Pressure drop through a slice/slot
Pressure drop through a slice/slot
(OP)
Friends
I want to calculate the pressure drop of a fluid that flows out through a slotted opening. The slot is exactly 10 feet wide and 0.637 inches high. The flow is 5107 USGPM and the pressure (total head) is 9.427 PSIG. If I now reduce the slot opening to 0.433 inches, what would the required head be, and how would one calculate that?
I have done a calculation, obtaining the equivalent circular diameter. Doing a straight square edge pressure drop calc I found the required pressure to be around 22 PSIG.
Any comments and help would be appreciated.
Marius
I want to calculate the pressure drop of a fluid that flows out through a slotted opening. The slot is exactly 10 feet wide and 0.637 inches high. The flow is 5107 USGPM and the pressure (total head) is 9.427 PSIG. If I now reduce the slot opening to 0.433 inches, what would the required head be, and how would one calculate that?
I have done a calculation, obtaining the equivalent circular diameter. Doing a straight square edge pressure drop calc I found the required pressure to be around 22 PSIG.
Any comments and help would be appreciated.
Marius





RE: Pressure drop through a slice/slot
I ran your problem from the Eng-Tips.com posting as I would a nozzle pressure drop in a heat exchanger. Based on a liquid density of 62.4#/ft^3, I came up with a pressure drop of 3.1 psi in the first case and 6.7 psi in the second case. This is based on a sharp-edge sudden expansion only. I would multiply if by 1.5 if there is also a sudden contraction, as in a slot through a plate.
I don't know why my answers are so different from yours, but they seem to be consistent with other's results for nozzle drops.
Regards,
speco (www.stoneprocess.com)
RE: Pressure drop through a slice/slot
RE: Pressure drop through a slice/slot
Don Coffman
RE: Pressure drop through a slice/slot
remove.marius_che@yahoo.com
RE: Pressure drop through a slice/slot
I have sent you a email at remove.marius_che@yahoo.com
Don Coffman
RE: Pressure drop through a slice/slot
Best
M
remove.marius_che@yahoo.com
RE: Pressure drop through a slice/slot
What is the discharge coefficient that you used/obtained?
Marius
remove.marius_che@yahoo.com
RE: Pressure drop through a slice/slot
Marius,
Here's what I used:
G^2
Pressure drop (psi) = -------------------------------
1.2E11 * Rho
where: G = mass velocity through the opening in #/hr-ft^2
Rho = density in #/ft^3
Regards,
speco (www.stoneprocess.com)
RE: Pressure drop through a slice/slot
what consistency are you running through the slice?
RE: Pressure drop through a slice/slot
Thank you for your assistance. Especialy to Don for the XL sheet.
What we found out is that Bernoulli applies. The reason why it was not obvious is because the mass balance cast doubt on the accuracy of the pressure indicator. I tried the calc but it failed against the mass balance - which is why I asked for a coefficient - Thanks. The PI was faulty, in the end, as well.
Thanks a lot, guys. Let me know if I can help you in future.
Marius
If you can't calculate you can't engineer.
remove.marius_che@yahoo.com