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Heating devices for central heating systems. Types of heating systems Types of heating devices heating systems

Heating devices systems central heating are called devices for transferring heat from a coolant to a heated room. Heating devices must best transfer heat from the coolant into the room, ensure a comfortable thermal environment in the room, without deteriorating its interior at the lowest cost of funds and materials.

The types and designs of heating devices can be very diverse. The devices are made of cast iron, steel, ceramics, glass, in the form of concrete panels with tubular heating elements embedded in them, etc.

The main types of heating devices are radiators, finned tubes, convectors and heating panels.

The simplest is heating device made of smooth steel pipes . It is usually implemented in the form of a coil or a register. The device has a high heat transfer coefficient and can withstand high coolant pressure. However, devices from smooth pipes expensive and take up a lot of space. They are used in rooms with significant dust emissions, for heating skylights in industrial buildings, etc.

The most widely used heating devices are radiators . Their different types differ from each other in size and shape. Radiators are assembled from sections, which allows you to assemble devices of different sizes. Typically the sections are cast from cast iron, but they can be steel, ceramic, porcelain, etc.

Quite widely used in heating systems cast iron finned pipes . The ribs on the surface of the pipe increase the heat-transfer surface area, but reduce the hygienic qualities of the device (dust accumulates, which is difficult to remove) and give it a rough appearance.

Convectors They are steel pipes with sheet steel fins. The most advanced among convectors is a convector in a casing made of steel sheet. The device is equipped with a cap to regulate heat transfer. Intense air circulation occurs between the finned surfaces of the device and the casing under the influence of gravitational pressure. This increases heat removal from the finned surface by 20% or more. Convectors in a casing are compact and have a good appearance. In some designs, convectors are equipped with a special type of fan that provides intense air movement. Artificial stimulation of air movement significantly increases heat removal from the device. Some disadvantage of convectors is the need and difficulty of cleaning from dust.

Concrete heating panels They are slabs with coils of steel pipes embedded in them. Such panels are usually located in the structures of room fencing. Sometimes they are installed freely near walls.

Currently, for heating large industrial workshops, suspended panels with reflective screens .

The use of panels for heating buildings satisfies the requirements of prefabricated construction and allows saving metal spent on heating devices. The disadvantages of panel heating include: large thermal inertia, which complicates the regulation of heat transfer; impossibility of changing the heating surface; the danger of pipe clogging and the difficulty of eliminating it; complexity of system repair; the possibility of internal corrosion and, as a result, a violation of the hydraulic tightness of the pipes.

IN heating system Heating devices are used to transfer heat to the room. Manufactured heating devices must meet the following requirements:

  1. Economic: low cost of the device and low material consumption.
  2. Architectural and construction: the device must be compact and match the interior of the room.
  3. Production and installation: mechanical strength of the product and mechanization in the manufacture of the device.
  4. Sanitary and hygienic: low temperature surfaces, small horizontal surface area, ease of cleaning surfaces.
  5. Thermal engineering: maximum heat transfer into the room and heat transfer control.

Classification of devices

The following indicators are distinguished when classifying heating devices:

  • — the magnitude of thermal inertia (large and small inertia);
  • - material used in manufacturing (metallic, non-metallic and combined);
  • — method of heat transfer (convective, convective-radiative and radiation).

Radiation devices include:

  • ceiling radiators;
  • sectional cast iron radiators;
  • tubular radiators.

Convective-radiation devices include:

  • floor heating panels;
  • sectional and panel radiators;
  • smooth-tube devices.

Convective devices include:

  • panel radiators;
  • finned tubes;
  • plate convectors;
  • tubular convectors.

Let's consider the most applicable types of heating devices.

Aluminum sectional radiators


Advantages

  1. high efficiency;
  2. light weight;
  3. ease of installation of radiators;
  4. efficient operation of the heating element.

Flaws

  1. 1. not suitable for use in old heating systems, since heavy metal salts destroy the protective polymer film aluminum surface.
  2. 2. Long-term operation leads to the unsuitability of the cast structure and to rupture.

    3. Mainly used in central heating systems. Operating pressure Radiator operation from 6 to 16 bar. Note that radiators that were cast under pressure can withstand the greatest loads.

Bimetallic models


Advantages

  1. light weight;
  2. high efficiency;
  3. possibility of quick installation;
  4. heat large areas;
  5. withstand pressure up to 25 bar.

Flaws

  1. have a complex structure.

These radiators will last longer than others. Radiators are made of steel, copper and aluminum. Aluminum material conducts heat well.

Cast iron heating devices


Advantages

  1. not subject to corrosion;
  2. transfer heat well;
  3. withstand high pressure;
  4. it is possible to add sections;
  5. The quality of the coolant does not matter.

Flaws

  1. significant weight (one section weighs 5 kg);
  2. fragility of thin cast iron.

The operating temperature of the coolant (water) reaches 130°C. Cast iron heating devices last quite a long time, about 40 years. Heat transfer rates are not affected by mineral deposits inside the sections.

There is a wide variety of cast iron radiators: single-channel, two-channel, three-channel, embossed, classic, enlarged and standard.

In our country economical option cast iron appliances are most widely used.

Steel panel radiators


Advantages

  1. increased heat transfer;
  2. low pressure;
  3. easy cleaning;
  4. simple installation of radiators;
  5. light weight compared to cast iron.

Flaws

  1. high pressure;
  2. metal corrosion, in the case of using ordinary steel.

Today, a steel radiator heats up better than a cast iron one.

Steel heating appliances have built-in thermostats that provide constant temperature control. The design of the device has thin walls and responds fairly quickly to the thermostat. Discreet brackets allow you to mount the radiator on the floor or wall.

The low pressure of steel panels (9 bar) does not allow them to be connected to a central heating system with frequent and significant overloads.

Steel tubular radiators


Advantages

  1. high heat transfer;
  2. mechanical strength;
  3. aesthetic appearance for interiors.

Flaws

  1. high price.

Tubular radiators are quite often used in room design because they add beauty to the room.

Due to corrosion, normal steel radiators not currently released. If you subject the steel to anti-corrosion treatment, this will significantly increase the cost of the device.

The radiator is made of galvanized steel and is not subject to corrosion. It has the ability to withstand pressure of 12 bar. This type of radiator is often installed in multi-storey buildings. residential buildings or organizations.

Heating devices of convector type


Advantages

  1. low inertia;
  2. small mass.

Flaws

  1. low heat transfer;
  2. high requirements for coolant.

Convector-type appliances heat the room quickly enough. They have several manufacturing options: in the form of a plinth, in the form of a wall block and in the form of a bench. There are also in-floor convectors.

This heating device uses copper tube. The coolant moves along it. The tube is used as an air stimulator ( hot air the top goes up and the cold one goes down). The air change process takes place in a metal box, which does not heat up.

Convector-type heating devices are suitable for rooms with low windows. Warm air from a convector installed near a window prevents cold air from entering.

Heating devices can be connected to a centralized system, as it is designed for a pressure of 10 bar.

Heated towel rails

Advantages

  1. variety of shapes and colors;
  2. high pressure levels (16 bar).

Flaws

  1. may not perform its functions due to seasonal interruptions in water supply.

Steel, copper and brass are used as manufacturing materials.

Heated towel rails are available in electric, water and combined types. Electric ones are not as economical as water ones, but they allow buyers not to depend on the availability of water supply. Combined heated towel rails must not be used if there is no water in the system.

Radiator selection

When choosing a radiator, you need to pay attention to the practicality of the heating element. Next, you need to remember the following characteristics:

  • overall dimensions of the device;
  • power (per 10 m2 area 1 kW);
  • operating pressure (from 6 bar - for closed systems, from 10 bar for central systems);
  • acidic characteristics of water as a coolant (this coolant is not suitable for aluminum radiators).

After clarifying the basic parameters, you can proceed to the selection of heating devices based on aesthetic indicators and the possibility of its modernization.

Heating devices are the main element of the heating system and must meet certain thermal, sanitary and hygienic, technical and economic, architectural, construction and installation requirements.

Thermal requirements consist mainly in the fact that heating devices must transfer heat well from the coolant (water or steam) to the heated rooms, i.e. so that their heat transfer coefficient is as high as possible, no less than 9...10 W/(m 2 ·K), taking into account that for modern designs of heating devices it is in the range of 4.5...17 W/(m 2 ·K).

Sanitary and hygienic requirements requirements for heating devices are that the design and shape (type) of their surface do not lead to the accumulation of dust and allow it to be easily removed.

The technical and economic requirements are as follows: minimum factory cost; minimum consumption metal; compliance of the device design with the requirements of their mass production technology; sectionality, allowing the device to be configured with the required heating surface area.

The criterion for thermotechnical and technical-economic assessment of metal heating devices is the thermal voltage of the metal of the device M, W/(kg K), which represents the ratio of the heat flux of the device with a difference in the average temperatures of the surface of the device and the ambient air of the room of 1 ° C, referred to weight of the metal of the device.

The higher the thermal stress of the metal of the heating device, the more profitable it is. Modern devices operate with a metal thermal voltage of 0.9…1.6 W/(kg K).

Architectural and construction requirements include reducing the area occupied by heating appliances and ensuring they have a pleasant appearance. To meet these requirements, heating devices must be compact, with a surface that is easily accessible for inspection and cleaning from dust, and must correspond to the interior of the room.

Installation Requirements reflect, first of all, the need to increase labor productivity in the manufacture and installation of heating devices. Their design should be conducive to production automation and be easy to install. The devices must be durable, easy to transport and install, and their walls must be steam- and waterproof and temperature-resistant.

The wide variety of types and types of heating devices is explained by the fact that it is very difficult to satisfy all the considered requirements at the same time.

All heating devices are divided according to the following signs: according to the predominant method of heat transfer; by surface type; according to the material used; in height and construction depth.

According to the predominant method of heat transfer, devices are divided into 3 groups:

1. Radiation devices, transmitting by radiation at least 50% of the total heat flux. The first group includes ceiling heating panels and radiators.

2. Convection-radiation devices, transmitting by convection from 50 to 75% of the total heat flow. The second group includes sectional and panel radiators, smooth-tube appliances, and floor heating panels.

3. Convective devices , transmitting at least 75% of the total heat flow by convection. The third group includes convectors and finned tubes.

According to the material used There are metallic, combined and non-metallic heating devices. Metal devices made mainly of gray cast iron and steel (sheet steel and steel pipes). Also used copper pipes, sheet and cast aluminum and other metals.

IN combined instruments They use heat-conducting material (concrete, ceramics) into which steel or cast iron heating elements (panel radiators) are embedded. Finned metal pipes placed in a non-metallic casing (convectors).

TO non-metallic devices include concrete panel radiators, ceiling and floor panels with embedded plastic heating pipes or with voids without pipes, as well as ceramic, plastic and similar radiators.

By height vertical heating devices are divided into high(over 650 mm high), average(more than 400 to 650 mm) and low(more than 200 to 400 mm). Devices with a height of 200 mm or less are called baseboards.

By depth(thickness) devices used small(up to 120mm), average(more than 120 to 200mm) and big depth (more than 200mm).

Let's consider the main types of heating devices widely used in residential, public and industrial buildings.

Radiators- heating devices, the radiation heat transfer of which is significant (25...50%). Radiators are made of cast iron and steel.

Cast iron radiators, the most common heating devices, consist of individual elements(sections) made by casting from gray cast iron into special molds.

Cast iron radiators have relatively high thermal performance. The heat transfer coefficient of modern cast iron radiators is 9.1...10.6 W/(m 2 °C). A positive property is their high corrosion resistance.

However, the relatively low thermal stress of the metal is 0.29...0.36 W/(kg°C), high metal consumption, unattractive appearance, labor-intensive manufacturing and installation, as well as low mechanical strength (withstands hydraulic pressure 0.6 MPa), lead to a reduction in their production in our country due to an increase in the production of radiators made of steel, aluminum and alloys.

Finned cast iron pipes cast from gray cast iron with round ribs on the side in contact with air. The fins dramatically increase the air heating surface. The heat transfer of these heating devices by convection is 50%.

Thermal performance indicators of finned cast iron pipes very high. The relative ease of manufacturing and installation of finned tubes and their low cost contribute to the widespread use of these heating devices in industrial and agricultural construction. However, the low hygienic and aesthetic qualities of ribbed cast iron pipes make them unsuitable for civil and residential construction.

Concrete heating panels with steel pipes built into them are used in panel radiant heating systems for placement under windows, in partitions and platforms stairwells. The main part of the thermal energy of such panels is transferred into the room by radiation. They don't occupy usable area, hygienic, have good installation.

Their significant disadvantages include the difficulty of repair and significant inertia in regulating thermal performance during operation.

Aluminum heating devices have greater heat transfer compared to steel and cast iron, have less mass, thermal inertia, can be decorated, but have less mechanical strength and are less chemically resistant.

Bimetallic heating devices are predominantly steel channels for coolant covered with cast aluminum heat-transmitting elements. They combine mechanical strength and chemical resistance steel appliances with the thermal characteristics of aluminum appliances.

Convector They are a tubular-finned heating element enclosed in a casing, which ensures intensive air flow around the fins of the convector. Steel pipes with sheet steel ribs pressed onto them are often used as a heating element. The functions of the casing can be performed by fin elements due to their special shape, in this case the device is called a convector without a casing.

Basic designs heating devices are shown in Fig. 7.2.

Rice. 7.2. Design of heating devices various types
(cross sections):

A– sectional radiator, b– steel panel radiator, V– smooth-tube device (register), G– convector with casing, d– finned tube (register); 1 – channel for coolant, 2 – fins made of steel plates, 3 – connecting flange.

Accommodation heating devices in rooms is carried out in the lower zone of the room, mainly near the outer walls. In residential and public buildings, heating devices are placed mainly in window sill niches, both with and without window sills. This placement of heating devices is due to the need to warm up the lower zone of the room, protect the room from radiation cooling from the external walls and heat the infiltration air. Low-profile devices provide more uniform heating of the room due to the longer length of the device with equal heat transfer (Fig. 7.3, b). Tall and shorter appliances cause an intense rise in the flow of heated air near the appliance, which leads to overheating of the upper zone of the room and the penetration of cooled air on both sides of the appliance into the serviced area (Fig. 7.3, b).

Rice. 7.3. Placement of a heating device under a window:

A– low and long, b– tall and short

Despite the indicated advantages of low-profile devices, their use is limited by their relatively higher cost (due to the large number of sections for the same heat transfer) and labor-intensive installation.

To compensate for the heat loss of the room, it is necessary to select a standard size of the heating device that will ensure, at the design coolant temperatures, the heat transfer of the heating device equal to the heat loss of the room.

Part 2 HEATING DEVICES Classification Area of ​​application various designs Features of installation in premises Regulating heat transfer Determining the heating surface

REQUIREMENTS FOR HEATING DEVICES 1. Sanitary and hygienic: - n/a must have the lowest possible surface temperature to prevent dust sublimation; - have a minimum horizontal surface to reduce dust deposits; - the design must allow the surface of the device to be cleaned from dust. 2. Economic: - n/a should have the lowest reduced costs for their production, installation and operation; - have low metal consumption, providing increased thermal stress of the metal. The thermal stress indicator of metal n/a is defined as: where Qnp is the thermal load n/a, W; Gm – mass of metal n/a, kg; , W/(kg K) Δt - temperature pressure n/a, ºС; The higher the thermal stress indicator, the more economical the device is in terms of metal consumption. The value of the M indicator for modern n/a is in the range: 0.2 ≤ M ≤ 0.6 3. Architectural and construction: Appearance n/a must correspond to the interior of the room, and the volume it occupies must be minimal. 4. Production and installation: - maximum mechanization of work during production and installation must be ensured; - n/a must have sufficient mechanical strength. 5. Operational: - n/a must ensure controllability of their heat transfer (depends on the thermal inertia of n/a); N/P must ensure temperature resistance and water resistance at the maximum permissible hydrostatic pressure inside the N/P under operating conditions. 6. Thermal engineering: - n/a must provide highest density specific heat flux per unit area, W/m2. To fulfill this requirement, the item must have an increased heat transfer coefficient.

Classification of heating devices By heat transfer according to the material used By height By depth By thermal inertia value Radiation metal high low low inertia convective-radiative non-metallic medium medium high inertia low large Convective baseboard

Shares of consumption of various types of heating devices per Russian market in 2011 29% - cast iron radiators Cast iron radiators 3% - steel tubular radiators 20% - steel panel radiators 27% - aluminum and bimetallic radiators 21% - convectors (including special ones) Steel tubular radiators Steel panel radiators Total consumption about 6 million kW/year

Section cast iron radiator: hм – installation height of the device, m; hп – construction height of the device, mm; a – depth of the device, mm; b – width of one section of the device, mm

Cast iron sectional radiators: high operational reliability in domestic conditions, can be used in dependent heating systems of buildings for various purposes; price domestic models on average 1500 rub. /To. W; the cost of design radiators is 4000 -6000 rubles. /To. W additional cost of regrouping, leak testing, installation and painting is 400 - 500 rubles. /To. W; the share of consumption in Russia is about 29%

Steel panel radiators: modern design; wide range; full construction readiness; high hygiene of models without fins; There are models with a built-in thermostat; all models strictly require compliance with operating rules; cost 1500 – 2000 rub. /To. W (without built-in thermostat); the share of consumption in Russia is 20%.

Basic requirements for the coolant of heating systems with aluminum heating devices Name of indicators and their dimensions Hydrogen indicator p. N Optimal values ​​Acceptable values ​​Indicator values ​​7 – 8.5 Dissolved oxygen content, mcg/dm 3, no more than 20 Iron compounds content, mg/dm 3, no more than 0.3 Total hardness, mEq/dm 3, no more 0, 7 Amount of suspended substances, mg/dm 3, no more than 5 The use of aluminum radiators is allowed only in independent and autonomous systems heating Direct connection of the heads of aluminum radiator sections with steel and copper heat pipes is prohibited. The use of galvanized plugs is prohibited; the use of aluminum and cadmium-plated plugs is recommended. The use of cadmium-plated nipples is recommended.

Comparison of aluminum and bimetallic radiators Parameter Aluminum Bimetal Design The radiator is completely aluminum. Radiators are made using two methods. The extrusion method produces cheap and lightweight products that are not very High Quality(This method is not used in Europe). Radiators made by casting will be more expensive, but more durable. Bimetallic radiators are made from two different metals. The body, equipped with ribs, is made of aluminum alloy. Inside this housing there is a core of pipes through which coolant flows (hot water from the heating system). These pipes are made either from steel or copper (and the latter are practically never found here). Their diameter is smaller than that of aluminum models, so they are more likely to clog. Heat dissipation Heat dissipation from one section depends on the model and manufacturer. It is slightly lower than that of the manufacturer. 1 section is capable of delivering 140 - 210 W. aluminum radiator, since the steel core helps reduce overall heat transfer. 1 section gives off Has minimal thermal inertia. 130 – 200 W. From 6 to 16 (some models up to 20) ati. From 20 to 40 ati ( this parameter is important if you choose radiators for an apartment with a centralized heating system. If you choose these radiators for a private home, then this parameter is not a minus for aluminum radiators, since there is no excess pressure in the local heating network.). Relation to coolant Aluminum undergoes various chemical reactions, which leads to corrosion of the walls of the device. And still in progress chemical reactions aluminum releases hydrogen, which is a fire hazard. Therefore, it requires the installation of a special valve in the upper radiator cap. Steel pipes in the middle of a bimetallic radiator are less demanding on the quality of the water flowing through them. A bimetallic radiator is more protected from coolant. Maximum temperature water Up to 110 0 C. Up to 130 0 C. Durability Up to 10 years. 15 – 20 years. Operating pressure

Radiators from aluminum alloys, bimetallic with aluminum collectors (sectional, columnar and block): modern design; wide range; full construction readiness; all models except completely bimetallic ones require strict adherence to installation and operation rules; bimetallic models are equivalent in performance to cast iron radiators; the cost of radiators made of aluminum alloys is ~ 1700 - 2200 rubles. /To. W; the cost of “semi-bimetallic” radiators is 2000 - 2800 rubles. /To. W; the cost of bimetallic radiators is 2800 - 4000 rubles. /To. W; the share of consumption in Russia is 27%, including 14% bimetallic and bimetallic with aluminum collectors.

Steel tubular radiators and design radiators (sectional, columnar, block and block-sectional): modern design and hygiene; full construction readiness; wide range; There are models with a built-in thermostat; require strict adherence to operating rules; There are models with increased anti-corrosion resistance; price: tubular radiators 3800 rub. /To. W; design radiators – 8000 rub. /To. W; the share of consumption in Russia is 3%.

convectors Without casing (adjustment of heat transfer through water) With casing: - adjustment of heat transfer through water; - adjustment of heat transfer through the air.

Sketches of convectors: a) “Comfort-20” with a casing; b) “Accord” without casing; 1 – plate (heating element; 2 – casing; 3 – air valve

Convectors (wall-mounted, floor-mounted, with a casing, without a casing, steel, using non-ferrous metals): high operational reliability in domestic conditions, can be used in dependent heating systems of buildings for various purposes; low inertia; wide range; full construction readiness; modern design; low temperature of the external elements of the convector structure, eliminating the risk of burns; There are models with a built-in thermostat; cost: steel ~ 1300 rub. /To. W; with copper-aluminum heating element ~ 3000 rub. /To. W; share of consumption in Russia (including special convectors) – 21%.

Cases of improper installation of wall convectors The gap between the device and the floor or window sill is small (less than 70% of the depth of the device). Reduction of heat flow by 5 -50% Installation of brackets on an unprepared surface (subsequent plaster) - it is impossible to hang the casing Air flow past the heating element. Heat flow reduction by 5 -20% A heating element not installed horizontally. Decrease in heat flow by 4-7% Incorrect marking of bracket installation locations - it is impossible to hang the casing Lagging of the casing, gap between the wall and the casing. Heat flow reduction by 3 -20%

6. Special heating devices - convectors built into the floor structure, fan convectors: complete construction readiness; modern design; low inertia; There are models with built-in fans and thermostats; designed for luxury buildings and cottages; fan convectors operating in heat pump mode are characterized by high energy efficiency; cost 4000 -10000 rub. /To. W; the share of consumption in Russia is about 4% (in the general group of convectors).

Basic requirements for the design of heating devices in accordance with GOST 31311 -2005 “Heating devices. Are common technical specifications" and STO NP "AVOK" 4. 2. 2 -2006 "Heating radiators and convectors" 1. Devices must withstand the static strength test: 1. 1. The destruction pressure must exceed the maximum operating excess pressure of the coolant declared by the manufacturer: - for cast devices – no less than 3 times; - for other devices - no less than 2.5 times. 1. 2. Test pressure (factory) must exceed the declared maximum operating excess pressure: - for cast devices - no less than 1.5 times or no less than 0.6 MPa; - for other devices - no less than 1.5 times. 2. The nominal heat flux of wall-mounted devices with a height of up to 600 mm inclusive and a thermal density of up to 2000 W/m should be no more than 400 W for the minimum standard size and no less than 2000 W for the maximum. 3. The average nomenclature step of the nominal heat flux of wall-mounted devices with a height of up to 600 mm inclusive and a thermal density of up to 2000 W/m in the range of values ​​from 400 to 1400 W should not exceed 200 W, and over 1400 W - no more than 400 W. 4. The thickness of the wall of the device in contact with water must be no less than: - for a cast iron radiator - 2.7 mm; - for steel panel radiator– 1.2 mm; - y steel pipe tubular and bimetallic radiators – 1.25 mm; - for cast and extruded aluminum radiators – 1.5 mm.

Basic requirements for coolant according to the “Rules” technical operation power stations and networks Russian Federation» for heat supply systems made of steel heat pipelines Name of indicators and their dimensions Values ​​of indicators for open closed heat supply systems 8, 3 – 9, 0 8, 3 – 9, 5 8, 0 – 9, 5 Content of dissolved oxygen, µg/dm 3, not more than 20 20 Content of iron compounds, mg/dm 3, no more than 0.3 0.5 Total hardness, mEq/dm 3, no more than 0.7 5 5 Hydrogen index p. N: optimal values permissible values ​​Amount of suspended substances, mg/dm 3, no more

Schemes for installing heating devices with different coverage coefficients β 4: a) β 4 = 1, 2; b) β 4 = 1.05; c) β 4 = 1.05; d) β 4 = 0.9; e) β 4 = 1.25

Installation diagrams for heating devices under windows: a) installation of the heating device relative to the edge of the window; b) installation of radiators; c) installation of a convector with a casing; d) installation of a convector without a casing

Heat transfer coefficient n/a The intensity of heat transfer from the coolant through the heat transfer medium into the room is characterized by the heat transfer coefficient of the heating device - Knp. It expresses the heat flux density per outer surface walls n/p with a temperature difference of 1 C: where Rnp – thermal resistance heat transfer of the heating device: where Rin is the thermal resistance to heat transfer from the heated liquid to the inner surface of the wall (heat exchange occurs due to convection + thermal conductivity); Rst – thermal resistance to heat transfer from the inner to the outer surfaces of the wall of the heating device (thermal conductivity); Rн – thermal resistance to heat transfer from the outer surface of the wall to the cold medium (liquid or gas) (heat exchange occurs due to convection + radiation). The main factors determining Knp: type and design features n/a and temperature difference The heat transfer coefficient of newly developed n/a is determined experimentally. The type of n/a allows you to judge in advance possible meaning Knp. The results of experiments to determine Knp showed that it can be described: - for the water coolant: where: m, n, p – experimental coefficients that are determined for each type of n/p; - temperature pressure n/a; - air temperature in the heated room, ºС; - temperature of the coolant, respectively, at the inlet to the reservoir and at the outlet from it, ºС; G – relative water flow in n/a, kg/h, - the ratio of the actual flow rate through n/a to the nominal one, accepted during the thermal test of n/a. When testing samples of n/a, a flow rate of 360 kg/h was taken as such a flow rate (previously, tests of each type of n/a were carried out at different nominal water flow rates: for radiators 17.4 kg/h, for convectors 300 kg/h).

Schemes of water movement through the heating device: a) from top to bottom; b) from bottom to top; c) from below - down

Thermal calculation of heating devices (determination of the heating surface), W (kcal/h), where is the nominal conditional heat flow n/a, according to which the standard size of the device is selected using catalogs n/a or a reference book. – complex coefficient of adaptation to design conditions. - for water: - temperature pressure n/a (for coolant - water), ºС; - coolant flow through n/a, kg/h; b – accounting factor atmospheric pressure; - factor taking into account the direction of movement of the coolant in n/a; n, p, c – constant coefficients for this type of n/a.

Small circulation rings in single-pipe heating systems Small circulation rings in a single-pipe heating system are radiator units, which include closing sections, connections to heating devices and the heating device itself. The water flow through the heating device in a heating system with a three-way valve KRT is equal to the water flow through the riser, since the working design position of the KRT is “fully open”. The riser in this case turns out to be flow-regulated. The water flow through the heating device with the closing section and the KRP pass-through valve is determined by the coefficient of water flow into the heating device: where: Gnp is the flow rate of water passing through the heating device, kg/h; Gst - water consumption in the riser, kg/h; αнп = 0 – the heating device is closed; αнп = 1 – the heating device is fully open (at KRT).

Depending on the various features designs of heating devices on the market have different characteristics. The main thing when installing them is correct selection the desired model, optimally suited for specific case.

Varieties

Most often, the classification of heating devices is carried out according to the following criteria:

  • the coolant used, which can be heated water, gas or even air;
  • material of manufacture;
  • operational characteristics: size, power, installation method and the ability to regulate the heating rate.

It is better to select the optimal option, taking into account the characteristics of the building’s heating system, operating conditions, observing all the requirements for heating devices.

In addition to the performance of devices, it is worth considering the possibility of their installation. So, for example, in the absence of gas supply and the impossibility of organizing water heating the only option will electrical devices.

Water system

The most commonly used and therefore have the widest range of heating devices are water heating systems. This is explained by their good efficiency and optimal level costs of acquisition, installation and maintenance.

Structurally, the devices are not too different from each other. Inside each there are channels for flow hot water, the heat from which is transferred to the surface of the device, and then, using convection, to the air of the room. For this reason they are called convection.


In water heating systems can be used the following types radiators:

  • cast iron;
  • steel;
  • aluminum;
  • bimetallic.

All of these heating devices have their own characteristics, due to which they are selected for each specific case depending on the area of ​​the room, the nuances of installation, the quality and type of coolant (which is sometimes antifreeze).

The power of each device is regulated by the number of sections, which can be selected by almost anyone. Although, if the estimated length of one battery is more than 1.5–2 m, it is recommended to install two smaller devices next to each other.

Cast iron was one of the most popular materials in domestic systems heating. His choice, as a rule, was due to the relatively low cost. Later, such devices began to be used less frequently, since they have a small heat transfer coefficient (only 40%), due to which the power of one section is approximately 130 W. Although they can still be found in old-style systems. In modern interiors, designer models of cast iron radiators are sometimes used.


The advantages of such devices are a large surface area that transfers heat to the room, and a long operating period (up to 50 years). Although there are still more disadvantages - these include the relatively large volume of coolant used (up to 1.4 liters), the difficulty of repair, and the inertia of heating, due to which the temperature of the device increases relatively slowly, and even the need for periodic (at least once every 3 year) cleaning. In addition, heavy sections are very difficult to install.

The use of aluminum radiators allows us to ensure the maximum level of heat transfer - the power of the section can reach 200 W (which is enough to heat 1.5–2 sq. m).


Their cost is quite affordable, and their low weight allows you to install them yourself. True, the operation of the device is possible for only 20–25 years.

Their advantages include the presence in the design of convection panels that improve air circulation over the surface, ease of installation of devices for regulating the intensity of coolant flow, as well as ease of installation. The radiator section, with a power of up to 180 W, is capable of heating about 1.5 square meters. m area.


Despite the advantages that such heating devices have, there are also problems with their use. For example, for bimetallic radiators it is not recommended to dilute water with antifreeze, which, although they do not allow the system to freeze, have a negative effect on internal surfaces heating devices.

In addition, these options are the most expensive of all that are used in a water heating system.

Electric heating devices

All electrical appliances used if it is impossible to install a water heating system have different features and characteristics - from power to heat generation principles. At the same time, the main disadvantages of any such equipment are the high cost of operation and the need to install an electrical network capable of withstanding heavy loads (with a total power of electric heaters of more than 9–12 kW, a network with a voltage of 380 V is required). Each variety has its own advantages.

The design that electric heating devices This type allows you to quickly heat the room with the help of air flows moving through them.


Air enters the devices through holes in the lower part, it is heated using a heating element, and the exit is ensured by the presence of upper slits. Today there are electric convectors power from 0.25 to 2.5 kW.

Oil devices

Electric oil heaters also use a convection heating method. Inside the case there is a special oil, which is heated by the heating element. In this case, heating can be regulated using a thermostat, which turns off the device when the air reaches the set temperature.

A special feature of the heaters is their high inertia. Due to this, heating devices heat up very slowly, however, even after turning off the power supply, their surface continues to emit heat for a long period of time.


In addition, the surface oil equipment heats up to 110–150 degrees, which is much higher than the parameters of other devices and requires special handling - for example, installation away from objects that can ignite.

The use of such radiators makes it possible to conveniently regulate the heating intensity - almost all of them have 2-4 operating modes. In addition, taking into account the productivity of one section of 150–250 kW, selecting a device for a specific room is quite easy. And the range of most manufacturers includes models with power up to 4.5 kW.

By choosing heating devices whose operating principle is based on the radiation of heat waves in the infrared range, the owner of a private home or other premises receives the following advantages:


  • a noticeable reduction in electricity consumption compared to traditional electrical equipment (within 30%);
  • no reduction in oxygen content in the air, which relieves people in the room from headaches;
  • Very high speed heating (even cold room warms up within a few minutes).

Usually use electric infrared heaters. Much less common are gas appliances intended mainly for heating streets, production workshops and sites or cottages.

Kinds

Classification of devices for infrared heating produced by the method of emitting waves. There are film devices that transmit radiation from resistor conductors located on the surface of a special film to surrounding objects. Power – within 800 W per 1 sq. m.


The second type is carbon. In them, radiation comes from a spiral inside a sealed glass flask. Appliances of this type have a power from 0.7 to 4.0 kW.

The advantage of the former is the ability to use them as electric heated floors. While carbon heaters are much more powerful, although they require increased fire safety measures.

Gas heating

In order to reduce heating costs, gas-fired heating appliances are often used. One of the most simple types Such equipment is a gas convector connected either to a gas supply system or to a cylinder with liquefied propane. In this case, the burner does not come into contact with the surrounding atmosphere, and oxygen enters it through a special pipe (which can be taken outside to maintain normal indoor air quality).

These types of heating devices have high power (up to 8 kW or more) and are relatively cheap to operate due to the low cost of energy.

The disadvantages include: the need to register with regulatory organizations, arrangement high-quality ventilation and the need for periodic cleaning of injectors. In addition, if equipment malfunctions, the amount of hazardous materials in the room may increase. carbon dioxide. Therefore, such devices are rarely used in apartments and other premises with constant occupancy - whereas, for example, for a dacha or garage they can be simply irreplaceable.