Convective Heat Transfer at Particle‐Liquid Interface in Continuous Tube Flow at Elevated Fluid Temperatures

Liquid‐to‐particle convective heat transfer coefficients are useful in developing aseptic food processing systems. They were determined for continuous flow through a holding tube at 115.5°C using liquid crystal and relative velocity methods with sodium carboxymethylcellulose solution to simulate non‐Newtonian fluid characteristics. An on‐line tube viscometer was used for in situ estimation of rheological characteristics. Minimum and maximum values of h fp determined from the liquid crystal method ranged from 986 W/m 20 K to 2270 W/m 20 K, (Nusselt numbers from 26.4 to 54.6). Values from the relative velocity method ranged from 1143 to 2270 W/m 20 K (Nusselt numbers from 33.2 to 63.1) when using the Ranz and Marshall relation, and from 598 to 1456 W/m 20 C (Nusselt numbers from 13.6 to 24.1) with a flat‐plate correlation. Heat transfer coefficients increased significantly with decreasing carrier medium viscosity and decreasing particle‐to‐tube diameter ratio and increased with flow rate.