1. What is Air Flow Rate?

Air flow rate (Q) measures the volume of air moving through a given cross-sectional area per unit time, typically expressed in cubic feet per minute (CFM). It's essential for HVAC system design, ventilation planning, and industrial applications.

2. How Does the Calculator Work?

The calculator uses the air flow rate formula:

Where:

• \( Q \) — Air flow rate (ft³/min)
• \( Area \) — Cross-sectional area (ft²)
• \( Velocity \) — Air velocity (fpm)

Explanation: The formula calculates the volume of air passing through a duct or opening by multiplying the cross-sectional area by the air velocity and converting to per-minute units.

3. Importance of Air Flow Rate Calculation

Details: Accurate air flow rate calculation is crucial for proper ventilation system design, ensuring adequate air exchange, maintaining indoor air quality, and optimizing energy efficiency in HVAC systems.

4. Using the Calculator

Tips: Enter area in square feet (ft²) and velocity in feet per minute (fpm). Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between CFM and ACH?
A: CFM (cubic feet per minute) measures volume flow rate, while ACH (air changes per hour) measures how many times the air in a space is replaced per hour.

Q2: What are typical air flow rates for residential HVAC?
A: Typical residential systems range from 400-2000 CFM depending on the size of the home and system capacity.

Q3: How do I measure air velocity accurately?
A: Use an anemometer at multiple points across the duct cross-section and calculate the average velocity for best accuracy.

Q4: Can this formula be used for round ducts?
A: Yes, for round ducts, calculate area using \( Area = \pi \times r^2 \) where r is the radius in feet.

Q5: What factors affect air flow rate?
A: Duct size, shape, length, bends, filters, and fan capacity all influence the actual air flow rate in a system.