Hydraulic calculation of water heating networks is carried out in order to determine the diameters of pipelines, pressure losses in them, and linking the thermal points of the system.
results hydraulic calculation are used to construct a piezometric graph, select schemes of local heating points, select pumping equipment and technical and economic calculations.
The pressure in the supply pipelines through which water with a temperature of more than 100 0 C moves must be sufficient to prevent steam formation. We take the temperature of the coolant in the main line to be 150 0 C. The pressure in the supply pipelines is 85 m, which is sufficient to exclude steam formation.
To prevent cavitation, the pressure in the suction pipe of the network pump must be at least 5 m.
For elevator mixing at the user input, the available pressure must be at least 10-15 m.
When the coolant moves through horizontal pipelines, a pressure drop is observed from the beginning to the end of the pipeline, which consists of a linear pressure drop (friction loss) and pressure loss in local resistances:
Linear pressure drop in a pipeline of constant diameter:
Pressure drop in local resistances:
Given pipeline length:
Then formula (14) will take its final form:
Let us determine the total length of the design highway (sections 1,2,3,4,5,6,7,8):
Let's carry out a preliminary calculation (Involves determining diameters and speeds). The share of pressure losses in local resistances can be approximately determined using the B.L. formula. Shifrinson:
where z =0.01 is the coefficient for water networks; G is the coolant flow rate in the initial section of the branched heat pipeline, t/h.
Knowing the proportion of pressure loss, we can determine the average specific linear pressure drop:
where is the available pressure difference to all subscribers, Pa.
According to the assignment, the available pressure difference is specified in meters and is equal to?H=60 m. Because pressure losses are distributed evenly between the supply and return lines, then the pressure drop on the supply line will be equal to? H = 30 m. Let us convert this value into Pa as follows:
where = 916.8 kg/m3 is the density of water at a temperature of 150 0 C.
Using formulas (16) and (17), we determine the share of pressure losses in local resistances, as well as the average specific linear pressure drop:
Based on the magnitude and flow rates G 1 - G 8, using the nomogram we find the pipe diameters, coolant speed and. We enter the result in table 3.1:
Table 3.1
|
Plot number |
Advance paynemt |
Final settlement |
|||||||
Let's make the final calculation. We clarify the hydraulic resistance in all sections of the network for the selected pipe diameters.
We determine the equivalent lengths of local resistances in the design sections using the table “equivalent lengths of local resistances”.
dP = R*(l+l e)*10 -3, kPa (18)
We determine the total hydraulic resistance for all sections of the design main, which are compared with the pressure drop located in it:
The calculation is satisfactory if the hydraulic resistance does not exceed the available pressure drop and differs from it by no more than 25%. The final result is converted to m. water. Art. to construct a piezometric graph. We enter all data in Table 3.
We will carry out the final calculation for each calculation section:
Section 1:
The first section has the following local resistance with their equivalent lengths:
Gate valve: l e = 3.36 m
Tee for dividing flows: l e = 8.4 m
We calculate the total pressure loss in sections using formula (18):
dP = 390*(5+3.36+8.4)*10 -3 =6.7 kPa
Or m. water. Art.:
H= dP*10 -3 /9.81 = 6.7/9.81=0.7 m
Section 2:
In the second section there are the following local resistances with their equivalent lengths:
U-shaped compensator: l e = 19 m
dP = 420*(62.5+19+10.9)*10 -3 =39 kPa
H= 39/9.81=4 m
Section 3:
In the third section there are the following local resistances with their equivalent lengths:
Tee for dividing flows: l e = 10.9 m
dP = 360*(32.5+10.9) *10 -3 =15.9 kPa
H= 15.9/9.81=1.6 m
Section 4:
In the fourth section there are the following local resistances with their equivalent lengths:
Branch: l e = 3.62 m
Tee for dividing flows: l e = 10.9 m
dP = 340*(39+3.62+10.9) *10 -3 =18.4 kPa
H=18.4/9.81=1.9 m
Section 5:
In the fifth section there are the following local resistances with their equivalent lengths:
U-shaped compensator: l e = 12.5 m
Branch: l e = 2.25 m
Tee for dividing flows: l e = 6.6 m
dP = 590*(97+12.5+2.25+6.6) *10 -3 = 70 kPa
H= 70/9.81=7.2 m
Section 6:
In the sixth section there are the following local resistances with their equivalent lengths:
U-shaped compensator: l e = 9.8 m
Tee for dividing flows: l e = 4.95 m
dP = 340*(119+9.8+4.95) *10 -3 =45.9 kPa
H= 45.9/9.81=4.7 m
Section 7:
In the seventh section there are the following local resistances with their equivalent lengths:
Two branches: l e = 2*0.65 m
Tee for dividing flows: l e = 1.3 m
dP = 190*(107.5+2*0.65+5.2+1.3) *10 -3 =22.3 kPa
H= 22.3/9.81=2.3 m
Section 8:
In the eighth section there are the following local resistances with their equivalent lengths:
Gate valve: l e = 0.65 m
Branch: l e = 0.65 m
dP = 65*(87.5+0.65+.065) *10 -3 =6.2 kPa
H= 6.2/9.81= 0.6 m
We determine the total hydraulic resistance and compare it with the available differential according to (17=9):
Let's calculate the difference in percentages:
? = ((270-224,4)/270)*100 = 17%
The calculation is satisfactory because hydraulic resistance does not exceed the available pressure drop, and differs from it by less than 25%.
We calculate the branches in the same way and enter the result in Table 3.2:
Table 3.2
|
Plot number |
Advance paynemt |
Final settlement |
||||||||
Section 22:
Available pressure at the subscriber: ?H22 = 0.6 m
At the 22nd section there are the following local resistances with their equivalent lengths:
Branch: l e = 0.65 m
U-shaped compensator: l e = 5.2 m
Gate valve: l e = 0.65 m
dP = 32*(105+0.65+5.2+0.65)*10 -3 =3.6 Pa
H= 3.6/9.81=0.4 m
Excess pressure in the branch: ?H 22 - ?H = 0.6-0.4=0.2 m
? = ((0,6-0,4)/0,6)*100 = 33,3%
Section 23:
Available pressure at the subscriber: ?H 23 = ?H 8 +?H 7 = 0.6+2.3=2.9 m
At the 23rd section there are the following local resistances with their equivalent lengths:
Branch: l e = 1.65 m
Valve: l e = 1.65 m
dP = 230*(117.5+1.65+1.65)*10 -3 =27.8 kPa
H= 27.8/9.81=2.8 m
Excess pressure in the branch: ?H 23 - ?H = 2.9-2.8=0.1 m<25%
Section 24:
Available pressure at the subscriber: ?H 24 = ?H 23 +?H 6 = 2.9+4.7=7.6 m
At the 24th section there are the following local resistances with their equivalent lengths:
Branch: l e = 1.65 m
Valve: l e = 1.65 m
dP = 480*(141.5+1.65+1.65)*10 -3 = 69.5 kPa
H=74.1 /9.81=7.1 m
Excess pressure in the branch: ?H 24 - ?H = 7.6-7.1=0.5 m<25%
Section 25:
Available pressure at the subscriber: ?H 25 = ?H 24 +?H 5 = 7.6+7.2=14.8 m
At the 25th section there are the following local resistances with their equivalent lengths:
Branch: l e = 2.25 m
Gate valve: l e = 2.2 m
dP = 580*(164.5+2.25+2.2)*10 -3 =98 kPa
H= 98/9.81=10 m
Excess pressure in the branch: ?H 25 - ?H = 14.8-10=4.8 m
? = ((14,8-10)/14,8)*100 = 32,4%
Because The discrepancy between the values is more than 25% and it is not possible to install pipes with a smaller diameter, then it is necessary to install a throttle washer.
Section 26:
Available pressure at the subscriber: ?H 26 = ?H 25 +?H 4 = 14.8+1.9=16.7 m
At the 26th section there are the following local resistances with their equivalent lengths:
Branch: l e = 0.65 m
Gate valve: l e = 0.65 m
dP = 120*(31.5+0.65+0.65)*10 -3 =3.9 kPa
H= 3.9/9.81=0.4 m
Excess pressure in the branch: ?H 26 - ?H = 16.7-0.4=16.3 m
? = ((16,7-0,4)/16,7)*100 = 97%
Because The discrepancy between the values is more than 25% and it is not possible to install pipes with a smaller diameter, then it is necessary to install a throttle washer.
Section 27:
Available pressure at the subscriber: ?H 27 = ?H 26 +?H 3 = 16.7+1.6=18.3 m
At the 27th section there are the following local resistances with their equivalent lengths:
Branch: l e = 1 m
Valve: l e = 1 m
dP = 550*(40+1+1)*10 -3 =23.1 kPa
H= 23.1/9.81=2.4 m
Excess pressure in the branch: ?H 27 - ?H = 18.3-2.4=15.9 m
Reducing the diameter of the pipeline is not possible, so it is necessary to install a throttle washer.
Greetings, dear and respected readers of the site “site”. A necessary step in the design of heat supply systems for enterprises and residential areas is the hydraulic calculation of pipelines for water heating networks. It is necessary to solve the following tasks:
- Determination of the internal diameter of the pipeline for each section of the heating network d B, mm. By 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.
- Determination of network water pressure loss or network water pressure loss Δh, m; ΔР, MPa. These losses are the initial data for sequential calculations of the pressure of network and make-up pumps on heating networks.
Hydraulic calculation of heating networks is also performed for existing operating heating networks, when the task is to calculate their actual throughput, i.e. when there is a diameter, length and you need to find the flow rate of network water that will pass through these networks.
Hydraulic calculations of heating network pipelines are performed for the following operating modes:
A) for the design operating mode of the heating network (max G O; G B; G DHW);
B) for summer mode, when only G hot water flows through the pipeline
C) for static mode, the network pumps at the heat supply source are stopped, and only the make-up pumps are running.
D) for emergency mode, when there is an accident in one or several sections, the diameter of jumpers and backup pipelines.
If heating networks operate for a water-based open heating system, then it is also determined:
E) winter mode, when network water for the hot water supply system of buildings is taken from the return pipeline of the heating network.
E) transition mode, when network water for hot water supply of buildings is taken from the supply pipeline of the heating network.
When performing hydraulic calculations of heating network pipelines, the following values must be known:
- Maximum load on heating and ventilation and average hourly load on DHW: max Q O, max Q VENT, Q CP DHW.
- Temperature graph of the heating system.
- Temperature graph of network water, temperature of network water at the break point τ 01 NI, τ 02 NI.
- Geometric length of each section of heating networks: L 1, L 2, L 3 ...... L N.
- Condition of the internal surface of the pipeline in each section of the heating network (amount of corrosion and scale deposits). k E – equivalent pipeline roughness.
- The number, type and arrangement of local resistances that are available in each section of the heating network (all valves, valves, turns, tees, compensators).
- Physical properties of water p V, I V.
How hydraulic calculations of heating network pipelines are performed will be considered using the example of a radial heating 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 – heat supply source
Hydraulic calculation of the designed heating networks is performed in the following sequence:
- Based on the principle diagram of heating networks, the consumer who is furthest from the heat supply source is determined. The heating network laid from the heat supply source to the most distant 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 main (branch).
- The estimated direction of movement of network water from the heat supply source to the most distant consumer is outlined.
- The calculated direction of movement of network water is divided into separate sections, in each of which the internal diameter of the pipeline and the flow rate of network water must remain constant.
- 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 UC = G O P + G V P + k 3 *G G SR
G О Р = Q О Р / С В *(τ 01 Р – τ 02 Р) – maximum heating consumption
k 3 – coefficient taking into account the share of consumption of network water supplied to the hot water supply
G В Р = Q В Р / С В *(τ 01 Р – τ В2 Р) – maximum ventilation flow
G G SR = Q GW SR / C B *(τ 01 NI – τ G2 NI) – average consumption for DHW
k 3 = f (type of heat supply system, consumer heat load).
Values of k 3 depending on the type of heat supply system and heat loads connecting heat consumers
- Using reference data, the physical properties of network water in the supply and return pipelines of the heating network are determined:
P IN POD = f (τ 01) V IN POD = f (τ 01)
P V OBR = f (τ 02) V V OBR = f (τ 02)
- The average density of network water and its speed are determined:
P IN SR = (P IN UNDER + P IN OBR) / 2; (kg/m3)
V IN SR = (V IN UNDER + V IN OBR) / 2; (m 2 /s)
- A hydraulic calculation of pipelines for each section of heating networks is performed.
7.1. They are set by the speed of movement of network water in the pipeline: V V = 0.5-3 m/s. The lower limit of VB 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 water circulation stops and the pipeline may freeze.
V V = 0.5-3 m/s. – the higher value of the speed in the pipeline is due to the fact that when the speed increases above 3.5 m/s, a water hammer may occur in the pipeline (for example, when the 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 = sqrt[(G SUM UCH *4)/(p V SR *V V *π)] (m)
7.3. Based on reference data, the closest values of the internal diameter are accepted, which correspond to GOST d V GOST, mm.
7.4. The actual speed of water movement in the pipeline is specified:
V V Ф = (4*G SUM UC) / [π*р V SR *(d V GOST) 2 ]
7.5. The mode and zone of flow of network water in the pipeline is determined, for this purpose 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 = 568 * d V GOST / k E
For different types of pipelines and different degrees of pipeline wear, k E lies within the range. 0.01 – if the pipeline is new. When the type of pipeline and the degree of wear are unknown according to SNiP “Heating Networks” 02/41/2003. It is recommended to select the kE value equal to 0.5 mm.
7.7. The coefficient of hydraulic friction in the pipeline is calculated:
— if criterion Re< 2320, то используется формула: λ ТР = 64 / Re.
— if the Re criterion lies within (2320; Re PR I ], then the Blasius formula is used:
λ TR =0.11*(68/Re) 0.25
These two formulas must be used for laminar flow of water.
- if the Reynolds criterion lies within the limits (Re PR I< Re < =Re ПР II), то используется формула Альтшуля.
λ TR = 0.11*(68/Re + k E/d V GOST) 0.25
This formula is applied during the transitional movement of network water.
- if Re > Re PR II, then the Shifrinson formula is used:
λ TR = 0.11*(k E /d V GOST) 0.25
Δh TR = λ TR * (L*(V V F) 2) / (d V GOST *2*g) (m)
ΔP TP = p V SR *g* Δh TP = λ TP * / (d V GOST *2) = R L *L (Pa)
R L = [λ TR * r V SR *(V V F) 2 ] / (2* d V GOST) (Pa/m)
R L – specific linear pressure drop
7.9. The pressure losses or pressure losses in local resistances along the pipeline section are calculated:
Δh M.S. = Σ£ M.S. *[(V V Ф) 2 /(2*g)]
Δp M.S. = p V 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. accepted according to reference data.
7.10. The total pressure loss or total pressure loss on the pipeline section is determined:
h = Δh TR + Δh M.S.
Δp = Δp TR + Δр M.S. = p In SR *g* Δh TP + p In SR *g*Δh M.S.
Using this method, calculations are carried out for each section of the heating network and all values are summarized in a table.
Main results of hydraulic calculation of pipelines of water heating network sections
For approximate calculations of sections of water heating networks when determining R L, Δр TR, Δр M.S. The following expressions are allowed:
R L = / [r V SR *(d V GOST) 5.25 ] (Pa/m)
R L = / (d V GOST) 5.25 (Pa/m)
A R = 0.0894*K E 0.25 – empirical coefficient that is used for approximate hydraulic calculations in water heating networks
A R B = (0.0894*K E 0.25) / r V SR = A R / r V SR
These coefficients were derived by E.Ya. Sokolov. and are given in the textbook “Heating and heating networks”.
Taking into account these empirical coefficients, head and pressure losses are determined as:
Δp TR = R L *L = / [p V SR *(d V GOST) 5.25 ] =
= / (d V GOST) 5.25
Δh TR = Δp TR / (p V SR *g) = (R L *L) / (p V SR *g) =
= / (p V SR) 2 * (d V GOST) 5.25 =
= / p V SR * (d V GOST) 5.25 * g
Also taking into account A R and A R B; Δр M.S. and Δh M.S. will be written like this:
Δр M.S. = R L * L E M = /r V SR * (d V GOST) 5.25 =
= /(d V GOST) 5.25
Δh M.S. = Δр M.S. / (p V SR *g) = (R L *L E M) / (p V SR *g) =
= / p V SR * (d V GOST) 5.25 =
= /(d IN GOST) 5.25 *g
L E = Σ (£ M.S. * d V GOST) / λ TR
The peculiarity of the equivalent length is that the pressure loss of local resistances is represented as the pressure drop in a straight section with the same internal diameter and this length is called equivalent.
Total pressure and head losses are calculated as:
Δh = Δh TR + Δh M.S. = [(R L *L)/(r V SR *g)] + [(R L *L E) / (r V SR *g)] =
= *(L + L E) = *(1 + a M.S.)
Δр = Δр TR + Δр M.S. = R L *L + R L *L E = R L (L + L E) = 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 a hydraulic calculation of pipelines and you yourself will be able to perform a hydraulic calculation of heating networks. Tell us in the comments what you think, maybe you do the hydraulic calculation of pipelines in Excel, or do you use an online calculator for hydraulic calculation of pipelines or use a nomogram for hydraulic calculation of pipelines?
A reference manual covering the design of heating networks is the “Designer's Handbook. Design of heating networks." The reference book can, to a certain extent, be considered as a manual for SNiP II-7.10-62, but not for SNiP N-36-73, which appeared much later as a result of a significant revision of the previous edition of the standards. 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 setup and operation of water heating networks.” Books from the series of reference books “Thermal Power Engineering and Heat Engineering” can be used as a source of reference materials on design issues. 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 water vapor; more detailed data 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 water vapor, as well as on the density, thermal conductivity and heat capacity of some building and insulating materials. The fourth book “Industrial Thermal Power Engineering and Heat Engineering” has a section devoted to district heating and heating networks
www.engineerclub.ru
Gromov - Water heating networks (1988)
The book contains regulatory materials used in the design of heating networks and heating points. Recommendations are given for the selection of equipment and heat supply schemes. Calculations related to the design of heating networks are considered. Information is provided on the laying of heating networks, on the organization of construction and operation of heating networks and heating points. The book is intended for engineers and technicians involved in the design of heating networks.
Housing and industrial construction, requirements for fuel economy and environmental protection predetermine the feasibility of intensive development of centralized heat supply systems. Thermal energy for such systems is currently produced by combined heat and power plants and district boiler houses.
Reliable operation of heat supply systems with strict adherence to the required parameters of the coolant is largely determined by the correct choice of heating network diagrams and heating points, laying designs, and equipment used.
Considering that the correct design of heating 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 HEATING NETWORKS AND HEATING STATIONS
1.1. District heating systems and their structure
District heating systems are characterized by a combination of three main links: heat sources, heating networks and local heat use (heat consumption) systems of individual buildings or structures. Heat sources produce heat by burning various types of organic fuel. Such heat sources are called boiler houses. When heat sources use the heat released during the decay of radioactive elements, they are called nuclear heat supply plants (ACT). In some heat supply systems, renewable heat sources are used as auxiliary heat sources - geothermal energy, solar energy, etc.
If the heat source is located together with heat receivers in the same building, then the pipelines for supplying coolant to the heat receivers running 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 utilization systems of individual buildings are connected.
The scale of district heating systems can vary widely: from small ones serving several neighboring buildings to large ones 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 based on the number of consumers served. Utility systems include systems that supply heat mainly to residential and public buildings, as well as individual industrial and municipal warehouse buildings, the placement of which in the residential zone of cities is permitted by regulations.
It is advisable to base the classification of communal systems according to their scale on the division of the territory of a residential zone into groups of neighboring buildings (or blocks in old building areas), accepted in the norms of urban planning and development, which are united 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 provide for the formation of residential areas from several microdistricts with a population of 25 - 80 thousand people. The corresponding centralized heat supply systems can be characterized as group (quarter), microdistrict and district.
Heat sources serving these systems, one for each system, can be classified respectively as group (quarter), microdistrict and district boiler houses. 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 public heating systems is possible.
With large scale heat production, especially in city-wide systems, it is advisable to combine heat and electricity. This provides significant fuel savings compared to the separate production of heat in boiler houses and electricity in thermal power plants by burning the same types of fuel.
Thermal power plants designed for the combined production of heat and electricity are called combined heat and power plants (CHP).
Nuclear power plants, which use the heat released during the decay of radioactive elements to generate electricity, are also sometimes useful as heat sources in large heat supply systems. These plants are called nuclear combined heat and power plants (NCPPs).
District heating systems that use thermal power plants as the main heat sources are called district heating systems. Issues of construction of new centralized heat supply systems, as well as expansion and reconstruction of existing systems require special study, based on the development prospects of the relevant settlements for the coming period (A0-15 years) and an estimated period of 25 - 30 years).
The standards provide for the development of a special pre-project document, namely a heat supply scheme for a given locality. The scheme examines several options for technical solutions for heat supply systems and, based on a technical and economic comparison, justifies the choice of the option proposed for approval.
Subsequent development of projects for heat sources and heating networks should, in accordance with regulatory documents, be carried out only on the basis of decisions made in the approved heat supply scheme for a given locality.
1.2. General characteristics of heating networks
Heating 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 coolants in heating networks are hot water and water steam. Water vapor as a coolant is widely used in heat sources (boiler houses, thermal power plants), and in many cases - in heat use systems, especially industrial ones. Communal heat supply systems are equipped with water heating networks, and industrial ones 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 heating networks is also typical for city-wide 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 use systems and return pipelines for returning the 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 use systems, form closed water circulation loops. This circulation is supported by network pumps installed in heat sources, and for long water transport distances - also along the network route (pumping stations). Depending on the adopted scheme for connecting hot water supply systems to networks, closed and open schemes are distinguished (the terms “closed and open heat supply systems” are more often used).
In closed systems, heat is released from the networks in the hot water supply system by heating cold tap water in special water heaters.
In open systems, hot water supply loads are covered by supplying consumers with water from the supply pipelines of the networks, and during the heating period - in a mixture with water from the return pipelines of heating and ventilation systems. If, in all modes, water from return pipelines can be used entirely for hot water supply, then there is no need for return pipelines from heating points to the heat source. Compliance with these conditions, as a rule, is only possible through the joint operation of several heat sources on common heating networks with the assignment of covering the hot water supply loads 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. Heating networks are recharged in closed and open systems through the operation of make-up pumps and make-up water preparation units. In an open system, their required performance is 10-30 times greater than in a closed system. As a result, with an open system, capital investments in heat sources are large. At the same time, in this case there is no need for tap water heaters, and therefore the costs of connecting hot water supply systems to heating networks are significantly reduced. Thus, the choice between open and closed systems in each case must be justified by technical and economic calculations, taking into account all parts of the centralized heat supply system. Such calculations should be performed when developing a heat supply scheme for a populated area, i.e., before designing the corresponding heat sources and their heating networks.
In some cases, water heating networks are made with three or even four pipes. Such an increase in the number of pipes, usually provided only in certain sections of 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 division significantly 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 centralized 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 standards provide for the division of heating networks into three categories: main ones from heat sources to inputs into microdistricts (blocks) 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 nodes connecting the heat use systems of individual buildings to them. It is advisable to clarify these names in relation to the classification of centralized heat supply systems adopted in § 1.1 according to their scale and the number of consumers served. Thus, if in small systems one heat source supplies heat only to a group of residential and public buildings within a microdistrict or industrial buildings of one enterprise, then there is no need for main heating networks and all networks from such heat sources should be considered as distribution networks. This situation is typical for the use of group (quarter) and microdistrict boiler houses as heat sources, as well as industrial boilers serving one enterprise. When moving from such small systems to district ones, and even more so to inter-district ones, a category of main heating networks appears, to which the distribution networks of individual microdistricts or enterprises of one industrial region are connected. Connecting individual buildings directly to main networks, in addition to distribution networks, is extremely undesirable for a number of reasons, and therefore is used very rarely.
Large heat sources of district and interdistrict centralized heat supply systems, according to the standards, must be located outside the residential zone in order to reduce the impact of their emissions on the state of the air basin in this zone, as well as to simplify the systems for supplying them with liquid or solid fuel.
In such cases, initial (head) sections of trunk networks of considerable length appear, within which there are no connection nodes for distribution networks. Such transport of coolant without its accompanying distribution to consumers is called transit, and it is advisable to classify the corresponding head sections of main heating networks into a special category of transit.
The presence of transit networks significantly worsens the technical and economic indicators of coolant transport, especially when the length of these networks is 5 - 10 km or more, which is typical, in particular, when using nuclear thermal power plants or heat supply stations as heat sources.
1.3. General characteristics of heating points
An essential element of centralized heat supply systems are installations located at connection points to heating networks of local heat use systems, as well as at the junctions of networks of various categories. In such installations, the operation of heating networks and heat utilization systems is monitored and managed. Here, the parameters of the coolant are measured - pressures, temperatures, and sometimes flow rates - and the heat supply is regulated at various levels.
The reliability and efficiency of heat supply systems as a whole largely depend on the operation of such installations. These installations are called heating points in regulatory documents (previously the names “connection nodes for local heat utilization systems”, “heat centers”, “subscriber installations”, etc.) were also used.
However, it is advisable to clarify the classification of heating points adopted in the same documents somewhat, since in them all heating points are either central (central heating points) or individual (ITP). The latter include only installations with connection points to heating networks of heat utilization systems of one building or part of them (in large buildings). All other heating points, regardless of the number of buildings served, are classified as central.
In accordance with the accepted classification of heating networks, as well as the various stages of regulation of heat supply, the following terminology is used. Regarding heating points:
local heating points (MTP), servicing the heat utilization systems of individual buildings;
group or microdistrict heating points (GTS), serving a group of residential buildings or all buildings within the microdistrict;
district heating points (RTS), serving all buildings within a residential area
Regarding the stages of regulation:
central - only at heat sources;
district, group or microdistrict - at the corresponding 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).
Heat networks design reference guide
Home Mathematics, chemistry, physics Design of a heat supply system for a hospital complex
27. Safonov A.P. Collection of problems 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 testing methods for heating networks Lecture notes. SPb.: SPb GGU RP. 1998.
29. Instructions for the operation of heating networks M.: Energy 1972.
30. Safety rules for servicing heating networks M: Atomizdat. 1975.
31. Yurenev V.N. Thermotechnical reference book in 2 volumes M.; Energy 1975, 1976.
32. Golubkov B.N. Heating equipment and heat supply for industrial enterprises. M.: Energy 1979.
33. Shubin E.P. Basic issues in the design of heat supply systems. M.: Energy. 1979.
34. Guidelines for drawing up a report from a power plant and a joint stock company for energy and electrification on the thermal efficiency of equipment. RD 34.0K.552-95. SPO ORGRES M: 1995.
35. Methodology for determining specific fuel consumption for heat depending on the parameters of steam used for heat supply purposes RD 34.09.159-96. SPO ORGRES. M.: 1997
36. Guidelines for analyzing changes in specific fuel consumption at power plants and energy associations. RD 34.08.559-96 SPO ORGRES. M.: 1997.
37. Kutovoy G.P., Makarov A.A., Shamraev N.G. Creating a favorable base for the development of the Russian electric power industry on a market basis “Thermal power engineering”. No. 11, 1997. pp. 2-7.
38. Bushuev V.V., Gromov B.N., Dobrokhotov V.N., Pryakhin V.V., Scientific, technical and organizational and economic problems of introducing energy-saving technologies. "Thermal power engineering". No. 11. 1997. p.8-15.
39. Astakhov N.L., Kalimov V.F., Kiselev G.P. New edition of guidelines for calculating thermal efficiency indicators of thermal power plant equipment. "Energy saving and water treatment." No. 2, 1997, pp. 19-23.
Ekaterina Igorevna Tarasevich
Russia
Chief Editor -
Candidate of Biological Sciences
NORMATIVE HEAT FLOW DENSITY AND HEAT LOSSES THROUGH THE HEAT-INSULATED SURFACE FOR MAIN HEATING NETWORKS
The article discusses changes to a number of published regulatory documents for thermal insulation of heating systems, which are aimed at ensuring the longevity 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 research relates to heat supply systems and thermodynamics. Recommendations are given for calculating standard heat losses through the insulation of pipelines of heating networks.
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. Correct design and calculation of a thermal insulation structure is much more important than simply choosing an insulating material. The results of a comparative analysis of heat losses are presented.
Thermal calculation methods for calculating the heat loss of heating network pipelines are based on the application of the standard heat flux density through the surface of the thermal insulation structure. In this article, using the example of pipelines with polyurethane foam insulation, a calculation of heat losses was carried out.
Basically, the following conclusion was made: the current regulatory documents provide the total values of heat flux density for the supply and return pipelines. 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, it is necessary to use the previous standard. The total values of heat flow density in the standards can be divided between the supply and return pipelines in the same proportions as in the replaced standards.
Keywords
Literature
SNiP 41-03-2003. Thermal insulation of equipment and pipelines. Updated edition. – M: Ministry of Regional Development of Russia, 2011. – 56 p.
SNiP 41-03-2003. Thermal insulation of equipment and pipelines. – M.: Gosstroy of Russia, FSUE TsPP, 2004. – 29 p.
SP 41-103-2000. Design of thermal insulation of equipment and pipelines. M: Gosstroy of Russia, FSUE TsPP, 2001. 47 p.
GOST 30732-2006. Steel pipes and fittings with thermal insulation made of polyurethane foam with a protective sheath. – M.: STANDARDINFORM, 2007, 48 p.
Standards for the design of thermal insulation for pipelines and equipment of power plants and heating networks. M.: Gosstroyizdat, 1959. – URL: http://www.politerm.com.ru/zuluthermo/help/app_thermoleaks_year1959.htm
SNiP 2.04.14-88. Thermal insulation of equipment and pipelines/Gosstroy USSR.- M.: CITP Gosstroy USSR, 1998. 32 p.
Belyaykina I.V., Vitaliev V.P., Gromov N.K. and etc.; Ed. Gromova N.K.; Shubina E.P. Water heating networks: Design reference guide. M.: Energoatomizdat, 1988. – 376 p.
Ionin A.A., Khlybov B.M., Bratenkov V.N., Terletskaya E.N.; Ed. A.A. Ionina. Heat supply: Textbook for universities. M.: Stroyizdat, 1982. 336 p.
Lienhard, John H., A heat transfer textbook / John H. Lienhard IV and John H. Lienhard V, 3rd ed. Cambridge, MA: Phlogiston Press, 2003
Silverstein, C.C., “Design and Technology of Heat Pipes for Cooling and HeatExchange,” Taylor & Francis, Washington DC, USA, 1992
European Standard EN 253 District heating pipes — Preinsulated bonded pipe systems for directly buried hot water networks — Pipe assembly of steel service pipe, polyurethane thermal insulation and outer casing of polyethylene.
European Standard EN 448 District heating pipes. Preinsulated bonded pipe systems for directly buried hot water networks. Fitting assemblies of steel service pipes, polyurethane thermal insulation and outer casing of polyethylene
DIN EN 15632-1:2009 District heating pipes - Pre-insulated flexible pipe systems - Part 1: Classification, general requirements and test methods
Sokolov E.Ya. District heating and heating networks Textbook for universities. M.: MPEI Publishing House, 2001. 472 p.
SNiP 41-02-2003. Heating network. Updated edition. – M: Ministry of Regional Development of Russia, 2012. – 78 p.
SNiP 41-02-2003. Heating network. – M: Gosstroy of Russia, 2004. – 41 p.
Nikolaev A.A. Design of heating networks (Designer's Handbook) / A.A. Nikolaev [etc.]; edited by A.A. Nikolaeva. – M.: NAUKA, 1965. – 361 p.
Varfolomeev Yu.M., Kokorin O.Ya. Heating and heating networks: Textbook. M.: Infra-M, 2006. – 480 p.
Kozin V. E., Levina T. A., Markov A. P., Pronina I. B., Slemzin V. A. Heat supply: A textbook for university students. – M.: Higher. school, 1980. – 408 p.
Safonov A.P. Collection of problems on district heating and heating networks: Textbook. manual for universities. 3rd ed., revised. M.: Energoatomizdat, 1985. 232 p.
- There are currently no links.
Determination of local loss coefficients in heating networks of industrial enterprises
Publication date: 06.02.2017 2017-02-06
Article viewed: 186 times
Bibliographic description:
Ushakov D.V., Snisar D.A., Kitaev D.N. Determination of local loss coefficients in heating networks of industrial enterprises // Young scientist. 2017. No. 6. pp. 95-98. URL https://moluch.ru/archive/140/39326/ (access date: 07/13/2018).
The article presents the results of an analysis of the actual values of the local loss coefficient used in the design of heating 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 have been found that allow one to calculate the coefficient of local losses depending on the diameter of the network pipeline.
Keywords : heating networks, hydraulic calculation, local loss coefficient
When hydraulically calculating heating networks, it becomes necessary to set a coefficient α , taking into account the share of pressure losses in local resistances. In modern standards, the implementation of which is mandatory during design, there is no mention of the standard method of hydraulic calculation and specifically the coefficient α. 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 expansion joints
Conditional diameter of the pipeline, mm
Branched heating networks
U-shaped with bent bends
U-shaped with welded or steeply 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. An increase in value can be observed with increasing pipeline diameter.
In the literature, for preliminary calculations, when pipe diameters are not known, the share of pressure losses in local resistances is recommended to be determined using the formula of B. L. Shifrinson
Where z- coefficient accepted for water networks is 0.01; G- water consumption, t/h.
The results of calculations using formula (1) at different water flow rates in the network are presented in Fig. 1.
Rice. 1. Addiction α from water consumption
From Fig. 1 it follows that the value α at high flow rates it can be more than 1, and at small flow rates it can be less than 0.1. For example, at a flow rate of 50 t/h, α=0.071.
The literature provides an expression for the local loss coefficient
where is the equivalent length of the section and its length, respectively, m; - the sum of the local resistance coefficients on the site; λ - coefficient of hydraulic friction.
When designing water heating networks under turbulent movement conditions, to find λ , use the Shifrinson formula. Taking the equivalent roughness value 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 meaning α increases with decreasing section length and increasing diameter.
In order to determine the actual local loss coefficients α , existing projects of water heating networks of industrial enterprises for various purposes were reviewed. Having hydraulic calculation forms available, the coefficient was determined for each section α according to formula (2). Weighted average values of the local loss coefficient for each network were found separately for the main line and branches. In Fig. 2 shows the calculation results α along calculated highways for a sample of 10 network diagrams, and in Fig. 3 for branches.
Rice. 2. Actual values α along designated 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, the following conclusions can be drawn. According to table. 1 for the considered schemes value α =0.3 for mains and α=0.3÷0.4 for branches, and the actual averages are 0.19 and 0.231, which is slightly less than the recommended ones. Actual value range α does not exceed the recommended values, i.e. the table 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 local loss coefficients α
From the analysis of Table 2 it follows that with an increase in pipeline diameter, 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:
In Fig. Figure 4 presents the results of calculations using 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, averaged values of local loss coefficients 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 have been obtained that make it possible to calculate the local loss coefficient depending on the diameter of the network pipeline for mains and branches.
- Kopko, V. M. Heat supply: a course of lectures for students of specialty 1–700402 “Heat and gas supply, ventilation and air protection” of higher educational institutions / V. M. Kopko. - M: Publishing House ASV, 2012. - 336 p.
- Water heating networks: Design reference guide / N. K. Gromov [et al.]. - M.: Energoatomizdat, 1988. - 376 p.
- Kozin, V. E. Heat supply: a textbook for university students / V. E. Kozin. - M.: Higher. school, 1980. - 408 p.
- Pustovalov, A.P. Increasing the energy efficiency of engineering systems of buildings through the optimal selection of control valves / A.P. Pustovalov, D.N. Kitaev, T.V. Shchukina // Scientific Bulletin of the Voronezh State University of Architecture and Civil Engineering. Series: High technologies. Ecology. - 2015. - No. 1. - P. 187–191.
- 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). - P. 78–83.
- Kitaev, D. N. The influence of modern heating devices on the regulation of heating networks / D. N. Kitaev // Scientific journal. Engineering systems and structures. - 2014. - T.2. - No. 4(17). - pp. 49–55.
- Kitaev, D. N. Variant design of heat supply systems taking into account the reliability of the heating network / D. N. Kitaev, S. G. Bulygina, M. A. Slepokurova // Young scientist. - 2010. - No. 7. - P. 46–48. What laws did Vladimir Putin sign on the last day of the outgoing year? By the end of the year, a bunch of things always accumulate that you want to complete before the chimes strike. Well, so as not to drag old debts into the New Year. State Duma […]
- Organization FGKU "GC VVE" Ministry of Defense of Russia Legal address: 105229, MOSCOW, GOSPITALNAYA PL, 1-3, PAGE 5 OKFS: 12 - Federal property OKOGU: 1313500 - Ministry of Defense of the Russian Federation […]
Energy is the main product that man has learned to create. It is necessary both for everyday life and for industrial enterprises. In this article we will talk about the norms and rules for the design and construction of external heating networks.
What is a heating network
This is a set of pipelines and devices that reproduce, transport, store, regulate and provide all power supply points with heat through hot water or steam. From the energy source it enters the transmission lines and is then distributed throughout the premises.
What is included in the design:
- pipes that undergo pre-treatment against corrosion and are also subject to insulation - the sheathing may not be along the entire route, but only in the area that is located on the street;
- compensators - devices that are responsible for movement, temperature deformation, vibration and displacement of the substance inside the pipeline;
- fastening system - depending on the type of installation, there are different options, but in any case, support mechanisms are required;
- trenches for laying - concrete gutters and tunnels are equipped if laying takes place above ground;
- shut-off or control valves - temporarily stops the pressure or helps to reduce it, blocking the flow.
Also, the building’s heat supply project may contain additional equipment within the heating and hot water supply engineering system. So the design is divided into two parts - external and internal heating networks. The first can come from the central main pipelines, or maybe from a heating unit or boiler room. There are also systems inside the premises that regulate the amount of heat in individual rooms, workshops - if the issue concerns industrial enterprises.
Classification of heating networks according to basic characteristics and basic design methods
There are several criteria by which the system can differ. This includes the method of their placement, their purpose, the area of heat supply, their power, as well as many additional functions. At the time of designing a heat supply system, the designer must find out from the customer how much energy the line must transport daily, how many outlets it has, what operating conditions will be - climatic, meteorological, and also how not to spoil the urban development.
According to these data, you can choose one of the types of gasket. Let's look at the classifications.
By type of installation
There are:
- Airborne, they are also aboveground.
This solution is not used very often due to the difficulties of installation, maintenance, repair, and also because of the unsightly appearance of such bridges. Unfortunately, the project usually does not include decorative elements. This is due to the fact that boxes and other camouflage structures often prevent access to pipes and also prevent timely detection of a problem, such as a leak or crack.
The decision to design air heating networks is made after engineering surveys to examine areas with seismic activity, as well as high groundwater levels. In such cases, it is not possible to dig trenches and conduct above-ground installation, as this can be unproductive - natural conditions can damage the casing, humidity will affect accelerated corrosion, and soil mobility will lead to pipe breaks.
Another recommendation for carrying out above-ground structures is in dense residential areas, when it is simply not possible to dig holes, or in the case when one or more lines of existing communications already exist in this place. When carrying out earthworks in this case, there is a high risk of damaging the city's engineering systems.
Air heating networks are mounted on metal supports and poles, where they are attached to hoops.
- Underground.
They are, accordingly, laid underground or on it. There are two options for the design of a heat supply system - when installation is carried out in a duct way and in a non-duct way.
In the first case, a concrete channel or tunnel is laid. The concrete is reinforced, and pre-prepared rings can be used. This protects the pipes, the windings, and also makes inspection and maintenance easier by keeping the entire system clean and dry. Protection occurs simultaneously from moisture, groundwater and flooding, as well as from corrosion. These precautions also help prevent mechanical impact on the line. Channels can be monolithic poured with concrete or prefabricated, their second name is trough.
The channelless method is less preferable, but it takes much less time, labor costs and material resources. This is a cost-effective method, but the pipes themselves are not ordinary, but special ones - with or without a protective shell, but then the material must be made of polyvinyl chloride or with its addition. The process of repair and installation becomes more difficult if it is planned to reconstruct the network or expand the heating network, since it will be necessary to carry out excavation work again.
By coolant type
Two elements can be transported:
- Hot water.
It transmits thermal energy and can simultaneously serve for water supply purposes. The peculiarity is that such pipelines cannot be laid alone, even main ones. They must be carried out in multiples of two. Typically these are two-pipe and four-pipe systems. This requirement is due to the fact that not only the supply of liquid is needed, but also its removal. Usually the cold flow (return) returns to the heating point. In the boiler room, secondary processing occurs - filtration, and then heating of the water.
These are more difficult to design heating networks - an example of their standard design contains conditions for protecting pipes from super-hot temperatures. The fact is that the vapor carrier is much hotter than the liquid. This gives increased efficiency, but contributes to deformation of the pipeline and its walls. This can be prevented by using high-quality building materials and regularly monitoring possible changes in pressure pressure.
Another dangerous phenomenon is the formation of condensation on the walls. It is necessary to make a winding that will remove moisture.
Danger also lurks due to possible injuries during maintenance and breakthrough. Steam burns are very strong, and since the substance is transmitted under pressure, it can lead to significant damage to the skin.
According to design schemes
This classification can also be called by meaning. The following objects are distinguished:
- Trunk.
They have only one function - transportation over long distances. Typically this is the transfer of energy from the source, the boiler house, to the distribution nodes. There may be heating points here that deal with the branching of routes. The mains have powerful indicators - content temperature is up to 150 degrees, pipe diameter is up to 102 cm.
- Distribution.
These are smaller lines whose purpose is to deliver hot water or steam to residential buildings and industrial plants. They can be different in cross-section; it is chosen depending on the energy flow per day. For apartment buildings and factories, the maximum values are usually used - they do not exceed 52.5 cm in diameter. While for private properties, residents usually have a small pipeline installed that can satisfy their heating needs. The temperature usually does not exceed 110 degrees.
- Quarterly.
This is a subtype of distribution. They have the same technical characteristics, but serve the purpose of distributing the substance throughout the buildings of one residential area or block.
- Branches.
They are designed to connect the main line and the heating point.
By heat source
There are:
- Centralized.
The starting point of heat transfer is a large heating station that supplies the entire city or most of it. These can be thermal power plants, large boiler houses, nuclear power plants.
- Decentralized.
They are engaged in transportation from small sources - autonomous heating stations, which can only supply a small residential building, one apartment building, or a specific industrial production. Autonomous power supplies, as a rule, do not require sections of highways, since they are located next to the object or structure.
Stages of drawing up a heating network project
- Collection of initial data.
The customer provides the technical specifications to the designer and, independently or through third-party organizations, compiles a list of information that will be needed in the work. This is the amount of heat energy required per year and daily, the designation of power points, as well as operating conditions. Here you may also find preferences for the maximum cost of all work and the materials used. First of all, the order must indicate why the heating network is needed - residential premises, production.
- Engineering survey.
The work is carried out both on site and in laboratories. The engineer then completes the reports. The inspection system includes soil, soil properties, groundwater levels, as well as climatic and meteorological conditions, and seismic characteristics of the area. To work and prepare reports, you will need the + + link. These programs will ensure automation of the entire process, as well as compliance with all norms and standards.
- Engineering system design.
At this stage, drawings and diagrams of individual components are drawn up, and calculations are performed. A real designer always uses high-quality software, for example, . The software is designed to work with utility networks. With its help, it is convenient to trace, create wells, indicate the intersections of lines, as well as mark the cross-section of the pipeline and make additional marks.
The regulatory documents that guide the designer are SNiP 41-02-2003 “Heat networks” and SNiP 41-03-2003 “Thermal insulation of equipment and devices”.
At the same stage, construction and design documentation is drawn up. To comply with all the rules of GOST, SP and SNiP, you must use the program or. They automate the process of filling out papers according to legal standards.
- Project approval.
First, the layout is offered to the customer. At this point it is convenient to use the 3D visualization function. The three-dimensional model of the pipeline is clearer; it shows all the nodes that are not visible in the drawing to a person who is not familiar with the rules of drawing. And for professionals, a three-dimensional layout is necessary to make adjustments and provide for unwanted intersections. The program has this function. It is convenient to draw up all working and design documentation, draw and perform basic calculations using the built-in calculator.
Then approval must take place in a number of instances of the city government, as well as undergo an expert assessment by an independent representative. It is convenient to use the electronic document management function. This is especially true when the customer and the contractor are in different cities. All ZVSOFT products interact with common engineering, text and graphic formats, so the design team can use this software to process data obtained from various sources.
Composition of a typical heating network design and example of heating mains
The main elements of the pipeline are mainly produced by manufacturers in finished form, so all that remains is to correctly position and install them.
Let's look at the contents of the parts using the example of a classical system:
- Pipes. We examined their diameter above in connection with the typology of structures. And the length has standard parameters - 6 and 12 meters. You can order individual cutting at the factory, but it will cost much more.
It is important to use new products. It is better to use those that are produced immediately with insulation. - Connection elements. These are knees at an angle of 90, 75, 60, 45 degrees. This group also includes: bends, tees, transitions and pipe end caps.
- Shut-off valves. Its purpose is to shut off the water. Locks may be located in special boxes.
- Compensator. It is required on all corners of the track. They relieve pressure-related processes of expansion and deformation of the pipeline.
Make a heating network project with high quality together with software products from ZVSOFT.
Competent and high-quality work is one of the main conditions for the rapid commissioning of a facility.
Heating network designed to transport heat from heat sources to consumers. Heat networks belong to linear structures and are one of the most complex engineering networks. The design of networks must necessarily include calculations for strength and temperature deformation. 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 the heating network should be the architectural and construction part (AC) and reinforced concrete or metal structures (KZh, KM), in which fasteners, channels, supports or overpass are developed (depending on the installation method).
Heat networks are divided according to the following characteristics
1. According to the nature of the transported coolant:
2. According to the method of laying heating networks:
- duct heating networks. The design of duct heating networks is carried out if it is necessary to protect pipelines from the mechanical influence of soil and the corrosive influence of soil. Channel walls facilitate the operation of pipelines, therefore the design of channel heating networks is used for coolants with pressures up to 2.2 MPa and temperatures up to 350°C. - channelless. When designing a channelless installation, pipelines operate under more difficult conditions, since they take up additional soil load and, with unsatisfactory protection from moisture, are susceptible to external corrosion. In this regard, the design of networks in this way of installation is provided for at a coolant temperature of up to 180°C.
- air (above ground) heating networks. Design of networks using this method of installation is most widespread in the territories of industrial enterprises and in areas free of buildings. The above-ground method is also designed in areas with high groundwater levels and when laying in areas with very rough terrain.
3. In relation to diagrams, heating networks can be:
- main heating networks. Heat networks, always transit, transporting coolant from the heat source to distribution heat networks without branches;
- distribution (quarter) heating networks. Heating networks that distribute coolant throughout a designated quarter, supplying coolant to branches to consumers.;
- branches from distribution heating networks to individual buildings and structures. The separation of heating networks is established by the project or operating organization.
Comprehensive network design in accordance with project documentation
STC Energoservice carries out complex work on, including city highways, intra-block distribution and intra-house networks. The design of networks of the linear part of heating mains is carried out using both standard and individual nodes.
A high-quality calculation of heating networks makes it possible to compensate for thermal elongations of pipelines due to the angles of rotation of the route and to check the correctness of the planned and height position of the route, the installation of bellows expansion joints and fastening with fixed supports.
Thermal elongation of heat pipes during ductless installation is compensated by the angles of rotation of the route, which form self-compensating sections of the P, G, Z-shape, installation of starting compensators, and fastening with fixed supports. At the same time, at the corners of turns, between the trench wall and the pipeline, special pillows made of foamed polyethylene (mats) are installed, which ensure the free movement of pipes during their thermal elongation.
All documentation for design of heating 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 “Heating networks” (heating networks enterprise);
- GOST 21-605-82 “Heating networks (thermomechanical part)”;
- Rules for the preparation and execution of excavation work, arrangement and maintenance of construction sites in the city of Moscow, approved by Decree of the Moscow Government No. 857-PP dated December 7, 2004.
- PB 10-573-03 “Rules for the design and safe operation of steam and hot water pipelines.”
Depending on the conditions of the construction site, network design may involve the reconstruction of existing underground structures that interfere with construction. The design of heating networks and the implementation of projects involves working with the use of two insulated steel pipelines (supply and return) in special prefabricated or monolithic channels (through and non-through). To accommodate disconnecting devices, vents, vents and other fittings, the design of heating 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. When designing heating networks, our company’s specialists use the most modern methods, which allows us to guarantee good results and durable operation of all equipment.
When implementing, it is necessary to rely on many technical standards, violation of which can lead to the most negative consequences. We guarantee compliance with all rules and regulations regulated by various technical documentation described above.
