Numerical Analysis Of Fine Particle Coagulation Regularity In HVAC Duct

In recent years, the fine particulate matter has become one of the most important pollutants that threat to human health. It is difficult to make a major breakthrough on gas treatment work for fine particulate matter, the traditional air conditioning system purification efficiency of fine particulate matter is not high although it is as an important infrastructure to create a healthy indoor environment. By the way of coagulation, fine particulate matter becomes into particulate matter, which can significantly improve the efficiency of the system to capture the particles, reducing the spread of atmospheric fine particles to the interior. In this paper, numerical analysis on the fine particulate matter coagulation in the ventilation and air conditioning pipe is made, and experimental verification is done, the main conclusions are as follows:1. Morphology observation of the fine particle by scanning electron microscopy(SEM) and element analysis by X-ray spectrometer results show that the vast majority of particles is relatively rules round ball, the chain of granular and crystal structure of mineral grains with rules Is actually the most, the number of particles with biological characteristics is at least, element analysis results show that the spherical particles may comes from burning fossil fuels in the city such as coal, and chain particles may be derived from the motor vehicle exhaust emissions and dust on the ground. Morphology observation provides a theoretical basis for the assumption of spherical particles in mathematical modeling.2. Theoretical calculation for the force magnitude of fine particles in the air duct is done, which found that no matter in the turbulent core or in near wall region, for submicron particles, Brown force is the largest force magnitude, for micron particles, drag force is the largest force magnitude, brown diffusion is an important theoretical basis of fine particulate matter has no regulation motion. In the near wall region, Thermophoresis force, shear lift has important effect on the movement of particles in the direction perpendicular to the wall, magnus force can be ignored. In additional high-voltage electrostatic field, the electric force on charged particles could surpass drag in the electric field, which could cause the grain orientation movement.Based on particle swarm equilibrium theory, considering the particle collision efficiency a mathematical model of probability.is established, which can be used in the numerical calculation of fine particle coagulation probability.3. Numerical analysis of the influencing factors on particle coagulation in the duct. Under the influence of brown diffusion and turbulent pulsation,coagulation phenomenon occured obviously on submicron particles in the process of movement in air duct, coagulation strength enhanced obviously as the the particle concentration increased and the increase of the inlet air flow velocity. Under monodisperse entry conditions, the condensing and strength increased as the particle size of the entrance gradually decreased; Compared with free molecule probability model and the turbulent probability model results show that the established probability model in this paper can give a more reasonable description of coagulation process between fine particulate matters in the duct flow.4. Natural setting caused by brown and turbulent diffusion actions have a significant influence on the submicron particles, little impact on micron particles; When the inlet wind speed reaches 7.80 m/s, The size distribution altered obviously in the tube; Disturbance device is opened, coagulation will further aggravate between particles in the duct.