Research On Transport Model Of Ultrafine Particle In The Indoor Environment

With the rapid development of nano-technology industry, more and more nano-scale materials have been used in various fields. For HVAC and aerosol research, a new definition named"ultrafine particle"has been developed. They are defined as those particles whose diameters are in the range of 1nm-1μm . These ultrafine particles may have negative effect for residents'health or even cause sicks, and they may affect the quality of the products which are sensitive to ultrafine particles.From last century, more and more attention has been paid on the IAQ (Indoor Air Quality), so the particle pollution has been researched for decades. As a crucial factor, the forces exerted on the particle have been studied systematically and the force equation for particles whose diameter is larger than 1000nm has been developed already. The classic model is Lagrange model which uses all force vectors as the impetus of transport, including drag force, gravity, pressure gradient force, virtual mass force, Basset force, Saffman force, Magnus force and thermophoresis.However, the transport properties of ultrafine particles are much different from that of larger ones. Some of the forces definitions depend on an assumption that the air is constant phase, but for calculation of forces exerted on ultrafine particles, the air is discrete phase and should be assumed as millions of air molecules. The cause of the forces exerted on the ultrafine particles is the collision between air molecule and ultrafine particle, so the classic model becomes invalid. Furthermore, the ventilation system and the location of particle source will also influence the distribution of particles in the indoor environment.According to the analytical investigation and calculation, this paper concludes the transport model for the ultrafine particle in the indoor environment. Additionally, by analyzing different styles of ventilation system, it predicts the particle distribution under various ventilation systems in the indoor environment. In sum, the particle distribution model provides a basic foundation for further research on ultrafine particle transport and distribution in the indoor environment.