Example from Newsletter 3(4) March 26, 2001

The image below is a screen capture of our Pipe Network page. None of the fields are click-able since it is a screen capture.

Copy of Newsletter:

LMNO Engineering, Research, and Software, Ltd.
The fluid flow calculations website: https://www.LMNOeng.com
7860 Angel Ridge Rd. Athens, OH 45701 USA (740) 707-2614
LMNO@LMNOeng.com

Newsletter. Vol. 5, No. 8. October 9, 2003

Pipe Network Example
https://www.LMNOeng.com/Pipes/PipeNetwork.htm

I will present an example of how to determine the height of a city water tower using our Pipe Network calculation. Fluid: water at 20C. Pipe material: ductile iron (cast iron). Flow in gpd (gallons (US)/day), Elevations in ft, Diameters in inch, Pressure in psi, Head loss in psi, Lengths in ft, Z+P/S in ft. The water tower will be at node D.

In this example, the water tower is placed on a hill. The hill elevation is 50 ft. above all of the other nodes. All other nodes have the same elevation. All pipes are 10 inch inside diameter and 1000 ft. long. Each outfow node represents a collection of businesses or houses. For simplicity, let's say the required flows out of nodes A-C and E-I is 500,000 gpd each and the pressure requirement is 100 psi at each node. Therefore, set the pressure at the furthest node from the water tower to 100 psi to guarantee that all nodes will have at least 100 psi pressure. The node furthest from the water tower will be C or I (both are the same distance from node D since all pipes have the same length). I'll use node I.

Summary of inputs: Select "P known at node I". Enter Q node for nodes A-C and E-I as -5e5 gpd (be sure to use the negative sign since these are withdrawals). Enter Q node for node D as 4e6 gpd (this number is positive since it is the inflow to the system. I got 4e6 from 5e5 x 8 nodes). Enter the elevation of node D as 50 ft and all other node elevations as 0.0 ft. Enter the pressure at node I as 100 psi. Enter the diameter of each pipe as 10 inches and the length of each pipe as 1000 ft.

After making the proper data entries, click the "Calculate" button and look at the results. All node pressures A-C and E-I are at least 100 psi as required. Look at the node D results: the water tower required height is 238.71964 ft - 50 ft = 189 ft. (rounding to the nearest ft). The pressure of 81.7 psi is at the base of the tank (at an elevation of 50 ft). The pipe "H,V,Re pipe" fields are scrollable with your arrow keys, so you can see the head loss, velocity, and Reynolds number for each pipe. You can see the flowrate in each pipe and the direction of flow from the arrows. You might try reducing the diameters for pipes 5 and 10 to save money since they don't carry much flow.

A copy of this example is viewable at https://www.LMNOeng.com/Pipes/example3(4).htm . Note that the "H,V,Re pipe" field is not scrollable in the gif file.

I hope this example has been helpful,
Ken Edwards, Ph.D., P.E. (Owner/Engineer/Programmer)
LMNO Engineering, Research, and Software, Ltd.

LMNO Engineering, Research, and Software, Ltd.
7860 Angel Ridge Rd. Athens, Ohio USA (740) 707-2614
LMNO@LMNOeng.com https://www.LMNOeng.com