A new method for liquid viscosity measurements: Inclined-tube viscometry

In this article, a method which can be used to measure the viscosity of liquids with an inclined tube at high pressures and for low-boiling substances is described. The measurement equation was established. The measuring methods for two unknown parameters which are in the measurement equation are presented, and a viscosity measurement system was designed and constructed, which consists of an experimental cell, an inclination-angle control subsystem, a constant temperature subsystem, and a data collection and process subsystem. At atmospheric pressure, the kinematic viscosity of pure water was measured at temperatures from 273.15 K to 333.15 K to demonstrate the performance of the apparatus. The results show that the absolute average relative deviation is 0.84% in comparison with reliable literature values. The kinematic viscosity of saturated liquid R134a and R600a were also measured at temperatures from 273.15 K to 295.15 K and 273.15 K to 300.15 K, respectively, and the corresponding absolute average relative deviations are 1.04% and 1.02% in comparison with reliable literature values. These experimental results demonstrate the performance of the apparatus, while providing estimates of the uncertainty and reliability of the experimental system.