Balanced beam tube viscometry vs rotational viscometry: A comparison

Abstract

Energy gradient prediction is arguably the most important aspect of slurry pipeline design. For non-Newtonian slurries, pipeline design, operation and optimisation is dependent on how well the flow curve of the slurry can be measured. Because of geometric similarity, tube viscometry for flow curve measurement is often preferred to rotational viscometry. The Flow Process Research Centre [FPRC] has been developing the concept of the Balanced Beam Tube Viscometer [BBTV] for some time now, and this has proved to be a most valuable tool for both research and routine slurry characterisation. Comparing tube viscometer data with rotational viscometer data has a number of problems. The shear rate measured in a tube viscometer is a pseudo shear rate that has to be converted to true shear rate using either the Rabinowitch-Mooney transformation (which assumes no wall slip) or the Tikonov regularisation (which takes wall slip into account). The coaxial cylinder viscometer has problems associated with the assumptions made with regard to the shear field between the bob and the cup as well as the bob design giving rise to end effects. A comparison is made between the two approaches using Newtonian and non-Newtonian materials.