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How many radiators are needed for a low-temperature heating system. How to correctly calculate the power and number of sections of heating radiators. Devices for low-temperature heating systems

Radiators are traditionally considered attributes of heating systems with high temperature parameters. But the postulates on which this point of view was based are outdated. Saving metal and building thermal insulation is not put today above the saving of energy resources. BUT specifications modern radiators allow us to talk not only about the possibility of their use in low-temperature systems, but also about the advantages of such a solution.

Radiators are traditionally considered attributes of heating systems with high temperature parameters (in the literature, the terms "high-temperature" and "radiator" are often even used as synonyms, in particular, when we are talking about the contours of heating systems). But the postulates on which this point of view was based are outdated. Saving metal and building thermal insulation is not put today above the saving of energy resources. And the technical characteristics of modern radiators allow us to talk not only about the possibility of their application in low-temperature systems, but also about the advantages of such a solution. It prove Scientific research, carried out for two years on the initiative of Rettig ICC, the owner of the brands Purmo, Radson, Vogel & Noot, Finimetal, Myson.

Reducing the coolant temperature is the main trend in the development of heating technology in recent decades in European countries. This became possible as the thermal insulation of buildings improved, heating appliances. In the 1980s, the standard settings were reduced to 75/65 ºC (supply/return). The main benefit from this was the reduction of losses in the generation, transport and distribution of heat, as well as greater safety for users.

With the growing popularity of outdoor and other types panel heating in systems where they are used, the supply temperature is reduced to a level of 55 ºC, which is taken into account by the designers of heat generators, control valves, etc.

Today, the flow temperature in high-tech heating systems can be 45 and even 35 ºC. The incentive to achieve these parameters is the ability to make the most efficient use of heat sources such as heat pumps and condensing boilers. At a secondary circuit temperature of 55/45 ºC, the efficiency factor COP for heat pump type "ground-water" is 3.6, and at 35/28 ºC already - 4.6 (when working only for heating). And the operation of boilers in condensing mode, requiring cooling flue gases return line water below the "dew point" (when burning liquid fuel - 47 ºC), gives an efficiency gain of about 15% or more. Thus, lowering the temperature of the coolant provides significant energy savings, and, accordingly, a reduction in carbon dioxide emissions into the atmosphere.

Until now, the main solution that provides space heating at a low coolant temperature was considered to be a "warm floor" and convectors with copper-aluminum heat exchangers. Research initiated by Rettig ICC has added to this range steel panel radiators. (However, practice in this case goes ahead of theory, and such heating devices have been used for a long time as part of low-temperature systems in Sweden, rice. one).

Fig.1

With the participation of several scientific organizations, including the universities of Helsinki and Dresden, radiators have been tested under various controlled conditions. The results of other works on the study of the functioning of modern heating systems are attached to the "evidence base".

At the end of January 2011, research materials were presented to journalists from leading European specialized publications at a seminar held at the Purmo-Radson training center in Erpfendorf (Austria). Presentations were made by Professor of the University of Brussels (Vrije Universitet Brussels, VUB) Lin Peters and Head of the Department of Energy Systems of the Institute of Building Physics. Fraunhofer (Fraunhofer-Institute for Building Physics, IBP) Dietrich Schmidt.

Lyn Peters' report addressed issues of thermal comfort, accuracy and responsiveness of the heating system to changing conditions, and heat losses.

In particular, it was noted that the causes of local temperature discomfort are: radiation temperature asymmetry(depends on heat transfer surface and orientation heat flow); floor surface temperature (when it is outside the range of 19 to 27 ºC); vertical temperature difference (the difference in air temperature - from the ankle to the head of a standing person - should not exceed 4 ºC).

At the same time, not static, but “moving” temperature conditions are most comfortable for a person (conclusion of the University of California, 2003). Interior space with areas with low temperature differences enhances the feeling of comfort. But large temperature changes are the cause of discomfort.

According to L. Peters, radiators that transfer heat both by convection and radiation are the most suitable for providing thermal comfort.

Modern buildings are becoming more and more thermally sensitive due to improved thermal insulation. External and internal thermal disturbances (from sunlight, household appliances, presence of people) can strongly influence the indoor climate. And radiators react to these thermal changes more precisely than panel heating systems.

As you know, a "warm floor", especially arranged in a concrete screed, is a system with a large heat capacity, slowly responding to regulatory influences.

Even if the "warm floor" is controlled by thermostats, a quick reaction to the supply of third-party heat is impossible. When laying heating pipes in concrete screed the response time of underfloor heating to a change in the amount of incoming heat is about two hours.

Responding quickly to external heat room thermostat switches off the underfloor heating, which continues to produce heat for about two more hours. When the supply of external heat is stopped and the thermostatic valve is opened, the full heating of the floor is achieved only after the same time. Under these conditions, only the effect of self-regulation is effective.

Self-regulation is a complex dynamic process. In practice, it means that the heat supply from the heater is regulated in a natural way due to the following two laws: 1) heat always spreads from a hotter zone to a colder one; 2) the magnitude of the heat flux is determined by the temperature difference. The well-known (it is widely used when choosing heating appliances) equation allows you to understand the essence of this:

Q = Qnom. ∙ (ΔT/ΔTnom.)n,

where Q is the heat transfer of the heater; ΔT is the temperature difference between the heater and the air in the room; Qnom. - heat transfer under nominal conditions; ΔTnom. - the difference between the temperature of the heater and the air in the room under nominal conditions; n is the heater exponent.

Self-regulation is typical for both underfloor heating and radiators. At the same time, for a "warm floor" the value of n is 1.1, and for a radiator - about 1.3 (the exact values ​​\u200b\u200bare given in the catalogs). That is, the response to a change in ΔT in the second case will be more “pronounced”, and the restoration of the given temperature regime happen faster.

It is also important from the point of view of regulation that the surface temperature of the radiator is approximately equal to the temperature of the coolant, and in the case of floor heating it's not like that at all.

In case of short-term intensive external heat inputs, the “warm floor” control system cannot cope with the work, as a result of which room and floor temperature fluctuations occur. Some technical solutions allow them to be reduced, but not eliminated.

They are considered attributes of heating systems with a high temperature parameter. But the foundations on which such ideas were built are outdated. The saving of metal and thermal insulation is not put today as a priority of saving energy resources. And the characteristics of current radiators allow us to talk not only about the likelihood of their use in low-temperature communications, but also about the advantages of such a conclusion. This is substantiated by scientific research that has been implemented for a couple of years at the suggestion of Rettig ICC, the owner of the Purmo, Radson, Vogel, Finimetal, Myson brands. European countries. This was implemented as the thermal insulation of buildings improved, heating equipment. In the 1980s, normal settings were reduced to 75/65 ºC (supply/return). The main advantage of this was the reduction of losses during the formation, transportation and distribution of heat, as well as safety for consumers. Progress regarding water supply does not stand still. In order to protect the internal surfaces of pipes from corrosion and high level wear, use the shutter avk. This is a certain element of pipeline fittings, the main parts of which are in the form of a disk. The high performance characteristics of the avk valve are provided by the carbon nickel plated steel from which it is made, as well as the epoxy coating. Used avk valve for water and neutral liquids.

With the increasing popularity of floor and other types of surface heating in systems where they are used, the supply temperature has been lowered to 55 ºC, which is taken into account by the creators of heat generators, balancing fittings, etc. Now, the supply temperature in ultra-tech heating systems can be 45 and 35 ºC . The impetus for achieving these parameters is the ability to operate sources such as heat pumps and condensing boilers more efficiently. At a medium temperature of the secondary circuit of 55/45 ºC, the COP efficiency element for a ground-water heat pump is 3.6, and at 35/28 ºC it is already 4.6 (during heating operation). And the use of boilers in a condensing state, requiring cooling of flue gases with water from the return below the “dew mark” (when burning fuel - 47 ºC), gives a bonus in efficiency of about 15% or more. Thus, lowering the temperature of the carrier provides significant resource savings and a reduction in the release of carbon dioxide into the air. Until now, the basic solution that supplies heat to the premises at a low carrier temperature has been a "warm floor" and convectors with copper-aluminum exchangers.

Studies initiated by Rettig ICC made it possible to add steel panel radiators to this category. With the assistance of several scientific institutions, including institutions in Helsinki and Dresden, they were tested under various research conditions. The results of other works on the functioning of modern heating communications were added to the "evidence base". At the end of January last year, the results of the research were handed over to journalists from leading European publications at an event held at the Purmo-Radson center in Erpfendorf.

There are no special statistics here, if the height of the floors allows, then the choice is definitely in favor of water (liquid) heat carriers. Ceteris paribus, such heating will be much cheaper than electric heating for a long time to come.

Electric heaters are also used, they are minimal in maintenance and give ample opportunities in controlling not only the climate, but also individual sections of the built-in converter. Therefore, such options are also very popular, especially considering that they do not require a deep channel for installation.

An elegant solution showing the effectiveness of built-in converters, these are examples of heating rooms using a return. When the cooling coolant first enters the converter and gives off the remaining heat to the heated air. This kind of "secondary" contours are actually the most striking examples. effective work converters in low-temperature circuits, where the carrier temperature can be as high as 40 degrees. And the air temperature and large volume heating is provided by the physical dimensions of the converter, the largest area of ​​the elements that give off heat.

So now the most common converter is water, and to a lesser extent electric. There are combined systems on the market where electric heating helps in precise temperature control, or generally aims at effective use converter. In such a system, electric heating is an intermediate link in increasing the temperature of the coolant, and so far they belong to exotic types of converters.

We only note that such a combination is appropriate where it is the coolant that is heated, in other situations it is more reasonable to heat the air with an electric heating element. And just the combination in which the converter coolant is heated by electricity has a special advantage. For a closed converter of this type (with electric heating of the coolant), no pipes are required, which makes it possible to modernize the heating system in ready-made houses with decoration.

Regardless of the type used, built-in convectors, in addition to heating, generally help maintain a better microclimate. Not only water, but also electric convectors do not “dry” the air so much, so buy a humidifier even when large sizes you don't need a converter.

There are other advantages, which are discussed below, but in terms of choosing what will heat your converter, proceed from operating costs. Electric heating will cost more, and water heating will require maintenance and care costs. Shut-off valves, automation (or manual control) - all these are connections, which means that there is a need to monitor leaks, and in general, pay attention to this system.

Some advantages of built-in converters in low-temperature circuits

First of all, we recall that the converter allows the use of both hot and low-temperature coolant, the result will still be good. But the very design of the converter is such that it excludes burns when touching a hot surface (it is closed with a grate) and the so-called. "radiant" energy of the heater. This effect is well known to anyone who has walked past a hot radiator when it seems that a "cold blow" is blowing from a cold wall. The fact is that the radiator produces part of the heating with the help of thermal radiation, when the heated metal itself heats not the air, but everything around. The built-in converter does not give such an unpleasant effect.

The operation of the heating system with a low coolant temperature significantly extends its service life. A rather obvious conclusion, because there are no significant temperature deformations, the coolant does not work in critical modes and the system as a whole is more comfortable. Less salt deposits inside the pipes, all connections last longer, the pressure in the system can be lower than in a conventional system, which reduces the risk of water hammer and emergency situations.

The protection of the heating element of the converter allows manufacturers to use materials that have a very high heat transfer: copper, aluminum, etc. A number of modern radiators use similar materials, but the entire radiator is covered with a protective box, and this reduces the efficiency of air heating. And the thickness of the plates, the most efficient heaters, in the radiator is greater, for reasons of overall structural strength.

The aesthetics of the heating device itself also matters. For low-temperature circuits, decorative converter grilles made of stone or other materials are applicable, which makes this heater an element of the interior, and not a stain that you want to hide.


Installing a fan in converters with forced convection allows for efficient heat transfer. In the low-temperature circuit, the difference in the temperature of the coolant at the inlet and outlet can be 10-15 degrees, but this difference is enough to heat the room with a margin. Remember the beginning of the article, in radiators for warming up a room, this difference can be 20-25 degrees, without the use of additional measures.

The thermal insulation of the built-in converter reduces heat loss, and at the same time the floor around it is also heated, heating the air. In a standard placement, the radiator warms up well only the wall on which it hangs, and the floor under it can be very cold.

The converter, in terms of heating area, is close to warm floor, but devoid of its drawback - low floor temperature. If the floor is heated to 25 degrees, this will completely solve the problem of air heating, but walking on such a floor will be very problematic. And at the same time, the converter works just in the floor area, providing comfortable heating where it is needed, because it is always unpleasant to walk on a cold floor even in a warm room.

And, ultimately, in low-temperature circuits, built-in convectors not only successfully and effectively solve the problems of heating rooms, but also do it gently. In the rooms that the converter heats, there are no so-called zones of different temperatures, when it is hot near the radiator and cool near the door. The uniformity and constancy of heating is another advantage of this heater, which we recommend that you pay close attention to.

Unless, of course, you have the opportunity to plan the installation of just such a heater.

Low-temperature heating is called, in which the heating of the coolant is 55-45 degrees. This means that the water temperature at the outlet of the boiler should not exceed 55 degrees, and the temperature return water must be at least 45 degrees. In this case, the surface of the heating radiator will be heated by about 38-40 degrees in the upper part of the device.

You can't call it hot, in the generally accepted sense of the word. You should not count on intense thermal radiation from radiators at such a coolant temperature, just as convectors should not be installed in low-temperature heating systems - they are effective only at water temperatures not lower than 70C and are used in high-temperature (traditional) heating systems.

Heat sources for low temperature heating

In a conventional heating system, the water temperature at the outlet of the boiler is much higher and is approximately 70-80 degrees, while the return temperature is 20 degrees lower.

It should be noted that low-temperature heating systems are used not because they are better and more efficient, but because only with their help it is possible to heat a house using heat pumps, geothermal heat sources or condensing heating boilers.

The so-called traditional heating boilers in low-temperature systems can only be used in conjunction with an elevator unit that ensures the mixing of cold coolant with hot water from the boiler and bringing the coolant temperatures to the required (55-45) parameters.

Long-term operation of a conventional boiler for heating a return at a low temperature can lead to excessive formation of condensate in the chimney and its premature failure. Therefore, in low-temperature heating systems operating on conventional heating boilers, the coolant from the return pipeline must be heated before being fed into the boiler, using part of the heat generated by the boiler for this.

All this complicates the design of the heating system and leads not only to an increase in its cost, but also greatly complicates the process of operation and maintenance.

Only condensing heating boilers can operate on a heat carrier with a low temperature.

Low temperature springs

As already mentioned, low-temperature heating is focused on the consumption of thermal energy generated by heat pumps, as well as heat received from the sun and geothermal heat. It is these sources that are optimal for low-temperature systems. If it is decided to use low-temperature heating without the use of renewable energy sources, it is easier and more economical to install a condensing boiler.

But the system for obtaining "soft heat", as low-temperature heating is often called, will only work when right choice heating appliances.

Heating appliances for low temperature systems

Conventional radiators are not suitable for low-temperature heating systems. They simply will not be able to work at full capacity, and the house will be cold. It is necessary to heat the house with a low-temperature heating system using heating surfaces. It can be underfloor heating or warm walls. The ratio is simple: the larger the heating surface, the warmer it will be in the house.

It should be noted that low-temperature heating systems have a number of advantages:

  • Heating surfaces with a temperature of approximately 35-40C radiate heat in the most comfortable wave range for humans
  • Warm floors allow you to redistribute heat in the room. If, when installing conventional radiators, the warmest air in the room (and with it the warmest zone) is under the ceiling, then when using a warm floor, it is located under the feet, which is more natural and comfortable for a person.
  • Use of geothermal heat and solar energy reduces heating costs and has a positive effect on the environment.

What is more expensive?

Unfortunately, today it is premature to talk about real savings when using low-temperature heating.

In our country, it is cheaper to heat with gas, using traditional boilers complete with convectors and heating radiators.

For those who want to enjoy the soft warmth of the heating surfaces, it is better to install a condensing boiler. It costs more, but allows you to reduce gas consumption by 15-20%.

A. Nikishov

The development of technical thought has allowed modern man to have a large selection of heating systems, depending on the requirements and material possibilities, which even the previous generation did not have. The gradual development of household thermal power engineering has led to the fact that low-temperature heating systems for housing have become increasingly popular among the population, which will be discussed in this article.

Practice has shown that when comparing two heat sources - with high and low temperatures - the most comfortable conditions for a person are created precisely by a low-temperature heating device, which provides a small temperature difference in the room and does not cause negative sensations. The upper limit of the so-called low temperatures, according to the definition of power engineers, is in the region of 40˚С. Low-temperature heating systems using a coolant operate with temperatures of 40-60˚С - at the inlet to the heat-producing device and at its outlet. And air, electric and radiant heating systems also use lower temperatures, comparable to the temperature of the human body. So the very concept of low temperatures is rather arbitrary, and, nevertheless, the use of a coolant or other heat sources with a temperature of up to 45˚ has many advantages that affect the choice of such a system for home heating, and, due to its features, organically fits into applications with renewable sources of energy.

All heating systems are subject to certain requirements, which are designed to make their use more efficient, comfortable and safe. Construction, climatic, hygienic and technological requirements are detailed in DBN V.2.5-67:2013 in paragraphs 4, 5, 6, 7, 9, 10 and 11. These requirements make it possible to minimize negative and at the same time increase positive impacts on human body provided by heating systems.

It should be noted that one of the most important conditions for the efficiency of any heating systems is careful consideration of heat losses, and for low-temperature systems this is perhaps the most important. Otherwise, such systems will be inefficient and unnecessarily energy-consuming, and, therefore, materially costly.

Classification

Low-temperature heating systems can be conditionally divided - according to the method of heat preparation - into monolithic, bivalent and combined. Monolithic systems are characterized by the use of one or more heat generating units. In bivalent heat generators, two heat generators are used that have different operating principles, one of which can be turned on as an additional heat source at very low temperatures outside air. Several heat-producing installations connected in parallel form a combined heating system.

Heating of the heat carrier in all heating systems can be carried out directly or indirectly. An example direct heating are water heating boilers various types operating on solid, liquid or gaseous fuels, as well as electric boilers. The coolant is heated indirectly in heat exchangers (boilers) or heat accumulators. This method very widely used in systems powered by renewable energy sources - wind and solar.

Also, low-temperature heating systems can be divided according to the type of coolant - liquid, gas, air and electric, and according to the type of heating devices - surface, convection and panel-beam.

Description of systems

Low-temperature heating systems are becoming increasingly popular due to the fact that they are very harmoniously combined with equipment operating on renewable energy sources. In times when traditional energy is becoming more and more expensive, this is an important factor.

Water heating

All systems of this type are characterized by three main parameters - the temperature of the coolant at the outlet of the heat-producing device (in this case, water-heating boilers for solid, liquid, gaseous fuels and electric ones are used), the temperature at its inlet and the air temperature in the heated room. Such a sequence of numbers is indicated in all documents for boilers.
Modern low-temperature heating systems are mainly based on the European standard EN422, which introduces the concept of "soft heat", which involves the use of a coolant with a temperature at the outlet of the heat-producing device of 55˚С, and at the inlet - 45˚С.

This type of heating involves the use of circulation pumps in the system, which are placed in the same way as in conventional heating systems. The most economical are "open" systems with accommodation expansion tank at the top point. Installing pumps in the coolant supply line allows avoiding possible rarefaction zones, which occurs when installing circulation pumps on the return line.

AT closed systems working with high blood pressure, as well as circulation pump it is necessary to use an automatic air vent and relief valve, as well as a pressure gauge showing the pressure in the system. The expansion tank in this case is placed in a convenient place for the user.

One of the requirements that determine the efficiency of open-type heating systems is the need for good thermal insulation of the expansion tank. Sometimes - in the case of placing it in the attics of buildings - its forced heating is also required.

One of the most common types of low-temperature heating systems is the well-known "warm floor" (Fig. 1). Surface heating systems, for example, manufactured by Oventrop (Germany), include pipes that can be installed in the floor, ceiling, and walls. In this case, the interior is not affected at all.

Rice. 1. Heating system with "warm floor"

In these systems, due to predominantly radiant heat exchange, there is absolutely no air movement, and heat is evenly distributed throughout the room. Electronic programmable controllers significantly increase the efficiency of the system.

The supply line of surface heating systems contains a heat carrier with a temperature of 40-45˚С, which allows using the capabilities of condensing boilers with maximum effect, as well as alternative (renewable) energy sources. The system typically uses a XLPE pipe with an oxygen barrier layer.

Steam heating

This type of heating is characterized by the use of "saturated" steam as a heating medium, which leads to the need to ensure adequate collection of condensate. And if there is one heater in the heating system, which does not create problems, then with an increase in their number, it becomes more and more difficult to remove condensate. The solution to this problem was found in the use of "cold" steam as a coolant. His role in modern systems low-temperature steam heating plays, in particular, freon-114 - non-flammable, non-toxic, odorless and chemically stable inorganic compound.

The "cold" steam system works by using the heat released during the condensation of saturated vapors, which heats the heating devices. The condensate pipelines operate in a "wet" mode, which is due to the condensate back-up. In this case, steam traps are not needed - the condensate returns to the evaporator by gravity. A make-up pump is also not required. Both steam pipelines and condensate pipelines are mounted both horizontally and vertically. Moreover, it is not necessary to comply with the slope. When vertical mounting the supply steam line can be placed both above and below.

The adjustment of a system operating on “cold” steam is carried out by influencing the steam pressure and its temperature, for which the system is calculated on a pressure corresponding to the maximum possible steam temperature.

As heating devices in the system of low-temperature steam heating are usually used sectional radiators and convector panels. To regulate heat transfer, each heating device is equipped with a membrane valve.

Air systems

The use of this type of system (Fig. 2) is rather limited. Several factors influence this. Firstly, a rather low degree of heat exchange between air and a heat-producing device or heat exchanger. Secondly, for hygienic reasons. Air currents carry dust, while air channels and heat exchangers create good conditions for the development of unwanted bacteria and microorganisms, and require special protection. And, thirdly, such systems are very material-intensive, and, therefore, have a high cost.

Rice. 2. Air heating system

But despite this, air systems low temperature heating can be used in the following cases:

  • if it is necessary to provide centralized heating at low air velocity in the channels. This method is suitable for heating small houses and cottages using a plinth duct;
  • if it is required to provide central heating with high air velocity in the channels - the system high pressure. In this case, special air distribution equipment is required, which ensures uniform air supply to all rooms and has noise-absorbing properties. The adjustment of this system is carried out in two ways: primary - on the heat exchanger, and secondary - the amount of supply warm air;
  • if you need local heating of several rooms or one large one. Such systems are familiar to everyone in large stores - they are used and air curtains at the entrance to the premises, and additional air ducts with warm air in the required places.

Electric heating

This system is represented on the market of heating systems by many manufacturers. It is based on the principle of heating a special resistive cable (Fig. 3) electric shock. The heat removed from the cable is transferred to environment, creating a soft heating of the room. The system package may include heating cables or prefabricated mats, thermostats and an installation kit for quick and easy installation.

Rice. 3. Electric "warm floor"

Structural elements of systems

All heating systems, as mentioned above, are designed to maintain an optimal and comfortable ratio of three parameters - the temperature of the coolant after the heat-producing device, the temperature of the heater and the air temperature in the room. This ratio can be achieved the right choice important elements of the system.

Heat producing devices

All devices for the production of heat can be divided into three groups.

The first group - heat generators based on the use of traditional fuel and electricity. For the most part, these are various hot water boilers operating on solid, liquid, gaseous fuels and electrical energy. Even for indirect heating"cold" steam in steam systems of low-temperature heating, all the same water-heating devices are used.

In this group of devices, a household condensing boiler can be noted, which is a device that has appeared as a result of innovative developments in the rational use of water vapor generated during fuel combustion. Research that aims to make fuller use of energy while minimizing negative impact on the environment, made it possible to create a new type of heating equipment - a condensing boiler - which allows, through condensation, to obtain additional heat from flue gases.

For example, the Italian manufacturer Baxi produces a line of condensing boilers, both floor-standing and wall-mounted. The lineup wall-mounted boilers Luna Platinum (Fig. 4) consists of single-circuit and double-circuit condensing boilers, with a power of 12 to 32 kW. key element is a heat exchanger made of stainless steel AISI 316L. Various constituent parts The boiler is controlled by an electronic board, there is a removable control panel with a liquid crystal display and a built-in temperature control function. The burner power modulation system allows the boiler output to be adapted to the energy consumed by the building in the range of 1:10.

Rice. 4. Condensing boiler BAXI Luna Platinum

The second group is installations that use the heat of non-system coolants. In such cases, heat accumulators are used.

The third group includes devices that use an external coolant for indirect heating. They successfully use surface, cascade or bubbling ball heat exchangers. It is this type that is used for heating "cold" steam in low-temperature steam heating systems.

Heating appliances

Heating appliances are divided into 4 groups:

  • devices with surfaces equal in area, both on the heat carrier side and on the air side. This type of device is known to everyone - these are traditional sectional radiators;
  • convection-type devices, in which the surface area in contact with air is much larger than the surface on the coolant side. In these devices, heat radiation is of secondary importance;
  • plate air heaters with stimulating air flow;
  • panel-type devices - floor, ceiling or wall. In this line of heating panels, for example, one can note the Czech panel steel radiators Korado called Radik, produced in two versions - with a side connection (Klasik), and with a lower one with a built-in thermostatic valve (VK). Panel steel radiators are also offered by Kermi (Germany).

Rice. 5. Panel steel radiator Korado

Heating devices of low-temperature systems include various types of sectional and panel heaters, heating convectors, heaters and heating panels.

Heat accumulators

These devices are required in bivalent low temperature heating systems that use energy from renewable sources or waste heat. Heat accumulators can be liquid or solid filled, using the heat capacity of the filler for heat storage.

Devices in which heat is released at the time of phase transformations are becoming more and more widespread. In them, heat accumulates in the process of melting a substance or when its crystalline structure undergoes certain changes.

Thermochemical heat accumulators also work effectively, the principle of operation of which is based on the accumulation of heat as a result of chemical reactions occurring with the release of heat.

Heat accumulators can be connected to the heating system both according to a dependent circuit, and according to an independent one, when heat is accumulated in them from an off-system coolant.

Thermal accumulators can also be ground, rock, and even underground lakes can be used as heat storage.

Ground thermal accumulators are obtained by placing registers made of pipes in increments of one and a half to two meters. Rock heat accumulators are equipped by drilling vertical or inclined wells in rocks to a depth of 10 to 50 m, where the coolant is pumped. The use of underground lakes as heat accumulators is possible if pipes with a coolant pumped into them are placed in the lower layers of water. Heat is taken from pipes located in the upper layers of underground lakes.

Heat pumps

When using a heat source in low-temperature heating systems, the temperature of which is lower than the air temperature in the room, as well as to reduce the material consumption of heating devices, heat pumps can be included in the system (Fig. 6). The most common devices in this group are compression heat pumps, which, when condensing, give a temperature of 60 to 80 ° C.

Rice. 6. How a heat pump works

The efficient operation of the heat pump in a low-temperature heating system is ensured by the inclusion of a heat accumulator in the evaporator circuit, which helps to stabilize the evaporation temperature of the "cold" steam. The adjustment of this system is carried out by changing the heat transfer of the pump itself.

Advantages and disadvantages

Low-temperature heating systems win their supporters by creating more comfortable conditions in the room than traditional ones with high heating of heating devices. There is no excessive "drainage" of the air, there is no - again excessive - dustiness of the room due to the inevitable movement of air with very hot heaters.

The use of heat accumulators in the system makes it possible to accumulate heat and instantly use it if necessary.

The low temperature spread - output from the heat producing device and the room air - makes it easy to regulate the system using programmable thermostats.

As for the shortcomings, it is, in fact, one - the cost of the finished system is somewhat, if not several times higher than that of the traditional high-temperature one.

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