Prediction of latent heat of vaporization of multicomponent mixtures

A very simple method has been developed for predicting the differential latent heat of vaporization involved in vapor-liquid equilibria of multicomponent mixtures. The technique uses the UNIFAC method for predicting activity coefficients. In order to establish this method, 88 binary systems and 13 ternary systems, both nonazeotropic and azeotropic, were tested successfully. On the basis of the 101 systems investigated, the mean overall deviation between the observed and predicted values was found to be 4.6%. Despite the fact that the majority of the systems tested were azeotropic, a consequence of the small amount of data available for the differential heats of nonazeotropic systems, the method proposed is equally applicable to nonazeotropic systems. For azeotropic mixtures, it is possible to predict the latent heat (integral or differential) by means of an analytical equation which involves only the parameters of Antoine's equation, with a mean overall deviation of 6.1%. From the differential heats obtained by the proposed method, it is possible to calculate integral heats by applying equations derived here which relate these quantities.