Head Pressure and Flow Rate 1

[TTW2]

Hi,

I have a rather simple problem but am just not sure if I am correct. Basically I need to determine flow rate in a pipe that is gravity fed. I have a tank which is fed by two pipes and this tank drains into a larger tank via a large pipe. The drain is a gravity feed and the drain pipe has a drop of 3 degrees. Now I can work out the pressure at the entrance to the drain using rho*r*h and pressure at the outlet. But I am not sure about the flow velocity. Is V at the pipe entrance the same as near the exit?

This tank overflows so can I determine if by increasing the wall height of the tank (and head pressure) will this stop the tank overflowing?

Thanks

 

[BigInch]

Assuming its a liquid like water or something else relatively incompressible at low pressures, V in = V out for constant cross sections of flow area.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[zdas04]

BigInch,
That is true as long as the pipe is running full. For a pipe with 3 degree slope, the nozzle losses at the beginnning will make sure that it doesn't run full. While mass flow rate must be constant, the velocity will change to keep it so as the liquid level in the pipe changes.

This simple problem is really not all that simple.

David

 

[BigInch]

Dave, Technically I suppose you caught me looking on that one, but I get the distinct impression the top of the drain is lower than the tank's liquid surface in this case, or soon will be when he increases the height of the tank wall.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[TTW2]

Hi,

Thanks for your responses. I think I can determine the flow in the pipe using the energy eqn. The fluid is a hydrate so I am going to assume water. Thanks again.

 

[sundha007]

Hi
Please let me know how to calculate the branch pipe size for residential multi storey building? I have calcualted branch pipe adding the each flat GPM(arrived from IPC wsfu table) up to the vertical riser.
Another procedure is to consider the total GPM(considering table 103.3(3) of IPC) of the floor and size the branch.
Since the pipes size against the GPM for total and individual varies.
Kindly clarrify whihch one is to be followed.

Regards
Sundar

 

[BigInch]

Sundar, Please start a new thread.

**********************
"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/