1. What is the CFM Equation for Air Flow?

Definition: This calculator determines the volumetric flow rate of air in cubic feet per minute (CFM) based on velocity and cross-sectional area.

Purpose: It's essential for HVAC system design, ventilation calculations, and airflow analysis in various engineering applications.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Q_{cfm} \) — Air flow rate (cubic feet per minute)
• \( V \) — Velocity of air (feet per second)
• \( A \) — Cross-sectional area (square feet)
• 60 — Conversion factor (seconds to minutes)

Explanation: The velocity multiplied by area gives flow per second, which is then converted to minutes.

3. Importance of Air Flow Calculation

Details: Proper airflow calculation ensures adequate ventilation, efficient HVAC system operation, and compliance with building codes.

4. Using the Calculator

Tips: Enter the air velocity in ft/s and cross-sectional area in ft². Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What's a typical air velocity for ventilation?
A: Typically 500-900 ft/min (8-15 ft/s) for main ducts, lower for branch ducts.

Q2: How do I measure duct area?
A: For round ducts: \( A = \pi r^2 \). For rectangular ducts: \( A = width \times height \).

Q3: Why convert to CFM?
A: CFM is the standard unit for airflow measurement in HVAC systems.

Q4: What if my velocity is in ft/min?
A: Divide by 60 first (1 ft/s = 60 ft/min) or adjust the formula by removing the ×60 factor.

Q5: Does this account for pressure changes?
A: No, this is for ideal conditions. Actual systems require additional calculations for pressure drops.