A great variety of heating unit models are offered. Despite such diversity, they can be structurally divided by the type of combustion chamber and the material from which it is made. heat exchanger.

There are two main types of combustion chamber

Open combustion chamber - pros and cons

Almost everyone is familiar with boilers with such a chamber. Air enters the furnace through special air intake holes in the heating boiler unit, due to the vacuum region that occurs in it during combustion. The heat exchanger in such a chamber is usually installed above the torch.

The advantages of a boiler with an open chamber include:

• low noise level during operation
• enough, simple design,
• easy installation
• easy maintenance.

The disadvantages include:

• risk of fire due to the presence of open flames,
• the need for mandatory supply ventilation in the place where the heat generating device is installed.

Closed combustion chamber - pros and cons

In this type of heating boiler, air is forcedly supplied using a special electric fan. The firebox itself resembles a barrel with double walls, between which there is a coolant, and a torch burns in the center.

The advantages of a boiler with closed camera include:

• Higher efficiency, which is explained by the large volume of the heat exchanger.

Also, due to the fact that the combustion chamber is isolated (closed) from the room where such a boiler unit is installed, then the probability of fire is zero.

• Air can enter a closed firebox directly from the street, but in the case severe frosts it must be preheated.

The disadvantages include

• Increased noise
• high costs due to fan operation,
• the possibility of attenuation of the thermal boiler in the absence of electricity,
• higher price compared to atmospheric (open) boilers.

Design of modern domestic boilers

Designs of modern domestic boilers intended for autonomous heating are designed in such a way that most of them (up to 85.0%) are the surfaces of the heat exchanger, which is its main unit. The characteristics of the heating unit, such as efficiency, efficiency and environmental friendliness, directly depend on what shape it has and what material was used for its manufacture.

Currently, the main materials from which heat exchangers are made are -

• steel
• cast iron
• copper

Although models of boiler equipment have already begun to appear that have heat exchangers made of aluminum alloys And of stainless steel, we will not consider them due to the isolated cases.

Steel heat exchangers

The simplest from the point of view of manufacturing technology are heating units with steel heat exchangers. This type is the most common among domestically produced heating devices.

The positive aspects of steel heat exchangers are

• low and affordable cost of boiler installations,
• as well as the plastic characteristics of the material.

The last indicator is very important for high-quality and long-term work heating device, since when heated under the action of a burner fire, the walls of the heat exchanger are subjected to various stresses, which can lead to their deformation and even the formation of cracks.

A significant disadvantage of steel heat exchangers is the destructive effect of corrosion. At the same time, both its external and internal parts are subject to it, leading over time to its failure. Also, a negative factor in using steel for a heat exchanger is its relatively heavy weight and the volume for which a certain part of the gas will be consumed for heating, as a result of which the boiler efficiency decreases.

Cast iron heat exchangers

Unlike its steel counterpart, a cast iron heat exchanger has high durability to corrosion and long service life. But on the other hand, cast iron is more demanding, both in the process of manufacturing a heating boiler and during its operation. For example, if a cast iron heat exchanger heats up unevenly (due to scale formed inside it, due to poor quality water), this will lead to cracks and leakage.

There is also the possibility of cracks appearing when the temperature in the heating zone differs greatly from the readings of the coolant coming from the opposite direction heating system. To avoid this situation, the heating circuit of a cast iron boiler includes a 4-way mixing valve, through which hot water is added before the return line enters the heat exchanger. If all operating rules are followed, heating equipment with a cast iron heat exchanger will last 20 years or more.

The main disadvantages of heat exchangers made of cast iron are high cost, formation of cracks due to poor-quality coolant and non-compliance with operating rules, high inertia due to significant volume and mass.

Copper heat exchangers

The last main type of heat exchanger is a copper product. The most important advantages of such a heat exchanger are small volume and weight (as a result of low inertia), high corrosion resistance, and compact boiler design. And although it was believed that a copper heat exchanger is not reliable enough, this is no longer true, thanks to the use in its manufacture modern technologies and equipment.

This mistrust manifested itself due to the fact that copper heat exchangers were installed in the same combustion chambers as cast iron and steel products. And since such intense heating was unacceptable for copper, its heat exchangers quickly failed. Modern models heating boilers with copper heat exchangers have a burner flame power reduced by almost three times (up to 30.0%). Therefore, with the same power indicators, copper boilers are considered more economical, and in terms of service life they are almost equal to cast iron models.

Through which the coolant circulates, more. As a result, they become less clogged with salt deposits. Consequently, cleaning the internal cavities of mono-devices will have to be done much less frequently than servicing a bithermal heat exchanger. First of all, this applies to the DHW circuit device; he gets involved when needed.

High maintainability. Depressurization of separate heat exchangers is easier to eliminate, even at home (by soldering). Moreover, this can be done many times; you just need to be able to use a soldering iron and know how different brands of solder differ.

Convenience. If the DHW heat exchanger requires repair or replacement, it is not necessary to stop the boiler. The device is dismantled after taking measures to prevent operation three way valve. The importance of this during heating season no explanation needed.

Low cost. A monoheat exchanger is much cheaper than its bithermic counterpart.

Minuses

• Tight boiler layout. Other elements of the circuit are added to the two heat exchangers; service heating installation becomes more complicated.
• The likelihood of breakdowns increases. The more structural elements, the higher the risk of failure of any of them. "Weak link" in wall-mounted boilers– the already mentioned tap (three-way).
• The cost of equipment is increasing precisely because large quantity components.

Bithermic heat exchanger

pros

• More rational layout of boiler equipment; There is no three-way valve, second heat exchanger, or connecting pipes.
• Fewer parts means higher product reliability.
• Lack of inertia of the DHW circuit. As soon as the tap opens, hot water at a pre-set temperature immediately flows out. If it is used frequently, we can talk about some fuel savings, since the fluid is not preheated.

On a note! Two heat exchangers prepare water for different circuits; one for heating, the other for hot water supply. The bithermic device is universal in this regard: it works on both systems.

Minuses

• Demanding quality of water treatment. Additional activities – certain monetary investments. But the cost of treatment plants and their maintenance is “unaffordable” for many, and this is one of the arguments against choosing a boiler with a bithermal heat exchanger. If the water in the area is “clean” and soft, this minus is automatically leveled out.
• Cannot be repaired (in 90% of cases). It is rare that in a specialized workshop it is possible to extend the life of a bithermal heat exchanger, but the craftsmen take on this reluctantly and do not give any promising guarantees. In practice, for the boiler it is purchased new device. Recommendations for servicing heat exchangers at home (just spend ⅓ an hour, and it’s as good as new) are given by people who have hardly ever done this themselves. Most likely, advice is based on the principle “I heard, I read, my friend told me.” Incorrectly prepared solution, violation of the washing technology - and depressurization of the housing is guaranteed.
• The likelihood of leaks increases. The explanation is simple - more internal connections.
• High price. A bithermal heat exchanger is more expensive than any of the mono-devices.

One of the most important components of any heating boiler is the primary heat exchanger, in which thermal energy from hot combustion products is transferred to the coolant. It is on the characteristics of this component that the performance characteristics equipment: its efficiency and cost-effectiveness, service life and cost. In conditions of fierce competition between manufacturers, all components of domestic boilers tend to simplify their design and reduce their cost. At the same time, there is a stable demand for premium gas boilers with a copper heat exchanger. Why do consumers choose them, despite the high price, and what are the advantages of copper as a structural material?

Metal is different from metal

The material from which the heat exchanger is made is the intermediary that transmits thermal energy from combustion products to the coolant. During the operation of the boiler, it must withstand high temperatures (up to 400-600 oC) for many months of the heating period without reducing its strength characteristics. Also, the heat exchanger material comes into contact with two media - hot flue gases and coolant (usually water). Therefore, very stringent requirements are imposed on the material, which are met by a narrow list of metals and alloys.

Currently, three materials are used for the manufacture of household gas boilers: steel, cast iron and copper. Each of them has its own strengths and weaknesses.

The most common and a budget option- these are steel heat exchangers. Steel has a rare combination of high ductility and strength even when exposed to high temperatures and mechanical loads. This characteristic of the heat exchanger material is especially important when it is exposed to thermal stress. In the high temperature zone, thermal stresses form in the metal, and only plasticity prevents cracks from appearing.

But steel heat exchangers also have serious disadvantages: they are susceptible to corrosion, both from the smoke pipes and from the coolant. To increase service life, manufacturers increase the thickness of the heat exchanger wall, which reduces efficiency and increases fuel consumption.

Cast iron corrodes much more slowly than steel when in contact with chemically active media. But due to reduced ductility, when using this metal, strict requirements are imposed on operating conditions gas equipment. Sudden temperature changes can cause cracks to appear.

So, for example, for different models with a cast iron heat exchanger, the temperature difference between the coolant in the supply and return lines of the heating circuit cannot exceed 20-45 oC. To achieve this, complex systems for mixing hot coolant are used. This also imposes strict restrictions on the stability of the circulation pump.

Another traditional material for heat exchangers of boiler equipment it is copper. It has a unique combination physical and chemical properties, which makes it an almost ideal material for these purposes. First of all, copper stands out for its exceptionally high thermal conductivity - 385 W/m*K (higher only for silver). For comparison: the thermal conductivity of cast iron is 50-60 W/m*K, and steel - from 47 W/m*K and lower (depending on the temperature and grade of steel).

The high resistance of copper to corrosion is also very valuable. During operation of a copper heat exchanger, a thin but dense film of oxide appears on the surface of the metal, which protects the underlying layers from corrosion.

Another important property of copper is its very low roughness coefficient, which is 133 times lower than that of steel. This has two consequences: low hydrodynamic resistance of copper pipes and a significantly lower rate of overgrowing with soot and contaminants.

Among the disadvantages of this metal, one stands out - its high price. Pure copper is up to 15-20 times more expensive than steel alloys used for heat exchangers, which automatically places boilers using large amounts of copper in the high price segment.

Heat exchangers with fins and their problems

The choice of material for the primary heat exchanger largely determines its design. In particular, the developers of low thermal conductivity of steel and cast iron heating equipment compensated by increasing the heat exchange surface. It was this idea that formed the basis of the most common domestic boilers tubular heat exchangers with fins. There are many plates installed in vertical rows on a curved (S-shaped) pipe. This heat exchanger is located in the upper part of the combustion chamber. Flue gases pass through the narrow gaps between the plates from bottom to top, releasing energy to the coolant.

In addition to steel, copper is sometimes used to make such heat exchangers. IN double-circuit boilers Some manufacturers still use bithermal heat exchangers: in the external copper pipe coolant circulates with the fins, and inner tube serves to heat water for domestic hot water.

To increase power and efficiency in heat exchangers of this type, the clearance between the fin plates can be only 1.5-2.5 mm. This significantly increases the rate of clogging of the lumen with soot and soot (natural gas combustion products), which prevents complete combustion gas and leads to increased fuel consumption.

The small internal cross-section of the pipes also increases the sensitivity of this unit to the accumulation of lime deposits in the lumen. The deposition of hardness salts and dirt inside the heat exchanger significantly reduces heat transfer due to a decrease in the thermal conductivity of the walls and disruption of coolant circulation.

It is estimated that just 1 mm of limescale deposits on the walls of the heat exchanger reduces boiler performance by an average of 5%. But what is much more dangerous, mineral deposits disrupt the cooling process of the thin walls of the heat exchanger, which can burn out because of this.

As a result, boilers with this type require more frequent and labor-intensive after-sales service: cleaning the combustion chamber and descaling.

Copper heat exchanger: traditions and technologies

The use of copper with its extraordinary thermal conductivity allows us to abandon the heat exchanger design in the form of a finned tube in favor of a simpler and reliable design. Its principle is borrowed from the traditional samovar, which smoke pipe passes through the water tank.

“Since 1948, when inventor Maurice Friske released the first French gas boiler HYDROMOTRIX, the copper tubular heat exchanger has become business card products of our company,” says Roman Gladkikh, technical director of FRISQUET, the leader of the French heating equipment market. - Its design is fundamentally different from the so common tubular heat exchangers with fins. The basis of the heat exchanger is a large-capacity copper boiler body, inside of which there are pipes for exhaust flue gases. They contain stainless steel turbulators (dividers), which reduce the speed of flue gases to increase heat transfer.”

The result is a massive heat exchanger cylindrical, the production of which requires 25 kg pure copper. For comparison: steel analogues with fins of comparable power weigh up to 5 kg. Such a heat exchanger operates without temperature shocks in softer and more gentle conditions than a thin tube with fins.

The described heat exchanger design has whole line important consequences. Due to the resistance to corrosion and ductility of copper, the service life of this unit exceeds 20 years. The diameter of each smoke tube is 30 mm, which makes them much less susceptible to soot accumulation. In one heating season The narrowing of the lumen in heat exchangers with fins can reach 40% (versus 3% in tubular ones). Based on data accumulated in European countries After several decades of operation of copper tubular heat exchangers, we can conclude that they have on average twice the service life compared to steel finned counterparts.

In addition, it is copper tubular heat exchangers that make it possible to achieve maximum efficiency - 95%, which leads to significant savings in energy resources and reduced boiler operating costs.

The unique design with a large-capacity boiler body significantly expands the functionality of heating equipment. Thus, in double-circuit FRISQUET boilers, secondary heat exchangers are made in the form of copper coils located inside the boiler body. As a result, all boilers from this manufacturer, as standard, allow you to connect an additional boiler or second and third heating circuits. For example, one heating circuit can provide heat wall radiators(coolant temperature - up to + 85 oC), and the second - systems heated floors(+20-45 oС).

Consumer choice

The presence of a copper tubular heat exchanger in the boiler is good reference for those who are looking for a reliable and economical solution for their property. However, to make a responsible choice, you need to pay attention to other nuances.

Manufacturer certification according to ISO 9001 standard. For the buyer, this means that the boiler has passed multi-stage quality control during production.

“In our ISO 9001 certified plant, all stages from component acceptance to starting materials from third-party suppliers to the final assembly of units, have multi-stage control. Each operation performed is marked with the personal mark of the worker who performed it, says Roman Gladkikh (FRISQUET). - After assembly is completed, each assembled boiler goes to a test stand, where it is tested according to 15 parameters. In addition, in a certified laboratory according to the ISO45001 standard, not only the initial components are tested, but also life tests of the equipment are carried out continuously on special stands.”

The presence of safety systems in the boiler design, including coolant pressure, coolant temperature, gas and draft overturn sensors, as well as ionization flame control.

The presence of intelligent functions - the ability to select scenarios, program and remote control boiler operation, which significantly increases the efficiency of the heating system and increases its service life.

As we see, copper is like construction material for boiler heat exchangers has many undeniable advantages. Private and corporate consumers are interested in such equipment, for whom reliability, low operating costs and long term Boiler service is of utmost importance.

Heat exchanger - important element modern equipment for space heating and water heating. When choosing a boiler, it is worth considering what metal it is made of, as this directly affects its service life, efficiency, performance and specifications generally.

Advantages of a copper heat exchanger

In gas hot water boilers Hydronic where they are used copper heat exchangers, the coolant passes through the system at a speed of 2.1 m/s. The fast-moving fluid removes solid particles from the pipes, which prevents the formation of scale and blockages from mechanical deposits. This also ensures constant boiler efficiency and allows the use of coolant with any chemical characteristics.

A gas boiler, in which it is installed copper heat exchanger, has a number of other advantages:

• The copper heat exchanger has compact dimensions and low weight. Compared to steel or cast iron, such boilers are 2-3 times smaller and lighter;
• As a metal, copper is virtually resistant to corrosion;
• Copper heat exchanger It has low inertia, due to which it heats up quickly and cools down just as quickly. Uniform heating leads to a complete absence of mechanical stress in the pipes (compression, tension, rupture);
• Easy to repair and replace components;
• Due to the small capacity, it does not require a large amount of coolant, which significantly saves the budget;
• Absolutely explosion-proof.

Boiler equipment with copper heat exchangers from HYDRONMASH

The GIDRONMASH company together with the American company Laars Heating Systems design, manufacture and install gas water heating equipment. All devices can be used for autonomous heating and supply hot water in buildings, industrial and residential facilities, kindergartens, schools, hospitals and even swimming pools. Based on the installation principle, boilers can be divided into two groups:

• Gas boilers with copper heat exchanger become more compact and easily fit into doorways. That is why they are most often used in public utilities.
• Floor standing gas boiler with copper heat exchanger - the device that received wide application in heating industrial complexes, factories, greenhouses, administrative buildings, etc. Due to its light weight and dimensions, it can be installed by two specialists within a day. The absence of the need to use heavy lifting equipment made it possible to install it on rooftops or high floors.

Heat exchanger for gas boiler: types and principle of operation

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A heat exchanger for a gas heating boiler is a structure of first importance, inside which the coolant moves. The device is placed inside the combustion chamber, where it is heated by the outgoing flow of heat energy when it is burned. natural gas. Therefore, the efficiency of the boiler largely depends on the condition of the heat exchanger installed in it.

Modern steel heat exchanger for gas boiler

Heat exchangers for gas boilers. Classification

There are different classifications of heat exchangers for gas boilers.

According to purpose:

• heating;
• evaporative;
• condensing;
• cooling heat exchangers.

According to the material of manufacture:

• steel;
• cast iron;
• copper;
• made of stainless steel (for boiler equipment);
• from aluminum alloys (for boiler material).

According to the method of heat transfer to the fluid of heat exchangers:

• primary;
• secondary;
• combined (bithermic).

Let's look at some classifications in more detail.

Steel

Is the most common option. This is due to the availability of steel and its easy processing, and, as a consequence, low cost. Heat exchangers made of steel have their differences. They are characterized by ductility and durability. Upon contact with high temperature, plasticity plays a paramount role. It is this that prevents cracks from forming when inside the metal in place direct action thermal stresses are created.

The disadvantages of steel heat exchangers include corrosion, which is inevitable for metals. Naturally, this destruction process shortens the life of the heat exchanger. In addition, corrosion can also appear on outside devices, and on the inside.

Another disadvantage is that they have big size, weight and this, in addition, increases fuel consumption for heating a large amount of coolant. This happens because manufacturers (in order to achieve a high degree of inertness) increase the size of the internal cavities of the heat exchanger, as well as the thickness of its wall.

Cast iron

The difference between a gas boiler with a cast iron heat exchanger and a steel one is that it does not rust when in contact with water. This allows it to extend its service life. However, cast iron heat exchangers require careful maintenance.

Example cast iron heat exchanger

One of the properties of this metal is fragility. Due to scale, uneven heating may occur, which leads to cracks in it.

The solution is washing. This is an important element in the operation of a gas boiler. Usually, if used running water(as a coolant), then flushing is carried out once a year. If antifreeze, then once every two years. If the water is purified, then once every four years.

Copper

A copper heat exchanger has more advantages than disadvantages. This metal is light in weight, compact, and has small capacity. It is resistant to corrosion and requires less fuel for heating. This provides the copper heat exchanger big advantage. Despite all this, it has a high price and is quite unreliable when heating the element.

Copper heat exchangers are typical for imported wall-mounted gas boilers. Domestic manufacturers prefer to use heat exchangers made of steel.

Copper heat exchanger

Primary

The part looks like big pipes, curved in the shape of a coil. It is made from rust-resistant metals (copper, stainless steel). In addition, in the plane there are also various sizes plates.

To protect working surfaces from corrosion, they are coated with special paint.

Gas boiler device

The principle of operation of the heat exchanger in this case is to transfer energy from gas to the coolant itself. The power of the heat exchanger depends on the length of the pipe, as well as on the number of “fins”.

The performance of the parts may be negatively affected by external factors(soot, dirt) and internal (salt deposits). This can lead to a failure in the circulation processes in the coolant and a decrease in the thermal conductivity of the walls of the device.

Maintenance of the primary heat exchanger must be given due attention, flushing and cleaning must be carried out in a timely manner.

It wouldn’t hurt to additionally purchase for it, which increase the service life of the gas boiler and protect the heat exchanger from negative impacts and various savings.

Secondary or hot water supply (DHW)

Unlike the primary heat exchanger, the secondary one has special plates connected to each other. They are usually made from stainless steel.

The secondary heat exchanger for a gas boiler, due to its large heat exchange area and its good thermal conductivity, ensures the required heat exchange. As a result, the process of corrosion on the walls of such a heat exchanger slows down significantly. In this type of heat exchanger, energy transfer occurs from the liquid to the coolant. The strength of the device directly depends on the heat exchange area and the number of special plates.

Combined (bithermic)

Bithermic heat exchanger for gas boiler

This heat exchanger has its own peculiarity - double heat exchange, namely from the coolant to water and from gas to the coolant. In the pipe, water is heated from the outside for the heating system, while the internal section prepares DHW water.

Combined heat exchangers for boilers have one undoubted advantage - simplified design. There is no need for a secondary heat exchanger, which makes the boiler cheap and at the same time compact and reliable.

The disadvantage is the low power in DHW mode.