Airflow

When engineers choose a cooling fan, the number they usually look at first is maximum airflow. It is also, surprisingly often, the number that leads them astray. In a real enclosure — behind fins, filters, and perforated panels — the airflow a fan actually delivers can be far below its catalog value. The key to avoiding this gap is understanding three things: airflow, static pressure, and the PQ curve that connects them. 1. Airflow: The Ceiling of Cooling Capacity Airflow is the volume of gas moved through the fan per unit of time, typically expressed in CFM (cubic feet per minute) or CMM (cubic meters per minute). As a first approximation, more airflow means more heat carried away per second. This follows directly from the heat-transfer relationship: Q = ρ · cp &mid...