Introduction of topic -
A fan is a power driven rotary machine which causes a continuous flow of air. A fan has a rotating bladed impeller. The blades exert force on air, raising its pressure and maintaining a continuous flow. Since the primary function of the fan is to provide a continuous flow of air, this first article will be devoted to an understanding of air in motion. In HVAC applications, air is moved from one place to another in a system of ducts which may contain other system elements such as filters, coils, dampers and diffusers. Air moving inside a ducted system has a certain amount of pressure associated with it. This pressure can be divided into two types – Static and Velocity.