flowmeter basics

[all2win]

hi Guys,

One simple Question.Why all volumetric flow meters measure flow in Nm3/hr , not in M3/hr?

all2win

 

[Skogsgurra]

N stands for Normal. This applies to gas flow meters and it means that the volume is given at normal pressure and normal temperature - even if the gas in the meter is at high pressure and temperature.

 

[zdas04]

As has been discussed at length in other fora (see Piping & Fluid Mechanics Engineering for example), reporting gas at "Normal" or "Standard" volume flow rates allows a set of volumetric units to stand-in for a set of mass flow units (which are not pressure and temperature dependent). It is important to realize that this is simply a reporting tool - the parameters that go into inferring gas-flow from a differential pressure will result in a a flow rate at actual conditions that can then be converted to a simulated flow rate that the stream would have if it was flowing at standard conditions.

I'll never understand why people require gas to be presented in volume-flow-rate units, but they do and the STP representation is far more effective than asking people to convert actual flow rates at a variety of pressures and temperatures to a common set of conditions for aggregation.

David Simpson, PE
MuleShoe Engineering

http://www.muleshoe-eng.com

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