Fernandes da Silva João Henrique, da Silva Neto José Sabino, Souza da Silva Edilene, de Souza Cavalcanti Danilo Emídio, Azoubel Patrícia Moreira, Benachour Mohand
Federal University of Pernambuco, Department of Chemical Engineering, Av. Prof. Arthur de Sá, s/n, Cidade Universitária, Recife-PE, 50740-521, Brazil.
Food Technol Biotechnol. 2020 Dec;58(4):381-390. doi: 10.17113/ftb.58.04.20.6813.
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). 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 computational fluid dynamics (CFD). 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 CFD satisfactorily describes the drying process. 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.
干燥是食品保存最传统的工艺之一。优化该工艺可使产品在价格和质量方面在市场上具有竞争力。作为干燥预处理常用的一种方法是超声处理。这项工作的目的是分析在有无超声（US）预处理的情况下不同干燥方法对传热和传质的影响，通过计算流体动力学（CFD）对温度分布进行数值模拟。将甜瓜片在25kHz下分别用超声预处理10（US10）、20（US20）和30（US30）分钟，并评估其水分损失和固形物增加情况。样品在不同温度（50、60和70℃）下进行干燥。估算了有效扩散系数，并使用经验模型对实验数据进行建模。利用计算流体动力学（CFD）模拟了干燥机内的气流和甜瓜片内的温度分布。超声预处理使干燥时间减少了25%（50℃下的US20和US30样品）至40%（70℃下的US20和US30样品）。双项指数模型对实验数据拟合效果最佳，扩散系数呈现出随着甜瓜暴露于超声波的时间增加而增大的趋势。预处理的水分损失和固形物增加行为以及干燥动力学和扩散数据被用于选择最佳实验条件，以便用CFD进行模拟。通过CFD进行的传热建模表明，沿甜瓜片的温度分布具有代表性。因此，通过CFD获得的温度分布能令人满意地描述干燥过程。在实际过程中使用模拟工具能够监测和改进现有技术，比如涉及复杂机制、难以获取某些数据的食品干燥工艺。CFD在果蔬干燥过程中的应用仍处于起步阶段，是一个有待深入探索的领域。文献中没有关于在甜瓜干燥中使用CFD的记录。
