Ugarte-Anero Ainara, Fernandez-Gamiz Unai, Portal-Porras Koldo, Lopez-Guede Jose Manuel, Sanchez-Merino Gaspar
Nuclear Engineering and Fluid Mechanics Department, University of the Basque Country, UPV/EHU, Nieves Cano 12, Vitoria-Gasteiz, 01006, Araba, Spain.
Bioaraba, New Technologies and Information Systems in Health Research Group, Vitoria-Gasteiz, Spain.
Heliyon. 2023 Sep 7;9(9):e19961. doi: 10.1016/j.heliyon.2023.e19961. eCollection 2023 Sep.
The air quality is a parameter to be controlled in order to live in a comfortable place. This paper analyzes the trajectory of aerosols exhaled into the environment in a classroom. Three scenarios are investigated; without ventilation, with natural and with mechanical ventilation. A multi-phase computational fluid study based on Eulerian-Lagrangian techniques is defined. Temperature and ambient relative humidity, as well as air velocity, direction and pressure is taken into account. For droplets evaporation, mass transfer and turbulent dispersion have been added. This work tends to be of great help in various areas, such as the field of medicine and energy engineering, aiming to show the path of aerosols dispersed in the air. The results show that the classroom with a mechanical ventilation scheme offers good results when it comes to an efficient control of aerosols. In all three cases, aerosols exhaled into the environment impregnate the front row student in the first 0.5 s. Reaching the time of 4, 2 and 1 s, in the class without ventilation, mechanical and natural ventilation, respectively, the aerosols have been already deposited on the table of the person in the first row, being exposed for longer in the case of no ventilation. Particles with a diameter of less than 20 μm are distributed throughout the classroom over a long period. The air jet injected into the interior space offers a practically constant relative humidity and a drop in temperature, slowing down the process of evaporation of the particles. In the first second, it can be seen that a mass of 0.0025 mg formed by 9 million droplets accumulates, in cases without ventilation and natural ventilation. The room with a mechanical installation accumulated 5.5 million particles of mass 0.0028 mg in the first second. The energy losses generated by natural ventilation are high compared to the other scenarios, exactly forty and twenty times more in the scenario with mechanical ventilation and without ventilation, respectively.
空气质量是为了生活在舒适环境中而需要控制的一个参数。本文分析了在教室中呼出到环境中的气溶胶的轨迹。研究了三种场景：无通风、自然通风和机械通风。定义了基于欧拉-拉格朗日技术的多相计算流体研究。考虑了温度、环境相对湿度以及空气速度、方向和压力。对于液滴蒸发，增加了传质和湍流扩散。这项工作在医学和能源工程等各个领域往往有很大帮助，旨在展示空气中分散的气溶胶的路径。结果表明，在有效控制气溶胶方面，采用机械通风方案的教室效果良好。在所有三种情况下，呼出到环境中的气溶胶在最初的0.5秒内就影响到了前排学生。在无通风、机械通风和自然通风的教室中，分别在4秒、2秒和1秒时，气溶胶已经沉积在前排人员的桌子上，在无通风的情况下暴露时间更长。直径小于20μm的颗粒在很长一段时间内分布在整个教室。注入室内空间的气流提供了几乎恒定的相对湿度和温度下降，减缓了颗粒的蒸发过程。在最初的一秒内，可以看到在无通风和自然通风的情况下，由900万个液滴形成的质量为0.0025mg的物质积累起来。装有机械装置的房间在最初一秒内积累了550万个质量为0.0028mg的颗粒。与其他场景相比，自然通风产生的能量损失很高，分别比机械通风和无通风的场景高40倍和20倍。
