Determination of food particle residence time distributions in coiled tube and straight tube with bends at high temperature using correlation analysis

The effects of tube geometry (coiled and straight), particle concentration (0–30% v/v), average product flow rate, and carrier fluid temperature (96–124 °C) on residence time distributions of model food particles in the holding section of an aseptic processing system were investigated by means of correlation analysis. Hold tube geometry and flow rate exerted significant effects on the mean normalized residence time. Minimum normalized residence time was significantly influenced by the fluid temperature and the interaction between hold tube geometry and particle concentration. In the coiled tube, standard deviation of normalized residence time decreased with an increase in particle concentration. The fastest-moving particles in the coiled tube possessed a velocity of 1.96 times the average product velocity, whereas the velocity of fastest-moving particle in the straight tube was 1.8 times the average product velocity. Based on empirical expressions of the residence time parameters as functions of particle concentration and dimensionless groups (Frf, Regp, and Arf), variable influence of several forces on particle residence time of particulate food suspensions in different settings was deduced.