A versatile thermostatted glass tube MRI rheometer

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 r heometer 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 r ange 10-60 degrees C, which showed that measured shear viscosity was indepe ndent of the radial position, demonstrate that the temperature control is r eliable. The good agreement of MRI measured viscosities with those produced by classical rheometry indicates the accuracy of the MRI rheometer. Result s 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 predomina nt for the fluid flowing in the central region of the tube; in contrast, th e flow in the region near the wall showed the time-independent characterist ic of power law fluid. Comparisons with data from cone-and-plate rheometry demonstrate the complementary power of MRI for studies of theologically com plex fluids; importantly, the MRI method can be used to measure the effects of 'shear history' on the flow rheology.