Air Flow Measurement in a fan system


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When designing AC or DC fan systems, it is sometimes critical to know how much airflow your fan is actually generating.

Airflow measurements are often made using a unit called “CFM” (Cubic Feet per Minute) . CFM indicates a certain volume of air that a fan will move in one minute. This parameter is often used to describe the total capacity of heating, ventilation and air conditioning systems.

  • Here is a simple formula to estimate CFM in the application
    CFM = Internal volume of the application (Length X Width X Height, in cubic feet) / 60 minutes

To design a fan system using CFM specifications of a particular fan, you can estimate how many times the air will be fully circulated, or “turned over” in 1 minute.

Please note that each cooling applications requires different levels of air circulation. For examples, in a cramped server room with a lot of heat-generating equipment, it may require to turn the air over 10 time per minute. But in the bathroom, it may only be require to “keep the air moving” with one full turn-over per minute.