A reliable centrifugal fan is considered one of the simplest and most convenient devices for pumping the required amount of air mass in autonomous mode. It is divided into several types according to degrees of pressure and type of construction. Before buying such a device, it is worthwhile to study in advance its characteristics, specification and principle of operation, as well as possible advantages and disadvantages.
Design features and specification
The radial centrifugal fan is a pumping mechanism for generating pressure in a different range. Devices of this type are used in ventilation systems of industrial, municipal and commercial buildings in order to supply clean air and eliminate hazardous volatile components. They have the most simple structure, which includes a spiral-shaped casing, an impeller, blades, and an engine. The internal mechanism of the fan is set in motion by an electric motor or an element responsible for the rotation of the shaft with the impeller. Devices in this category can be installed in rooms where certain conditions are met:
- maintaining the temperature at a level not exceeding 80 degrees;
- the content of mechanical components in the air is not more than 1 g / m3;
- absence of fibrous particles and sticky substances in the thick of the air mass.
The rotary centrifugal fan is suitable for ventilation and heating systems of individual and multi-storey buildings, filtering agricultural devices, delivery and purification of air in non-residential buildings. In addition, blowers are used in fire extinguishing systems and for the rapid replacement of air masses in confined spaces. Models with wheels, the blades of which are bent back, are considered more economical, since they consume much less electricity and quickly cope with system overloads.
Before buying, it is worth knowing in advance what a centrifugal fan consists of in order to eliminate possible malfunctions in time if necessary and prevent an accident.
Principle of operation
Fans of this type are available in two versions: with a radial or axial inlet for air intake. At the initial stage, air masses come out to the surface of the rotating impeller. Further, the impeller blades divide them and transfer them into the standard chamber, where the air masses are compressed. At the next stage, the process of pumping flows in the chamber starts and the gas pressure rises.
The final cycle of the fan operation includes the discharge of the compressed gas substance to the outlet opening, after which the air begins to flow into the central air duct and move in a predetermined direction. During vacuum, the air mass moves from the pipeline or from the enclosed space and then is discharged into the environment or an additional room.
Types of centrifugal fans
The principle of operation and the device of the fan directly depend on its type. Taking into account the direction of movement of air masses, such devices can be exhaust or equipped with a suction function from both sides.They are also delimited by the direction of rotation, which is left or right. The main criterion is the amount of air pressure inside the structure.
Low pressure
Low pressure is considered to be up to 1000 Pa, such fans have a continuous spectrum of noise level, consisting of vortex and border noise. They are divided into two categories depending on the speed of rotation of the main wheel, which is less than 30 m / s for the first class and 30-50 m / s for the second class.
Medium pressure
Medium-type devices create air flows with a pressure in the range of 1000-3000 Pa. They are installed in heating and ventilation systems designed for large rooms for various purposes. These fans are equipped with inlets with a smaller diameter and number of blades compared to their low pressure counterparts.
High pressure
Such devices are capable of creating an air flow pressure exceeding 3000 Pa, and are used for installation in systems for ventilation of premises with a large area, including warehouses, production and trade. They are also used to dispense air masses into drying ovens, during the installation of pneumatic cargo handling systems and for other needs.
Constructive designs
The standard exhaust centrifugal fan can be floor-standing or table-top, depending on the design. Variants of the first type are designed for large rooms, they are more often used in production. Desktop models are more compact and easier to maintain, in addition, they do not cause problems during the installation process. Ventilation devices also differ in the direction of motion of stationary wheels, right-handed rotate clockwise, left-handed in the opposite direction. The wheels can be secured in various ways and started with an electric motor or V-belt drive.
Selection rules
Experts recommend choosing models that require less energy and have the highest efficiency at the operating point. The device is selected according to a special schedule, giving preference to the options that are closest to the specified parameters. On such a diagram, the operating mode or point is determined, taking into account the intersection of this point with a straight line of equal efficiency, this selection method is the main one.
At the point, the limiting calculations of the ventilation network are also made, in which the tolerances for the full pressure are taken into account. When choosing a centrifugal device, one should take into account aerodynamic, noise and other options that are present in general type fans. The best option would be a modern soundproofing model, complemented by an extractor hood and a cooling system.
Before purchasing a device, you need to know in advance in what environment it will work. Conventional devices can operate at air temperatures up to 80 degrees, in an air mass that does not contain chemically active substances. For use in harsh conditions, centrifugal asynchronous fans are used, the purpose and design of which allows them to cope with polluted air.
Advantages and disadvantages
Centrifugal devices differ from their counterparts in a high level of performance, allowing them to quickly and efficiently cool air in rooms. These models are completely safe and comfortable due to the downward air flow, which makes them the ideal choice for production needs. The optimal ratio of price and quality makes it possible to use them in everyday life, choosing the right model for a specific interior design and individual needs. The list of the main advantages of centrifugal devices includes:
- compact dimensions;
- a small number of starting currents;
- the ability to adjust performance;
- protection against excessive loads.
There are practically no downsides to centrifugal devices. Some users note a higher noise level of centrifugal fans, especially duct and kitchen fans, compared to similar devices.
