1. What is Equivalent Diameter of Duct?

The equivalent diameter of a rectangular duct is the diameter of a circular duct that would have the same pressure drop and flow characteristics as the rectangular duct when the air velocity is the same. This concept is crucial in HVAC system design for comparing different duct shapes.

2. How Does the Calculator Work?

The calculator uses the equivalent diameter formula:

Where:

• \( D_e \) — Equivalent diameter (m)
• \( a \) — Longer side of rectangular duct (m)
• \( b \) — Shorter side of rectangular duct (m)

Explanation: This formula provides the diameter of a circular duct that would offer the same hydraulic performance as the given rectangular duct when air velocity remains constant.

3. Importance of Equivalent Diameter Calculation

Details: Calculating equivalent diameter is essential for HVAC system design, allowing engineers to compare different duct shapes, optimize airflow, reduce pressure losses, and ensure efficient system performance while maintaining the same air velocity characteristics.

4. Using the Calculator

Tips: Enter both longer and shorter side dimensions in meters. Ensure values are positive and represent actual duct dimensions. The calculator will provide the equivalent circular diameter that maintains the same air velocity performance.

5. Frequently Asked Questions (FAQ)

Q1: Why use equivalent diameter instead of actual dimensions?
A: Equivalent diameter allows comparison between different duct shapes and helps in standardizing calculations for pressure drop, flow rates, and system design across various duct configurations.

Q2: When is this calculation most useful?
A: This calculation is particularly useful in HVAC system design, ventilation engineering, and airflow optimization where rectangular ducts need to be compared with or converted to equivalent circular ducts.

Q3: Does this formula account for all flow characteristics?
A: This formula provides equivalent diameter for the same velocity conditions. For complete hydraulic equivalence, additional factors like Reynolds number and surface roughness may need consideration.

Q4: Can this be used for very large or very small ducts?
A: Yes, the formula works for all sizes as long as the dimensions are accurately measured and the duct maintains a rectangular cross-section.

Q5: How accurate is this equivalent diameter calculation?
A: The calculation is mathematically precise for the given formula. However, actual system performance may vary slightly due to factors like duct material, bends, and fittings.