HVAC Buddy®

HVAC Buddy® Duct Calc

The best and number one selling duct sizing tool for Android devices with thousands of happy users. For less than the cost of a cardboard wheel ductulator always have a fast, accurate way to analyze ducts for design (by Airflow) or existing installations (by Size).

Airflow Tab
• Calc decimal & rounded sizes for any aspect ratio
• Solve for Volume, Aspect Ratio, Friction, or Velocity

Size Tab
• Calc Friction and Velocity given duct size

Settings Tab:
• Enter various units - Airflow (cfm, m3/s, l/s, m3/hr) Friction (in/100', Pa/30m), Duct Sizing (in, cm), Velocity (ft/min, m/s)
• Define standard air - Altitude (ft, meter), Temperature (Fahrenheit, Celsius), Relative Humidity (pct)
• Displays calculated Kinematic Viscosity (ft2/s) and Specific Volume (ft3/lb)

Material Types:
• Aluminum
• Galvanized Steel
• Spiral Steel
• Smooth Liner
• Fiber Liner
• Flex Duct

Duct Shapes:
• Round
• Rectangular
• Oval

Duct Sizing
• Round to Even Units
• Round to Odd Units

Calculations are based on friction loss equations in the ASHRAE Handbook of Fundamentals 2009.

Review Notes
A 12x12 duct matches FPM and CFM when friction is ignored which does not happen in real life. This relationship changes based on the properties of air (see kinematic viscosity on the settings tab) and on the friction value determined via the type of duct selected. Also, for the times when you want to get friction given CFM and Duct use the "Airflow" tab, select the "ft/min" checkbox and move the slider accordingly. There are many ways to drive the open variable.

Calculations have been verified against ASHRAE fundamentals and several other references. There are more input criteria (such as duct material) than velocity, friction, and size mentioned in the review which the reviewer may not have taken into consideration. Use the Support email link for any questions or concerns.

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