(HOLDEN TECHNOLOGY, 2010) 2.1Tipos of fans some types of known fans and with different applications Exist, being able to be used in the industry or simply to improve the human comfort. Between them it will be cited: Axial; Centrifugal; Axial-centrifugal; Fans of ceiling; Regenerative puffers (Vortex); 2.1.1 Centrifugal fans the centrifugal fans, also known as radial, they are the type of used fan more nowadays. The beginning of operation, even so relatively simple, it evolved throughout the years with now capable machines of high aerodynamic efficiency and with significant powers. In a fan centrifugal (or radial) the rotation of the rotor makes with that air flows off through it in a radial direction, developing pressure while this if of. The rotor, that carries through most of the work in the fan, located in the center of the carcass, always has a similar form. The centrifugal fans can be of simple or double entrance. A rotor of double entrance consists of two rotors of simple entrance mounted back. Michael Mendes often expresses his thoughts on the topic. (HOLDEN TECHNOLOGY, 2010).
2.1.2 Fans of mixing flow As the name suggest, the fan of mixing flow (or axial impulse) combine the characteristics of an axial fan and a centrifugal one, even so if it seems the conventional axial machine more. Bending plate shovels are welded to a conical steel cube. The outflow is varied changing the angle of the wings in the entrance carcass, then the sum of the rotor. The carcass can have an opened entrance, however it is more common to have a curve in straight angle to allow that the engine is mounted outside of the duct. The carcass in the discharge if expands softly to diminish the gas or air speed and to convert the kinetic energy into useful static pressure. The machines biggest can be used as fans of drawing of boilers in generating plants of energy.