Assessment of a solid-state bulk acoustic wave sensor to measure viscosity of Newtonian and Non-Newtonian fluids under static and flow conditions

Abstract

Monitoring and control of inline viscosity is crucial for process optimisation and for ensuring a high quality final product but currently this parameter is still under-utilised in the dairy industry. This study investigated a solid-state bulk acoustic wave sensor to measure the viscosity of Newtonian (oil standards) and Non-Newtonian fluids (reconstituted skim milk (RSM) at different concentrations) under static (off-line measurements) and flow conditions (in-line measurements). Results illustrated that an increase in total solids (TS) of RSM gave an increase in acoustic viscosity. Non-linear regression was applied to the experimental data to successfully transform the acoustic viscosity outputs into commonly-used reference viscosity values. RSM at higher TS presented a non-Newtonian behaviour and demonstrated shear-thinning properties. Under flow conditions the viscosity of the RSM decreased as a result of shearing experienced in the pipe. This study demonstrated the potential of an acoustic wave sensor to measure in-line viscosity in dairy applications.