Microwave-induced temperature fields in cylindrical samples of graphite powder – Experimental and modeling studies

Moon, Ethan M.; Yang, Chuqiao; Yakovlev, Vadim V.

doi:10.1016/j.ijheatmasstransfer.2015.02.021

Cited by 22 publications

(3 citation statements)

References 38 publications

(45 reference statements)

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“…This algorithm implemented in the 3D FDTD simulator QuickWave [28] allows for determining the time evolution of the 3D temperature distribution. Examples of simulations of the heating processes are reported in [31], [32], [33], [34].…”

Section: B Multiphysics Simulations Of Temperature Evolutionmentioning

confidence: 99%

Solid-State Power Combining for Heating Small Volumes of Mixed Waste Materials

et al. 2023

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Microwave heating of waste results in chemical breakdown that can lead to conversion of mixed waste materials to fuel. Heating waste mixtures with microwave energy rather than incineration results in faster breakdown and can therefore be more efficient. Here we address heating of small volumes of mixed food waste materials with widely differing and temperature-dependent electrical properties. Uniform heating is accomplished with mode mixing within a loaded cavity and by spatial power combining of solid-state power amplifiers (SSPAs). We present a heating comparison of two circuit-combined and spatially-combined 2.45 GHz 70-W 65% efficient GaN SSPAs with controlled relative phase. The heating efficacy is shown to improve by volumetric combining inside the waste loading. The temperature changes in several locations and for several common waste materials and mixtures are investigated and compared to FEM electromagnetic simulations, as well as FDTD multi-physics simulations that incorporate thermal dependence of material properties. The approach is scalable in volume and power, demonstrated by a simulation comparison of the 1.4 L small cavity to a 5.2 L volume.INDEX TERMS Microwave heating, power amplifiers, efficiency, power combining, multi-physics modelling.This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.

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Section: B Multiphysics Simulations Of Temperature Evolutionmentioning

confidence: 99%

Solid-State Power Combining for Heating Small Volumes of Mixed Waste Materials

et al. 2023

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“…A number of earlier researchers also carried out studies on the role of various twodimensional shapes (circle, square and rectangle) (Nam and Song, 2007;Franca, 2000, 2002;Rattanadecho et al, 2009;Ayappa et al, 1997;Bhattacharya et al, 2014;Ayappa, 2001, 2002;Yang and Gunasekaran, 2004;Tao et al, 2005;Basak, 2008Basak, , 2011Hossan et al, 2010;Campanone et al, 2014;Moon et al, 2015;Choi et al, 2015) and three-dimensional geometries (Huo and Li, 2005;Zhu et al, 2007aZhu et al, , 2007bZhu et al, , 2007c for microwave heating effects. The resonance effect of microwave heating was found to occur within cylinders for specific sample radii (Ayappa et al, 1997;Bhattacharya et al, 2014;Ayappa, 2001, 2002).…”

Section: Hff 3010mentioning

confidence: 99%

Finite element (GFEM) simulations on the effect of microwave heating for lossy dielectric samples with various shapes (circle, square and triangle)

Basak

2020

HFF

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Purpose This paper aims to investigate the thermal performance involving larger heating rate, targeted heating, heating with least non-uniformity of the spatial distribution of temperature and larger penetration of heating within samples vs shapes of samples (circle, square and triangular). Design/methodology/approach Galerkin finite element method (GFEM) with adaptive meshing in a composite domain (free space and sample) is used in an in-house computer code. The finite element meshing is done in a composite domain involving triangle embedded within a semicircular hypothetical domain. The comparison of heating pattern is done for various shapes of samples involving identical cross-sectional area. Test cases reveal that triangular samples can induce larger penetration of heat and multiple heating fronts. A representative material (beef) with high dielectric loss corresponding to larger microwave power or heat absorption in contrast to low lossy samples is considered for the current study. The average power absorption within lossy samples has been computed using the spatial distribution and finite element basis sets. Four regimes have been selected based on various local maxima of the average power for detailed investigation. These regimes are selected based on thin, thick and intermediate limits of the sample size corresponding to the constant area of cross section, Ac involving circle or square or triangle. Findings The thin sample limit (Regime 1) corresponds to samples with spatially invariant power absorption, whereas power absorption attenuates from exposed to unexposed faces for thick samples (Regime 4). In Regimes 2 and 3, the average power absorption non-monotonically varies with sample size or area of cross section (Ac) and a few maxima of average power occur for fixed values of Ac involving various shapes. The spatial characteristics of power and temperature have been critically analyzed for all cross sections at each regime for lossy samples. Triangular samples are found to exhibit occurrence of multiple heating fronts for large samples (Regimes 3 and 4). Practical implications Length scales of samples of various shapes (circle, square and triangle) can be represented via Regimes 1-4. Regime 1 exhibits the identical heating rate for lateral and radial irradiations for any shapes of lossy samples. Regime 2 depicts that a larger heating rate with larger temperature non-uniformity can occur for square and triangular-Type 1 lossy sample during lateral irradiation. Regime 3 depicts that the penetration of heat at the core is larger for triangular samples compared to circle or square samples for lateral or radial irradiation. Regime 4 depicts that the penetration of heat is still larger for triangular samples compared to circular or square samples. Regimes 3 and 4 depict the occurrence of multiple heating fronts in triangular samples. In general, current analysis recommends the triangular samples which is also associated with larger values of temperature variation within samples. Originality/value GFEM with generalized mesh generation for all geometries has been implemented. The dielectric samples of any shape are surrounded by the circular shaped air medium. The unified mesh generation within the sample connected with circular air medium has been demonstrated. The algorithm also demonstrates the implementation of various complex boundary conditions in residuals. The numerical results compare the heating patterns for all geometries involving identical areas. The thermal characteristics are shown with a few generalized trends on enhanced heating or targeted heating. The circle or square or triangle (Type 1 or Type 2) can be selected based on specific heating objectives for length scales within various regimes.

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“…In this study, the pin structure design of the LaVAi-1.5-1400 microwave vertical tubular furnace was based on COMSOL Multiphysics, which is a general engineering simulation software platform. COMSOL Multiphysics is based on the finite element method to realize the simulation of real physical phenomena by solving partial differential equations (single field) or systems of partial differential equations (multi-field), and researchers have used COMSOL Multiphysics to simulate the microwave heating process of charcoal [19] and graphite [20]. The information obtained from this study, such as the electric field distribution within the microwave heating cavity and the temperature of the composite material, helps to further understand the microwave heating process of Al 2 O 3 /SiC composite materials.…”

Section: Introductionmentioning

confidence: 99%

The Pin Structure Design of LaVAi-1.5-1400 Microwave Vertical Tubular Furnace Based on COMSOL

Li,

Zhou,

Wang

2024

Applied Sciences

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The microwave heating process will involve a variety of physical phenomena, including the distribution of the electromagnetic field in the heating cavity, the heat generated by electromagnetic loss, and the transfer of heat inside the material during heating. In this paper, the simulation software COMSOL Multiphysics 5.6 based on the finite element analysis method is used to establish the microwave heating model of Al2O3/SiC composites and design the pinning structure of the experimental furnace for multi-mode microwave heating. From the uniformity of microwave heating of the sample and the coupling with microwave, the heating characteristics of the sample with different pin spacing, pin radius, and pin insertion depth were simulated and analyzed. This pin structure design can be used to control the heating conditions of Al2O3/SiC composites in microwave heating ovens to meet industrial requirements.

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Microwave-induced temperature fields in cylindrical samples of graphite powder – Experimental and modeling studies

Cited by 22 publications

References 38 publications

Solid-State Power Combining for Heating Small Volumes of Mixed Waste Materials

Solid-State Power Combining for Heating Small Volumes of Mixed Waste Materials

Finite element (GFEM) simulations on the effect of microwave heating for lossy dielectric samples with various shapes (circle, square and triangle)

The Pin Structure Design of LaVAi-1.5-1400 Microwave Vertical Tubular Furnace Based on COMSOL

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