Pipe/pumping question

[AG1412]

Hi,

I have design situation where I have one main pipe that receives flows from several pipes at regular intervals in length of the main pipe. So ultimately the main pipe must handle flows from all individual small pipes and pump it to the next unit in operation. The flows from several small pipes are equal. I have to calculate head loss in the main pipe.

My approach-
Size the main pipe to handle the flows coming in from every small pipe. I sized it to maintain a minimum velocity in the main pipe. Because the flow increases over the length of the main pipe (due to flows from small pipes), the diameter increases over the length. Calculate the frictional head loss for every section of the main pipe based on pipe material, velocity in that length of the pipe and diameter. And add the frictional headlosses obtained so over the total length of the main pipe. Is this correct?
The pipe does not flow through gravity. How to view this pipe network -series/parallel?

 

[bimr]

AG1412,

For the scope of work that you have described, don't even worry about pressure drops in the piping. The pipe lengths will be small (unless you are pumping for hundreds of meters) and the major power requirement will be from moving water from tank to tank. Assume the tanks are empty and calculate the maximum head from empty tank to full tank.

For this application, most will use centrifugal pumps because they are inexpensive. Assume 60% pumping efficiency.

 

[itdepends]

What sort of flows are we talking about here? Is it water?
Do you have a Process Flow Diagram? (which would include this information).

There's little point diving into detailed or even preliminary sizing calculations until you know where the pumps are going to go and how big they are.

As a chem eng/metallurgist the first part of any answer I give starts with "It Depends"

 

[bimr]

itdepends, he posted on 12/15 that it for a fish farm (aquaculture).

 

[SteveWag]

Google "small diameter variable grade sewer design" and read over the design guides. You are essentially carrying waste. Keep the velocity above 2.5 fps. There will be talk about “grinder pumps” you may (?) ignore the grinder aspect, your choice. BTW, depending upon individual flows, residential units may work well. Does this involve more than 10 pumps? If so, contacting a Barnes, E-One or Flygt pump vendor mat result in a factory design for “free”. Don’t listen too much to the sales pitch; everyone claims to have a better product. And remember the design may be worth what you pay, so verify, but at lease you have a starting place.
Steve