Differential Chart Calculation

You have obviously not done a Google search for the information.

You want someone to do the work for you with a ready to use answer.

It took me about 10 seconds to find this link,and many others.

Follow this link and do your own homework:

http://www.efunda.com/formulae/fluids/calc_orifice_flowmeter.cfm

I did checked google but I was not getting what I want hence the post.

Are you sure you tried Google.

"not getting what I want"

If you want the answer without doing the work, look elsewhere.

HTRN gave you s plug in calculator. All you have to do is plug in the numbers and the answers will appear.

You should learn to use a search engine..

If you're interested in the theory and formulas, this might help.

https://www.emerson.com/documents/automation/white-paper-fundamentals-of-orifice-meter-measurement-daniel-en-us-188730.pdf

Ban all anonymous posts!

https://www.amazon.com/Anonymous-POSTER-27-x-40/dp/B01LYKE5ZX

This one too?

Good idea.

Ok,here is your bite size,easy to digest calculator,directly from Daniel.

It is a downloadable program that you can install on your computer for future use.

You will have to know your minimum and maximum flow rate before deciding on the scale of your chart,only you will know what that is.

If you need more than this,hire a pro.

https://www.spartancontrols.com/documentation/document-library/measurement-instrumentation/daniel/software/daniel-orifice-flow-calculator/

I called Daniel, He could not take the call as he was busy fixing a hole in his plate. His beans are all over the floor. Daniel will revert to me when he has charted his progress. I hope you are grateful for this contribution. Daniel will be grateful for a contribution as he needs to buy a new plate and a tin of beans.

You need to know how the orifice is mounted, the design of the hole in the plate, and the locations of the pressure differential taps, such as flange taps.

The chart could display the actual differential pressure, or it could be transformed into mass flow units using the equations the other posters have listed. The equations are very specific for the orifice design and mount, and the fluid. They have typically very limited flow ranges, perhaps a 4:1 turn down from the original design.

Mr. Richard W. Miller wrote an excellent reference on this subject, and other flow instruments, titled "Flow Measurement Engineering Handbook", I have the 3rd edition, 1996, from McGraw Hill. Chapter 6 has a good section on selection, and Bernoulli's streamline energy equation, which is the basis for flow measurement using a differential producer, such as an orifice.

Simples. Use the information in Perry, The Chemical Engineer’s Handbook, any edition.

...though do be aware that, as a measuring technique to measure flow, differential pressure across an orifice plate is sooooooo 1973.

You need the relationship for the DP at (generally, the maximum measured) flow rate. This is usually provided in a "sizing sheet" that accompanies the primary flow element (orifice plate, averaging pitot tube, venturi, flow nozzle, whatever).

For instance, it might be an orifice plate sized for a flow rate of 500 l/min at a DP of 15000 mmH2O at design (static line pressure and medium temperature) conditions.

The DP at maximum flow rate is considered 100% flow.
The value 100% when 'normalized' is 1.00

The calculation is not "the square root of the DP" value itself, but the square root of the percentage of the normalized DP, normalized to 100% flow rate.

The square root of the percentage of the normalized DP is the percentage of the maximum flow rate.

For the example above, where the primary flow element is produces 15000 mmH2O DP at a 'maximum' 500 l/min flow rate, an instantaneous flow rate producing 9600 mmH2O DP would have a flow rate calculated as

9600/15000 = 0.64 (64% of DP at maximum flow rate)
Square root of 0.64 = 0.80
0.80 = 80%
80% of max flow rate = 0.80 * 500 l/min = 400 l/min

9600 mmH2O represents a flow rate of 400 l/min