Study On The Diffusion And Transport Laws Of Exhaled Aerosol Particles And Optimization Of Flow Field Control Mode In A Medical Room

The outbreak of COVID-19 has posed a serious threat to the life and health of people around the world,and has caused countless economic losses.According to statistics from the World Health Organization,lower respiratory infections rank fourth among the top ten leading causes of death worldwide.Therefore,studying the diffusion patterns of virus-carrying aerosol particles and methods to inhibit their spread is of great practical significance.China’s research in this area started relatively late,especially in the study of aerosol diffusion in small medical rooms,which is still far from enough.In this article,we used three methods of theoretical analysis,experimental verification,and numerical simulation to study the diffusion and transport of exhaled aerosol particles in small medical spaces,and provided suggestions for optimizing ventilation modes to inhibit the spread of particles on a large scale.The main achievements obtained are as follows:(1)Airflow measurement and microbial collection experimental platform.Based on the existing experimental platform,an experimental thermal mannequin was designed,and Bacillus subtilis var.niger was used to replace the exhaled aerosol particles of patients.The indoor flow field was measured using a wind speed tester,aerosol generator,sampler,and various auxiliary equipment.Microbial collection experiments were conducted at various sampling points indoors,and the diffusion patterns of indoor aerosol particles with changes in ventilation modes were obtained.(2)Mathematical and physical models of indoor exhaled aerosol particle diffusion.A three-dimensional physical model of a small medical room that can implement various ventilation modes was established.A physical model of single/multiple human bodies was constructed to study the diffusion process of exhaled aerosol particles in the medical room.Based on the basic theory of gas-solid two-phase flow,the Realizable k-ε turbulence model was used,and the Euler-Lagrange method was adopted to construct a mathematical model of the diffusion of exhaled aerosol particles in the medical room with the wind.This provides a foundation for subsequent numerical research.(3)Flow field,temperature field,and diffusion and transport of aerosol particles in a medical room.The influence of different ventilation modes and air exchange rates,as well as the effect of human thermal plumes,on the flow field,temperature field,and diffusion and transport of aerosol particles in a medical room were studied.It was found that the flow field was relatively stable with the up-supply and down-return ventilation mode,and the airflow could drive the thermal plumes around the human body to diffuse towards the outlet.The study revealed that the down-supply and up-return ventilation mode had a more advantageous effect on suppressing the diffusion of aerosol particles than the up-supply and down-return mode.Moreover,the down-supply and up-return mode could achieve a higher removal rate of aerosol particles in a short period of time.(4)Optimization of flow field to suppress indoor aerosol particle diffusion.Based on the analysis of indoor air age,it is recommended to use the down-supply and up-return ventilation mode for a medical room with two beds.This mode can effectively suppress the large-scale diffusion and transport of aerosol particles while ensuring the safety of nearby patients and medical staff.Comparative analysis shows that the ventilation mode of 15 air changes per hour and down-supply and up-return mode has the best overall effect in this study.