Simulation on hydrodynamics of non-spherical particulate system using a drag coefficient correlation based on artificial neural network

Fluidization of non-spherical particles is very common in petroleum engineering.Understanding the complex phenomenon of non-spherical particle flow is of great significance.In this paper,coupled with two-fluid model,the drag coefficient correlation based on artificial neural network was applied in the simulations of a bubbling fluidized bed filled with non-spherical particles.The simulation results were compared with the experimental data from the literature.Good agreement between the experimental data and the simulation results reveals that the modified drag model can accurately capture the interaction between the gas phase and solid phase.Then,several cases of different particles,including tetrahedron,cube,and sphere,together with the nylon beads used in the model validation,were employed in the simulations to study the effect of particle shape on the flow behaviors in the bubbling fluidized bed.Particle shape affects the hydrodynamics of non-spherical particles mainly on microscale.This work can be a basis and reference for the utilization of artificial neural network in the investigation of drag coefficient correlation in the dense gas-solid two-phase flow.Moreover,the proposed drag coefficient correlation provides one more option when investigating the hydrodynamics of non-spherical particles in the gas-solid fluidized bed.

A review of membrane distillation enhancement via thermal management and molecular transport through nanomaterial-based membranes

Low-energy,high-efficiency desalination techniques are important because of the critical water-energy nexus.In particular,membrane distillation has great potential to harness low-grade and renewable energy sources.Composite membranes using micro-and nanomaterials have new capabilities and characteristics.This review focuses on the most recent developments and potential capabilities in membrane distillation systems from the perspective of nanomaterial enhancements,thermal management,and water transport.Self-heating nanomaterial membrane distillations using permeable composite membranes with significant photothermal or Joule-heating conversion capabilities enable macroscale thermal management and mitigate temperature polarization effects.Modifying the membrane structure and its interaction with water can accelerate water transport and evaporation,improving distillation at the microscopic level.This is expected to provide directions for the fabrication and manipulation of novel micro-and nanocomposite membranes for distillation processes at various levels,and enhance their applications.

Multiphysics numerical investigation of photothermal self-driving characteristics of SiO_(2)@Au Janus microparticles for drug delivery

The photothermal self-driving process of Janus microparticles has wide application prospects in the fields of biomedicine.Since silica and gold have good biocompatibility and high photothermal conversion efficiency,the SiO_(2)@Au Janus microparticles are widely used as drug carriers.Based on the multiphysics coupling method,the photothermal self-driving process of SiO_(2)@Au Janus microparticles was investi-gated,wherein the substrate was SiO_(2)particles and one side of the particles was coated with gold film.Under a continuous wave laser with irradiation of 20 W/cm^(2),the distance covered by the Janus particles was increased by increasing the thickness of the gold film and reducing the size of the SiO_(2)particles;the self-driving characteristics of the Janus particles were controlled substantially by increasing the intensity of the incident laser.Based on the simulation results,the thermophoretic motion and Brownian motion of particles can be measured by comparing the absolute values of the thermophoretic force impulse,Brownian force impulse,and drag force impulse.The Brownian force acting on Janus microparticles under low laser power cannot be ignored.Furthermore,the minimum laser power required for Janus particles to overcome Brownian motion was calculated.The results can effectively guide the design of Janus particles in biomedicine and systematically analyze the mechanism of particle thermophoretic motion during drug delivery.

Multi-Scale Numerical Simulation of Flow,Heat and Mass Transfer Behaviors in Dense Gas-Solid Flows:A Brief Review

Dense gas-solid flows are very common in actual production and industrial fields,so it is significant to understand their hydrodynamic characteristics and heat and mass transfer behaviors.This article provides a brief review of multi-scale numerical simulation of flow,heat and mass transfer behaviors in dense gas-solid flows.It describes multiscale models(direct numerical simulation,discrete particle model,and two-fluid model)and the results of related research.Finally,it discusses possible future developments in research on the flow,heat and mass transfer characteristics of dense gas-solid two-phase flows.

Non-spherical particle mixing behaviors by spherical inert particles assisted in a fluidized bed

Fluidized beds are widely used in many industrial fields such as petroleum,chemical and energy.In actual industrial processes,spherical inert particles are typically added to the fluidized bed to promote fluidization of non-spherical particles.Understanding mixing behaviors of binary mixtures in a fluidized bed has specific significance for the design and optimization of related industrial processes.In this study,the computational fluid dynamic-discrete element method with the consideration of rolling friction was applied to evaluate the mixing behaviors of binary mixtures comprising spherocylindrical particles and spherical particles in a fluidized bed.The simulation results indicate that the differences between rotational particle velocities were higher than those of translational particle velocities for spherical and non-spherical particles when well mixed.Moreover,as the volume fraction of the spherocylindrical particles increases,translational and rotational granular temperatures gradually increase.In addition,the addition of the spherical particles makes the spherocylindrical particles preferably distributed in a vertical orientation.

Synthesis of size-controlled hollow Fe3O4 nanospheres and their growth mechanism

Size-controlled hollow Fe3O4 nanospheres were synthesized via a one-pot hydrothermal method as a function of reaction time and sodium citrate,polyacrylamide,and urea content.Multiple characterization techniques such as scanning and transmission electron microscopy and Raman spectroscopy were employed to investigate the crystal structure and morphology of the obtained nanospheres.The Fe3O4 nanosphere formation mechanism was elucidated from analyzing the characterization data.High levels of sodium citrate and longer reaction times were observed to increase the diameter of the nanospheres until hollow structures formed.Furthermore,polyacrylamide and urea promoted the formation of hollow structures.The hollow-structured Fe3O4 nanospheres exhibited high magnetization saturation values in the range of 48.8-58.7 emu/g.The facile synthesis method described herein,to generate size-controlled Fe3O4 nanospheres with tailored properties,demonstrates potential across a wide range of fields from drug-delivery and stealth devices,to environmental and energy applications.

Solar heating assisted rapid cleanup of viscous crude oil spills using reduced graphene oxide-coated sponges

The rapid cleanup of heavy crude oil spills is challenging due to the poor mobility of highly viscous oil.Traditional absorption strategies involve heating oils to a relatively high temperature to reduce their viscosity,but this method is expensive.Herein,a solar-heated reduced graphene oxide(rGO)-wrapped melamine sponge(MS)was proposed to rapidly absorb oil.The prepared rGO-MS exhibited good hydrophobicity and oleophilicity and could be used for the rapid cleanup of oil spills from water.In addition,the excellent photothermal conversion effect of rGO enabled the rGO-MS composite to achieve a solar energy absorption efficiency of 91%.Due to the localized solar energy collection and wetting properties of rGO-MS,viscous oil near the contact region was effectively heated,enabling rapid heavy oil recovery under solar light illumination.This proposed solar heating-assisted viscous oil sorbent has great promise for use in heavy oil spill cleanups in the future.