Abstract To understand Microwave (MW) heating and boiling of binary liquid mixtures, a new multiphysics model was developed. The new model solves Maxwell's equations for the electromagnetic field distribution. Concerning the coupled dispersed and segregated vapor-liquid flow during MW boiling, it was modelled based on a hybrid Two-Fluid-Volume-of-Fluid method. As for the modelling of heat and mass transfer, Two-fluid energy and species conservation equations were solved, with new dispersed and segregated interphase heat and mass transfer closures formulated using appropriate interface jump conditions combined with vapor-liquid equilibrium relations. The new model showed reasonably good agreement with the experimental data. The capability of the model to simulate MW heating, superheating, superboiling, and interphase transfer phenomena in methanol-water mixture (heated in a multi-mode MW cavity) was demonstrated, and the associated physics was investigated. The simulation results revealed three underlying mechanisms that lead to superheating (up to 9.5 ° C at 300 W) in binary mixtures, namely limited bubble nucleation, inefficient mixing, and higher interfacial saturation temperature compared to that in bulk liquid (about 2 ° C higher). Besides, the results also showed that the increase of heating time mainly increases the amount of superheat rather than the superheat temperature. It was also found that MW superheating tends to reduce the mass fraction of the lighter component in the released vapor (by up to 2%). In the subsequent study, the effects of several operating conditions were examined. The simulation results generally showed that higher liquid methanol concentration, higher MW power, rectangular sample geometry, and smaller sample volume lead to higher superheat intensity, but poorer methanol concentration in the vapor released. The new model and findings could open up new avenues for the design and improvement of processes such as MW-assisted synthesis, extraction, biodiesel production, and distillation.

中文翻译：

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使用 OpenFOAM 对二元液体混合物中的微波加热和沸腾现象进行数值模拟和研究

摘要 为了理解二元液体混合物的微波 (MW) 加热和沸腾，开发了一种新的多物理场模型。新模型求解电磁场分布的麦克斯韦方程组。关于 MW 沸腾过程中耦合分散和分离的汽液流动，它是基于混合双流体体积流体方法建模的。对于传热和传质建模，求解了两流体能量和物种守恒方程，使用适当的界面跳跃条件结合汽液平衡关系制定了新的分散和分离的相间传热和传质闭包。新模型与实验数据显示出相当好的一致性。该模型能够模拟 MW 加热、过热、超级沸腾、证明了甲醇-水混合物（在多模式 MW 腔中加热）中的相间转移现象，并研究了相关的物理学。模拟结果揭示了导致二元混合物过热（在 300 W 时高达 9.5°C）的三种潜在机制，即有限的气泡成核、低效混合以及与散装液体相比更高的界面饱和温度（高出约 2°C）。 ）。此外，结果还表明，加热时间的增加主要增加过热量而不是过热温度。还发现 MW 过热趋于降低释放的蒸汽中较轻组分的质量分数（最多 2%）。在随后的研究中，检查了几种操作条件的影响。模拟结果普遍表明，较高的液体甲醇浓度、较高的 MW 功率、矩形样品几何形状和较小的样品体积导致较高的过热强度，但释放的蒸汽中甲醇浓度较低。新模型和研究结果可以为微波辅助合成、提取、生物柴油生产和蒸馏等工艺的设计和改进开辟新途径。