MAGNETIC-RESONANCE-IMAGING OF LIQUID FLOW AND PORE STRUCTURE WITHIN PACKED-BEDS

Magnetic resonance imaging (MRI) volume- and velocity-measurement tech niques are used to probe structure-flow correlations within the interp article space of a packed bed of ballotini. Images of the three mutual ly orthogonal components of the velocity field are obtained in two per pendicular slices within a bed of 5 mm diameter ballotini packed withi n a glass column of internal diameter 4.6 cm. Comparison of flow image s obtained for two beds of identical column-to-particle diameter ratio but of differing length show that velocity enhancements at the walls of the bed are greater in the shorter, more ordered, bed. A three-dime nsional volume image of each bed is also obtained and analysed to part ition the interparticle space into individual pores and determine the location of pore necks. Correlations between volume flow rate and the surface area of the constrictions (pore necks) within the interparticl e space lie between two limiting behaviours. For pores associated with low local Reynolds number, the volume flow rate through the constrict ions scales as the square of the cross-sectional area of the constrict ion, whereas at the extreme of high local Reynolds number pores show v olume flow rates scaling with cross-sectional area. (C) 1997 Elsevier Science Ltd. All rights reserved.