Browsing by Author "Sastry, Sudhir K."
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- Dimensionless analysis of fluid-to-particle heat transfer coefficientsPublication . Baptista, Paulo N.; Oliveira, Fernanda A.R.; Oliveira, Jorge C.; Sastry, Sudhir K.Average fluid-to-particle heat transfer coefficients were experimentally determined for spherical aluminium particles heated in car☐ymethylcellulose solutions. Two situations were considered: a still panicle immersed in a moving fluid, and a particle rotating in an otherwise stagnant fluid. Fluid flow rate, rotating particle velocity, particle diameter and fluid rheological properties were varied, covering a large range of the generalized Reynolds (0 to 801) and Prandtl (69 to 5358) numbers. Average heat transfer coefficients ranged between 56 and 2612 W/m2K. The results were compared with values predicted by published dimensionless correlations, showing that correlations based on a Fro¨szling-type equation were more adequate. It was found that the contribution due to natural convection should be considered for proper correlation of the results at low Reynolds numbers. The results also show the importance of the fluid velocity profile.
- Effect of product and process variables in the flow of spherical particles in a carrier fluid through straight tubesPublication . Baptista, Paulo N.; Oliveira, Fernanda A. R.; Caldas, Susana M.; Oliveira, Jorge C.; Sastry, Sudhir K.Residence time of particles and fluid-to-particle heat transfer coefficient, two of the major unknowns in the aseptic processing of particulate fluid foods, are intimately related with the linear and rotational velocities of the solid particles. These two velocities were measured by videotaping the flow of individual spherical particles in transparent straight tubes. The effect of fluid velocity and viscosity, particle diameter and density and tube diameter and upward inclination was statistically evaluated using a replicated full factorial design at two levels. Particle linear velocities between around one third of the average fluid velocity and 15% higher were obtained. Rotational velocities were usually lower, but of the same order of magnitude. Particle density and particle diameter had a significant effect on the two particle velocities analysed. The effect of fluid velocity was