A numerical study of a protection technique against tube erosion

Erosion of tubes by coal particles or coal ash impingement has caused serio us problems for many pulverized coal energy conversion systems. It is impor tant to study erosion protection methods for heat exchanger tubes undergoin g erosion. In this paper, a new type of erosion-protection technique, the f inned tube erosion-protection technique, is proposed. Fins located on both sides of tubes alleviate tube erosion in the way they change gas flow held, then consequently change particle trajectories, particle-tube collision fr equency, and erosion damage of tubes. A numerical study has been conducted for the flow of a dilute particle-laden gas moving past a finned tube under going erosion. Eulerian equations are used to describe gas-phase motion, wi th the turbulence viscosity evaluated from the turbulent kinetic energy k a nd its dissipation epsilon model of turbulence. The prediction of particle velocities and trajectories takes into account the effect of the turbulence with a stochastic particle dispersion model. The particle impaction/reboun d model and the erosion model of ductile alloys are used to predict the par ticle-rebound phenomena and the erosion damage to the tubes. The present pa per discusses the effect of relative length of fins, free stream velocity a nd particle size on particle-tube collision frequency and erosion damage of the tubes. The results show that the finned tube is a simple and efficient erosion protection method in most industrial two-phase systems where erosi on occurs. (C) 1999 Published by Elsevier Science S.A. All rights reserved.