Verification Case 27

PRODUCT: AFT Fathom

REFERENCE: Michael R. Lindeburg, P.E., Mechanical Engineering Review Manual, 7th Ed., Professional Publications, Page 5-6, Example 5.6

FLUID: Air

ASSUMPTIONS: Air is at 70 deg. F, inlet pressure is 5 inches of water, gauge, wall roughness is 0.00538 inches

RESULTS:

Parameter	Lindenburg	AFT Fathom
Velocity (feet/min)	2200	2170
Pressure loss(in. water per 100 feet)	0.5	0.4867

DISCUSSION:

The reference solves the problem using a chart. No roughness data for the duct is given. Using the chart on page 5-7 of the reference, a representative roughness was determined as follows: for a 12 inch duct at 3000 feet/min, the pressure drop is 1 inch of water per 100 feet. This information was entered into the AFT Pipe Sizing Utility (PSU, part of the Engineering Utility Suite) to obtain an effective duct roughness. A value of 0.00538 inches was obtained, and this was used in AFT Fathom. Results from PSU are given below.

Slight differences in predictions above result from the reference's round-off errors and reading the solution from a chart.

PSU Results
- Friction Factor = 0.01788
- Epsilon = 0.00538 inches
- Hazen-Williams Factor = 110.390
Input Parameters
- Delta Pressure = 1.000 in. H2O std.
  - Velocity = 3000 feet/min
  - Vol. Flow Rate = 39.270 ft3/sec
  - Mass Flow Rate = 2.941 lbm/sec
  - Reynolds Number = 306548
Geometry: Cylindrical Pipe
- Diameter = 12 inches
- Area = 0.78540 ft2
- Wetted Perimeter = 37.699 inches
- Length = 100 feet
Fluid = Air @ 1 atm (vapor)
- Temperature = 70 deg. F
- Density = 0.0749 lbm/ft3
- Dynamic Viscosity = 0.04398 lbm/hr-ft

Note this model uses fluid properties from the AFT Standard fluid library. The AFT Standard fluid library was updated in AFT Fathom 12, thus the AFT Fathom results will be slightly different for this verification case when compared to previous versions of AFT Fathom.

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