Complex HVAC systems are designed with many factors in mind. Subsequent installation requires special attention: air ducts, heaters, silencers, diffusers, grilles and valves must be in place, and fans and air conditioners must have the appropriate capacity.
A fan, centrifugal or axial, can generally be called the heart of the system, because it is he who pushes the air through the vessels of the system - air ducts in the right direction. Despite the fact that such units are necessary to perform the same function - forced air movement, each of them has a special design.
Centrifugal fan. Device, principle of operation and distinctive features
This equipment consists of an impeller, which is mounted on a special shaft, an inlet and outlet pipe and a volute casing. Air (displaced gas) is sucked in by the collector and, getting into the fan housing, is captured by the blades of the rotating wheel. Thus, the direction of the air flow (gas) itself changes: from a straight line, parallel to the axis, it becomes radial. Further, the acting centrifugal force pushes the air through a special hole in the casing.
Such features of the operation of this unit became the reason for its name - a centrifugal fan, also known as a radial fan. Another "nickname" - a snail - this equipment received due to its spiral body.
The rotation of the impeller in such a fan can be right or left. The number of blades affects the type and purpose of the equipment. There is one more nuance: in which direction the blades themselves are bent (forward or backward) - this in some cases is of fundamental importance. For example, a centrifugal fan equipped with backward-curved blades saves up to 20% of electricity, and air flow overloads are permissible during its operation.
Forward-curved blades, in turn, make it possible to reduce the diameter of the wheel to which they are attached, and, accordingly, the fan itself can be more compact. Another plus: the speed is lower, and the noise level is reduced.
The centrifugal fan can be used in the installation of forced exhaust systems for canteens and laundries, in the metallurgical and chemical industries, at oil refineries. At the same time, it should be taken into account that if it is planned to move relatively clean, not polluted air, then it is enough"snail" made of carbon steel. In cases where explosive gases are present, equipment with a casing made of aluminum alloy or cast iron is used. In enterprises where there is a need to remove air containing impurities of gases or aggressive vapors, it is recommended to install special fans. Their distinguishing feature is that the internal part through which dangerous air will flow (impeller with blades, casing, shaft) are made of acid-resistant alloys of steel, plastic and aluminum. It is obvious that if the ventilation device requires specific equipment, in particular a centrifugal fan, the price for it will be higher than for a standard carbon steel one.
