In a plant factory, improper design of the indoor ventilation system may cause tip burn on lettuce plants due to the existence of stagnant air in the leaf boundary layer and low transpiration rates. In this study, three types of air ducts with different pore numbers and diameters were designed to generate a constant horizontal airflow on the surface of plant canopy. A three-dimensional computational fluid dynamics (CFD) model was established to analyse the airflow pattern on the crop canopy under different ventilation modes in a single cultivation bed. For this simulation model, the lettuce leaves were treated as a porous medium, and the drag coefficient (CD) was assumed to be 0.02, which resulted in a permeability (Kp) and nonlinear momentum loss coefficient (CF) of 0.02 and 0.134, respectively. The LED lamps were set as the energy source, and the heat released was calculated to be 297.5 kW m−3. All the data above were validated. Three Designs with different pore numbers and diameters were simulated to predict the distribution of airflow. The design with 12 pores and 15 mm diameter was predicted to give the highest percentage of mean air velocity between 0.28 m s−1 and 1.04 m s−1 on the lettuce canopy surface, at 70.3%. This duct design is recommended as the best of the three Designs in this study.

中文翻译：

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考虑作物阻力和LED散热的植物工厂改善生菜冠层气流分布的CFD分析

在植物工厂中，室内通风系统设计不当可能会由于叶片边界层中存在停滞空气和低蒸腾率而导致生菜植株尖端烧伤。在这项研究中，设计了三种不同孔隙数和直径的风管，以在植物冠层表面产生恒定的水平气流。建立了三维计算流体动力学（CFD）模型，分析了单个栽培床不同通风模式下作物冠层的气流模式。对于该模拟模型，将莴苣叶视为多孔介质，假设阻力系数 (CD) 为 0.02，这导致渗透率 (Kp) 和非线性动量损失系数 (CF) 分别为 0.02 和 0.134 . LED灯被设置为能源，释放的热量经计算为 297.5 kW m-3。以上数据均经过验证。模拟了具有不同孔数和直径的三种设计来预测气流的分布。预测具有 12 个孔和 15 毫米直径的设计在生菜冠层表面上提供 0.28 m s-1 和 1.04 m s-1 之间的平均空气速度百分比最高，为 70.3%。这种风管设计被推荐为本研究中三种设计中最好的一种。