RESIDENCE TIME DISTRIBUTION OF CYLINDRICAL PARTICLES IN A CURVED SECTION OF A HOLDING TUBE: THE EFFECT OF PARTICLE SIZE AND FLOW RATE

摘要

The residence time and the residence time distributions of cylindrical particles (density 1130 kg/m~3 and particle concentration 20% v/v) in a U-bend of 22 cm radius of curvature were studied. All experiments were conducted at room temperature and with an aqueous solution of sodium carboxymethylcellu-lose (0.5% CMC) as the carrier medium. Two levels of particle size (11 and 20 mm) and three levels of product flow rates (0.66 x 10~(-3), 0.81 x 10~(-3), and 0.97 x 10~(-3) m~3/s) were used. The results obtained from this study showed that the mean and the standard deviation of the normalized residence time of particles decreased as either particle size or flow rate was increased. The E(θ) and F(θ) curves indicated that flow profile of particles approached the plug flow profile as the particle size or the flow rate was increased. Results obtained from regression analyses revealed that the mean and the standard deviation of the normalized residence time were significantly influenced by particle Froude number and most strongly by particle-to-tube diameter ratio.