Temperature-Viscosity Calculator V 1.02 Copyright © 2021 Henning Umland
The viscosity of newtonian liquids generally decreases with increasing temperature. The relationship between dynamic viscosity, η, and absolute temperature, T, can be described by the equation
ln η = a + b / T c .
This is a modification of the well-known Andrade equation (c = 1) with improved accuracy over a wide temperature range. a, b, and c are material constants. The program requires three data points (Ti , η i) with T1 < T2 < T3 to find b and c by iteration (secant method). With these values the programm calculates a and, optionally, the viscosity at an arbitrarily chosen temperature, T4. Preferably, the latter should be inside the interval [T1 , T3]. Extrapolated viscosities are possible but become less accurate as one moves farther away from the interval limits. T2 should be roughly halfway between T1 and T3 for best accuracy. All measurements must be made as accurately as possible since any error will directly affect the final result. Bad measurements, bad results! The method itself is very accurate. It has been cross-checked with temperature-viscosity tables for many liquids (water, alcohols, esters, lubricant oils, mercury, molten lead) and with own measurements (polyesters, molten hydrocarbon resins and asphalts). The systematic error rarely exceeds 1% and usually stays within the experimental error.
Calculated viscosity @ T4:
Disclaimer: This is experimental software. Although it has been thoroughly tested, it still may contain errors. The author assumes no responsibility for any damage resulting from the use of this software.