4 replies to this topic

[Enginnerd]

Hello Everyone,

I have been having a very difficult time getting a hold of the extended Antoine Coefficients for calculating saturation pressure.

The Equation I am using is:

Psat = Exp( A +( B / (C + T) ) + D * ln(T) + E * T ^ F)

Where: A, B, C, D, E, F are constants, T=Temp, and Psat= Saturation Pressure.

The constants A, B, and C were very easy to find. A few minutes in the library, and I had them.

The constants D, E, and F are somehow nowhere to be found.

I have exhausted my resources on the internet and the library for 3 weeks now hoping to find the extended coefficients but have had no luck. I have even wrote a computer program to generate random numbers to solve for the coefficients but it crashes after a little while due to the extensive amount of work.

PLEASE HELP! I have been trying to write an excel spreadsheet to do Flash Calculations using the Peng-Robinson EOS, but i cannot continue until I get the correct Vapor Pressure (to estimate a K Value).

-Tyler

[breizh]

Let you check this spreadsheet ( data bank) , you may find what you are looking for .
Hope this helps .

Note : you should be able to identify the coefficients doing math !

Breizh

[Enginnerd]

Let you check this spreadsheet ( data bank) , you may find what you are looking for .
Hope this helps .

Note : you should be able to identify the coefficients doing math !

Breizh

Thank you so much for the reply!

Unfortunately, I am a mechanical engineering student teaching myself this as i go (I thought it would be fun to learn), and I do not really know the relationship with the data bank coefficients with a different formula and the one I am trying to use.

I want to use the formula stated in the original post because (i believe) that it linearizes so i can actually estimate pressures that are outside of the temperature ranges through convergence.

I apologize for the added difficulty, I just really want to learn all this and it seems that the chemical professors at my school find this stuff beyond their knowledge

[breizh]

I've added an other data bank to support your query .
http://infosys.korea.../kdb/index.html
Breizh

[MrShorty]

Are you married to the extended Antoine? Most people seem to prefer the Wagner equation (for which I know The Properties of Liquids and Gases has a databank of constants). DIPPR prefers the Riedel equation. If you are willing to use the Harlacher equation (I don't know why you would), we have a spreadsheet in the downloads section here (called, deceptively, vapor pressure from antoine coefficients), where the user extracted the data from the 3rd edition of the Properties of Liquids and Gases which seemed to like the Harlacher equation (though nobody uses it anymore).

My point is that you might have better luck finding vapor pressure equation coefficients if you are willing to consider a different vapor pressure equation.