Evaluation of factors influencing tube-flow fluid-to-particle heat transfer coefficient using a calorimetric technique Original Research Article

A previously developed calorimetric technique involving bulk or mass average temperature measurement of a moving particle without interfering in its motion was used to evaluate the effect of fluid flow rate, viscosity and temperature as well as particle size on the associated fluid-to-particle heat transfer coefficient (hfp) under tube-flow condition. Experiments were carried out for different flow rates (9–19 l/min), concentrations of carboxymethyl cellulose (CMC) in the carrier fluid (0–1% CMC solution) and temperature (50–70°C) as well as particle size (19–25.4 mm). The results of over 300 experiments indicated that the hfp values, which ranged from 650 to 2660 W/m2 K depending on the experimental conditions, increased significantly with an increase in fluid flow rate and particle size, and decreased with CMC concentration and temperature. A dimensionless correlation obtained between Nusselt number and a group of other dimensionless numbers yielded a high R2 value of 0.97 demonstrating an excellent suitability for the conditions tested.