The objective of the study is to develop a mathematical model of continuous mixing of granular materials, which takes into account the crosswise non-homogeneity of particulate flow inside a mixer. The target function of modeling is the residence time distribution of a tracer injected into the inflow. The model is built on the basis of the theory of Markov chains. The working space of a mixer is presented as a 2D array of perfectly mixed cells, through which the tracer travels according to the matrix of transition probabilities. The model covers the tendency of the tracer to upward/downward segregation. Finally, for a given flow pattern, the model allows calculating the RTD curves for various throughputs and for various properties of an imperfect tracer.
Cereal Chem. 93(4):395-401Solid-state milling is an effective physical modification method applied to improve functional properties of starch. In this work the effect of solidstate milling on the viscoelastic characteristics of maize starch gelatinized dispersions (gels) was investigated by using oscillatory squeeze film rheometry. The relaxation spectrum of the samples under study was calculated from the data obtained. It was found that solid-state milling resulted in a decrease of the storage (G9) and loss (G0) moduli; meanwhile, loss tangent (tan d)increased. At a starch milling time more than 10 h, G0 > G9 and the gelatinized starch dispersions behaved as liquid-like systems. The relaxation maxima shifted to shorter relaxation times, and the heights of the maxima decreased with increasing milling time. The relationship between the complex viscosity h* and steady-shear viscosity h gradually altered from h* > h to h* < h as the milling time increased. The results can be used to determine the processing conditions of milled starch.
The objective of this study was to build a model that describes evolution of the state of a mixture where microscale mixing (penetration of particles into the closest neighborhood of its position during a small period of time) is accompanied by macroscale mixing (periodical exchange of large parts of the mixture inside a mixing volume after a certain period of time). The mixing kinetics for segregation and nonsegregation mixtures, agitated by blades placed in a certain sequence inside the mixing volume, was modeled. The case of exchange by the halves of material was examined as well. Two variants of the exchange were examined: the parallel displacement and the symmetric turn. It is shown that there exist optimal parameters of the macroscale transitions providing the highest rate of mixing. The proposed model helps to achieve better understanding of the process and suggests some ideas to improve the design of the mixers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.