Experimental data.
The first day of the experiment.
All graphs show temperature changes from 8.00 am to midnight.
Heat carrier temperature 42ºС.
The graph shows that the system worked more efficiently while the temperature difference between the air and the battery was large. When the difference decreased, the system stabilized.
The air temperature in the center of the room at a height of 65 cm from the floor rose from 15 ° C to 20 ° C in 9 hours.
Subsequently, the temperature increased by another 0.5 ° C.
The power consumption of the fan was 35.2 watts.
When, during the experiment, I left my room into the corridor, I immediately felt the temperature difference, because by that time I had already taken off the warm clothes.
I went to the barn and brought another fan from there. This fan was not equipped with a power switch, so I connected it through a homemade triac regulator, the design of which is described in detail here.
Well, life has become better, life has become more fun!
The second day of the experiment.
In the morning, I again measured the temperature of the coolant, as well as the temperature of the air in the room. All values remained unchanged, including the temperature overboard.
No temperature changes were noticed during the day.
The third day of the experiment.
The coolant temperature increased by one degree and amounted to 43ºС.
The temperature outside decreased and reached -15 ° C.
At the same time, the temperature in the room increased by another 0.5 ° C and reached 21.5 ° C.
The fourth day of the experiment.
The coolant temperature is still 43 ° C.
Temperature outside in the morning is -15 ° C.
The temperature in the room in the morning was 21.5 ° C.
Since no significant temperature changes were noted over the past day, I decided to increase the air flow and installed a second fan at 10.00.
After 10-15 minutes, the air temperature immediately increased by one degree, and then by another half a degree and reached 23 ° C.
Walking like that, I thought, and at 19.00 I turned on both fans at full power. The temperature in two hours increased by one more degree and reached 24 ° C.
How a room is heated by a central heating radiator
Central water heating is the main complex that provides the standard air temperature in the premises of apartments in multi-storey residential buildings. How a room is heated by a central heating radiator - this publication gives an answer to this question.
Radiators for hot water heating most often have a sectional device. The section design is a hollow vessel, inside which the heating medium of the heating system moves. The following main materials for the manufacture of heating radiators are distinguished:
1. Cast iron;
2. Aluminum;
3. Steel;
4. Bimetallic alloy (steel + aluminum).
These materials differ in physical characteristics. For heat engineering, the main indicator is the heat transfer coefficient.
The hot coolant flows inside the heater. In this case, the walls of the product receive heat from it (they heat up). The outer surface of the batteries, in turn, gives off heat to the air of the heated room. This is the basic principle of the heater.
The heat dissipation method of the radiator has 2 components:
1. Radiant (heat radiation);
2. Convective (heating the air flow).
Radiant heat exchange realizes the transfer of heat by direct heating of surrounding objects, it can also be called thermal radiation. Heated objects and building structures, in turn, give off heat to the surrounding air.
The second component - convective - implements heat transfer through heating the circulating air. Convective air movement is based on the density difference - cold air is in the lower sector of the room, heated air always tends upward.
Radiators are installed with a standard clearance from the floor - cold air gradually heats up, getting into the sectional space of the radiator, flows through it and rises up. A new portion of air takes its place. This principle of movement is implemented on an ongoing basis - there is a constant heating of the air in the room.
It is recommended to install radiators in areas of greatest heat loss, primarily under windows. The very meaning of the operation of the heating complex implies compensation for the heat losses of the room. The radiator located under the window has an upward flow of warm air above it and optimally implements this task.
To improve the quality of heat transfer, the surfaces of the radiators are equipped with fins. The presence of the plates increases the heat transfer surface of the battery. In addition, the orientation of the fins optimizes the direction of convective air movement, increasing the efficiency of the radiator.
The power (temperature) of the heating radiator is changed using shut-off and control valves. In addition, heat supply organizations change the temperature of the coolant supplied to the network according to graphs built depending on the outside air temperature.
Hot water radiators are the main type of heating devices in the district heating systems of apartment buildings. This type of heating device is installed most often; radiators do an excellent job of heating air in rooms and maintaining comfortable living conditions.
Ways to improve battery heat dissipation
There are a lot of such methods, using several of them, you can significantly increase the heat transfer of the batteries.
Natural convention. This is the simplest way to increase heat transfer, based on an elementary natural law. The heated air rises to the upper part of the room, and after cooling down, it goes down again. To
Natural convention worked at full capacity the batteries are best installed under a window. This will allow the cold air coming from the window to immediately heat up and rise to the top, and not pass into the room unheated.
Freeing up space around the battery. This method will help the cold air to heat up faster, since nothing will interfere with it. Installed furniture, dense textiles and various decorative ornaments of the battery significantly degrade and slow down the heating of the air.
If the batteries are open, the air circulation will not be disturbed and it will heat up quickly enough. Therefore, it is best to leave the space in front of the battery free.
Reflective screen. This screen is needed so that the battery does not heat the cold wall behind it, but directs all its heat into the room. The reflective screen helps with this, it allows you to direct the heat emanating from the battery in the right direction. It is quite simple to make such a screen.
It can take either foil or any other material with a foil surface and attach it to the battery. The main thing to remember is that there must be a space of at least two centimeters between the material and the battery. This is necessary so that the air can circulate normally.
Electric fan. The installation of such a device will improve air circulation, thereby speeding up the process of heating the air.This method is very effective and makes it possible to increase the temperature in the room by several degrees in a short time.
The main thing to remember is that the appliance can overheat itself, so you need to turn it on exclusively under viewing and not for a long time.
In order for the heat transfer of the battery not to deteriorate, it is necessary to regularly wet clean. Dust significantly impairs the heat transfer of heating devices and pollutes the air in the room.
Also, before the start of the heating season, it is necessary to bleed air from the batteries, since it greatly impairs the heating capacity. It is necessary to carry out such a procedure only after water has been run through the pipes. Reading the battery this way will improve its heat dissipation.
Such methods are quite effective, thanks to their use, the heat transfer of the batteries can be significantly improved and the temperature in the room can be increased by several degrees. If these methods do not help in any way, then most likely you will still have to change the batteries to new and more powerful ones.
But the replacement can no longer be carried out without the help of specialists, since this process requires certain knowledge and skills.
And it also entails a considerable amount of material costs, so it is better not to replace and install new batteries on your own, it is better to turn to knowledgeable and experienced craftsmen.
Warm air circulation
The circulation of warm air is not directly related to the heat exchange of the battery, but the temperature in the house largely depends on this, so this advice cannot be ignored. Heat, according to the laws of physics, rises upward, therefore, near the ceiling, the degree of warming up of the room is always higher. The problem is that a person does not live on the ceiling, he needs a normal temperature at a height of 1-2 meters.
A computer cooler, that is, a mini-fan that can be installed behind a radiator, will help to solve this problem. It will direct the flow of heat in the right direction and the owners will not have to use a stepladder to “warm the bones” near the ceiling. You can connect the cooler through the old power side, its power is 2-2.5 W, and the price is 100-200 rubles, so there will be no big expenses.
These tips will help to raise the temperature in the apartment by 2-4 degrees, if you also want to increase the temperature in the kopeck piece with a heater, then you will have to pay an additional 1.5 thousand rubles a month for electricity - count.
What is efficiency and how to calculate it
The heat transfer from heating devices, which include batteries or radiators, consists of a quantitative indicator of the heat that is transferred by the battery over a certain period of time and is measured in watts. The process of heat dissipation by batteries takes place as a result of processes known as convection, radiation and heat transfer. Any radiator uses these three types of heat transfer. In percentage terms, these types of heat transfer can vary for different types of batteries.
What will be the efficiency of heaters, in the overwhelming majority of cases, depends on the material from which they are made. Let's consider what are the advantages and disadvantages of radiators made of different types of material.
- Cast iron has a relatively low thermal conductivity, so batteries made from this material are not the best option. In addition, the small surface of these heating devices significantly reduces heat transfer and occurs due to radiation. Under normal conditions of an apartment, the power of a cast iron battery is no more than 60 watts.
(See also: Which is better to choose a heating radiator)
Steel is slightly higher than cast iron. More active heat transfer occurs due to the presence of additional ribs, which increase the area of heat radiation. Heat transfer occurs as a result of convection, the power is approximately 100 W.
Aluminum has the highest thermal conductivity of all the previous options, their power is about 200 watts.
In addition, for the most efficient heating, it is necessary to consider how much power may be required. When calculating the power of heating devices required for a room, the number of walls facing the street and windows is used. For every 10 m2 of floor in the presence of 1 outer wall and a window, about 1 kW of thermal power of the battery is required. If there are 2 external walls, then the required power is already 1.3 kW. (See also: Hot water heaters)
The bottom connection is used if the heat transfer pipes are hidden under the floor screed and does not exclude heat loss in an amount of up to 10% of the original value. One-pipe connection is considered the least effective, since the power loss of the heating device with this method can reach 45%.
Comparison of heat transfer indicators ↑
Radiators have different characteristics due to the characteristics of the metal from which they are made. Materials differ in the degree of thermal conductivity, heat transfer and other indicators. Therefore, when choosing, it is worth studying them in order to choose the option that is most optimal for specific conditions. The heat transfer of heating radiators, the table for the main indicators of which is presented below, is expressed in calories per hour or watts and is otherwise called power. Its importance also lies in the fact that at a low temperature of the coolant, the radiator is able to warm up and transfer heat to the room. This allows the boiler to operate at a lower load, which extends its service life.
In addition to heat transfer, it is worth paying attention to the parameter of thermal radiation and for what pressure the radiator is designed
Aluminum radiators are the most economical and efficient option. For an apartment, bimetal will be optimal in terms of characteristics, which costs a little more.
From the table, it becomes clear that aluminum radiators have a significantly higher heat transfer rate, since the material itself has a high heat transfer rate. Steel and bimetallic (which are made of steel and aluminum, therefore they have the characteristics of both materials) are distinguished by low power, and cast iron has the lowest indicator. It would seem, based on this, it is worth choosing an aluminum radiator. But not everything is so simple. Aluminum batteries are very demanding on the quality of water (coolant), therefore they are recommended to be used only for an autonomous system of a private house. They are also more susceptible to corrosion than other types. And for an apartment, bimetallic or steel or even traditional cast iron are better suited. In apartment buildings, water is regularly drained from the pipeline during the unheated period, which creates a favorable environment for corrosion, in addition, the water in the centralized heating system is usually mercilessly "flavored" with various kinds of modifying additives.
Cast iron batteries in a retro style can decorate the interior of the room
There are other important characteristics of batteries, such as heat radiation. Cast iron has the highest radiation, which means that at the same temperature of the coolant, cast iron will transfer more heat into the room than other types of radiators. That is, they will reduce heating costs, since they do not require heating the coolant to a high value. Or if the batteries in an apartment building are poorly heated, a cast-iron heater will be able to "give out" the maximum possible.
Heat transfer of cast-iron heating radiators, judging by the above table, is the highest.
Cast iron is also capable of storing heat and releasing it for several hours after the heating system is turned off. But it has a slow heating rate.
CONCLUSION: It is simply impossible to unequivocally answer the question of which radiator is better, and it is worth choosing the one that seems most acceptable for specific conditions, taking into account the above.
Common reasons for a decrease in heat transfer from a heating battery
The most common reason for a decrease in heat transfer from radiators is scale and rust that accumulates inside. If the radiator itself is flushed (which utilities should do annually), then the heat transfer will increase significantly. The same applies to heating risers. However, such a procedure cannot be carried out on its own due to the fact that during the production of such work (even in summer), it is necessary to drain the water from the system. Here you cannot do without the help of specialists. The same applies to the replacement of radiators from cast iron to bimetallic - they have a high heat transfer. Therefore, we will not dwell on such complex and time-consuming options. It is better to consider simpler methods that any home craftsman can perform, even without experience in a similar field.
The heat transfer of bimetallic radiators is higher than that of cast iron
We use a reflector screen: the use of polyethylene foam
Using a reflective screen is a fairly popular method of increasing heat dissipation. Foamed polyethylene foam on one side is ideal for this purpose. Such a screen (it should be larger than the radiator itself) is placed behind the battery with foil in the direction of the room and fixed on the wall with double-sided tape or liquid nails. Foamed polyethylene provides additional insulation, and the foil reflects the heat that warmed up the wall before installing the screen, directing it into the room.
Important information! It is best when such moments are thought out even at the stage of installing heating batteries. In this case, a steel ribbed shield can be fixed behind the radiator, which will accumulate heat, and then direct it into the room. Such shields are convenient if heating shutdowns occur frequently.
Something like this looks like a screen made of foamed polyethylene foam
Also, basalt slabs with an aluminum coating have proven themselves well as a screen.
Increased heat transfer with accessories and painting
To increase the air temperature in the room, special aluminum casings are used, which are put on the radiator. With their help, the area of the heating battery increases and, as a result, their heat transfer. The cost of such casings is low, and the effect is quite significant.
The color in which the radiators are painted is also of great importance. It is better to choose darker shades for these purposes. For example, a brown-colored radiator has 20-25% more heat transfer than white ones.
This casing improves appearance and increases heat dissipation.
Improving convection by increasing air circulation
Everyone knows that improved air circulation helps to warm up the room faster. For these purposes, you can use a fan, which is installed in such a way as to achieve the maximum flow of warm air towards the room.
Helpful information! If there are computer coolers at home that are not in use, you can install them under the radiator, directing the air flow upward. This will maximize convection, resulting in a significantly warmer room.
You can increase convection (if the radiator is recessed under the window sill) by cutting holes in the window sill and closing them with screens or decorative covers. Thus, warm air will not be trapped in the niche, which will improve circulation.
This country can not be defeated! Self-assembly of fans to improve convection:
Battery cleanliness and color
The batteries must be clean, a dirty radiator is not only not aesthetically pleasing, but also bad for heat transfer. Dust and dirt on the elements of the heating system is lost heat, which will have to be paid for.
Interesting results were shown by the change in the color of the radiators. A battery painted brown or bronze has a heat transfer rate 20-25% higher than a white radiator. This innovation is well known to the residents of Ukraine, who thus increase the degree of heat in their apartments when there are problems with the quality of energy supply to the houses.
According to the laws of physics, the darker the color of the battery, the better its heat dissipation.
Prologue.
This year we have unprecedented frosts. In some regions of the republic, the air temperature dropped to -24 ° C, which is an anomalous phenomenon for warm Moldova. I don't have a thermometer in my room, but I felt that the hand on the table began to freeze, and I had to put a piece of foam rubber under it.
We, in general, like the Amundsen, are already accustomed to the coolness, but yesterday the chairman of our condominium, collecting signatures under the appeal to the heat supplier, asked what the temperature in our apartment was. It is unlikely that the heat supplier will increase the temperature of the coolant, but perhaps the chairman wants to demand a penalty under the pretext of providing poor quality services.
Whatever it was, but this event first pushed me to measure the air temperature in the apartment, and then to conduct this experiment.
Of course, to say that this experiment was unclean is to say nothing. There are too many variables that could affect the accuracy of the result, from the direction of the wind overboard to the activity of the computer working in the test room.
But, the most important parameter, which at another time would not allow this experiment to be carried out at all, is the stability of the coolant temperature.
The fact is that in warmer periods of time, the temperature of the coolant is actively regulated throughout the day to save energy consumption. When there is an abnormal temperature outside, then all the valves are wide open.
Ways to increase heat transfer
At the moment, there are several ways to increase heat output from an already created and used heating system that did not meet your expectations:
- Installation of convectors. This construction is made of a pipe with metal plates strung on it, made by hand, or factory-made.
- Coloring of the main pipeline in black or other dark color. This method, for all its simplicity, is quite effective. In addition, the color scheme can organically fit into the modern design of the premises, in contrast to the recent past, when it was considered a necessary measure.
Note! Paint is just an additional method, which is relevant in rare cases, since the efficiency is too low to "admire" the black stripes.
- Installation of registers in the heating system. The register consists of several large-diameter pipes connected to each other and with welded ends. These designs include heated towel rails in the form of a coil with several loops.
- Rearrangement of radiators with the addition of sections. This option is the most costly, but also in terms of efficiency it is higher than the rest.
If you decide to add radiators, then place them necessarily under the windows or next to the front door (as in the photo)
Recommended! Remember that installing additional insulation materials will also increase heat dissipation by reducing the loss of heat generated. However, it is possible only when erecting a residential building from the foundation, or when dismantling the facade.
Increased heat dissipation from the battery
Consider them:
- Dust must not be allowed to collect on the heating device, since microparticles significantly reduce heat transfer, it is also necessary to keep the inside of this device clean;
- It is better to paint heating devices in a dark color, since it is these shades that contribute not only to the absorption, but also to the emission of light. For this, it is better to use zinc-based whitewash, and then the efficiency of the heating system, and in particular the battery, will increase by almost 15%;
- The simplest answer to the question: - how to increase the heat transfer of batteries? - there is a tip: - it is necessary to hang a reflective screen on the wall behind the radiator; ordinary foil is suitable for this, which will redirect the heat that goes outside to the inside of the room. Take this material or metal sheet and fix it on the wall (behind the heater) and you will immediately feel that the air has warmed up;
- In order for the heat transfer of the heating battery to increase, it is necessary to increase the surface area of the radiator; for this, casings are used, which can be made of aluminum. In the event that the battery does not heat the room well, then just such casings are used, since this metal heats up quickly and gives off heat.
- If the batteries are often disconnected, you need to purchase an iron element that heats up longer and transfers heat for a longer time;
- When warm air from the battery circulates in an unnecessary direction, then the air flow from the operating fans is directed to the radiator, which will redirect the hot air in the right direction;
- If there are several computer coolers at home that are not used, then they are located at the bottom of the radiator, and they will help warm air circulate faster from floor to ceiling.
The considered cases give an answer to the question: - how to increase the heat transfer of batteries? but besides this, other factors must be taken into account, such as - the power of the heater, its quality, the way of connection and compliance with some rules during installation.
Registers
This was a very simple and cheap solution in situations where heating of large areas was required. Although if we talk about the heat transfer of a pipe in such a register in comparison with an aluminum radiator, the difference in efficiency is staggering. Due to the larger area of the heat exchanger of the radiator and the thermal conductivity of aluminum, modern equipment is undoubtedly preferable. And outwardly, the registers looked rather crude.
Nevertheless, registers were acceptable for their time due to their low cost and simplicity. It can be noted that the welded seams on them were very strong, and the clogging of the pipe did not interfere with their functioning.
Underfloor heating systems
If we are talking about a water-heated floor, in contrast to an electric analogue, metal pipes are used as a heating circuit in it, although they have recently become less and less used.
The main reason for the decrease in demand for a water-heated floor is the gradual wear of steel pipes, a decrease in the clearance in them. In addition, the installation method is also important - not everyone can perform welded seams, and a threaded connection threatens with a coolant leak after a while. Naturally, no one will like the result of water leakage from the system in the floor with a screed - the ceiling of the lower floor or basement will be flooded, and the ceiling will gradually become unusable.
For these reasons, steel pipes in warm water floors were first replaced by metal-plastic coils, the fittings to which were attached outside the screed, and now they prefer reinforced polypropylene.
This material is characterized by a slight thermal expansion, and with proper installation and operation, they can last for more than a dozen years. Alternatively, other polymeric materials are also used.
Please note that the gaps for thermal expansion of reinforced polypropylene still need to be left, although it is small
Small details.
To measure the temperature of the steam heating battery faster and more accurately, it is enough to apply a small amount of heat-conducting paste "KPT-8" to the ball of the digital thermometer sensor. The place of contact during the measurement must be covered with several layers of fabric or a layer of foam rubber.
The above experiment made me question the accuracy of my digital thermometer. To make sure that his readings are correct, I compared them with the readings of a mercury thermometer. To do this, I immersed both thermometers in hot water to the same depth and followed the readings as the water cooled.
Long-term operation of the fans immediately revealed the weak point of modern devices.
If the 1973 Penguin fan has a front plain bearing equipped with an oil seal (the arrow marks the opening for filling the oil seal with oil), which allowed it to work for almost 40 years, then there is no trace of such an oil seal in a modern fan.
In addition, the "Penguin" has a spring that prevents the occurrence of longitudinal beats of the shaft. The new fan, after two days of operation, began to rumble, since due to the longitudinal beating of the shaft caused by the eccentricity of the propeller, one of the fluoroplastic gaskets quickly worn out.
To eliminate the longitudinal backlash, several ordinary and two thin-walled washers were needed, as well as a gasket cut from foam rubber.
First, I disassembled the stator.
Then he put thin-walled washers and a gasket on the motor shaft, and with the rest of the washers increased the clearance between the bearings.
To ensure any kind of long-term operation of the fan, I cut out an oil seal from the felt, and from some nylon cover, an oil seal plug and pressed it all into a recess around the shaft. Naturally, he did not regret the oil either.
I started thinking about buying two dozen 120mm computer fans. I think if you install them directly between the sections of the batteries, then this should reduce noise and increase the efficiency of heat transfer.
Methods for increasing heat transfer
The round shape does not at all contribute to an increase in the heat transfer of metal pipes. An even lower coefficient of the ratio of volume and surface can be found only in the sphere.
Consequently, the problem of how to increase the heat transfer of the pipe undoubtedly faced the developers of the first simple heating devices.
To increase the heat transfer coefficient of a steel pipe, the following methods were previously used:
- The surface of the tube was coated with a matte black paint to enhance the infrared radiation of the heating element. This made it possible to achieve a significant increase in the room temperature. It is worth noting that modern chrome plating on heated towel rails is extremely ineffective for enhancing heat transfer - it is, rather, for beauty.
- An increase in the heat transfer of the pipe due to the welding of additional ribs on it, which made the area of the heating element, and hence the heat transfer, significantly larger. The most advanced use of this method can be called a convector, that is, a section of a bent pipe with welded transverse ribs. Although the pipe itself in this case gives off a minimum of heat.
Any of these methods can be used if the question is how to increase the heat transfer of the heating pipe with your own hands, because they are not at all complicated and are quite feasible at home.
Complex methods of increasing the efficiency of radiators
If simple ways to increase the heat transfer of central heating batteries did not bring any effect, or for some reason interferes with a comfortable pastime in the room, then you can try to solve the problem with the following cardinal methods:
- Change heating batteries.To do this, it is imperative to use a specially designed table, which indicates the thermal power and thermal conductivity of the radiators.
- Increase the number of radiator sections. In this case, it should be borne in mind that the larger the area of the battery, the higher the heat transfer will be.
- Clean the internal parts of all radiator sections from possible contamination.
- Change the type of connection of the heating system.
It is worth saying that all of the above work should be carried out only with the heating turned off. Therefore, such methods can be carried out exclusively in the warm season.
If the heating system changes, it is recommended to install special shut-off valves at the outlet and inlet, which will allow disconnecting from the central heating supply at any time.
Radiator painted dark
Another opinion that wanders the Internet is that painting a battery black or brown increases heat transfer by radiation. In most cases, such judgments are based on the physical concept of a "black body", which absorbs and radiates the most. All this also applies to the heating battery. Those painted with light paint emit less than those painted with dark ones. Let's estimate how much.
A bit of physics. According to the Stefan-Boltzmann law, the radiation of an absolutely black body is proportional to the absolute temperature to the 4th degree.
R (T) = σ × T4, where
σ = 5.67 10-8 W / (m2K4) - Stefan-Boltzmann constant.
Real bodies are "gray". For a real "gray" you need to take into account its emissivity ε. The battery itself absorbs infrared radiation from the room, and the textbooks give the corresponding formula, which includes the temperatures of both the battery and the room (in Kelvin to the 4th degree). It is easy to show that if the battery is heated from 20 ° C to 40 degrees, then its radiation will increase 81 times. The calculation (approximate, of course) shows the following. Let a battery with an area of 1 sq. m painted with brown oil paint (ε ≈ 0.8 for it). Let the water temperature in it be 70 ° С, and the rooms - 20 ° С. Then the power of infrared radiation of such a battery will be 300 watts. Not so little! The battery painted with black matte (not glossy!) Paint will heat even more. And if the paint is white, the radiation power will be lower. But aesthetic considerations usually prevail, and batteries (open) are usually painted with light colors.
Black radiators can also be freely found on sale Commentary Sergey Kharitonov Leading Heating, Ventilation and Air Conditioning Engineer Spetsstroy LLC Ask a question “Physics directly proves the effectiveness of painting a radiator in dark colors, but all this refers to ideal operating conditions. Let me remind you that convective heat transfer prevails in conventional water batteries and the color does not affect it in any way. In addition, you need to be confident in the quality of the entire heating system. If 30 ° C comes to your radiator, then don't paint, there will be no sense. Well, do not forget about the aesthetic component. Are you ready to contemplate black "coffins" every day for the sake of a few dozen extra watts? "
Conclusion: effective, but requires ideal operating conditions.
How to increase the efficiency of heat transfer from heating radiators
A key indicator of the efficiency of any heating radiator is heat transfer. This indicator is individual for each model of radiators, in addition, it is influenced by the type of connection of the device, the features of its placement and other factors. How to choose an optimal radiator in terms of heat transfer, how to connect it as efficiently as possible, how to increase heat transfer?
Heat dissipation is an indicator that indicates the amount of heat transferred by a radiator to a room in a given time. Synonyms for heat transfer are terms such as radiator power, heat power, heat flux, etc.The heat transfer of heating devices is measured in Watts (W). In some sources, the heat output of the radiator is given in calories per hour. This value can be converted to Watts (1 W = 859.8 cal / h).
Heat transfer from the heating radiator is carried out as a result of three processes: - Heat exchange; - Convection; - Radiation (radiation). Each heating radiator uses all three types of heat transfer, however, their ratio is different for different types of heating devices. By and large, only those devices in which at least 25% of thermal energy is transmitted as a result of direct radiation can be called radiators, but today the meaning of this term has expanded significantly. Therefore, very often under the name "radiator" one can find convector-type devices.
The choice of heating radiators for installation in a house or apartment should be based on the most accurate calculations of the required power. On the one hand, everyone wants to save money, so they should not buy extra batteries, but on the other hand, if there are not enough radiators, then the apartment will not be able to maintain a comfortable temperature.
There are several ways to calculate the required thermal power of heating devices. The easiest way is based on the number of exterior walls and windows in them. The calculation is made as follows: - If there is one outer wall and one window in the room, then for every 10 m2 of the room area, 1 kW of thermal power of the heating batteries is needed. - If there are two external walls in the room, then for every 10 m2 of the area of the room, at least 1.3 kW of thermal power of the heating batteries is required. The second method is more complicated, but it makes it possible to obtain the most accurate value of the required power. The calculation is made according to the formula: S x h x41where: S - the area of the room for which the calculation is made. h - the height of the room. 41 - standard indicator of minimum power per 1 cubic meter of room volume. The resulting value will be the required power of heating devices. Next, this power should be divided by the nominal heat transfer of one section of the radiator (as a rule, this information is contained in the instructions for the heater). As a result, we get the number of sections required for efficient heating. If, as a result of dividing, you get a fractional number, round it up, since the lack of heating power reduces the level of comfort in the room much more than its excess.
Heating devices made of different materials differ in heat transfer. Therefore, when choosing radiators for an apartment or a house, it is necessary to carefully study the characteristics of each model - very often, even radiators that are close in shape and size have different power. Cast iron radiators - have a relatively small heat transfer surface, are characterized by a low thermal conductivity of the material. Heat transfer occurs mainly due to radiation, only about 20% is accounted for by convection. "Classic" cast-iron radiator Rated power of one section of the MC-140 cast-iron radiator at a coolant temperature of 90 degrees. C is about 180 W, but these figures are valid only for laboratory conditions. In fact, in district heating systems, the temperature of the coolant rarely rises above 80 degrees, while some of the heat is lost on the way to the battery itself. As a result, the surface temperature of such a radiator is about 60 degrees. C, and the heat transfer of one section does not exceed 50-60 W.
Steel radiators combine the positive qualities of sectional and convection radiators. Typically, a steel radiator includes one or more panels, inside of which the coolant circulates. To increase the heat output of the radiator, steel fins are additionally welded to the panels, which function as a convector.The heat transfer of steel radiators is not much higher than that of cast-iron ones - therefore, the advantages of such heating devices can be attributed only to a relatively small weight and a more attractive design. With a decrease in the temperature of the coolant, the heat transfer of the steel radiator decreases very strongly. Therefore, if water circulates in your heating system with a temperature of 60-750, the heat transfer rates of a steel radiator may be strikingly different from those declared by the manufacturer.
Heat dissipation of aluminum radiators significantly higher than that of the two previous varieties (one section - up to 200 W), but there is a factor that limits the use of aluminum heating devices. This is the quality of water: when using an excessively contaminated heating medium, the inner surface of an aluminum radiator gradually corrodes. That is why, despite good performance indicators, aluminum radiators are mainly installed in private houses with an autonomous heating system.
Bimetallic radiators in terms of heat transfer, they are in no way inferior to aluminum. But you always have to pay for efficiency, and therefore the price of bimetallic radiators is slightly higher than that of batteries made of other materials.
How can you still control the heat transfer of an already purchased radiator, depending on the connection. The heat transfer of the radiator depends not only on the temperature of the coolant and the material from which the radiator is made, but also on the method of connecting the radiator to the heating system: Direct one-way connection is considered the most advantageous in terms of heat transfer. That is why the rated power of the radiator is calculated precisely with a direct connection (the diagram is shown in the photo). Diagonal connection it is used if a radiator with more than 12 sections is connected. Such a connection minimizes heat loss. Lower radiator connection used to connect the battery to the heating system hidden in the floor screed. Heat transfer losses with such a connection are up to 10%. One pipe connection is the least advantageous in terms of power. Heat transfer losses with such a connection can range from 25 to 45%.
No matter how powerful your radiator is, often want to increase its heat transfer... This desire becomes especially relevant in winter, when the radiator, even operating at full capacity, cannot cope with maintaining the temperature in the room. There are several ways to increase heat transfer from radiators: The first method is regular wet cleaning and cleaning of the radiator surface. The cleaner the radiator, the higher the level of its heat transfer. It is also important to paint the radiator correctly, especially if you are using cast iron sectional batteries. A thick layer of paint impedes effective heat transfer, therefore, before painting the batteries, it is necessary to remove the layer of old paint from them. It will also be effective to use special paints for pipes and radiators with low heat transfer resistance. In order for the radiator to provide maximum power, it must be properly mounted. Among the most common mistakes in the installation of radiators, experts highlight the inclination of the battery, installation too close to the floor or wall, overlapping radiators with unsuitable screens or interior items.
Correct and Incorrect Installation To improve efficiency, it is also possible to inspect the interior of the radiator. Often, when connecting the battery to the system, burrs remain on which, over time, a blockage forms, which impedes the movement of the coolant. Another way to get the most out of it is to wall-mount a heat-reflecting foil shield behind the radiator. This method is especially effective when improving radiators installed on the outer walls of a building.
How to install any radiators
The coolant in central heating has special impurities that negatively affect many radiator models. Therefore, they are not installed in apartments. In fact, in order to solve this problem, it is necessary to make sure that instead of the CHP heat carrier, there is our ordinary water.
For these purposes, you need to mount a heat exchanger at the entry point of the central heating risers into the apartment.
A heat exchanger is a device that removes heat from one source and transfers it to another. Simply put, this is our intermediary who will simply take heat from the CHP and transfer it to our own heating system inside the apartment.
What are the benefits of a heat exchanger?
- Performs the function of a boiler by removing heat
- Allows you to create your own heating system inside the apartment with its own heat carrier and pressure.
- Allows you to implement any heating options
There are also disadvantages to using a heat exchanger:
- It gets clogged periodically. Requires dismantling and flushing
- In addition to the heat exchanger, it is necessary to install an expansion tank, a pump and related fittings.
Having installed a heat exchanger, you can mount any radiator system: radial, two-pipe, and others. You can hide the pipes in the screed. You can use any pipe materials without worrying that they will become unusable. Any brand of radiator can be used.
Estimated indicators
To calculate the power of the heating equipment, as well as to find out the scale of heat loss during the transportation of the coolant, it will be necessary to perform heat removal from the pipe at certain temperatures of the liquid inside it and the air outside. The thermal insulation layer serves as an additional parameter.
The formula for calculating the heat transfer of a steel pipe looks like this:
Q = K × F × dT, in which:
Q is the desired result of heat transfer from a steel pipe in kilocalories;
K is the coefficient of thermal conductivity. It depends on the material of the pipe, its cross-section, the number of circuits of the heating equipment, as well as the difference in temperatures between the outside air and the coolant;
F is the total surface area of a pipe or several pipes in the device;
dT is the temperature head, that is, ½ the total temperature of the liquid at the inlet and outlet from the pipe minus the air temperature in the room.
If the pipes are additionally wrapped with a layer of thermal insulation, then its efficiency in percentage terms (the amount of heat passed through it) is multiplied by the obtained heat transfer rate.
For example, we will calculate the heat transfer of a register from three pipes with a cross section of 100 mm and a length of 1 m.In the room, the temperature is 20 ℃, and the coolant when passing through the pipe cools down from 81 to 79 ℃.
According to the formula S = 2pirh, we calculate the surface area of the cylinder:
S = 2 × 3.1415 × 0.05 × 1 = 0.31415 m2. If there are three pipes, then their total area will be 0.31415 × 3 = 0.94245 m2.
Indicator dT = (79 + 81): 2-20 = 60.
The value of K for a register of three pipes with a temperature head of 60 and a cross-section of 1 meter is taken equal to 9. Therefore, Q = 9 × 1 × 60 = 540. That is, the heat transfer of the register will be equal to 540 kcal.
Thus, we examined the concepts of heat transfer, as well as ways to minimize heat loss of a steel pipe for certain cases. There is nothing very complicated about this. The main thing is to approach the issue responsibly.
Summarize
There are a lot of ways to increase the heat transfer of heating radiators. Today we have considered only the main ones. However, it should be remembered that it is always easier to think over everything in advance, at the installation stage, than to put a lot of effort later, without the confidence that the result will be significant. Unfortunately, in Russia everything is done at random. The final advice of the editors of Homius.ru will be the following recommendation: think about the future and spare no expense during installation. The financial resources saved today can turn into costs tomorrow, which will significantly exceed your savings.
The most optimal option is that all the heat rises upwards, due to which a normal heat exchange is created.
We hope that the information presented in today's article was interesting and useful to our Dear Reader. Despite the fact that we have tried to present everything in sufficient detail, you may still have questions about the material. In this case, ask them in the discussions below - Homius.ru editors will be happy to answer them as soon as possible. If you know a way to improve the heat transfer of radiators, which was not reflected in today's article, please share it with other home craftsmen - this information will be very useful. And finally, we suggest watching a short, but rather informative video on today's topic.
How to increase the heat transfer of radiators
A decrease in heat transfer from a radiator can be caused by a number of reasons. The most common is blockages. This is quite relevant in centralized heating systems: the coolant contains a large amount of various kinds of impurities. They settle on the slightest irregularities. Therefore, inlet and outlet pipes, filters and radiator fittings are often clogged. If your radiator has begun to heat up worse, first of all check and clean all fittings and pipes inlet / outlet of the coolant.
Manual regulators on radiators. They could get clogged. Check and clean them
If control valves are installed at the inlet, check if they are broken. It is also worth checking the functionality of the radiator thermostat. With them, everything is easier: remove the thermal head, perhaps the point is in it. Regulating valves will have to be removed and replaced with squeegees. By themselves, these devices already greatly reduce the amount of coolant passing through the radiator. So by getting rid of them, you can increase the heat dissipation.
Sometimes the battery gets cold on top. This means that air has accumulated in the radiator. To remove it, there is usually a Mayevsky crane, an automatic air vent or an ordinary crane at the top right or left. To release air, you need to open them, first substituting a container for collecting water (it will go after the air comes out).
This is the "Mayevsky" faucet with its help you can bleed air from heating radiators
But what if the heat transfer of the heating battery was initially insufficient? How to increase the heat output in this case, and is it possible at all? For a radical change, difficult work will be required. They need to be carried out, as a rule, with the heating system turned off, which is very difficult during the season. But there are several options that will make it possible to "hold out" until the end of the season in more comfortable conditions.
- Installing a heat-reflecting shield behind the radiator. Buy foil (preferably) or metallized thin insulation, cut it to the size of the radiator, and attach it to the wall behind the heater. For greater efficiency, it is not easy to refuel it behind the radiator, namely, to attach it to the wall. In this case, there will be a certain distance between the radiator and the foil layer, which will increase the efficiency of reflection of thermal radiation.
Installing a heat-reflecting shield behind the battery can slightly increase its heat dissipation.
- A simple way to increase the heat transfer of the radiator is to hang an aluminum (the best option) or steel protective and decorative screen on it. Only it should be the size of the heater, and not larger. Thus, you increase the area, heat dissipation, and the air will warm up better. But the screen should be with a lot of holes so as not to "block" the air behind the battery.
- Greatly reduces the amount of heat released, dust and excess paint layers. It is clear that no one will repaint during the season, but you can wash it from dust at any time.
- Sometimes the batteries are hot and the room is cold.This can happen due to the fact that convection (air movement) is disturbed near the radiator. Place the fan and point it at the heater. The heat will be actively dissipated and spread throughout the room, it will immediately become warmer. The fan is not necessarily big, even old computer coolers can make a difference. They spend little electricity, work quietly, take up little space - a good option.
- If the radiator has temperature controls (automatic or manual), remove them. Firstly, they are often clogged, and secondly, even in the open position, they reduce the amount of coolant passing through the radiator by almost half.
The heat transfer of the radiator depends on the speed of air movement past its heated parts. Putting a fan down below will help heat the room better.
There are probably all options for quickly improving the heat transfer of heating radiators. There are still technical options. There are not so many of them either:
- Check the condition of the supply and discharge pipelines, replace them if necessary.
- Change the radiator connection. This measure may be more effective than increasing the number of sections. For example, with a one-sided side connection (both pipes on one side), it makes no sense to install more than 8 sections. Heat dissipation will not increase. But by redoing the connection to a diagonal one, you will get increase in heat transfer by 10-15%. In this case, it also makes sense to add multiple sections.
In one-pipe systems with forced circulation, the bottom saddle connection works well (this is when pipes enter and exit from the bottom from different sides). It can be more effective than the diagonal one. Plus it looks better.
- Increase the number of radiator sections. You will need to purchase several sections, and you need to find the same manufacturer. Drain the system, remove the radiator, unscrew the plugs and / or the Mayevsky valve from it. Clean the joints and, using nipple-nuts, attach new sections with a special wrench.
- If the radiators are old and clogged, it makes sense to flush them. If you have shut-off valves (ball valves) installed at the inlet and outlet of the radiators, you can do this during the heating season. If they are not provided, it is required to drain the system. Then remove them and then rinse. Sometimes water is sufficient, but in some cases chemistry is required. Which one depends on the nature of the deposits.
The most drastic way out is to increase the number of sections, but this does not always give the expected results. Changing the connection type is more efficient.
As you can see, there are not very many technical solutions. But something from this list will definitely help you.
Read how to calculate the radiator sections here.
For the inhabitants of apartments in multi-storey buildings, there is another option, but almost nothing depends on you here: your heat transfer may decrease due to the alteration of the heating system of the neighbors from above. In houses of an old building, heating wiring is almost everywhere one-pipe with an upper supply. And if in your apartment the riser at the top has become barely warm, someone above you contributed to this. In this case, it makes sense for you to contact the management company - they will check the condition of the riser and find out the reason for the decrease in heat transfer.
