Theoretical and Experimental Study of the Precision Falling Tube Viscometer
A new viscometer, the falling tube viscometer (FTV) has been developed. It possesses a large measurement range for viscosity from 0.005 to 10^7 poise. In this study, entrance and exit effects and the inertial effect have been taken into account. The fluid flow pattern, shear stress, and pressure distribution have been obtained numerically using the finite difference method. Theoretical and experimental investigations on the performance of the falling tube viscometer, over a wide range of tube diameters and lengths, have been carried out. A new variable, called the Geometry number which well characterizes the FTV has been defined. It is a critical constant for a given viscometer and is solely determined by the dimensionless tube diameters and length. Correlation equations of the Geometry number are presented as a function of dimensionless tube geometry for both the FTV and its asymptotic case, the falling cylinder viscometer (FCV). The agreement between the analytical and experimental results of the Geometry number and viscosity, the viscometer repeatability as well as the viscometer accuracy are all within 1%. Both the theoretical analysis and experimental data indicate that falling tube viscometers based on the correlated equations are accurate and absolute viscometers.
- Pub Date:
- Engineering: Mechanical; Physics: Fluid and Plasma