Discharge Coefficient

[blckwtr]

I am searching for a method of calculating different discharge coefficients for different nozzle geometries. I thought I have found the connection, but it seemed my assumptions were wrong.

The problem; we have calculated the pressure drop in a "nozzle" for a given flow and liquid using bernoulli with discharge coefficient and geometry factor. The nozzle has three openings, giving a correction factor (on hydraulic diameter) which is the same for ALL tests we have performed. However, with the same application the number of openings were increased to 6 trying to increase the hydraulic diameter, which it did. But the connection to "my factor" were lost. Of course the geometry were changed...

Does it exist an overview of different Cd with different geometry?

 

[BigInch]

Correlations have been made for various edge and entry conditions and distances from the bottom of a tank, but I have never seen any correlations for more than 1 outlet.

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"Pumping accounts for 20% of the world’s energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies)

http://virtualpipeline.spaces.live.com/

 

[blckwtr]

Maybe I should make them then, I mean since it doesn't exist on the internet or any of the litterature I possess?! It isn't for a tank, but for a pipe with a restriction inside (our application) which need to be driven by a given pressure...

Thank's anyway...

 

[hacksaw]

if you've increased the nozzles,the discharge coefficient can only change if the flow paths for the orfices is modified.

sometimes you can make engineering judgements about the flow balance between nozzles and still arrive at a reasonable estimate. if not then you have flow testing and cfd

 

[blckwtr]

thank's hacksaw, I got approximately the same discharge coefficient for the same nozzle geometry, flow regime between 400 and 1400 liters/min. But noticed that larger holes gives very little contribution to the discharge coefficient, except that for larger holes the discharge coefficient is slightly larger, meaning the flow must be larger to produce the same delta P.

But a quite extreme effect on more holes with the same cross section area (flow area), exponentially larger without having seen all data yet.

Interesting...