Open and closed DHW systems: differences, how to switch to a closed circuit. Open and closed heating system - advantages and disadvantages in comparison

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Thanks to the heat supply, houses and apartments are provided with heat, and, accordingly, it is comfortable to stay in them. Simultaneously with heating residential buildings, industrial facilities, public buildings receive hot water for domestic or industrial needs. Depending on the method of delivery of the coolant, today there are open and closed heat supply systems.

At the same time, schemes for arranging heat supply systems are:

• centralized - they serve entire residential areas or settlements;
• local - for heating one building or group of buildings.

Open heating systems

In an open system, water is constantly supplied from the heating plant and this compensates for its consumption even if it is completely disassembled. AT Soviet time Approximately 50% of heating networks functioned according to this principle, which was explained by efficiency and minimization of heating and hot water costs.

But an open heating system has a number of disadvantages. The purity of water in pipelines does not meet the requirements of sanitary and hygienic standards. Since the liquid moves through pipes of considerable length, it becomes a different color and acquires unpleasant odors. Often, when water samples are taken by employees of sanitary and epidemiological stations from such pipelines, harmful bacteria are found in it.

The desire to purify the liquid flowing through an open system leads to a decrease in the efficiency of heat supply. Even the most modern ways elimination of water pollution are not able to overcome this significant drawback. Since the networks are long, the costs increase, but the cleaning efficiency remains the same.

An open heat supply scheme operates on the basis of the laws of thermodynamics: hot water rises, due to which a high pressure, and at the entrance to the heat generator - a small vacuum. Further, the liquid is directed from the zone of high pressure to the zone of lower pressure and, as a result, natural circulation coolant.

Being in a heated state, water tends to increase in volume, therefore, for of this type heating system an open expansion tank is required, such as in the photo - this device is completely leaky and directly connected to the atmosphere. Therefore, such heat supply received the appropriate name - open water system heat supply.

AT open type water is heated to 65 degrees and then supplied to the taps, from where it goes to consumers. This type of heat supply allows you to use cheap mixers instead of expensive ones. heat exchange equipment. Since the analysis of heated water is uneven, for this reason the supply lines to the final consumer are calculated taking into account the maximum consumption.

Closed heating systems

Represents closed system heat supply design in which the coolant circulating in the pipeline is used only for heating and water from the heating network is not taken for hot water supply.

AT closed version providing space heating, the heat supply is centrally regulated, and the amount of liquid in the system remains unchanged. The consumption of thermal energy depends on the temperature of the coolant circulating through the pipes and radiators.

In heating systems closed type, as a rule, heat points are used, in which hot water is supplied from a heat supplier, such as a CHP. Further, the temperature of the heat carrier is brought to the required parameters for heat supply and hot water supply and sent to consumers.

When a closed heat supply system is operating, the heat supply scheme provides high quality DHW and energy saving effect. Her main disadvantage- the complexity of water treatment due to the remoteness of one heating point from another.

Dependent and independent heating systems

Both open and closed heating systems can be connected in two ways - dependent and independent.

1. Formulation of the problem according to the considered method (technology) of increasing energy efficiency; forecast of overspending of energy resources, or a description of other possible consequences nationwide while maintaining the status quo

In most cities of the Russian Federation today, hot water supply to consumers is carried out according to an open scheme.

The existence of such a scheme has the following disadvantages:
- increased costs heat for heating and hot water supply;
- high specific consumption of fuel and electricity for heat production;
- increased costs for the operation of boiler houses and heating networks;
- high-quality heat supply to consumers is not ensured due to big losses heat and the amount of damage on heating networks;
- increased costs for chemical water treatment.

2. Availability of methods, methods, technologies, etc. to solve the given problem

It is necessary to transfer the systems of transport and distribution of thermal energy to work according to a closed scheme with the construction of new and reconstruction of existing heating points in accordance with SP 41-101-95, the reconstruction of heat consumption systems in houses.

3. Short description the proposed method, its novelty and awareness of it, the availability of development programs; result in mass implementation nationwide

With a closed heating circuit, cooking hot water occurs in heating points, which receive purified cold water and coolant. In the heat exchanger, cold water, passing along the heat carrier tubes, heats up. Thus, there is no mixing cold water into the coolant and hot water in such a system is heated cold water going to the consumer. The spent coolant (its temperature drops at the outlet of the heat exchanger) is added to the new coolant and this “technical” water is coming for heating according to a dependent or independent scheme.

The transition to a closed scheme for connecting DHW systems will ensure:
- reduction of heat consumption for heating and hot water supply due to the transfer to qualitative and quantitative regulation of the temperature of the heat carrier in accordance with the temperature schedule;
- reduction of internal corrosion of pipelines (for the northern regions of the country) and salt deposits (for regions located to the south);
- reduction in the rate of wear of equipment of thermal stations and boiler houses;
- a fundamental improvement in the quality of heat supply to consumers, the disappearance of "overheating" during positive outdoor temperatures during the heating season;
- reduction of volumes of work on chemical water treatment of make-up water and, accordingly, costs;
- reduction of accident rate of heat supply systems.

4. Forecast of the effectiveness of the method in the future, taking into account:
- rising prices for energy resources;
- the growth of the welfare of the population;
- introduction of new environmental requirements;
- other factors.

As a result, after abandoning the heat supply scheme open for hot water supply and switching to a closed scheme, it will be possible to use the saved thermal power stations and boiler houses for heat supply of newly connected consumers.

5. List of groups of subscribers and objects where this technology can be used c maximum efficiency; the need for additional research to expand the list

The maximum efficiency from the implementation of this measure will be observed in cities with intensive development. The construction of new microdistricts, coupled with the organization of their heat supply according to a closed scheme, is most expedient within the framework of the relevant city programs.

6. State the reasons why the proposed energy efficient technologies not applied on a mass scale; outline an action plan to remove existing barriers

Currently most of heating systems in the capital (JSC "Moscow United Energy Company" and JSC "Moscow Heat Network Company") operates precisely according to a closed scheme.

The situation is different in the regions. Since Soviet times, there has been a policy of limiting financial resources for the construction and maintenance of housing and communal facilities. Side-effects of this policy were the creation of large district heating systems and the introduction in many cities of open circuit.

7. Availability of technical and other restrictions on the application of the method on various objects; in the absence of information on possible limitations, it is necessary to determine them by testing

Inappropriate commissioning of closed DHW schemes in cities with tap water, characterized by low salinity and high corrosivity requiring deaeration, as, for example, in St. Petersburg.

8. The need for R&D and additional testing; themes and objectives of the work

The need for R&D and additional testing during the implementation of this measure is not required

9. Existing incentives, coercion, incentives for the implementation of the proposed method and the need to improve them

Existing measures to encourage and enforce implementation this method missing.
It is advisable to conduct energy audits of existing heat supply systems with the identification of all negative consequences use of open circuits. The result of such surveys are technically sound conclusions and recommendations for the transfer to a closed scheme.

10. The need to develop new or change existing laws and regulations

It is necessary to develop regulatory documentation for the implementation and operation of hot water supply systems in a closed scheme. Perhaps, it is necessary to adopt legal acts of a compulsory nature on the transfer to a closed heat supply scheme, first of all, when hot water is supplied to consumers according to an open scheme that does not meet sanitary and epidemiological standards.

11. Availability of decrees, rules, instructions, standards, requirements, prohibitive measures and other documents regulating the use of this method and mandatory for execution; the need to make changes to them or the need to change the very principles of the formation of these documents; the presence of pre-existing regulatory documents, regulations and the need for their restoration

To date, there are no regulatory documents regulating the use of this measure.

12. Availability of implemented pilot projects, analysis of their real effectiveness, identified shortcomings and proposals for improving the technology, taking into account the accumulated experience

The following pilot projects can be mentioned as ongoing pilot projects for the conversion of an open heating system to a closed one.

JSC VNIPIenergoprom specialists have developed technical solutions on translation existing system heat supply of the city of Zelenograd on a closed scheme.

Within the framework of the international program "Northern Dimension", on the basis of GOUTP "TEKOS", a project was developed for the reconstruction of the heat supply system of the Leninsky district of Murmansk with a transfer to a closed heat supply scheme.

Teploenergo's specialists have developed and are implementing a pilot project for the transfer of microdistrict No. 2 "Meshcherskoye Lake" to a closed hot water supply scheme as part of the relevant investment program.

13. The possibility of influencing other processes during the mass introduction of this technology (changes in the environmental situation, possible impact on people's health, increasing the reliability of power supply, changing daily or seasonal schedules for loading power equipment, changing economic indicators generation and transmission of energy, etc.)

With hot water supply to microdistricts, performed according to an open scheme, consumers are often supplied from the heating system with water that has unsatisfactory organoleptic and bacteriological indicators. As part of the implementation of the measure under consideration, hot water supplied through a closed scheme will have the quality of drinking water and will comply with sanitary rules and norms.

The introduction of closed DHW circuits is an energy-saving measure. As a result of the implementation of this measure, not only the consumption of energy resources (electricity, heat and water) is reduced, but emissions into the atmosphere are also reduced and the reliability of the heat supply system is increased.

14. Availability and sufficiency of production capacities in Russia and other countries for the mass implementation of the method

The implementation of the event under consideration on a massive scale is currently problematic, since it requires significant investment.

15. The need for special training of qualified personnel for the operation of the implemented technology and the development of production

The situation is aggravated by the shortage of qualified personnel due to the low level of wages and the lack of specialized training, which is urgently needed.

16. Suggested implementation methods:
1) commercial financing (with cost recovery);
2) a competition for the implementation of investment projects developed as a result of work on energy planning for the development of a region, city, settlement;
3) budget financing for efficient energy-saving projects with long payback periods;
4) introduction of prohibitions and mandatory requirements for the use, supervision of their observance;
5) other offers.

To increase interest in the implementation of this type of measures, a consistent and methodical "break" in the psychology of customers, designers, installers and operating services is required, who still consider the most relevant implementation of outdated traditional heat supply schemes that do not need maintenance and adjustment.

It is also necessary to further create specialized organizations capable of taking on the entire chain of work from design and installation to commissioning and maintenance. modern systems heat supply. For this purpose, it is necessary to carry out purposeful work to train specialists in the field of energy conservation.

Only the combination of these measures will lead in the future to a greater interest of city administrations in the implementation of energy-saving measures of this scale. It is obvious that the most appropriate is the implementation of these activities within the framework of strategic projects for the development of heat sources and heating networks and city programs for the modernization of the housing and communal complex with budgetary and commercial financing.

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Specialists of the State Unitary Enterprise SO "Oblkommunenergo" warn their consumers about the upcoming cardinal changes in the legislation regulating heat supply. This was reported to UralPolit.Ru in the press service of the enterprise today, December 4th.

From January 1, 2013, amendments to the federal law of July 27, 2010 No. 190-FZ "On Heat Supply" will come into force. One of the most significant - addition to article 29 part 8:

8. From January 1, 2013 connection of objects capital construction consumers to centralized open heat supply systems (hot water supply) for the needs of hot water supply, carried out by selecting a coolant for the needs of hot
water supply is not allowed.

Besides: addition to article 29 part 9:

9. From January 1, 2022, the use of centralized open heat supply systems (hot water supply) for the needs of hot
water supply, carried out by taking the coolant for the needs of hot water supply, is not allowed.

An open hot water supply scheme assumes that residents take hot water for their needs from the heat supply system, and a closed DHW system assumes the presence of special equipment for heating cold water and supplying it to residents at home as hot. The heating system works autonomously in this case.

Open analysis of hot water from the heating system has become a big problem and a headache for power engineers throughout Russia - today at least 70% of residential buildings supply hot water in this way.

Experts warn that the task set is truly revolutionary, large-scale and brings with it many related problems that will also need to be solved, but this has not yet been indicated by the legislator.

We present expert opinion about this deputy CEO State Unitary Enterprise SO "Oblkommunenergo" Evgeny Volkov:

In accordance with the amendments and additions made to the federal law No. 190-FZ of July 27, 2010 "On heat supply" (introduced by federal law No. 417-FZ of December 7, 2011), approaches to the creation of hot water supply systems will radically change . If earlier both systems had the right to exist - open and closed, then from January 1, 2013, the connection of newly commissioned capital construction facilities to hot water supply systems will have to be carried out only according to a closed scheme. And from January 1, 2022, open heating systems should disappear as a species, at least the authors of the law believe. Let us briefly recall what the types of heat supply systems are. An open heat supply system is when the coolant is used both for heating purposes and for hot water supply purposes. That is, hot water heating appliances and the faucet in the kitchen, in the bathroom - the same thing. A closed heat supply system assumes that the coolant circulates in a closed circuit, consuming thermal energy only for heating. Hot water supply in this case is carried out by heating cold water with the same coolant, but through a heat exchanger. Let's try to compare the pros and cons of both systems and understand the idea behind the new legislation.

With an open system, the entire coolant undergoes mandatory water treatment at a heat source - a boiler house or a CHP. Cold water, before becoming a heat carrier, as a rule, requires a decrease in hardness in order to avoid scale formation when it is heated in boilers. In the absence of water treatment, hard water can disable an entire boiler room in a matter of months. Therefore, on any heat source, great attention is paid to the observance of the water-chemical regime. Reagents are spent on water treatment ( salt or sulfuric acid), electricity for water supply, routine maintenance of filters, funds are spent on the current operation and repair of equipment. With a closed circuit, all this will not happen, but who said that cold water for heating in the heat exchanger does not need to be prepared?

After all, if water has increased hardness, then when it is heated in the heat exchanger, intensive formation of hard-to-remove scale will also occur. That is, the solution to the problem of water treatment during the transition from an open to a closed circuit will move from generating facilities to consumers. But this will no longer be a single enlarged complex, but many small installations that will also need to be serviced, incurring the costs of reagents and maintenance personnel. At the same time, it is appropriate to recall the well-known rule - when a single whole is divided into several segments, the amount of costs increases. There is another factor - the level of maintenance of systems and equipment. It is impossible to compare the level of a plumber tightening nuts in the apartments of tenants, and complex system engineering support at large energy enterprises. It is unlikely that organizations servicing the internal systems of buildings will be able to ensure the proper level of operation of energy equipment (water treatment system, heat exchangers, automation to maintain the required water parameters).

The disadvantage of an open circuit is the so-called overheating. This means that during relatively warm periods, when the outdoor air temperature is close to zero or above zero, the heat supply company is forced to maintain the minimum temperature of the heat carrier at a level of at least 60 degrees, as required by SanPiN in terms of hot water quality requirements. But for heating systems, such temperatures are not required during warm periods. For example, at zero degrees outdoor temperature the coolant temperature indicator is 52 degrees. At plus 5 outside, the coolant temperature should already be 45 degrees, and at plus eight - 41 degrees.

The literature on the adjustment of heat supply systems mentions the so-called "cutoff" temperature chart according to the terms of the GVS. I.e minimum temperature coolant is taken 60 degrees, and in warm periods heating season(usually September, October, April, May) consumers receive much more heating than it would be required by the standard. It should be noted that the requirements for hot water temperature for closed systems are somewhat softer: the required minimum temperature is 55 degrees. As a consequence, there is fuel savings compared to an open system, though. this is a relative circumstance - many heat supply organizations, looking at open windows in warm weather, already actually withstand temperatures in the region of 55-57 degrees.

A clear disadvantage of a closed system is the need to replace water supply networks. To date, the wear and tear of these networks is quite large, and many sections have undergone sanitation over the past 5-6 years ( polyethylene pipes), i.e. their diameter has decreased. The question arises before the water utilities - when switching to a closed system, it is necessary to increase throughput water networks almost twice. Given the above circumstances, an impressive volume of pipelines will have to be changed. But water tariffs are among the lowest and do not replace even the normative number of networks.

One of the options for a closed system is the supply of hot water from heat sources through a separate circuit (in Federal Law No. 190-FZ of July 27, 2010 “On Heat Supply”, oddly enough, only the concept of “open heat supply system” is formulated. There is nothing about a closed said, however, in some technical normative documents the term "closed system" is explained precisely in terms of installation heat exchangers at consumers. Therefore, whether the idea of ​​the author of these lines will have the right to exist is not yet clear). Nevertheless, to solve this problem, it is necessary to install again or separate from the existing boiler at the heat source, which will heat water only for the needs of domestic hot water. There is no need to "fence the garden" in the form of water treatment systems and heat exchangers for consumers, to change water supply networks. But there is new problem: almost all heating network it will be necessary to shift anew to create dedicated hot water pipelines. For example, if now the heating network consists of two pipes (supply and return), then with a separate circuit, two more pipes must be added. In addition, it will be necessary to change the design of the network channels, since during their construction, as a rule, no one assumes an increase in the number of “threads” of pipelines, and where two pipes have already been laid in the tray, two more will obviously not fit. In a word - global replacement all heating networks. By the way, why not? The problem of wear and tear of networks is known, the loss of thermal energy exceeds all conceivable and unthinkable limits - it will be very useful to kill not even two, but three or four birds with one stone with one shot. But the money for such modernization is unlikely to be found in the tariffs heat supply organizations. And even the normative percentage of network replacement (4% per year) does not solve the problem within the prescribed period - until 2022. It takes at least 25 years, and then with the most favorable combination of circumstances and with the help of the state budget.

State Unitary Enterprise SO "Oblkommunenergo" is a backbone enterprise of the region's communal power industry, which carries out a comprehensive modernization of the housing and communal services of the Sverdlovsk region. Covering all areas of utility business (power grid business, heat supply, water disposal and water supply), Oblkommunenergo systematically solves the issues of developing the energy complex and engineering infrastructure of 40 municipalities of the Sverdlovsk region.

© Editorial office "UralPolit.Ru"

For space heating, a closed and open heat supply system is used. The latter option additionally provides the consumer hot water. At the same time, it is necessary to control the constant replenishment of the system.

A closed system uses water only as a heat transfer medium. It constantly circulates in a closed cycle, where losses are minimal.

Any system consists of three main parts:

• heat source: boiler room, thermal power plant, etc.;
• heating networks through which the coolant is transported;
• heat consumers: heaters, radiators.

Features of an open system

The advantage of an open system is its economy. Due to the long length of pipelines, the quality of water is deteriorating: it becomes cloudy, acquires color, has bad smell. Attempts to clean it make the method of application expensive.

Heating pipes can be seen in big cities. They have a large diameter and are wrapped in a heat insulator. Leads are made from them to individual houses through a thermal substation. Hot water is supplied for use to heating radiators from a common source. Its temperature ranges from 50-75°C.

Connection of heat supply to the network is carried out in dependent and independent ways, implementing closed and open heat supply systems. The first is to supply water directly - using pumps and elevator nodes, where it is brought to the required temperature by mixing with cold water. An independent way is to supply hot water through a heat exchanger. It is more expensive, but the quality of water at the consumer is higher.

Features of a closed system

The heat main is made in the form of a separate closed loop. The water in it is heated through heat exchangers from the CHP main. Additional pumps are required here. Temperature regime the result is more stable, and the water is better. It remains in the system and is not taken by the consumer. Minimal water losses are restored by automatic make-up.

A closed autonomous system receives energy from the coolant entering the water. There, the water is brought to the required parameters. For heating systems and hot water supply, different temperature regimes are supported.

The disadvantage of the system is the complexity of the water treatment process. It is also expensive to deliver water to heat points located far from each other.

Heating network pipes

Currently domestic are in emergency condition. Due to the high wear and tear of communications, it is cheaper to replace the pipes for the heating main with new ones than to engage in constant repairs.

It is impossible to immediately update all the old communications in the country. during construction or overhaul houses install new pipes in several times reducing heat loss. Pipes for heating mains are made according to special technology, filling with foam the gap between the located inside steel pipe and shell.

The temperature of the transported liquid can reach 140°C.

The use of polyurethane foam as thermal insulation allows you to retain heat much better than traditional protective materials.

Heat supply of multi-apartment residential buildings

Unlike a dacha or a cottage, heat supply apartment building contains a complex layout of pipes and heaters. In addition, the system includes controls and security.

For residential premises, there are where critical temperature levels and permissible errors are indicated, depending on the season, weather and time of day. If we compare closed and open heat supply systems, the first one better supports the required parameters.

Public heat supply must ensure the maintenance of the main parameters in accordance with GOST 30494-96.

The greatest heat loss occurs in stairwells residential buildings.

The supply of heat is mostly produced by old technologies. In essence, heating and cooling systems should be combined into a common complex.

The disadvantages of centralized heating of residential buildings lead to the need to create individual systems. It is difficult to do this due to problems at the legislative level.

Autonomous heating of a residential building

In buildings of the old type, the project provides for a centralized system. Individual schemes allow you to choose the types of heat supply systems in terms of reducing energy costs. Here it is possible to turn them off mobile if not needed.

Design autonomous systems produced in accordance with heating standards. Without this, the house cannot be put into operation. Following the norms guarantees the comfort for the residents of the house.

The source of water heating is usually a gas or electric boiler. It is necessary to choose a method for flushing the system. AT centralized systems applied hydrodynamic method. For standalone, you can use a chemical. In this case, it is necessary to take into account the safety of the influence of reagents on radiators and pipes.

Legal basis of relations in the field of heat supply

Relations between energy companies and consumers are regulated by the Federal Law on heat supply No. 190, which entered into force in 2010.

1. Chapter 1 introduces the basic concepts and general provisions, defining the scope of the legal foundations of economic relations in heat supply. It also includes provision of hot water. General principles for the organization of heat supply are approved, which consist in the creation of reliable, efficient and developing systems, which is very important for living in the difficult Russian climate.
2. Chapters 2 and 3 reflect the extensive scope of authority of local authorities that manage pricing in the heat supply sector, approve the rules for its organization, accounting for heat energy consumption and standards for its losses during transmission. The fullness of power in these matters allows you to control the heat supply organizations related to monopolists.
3. Chapter 4 reflects the relationship between the supplier of heat energy and the consumer on the basis of a contract. All are considered legal aspects connections to heating networks.
4. Chapter 5 reflects the rules for preparing for the heating season and repairing heat networks and sources. It describes what to do in case of non-payment under the contract and unauthorized connections to heating networks.
5. Chapter 6 defines the conditions for the transition of an organization to the status of a self-regulating in the field of heat supply, the organization of the transfer of rights to own and use a heat supply facility.

Users of thermal energy must be aware of the provisions of the Federal Law on heat supply in order to assert their legal rights.

Drawing up a heat supply scheme

The heat supply scheme is a pre-project document that reflects legal relations, conditions for the functioning and development of the system for providing heat to an urban district, settlement. In relation to it, federal law includes certain rules.

1. for settlements are approved by authorities executive power or local government, depending on the population.
2. There should be a single heat supply organization for the respective territory.
3. The scheme indicates the energy sources with their main parameters (loading, work schedules, etc.) and range.
4. Measures are indicated for the development of the heat supply system, the conservation of excess capacities, and the creation of conditions for its uninterrupted operation.

Heat supply facilities are located within the boundaries of the settlement in accordance with the approved scheme.

Purposes of application of the heat supply scheme

• determination of a single heat supply organization;
• determination of the possibility of connecting capital construction objects to heat networks;
• inclusion of measures for the development of heat supply systems in the investment program of the organization of heat supply.

Conclusion

If we compare closed and open heat supply systems, the implementation of the first one is currently promising. allows you to improve the quality of the water supplied to the level of drinking.

Although new technologies are resource-saving and reduce air emissions, they require significant investment. At the same time, there is a shortage of qualified specialists due to the lack of special personnel training and low wages.

Ways of implementation are at the expense of commercial and budgetary financing, competitions for investment projects and other events.

The article presents the results of the analysis of the main directions for improving the efficiency of heat supply systems during the transition to a closed scheme. To assess the economic performance, the authors identified the main areas of possible cost reduction in the transition to a closed scheme - reducing the cost of chemical water treatment (CWT) and feeding the heating network at the CHPP. At the same time, additional funds will be required to equip heat points with hot water heaters and cold water systems.

In the proposed material, the authors carried out cost estimates on the example of a residential area with a heat load of about 70 MW. It has been established that the transfer of heat supply systems to a closed scheme is an expensive undertaking that requires significant capital investments, and the economic effect does not cover the costs of re-equipping the heating points of heat supply facilities.

According to the Federal Law of December 7, 2011 No. 417-FZ, the connection of capital construction facilities to centralized open heat supply systems with the selection of a heat carrier for the needs of hot water supply is not allowed. From January 1, 2022, the use of centralized open heat supply systems is not allowed. As a justification for the law, economic indicators and hygiene requirements to the quality of hot water in hot water supply systems. However, there is some misunderstanding of the problem and the lack of substantiated data confirming the effectiveness of the adopted strategic plan. In this regard, to justify the main design decisions, multivariate calculations are required, the need for which is indicated, for example, in the work.

The city of Yekaterinburg is one of the cities where they have already begun to develop closed heat supply schemes, when hot water is prepared by heating cold water in central (CTP) or individual (ITP) heating points.

In engineering practice, it is customary to evaluate the main decisions on economic conditions: best option must correspond minimum costs financial resources. The methodology for economic calculations of heat supply systems and the main directions of optimization are set out in the work.

SNiP 2.04.07-86* "Heat networks" states that the heat supply system (open, closed, including with separate hot water networks, mixed) is selected on the basis of a feasibility study submitted by the design organization various systems taking into account local environmental, economic conditions and the consequences of making a decision.

However, in the Code of Rules (SP) 124.13330.2012, a more vague wording is presented: “Clause 6.6. The heat supply system (open, closed) is selected based on the approved in due course heat supply schemes.

To assess the economic performance, the authors identified the main areas of possible cost reduction in the transition to a closed scheme: reducing the cost of electricity to feed the heating network at thermal power plants and reducing the cost of chemical water treatment (CWT) at CHPPs.

At the same time, additional funds will be required for the re-equipment of heat points: installation of hot water heaters and equipment of heat points with cold water systems.

In addition, it was necessary to evaluate the possible change in the flow rate of the heat carrier in the heating network during the transition to a closed circuit, the diameter of the pipes and heat losses during the transportation of the heat carrier.

Estimation of costs during the transition to a closed heat supply scheme was carried out using the example of a residential area with a heat load of about 70 MW, including about 60 MW for heating and ventilation, and about 10 MW for hot water supply (average).

The coolant flow rates were calculated according to SNiP 2.04.07-86* "Heat Networks", since the necessary formulas are not given in subsequent editions.

Despite the difference in the formulas for determining the coolant flow rates for hot water supply in open and closed systems, the values ​​of the total calculated flow rate differ by no more than 9%. Therefore, the diameter of the pipes, the thickness of the thermal insulation and the dimensions of the associated mechanical equipment and building structures will be the same in open and closed systems.

Let's compare the performance of make-up pumps at CHP. Recommendations for calculating the maximum hourly consumption of make-up water are given in SP 124.13330.2012 "Heat Networks".

For a closed circuit, the flow rate is taken to compensate for losses network water in the amount of 0.0025 of the volume of water in the system, taking into account the cost of filling the system. The volume of water is approximately equal to 65 m 3 per 1 MW of calculated heat flow, the water consumption for filling with a diameter of the main section of 400 mm is 65 kg / h.

With a calculated heat flow of 70 MW, the performance of make-up pumps at a CHPP will be for a closed circuit:

G closed \u003d 70 × 65 × 0.0025 + 65 \u003d 76.4 m 3 / h.

For open circuits, the performance of make-up pumps at CHP is taken equal to the sum water consumption to compensate for losses of network water in the amount of 0.0025 of the volume of water in the system and maximum flow water for hot water supply. The volume of water in an open system is 70 m 3 per 1 MW of calculated heat flow. We get:

G open \u003d 70 × 70 × 0.0025 + 1.2 × 40 × 3.6 \u003d 185 m 3 / h.

Thus, the performance of make-up pumps at CHPPs during the transition to a closed circuit can decrease by almost 2.5 times, which will affect the cost of chemical water treatment and the consumption of electricity for pumping water.

Chemical water treatment is milestone water treatment and ensures the reliability of the heat supply system as a whole. The cost of chemical water treatment is 15 rubles. per 1 m 3 of deaerated water and depends on the volume of make-up.

Accordingly, with a closed scheme for the conditions of the example, we obtain the value of the annual costs for water treatment:

W= 76.4 × 365 × 24 × 15 = 10 million rubles/year; with an open scheme, the cost of water treatment will be:

W= 185 × 365 × 24 × 15 = 24 million rubles/year.

Accordingly, the consumption of electricity and the cost of its payment increase. For closed circuit annual consumption of the power supply unit of the CHPP will be 43 thousand kWh, for an open-air one - 184 kWh.

At the cost of electricity 4 rubles. for 1 kWh, we get the cost of electricity for the CHP feed unit 148 thousand rubles / year and 736 thousand rubles / year for open and closed circuits, respectively. Table one.

Thus, the transition to a closed circuit can give an economic effect for the heat supply source of about 14.6 million rubles / year.

However, heat points will need to be equipped with heat exchangers and water treatment plants. The authors estimated the costs of re-equipping an individual heating point (ITP) using the example of a residential building with a heat load for heating of 290 kW and a maximum for hot water supply of 132 kW. The recommendations given in the works were used.

The results obtained make it possible to evaluate the energy efficiency of the heating network in accordance with the requirements of SP 124.13330.2012. It was shown that the consumption of heat and coolant, as well as the diameter of pipes in closed and open circuits, are almost the same. The main difference is in the amount of recharge and power consumption. However, with closed circuits, the load on cold water systems. It was no coincidence that the choice of an open or closed scheme is determined by the availability and capacity of water supply sources in the area of ​​the CHP and in the city.

According to local estimate, including the installation of heaters for hot water supply, thermometers, pressure gauges, water metering units, mud collectors, safety valves, regulators, as well as mounting and adjustment works, the costs amounted to about 645 thousand rubles. At the same time, the cost of a similar ITP for an open scheme does not exceed 213 thousand rubles.

Taking into account operating costs, the reduced costs for ITP of the specified capacity will amount to 882 thousand rubles / year for a closed circuit.

In table. 2 shows the results of comparing the economic indicators of open and closed heat supply schemes for IHS. The final data show that when transferring to a closed scheme, additional costs may amount to about 900 thousand rubles. for one IHS of a residential building with a total heat load of 420 kW. Given the number of facilities, the capital costs for the re-equipment of ITPs can amount to at least 6 million rubles for a residential area.

In addition, with a closed scheme, operating costs increase to 250 thousand rubles / year for one ITP, and for a quarter - up to 2.5 million rubles / year.

The results obtained make it possible to evaluate the energy efficiency of the heating network in accordance with the requirements of the Code of Rules SP 124.13330.2012. Energy efficiency is characterized by the ratio of thermal energy received by consumers to thermal energy issued from the source.

Let's compare the main indicators of open and closed circuits (Table 3). It was shown that the consumption of heat and coolant, as well as the diameter of the pipes in closed and open circuits, are almost the same. The main difference is in the amount of recharge and power consumption. However, with closed circuits, the load on cold water supply systems increases. It is no coincidence that experts pointed out that the choice of an open or closed circuit is determined by the availability and capacity of water supply sources in the area of ​​​​the CHP and in the city.

The analysis performed in this article confirms the need for detailed calculations and a feasibility study, taking into account regional conditions and plans for the development of municipalities.

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