Viscosity model for pure liquids based on Eyring theory and cubic EOS

Abstract

iscosity is an important transport property in process design and development. Knowledge of viscosity of pure liquids and of the liquid mixtures plays a key role in solving chemical engineering problems dealing with heat-transfer and masstransfer operations, and fluid-flow processes. Much effort has been directed towards the development of reliable models for correlating and predicting viscosities of pure nonpolar and polar liquids. However, there is still a lack of a sound theory for the accurate prediction of liquid viscosities within a wide Ž . range of temperatures and pressures Reid et al., 1987 . Furthermore, viscosity models based on similarities either with gas-like or solid-like behavior have not successfully been proven to yield values of liquid viscosity for pure liquids and Ž . mixtures as functions of temperature Chhabra, 1992 . Consequently, most of the viscosity models reported in the literature have been developed under semi-empirical and empirical considerations. Pertinent literature on viscosity models for pure liquids has been reviewed and evaluated by Przezdziecki Ž . Ž . Ž . and Sridhar 1985, Reid et al. 1987, Mehrotra 1991 , Mon-Ž . Ž . nery et al. 1995, Mehrotra et al. 1996 , and Poling et al. Ž . 2001 . A thorough review of the literature reveals that numerous empirical and semiempirical models have been published for viscosities of pure liquids with exponential viscosity-temperature functions receiving most of the attention. The corresponding states principle along with the Eyring's absolute rate theory are the most widely used approaches to represent the Ž . viscosity of pure liquids. Recently, Lei et al. 1997 presented a two-parameter model based on the Eyring's absolute rate theory for the correlation of the viscosity of pure liquids under saturated conditions. Their correlating results yielded an overall ADD of 1.51% in the representation of experimental liquid viscosities of 106 pure nonpolar and polar fluids. An important feature of the model proposed by Lei et al. is that, at a given temperature, the liquid viscosity can directly be computed from equilibrium properties such as vapor presCorrespondence concerning this article should be addressed to R. Macıas-Salinas. sure, heat of vaporization, and compressibility factors of the phases at equilibrium. Based on the two-parameter model of Ž . Lei et al. 1997 , the purpose of the present study is three fold. The first purpose is to make use of a well-known cubic equation of state to calculate all of the thermodynamic properties required in the model, thus enabling the simultaneous calculation of vapor-liquid equilibria and saturated liquid viscosity. The second purpose is to improve the correlation of liquid viscosity over a wider temperature range by modifying the functionality between the activation energy and the internal energy of vaporization, and, the third purpose is to extend the use of the model to the calculation of compressed Ž liquid viscosities at pressures larger than the saturation . point .

High pressure viscosity modeling of pure alcohols based on classical and advanced equations of state

“…EoSs are the useful tools to relate pressure, volume and temperature of a fluid to each other. Some viscosity models in the literature use from EoSs to involve pressure effect in the viscosity estimation [1][2][3][4][5][6][7]. Basically the effect of pressure on the viscosity models in the literature has been studied as direct and indirect methods.…”

“…Much efforts have been directed towards the development of reliable and accurate models applied to the wide ranges of temperature and pressure for correlating and predicting viscosities of pure nonpolar and polar liquids [1,3]. The most of the viscosity models found in the literature have been developed in a large spectrum from highly theoretical to simple empirical correlations [2,3].…”

“…The most of the viscosity models found in the literature have been developed in a large spectrum from highly theoretical to simple empirical correlations [2,3]. Many of the viscosity models are only valid to predict either the liquid or the gas phase viscosity.…”

“…Knowledge of viscosity of pure liquids and liquid mixtures is essential in a wide range of chemical engineering problems dealing with for example heattransfer, mass transfer operations, and fluid-flow processes [3]. In spite of the essential role of viscosity in transport properties in engineering design, our understanding of such properties is low-order to that of equilibrium properties [2].…”

“…Basically the effect of pressure on the viscosity models in the literature has been studied as direct and indirect methods. For instance, Eyring's Nomenclature Roman a 1 , a 2 , a 3 Adjustable parameters of friction theory ã assoc Reduced Helmholtz free energy of associating contribution ã disp Reduced Helmholtz free energy of dispersion contribution ã hc Reduced Helmholtz free energy of hard-chain contribution ã res Residual Helmholtz free energy b 1 , b 2 , b 3 Adjustable parameters of friction theory B…”