Air Duct Sizing - SI & Imperial Units
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Air Duct Sizing - SI & Imperial Units
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This spreadsheet template can be helpful when calculating dimensions and pressure loss in air duct systems.
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- Equal Friction Method
https://www.engineeringtoolbox.com/equal-friction-method-d_1028.html
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- Velocity Method
https://www.engineeringtoolbox.com/sizing-ducts-d_207.html
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How to use:
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1. Use "File" menu above to make your own editable copy of this document. You are free to use the copy as you want!
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2. Select the table with the units you want to use - delete the lines with the other table
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3. Make a simplified sketch for the system you want to calculate
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4. Add the sections to the table - insert new lines by selecting similar lines - right click and copy the lines - right click and insert the lines above/below where you want it - paste in the copied line
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5. Add volume flows for terminals - add sumarized formulas for the volume flows in the main sections
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6. Add duct diameters
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7. Add sumarized minor dynamic loss coefficients for each seaction
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8. Add the pressure loss paths from node 0 to the end of all terminals - connect the pressure drops in each section - summarize the pressure drops for each path
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9. Evaluate the velocities and pressure losses for each section and for the total system to your criteria - modify duct sizes if necessary
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10. Add pressure loss in dampers to balance the system - the total pressure drop for all paths should be close
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Project:
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Date:
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SI - Units
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Air density:
1.2(kg/m3)
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SectionLength (m)Airflow (m3/s)Diameter (mm)Velocity (m/s)Friction Loss (Pa/m)Friction Loss Section (Pa)Minor Dynamic Loss Coeff. (ξ)Minor Dynamic Loss Section (Pa)Pressure Loss Damper (Pa)Total Pressure Loss (Pa)Pressure Loss Path 0-1-2 (Pa)Pressure Loss Path 0-1-3-4 (Pa)Pressure Loss Path 0-1-3 5 (Pa)
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0-12038006.00.4592.65665656565
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1-22015005.10.59121.320185050
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1-31028004.00.212110121212
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3-41015005.10.5962313737
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3-51515005.10.5992314040
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115113116
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Imperial - Units
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SectionLength (ft)Airflow (cfm)Diameter (in)Velocity (ft/min)Friction Loss (in H2O/ft)Friction Loss Section (in H2O)Minor Dynamic Loss Coeff. (ξ)Minor Dynamic Loss Section (in H2O)Pressure Loss Damper (in H2O)Total Pressure Loss (in H2O)Pressure Loss Path 0-1-2 (in H2O)Pressure Loss Path 0-1-3-4 (in H2O)Pressure Loss Path 0-1-3 5 (in H2O)
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0-16663603012960.0007070.0472.60.270.320.320.320.32
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1-2662120209720.0006710.0441.30.080.090.210.21
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1-3334240308640.0003270.01110.050.060.060.06
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3-4332120209720.0006710.02220.120.140.14
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3-5502120209720.0006710.03420.120.150.15
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0.530.520.53
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