A Study On The Individualized Air Supply Mode Of Air Conditioners To Reduce The Spread Of Viruses

HVAC systems of buildings are primarily used to create an indoor environment with acceptable and comfortable temperature,humidity,airflow velocity,and keep a good indoor air quality.However,since the outbreak of COVID-19,people have worried that central air conditioning may accelerate the infection probability among indoor personnel,so in many public places,the existing central air-conditioning system can only be turned off,which resulted in a significant reduction in indoor comfort.With the arrival of an era when the epidemic may become normalized,it is imperative to propose a new air-conditioning method that can reduce the spread of the virus.The main research contents of this thesis are as follows:In this thesis,a new air supply port,for short,is proposed to reduce virus diffusion.The tuyere is integrated with the air supply and return,and the tuyere can form a rotating airflow,which can achieve different ranges and jet radii according to different needs of users,and can realize various air supply methods such as top delivery and station side delivery.The tuyere mainly includes a tangential air inlet,an outer cylinder and an inner cylinder.The air supply from the air conditioner passes through the outer cylinder to form a rotating airflow at a certain angle,forming a jet air curtain in the working area of the staff,The air curtain can be adjusted to different jet shapes according to the needs of the personnel’s working range,and a local comfort area can be formed in the air curtain according to the individual comfort needs of the personnel;Through the return air,the gas produced by human breathing can be sent back to the system exhaust duct.AVSD is an innovative air-conditioning method,which not only saves energy,but also effectively prevents the spread of viruses.It is the development direction of future air-conditioning systems.Secondly,the shape and related parameters of the air outlet are given.The resistance coefficient of tuyere under different conditions was tested by experiments,at the same time,the influence of the number of blades,blade angle,blade shape,etc.On the drag coefficient of the tuyere is analyzed.The air outlet structure with less resistance was determined.Through field test,the velocity field formed by the tuyere in space is studied,and the attenuation law of jet flow along the tuyere and radial flow is obtained.Through numerical simulation,the distribution law of jet flow field formed by three kinds of personalized air supply modes with the return air outlet placed inside the air supply outlet,below the air supply outlet and on the same side with the air supply outlet is studied.The jet flow pattern under different working conditions,the position of the main flow line and the numerical value change are obtained,the formula of average velocity and total flow rate of each section along the jet direction are obtained through theoretical analysis and fitting.According to the simulation results,the optimal position of the return air outlet can be determined.The thermal comfort PMV at any point in the jet region can be determined according to the cross-sectional average velocity formula obtained in the previous study.The simulation results show that the thermal comfort degree of personnel is in the range of-0.5 to +0.5 when using AVSD tuyere and jet development section,and the comfort degree is better in the working area.Finally,the prevention and control effect of AVSD on virus was simulated by using Euler-Lagrange method.By comparing with the room without AVSD,when the infected person is in the jet area of AVSD,the simulation simulates the sneezing of the infected person in the initial sneezing period of 0.2s-2s,2s-20 s and 20S-200 s,and when the personalized air supply mode of AVSD is adopted and not adopted.The spread distance and quantity of virus and particulate matter produced by sneezing.The results showed that the total amount of virus and particulate matter around the person was greatly reduced and the spread distance of virus was shortened from 7m to 2.85 m when the AVSD personalized air supply mode was adopted at the end of 200 s after the sneeze.This shows that AVSD tuyere has obvious effect of anti-virus diffusion.