Finding the flow rate through an open-end pipe

Click For Summary
SUMMARY

The discussion focuses on calculating the flow rate through a 15 mm diameter, 20-meter long pipe under 5 bars of static pressure. Participants utilized various methods, including orifice flow calculations and iterative approaches using Bernoulli's equation and the Darcy-Weisbach equation. Initial estimates suggested flow rates around 12.5 m³/hr, but further calculations using the Moody Chart and adjustments for kinematic viscosity led to refined results of approximately 3.54 m³/hr and 4.254 m³/hr. The conversation highlights the importance of accurate viscosity values and friction factors in flow rate calculations.

PREREQUISITES
  • Understanding of fluid dynamics principles, particularly Bernoulli's equation and Darcy-Weisbach equation.
  • Familiarity with the Moody Chart for determining friction factors.
  • Knowledge of kinematic viscosity and its impact on Reynolds number calculations.
  • Experience with iterative calculation methods for flow rate estimation.
NEXT STEPS
  • Study the application of the Darcy-Weisbach equation in fluid flow analysis.
  • Learn how to effectively use the Moody Chart for friction factor calculations.
  • Explore the Swamee-Jain equation for estimating head loss in pipes.
  • Investigate the relationship between kinematic viscosity and flow rate in various fluids.
USEFUL FOR

Engineers, fluid dynamics specialists, and anyone involved in hydraulic system design or analysis will benefit from this discussion, particularly those focused on flow rate calculations in piping systems.

  • #31
Chestermiller said:
Well the Darcy friction factor is 4x the fanning friction factor, so you decide.

Great catch, I got sloppy with my friction factors and wasn't distinguishing between Fanning and Darcy.

Here's the updated equation set:
upload_2017-2-2_15-53-2.png


And the results:
upload_2017-2-2_15-56-8.png


Looks like this is about as accurate a calculation as I can provide given the parameters known? Thanks @Chestermiller and @JBA , I learned a good deal in this thread!
 

Attachments

Engineering news on Phys.org
  • #32
I thought of one more possible error- the water main's pressure will probably be specified at gauge pressure, meaning the discharge pressure P2 would be zero, not 1 atm (gauge pressure of zero).

That increases the flow a bit, see here:
upload_2017-2-2_16-13-21.png


I also tried a quick check by comparing calculated flow rates against a hose discharge chart here: http://www.engineeringtoolbox.com/water-discharge-hose-d_1524.html. The flow rates calculated by my sheet appear to be right in-line with the values from this chart.

Calculated values from my sheet (100 ft length for all):
  • 1/8" hose, 100 psi: 0.25 gpm
  • 1/2" hose, 40 psi: 6.38 gpm
  • 1/2" hose, 100 psi: 10.75 gpm
  • 3/4" hose, 40 psi: 19.02 gpm
  • 3/4" hose, 100 psi: 32.03 gpm
  • 6" hose, 10psi: 1965 gpm
  • 6" hose, 60 psi: 5202 gpm
Compare to chart from EngineeringToolBox.com:
water-discharge-hose-diagram.png
 

Attachments

Last edited:

Similar threads

  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 38 ·
2
Replies
38
Views
4K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 31 ·
2
Replies
31
Views
5K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
6
Views
4K