Hydraulic circuits (water) : serial & parallel orifices

[Feldmann359]

Good Morning!

I have a question concerning the water flow in a hydraulic
system. In different positions of the system, I have
to install sharp edged orifices to regulate the mass flow.
Now I am searching for a good approach for testing & calculations.

For the orifice, I determine the pressure drop as a function of the mass flow by experiment and then
calculate the discharge coefficient Cd=m./(A0*sqrt(2*rho*DP))
with
CD=discharge coefficient [/]
m. = mass flow dm/dt [kg/s]
A0 = orifice area [m**2]
rho = water density (function of temp) [kg/m**3]
DP = pressure drop [Pa]

What happens now if I install two orifices in parallel/serie
al connection?

Is it possible to calculate with discharge coefficients or is there a better way?

Thanks in advance,
Stephan

 

[tjkall]

Stephan:
If I understand the question......
In a similar situation I built a manometer an pipe taps and measured the differential pressure across the orifice plates. with known flowrates you can back out the discharge coefficient(s).
Tom

 

[Feldmann359]

Thank you Tjkall for your answer!
Your suggestion is in fact that what I am doing first:

I have a batch of approx. 100 different orifices from
0.05 - 0.1 in diameter. Then I will perform one
delta p measurement at one fixed mass flow - for
example at 0.7 GPM - resulting in an discharge coefficent
(see formula from my first post) for each orifice.

Later on, when I have to do an initial setup of a new facility, I have to select an appropriate orifice.
If the orifice I am looking for is not available,
is it perhaps possible to do a series connection of two
orifices?

How should I then perform the calculation?

Cd (total) = Cd.1 * Cd.2, like I do for efficincy factors?

Thanks in advance,
Stephan

 

[tjkall]

I guess I would build the apparatus with two orifice plates and measure the pressure drop across them and see what type of relationship exists for the series arrangement at a fixed distance apart. Maybe take several measurements and fit a curve to the data.

I spent all day yesterday soaking wet trying to solve a similar, though not quite as interesting, problem. I would like to hear what your findings are.
Tom

 

[Feldmann359]

Hi Tom!

I will do that. In one ore two weeks I will post the results; I have lots to do at the moment and this is not my main task.

Greetings,
Stephan