According to the equal friction chart, what is the velocity in a 20" diameter pipe that delivers 2000 CFM?

In determining the velocity of air in a duct based on the equal friction method, one must consider the diameter of the duct and the volume of air being conveyed. For a 20-inch diameter pipe carrying 2000 CFM, using the equal friction chart is essential for finding the specific velocity.

The correct choice indicates that the velocity calculated for air flowing through a 20-inch duct at 2000 CFM is 900 feet per minute. This figure is derived from the principles of fluid dynamics and duct design, which indicate that as the cross-sectional area of the duct increases (as it does with a 20-inch diameter), the velocity of the air must adjust to accommodate the flow rate.

When applying the equal friction principle, one can reference charts or calculators that map out the velocity of air based on both the duct size and the cubic feet per minute (CFM) being delivered. For a 20-inch duct, this specific CFM value aligns with a calculated velocity of approximately 900 feet per minute.

This understanding is crucial for maintaining efficient airflow, ensuring that the ventilation system operates effectively while minimizing pressure losses and noise. Achieving the right velocity also helps with compliance with building codes and standards for HVAC systems.