Of all the methods of heating that exist today, air heating is considered the rarest. Despite the fact that even 50–70 years ago these heating systems were popular and were installed in large quantities, today it is rather difficult to find such objects. The exceptions are fireplaces and traditional European stoves, which are not full-fledged air heating systems.
Of all the equipment and devices that work on the same principle, we are most familiar with heat guns, fan heaters and convectors. Heating, where the main focus is on solid fuel boilers that provide air heating, is used today in rare cases. Consider the reasons why air heating is not as popular today as other types of heating. Let’s deal with the principle of operation of an air heating device that runs on solid fuel.
The essence of air heating. Main advantages
An air heating system is a complex of devices and devices that closely interact with each other. As in other heating methods, here the thermal energy obtained as a result of combustion is transferred to the surrounding space, objects. The essential difference of this method lies in the absence of a coolant, which plays the role of an intermediary in most heating systems. Heating of premises is carried out due to the circulation of air heated to a certain temperature.
There are two types of air exchange: natural air circulation and forced.
Looking at a burning fireplace, you can roughly imagine how air heating works. However, here the heat as a result of burning firewood is not spent rationally, most of it is wasted. It is fundamentally important to force the heated air to move through the duct and give off heat to the heated rooms. This is what a solid fuel boiler does in the air heating system.
The main advantages that air heating and a heating device of this type have are as follows:
- lack of great inertia. In comparison with water boilers, the air heating unit warms up quickly enough and in the same way cools down faster;
- simple and unpretentious in work design of heating devices. Low cost of boiler equipment operating on the principle of air heating;
- good resistance of the entire system and the heating boiler in particular to low temperatures. The absence of a liquid coolant allows you to safely leave the heating equipment turned off for a long time;
- fast and concealed installation. No need to lay a piping system and install heating radiators.
In each case, there is something to think about. The low inertia of air heating units is one of the significant advantages. When installing such equipment, you do not have to install either a buffer tank or heat accumulators. The boiler is brought to the optimal operating mode in a matter of minutes. The same factor plays an important role in terms of equipment resistance to low temperatures. In the absence of a liquid heat carrier, you should not be afraid of defrosting the system during the cold period.
If we talk about the cost of equipment, then solid fuel air boilers are significantly inferior in price to their counterparts working with water heating systems. Aluminum pipes for air ducts are an order of magnitude cheaper than the materials and components required for piping equipment in a house.
For reference: Heating of residential premises in this way was first used in ancient Rome. In the houses of noble nobles, in public places, air stoves were used, which had to be heated with firewood.
The circulation of the heated air mass was carried out in a natural way, due to the action of the laws of physics. When air is heated, it expands, convection processes occur, leading to the appearance of natural draft. Hot air spreads, and a new portion of fresh, cool air takes its place. Even in antiquity, the great importance of ventilation was discovered to achieve greater efficiency of heating measures. The intensity of combustion and the movement of heated air masses directly depend on the possibility of inflow and outflow. The greater the thrust, the higher the intensity of combustion and, accordingly, the heating of the air. The thrust decreases, the intensity of all the process slows down.
Today, instead of primitive air ovens, solid fuel heating devices have come. Air solid fuel units are able to more efficiently and efficiently heat the air mass for space heating. Modern models are characterized by high efficiency, economical and easy to use. The air heating system is considered undeservedly forgotten.
An important technical aspect
The main reason for this attitude to air heating was the technological requirements associated with the organization of the heating process. There is one technical nuance of air heating, which over time has grown into a clear disadvantage.
Your heating boiler is located in the boiler room and in order for warm air to get into other rooms, it is necessary to have a developed air duct system. There is not always a physical and constructive possibility to lay air duct channels that are sufficiently large in cross section in a limited space.
The principle of operation of air heating is not complicated. The main process proceeds in a simple and uncomplicated way. With the ventilation system of a solid fuel air boiler, the issue can still be solved somehow by placing the main communications under the ceiling. The flow of hot air is provided by the lower location of the air duct. Due to the temperature difference between warm and cold air, convection occurs, and air masses are replaced. In other words, with the existing draft in the room, the desired effect can be achieved. Whether you like constant drafts at home or not, it’s up to you.
Another, no less important detail that follows from the physical properties of air exchange, which should be paid attention to, is the lower location of the air ducts. Usually, for these purposes, air ducts are laid underground, between the lags, or the air duct is equipped directly in the wall panels. When re-equipping the premises or replacing communication lines, it is necessary to take into account the presence of air channels in the structural elements of the building. This is the main design flaw that marks the air heating system.
Important! The lower location of the duct allows the use of natural circulation. With the option with the top arrangement of air channels, it will be necessary to install a blower for forced circulation and increase the speed of the air flow.
Solid fuel boiler — the main source of heat. Principle of operation
How do we imagine a solid fuel boiler due to which the home heating system functions? This is a pyrolysis-type heating device familiar to many of us. Due to the combustion, first of fuel, and then of combustible wood gas, there is an intense release of heat from the interaction, with which the heat exchanger is heated. More precisely, an air exchanger. Heated to a certain temperature in the pipes of the heat exchanger, the air circulates through the duct system, heating the interior.
Such a heating device can be installed almost anywhere in a residential building or other premises.
On a note: Today, models of solid fuel air heating units are produced, the design and appearance of which allows them to successfully fit into the interior of residential premises.
If the owner of the house wishes, the air can be distributed through the duct naturally or under the action of blowers, which significantly increases the speed and density of the air flow. The boiler has, as a rule, a spacious combustion chamber where the fuel burns. The furnace has a special hatch through which firewood is loaded. At the bottom of the combustion chamber there is a grate on which the fuel is placed and the combustion itself is carried out directly. As in other solid fuel units, a podzolnik is located in the lower part of the structure — a box for collecting ash and large remains of unburned wood.
Air boiler device
If preference is given to the pyrolysis method of fuel combustion, then a boiler equipped with two combustion chambers is required. In one compartment, as a result of the smoldering of the fuel mass, an intensive release of wood gas is carried out. In the second furnace, volatile combustible compounds, reacting with oxygen, ignite, releasing a huge amount of thermal energy. This method is fuel efficient. In the process of burning firewood, there are practically no large residual fragments left. The air heating system with a pyrolysis-type solid fuel boiler is distinguished not only by fast and high-quality heating of rooms, but also by high performance.
Heated air accumulates in the space between the body of the heating unit and the firebox (combustion chamber). This is the heat exchanger in this case.
Due to the influx of air, the walls of the combustion chamber are constantly washed by new air flows. Both primary and secondary air are used for heating. Thanks to pyrolysis in the boiler, primary and secondary air do the main work. Primary air masses are the main source of heat. Air entering from outside, i.e. preheated to reduce heat loss, and only then enters the furnace. Secondary air is a gas-air mixture consisting of air and hot combustion products.
On a note: solid fuel in most cases burns down by 90%. The remaining 10% are presented in the form of the smallest particles that make up the smoke. The main advantage of secondary air is that it already has a high temperature. Additional heating is not required to reach the required temperature. Due to such air exchange, a high heat capacity of the operating unit is achieved, and the efficiency of heating equipment increases.
The selection of secondary air masses is carried out from the uppermost part of the duct. The intensity of the intake is regulated by the position of the damper. The intensity of combustion on this equipment determines the amount of air supplied to the combustion chamber. More air, more intense combustion. Air supply in simple models is carried out in manual mode, due to the natural flow of air. In expensive models, a fan is used for this purpose, which turns on and off automatically. Such fans are called blowers. In order to achieve the maximum possible effect of the boiler operation, a smoke exhauster is installed on the chimney, the task of which is to improve the removal of residual combustion products from the combustion chamber.
To date, solid fuel air units of various degrees of equipment are on sale. Most models include:
- combustion process control system (temperature sensors, dampers, blowers);
- mechanisms and devices that supply fuel.
Due to the interaction of all systems, the boiler allows you to control the heating temperature in the premises.
Features of the air heating system
The air heating system has its own technical features and nuances that must be taken into account during installation. Approximately the following values are taken for calculations:
- the average air consumption for an autonomous heating system is 1000–4000 m3/hour;
- the pressure in the system should be 150 Pa;
- hot air boiler power (depending on model and type);
- the amount of heat loss in residential premises.
Calculations are carried out in order to achieve the maximum possible effect from a working heating system. Lack of accurate calculations can lead to the following negative consequences:
- heater overheating:
- duct vibration, additional technical noise;
- constant drafts inside the building.
The length of the main air duct should not exceed 30 m. Branches should not be longer than 15 meters. For the operation of a home heating system, solid fuel air boilers with a capacity of 10–50 kW are sufficient. Large premises with extensive interior space require the installation of units of much higher power (up to 1 MW). Large industrial buildings, shopping centers and premises of social and urban infrastructure, as a rule, are heated by high-capacity air solid fuel devices (up to 5–10 MW).
Important! When choosing a model, ranging from the simplest (Bulleryan type) to the most complex and powerful pyrolysis-type units, it is necessary to provide a mechanism for adjusting the intensity of fuel combustion.
Existing automatic damper movement systems will allow you to significantly increase the safety of boiler equipment and reduce the likelihood of excessive fuel consumption.
Solid fuel boilers are again becoming of interest to a wide range of consumers. The main advantage that they have, efficiency and simple operation, are the main trump cards of such equipment. For private and country houses today it is much easier to equip an air heating system. The absence of complex additional mechanisms and devices, convenient adjustment by processes, makes such units very convenient and practical in operation.
Air heating units, unlike hot water boilers, have an order of magnitude longer service life. In terms of security, this technique seems to be preferable.