Study Of The Characteristics Of Settlement Of The Aerosol Particles In The Air Conditioning Duct Systems

The particles in air conditioning duct system enriched in plenty of heavy metals, acid oxides, organic pollutants,and they are also the carrier of the micro-organisms (bacteria, pathogen and epiphyte, etc.) breeding and the radon daughters diffuse. Particles pollution have aroused extensive attention due to deterioration of indoor air quality. Domestic and foreign scholar have done a lot of theoretical research on particles sedimentation in the ventilation ducts,but research in particles sedimentation in the air-conditioning duct is imperfect and unsystematic. As the simulation for particle sedimentation in air-conditioning duct with actual size is lacking ,and the same as actual tested data.This paper reviewed experimental methods and theoretical prediction model of particles deposition in the ventilation and air conditioning duct system, then presents the method and content in this text. Analyses particles deposition sampling data in last three months based on field-testing and survey of an air- conditioning system in one mall of Hengyang City .Analysing differences of relevant parameters (such as aerosol concentration, temperature and humidity, speed, TVOC, CO2) inside the duct and in and out of room , contamination concentration changes of supply outlet and return air inlet,the rule of different pollutants contamination concentration changes with time and the parameters change along the duct , then propose some improvement for design, installation, maintenance in air- conditioning system.Second, this paper integrately discussed particle deposition in rectangle air- conditioning duct using RSM air flow flied model and random trajectory particle model .Simulation of particle deposition in internal surface of smooth horizontal duct and tee with nominal particle diameters of 10~200μm were carried out with air speed 4 m/s, 6 m/s,and 8m/s, respectively, in the section size of 160×120, 500×250, 1000×320mm . In simulation, this paper compared and analysis the influence factor of particles deposition in particle diameters, velocity,volume surface ratio, flow regime in the rectangular air-conditioning duct. The results show that the main factor for particles sedimentation is particle diameters and entrance average air speed in range of the referred particle diameters, the influence of volume surface ratio is consistent, dimensionless deposition rate increases with volume surface ratio;the influence by flow regime decreases with entrance average air speed increasing.Finally, this paper summarizes the field survey and simulation, discuss the deficiencies in this actual work, and puts forward the future research direction , and provides reference for carrying out future research and control in aerosol pollution.