Minimum Velocity of Impingement Fluidization for Parachute-Shaped Vegetables

Abstract

Accurate calculation of the minimum fluidization velocity makes it possible to reduce raw material losses due to the use of excessively high or excessively low air velocities. This is particularly true for impingement fluidization, which is little studied, especially when treating parachute-shaped raw material. This paper focused on determining the drag coefficient for cauliflower florets, mushrooms, and broccoli. Analysis of the critical particle lift velocity showed that the lowest value of the drag coefficient was found for mushrooms (0.9). The parachute-shaped vegetables analyzed had a large scatter of drag coefficient values associated with their specific shape (standard deviation: mushrooms 0.10 broccoli 0.14, and for cauliflower 0.15). The measured mean values of the minimum fluidization velocity of the tested vegetables in the impingement fluidization method ranged from 6.9 m∙s−1 to 10.97 m∙s−1. Application of the procedure recommended by Shilton and Narajan for calculating the minimum fluidization velocity on the basis of the shape coefficient ε resulted in large discrepancies between the calculated and experimental values (from 2.4 m∙s−1 to 3.8 m∙s−1).