Calculation of radiators: rules and examples

Sooner or later, the owners of apartments, cottages, as well as specialists in warehouse, retail, office and other premises are faced with the problem of buying radiators. Regardless of whether the batteries change or a new heating system is installed, a competent calculation of the required number of sections of any type of radiator will allow creating an optimal microclimate for living or temporarily staying people in the room, as well as providing the optimum temperature for storing the goods. However, before calculating the radiator, it is necessary to determine the size of the product and the type of metal, since the thermal conductivity of all materials is not the same.

Varieties of heating radiators

Currently, the basic materials for manufacturingradiators, photos of which are presented in the article, are steel, cast iron and aluminum. Given that the different properties of materials used in the manufacture of radiators, affect the performance characteristics of the finished product is not the same, then the variety of batteries is combined into 4 groups.

Cast iron radiators

Batteries made of cast iron have been in high demand for several decades. However, unlike the old ones, modern models are more aesthetically pleasing and allow them to be laconically inscribed in an interior of different styles without the use of protective screens.

Advantages:

• high resistance to aggressive coolant impurities;
• ability to withstand significant hydraulic shocks;
• good heat storage capacity;
• sufficient internal cross section eliminates the clogging of the radiator;
• durability;
• reasonable cost.

Disadvantages:

• the duration of warming up the room with the initial supply of coolant;
• need for periodic coloring;
• The roughness of the internal surface promotes the formation of various types of deposits, slightly reducing the performance of the product over time;
• complexity of installation, due to the large weight.

Despite all the advantages and disadvantages, cast-iron radiators are ideal for both autonomous and central heating systems.

Steel radiators

The huge variety of steel radiators produced by domestic and foreign manufacturers is divided into:

• panel. Relatively different types of radiators are characterized by simplicity of design and more compact dimensions. The return of heat energy in most panel radiators occurs on the principle of convection, as a result of which there is an uneven heating of the air masses. It would seem that the minimum number of welds should ensure a good design reliability. However, a small cross-section of pipes leads to a fairly rapid clogging of the radiator with a poor-quality coolant containing various impurities, so it is necessary to install panel radiators in multi-storey houses with caution;

• tubular. An advantageous feature of tubular radiators is the absence of sharp corners and a diverse design of execution. Unlike panel devices, heat transfer is carried out through radiation, and pipes with a larger cross section are less susceptible to water hammering and clogging. In this case, docking seams made by spot welding, after a short operating period give a leak.

Advantages:

• diverse range of models;
• good heat dissipation with low thermal inertia;
• wide price range, depending on the type of battery, dimensions and manufacturing technologies used to minimize various disadvantages.

Cons:

• high requirements for quality of coolant;
• low corrosion resistance, especially when draining the heating system for more than 2 weeks;
• the need for periodic staining;
• average life rarely exceeds 10 years.

Steel heating radiators are most popular when installed in private homes or premises heated from an autonomous system.

Aluminum radiators

Batteries made of aluminum began to be produced relatively recently. Compared with products made of cast iron, steel, aluminum batteries are quite attractive design in a wide variety of designs.

Pros:

• the maximum level of heat transfer, carried out by means of convection and thermal radiation;
• quick warm-up of the room;
• excellent corrosion resistance;
• light weight facilitates easy installation;
• reasonable cost.

Cons:

• periodic system air purification;
• does not have hydro impact resistance;
• it is not possible to use copper elements when installing the system, which in a short period of time disables the battery;
• is a small operating period, rarely exceeding 10 years.

Despite a number of positive and negative points, some performance characteristics of aluminum radiators depend on the way of manufacturing the products.

Currently, aluminum batteries are manufactured by:

• casting, when the required number of prefabricated sections is combined into a single structure by steel nipples and gaskets. The main feature of radiators, made by casting, is the production of products of rather complex shapes, which allows you to choose the size of the radiator, based on the specific conditions of future operation. In this case, the joints of individual sections rarely withstand the pressure of central heating systems;

• extrusion, when the aluminum profile, passed through special equipment, is converted into a finished product. Unlike casting, radiators made by the extrusion method have greater resistance to pressure drops inside the heating system. It is simply impossible to remove or add sections from the finished product. The number of sections of the finished radiator varies within 3-16.

Anodized products are a kind of aluminum heating radiators, the production of which is made of metal, which has undergone more qualitative cleaning and undergone anodic oxidation. Unlike simple aluminum, the anodized radiators have a fairly high resistance to the chemicals present in the heat carriers of central heating. In addition, the connection of individual sections is carried out not by means of nipples, but by couplings fixed from the outside of the product, which increases the strength of the batteries before sudden pressure fluctuations in the system. However, anodized instruments cost an order of magnitude more expensive than their counterparts, so they are not popular among a large number of consumers.

Thus, it is not necessary to install aluminum batteries in rooms with central heating, and to evenly warm the rooms heated from an autonomous system, it is desirable to install a circulation pump.

Bimetal radiators

Thanks to the ideal combination of steel and metal, bimetallic heating radiators transform the disadvantages of metals used in the production process into the advantages of a finished structure including steel pipes for moving the coolant that are externally encased in aluminum. Along with aluminum devices, bimetallic batteries are produced by casting and extrusion.

Pros:

• aesthetic appeal;
• excellent thermal conductivity inherent in aluminum batteries;
• good strength indicators;
• high resistance to hydraulic shocks;
• light weight;
• for a long period of operation.

Cons:

• clogged radiator due to the use of small diameter steel pipes;
• high cost.

Thus, to choose bimetallic and other radiators is subject to the conditions of their future operation. For central heating systems, it is preferable to stop the choice of cast-iron and bimetallic radiators of monolithic construction, while for an autonomous system batteries suitable for any type of metal are suitable. In this case, do not forget about the correspondence between the size of the radiator and the place intended for installation.

Dimensions of radiators

For correct calculation of sections of radiators of heating it is necessary to know the thermal conductivity of one section, which depends not only on the material, but also on the dimensions of the finished product. In this case, the dimensions of the radiators are selected taking into account the following factors:

• Ideally, the battery length should occupy not less than 50-60% of the window opening.
• Optimum height of the heating radiator = Distance from the window sill to the floor covering minus 15-20 cm, since the distance from the battery to the window sill during installation must be at least 8-10 cm, and the distance from the floor to the bottom of the battery also varies within 8-10 cm
• The thickness of the battery is determined by the layout features, although the maximum heat output is achieved if the radiator protrudes 4-5 cm beyond the window sill.

Given the dimensions of the product at the stage of calculating the required number of sections, the buyer pre-insures himself against inaccuracies in determining the required amount of heat for a particular room.

Calculation of heating radiators

The optimum power of the radiator is determined for each room separately, since the volume of heated air in different rooms is unlikely to be the same. Depending on the required degree of accuracy of the final result, one of the calculation methods is chosen.

Area calculation

According to SNIP, for heating 1 m², 100 W of thermal energy is needed, therefore:

Number of sections = Room area * 100 W / heat transfer of the selected radiator section( taken from the documentation supplied with the radiator).

For example, to heat a room 3 m wide and 5 m long with a bimetal radiator, the average power of the section is 200 W, you will need: Number of sections = 15 * 100/200 = 7.5.Since the result is in the form of a fractional number, it must be rounded to the whole in the direction of increase, i.e.for heating a room of 15 m² , 8 sections are required, which are divided into 2 radiators.

Calculation of the heating radiator by area refers to a less labor-intensive method, which causes a rather approximate result.

Calculated by volume

Based on the SNIP, 41 mW are required for preheating 1 m³ in panel, brick houses without additional insulation measures, and 34 W are sufficient in insulated houses equipped with modern double-glazed windows. The calculation is made as follows:

Number of sections = Room volume( area * height) * 41 W( or 34 W) / power of the radiator section.

For example, the volume of the room located in the old Khrushchevka is 37.5 m³( 3 * 5 * 2.5).As an acquisition, a cast-iron battery with a heat output of 100 W is considered. Based on their data, the number of sections = 37.5 * 41/100 = 15.375.Rounding the result, the desired value is obtained in 16 sections.

Unlike the previous calculation method, determining the number of sections by volume gives a more accurate result, but not the most reliable one.

Using the correction factors

The peculiarity of the method is that in calculating the number of radiators, various coefficients are taken into account, which to some extent influence the storage of heat in the room. The calculation formula has the following form:

Required power of the radiator = Room area * 100 W( heat norm for 1 m²) * Ko * Ktep * Kpl * Ktem * Ksten * Ktyp * Kvys / power section of the radiator, where:

• Co - type of glazingordinary windows - 1.27, double glazed windows - 1.0, triple glazed windows - 0.85);
• KTEP - the degree of thermal insulation of walls( low or without insulation - 1.27, medium - 1.0, high degree of thermal insulation, made with the use of modern materials - 0.85);
• Kpl - the ratio of the area of ​​window openings to the floor of the room( 10% -0.8, 20% -0.9, 30% -1.0, 40% -1.1, 50% -1.2);
• Ktem - minimum air temperature outside the window in the coldest time( -10 ° C -0.7; -15 ° C -0.9; -20 ° C-1.1; -25 ° C-1.3; -35 ° C-1.5);
• Ksten - number of external walls( 1-1,1, 2-1,2, 3-1,3, 4-1,4);
• Ktype - coefficient correcting the required battery power, based on the room above the room( loft not heated - 1,0; residential apartment - 0,8; attic heated - 0,9);
• Kvys - height of ceilings( up to 2.5 m-1.0, from 2.5 m to 3 m - 1.05, from 3 m to 3.5 m -1.1, from 3.5 m to 4 m- 1,15, from 4,5 m and above - 1,2).

For example, the area of ​​the premise located on the 3rd floor in a 5-storey panel house is 15 m² with a room height of 2.5 m. External insulation is made using cheap thermal insulation materials. The room has one window with triple-glazed windows and, accordingly, one external wall. The ratio of the floor to the window opening is about 10%.In winter, the temperature drops to -35 ° C.The power of the radiator is 200W.

Required battery power = 15 * 100 * 0.85 * 1.0 * 0.8 * 1.5 * 0.8 * 1.0 / 200 = 6.12.

To heat the room will require 7 sections of the radiator with a power of 200 watts.

Thus, the calculation of radiators with allowance for correction factors gives a more accurate result, which may well be less than determining the number of sections using approximate calculations.