表面沉积呼出飞沫蒸发残留物再悬浮特性及病房环境控制方法研究

新冠肺炎感染者早期的上呼吸道新冠病毒脱落率非常高，因此口腔和喉模态呼出的粒径大于100 μm的飞沫病毒载量高，占了呼出飞沫总质量的99%以上。大飞沫在病房内很快沉降到物体表面，其蒸发残留物再悬浮产生的扬尘是室内气溶胶的重要来源，因此迫切需要开展研究来揭示“飞沫沉积–蒸发残留物–扬尘气溶胶”的转移规律。本项目将定量刻画物体表面病原体自然沉积速率与病原体点源距离的规律，阐明渗透性和非渗透性表面液滴蒸发残留物的结构和形态，揭示在整理床铺和人员走动等扰动下表面生物颗粒群裂解及再悬浮特性。基于实测的病房新风换气次数分布，建立医护人员黏膜及呼吸道暴露模型，利用改进的Wells-Riley模型评估感染风险。构建适应平时/疫情的病房辐射空调系统，在自然通风的同时有效保障热舒适水平，并提出新型通断调节方式杜绝冷辐射吊顶结露风险。本研究为降低呼吸道传染病院内感染及平疫结合的病房环境控制提供理论指导。

SARS-Cov-2 transmits efficiently through active pharyngeal viral shedding at a time when symptoms are still mild and typical of upper respiratory tract infection. The droplets with a diameter larger than 100 μm expired by laryngeal mode and oral cavity mode carry a large amount of virus and occupy over 99% of the total mass of the expired droplets in a cough and a sneeze. The large droplets (> 100 μm) settle on the surfaces (e.g., bed and floor) inside the wards in seconds. Droplets land on a surface and dry to become desiccated. Bed-making activities and walking can eject dry particles into the air, which is an important source of the aerosol. There are urgent needs on basic research for the transfer mechanism from droplet settling, deposition pattern of drying droplets, to bio-particle resuspension. The spatial deposition speed of pathogens on surfaces in a ward is first shed light on. The deposition pattern (i.e., the quasi-two-dimensional aggregates) of drying expired droplets on fabric surfaces and impermeable surfaces is investigated. The bed-making and walking induced particle resuspension from the completely desiccated droplet on a surface is theoretically and experimentally studied. On the basis of the on-site measured fresh air change rate distribution of wards, the mucosa exposure and respiratory exposure model for healthcare workers is developed and the infection risk is evaluated via a revised Wells-Riley model. A radiant heating and cooling ceiling system adapting to infectious disease epidemics is developed for wards to maintain the indoor operative temperature during natural ventilation. A novel pulsed flow control strategy is proposed to eliminate condensation risk on the radiant cooling ceiling surface with the help of the frequent condensation-evaporation cycle. It is believed that the theoretical guide could be obtained for decreasing nosocomial infection and improving the indoor thermal built environment in wards.