Moozhan Ansari - Shiraz University, School of Engineering, Chemical& Petroleum Engineering Department
Samane Bahrani - Shiraz University, School of Engineering, Chemical& Petroleum Engineering Department
Ali Basiri - Shiraz University, School of Engineering, Chemical& Petroleum Engineering Department
Mohammadsadegh Tavallali - Shiraz University, School of Engineering, Chemical& Petroleum Engineering Department

One of the wellknown thermodynamic parameters is vapor pressure which all the chemical engineers are familiar with. There are different equations for calculating this parameter. Antoine’s and Clapeyron’s equations are two of them which have been discussed in this article. Using the available data for four different materials including steam, methane, ammonia and nitrogen and by the use of curve fitting tool box of Matlab software we found these two equations’ constants. Here according to analysis, it is shown that the number of data and its range is important to the accuracy of the results in the way that the shorter range of data and simultaneously the more the data used, better the results. That was understood from the values of calculated errors. The maximum error of this calculation on a wide range of temperature (in contrast to the short range of Antoine presented in the literature) for steam was 1.49%. Also we tried to check the effect of these calculations on the other thermodynamics parameters, such as specific volume, from the view point of the accuracy.

Vapor pressure equation, Antoine equation, Clapeyron equation, Curve fitting, Compressibility factor