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# How to convert Kg/hr to Nm3/hr

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## How to convert Kg/hr to Nm3/hr

(OP)
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

Thanks.

### RE: How to convert Kg/hr to Nm3/hr

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).

### RE: How to convert Kg/hr to Nm3/hr

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?).

David

### RE: How to convert Kg/hr to Nm3/hr

(OP)
Thanks for your help with this.

### RE: How to convert Kg/hr to Nm3/hr

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
or
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.

### RE: How to convert Kg/hr to Nm3/hr

purdster

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

Regards
David

### RE: How to convert Kg/hr to Nm3/hr

What is the "gas constant" for a liquid?

David

### RE: How to convert Kg/hr to Nm3/hr

Sheiko,
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.

David

### RE: How to convert Kg/hr to Nm3/hr

David,

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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