Reference:  Flow of Fluids – Technical Paper No 410, 1988, Crane Co. Appendix B-15.


Pipe Flow Expert File: Case_38_Air_Flow_Through_100ft_Lengths_Of_Steel_Pipes.pfe


Problem Description: 

Compressed air at 100 psi gauge and 60°F flows through 100 feet long schedule 40 steel pipes.


Find the pressure drop in each of the pipes.


Note: This case is solved here using Pipe Flow Expert’s non-compressible calculation engine. See the commentary below for more details. 

This case has also been solved using Pipe Flow Expert’s compressible calculation engine and the results are reported in the separate Compressible Results Verification document (Case 26).


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Fluid Data: Air at 100 psi gauge and 60°F


Result Comparison: 


Pipe Details

Free Air ft³/min

Compressed Flow ft³/min

Published Pressure Drop (psi)

Pipe Flow Expert Pressure Drop (psi)

4.0” Diameter Schedule 40 Steel Pipe, 100 ft long

    650

    83.3

0.086

0.0857

6.0” Diameter Schedule 40 Steel Pipe, 100 ft long

14000

1794

4.21

4.2741

8.0” Diameter Schedule 40 Steel Pipe, 100 ft long

16000

2051

1.33

1.3460

10.0” Diameter Schedule 40 Steel Pipe, 100 ft long

24000

3076

0.918

0.9275

12.0” Diameter Schedule 40 Steel Pipe, 100 ft long

28000

3588

0.505

0.5099


Commentary: 

The published data and the calculated results compare well.

Since the calculated pressure drop in the system is less than 10% of the pressure at the compressible fluid entry point, then the results may be considered to be reasonably accurate.


If the pressure drop in the pipes is greater than 10% but less than 40% of the pressure at the compressible fluid entry point then the calculations would need to be repeated using the average density of the fluid in the pipeline system (the volumetric flow rates would need to be increased slightly to maintain the same mass flow rate).


If the pressure drop in the pipes is greater than 40% of the pressure at the compressible fluid entry point then the Darcy-Weisbach equation is not suitable and Pipe Flow Expert should be used with the Compressible Flow calculation engine to analyze the system.