The heat exchanger for heating is the most important component of any boiler. The “life” of the heating unit depends on its performance. Let's look at which heat exchanger for the heating system will ensure the efficient functioning of the boiler and extend its service life.
What are units of this category?
A plate heat exchanger for heating is a technically complex system, with the help of which energy is transferred between hot and cold coolant. In practice, liquids and vapors are used for this, less commonly gases, solid bases.
In other words, a heat exchanger for heating is a device that does not have its own heat source, and its functionality is provided by energy, which comes from a centralized heating system. That is, a boiler or stove does not belong to units of this category by definition. However, a stove bench or a shield that reflects the heat of the flue gases from the stove can be considered examples of a heat exchanger, since the air in the room is heated from them.
The energy transfer efficiency here depends on the following:
- Temperature differences between the media (the presence of a significant difference causes a more impressive transfer of energy).
- Area of contact of individual media with a heat exchanger.
- Indices of thermal conductivity of materials of construction design.
In fact, a heat exchanger for hot water from heating can be represented by any pipe that is used to transfer a particular working environment, which has a temperature different from the indicators of the surrounding space.
Types
One of the determining criteria when choosing a heat exchanger of a certain plan is not only the nature of the coolant, but also its quality. If in the form of a working medium it is supposed to use softened or chemically purified water, it is better to give preference to plate constructions of a brazed type. The same applies to the use of coolants that do not leave behind any deposits on the walls of the structure, for example alcohol, freon or ethylene glycol.
When it comes to large-scale heat points, such as boiler houses, here most often you can see a heat exchanger for hot water from a collapsible type of heating. The use of such solutions can be explained by the presence of a low-quality working environment, which is used in centralized heating networks.
The simplicity of the design of collapsible plate aggregates contributes to their convenient maintenance, in particular, quick disassembly if it is necessary to remove scale from the internal channels. At the same time, the replacement of parts of such a heat exchanger, whether flanges or gate valves, is affordable even for inexperienced craftsmen.
According to the method of energy transfer, it is worth highlighting a mixing and surface heat exchanger for heating. The first operates according to the principle of energy distribution in direct contact between individual heat carriers. The second type transfers energy through the plates without direct contact of the working media.
If it is necessary to use a heat exchanger for heating as an element for heating water in a pool or as a cooler in industrial plants, plate and solder units are recommended for this purpose. Such designs allow you to quickly achieve the most efficient heat transfer between the two fluids.
Materials
The heat exchanger for heating a house can be made of steel or cast iron plates connected by brazing with copper or nickel solder. Copper brazed designs are common in centralized heating systems. At the same time, systems whose elements are connected using nickel are mainly used to meet the needs of industrial sectors and, if necessary, work with chemically aggressive environments.
Cast iron
Giving preference to cast-iron heat exchangers it is worth paying attention to several points:
- Enough impressive weight, which must be taken into account when developing a project to equip a boiler room. As for the introduction of such structures in the heating system of a private house, the latter should be distinguished by a small volume of sections, a minimum number of smoke channels that are used to move combustion products.
- Cast-iron units are distinguished by the possibility of sectional transportation in disassembled form, which becomes convenient during installation and subsequent maintenance.
- Despite the weightiness, the material is quite fragile. Therefore, during transportation and installation, mechanical influences on structural elements should be avoided. Another danger is thermal shock. When abruptly placing an impressive volume of cold working medium in a non-cooled unit, the walls of the heat exchanger can crack.
- Cast iron lends itself to both wet and dry corrosion. The first is formed as a result of exposure to acid condensate on the material. The second slowly covers the surface of the structure in the form of a film of rust during operation. Since heat exchangers for heating a private house made of cast iron have thick walls, these processes can stretch for many years.
- Such systems heat up for a long time, but they cool extremely slowly, which significantly reduces fuel consumption and increases the efficiency of space heating.
Steel
The presence of a steel “heart” does not lead to a significant weighting of the system. Therefore, a water heat exchanger for heating, made of this material, is often used to service large areas.
As for the convenience of mounting a steel structure, the final assembly, unlike cast-iron units, takes place in the factory. One-piece candy bar is quite difficult to bring in a cramped room. In addition, the factory assembly somewhat complicates the repair and maintenance of the system.
The installed steel heat exchanger in the furnace for heating, which received serious damage, is almost impossible to bring back to life at home. You have to either resort to the complete dismantling of the system and sending it for repair to an industrial workshop, or get rid of the structure by performing its replacement.
At the same time, a water heat exchanger for heating from steel is not afraid of either thermal shock or significant mechanical stresses. The material is characterized by a high rate of elasticity and therefore copes well with sharp temperature extremes. However, with prolonged exposure to extreme cold or heat, small cracks can form on the welds.
If we talk about the ability to withstand corrosion, a steel heat exchanger is subject only to electrochemical influences. Particularly quickly during prolonged contact with aggressive media, thin walls corrode with rust. At the same time, the life of the system can be systematically reduced for a period of 5 to 15 years. Proceeding from this, manufacturers often cover the inner walls of steel heat exchangers with cast iron.
Systems made of this material heat up almost instantly and cool just as quickly. Despite the obvious convenience, if necessary, rapid heating of the premises, a similar property has the opposite, negative side. Thus, the effect of metal fatigue in certain sections of the structure can lead to the appearance of minor damage.
How to calculate heat exchanger?
Performing independent calculations is one of the most common questions from consumers. In fact, it is extremely difficult to cope with the task, since manufacturers of heat exchangers try to hide the secrets of their own designs from outsiders, including from users.
For the above reason, it becomes difficult to find out the actual energy consumption during heat transfer. If this indicator is deliberately low, respectively, the efficiency of the heat exchanger will be insufficient to meet existing needs.
To increase system performance, it is often necessary to install volumetric units. However, to reduce the number of used heat exchanger plates, it is enough to use the special calculation program that every serious manufacturer of heating equipment has.
DIY heat exchangers
How to make an effective design with your own hands that will cope with the heat transfer functions? To do this, it is enough to return to the definition that is typical for devices in this category. It turns out that to assemble a simple heat exchanger, it is enough to take a metal pipe of a certain length, roll it into a ring and place it in a container filled with water.
Thanks to the output of the outlet and entrance of the pipe, you can get a functional design that will either heat or cool the working fluid, depending on the existing need.
Water jacket heat exchanger
In addition to a coil-shaped system, a heat exchanger known as a “water jacket” can be made with one's own hand. Similar systems operate on the basis of the principle of energy distribution between several sealed containers placed in each other.
Heat transfer according to this principle has been successfully applied in small-size solid fuel boilers. Despite the general simplicity of the design, the disadvantage of such systems is the presence of a relatively low operating pressure for which these units are designed. In addition, an experienced welder should be involved in the manufacture of heat exchangers operating on the principle of a "water jacket". Designing and assembling such a system from improvised materials without the appropriate skills is quite problematic.
Tube Board Heat Exchanger
Probably the most difficult of all the options available for independent manufacture is the system called the “tube board”. This definition was attached to self-made heat exchangers that contain a substantial amount of milling pipe joints.
Such units are presented in the form of three sealed containers. Two of them are located on opposite edges of the structure and are connected by metal conductors of the working medium, which are expanded at the ends of such vessels. Heat transfer is carried out in the third - middle - part due to the movement of the liquid working medium between the tanks through the pipes.
Finding Alternative Solutions
If there is no possibility for self-assembly of the heat exchanger by the above methods, you can try to find materials for the manufacture of the future system in your own closet or in a landfill. For example, an old heated towel rail will be a great solution for creating a device in the form of a coil. Any household radiator that does not have leaks is also suitable.
As for the use of radiators from automobile stoves, in fact, they can be immediately used as a heating element by combining individual units with adapters to increase the area of heat energy exchange.
An effective device can be created on the basis of an old water heater. In this case, you don’t even have to redo anything.
Eventually
As you can see, the principle of operation of heat exchangers is approximately the same everywhere. Depending on the operating conditions, such units can work both for heating and for cooling the working medium: gas, liquid or solid.
When choosing a factory solution, a lot depends on the tasks that are assigned to the heat exchanger, and in the case of self-assembly, from the engineering imagination of the master.