Closed heating system. Classification of heat supply systems (ST)

In our latitudes, it is impossible to do without heating. Too cool autumn and spring, long winter leave no choice - all rooms have to be heated to create comfortable conditions life. At the same time, along with heat, hot water is also supplied to apartments, organizations and enterprises.

In order to provide heat supply services, in accordance with the law, an appropriate agreement must be concluded between the supplier and the consumer.

Space heating systems are divided into open or closed.

At the same time, heating also happens:

• centralized (when heating is provided by one boiler house for the whole microdistrict);
• local (installed in a separate building or serving a small complex of buildings).

The difference between closed systems and open systems is quite significant. The latter involves the supply of heated water to consumer homes, while taking it directly from the heating network.

Open heating system

In this format, boiling water is sent to the water supply directly from the heating pipes, which allows you to completely avoid full consumption even if its entire volume is taken. In Soviet times, the work of about half of all heating networks was based on this principle. Such popularity was due to the fact that the scheme helped to use energy resources more economically and significantly reduce heating costs in winter period and hot water supply.

However, this method of supplying residential buildings with heat and boiling water has many disadvantages. The thing is that very often heated water, due to its dual purpose, does not meet sanitary and hygienic standards. The heat carrier can circulate through the metal pipes enough long time before it enters the faucets. As a result, it often changes its color and acquires bad smell. In addition, employees of the sanitary and epidemiological services have repeatedly identified dangerous microorganisms in it.

The need to filter such water before supplying it to the hot water supply system greatly reduces efficiency and increases the cost of heating. At the same time, there is no truly effective way to purify such water until now. The significant length of the pipelines actually makes this procedure useless.

The circulation of water in such a system occurs due to the consideration of thermodynamic processes in the design. The heated liquid rises and leaves the heater due to the increase in pressure. At the same time, cool water creates a slightly lower pressure at the boiler inlet. This is what allows the coolant to move independently through communications.

Water, like any other liquid, increases in volume when heated. Therefore, in order to prevent excessive load on the heating networks, their design necessarily includes a special open expansion tank located above the level of the boiler and pipes. Excess coolant is squeezed out there. This gives grounds to call such a system open.

Heating in this case occurs up to 65 degrees Celsius, and then water flows directly through the taps to the consumers' houses. This system allows the installation of inexpensive simple mixers.

Due to the fact that to predict how much hot water will be used, it is impossible, it is always served according to the highest consumption.

Closed circuit heating systems - what is it

The difference between this scheme of centralized heating of houses and the previous one is that hot water is used exclusively for heating. Hot water supply is provided by a separate circuit or individual heating devices.

The circulation of the coolant occurs in a vicious circle; minor losses that occur are made up for by automatic pumping in case of pressure loss.

The temperature of the supplied water is regulated directly in the boiler room. The volume of boiling water in this system remains the same. Thus, the intensity of space heating directly depends on the temperature of the liquid circulating through the pipes.

Heat points play an important role in this home heating scheme. In them, water comes from a thermal power plant, and already there, with its help, the coolant is heated, which is supplied to consumers.

Open System Phase Out

At the beginning of 2013, amendments to the law regulating the provision of heat supply services were put into effect.

In accordance with them, a complete transition from an open scheme for the distribution of heat and hot water should be completed in 2022. It is already forbidden to connect new buildings to this type of heating and water supply. According to experts, it will take a truly titanic effort to ensure the implementation of this plan. But legislators are confident that it is quite possible to cope with this task.

It is noted in this regard that due to the transfer of the entire country to closed systems, it will be ensured:

• reduction of heat losses;
• extension of the service life of communications;
• slowing down the aging of heating equipment;
• improving the quality of services provided;
• reduction in the number of accidents at heating mains.

At the same time, due to the release of resources, heating of new buildings will be organized without construction by old facilities.

Experts expect to get the greatest effect in those settlements where housing construction is most actively carried out.

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 open circuit.

The existence of such a scheme has the following disadvantages:
- increased heat consumption 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 large heat losses and the number of damages in 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. A brief description of the proposed method, its novelty and awareness of it, the availability of development programs; result in mass implementation nationwide

With a closed heat supply scheme, the preparation of hot water takes place in heating points, which receive purified cold water and a coolant. In the heat exchanger, cold water, passing along the heat carrier tubes, heats up. Thus, there is no mixing of 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 used 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 of stations and boiler houses for heat supply to newly connected consumers.

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

Maximum efficiency from implementation this event 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. Identify the reasons why the proposed energy efficient technologies are not applied on a mass scale; outline an action plan to remove existing barriers

Currently, most of the heat supply systems in the capital (JSC Moscow United Energy Company and OJSC Moscow Heat Network Company) operate 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 of an open scheme in many cities.

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

It is impractical to put into operation closed hot water circuits in cities with tap water characterized by low salinity and high corrosive activity 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

There are no existing measures to encourage and coerce the introduction of this method.
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

Development needed normative documentation on the introduction and operation of hot water 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 heat supply system to a closed one.

Specialists of OAO VNIPIenergoprom have developed technical solutions for transferring the existing heat supply system of the city of Zelenograd to 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 (changing the environmental situation, possible impact on human health, increasing the reliability of energy supply, changing daily or seasonal load schedules for 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 be of drinking quality and comply with sanitary rules and standards.

Introduction of closed DHW schemes 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 exacerbated by a shortage of qualified personnel due to low salaries and a 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 suggestions.

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 of modern heat supply systems. 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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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 is created at the boiler outlet, and a slight vacuum is created at the inlet to the heat generator. Further, the liquid is directed from the zone of high pressure to the zone of lower pressure, and as a result, the natural circulation of the coolant is carried out.

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

In the open type, water is heated to 65 degrees and then supplied to the taps, from where it is supplied 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

It is a closed heat supply system 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.

In the closed version of providing space heating, the heat supply is controlled centrally, 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 closed type heat supply systems, 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 in operation, the heat supply scheme ensures high quality of hot water supply and energy-saving effect. Its main drawback is the complexity of water treatment due to the remoteness of one heat point from another.

Dependent and independent heating systems

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

Dependent way of connecting an open system means connecting through elevators and pumps. In the independent type, hot water enters through a heat exchanger.

An example of an open heating system on video:

For space heating, a closed and open heat supply system is used. The latter option additionally provides the consumer with 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 deteriorates: it becomes cloudy, acquires color, and has an unpleasant odor. 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. Branches 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 units, 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 circuit. The water in it is heated through heat exchangers from the CHP main. Required here. The temperature regime 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 supplied to the heat points. There, the water is brought to the required parameters. For heating and hot water systems, different

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 disrepair. 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 a special technology, filling the gap between the steel pipe located inside and the shell with foam.

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

For residential premises, there are heating standards, which indicate critical temperature levels and permissible errors, 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.

Most occur 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.

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.

Autonomous systems are designed taking into account 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. In centralized systems, the hydrodynamic method is used. 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 outlines the basic concepts and general provisions that define the scope of the legal foundations of economic relations in heat supply. It also includes providing 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 legal aspects of connection to thermal networks are considered.
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, the conditions for the functioning and development of the system for providing heat to an urban district, settlement. In relation to her the 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 organization of heat supply.

Conclusion

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

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.

Implementation methods are found at the expense of commercial and budgetary financing, competitions for investment projects, and other events.

It happens that private houses located within the city are located next to the laid district heating networks, and some are even connected to them. Of course, at the present time, the priority is individual heating, and centralized heating is gradually becoming a thing of the past. But if the house is already connected to the network or there are problems with the autonomous system, then you need to use what is available. For the joint operation of the heat source with consumers, a dependent and not dependent system heating. What they are, as well as the pros and cons of both schemes will be outlined in this material.

Dependent (open) heat supply system

The main feature of the dependent system is that the coolant flowing through the main networks directly enters the house. It is called open because the coolant is taken from the supply pipeline to provide the house with hot water. Most often, such a scheme is used when connecting multi-apartment residential buildings, administrative and other buildings to heating networks. common use. The operation of the scheme of the dependent heating system is shown in the figure:

When the temperature of the coolant in the supply pipe is up to 95 ºС, it can be directed directly to the heating devices. If the temperature is higher and reaches 105 ºС, then a mixing elevator unit is installed at the entrance to the house, whose task is to mix the water coming from the radiators into the hot coolant in order to lower its temperature.

For reference. The centralized dependent heating system has a calculated and actual temperature schedule. The calculated graph characterizes the maximum water temperature and in an open system it can be 105 / 70 ºС or 95 / 70 ºС. Actual schedule depends on weather conditions and can change daily, it is maintained at the central heating point. When there are no severe frosts outside, the coolant temperature is much lower than the calculated one.

The scheme was very popular during the Soviet era, when few people cared about energy consumption. The point is that the dependent connection with elevator nodes mixing works quite reliably and practically does not require supervision, and installation work and material costs are quite cheap. Again, there is no need to lay additional pipes to supply hot water to houses when it can be successfully taken from the heating main.

But this is where the positive aspects of the dependent scheme end. And there are many more negative ones:

• dirt, scale and rust from the main pipelines safely enters all consumer batteries. old cast iron radiators and steel convectors didn’t care about such trifles, but modern aluminum and other heating devices definitely didn’t care;
• due to a decrease in water intake, repair work and other reasons, a pressure drop often occurs in a dependent heating system, and even water hammer. This threatens with consequences for modern batteries and polymer pipelines;
• the quality of the coolant leaves much to be desired, but it goes directly to the water supply. And, although the water in the boiler room goes through all the stages of purification and desalination, kilometers of old rusty highways make themselves felt;
• it is not easy to regulate the temperature in the rooms. Even full bore thermostatic valves fail quickly due to Bad quality coolant.

Independent (closed) heating system

At present, when installing new boiler houses, an independent scheme for connecting the heating system has become more often used. It has a main and an additional circulation circuit, hydraulically separated by a heat exchanger. That is, the coolant from the boiler house or CHP goes to the central heating point, where it enters the heat exchanger, this is the main circuit. An additional circuit is a house heating system, the coolant in it circulates through the same heat exchanger, receiving heat from the network water from the boiler room. The scheme of operation of an independent system is shown in the figure:

For reference. Previously, bulky shell-and-tube heat exchangers were installed in such systems, which took up a lot of space. This was the main difficulty, but with the advent of high-speed plate heat exchangers, this problem ceased to exist.

But what about the centralized supply of hot water, because now it is impossible to take it from the main, the temperature is too high there (from 105 to 150 ºС)? It's simple: an independent connection scheme allows the installation of any number of plate heat exchangers connected to the main pipelines. One will provide heat for the heating system at home, and the second can prepare water for household needs. How this is implemented is shown in the diagram:

To ensure that hot water always arrives at the same temperature, the DHW circuit is closed with the organization of automatic make-up in the return pipeline. In apartment buildings, the DHW circulation return line can be seen in the bathroom, heated towel rails are connected to it.

Obviously, the operation of an independent heating system has a lot of advantages:

• the home heating circuit does not depend on the quality of the external coolant, the condition of the main networks and pressure drops. The entire load falls on the plate heat exchanger;
• it is possible to regulate the temperature in the rooms with the help of thermostatic valves;
• the coolant in a small circuit can be filtered and cleaned of salts, the main thing is that the pipes are in good condition;
• in the DHW system there will be drinking quality water entering the house through the water main.

However, due to the dirty low-quality coolant in the central network, periodic flushing of an independent heating system, or rather, a plate heat exchanger, will be required. Fortunately, this is not so difficult to do. Another disadvantage is the higher costs for the purchase of equipment, namely: heat exchangers, circulation pumps and shut-off and control valves. But a closed system is more reliable and safer than an open one, it meets modern requirements more and is better adapted to new equipment.

Conclusion

If for some reason you happen to choose a scheme for connecting to centralized networks, then an independent heating system of a private house is preferable. Even if the temperature in the line is low, you still should not supply this water to your system, it is better to hydraulically separate it from the central one. Provided that such an opportunity exists in the material plane, and if not, you will have to crash directly, according to a dependent scheme.

Heat supply is the supply of heat to residential, public and industrial buildings and structures to provide both domestic (heating, ventilation, hot water) and technological needs of consumers.

Heat supply is local and centralized. The district heating system serves residential or industrial areas, while the local heating system serves one or more buildings. In Russia, district heating has gained the most importance.

Depending on the method of connecting the hot water supply system to the heat supply system, the latter is divided into open and closed.

Open heating systems

Open heat supply systems are characterized by the fact that hot water for the needs of the consumer is drawn directly from the heating network, and it can be either full or partial. The hot water remaining in the system continues to be used for heating or ventilation.

The water consumption in the heating network with this method is compensated by the additional amount of water that is supplied to the heating network. The advantage of an open heating system lies in its economic benefits. During the Soviet period, almost 50% of all heat supply systems were open.

At the same time, one cannot discount the fact that such a heat supply system also has a number of significant drawbacks. First of all, this is a low sanitary and hygienic quality of water. Heating devices and pipeline networks give the water a specific smell and color, various impurities appear, as well as bacteria. To purify water in an open system, they are usually used various methods, but their use reduces the economic effect.

An open heat supply system can be dependent on the method of connection to heat networks, i.e. connected through elevators and pumps, or connected according to an independent scheme - through heat exchangers. Let's dwell on this in more detail.

Dependent heating systems

Dependent heat supply systems are such systems in which the coolant through the pipeline enters immediately into the consumer's heating system. There are no intermediate heat exchangers, heat points and hydraulic isolation. Undoubtedly, such a connection scheme is understandable and structurally simple. It is easy to maintain and requires no additional equipment such as circulation pumps, automatic control and monitoring devices, heat exchangers, etc. Most often, this system attracts with its, at first glance, efficiency.

However, it has a significant drawback, namely, the inability to adjust the heat supply at the beginning and end of the heating season, when there is an excess of heat. This not only affects the comfort of the consumer, but also leads to heat loss, which reduces its initial apparent efficiency.

When energy saving issues become relevant, methods are being developed and actively implemented for the transition of a dependent heat supply system to an independent one, this allows saving heat by about 10-40% per year.

Independent heating systems

Independent heat supply systems are systems in which the heating equipment of consumers is hydraulically isolated from the heat producer, and additional heat exchangers of central heating points are used to supply heat to consumers.

An independent heating system has a number of undeniable advantages. This is:

• the ability to control the amount of heat delivered to the consumer by regulating the secondary heat carrier;
• its higher reliability;
• energy-saving effect, with such a system, heat savings are 10-40%;
• opportunity to improve operational and technical qualities coolant, which significantly increases the protection of boiler installations from pollution.

Thanks to these advantages, independent heat supply systems have become actively used in major cities, where the heating networks are quite long and there is a large spread of thermal loads.

At present, technologies for the reconstruction of dependent systems into independent ones have been developed and are being successfully implemented. Despite the significant investment, this eventually gives its effect. Naturally, an independent open system is more expensive, but it significantly improves water quality compared to a dependent one.

Closed heating systems

Closed heat supply systems are systems in which the water circulating in the pipeline is used only as a heat carrier and is not taken from the heat system for the needs of providing hot water. With this scheme, the system is completely closed from the environment.

Of course, coolant leaks are also possible with such a system, however, they are very small and easily eliminated, and water losses are automatically replenished without problems using the make-up regulator.

Heat supply to closed systems e heat supply is regulated in a centralized way, while the amount of heat carrier, i.e. water remains unchanged in the system. The heat consumption in the system depends on the temperature of the circulating coolant.

As a rule, in closed heat supply systems, the capabilities of heat points are used. A heat carrier is supplied to them from a heat energy supplier, for example, a CHPP, and its temperature is regulated to the required value for the needs of heating and hot water supply by district central heating points, which distribute it to consumers.

Advantages and disadvantages of a closed heating system

The advantages of a closed heating system are high quality hot water supply. In addition, it gives an energy-saving effect.

Its, practically, the only drawback is the complexity of water treatment due to the remoteness of heat points from each other.

Topic 6 Heat supply systems

Classification of heat supply systems.

Thermal schemes heat sources.

Water systems.

Steam systems.

Air systems.

The choice of heat carrier and heat supply system.

Classification of heat supply systems (ST)

Heat supply system (ST) is a set of heat sources, devices for heat transport (heat networks) and heat consumers.

The heat supply system (ST) consists of the following functional parts:

Source of heat energy production (boiler house, CHPP);

Transporting devices of thermal energy to the premises (heat networks);

Heat-consuming devices that transmit thermal energy consumer (heating radiators, heaters).

Heat supply systems (ST) are divided into:

1. At the place of heat generation at:

centralized and decentralized.

In decentralized systems The heat source and heat sinks of consumers are combined in one unit or are close to each other, so no special devices for heat transport (heating network) are required.

AT centralized system The source and consumers of heat supply are significantly removed from each other, so heat is transferred through heating networks.

Systems decentralized heat supplies are divided into individual and local .

ATindividual systems, the heat supply of each room is provided from a separate own source (stove or apartment heating).

ATlocal systems, heating of all premises of the building is provided from a separate common source (house boiler).

centralized heat supply can be divided into:

- for group - heat supply from one source of a group of buildings;

- regional - heat supply from one source of the district of the city;

- urban - heat supply from one source to several districts of the city or even the city as a whole;

- intercity - heat supply from one source of several cities.

2. according to the type of transported coolant :

steam, water, gas, air;

3. According to the number of pipelines for transferring the coolant to:

- one-, two- and multi-pipe;

4. according to the method of connecting hot water supply systems to heating networks:

-closed(water for hot water supply is taken from the water supply and heated in the heat exchanger with network water);

- open(water for hot water supply is taken directly from the heating network).

5. by type of heat consumer for:

- communal - household and technological.

6. according to the schemes for connecting heating installations to:

-dependent(the coolant heated in the heat generator and transported through heating networks enters directly into the heat-consuming devices);

-independent(the coolant circulating through the heating networks in the heat exchanger heats the coolant circulating in the heating system.

Figure 6.1 - Schemes of heat supply systems

When choosing the type of coolant, it is necessary to take into account its sanitary and hygienic, technical, economic and operational indicators.

gasesare formed during the combustion of fuel, they have a high temperature and enthalpy, however, the transportation of gases complicates the heating system and leads to significant heat losses. From a sanitary and hygienic point of view, when using gases, it is difficult to ensure the permissible temperatures of the heating elements. However, being mixed in a certain proportion with cold air, gases in the form of a now gas-air mixture can be used in various technological installations.

Air- easily movable coolant, used in air heating systems, allows you to quite simply regulate the constant temperature in the room. However, due to low heat capacity(about 4 times less than water), the mass of air heating the room must be significant, which leads to a significant increase in the dimensions of the channels (pipelines, ducts) for its movement, an increase in hydraulic resistance and energy consumption for transportation. Therefore, air heating industrial enterprises carried out either combined with ventilation systems, or by installing special heating installations in the shops ( air curtains etc.).

Steamduring condensation in heating devices (pipes, registers, panels, etc.) it gives off a significant amount of heat due to the high specific heat of conversion. Therefore, the mass of steam at a given thermal load is reduced compared to other coolants. However, when using steam, the temperature outer surface heating devices will be above 100 ° C, which leads to the sublimation of the dust settled on these surfaces, to the release in the premises harmful substances and unpleasant odors. In addition, steam systems are sources of noise; the diameters of the steam pipelines are quite significant due to the large specific volume of steam.

Waterhas a high heat capacity and density, which allows you to transfer large quantities heat over long distances with low heat losses and small pipeline diameters. The surface temperature of water heating devices meets sanitary and hygienic requirements. However, the movement of water is associated with high energy costs.

Let's see what is the difference between an open heating system and a closed one.

Open heating systems are usually pipelines with natural circulation of the coolant and an open expansion tank, which is located at the top of the system. Heated by the heating source (heating boiler), the coolant rises to the top, to the expansion tank, from where it naturally spills over heat consumers (heating radiators) and returns to the boiler for subsequent heating. At first glance, everything is simple, and the system turns out to be non-volatile, but there are some nuances.

Pipelines in an open heating system are much larger in diameter than in closed heating systems, since the coolant needs room to maneuver. The diameter of the pipes is calculated depending on the power of the system.

In open heating systems, it is impossible to use water-heated floors, as they simply will not work.

Evaporation occurs in an open-type expansion tank, and therefore the system requires constant replenishment. And this make-up is necessary according to the level of the coolant, since there is no pressure in open heating systems.

In addition, in open heating systems, heating devices (radiators) with a large flow diameter are required. Conventional modern radiators are not suitable for such systems.

Many owners of country houses, faced with an open heating system, begin to redo it and make mistakes by installing modern radiators. The open system stops working and you have to install a circulation pump, a closed expansion tank. The system immediately turns into a closed heating system, only with large diameters of pipelines and improper circulation of the coolant, but somehow it works.

The use of open systems occurred at a time when a Russian stove was used to heat houses, and heating boilers were not as common as they are now. And there were no domestic circulation pumps.

A closed heating system is a system with forced circulation coolant, through a circulation pump, the expansion of which occurs due to expansion tank membrane type.

Circulation in such systems occurs through pipelines of a much smaller diameter than in open heating systems. This system works more efficiently, and with the correct calculation, fast and uniform heating of all heat consumers occurs. In closed-type heating systems, it is possible to use any heat consumers (heating radiators, water heated floors, forced ventilation, boiler indirect heating, etc.). When using modern energy-saving circulation pumps, a closed heating system consumes a negligible amount of electricity, and you can protect yourself from turning it off with an uninterruptible power supply of very low power.

To equip a house today with an open heating system would be at least stupid, since it has already become obsolete. It's just like using an old tube TV today. It shows badly, it consumes a lot of electricity, it makes noise, but somehow it works.

Reworking, adding, breaking the scheme of an open heating system, you immediately reduce the efficiency of its work. It is easier to refuse any modifications or processing in an open heating system and immediately mount a closed heating system.

Comparing the open and closed heating systems, we can conclude that by giving preference to the second one, only pluses are obtained, and with the correct heat engineering calculation and qualified installation, it will work for many years.

Open and closed heating systems.

Descriptions of open and closed heat supply systems, their fundamental differences on the Internet can be found a huge amount, therefore detailed description we will not give. Let us dwell only on their fundamental differences, without understanding which it will be difficult to understand examples from practice in the future. As a basis, we take what the reader is not yet in the subject. For specialists in housing and communal services, this section can be skipped, rightly believing that this information is not of particular value to him, he already knows everything and understands everything.

So let's start with the main differences. Heat supply systems are fundamentally divided into two main groups. These are open systems and closed systems. The fundamental and main difference is that in open heat supply systems, hot water supply is taken directly from the heat supply system of a residential building (heating system), which creates problems with the quality of hot water supply. The presence of various suspensions, rust and other substances is possible in water. Represents a particular complexity and the possibility of flushing, maintenance of this system. Despite the negative attitude towards the open heating system at present, the system received wide use during the construction boom in the second half of the twentieth century due to its simplicity of design and installation in the construction of new houses, relatively low cost. In those years, energy conservation issues were in last place, we somehow did not consider resources, assuming that they were eternal. And the issue of further operation of these systems was not taken into account at all.

In turn, open heat supply systems are divided into dependent and independent. The simplest is an open, dependent heat supply system. The diagram below shows that the coolant goes to the consumer directly from the boiler room and the selection of hot water in a residential building (not shown in the diagram) is taken into DHW system directly from the heating system of a residential building. The simplest and at the same time inefficient heating system.

An open heat supply system (independent) is already a new stage in the development of heat supply systems. The system, due to the use of a heat exchanger in the system, has a separate circuit. That is, boiler water circulates in its own circuit, the consumer's heating system in its own way. When using this system, the organization dealing with the operation of the heating network got the opportunity to chemically treat network water, which undoubtedly affected the durability of the systems and boiler plants. Currently, a mass transfer of systems from a dependent scheme to an independent one is being carried out. However, an independent system did not solve the problem of the quality of hot water supply. DHW remained the most vulnerable system due to the intake of hot water from the heating system.

The final stage in the development of heat supply systems at the present time has rightfully become a closed heat supply system, which solved the problem of providing residents with high-quality hot water supply. There are many schemes for the execution of closed heat supply systems, but the main principle for it is the same. This is the presence of separated circuits, both heating systems and hot water systems. This is clearly seen in the diagram below (to unload the circuit, we did not show the piping of the central heating equipment and the circulation pumps that are present in this diagram).