THE EFFECT OF TRANSLATIONAL AND ROTATIONAL RELATIVE VELOCITY COMPONENTS ON FLUID-TO-PARTICLE HEAT-TRANSFER COEFFICIENTS IN CONTINUOUS TUBE FLOW

A liquid crystal technique was used to determine average fluid-to-part icle heat transfer coefficients (hfp) for single spherical hollow alum inium particles heating in carboxymethylcellulose solutions in continu ous tube flow. The particles' linear and rotational velocities were al so measured by videotaping the particle motion at a bottom position. P articles with different diameter and density were used in solutions wi th different viscosities and at different flow rates (7 < Reynolds < 2 84; 144 < Prandtl < 1755). The values of the average heat transfer coe fficient were between 334 and 1497 W/m(2)C. The results showed that bo th the relative fluid-to-particle velocity and the particle rotational velocity influence the heat transfer coefficients, although it is not possible to individualize their effects. However, the addition of the individual effects, predicted by using published dimensionless correl ations, yielded a good fit with the experimental values. (C) 1997 Publ ished by Elsevier Science Ltd on behalf of the Canadian Institute of F ood Science and Technology.