Open and closed heating system - advantages and disadvantages in comparison. Closed and open heat supply system: features, disadvantages and advantages

Gives the following definition of the term "heat supply":

Heat supply- a system for providing heat to buildings and structures, designed to provide thermal comfort for the people in them or to be able to comply with technological standards.

Any heating system consists of three main elements:

1. heat source. This may be a CHP plant or a boiler house (with a district heating system), or simply a boiler located in a separate building (local system).
2. Thermal Energy Transportation System(heating network).
3. Heat consumers(heating radiators (batteries) and heaters).

Classification

Heat supply systems are divided into:

• Centralized
• Local(they are also called decentralized).

They may be water and steam. The latter are rarely used today.

Local heating systems

Everything is simple here. AT local systems ah, the source of thermal energy and its consumer are located in the same building or very close to each other. For example, a boiler is installed in a separate house. The water heated in this boiler is subsequently used to meet the heating needs of the house and hot water.

District heating systems

In a centralized heat supply system, the source of heat is either a boiler house that produces heat for a group of consumers: a quarter, a city district, or even an entire city.

With such a system, heat is transported to consumers through the main heating networks. From the main networks, the coolant is supplied to central heating points (CHP) or individual heating points (ITP). From the central heating station, heat is already delivered through quarterly networks to the buildings and structures of consumers.

According to the method of connecting the heating system, heat supply systems are divided into:

• Dependent systems- the heat carrier from the source of thermal energy (CHP, boiler house) goes directly to the consumer. With such a system, the scheme does not provide for the presence of central or individual heating points. Speaking plain language, water from heating networks flows directly into the batteries.

• Independent systems - in this system there are TsTP and ITP. The coolant circulating through the heating networks heats the water in the heat exchanger (1st circuit - red and green lines). The water heated in the heat exchanger circulates already in the heating system of consumers (circuit 2 - orange and blue lines).

With the help of make-up pumps, water losses through leaks and damages in the system are replenished and pressure is maintained in the return pipeline.

According to the method of connecting the hot water supply system, heat supply systems are divided into:

• Closed. With such a system, water from the water supply system is heated by a coolant and supplied to the consumer. I wrote about her in an article.

• Open. In an open heating system, water for DHW needs is taken directly from the heating network. For example, in winter you use heating and hot water from one pipe. For such a system, the figure dependent system heat supply.

In open heat supply systems, the water prepared in the boiler unit not only serves as a heat carrier, but also goes to the needs of hot water supply, i.e., water is taken directly from the pipelines of the heating network without intermediate heaters. The amount of make-up water in this case is determined by the loss of water in the networks, in the boiler room (2 - 2.5% of the consumption of network water) and the consumption of water for hot water supply needs. To equalize the daily load schedule for hot water supply, it is planned to install storage tanks, the volume of which is 9 times greater than the average hourly daily water consumption for hot water supply.

principled thermal scheme heating boiler house with an open two-pipe heat supply system is shown in fig. 7.9. Thermal and hydrodynamic modes of water-heating boiler units, water treatment of cold water treatment, recirculation units (line SD) and mixing bridge AB, creating a vacuum in the HP vacuum deaerator are similar to those considered earlier. Heat removed with steam D issue used to heat softened water in the T3 vapor cooler.

From the vacuum deaerator, the water supply enters by gravity into the tank of deaerated water BD, from where it is fed by a transfer pump PN to the storage tank BA. Usually at least two metal tanks are installed, inner surface which is protected by an anti-corrosion coating, and the outer one - by thermal insulation. Water is taken from the BA storage tank by the make-up pump PPN and supplied to the heating networks.

Operation of the heating network in winter heating mode. Water from the return pipeline with a pressure of 0.2 - 0.4 MPa is supplied to the suction manifold of the SN network pumps. Water is also supplied there from make-up pumps through the line KN(lines KL and EF blocked by valves), as well as chilled water from the heat exchangers of softened water T2 and raw water T1 (Fig. 7.9)

Rice. 7.9. circuit diagram heating boiler room with an open two-pipe
heating system

Return network water is pumped by network pumps SN into the hot water boiler unit KA, where it is heated to a temperature of 150 ° C, and at the outlet of the boiler it is divided into three streams: heating network, for recycling and for the own needs of the boiler house, which include water consumption:

for the oil industry,

for water heating up to 70 °C in a vacuum deaerator,

on the T2 heat exchanger for heating up to 65 ° C of softened water,

on the T1 heat exchanger for heating up to 30 ° C of the source water .

Chilled water from the heat exchangers T1 and T2 enters the suction manifold of the network pumps SN. The water flow through the hot water boiler units is determined for the maximum winter mode and, according to the operating conditions, is taken constant under various modes.

The temperature of the water entering the heating and ventilation system of the consumer, ~ 95 °C, regulated by the elevator unit E by mixing direct network water with return water from the heating system.

The average hourly consumption of hot water supplied to the consumer per day is a calculated value, constant and independent of the season. In the maximum winter mode, the DHW consumer, directly to the water taps, receives return network water from the heating and ventilation system. In other modes of operation during the heating period, the temperature of the return network water drops below the temperatures normalized for hot water supply, therefore, in the hot water preparation unit S to the return network water through the temperature controller RTG, mixed required amount direct network water.

Part of the water (5 - 10% of the consumer's consumption) passes through the heated towel rails, cools down to a temperature of 40 - 45 ° C and through the circulation line circulation pump The CH is returned to the return pipeline of the heating system.

When working during the heating period, it must be taken into account that due to the high water consumption through the water treatment unit, the make-up water supplied to the return pipeline and the used heating water (units M and N) are mixed with return network water and significantly change the flow temperature. After calculating the final temperature of the flow, the coolant flow rates are determined along the recirculation line and through the mixing bridge.

At the final stage, the correctness of the calculation of the operating modes of the thermal scheme is controlled by checking the compliance of the heat consumption values ​​accepted and obtained as a result of the calculation for own needs and the total heat output of the boiler house. If the discrepancy exceeds 2%, the calculation is repeated.

Operation of the thermal circuit in summer mode. The presence in the storage tanks of make-up water in the amount and temperature corresponding to the purposes of hot water supply makes it possible in the summer, in the absence of a heating and ventilation load, to supply this water directly to the heating network. Through the return pipeline, only circulating water from local hot water supply systems will return to the boiler room, which is sent through the unit E to the BA accumulator tanks along the line EF.

Thus, in summer period the hot water boiler unit is disconnected from the heating network on the site NE return pipeline and at the site BL supply pipeline. Water for hot water supply will be supplied to the supply pipeline of the heating system directly from the BA accumulator tanks through the line KL make-up pump, which in this case is called "summer" (line KN at the same time closed with a valve).

The boiler unit in the summer is turned on only for load q sn, and the water flow through the boiler unit is the sum of the heating water flows , entering the heat exchangers T1, T2 and the HP vacuum deaerator. Therefore, with a low share of the load of the hot water supply of the boiler house (0.25 - 0.3) in the summer, the number of boiler units is reduced to one.

For space heating, closed and open system heat supply. 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 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 large diameter and wrapped in thermal insulation. 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 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 circuit. 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 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 using a special technology, filling the gap between the inside with foam 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.

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. AT centralized systems 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 introduces the basic concepts and general provisions, defining the scope legal framework economic relations in heat supply. It also includes provision of hot water. Approved general principles organization of heat supply, which consists in the creation of reliable, efficient and developing systems, which is very important for living in a 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 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.

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

Supply of heat with the help of a coolant (hot water or steam) for heating, ventilation, hot water supply systems of residential, societies. and prom. buildings and technology consumers. The most promising is district heating, which provides heat to many consumers located outside the place of generation. Such a center can be: a boiler room in the basement of a house serving several buildings; a separate boiler house providing heat for a quarter, several quarters or a district of the city, prom. enterprise or industry node; urban or industrial combined heat and power plant (CHP). The creation of centralized heat supply is the main direction in the development of heating in the USSR.

District heating system consists of a heat source (boiler house or CHP), a system of pipelines (heat networks) supplying heat from the source to consumers. Boiler plants as sources of heat in heat supply systems are used to heat water (up to 200 ° C) or produce steam (up to 20 am). Generation-based heat recovery for district heating electrical energy is carried out at the CHP, where for this purpose special heating turbines are installed. According to the nature of the satisfaction of thermal loads, communal, industrial and district thermal power plants are distinguished. According to the initial steam pressure, CHPPs are: medium, high, increased and over high pressure(35, 90, 110 and 240 am).

The steam produced in the CHPP boilers enters the heating turbine through the intra-station steam pipelines, where it drives the turbine rotor and through it the electric rotor. generator. In this process, part of the thermal energy of the steam is converted into electricity, and the steam, with the remaining part of the thermal energy in it, leaves the turbine and is used for the purpose of heat supply.

If consumers require steam as a heat carrier (for technological needs), the last from the turbine enters the heating network directly through a steam compressor or steam converter. Through the steam converter, steam is supplied to such consumers, which cannot return condensate that meets the requirements for supplying high-pressure boilers at a thermal power plant. The steam that gave up its heat to consumers (or in the steam converter when receiving secondary steam) turns into condensate, which is sent to the boiler, where it turns back into fresh steam and enters the turbine.

If consumers need hot water as a heat carrier (for heating, ventilation and hot water supply), steam from the turbine is sent to water heaters, where it heats the water circulating in the heat supply system to the required temperature. In the heat supply system, a closed circulation of water is carried out using centrifugal (network) pumps.

At the subscriber inputs of district heating systems, a connection is made between heat sources and consumers. Consumers extract heat from the heating system at the expense of installed heat exchangers: heaters (in heating systems), heaters (in ventilation systems), water-water or steam-water heaters of tap water in hot water supply systems, and heat exchangers of various technological units. consumers.

Water, as a heat carrier, has a number of advantages compared to steam: the possibility of central high-quality control of heat supply; maintaining the necessary hygiene temperature conditions of heating devices (including below 100 ° C); decrease in the average daily steam pressure for heating water circulating in heating networks, and next. reduction of fuel consumption for heat supply from CHP; simplicity of connections to thermal networks; ease of maintenance and quiet operation.

Depending on the method of connecting the hot water supply systems of buildings to water and heat networks, there are closed and open heating systems. If the building's hot water supply systems are connected to heating networks through water heaters, when all the network water from the T. system returns to the T. source, then the system is called. closed; in the case when hot water is directly taken from the heating network - open. Water heating systems for buildings can be connected directly through an elevator or independently through a water heater. Closed heat supply systems require devices from consumers of heat exchangers to heat tap water supplied to hot water supply, and sometimes water treatment. Heat exchangers and water treatment equipment, depending on the amount of water consumption of the subscriber, can be installed in individual heating points (I.T.P.) or central (Ts.T.P.). I. T. P. are arranged only at large facilities. In the absence of cellars, central heating stations are arranged for a group of houses or a quarter of the city, which leads to the construction (from these central heating stations to consumers) of expensive four-pipe heating systems.

With an open heating system, water treatment for hot water supply is carried out centrally in a boiler house or CHP and is carried out without fail, which eliminates the possibility of corrosion and scale formation in heating networks. For an open heating system, it is economical and promising to switch to a single-pipe direct-flow system when using a coolant - water for heating and hot water supply without returning to the heating source (boiler house or CHP) in the presence of storage tanks.

Steam heating systems arranged for the needs of technology. consumers. For prom. enterprises, the use of a single coolant - steam, to cover all loads, including heating, is allowed with an appropriate technical and economic. justification.

If necessary, meet technological consumers with steam and the availability means that heating loads are sometimes satisfied by mixed T. systems with water supply for heating, ventilation and hot water supply and steam for technological purposes. needs. Depending on the technical and economic justification for the needs of hot water supply and ventilation, steam can also be supplied.

Technological consumers, steam heating systems and ventilation systems are connected to the steam networks of the heat supply system directly, if the steam pressure in the network and at the consumer are the same, or through a reducer, if it is necessary to reduce the steam pressure. Condensate is returned to heat supply sources from consumers by pumping or by gravity. Hot water supply systems are connected to the steam systems of T. through steam-water heaters of tap water. If it is required to install water heating systems for consumers with steam heating systems, water is also heated through steam-water heaters.

Lit .: Kop'ev S.F.. Kachanov N.F., Fundamentals of heat supply and ventilation, M., 1964.

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Heat supply - a system for supplying heat to buildings to maintain comfortable temperatures indoors during the cold season. Heat supply systems are centralized and decentralized, dependent and independent open and closed. This article provides a detailed explanation of the principles of operation, as well as a comparison of the advantages and disadvantages of closed and open heating systems.

The heat supply system consists of the following components:

• an enterprise that produces heat (boiler house, power plant);
• pipelines for transportation of thermal energy (heating networks);
• heat consumers (radiators installed in the premises).

Classification of heat supply systems

There are the following types of heat supply schemes.

According to the amount of heat generated classify centralized and decentralized types of heat supply. In centralized systems, one heat source supplies several buildings. In a decentralized system, each building or group of houses, individual rooms generate heat independently.

Classification of decentralized types of heat supply, subdivides them into individual, when each apartment is heated independently and local - where the heat source heats the entire apartment building.

How to connect to networks classify dependent and independent types of heat supply systems. Dependent - when the coolant (liquid or steam) is heated in the boiler room and, passing through the pipeline network, enters the radiators of the heated room. Independent - liquid from the heating network passes through the heat exchanger and heats the home heating coolant (the coolant that is heated in the boiler room does not enter the house heat supply system).

According to the method of hot water supply and water heating Distinguish between open and closed types of heat supply.

Open heating system

In an open heat supply scheme, water heated in a boiler house is used simultaneously in hot water supply and as a heat carrier for heating appliances. Constant flow of water for the needs of hot water supply leads to the need for regular replenishment of the heating network. Due to the use of water in hot heat supply, its temperature should be 65-70 degrees. This scheme is very outdated, it was widely used in the USSR.

Advantages and disadvantages of open heating

Advantages open type coolant supply:

• minimum equipment as no heat exchangers are required;
• due to the fact that the water temperature is lower, the losses during transportation along heating mains over long distances are less than in a closed system.

disadvantages open circuit:

Dirty water. Due to the large length of the heating main, the liquid entering the hot water supply pipelines contains a large number of dirt, rust, which it collects along the way from the boiler house to the consumer. Due to the long length of heat supply pipelines, the water in the tap may have an unpleasant odor and color and may not comply with sanitary standards. Installing water treatment devices in every home will require significant cash costs.

The high demand for hot water during peak hours leads to a noticeable drop in pressure in the pipelines. Because of this, it forces resource-supplying enterprises to install additional booster pumps and automation to control the pressure in the system. Otherwise, the pressure drop will lead to a smaller amount of coolant passing through the heaters in the apartments, and as a result, a decrease in the air temperature in the premises.

High losses of liquid from the thermal system are forcing the installation of massive water treatment plants at boiler houses, thermal power plants and other energy-producing enterprises, which purify river water from salts and other impurities.

Differences between open and closed water supply schemes

In a closed system, unlike an open system, the liquid used as a heat carrier circulates through pipelines without leaving them. For hot water supply, drinking tap water is used, which is heated by a coolant in special devices (heat exchangers) installed in houses or central heating points. In closed circuits, the water temperature in the heating main ranges from 120 to 140 degrees, and fluid losses are absent or minimal.

Pros of a closed circuit:

• for hot water supply, clean tap water is connected, unlike an open circuit, which meets all sanitary and hygienic standards without impurities and unpleasant odors;
• there is no need to install additional pumps and devices for automatic control of parameters at heat supply enterprises, since the pressure in the heating network is constant and does not depend on the flow of hot water;
• on boiler houses and other sources of heat supply, it is not necessary to install additional water treatment plants, because the circulating liquid is already desalinated and contains a minimum amount of impurities;
• energy-saving effect achieved by adjusting desired temperature heat supply at heating points, performed in automatic mode.

The disadvantages of this heating system include expensive equipment and automation necessary for the installation of energy exchange points, where the temperature of heating tap water is regulated.

The second drawback is the high temperatures of heat carriers in the main heating mains and, as a result, high heat losses. This disadvantage has now lost its relevance due to the use of polyurethane foam pipe insulation technology, which ensures the strength of the insulation coating and effective protection from heat loss.

Use of heat points

To reduce the cost of a closed heat supply system, a central heating point (CHP) is installed for several houses or a microdistrict. CHP is a room with heat exchangers, pumps and automatic devices to regulate the water supply. Water supply pipelines and heating networks are connected to this building.

Important! tap water passes through heat exchangers, and, heating up, is fed into a circular hot water supply system, where it circulates along the circuit and, as necessary, is consumed by consumers.

The use of the central heating substation allows saving costs for the construction of heat points. Since the enlargement of the heat exchange installation by several blocks or a microdistrict, it reduces the cost of purchasing and installing equipment and automation, in comparison with the installation of a heat point in each house.