Development and Validation of Tandem Capillary Tubes Method to Measure Viscosity of Fluids

抄録

The viscosity of working fluids is an essential thermophysical property to design heat exchanger, efficient processes, equipment, and simulation. Different types of conventional methods are used to measure the viscosity of fluids. The capillary tube method is based on the theoretical principle, and it is a reliable method. Nevertheless, it is tough to measure viscosity precisely because of problems involved in an equipment. In the present study, the tandem capillary tube method is proposed, and reliability of this method is explained. In this method, the pressure changes at the ends of the tube can be canceled, and the viscosity can be easily obtained from the Hagen-Poiseuille equation. A way to eliminate an effect of diameter difference between tubes is also proposed. The reliability and accuracy have been verified by comparing the measured viscosities of R134a to the reference values calculated by REFPROP ver.9.1. Most of the data agreed well within ±1.5 % deviation. These results show the validity of the proposed equation in the present viscosity measurement system. The expanded uncertainty of viscosity measurement was estimated as 2.2 %.