The Venlo ventilation system is one of the most widely adopted designs for greenhouses, and it is known for its distinctive roof structure that promotes natural airflow. However, despite its widespread use, it is often inadequate in maintaining the desired temperatures during the summer. This increases the risk of heat stress for greenhouse workers, particularly under the high humidity conditions typically encountered in aquaponic greenhouses. In this study, we developed computational fluid dynamics (CFD) models simulating temperature and air velocity distributions using a commercial-scale Venlo-style aquaponic greenhouse as a reference. The study aimed to evaluate the impact of applying reflective whitewash and installing positive pressure ventilation tubes (PPVT) in worker areas on the heat stress experienced by the workers. The standard k-ε turbulence and solar ray tracing models were employed in CFD simulations. A total of 1,776 lettuce at three different growth stages were placed inside the aquaponic pools. The CFD models were validated using an experimental-scale greenhouse, and with these validated models, air velocities at the worker’s height were calculated to be 3.1±0.13 m s−1, 3.2±0.16 m s−1, and 3.8±0.04 m s−1 for the control, whitewash, and PPVT + whitewash conditions, respectively. When whitewash and positive pressure ventilation tubes were both in use, the air exchange rate increased from 27.3 to 31.8 per hour. Although there was only a 4.5 increase in air exchanges, strategically placing the ventilation tubes resulted in a 7.3 °C decrease in temperature at the average worker height. This reduction shifted the heat index from the “extreme danger” to the “caution” zone, allowing workers to safely work up to four consecutive hours with adequate water intake. The annual cost for running the PPVT inline fans was calculated to be as low as $245, which was 2.6 times less than the previously reported operating costs for greenhouse ventilation systems.

中文翻译：

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使用计算流体动力学 （CFD） 仿真减轻农业工人的热应激


Venlo 通风系统是温室采用最广泛的设计之一，它以其促进自然气流的独特屋顶结构而闻名。然而，尽管它被广泛使用，但它往往不足以在夏季维持所需的温度。这增加了温室工人的热应激风险，尤其是在水生温室中通常遇到的高湿度条件下。在这项研究中，我们开发了计算流体动力学 （CFD） 模型，使用商业规模的 Venlo 式水生温室作为参考来模拟温度和空气速度分布。该研究旨在评估在工人区域应用反光粉刷和安装正压通风管 （PPVT） 对工人热应激的影响。CFD 仿真采用了标准的 k-ε 湍流和太阳光线追踪模型。共有 1,776 棵处于三个不同生长阶段的生菜被放置在水生池中。CFD 模型使用实验规模的温室进行了验证，使用这些经过验证的模型，在对照、粉刷和 PPVT + 粉刷条件下，工人高度的空气速度分别为 3.1±0.13 m s-1、3.2±0.16 m s-1 和 3.8±0.04 m s-1。当白刷通风管和正压通风管同时使用时，空气交换率从每小时 27.3 次增加到每小时 31.8 次。虽然空气交换仅增加了 4.5 °C，但战略性地放置通风管导致平均工人身高的温度降低了 7.3 °C。这种降低将热指数从“极度危险”转变为“谨慎”区域，使工人能够在充足的饮水量下安全地连续工作长达四个小时。 据计算，运行 PPVT 直列式风机的年成本低至 245 美元，比之前报告的温室通风系统运营成本低 2.6 倍。