Numerical Study of Particle Concentration Effect on Deposition Characteristics in Turbulent Pipe Flows

The present study focuses on the particle concentration effect on the 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 technical 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. The subsequent particle motion was tracked individually using a simple Lagrangian equation. To investigate the particle concentration effect on the rate of particle deposition, "two-way method" was applied, in which the two-way interactions between the continuous phase and the particles were taken into consideration. The calculated results showed that the mass transfer coefficient of particle deposition decreased noticeably with an increase in the particle concentration. This tendency was consistent with the experimental observations and empirical correlations. The present numerical results indicated that the turbulence modulation in the continuous gas phase is one of the primary causes of the reduction of the deposition mass transfer coefficient observed under high-droplet-concentration conditions.