The most important structural element of heating boilers are heat exchangers. The economic and environmental characteristics of heat generators are largely determined by the geometric parameters and the material from which the heat exchangers are made.
One of the types of heat exchangers is made of copper. Their positive qualities are: low weight, corrosion resistance, compactness. There are a number of models with copper heat exchangers on the market for heat generators.
Frisquet (France) - reliable and durable heating equipment
The high thermal performance of Frisquet units is largely due to the use of a fire-tube heat exchanger made of copper. This noble material has the highest coefficient of thermal conductivity and heat transfer, as well as excellent anti-corrosion characteristics.
Frisquet heating equipment is equipped with a tubular heat exchanger manufactured using technology that is used in industrial heat generators. The use of this technology ensures high performance, ease of operation and durability of the heat exchangers and the units themselves. An increase in the heat exchange surface is achieved by the presence of built-in fire tubes. Flue gas is transferred through each tube, and the outer surface of the tubes is in contact with water.
This design allows operation at low water temperatures. Each tube contains a turbulator made of stainless steel alloyed with titanium. Turbulator provides distribution and cooling of exhaust gases.
The units of this company have a service life that is approximately two times higher than the service life of boilers with fins. This effect is achieved using a simple and reliable heat exchanger manufacturing technology and the use of copper.
The approximate cost of Frisquet heating units with a capacity of 23 kW is almost three thousand dollars.
Models of heating units with copper heat exchangers
Highly efficient copper heat exchangers are used in BAXI COPPER gas heating units and Hermann Habitat Italian models.
Modular Russian-made "STG-Classic" and "STG-premier" are equipped with modern bimetallic copper-cast iron heat exchangers. The heat exchanger is a structure with copper finned tubes connected by two annular cast iron collectors. Such a heat exchanger device provides a good transfer of heat from the combustion of fuel to the water circulating through the pipes.
This equipment is an ideal option for boiler rooms that are located on the roof of housing construction.
A heat exchanger is one of the elements of devices where thermal processes take place to transfer energy from a heated body to a cold one. All modern heat engines, from a home heating system to a nuclear reactor, which, in fact, is the same boiler, are equipped with such heat transfer parts. Only they are made of different materials and have complex control and safety systems.
Purpose, types of metal heat exchangers
The design and performance of heating devices depend on the purpose, principle of operation, and the material of the heat exchanger. For example, it is impossible to create a compact cast iron product for a parapet or wall heater. Since carbon steel or cast iron have a significant density, and hence the mass. The old cast iron boilers are a thing of the past. Today, small-sized heating structures with light parts and a higher level of energy transfer are popular. These include gas wall-mounted boilers with a copper heat exchanger.
In the production of a thermodynamic structure, materials such as:
copper;
steel of different grades;
cast iron;
aluminum;
silumin.
In modern household heating boilers, most of its surface is occupied by a heat exchange unit. The economic and environmental parameters of the boiler depend on the design and type of material.
Depending on the purpose, by such types as heating, cooling, condensing, evaporating. According to the principle of operation, the blocks are regenerative, recuperative and mixing. The first two types have the common name "thermal surface apparatus". One example of such units is radiators in cars. Their purpose is to participate in the operation of the engine cooling system. Heated water is in contact with air through the walls of copper-aluminum heat exchangers.
In mixing (contact) machines, two working streams (hot and cold) are mixed with each other. A similar process is observed in jet condensers, where the atomized liquid uses the energy of condensation. They are easier to manufacture and are characterized by increased heat capacity. But the scope is limited.
Which heat exchangers are better - copper or aluminum?
In heating equipment, the material of the future is increasingly being used - an alloy of aluminum and silicon. A similar eutectic structure made it possible to combine two dissimilar substances - a metal and a mineral. The result is a material with excellent casting properties. Heat exchangers without welds and complex shapes increase the energy exchange surface. The task of creating such structures is to optimize heat transfer with the minimum dimensions of the heat transfer unit.
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Aluminum-silicon alloy heat exchanger has good anti-corrosion resistance. The absence of welds, folds gives the product high strength. Another advantage is the optimal mechanical resistance to the low-temperature reverse flow of the coolant. Now the large temperature gradient of the supply and return circuits is not dangerous for the metal.
Thermal devices made of steel and copper alloys
Since the mass production of household appliances is focused on the manufacture of ferrous metal heat exchangers, gas boilers with a copper heat exchanger are considered a prestigious product. Copper has high heat transfer characteristics. Therefore, small boilers with a small amount of coolant can be used to heat a large house. As a result, the devices are very compact.
Important! Often, buyers are interested in which heat exchanger to choose - steel or copper. It is necessary to proceed from the physico-chemical properties of ferrous and non-ferrous metals. The specific heat capacity of copper is lower than that of steel.
That is, to heat an equal amount of a substance, copper needs to transfer less heat than steel. Accordingly, the inertia of the heating system, where the steel heat transfer unit is located, is greater. The automation of the boiler, working with a copper heat transfer unit, reacts faster to an increase in the temperature of the coolant. As a result, this leads to fuel savings. An even greater reaction of the heating system to heating occurs when the pump is running. In addition, it provides improved circulation even with broken pipe slopes and prevents water from boiling.
Comparing copper heat exchangers for boilers with steel ones, we can say that the latter are more plastic. This factor is important because there is a constant process of interaction with open fire. As a result, thermal stresses of the metal develop and cracks appear. Steel is more durable in this regard and can withstand a large number of cycles: heating - cooling.
The note! The disadvantages of steel, in addition to inertia, increased specific heat, include:
susceptibility to corrosion;
increased surface area of the heater;
a large amount of coolant;
a significant amount of heating devices.
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Steel gas boilers by weight range from 70 kg and above. The more power, the larger the dimensions. A very important parameter of the boiler is the thickness of the metal wall.
The manufacture of copper heat exchangers compared to steel heat exchangers is advantageous even from the point of view of their maintenance. The roughness coefficient of copper is 130 times less than that of steel. Due to this, the hydrodynamic resistance of copper products during the movement of liquid through them reduces the degree of pollution and scale formation.
Important! Today, manufacturers save on metal and reduce the thickness to the limit. This increases the likelihood of rapid burnout. Therefore, when buying, it is necessary to focus on the wall thickness of the heater at least 3 mm.
Geyser with a copper heat exchanger
The geyser incorporates a heat exchanger, the water in which is heated by a burner. Copper with a high heat transfer coefficient quickly transfers heat to the bath water. Copper products work the better, the less different impurities in the alloy. In their presence, the walls of the container heat up unevenly, which causes them to quickly burn out. Sometimes, in order to lower the price of a copper heat exchanger, they reduce the wall thickness and the diameter of the tubes. The mass of the empty apparatus is up to 3.5 kg.
The heat exchange block is made in the form of a tube. In the lower part, it has the shape of a snake with ribs. A metal sheet is installed around it, and a spiral pipe is installed on top of it. In addition to copper, galvanized and stainless steel are used. Which heat exchanger is better, copper or stainless steel, says the very fact of the cost of the device. Copper is 20 times more expensive than steel alloy. But it transfers heat better and is more economical in operation. Stainless steel is more durable.
Important! Before you buy a gas water heater with a copper body exchanger, you should study its technical parameters. A good thing won't be cheap. Copper oxidizes when in contact with water. This process is especially observed at the point of supply of cold water. There is condensation. High humidity corrodes the tube wall, and fistulas appear. On thin walls, they form quickly. Good quality products will last a lifetime.
Cleaning the Copper Heat Exchanger
As a result of many years of work on heating the coolant, layers are formed on the surface. They degrade the performance of the boiler. If they are ignored for a long time, the unit may fail. To eliminate calcium and other inorganic substances, copper heat exchangers are washed with special chemicals or air is supplied to the cavity under high pressure.
The gas heat exchanger is the main unit of the gas boiler, but most often it is he who fails first due to the constant aggressive loads that it undergoes during operation. As a key element of the boiler, the heat exchanger ensures the transfer of heat from the heating substance to the heated medium. How aggressive the loads that arise on it, evaluate for yourself:
- Outside, the coil is heated to high temperatures as a result of gas combustion. Often, heat exchange equipment fails precisely because of “burning out”.
- From the inside, hot water acts on its walls, the temperature of which rises to 90 ° C. As a result, scale settles on them, the diameter of the pipes narrows, and the performance of the boiler deteriorates.
- Sharp temperature drops also do not pass without a trace, often leading to the appearance of cracks in the metal.
Given this, you need to choose a boiler, the gas heat exchanger of which is able to endure such loads for a long time without destruction. The gas equipment market offers various boilers of a wide range of prices, but this is not the case when low price or spectacular design should be the factors that determine the choice. It is much more important, for example, to pay attention to the weight of the boiler. Heavy boilers last much longer than lighter models. Everything is very simple - the main weight of the heating unit - over 90% - falls on the recuperator, and the heavier the boiler, the thicker the coil walls and the longer it will work in the heating system without repair. You should not choose the most inexpensive models either - it is likely that they will soon require pipe cleaning to remove lime deposits from the walls, as well as the replacement of individual components.
Gas boilers with a heat exchanger have many advantages: they are economical, efficient, comfortable to use. But at the same time, the use of gas as a fuel carries certain risks, and in order to minimize them, it is necessary to correctly select all elements of the heating system and carry out their installation in a quality manner.
Types of heat exchangers for the boiler
Manufacturers offer various heat exchange equipment, which is divided into three types according to the method of heat transfer:
If you want the purchased boiler to serve for a long time and efficiently, it is advisable to conduct a chemical analysis of the water that you will use in the home heating system before buying it and choose a model based on its results.
According to the material of manufacture, gas recuperators are steel, cast iron or copper.
Steel heat exchanger
Widespread option due to ease of manufacture and affordable price. Heat exchangers made of steel alloys are plastic, strong enough and resistant to mechanical stress. At the same time, their service life is short due to frequent corrosion processes, and operation requires increased fuel consumption to heat the coolant and maintain the standard temperature regime.
Cast iron heat exchanger
Not subject to corrosion, therefore, more durable than steel. Requires special attention to operating conditions. The most vulnerable point is the boundary between the hot and warm parts of the heat exchanger. Operational errors increase the risk of cracks in the metal in this area. To prevent this, you should regularly flush the gas heat exchanger. The installation of a three-way mixing valve on the return line near the heat exchange unit, which pre-mixes hot and already cooled water and supplies liquid of moderate temperature into the cavity, will also help to minimize the risks. It should be remembered that boilers of foreign manufacturers with cast iron recuperators are not adapted to Russian operating conditions, therefore they are very vulnerable.
Copper heat exchanger
Its advantages include low specific gravity and small capacity of the device, compactness, resistance to corrosion, low fuel consumption for heating to operating temperature. The main disadvantages of such heat exchange equipment are high cost and insufficient reliability.
Flushing the heat exchanger will extend the life of the boiler
Even a properly selected boiler can last a long time or not very much, depending on what the operating conditions are. Today there is no need to talk about the high quality of the heat carriers used in heating systems, so their timely and regular cleaning will help extend the life of the boiler and gas heat exchanger.
Boiler flushing can be carried out manually, as well as hydraulically and chemically. In the first case, deposits are removed with scrapers after opening the boiler. Hydraulic flushing is carried out using a pump that supplies pressurized tap water to the heating unit, which exfoliates deposits and is discharged into the sewer system using a hose. In the third option, flushing is carried out using chemicals that soften and decompose the sediment on the surfaces of the plate heat exchanger.
heat exchanger- one of the most important elements of modern gas boiler equipment. And if you want the boiler you are purchasing to work with the highest possible efficiency, then first of all you need to look at what material it is made of, as well as how high quality this material is.
Actually, heat exchanger material can be anything, but in modern conditions the most widespread copper, steel and cast iron heat exchangers. Each of these materials has its own advantages and disadvantages, as well as the degree of efficiency, on which the performance of the purchased boiler equipment will depend. We suggest that you immediately begin to consider each of these types of heat exchangers.
Copper heat exchanger
Let's start with the most unpopular variety. Copper, of course, at one time was quite common. But only in view of the fact that other materials were either too expensive or simply unavailable for technical reasons. Therefore, with the advent of steel and cast iron, copper began to gradually fade into the background. And yet, if you suddenly come across a copper heat exchanger, then know that it has two critical drawbacks.
- The first is a rather high price.
- The second is a rapid burnout, leading to a quick failure of the entire heat exchanger.
Cast iron heat exchanger
Cast iron often called "eternal" material, the durability of which reaches 50 years or more. For an element such as a heat exchanger, this is very . The reason for such a high durability is the resistance of the cast iron material to burn-through, which is a real scourge of copper. In addition, cast iron, by its nature, is perfectly protected from corrosive processes (rust), without the need for any additional anti-corrosion coating.
However, the cast-iron heat exchanger cannot be called ideal. You need to know that it has two important drawbacks.
- First, cast iron is an extremely heavy material. If you have ever moved a cast-iron bath from place to place, then you know what we are talking about.
- Secondly, the cast iron heat exchanger is very fragile. Even temperature changes can damage it, not to mention purely physical damage. One single strong blow can cause a crack to appear. And it is no longer possible to use a cracked heat exchanger. By the way, cast iron is not the cheapest material, which should also be taken into account.
Steel heat exchanger
Steel heat exchangers today are the most common for the reason is simple. Steel is the cheapest of the above materials. And in terms of its technical characteristics, it is not so far behind cast iron. Of course, the durability here will not be 50 years, but, say, 15 years, no more.
If low-quality steel is used, then you will have to change such a heat exchanger after 5 years. The reason for this is the rather rapid burning of the material under the influence of high temperatures. Well, the fact that steel is afraid of rust (corrosive processes) is known even to small children. This fact also affects the durability of the material.
This question necessarily arises among those who first choose a boiler for heating.
If space permits, at first glance, a cast iron heat exchanger is preferable. But this is only at first glance. Let's take a look at some of the misconceptions that lead people to opt for a bulky, expensive, and heavy floor-mounted cast-iron boiler, while ignoring light wall mounts, which are also cheaper. At the same time, we will not focus on the psychology of such a choice.
- The main arguments of the advocates of cast iron:
- Easy to install and commission.
- The gas consumption of a cast-iron boiler is the same as that of a wall-mounted one, since the efficiency of the boilers is the same.
- Such boilers are cheaper to operate (no need to periodically flush the heat exchanger).
- The heat exchanger from cast iron is not subject to corrosion.
- The boiler will last 50 years or more.
Point one.
On the first point. Cast iron is very sensitive to temperature changes. Therefore, it is very important to correctly design the connection of such a boiler. For example, make-up of the heating system should in no case be carried out before the boiler. The difference between the supply and return should not exceed 20°C; to ensure this parameter, it is necessary to provide a system for automatic mixing of water from the supply to the return. The choice of circulation pump plays an important role. It must fully comply with the boiler, otherwise the boiler will either overheat or turn on and off frequently. Both of these are unacceptable.
The wall-mounted boiler is not afraid of temperature changes. The make-up valve for many wall-mounted models is already provided in the boiler design, as well as the circulation pump, which is selected when designing the boiler and fully complies with the calculated parameters.
Point two.
The fact is that the passport shows the values \u200b\u200bof the efficiency of the boiler when it is operating under ideal conditions. Those. water temperature in the boiler is 60°C, there are no deposits on the heat exchanger, no soot or scale. With an increase or decrease in the temperature of the heating water, the efficiency will decrease, since in the first case, with a decrease in the temperature difference, heat transfer will decrease, in the second case, the flue gases will be colder, which will lead to a decrease in thrust and underburning of gas.
To combat this phenomenon, modulating (with varying gas flow) burners have been designed. In boilers with a cast-iron heat exchanger, there are burners with power adjustment from 70 to 100%, and in boilers with a copper heat exchanger - from 30 to 100%. As a result, the efficiency of a wall-mounted boiler in real conditions is higher than that of a cast-iron one.
In addition, the large mass of the boiler and the large volume of water in it leads to a large thermal inertia of the system as a whole. Such a system heats up for a long time and cools down for a long time; when the heating mode is changed, the boiler either stands idle for a long time or operates with reduced efficiency. It should be noted that the downtime of the boiler, paradoxically, increases the gas consumption in general. This happens because the air in the combustion chamber is heated from the heat exchanger, draft is created through the chimney and the heated air rushes into the atmosphere, while taking heat away from the heating system.
Point three.
Here they are right. It makes no sense to wash a cast-iron heat exchanger with connecting dimensions of 2 "in the field. Scale will still remain on the walls. But it should be remembered that the deposition of 1 mm sediment on the walls of the heat exchanger reduces the boiler performance by 5%, while you will not notice anything, a decrease in efficiency can be installed only with the help of devices.In a copper heat exchanger, the flow rate will decrease with the growth of such a layer of deposits, which will signal the need for maintenance.By spending 1 - 2 thousand rubles, you will completely restore the operation of the boiler.
Point four.
This is also correct. Although if you do not flush the boiler, deposits inside the heat exchanger will cause uneven water cooling of the walls, leading in turn to thermal deformation of the cast iron, which can lead to the formation of cracks.
Point five.
Yes. A cast-iron boiler can work for 50 years, and a wall-mounted one for only 15. Only technology and legislation do not stand still. Who knows if in 10 years all boilers except condensing ones will be outlawed?
