Monte Carlo analysis of wall erosion and direct contact heat transfer by impinging two-phase jets

Abstract

A stochastic model, based on the Boltzmann kinetic equation, is suggested for describing the flow of solid particles in impinging two-phase jets. The model is valid for highly nonequilibrium dilute impinging flows in which the inertia of the particles is very high and dynamic coupling with the fluid is low. The model includes the effects of interparticle collisions and is employed for predicting wall erosion rates by particle impacts and direct contact heat transfer from a surface by the colliding particles. A Monte Carlo simulation procedure is proposed, and numerical results are presented. The numerical results confirm experimental observations on reduced erosion rates caused by surface shielding by rebounding particles. Laminar and turbulent flow patterns as well as brittle and ductile erosion modes are studied. The results indicate, in accordance with experimental observations, an increase in the shielding effect, when increasing the particles' volume fraction, elasticity, and angle of incidence and decreasing the particles' diameter. Interparticle collisions are shown to increase ductile erosion rates and decrease brittle erosion rates. In heat transfer from a wall, at low particle concentrations, interparticle collisions improve the heat transfer resulting from decreased impact velocities, but at higher concentrations the heat transferred by particles decreasesmore » because of surface shielding by rebounding particles. 37 references.« less