Particle deposition from natural convection boundary layer flow onto an isothermal vertical cylinder

Abstract

Consideration is given to analyse the sub-micron deposition from a laminar free convection boundary layer developing on a heated isothermal vertical cylinder. A finite-difference method, as proposed by Cebeci and Smith [28], has been used to theoretically calculate the local cumulative particle deposition, with the thermophoretic velocity being that proposed by Talbot et al. [19]. It was demonstrated that the thermophoresis has a pronounced effect on the particle transfer but only a slight effect on the very smaller particles (<0.01 μm) and that the effect increases with particle size and distance along the cylinder. Experiments were also conducted using mono-disperse flourescent uranin, particles with mean diameter of 0.05 μm. A calibrated flourimeter was used to measure the mass of the particles deposited at different axial locations of the cylinder. Results showed similar trends to the theoretical model, but absolute values of the deposits were greater than theoretical predictions.