For the purpose of high-quality cleaning of air masses in rooms, as well as maintaining the microclimate by heating or cooling, mechanical ventilation is used. Industrial premises use industrial fans.
The movement of air flows can be carried out by stretching or forcing. An industrial axial exhaust fan can also be installed in cafes, offices, warehouses and other large rooms.
Device
The device includes the following elements:
- screw and blades (impeller);
- axis;
- housing;
- electric motor for rotation of the impeller.
How does a fan work?
The engine is selected for the required number of fan revolutions. It transfers the energy of rotation of the axis with the impeller installed on it, which moves the air mass in the axial direction with the blades. The minimum dimensions of the blades are several tens of centimeters for household models, and the maximum - a few meters for industrial ones. Axial fans create low air pressure.
The impeller is made of plastic, aluminum alloys or stainless steel. Due to the small weight of the blades does not require large engine power. Even for industrial fans, it usually does not exceed 800 watts.
Types of axial fans
Axial fans for exhaust ventilation are primarily classified by purpose.
- Wall mounted . Are placed inside or at the exit of ventilation shafts. Improved aerodynamic properties of the devices are achieved by installing a diffuser at the output.
- Ceiling . The impeller is mounted on a long axis and produces air circulation in the room.
- Roof Devices are installed on the roof. These also include smoke exhaust fans.
- Panel or grille. Mounted on a window pane or wall with a ventilation hole. Provide quick extraction or filling the premises with fresh air at low energy consumption.
- Floor standing . Devices are household appliances for heating or cooling air.
- Household . Fans are built into household appliances (cooling computer parts, cooling a car engine, supplying a stream of hot air from a hair dryer, etc.).
- Case . Low-noise, low-power models are used to circulate air in rooms or to cool electrical appliances.
- Exhaust . Devices intensively suck in air, but blow out weakly.
- Forcing . They blow out air intensively, but they suck it weakly.
According to the methods of operation and the composition of the transported media, the fans are as follows: general purpose, for smoke removal, resistant to corrosion or elevated temperature, explosion-proof execution.
Advantages
Axial fans are widespread due to the following advantages:
- low noise, which provides the structure of the blades;
- compactness;
- reliability and low price;
- profitability;
- simplicity of construction and repair.
The axial exhaust fan is high-speed and pumps air more than centrifugal, but the pressure drop is lower.
disadvantages
The disadvantage is the small air pressure generated by the fan. The design is also sensitive to axial thrust. For high loads, the blades are made of metal or reinforced plastic.
Duct fans for hoods
The duct axial exhaust fan is selected according to several parameters. First of all, it depends on the purpose for which it should be applied. The shape of the case and the ventilation duct in which it is placed must be the same.
They are round, square and rectangular. The former are suitable for household models, the rest are suitable for industrial applications. For a square cross-section of the channel, a round case is quite suitable if it is mounted on a suitable lattice.
Cases of fans are made of plastic (household models) and metal (industrial). Preference is given to materials that have reliable protection against corrosion, since air is constantly moisture and ventilation systems always have condensation.
The main indicator is productivity - how much air is able to draw the device per unit of time. The household model is designed for productivity up to 350 m 3 / h, and the industrial one - up to 17 thousand cubic meters.
The flow rate of the transported medium depends on the diameter and shape of the blades. The larger their front bend, the more air the fan is able to let through, but the noise level increases. Blades with a back bend work almost silently and economically. The noise level of duct fans is not higher than 40 dB.
Fan performance depends on the volume of the room and the required frequency of updating air in it.
The duct fan can be installed anywhere. No connecting flanges or reducers are needed here. Connection to the box is made using worm clamps. Typically, the fan is mounted on the inlet of the duct. This makes it easier to maintain. The case is attached to the ventilation duct with a snug fit, which reduces losses during operation of the device. Fans are designed to take air in certain areas, after which the air flow is collected in one duct. This is important for removing contaminated air generated in the workplace.
The industrial axial exhaust fan has a working area protection with the help of blinds equipped with a manual or automatic drive. During operation, they open, and after turning off the engine, they close.
Check valves for ventilation
In order to prevent extraneous odors from outside through the ventilation duct during reverse draft, a non-return valve is installed in it. This blocks the movement of air flow in the opposite direction.
The axial exhaust fan with non-return valve operates in such a way that air flows in only one direction. As soon as it reverses, the channel overlaps. The locking device may be a grill (blinds), butterfly, petal or membrane.
Lattices are installed at the entrance or exit of the channel and have a different shape. The butterfly valve consists of two spring-bound plates. The petal, or membrane, is a flap that rotates on an axis that blocks or opens the channel, depending on which side the air stream is moving.
Window axial fans
Exhaust axial window fans are installed directly in the window or window opening, due to their small size and light weight. The devices are used in industrial and domestic premises, offices, canteens, etc.
To prevent cold air from entering the room, the exhaust fan is equipped with a check valve in the form of shutters that close when the draft in the ventilation duct changes to the opposite.
For a home kitchen, a fan with a power supply of 220 V is suitable. In industrial systems, a three-phase voltage of 380 V is used.
Supply and exhaust fans
It is advantageous to use axial supply and exhaust fans of a reversible type. Depending on the direction of rotation of the blades, dirty air is removed from the room or fresh air is pumped.
The non-return valve will not work here, but you can install blinds that will close when the fan is not working.
For supply devices, it is necessary to provide electric heating of the forced air. Supply fans in the rooms should provide 1-1.5-fold air exchange per hour. For the kitchen, the performance of the equipment should provide a 6-12-fold air exchange when cooking is done. If there is no fresh air in it, the exhaust fan will rotate without distilling the air masses. Therefore, the ventilation of the room is ensured by opening a window or door to the room. When plastic windows are installed, micro-ventilation devices should be provided.
Conclusion
Axial fans are widespread due to their low noise level and high performance. For domestic premises, it is advisable to install an axial exhaust fan in the ventilation duct or in the window opening. For a window, a supply and exhaust device of a reversible type is well suited.