Research Of Particle Movement And Deposition Regularity In HVAC Ducts

Nowadays, as indoor air pollution is increasingly serious, aerosol particles become animportant factor which effect the in door air quality. The HVAC system has a significantimpact in the in door air quality, so comprehend the regulation of particle movement in HVACduct have advantages for people solving the in door air quality problem. And it has animportant implication for controling the particles and improving indoor living environment.This thesis used numerical and experimental method to research the particle movement inHVAC duct. The main contents and conclusions are as follows:1. The particle force analysis and the validation of the movement equation. Themagnitude of the force of particle movement in air flow were compared, and then, the equtionof the particle movement was established. The result indicated that the drag force, gravity,brownian force and suffman force were the main forces of aerosol particles in HVAC ductflow, and if the air flow had temperature gradient, the thermophoretic force should also beconsidered. When the particle diameter dp<0.1μm, the brownian force is the main force; when0.1<dp<10μm, the drag force is the main force; and when dp>10μm, the main force becomesto the particle gravity.2. The validation of numerical method. Different turbulent models were compared to findout the most accurate numerical calculation method. The results showed that RSM modelcombined with enhanced wall treatment were the most accurate numerical method, itconsidered the turbulence anistropy.3. Analysis of the factors in particle deposition in duct. This thesis used numericalmethod to discuss the effect of air velocity, flow statement, air temperature and humidity inparticle deposition in duct. The results showed that the air speed and flow statement all had aeffect on particle deposition. The particle dimensionless deposition velocity on all surfaceswere all increased as the air velocity increasing. The particle deposition velocity was higher infully developed duct than developing duct. When there was a big difference in temperaturebetween air and wall, the smaller particle deposition may increased, when the air temperaturedecreased or humidity increased, the particle deposition velociy increased a little.4. Research of particle deposition in90°bend. This thesis used numerical andexperimental method to research the particle deposition in90°bend. And two formula wereproposed to calulate the deposition velocity in and behind a bend. The result showed that theparticle penetration in bend had a relationship with particle stokes number, and it decreased asparticle stokes number increased. The particle deposition more after bend than before bend.The formula can predicate the particle deposition in bend ducts which has some guidances.