A versatile thermostatted glass tube MRI rheometer

Abstract

A glass tube rheometer optimized for use with a magnetic resonance imaging (MRI) scanner has been developed. Mounted on a trolley, its `plug-and-play' design allows flow- and temperature-equilibria to be attained before the rheometer is inserted in the magnet without disruption of the flow of fluids. Design principles, construction details and rheological test results for water, and aqueous solutions of sucrose (50% w/w) and xanthan gum (0.5% w/w) are presented. Results for water and aqueous sucrose in the temperature range 10-60 °C, which showed that measured shear viscosity was independent of the radial position, demonstrate that the temperature control is reliable. The good agreement of MRI measured viscosities with those produced by classical rheometry indicates the accuracy of the MRI rheometer. Results for 0.5% w/w aqueous xanthan gum reveal an initial time dependency before the flow reached a steady state. The initial time dependency was predominant for the fluid flowing in the central region of the tube; in contrast, the flow in the region near the wall showed the time-independent characteristic of power law fluid. Comparisons with data from cone-and-plate rheometry demonstrate the complementary power of MRI for studies of rheologically complex fluids; importantly, the MRI method can be used to measure the effects of `shear history' on the flow rheology.