Multiscale modeling of microwave-heated multiphase systems

Goyal, Himanshu; Vlachos, Dionisios G.

doi:10.1016/j.cej.2020.125262

Cited by 18 publications

(24 citation statements)

References 40 publications

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“…The techniques to stimulate catalyst change are distinct from other reactor technologies that merely supply energy to a reactor. While techniques such as microwave irradiation (131) , plasma (116) , and pulsed heating (132) or pulse pressure (133) can be used continuously or dynamically with catalysts leading to unique, beneficial, reactor behavior, they do not manipulate the catalyst itself and are not the focus of this perspective. Catalyst stimulation exists in three categories related to the general approach of mechanical, electrical, or photochemical perturbations from their resting structures.…”

Section: Stimulating Methods For Dynamic Catalysismentioning

confidence: 99%

The Catalytic Mechanics of Dynamic Surfaces: Stimulating Methods for Promoting Catalytic Resonance

et al. 2020

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Transformational catalytic performance in rate and selectivity is obtainable through catalysts that change on the time scale of catalytic turnover frequency. In this work, dynamic catalysts are defined in the context and history of forced and passive dynamic chemical systems, with classification of unique catalyst behaviors based on temporally-relevant linear scaling parameters. The conditions leading to catalytic rate and selectivity enhancement are described as modifying the local electronic or steric environment of the active site to independently accelerate sequential elementary steps of an overall catalytic cycle. These concepts are related to physical systems and devices that stimulate a catalyst using light, vibrations, strain, and electronic manipulations including electrocatalysis, back-gating of catalyst surfaces, and introduction of surface electric fields via solid electrolytes and ferroelectrics. These catalytic stimuli are then compared for capability to improve catalysis across some of the most important chemical challenges for energy, materials, and sustainability. File list (2) download file view on ChemRxiv Perspective_Manuscript_ChemRxiv.pdf (3.88 MiB) download file view on ChemRxiv Perspective_Supporting_Information_ChemRxiv.pdf (149.75 KiB)

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Section: Stimulating Methods For Dynamic Catalysismentioning

confidence: 99%

The Catalytic Mechanics of Dynamic Surfaces: Stimulating Methods for Promoting Catalytic Resonance

et al. 2020

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“…u is obtained from solving the Navier–Stokes and continuity equations in the laminar flow regime for a fluid of density ρ, which varies as a function of temperature (gravity effects are ignored). The magnitude of the electromagnetic energy dissipated per unit volume, i.e., the power loss, Q̇ j ,emw in phase j is obtained from the following eq: , where E is the electric field vector, f is the frequency of the microwave radiation, ϵ o is the permittivity of vacuum, ϵ c is the complex part of the relative permittivity, and σ is electrical conductivity. E is obtained by solving Maxwell’s equations using the impedance boundary conditions for the metallic cavity to minimize the computational load.…”

Section: Methodsmentioning

confidence: 99%

“…Simultaneous experimental measurement of both solid and fluid temperatures within structured reactors remains a challenge. Predictive models can help overcome this challenge by providing insights into the temperature field inhomogeneity − and methods for engineering it.…”

Section: Introductionmentioning

confidence: 99%

Temperature Homogeneity under Selective and Localized Microwave Heating in Structured Flow Reactors

Malhotra

Chen

Goyal

et al. 2021

Ind. Eng. Chem. Res.

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Selective heating of different phases of multiphase systems via microwaves can result in energy savings and suppression of side reactions. However, materials properties and operating conditions that maximize temperature gradients are poorly understood. Here we utilize computational fluid dynamics (CFD) computations and temperature measurements in structured flow reactors (monoliths) in a monomodal microwave cavity to assess the temperature difference between the walls and the fluid and develop a simple lumped model to estimate when temperature gradients exist. We also explore the material's thermal and electrical properties of structured reactors for isothermal catalyst conditions. We propose that CFD simulations can be used as a nonintrusive, predictive tool of temperature homogeneity. Importantly, we demonstrate that localized heating in the bed under several conditions rather than selective heating is responsible for the selectivity enhancement. Our results indicate that structured beds made of high thermal conductivity materials avoid arcing and enable temperature homogeneity and low electrical conductivity materials allow microwaves to penetrate the domain.

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“…A recent study by Goyal and Vlachos simulates microwave heating of multiphase systems by using COMSOL Multiphysics to resolve EM field from a single particle to bulk. The proposed methodology is a cost-efficient model for multiphase systems as it homogenizes the system benefiting from the large gaps within length scales.…”

Section: Numerical Modeling Of Microwave Continuous Flow Systemsmentioning

confidence: 99%

Microwave-Promoted Continuous Flow Systems in Nanoparticle Synthesis—A Perspective

Saleem

Torabfam

Fidan

et al. 2021

ACS Sustainable Chem. Eng.

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Microwave-promoted continuous flow systems have emerged as a game-changer in nanoparticle synthesis. Owing to the excellent compatibility between fast, sustainable microwave heating and one-step, efficient flow chemistry, this promising technology is meant to enhance the synthetic abilities of nanoscientists. This Perspective aims to present a panoramic view of the state of the art in this field. Additionally, the effect of various microwave and flow parameters on the properties of nanoparticles is discussed along with a comparative glance at the features that make flow reactors more practical and sustainable than their batch counterparts. The overview has also analyzed various microwave continuous flow reactors available in the literature, with an acute emphasis on the nanosynthesis route and design features. Moreover, a discussion on the numerical modeling of microwave flow systems has been made a part of this perspective to reiterate its significance and encourage research in this domain. The Perspective also briefly comments on existing challenges and future prospects of this technology.

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Multiscale modeling of microwave-heated multiphase systems

Cited by 18 publications

References 40 publications

The Catalytic Mechanics of Dynamic Surfaces: Stimulating Methods for Promoting Catalytic Resonance

The Catalytic Mechanics of Dynamic Surfaces: Stimulating Methods for Promoting Catalytic Resonance

Temperature Homogeneity under Selective and Localized Microwave Heating in Structured Flow Reactors

Microwave-Promoted Continuous Flow Systems in Nanoparticle Synthesis—A Perspective

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