Gas Density - Nitrogen

[PhilEduard]

Hi there guys,

I know this is the right forum for this question and I believe too mostly are working on process engineering. This question could be very simple for you but it took me a while to figure it out simply becuase of the metric unit I'm not use to. I have a system running on compressed nitrogen gas at 1650 psig and 150 deg F. Using ideal gas equation, density = p/RT where p is the operating pressure in lbm/cu. ft., R is specific gas constant equal to .2968 Kj/Kg-K from my research, and T is the temp at deg R. Since R has to be in consistent unit of ft-lbf/lbm-degR, I managed to convert the specific gas constant R in metric to customary english units and I am getting 3.8 lb/cu ft. To those who are more orineted in this kind of job, please correct me or kindly validate this calculation. Thanks a lot for all of your help or hints on this issue.

Regards,

 

[katmar]

Phil,

I believe you have made a mistake somewhere, but your formula is correct. The numbers I get are

P = 1650 psig = 239717 lbf/ft² absolute
R = 55.191 ft.lbf/lb.R
T = 150 deg F = 609.7 deg R

Density = 1/V = 239717 / (55.191 x 609.7) = 7.12 lb/ft³

This is a very error prone process because of all the conversions. I have written a calculator that does it all for you. You can download Uconeer from

http://www.katmarsoftware.com

for free and the gas density calculator is part of the gas flowrate convertor (click the fan icon to run).

Harvey

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[PhilEduard]

Hi there Harvey,

We'll sure you are absolutely right. My pressur is in gauge and I need to add 14.7 to make it absolute. I'll surely download your software and I'll visit your software homepage too. Thanks a lot for your quick help.

Regards,

Phil

 

[25362]

The value from the NIST tables is 6.92 lb/cuft.