Research background: Drying is one of the most traditional processes of food preservation. Optimizing the process can result in a competitive product on the market regarding its price and quality. A common method in use as a pretreatment to drying is ultrasound. The goal of this work is to analyze different drying methods with and without applying ultrasound (US) pretreatment, on heat and mass transfer, simulating numerically the temperature profile by computational fluid dynamics (CFD). Experimental approach: The melon slices were pretreated with ultrasound for 10 (US10), 20 (US20) and 30 (US30) min at 25 kHz, and the water loss and solid gain were evaluated. Samples were dried at different temperatures (50, 60 and 70 °C). The effective diffusivity was estimated, and experimental data were modelled using empirical models. The airflow in the dryer and the temperature profile in the melon slice were simulated via computational fluid dynamics (CFD). Results and conclusions: Ultrasound pretreatment reduced the drying time from 25% (samples US20 and US30 at 50 °C) to 40% (samples US20 and US30 at 70 °C). The two-term exponential model presented the best fit to the experimental data, and the diffusivity coefficients showed a tendency to increase as the time of exposure of the melon to ultrasonic waves increased. Pretreatment water loss and solid gain behaviour and drying kinetic and diffusion data were used to choose the best experimental conditions to be simulated with CFD. The heat transfer modelling through CFD showed that the temperature distribution along the melon slice was representative. Therefore, the profile obtained via CFD satisfactorily describes the drying process. Novelty and scientific contribution: The use of simulation tools in real processes allows the monitoring and improvement of existing technologies, such as food drying processes, that involve complex mechanisms, making it difficult to obtain some data. Application of CFD in the drying processes of fruits and vegetables is still very recent, being a field little explored. There is no record in the literature that uses CFD in the drying of melon.

中文翻译：

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超声波预处理对甜瓜干燥和热分布计算流体动力学建模的影响。

研究背景：干燥是最传统的食品保存过程之一。优化工艺可以在价格和质量上产生具有市场竞争力的产品。用作干燥预处理的常用方法是超声。这项工作的目的是分析传热和传质时是否使用超声波（US）预处理和不进行超声波（US）预处理的不同干燥方法，并通过计算流体动力学（CFD）数值模拟温度曲线。实验方法：在25 kHz的条件下，用超声波对甜瓜片进行10分钟（US10），20分钟（US20）和30分钟（US30）的超声波预处理，然后评估其水分损失和固体增益。样品在不同的温度（50、60和70°C）下干燥。估计有效扩散率，并使用经验模型对实验数据进行建模。通过计算流体动力学（CFD）模拟了干燥机中的气流和瓜片中的温度曲线。结果与结论：超声预处理将干燥时间从25％（50°C下的US20和US30样品）降低到40％（70°C下的US20和US30样品）。两项指数模型最适合实验数据，并且随着甜瓜暴露于超声波的时间增加，扩散系数显示出增加的趋势。使用预处理失水量和固体增益行为以及干燥动力学和扩散数据来选择要用CFD模拟的最佳实验条件。通过CFD进行的传热模型表明，沿瓜片的温度分布具有代表性。因此，通过CFD获得的轮廓令人满意地描述了干燥过程。新颖性和科学贡献：在实际过程中使用仿真工具可以监视和改进涉及复杂机制的现有技术（例如食品干燥过程），从而难以获取某些数据。CFD在水果和蔬菜干燥过程中的应用仍然是最近的，这是一个很少探索的领域。在文献中没有记录使用CFD干燥瓜。