Nm3/hr – Normal Metres Cubed per Hour
This is at a Temp of 0 deg C and 101.325 kPa
Sm3/hr – Standard Metres cubed per hour
This is an old throw back from SCFM and based on 60 Deg F and Atmospheric pressure……………i.e. 101.325 kPa and 15.6 Deg C
Am3/hr – Actual Metres cubed per hour
As it says “Actual” at the temperature and pressure conditions stated.
To convert Nm3/hr to Sm3/hr it’s a ratio of the absolute temperatures –
(The difference between 0 and 15.5 deg C)
10 Nm3/hr *(15.6+273)/ (0+273) = 10.57 Sm3/hr
Where -273 is absolute zero on the temperature scale.