Numerical Simulation Study On The Diffusion And Distribut Ion Of Pathogenic Microbial Aerosols In Hospital Wards

Th:release and transmission of microbiological aerosols containing pathogens in the air arc one of The main routes of transmission of respiratory infectious diseases such as COVID-19.Hospital wards are a high-risk area for cross-infection of respiratory infectious diseases.With the continuous spread of COVID-19 virus globally in recent years,how to reduce the cross-infection caused by pathogenic aerosols in hospital wards through design methods such as ventilation design has become a hot topic in domestic and foreign research.This study takes thn tospital Negative pressure isolation ward.as the research object and uses numerical simulation to investigate the diffusion and distribution characteristics of pathogenic aerosols under different ventilation modes,air exchange rates and door opening aethods,providing scientific bases for a clean and safe medical environment,Firstly,the FLUENT software wab usad to establish the airflow ficld and distribution model of pathogenic aerosols in a typical hospital ward,and the model was validated,Based on this model,the airflow distribution and distribution characteristics of aerosol pollutants in the ward under two ventilation modes,downward and horizontal ventilation,were studied.The results showed that when pathogenic aerosols were released by patient’s breath:the deposition rates of pathogenic aerosols in the downward and horizontal ventilation modes were similar,with values of 34.54%and 32.92%,respectively.The removal rate of pathogenic aerosols in the horizontal ventilation mode was higher than that in the downward ventilation mode at 40.12%and 24.78%,respectively.The suspension rate of pathogenic aerosols in the horizontal ventilation mode was lower than that in the downward ventilation mode at 27.06%and 40.68%,respectively,When pathogenic aerosols were released from external personnel,the highest aerosol concentration was observed in the breathing zone of BR2 in the downward ventilation mode(6.5 E-12 kg/m3),white the aerosol concentration in the patient’s breathing zone was 0 E-12 kg/m3 in the horizontal ventilation mode.Therefore,for suppressing the spread of virus-laden aerosols,the horizontal ventilation mode is superior to the downward ventilation mode.Furthermore,the airflow field and distribution characteristics of pathogenic aerosols in the ward under five air exchange rates(6ACH,9 ACH,12ACH,15 ACH,and 18 ACH)were simulated for both ventilation modes.The study showed that as the air exchange rate increased,the deposition rates and removal rates of aerosols in the ward under both ventilation modes increased,while the suspension rate decreased.When the air exchange rate reached 18 ACH,the suspension rate could be reduced to below 10%.Under different ventilation frequencies,the deposition of aerosols in the ward shows a similar trend with the increase of ventilation frequency.Under the downward ventilation mode,the surface deposition of X-,Y+,and BR2 aerosols gradually increases with the increase of ventilation frequency,while that of Y-and BR2 decreases gradually.The X-wall has the largest increase in aerosol deposition,from 10.73%(6ACH)to 33.54%(18ACH).In the horizontal ventilation mode,the surface deposition of X-and Y+aerosols gradually decreases with the increase of ventilation frequency,while that of Y-,Z+,Z-,two medical staff,and two patients gradually increases.The surface deposition of BR1 aerosols increases the most,from 13.9%(6ACH)to 21.22%(18ACH),with an increase of 7.32%.The results show that it is crucial to adjust the ventilation frequency when exchanging the ordinary ward with the negative pressure isolation ward.It is also important to pay attention to the changes in the deposition ratio of aerosols on different surfaces under different ventilation frequencies,and carry out different levels of cleaning and disinfection for different surfaces under different ventilation frequencies to further protect the health and safety of personnel inside the ward.These results provide a reference for the exchange use of ordinary wards and negative pressure isolation wards in real life,and also explain the issue of cleaning and disinfecting different surfaces during the exchange use.Finally,the study explored the diffusion and distribution characteristics of pathogenic aerosols in a typical hospital negative pressure isolation ward.under three different door opening modes:sliding doors,swing doors-inward-opening,and swing doors-outward-opening.The research showed that when the entrance pressure was 0Pa,the impact of all door opening modes on aerosol deposition on interior surfaces was minimal,and the main difference lay in the aerosols escaped from the door,with the highest scattering amount being observed for swing doorsinward-opening,at 57.12‰.When the entrance pressure reached 5Pa,there were no aerosols escaping from the door.At this point,there was a more significant change in the deposition of aerosols on interior surfaces.Taking into account both the scattering and settling of aerosols indoors,the sliding door had the least impact on the indoor environment among the three door opening modes,and should be given priority consideration in ward design.This study provides practical recommendations for selecting appropriate ventilation strategies,door opening modes,and the rational use of isolation rooms.It offers reliable scientific evidence for the design and clinical use of isolation rooms.It also provides guidance and recommendations for hospital ward cleaning and disinfection to ensure a clean and safe medical environment.