S21 -- Fans (SI)

A fan uses a power-driven rotating impeller to move air. The impeller does work on the air, imparting to it both static and kinetic energy, which vary in proportion, depending on the fan type. This chapter discusses types of fans used in HVAC design and the underlying principles of their use. Types of Fans Principles of Operation Testing and Rating Field Testing of Fans for Air Performance Fan Laws Fan and System Pressure Relationships Air Temperature Rise Across Fans Duct System Characteristics System Effects Selection Parallel Fan Operation Series Fan Operation Noise Vibration Arrangement and Installation Fan Control Fan Inlet Cone Instrumented for Airflow Measurement Fan Terminology Symbols