The use of single and twin-screw extruders for solid-phase reactions is a promising method to intensify a process in a more sustainable manner.In this manuscript,we report a detailed analysis of the residence time dis...The use of single and twin-screw extruders for solid-phase reactions is a promising method to intensify a process in a more sustainable manner.In this manuscript,we report a detailed analysis of the residence time distribution(RTD)in vertical single-screw reactors.The results will help in the selection of the right screw design that would help achieve the desired residence time,which is necessary for a reaction to happen.Experiments were conducted in three vertical screw reactors(having fixed shaft diameter)with varying dimensions using granular free-flowing powders of sodium chloride and silica with a mean particle size of∼25μm.RTD behavior was modeled using the radial particle velocities in the screw reactor's centrifugal field.Further,a method is proposed for estimating the axial dispersion coefficient of dry powders in such sheared flows using true and bulk densities of the powder and the screw shear rate.This dispersion coefficient is used in the axially dispersed plug flow model to describe the RTD behavior of screw reactors with acceptable accuracy.The theoretically predicted and experimentally obtained dispersion coefficients are found to be similar thereby confirming the suitability of the model.展开更多
This paper proposes a novel hybrid method to simulate the dry granular flow of materials over a wide range of inertial numbers that simultaneously covers the quasi-static and dense granular flow regimes. To overcome t...This paper proposes a novel hybrid method to simulate the dry granular flow of materials over a wide range of inertial numbers that simultaneously covers the quasi-static and dense granular flow regimes. To overcome the lack of incremental objectivity whenever large deformations occur in solid-like regimes and to remove computational singularities in fluid-like regimes close to rest, the elastic–perfectly plastic theory based on the Drucker–Prager yield criterion is combined with the theory of dense granular flows. By implementing some new modifications at the boundaries and removing all ghost particles, smoothed particle hydrodynamics （SPH） is used as the framework for the method. A number of benchmark problems have been solved to show the capabilities of the new modified SPH method. Precise prediction of both location and pressure makes the modifications comparable with the previous works on SPH. Finally, the method is used to solve the classic 2D dry granular cliff collapse problem and to model dry granular material flow inside a rotary drum. The outcomes of the numerical simulation show good agreement with tabletop experiments and published results.展开更多
基金funding from CSIR(MLP100926)and SERB(DST,Govt.of India)(CRG//2023/001897-G)for this work.
文摘The use of single and twin-screw extruders for solid-phase reactions is a promising method to intensify a process in a more sustainable manner.In this manuscript,we report a detailed analysis of the residence time distribution(RTD)in vertical single-screw reactors.The results will help in the selection of the right screw design that would help achieve the desired residence time,which is necessary for a reaction to happen.Experiments were conducted in three vertical screw reactors(having fixed shaft diameter)with varying dimensions using granular free-flowing powders of sodium chloride and silica with a mean particle size of∼25μm.RTD behavior was modeled using the radial particle velocities in the screw reactor's centrifugal field.Further,a method is proposed for estimating the axial dispersion coefficient of dry powders in such sheared flows using true and bulk densities of the powder and the screw shear rate.This dispersion coefficient is used in the axially dispersed plug flow model to describe the RTD behavior of screw reactors with acceptable accuracy.The theoretically predicted and experimentally obtained dispersion coefficients are found to be similar thereby confirming the suitability of the model.
文摘This paper proposes a novel hybrid method to simulate the dry granular flow of materials over a wide range of inertial numbers that simultaneously covers the quasi-static and dense granular flow regimes. To overcome the lack of incremental objectivity whenever large deformations occur in solid-like regimes and to remove computational singularities in fluid-like regimes close to rest, the elastic–perfectly plastic theory based on the Drucker–Prager yield criterion is combined with the theory of dense granular flows. By implementing some new modifications at the boundaries and removing all ghost particles, smoothed particle hydrodynamics （SPH） is used as the framework for the method. A number of benchmark problems have been solved to show the capabilities of the new modified SPH method. Precise prediction of both location and pressure makes the modifications comparable with the previous works on SPH. Finally, the method is used to solve the classic 2D dry granular cliff collapse problem and to model dry granular material flow inside a rotary drum. The outcomes of the numerical simulation show good agreement with tabletop experiments and published results.
