Effects of Particle Relaxation Time and Continuous-Phase Reynolds Number on Particle Deposition in Vertical Turbulent Pipe Flows

Abstract

The present study focuses on the mechanism of particle deposition onto a channel wall in numerically simulated turbulent pipe flows. Large eddy simulation of the incompressible Navier-Stokes equations was performed to calculate the time-dependent turbulent flow field of continuous gas phase. Considering the engineering application to the droplet motion in boiling water reactor subchannels, the flow direction was set to be vertically upward. The particles were placed at random initial locations in the pipe, assuming that the initial velocities in the lateral direction are equal to zero. The subsequent motion of particles was tracked individually using a simple Lagrangian equation. It was shown that small particles tended to accumulate in the viscous sublayer while large particles moved parallel to the pipe wall. The deposition coefficient was hence highest when the particles were intermediate in size or in relaxation time. The calculated results indicated that the effect of the continuous-phase Reynolds number on the deposition mass transfer coefficient was not negligible since it affected the drag and the lift coefficients and, consequently, the particle motion in the lateral direction.