The airborne droplets released by humans while speaking or coughing are the main sources of human-to-human contagion for airborne transmissible diseases. Due to the recent SARS-Cov2 pandemic, indoor transmission in classrooms and other environments is an interesting topic investigated by the scientific community. In this work, the thermofluid dynamic conditions and the droplet transport was analysed in a large University Classroom (UC), as a function of the inlet airflow and the occupancy rate. These parameters assume a relevant role in the design stage. However, their effects on droplet transport were not deeply investigated in the literature. Therefore, different conditions were analysed, such as: full occupancy, which represents the design condition where no social distancing is enforced; half occupancy, which is representative of social distancing; and empty UC, to be considered as a term of comparison. The main novelty of this work is related to the analysis of the combined effect of thermal plume and airflow in a large UC. The numerical model for the thermofluid dynamics simulation was validated in a previous work and the droplet emission model was retrieved from the literature. High volumetric airflow is not always beneficial for the reduction of the airborne transmission risk. An important aspect is related to the combined effect of the inlet airflow and the thermal plume, which cannot be ignored if the occupancy rate assumes a significant value. Moreover, the evacuation rate and the age of the droplets are relevant indicators to assess the cleaning time.

人类说话或咳嗽时释放的空气飞沫是空气传播疾病人际传染的主要来源。由于最近的 SARS-Cov2 大流行，教室和其他环境中的室内传播是科学界研究的一个有趣的话题。在这项工作中，分析了大型大学教室 (UC) 中的热流体动力学条件和液滴传输，作为入口气流和占用率的函数。这些参数在设计阶段发挥着相关作用。然而，文献中并未深入研究它们对液滴传输的影响。因此，我们分析了不同的条件，例如：满员，代表不强制保持社交距离的设计条件；半入住率，代表社交距离；和空 UC，被视为比较项。这项工作的主要新颖之处在于对大型UC中热羽流和气流的综合效应的分析。热流体动力学模拟的数值模型在之前的工作中得到了验证，并且液滴发射模型是从文献中检索到的。高体积气流并不总是有利于降低空气传播风险。一个重要的方面与入口气流和热羽流的综合影响有关，如果占用率取一个显着的值，则不能忽视这一点。此外，疏散率和液滴年龄是评估清洁时间的相关指标。