Etc.) about the unprecedented efficiency of their equipment in modern high-efficiency low-temperature heating systems. But no one bothered to explain - where does this efficiency come from?

First, let's look at the question: "What are low-temperature heating systems for?" They are needed in order to be able to use modern highly efficient sources of thermal energy, such as condensing boilers and heat pumps... Due to the specificity of this equipment, the temperature of the coolant in these systems ranges from 45-55 ° C. Heat pumps are physically unable to raise the temperature of the heat carrier higher. And condensing boilers are economically impractical to heat above the steam condensation temperature of 55 ° C due to the fact that when this temperature is exceeded, they cease to be condensing boilers and work like traditional boilers with a traditional efficiency of about 90%. In addition, the lower the temperature of the coolant, the longer they will work polymer pipes, because at a temperature of 55 ° C they degrade for 50 years, at a temperature of 75 ° C - 10 years, and at 90 ° C - only three years. In the process of degradation, pipes become brittle and break in loaded places.

We decided on the temperature of the coolant. The lower it is (within acceptable limits), the more efficiently energy carriers (gas, electricity) are consumed, and the longer the pipe works. So, the heat from the energy carriers was released, the heat carrier was transferred, it was delivered to the heater, now the heat must be transferred from the heater to the room.

As we all know, heat from heating devices enters the room in two ways. The first is thermal radiation. The second is heat conduction, which turns into convection.

Let's take a closer look at each method.

Everyone knows that thermal radiation is the process of transferring heat from a warmer body to a less heated body by means of electromagnetic waves, that is, in fact, it is heat transfer by ordinary light, only in the infrared range. This is how the heat from the Sun reaches the Earth. Because thermal radiation is essentially light, the same physical laws apply to it as to light. Namely: solids and steam practically do not transmit radiation, and vacuum and air, on the contrary, are transparent to heat rays. And only the presence of concentrated water vapor or dust in the air reduces the transparency of the air for radiation, and part of the radiant energy is absorbed by the environment. Since the air in our houses contains neither steam nor dense dust, it is obvious that it can be considered absolutely transparent for heat rays. That is, the radiation is not delayed or absorbed by the air. The air is not heated by radiation.

Radiant heat transfer continues as long as there is a difference between the temperatures of the emitting and absorbing surfaces.

Now let's talk about heat conduction with convection. Thermal conductivity is the transfer of thermal energy from a heated body to a cold body during their direct contact. Convection is a type of heat transfer from heated surfaces due to the movement of air created by Archimedean force. That is, the heated air, becoming lighter, tends upward under the action of the Archimedean force, and cold air takes its place near the heat source. The higher the difference between the temperatures of hot and cold air, the more lifting force which pushes heated air upward.

In turn, convection is hampered by various obstacles, such as window sills, curtains. But the most important thing is that the air itself, or rather, its viscosity, interferes with air convection. And if on the scale of the room the air practically does not interfere with convective flows, then, being "sandwiched" between the surfaces, it creates significant resistance to mixing. Remember the glass unit. The layer of air between the glasses slows down itself, and we get protection from the outside cold.

Well, now that we have figured out the methods of heat transfer and their features, let's look at what processes take place in heating devices when different conditions... At high temperature all heating devices heat the coolant equally well - powerful convection, powerful radiation. However, with a decrease in the temperature of the coolant, everything changes.

Convector. The hottest part of it - the coolant pipe - is inside the heater. The lamellas are heated from it, and the farther from the pipe, the colder the lamellas. The lamella temperature is practically equal to the temperature the environment... There is no radiation from cold lamellas. Convection at low temperatures interferes with the viscosity of the air. There is very little heat from the convector. To make it warm, you need to either increase the temperature of the coolant, which will immediately reduce the efficiency of the system, or artificially blow warm air out of it, for example, with special fans.

Aluminum (sectional bimetallic) radiator structurally very similar to a convector. The hottest part of it - a collector pipe with a coolant - is located inside the sections of the heater. The lamellas are heated from it, and the farther from the pipe, the colder the lamellas. There is no radiation from cold lamellas. Convection at a temperature of 45-55 ° C interferes with the viscosity of the air. As a result, the heat from such a "radiator" under normal operating conditions is extremely small. To make it warm, you need to increase the temperature of the coolant, but is this justified? Thus, we almost everywhere come across an erroneous calculation of the number of sections in aluminum and bimetallic devices, which are based on the selection "according to the nominal temperature flow", and not on the basis of the actual temperature operating conditions.

The hottest part of a steel panel radiator - the external heat carrier panel - is located outside the heater. The lamellas are heated from it, and the closer to the center of the radiator, the colder the lamellas. And the radiation from outer panel always goes

Steel panel radiator. The hottest part of it - the outer panel with the coolant - is located outside the heater. The lamellas are heated from it, and the closer to the center of the radiator, the colder the lamellas. Convection at low temperatures interferes with the viscosity of the air. What about radiation?

Radiation from the outer panel lasts as long as there is a difference between the temperatures of the surfaces of the heater and the surrounding objects. That is, always.

In addition to the radiator, this useful property inherent in radiator convectors such as, for example, Purmo Narbonne. In them, the coolant also flows from the outside along rectangular pipes, and the lamellas of the convective element are located inside the device.

The use of modern energy-efficient heating devices helps to reduce heating costs, and a wide range of standard sizes of panel radiators from leading manufacturers will easily help to implement projects of any complexity.

The question, what is low-temperature heating, arises for many people. Typically, such systems are characterized by heating the coolant up to 60 degrees Celsius. At the same time, at the entrance to the system, it has a temperature of about 40 degrees, and at the exit - about 60. Let's consider how this is achieved.

Temperature regime heating systems can be described by three characteristics:

• ... Heating agent temperature at the boiler inlet.
• . Outlet temperature.
• . The temperature in the heated room.

The boiler data must be indicated in the product data sheet in this sequence. Heating systems of the traditional type (including central heating) were calculated in such a way that the water leaving the heater should have a temperature of about 80 degrees at a temperature of 60 degrees at the inlet. However, these days, such indicators are somewhat outdated. The temperature can be reduced either by the heating network, or by the user himself. European boilers, which today have almost completely supplanted Soviet heating counterparts, operate according to slightly different schemes.

According to the European standard, the normal operation of heating systems assumes a temperature of 60-75 degrees Celsius. But here it is also said about the concept of the so-called "soft heat", which presupposes the parameters of a system with a temperature of up to 55 degrees. And it is this regime that may become normative in the near future, if we take into account all the tightening requirements for savings. Thus, installation of warm floors becomes more and more relevant.

Perhaps everyone has heard about "warm floors". It is this system that is one of the most striking examples of low-temperature heating. In addition, most owners of a private house today reduce the temperature of the boilers to "one" in order to bring the temperature of the heat carriers to 50-60 degrees.

What are the advantages of low temperature heating

At installation of a water underfloor heating system, you get the following benefits:

1. 1. The main advantage is the level of comfort. It's no secret that too hot batteries dry the air, forming excessive convection in the house, which raises a lot of dust in the house, having a negative effect on the human body.
2. 2. Profitability. By abandoning intensive heating in favor of selective heating, which is characterized by separate temperature control, you can save up to 20% of heating fluids.
3. 3. Technological efficiency. Using the mode warm pipes, you can discover two possibilities for heating at once - condensing boilers with efficiency up to 95%, and solar collectors allowing you to get "free" energy.

Eliminating the main sources of heat loss and wanting to reduce costs when the system will pay off in 5-10 years, homeowners can start re-equipping heating systems for a more economical mode of operation.

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 interchangeably, in particular when it comes to heating circuits). But the postulates on which this point of view was based are outdated. Saving metal and building insulation is not considered higher today than saving energy resources. BUT specifications modern radiators allow us to speak not only about the possibility of their use in low-temperature systems, but also about the advantages of such a solution. This is proven Scientific research, for two years carried out at the initiative of Rettig ICC, the owner of the brands Purmo, Radson, Vogel & Noot, Finimetal, Myson.

If you want to buy heating equipment, then you can go to the corresponding section:

Reducing the temperature of the coolant is the main trend in the development of heating technology in recent decades in European countries. This became possible with the improvement of the thermal insulation of buildings, the improvement of heating devices. In the 1980s, the standard was reduced to 75/65 ºC (flow / return). The main benefit from this was the reduction of losses in the generation, transportation 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 55 ºC, which was taken into account by the designers of heat generators, control valves, etc.

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

Until now, the "warm floor" and convectors with copper-aluminum heat exchangers were considered the main solution providing heating of premises at a low temperature of the heat carrier. Research initiated by Rettig ICC allowed steel panel radiators to be added to this range. (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 .

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

At the end of January 2011, research materials were presented to journalists from leading specialized publications in Europe 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 the head of the Department of Energy Systems of the Institute of Building Physics. Fraunhofer-Institute for Building Physics (IBP) Dietrich Schmidt.

The report by Lin Peters considered the issues of thermal comfort, accuracy and responsiveness of the heating system to changing conditions, heat losses.

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

At the same time, the most comfortable for a person are not static, but "moving" temperature conditions(conclusion of the University of California, 2003). Inner space with zones with a slight temperature difference, increases the feeling of comfort. But large temperature changes are the cause of the discomfort.

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

Modern buildings are increasingly becoming thermally sensitive - thanks to improved thermal insulation. External and internal thermal disturbances (from sunlight, household appliances, the presence of people) can strongly affect the indoor climate. And radiators respond to these thermal changes more accurately than panel heating systems.

As you know, a "warm floor", especially located in a concrete screed, is a system with a high heat capacity, slowly reacting to regulatory influences.

Even if the "warm floor" is controlled by thermostats, a quick reaction to the supply of external heat is not possible. When laying heating pipes in concrete screed the response time of the underfloor heating to changes in the amount of incoming heat is about two hours.

Quickly reacted to the incoming heat room thermostat turns off the underfloor heating, which continues to release heat for about two more hours. When the supply of external heat stops and the thermostatic valve is opened, the floor is completely heated 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 supply of heat from the heater is regulated in a natural way due to the following two laws: 1) heat always spreads from a warmer 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 devices) equation allows you to understand the essence of this:

Q = Qnom. ∙ (ΔT / ΔTnom.) N,

where Q is the heat transfer from the heater; ΔT is the difference between the temperature of 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 exponent of the heater.

Self-regulation is common for both underfloor heating and radiators. In this case, for the "warm floor" the value of n is 1.1, and for the radiator - about 1.3 (exact values ​​are given in the catalogs). That is, the response to the change in ΔT in the second case will be more "pronounced", and the restoration of the set temperature regime will occur faster.

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

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

On the rice. one shows graphs of changes in operating temperature under simulated conditions individual house when it is heated by adjustable high-, low-temperature radiators and "warm floor" (research work by L. Peters and J. Van der Vecken).

The house is designed for four people and is equipped natural ventilation... Sources of third-party heat inputs are people and Appliances... The operating temperature is set as the comfort temperature.

21 ºC. The graphs consider two options for maintaining it: without switching to energy-saving (night) mode and with it.

Note: the operating temperature is an indicator characterizing the combined effect on a person of air temperature, radiation temperature and the speed of movement of the surrounding air.

Experiments have confirmed that radiators are clearly faster than a "warm floor" to respond to temperature fluctuations, providing smaller deviations.

The next reason for radiators in the workshop is a more comfortable and energy efficient indoor temperature profile.

In 2008, John R. Meichren and Stur Holmberg published in the international journal Energy and Buildings the work “Temperature distribution and thermal comfort in a room with a panel radiator, floor standing and wall heating»(F low patterns and thermal comfort in a room with panel, floor and wall heating). It, in particular, compares the vertical temperature distribution in rooms of the same area and layout (without furniture and people), heated by a radiator and a "warm floor" ( rice. 2). The outdoor temperature was -5 ºC. The air exchange rate is 0.8.

We build or remodel a private house, got involved in the overhaul of the apartment. We equip an office, a warm garage, a heated room for other purposes. We thought over a heating system, selected the main equipment: a boiler and its piping, a boiler, underfloor heating systems. Or, if this is an apartment, they decided to replace the existing heating device with a more aesthetic and efficient one, maybe add a few additional sections old battery... We will assume that we have already made a choice of the type of heating devices: type-setting sectional cast iron, aluminum batteries, bimetallic devices or ready-made panel steel radiators... Let's not forget that the batteries must withstand the pressure of the coolant in the system, which in multi-storey building an order of magnitude higher than in a cottage. To achieve thermal comfort, it is important for us to correctly calculate the heating radiators.

Calculation principles

To provide required temperature in the room, the calculation of the power of heating radiators and the entire system must take into account the heat loss from each room and climatic conditions region. When preparing a project, heating engineers determine the thermal balance of the outer walls, roof, basement of the building, window and door designs... Air exchange in the ventilation system, the height of the premises, the movement of air flows and many other factors are also taken into account. The basic document prescribing the principles of designing a heating system - SNiP 2.04.05-91. Designers use a number of other regulations ( total up to two dozen), regulating the heating device for buildings and premises for various purposes.

The exact calculation of heating radiator sections according to all the rules is quite complicated, and it is not easy to do it yourself, without having special knowledge. When building a serious country house it makes sense to contact a specialist and order a complete heating project: rational decisions, thermal comfort and optimal fuel consumption will justify the costs. If this is not possible, you can make an approximate calculation of the heating batteries yourself.

What is the thermal power of heating radiators

Thermal power, heat transfer or heat flux of a heater indicates the amount of thermal energy (in kilowatts or watts) that a radiator or one modular element (section) is able to transfer to a room per unit of time (hour). Less common is the designation in calories / hour. One watt equals 0.86 calories. The amount of heat transfer depends not only on the design of the radiator, its dimensions, the material from which it is made. Of no less importance are the parameters of the coolant: its temperature and the speed with which the liquid flows through the batteries. For most heaters, it is indicated thermal power at standard values ​​of the heating medium temperature 60/80 ° C. Accordingly, when the operating services from the bounty of the budget give in to the heat and put boiling water into the system (rarely, but it happens), the heat transfer will increase. A little warm water will go at a low speed (this happens much more often) - it will go down. Significantly affects the amount of heat flux and the method of connecting the device.

Please note that not all connection schemes provide full heat transfer from the heater. The most common is the standard lateral (1); for other cases (3, 4), a reduction factor is introduced in the calculation.

Heat dissipation of one section in a traditional cast iron radiator Soviet-style - 160 watts. To determine total power batteries, we multiply this figure by the number of sections.

Aluminum radiators are also sectional. The heat flux depends on the model, but with a standard center-to-center height of 500 mm, it averages 200 W for one section. That is, such aluminum sections it will take about 20% less than cast iron.

Aluminum radiator design. IN standard version the A value is 500 mm. Attention should be paid to the distance from the outer edges of the device to the floor and window sill. If they are less than indicated, the heat transfer will decrease slightly.

Steel panel radiators are non-separable and have a fixed amount of heat transfer. As an example: depending on the design, the panel standard height and a length of 800 mm can give a heat flux from 700 to 1500 W.

Simplified calculation

In the central regions of Russia for heating a living room with one outside wall in a typical panel house you will need about 100 watts of thermal energy for one square meter area. This is a very indicative figure. If the apartment is located on the first or top floor, it is worth adding about 20%. For a corner room, increase the figure by one and a half times. Let's not forget that there is a dependence on the connection diagram, if necessary, we will take into account the correction factor. It is a battery of ten cast iron sections. Naturally, for Yakutia and Krasnodar, the value of heat transfer per unit area will differ significantly. Thus, for the Moscow region, a 16 m2 room in a standard "socket" will require 1600 watts.

Modern house with walls made of "warm" cellular blocks, and even with a "thermal coat", energy-efficient glazing will have much less heat loss and required power the radiator should also be lower. Some sellers heating equipment facilitate potential buyers choice by placing on your website a calculator for calculating the number of heating radiator sections. With the help of such an online service, it is possible to make a more or less accurate calculation of a heating radiator for a room.

Radiator layout plan, one of the many pages of a "correct" heating system design. For each room, the calculated value of heat loss is indicated (numbers in a rectangle). When building expensive apartments, save on design works not worth it

Do you need a power reserve

It is desirable. You do not always get a coolant of the required temperature from the ZhES, so it is worth increasing the battery power by 20-25%. It is advisable to put a heat regulator at the entrance: a thermostat or a regular ball valve.

"Correct" installation of the radiator (5). The thermostatic valve (4) will ensure constant maintenance of the set temperature in the room, the connecting parts (1-3) will help you quickly remove and reinstall the battery. Bypass (a jumper between the inlet and outlet pipes) will allow the coolant to circulate through the riser even with the device removed, so as not to infringe on the interests of neighbors in the house

Low temperature heating systems and radiator calculation

In Europe, modern low-temperature heating systems prevail, and in Russia, modern low-temperature heating systems are increasingly used. They are built on the basis of energy efficient condensing heating boilers and heat pumps. To get the maximum economic effect, for radiator heating, as well as for underfloor heating, use a coolant with a low temperature - 40-55 ° C. Heat transfer from radiators is reduced by about 1.8 times. Accordingly, they must have greater power and dimensions. Despite the rise in the cost of the system, this approach is justified: rationally designed, correctly mounted and correctly configured low temperature system allows you to achieve significant gas savings. Heat pumps do not need fuel at all. To calculate such systems, all famous manufacturers indicate the heat transfer of devices for various parameters of the coolant. The calculation of the number of heating radiators should also take into account the effect of underfloor heating.

Efficiency ratio of traditional and modern condensing gas boilers. To achieve the indicated savings, a coolant with a low temperature must also circulate in the radiators. Accordingly, the heat dissipation of devices should be taken based on indicators of 40-55 ° C

In conclusion, we say that the heater should not be covered by anything: blackout curtains, a solid decorative screen, close-up furniture will significantly reduce its effectiveness. If the fashionable sill table top completely covers the battery on top, warm air passes the surface of the window glass, and it can be too cold and "cry". In this case, place ventilation grilles in the window sill.

The most important task in the development of technologies is to improve energy efficiency. To solve this problem in heating systems, the most effective way is to reduce the temperature of the coolant. That is why low-temperature heating is today a key trend in the development of modern heating technology.

A low-temperature heating system during operation consumes a much smaller amount of heat carrier compared to a traditional system. This provides significant savings. An additional plus is the reduction in the volume of harmful emissions into the atmosphere. In addition, operation with a "soft" temperature regime allows the use of alternative types of equipment - heat pumps or condensing boilers.

The main problem in the development of low-temperature heating for a long time remained the fact that at low heating temperatures it was very difficult to create comfortable conditions in heated rooms. However, with the development of construction technologies allowing the construction of energy efficient buildings, this problem has been resolved. Application of modern construction and thermal insulation materials makes it possible to significantly reduce heat losses buildings. Thanks to this, the low-temperature heating system can heat the house efficiently and efficiently. The achieved effect of saving the heat carrier significantly exceeds the additional costs that have to be borne for the thermal insulation of buildings.

Application of radiators

Initially, only the so-called panel heating systems were considered as low-temperature ones, the most common representatives of which are underfloor heating systems. They are characterized by a significant heat exchange surface, which makes it possible to provide high-quality heating at a low temperature of the coolant.

Today, the development of production technologies has contributed to the fact that it became possible to use radiators for low-temperature heating. At the same time, batteries must meet increased energy efficiency requirements:

• high thermal conductivity of the metal;
• significant heat transfer surface area;
• maximum convective component.

TM Ogint offers energy-efficient aluminum radiators that fully meet the listed requirements and are ideal for completing low-temperature heating systems. At the same time, they are produced in full compliance with Russian standards and are fully adapted to domestic operating conditions.

So, the use of aluminum radiators of the Ogint Delta Plus model when creating low-temperature systems gives important advantage compared with warm floors... Optimum indicators of economy and comfort are provided in cases where the heating system quickly reacts to changes in the outside temperature (when it rises, the coolant temperature decreases, and when it decreases, it increases). Modern automation used in boiler equipment provides all the possibilities for this. The disadvantage of underfloor heating is their inertia. Radiator systems are able to respond to changes external conditions almost instantly.

Advantages and Disadvantages of Low Temperature Heating Systems

Low-temperature systems have a number of significant advantages:

• significant cost savings by reducing energy consumption;
• reducing the volume of harmful emissions into the atmosphere;
• improved comfort indicators. Due to the low heating of the radiators in the room, the air does not dry out and there are no strong convective currents that raise dust;
• safety. You cannot burn yourself with a radiator with a temperature of + 50 ... + 60 ° C, which cannot be said about a battery heated to + 80 ° C;
• reducing the load on the boiler, which increases the service life of the equipment;
• the possibility of using heat pumps, condensing boilers and other types alternative equipment with low temperature conditions.

The disadvantages of this type of heating system are relative. So, a certain disadvantage can be called increased requirements for the used radiators... However, the use of Ogint Delta Plus batteries completely solves all the problems of choosing heating devices.

It should also be noted that for severe frosts low temperature systems cannot always cope with heating buildings. At the same time, the system can be transferred to work in a higher temperature mode without any special problems if necessary.

In general, low temperature heating systems are more efficient, economical and safer than traditional systems... Therefore, today we can confidently say that the future lies precisely with low-temperature heating.