Evaluation of tube-flow fluid-to-particle heat transfer coefficients under controlled particle oscillatory motion

Abstract

A previously developed particle oscillatory motion technique, with direct temperature measurement of particles in motion under tube-flow conditions, was evaluated for studying the effect of several influencing factors associated with fluid-to-particle heat transfer coefficient ( h fp). A full factorial experimental design was employed involving spherical particles made of aluminum epoxy and Nylon of different sizes (12.7–17.5 mm), different particle linear velocities (0.06–0.21 m/s), heating medium viscosities (0 to 1% concentration of carboxymethyl cellulose solution, CMC) and fluid temperatures (60–80°C). Statistical analysis of experimental data indicated that all factors investigated had a significant ( P<0.001) effect on h fp. A t-test grouping analysis showed that mean values of h fp were different ( α=0.05) among the levels of the various factors. As expected, the fluid-to-particle heat transfer coefficient increased with particle velocity and fluid temperature, and decreased with CMC concentration. In agreement with some reports, h fp decreased with particle size. Further, the values of h fp associated with the aluminum epoxy particle were generally higher than that for the Nylon particle of the same size. The study thus demonstrates the feasibility and usefulness of the technique for gathering tube-flow h fp data under a range of conditions involving particle oscillatory motion.