EA037492B1 - Method for reducing heat losses and capital costs for pipelines of heat distribution network - Google Patents

Abstract

The invention relates to the field of construction and power engineering and is intended to reduce capital costs during construction, operation of a heat network, as well as to reduce heat losses during transportation of heat energy. The objective of the invention is to optimize heat networks and transport the heat carrier with minimum heat losses from a heat source to a consumer, as well as to reduce the construction and operating costs of heat networks. The technical result of the invention is to reduce the amount of heat loss in the pipelines of a heat network. Not considered separately for trunk lines and separately for distribution networks. The specified objective and technical result are achieved by the method of reducing heat losses of a heat transfer pipeline of a distribution heat network, in which the supply pipeline and the return pipeline of a heat network are replaced with a pipeline of a smaller diameter, the speed of movement of the heat carrier is increased, and the excessive pressure is suppressed by automation or a choke. At the same time, to select the optimum diameter of the pipeline, the permissible pressure loss in the pipeline of a distribution heat network is calculated using the formula: dHloss = dHnet - dHnode, where: dHnet is the available pressure on the main at the point of connection of the distribution heating network; dHnode is the required sufficient available head at a consumer of a heat network. The estimated pressure losses are calculated by the formula: dP = (dh*ke*B*L)/1000, in meters, where: dh is hydraulic losses at the estimated flow rate of the heating medium, kgf/m2*m; ke is the actual coefficient of the pipeline roughness, mm; B is a correction factor for local resistance of the pipeline; L is the total length of the heat network pipeline, m; 1000 is the conversion factor, mm in m, the residual chocked head pressure for suppression at the pipeline node is calculated according to the formula dPnode = dHnet - dHnode - dP, m, and then the estimated pressure loss dP in the supply and return pipelines, which should not be more than dHloss, m to confirm the optimality of the selected pipeline diameter.

Description

The invention relates to the field of construction and energy and is intended to reduce capital costs during construction, operation of a heating network, as well as to reduce heat losses during transportation of thermal energy.

State of the art

The construction of heating networks is a rather costly component of the heat supply system of any settlement with centralized heat supply (CHP, ROK) - licensing, design, land allotments, approvals, the cost of a pre-insulated pipe, transportation, development of trenches, preparation of the bottom for laying pipes, checking welds, insulation of welded joints, installation of supports, expansion joints, density tests, specialized equipment, fuels and lubricants, garages, equipment maintenance, trained human resources, salary, etc.). These are capital costs.

The operation of the heating network, that is, maintaining it in working order constantly is one of the serious costs on the scale of the heated city (materials for installation, transportation, specialized equipment, fuels and lubricants, garages, maintenance of equipment, trained human resources, salary, etc. .). These are recurring costs.

One of the significant costs is the cost of the district heating pipes used, their installation and operation.

Transportation of heat energy is a constant issue of reducing the amount of heat losses in heat networks, which are divided into main and distribution networks. At the current stage of heat supply development, the most advanced solution is the use of a pipe with pre-insulation made of polyurethane foam, which has heat losses significantly less than other types of insulation (with a price-quality ratio).

At the moment, there are no proposals to reduce the magnitude of heat losses, except for increasing the thickness of the insulation. Such examples can be document RU 2189521, which discloses a method of heat and waterproofing of a pipe, which consists in installing it in a waterproof polyethylene shell, sealing the shell and applying a liquid thermal insulation composition to the pipe, foaming and hardening it, and the inner surface of the polyethylene shell is treated with an electric spark discharge voltage of 28000 V during extrusion, and the outer surface of the steel pipe is shot blasting with the required roughness.

Also from the document RU 2325590 there is known a method for regulating the flow of water and simultaneously reducing noise during the operation of a heat and water-collecting point, equipped mainly with an automated metering unit, which consists in the fact that the water flow is passed through a set of axisymmetric local resistances that is stepwise reduced at the input and stepwise increased at the output through the pipeline diameter reduced on the calculated length located between them.

An increase in the thickness of the thermal insulation layer causes an increase in the cost of the pipe, as well as the costs for the width of the trench, and other related work and materials, both during construction and during maintenance, increase.

The essence of the invention

The objective of the invention is to optimize heating networks and transport the heat carrier with minimal heat losses from the heat source to the consumer, as well as to reduce the construction and operating costs of heating networks.

The technical result of the invention is to reduce the amount of heat loss in the pipelines of the heating network. Not considered separately for trunk lines and separately for distribution networks.

This task and the technical result is achieved by a method of reducing heat losses of the heat transfer pipeline of the distribution heating network, in which the supply pipeline and the return pipeline of the heating network are replaced with a pipeline of a smaller diameter, while the speed of movement of the coolant increases, the remaining excess pressure is extinguished by automation or a choke. At the same time, to select the optimal diameter of the pipeline, the permissible value of pressure losses in the pipeline of the distribution heating network is calculated using the formula:

dHloss = dHnetwork-dHnode, where dHnetwork is the available head on the main at the point of connection of the distribution heating network, m;

dH node is the required sufficient available head at the consumer of the heating network, m;

dH loss - calculate the calculated pressure loss using the formula:

dP = (dh · ke · V · L) / 1000, in meters, where dh - hydraulic losses at the design flow rate of the heating medium, kgf / m ² -m;

ke is the actual coefficient of pipeline roughness, mm;

B - correction factor for local resistance of the pipeline;

L is the total length of the heating network pipeline, m;

1000 - conversion factor, mm in m,

- 1 037492 calculate the limiting throttled head for extinguishing by automation or a throttle at the pipeline node according to the formula dPnode = dHnetwork-dHnode-dP, m, and then the calculated pressure loss dP in the supply and return pipelines is subtracted from the permissible pressure loss in the pipeline of the distribution heating network dHnoTepb , which should be no more than dHloss, m, to confirm the optimality of the selected pipeline diameter.

According to the Rules for the technical operation of power plants and networks, approved by order of the Minister of Energy of the Republic of Kazakhstan dated March 30, 2015 No. 247, section 2 Organization of operation, paragraph 5 Control over the efficiency of the operation of energy enterprises, paragraph 38 states: In heat networks, energy characteristics are compiled according to the following indicators:

1) heat losses;

2) specific consumption of electricity for the transport of heat energy;

3) specific average hourly consumption of network water;

4) the temperature difference in the supply and return pipelines;

5) leakage of network water.

Heat losses are the first energy characteristic of a heating network.

The requirement to control the magnitude of heat losses and their reduction is a constant ongoing work of both the current standards and designers, experts, installers, and operators.

During the transfer of heat energy, the system is switched on: source - heat networks - consumer. The end result of the operation of this system is the provision of the necessary (contractual) amount of heat energy to each consumer with the required temperature of the heating coolant in the supply pipeline.

The very understanding of heat, as one of the lowest forms of energy, in heat supply is described by the formula: Q = G-dT-c, where

Q is the amount of heat energy, Mcal / h;

G — consumption of the heating medium, t / h;

dT is the temperature difference between the supplied and removed coolant, C;

с - heat capacity of the coolant, kcal / kg.

The criterion for the quality of hydraulic and temperature regimes of heat supply is according to the document Rules for the technical operation of power plants and networks, approved by order of the Minister of Energy of the Republic of Kazakhstan dated March 30, 2015, section 6 Thermal mechanical equipment of power plants and heating networks, paragraph 19 Station heating installations, paragraph 579: Deviations from the specified mode behind the head valve of the power plant is provided at a level not exceeding: by the temperature of the water entering the heating network, ± 3%; by pressure in the supply pipeline of water entering the heating network, ± 5%, by pressure in the return pipeline ± 0.2 kgf / cm ² (± 20 kPa). The task of the source is to generate heat energy, heat networks - transportation with minimal heat losses from the heat source to the consumer.

Heating networks are divided into main (main, with large diameters) and distribution (intra-quarter, with smaller diameters). When transporting the coolant through the pipelines of the heating network, hydraulic losses appear (pressure losses due to friction). According to the designer's handbook Design of heating networks, Moscow, 1965 (which is the reference book of the designer of heating networks), chapter 9 Hydraulic calculations of pipelines, paragraph 9.1. Basic provisions, the throughput of heating networks for average conditions of coolant transport can be determined from Table 9.1. - The throughput of pipelines of water heating networks (with an equivalent roughness coefficient ke = 0.5 mm, specific gravity of water y = 958.4 kg / m ³ ). The maximum throughput of various diameters of pipelines is determined for pressure losses in dH = 5, 10, 15, 20 kgf / m ² -m. The speed of water movement is not considered in this case. Only hydraulic losses are taken into account.

According to paragraph 9.2. The main calculation formulas for friction pressure loss are determined by the formula: dHtr = dh · L, kgf / m ² , where dh is the specific friction loss, kgf / m ² -m;

L is the length of the pipeline section, m.

That is, the main factor in the operation of the heating network is the friction pressure loss (both linear and local).

The principal difference of thermal networks of pipelines of different functions allowable pressure loss in kg / m ² -m 1 m tube running at rated roughness factor of 0.5 mm (for steel pipes). Ke is the roughness coefficient of steel pipelines, and its value has not changed over the past 50 years - in all regulatory documents and technical literature it is equal to 0.5 mm, or 0.0005 m.

According to paragraph 9.4. Hydraulic calculation of pipelines of water heating networks, p. 132, in hydraulic calculations of water heating networks, the specific pressure loss due to friction in the pipe

- 2 037492 waters are recommended to take:

1) for sections of the calculated pipeline from the heat source to the most distant consumer - up to 8 kgf / m-m.

2) for a branch from the design line - according to the available pressure drop, but not more than 30 kgf / m ² -m.

If, at the assumed specific pressure losses due to friction, the excess pressure drop across the branches from the mains is not fully used, the remaining differential is used at the inputs to consumers in the elevators or throttled with washers.

According to the norms of SNiP II-36-73 Heating networks, paragraph 7 Hydraulic calculations and modes of heating networks, paragraph 7.10. It reads: Specific frictional pressure loss during hydraulic calculations water heat networks should be taken: a) to heat portions of water from the source network to the furthest consumer - 8 kgf / m ² -m; b) for other sections of water heating networks according to the available pressure drop, but not more than 30 kgf / m ² -m. In this case, the water velocity should not exceed 3.5 m / s.

According to the norms of SNiP 2-04.07-86 Heating networks, paragraph 5 Hydraulic calculations and modes of heating networks, paragraph 5.8. states: Specific frictional pressure losses in hydraulic calculations of water heating networks should be determined on the basis of technical and economic calculations. The value of the specific pressure loss for calculating the existing heating networks is allowed to be taken on the basis of the test results.

According to the norms of SNiP 2-04.07-86 Heating networks, paragraph 5 Hydraulic calculations and modes of heating networks, paragraph 5.8. states: Specific frictional pressure losses in hydraulic calculations of water heating networks should be determined on the basis of technical and economic calculations. The value of the specific pressure loss for calculating the existing heating networks is allowed to be taken on the basis of the test results.

In MSN 4.02-02-2006 Heat networks, paragraph 8 Hydraulic modes, the magnitude of pressure losses in heat networks is not considered.

In SP RK 4.02-104-2013 Heat networks, paragraph 4.7. Design, section 4.7.3. He does not consider hydraulic modes of pressure losses in heating networks.

In SP RK 4.02-04-2013 Heating networks, paragraph 5. Requirements for performance, section 5.4. Requirements for the design of heating networks and structures on heating networks does not consider the magnitude of pressure losses in heating networks.

Over time, the values of permissible hydraulic losses in the norms for the design of heating networks have changed - from clearly indicated to amorphous, or none at all.

Excessive pressure in heating networks is extinguished at heating units by throttle bodies (nozzles, washers).

The question arises about the efficiency of the joint operation of network pumps that develop pressure, which, in case of its excess, is simply extinguished at the heating units, and the operation of the heating network, designed and operated under these conditions.

It is necessary to consider a more rational use of the excess pressure from the heating network wasted at heating nodes.

The noise level in the pipelines of the heating network is not considered anywhere; according to the Instructions for the operation of heating networks, Moscow, 1972, chapter IX Adjustment of water systems of district heating, paragraph 4 Hydraulic regime of the water heating network, the speed of water movement in pipelines of the heating network is not considered. Only a correction factor is introduced, which is applied when the value of the equivalent roughness is different ke = 0.5 mm. During operation, this value can change upwards - heating networks regularly test pipelines for actual roughness - and reach the value ke = 2.0-5.0-7.0 mm.

According to SNiP 4.02-42-2006 Heating, ventilation and air conditioning, paragraph 7.4., Clause 7.4.4. reads: The speed of movement of the coolant in the pipes of water heating systems should be taken depending on the permissible equivalent sound level in the room above 40 dBA: in rooms for various purposes - from 1.5 m / m to 3.0 m / s. With the open method of laying pipes of the heating system in rooms, the speed of movement of the coolant is allowed to be almost the same as the maximum in pipelines of the heating network, insulated and laid, as a rule, by an underground method. The use of a higher speed of movement of the coolant in pipelines of a heating network does not pose a danger from the point of view of noise acoustics.

When designing the heating network, the existing range of pipelines was taken, which has not changed over the past 50 years - steel pipes of a certain diameter. The priority for the selection of the calculated diameter of the pipeline was the throughput, determined in tons of water per hour, determined when coordinating the projects of heating networks by local operating conditions, taking into account the pressure losses allowed by the organization transporting heat energy. Thus, the actual pressure loss in the pipelines, on average, was taken equal to 4-6-9 kgf / m ² -mm, as

- 3 037492 in the main and distribution heating networks. This is much less than that allowed in the heat distribution networks - 30 kgf / m ² -m. A decrease in the speed of movement of the coolant by an average of 2 times from the permissible caused increased heat losses in pipelines.

The design standards for permissible pressure losses in heating networks proceeded from the presence of automatic control systems at heating units - differential pressure (flow) regulators and direct-acting temperature regulators (produced in the USSR), which had a low tuning accuracy (error up to 30%) and a fairly high cost compared to the cost of heat energy in the same period of time. There was practically no automation of heat points in the USSR. The external enclosing structures of the building had a significant thermal inertia in comparison with modern ones, which have various insulation materials. The release of heat energy was carried out from the source with the correction of the temperature of the direct heating water 2 times a day, which corresponded to the thermal inertia of the building and the design conditions for the design of heating systems.

In fact, in the absence of automation in thermal units and nevyderzhivaniem temperature chart on the source of the design and coordination of heating networks projects carried out by the minimum acceptable pressure losses - up to 10 kg / m ² th - to be able to compensate for the missing temperature heating medium flow rate increased heating medium. This requirement has extended to both intra-quarter networks and heating units. The result is that heat losses in networks have always been increased due to an artificial decrease in the speed of movement of the coolant.

The amount of heat losses is determined by calculation by the power transmission organization in accordance with the guidelines for compiling energy characteristics RD 153-34 RK.0-20.52302, part II (Guidelines for compiling the energy characteristics of water heating networks in terms of heat losses), where it is indicated that heat losses depend on the type of heat-insulating structure and used heat-insulating materials;

types of laying (ground, underground duct, channelless, in the basement, indoors); temperature regime of heating systems;

environmental parameters: ambient air temperature, soil.

The speed of water movement is not considered in principle in the current regulations. In principle, it can be imagined that during the instant transportation of the heating medium from the source to the consumer, the water does not have time to cool down with any type of insulation, type of gasket, temperature regime, and outside air temperature. Therefore, you should pay attention to the speed of movement of water in the heating network.

When transporting thermal energy from the source to the consumer, the main task is to ensure the necessary pressure at the heating units, taking into account the pressure losses in the main and distribution heating networks at the estimated consumption of the heating coolant. For this, in preparation for the heating season, a hydraulic calculation of the heating network is performed annually to determine the required dimensions of throttling devices (nozzles, washers) and is constantly corrected during the heating season when new constructed facilities are connected. A necessary requirement of the hydraulic calculation is to ensure the available pressure at each heat input for consumers. According to SN RK 4.02-04-2013 Heating networks, paragraph 5.4.4 Hydraulic modes, paragraph 5.4.4.15., Part f): When determining the pressure of network pumps, the pressure difference at the input of two-pipe water heating networks into buildings (with elevator connection of heating systems) should be taken equal to the calculated pressure loss at the inlet and in the local system with a factor of 1.5, but not less than 0.15 MPa. It is necessary to extinguish the excess pressure in the heating points of buildings. This value ensures the normal operation of both dependent elevator systems for connecting to heating networks, and independent automated connection schemes, the installation of which at heating units is the current SNiP standards. Excessive pressure is extinguished in the throttle bodies. Applied, in particular, in Astana, the method of selection of automation at automated heating units allows you to obtain the required amount of heat with an available head of only 10 m.

When performing a hydraulic calculation of a heating network, the calculated available heads at the inputs of consumers located at the minimum and maximum distance from the source, or the pumping station, have different values. The ones located closer can be from 60 to 45 m, remote from 25 to the required 15 m.Excessive pressure available at the inputs must be extinguished by automatic pressure regulators in the presence of automation, in its absence, throttling (extinguishing of excess pressure) occurs in the regulating body (nozzle, washer).

In the previously developed norms SNiP 2.04.07-86 Heating networks, SNiP 2.2.04.07-86 * Heating networks, MSN 4.02-02-2004 Heating networks currently operating SP RK 4.02-104-2013 Heating networks, SN RK 4.02- 04-2013 Heating networks, the speed of movement of the coolant was not standardized and is not standardized (except for the 1973 standards). The actual speed of water movement is the result of a pipe of a certain diameter adopted by the project with permissible hydraulic losses.

In the previously developed norms SNiP II-36-73 Heating networks, paragraph 7 Hydraulic calculations and modes of heating networks, paragraph 7.10. read: Diameters of the supply and return pipelines

- 4 037492 two-pipe water heating networks with joint heat supply for heating, ventilation and hot water supply should be assumed to be the same.

In SNiP 2.04.07-86 Heating networks, paragraph 5 Hydraulic calculations and modes of heating networks, paragraph 5.9. read: The diameters of the supply and return pipelines of two-pipe water heating networks with joint heat supply for heating, ventilation and hot water supply should be taken, as a rule, to be the same.

In SNiP 2.2.04.07-86 * Heating networks, paragraph 9 Hydraulic calculations and modes of heating networks, paragraph 5.9. read: The diameters of the supply and return pipelines of two-pipe water heating networks with joint heat supply for heating, ventilation and hot water supply should be taken, as a rule, to be the same.

MSN 4.02-02-2004 Heating networks, paragraph 8 Hydraulic modes, paragraph 8.5. read: The diameters of the supply and return pipelines of two-pipe water heating networks with joint heat supply for heating, ventilation and hot water supply are recommended to be the same.

In the currently operating SN RK 4.02-04-2013 Heating networks, paragraph 5 Performance requirements, section 5.4 Requirements for the design of heating networks and structures on heating networks, subsection 5.4.4. Hydraulic modes, clause 5.4.4.5 reads: The diameters of the supply and return pipelines of two-pipe water heating networks with the joint supply of heat for heating, ventilation and hot water supply are assumed to be the same.

SP RK 4.02-104-2013 Heating networks does not consider this issue. The requirements for the diameters of heating networks are constantly changing over time. They are considered either unambiguously, then as a rule, sometimes recommended, then again unambiguously. There is simply no clear decision on this issue. Here it is possible to consider the existing regulation from the point of view of energy saving. With a feasibility study, it is possible to reduce the diameters of pipelines in the distribution heating network.

According to SNiP 2.04.14-88 Thermal insulation of equipment and pipelines, SP 41-103-2000 Design of thermal insulation of equipment and pipelines, MSN 4.02-03-2004 Thermal insulation of equipment and pipelines, SN RK 4.02-03-2011 Design of thermal insulation of equipment and pipelines any dependence of heat losses through insulation when changing the speed of water movement in pipelines of the heating network is not considered anywhere.

Thus, part of the energy generated by the network pumps is spent on suppressing the pressure in the regulating bodies of the heating unit (with overestimated pipe diameters, in which pressure losses are minimal), that is, it is wasted.

The priority in the design of pipelines has always been the permissible value of hydraulic losses in heating networks (main, distribution) with the provision of the required available pressure at the end heating unit of the consumer.

The accuracy of hydraulic calculations depends on the length, the condition of the pipelines of the heating network (actual roughness), which increases during operation, and the correctness of the contractual loads of consumers connected to the heating networks. Having such data (tests for the actual roughness of pipelines are carried out by heating networks regularly according to the PTE), it is not difficult to perform a hydraulic calculation with drawing up a piezometric graph (pressure graph at each point of the heating network) (there are specialized programs).

Note that the temperature schedule of heat energy supply is the relationship between heat and hydraulic losses in the heat network. With a decrease in hydraulic losses in pipelines, heat losses increase, due to this, the speed of the heating coolant decreases. Literally the water goes on foot. Thus, the increased speed of water movement in the pipelines of the heating network leads to a decrease in heat losses.

There is no clearly standardized value for permissible heat losses. According to the recommendations of the technical literature (Heating and heating networks, Sokolov E.Ya, Moscow, 1975), the average annual losses in urban heating networks are on average 4-8% of the heat supplied from the station (p. 51), with a satisfactory state of heating networks the value heat losses are about 5% of the annual supply of gepla (p. 287). This figure in monetary terms is quite large.

Reducing the amount of heat losses from actual ones without increasing costs or with reducing them at all necessary stages - from design to operation - is the rational use of energy resources, that is, energy efficiency.

The magnitude of heat losses in pipelines of a heating network is not considered separately for mains and separately for distribution networks.

For a more complete understanding of the meaning of the resulting savings in heat loss, one can consider the ratio of the flow rate of the heating coolant in the pipeline of the heating network to the circumference of the pipeline and the thickness of the insulation of this pipeline. Heat loss occurs through the pipe wall and the thermal insulation layer. Let us consider the ratio at the maximum design flow rate of the heating medium with hydraulic losses of 10 mm per 1 m of the pipe stroke (maximum throughput) and the circumference of the pipe wall of the heating network of the existing assortment (distribution heat

- 5 037492 out networks). The data are summarized in the following table.

DN, mm Ohm, tons / hour Circumference Ratio

pipes, mm, C = n * Ostenki pipes with flow rate, k = L / G. 32 1.16 100.48 86.62 40 1.94 125,60 64.74 fifty 3.50 157.00 44.86 70 8.40 219.80 26.17 80 13.20 251.20 19.03 100 22.00 314.00 14.27 125 40,00 392.50 8.24 150 64.00 471.00 7.36 200 152,00 628,00 4.13 250 275,00 785,00 2.85 300 430,00 942,00 2.19

Based on the data obtained, it is clearly seen that the largest specific heat losses will be in pipes of a smaller diameter, which are just the most used in distribution heating networks. The larger the pipe diameter, the lower the specific heat losses (due to the higher flow rate of the heating coolant).

In addition, we note that according to the Instructions for the operation of heating networks, Moscow, 1972, p. 203 - The method of testing heating networks for the design temperature of the coolant (that is, the quality of the state of the insulation of pipelines), clause 1 says: Heating networks are usually tested with a pipe diameter of 100 mm and above. Pipelines of distribution heating networks with diameters of 2D 40 mm, 2D 50 mm, 2D 70 mm, 2D 80 mm, which actually have the most significant specific heat losses, are not tested in principle.

Taking into account the thicknesses of polyurethane foam insulation available from the manufacturer (for example, the Almaty plant of insulated pipes AlmaZIT), shown in table. 1, it can be seen that the thickness of the insulation for the DN 50 mm pipe and the DN 300 mm pipe is 38.5 and 79.5 mm, respectively. The insulation layer of polyurethane foam (for type 2) is only doubled. Based on the information provided, it can be concluded that the greatest heat losses occur in distribution networks, and not in the main ones.

Calculation examples for the claimed method

Example 1 (with ke = 5.0 mm).

The available head on the mains at the point of connection of the distribution heating network dHnetwork = 45 m. The required sufficient available head at the consumer dHnode = 15 m. The permissible value of pressure loss in the pipeline of the distribution heating network is:

dHloss = dHnetwork-dHnode = 45-15 = 30 m

The estimated flow rate of the heating coolant is 7.0 t / h (84% of the pipeline load from the standard one, with permissible hydraulic losses in the heating network pipelines up to 10 kgf / m ² -m).

The accepted design diameter of the pipeline for a design flow rate of 2Ду70 mm at a speed of movement of the coolant of 0.55 m / s and a pressure loss of 7.2 mm per 1 m (ke = 0.5 mm). Distance from the main to the heating unit (supply + return) - 200 m (100 + 100).

For the calculation, we will take the maximum roughness of the pipeline ke = 5.0 mm per 1 m (instead of the calculated ke = 0.5 mm per 1 m).

Calculated pressure losses are:

dP = (dh · ke · V · L) / 1000, m, where dh - hydraulic losses at the design flow rate of the heating coolant, kgf / m ² -m;

ke is the actual roughness coefficient, mm;

B - correction factor for local resistance;

L is the total length of the heating network pipeline, m;

1000 - conversion factor, mm in m;

dP = (7.2-5-1.3-200) / 1000 = 9.36 m

The throttled head at the node will be:

dPnode = dHnetwork-dHmin-dP, m.

- 6 037492 dPnodes = 45-15-9.36 = 20.64 m. This pressure must be extinguished by the automatics or throttle (nozzle, washer), that is, it is excessive.

With a decrease in the pipe diameter by 2Du 50 mm with the same flow rate of 7.0 t / h, the water velocity increases to 1.1 m / s - 2 times from the existing one, the pressure loss is 39 mm per 1 m. The length of the pipe is the same.

Calculated pressure losses are:

dP = (39-5-1.3-200) / 1000 = 50.70 m.

50.7 m more than the permissible pressure loss limit of 30.0 m.

Leave the supply pipeline 1 DN 50 mm, return 1 DN 70 mm.

The pressure loss in the supply pipeline is:

dP = (39-5-1.3-100) / 1000 = 25.35 m.

Return pressure loss:

dP = (7.2-5-1.3-100) / 1000 = 4.68 m.

The total pressure loss is 30.03 m - within the permissible value.

Conclusion: in fact, it is possible to replace 1 DN 70 mm of the supply pipeline with 1 DN 50 mm.

Example 2 (with ke = 0.5 mm).

The available head on the mains at the point of connection of the distribution heating network dHnetwork = 45 m. The required sufficient available head at the consumer dHnode = 15 m. The permissible value of pressure loss in the pipeline of the distribution heating network is:

dHloss = dHnetwork-dHnode = 45-15 = 30 m.

The estimated flow rate of the heating coolant is 7.0 t / h (84% of the pipeline load from the standard one, with permissible hydraulic losses in the heating network pipelines up to 10 kgf / m ² -m).

The accepted design diameter of the pipeline for a design flow rate of 2Ду70 mm at a speed of movement of the coolant of 0.55 m / s and a pressure loss of 7.2 mm per 1 m (ke = 0.5 mm). The distance from the main to the heating unit (supply + return) is 200 m.

For the calculation, we take the usual roughness of the pipeline ke = 0.5 mm per 1 m.

Calculated pressure losses are:

dP = (dh · ke · V · L) / 1000, m, where dh - hydraulic losses at the design flow rate of the heating coolant, kgf / m ² -m;

ke is the actual roughness coefficient, mm;

B - correction factor for local resistance;

L is the total length of the heating network pipeline, m;

1000 - conversion factor, mm in m.

dP = (7.2-0.5-1.3-200) / 1000 = 0.936 m

The throttled head at the node will be:

dPnode = dHnetwork-dHmin-dP, m.

dPnode = 45-15-0.936 = 29.06 m. This pressure must be extinguished by automatic equipment or by a throttle (nozzle, washer).

With a decrease in the pipe diameter by 2Du 50 mm with the same flow rate of 7.0 t / h, the water velocity increases to 1.1 m / s - 2 times from the existing one, the pressure loss is 39 mm per 1 m. The length of the pipe is the same.

Calculated pressure losses are:

dP = (39-0.5-1.3-200) / 1000 = 5.07 m.

5.07 m is not more than the permissible pressure loss limit of 30.0 m.

Leave the supply and return pipelines 2 DN 50 mm.

The overpressure throttled at the node is 30.0-5.07 = 24.93 m.

Conclusion: in fact, it is possible to replace 2D 70 mm of the supply and return pipelines with 2D 50 mm with an increase in the speed of movement of the coolant by 2 times.

With a decrease in the diameter of the pipe 2Ду 70 mm by DN 40 mm with the same flow rate of 7.0 t / h, the water velocity increases to 1.6 m / s - 3 times of the existing one, the pressure loss is 132 mm per 1 m. the same.

The calculated pressure losses in the supply and return pipelines are:

dP = (132-0.5-1.3-200) / 1000 = 17.16 m.

17.16 m not more than the permissible pressure loss limit of 30.0 m.

Leave the supply and return pipelines DN 40 mm.

The overpressure throttled at the node is 30.0-17.16 = 12.84 m.

Conclusion: in fact, it is possible to replace 2Du 70 mm of the supply and return pipelines with 2Du 40 mm with an increase in the speed of movement of the coolant by 3 times.

The result is a decrease in the diameters of pipelines of the distribution heating network (capital and operating costs) and a decrease in heat losses due to an increase in the speed of movement of the coolant while maintaining the minimum required available pressure at the heating unit. In addition, we note that the work of the automated heating unit for the circuit developed for Astana city, the minimum permissible value of the available head is only 10.0 m. That is, in heating networks there is always

- 7 037492 there is a pressure reserve of 5.0 m (in case of connecting a small additional load).

There is a principle of operation of the district heating network - a quantitative assessment of the hydraulic stability of subscriber units is made according to the coefficient of hydraulic stability, equal to the ratio of the calculated amount of network water through the subscriber unit to the maximum possible flow rate under the conditions of operation of centralized heat supply (Heating and heating networks, Sokolov E.Ya, Moscow, 1975 g).

The hydraulic stability is the higher, the less the pressure loss in the heating network and the greater the pressure loss at the subscriber input (Heating and heating networks, Sokolov E.Ya., Moscow. 1975). At the same time, we come to the conclusion that an increase in the speed of movement of the coolant is possible only on distribution (intra-quarter) heating networks while maintaining the existing permissible pressure losses in the main ones. An increase in the speed of movement of the coolant will lead to an increase in hydraulic losses in the distribution heating networks, but at the same time, heat losses are reduced, and most importantly, it is possible to reduce the diameter of the pipeline in the distribution heating network. The final result of the calculation of intra-quarter heating networks remains the minimum allowable available head at the heating unit in the minimum allowable 15 m (norm SN RK 4.02-04-2013 Heating networks and previously applicable design standards). The remaining pressure difference between the main heating networks and the required available pressure at the consumer can be effectively used in district heating pipelines - to increase the speed of movement of the coolant with an increase in hydraulic losses in the pipelines of the distribution heating network. With an increase in the speed of movement of the coolant, hydraulic losses in the pipeline of the distribution heating network will increase: the excess pressure is still uselessly extinguished at the heating unit, but at the same time, heat losses will decrease and the diameter of the pipelines of the intra-quarter heating network will decrease.

At the same time, for consumers who are closer to the heat source, the change in diameters downward from the accepted standard ones (with pressure losses up to 10 mm / m) will be greater than for the end ones. If necessary, it is possible to reduce only the supply pipeline, without reducing the diameter of the return pipe, or any part of it calculated along the length.

When designing heat distribution networks, it is necessary to take into account the maximum roughness of these pipelines arising during operation, and take into account the prospective pressure losses in the main pipelines, taking into account the change in roughness, but taking into account the permissible pressure loss of no more than 10 mm per 1 m. vibration inserts on heating units.

When applying this calculation method, it is necessary to take into account the current norms of the joint venture and the CH Heating networks, instructions for the operation of heating networks, current regulatory and technical documents.

In the hydraulic calculation of the heating network, 3 operational periods of the year are taken into account - winter, transitional and summer.

The winter period (at Тн = from 0 to -35 ° С) has the highest load of the heating network. There is a use of loads of heating, ventilation and hot water supply. At this period of operation, the load of the heating network is close to the maximum calculated. For this period, the diameters of pipelines of distribution heating networks are calculated.

The transition period (at Тн = from 0 to + 10 ° С), the load on the networks decreases due to the cut-off for hot water supply. The temperature of the transported coolant is not lower than T1 = + 70 ° C. The required temperature for heating systems is much lower - there is a decrease in the consumption of the heating coolant and, accordingly, a decrease in the speed of the coolant.

Summer period - all the rest of the time - only the transportation of the coolant for the needs of hot water supply takes place. Heat losses in summer are the most significant. But with a decrease in the diameters of the distribution heating network, it will decrease.

This proposal to reduce construction, operating costs, as well as to reduce heat losses is applicable if there are correct loads of consumers by types of heat consumption, keeping the temperature schedule by the source and a well-calculated hydraulic regime.

An additional advantage of this proposal is an increase in the hydraulic stability of heating networks: the consumer does not receive excess heat in the form of an additional consumption of the heating medium when the actual load is overestimated over the design one, the pipelines of the heating network will not be able to pass overstated from the maximum estimated consumption of the heating medium without reducing the guaranteed (or calculated) available pressure at the consumer's heating unit. This will reduce the consumption of the heating medium at the heating unit, and, as a consequence, the quality of heat supply.

The design and implementation of the replacement of heating mains can be carried out both in the process of designing new heating networks and on a planned basis as the existing distribution heating network deteriorates, taking into account the permissible deviations in pressure and temperature. When calculating any existing distribution heat network, one should take into account the quality of the heating system of this facility (no complaints when working at the estimated flow rate) and the readings of the heat meter,

- 8 037492 accepted for commercial accounting, that is, the actual heat consumption of the facility.

List of normative and technical literature.

1. Rules for the technical operation of power plants and networks, approved by order of the Minister of Energy of the Republic of Kazakhstan dated March 30, 2015.

2. Designer handbook Design of heating networks, Moscow, 1965

3. Heating and heating networks, Sokolov E.Ya, Moscow, 1975

4. Instruction for the operation of heating networks, Moscow, 1972

5. Guidelines for the compilation of energy characteristics RD 153-34 RK.O-20.52302, part II.

6. SNiP 4.02-42-2006 Heating, ventilation and air conditioning.

7. СН RK 4.02-04-2013 Heat networks.

8. SP RK 4.02-104-2013 Heating networks.

9. SNiP II-36-73 Heating networks.

10. SNiP 2.04.07-86 Heating networks.

11. SNiP 2.2.04.07-86 * Heating networks.

12. MSN 4.02-02-2004 Heating networks.

13. SNiP 2.04.14-88 Thermal insulation of equipment and pipelines.

14. SP 41-103-2000 Design of thermal insulation of equipment and pipelines.

15. MSN 4.02-03-2004 Thermal insulation of equipment and pipelines.

16. SN RK 4.02-03-2011 Design of thermal insulation of equipment and pipelines.

Table 1. Dimensions of pipes in a polyethylene sheath

Outside diameter and minimum wall thickness of steel pipes * Type 1 Type 2 __ Average outer diameter of insulated pipes with polyethylene sheath Estimated thickness of the polyurethane foam layer on Average outer diameter of insulated pipes with polyethylene sheath ΐ Estimated thickness of the polyurethane foam layer on Rated Limit oe deviations e (+) Rated Limit deviation (+) 32 x 3.0 90; 110; 125 2.7; 3.5; 26.0: 36.5; 43.5 - - - 38 ^χλ0 j 110; 125 3.2; 3.7 33.0; 40.5 - - - 45x3.0 125 3.7 37 - - - 57x3.0 125 3.7 31.5 140 4.1 ! D, 5__T 76x3.0 | 140 4.1 29.0 160 4.7 i 39.0 _ 89x43) __ ί 160 4.7 32.5 180 5.4 42.5 J08x4У _ ___ [80__ 5.4 33.0 200 5.9 43.0 133x4.0 225 6.6 42.5 250 7.4 54.5 159x4.5 250 7.4 41.5 280 8.3 55.5 219x6.0 ; 315 9.8 42.0 355 10.4 62.0 273x7.0 (400 H, 7 57.0 450 13.2 81.5 325x7.0 1 450 13.2 55.5 J 500 14.6 79.5 Ο / ΟχΤ) ^! 560__ 16.3 58.2 600.630 16.3 77.6; 92.5 “'Zz 0x7.0 7 ΐ 710 ___ 20.4 78.9 one - | - - 630x8,0 s 800 1 23.4 72.5 | - one - - _720x8.0 900__ 1 26.3 76.0 | - one - - 820x9.0 1000 1 29.2 i 72.4 | __ioo ___ | 32.1 ί _______ 122.5; 920x10 1100 1 32.1 74.4 | 1200 | 35.1 j 120.5 1020x11 1200 1 35.1 70.4 | - one - one - * The wall thickness of the steel pipe is set in the project. By agreement with the design organization, it is also allowed to use pipes of other diameters.

CLAIM

Claims (2)

CLAIM 1. A method for reducing heat losses of a distribution heating network pipeline, in which the supply pipeline and the return pipeline of the heating network are replaced with a pipeline of a smaller diameter in size than the pipeline of the distribution heating network actually laid or projected for the future, thereby increasing the speed of movement of the coolant and extinguish the residual overpressure at the pipeline node, while, to select the optimal pipeline diameter, calculate the permissible pressure loss in the pipeline of the distribution heating network using the formula: - 9 037492 dHloss = dHnetwork-dHnode, where dHcemu is the available head on the main at the point of connection of the distribution heating network, dHnode is the required sufficient available head at the consumer of the heating network, the estimated pressure loss in the supply and return pipelines of the heating network is determined by the formula: dP = (dh ke V L) / 1000, m, where dh is the hydraulic loss at the design flow rate of the heating medium, kgf / m ² -m, ke is the actual roughness coefficient of the pipeline, mm, B - correction factor for local pipeline resistance, L is the total length of the heating network pipeline, m, 1000 - conversion factor, mm in m, calculate the residual throttled head for damping at the pipeline node according to the formula dPnode = dHnetwork-dHnode-dP, m, and then the calculated pressure loss dP in the supply and return pipelines, which should be no more than dH losses, m, to confirm the optimality of the selected pipeline diameter. 2. A method for reducing heat losses of a distribution heating network pipeline according to claim 1, characterized in that the residual overpressure in the pipeline is extinguished by increasing the speed of movement of the heating coolant with an increase in hydraulic losses in the pipeline, and the residual overpressure is extinguished at the heating unit by automation or a choke.