Viscosity of Pure Liquid Estimation Equation and Calculator

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Viscosity of Pure Liquid Estimation Equation and Calculator

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Viscosity of a Pure Liquid Estimation Equation and Calculator

Eq. 1
µ = ( N h / V ) · exp ( 3.8 · T_b / T )

Where:

N = Avogadro Number, (g/mol)
h = Planck Constant (g cm²/s)
V = Volume of a Mole of Liquid (cm³/g mol)
T_b = Boiling Point (K)
T = Ambient Temperature (K)
µ = Viscosity of a Pure Liquid (g/(cm · s))

This formula although is only approximate in nature, does give the observed decrease of viscosity with temperature, but errors of as much as 30% are common when Eq. 1 are used.This formula should not be used for very long slender molecules, such as n-C₂₀H₄₂.

There are, in addition, many empirical formulas available for predicting the viscosity of liquids and liquid mixtures. For these, physical chemistry and chemical engineering textbooks should be consulted.

Source:

Bird, R.B., Stewart, W.E. and Lightfoot, E.N. (2002). Transport Phenomena (Second Ed.). John Wiley & Sons, Chapter: 1, Page: 31.