Effect of a Symmetric Contraction on the Concentration Profiles of a Particleladen Slurry

Abstract

The effect of a symmetric contraction on the concentration profiles of a xylene- 2 amino, 4, 6 dimethyl pyrimidine (ADP) slurry flowing in a cylindrical pipe were simulated using computational fluid dynamics. ANSYS FLUENT 12.0 was used as the computational fluid dynamic software. Variations in the pipe Reynolds number, initial efflux concentration, and the particle size were considered. An ASME flow nozzle, that served the purpose of a contraction, was incorporated in the fully-developed region of the pipe geometry. The pipe had an L/D ratio of 55. The k-epsilon turbulence model with standard wall functions coupled with the mixture multi-phase model was used to simulate all the test cases. A grid independence study was performed for both the velocity and concentration profiles. The model was validated with experimental data sets available in the literature. The concentration profiles at the exit plane were compared with those registered at the fully-developed region. The present computational model predicts the velocity and the concentration profiles of a slurry with an acceptable degree of accuracy. The accuracy of the simulated results is compromised in the near-wall region. It was found that the concentration profiles in all the test cases displayed reduced spatial variation at the exit plane of the geometric contraction. At higher Reynolds number (ReD) the concentration profiles of 38 m ADP particles realized at the exit plane and the fully-developed region were almost identical. It was found that the gradient of concentration along the vertical diameter of the geometry for heavier particles decreases with an increase in pipe Reynolds number. The turbulence intensity of the flow field at the exit plane of the contraction was found to be lower than that registered at the fully-developed region. Owing to this, the exit plane of the geometric contraction may serve as a suitable location for performing near infra-red and mass spectral analysis of a particle-laden slurry.