Fluid flow velocity in pipes
Fluid flow velocity in pipes
(OP)
Hello, I'm tasked with using nitrogen to push some glycol out of a pipe assembly that we have, though there is one single 2" diameter pipe that has some sensitive equipment in it that can't see very fast flows(I'm told) I was wondering if I knew the pressure difference across this length of 2" pipe, knew the length, etc, how could I estimate the velocity across it? The length is only a few feet. Thanks in advance.





RE: Fluid flow velocity in pipes
hf = (z1 + p1/(rho*g)) - (z2 + p2/(rho*g)
= change in z + (change in p)/(rho*g)
Once you know the head loss, the velocity can be found:
hf = f * (L/d) * (V^2 / 2*g)
Where, z1 = initial height
z2 = final height
p1 = initial pressure
p2 = end pressure
L = pipe length
d = pipe diameter
V = bulk velocity
rho= denstiy
f = friction factor
The friction factor is found using the Moody chart which you should be able to find on the net somewhere. To find it you'll need to know the relative roughness of the pipe.
I am not sure what effect the equipment you have in the pipe will have on the minor losses but to get an accurate value for the speed of the flow you would have to take them into account.
Hope this is of some help,
James.
RE: Fluid flow velocity in pipes
In this case the friction factor is f = 64/ReD, ReD is the Reynold's Number corresponding to the ID of the pipeline. Therefore, average roughness is not required in order to deduce friction factor.
Otherwise, good job on the theory!
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Fluid flow velocity in pipes
Otherwise in laminar flow pressure loss is independent of roughness as previously pointed out.
RE: Fluid flow velocity in pipes
Every 25 years for gases and hydrocarbons
Every 15 years for medium petroleum distillates
Every 10 years for (petroleum) distillation residues