- Design features and types of
Fresh air saturated with oxygen is what is commonly called a “healthy atmosphere” - a prerequisite for comfortable and cozy accommodation. But the features of the layout of modern homes, the installation of plastic windows make insufficient amount of natural ventilation. But modern apartments, with their abundance of plastic and chemicals, especially need regular air exchange. Installing a forced ventilation system solves the problem of air circulation. The fan is the main component of these systems. Let us consider in more detail what are the devices, the features of their design and operation.
Design features and types of
A fan is a mechanical device intended for feeding, withdrawing and mixing air masses. Air circulation is formed by creating a pressure difference that occurs between the outlet and inlet channels of the ventilation unit. Such equipment is classified by purpose, location and methods of installation, performance, technical features. The most common method of grouping - on the basis of, or device. There are five types of fans.
Axial( also called axial) models are widely spread due to their simple and robust design:
- main element is a cylindrical body / casing, which has special mounting holes for mounting the fan;
- wheel with blades - the blades are rigidly fixed, the selection of the distance and angle of rotation of the blades allows you to adjust the pressure and speed of the air flow;
- drive - the electric motor is built into the device itself, provides rotation of the wheel with blades;
- manifolds, fairings and diffusers - improve the aerodynamic characteristics of the model and its performance, reduce hydraulic losses.
The principle of the axial fan - blades due to rotation capture air and move it through the device. The air flow moves along the axis of rotation of the wheel with blades, and there is practically no movement in the radial direction( i.e., from the center to the edges of the body).
- compact size, so they do not require much space for installation;
- high efficiency, with low power consumption, you can get a dense air flow;
- low price;
- low noise;
- ease of operation, maintenance and repair.
The axial fan can also be used in the reverse direction, but then its efficiency decreases by 40–50%.There is one drawback - the axial type of technology can not create a very powerful air flow, which is necessary in industrial facilities. Therefore, they are most common in everyday life and home ventilation systems, for example, as exhaust in the kitchen or bathroom.
The basis of the radial fan( it is also called centrifugal) is made up of a casing, shaped like a snail, inside of which is placed an impeller. During rotation, a centrifugal force occurs, which draws air through the suction opening in the center of the device. After that, the air mass is sent to the peripheral part of the fan, from where it is forced through the duct into the ventilated room. Another feature is that the air flow enters it axially, and is pushed out by moving radially( its direction is tangential to the casing of the case), it is always perpendicular to the incoming flow.
The main working element is a cylinder with blades fixed at the same distance around the circumference. Depending on the shape and location of the blades, a different effect can be achieved:
- curved forward - they create high pressure and work with large volumes of air;
- curved back - to avoid the accumulation of dust, suitable for work in an environment with high oppression;
- aerodynamic wing - very low noise figure and high performance.
The main advantages of radial fans are high pressure air flow with a fairly small footprint, durability, low noise level and the possibility of continuous operation. Therefore, they are widely used in industry, especially where strong, constant ventilation is needed - in large office buildings and shopping malls, supermarkets, warehouses, garages, etc. With the ability to quickly remove contaminated air, they are actively used in hazardous industries. In everyday life, radial fans are increasingly used in kitchen hoods, duct ventilation.
The design feature of a diagonal fan is a combination of the advantages of axial and radial types of fans. The use of the conical shape of the casing and the impeller of a special form made it possible to increase the speed of movement of air masses. The design of the diagonal model is a compromise solution that optimizes three indicators at once - performance and noise level while maintaining compact dimensions. Diagonal fans are mounted in ventilation systems with extended air ducts.
Diametric( tangential) fan with an elongated body, which has a nozzle and a diffuser. Inside mounted drum impeller. Inclined blades provide double movement of air perpendicular to the axis of rotation. The main advantage is uniform flat and wide airflow. Used in thermal curtains and fan coils.
The design and operation of this type of fan is very different from those discussed above. This is an absolutely safe device, as there are no blades. It is possible to choose the floor option for installation in rooms where children or pets have access.
The air flow in the direct-flow model is formed by a special turbine, which is installed at the base. Through the slots in the base, the turbine pulls in the air, squeezes it strongly and directs it into the frame with very narrow directional slots. The air coming out under pressure, according to the laws of aerodynamics, pulls behind it other adjacent layers of air. In the back zone of the fan, a vacuum zone is formed into which air masses rush. Such a technology of "air multiplication" allows you to get the air flow passing through the frame, which is 15–20 times greater than the volume that is injected by the turbine. The frame can have any shape - from a perfect circle to a very elongated oval, which opens up great opportunities for designers.
Additional advantages over traditional types of equipment:
- the ability to smoothly adjust the intensity of the air flow, its direction - just turn the ring;
- electricity savings - with equal performance with an axial device, the once-through consumes 20% less electricity.
The main disadvantages of a direct-flow fan are the high price and high noise, because the air passes through narrow gaps at a speed of 85–90 km / h.