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purdster (Mechanical) (OP)
22 Jan 09 6:43
Can anyone help....

How do I convert Kg/hr to Nm3/hr?

The liquid is Ammonia, Flow Rate is 7200 Kg/hr, Density is 681 Kg/m3 & Pressure is 17.5 Barg

KenA (Chemical)
22 Jan 09 8:14
Nm3/h is commonly used as a unit of measure for flow of compressible fluid (e.g. vapour) because the volume varies with pressure.
If your flow is LIQUID ammonia then you can pretty safely assume that this is incompressible and thus volume does not vary with pressure (density is constant with pressure).
Simply divide the kg/h by density (kg/m3) to get m3/h (actual m3 of ammonia flowing per hour).
zdas04 (Mechanical)
22 Jan 09 9:13
Another way of saying that is that Nm3/h or SCFM do not have any meaning for liquid flows because the difference in density between 0C and 0 barg and 15C and 17.5 barg is very small.  I suppose you could come up with your own (maybe convert actual cubic meters per hour to a water equivilent, but why?).

purdster (Mechanical) (OP)
22 Jan 09 9:26
Thanks for your help with this.
jmw (Industrial)
22 Jan 09 10:57
Unless I am sadly wrong, there are two commonly used volumes;
1) the volume at actual conditions which you obtain by dividing by the density at the process temperature
2) the standard volume where you divide by the density at 15degC (or, 60degF dependent as appropriate).

These calculations are quite familiar (the other way round) in hydrocarbon metering where volumetric flow measurements are often made but where the mass is required, and often the volume amounts are recorded as at standard conditions rather than the sometimes variable process conditions.



Flareman (Petroleum)
22 Jan 09 13:44

Use density = (MW * Pressure) / (gas constant * temp(abs))
Nm^3 are Normal
Temperature = 0 degC (273.15 degK)
Pressure = 760 mm Hg


zdas04 (Mechanical)
22 Jan 09 14:51
What is the "gas constant" for a liquid?

sheiko (Chemical)
6 Mar 09 16:54

"We don't believe things because they are true, things are true because we believe them."

zdas04 (Mechanical)
6 Mar 09 19:23
Have you even read this thread or did you just jump from the old question to a pointless answer?  The OP hasn't been back in this thread in over a month.

sheiko (Chemical)
7 Mar 09 12:08

Flareman stated: "Nm^3 are Normal Temperature = 0 degC (273.15 degK) Pressure = 760 mm Hg"

The link namely shows that many different definitions of standard references conditions are currently being used by organizations all over the world...

"We don't believe things because they are true, things are true because we believe them."

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