Multiphase Hydrodynamics in Steady and Pulse Jet Mixing Systems.

摘要

The goal of the present study is to evaluate the mixing performance of jet mixers in both liquid and solid-liquid mixing processes. Jet mixers have been studied for decades for its uses in liquid blending and solid-liquid mixing applications. In solid suspension processes, jet mixers can be just as useful if not more useful than conventional impeller mixers. However, there is a lack of phenomenological models that exist. The erosion and subsequent suspension of solids beds, as well as the suspension of a low concentration of solid particles must be better understood. The specific objectives were to develop analytical, experimental and numerical models that simulate a liquid, submerged, steady or pulsing jet mixer. Furthermore, specific objectives were to determine the performance of jet mixers in solid suspension processes by measuring the cloud height, develop a model that describes the erosion of a solids bed, and determine the effect of cohesive particles on the dispersion of particles once eroded. The results showed that the mixing performance, in terms of mixing time, was not enhanced with the use of pulsing jet flows. The results showed that the cloud height below about 24000 is not dependent on the jet Reynolds number. The erosion profiles of solids were found for solids beds composed of particles with different Archimedes numbers and results showed that there appears to be two different regimes present. The regimes occur based on the erosion mechanisms that are taking place, mainly entrainment and surface erosion. Results of the axial concentration studies showed that the time dependence of the concentration ceases to exist after a certain period, which is a function of the weight percent of cohesive particles.