Study On The Evaporation And Diffusion Law Of Cough Droplets And The Evaluation Of Infection Risk Under The Influence Of Airflow

The cough activity of human body brings a large number of droplets splashing,and then the microbes attached to the droplets enter the room.The diffusion of microorganism is mainly affected by the air flow in the room.Meanwhile,the survival ability of microorganism in the air and the evaporation process of droplets in the air are closely related to the indoor temperature and humidity conditions.Therefore,this paper discusses the influence of air distribution on the evaporation and diffusion of cough drops,and attempts to evaluate the infection risk of medical staff.The user-defined function is compiled to introduce saturated vapor pressure,cough speed curve and vapor diffusion coefficient into the discrete phase model,add the statistical function of droplet position and evaporation state,so as to establish the cough droplet evaporation and diffusion model,and verify the reliability of the model according to the existing experimental data.In addition,the Dose-response model was optimized from the aspects of establishing respiratory region,introducing evaporation factor and discrete observation time,so as to establish the MSDR infection risk assessment model.The model was used as the quantitative assessment mechanism of infection risk.Using these models to study the evaporation and diffusion of cough droplets and the infection risk of medical staff,the main results are as follows:(1)The evaporation duration of the droplets in the high temperature and low humidity environment was 70% less than that in the low temperature and high humidity environment,the effect of relative humidity on the evaporation of cough drops is greater.The air environment with low temperature and high humidity could inhibit the diffusion of coughing droplets,but the inhibition effect is limited.(2)Under the condition of air supply speed of 0.24m/s and air change times of 16 times/h,the upward and downward air supply on the opposite side of the grille can achieve a better cough liquid drop removal effect in the shortest time.The upward and downward air supply on the different side of double slot has a stronger ability to remove large droplets,and the upward and downward air supply on the opposite side of the grille has a stronger ability to remove small droplets.(3)The infection risk of the upward and downward air supply on the opposite side of the grille is less than that of the other three air supply forms after the droplet incident for 20 s,and the longer the time is,the more obvious the advantage is.Under this type of air supply,0.24m/s air supply speed corresponds to the least risk of infection.