b + D maz |
4,98+7,14= 12,12 |
4,98+9,13= 14,11 |
4,98+2,93= 7,91 |
0,53+0,43= 0,96 |
|||
|
The amount of condensate from heating water heaters and from production |
G b + G cons |
7,19+3,98= 11,12 |
9,13+3,98= 13,11 |
2,93+3,98= 6,91 |
0,43+0,42= 0,85 |
|||
|
0,148*0,6= 0,089 |
0,148*0,70= 0,104 |
0,148*0,39= 0,060 |
0,148*0,05= 0,007 |
|||||
|
The amount of purge water at the outlet of the continuous purge separator |
G "pr - D pr |
0,6-0,089= 0,511 |
0,70-0,104= 0,596 |
0,32-0,060= 0,33 |
0,05-0,007= 0,043 |
|||
|
Intra-body steam losses |
0,02*1212* 0,24 |
0,02*14,11= 0,28 |
0,02*7,91= 0,16 |
0,02*0,96= 0,02 |
||||
|
D + G pr + P ut | ||||||||
|
Evaporation from the deaerator |
0,002*13,44= 0,027 |
0,002*15,53= 0,03 |
0,002*9,02= 0,018 |
0,002*2,07= 0,004 |
||||
|
The amount of softened water entering the deaerator |
(D pot -G pot) + + G "pr + D pot + D out + G ut | |||||||
|
K s.n. needles * G needles | ||||||||
|
Gw * (T 3 -T 1) * C / (i 2 -i 6) * 0.98 | ||||||||
|
The amount of condensate from raw water heaters entering the deaerator | ||||||||
|
The total weight of the streams entering the deaerator (except for heating steam) |
G to + G xvo + G s + D pr -D issue | |||||||
|
The share of condensate from heating water heaters and from production in the total weight of the flows entering the deaerator | ||||||||
|
Steam consumption for feed water deaerator and raw water heating |
0,75+0,13= 0,88 |
0,82+0,13= 0,95 |
0,56+0,12= 0,88 |
0,15+0,024= 0,179 |
||||
|
D + (D g + D s) |
12,12+0,88= 13,00 |
14,11+0,9= 15,06 |
7,91+0,68= 8,59 |
0,96+0,179= 1,13 |
||||
|
Intra-body steam losses |
D "* (K pot / (1-K pot)) | |||||||
|
The amount of purge water entering the continuous purge separator | ||||||||
|
The amount of steam at the outlet of the continuous blowdown separator |
G pr * (i 7 * 0.98-i 8) / (i 3 -i 8) | |||||||
|
The amount of purge water at the outlet of the continuous purge separator | ||||||||
|
The amount of water for feeding the boilers |
D sum + G pr | |||||||
|
The amount of water at the outlet of the deaerator |
G pit + G ut | |||||||
|
Evaporation from the deaerator | ||||||||
|
The amount of softened water entering the deaerator |
(D pot -G potr) -G "pr + D sweat + D out + G ut | |||||||
|
The amount of raw water supplied to chemical water treatment |
K s.n. needles * G needles | |||||||
|
Steam consumption for heating raw water |
G c. v. * (T 3 -T 1) * C / (i 2 -i 8) * 0.98 | |||||||
|
The amount of condensate entering the deaerator from raw water heaters | ||||||||
|
The total weight of the flows entering the deaerator (except for heating steam) |
G k + G xvo + G c + D pr -D vyp | |||||||
|
Condensate fraction from heaters |
11,12/13,90= 0,797 |
13,11/16,04= 0,82 | ||||||
|
Specific steam consumption for the deaerator | ||||||||
|
Absolute steam consumption for the deaerator | ||||||||
|
Steam consumption for deaeration of feed water and heating of raw water | ||||||||
|
Steam load on the boiler room without taking into account intra-boiler losses |
12,12+0,87= 12,9 |
14,11+0,87= 15,07 |
7,91+0,67= 8,58 |
0,96+0,17= 1,13 |
||||
|
Percentage of steam consumption for auxiliary needs of the boiler room (deaeration heating of raw water) |
(D g + D s) / D sum * 100 | |||||||
|
Number of operating boilers |
D sum / D to nom | |||||||
|
Loading percentage of operating steam boilers |
D sum / D to nom * N cr. * *100% | |||||||
|
The amount of water passed in addition to the heating system water heaters (through the jumper between the supply and return water pipelines) |
G set * (t max 1 -t 1) / / (t max 1 -t 3) | |||||||
|
The amount of water passed through the heating system water heaters |
G set - G set. |
94,13-40,22= 53,91 |
66,56-49,52= 17,04 |
9,20-7,03= 2,17 |
||||
|
Supply water temperature at the inlet to steam-water heaters |
/ (i 2 - t c. b. s.) | |||||||
|
Temperature of softened water at the outlet of the purge water cooler |
T 3 + G "pr / G xvo * (i 8 / s --t pr) | |||||||
|
Temperature of softened water entering the deaerator from the steam cooler |
T 4 + D out / G xvo * (i 4 -i 5) / s | |||||||
The basic thermal diagram indicates the main equipment (boilers, pumps, deaerators, heaters) and the main pipelines.
Saturated steam from boilers with a working pressure of P = 0.8 MPa enters the general steam line of the boiler house, from which a part of the steam is taken to the equipment installed in the boiler room, namely: heating water heater; hot water heater; deaerator. Another part of the steam is directed to the production needs of the enterprise.
Condensate from the industrial consumer is returned by gravity, in the amount of 30% at a temperature of 80 ° C, to the condensate collector and then by the condensate pump is sent to the hot water tank.
Heating of network water, as well as heating of hot water, is performed by steam in two sequentially connected heaters, while the heaters operate without condensate traps, the spent condensate is sent to the deaerator.
The deaerator also receives chemically purified water from the water treatment plant, which replenishes condensate losses.
The raw water pump sends water from the city water supply to the water treatment plant and to the hot water tank.
Deaerated water with a temperature of about 104 ° C is pumped into economizers by a feed pump and then enters the boilers.
Make-up water for the heating system is taken by the make-up pump from the hot water tank.
The main purpose of calculating the thermal circuit is:
determination of total heat loads, consisting of external loads and steam consumption for auxiliary needs,
determination of all heat and mass flows necessary for the selection of equipment,
determination of the initial data for further technical and economic calculations (annual heat, fuel, etc.).
Calculation of the heat circuit allows you to determine the total steam capacity of the boiler plant in several modes of its operation. The calculation is performed for 3 typical modes:
maximum winter,
coldest month
|
Physical quantity |
Designation |
Justification |
The value of the quantity under typical operating modes of the boiler room. |
||||
|
Maximum - winter |
Coldest month |
summer |
|||||
|
Heat consumption for production needs, Gcal / h. | |||||||
|
Heat consumption for heating and ventilation, Gcal / h. | |||||||
|
Water consumption for hot water supply, t / h. | |||||||
|
Hot water temperature, о С |
SNiP 2.04.07-86. | ||||||
|
Estimated outside air temperature for Yakutsk, о С: | |||||||
|
- when calculating the heating system: | |||||||
|
- when calculating the ventilation system: | |||||||
|
Condensate return to the industrial consumer,% | |||||||
|
Enthalpy of saturated steam with a pressure of 0.8 MPa, Gcal / t. |
Water vapor table | ||||||
|
Boiler water enthalpy, Gcal / t. | |||||||
|
Enthalpy of feed water, Gcal / t. | |||||||
|
Enthalpy of condensate at t = 80 о С, Gcal / t. | |||||||
|
Enthalpy of condensate with “passing” vapor, Gcal / t. | |||||||
|
Temperature of condensate returned from production, о С | |||||||
|
Raw water temperature, о С | |||||||
|
Periodic blowing,% | |||||||
|
Water loss in a closed heat supply system,% | |||||||
|
Steam consumption for auxiliary needs of the boiler house,% | |||||||
|
Steam losses in the boiler room and at the consumer,% | |||||||
|
Coefficient of consumption of raw water for the auxiliary needs of the water treatment plant. | |||||||
CALCULATION of the annual demand for heat and fuel on the example of a boiler house of a secondary school with 800 students, Central Federal District.
LIST of data to be submitted together with the application for establishing the type of fuel for enterprises (associations) and fuel-consuming installations.
1.General questions
| Questions | Answers |
| Ministry (department) | MO |
| Enterprise and its location (republic, region, settlement) | Central Federal District |
| Object distance to: A) railway station B) gas pipeline (its name) C) base of petroleum products D) the nearest source of heat supply (CHP boiler house), indicating its capacity, workload and belonging | B) 0.850 km |
| The readiness of the enterprise to use fuel and energy resources (operating, reconstructed, under construction, projected), indicating its category | Acting |
| Documents, approvals, (date, number, name of the organization) A) on the use of natural gas, coal and other types of fuel B) on the construction of an individual or expansion of the existing boiler house (CHP) On the basis of which document the enterprise is designed, built, expanded, reconstructed. | MO task |
| Type and quantity (thousand, toe) of fuel currently used and on the basis of which document (date, number) the consumption is established, (for solid fuel, indicate its deposit and brand) Type of fuel requested, total annual consumption (thousand, toe) and year of the beginning of consumption Year of the enterprise reaching its design capacity, total annual consumption (thousand, toe) this year | Natural gas; 0.536; 2012 2012; 0.536 |
2. Boiler plants and CHP
A) Demand for heat energy
| What needs | Attached maxim. heat load (Gcal / h) | Number of hours of work per year | Annual heat demand (thousand Gcal) | Coverage of heat demand, thousand Gcal / year | ||||
| Exs. | NS. incl. present | Exs. | NS. incl. present | Boiler room (CHP) | Secondary energy resources | Parties | ||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
Heating | 1,210 | 5160 | 2,895 | 2,895 | ||||
Ventilation | 0,000 | 0,000 | 0,000 | 0,000 | ||||
| 0,172 | 2800 | 0,483 | 0,483 | |||||
Technological needs | 0,000 | 0,000 | 0,000 | |||||
Own needs of the boiler house (CHP) | 0,000 | 0,000 | 0,000 | |||||
Losses in heating networks | 0,000 | 0,000 | 0,000 | |||||
| 1,382 | 3,378 | 3,378 | ||||||
B) Composition and characteristics of boiler equipment, type and annual fuel consumption
| Boiler type by group | Qty | Total power Gcal / h | Fuel used | Requested fuel | ||||
| Main (backup) type | Specific consumption, kg.c.t./Gcal | Annual consumption, thousand tons of fuel equivalent | Main (backup) type | Specific consumption, kg.c.t./Gcal | Annual consumption, thousand tons of fuel equivalent | |||
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| The operating | ||||||||
| Dismountable | ||||||||
Installed boilers Buderus Logano SK745-820 VAHI (820kW) | 2 | 1,410 | Natural gas (none) | 158.667 | 0,536 | |||
| Reserve | ||||||||
Note:
1. Specify the total annual fuel consumption by boiler group.
2. Specify the specific fuel consumption, taking into account the own needs of the boiler house (CHP)
3. In columns 4 and 7, indicate the method of fuel combustion (layered, chamber, in a fluidized bed).
4. For CHPP, indicate the type and brand of turbine units, their electrical capacity in thousand kW, annual generation and supply of electricity in thousand kWh,
annual heat supply in Gcal., specific fuel consumption for the supply of electricity and heat (kg / Gcal), annual fuel consumption, production of electricity and heat for the CHPP as a whole.
5. With a consumption of more than 100 thousand tons of standard fuel per year, the fuel and energy balance of the enterprise (association) must be submitted
2.1 General
The calculation of the annual fuel demand for a modular boiler room (heating and hot heating) of a secondary school, was carried out on the instructions of the MO. The maximum winter hourly heat consumption for heating the building is determined by aggregated indicators. Heat consumption for hot water supply is determined in accordance with the instructions of clause 3.13 SNiP 2.04.01-85 "Internal water supply and sewerage of buildings". Climatological data were adopted according to SNiP 23-01-99 "Construction climatology and geophysics". The calculated averaged temperatures of the internal air are taken from the "Guidelines for determining the consumption of fuel, electricity and water for heat generation by heating Boiler houses of communal heat and power enterprises". Moscow 1994
2.2 Heat source
For heat supply (heating, hot water supply) of the school, it is planned to install two Buderus Logano SK745 boilers (Germany) with a capacity of 820 kW each in a specially equipped boiler room. The total capacity of the installed equipment is 1.410 Gcal / h. Natural gas is requested as the main fuel. No backup required.
2.3 Initial data and calculation
| P / p No. | Indicators | Formula and calculation |
| 1 | 2 | 3 |
| 1 | Estimated outdoor temperature for heating design | T (P.O) = -26 |
| 2 | Estimated outdoor temperature for ventilation design | T (R.V) = -26 |
| 3 | Average outdoor temperature for the heating period | T (CP.O) = -2.4 |
| 4 | Estimated average temperature of indoor air of heated buildings | T (BH.) = 20.0 |
| 5 | Heating period duration | P (O) = 215 days. |
| 6 | The number of hours of operation of heating systems per year | Z (O) = 5160 h |
| 7 | The number of hours of operation of ventilation systems per year | Z (B) = 0 h |
| 8 | The number of hours of operation of hot water supply systems per year | Z (G.V) = 2800 h |
| 9 | The number of hours of operation of technological equipment per year | Z (B) = 0 h |
| 10 | Coeff. simultaneity of action and use. Maksim. technical load | K (T) = 0.0 h |
| 11 | Coeff. working days | KRD = 5.0 |
| 12 | Average hourly heat consumption for heating | Q (OCP) = Q (O) * [T (BH) -T (CP.O)] / [T (BH) -T (PO)) = 1.210 * [(18.0) - ( -2.4)] / [(18.0) - (- 26.0)] = 0.561 Gcal / h |
| 13 | Average hourly heat consumption for ventilation | Q (B.CP) = Q (B) * [T (BH) -T (CP.O)] / [T (BH) -T (P.B)) = 0.000 * [(18.0) - ( -2.4)] / [(18.0) - (- 26.0)] = 0.000 Gcal / h |
| 14 | Average hourly heat consumption for hot water supply for heating. period | Q (G.V. SR) = Q (G.V.) / 2.2 = 0.172 / 2.2 = 0.078 Gcal / h |
| 15 | Average hourly heat consumption for hot water supply in summer | Q (G.V.SR.L) = (G.V.SR) * [(55-1 5) / (55-5)] * 0.8 = 0.078 * [(55-15) / (55-5) ] * 0.8 = 0.0499 Gcal / h |
| 16 | Average hourly heat consumption per technology per year | Q (TECH.SR) = Q (T) * K (T) = 0.000 * 0.0 = 0.000 Gcal / h |
| 17 | Annual heat demand for heating | Q (O.YOD) = 24 * P (O) * Q (O. SR) = 24 * 215 * 0.561 = 2894.76 Gcal |
| 18 | Annual heat demand for ventilation | Q (V.YEAR) = Z (B) * Q (V.SR) = 0.0 * 0.0 = 0.00 Gcal |
| 19 | Annual heat demand for water supply | Q (G.V. YEAR) (24 * P (O) * Q (G.V. SR) + 24 * Q (G.V. SR.L) *) * КRD = (24 * 215 * 0.078 +24 * 0.0499 * (350-215)) * 6/7 = 483.57 Gcal |
| 20 | Annual heat demand for technology | Q (T. YEAR) = Q (TECH.CP) * Z (T) = 0.000 * 0 = 0.000 Gcal |
| 21 | Total annual heat demand | Q (YEAR) = Q (O. YEAR) + Q (V. YEAR) + Q (G. V. YEAR) + Q (T. YEAR) = 2894.76 + 0.000 + 483.57 + 0.000 = 3378.33 Gcal |
| TOTAL for existing buildings: | ||
| Annual heat demand for Heating Ventilation Hot water supply Technology Losses in t / s Own needs of the boiler room | Q (O. GOD) = 2894.76 Gcal Q (V. YEAR) = 0.000 Gcal Q (G.V. YEAR) = 483.57 Gcal Q (T. YEAR) = 0.000 Gcal ROTER = 0.000 Gcal SОВS = 0,000 Gcal |
|
| TOTAL: | Q (YEAR) = 3378.33 Gcal | |
| Specific consumption of equivalent fuel | B = 142.8 * 100/90 = 158.667 KG.U.T. / Gcal | |
| Annual consumption of equivalent fuel for heat supply of existing buildings | B = 536.029 T.U.T | |
To order the calculation of the annual demand for heat and fuel of the enterprise, fill in
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WITHobsession
Introduction
1. Calculation of heating, ventilation and hot water supply for a school for 90 students
1.1 Brief description of the school
1.2 Determination of heat loss through the outer fences of the garage
1.3 Calculation of the heating surface area and selection of heating devices for central heating systems
1.4 Calculation of school air exchange
1.5 Selection of heaters
1.6 Calculation of heat consumption for hot water supply to the school
2. Calculation of heating and ventilation of other objects according to the given scheme No. 1 with centralized and local heat supply
2.1 Calculation of heat consumption for heating and ventilation according to the enlarged standards of residential and public facilities
2.2 Calculation of heat consumption for hot water supply for residential and public buildings
3. Construction of an annual heat load schedule and selection of boilers
3.1 Building an annual heat load schedule
3.2 Choice of heating medium
3.3 Selection of boilers
3.4 Construction of an annual schedule for regulating the supply of a thermal boiler house
Bibliography
Introduction
The agro-industrial complex is an energy-intensive branch of the national economy. A large amount of energy is spent on heating industrial, residential and public buildings, creating an artificial microclimate in livestock buildings and protective ground structures, drying agricultural products, manufacturing products, obtaining artificial cold and for many other purposes. Therefore, the power supply of agro-industrial complex enterprises includes a wide range of tasks associated with the production, transmission and use of thermal and electric energy, using traditional and non-traditional energy sources.
In this course project, an option for the integrated power supply of the settlement is proposed:
· For a given scheme of objects of the agro-industrial complex, an analysis of the need for heat energy, electricity, gas and cold water is carried out;
· Calculation of heating, ventilation and hot water supply loads;
· The required capacity of the boiler house is determined, which could meet the needs of the economy in heat;
· The choice of boilers is carried out.
Calculation of gas consumption,
1. Calculation of heating, ventilation and hot water supply for a school for 90 students
1 . 1 Short haschool characteristics
Dimensions 43.350x12x2.7.
Room volume V = 1709.34 m 3.
The external longitudinal walls are load-bearing, made of facing and finishing, thickened brick of the KP-U100 / 25 brand in accordance with GOST 530-95 on a cement-sand mortar M 50, 250 and 120 mm thick and 140 mm of insulation - expanded polystyrene between them.
Internal walls are made of hollow, thickened ceramic bricks of the KP-U100 / 15 brand in accordance with GOST 530-95, with M50 mortar.
Partitions are made of KP-U75 / 15 bricks in accordance with GOST 530-95, with M 50 mortar.
Roof - roofing material (3 layers), cement-sand screed 20mm, expanded polystyrene 40mm, roofing material in 1 layer, cement-sand screed 20mm and reinforced concrete slab;
Floors - concrete М300 and soil compacted with rubble.
Double windows with double wooden sash, window sizes 2940x3000 (22 pieces) and 1800x1760 (4 pieces).
Single external wooden doors 1770х2300 (6 pcs)
Design parameters of outdoor air tн = - 25 0 С.
Estimated winter ventilation temperature of the outside air tн.в. = - 16 0 С.
The design temperature of the internal air is tв = 16 0 С.
The moisture zone of the area is normal dry.
Barometric pressure 99.3 kPa.
1.2 Air exchange calculation school
The learning process takes place at school. It is characterized by a long stay of a large number of students. No harmful emissions. The coefficient of air change for the school will be 0.95 ... 2.
where Q is air exchange, m3 / h; Vp - room volume, m?; K - the frequency of air exchange is taken = 1.
Fig. 1. The dimensions of the room.
Room volume:
V = 1709.34 m 3.
Q = 1 1709.34 = 1709.34 m 3 / h.
We arrange general ventilation in the room, combined with heating. We arrange natural exhaust ventilation in the form of exhaust shafts, the cross-sectional area F of the exhaust shafts is found by the formula: F = Q / (3600? N.vn). , having previously determined the air speed in the exhaust shaft with a height of h = 2.7 m
n c.vn. = = 1.23 m / s
F = 1709.34 / (3600 1.23) = 0.38 m?
Number of exhaust shafts
n lw = F / 0.04 = 0.38 / 0.04 = 9.5? ten
We accept 10 exhaust shafts with a height of 2 m and a free cross-section of 0.04 m? (with dimensions 200 x 200 mm).
1.3 Determination of heat loss through the external enclosures of the room
We do not take into account heat loss through the internal fences of the room, because the temperature difference in the shared rooms does not exceed 5 0 C. Determine the heat transfer resistance of the enclosing structures. The heat transfer resistance of the outer wall (Fig. 1) is found by the formula, using the data in Table. 1, knowing that the thermal resistance to heat absorption of the inner surface of the fence Rw = 0.115 m 2 0 С / W
where Rв - thermal resistance to heat absorption of the inner surface of the fence, m? ·? С / W; - the sum of the thermal resistances of the thermal conductivity of individual layers t - layer fencing with a thickness of di (m), made of materials with thermal conductivity li, W / (m Rн - thermal resistance to heat transfer of the outer surface of the fence Rн = 0.043 m 2 0 С / W (for external walls and attic floors).
Fig. 1 Structure of wall materials.
Table 1 Thermal conductivity and width of wall materials.
Outer wall heat transfer resistance:
R 01 = m? ·? С / W.
2) Resistance to heat transfer of windows Ro.ok = 0.34 m 2 0 С / W (found from the table on page 8)
Heat transfer resistance of external doors and gates 0.215 m 2 0 С / W (found from the table on page 8)
3) Resistance to heat transfer of the ceiling for an attic floor (Rw = 0.115 m 2 0 C / W, Rn = 0.043 m 2 0 C / W).
Calculation of heat losses through floors:
Fig. 2 ceiling structure.
Table 2 Thermal conductivity and width of floor materials
Heat transfer resistance of the ceiling
m 2 0 С / W.
4) Heat losses through the floors are calculated in zones - strips 2 m wide parallel to the outer walls (Fig. 3).
Areas of floor zones minus basement area:
F1 = 43 2 + 28 2 = 142 m 2
F1 = 12 2 + 12 2 = 48 m 2,
F2 = 43 2 + 28 2 = 148 m 2
F2 = 12 2 + 12 2 = 48 m 2,
F3 = 43 2 + 28 2 = 142 m 2
F3 = 6 0.5 + 12 2 = 27 m 2
Basement floor areas:
F1 = 15 2 + 15 2 = 60 m 2
F1 = 6 2 + 6 2 = 24 m 2,
F2 = 15 2 + 15 2 = 60 m 2
F2 = 6 2 = 12 m 2
F1 = 15 2 + 15 2 = 60 m 2
Floors located directly on the ground are considered non-insulated if they consist of several layers of materials, the thermal conductivity of each of which is l? 1.16 W / (m 2 0 С). The floors are considered to be insulated, the insulation layer of which has l<1,16 Вт/м 2 0 С.
Heat transfer resistance (m 2 0 С / W) for each zone is determined as for non-insulated floors, since thermal conductivity of each layer l? 1.16 W / m 2 0 С. So, the resistance to heat transfer Rо = Rn.p. for the first zone it is 2.15, for the second - 4.3, for the third - 8.6, the rest - 14.2 m 2 0 С / W.
5) The total area of window openings:
Fok = 2.94 3 22 + 1.8 1.76 6 = 213 m 2.
Total area of external doorways:
Fdv = 1.77 2.3 6 = 34.43 m 2.
Exterior wall area minus window and door openings:
Fn.s. = 42.85 2.7 + 29.5 2.7 + 11.5 2.7 + 14.5 2.7 + 3 2.7 + 8.5 2.7 - 213 - 34.43 = 62 m 2 ...
Basement wall area:
Fn.s.p = 14.5 2.7 + 5.5 2.7-4.1 = 50
6) Ceiling area:
Fpot = 42.85 12 + 3 8.5 = 539.7 m 2,
where F is the area of the fence (m?), which is calculated with an accuracy of 0.1 m? (the linear dimensions of the enclosing structures are determined with an accuracy of 0.1 m, observing the measurement rules); tв and tн - design temperatures of indoor and outdoor air,? С (app. 1 ... 3); R 0 - total resistance to heat transfer, m 2 0 С / W; n is a coefficient depending on the position of the outer surface of the fence in relation to the outside air, we take the values of the coefficient n = 1 (for outer walls, non-attic coatings, attic floors with steel, tiled or asbestos-cement roofs on a sparse lathing, floors on the ground)
Heat losses through external walls:
Fns = 601.1 W.
Heat losses through the outer walls of the basement:
Fn.s.p = 130.1W.
F n.s. = F n.s. + F n.s.p. = 601.1 + 130.1 = 731.2 W.
Heat losses through windows:
Fock = 25685 W.
Heat losses through doorways:
Fdv = 6565.72 W.
Heat loss through the ceiling:
FPot = = 13093.3 W.
Heat loss through the floor:
Fpol = 6240.5 W.
Heat losses through the basement floor:
Fpol.p = 100 W.
F floor = F floor. + F pol.p. = 6240.5 + 100 = 6340.5 W.
Additional heat losses through external vertical and inclined (elevation projection) walls, doors and windows depend on various factors. Fdob values are calculated as a percentage of the main heat losses. Additional heat losses through the outer wall and windows facing north, east, northwest and northeast are 10%, to the southeast and west - 5%.
Additional losses for infiltration of outside air for industrial buildings are taken in the amount of 30% of the main losses through all fences:
Finf = 0.3 7 watts
Thus, the total heat loss is determined by the formula:
Fogr = 78698.3 W.
1.4 Calculation of the heating surface area and selectionheating devices for central heating systems
The most common and universal heating devices in use are cast iron radiators. They are installed in residential, public and various industrial buildings. We use steel pipes as heating devices in production facilities.
Let us first determine the heat flow from the pipelines of the heating system. The heat flux given to the room by openly laid non-insulated pipelines is determined by formula 3:
Ftr = Ftr ktr
where Ftr = p? d · l - area of the outer surface of the pipe, m2; d and l - outer diameter and length of the pipeline, m (diameters of main pipelines are usually 25 ... 50 mm, risers 20 ... 32 mm, connections to heating devices 15 ... 20 mm); ktr - the heat transfer coefficient of the pipe W / (m 2 0 С) is determined according to table 4, depending on the temperature difference and the type of coolant in the pipeline,? С; h - coefficient equal to the supply line located under the ceiling, 0.25, for vertical risers - 0.5, for the return line located above the floor - 0.75, for connections to the heating device - 1.0
Supply pipeline:
Diameter-50mm:
F1 50mm = 3.14 73.4 0.05 = 11.52 m?;
Diameter 32mm:
F1 32mm = 3.14 35.4 0.032 = 3.56 m?;
Diameter-25 mm:
F1 25mm = 3.14 14.45 0.025 = 1.45 m?;
Diameter-20:
F1 20mm = 3.14 32.1 0.02 = 2.02 m?;
Return piping:
Diameter-25mm:
F2 25mm = 3.14 73.4 0.025 = 5.76 m?;
Diameter-40mm:
F2 40mm = 3.14 35.4 0.04 = 4.45 m?;
Diameter-50mm:
F2 50mm = 3.14 46.55 0.05 = 7.31 m?;
The heat transfer coefficient of pipes for the average difference between the temperature of the water in the device and the air temperature in the room (95 + 70) / 2 - 15 = 67.5 ° C is taken equal to 9.2 W / (m? C). in accordance with the data in table 4.
Direct heat pipe:
Ф п1.50mm = 11.52 9.2 · (95 - 16) 1 = 8478.72 W;
Ф п1.32mm = 3.56 9.2 · (95 - 16) 1 = 2620.16 W;
Ф п1.25mm = 1.45 9.2 · (95 - 16) 1 = 1067.2 W;
Ф п1.20mm = 2.02 9.2 · (95 - 16) 1 = 1486.72 W;
Return heat pipe:
Ф п2.25mm = 5.76 9.2 · (70 - 16) 1 = 2914.56 W;
Ф п2.40mm = 4.45 9.2 · (70 - 16) 1 = 2251.7 W;
Ф п2.50mm = 7.31 9.2 · (70 - 16) 1 = 3698.86 W;
Total heat flux from all pipelines:
Ф tr = 8478.72 + 2620.16 + 1067.16 + 1486.72 + 2914.56 + 2251.17 + 3698.86 = 22517.65 W
The required heating surface area (m2) of the devices is roughly determined by the formula 4:
where Fogr-Ftr is the heat transfer of heating devices, W; Ftr - heat transfer from open pipelines located in the same room with heating devices, W;
kпр - heat transfer coefficient of the device, W / (m 2 0 С). for water heating tпр = (tг + tо) / 2; tg and tо - design temperature of hot and chilled water in the device; for low pressure steam heating, tпр = 100? С, in high pressure systems tпр is equal to the steam temperature in front of the device at its corresponding pressure; tв - design air temperature in the room,? С; в 1 - a correction factor that takes into account the installation method of the heating device. For free installation against a wall or in a niche 130 mm deep in 1 = 1; in other cases, values in 1 are taken on the basis of the following data: a) the device is installed against a wall without a niche and is covered with a board in the form of a shelf with a distance between the board and the heater of 40 ... 100 mm; coefficient in 1 = 1.05 ... 1.02; b) the device is installed in a wall niche with a depth of more than 130 mm with a distance between the board and the heating device of 40 ... 100 mm; coefficient 1 = 1.11 ... 1.06; c) the device is installed in a wall without a niche and is closed by a wooden cabinet with slots in the upper board and in the front wall near the floor with a distance between the board and the heater equal to 150, 180, 220 and 260 mm, the coefficient in 1 is 1.25, respectively; 1.19; 1.13 & 1.12; in 1 - correction factor in 2 - correction factor, taking into account the cooling of water in pipelines. With open laying of hot water heating pipelines and with steam heating, 2 = 1. for hidden pipelines, with pumping circulation at 2 = 1.04 (one-pipe systems) and at 2 = 1.05 (two-pipe systems with top wiring); with natural circulation due to the increase in water cooling in the pipelines, the values of 2 should be multiplied by a factor of 1.04.
The required number of sections of cast-iron radiators for the calculated room is determined by the formula:
n = Fpr / fsec,
where fsec is the heating surface area of one section, m? (Table 2).
n = 96 / 0.31 = 309.
The resulting value n is approximate. If necessary, it is divided into several devices and, by introducing a correction factor of 3, taking into account the change in the average heat transfer coefficient of the device, depending on the number of sections in it, the number of sections accepted for installation in each heating device is found:
nset = n · in 3;
nset = 309 1.05 = 325.
We install 27 radiators in 12 sections.
heating water supply school ventilation
1.5 Selection of heaters
Air heaters are used as heating devices to increase the temperature of the air supplied to the room.
The selection of heaters is determined in the following order:
1. Determine the heat flux (W) for heating the air:
Fv = 0.278 Q? with? c (tв - tн), (10)
where Q is the volumetric air flow rate, m3 / h; с - air density at temperature tк, kg / m?; cf = 1 kJ / (kg? С) - specific isobaric heat capacity of air; tк - air temperature after the heater,? С; tн - initial temperature of the air entering the heater,? С
Air density:
c = 346 / (273 + 18) 99.3 / 99.3 = 1.19;
Fv = 0.278 1709.34 1.19 1 (16- (-16)) = 18095.48 W.
The estimated mass air velocity is 4-12 kg / s m ?.
3. Then, according to table 7, we select the model and the number of the heater with a free cross-sectional area in the air close to the calculated one. With a parallel (in the direction of air) installation of several heaters, their total area of the free cross-section is taken into account. We choose 1 K4PP No. 2 with a free air area of 0.115 m? and a heating surface area of 12.7 m?
4. For the selected air heater calculate the actual mass air velocity
5. After that, according to the graph (Fig. 10) for the adopted model of the heater, we find the heat transfer coefficient k depending on the type of coolant, its speed, and ns value. According to the schedule, the heat transfer coefficient k = 16 W / (m 2 0 С)
6. Determine the actual heat flux (W) transmitted by the heating unit to the heated air:
Фк = k F (t? Cf - tcr),
where k is the heat transfer coefficient, W / (m 2 0 С); F is the area of the heating surface of the air heater, m2; t? av is the average temperature of the heat carrier,? С, for the heat carrier - steam - t? av = 95? С; tav - the average temperature of the heated air t? av = (tc + tn) / 2
Фк = 16 12.7 (95 - (16-16) / 2) = 46451 2 = 92902 W.
2 plate heaters KZPP No. 7 provide a heat flow of 92902 W, and the required one is 83789.85 W. Therefore, heat transfer is fully ensured.
The heat transfer margin is = 6%.
1.6 Calculation of heat consumption for hot water supply to the school
Hot water is needed at school for sanitary needs. A school with 90 seats per day consumes 5 liters of hot water per day. Total: 50 liters. Therefore, we place 2 risers with a water flow rate of 60 l / h each (that is, a total of 120 l / h). Considering that, on average, hot water for sanitary needs is used for about 7 hours during the day, we find the amount of hot water - 840 l / day. 0.35 m3 / h is consumed per hour at school
Then the heat flow for water supply will be
Fgv. = 0.278 0.35 983 4.19 (55 - 5) = 20038 W
The number of showers for the school is 2. The hourly consumption of hot water in one cabin is Q = 250 l / h, we assume that on average the shower works 2 hours a day.
Then the total consumption of hot water: Q = 3 2 250 10 -3 = 1m 3
Fgv. = 0.278 1 983 4.19 (55 - 5) = 57250 W.
F G.V. = 20038 + 57250 = 77288 W.
2. Calculation of the heat load for district heating
2.1 RCalculation of heat consumption for heating and ventilation byconsolidated standards
The maximum flow of heat (W) consumed for heating residential and public buildings of the village included in the district heating system can be determined by aggregated indicators depending on the living space using the following formulas:
Photo.zh. = c? F,
Photo.j. = 0.25 Photo.j., (19)
where c is the enlarged indicator of the maximum specific heat flux consumed for heating 1 m? living space, W / m2. The values of q are determined depending on the estimated winter temperature of the outside air according to the schedule (Fig. 62); F - living area, m2.
1. For thirteen 16-apartment buildings with an area of 720 m 2 we get:
Photo.zh. = 13 170 720 = 1591200 W.
2. For eleven 8-apartment buildings with an area of 360 m 2 we get:
Photo.zh. = 8 170 360 = 489600 W.
3. For honey. item with dimensions 6x6x2.4 we get:
Photo total = 0.25 170 6 6 = 1530 W;
4.For an office with dimensions of 6x12 m:
Photos total = 0.25 170 6 12 = 3060 W,
For individual residential, public and industrial buildings, the maximum heat fluxes (W) consumed for heating and air heating in the supply ventilation system are roughly determined by the formulas:
Phot = qot Vn (tv - tn) a,
Фв = qв · Vн · (tv - tn.в.),
where q from and q in - specific heating and ventilation characteristics of the building, W / (m 3 · 0 С), taken according to table 20; V n - the volume of the building according to the external measurement without the basement, m 3, is taken according to standard designs or determined by multiplying its length by its width and height from the planning mark of the earth to the top of the cornice; t in = the average design air temperature typical for most rooms of the building, 0 С; t n = design winter temperature of the outside air, - 25 0 С; t n.v. - design winter ventilation temperature of the outside air, - 16 0 С; a - a correction factor that takes into account the effect on the specific thermal characteristics of local climatic conditions at tn = 25 0 С а = 1.05
Phot = 0.7 18 36 4.2 (10 - (- 25)) 1.05 = 5000.91W,
Fv.total = 0.4 5000.91 = 2000 W.
Brigade house:
Phot = 0.5 1944 (18 - (- 25)) 1.05 = 5511.2W,
School workshop:
Phot = 0.6 1814.4 (15 - (- 25)) 1.05 = 47981.8 W,
Fv = 0.2 1814.4 (15 - (- 16)) = 11249.28 W,
2.2 RCalculation of heat consumption for hot water supply forresidential and public buildings
The average heat flow (W) consumed during the heating period for hot water supply of buildings is found by the formula:
F G.V. = q onwards N w,
Depending on the rate of water consumption at a temperature of 55 0 С, the enlarged indicator of the average heat flow (W) spent on hot water supply for one person will be: is 407 watts.
For 16 apartment buildings with 60 residents, the heat flow for hot water supply will be: = 407 60 = 24 420 W,
for thirteen such houses - F. = 2442013 = 317460 W.
Heat consumption for hot water supply of eight 16-apartment buildings with 60 residents in summer
F g.v.l. = 0.65 F g. = 0.65 317460 = 206349 W
For 8 apartment buildings with 30 residents, the heat flow for hot water supply will be:
F G.V. = 407 30 = 12210 W,
for eleven such houses - F. = 1221011 = 97680 W.
Heat consumption for hot water supply of eleven 8-apartment buildings with 30 residents in summer
F g.v.l. = 0.65 F g. = 0.65 97680 = 63492 W.
Then the heat flow for the water supply of the office will be:
Fgv. = 0.278 0.833 983 4.19 (55 - 5) = 47690 W
Heat consumption for hot water supply of the office in summer:
F g.v.l. = 0.65 F g.c. = 0.65 47690 = 31000 W
Heat flow for water supply of honey. item will be:
Fgv. = 0.278 0.23 983 4.19 (55 - 5) = 13167 W
Heat consumption for hot water supply to honey. item in summer:
F g.v.l. = 0.65 F g.c. = 0.65 13167 = 8559 W
Hot water is also needed in workshops for sanitary needs.
The workshop contains 2 risers with a water flow rate of 30 l / h each (that is, a total of 60 l / h). Considering that on average hot water for sanitary needs is used for about 3 hours during the day, we find the amount of hot water - 180 l / day
Fgv. = 0.278 0.68 983 4.19 (55 - 5) = 38930 W
The flow of heat consumed for hot water supply to the school workshop in the summer:
Fgv.l = 38930 0.65 = 25304.5 W
Heat flow summary table
|
Calculated heat fluxes, W |
|||||||
|
Name |
Heating |
Ventilation |
Tech needs |
||||
|
School for 90 students |
|||||||
|
16 sq. House |
|||||||
|
Honey. paragraph |
|||||||
|
8 apartment building |
|||||||
|
School workshop |
|||||||
F total = F from + F to + F g.v. = 2147318 + 13243 + 737078 = 2897638 W.
3. Building an annual schedule of thosepayload and selection of boilers
3.1 Building an annual heat load schedule
The annual consumption for all types of heat consumption can be calculated using analytical formulas, but it is more convenient to determine it graphically from the annual heat load schedule, which is also necessary to establish the operating modes of the boiler house throughout the year. Such a schedule is plotted depending on the duration of action in a given area of various temperatures, which is determined according to Appendix 3.
In fig. 3 shows the annual load schedule of the boiler house serving the residential area of the village and a group of industrial buildings. The graph is built as follows. On the right side, along the abscissa, the duration of the boiler room operation is plotted in hours, on the left side - the outside air temperature; the ordinate is the heat consumption.
First, a graph of the change in heat consumption for heating residential and public buildings is plotted depending on the outside temperature. To do this, the total maximum heat flux spent on heating these buildings is plotted on the ordinate axis, and the found point is connected by a straight line to the point corresponding to the outside air temperature, equal to the average design temperature of the residential ones; public and industrial buildings tв = 18 ° С. Since the beginning of the heating season is taken at a temperature of 8 ° C, line 1 of the graph up to this temperature is shown with a dotted line.
Heat consumption for heating and ventilation of public buildings in the function tn is an inclined straight line 3 from tв = 18 ° С to the calculated ventilation temperature tn.v. for a given climatic region. At lower temperatures, room air is added to the supply air. recirculation occurs, and the heat consumption remains unchanged (the graph is parallel to the abscissa axis). In a similar way, graphs of heat consumption for heating and ventilation of various industrial buildings are plotted. The average temperature of industrial buildings is tв = 16 ° С. The figure shows the total heat consumption for heating and ventilation for this group of objects (lines 2 and 4 starting from a temperature of 16 ° C). Heat consumption for hot water supply and technological needs does not depend on tn. The general graph for these heat losses is shown by straight line 5.
The total graph of heat consumption depending on the outside air temperature is shown by broken line 6 (the break point corresponds to tn.v.), cutting off on the ordinate axis a segment equal to the maximum heat flux consumed for all types of consumption (? Fot +? Fw +? Fg. v. +? Ft) at a design outside temperature tн.
Adding the total loads, I got 2.9W.
To the right of the abscissa axis, for each outside temperature, the number of hours of the heating season (on an accrual basis) during which the temperature was kept equal to or lower than the one for which the construction is being made (Appendix 3) is plotted. And vertical lines are drawn through these points. Further, ordinates are projected onto these lines from the total heat consumption graph, corresponding to the maximum heat consumption at the same outside temperatures. The obtained points are connected by a smooth curve 7, which is a graph of the heat load for the heating period.
The area bounded by the coordinate axes, curve 7 and horizontal line 8, showing the total summer load, expresses the annual heat consumption (GJ / year):
Qyear = 3.6 10 -6 F m Q m n,
where F is the area of the annual heat load schedule, mm?; m Q and m n are the scales of the heat consumption and the operating time of the boiler house, respectively, W / mm and h / mm.
Qyear = 3.6 10 -6 9871.74 23548 47.8 = 40001.67J / year
Of which the heating season accounts for 31,681.32 J / year, which is 79.2%, for summer 6589.72 J / year, which is 20.8%.
3.2 The choice of coolant
We use water as a heat carrier. Since the thermal design load Фр is? 2.9 MW, which is less than the condition (Fr? 5.8 MW), it is allowed to use water with a temperature of 105 ° C in the supply line, and the water temperature in the return pipeline is taken equal to 70 ° C. At the same time, we take into account that the temperature drop in the consumer's network can reach 10%.
The use of superheated water as a heat carrier gives a great saving in the metal of pipes by reducing their diameter, reduces the energy consumption consumed by network pumps, since the total amount of water circulating in the system is reduced.
Since some consumers need steam for technical purposes, additional heat exchangers need to be installed at the consumers.
3.3 Selection of boilers
Heating and industrial boilers, depending on the type of boilers installed in them, can be hot water, steam or combined - with steam and hot water boilers.
The choice of conventional cast iron boilers with a low-temperature coolant simplifies and reduces the cost of local energy supply. For heat supply, we accept three cast-iron water boilers "Tula-3" with a thermal power of 779 kW each with gas fuel with the following characteristics:
Estimated power Fr = 2128 kW
Installed power Fu = 2337 kW
Heating surface area - 40.6 m2
Number of sections - 26
Dimensions 2249 x 2300 x 2361 mm
Maximum water heating temperature - 115? С
Efficiency when working on gas z k.a. = 0.8
When operating in steam mode, excess steam pressure - 68.7 kPa
When operating in steam mode, the power is reduced by 4 - 7%
3.4 Construction of an annual schedule for regulating the supply of a thermal boiler house
Due to the fact that the heat load of consumers varies depending on the outside air temperature, the operating mode of the ventilation and air conditioning system, the water consumption for hot water supply and technological needs, the economical modes of heat production in the boiler house should be ensured by central regulation of heat supply.
In water heating networks, high-quality regulation of the heat supply is used, carried out by changing the temperature of the coolant at a constant flow rate.
The graphs of water temperatures in the heating network are tp = f (tn,? C), tо = f (tn,? C). Having built a graph according to the methodology given in the work for tн = 95? С; tо = 70? С for heating (it is taken into account that the temperature of the coolant in the hot water supply network should not fall below 70? С), tpv = 90? С; tоv = 55? С - for ventilation, we determine the ranges of temperature change of the coolant in the heating and ventilation networks. The abscissa is the outside temperature, the ordinate is the temperature of the network water. The origin of coordinates coincides with the calculated internal temperature for residential and public buildings (18 ° C) and the temperature of the coolant, also equal to 18 ° C. At the intersection of the perpendiculars restored to the coordinate axes at the points corresponding to temperatures tp = 95 ° C, tn = -25 ° C, point A is found, and by drawing a horizontal line from the return water temperature of 70 ° C, point B. Connecting points A and With the origin of coordinates, we get a graph of the temperature change of the direct and return water in the heating network depending on the outside air temperature. In the presence of a load of hot water supply, the temperature of the coolant in the supply line of an open-type network should not fall below 70 ° C, therefore, the temperature graph for the supply water has a break point C, to the left of which φ p = const. The supply of heat for heating at a constant temperature is regulated by changing the flow rate of the heat carrier. The minimum return water temperature is determined by drawing a vertical line through point C up to the intersection with the return water curve. The projection of point D onto the ordinate axis shows the smallest pho value. The perpendicular, recovered from the point corresponding to the calculated outdoor temperature (-16 ° C), intersects lines AC and BD at points E and F, showing the maximum temperatures of direct and return water for ventilation systems. That is, temperatures are 91 ° C and 47 ° C, respectively, which remain unchanged in the range from tn.w and tn (lines EK and FL). In this range of outdoor air temperatures, the air handling units operate with recirculation, the degree of which is regulated so that the temperature of the air entering the heaters remains constant.
The graph of water temperatures in the heating network is shown in Fig. 4.
Fig. 4. Schedule of water temperatures in the heating network.
Bibliography
1. Efendiev A.M. Power supply design for agro-industrial complex enterprises. Toolkit. Saratov 2009.
2. Zakharov A.A. Workshop on the use of heat in agriculture. Second edition, revised and enlarged. Moscow Agropromizdat 1985.
3. Zakharov A.A. The use of heat in agriculture. Moscow Kolos 1980.
4. Kiryushatov A.I. Thermal power plants for agricultural production. Saratov 1989.
5. SNiP 2.10.02-84 Buildings and premises for storage and processing of agricultural products.
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