Efficient heating with a controlled microwave field

Chang, Tsun-Hsu; Chao, Hsien-Wen; Syu, F. H.; Fong, S. C.; Chin, Tsung‐Shune

doi:10.1063/1.3665920

Cited by 9 publications

(5 citation statements)

References 18 publications

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“…According to the thermal simulation, the temperature fluctuation between the surface and interior of SiC is less than 5 °C. 22) A calibrated infrared thermometer was used to measure the temperature on the top of NaCl or SiC. A mini camera was embedded in the metal wall with a small opening.…”

Section: Methodsmentioning

confidence: 99%

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Double-layer particlespout in strong and nonuniform microwave fields

Chang

Chao

Chen

et al. 2014

Jpn. J. Appl. Phys.

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We report a new phenomenon named particlespout in which the particles spout in a specially designed microwave cavity. An ionic crystal of sodium chloride was heated in the microwave applicator. Beyond the melting point, the particles began to evaporate and move upward owing to thermal convection. These particles formed a funnel shape similar to a waterspout but they had two layers. In comparison with conventional heating, only a single but unstable columnar vortex can be observed. A theoretical model is proposed that attributes the observed phenomenon to the rotational kinematics together with the ponderomotive force. These two effects confine the particles to the inner and outer bounds, respectively.

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Section: Methodsmentioning

confidence: 99%

“…To study the effect of a neutral particle in a strong microwave field, an applicator (cavity) operating at 2.45 GHz was chosen. 22) The schematic diagram of the experimental setup is illustrated in Fig. 1(a).…”

Section: Theoretical Modelmentioning

confidence: 99%

Double-layer particlespout in strong and nonuniform microwave fields

Chang

Chao

Chen

et al. 2014

Jpn. J. Appl. Phys.

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“…It is suggested here that monitoring of the local average field distributions E 0 (x, y, z) │ P or position-wise distribution of the absorbed microwave power Q MW (x, y, z) │ P such as presented in Figures 4C,D and 5A,B could be useful in the area of microwave applicator design. The current general framework for understanding the working of the applicator part of a microwave heating system (whether of the single-mode-type or the multimode-type) and its design optimization is based on modeling with analytical or numerical calculations [43][44][45][46][47][48][49][50] or multi-physicsbased simulations 25,[51][52][53] or using certain experimental techniques. [54][55][56][57][58] The applicator optimization is in terms of the best coupling of the magnetron output power to the applicator cavity via a short waveguide (and an isolator coupler) or for a given dielectric 'load', or the applicator dimensions being such that the reflection coefficient of the applicator is minimum at the input frequency 56,60 , or in terms of development of strategies for uniform heating of the 'load'.…”

Section: Measured Q Mw or E 0 (X Y Z) Distributionsmentioning

confidence: 99%

Probing multimode applicator of microwave heating system for E‐field distribution using a silicon carbide sensor and a shielded thermocouple

Iyer

Shivashankar

Sai

et al. 2022

Int J Ceramic Engine & Sci

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Measurement of the field distribution in a multimode applicator of a microwave heating system has been a challenging problem. We report here a simple but comprehensive scheme for its semi‐quantitative estimation under no‐load conditions. It involves the measurement of temperature (T) versus time (t) profiles in a small silicon carbide (SiC) sensor ring positioned at the junction end of a metal‐jacketed microwave‐compatible thermocouple probe arrangement. These heating profiles (T vs. t) were measured using a data acquisition system, keeping the SiC ring at different (x, y, z) positions in the applicator. Using this measurement scheme, the spatial positions with local field minimum as inferred from very high reflected power or those with local field maximum with associated thermal runaway type condition could be well identified. Given the thermal and the dielectric properties of SiC material and the physical dimensions of the sensor ring, a uniform microwave field‐based model with a thermal lumped element type approximation (with no thermal gradient across SiC) was applied for analysis of the T versus t heating profiles. Within this model, the locally effective electric field E could be inferred for low and moderate electric field ranges. While the accuracy of the field estimation is currently limited by the use of the metal‐jacketed thermocouple and other factors, this SiC sensor‐based methodology has the potential to be developed further to be useful in the area of microwave applicator design.

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“…This article reveals a microwave resonant cavity with a TM-mode of 2.45 GHz for PAN fiber's pre-oxidation process. An improved E-field is employed in the cavity for enhancing the interaction between microwave and the annealed material with a lower energy cost [15][16][17][18]. The PAN fiber is then annealed under several processing conditions and analyzed by scanning electron microscopy (SEM) [19][20][21] and X-ray diffraction (XRD) [22][23][24][25].…”

Section: Introductionmentioning

confidence: 99%

A Two-Step Microwave Annealing Process for PAN Pre-Oxidation through a TM-Mode Cavity

et al. 2021

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A novel microwave annealing system and a specific processing condition are proposed for the pre-oxidation of carbon fiber. The microwave annealing system consists of a TM-mode resonant cavity and a silicon carbide (SiC) susceptor. The TM-mode cavity enhances the electric field at the center. The SiC susceptor absorbs part of the microwave energy and converts it to heat. The enhanced fields and the SiC susceptor provide both nonthermal and thermal treatments for fibrous materials with various dielectric properties. Furthermore, a two-step microwave annealing process is used to oxidize polyacrylonitrile (PAN) fiber. The scanning electron microscopy (SEM) images, differential scanning calorimetry (DSC), and X-ray diffraction (XRD) results support the theory that the microwave annealing can achieve a high aromatic index of 66.39% in just 13 min, 9 times faster than the traditional processing time. The results of the Raman spectra also illustrate that the sheath-core factor of the microwave-heated specimen is closer to one than that of the conventional furnace-heated type, which agree with the images of the cross-section area.

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Efficient heating with a controlled microwave field

Cited by 9 publications

References 18 publications

Double-layer particlespout in strong and nonuniform microwave fields

Double-layer particlespout in strong and nonuniform microwave fields

Probing multimode applicator of microwave heating system for E‐field distribution using a silicon carbide sensor and a shielded thermocouple

A Two-Step Microwave Annealing Process for PAN Pre-Oxidation through a TM-Mode Cavity

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