INFLUENCE OF LARGE SOLID SPHERICAL-PARTICLES ON THE RESIDENCE TIME DISTRIBUTION OF THE FLUID IN 2-PHASE TUBULAR FLOW

The effect of large solid particles on the residence time distribution of the fluid in two-phase flow was studied in a pilot scale continuou s tubular system. The residence time distribution was characterized wi th four parameters: the normalized minimum and mean residence time, th e normalized standard deviation and the skewness. The effect of partic le concentration (1 and 3%) and particle diameter (diameters approxima tely 0.3 and 0.4 of the tube diameter) were analysed for fluids with d ifferent viscosities and at different flow rates. It was observed that the presence of particles, even at very low concentration, has a sign ificant effect, increasing the mean residence time and decreasing the standardized dispersion. This effect was attributed to particles break ing the velocity profile of the fluid and causing some localized mixin g due to their rotational velocity. Although the presence of particles affected the results, their concentration (or number) was not relevan t, in the range tested, which is very low for particulate foods.