Flow through RO plate

[snyper]

Hi all
I have a water tank fed by a centrifugal pump. In the line between the pump and the tank inlet is an RO plate. I know the orifice diameter, and have all the pump data, line sizes, etc. How do I find what the flow rate into the tank will be? All the orifice calculations I come across require pressure drop across the plate to be known - which I cannot measure.

 

[monaco8774]

Snyper

Why do you need to know, for an estimate of flow you can use any of the following

You need to estimate a flowrate then calculate the pressure drop through the orifice and the lines to your tank if this added to the delivery pressure in the tank is less than your actual pump discharge you increase your estimated flow and recalculate until the values match.

Alternatively you can simply mesure the rate of increase of level in your tank and work out the flow from the volume of the tank

Alternatively again look at your pump curve and using the pressure in the tank its coming from and discharge pressure work out where it is on its pump curve to give you flowrate

 

[katmar]

I agree with monaco8774 that the way to do this is to treat the RO as part of the line and work out the overall flowrate vs pressure drop curve and see where this intersects your pump curve.

The K-value of the RO can be estimated from the formula

K = 2.8 * ( 1 - B² ) * ( {1/B}⁴ - 1 )

Where B = orifice bore / pipe ID

This applies to well developed turbulent flow. The reference is Simpson and Weirick, Chemical Engineering, April 3, 1978



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