Standard & Normal Conditions 1

[MaNaTMoS]

Is there any difference between "standard" and "normal" conditions (pressure, temperature). Literature is quite confusing when dealing with this subject, because the temperature is sometimes neglected.
What is the [Nm3/h] of airflow, regarding previously mentioned standard and normal conditions?

 

[Fizzhead]

MaNaTMoS:

"Normal conditions" as I have been given to understand it, is the continental way to say "standard conditions". Standard conditions are defined conditions depending upon the system of units you utilize. That is to say, that in the English system they are different than in either the SI or cgs systems. Felder and Rousseau define it as follows:

SI & cgs 273K 1 atm
American 492 R 1 atm.

However, you have to watch it, especially in American unit texts because "standard" conditions are sometimes defined as 60F or 72F, etc. So, despite the fact that "normal" means "standard", they are often in fact neither one! Confusing eh? Shows you why correct referencing is so important!

 

[rmw]

Good discussion of the topic at thread378-97454

rmw

 

[mbeychok]

MaNaTMoS:

A normal cubic meter (Nm³) is the metric expression of gas volume at standard conditions and it is always defined as being measured at 0 °C and 1 atmosphere of pressure.

A standard cubic foot (scf) is the USA expression of gas volume at standard conditions and it is very often defined as being measured at 60 °F and 1 atmosphere of pressure. There are other definitions of standard gas conditions used in the USA besides 60 °F and 1 atmosphere, but that is the most common one ... and it is very widely used in the oil, gas and hydrocarbon processing industries.

That being understood:

1 Nm³ of any gas (measured at 0 °C and 1 atm. pressure) equals 37.326 scf of that gas (measured at 60 °F and 1 atm. pressure) ... and thus 1 Nm³ per hour of any gas equals 0.622 scf per minute of that gas.

1 kg-mol of any gas equals 22.414 Nm³ of that gas ... and 1 lb-mol of any gas equals 379.482 scf of that gas.

One should always include the temperature and pressure reference conditions when stating an scf or Nm³ value to avoid any misunderstanding.

Milton Beychok
mbeychok@xxx.net (replace xxx with cox)
(Visit me at

http://www.air-dispersion.com

 

[quark]

Unbelievable to have Milton Beychok (the real) on the board. I should blame myself for not going thoroughly through the site. It says you have been a member since 1999. I request your gracious and frequent presence (though you may be very busy).

Thanks for your great website and I think you will enjoy this recent discussion at thread798-101052.

Best regards,

 

[all2win]

Hi,
I am happy Someone asked this question.

 

[rmw]

Mr. Beychok,

I went to your webpage on Art Montemayor's say-so in the tread that quark referenced above, and I found it to be a valuable resource.

I even e mailed the kenyan game to a missionary acquaintence recently returned from Kenya and Tanzania, and he appreciated it. Blew his mind that he would receive such as it was from a couple of engineers.

I echo quark's invitation for your frequent presence and participation in these fora.

rmw

 

[tickle]

This topic regarding standard and normal conditions keeps being asked. Do people not do a search on the site before asking these questions? The previous responses to the questions provide a worthwhile read.

My addition to the topic is that most of the responses appear to be Americam based responses (apologies if this is not the case). BUT there are other standard conditions eg the Standard metric conditions used in Australia. In a world that is going metric these conditions seem to make the most sense (in my humble opinion).

Therefore MaNaTMoS do a search on ENGTIPS and read the previous responses.