What Is CFM?
CFM stands for cubic feet per minute. CFM is a volumetric unit of flow. CFM represents the maximum amount of air that a fan can move at maximum speed and without any restrictions. CFM is related to the fan’s motor (rotational speed), blade length, blade pitch and shape.
A fan is a device used to create airflow. A fan consists of a motor that provides the motion and a blade assembly that creates the airflow. The majority of fans are powered by electric motors, but there are also types powered by different power sources.
Fans are commonly used for cooling electronic devices and ventilation systems.
Although fans are thought to cool the air, they do not actually have the ability to cool the air. Fans only provide air flow.
CFM stands for cubic feet per minute. CFM is a volumetric unit of flow. CFM represents the maximum amount of air that a fan can move at maximum speed and without any restrictions.
CFM is related to the fan’s motor (rotational speed), blade length, blade pitch and shape. The larger the blade length and pitch, the more air the fan moves every minute. This results in a high CFM.
As the size of the fans increases, the airflow also increases. For example, a 12 cm wide high-performance computer fan can deliver an airflow of up to 85 CFM. Increasing the fan width to 14 cm increases the airflow to over 110 CFM.
To measure the amount of airflow, it is first necessary to measure the speed of the air. A measuring device called an anemometer is used to determine the air velocity. The air velocity is multiplied by the cross-sectional area of the fan duct to get the air flow.
Air flow (CFM) = Air velocity (FPM) * Cross-sectional area
CFM is measured when the fan is running at its highest speed. Fan manufacturers measure the speed, airflow and noise level of the fans separately for each model and write them in the technical file of the product.
According to the International System of Units (SI), which is accepted in many countries around the world, volumetric flow rate is expressed in cubic meters per hour (m³/h). The SI unit is easily converted to CFM. One m³/h is approximately 0.589 CFM and one CFM is approximately equal to 1.699 m³/h.
CFM = 0.589 * m³/h
m³/h = 1,699 * CFM
Fans produce some noise due to the fast airflow around the blades. High airflow means high noise. Therefore, it is not correct to choose high CFM in all cases. To avoid fan noise, a fan should be selected according to the airflow requirement or high-capacity fans should be properly throttled.