Heat Transfer Coefficients Associated with Canned Particulate/Non-Newtonian Fluid (CMC) System During End-Over-End Rotation

Heat transfer to canned Nylon particles suspended in carboxymethylcellulose (CMC) solutions during end-over-end rotation was studied in a pilot-scale, full water-immersion single cage rotary retort. Flexible thin wire thermocouples were used to measure the temperature at particle centres. Temperature distribution in the canned fluid was measured and found to be large as the concentration of CMC solution increased beyond 0.6%, which made conventional overall heat transfer coefficient (U) and fluid to particle heat transfer coefficient (hfp) calculations impractical. Therefore, an apparent heat transfer coefficient (hap) between retort and particle surface was proposed and evaluated. The hap concept effectively combines U and hfp and therefore permits direct predictions of particle temperature and lethality based on retort temperature, rather than fluid temperature inside the can. The effects of retort temperature (110-130°C), rotation radius (0-240 mm) and rotation speed (0-20 rpm) on hap were studied by a respond surface methodology. It was found that rotation speed was the most significant factor (P < 0.005) followed by retort temperature (P < 0.05) in influencing hap. The effect of rotation radius was not significant (P < 0.05).