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Equivalent Length Equation:
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Total Equivalent Length (TEL) is the sum of the actual straight length of duct plus the equivalent lengths of all fittings in the system. It's used to calculate pressure drop in duct systems by converting fittings to equivalent lengths of straight duct.
The calculator uses the TEL equation:
Where:
Explanation: Each type of fitting (elbows, tees, reducers) has an equivalent length value that represents how much straight duct would create the same pressure drop as that fitting.
Details: Accurate TEL calculation is crucial for proper HVAC system design, ensuring adequate fan selection and system performance by accounting for pressure losses in fittings.
Tips: Enter the actual straight duct length and equivalent lengths for up to three fittings. Values must be positive numbers. Refer to engineering tables for fitting equivalent lengths.
Q1: Where can I find equivalent lengths for fittings?
A: Engineering references like ASHRAE Handbook or SMACNA manuals provide standard equivalent lengths for various fitting types and sizes.
Q2: Does duct diameter affect equivalent length?
A: Yes, equivalent lengths are typically given for specific duct diameters. Larger diameters generally have longer equivalent lengths for the same fitting type.
Q3: How accurate is this calculation?
A: It provides a good estimate for standard conditions. For precise calculations, consult detailed engineering data or use specialized software.
Q4: Should I include all fittings in the system?
A: Yes, for accurate results all significant fittings should be included, especially those that create substantial turbulence.
Q5: Can I add more than three fittings?
A: This calculator handles up to three fittings. For more complex systems, sum all fitting equivalent lengths separately and enter the total as one value.