Fluid-to-particle convective heat transfer coefficient as evaluated in an aseptic processing holding tube simulator

A pilot scale aseptic processing holding tube simulator was fabricated for evaluating fluid-to-particle convective heat transfer coefficients at temperatures up to 110C. The simulator was calibrated to give carrier fluid flow rate as a function of CMC concentration, temperature, pump rpm and pipe diameter. Fluid-to-particle heat transfer coefficients (h(fp)) were estimated with model and real food particles held stationary in a moving liquid. Data were gathered under various conditions: CMC concentration (0 - 1.0% w/w), flow rate (1.0 - 1.9 x 10(-4)m(3)/s) and particle size (diameter: 21 and 25.4 mm; length: 24 and 25.4 mm). Depending on operating conditions, average heat transfer coefficients (h(fp)) ranged from 100 to 700 W/m(2)C with corresponding Biot numbers (Bi) ranging from 10 to 50. CMC concentration, fluid temperature and flow rate, as well as their interactions, had significant effect (p < 0.05) on h(fp) for both Teflon and potato particles. Some differences were observed with respect to the associated h(fp) for Teflon and potatoes due probably to differences in their structural/textural characteristics. Heat transfer coefficient associated with cooling were significantly lower (p < 0.05) than those associated with heating.