INVESTIGATION OF THE CORRELATIONS FOR PREDICTION OF SATURATED VAPOR VOLUME FOR PURE COMPONENTS AND MIXTURES

 The prediction of molar volume of saturated vapor can be calculated from many equations of state, some of these equations applied for both gas and liquid phase ,and some of them applied  for gas phase only . The accuracy of these equations are different .For pure compounds the molar volume of saturated vapor can be calculated from many equations ,such as Lee-Kesler equation that gave a very high deviation from the molar volume calculated from the PVT data , it is used to calculate the molar volume of three compounds (72 data points polar and non-polar ) with (average absolute percent deviation) AAD% 62.432%, and when its deviation found to be very high there is no need to used this equation for other compounds . Redlich –Soave equation was the second equation of state that used to calculate the deviation of the molar volume in this project , it gave AAD% 15.3125 for 299 data points for 14 compounds polar and non-polar . Peng –Robinson equation of state was used in this project and applied for 299 data points and gave AAD% 14.3476% which is relatively better than that obtained from Redlich-Soave equation .And finally Virial equation of state that can be used to calculate the molar volume with Virial truncated to second term and Virial truncated to third term ,the use of Virial equation truncated to second term gave AAD% 7.5525% for 299 data points (polar and non-polar ) this relatively high deviation is because of the ranges of pressures of some compounds in this project was relatively high ,and the second term of Virial equation is used for pressures relatively low 9not accede 15 bar) .While Virial equation truncated to third term gave better deviation the AAD% is 1.0955% this because it can be used for pressure range greater than that of second term (up to 50 bar) . From the above comparison, it is Easley considered that the truncated Virial equation is the best equation that can be used to calculate the molar volume of the saturated vapor ,and it is clearly showed that the Virial truncated to third coefficient is much better than second term for the conditions of this project (temperatures and pressures ). Correlations must be done on these coefficients of Virial equation in order to reduce the deviation of the calculated molar volume. For second Virial coefficient and by using statistical methods, the correlation was developed and this correlation modified the percent deviation from 7.5525% to 3.5209%
by using 89data points for 4 compounds (Cyclo propane, propanol, i-Butane, R.245) and then applied this correlation to 210 data points  The correlation developed to modify the percent deviation of the calculated molar volume of saturated vapor by using Virial truncated to third term gave a relatively acceptable deviation and reduce the deviation from 1.0955% to 0.7899% this correlation developed by using 60 data points for 3 compounds polar and non-polar and applied for 239 data points for 11 compounds (polar and non-polar). For binary mixtures ,the calculation of the molar volume of saturated vapor done by using three methods .The first method is done by using Virial equation truncated to second term with Virial mixing rule and this gave relatively high deviation from the molar volume obtained from the PVT data the AAD% is 8.3919% for 142 data points for 6 mixtures .The second method is done by using Teja equation with Virial mixing rule ,where the compressibility factor calculated from Teja equation and the
pseudo critical properties of each compounds  calculated from Virial mixing rule and this gave AAD% is 3.4669% for 142 data points for 6 mixtures ,and this is relatively better than that obtained from the modified  Virial truncated to second term .The third method is done by using the modified Virial equation truncated to third term with Virial mixing rule and this method gave the lowest deviation and the best accuracy than other two methods used to calculate the molar volume of saturated vapor for binary mixtures ,the AAD% is 1.4967% for 142 data points (6 mixtures ).