RESIDENCE TIME DISTRIBUTION OF FOOD AND SIMULATED PARTICLES IN A MODEL HORIZONTAL SWEPT SURFACE HEAT-EXCHANGER

The residence time distribution (RTD) of food and inert particles flow ing in a swept surface heat exchanger at room temperature was investig ated. The effects of selected experimental conditions on RTD include p article shape (cube, cylinder, and sphere), particle concentration (10 , 20, and 30% w/v), particle type (potato, carrot, turkey, green peas, and polystyrene), fluid viscosity (water, 0.5% CMC, and 1.0% CMC), bu lk flow rate (5.8 x 10(-4), 7.28 x 10(-4), and 8.71 x 10(-4) m(3)/s) a nd shaft rotational speed (30, 60, and 90 rpm). Although turkey cubes were denser than other food particles, they moved faster than potato a nd carrot particles. Mean particle normalized residence time (MNPRT) o f food particles (green peas) were found to be significantly higher th an that of simulated particles (polystyrene). Cylindrical particles st ayed longer than cubic particles in water, but not significantly in CM C solution. MNPRT values were found to be dependent on viscosity. Incr easing particle concentration (up to 30 %) tended to decrease MNPRT. B oth bulk flow rate and shaft rotational speed tend to decrease MNPRT, thus reducing the lethality achieved. The distribution of residence ti me curves were narrowed by decreasing particle concentration, bulk flo w rate, and shaft rotational speed, and by using fluids with high visc osity. In general, particle velocity was found to be higher than the a verage bulk velocity. The fastest particle velocity was found to be 3. 23 times the average bulk velocity while the ratio was 0.382 for the s lowest.