When the motor sheave is changed from 2" to 2.5" in diameter, and the initial CFM is 2100, what is the new CFM after the change?

To determine the new CFM (Cubic Feet per Minute) after changing the motor sheave diameter, we can apply the principle of proportionality related to changes in the sheave diameter. The capacity of the fan, or the airflow it generates, is influenced by the diameter of the sheave.

When the diameter of the motor sheave increases, the fan speed and, consequently, the airflow also increase. The relationship between the diameter of the sheave and the airflow can be approximated using the square of the ratio of the diameters. If the motor sheave diameter is increased from 2 inches to 2.5 inches, the ratio of the new diameter to the initial diameter is ( \frac{2.5}{2} = 1.25 ).

To find the impact on CFM, you can multiply the initial CFM by the square of the ratio of the diameters:

[

\text{New CFM} = \text{Initial CFM} \times \left(\frac{\text{New Sheave Diameter}}{\text{Old Sheave Diameter}}\right)^2

]

Calculating this gives:

[

\text{New CFM} = 2100 \times (1.