1. What is Duct Diameter Calculation?

The duct diameter calculation determines the appropriate size of air ducts in HVAC systems based on flow rate and air velocity. Proper duct sizing is essential for efficient airflow, energy conservation, and optimal system performance.

2. How Does the Calculator Work?

The calculator uses the duct diameter formula:

Where:

• \( D \) — Duct diameter (m)
• \( Q \) — Flow rate (m³/s)
• \( v \) — Air velocity (m/s)
• \( \pi \) — Mathematical constant (3.1416)

Explanation: This formula calculates the minimum duct diameter required to handle a specific airflow rate at a given velocity, ensuring efficient system operation.

3. Importance of Proper Duct Sizing

Details: Correct duct sizing prevents energy waste, reduces noise, maintains proper air pressure, and ensures even temperature distribution throughout the building. Undersized ducts increase resistance and energy consumption, while oversized ducts can lead to poor airflow and temperature stratification.

4. Using the Calculator

Tips: Enter flow rate in cubic meters per second (m³/s) and air velocity in meters per second (m/s). Both values must be positive numbers. Typical air velocities range from 2-8 m/s for low-pressure systems and 6-15 m/s for high-pressure systems.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical air velocity range for HVAC ducts?
A: For residential systems: 2-4 m/s, for commercial systems: 4-8 m/s, and for industrial systems: 8-15 m/s, depending on application and noise requirements.

Q2: How does duct diameter affect system performance?
A: Larger diameters reduce air velocity and pressure drop, lowering energy consumption but requiring more space. Smaller diameters increase velocity and noise but save space.

Q3: What are common flow rate units and conversions?
A: Common units include m³/s, L/s, CFM (cubic feet per minute). 1 m³/s = 1000 L/s = 2118.88 CFM.

Q4: When should rectangular ducts be used instead of circular?
A: Rectangular ducts are preferred when space constraints exist, particularly in ceiling cavities. However, circular ducts are more efficient for airflow and easier to seal.

Q5: How does duct material affect sizing calculations?
A: Different materials have varying roughness coefficients that affect friction loss. Smooth materials (like sheet metal) allow smaller diameters, while rough materials (like flexible duct) may require larger diameters for equivalent performance.