TS diagram vs Bietie-Bridgemann Equation

[hyeonje]

Hello,

I am trying to calculate an isothermal change of Nitrogen gas from 1000 cc at 100 bar compressing to 200 cc and I am looking for a final pressure of the gas.
Two methods were recommended by two different people. One was to use TS diagram and the other was to use one of the real gas equations, Bietie-Bridgemann Equation. Which one calculate closer to a real result and why? Why are they different?

Thanks in advance.

Hyeonje

 

[CastMetal]

The Bietie-Bridgemann has five empirically derived constants for each material that are used for the full range of gas states. Where as a T-S diagram is derived from empirical data over a wide range of conditions which would make it more accurate. For a mostly complete list of gas equations look here

http://www.ccl.net/cca/documents/dyoung/topics-orig/eq_state.html.

In general the more empirical constants applied the more accurate an equation will be over a wider range. Benedict, Webb and Rubin have an equation above and beyond Bridgemann with seven empirical constants.

 

[Latexman]

There is a TS diagram for nitrogen in Perry's Chemical Engineers' Handbook.

Good luck,
Latexman

 

[hyeonje]

Thank you for the responses.
Another question.... I've got TS diaram for Nitrogen prepared by F.DIN 1958 which is big and there are so many lines of pressures, entalpy and volumes. Do you mean that they are all empirical?

Hyeonje