Flow Rate calculation Help
Flow Rate calculation Help
(OP)
I'm new here and my background is Electrical so excuse the simplicity of the approach.
I'm doing some project work in the US and have the folllowing question (all measuers are US):
I have a 50,000 gallon Water Tank that overflows in the event of a main pump failure (catastrophic-happened twice already). Flow IN is 60,000Gal/Min, cannot be stopped or slowed down otherwise we damage equipment.
I want to notch the top of the well and have it spill over into a concrete spillway and redirect the flow away frmo the buildings. The questions is how big do I make the 'hole' at the neck of the well. I only have access to one side, so I can equate an answer in square metres (feet over here!) accordingly.
Thanks in advance.
A
I'm doing some project work in the US and have the folllowing question (all measuers are US):
I have a 50,000 gallon Water Tank that overflows in the event of a main pump failure (catastrophic-happened twice already). Flow IN is 60,000Gal/Min, cannot be stopped or slowed down otherwise we damage equipment.
I want to notch the top of the well and have it spill over into a concrete spillway and redirect the flow away frmo the buildings. The questions is how big do I make the 'hole' at the neck of the well. I only have access to one side, so I can equate an answer in square metres (feet over here!) accordingly.
Thanks in advance.
A





RE: Flow Rate calculation Help
RE: Flow Rate calculation Help
Thanks for pointing out my degree!
RE: Flow Rate calculation Help
Where:
d = nozzle diameter, in inches
hM = minimum design head above drawoff nozzle, in inches
q = flow rate, in gallons per minute
Example: Size of drawoff nozzle for a process vessel where hM is 48 inches and q is 60,000 gpm.
d = 0.5 [60,000/48 (0.5 power)] (0.5 power)
d = 46.5 inches
Notes:
1. This formula assumes that the nozzle will constitute a sharp-edged entrance.
2. This formula assumes a safety factor of four to allow for uncertainty in the resistance coefficient (K = 0.50 for sharp-edged entrance), and for liquid level variations due to agitation.
S. Bush
www.water-eg.com
RE: Flow Rate calculation Help
Bush gave you an answer of 46 inch diameter which would give you a flow velocity of about 10 feet per second coming out your "notch". This is going to require a substantial concrete spillway to contain this large flow as well as some sort of energy dissipation
RE: Flow Rate calculation Help
I ran the numbers through the following eqn and have someone double checking it for me:
A = Q / [ C x (sqrt {2xGxh)}]
C =0.62 (sharp edge concrete)
G = 32.2f/s
h = Height of notch x 0.5
Q = 133ft3/sec
and the results I have indicate I need a 13.5ft x 2ft notch to accomodate for the overflow INTO the channel and 32 ft x 1.5 ft to get the flow OUT.
Yes, the 60,000gpm is correct and yes, it does fill very quickly. It is a surge tank from a process prior to pumping to a cooling tower Header.
The solution is do-able and we have more than enough room.
If I'm missing something obvious here, any pointers would be appreciated.
Thanks
A
RE: Flow Rate calculation Help
Brater and King chapter 5)
weir equation Q = CLH^1.5
C values for this equation range from about 3.2 to 4.2 (see figure 5-3).
Assume a mid ranged C value of 3.7 and you get about 141 cfs. However this is assuming a horizontal approach channel. In your case, you have flow rising vertically and then turning 90 degrees to exit out the notch. This will result in an energy loss as the momentum of the fluid is lost. The result will be a higher water surface in the tank required to discharge the water through the slot. You may want to be conservative and make the notch a bit wider.
RE: Flow Rate calculation Help
I will be adding some safety factors in the numbers and creating more of a slipway than I need, both INTO and OUT of the spillway.
Thanks for the help, it's greatly appreciated.