热分层环境人际间飞沫传染风险与对策研究*
Interpersonal droplet transmission risk and countermeasures in thermally stratified environment
摘要：
方舱医院中上千名新型冠状病毒肺炎患者与医护人员同处一室，彼此近距离接触频繁，可能存在院内感染风险。冬季工况下，冷壁面贴壁流动容易引起热分层。采用2个精确描述人体几何特征的三维数值模型，运用计算流体力学（CFD）方法，模拟了典型温度分层条件下呼出飞沫的近距离散布。通过统计易感者口部吸入飞沫的数量，结合实验室结果，量化评估了人际间飞沫传染的风险。研究发现，将人员活动区域的竖直温度梯度由1.50 K/m减小到1.08 K/m，1 m内吸入传染者呼出的5 μm飞沫数量下降60%以上。因此，应优先增大新风量，并在玻璃幕墙下布置加热器降低贴壁流动，避免形成竖直温度分层，稀释人员所在区域的飞沫和飞沫核浓度，有效降低交叉感染风险。
Abstract：
Thousands of patients with COVID-19 share the same space with medical staff in the makeshift hospital and contact with each other frequently, which may be a risk of nosocomial infection. The downward wall jet along the inner glass facade is likely to cause thermal stratification under winter conditions. Utilizes two full-scaled numerical models to simulate the dispersion of expiratory droplets under typical thermal stratification conditions by the CFD method. By counting the number of droplets inhaled by the susceptible, combined with the laboratory result, quantifies the risk of interpersonal droplet transmission. It is found that the number of inhaled droplets by the susceptible decreases by more than 60%, when the vertical temperature gradient decreases from 1.50 K/m to 1.08 K/m within a mutual distance of 1 m. Therefore, it is necessary to increase ventilation rate, and locate heaters under the inner side of glass facade to diminish downward wall jets, avoid the formation of vertical temperature stratification, and dilute the concentration of droplets in occupied zone, which effectively reducing the risk of cross infection.
Keywords:makeshifthospital,buildingventilation,thermalstratification,droplettransmission,computationalfluiddynamics(CFD)