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CFM Formula:
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CFM (Cubic Feet per Minute) is a measurement of airflow volume, indicating how many cubic feet of air pass by a stationary point in one minute. It's commonly used in HVAC systems, ventilation, and air movement applications.
The calculator uses the CFM formula:
Where:
Explanation: This formula calculates the volume of air moving through a given area at a specific velocity over one minute.
Details: Accurate CFM calculation is essential for proper HVAC system design, ventilation requirements, industrial exhaust systems, and ensuring adequate air exchange rates for health and safety standards.
Tips: Enter the cross-sectional area in square feet and air velocity in feet per minute. Both values must be positive numbers greater than zero for accurate calculation.
Q1: What is the difference between CFM and ACH?
A: CFM measures airflow volume, while ACH (Air Changes per Hour) measures how many times the air in a space is replaced per hour. They are related but different metrics.
Q2: What are typical CFM requirements for residential HVAC?
A: Residential systems typically require 400-600 CFM per ton of cooling capacity, but this varies based on system design and building characteristics.
Q3: How do I measure air velocity for CFM calculation?
A: Air velocity can be measured using an anemometer at multiple points across the duct or opening, then averaged for accurate CFM calculation.
Q4: Does duct size affect CFM requirements?
A: Yes, larger ducts can move the same CFM with lower velocity, while smaller ducts require higher velocity to achieve the same CFM, affecting noise and pressure drop.
Q5: When is CFM calculation most important?
A: CFM calculation is critical during HVAC system design, ventilation system sizing, industrial process design, and when meeting building code requirements for air exchange.