Need flow thru annulus equations

[sprintcar]

Anyone have a simple way to calculate flow thru annular discharge? Discharge is pump gland - basically an orifice plate with a pipe running thru it - Thanks!!

 

[jproj]

sprintcar:

If you know the fluid discharge velocity, a simple equation to calculate flow is:

Q = AV Where:

Q = volumetric flow rate
A = Pipe cross sectional area
V = Fluid velocity

Pipe area of an annulus is found by subtracting the outer pipe area from the inner pipe area. (Area = PI/4 D^2) To get a mass flow rate, multiply Q by the fluid density.

Good luck,

jproj

 

[sprintcar]

Don't have flow velocity - just 10psi pressure, OD, ID

Thanks

 

[jproj]

sprintcar:

Well then, that makes it more interesting! For that situation, you're gonna have to use Bernoulli's equation. Unless you have a significant height change, you can ignore potential energy effects. For simplicity you could also ignore frictional losses. That would give you:

(P/rho)ref. - (P/rho)disc. = (V^2/2)disc. - (V^2/2)ref. Where:

P = pressure
rho = density
V = velocity
ref. = conditions at reference point upstream of discharge
disc. = conditions a discharge

If you are working with an incompressible fluid at (near) constant temperature between the upstream reference point and the discharge point, you can assume a constant fluid density.

To calculate the outlet velocity, you must know the upstream pressure, and either the upstream flow (use the equation in my previous post to solve for velocity) or the upstream velocity. You must also know the discharge pressure. Plug these into Bernoilli's equation and solve for the discharge velocity. Then use the equation from my previous post.

Hope this helps

jproj