Mechanical Insulation Design Guide
Calculates the Temperature Change of Air Flowing in a Duct (Reference: 2009 ASHRAE HoF, Chapter 4, Equation 48, (pg 4.21))
This calculator estimates the temperature drop (or rise) of air flowing in a duct.
(Input information may generally be be obtained from design documents or field measurements)
- Line 1. Enter the temperature of the air entering the duct
- Line 2. Enter the ambient temperature (the average temperature of the air surrounding the duct)
- Line 3. Enter the flow rate of the air carried by the duct in cubic feet per minute
- Line 4. Enter the length of the duct run in feet
- Line 5. Enter the perimeter of the duct in inches
- Line 6. Enter the R-value of the selected duct insulation. Available R-values will vary depending on insulation products selected.
Note: NA = Insulation Size Not Available. Some sizes and thicknesses may not be commercially available.
- One dimensional, steady state heat transfer
- Specific heat of air assumed constant at 0.24 Btu/(lbm·°F)
- U-factor of duct walls assumed constant
- Air film resistances (inner + outer) assumed constant at 0.85 h·ft2·°F/Btu
- The impact of duct leakage is neglected