flow calculation from given outlet pressure
flow calculation from given outlet pressure
(OP)
Hello everyone,
I have a problem in calculation of a system (figure) in which a pump is pumping fluid (Q0) into a pipe dividing into several branches. I would like to count which flow should I have at inlet (Q0) to achieve defined pressures 1 and 2. I assumed that the flow Q0 will split in two equal jets Q1 = Q/2 and Q2 = Q/2, which I know is not correct, because of different heights and losses. But I needed to assumed sth to calculate velocities, Reynolds number and losses in the flow.
I made an equation from Bernoulli law:
p0 + (ro*v0^2)/2+ro*g*h0 = p1 +(ro*v1^2)/2+ro*g*h1 + losses1 = p2 + (ro*v2^2)/2+ro*g*h2 + losses2
by losses I mean: (lambda*ro*l*v^2)/2d + (dzeta*ro *v^2)/2
I have assumed p1=200mbar, so for the first outlet the inlet pressure should be:
p0= 200mbar +(ro*v1^2)/2+ro*g*h1 + losses1 - (ro*v0^2)/2 - ro*g*h0
for p2 = 100mbar, inlet pressure should be:
p0= 100mbar +(ro*v2^2)/2+ro*g*h12 + losses2 - (ro*v0^2)/2 - ro*g*h0
Is my thinking correct? How can I count the inlet mass flow? Any help will be appreciated.
I have a problem in calculation of a system (figure) in which a pump is pumping fluid (Q0) into a pipe dividing into several branches. I would like to count which flow should I have at inlet (Q0) to achieve defined pressures 1 and 2. I assumed that the flow Q0 will split in two equal jets Q1 = Q/2 and Q2 = Q/2, which I know is not correct, because of different heights and losses. But I needed to assumed sth to calculate velocities, Reynolds number and losses in the flow.
I made an equation from Bernoulli law:
p0 + (ro*v0^2)/2+ro*g*h0 = p1 +(ro*v1^2)/2+ro*g*h1 + losses1 = p2 + (ro*v2^2)/2+ro*g*h2 + losses2
by losses I mean: (lambda*ro*l*v^2)/2d + (dzeta*ro *v^2)/2
I have assumed p1=200mbar, so for the first outlet the inlet pressure should be:
p0= 200mbar +(ro*v1^2)/2+ro*g*h1 + losses1 - (ro*v0^2)/2 - ro*g*h0
for p2 = 100mbar, inlet pressure should be:
p0= 100mbar +(ro*v2^2)/2+ro*g*h12 + losses2 - (ro*v0^2)/2 - ro*g*h0
Is my thinking correct? How can I count the inlet mass flow? Any help will be appreciated.





RE: flow calculation from given outlet pressure
Just assume a flow, distribute it at branches and add up the friction pressure drops to or from your pressure control points. Change the flow until the calculated pressure at a control point is equal to the control pressures.
Remember that every point on the hydraulic grade line must be higher than the corresponding elevation at that point.
you must get smarter than the software you're using.