Developed Correlations for Prediction of The Enthalpies of Saturated Vapor – Liquid Coexisting Phases

Farhod Chasib Al-Jiboury, Khalid; Omar Abdullah, Mahmoud

	Developed Correlations for Prediction of The Enthalpies of Saturated Vapor – Liquid Coexisting Phases
ALNAHRAIN JOURNAL FOR ENGINEERING SCIENCES
Article 1, Volume 13, Issue 2, 2010, Pages 116-128
Authors
Khalid Farhod Chasib Al-Jiboury; Mahmoud Omar Abdullah
Abstract
In this study a new criteria is adopted by the use of Rectilinear Diameter principle to express the saturated vapor and liquid enthalpies at the coexisting phases for pure substances and mixtures, this requires another relation that used to calculate enthalpies of vaporization at the corresponding temperatures. The relationships between saturated vapor enthalpy, saturated liquid enthalpy and pressure are investigated for many pure substances. These investigations show that the saturated vapor and liquid enthalpies cannot be described by pressure as a simple general relation. New simple correlations are developed for pure substances and mixtures. These correlations are based on the principle of Rectilinear Diameter depending on the law of corresponding states, where DH is introduced as a dimensionless term including the average reduced saturated enthalpies. The relations developed are: For Pure Substances For Mixtures The constants A and B are correlated by the following relations: The second relation developed by fitting of literature values using Maximum Likelihood Principle for twenty pure substances out of thirty, and then applying them successfully to the remaining components, which indicates the generality of this correlation. These correlations can be applied successfully up to the critical region. To use this method it requires the values of critical temperature and normal boiling point temperature, and any suitable correlation used to calculate enthalpies of vaporization. The present new method of calculation of saturated enthalpies compares favorably with any equation of state, for example when using Lee – Kesler equation of state. The comparison shows that the accuracy of the proposed method is better than that of Lee and Kesler at the saturation region. This is in addition to the fact that the present correlations are straight forward, easier, and simpler as compared with that of Lee and Kesler method. These correlations can be further developed to be used directly for design purpose of distillation operations, and other processes that involves vaporization, condensation phenomena.
Keywords
vapor; Liquid Equilibria; Saturated Enthalpy; Rectilinear Diameter principle

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