Viscosity of liquids

Abstract

Three viscosity correlations were tested for liquids at their boiling points. Compounds studied included normal paraffins, branched-chain hydrocarbons, aromatics, halogenated methanes and ethanes, water, and aliphatic alcohols. The correlations were tested for the most part with viscosity and thermodynamic data found in the literature. Some experimental viscosity measurements were made, however, for normal paraf3ns from pentane to octane at temperatures up to about 300"F., which is higher than has previously been reported.Two correlations are based on Eyring's theory of absolute reaction rates. The third is based on the compressibility factor of the saturated liquid, and this correlation is unique, as all available data for normal paraffins with eight or more carbon atoms are represented by a single curve. The three correlations presented here can be used to extrapolate viscosity data over large temperature ranges up to the critical temperature. Logical predictions of the viscosities of related compounds are possible.The theory of absolute reaction rates (17) was applied to the viscosity of liquids by Eyring and coworkers (16, 18, 22, 27, 39). It was postulated that before a molecule can flow (move) a "hole" must be available for it to move into. Energy is required to make this hole, and the following equation was developed to represent the relationship between the free energy of activation and the viscosity in centipoises:Since a flow process can be considered to be at constant volume, the energy required to make a hole the size of a molecule is the internal energy of vaporization. It was thought (22, 39) that the relationship between the internal energy of vaporization and the free energy of activation might be significant. The ratio of these two values has been designated the energy ratio n: Lylo F. .4lbright is at Purdue Universit W y t Lafayette, Indiana, and John Lohrens at t k University of Kansan, Lawrence, Kanaas.TEYERATLRZ. T Fig. 1. Vis-osity measurements of lightparaffin hydrocarbon liquids at their boiling points. Page 290This energy ratio was reported (22, 39)to be equal to approximately 2.45 for numerov liquids including water, alcohols, and hydrocarbons. The alcohols and hydrocarbons tested or the temperatures of any of the liquids however were not specified. Since at the critical temperature the internal energy of vaporization is zero and since the free energy of activation is still presumably finite, the energy ratio is also probably zero at this temperature. It appears, therefore, that the energy ratio is a function of temperature. Another equation (22) based on the theory of absolute reaction rates is as follows: temperature over a large pressure range within about 30% accuracy. As far as can be determined, however, the equation was tested for a given compound a t only one temperature. Viscosity data have been extrapolated frequently in the past by means of the following plots: (1) viscosity vs. temperature, (2) logarithm of viscosity vs. the reciprocal of absolute temperature, and (3) logarit...

Reference Correlation of the Viscosity of n-Heptane from the Triple Point to 600 K and up to 248 MPa

“…023103-8 MICHAILIDOU ET AL. 76 4.76 4.76 Fermeglia 77 2.02 2.02 Iwahashi 78 2.38 2.38 Brunson 79 5.57 À4.67 Fermeglia 77 2.02 2.02 Kouris 80 0.80 À0.80 Schrodt 81 0.39 À0.39 Chandrashekhar 82 1.39 À1.39 Rao 83 1.50 1.50 Wakefield 84 1.23 À1.23 Celda 85 0.77 À0.77 Senanayake 86 0.28 À0.28 Awwad 87 3.09 3.09 Awwad 88 1.05 1.05 Martin 89 0.76 À0.76 Kashiwagi 90 0.97 À0.97 Sreenivasulu 91 0.49 À0.49 Rabe 92 2.37 2.01 Dusart 93 0.87 0.87 Gouel 94 5.86 À5.47 Gunchuk 95 1.24 1.24 Öz 96 1.28 1.28 Badalov 97 1.73 À0.97 Mussche 98 1.64 1.64 Diaz Pena 99 6.83 6.83 Moore 100 0.51 À0.51 Ratkovics 101 0.20 0.20 Shikhaliev 102 7.28 7.03 Nauruzov 103 0.70 0.46 Zhigunov 104 5.05 5.05 Konobeev 105 1.62 1.62 Kuss 106 2.94 À2.94 Darmois 107 2.96 À2.96 Carmichael 108 2.45 2.45 Bidlack 109 0.22 À0.22 Bagdasarian 110 1.55 1.53 Agaev 111 7.37 7.37 Golubev 112 9.10 À7.73 McAllister 113 0.04 À0.04 Albright 114 10.97 10.97 Ledneva 115...…”

Residual Entropy Scaling for Long-Chain Linear Alkanes and Isomers of Alkanes

“…Using the global parameters n g, k according to Table of the residual entropy scaling model as described in Section , the fluid-specific scaling factors ξ have been refitted in this work for all linear alkanes and isomers of alkanes for which multiparameter equations of state are available. The experimental viscosity data has been taken from the ThermoData Engine (refs − …”