Đang chuẩn bị liên kết để tải về tài liệu:
Thermodynamics Kinetics of Dynamic Systems Part 7

Tham khảo tài liệu 'thermodynamics kinetics of dynamic systems part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Applications of Equations of State in the Oil and Gas Industry 169 26 were the first who introduced the volume shift concept i.e. shifting the volume axis and applied it to SRK vc v-c 10 where vc is the corrected molar volume and c is the correction term determined by matching the measured and predicted saturated liquid volumes at Tr 0.7. The volume shift generally improves the predicted liquid density and has a minimal effect on the vapor density at low and moderate pressures as its molar volume is relatively large compared to the value of c. At high pressure condition the inclusion of c parameter may not necessarily improve the predicted gas density as it is just a correction term for the liquid density. However it is advisable to adjust the gas phase volume by the third parameter to maintain consistency particularly near the critical point where properties of the two phases approach each other. Peneloux et al. correlated the volume translation parameter c as c 0.40768 0.29441- Zra RTc Pc 11 where ZRA is the Rackett compressibility factor. For a more detailed discussion reader is suggested to refer to Peneloux et al. 1982 . 2.2 Three-parameter EOS A two-parameter EOS predicts the same critical compressibility factor Z for for all substances i.e. 0.307 and 0.333 by PR and SRK respectively whereas Zc varies within a range of 0.2 to 0.3 for hydrocarbons. Although the inaccuracy of predicted volume at the critical point not necessarily leads to unreliable volumetric data at all conditions it demonstrates the inflexibility of two-parameter EOS for matching both the vapor pressure and volume. The inclusion of a third parameter relaxes the above limitation. The third parameter is generally determined by employing volumetric data. 2.2.1 Esmaeilzadeh-Roshanfekr ER EOS Both of PR and SRK equations assume a fixed value of the critical compressibility factor for all substances and as a result the predicted values for saturated liquid density differ considerably from their .