Pressure-driven capillary viscometer: fundamental challenges in transient flow viscometry

Area of Science:

• Rheology
• Fluid Dynamics
• Physical Chemistry

Background:

• Traditional viscometers often require multiple measurements to cover a broad shear rate range.
• Accurate viscosity determination is crucial for understanding fluid behavior in various scientific and industrial applications.

Purpose of the Study:

• To develop and validate an unsteady pressure-driven capillary viscometer.
• To enable continuous viscosity measurement across a wide shear rate range in a single experiment.
• To provide a method for accurate viscosity determination of Newtonian and non-Newtonian liquids.

Main Methods:

• Utilizing a compressed-air driven system to force liquid through a capillary tube.
• Measuring the decay of driving pressure over time as the fluid flows.
• Applying curve fitting techniques to experimental pressure-time data using an explicit expression for transient pressure.

Main Results:

• Demonstrated the theoretical validity of the pressure-driven capillary viscometer approach.
• Successfully determined the viscosity of both Newtonian and non-Newtonian liquids.
• Showcased the ability to cover a broad shear rate range within a single measurement.

Conclusions:

• The unsteady pressure-driven capillary viscometer is a valid and efficient tool for fluid viscosity analysis.
• This method offers a significant advantage by measuring viscosity across a wide shear rate spectrum continuously.
• The technique is applicable to a diverse range of fluids, including complex non-Newtonian types.