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Ductwork Heat Loss or Heat Gain & Condensation Analysis

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1. This computer program calculates the heat loss or heat gain from insulated round or rectangular ductwork. The program also checks for condensation on the inside duct surface and on the outside duct surface. The program will check for condensation at the start of the duct run and at the end of the duct run.

2. When you compare the air flow into the duct, to the air flow leaving the duct you will see the airflow (ACFM) has changed due to a change in the density of the air.. When air flows through a duct it will experience a pressure drop and a temperature change which changes the ACFM flow because of the change in air density. The mass flows (lbs/hour) are not affected by the air pressure change or the temperature change, therefore the mass flows are the same unless there is leakage.

3. Below are 2 examples one for rectangular ductwork and one for a round duct.



Example #1 - Ductwork Heat Gain & Condensation Analysis Computer Program Input Data

1. Duct Size: 12" x 12"

2. Insulation Type & Thickness:
Fiberglass Insulation
Density 6.0 lb/ft3
3 ½ inches thick
450 F max.

3. Insulation Jacket:
Aluminum
0.016 inches thick
Emissivity = 0.11

4. Air Entering The Duct:
Dry Bulb = 55 F
Relative Humidity = 80 %
Air Flow = 2,467.1345 ACFM
Dry air Mass Flow = 11,274.4717 lbs da/hour
Water Vapor Flow = 82.6950 lb w.v./hour

5. Ambient Conditions On The Outside Of The Duct:
Dry Bulb = 90 F
Relative Humidity = 80 %
Air Velocity = 100 ft/min

6. Ductwork:
Aluminum Duct
0.040 inches thick
50 feet long

AMBIENT3.txt
INTODUCT.txt
OUTDUCT.txt

Condensation Analysis of Air Flow Thru Insulated Pipe or Duct (PDF)
Beginning of Duct Run (PDF)
End of Duct Run (PDF)



Example #2 - Ductwork Heat Gain & Condensation Analysis Computer Program Input Data

1. Duct Size:
Round Duct
12.75 inches OD
12.00 inches ID
0.375 inches thick
Galvanized Steel

2. Insulation Type & Thickness:
Fiberglass Insulation
3 ½ inches thick
850 F max.

3. Insulation Jacket:
Aluminum
0.016 inches thick
Emissivity = 0.11

4. Air Entering The Ductwork:
Dry Bulb = 45 F
Relative Humidity = 80 %
Air Flow = 2,012.4127 ACFM
Dry Air Mass Flow = 9,413.0580 lb da/hour
Water Vapor Flow = 47.4084 lb w.v./hour

5. Ambient Conditions on the Outside of the Duct:
Dry Bulb = 90 F
Relative Humidity = 80 %
Air Velocity = 100 ft/min
= 1.1364 mph

AMBIENT.txt
AIRFLOW.txt
OUTDUCT2.txt

Round Duct Work Heat Gain Analysis (PDF)
Beginning of Duct Run - Round (PDF)
End of Duct Run - Round (PDF)



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