Duct Air Flow Calculation Formula

Air Flow Rate Formula:

\[ Q = A \times v \]

Air Flow Rate (Q):

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1. What is the Duct Air Flow Calculation Formula?

The duct air flow calculation formula (Q = A × v) calculates the volumetric flow rate of air through a duct system. This fundamental equation is essential for HVAC design, ventilation systems, and airflow analysis in various engineering applications.

2. How Does the Calculator Work?

The calculator uses the air flow rate formula:

\[ Q = A \times v \]

Where:

\( Q \) — Air flow rate (m³/s)
\( A \) — Cross-sectional area of duct (m²)
\( v \) — Air velocity through duct (m/s)

Explanation: The formula calculates the volume of air passing through a duct per unit time by multiplying the duct's cross-sectional area by the average air velocity.

3. Importance of Air Flow Rate Calculation

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

4. Using the Calculator

Tips: Enter cross-sectional area in square meters (m²) and air velocity in meters per second (m/s). Both values must be positive numbers greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical air velocity in HVAC ducts?
A: Typical velocities range from 2-8 m/s for low-pressure systems and up to 15 m/s for high-pressure systems, depending on application and noise considerations.

Q2: How do I calculate duct cross-sectional area?
A: For rectangular ducts: A = width × height. For circular ducts: A = π × (diameter/2)².

Q3: Why is air flow rate important in HVAC design?
A: Proper airflow ensures adequate heating/cooling capacity, maintains pressure balance, prevents moisture issues, and ensures occupant comfort and health.

Q4: What factors affect air velocity in ducts?
A: Fan capacity, duct size and shape, system pressure, duct material roughness, and number of bends/fittings all influence air velocity.

Q5: Can this formula be used for liquids?
A: Yes, the same principle applies to incompressible fluids, though additional factors like fluid density and viscosity may need consideration for precise calculations.