FLUID-TO-PARTICLE HEAT-TRANSFER COEFFICIENTS IN CANS DURING END-OVER-END PROCESSING

Convective heat transfer coefficients were measured during end-over-en d (EOE) processing of canned Newtonian fluids (oil and water) with a s uspended thermocouple equipped polypropylene spherical particle (diame ter = 19 mm). Particle transient temperatures were measured at the cen ter using a flexible Sine wire (0.0762 mm diameter) thermocouple, allo wing for particle movement inside the can during the EOE rotation. Thr ee retort temperatures (110 to 130 degrees C) and four rotational spee ds (0 to 20 rpm) were employed as variables in a water immersion rotar y retort (Stock PR-900) employed for processing. The fluid-to-particle heat transfer coefficient, h(fp), varied from 65 to 120 W/(m(2).K) (b etween water and particle) and 20 to 85 W/(m(2).K) (between oil and pa rticle) and overall heat transfer coefficient, U, varied from 480 to 8 80 W/(m(2). K) for water and 115 to 165 W/(m(2).K) for oil depending o n processing conditions. A dimensionless correlation was developed in terms of Nusselt number (Nu), Reynolds number (Re), Prandtl number (Pr ) and dimensionless temperature (phi), to predict the U: Nu = 115 + 18 Re(0.33)Pr(0.16)phi(3.61) The characteristic dimension in Nu and Re w as the diameter of rotation. This correlation, with R(2) = 0.88 is val id for Re : 240-48,000; Pr : 7.0-1175 and phi : 0.82-0.85.