Study Of The Particle Deposition Properties In Ventilation And Air Conditioning Duct Systems Under Adjacent Influence Conditions

Currently,both process and comfort air conditioning systems suffer from particle deposits leading to the accumulation of large amounts of dirt and dust in ventilation ducts,which in some cases can become a source of contamination for other pollutants,as well as being carriers of bacteria,new coronaviruses and other microorganisms,and when the accumulation reaches a certain level,can also cause re-suspension,thus affecting indoor air quality.Particular attention has been paid to the problem of dust deposits in air conditioning ventilation ducts forming a secondary source of contamination following the novel coronavirus(COVID-19)epidemic period in 2019.At the same time,coupled ventilation ducts consisting of several local components are more common in everyday life,while many studies have simplified the gas flow process to a fully developed state,in fact,the gas flow state inside them is more in a non-fully developed state.Therefore,the study of the particle deposition pattern of the duct wall is of great theoretical significance and value for the regular cleaning and maintenance of the duct,the selection of suitable filters and the rational design of the duct.In this paper,equations are derived for the deposition velocity of particles deposited onto each face of the tee member(top face,outer wall face,bottom face and inner wall face)using the principle of mass conservation.Simulations of tee-coupled pipes and elbow-coupled pipes under adjacent influence conditions were carried out by a combination of full-scale experiments and Lagrangian simulations.The deposition velocities of spherical particles of multiple particle sizes in the 1μm-200μm particle size range are analysed under adjacent influence conditions,where the influencing factors considered include the spacing between adjacent local components,particle size and air flow velocity.The results of the study show that the ventilation ducts under adjacent influence conditions have a complex effect on the flow field,which in turn affects the particle deposition.For the tee-coupled duct system,at the same flow velocity,compared to the tee-uncoupled duct: the total duct wall causeless deposition velocity is greater for the teecoupled duct,the particle factorless deposition velocity is greater on the bottom surface and less on the inner wall surface.The situation of the factorless deposition velocity of particles on the top,outer wall and bottom surfaces in the coupled duct: tee and tee are the largest and reducer and tee are the smallest,on the inner wall: reducer and tee are the largest and tee and tee are the smallest.In addition,the factorless deposition velocity of particles in tee-coupled pipes at high flow velocities is greater on the top and inner wall surfaces and smaller on the bottom surface compared to low flow velocities.For elbow coupled pipe systems,at the same flow velocity,compared to uncoupled pipes: the total pipe wall factorless deposition velocity is greater for coupled pipes.Particles are deposited at a greater factorless velocity on the top and bottom surfaces.The magnitude of the factorless deposition velocity of particles on the inner and outer curved surfaces also varies for different wind speeds and different elbows of the coupled duct.In addition,the factorless deposition velocity of particles in the coupled system at high flow velocities is greater on the top surface and smaller on the inner and outer arcs compared to low flow velocities.