A numerical study of a protection technique against tube erosion

Erosion of tubes by coal particles or coal ash impingement has caused serious problems for many pulverized coal energy conversion systems. It is important to study erosion protection methods for heat exchanger tubes undergoing erosion. In this paper, a new type of erosion-protection technique, the finned tube erosion-protection technique, is proposed. Fins located on both sides of tubes alleviate tube erosion in the way they change gas flow field, then consequently change particle trajectories, particle-tube collision frequency, 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 undergoing erosion. Eulerian equations are used to describe gas-phase motion, with the turbulence viscosity evaluated from the turbulent kinetic energy k and its dissipation ε 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/rebound model and the erosion model of ductile alloys are used to predict the particle-rebound phenomena and the erosion damage to the tubes. The present paper discusses the effect of relative length of fins, free stream velocity and 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 erosion occurs.