A Study of Transport Mechanisms of Aerosol Particles on the Wedge Flows

• Main Authors: En-Haw Lee, 李盈樺
• Other Authors: R. Tsai
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/34564873717036191288

碩士 === 中原大學 === 機械工程研究所 === 90 === The problems of airborne particles deposition onto surface are a commonly observed phenomenon and their studies have gained importance for engineering applications or indoor environments. Owing to nonisothermal convection gaseous flow, thermophoresis plays a significant role in enhancing small particle moving to cold surfaces. The study in the particle transport by combined effects of inertia, thermophonesis and other mechanisms is important for the control of aerosol particles. The goal of this study is to examine the coupling effect of inertia, thermophoresis and others on particle deposition onto surfaces. The interaction between these three transport mechanisms is expected to be very important for particle deposition rate. We define a dimensionless parameter that controls inertial effect as modified Stokes number. In the article the flow is modeled as a two-dimension wedge flow. The governing partial differential equations are transformed to be a system of similar or nonsimilar equations by using similarity analysis. Block-elimination method and finite difference scheme are used to solve those equations and defermine the deposition rates. Particles selected are in a range of 0.01~100. We can find that particle deposition rates are controlled by the effects of Brownian diffusion and thermophoresis for small particles . However, with increasing particle sizes the inertial effects become important. Moreover, the inertial effects on particle deposition rates in different wedge angles are also examined. When wall temperature is smaller than free stream temperature, the deposition rates will increase. When then wall temperature is smaller than free stream temperature, the deposition rates will increase. As a result of the thermophoretic effect, the particles blown away from the heated wall, the deposition rates will decrease.