Flow from pressure gauge
Flow from pressure gauge
(OP)
For the following system. Water is pumped to atmosphiric tank and there is pressure gauge at the end of the line in a location is very close to pipe exit. Can we use this reading and with pipe diameter to calculate flowrate? By Crane it is suggested to consider k=1 and use velocity head to find flowrate . But i think results is over than actual and i think there will be factor for exit loss.
Any ideas???
Any ideas???





RE: Flow from pressure gauge
Good luck,
Latexman
To a ChE, the glass is always full - 1/2 air and 1/2 water.
RE: Flow from pressure gauge
h we can get from P at the line end
What is the wrong of applying that.?
I think there is somthing missing or factor to be used.
RE: Flow from pressure gauge
RE: Flow from pressure gauge
The point i want to confirm is there factor or not instead of 1
RE: Flow from pressure gauge
Guage pressure = rho. g. h for an atmospheric tank
dP/dt = rho. g. dh/dt
Flowrate = F = tank csa . dh/dt
so
dP/dt = rho. g. F/tank csa
or
F= (dP/dt).tank csa/(rho.g)
Here, dP/dt is the rate of press rise at the base of this tank with time. The smaller the full scale range of the PG, the better.
RE: Flow from pressure gauge
Measure dP at a constant flow rate (constant dP) over a given time. Measure the volume increase in your tank. Repeat at some different flow rates
Best regards, Morten
RE: Flow from pressure gauge
Sorry i didn't explain the system in begining clearly.
In summary what i want to confirm, if only one reading of P is known and because it is atmospheric then P2 also known ( 0 barg).
Then this P equal v^2/2g multiply by some K.
Here to consider K=1 or there is another factor to use.?
Thanks for any idea
RE: Flow from pressure gauge
you have a pump curve (pressure vs. flow),
at pumpu discharge there is a short pipe (you know fluid, diameter and lenght then you can calculate dp vs. flow) and finally a static head (h inside tank),
for pump, p out = dp (pipe) + static head (measured by instrument, assuming pipe horizontal, no dH)
to estimate flow from pump curve you need to calculate dp across pipe (could be a table of values)
to estimate flow from pressure loss at end of pipe there are several formulations but probably the simple solution is to create a table of values as already suggested by others
RE: Flow from pressure gauge
RE: Flow from pressure gauge
of course you should start from Bernoulli and difference (measured p vs. static p which is that of your instrument when flow = 0 or may be estimated from H and density as suggested by georgeverghese)...
there are many different methods (including differentials across plates, bends etc.) to estimate flow in piping, you may consider alternatives.
RE: Flow from pressure gauge
BTW, I'm assuming this line connect near the bottom rather than the top of the tank.