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simple fluid flow question I hope

simple fluid flow question I hope

simple fluid flow question I hope

(OP)
I need to maintain a fairly constant flow rate of liquid nitrogen out of an orifice.  The liquid nitrogen is contained in a tank that has an internal pressure of 22psig.  My budget is minimal, so I plan on attaching a fitting with a hole drilled though it to the the outlet of the tank to restrict the flow.  The flow needs to be 250 mL/min or 0.250 L/min.  I need to estimate the diameter of the hole/orifice to produce that flow rate.

I found the following thread on this forum

http://www.eng-tips.com/viewthread.cfm?qid=119094

One response noted the following equations for water:

dL = sqrt(.0444)(QL / sqrtDP)
wheredL   = Diameter of orfice / in
sqrt = Square root
QL   = Required water flow / gpm
DP   = P1 - P2 / psi
P1   = Inlet pressure / psi
P2   = Outlet pressure / psi

or this for other liquids I'm assuming:

dL = sqrt(QL / .0001423 sqrt(DP / r))
wheredL  = Orifice diameter / micrometers
QL = Liquid flow rate / mL / min
r   = Liquid density

I have a few questions about the 2nd set of equations.  I changed all of the units to m-kg-s.  In the 2nd set of equations, the units come out to length^2/time instead of just length.  Does the constant (0.0001423) have any units that might change this?  

Alternative solutions or suggestions would be appreciated.


  

RE: simple fluid flow question I hope

wow, that's one heck of a conversion factor.

"We have a leadership style that is too directive and doesn't listen sufficiently well. The top of the organisation doesn't listen sufficiently to what the bottom is saying."  Tony Hayward CEO BP
"Being GREEN isn't easy." Kermitfrog http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.liv

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