8 replies to this topic

[Vish]

Dear all,

I just wannted to know, what is Normal cubic meter(Nm3) and Actual cubic meter(Am3)? What is their significance and where they are used? Specifically, why Nm3 is used in fan calculations and how it is calculated?

[ARAZA]

Hi There,

This is a very simple calculations involving basis gas laws, refer to any basis chemistry handbook for these kind of calculations.

Nm3 refers to gas volume occupied at normal temperature and pressures which are 0 deg c and 14.7 psia. Am3 refers to gas volume at actual operating conditions of the process. Use P1xV1/T1 = P2xV2/T2 for the conversion.

ARAZA

Dear all,

I just wannted to know, what is Normal cubic meter(Nm3) and Actual cubic meter(Am3)? What is their significance and where they are used? Specifically, why Nm3 is used in fan calculations and how it is calculated?

[ankur2061]

Vish,

I have posted a spreadsheet SCFM_to_ACFM.xls on the forum which explains about actual flow for fans and compressors. Use the search feature of the forum to look for the spreadsheet, it is self-explanatory as regards to inlet flow of air to fans and compressors. The only difference is that it uses imperial units instead of SI units but the units can be converted by the user as per his or her convenience.

Regards,
Ankur.

[gvdlans]

As discussed in previous threads, one should always mention the "standard" or "normal" conditions that are used, since these conditions prove not to be so standard or normal as their names suggest...

[sheiko]

Dear all,

I just wannted to know, what is Normal cubic meter(Nm3) and Actual cubic meter(Am3)? What is their significance and where they are used? Specifically, why Nm3 is used in fan calculations and how it is calculated?

Check out the following:

http://webwormcpt.bl...mtric-flow.html

[Vish]

Hi ankur,

I couldnt trace out the spreadsheet u were yalkin abt. Can u help me in finding that?

[Arvind Iyer]

Dear All,

I think this part was not yet answered:-

"What is their significance and where they are used?"

I view the use of Nm3 as a communications tool to avoid any ambiguity.

We know that Volume of a given amount of gas varies with both pressure and temperature.
As pressure increases, the gas volume decreases. As temperature increases, the gas volume increases.

Suppose that an engineer is in need of a compressor that should compress 1000 m3/hr of air.
This statement is not sufficient for him to ask for a compressor.

Imagine the confusion that would occur if the compressor is required in Holland
where the ambient temperatures are very low while the compressor manufacturer is in Saudi Arabia
where the ambient temperature is quite high.

So, 1000 m3/hr at which temperature?

In order to avoid these ambiguities, it is specified at a clearly mentioned reference conditions.
Using the P1V1/T1=P2V2/T2, it is always possible to convert back to the actual conditions
that we are required to run the compressor.

So, for example, the compressor manufacturer will test the compressor at the actual conditions there
but will specify the results at the agreed reference conditions to avoid ambiguities.

[ankur2061]

Hi ankur,

I couldnt trace out the spreadsheet u were yalkin abt. Can u help me in finding that?

Click the following linkf for the relevant post. When you are using the search feature and you want to do a search for the entire forum then remove the tick mark for the sub-forum or do a general search for the entire forum. I would expect all our readers to be that much savvy to use the search feature in the manner best suited to their need.

http://www.cheresour...x...758&hl=SCFM

Regards,
Ankur.

[Jiten_process]

Just to add one more point. Take care of relative humidity when you are converting from ACFM to SCFM. As relative humidity changes so do volume of air too.

Please find attached conversion spreadsheet i got from one of compressor vendor.

Good luck...

Attached Files

•  FAD_formated.XLS   48.5KB   1046 downloads
•  SCFM_versus_ACFM_versus_ICFM.htm   34.87KB   785 downloads