Numerical Analysis Of Airflow Organization And Aerosol Propagation Law In Air-conditioned Rooms Of Office Buildings

People in cities spend an average of 70%to 90%of their time in air-conditioned rooms,thus the impact of the indoor environment of air-conditioned rooms on human health is particularly significant.When there are patients with respiratory infections in the room,the behavior of patients breathing,coughing and talking will produce a large number of droplets or aerosols,and respiratory viruses can be spread through the air by attaching to aerosol particles.A reasonable airflow organization is an effective way to control the spread of virus aerosols,and airflow organization is determined by a variety of factors,so the ventilation system design should be optimized to improve the effectiveness of indoor ventilation to reduce the risk of infectious virus infection among indoor personnel,taking into account the ventilation method,the number of air changes and the internal structure of the room and other influencing factors.In this paper,three ventilation methods are designed and the corresponding geometric models are established,namely,top-feed and top-return,same-side top-feed and bottom-return,and opposite-side top-feed and bottom-return,taking the air-conditioned room of office building in summer as the research object.Then,FLUENT numerical simulation software is used,and the RNG k-εmodel is selected as the numerical simulation turbulence model.The finite volume method is used to discretize the flow and heat transfer control equations,and the SIMPLE algorithm is selected to solve the coupled pressure and velocity to establish the numerical model of indoor air flow and aerosol diffusion and verify them.Finally,by analyzing the mechanism of respiratory infectious disease transmission and aerosol characteristics,the aerosol propagation law of air-conditioned rooms in office buildings under three different ventilation methods is numerically simulated and analyzed by using CO₂ tracer gas instead of aerosol particles.The main research contents and analytical conclusions of the article are as follows:（1）The indoor airflow organization and aerosol particles under three ventilation modes with 5 and 10 air changes per hour were numerically simulated,the spatial distribution patterns of velocity field,temperature field and aerosol concentration were obtained,and the risk of virus infection for indoor personnel using the SEI（susceptibility exposure index）index was assessed.The results show that the velocity and temperature fields of the room can meet the requirements of indoor airflow organization design under two kinds of air exchange times;the risk of infectious disease infection can be reduced by moving away from patients;the risk of infectious disease infection can be reduced by increasing the number of air exchange times,and the aerosol concentration at the height of indoor breathing zone can be reduced and the ventilation efficiency of the room can be improved;the number of air exchange times has a certain influence on the distribution of indoor aerosols,but the dominant factor affecting the spread and control of aerosols is the aerosol concentration.The dominant factor affecting aerosol propagation and control is the path between the aerosol contamination source and the return air outlet,and aerosols are better controlled when the path is not disturbed by airflow.（2）In order to further study the influence of room aerosol pollution source and return air outlet path on indoor aerosol distribution,a partition is set in the air conditioning room,and the indoor airflow organization and aerosol particle distribution law are numerically simulated when the number of air changes is 5 times/h under three ventilation methods,and the simulation results are compared and analyzed with those without partition.The results show that:the room setting partition will affect the indoor velocity field and temperature field,in the airflow direction,the wind speed of the personnel behind the partition is smaller and the temperature is higher;the partition has a significant effect on the indoor aerosol distribution,and the results are reflected in the influence on the indoor airflow,when the partition is set between the aerosol pollution source and the return air outlet path,the effect of the partition on the indoor aerosol distribution is significantly enhanced;setting partition can optimize the ventilation design of the room,the ventilation efficiency of the room is increased,and the risk of infection of indoor personnel is different under the three ventilation modes.