1. What is a Velocity of Air Flow Calculator?

Definition: This calculator determines the velocity of air flow through a duct or pipe based on the flow rate and cross-sectional area.

Purpose: It helps HVAC professionals, engineers, and technicians design and analyze air distribution systems.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( V \) — Air velocity (feet per second)
• \( Q \) — Flow rate (gallons per minute)
• \( A \) — Cross-sectional area (square feet)
• 448.83 — Conversion factor (GPM to ft³/s)

Explanation: The flow rate is converted from GPM to cubic feet per second, then divided by the cross-sectional area to determine velocity.

3. Importance of Air Velocity Calculation

Details: Proper air velocity ensures efficient system operation, prevents excessive noise, and maintains proper air distribution.

4. Using the Calculator

Tips: Enter the flow rate in GPM and the cross-sectional area in square feet. Both values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What is a typical air velocity in HVAC systems?
A: Typically 600-900 ft/min (10-15 ft/s) in main ducts, 400-600 ft/min in branch ducts.

Q2: Why is 448.83 used in the formula?
A: It converts GPM to ft³/s (1 GPM = 0.002228 ft³/s, inverse is 448.83).

Q3: How do I measure cross-sectional area?
A: For round ducts: A = π × (diameter/2)². For rectangular ducts: A = width × height.

Q4: What if I have CFM instead of GPM?
A: For CFM, use V = Q/A where Q is in ft³/min and A is in ft² (no conversion factor needed).

Q5: What velocity is too high for air ducts?
A: Generally above 1500 ft/min (25 ft/s) causes excessive noise and pressure drop.