In Situ Rheological Monitoring of Viscous Non-Newtonian Fluids using a Helical Ribbon Agitator
Mechanically degraded food fluids were modelled as Power law fluids in a pilot scale (42 l) helical ribbon agitation vessel. Effective rheological representative flow curves determined from speed/torque data proved comparable to off-line laboratory rheometer measured data. Modelling effective viscosity as a Power law function gave effective consistency coefficient Keff which correlated strongly with K from the rheometer (R2<SUP2< sup>=0.99). Effective flow behaviour index neff was comparable in magnitude (average 5% difference) to rheometer measured equivalents. Determination of absolute consistency coefficient K using the mixer viscometer technique proved problematic with large differences in magnitude. Single point measurements of raw mixer torque data at a constant speed correlated well against reference off-line
techniques, namely the Bostwick Consistometer and consistency index from the rheometer (R2<SUP2< sup>=0.98 and R2<SUP2< sup>=0.99), coupled with low standard errors of estimate (4% & 3.2%) respectively. The helical ribbon system evaluated was capable of monitoring the rheological properties of fluids with large particulates.