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首页> 外文期刊>International Journal of Heat and Mass Transfer >Theoretical analysis on the role of annular metallic shapes for microwave processing of food dielectric cylinders with various irradiations
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Theoretical analysis on the role of annular metallic shapes for microwave processing of food dielectric cylinders with various irradiations

机译：环形金属形状在各种辐照条件下对食品介电筒进行微波处理的理论分析

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摘要

A theoretical analysis has been carried out to analyze efficient microwave assisted heating processes of food cylinders with various shapes of metallic annuli in presence of lateral and radial irradiation. Lateral irradiation represents the sample incident at one direction with source at infinity whereas the radial irradiation represents the situation where the sample is incident with microwave radiations from co-axial cylindrical cavity at infinity. A generic finite element method has been used to obtain computational mesh for all shapes of metallic annulus and Galerkin finite element method has been used to solve electric field and energy balance equations. Influence of metallic annulus has been illustrated for three representative sample lengths or regimes (I, II and III) as a function of wave number (N_w). Sample radius with regime I is smallest and largest sample radius corresponds to regime III. In general, power absorption due to lateral irradiation is larger for regime I whereas identical power with lateral or radial irradiation or larger power absorption with radial irradiation corresponds to regime II in absence of metallic annulus. The metallic annuli are found to enhance power absorption or heating rate for specific aspect ratios of both bread and beef samples. The aspect ratios are defined as the ratio of the dimension of metallic annulus and outer radius of the food sample. Lateral irradiation is found to give larger heating rates especially for regimes II and III for bread samples (low dielectric loss), but radial irradiation gives smaller degree of thermal runaway. On the other hand, radial irradiation gives significantly large heating rates with minimal thermal runaway for beef samples (high dielectric loss) with all regimes. It is interesting to observe that the metallic annuli enhance two to three times microwave power for beef samples involving regimes II and HI. Various shapes of metallic annuli are also found to play dominant role either to focus or to optimize heating effects.
机译：已经进行了理论分析，以分析在存在侧向和径向辐射的情况下，具有各种形状的金属环的食物筒的高效微波辅助加热过程。横向辐射表示样品在一个方向上入射，且源在无限远处，而径向辐射表示样品从同轴圆柱腔的微波辐射中在无限远处入射的情况。已使用通用有限元方法来获得所有形状的金属环的计算网格，并使用Galerkin有限元方法来求解电场和能量平衡方程。已经说明了金属环对于三个代表性样本长度或形式（I，II和III）的影响，该影响是波数（N_w）的函数。方案I的样本半径最小，最大样本半径对应于方案III。通常，对于方案I，由于横向辐射而产生的功率吸收较大，而与横向或径向辐射相同的功率，或者对于径向辐射具有较大的功率吸收，对应于方案II，不存在金属环。对于面包和牛肉样品的特定纵横比，发现金属环增强了功率吸收或加热速率。长宽比定义为金属环的尺寸与食物样品的外半径之比。发现横向辐射会产生较大的加热速率，尤其是对于面包样品的II和III方案（低介电损耗），而径向辐射会产生较小程度的热失控。另一方面，在所有情况下，径向辐照都能显着提高加热速率，同时使牛肉样品的热失控最少（高介电损耗）。有趣的是，对于涉及II和HI方案的牛肉样品，金属环的微波功率提高了2到3倍。还发现各种形状的金属环在聚焦或优化加热效果方面起主要作用。

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