Impact of solids fraction and fluid viscosity on solids flow in rotating cans

Solids motion in a fluid significantly contributes to particulate heat transfer with that fluid, particularly in the radial direction for axially rotating cans. In this paper, the flow pattern, velocity profile and residence time distribution of solids and the solids' position exchange frequency between the centre and the wall of cans have been investigated using the positron emission particle tracking (PEPT) technique. The results indicate that the solids flow is complex and varies significantly with the solids fraction and the liquid viscosity, but follows specific patterns. The solid trajectories took a D shape in water and golden syrup while a reflected D shape in dilute golden syrup. A good exchange of solids from wall to the central region was observed with the dilute golden syrup which had a viscosity of 2 Pa s. The optimum solids flow pattern for a fast and uniform heating of canned foodstuffs can be achieved by controlling the liquid viscosity, solids fraction and the solids/liquid density difference under monitoring using PEPT. (C) 2008 Elsevier Ltd. All rights reserved.