Restriction Orifice Plate Sizing
Restriction Orifice Plate Sizing
(OP)
Hi everyone,
I am currently working on a cooling system. I need to choke the piping network with restriction orifice plates in order to assure the desired flow in each branch and to make sure that the pump will deliver what it should. The thing is, I don't know how to size those plates, I would greatly appreciate if someone could help me with that.
Thank you,
Alex
I am currently working on a cooling system. I need to choke the piping network with restriction orifice plates in order to assure the desired flow in each branch and to make sure that the pump will deliver what it should. The thing is, I don't know how to size those plates, I would greatly appreciate if someone could help me with that.
Thank you,
Alex





RE: Restriction Orifice Plate Sizing
This pooped up straight away http://www.eng-tips.com/viewthread.cfm?qid=60695
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Restriction Orifice Plate Sizing
RE: Restriction Orifice Plate Sizing
I wanted to make sure I didn't make mistakes in my reasoning. Here is how I proceeded.
1- Calculate the head loss of the system with the desired flow in each branch.
2- Determine the additional pressure drop required to assure the desired flow in each branch and to match the pump.
After that I chose where to put my restriction orifice plates I determined the pressure drop needed for each plate.
Once done I used Bernoulli (This is where I am not sure).
dp = (RHO/2)*(V1^2-V2^2)
then
dp = (8*RHO*Q^2)/PI^2)*(1/D^4 - 1/d^4)
dp : Pressure drop needed [Pa]
RHO : Density of the fluid (P.glycol 30%) [kg/m^3]
Q : Flow [m^3/s]
D : Pipe diameter [m]
d : RO diameter [m]
I tried to verify my answer with the equation given in the topic you sent me (14.6mm vs 16.4mm). But I think there is something I didn't understand... Is the constant ''C'' is dimensionless? Because I did a dimension analysis on the given equation and I find myself with something that didn't match...
Thank you for your time.
RE: Restriction Orifice Plate Sizing
http://www.tlv.com/global/TI/calculator/water-flow...
Have to agree with BigInch, don't see why you are using orifices.
Why not use pressure reducing valves and rate setting valves? Orifices are not adjustable.
RE: Restriction Orifice Plate Sizing
MJCronin
Sr. Process Engineer
RE: Restriction Orifice Plate Sizing
Normally ROs are used to provide a physical limit to gas or liquid flow in the event of systems not working correctly.
alternatively they can be used to distribute flow from a header (think fire sprinklers).
~IMO they are only valid for what you're talking about if the percent pressure drop across the RO is over 50% of the total for any branch. It then becomes much less sensitive to any changes in flow, pressure etc, but implies large wasting of energy in your system.
If, as I and others here suspect, you're trying to use these as cheap "trimming" flow control devices, then you're doomed to failure and you really need to consider something else.
in terms of your question about C - I didn't write it, I just gave that post as an example of what is available on this site to guide you.
your best long term bet is some sort of simple flow control valve. This sort of thing is very common in HVAC cooling systems and many valves are available, this is just an example http://heating.danfoss.com/PCMPDF/VDC6Q602_AB-QM_D...
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Restriction Orifice Plate Sizing
And yes the RO will provide more than 50% of the pressure drop for each branch. The reason why we chose to put RO is because we don't want the flow in each branch to be re-adjusted after the installation since all the heat exchange calculation have been made with a given flow.
Mechanical Eng. Student
RE: Restriction Orifice Plate Sizing
RE: Restriction Orifice Plate Sizing
If you are having to use ROs on all the circuits then a better way might be to lower the supply pressure by having the pump impeller resized.
Katmar Software - AioFlo Pipe Hydraulics
http://katmarsoftware.com
"An undefined problem has an infinite number of solutions"
RE: Restriction Orifice Plate Sizing