Transmission Control Mechanism And Experimental Study Of Aerosols Based On Different Air Distribution In Air Conditioned Rooms

In recent years,the outbreak of a series of epidemics(SARS,H1N1 influenza,and new coronary pneumonia)has threaten human health and triggered the global attention to airborne diseases.How to effectively control aerosol diffusion and reduce human exposure through reasonable indoor air distribution has become a hot issue to be solved.Therefore,on the basis of literature research,this paper studied the transmission mechanism and distribution characteristics of aerosols in air conditioned rooms with different air distribution by combining theoretical analysis,experimental research and CFD numerical simulation,which is of great significance to reduce the risk of airborne diseases and protect human health and safety.Taking a lateral supply air conditioned room as the research object,an experimental platform that performs the mutual conversion of multiple air distribuion was designed.The paper focused on the analysis of the transmission of aerosol with the joint action of human thermal plume and different air distribuion from the perspective of pollution sources.The numerical model of continuous phase air flow and discrete phase aerosol movement was established.The equations of respiratory velocity and cough airflow velocity were proposed.The evaporation of droplets was considered.The reliability of the numerical model was verified by the experimental data.The effects of respiratory behavior,air temperature and humidity,air distribution,air change rate on the distribution characteristics of aerosols were analyzed.The movement rule of aerosols in air conditioned rooms with different air distribution was revealed.A dynamic measurement method of air bacteria content in the operating microenvironment was proposed to study the microbial aerosol in the operating room.The effects of personnel activities on the planktonic bacteria,settling bacteria and wind speed in the real mixing ventilation and vertical laminar ventilation operating rooms were analyzed.A full-scale mixing ventilation operating room experimental platform was built,and the trace gas was used to simulate the microbial aerosol pollutants produced by surgical staff.The effect of the air change rate on the pollutant concentration was revealed,and the effective control methods of pollutants at key positions in the operating room were proposed.A numerical model of microbial aerosol movement was esatablished.The effects of air change rate,number and the layout of outlets on the transmission of microbial aerosol were analyzed.The ventilation design of the mixing ventilation operating room was optimized.The results show that in the airflow distribution of two lower sides supply and two upper sides exhaust,the droplet aerosols of 1?m are mainly suspended in the front of the nostril within a short period of time after exhaling from the nostril,and"locking phenomenon"occurs.The initial velocity of droplets is related to the respiratory behavior,which directly affects the trajectory and distribution characteristics of aerosols.Compared with breathing behavior,airflow distribution and air change rate,the supply air temperature and relative humidity have less effect on the number of suspended aerosols in the air and escaped aerosols from the outlets.Increasing the air relative humidity increases the number of deposited aerosols.In the mixing ventilation operating room,the human activity intensity affects the planktonic bacteria number,and the change of human activity intensity has a delay time on the change of planktonic bacteria number.There is nonlinear relationship between the decrease of pollutant concentration and the increase of air change rate in the operation zone.The effect of the layout and number of outlets on the distribution characteristics of microbial aerosols is related to the air change rate in mixing ventilation operating room.When the air change rate is lower than 20h^-1,the study suggests a layout of four return air outlets arranged diagonally close to the pollution source.The research results provide theoretical basis and data support for controlling of indoor aerosol transmission effectively,and play a positive role in ensuring indoor air quality.