Study On Air Distribution And Airborne Particle Diffusion Characteristics In A Ward Based On Orifice Plate Air Supply

Indoor air distribution is important for air-conditioned rooms.Unreasonable air flow organization may cause problems such as indoor air flow velocity and uneven distribution of heat and cold,and may also cause the indoor air to be older and accumulate indoor pollutants.For isolation wards dealing with respiratory infectious diseases,a reasonable air flow organization can not only create a high thermal comfort environment,but also quickly remove aerosols and other pollutants,which has a good reference for disease prevention and control.Through numerical simulation,the purpose of this article is to explore the airflow structure and aerosol diffusion characteristics of wards based on commonly used mixed air supply and orifice air supply.The orifice air supply can make the indoor airflow organization uniform,but the air will produce a certain resistance through the orifice plate.Therefore,it is necessary to study the local resistance coefficient of the orifice plate.First of all,this paper discusses the influence of geometric structure,such as opening diameter,hole layout method,opening shape,opening ratio,etc.,on the orifice resistance coefficient.The results show that,relatively speaking,the resistance coefficient of the orifice plate is only related to the opening ratio of the orifice plate,and other geometric parameters have little effect on the resistance coefficient of the orifice plate.There is a power exponential relationship between the resistance coefficient of the orifice plate and the opening ratio.itis Eu=1.16·β^-2.03Subsequently,this paper chooses the negative pressure ward of the hospital as the research object.The effects of diffuser mixed air supply and orifice air supply on temperature distribution,wind speed distribution,human thermal comfort index and removal efficiency of aerosol particles exhaled by patients were discussed.The results show that the distribution of indoor temperature and velocity in the case of orifice plate air supply is relatively more uniform than that of mixed air supply.In addition,in the case of orifice plate air supply,the aerosol produced by patients’breathing can reach a lower equilibrium concentration faster in the room,which indicates that the orifice plate air supply is more conducive to aerosol deposition or discharge in the ward.Finally,at the end of this paper,the effects of four different orifice plate opening ratios,namely 0.01,0.05,0.1 and 0.5,on the air distribution,thermal comfort and pollutant diffusion distribution in the ward orifice plate were studied.The results show that when the opening ratio is large,the air flow in the local position of the room is chaotic,the indoor temperature is on the high side,and the thermal comfort is poor.Relatively speaking,the decrease of opening ratio is beneficial to improve the uniformity and thermal comfort of indoor air distribution.The smaller the opening ratio is,the easier the equilibrium concentration of indoor aerosol concentration.That is,aerosol,is to be excluded or settled.On the other hand,although the decrease of the opening ratio will improve the indoor thermal comfort and reduce the equilibrium concentration of aerosol,when the opening ratio is reduced to 0.05,the indoor air distribution is basically consistent with that when the opening ratio is 0.01.Considering that thedecrease of the opening ratio will further increase the resistance of the orifice plate,resulting in an increase in energy consumption.Therefore,when using orifice plate to supply air,the orifice plate with appropriate opening ratio should be used.