The influence of solid particles on the flow characteristics of the boundary layer for cross flow over a tube has been experimentally studied. A phase-Doppler anemometer was used to measure the mean and fluctuation velocities of both phases. Two separate tests were conducted with two particle size ranges (30-60μm and 80-150μm) and the freestream velocity and solid mass loading ratio were fixed, allowing the effects of particle sizes on the shape of the mean velocity profile and on the turbulent intensity levels. The measureraents clearly demonstrated that the larger particles damped fluid turbulence. For the smaller particies, this damping effect was less noticeable. The measurements further showed a delay in the separation point for two phase turbulent cross flow over a tube.

A modified model for particle-eddy interaction in two-phase turbulent flows is proposed to account for the turbulent dispersion of particles in a turbulent flow. In order to validate the proposed model, the structure of a turbulent, particle-laden, round jet, injected into a still environment, is studied both theoretically and experimentally. The numerical results show good agreement with the experimental data.

Erosion of tubes in tube banks by particles suspended in gas flows is a major problem in the chemical and power industry. In this paper, a numerical study has been conducted for the flow of a dilute turbulent particle-laden gas moving past two rows of staggered tubes undergoing erosion. Eulerian equations are used to describe gas-pbase motion, with the turbulence viscosity evaluated from a k-c model of turbulence. The prediction of impacting particle velocities and trajectories takes into account the effect of the turbulence with a stochastic particle dispersion model, as described by the authors. The particle impaetion/rebound model and the erosion model of ductile alloys obtained by Tabakoff et al. are used to predict the particle rebound phenomena and the erosion damage to tile tubes. The results from this study include the distributions of particle collision frequency and erosion damage to tube surfaces. The locations of maximum erosion damage to the tubes are predicted. Results indicate that the erosion damage to the second row of tubes in staggered tube banks is approximately twice that of the first row of tubes. The present paper also discusses the effect of free stream velocity and particle size on particle collision frequency and erosion damage.

Erosion of tubes by coal particles or coal ash impingement has caused serious problems to many pulverized coal energy conversion systems (such as the circulating fluidized bed combustion system). It is important to study erosion protection methods for tubes undergoing erosion. In this paper we present the results of numerical and experimental investigation of a new type of erosion-protection method: the finned tube erosion protection method. An experimental investigation of finned tube erosion processes was made by placing erosionprone wax cylinders with fins in a bench-scale cold flow circulating fluidized bed to simulate the long-term erosion effect. A numerical study was conducted for the flow of a dilute particle-laden gas moving past a finned tube undergoing erosion. An orthogonal curvilinear coordinate system was used to calculate turbulent flow around the finned tube. The calculation of particle trajectories took into account the effect of the turbulence with a stochastic particle dispersion model. The results from this study show that the finned tube is a simple and efficient erosion protection method in most industrial two-phase systems where erosion occurs. The fin relative height, the fin number and the ang]e between two adjacent fins are three important parameters which affect finned tube erosion protection abilities.

Erosion of tubes by coal particles or coal ash impingement has caused serious problems for many pulverized coal energy conversion systems. This type of erosion has led to many experimental investigations. This paper presents the numerical results of an investigation of coal particle dynamics about a tube. The calculation of particle trajectories takes into account the eftect of turbulence using a stochastic particle dispersion model. The results from this study include the frequency of particle impact and the erosion distribution on the tube surface. Good agreement is found between the numerical method and exoerhnent.