Is Nm^3 a Unit of Volume or Moles?

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Discussion Overview

The discussion revolves around the interpretation of the unit Nm³, specifically whether it represents a unit of volume or moles. Participants explore its application in flow measurements at different temperatures and pressures, particularly in the context of chemical engineering.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question whether Nm³ is a unit of volume or moles, seeking clarification on its meaning in practical applications.
  • One participant mentions that 1 Nm³ is equivalent to 44.6 moles at standard conditions (T=273.15K and P=1atm), but notes that this relationship may not hold at different temperatures.
  • Another participant speculates that the "N" in Nm³ might indicate a standard condition, suggesting it could represent an idealized volume of gas at specific conditions.
  • A participant provides information that Nm³/h stands for Normal Cubic Metres per hour, defined at 0°C and 1.01325 bars, and contrasts it with Standard Cubic Metres per hour (Sm³/h) used under different conditions.
  • There is a suggestion that the flow rate should be clarified with the professor, indicating uncertainty about the unit's application in the context of the participant's studies.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the interpretation of Nm³, with multiple competing views on its meaning and application. No consensus is reached on whether it is strictly a volume or a mole measurement.

Contextual Notes

Participants highlight that the relationship between volume and moles may depend on temperature and pressure conditions, indicating limitations in the assumptions made about the unit's application.

dRic2
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I'm panicking right know, and I wonder if someone can answer these questions:

1) Nm^3 is a unit of measurement for Volume or Moles?

2) I have a flow at T=500K and, let's say, it is Q = 100 Nm^3/h

When I find the value of the flow at T=500K I do ##Q_{real} = Q* \frac T {273.15K}##. The new Q is in m^3/h ore Nm^3/h?
 
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dRic2 said:
I'm panicking right know, and I wonder if someone can answer these questions:

1) Nm^3 is a unit of measurement for Volume or Moles?

2) I have a flow at T=500K and, let's say, it is Q = 100 Nm^3/h

When I find the value of the flow at T=500K I do ##Q_{real} = Q* \frac T {273.15K}##. The new Q is in m^3/h ore Nm^3/h?
please provide the exact wording of your homework problem
 
It is not an exercise, sorry. I'm a chemE students and I've been doing every exercise with the flow in mol/h for 2 years. This time our professor keeps giving us this strange unit of measurement and I can't understand what it means. I'm sorry I don't know ho to translate my problem correctly in English.

What I figured out is that 1 Nm^3 = 44.6 mol so 100 Nm^3/h = 44600 mol/h. But this works only at T=273.15K and P=1atm

If the volumetric flow remains constant if the the Temperature changes so does its density and the number of moles.
 
44.6 moles of ideal gas at STP occupy 1 m3. What the N is doing there I have no idea. Perhaps it is an idealisation of a real gas - the amount of the real gas that would occupy 1 m3 if it was ideal. Or "ideal at 1 atm and 273.15K". In which case it is equivalent to a number of moles (44.6).
Now I think about it, I have done gas adsorption experiments where the amount of gas adsorbed is expressed as "volume at STP (cc/g)", although it is at 77K, and mol/g would be a more relevant unit.
So that's what I think it is. It's an amount (moles) of gas expressed as a volume.
 
Thanks for the suggestion. I think the only way to know is to go ask him...
 
Nm3/h stands for Normal Cubic Metres per hour, i.e. the flow rate at 0°C, 1.01325 bars atmospheric pressure.
There's also a Standard Cubic Metres per hour, Sm3/h (just so you don't get confused in the future again), which is the flow rate at 20°C, 1.01325 bars atmospheric pressure
None of these are the standard units for volume flow rate. Sm3/h is probably only used in the US. It is not part of the SI system though.
 
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