Case 37: Air – Flow Through 100m Lengths of Steel Pipes
Reference: Flow of Fluids – Technical Paper No 410M, 1999, Crane Co. Appendix B-14.
Pipe Flow Expert File: Case_37_Air_Flow_Through_100m_Lengths_Of_Steel_Pipes.pfe
Problem Description:
Compressed air at 7 bar gauge and 15°C flows through 100 meter 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 25).
Fluid Data: Air at 7 bar gauge and 15°C
Result Comparison:
|
Pipe Details |
Free Air m³/min |
Compressed Flow m³/min |
Published Pressure Drop (Bar) |
Pipe Flow Expert Pressure Drop (Bar) |
|
1.0” Diameter Schedule 40 Steel Pipe, 100 m long |
0.800 |
0.101 |
0.044 |
0.0436 |
|
1-1/2” Diameter Schedule 40 Steel Pipe, 100 m long |
10.000 |
1.264 |
0.640 |
0.6391 |
|
2.0” Diameter Schedule 40 Steel Pipe, 100 m long |
20.000 |
2.528 |
0.685 |
0.6854 |
|
2-1/2” Diameter Schedule 40 Steel Pipe, 100 m long |
32.000 |
4.046 |
0.682 |
0.6900 |
|
3.0” Diameter Schedule 40 Steel Pipe, 100 m long |
30.000 |
3.793 |
0.197 |
0.1979 |
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.