I welcome you, dear and respected readers of the site "site". Necessary step in the design of heat supply systems for enterprises and residential areas is the hydraulic calculation of pipelines of water heating networks. It is necessary to solve the following tasks:

1. Determination of the inner diameter of the pipeline for each section of the heating network d V, mm. According to the diameters of the pipeline and their lengths, knowing their material and method of laying, it is possible to determine capital investments in heating networks.
2. Determination of pressure losses of network water or pressure losses of network water Δh, m; ΔР, MPa. These losses are the initial data for successive calculations of the head of network and make-up pumps in heat networks.

Hydraulic calculation of heat networks is also performed for existing operating heat networks, when the task is to calculate their actual throughput, i.e. when there is a diameter, length and you need to find the consumption of network water that will pass through these networks.

Hydraulic calculation of pipelines of heat networks is performed for the following modes of their operation:

A) for the design mode of operation of the heating network (max G O; G B; G DHW);

B) for summer mode, when only G DHW flows through the pipeline

C) for static mode, the network pumps are stopped at the heat supply source, and only make-up pumps are running.

D) for emergency operation, when an accident occurs in one or more sections, the diameter of the jumpers and reserve pipelines.

If heat networks work for a water open heat supply system, then it is also determined:

D) winter mode, when network water for DHW systems buildings is taken from the return pipeline of the heating network.

E) transient mode, when network water for hot water supply of buildings is taken from the supply pipeline of the heating network.

In the hydraulic calculation of pipelines of heat networks, the following quantities must be known:

1. The maximum load on heating and ventilation and the average hourly load on the hot water supply: max Q O, max Q VENT, Q SR DHW.
2. Temperature chart of the heat supply system.
3. Temperature graph of network water, temperature of network water at the break point τ 01 NI, τ 02 NI.
4. The geometric length of each section of heating networks: L 1 , L 2 , L 3 ...... L N .
5. The condition of the inner surface of the pipeline in each section of the heating network (the amount of corrosion and scale deposits). k E - equivalent roughness of the pipeline.
6. The number, type and arrangement of local resistances that are available in each section of the heating network (all gate valves, valves, turns, tees, compensators).
7. Physical properties of water p V, I V.

How the hydraulic calculation of pipelines of heat networks is performed will be considered using the example of a radial heat network serving 3 heat consumers.

Schematic diagram of a radial heating network transporting thermal energy for 3 heat consumers

1 - heat consumers (residential areas)

2 - sections of the heating network

3 - source of heat supply

Hydraulic calculation of the designed heat networks is performed in the following sequence:

1. According to the schematic diagram of heat networks, the consumer is determined, which is the most distant from the source of heat supply. The heat network laid from the source of heat supply to the most remote consumer is called the main line (main line), in the figure L 1 + L 2 + L 3. Sections 1.1 and 2.1 are branches from the main line (branch).
2. Planned design direction movement of network water from the source of heat supply to the most remote consumer.
3. The calculated direction of movement of network water is divided into separate sections, on each of which the inner diameter of the pipeline and the flow rate of network water must remain constant.
4. The estimated consumption of network water is determined in the sections of the heating network to which consumers are connected (2.1; 3; 3.1):

G SUM UCH \u003d G O R + G B R + k 3 * G G SR

G O R \u003d Q O R / C B * (τ 01 R - τ 02 R) - maximum flow for heating

k 3 - coefficient taking into account the share of consumption of network water supplied to hot water supply

G V R \u003d Q V R / S V * (τ 01 R - τ V2 R) - maximum flow for ventilation

G G SR \u003d Q GW SR / S V * (τ 01 NI - τ G2 NI) - average consumption for hot water supply

k 3 = f (type of heat supply system, thermal load consumer).

Values ​​k 3 depending on the type of heat supply system and heat loads of connection of heat consumers

1. According to the reference data are determined physical properties network water in the supply and return pipelines of the heating network:

P IN POD = f (τ 01) V IN POD = f (τ 01)

P IN OBR = f (τ 02) V IN OBR = f (τ 02)

1. The average values ​​of network water density and its velocity are determined:

P IN SR \u003d (P IN LOD + P IN OBR) / 2; (kg / m 3)

V IN SR \u003d (V IN UNDER + V IN OBR) / 2; (m 2 /s)

1. Hydraulic calculation of pipelines of each section of heating networks is carried out.

7.1. They are set by the speed of movement of network water in the pipeline: V B \u003d 0.5-3 m / s. The lower limit V B is due to the fact that at lower speeds, the deposition of suspended particles on the walls of the pipeline increases, and also at lower speeds, the circulation of water stops and the pipeline may freeze.

V B \u003d 0.5-3 m / s. - greater value speed in the pipeline is due to the fact that with an increase in speed of more than 3.5 m / s, a hydraulic shock may occur in the pipeline (for example, when valves are suddenly closed, or when the pipeline is turned in a section of the heating network).

7.2. The internal diameter of the pipeline is calculated:

d V \u003d sqrt [(G SUM PCH * 4) / (p V SR * V V * π)] (m)

7.3. According to the reference data, the closest values ​​of the inner diameter are taken, which correspond to GOST d V GOST, mm.

7.4. The actual speed of water movement in the pipeline is specified:

V V F \u003d (4 * G SUM UCH) / [π * p V SR * (d V GOST) 2]

7.5. The mode and zone of flow of network water in the pipeline is determined, for this a dimensionless parameter is calculated (Reynolds criterion)

Re = (V V F * d V GOST) / V V F

7.6. Re PR I and Re PR II are calculated.

Re PR I = 10 * d V GOST / k E

Re PR II \u003d 568 * d V GOST / k E

For various types pipelines and various degrees of wear of the pipeline k E lies within. 0.01 - if the pipeline is new. When the type of pipeline and the degree of their wear are unknown according to SNiP ” Heating network” February 41, 2003. The value of k E is recommended to be chosen equal to 0.5 mm.

7.7. The coefficient of hydraulic friction in the pipeline is calculated:

— if the criterion Re< 2320, то используется формула: λ ТР = 64 / Re.

— if the criterion Re lies within (2320; Re PR I ], then the Blasius formula is used:

λ TP =0.11*(68/Re) 0.25

These two formulas must be used for laminar water flow.

— if the Reynolds criterion lies within (Re PR I< Re < =Re ПР II), то используется формула Альтшуля.

λ TP \u003d 0.11 * (68 / Re + k E / d V GOST) 0.25

This formula is used in the transitional movement of network water.

- if Re > Re PR II, then the Shifrinson formula is used:

λ TP \u003d 0.11 * (k E / d V GOST) 0.25

Δh TP \u003d λ TP * (L * (V V F) 2) / (d V GOST * 2 * g) (m)

ΔP TR = p V SR *g* Δh TR = λ TR * / (d V GOST *2) = R L *L (Pa)

R L \u003d [λ TP * r V SR * (V V F) 2] / (2 * d V GOST) (Pa / m)

R L - specific linear pressure drop

7.9. Pressure losses or pressure losses in local resistances in the pipeline section are calculated:

Δh M.S. = Σ£ M.S. *[(V V F) 2 /(2*g)]

Δp M.S. = p B SR *g* Δh M.S. = Σ£ M.S. *[((V V F) 2 * R V SR)/2]

Σ£ M.S. - the sum of the local resistance coefficients installed on the pipeline. For each type of local resistance £ M.S. taken from reference data.

7.10. The total head loss or total pressure loss in the pipeline section is determined:

h = Δh TR + Δh M.S.

Δp = Δp TR + Δp M.S. = p B SR *g* Δh TP + p B SR *g*Δh M.S.

According to this method, calculations are carried out for each section of the heating network and all values ​​\u200b\u200bare summarized in a table.

Main results hydraulic calculation pipelines of sections of the water heating network

For indicative calculations of sections of water heating networks when determining R L, Δr TP, Δr M.S. the following expressions are allowed:

R L \u003d / [p V SR * (d V GOST) 5.25] (Pa / m)

R L \u003d / (d V GOST) 5.25 (Pa / m)

A R \u003d 0.0894 * K E 0.25 - an empirical coefficient that is used for an approximate hydraulic calculation in water heating networks

A R B \u003d (0.0894 * K E 0.25) / r B SR \u003d A R / r B SR

These coefficients were derived by Sokolov E.Ya. and are given in the textbook "Heat supply and heat networks".

Given these empirical coefficients, head and pressure losses are defined as:

Δp TR \u003d R L * L \u003d / [p V SR * (d V GOST) 5.25] \u003d

= / (d In GOST) 5.25

Δh TP = Δp TP / (p B SR *g) = (R L *L) / (p B SR *g) =

\u003d / (p V SR) 2 * (d V GOST) 5.25 \u003d

\u003d / p V SR * (d V GOST) 5.25 * g

Also taking into account A R and A R B; Δr M.S. and Δh M.S. will be written like this:

Δr M.S. \u003d R L * L E M \u003d / p V SR * (d V GOST) 5.25 \u003d

\u003d / (d In GOST) 5.25

Δh M.S. = Δp M.S. / (p B SR *g) \u003d (R L *L E M) / (r B SR *g) \u003d

\u003d / p V SR * (d V GOST) 5.25 \u003d

\u003d / (d In GOST) 5.25 * g

L E \u003d Σ (£ M. C. * d V GOST) / λ TR

The peculiarity of the equivalent length is that the head loss of local resistances is represented as a head drop in a straight section with the same inner diameter, and this length is called equivalent.

Total pressure and head losses are calculated as:

Δh = Δh TR + Δh M.S. \u003d [(R L *L) / (p B SR *g)] + [(R L *L E) / (r B SR *g)] =

\u003d * (L + L E) \u003d * (1 + a M. S.)

Δr \u003d Δr TP + Δr M. S. \u003d R L * L + R L * L E \u003d R L (L + L E) \u003d R L * (1 + a M. S.)

and M.S. - coefficient of local losses in the section of the water heating network.

In the absence of accurate data on the number, type and arrangement of local resistances, the value of a M.S. can be taken from 0.3 to 0.5.

I hope that now it has become clear to everyone how to correctly perform the hydraulic calculation of pipelines and you yourself will be able to perform the hydraulic calculation of heat networks. Tell us in the comments what you think, can you calculate the hydraulic calculation of pipelines in excel, or do you use an online calculator for the hydraulic calculation of pipelines or use a nomogram for the hydraulic calculation of pipelines?

A reference guide covering the design of heat networks is the “Designer's Handbook. Design of thermal networks. The handbook can to a certain extent be considered as a guide to SNiP II-7.10-62, but not to SNiP N-36-73, which appeared much later as a result of a significant revision of the previous edition of the norms. Over the past 10 years, the text of SNiP N-36-73 has undergone significant changes and additions.

Thermal insulation materials, products and structures, as well as the methodology for their thermal calculations, together with instructions for the implementation and acceptance of insulation work, are described in detail in the Builder's Handbook. Similar data on thermal insulation structures are included in SN 542-81.

Reference materials on hydraulic calculations, as well as on equipment and automatic regulators for heating networks, heating points and heat use systems are contained in the “Handbook for the Adjustment and Operation of Water Heating Networks”. As a source of reference materials on design issues, books from the series of reference books "Heat power engineering and heat engineering" can be used. The first book "General Questions" contains rules for the design of drawings and diagrams, as well as data on the thermodynamic properties of water and steam, more detailed information is given in. In the second book of the series “Heat and mass transfer. Thermal Engineering Experiment" includes data on the thermal conductivity and viscosity of water and steam, as well as on the density, thermal conductivity and heat capacity of some building and insulating materials. In the fourth book "Industrial heat power and heat engineering" there is a section on district heating and heat networks

www.engineerclub.ru

Gromov - Water heating networks (1988)

The book contains regulatory materials used in the design of heat networks and heat points. Recommendations are given on the choice of equipment and heat supply schemes. Calculations related to the design of heat networks are considered. Information is given on the laying of heating networks, on the organization of construction and operation of heating networks and heating points. The book is intended for engineering and technical workers involved in the design of thermal networks.

Residential and industrial construction, fuel economy and protection requirements environment predetermine the feasibility of intensive development of district heating systems. The generation of thermal energy for such systems is currently carried out by thermal power plants, boiler houses of regional significance.

Reliable operation of heat supply systems with strict observance of the necessary parameters of the heat carrier is largely determined by the correct choice of schemes for heat networks and heat points, gasket designs, and equipment used.

Considering that the correct design of heat networks is impossible without knowledge of their structure, operation and development trends, the authors tried to provide design recommendations in the reference manual and give a brief justification for them.

GENERAL CHARACTERISTICS OF HEAT NETWORKS AND HEAT POINTS

1.1. District heating systems and their structure

District heating systems are characterized by a combination of three main links: heat sources, heat networks and local systems heat use (heat consumption) of individual buildings or structures. In heat sources, heat is obtained by burning various types of fossil fuels. Such heat sources are called boiler rooms. In the case of use in heat sources of heat released during the decay of radioactive elements, they are called nuclear power plants (ACT). AT individual systems heat supply are used as auxiliary renewable heat sources - geothermal energy, energy solar radiation etc.

If the heat source is located together with the heat sinks in the same building, then the pipelines for supplying the coolant to the heat sinks passing inside the building are considered as an element of the local heat supply system. In district heating systems, heat sources are located in separate buildings, and heat is transported from them through pipelines of heating networks, to which the heat use systems of individual buildings are connected.

The scale of district heating systems can vary widely, from small, serving a few neighboring buildings, to the largest, covering a number of residential or industrial areas, and even the city as a whole.

Regardless of the scale, these systems are divided into municipal, industrial and citywide according to the contingent of consumers served. Utilities include systems that supply heat mainly to residential and public buildings, as well as individual buildings for industrial and utility-storage purposes, the placement of which in the residential zone of cities is allowed by the norms.

It is advisable to base the classification of communal systems according to their scale on the division of the territory of a residential area into groups of neighboring buildings (or quarters in areas of old buildings) accepted in the norms of planning and development of cities, which are combined into microdistricts with a population of 4-6 thousand people. in small towns (with a population of up to 50 thousand people) and 12-20 thousand people. in cities of other categories. The latter envisage the formation of residential areas with a population of 25-80 thousand people from several microdistricts. The corresponding systems of district heating can be characterized as group (quarterly), micro-district and district.

Heat sources serving these systems, one for each system, can be categorized as group (quarterly), microdistrict and district boiler houses, respectively. In large and largest cities(with a population of 250-500 thousand people and more than 500 thousand people, respectively), the norms provide for the unification of several adjacent residential areas into planning areas limited by natural or artificial boundaries. In such cities, the emergence of the largest inter-district systems of communal heat supply is possible.

At large scales of heat generation, especially in citywide systems, it is expedient to jointly generate heat and electricity. This provides significant fuel savings in comparison with the separate generation of heat in boiler houses, and electricity - at thermal power plants by burning the same types of fuel.

Thermal power plants designed for the joint generation of heat and electricity are called combined heat and power plants (CHP).

Nuclear power plants, which use the heat released by the decay of radioactive elements to generate electricity, are also sometimes useful as heat sources in large heating systems. These stations are called nuclear combined heat and power plants (ATES).

District heating systems that use CHP as the main heat sources are called district heating systems. Construction of new district heating systems, as well as expansion and reconstruction existing systems require special study, based on the prospects for the development of the relevant settlements for the next period A0-15 years) and the estimated period of 25-30 years).

The norms provide for the development of a special pre-project document, namely, a heat supply scheme for this settlement. The scheme has several options technical solutions on heat supply systems and on the basis of a technical and economic comparison, the choice of the option proposed for approval is substantiated.

The subsequent development of projects for heat sources and heat networks should, in accordance with regulatory documents, be carried out only on the basis of decisions made in the approved heat supply scheme for this settlement.

1.2. general characteristics heating networks

Thermal networks can be classified according to the type of coolant used in them, as well as according to its design parameters (pressures and temperatures). Almost the only heat carriers in heat networks are hot water and water vapor. Water vapor as a coolant is widely used in heat sources (boilers, CHPs), and in many cases in heat use systems, especially industrial ones. Municipal heating systems are equipped with water heating networks, and industrial systems are equipped with either only steam or steam in combination with water, used to cover the loads of heating, ventilation and hot water supply systems. This combination of dropsy and steam heat networks is also typical for citywide heat supply systems.

Water heating networks are mostly made of two pipes with a combination of supply pipelines for supplying hot water from heat sources to heat recovery systems and return pipelines for returning water cooled in these systems to heat sources for reheating. The supply and return pipelines of water heating networks, together with the corresponding pipelines of heat sources and heat recovery systems, form closed water circulation circuits. This circulation is supported by network pumps installed in heat sources, and for long distances of water transport, also on the route of networks ( pumping stations). Depending on the adopted scheme for connecting to networks of hot water supply systems, closed and open circuits(the terms “closed and open heat supply systems” are more often used).

In closed systems, the release of heat from networks in the hot water supply system is carried out due to heating, cold tap water in special water heaters.

In open systems, hot water supply loads are covered by supplying water to consumers from supply pipelines of networks, and during heating period- in a mixture with water from the return pipelines of heating and ventilation systems. If in all modes for hot water supply water from the return pipelines can be used completely, then there is no need for return pipelines from the heating points to the heat source. Compliance with these conditions, as a rule, is possible only with the joint operation of several heat sources on common heat networks with the assignment of covering the loads of hot water supply to some of these sources.

Water networks, consisting only of supply pipelines, are called single-pipe and are the most economical in terms of capital investments in their construction. The make-up of heating networks in closed and open systems is carried out due to the operation of make-up pumps and make-up water treatment plants. In an open system, their required performance is 10-30 times greater than in a closed one. As a result, with an open system, capital investments in heat sources turn out to be large. At the same time, in this case, there is no need for tap water heaters, and therefore the costs for the nodes for connecting hot water supply systems to heating networks are significantly reduced. Thus, the choice between open and closed systems in each case should be justified by technical and economic calculations, taking into account all links in the district heating system. Such calculations should be performed when developing a heat supply scheme for a settlement, that is, before designing the corresponding heat sources and their heat networks.

AT individual cases water heating networks are made with three or even four pipes. This increase in the number of pipes, usually provided only for separate sections networks, is associated with doubling either only supply (three-pipe systems), or both supply and return (four-pipe systems) pipelines for separate connection to the corresponding pipelines of hot water supply systems or heating and ventilation systems. This separation greatly facilitates the regulation of heat supply to systems for various purposes, but at the same time leads to a significant increase in capital investments in the network.

In large district heating systems, there is a need to divide water heating networks into several categories, each of which can use its own heat supply and transport schemes.

The norms provide for the division of heat networks into three categories: main lines from heat sources to inputs to microdistricts (quarters) or enterprises; distribution from main networks to networks to individual buildings: networks to individual buildings in the form of branches from distribution (or in some cases from main) networks to the nodes of connection to them of heat use systems of individual buildings. It is advisable to clarify these names in relation to the classification of district heating systems adopted in § 1.1 according to their scale and contingent of consumers served. So, if in small systems from one heat source heat is supplied only to a group of residential and public buildings within the neighborhood or industrial buildings one enterprise, then there is no need for main heat networks and all networks from such heat sources should be considered as distribution networks. This situation is typical for the use of group (quarterly) and micro-district boiler houses as heat sources, as well as industrial boilers serving one enterprise. In the transition from such small systems to regional, and even more so to inter-district, a category of main heating networks appears, to which distribution networks of individual microdistricts or enterprises of one industrial region join. The connection of individual buildings directly to the main networks, in addition to distribution networks, is highly undesirable for a number of reasons, and therefore is used very rarely.

Large heat sources of district and inter-district district heating systems, according to the norms, should be located outside the residential area in order to reduce the impact of their emissions on the state of the air basin of this area, as well as to simplify the systems for supplying liquid or solid fuel to them.

In such cases, the initial (head) sections of trunk networks of considerable length appear, within which there are no nodes for connecting distribution networks. Such transport of a coolant without passing it to consumers is called transit, while it is advisable to single out the corresponding head sections of main heating networks into a special category of transit ones.

The presence of transit networks significantly worsens the technical and economic indicators of coolant transport, especially when these networks are 5–10 km or more in length, which is typical, in particular, when nuclear thermal power plants or heat supply stations are used as heat sources.

1.3. General characteristics of heat points

An essential element of district heating systems are installations located at the nodes of connection to heat networks of local heat use systems, as well as at the junctions of networks of various categories. In such installations, the operation of heat networks and heat use systems is monitored and controlled. Here, the parameters of the coolant are measured - pressures, temperatures, and sometimes flow rates - and the regulation of heat supply at various levels.

The reliability and efficiency of heat supply systems as a whole depend to a large extent on the operation of such installations. These settings are in normative documents are called heat points (previously, the names “connection nodes of local heat use systems”, “heat centers”, “subscriber installations”, etc.) were also used.

However, it is advisable to somewhat clarify the classification of heat points adopted in the same documents, since in them all heat points are either central (CHP) or individual (ITP). The latter include only installations with nodes for connecting to heat networks of heat use systems of one building or part of them (in large buildings). All other heat points, regardless of the number of buildings served, are central.

In accordance with the accepted classification of heat networks, as well as various levels of regulation of heat supply, the following terminology is used. In terms of heating points:

local heating points (MTP) serving the heat use systems of individual buildings;

group or micro-district heating points (GTP) serving a group of residential buildings or all buildings within the micro-district;

district heating substations (RTP) serving all buildings within a residential

In terms of regulation levels:

central - only at heat sources;

district, group or microdistrict - at the respective heating points (RTP or GTP);

local - at local heating points of individual buildings (MTP);

individual on separate heat receivers (devices of heating, ventilation or hot water supply systems).

Heating networks design reference guide

Home Mathematics, Chemistry, Physics Designing a heating system for a hospital complex

27. Safonov A.P. Collection of tasks on district heating and heating networks Textbook for universities, M.: Energoatomizdat. 1985.

28. Ivanov V.D., Gladyshey N.N., Petrov A.V., Kazakova T.O. Engineering calculations and test methods for thermal networks Lecture notes. SPb.: SPb GGU RP. 1998.

29. Instructions for the operation of thermal networks M .: Energia 1972.

30. Safety regulations for the maintenance of heating networks M: Atomizdat. 1975.

31. Yurenev V.N. Thermotechnical reference book in 2 volumes M.; Energy 1975, 1976.

32. Golubkov B.N. Heat engineering equipment and heat supply of industrial enterprises. Moscow: Energy 1979.

33. Shubin E.P. The main issues of designing heat supply systems. M.: Energy. 1979.

34. Guidelines for the preparation of the report of the power plant and joint-stock company energy and electrification about the thermal efficiency of equipment. RD 34.0K.552-95. SPO ORGRES M: 1995.

35. Methodology for determining the specific fuel consumption for heat depending on the parameters of the steam used for heat supply RD 34.09.159-96. SPO ORGRES. M.: 1997

36. Guidelines for the analysis of changes in specific fuel consumption at power stations and power associations. RD 34.08.559-96 SPO ORGRES. M.: 1997.

37. Kutovoy G. P., Makarov A. A., Shamraev N. G. Creation of a favorable base for the development of the Russian electric power industry on a market basis "Heat power engineering". No. 11, 1997. pp. 2-7.

38. V. V. Bushuev, B. N. Gromov, V. N. Dobrokhotov, V. V. Pryakhin, Scientific, technical, organizational and economic problems of introducing energy-saving technologies. "Heat power engineering". No. 11. 1997. pp.8-15.

39. Astakhov N.L., Kalimov V.F., Kiselev G.P. New edition guidelines on the calculation of indicators of thermal efficiency of TPP equipment. "Energy saving and water treatment". No. 2, 1997, p. 19-23.

Ekaterina Igorevna Tarasevich
Russia

Chief Editor -

candidate of biological sciences

RATED HEAT FLOW DENSITY AND HEAT LOSS THROUGH A HEAT-INSULATED SURFACE FOR MAIN HEAT NETWORKS

The article discusses the change in a number of published regulatory documents for the thermal insulation of heat supply systems, which are aimed at ensuring the durability of the system. This article is devoted to the study of the influence of the average annual temperature of heating networks on heat losses. The study relates to heat supply systems and thermodynamics. Recommendations are given for the calculation of normative heat losses through the insulation of heating network pipelines.

The relevance of the work is determined by the fact that it addresses little-studied problems in the heat supply system. The quality of thermal insulation structures depends on the heat losses of the system. Proper design and calculation of a thermal insulation structure is much more important than just choosing insulating material. Results are given comparative analysis heat losses.

Methods of thermal calculations for calculating heat losses of pipelines of heating networks are based on the use of the standard heat flux density through the surface of a heat-insulating structure. In this article, on the example of pipelines with polyurethane foam insulation, the calculation of heat losses was carried out.

Basically, the following conclusion was made: in the current regulatory documents, the total values ​​of the heat flux density for the supply and return pipelines are given. There are cases when the diameters of the supply and return pipelines are not the same, three or more pipelines can be laid in one channel, therefore, the previous standard must be used. The total values ​​of the heat flux density in the norms can be divided between the supply and return pipelines in the same proportions as in the replaced norms.

Keywords

Literature

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Belyaykina I.V., Vitaliev V.P., Gromov N.K. and etc.; Ed. Gromova N.K.; Shubina E.P. Water heating networks: A reference guide for design. M.: Energoatomizdat, 1988. - 376 p.

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Determination of coefficients of local losses in heat networks of industrial enterprises

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Ushakov D.V., Snisar D.A., Kitaev D.N. Determination of coefficients of local losses in thermal networks of industrial enterprises // Young scientist. - 2017. - No. 6. - S. 95-98. — URL https://moluch.ru/archive/140/39326/ (date of access: 07/13/2018).

The article presents the results of the analysis of the actual values ​​of the coefficient of local losses used in the design of heat networks at the stage of preliminary hydraulic calculation. Based on the analysis of actual projects, averaged values ​​were obtained for networks of industrial sites divided into mains and branches. Equations are found that make it possible to calculate the coefficient of local losses depending on the diameter of the network pipeline.

Keywords : heat networks, hydraulic calculation, local loss coefficient

In the hydraulic calculation of heat networks, it becomes necessary to set the coefficient α , which takes into account the share of pressure losses in local resistances. In modern standards, the implementation of which is mandatory in the design, about the normative method of hydraulic calculation and specifically the coefficient α is not mentioned. In modern reference and educational literature, as a rule, the values ​​recommended by the canceled SNiP II-36-73 * are given. In table. 1 values ​​are presented α for water networks.

Coefficient α to determine the total equivalent lengths of local resistances

Type of compensators

Conditional passage of the pipeline, mm

Branched heating networks

U-shaped with bent branches

U-shaped with welded or curved bends

U-shaped with welded bends

From table 1 it follows that the value α can be in the range from 0.2 to 1. There is an increase in the value with an increase in the diameter of the pipeline.

In the literature for preliminary calculations when the pipe diameters are not known, the proportion of pressure losses in local resistances is recommended to be determined by the formula of B. L. Shifrinson

where z- coefficient accepted for water networks 0.01; G- water consumption, t/h.

The results of calculations according to formula (1) at various water flow rates in the network are shown in fig. one.

Rice. 1. Addiction α from water consumption

From fig. 1 implies that the value α at high costs it can be more than 1, and at low costs it can be less than 0.1. For example, at a flow rate of 50 t/h, α=0.071.

The literature gives an expression for the coefficient of local losses

where - the equivalent length of the section and its length, respectively, m; - the sum of the coefficients of local resistance in the area; λ - coefficient of hydraulic friction.

When designing water heating networks in a turbulent mode of motion to find λ , use the Shifrinson formula. Taking the value of the equivalent roughness k e=0.0005 mm, formula (2) is converted to the form

.(3)

From formula (3) it follows that α depends on the length of the section, its diameter and the sum of the local resistance coefficients, which are determined by the network configuration. Obviously the value α increases with a decrease in the length of the section and an increase in diameter.

In order to determine the actual coefficients of local losses α , the existing projects of water heating networks of industrial enterprises for various purposes were considered. Having hydraulic calculation forms, for each section the coefficient was determined α according to formula (2). Separately, for the main and branches, the weighted average values ​​of the coefficient of local losses for each network were found. On fig. 2 shows the results of calculations α on calculated highways for a sample of 10 network schemes, and in Fig. 3 for branches.

Rice. 2. Actual values α on calculated highways

From fig. 2 it follows that the minimum value is 0.113, the maximum is 0.292, and the average value for all schemes is 0.19.

Rice. 3. Actual values α by branches

From fig. 3 it follows that the minimum value is 0.118, the maximum is 0.377, and the average value for all schemes is 0.231.

Comparing the obtained data with the recommended ones, we can draw the following conclusions. According to Table. 1 for the schemes considered α =0.3 for mains and α=0.3÷0.4 for branches, while the actual averages are 0.19 and 0.231, which is slightly less than recommended. Actual value range α does not exceed the recommended values, i.e. the tabular values ​​(Table 1) can be interpreted as "no more".

For each pipeline diameter, average values ​​were determined α along highways and branches. The calculation results are presented in table. 2.

Values ​​of actual coefficients of local losses α

From the analysis of Table 2 it follows that with an increase in the diameter of the pipeline, the value of the coefficient α increases. Using the least squares method, linear regression equations were obtained for the main and branches, depending on the outer diameter:

On fig. 4 shows the results of calculations according to equations (4), (5), and the actual values ​​for the corresponding diameters.

Rice. 4. Results of coefficient calculations α according to equations (4),(5)

Based on the analysis of real projects of thermal water networks of industrial sites, the averaged values ​​of the coefficients of local losses were obtained, divided into mains and branches. It is shown that the actual values ​​do not exceed the recommended ones, and the average values ​​are slightly less. Equations are obtained that make it possible to calculate the coefficient of local losses depending on the diameter of the network pipeline for mains and branches.

1. Kopko, V. M. Heat supply: a course of lectures for students of the specialty 1–700402 "Heat and gas supply, ventilation and air protection" of higher educational institutions/ V. M. Kopko. - M: DIA Publishing House, 2012. - 336s.
2. Water heating networks: A reference guide for design / N.K. Gromov [et al.]. - M.: Energoatomizdat, 1988. - 376 p.
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5. Semenov, V. N. The influence of energy-saving technologies on the development of heating networks / V. N. Semenov, E. V. Sazonov, D. N. Kitaev, O. V. Tertychny, T. V. Shchukina // News of higher educational institutions. Construction. - 2013. - No. 8 (656). - pp. 78–83.
6. Kitaev, D. N. Influence of modern heating appliances on the regulation of heat networks / D. N. Kitaev // Scientific journal. Engineering systems and structures. - 2014. - V.2. - No. 4(17). - pp. 49–55.
7. Kitaev, D.N., Bulygina S.G., Slepokurova M.A. Variant design of heat supply systems taking into account the reliability of the heat network // Young scientist. - 2010. - No. 7. - S. 46–48.
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Do you have a question about connecting to district heating networks? This article is for you: what types of heating networks are there, what this communication consists of, which organizations and why are the most suitable for developing a project and what you can sometimes save on, read right now.

Briefly about thermal networks

Many people imagine what a heating network is, but for a more accessible narrative, a few common truths should be recalled.

Firstly, the heating network does not supply hot water directly to the batteries. Heat carrier temperature in main pipeline on the coldest days it can reach 150 degrees and its direct location in the heating radiator is fraught with burns and dangerous to human health.

Secondly, the coolant from the network in most cases should not enter the hot water supply system of the building. This is called a closed DHW system. Drinking water (from the tap) is used to meet the needs of the bathroom and kitchen. It has been decontaminated, and the coolant only provides heating up to certain temperature at 50-60 degrees by means of a contactless heat exchanger. The use of network water from heating pipelines in the DHW system is at least wasteful. The coolant is prepared at the source of heat supply (boiler house, CHP) by chemical water treatment. Due to the fact that the temperature of this water is often above the boiling point, from it to without fail hardness salts that cause scale are removed. The formation of any deposits on the nodes of the pipeline can damage the equipment. Tap water does not heat up to such an extent and, therefore, expensive desalination does not take place. This circumstance influenced the fact that open DHW systems, with direct water intake, are practically not used anywhere.

Types of laying heating networks

Consider the types of laying heating networks by the number of pipelines laid next to each other.

2-pipe

The structure of such a network includes two lines: supply and return. The preparation of the final product (lowering the temperature of the heat carrier for heating, heating drinking water) takes place directly in the heat-supplying building.

3-pipe

This type of laying of heating networks is used quite rarely and only for buildings where interruptions in heat are not acceptable, for example, hospitals or kindergartens with a permanent stay of children. In this case, a third line is added: a reserve supply pipeline. The unpopularity of this reservation method lies in its high cost and impracticality. The laying of an extra pipe is easily replaced by a permanently installed modular boiler room and the classic 3-pipe version is practically not found today.

4-pipe

Type of laying when both the coolant and hot water of the water supply system are supplied to the consumer. This is possible if the building is connected to distribution (intra-quarter) networks after the central heating point, in which drinking water is heated. The first two lines, as in the case of a 2-pipe gasket, are the supply and return of the coolant, the third is the supply of hot drinking water, and the fourth is its return. If we focus on the diameters, then the 1st and 2nd pipes will be the same, the 3rd may differ from them (depending on the flow rate), and the 4th is always less than the 3rd.

Other

There are other types of laying in the operated networks, but they are no longer associated with functionality, but with design flaws or unforeseen additional development of the area. So, if loads are incorrectly determined, the proposed diameter can be significantly underestimated, and in the early stages of operation, it becomes necessary to increase the throughput. In order not to shift the entire network again, another pipeline of a larger diameter is reported. In this case, the supply goes through one line, and the return line goes through two, or vice versa.

When building a heating network to an ordinary building (not a hospital, etc.), either a 2-pipe or 4-pipe option is used. It depends only on which networks you were given a tie-in point.

Existing methods of laying heating mains

Overground

Most profitable way in terms of operation. All defects are visible even to a non-specialist; no additional control systems are required. There is also a drawback: it can rarely be used outside the industrial zone - it spoils the architectural appearance of the city.

Underground

This type of gasket can be divided into three types:

Channel (heating network is placed in the tray).

Pros: protection from external influences (for example, from damage by an excavator bucket), safety (if pipes break, the soil will not be washed out and its failures will be excluded).

Minuses: the cost of installation is quite high, with poor waterproofing, the channel is filled with ground or rain water, which negatively affects the durability of metal pipes.

Channelless (the pipeline is laid directly into the ground).

Pros: Relatively low cost, easy installation.

Minuses: in the event of a pipeline rupture, there is a danger of soil erosion, it is difficult to determine the place of the rupture.

In sleeves.

Used to neutralize vertical load on the pipes. This is mainly necessary when crossing roads at an angle. It is a heating network pipeline laid inside a pipe of a larger diameter.

The choice of laying method depends on the area through which the pipeline passes. The channelless option is optimal in terms of cost and labor, but it cannot be applied everywhere. If the section of the heating network is located under the road (does not cross it, but runs parallel under the carriageway), channel laying is used. For ease of use, the location of the network under driveways should be used only if there are no other options, because if a defect is found, it will be necessary to open the asphalt, stop or restrict traffic along the street. There are places where the channel device is used to improve security. This is mandatory when laying a network across the territories of hospitals, schools, kindergartens, etc.

The main elements of the heating network

A heat network, to which variety it does not belong, is essentially a set of elements assembled in a long pipeline. They are produced by the industry in finished form, and the construction of communication comes down to laying and connecting parts to each other.

The pipe is the base brick in this constructor. Depending on the diameter, they are produced in lengths of 6 and 12 meters, but on order at the factory, you can purchase any footage. It is recommended to adhere, oddly enough, namely standard sizes- factory cutting will cost an order of magnitude more expensive.

Mostly for heating systems are used steel pipes covered with a layer of insulation. Non-metallic analogues are rarely used and only on networks with a greatly reduced temperature curve. This is possible after central heating points or when the source of heat supply is a low-power hot water boiler, and even then not always.

For the heating network, it is necessary to use exclusively new pipes, reuse used parts leads to a significant reduction in the service life. Such savings on materials lead to significant expenses for subsequent repairs and rather early reconstruction. It is undesirable to use any type of pipe laying with a spiral weld for heating mains. Such a pipeline is very time-consuming to repair and reduces the speed of emergency repair of gusts.

Elbow 90 degrees

In addition to conventional straight pipes, the industry also produces fittings for them. Depending on the type of pipeline chosen, they may vary in quantity and purpose. In all options, there are necessarily bends (pipe turns at an angle of 90, 75, 60, 45, 30 and 15 degrees), tees (branches from the main pipe welded into it with a pipe of the same or smaller diameter) and transitions (change in pipeline diameter). The rest, for example, the end elements of the operational system remote control are issued as needed.

Branch off the main network

An equally important element in the construction of a heating main is shutoff valves. This device blocks the flow of coolant, both to and from the consumer. The absence of shutoff valves on the subscriber's network is unacceptable, since in the event of an accident at the site, not only one building, but the entire neighboring area will have to be turned off.

For air laying of the pipeline, it is necessary to provide for measures that exclude any possibility of unauthorized access to the control parts of the cranes. In case of accidental or intentional closure or restriction of the throughput of the return pipeline, unacceptable pressure will be created, which will result not only in a rupture of the pipes of the heating network, but also in the heating elements of the building. Most dependent on battery pressure. And new design solutions radiators are torn much earlier than their Soviet cast-iron counterparts. It is not difficult to imagine the consequences of a bursting battery - rooms flooded with boiling water require quite decent sums for repairs. To exclude the possibility of control of valves by strangers, it is possible to provide boxes with locks that close the controls with a key, or removable handwheels.

At underground laying pipelines to fittings, on the contrary, it is necessary to provide access for maintenance personnel. For this, thermal chambers are being built. Descending into them, workers can perform the necessary manipulations.

At channelless laying pre-insulated pipe fittings look different from theirs standard view. Instead of a control wheel, the ball valve has a long stem, at the end of which there is a control element. Closing / opening occurs with a T-shaped key. It is supplied by the manufacturer complete with the main order for pipes and fittings. To organize access, this rod is placed in a concrete well and closed with a hatch.

Stop valves with reducer

On pipelines of small diameter, you can save on reinforced concrete rings and manholes. Instead of concrete products, rods can be placed in metal carpets. They look like a pipe with a lid attached on top, mounted on a small concrete pad and buried in the ground. Quite often, designers on small pipe diameters suggest placing both valve stems (supply and return pipelines) in one reinforced concrete well with a diameter of 1 to 1.5 meters. This solution looks good on paper, but in practice, such an arrangement often leads to the impossibility of controlling the valve. This happens due to the fact that both rods are not always located directly under the hatch, therefore, it is not possible to install the key vertically on the control element. Fittings for pipelines of medium and above diameter are equipped with a gearbox or an electric drive, it cannot be placed in a carpet, in the first case it will be a reinforced concrete well, and in the second - an electrified thermal chamber.

Installed carpet

The next element of the heating network is a compensator. In the simplest case, this is the laying of pipes in the form of the letter P or Z and any turn of the route. In more complex versions, lens, stuffing box and other compensating devices are used. The need to use these elements is caused by the susceptibility of metals to significant thermal expansion. In simple words, pipe under action high temperatures increases its length and in order to prevent it from bursting as a result of excessive load, at certain intervals special devices or angles of rotation of the route are provided - they relieve the stress caused by the expansion of the metal.

U-shaped compensator

For the construction of subscriber networks, it is recommended to use only simple line turn angles as compensators. More complex devices, firstly, they cost a lot, and secondly, they require annual maintenance.

For channelless laying of pipelines, in addition to the angle of rotation itself, they also provide small space for his work. This is achieved by laying expansion mats at the bend of the net. The absence of a soft section will lead to the fact that at the time of expansion the pipe will be pinched in the ground and simply burst.

U-shaped compensator with stacked mats

An important part of the designer of thermal communication is drainage. This device is a branch from the main pipeline with fittings, descending into a concrete well. If it is necessary to empty the heating network, the valves are opened and the coolant is dumped. This element of the heating main is installed at all lower points of the pipeline.

drainage well

Discharged water is pumped out of the well with special equipment. If it is possible and the appropriate permission has been obtained, then it is possible to connect the waste well to domestic or storm sewer networks. In this case, special equipment for operation is not required.

On the small areas networks, up to several tens of meters long, drainage may not be installed. When repairing, excess coolant can be discarded grandfather's method- cut the pipe. However, with this emptying, the water must significantly reduce its temperature due to the risk of burns to personnel and the timing of the completion of the repair is slightly delayed.

Another structural element, without which the normal functioning of the pipeline is impossible, is an air vent. It is a branch of the heating network, directed strictly upwards, at the end of which there is a ball valve. This device serves to release the pipeline from air. Without removing gas plugs, normal filling of pipes with coolant is impossible. This element is installed at all upper points of the heating network. It is impossible to refuse to use it in any case - another method for removing air from pipes has not yet been invented.

Tees with vent ball valve

When installing an air vent, in addition to functional ideas be guided by the principles of personnel safety. When deflated, there is a risk of burns. The air outlet tube must always be directed to the side or down.

Design

The work of a designer when creating a heating network is not based on templates. Each time new calculations are carried out, equipment is selected. The project cannot be reused. For these reasons, the cost of such work is always quite high. However, the price should not be the main criterion when choosing a designer. The most expensive is not always the best, and vice versa. In some cases, the excessive cost is not caused by the laboriousness of the process, but by the desire to fill one's own worth. Experience in the development of such projects is also a considerable plus in the selection of an organization. True, there are times when a company has gained a status and completely changed its specialists: it abandoned experienced and expensive ones in favor of young and ambitious ones. It would be nice to clarify this point before the conclusion of the contract.

Rules for choosing a designer

Price. It should be in the middle range. Extremes are not appropriate.

An experience. To determine the experience, the easiest way is to ask for the phones of customers for whom the organization has already completed similar projects and not be too lazy to call several numbers. If everything was “at the level”, then you will receive the necessary recommendations, if “not very” or “more or less”, you can safely continue the search further.

Availability of experienced staff.

Specialization. You should avoid organizations that, despite the small staff, are ready to make a house with a pipe and a path to it. The lack of specialists leads to the fact that the same person can develop several sections at once, if not all. The quality of such work leaves much to be desired. The best option will become a narrowly focused organization with a bias in communication or energy construction. Large civil engineering institutions are also not a bad option.

Stability. Fly-by-night firms should be avoided, no matter how tempting their offer may be. It is good if there is an opportunity to apply to the institutes that were created on the basis of the old Soviet research institutes. Usually they support the brand, and employees in these places often work all their lives and have already “eaten the dog” on such projects.

The design process begins long before the designer picks up a pencil (in modern version before he sat down in front of the computer). This work consists of several successive processes.

Design stages

Collection of initial data.

This part of the work can be entrusted to both the designer and carried out independently by the customer. It is not expensive, but it takes some time to visit a certain number of organizations, write letters, applications and receive answers to them. You should not engage in self-collection of initial data for design only if you cannot explain what exactly you want to do.

Engineering survey.

The stage is rather complicated and cannot be performed independently. Some design organizations do this work themselves, some give it to subcontractors. If the designer works according to the second option, it makes sense to select a subcontractor on your own. So the cost can be somewhat reduced.

The design process itself.

It is carried out by the designer, at any stage it is controlled by the customer.

Project approval.

The developed documentation must be checked by the customer. After that, the designer coordinates it with third-party organizations. Sometimes, to speed up the process, it is enough to participate in this process. If the customer travels together with the developer as agreed, firstly, there is no way to delay the project, and secondly, there is a chance to see all the shortcomings with your own eyes. If there will be any contentious issues, it will be possible to control them also at the construction stage.

Numerous development organizations project documentation, offer alternative options for its type. 3D design, color design of drawings is gaining popularity. All these decorative elements are purely commercial in nature: they add the cost of design and do not raise the quality of the project itself. Builders will perform the work in the same way for any type of design and estimate documentation.

Drafting a design contract

In addition to what has already been said, it is necessary to add a few words about the design contract itself. A lot depends on the items in it. It is not always necessary to blindly agree to the form proposed by the designer. Quite often, only the interests of the project developer are taken into account.

The design contract must contain:

· full names of the parties

· price

· deadline

· subject of the contract

These items must be clearly spelled out. If the date is at least a month and a year, and not a certain number of days or months from the beginning of the design or from the beginning of the contract. Indicating such a wording will put you in an awkward position if you suddenly have to prove something in court. It should also be given Special attention the name of the subject matter of the contract. It should not sound like a project and a point, but like “design work for the heat supply of such and such a building” or “designing a heat network from a certain place to a certain place”.

It is useful to prescribe in the contract and some points of fines. For example, a delay in the design period entails the payment by the designer of 0.5% of the contract amount in favor of the customer. It is useful to prescribe in the contract the number of copies of the project. The optimal quantity is 5 pieces. 1 for myself, 1 more for technical supervision and 3 for builders.

Full payment for the work should be made only after 100% readiness and signing of the acceptance certificate (certificate of work performed). When drawing up this document, be sure to check the name of the project, it must be identical to that specified in the contract. If the records do not match even by one comma or letter, you run the risk of not proving payment under this particular agreement in the event of a dispute.

The next part of the article is devoted to construction issues. It will shed light on such points as: the features of the selection of a contractor and the conclusion of a contract for the performance of construction work, give an example of the correct installation sequence and tell you what to do when the pipeline is already laid in order to avoid negative consequences during operation.

Olga Ustimkina, rmnt.ru

http://www. rmnt . ru/ - RMNT website. en

Features of designing a heat network

1. Basic conditions for designing a heat network:

Depending on the geological, climatological features of the area, we choose the type of network laying.

• 2. The source of heat is located depending on the prevailing wind direction.
• 3. We lay pipelines along a wide road so that construction work can be mechanized.
• 4. When laying heating networks, you need to choose the shortest path in order to save material.
• 5. Depending on the relief and development of the area, we try to carry out self-compensation of heating networks.

Rice. 6.

Hydraulic calculation of the heat network

Technique of hydraulic calculation of the heat network.

The heating network is a dead end.

The hydraulic calculation is made on the basis of nanograms for the hydraulic calculation of the pipeline.

We are looking at the main road.

We select the pipe diameters according to the average hydraulic slope, taking specific losses pressure up to? P=80 Pa/m.

2) For additional sections G, not more than 300 Pa/m.

Pipe roughness K= 0.0005 m.

Record the pipe diameters.

After the diameter of the heating network sections, we calculate the sum of the coefficients for each section. local resistances (?o), using the TS scheme, data on the location of valves, compensators, and other resistances.

Then for each section we calculate the equivalent local resistance length (Lek).

Based on the pressure losses in the supply and return lines and the required available pressure "at the end" of the line, we determine the required available pressure on the outlet collectors of the heat source.

Table 7.1 - Definition of Leqv. at? W = 1 by du.

Table 7.2 - Calculation of equivalent lengths of local resistances.

Every 100m. a thermal expansion compensator was installed.

For pipeline diameters up to 200 mm. we accept U-shaped compensators, more than 200 - omental, bellows.

Losses of pressure DPz are on a nanogram, Pa/m.

The pressure loss is determined by the formula:

DP \u003d DPz * ?L * 10-3, kPa.

V (m3) of the plot is determined by the formula:

Calculation of pipeline water consumption, m (kg / s).

mot+vein = = = 35.4 kg/sec.

mg.c. = = = 6.3 kg/sec.

total \u003d mot + veins + mg.v. = 41.7 kg/s

Calculation of water consumption by plots.

Qkv = z * Fkv

z = Qtotal / ?Fkv = 13320/19 = 701

Qkv1 \u003d 701 * 3.28 \u003d 2299.3 kW

Qkv2 \u003d 701 * 2.46 \u003d 1724.5 kW

Qkv3 \u003d 701 * 1.84 \u003d 1289.84 kW

Qkv4 \u003d 701 * 1.64 \u003d 1149.64 kW

Qkv5 \u003d 701 * 1.23 \u003d 862.23 kW

Qkv6 \u003d 701 * 0.9 \u003d 630.9 kW

Qkv7 \u003d 701 * 1.64 \u003d 1149.64 kW

Qkv8 \u003d 701 * 1.23 \u003d 862.23 kW

Qkv9 \u003d 701 * 0.9 \u003d 630.9 kW

Qkv10 \u003d 701 * 0.95 \u003d 665.95 kW

Qkv11 \u003d 701 * 0.35 \u003d 245.35 kW

Qkv12 \u003d 701 * 0.82 \u003d 574.82 kW

Qkv13 \u003d 701 * 0.83 \u003d 581.83 kW

Qkv14 \u003d 701 * 0.93 \u003d 651.93 kW

Table 7.3 - Water consumption for each quarter.

The water consumption for each section is (kg / s):

mg4-g5 = m10+ 0.5 * m7 = 1.98+0.5*3.42 = 3.69

mg3-g4 = m11 + mg4-g5 = 3.69+0.73=4.42

mg2-g3 = m12+mg3-g4=4.42+1.71=6.13

mg1-g2 = 0.5*m7 + 0.5*m8+mg2-g3=0.5*3.42+0.5*2.57+6.13=9.12

m2-g1 = m4+0.5*m5+mg1-g2=9.12+3.42+0.5*2.57=13.8

m2-in1=m1+0.5*m2=9.42

m1-2=m2-g1+m2-v1=13.8+9.42=23.22

ma2-a3= m13+m14=3.67

ma1-a2=0.5*m8+m9+ma2-a3=0.5*2.57+1.88+3.67=6.83

m1-а1=0.5*m5+m6+ma1-а2=9.99

m1-b1=0.5*m2+m3=6.41

mi-1=m1-b1+m1-а1+m1-2=6.41+9.99+23.22=39.6

We write the received data in table 8.

Table 8 - Hydraulic calculation of the district heating network. 7.1 Selection of network and make-up pumps.

Table 9 - To build a piezometric graph.

Hseat=0.75mHad=30 m

H bay = 4 m

V= 16.14 m3/h - to select the make-up pump

hfeed= 3.78 mhTGU= 15 m

hreturn = 3.78 mhsnap = 4 m

hset=26.56 m; m=142.56 m3/h - to select the network pump

For closed system heat supply operating at elevated graphics control with a total heat flow Q = 13.32 MW and with an estimated coolant flow rate G = 39.6 kg / s = 142.56 m3 / h, select network and make-up pumps.

Required head of the network pump H = 26.56 m

By methodological guide we accept for installation one network pump KS 125-55 providing the required parameters.

The required pressure of the make-up pump Hpn = 16.14 m3/h. Required boost pump head H = 34.75 m

Make-up pump: 2k-20/20.

According to the manual, we accept for installation two series-connected make-up pumps 2K 20-20 providing the required parameters.

Rice. eight.

Table 10 - Technical characteristics of pumps.

Competent and high-quality is one of the main conditions for the quick commissioning of the facility.

Heating network designed to transport heat from heat sources to the consumer. Thermal networks are linear structures and are one of the most complex engineering networks. The design of networks must necessarily include a calculation for strength and temperature deformations. We calculate each element of the heating network for a service life of at least 25 years (or another at the request of the customer), taking into account the specific temperature history, thermal deformations and the number of starts and stops of the network. An integral part of the design of a heat network should be the architectural and construction part (AS) and reinforced concrete or metal constructions(KZh, KM), in which fasteners, channels, supports or overpasses are developed (depending on the laying method).

Thermal networks are divided according to the following criteria

1. By the nature of the transported coolant:

2. According to the method of laying heating networks:

• channel heating networks. The design of channel heating networks is carried out if it is necessary to protect pipelines from the mechanical impact of soils and the corrosive effects of soil. Channel walls facilitate the operation of pipelines, therefore, the design of channel heating networks is used for heat carriers with pressures up to 2.2 MPa and temperatures up to 350 ° C. - channelless. When designing channelless laying, pipelines operate in more difficult conditions, since they perceive an additional load of the soil and, with inadequate protection from moisture, are subject to external corrosion. In this regard, the design of networks in this way of laying is provided for at a coolant temperature of up to 180 ° C.
• air (aerial) heating networks. The design of networks by this method of laying has become most widespread in the territories of industrial enterprises and on sites free from buildings. The overhead method is also being designed in areas with high ground water and when laying in areas with very rugged terrain.

3. With regard to schemes, heat networks can be:

• main heating networks. Heating networks, always in transit, without branches transporting the coolant from the heat source to distribution heating networks;
• distribution (quarterly) heating networks. Heating networks distributing the heat carrier over the selected quarter, supplying the heat carrier to the branches to consumers .;
• branches from distribution heat networks to individual buildings and structures. The separation of heat networks is established by the project or the operating organization.

Integrated network design in accordance with project documentation

STC Energoservice performs complex work on, including city highways, intra-quarter distribution and home networks. The design of networks of the linear part of heating mains is carried out using both standard and individual nodes.

Qualitative calculation of heat networks makes it possible to compensate for thermal elongation of pipelines due to the angles of turns of the route and to check the correctness of the planned-altitude position of the route, the installation of bellows expansion joints and fixing with fixed supports.

Thermal elongation of heat pipelines during channelless laying is compensated due to the angles of turns of the route, which form self-compensating sections of the П, Г, Z-shaped form, the installation of starting compensators, and fixing with fixed supports. At the same time, at the corners of the turns, between the trench wall and the pipeline, special polyethylene foam cushions (mats) are installed, which ensure the free movement of pipes during their thermal elongation.

All documentation for design of thermal networks is developed in accordance with the following regulatory documents:

SNiP 207-01-89* Urban planning. Planning and development of cities, towns and rural settlements. Network design standards”;
- SNiP 41-02-2003 "Heat networks";
- SNiP 41-02-2003 "Thermal insulation of equipment and pipelines";
- SNiP 3.05.03-85 "Heat networks" (heat network enterprise);
- GOST 21-605-82 "Heat networks (thermal mechanical part)";
- Rules for the preparation and production of earthworks, arrangement and maintenance of construction sites in the city of Moscow, approved by the Decree of the Government of Moscow No. 857-PP dated 07.12.2004.
- PB 10-573-03 "Rules for the device and safe operation steam and hot water pipelines.

Depending on the conditions of the construction site, the design of networks may be associated with the reconstruction of existing underground structures that interfere with construction. The design of heat networks and the implementation of projects involves the use of two insulated steel pipelines (supply and return) in special prefabricated or monolithic channels (through and through). To accommodate disconnecting devices, drains, air vents and other fittings, the design of heat networks provides for the construction of chambers.

At network design and their throughput, the problems of uninterrupted operation of hydraulic and thermal modes are relevant. Carrying out the design of heating networks, the specialists of our company use the most modern methods, which allows us to guarantee a good result and durable operation of all equipment.

When carrying out, it is necessary to rely on many technical standards, the violation of which can lead to the most negative consequences. We guarantee compliance with all norms and rules regulated by various technical documentation described above.