Heat transfer table of cast iron and bimetallic heating radiators

Leading classification

This will depend on the type and quality of the material used in the manufacture of the radiators. The main varieties are:

• cast iron;
• bimetal;
• made of aluminum;
• of steel.

Each of the materials has some disadvantages and a number of features, therefore, to make a decision, you will need to consider the main indicators in more detail.

Made of steel

They function perfectly in combination with an autonomous heating device, which is designed to heat a substantial area. The choice of steel heating radiators is not considered an excellent option, since they are not able to withstand significant pressure. Extremely resistant to corrosion, light and satisfactory heat transfer performance. Having an insignificant flow area, they rarely clog. But the working pressure is considered to be 7.5-8 kg / cm 2, while the resistance to possible water hammer is only 13 kg / cm 2. The heat transfer of the section is 150 watts.

Steel

Made of bimetal

They are devoid of the disadvantages that are found in aluminum and cast iron products. The presence of a steel core is a characteristic feature, which made it possible to achieve a colossal pressure resistance of 16 - 100 kg / cm 2. The heat transfer of bimetallic radiators is 130 - 200 W, which is close to aluminum in terms of performance. They have a small cross-section, so over time, there are no problems with pollution. The significant disadvantages can be safely attributed to the prohibitively high cost of products.

Bimetallic

Made of aluminum

Such devices have many advantages. They have excellent external characteristics, moreover, they do not require special maintenance. They are strong enough, which allows you not to fear water hammer, as is the case with cast iron products. The working pressure is considered to be 12 - 16 kg / cm 2, depending on the model used. The features also include the flow area, which is equal to or less than the diameter of the risers. This allows the coolant to circulate inside the device at a tremendous speed, making it impossible for sediments to accumulate on the surface of the material. Most people mistakenly believe that too small a cross section will inevitably lead to a low heat transfer rate.

Aluminum

This opinion is erroneous, if only because the level of heat transfer from aluminum is much higher than, for example, that of cast iron. The cross section is compensated by the ribbing area. Heat dissipation of aluminum radiators depends on various factors, including the model used and can be 137 - 210 W. Contrary to the above characteristics, it is not recommended to use this type of equipment in apartments, since the products are not able to withstand sudden temperature changes and pressure surges inside the system (during the run of all devices). The material of an aluminum radiator deteriorates very quickly and cannot be recovered later, as in the case of using another material.

Made of cast iron

The need for regular and very careful maintenance. The high inertness rate is almost the main advantage of cast iron heating radiators. The heat dissipation level is also good. Such products do not heat up quickly, while they also give off heat for a long time. The heat transfer of one section of a cast-iron radiator is equal to 80 - 160 W. But there are a lot of shortcomings here, and the following are considered to be the main ones:

1. Perceptible weight of the structure.
2. Almost complete lack of ability to resist water hammer (9 kg / cm 2).
3. A noticeable difference between the cross-section of the battery and the risers. This leads to a slow circulation of the coolant and a fairly rapid pollution.

Heat dissipation of heating radiators in the table

Device

Why were such constructive additions to the aluminum radiator required? After all, the heat transfer of this metal is much higher than steel, respectively, in an apartment with aluminum heating devices it will be noticeably warmer.

It is clearly seen that the heat transfer of aluminum is 2 times more than iron.

But the fact is that aluminum has “vulnerabilities,” and first of all, it is associated with the quality of the heat carrier used for urban heating networks. The coolant used carries with it all kinds of impurities, including alkalis and acids, which destroy aluminum.

The second important point is the inability to withstand hydraulic pressure, which is not uncommon for homes connected to a central heating system.

Properties

The following facts speak in favor of bimetallic heating devices:

The radiator consists of a steel bushing and an aluminum body

Thus, all the positive qualities of aluminum devices are preserved in bimetallic radiators.

They possess:

• high heat transfer;
• attractive appearance;
• good compactness.

Taking into account their design features, it is safe to say that they will be the ideal choice when installing a heating system in city apartments with your own hands.

Comparative table of heat transfer of bimetallic heating radiators demonstrates the difference between models of different manufacturers

Heat dissipation and connection method

Having the right number of radiator sections for a particular room is only half the job. The rest is to find the best way to connect the heater so that it can fully show its qualities. So, you have to choose from the following options:

Heat transfer of one section of a bimetallic radiator with two-pipe direct one-sided connection is the maximum

It can be concluded that:

• if you want to achieve maximum heat transfer from heaters with a standard number of sections 7-10, it is necessary to focus on their direct one-way connection to central heating;
• in the case when the area of ​​the room is large enough and it is required to install radiators with the number of sections exceeding 12, diagonal switching on of the device in a two-pipe system (supply + return) is suitable.

In the photo - a diagonal way to connect a radiator of 12 sections

Correct mounting location

Another important question that we often forget about, considering that it is not so essential. The classic option is under the window, but why?

This is due to the access of cold air to the room:

• much more enters through the window than through the outer walls;
• he immediately goes down and begins to creep along the floor, causing discomfort and a desire to rise higher.

Therefore, you need to install a thermal barrier that will dilute or even completely negate the cold flow.

Advice: use a radiator with a width of 70-90% of the window opening, then the air coming from the street will immediately begin to warm up.

There are also certain installation rules that must be followed in order to create good convection and thereby improve heat transfer:

• leave a gap of 60 mm or more between the heater and the floor;
• the distance from the window sill to the upper part of the radiator should be almost the same - 50-60 mm or more;
• the wall should be retreated by 25 mm or more.

Heat transfer of 1 section of bimetallic radiators depends directly on the correct placement of the heater

We also recommend:

• in a corner room with an additional outer wall to reduce heat loss, install another device on a cold wall. Its main task will be power compensation, and the installation height does not play a role in this, take the level of batteries installed under the window openings as an example;
• before installing radiators, calculate the number of sections so that the heat output is sufficient, taking into account losses through walls and windows.

Tip: to increase heat transfer, install a foil foam screen behind the device, with the metal side towards the inside of the room.

Formulas for calculating the power of the heater for various rooms

The formula for calculating the power of the heater depends on the height of the ceiling. For rooms with a ceiling height

• S is the area of ​​the room;
• ∆T is the heat transfer from the heater section.

For rooms with a ceiling height> 3 m, calculations are carried out according to the formula

• S is the total area of ​​the room;
• ∆T is the heat transfer from one section of the battery;
• h - ceiling height.

These simple formulas will help to accurately calculate the required number of sections of the heating device. Before entering data into the formula, determine the real heat transfer of the section using the formulas given earlier! This calculation is suitable for an average temperature of the incoming heating medium of 70 ° C. For other values, the correction factor must be taken into account.

Here are some examples of calculations. Imagine that a room or non-residential premises has dimensions of 3 x 4 m, the ceiling height is 2.7 m (the standard ceiling height in Soviet-built city apartments). Determine the volume of the room:

3 x 4 x 2.7 = 32.4 cubic meters.

Now let's calculate the thermal power required for heating: we multiply the volume of the room by the indicator required to heat one cubic meter of air:

Knowing the real power of a separate section of the radiator, select the required number of sections, rounding it up. So, 5.3 is rounded up to 6, and 7.8 - up to 8 sections.When calculating the heating of adjacent rooms that are not separated by a door (for example, a kitchen separated from the living room by an arch without a door), the areas of the rooms are summed up. For a room with a double-glazed window or insulated walls, you can round down (insulation and double-glazed windows reduce heat loss by 15-20%), and in a corner room and rooms on high floors add one or two sections "in reserve".

Why doesn't the battery warm up?

But sometimes the power of the sections is recalculated based on the real temperature of the coolant, and their number is calculated taking into account the characteristics of the room and installed with the necessary margin ... and it is cold in the house! Why is this happening? What are the reasons for this? Can this situation be corrected?

The reason for the decrease in temperature may be a decrease in the water pressure from the boiler room or repairs from neighbors! If, during the repair, a neighbor narrowed the riser with hot water, installed a "warm floor" system, began to heat a loggia or a glazed balcony on which he arranged a winter garden - the pressure of hot water entering your radiators will, of course, decrease.

But it is quite possible that the room is cold because you installed the cast iron radiator incorrectly. Usually, a cast-iron battery is installed under the window so that the warm air rising from its surface creates a kind of thermal curtain in front of the window opening. However, the back side of the massive battery heats not the air, but the wall! To reduce heat loss, glue a special reflective screen on the wall behind the heating radiators. Or you can buy decorative cast-iron batteries in a retro style, which do not have to be mounted on the wall: they can be fixed at a considerable distance from the walls.

General provisions and algorithm for thermal calculation of heating devices

The calculation of heating devices is carried out after the hydraulic calculation of the pipelines of the heating system according to the following method. The required heat transfer of the heating device is determined by the formula:

, (3.1)

where is the heat loss of the room, W; when several heating devices are installed in a room, the heat loss of the room is distributed equally between the devices;

- useful heat transfer from heating pipelines, W; determined by the formula:

, (3.2)

where is the specific heat transfer of 1 m of open-laid vertical / horizontal / pipelines, W / m; taken according to the table. 3 appendix 9 depending on the temperature difference between the pipeline and air;

- total length of vertical / horizontal / pipelines in the room, m.

Actual heat dissipation of the heater:

, (3.4)

where is the nominal heat flux of the heating device (one section), W. It is taken according to the table. 1 appendix 9;

- temperature head equal to the difference of the half-sum of the temperatures of the coolant at the inlet and outlet of the heating device and the temperature of the room air:

, ° С; (3.5)

where is the flow rate of the coolant through the heating device, kg / s;

- empirical coefficients. The values ​​of the parameters depending on the type of heating devices, the flow rate of the coolant and the scheme of its movement are given in table. 2 applications 9;

- correction factor - the method of installation of the device; taken according to the table. 5 applications 9.

The average water temperature in the heater of a one-pipe heating system is generally determined by the expression:

, (3.6)

where is the temperature of the water in the hot line, ° C;

- cooling of water in the supply line, ° C;

- correction factors taken according to table. 4 and tab. 7 applications 9;

- the sum of heat losses of the premises located before the considered premises, counting along the direction of water movement in the riser, W;

- water consumption in the riser, kg / s / is determined at the stage of hydraulic calculation of the heating system /;

- heat capacity of water equal to 4187 J / (kggrad);

- coefficient of water flow into the heating device.It is taken according to the table. 8 applications 9.

The flow rate of the coolant through the heating device is determined by the formula:

, (3.7)

Cooling of water in the supply line is based on an approximate relationship:

, (3.8)

where is the length of the main line from the individual heating point to the calculated riser, m.

The actual heat transfer of the heating device must be no less than the required heat transfer, that is. The inverse ratio is allowed if the residual does not exceed 5%.

Steel batteries

Old steel radiators have a fairly high thermal power, but at the same time they do not retain heat well. They cannot be disassembled or added to the number of sections. Radiators of this type are susceptible to corrosion.

Steel radiators

Currently, steel panel radiators have begun to be produced, which are attractive because of their high heat output and small dimensions compared to sectional radiators. The panels have channels through which the coolant circulates. The battery can consist of several panels, in addition, it can be equipped with corrugated plates that increase heat transfer.

Construction of steel panel radiators

The thermal power of steel panels is directly related to the dimensions of the battery, which depends on the number of panels and plates (fins). The classification is carried out depending on the radiator fins. For example, Type 33 is assigned to three-plate heaters with three plates. The range of battery types is 33 to 10.

Self-calculation of the required heating radiators is associated with a large amount of routine work, so manufacturers began to accompany products with tables of characteristics, which were formed from the records of test results. This data depends on the type of product, installation height, inlet and outlet temperature of the heating medium, target room temperature and many other characteristics.

Steel panel radiator

Characteristics and features

The secret of their popularity is simple: in our country there is such a coolant in centralized heating networks that even metals dissolves or erases. In addition to a huge amount of dissolved chemical elements, it contains sand, rust particles that have fallen off pipes and radiators, “tears” from welding, bolts forgotten during repairs, and a lot of other things that got inside it is not known how. The only alloy that does not care about all this is cast iron. Stainless steel also copes well with this, but how much such a battery will cost is anyone's guess.

MS-140 - an undying classic

And another secret of the popularity of the MC-140 is its low price. It has significant differences from different manufacturers, but the approximate cost of one section is about $ 5 (retail).

Advantages and disadvantages of cast iron radiators

It is clear that a product that has not left the market for many decades has some unique properties. The advantages of cast iron batteries include:

• Low chemical activity, which ensures a long service life in our networks. Officially, the warranty period is from 10 to 30 years, and the service life is 50 years or more.
• Low hydraulic resistance. Only radiators of this type can stand in systems with natural circulation (in some, aluminum and steel tubulars are still installed).
• High temperature of the working environment. No other radiator can withstand temperatures above +130 o C. Most of them have an upper limit of +110 o C.
• Low price.
• High heat dissipation. For all other cast iron radiators, this characteristic is in the "disadvantages" section. Only in MS-140 and MS-90 thermal power of one section is comparable to aluminum and bimetallic ones. For MS-140 heat transfer is 160-185 W (depending on the manufacturer), for MS 90 - 130 W.
• They do not corrode when the coolant is drained.

MS-140 and MS-90 - the difference in section depth

Some properties under some circumstances are a plus, under others - a minus:

• Large thermal inertia. While the MC-140 section warms up, it may take an hour or more. And all this time the room is not heated. But on the other hand, it is good if the heating is turned off, or an ordinary solid fuel boiler is used in the system: the heat accumulated by the walls and water maintains the temperature in the room for a long time.
• Large cross-section of channels and collectors. On the one hand, even a bad and dirty coolant will not be able to clog them in a few years. Therefore, cleaning and flushing can be carried out periodically. But because of the large cross-section in one section, more than a liter of coolant is "placed". And it needs to be "driven" through the system and heated, and this means extra costs for equipment (more powerful pump and boiler) and fuel.

"Pure" disadvantages are also present:

Great weight. The mass of one section with a center distance of 500 mm is from 6 kg to 7.12 kg. And since you usually need from 6 to 14 pieces per room, you can calculate what the mass will be. And it will have to be worn, and also hung on the wall. This is another drawback: complicated installation. And all because of the same weight. Brittleness and low working pressure. Not the most pleasant characteristics

For all the massiveness, cast iron products must be handled carefully: they can burst upon impact. The same fragility leads to not the highest working pressure: 9 atm

Pressing - 15-16 atm. The need for regular staining. All sections are only primed. They will need to be painted often: once a year or two.

Thermal inertia is not always a bad thing ...

Application area

As you can see, there are more than serious advantages, but there are also disadvantages. Putting it all together, you can define the scope of their use:

• Networks with a very low quality of the coolant (Ph above 9) and a large amount of abrasive particles (without mud collectors and filters).
• In individual heating when using solid fuel boilers without automation.
• In natural circulation networks.

What is a bimetallic radiator

Basically, a bimetallic heater is a mixed design that incorporates the advantages of steel and aluminum heating systems. The radiator device is based on the following elements:

• The heater consists of two bodies - an inner steel and an outer aluminum one;
• Due to the inner shell made of steel, the bimetallic casing is not afraid of aggressive hot water, withstands high pressure and ensures high strength of the connection of individual radiator sections into one battery;
• The aluminum housing is the best for transmitting and dissipating the heat flux in the air, it is not afraid of corrosion of the outer surface.

As a confirmation of the high heat transfer of the bimetallic case, you can use the comparative table. Among the closest competitors are radiators made of CG cast iron, TS steel, AA and AL aluminum, the BM bimetallic radiator has one of the best heat transfer rates, high operating pressure and corrosion resistance.

For your information! Almost all tables use manufacturers' information on heat transfer, reduced to standard conditions - a radiator height of 50 cm and a temperature difference of 70 ° C.

In reality, the situation is even worse, most manufacturers indicate the amount of heat transfer as a value of heat output per hour for one section. That is, the packaging may indicate that the heat transfer of the bimetallic section of the radiator is 200 W.

This is done forcibly, the data does not lead to a unit of area or a temperature difference of one degree, in order to simplify the buyer’s perception of the specific technical characteristics of the heat transfer of the radiator, at the same time making a small advertisement.

What determines the power of cast iron radiators

Cast iron sectional radiators are a proven way of heating buildings for decades.They are very reliable and durable, however there are a few things to keep in mind. So, they have a slightly small heat transfer surface; about a third of the heat is transferred by convection. First, we recommend watching about the advantages and features of cast iron radiators in this video.

The area of ​​the section of the MC-140 cast-iron radiator is (in terms of the heating area) only 0.23 m2, weight 7.5 kg and holds 4 liters of water. This is quite small, so each room should have at least 8-10 sections. The area of ​​the section of a cast-iron radiator should always be taken into account when choosing, so as not to hurt yourself. By the way, in cast-iron batteries the heat supply is also somewhat slowed down. The power of the cast iron radiator section is usually about 100-200 watts.

The working pressure of a cast iron radiator is the maximum water pressure it can withstand. Usually this value fluctuates around 16 atm. And heat transfer shows how much heat is given off by one section of the radiator.

Often, manufacturers of radiators overestimate the heat transfer. For example, you can see that cast iron radiators heat transfer at a delta t 70 ° C is 160/200 W, but the meaning of this is not entirely clear. The designation "delta t" is actually the difference between the average air temperatures in the room and in the heating system, that is, at a delta t 70 ° C, the heating system's work schedule should be: supply 100 ° C, return 80 ° C. It is already clear that these figures do not correspond to reality. Therefore, it will be correct to calculate the heat transfer of the radiator at a delta t 50 ° C. Nowadays, cast-iron radiators are widely used, the heat transfer of which (more specifically, the power of the cast-iron radiator section) fluctuates in the region of 100-150 W.

A simple calculation will help us to determine the required thermal power. The area of ​​your room in mdelta should be multiplied by 100 W. That is, for a room with an area of ​​20 mdelta, a 2000 W radiator is needed. Be sure to keep in mind that if there are double-glazed windows in the room, subtract 200 W from the result, and if there are several windows in the room, too large windows or if it is angular, add 20-25%. If you do not take these points into account, the radiator will work ineffectively, and the result is an unhealthy microclimate in your home. You should also not choose a radiator by the width of the window under which it will be located, and not by its power.

If the power of cast iron radiators in your home is higher than the heat loss of the room, the devices will overheat. The consequences may not be very pleasant.

• First of all, in the fight against the stuffiness arising due to overheating, you will have to open windows, balconies, etc., creating drafts that create discomfort and illness for the whole family, and especially for children.
• Secondly, due to the highly heated surface of the radiator, oxygen burns out, the humidity of the air drops sharply, and even the smell of burnt dust appears. This brings special suffering to allergy sufferers, since dry air and burnt dust irritate the mucous membranes and cause an allergic reaction. And this also affects healthy people.
• Finally, the incorrectly selected power of cast iron radiators is a consequence of uneven heat distribution, constant temperature drops. Radiator thermostatic valves are used to regulate and maintain the temperature. However, it is useless to install them on cast-iron radiators.

If the thermal power of your radiators is less than the heat loss of the room, this problem is solved by creating additional electric heating or even a complete replacement of heating devices. And it will cost you time and money.

Therefore, it is very important, taking into account the above factors, to choose the most suitable radiator for your room.

Cast iron radiators: characteristics

Cast iron radiators differ in height, depth and width, depending on the number of sections in the assembly. Each section can have one or two channels.

The larger the area is required to be heated, the wider the battery will be needed, the more sections it will contain and the more heat transfer is required. Cast iron heating radiators (the table will be given below) have the highest rate. It should also be borne in mind that the indoor temperature will be affected by the number and size of window openings and the thickness of the walls in contact with the outdoor air space.

The height of the radiator can vary from 35 centimeters to the maximum one and a half meters, and the depth - from half a meter to one and a half meters. Batteries made of this metal are quite heavy (about six kilograms - the weight of one section), therefore, strong fasteners are required for their installation. There are modern models available on legs.

For such radiators, the quality of the water does not matter, and from the inside they do not rust. Their working pressure is approximately nine to twelve atmospheres, and sometimes more. With proper care (draining and flushing), they can last for a long time.

In comparison with other competitors that have appeared recently, the price of cast iron radiators is the most favorable.

The heat transfer table of cast iron heating radiators is presented below.

Advantages and disadvantages of cast iron radiators

Cast iron radiators are made by casting. The cast iron alloy has a homogeneous composition. Such heating devices are widely used both for central heating systems and for autonomous heating systems. The sizes of cast iron radiators may vary.

Among the advantages of cast iron radiators are:

1. the ability to use for a coolant of any quality. Suitable even for heat transfer fluids with a high alkali content. Cast iron is a durable material and it is not easy to dissolve or scratch it;
2. resistance to corrosion processes. Such radiators can withstand the coolant temperature up to +150 degrees;
3. excellent heat storage properties. An hour after the heating is turned off, the cast iron radiator will radiate 30% of the heat. Therefore, cast iron radiators are ideal for systems with irregular heating of the coolant;
4. do not require frequent maintenance. And this is mainly due to the fact that the cross-section of cast iron radiators is quite large;
5. long service life - about 50 years. If the coolant is of high quality, then the radiator can last a century;
6. reliability and durability. The wall thickness of such batteries is large;
7. high heat radiation. For comparison: bimetallic heaters transfer 50% of the heat, and cast iron radiators - 70% of the heat;
8. for cast-iron radiators, the price is quite acceptable.

Among the disadvantages are:

• great weight. Only one section can weigh about 7 kg;
• installation should be carried out on a previously prepared, reliable wall;
• radiators must be painted. If after a while it is necessary to paint the battery again, the old layer of paint must be sanded. Otherwise, heat transfer will decrease;
• increased fuel consumption. One segment of a cast iron battery contains 2-3 times more liquid than other types of batteries.

Characteristics of aluminum batteries

Aluminum radiators are characterized by the fact that the outer side is coated with a powder layer that is resistant to external corrosion, and the inner side is coated with a polymer protective coating.

They have a neat appearance, light in weight, and belong to the middle price category.

The heating method for aluminum radiators is convection, they can withstand pressure up to sixteen atmospheres.

Structurally, this type of device is divided into extruded and cast. In the first case, the production process consists of two stages: first, plastic aluminum is extruded in sections, and the top and bottom are molded under pressure, and then the components are glued together with a special compound. In the second case, the entire section is cast at once under pressure.This method makes the structure more durable, making it possible to more stably withstand water shocks that occur during pressure testing of heating systems before the onset of winter.

The following are the heat transfer characteristics of aluminum heating radiators in the table.

Connection method

Not everyone understands that the piping of the heating system and the correct connection affect the quality and efficiency of heat transfer. Let us examine this fact in more detail.

There are 4 ways to connect a radiator:

• Lateral. This option is most often used in urban apartments of multi-storey buildings. There are more apartments in the world than private houses, so manufacturers use this type of connection as a nominal way to determine the heat transfer of radiators. A factor of 1.0 is used to calculate it.
• Diagonal. Ideal connection, because the heating medium passes through the entire device, evenly distributing heat throughout its volume. Usually this type is used if there are more than 12 sections in the radiator. A multiplying factor of 1.1–1.2 is used in the calculation.
• Lower. In this case, the supply and return pipes are connected from the bottom of the radiator. Typically, this option is used for hidden pipe wiring. This type of connection has one drawback - heat loss of 10%.
• One-pipe. This is essentially a bottom connection. It is usually used in the Leningrad pipe distribution system. And here it was not without heat loss, however, they are several times more - 30-40%.

How to increase the heat dissipation of the radiator?

What to do if the battery has already been purchased, and its heat dissipation does not correspond to the declared values? And you have no complaints about the quality of the radiator.

In this case, there are two options for actions aimed at increasing the heat transfer of the battery, namely:

• Increase in coolant temperature.
• Optimization of the radiator connection diagram.

In the first case you will have to purchase a more powerful boiler or increase the pressure in the system, spurring the circulation rate of the coolant, which simply does not have time to cool down in the return line. This is a fairly effective method, although very costly.

Optimization of the radiator connection diagram

In the second case you need to revise the battery wiring diagram. Indeed, according to the standards and the radiator passport, 100% thermal power can be obtained only with a one-way direct connection (pressure is at the top, return flow is at the bottom and both pipes are on one side of the battery).

Cross Mount - Diagonal: pressure at the top, return flow at the bottom - assumes power losses at the level of 2-5 percent of the passport value. The lower connection diagram - pressure and return flow at the bottom - will lead to losses of 10-15 percent of thermal power. Well, the most unsuccessful is the one-pipe connection - the pressure and return flow below. On one side of the battery. In this case, the radiator loses up to 20 percent of its power.

Thus, by returning to the recommended way of tapping the battery into the wiring, you will get a 5 or 20 percent increase in thermal power on each radiator. And without any investment.

We also recommend reading:

How to correctly calculate the real heat transfer of batteries

You must always start with the technical passport that is attached to the product by the manufacturer. In it, you will definitely find the data of interest, namely, the thermal power of one section or a panel radiator of a certain standard size. But do not rush to admire the excellent performance of aluminum or bimetallic batteries, the figure indicated in the passport is not final and requires adjustment, for which you need to calculate the heat transfer.

You can often hear such judgments: the power of aluminum radiators is the highest, because it is well known that the heat transfer of copper and aluminum is the best among other metals. Copper and aluminum have the best thermal conductivity, this is true, but heat transfer depends on many factors, which will be discussed below.

The heat transfer prescribed in the passport of the heater corresponds to the truth when the difference between the average temperature of the coolant (t supply + t return flow) / 2 and in the room is 70 ° C. With the help of a formula, this is expressed as follows:

For reference. In the documentation for products from different companies, this parameter can be designated in different ways: dt, Δt or DT, and sometimes it is simply written “at a temperature difference of 70 ° C”.

What does it mean when the documentation for a bimetallic radiator says: the thermal power of one section is 200 W at DT = 70 ° C? The same formula will help to figure it out, only you need to substitute the known value of room temperature - 22 ° С into it and carry out the calculation in the reverse order:

Knowing that the temperature difference in the supply and return pipelines should not be more than 20 ° С, it is necessary to determine their values ​​in this way:

Now you can see that 1 section of the bimetallic radiator from the example will give off 200 W of heat, provided that there is water in the supply pipeline heated to 102 ° C, and a comfortable temperature of 22 ° C is established in the room. The first condition is unrealistic to fulfill, since in modern boilers heating is limited to a limit of 80 ° C, which means that the battery will never be able to give the declared 200 W of heat. Yes, and it is a rare case that the coolant in a private house is heated to such an extent, the usual maximum is 70 ° C, which corresponds to DT = 38-40 ° C.

Calculation procedure

It turns out that the real power of the heating battery is much lower than that stated in the passport, but for its selection you need to understand how much. There is a simple way for this: applying a reduction factor to the initial value of the heating power of the heater. Below is a table where the values ​​of the coefficients are written, by which it is necessary to multiply the passport heat transfer of the radiator, depending on the value of DT:

The algorithm for calculating the real heat transfer of heating devices for your individual conditions is as follows:

1. Determine what should be the temperature in the house and the water in the system.
2. Substitute these values ​​into the formula and calculate your real Δt.
3. Find the corresponding coefficient in the table.
4. Multiply the nameplate value of the radiator heat transfer by it.
5. Calculate the number of heating devices required to heat the room.

For the above example, the thermal power of 1 section of a bimetallic radiator will be 200 W x 0.48 = 96 W. Therefore, to heat a room with an area of ​​10 m2, you will need 1 thousand watts of heat or 1000/96 = 10.4 = 11 sections (rounding always goes up).

The presented table and the calculation of the heat transfer of the batteries should be used when the Δt is indicated in the documentation, equal to 70 ° С. But it happens that for different devices from some manufacturers, the power of the radiator is given at Δt = 50 ° C. Then it is impossible to use this method, it is easier to collect the required number of sections according to the passport characteristics, only take their number with a one and a half stock.

For reference. Many manufacturers indicate the values ​​of heat transfer under such conditions: supply t = 90 ° С, return t = 70 ° С, air temperature = 20 ° С, which corresponds to Δt = 50 ° С.

Standard power value for sections with a center distance of 500 and 350 mm

The heat transfer value of bimetallic radiators is indicated in the technical data sheet for the product. Before buying, it is advisable to familiarize yourself with the documentation for the device, since this parameter is individual for each model. If there is no data in the data sheet, you can use the average power value of 1 section of a bimetallic radiator:

• Devices with a center distance of 500 mm are standardare the most popular. Traditionally installed in apartments. The average heat transfer value of one section of a bimetallic radiator is from 170 to 210 W. It is important to take into account that the declared indicators usually turn out to be slightly higher than the real ones, since the measurements are carried out under ideal conditions.Therefore, it is more correct to focus on the minimum power indicator of one section of a bimetallic radiator of 150 watts. The working pressure of one section is 20 bar, the crimping pressure is 30 bar, the average weight is about 1.92 kg.
• Devices with a center distance of 350 mm usually mounted next to large windows or in hard-to-reach places... According to the technical data sheet, the standard power value of 1 section of a bimetallic radiator is from 120 to 150 W. The real value is slightly lower - 100-120 W. The working pressure of each section is 20 bar, the crimping pressure is 30 bar, the average weight is about 1.36 kg.

Expert advice: when determining the optimal power of a bimetallic radiator, it is advisable to leave a small "margin", otherwise it may become necessary to build up the device - to install additional sections.

Heat dissipation of the radiator which means this indicator

The term heat transfer means the amount of heat that the heating battery transfers to the room over a certain period of time. There are several synonyms for this indicator: heat flow; thermal power, power of the device. The heat transfer of heating radiators is measured in Watts (W). Sometimes in the technical literature you can find the definition of this indicator in calories per hour, while 1 W = 859.8 cal / h.

Heat transfer from radiators is carried out due to three processes:

• heat exchange;
• convection;
• radiation (radiation).

Each heating appliance uses all three heat transfer options, but their ratio differs from model to model. Earlier it was customary to call radiators devices in which at least 25% of thermal energy is given as a result of direct radiation, but now the meaning of this term has expanded significantly. Now, convector-type devices are often called this way.

Important aspects of choosing a radiator

When choosing a radiator, one must remember about the water hammer that occurs in the district heating networks during the first start-up of the system. For these reasons not every radiator is suitable for this type of heating system... It is advisable to conduct heat transfer from the heating device taking into account the strength characteristics of the heating device.
An important indicator of the choice of a radiator is its weight and the capacity of the heat carrier, especially for private construction. The capacity of the radiator will help in calculating the required amount of heat carrier in a private heating system, calculate the cost of heating it to the required temperature.

It is necessary to take into account the climatic conditions of the region when choosing heating devices. The radiator is usually attached to the load-bearing wall; heating devices are located around the perimeter of the house, so their weight must be known to calculate and select the method of fastening. As a comparison of the heat transfer of heating radiators, the table in it the data of the well-known company RIFAR are given, producing heating devices made of bimetal and aluminum, as well as parameters of cast iron heating devices of the MS-410 brand.

Technical characteristics of cast iron radiators

The technical parameters of cast iron batteries are related to their reliability and endurance. The main characteristics of a cast iron radiator, like any heating device, are heat transfer and power. As a rule, manufacturers indicate the power of cast iron heating radiators for one section. The number of sections can be different. As a rule, from 3 to 6. But sometimes it can reach 12.The required number of sections is calculated separately for each apartment.

The number of sections depends on a number of factors:

1. area of ​​the room;
2. room height;
3. number of windows;
4. floor;
5. the presence of installed double-glazed windows;
6. corner placement of the apartment.

The price per section is given for cast iron radiators, and may vary depending on the manufacturer. The heat dissipation of batteries depends on what kind of material they are made of. In this regard, cast iron is inferior to aluminum and steel.

Other technical parameters include:

• maximum working pressure - 9-12 bar;
• the maximum temperature of the coolant is 150 degrees;
• one section holds about 1.4 liters of water;
• the weight of one section is approximately 6 kg;
• section width 9.8 cm.

Such batteries should be installed with the distance between the radiator and the wall from 2 to 5 cm. The installation height above the floor should be at least 10 cm. If there are several windows in the room, batteries should be installed under each window. If the apartment is angular, then it is recommended to carry out external wall insulation or to increase the number of sections.

It should be noted that cast iron batteries are often sold unpainted. In this regard, after purchase, they must be covered with a heat-resistant decorative compound, and must be stretched first.

Among domestic radiators, the model ms 140 can be distinguished. For cast iron heating radiators ms 140, the technical characteristics are given below:

1. heat transfer of section МС 140 - 175 W;
2. height - 59 cm;
3. the radiator weighs 7 kg;
4. the capacity of one section is 1.4 liters;
5. section depth is 14 cm;
6. section power reaches 160 W;
7. section width is 9.3 cm;

• the maximum temperature of the coolant is 130 degrees;
• maximum working pressure - 9 bar;
• the radiator has a sectional design;
• pressure test is 15 bar;
• the volume of water in one section is 1.35 liters;
• Heat-resistant rubber is used as the material for the intersection gaskets.

It should be noted that the ms 140 cast iron radiators are reliable and durable. And the price is quite affordable. This is what determines their demand in the domestic market.

Features of the choice of cast iron radiators

To choose which cast-iron heating radiators are best suited for your conditions, you must take into account the following technical parameters:

• heat transfer. Choose based on the size of the room;
• radiator weight;
• power;
• dimensions: width, height, depth.

To calculate the thermal power of a cast-iron battery, one must be guided by the following rule: for a room with 1 outer wall and 1 window, 1 kW of power per 10 sq.m. is needed. the area of ​​the room; for a room with 2 external walls and 1 window - 1.2 kW .; for heating a room with 2 outer walls and 2 windows - 1.3 kW.

If you decide to buy cast-iron heating radiators, you should take into account the following nuances:

1. if the ceiling is higher than 3 m, the required power will increase proportionally;
2. if the room has windows with double-glazed windows, then the battery power can be reduced by 15%;
3. if there are several windows in the apartment, then a radiator must be installed under each of them.

Modern market

Imported batteries have a perfectly smooth surface, they are of higher quality and look more aesthetically pleasing. True, their cost is high.

Among domestic counterparts, cast iron radiators konner can be distinguished, which are in good demand today. They are distinguished by a long service life, reliability, and fit perfectly into a modern interior. Cast iron radiators konner heating in any configuration are produced.

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Calculation of the indicator

To accurately calculate the required amount of heat for a room, many factors should be taken into account: the climatic features of the area, the volume of the building, possible heat loss of the walls, ceiling and floor (the number of windows and doors, building material, the presence of insulation, etc.). The heat transfer parameters of heating radiators are shown in the table below.

This computation system is rather laborious and is used in rare cases. Basically, the calculation of heat is determined based on the established indicative coefficients: for a room with ceilings not higher than 3 meters per 10 m2, 1 kW of thermal energy is required. For the northern regions, the indicator increases to 1.3 kW.

What you need to consider when calculating

Calculation of heating radiators

Be sure to take into account:

• The material from which the heating battery is made.
• Its size.
• The number of windows and doors in the room.
• The material from which the house is built.
• The side of the world in which the apartment or room is located.
• The presence of thermal insulation of the building.
• Type of piping routing.

And this is only a small part of what must be taken into account when calculating the power of a heating radiator. Do not forget about the regional location of the house, as well as the average outdoor temperature.

There are two ways to calculate the heat dissipation of a radiator:

• Regular - using paper, pen and calculator. The calculation formula is known, and it uses the main indicators - the heat output of one section and the area of ​​the heated room. Coefficients are also added - decreasing and increasing, which depend on the previously described criteria.
• Using an online calculator. It is an easy-to-use computer program that loads specific data about the dimensions and construction of a house. It gives a fairly accurate indicator, which is taken as the basis for the design of the heating system.

For a simple layman, both the one and the other option is not the easiest way to determine the heat transfer of a heating battery. But there is another method for which a simple formula is used - 1 kW per 10 m² of area. That is, to heat a room with an area of ​​10 square meters, you will need only 1 kilowatt of thermal energy. Knowing the heat transfer rate of one section of a heating radiator, you can accurately calculate how many sections need to be installed in a particular room.

Let's look at a few examples of how to correctly carry out such a calculation. Different types of radiators have a large size range, depending on the center distance. This is the dimension between the axes of the lower and upper manifold. For the bulk of heating batteries, this indicator is either 350 mm or 500 mm. There are other parameters, but these are more common than others.

This is the first thing. Second, there are several types of heating devices made of various metals on the market. Each metal has its own heat transfer, and this will have to be taken into account when calculating. By the way, everyone decides for himself which one to choose and install a radiator in his home.

Size and volume of one section

The power of a bimetallic radiator is directly related to its size and capacity. Consumers are well aware that the less media in the battery, the more economical and efficient it is. This is due to the fact that a small amount of the same water heats up much faster than when there is a lot of it, which means less electricity will be spent.

Depending on the center distance, the volume of the radiators varies:

• At 200 mm - 0.1-0.16 l.
• The center-to-center distance of 350 mm contains from 0.17 to 0.2 liters.
• With a parameter of 500 mm - 0.2-0.3 liters.

Knowing, for example, the capacity and power of the 500 mm bimetallic radiator section, it is possible to calculate how much coolant is required for a particular room. If the structure consists of 10 sections, then they will fit from 2 to 3 liters of water.

In stores, devices are presented with ready-made models of bimetallic radiators, consisting of 8, 10, 12 or 14 sections, but consumers, most often, prefer to buy each element separately.