Numerical calculation of particle‐laden gas flows past tubes

Abstract

A numerical study has been conducted for the flow of a dilute particleladen gas moving past one or more tubes undergoing erosion. A nonorthogonal body-fitted coordinate system was used to calculate three tube configurations for laminar and turbulent flow regimes. The sssumption of one-way coupling allows the calculation of individual particle velocities from the fluid flow field. The significant effects of turbulent velocity fluctuations are taken into account by means of the stochastic separated flow model. The particle flow field information is then used to predict circumferential distributions of particle flux and erosion. Predictions of trajectories for the case of two in-line tubes show that particles with inertia numbers X > 1 will strike many tubes in a tube bank due to particle rebounding from tube surfaces. By contrast, particles with X -= 1 are entrained in the bulk flow between tubes. In general, the effect of increasing the particle-gas suspension temperature is to couple the particle-fluid motion more closely through viscous drag and, thus, to decrease erosion. Introduction The problem of interestThe erosion of tubes in tube banks by particles suspended in gas flows is a major problem in the power industry. Such erosion is especially important in the reheaters and economizers of coalfired boilers utilizing fluidized bed combustors. A survey of the literature on the subject, available in Schuh (1987), has uncovered a considerable amount of work on single-phase flow and heat transfer for single tubes, but less for the case of tube banks. In addition, much of what is available for tube banks tends to be semiempirical or qualitative in nature and often in the vein of correlations for predicting overall values of pressure drop and heat transfer. The level of corresponding information relating to particle-laden gas flows, especially the effects of fluid motion on particle motion and hence on tube erosion, is virtually nil.The study reported here is part of a research effort aimed at measuring and rendering predictable the flow of dilute concentrations of solid spherical particles suspended in isothermal gas streams moving past one or two in-line tubes, or past a tube in a tube bank. The turbulent flow regime is of special interest for

Prediction of turbulent gas-solids flow in curved ducts using the Eulerian-Lagrangian method

“…Tsuji and Morikawa [7] have also conducted similar experimental studies for gas-solids flow in a horizontal circular pipe. For other configurations, such as pipe bends and tube bundles, the characteristics of the particulate two-phase flow and their erosion potential have been reported by Pourahmadi and Humphrey [8], Mason and Smith [9], Humphrey [10], Schuh et al [11] and Beacher et al [12]. More recently Tu and Fletcher [13] have computed gas-solids flow in a square sectioned 90°bend and compared their predictions with the laser Doppler anemometry (LDV) experimental data of Kliafas and Holt [14].…”

Numerical Simulation and Validation of Dilute Gas-Particle Flow Over a Backward-Facing Step

“…in the ε g equation, where κ gp and ε gp are provided below from the particle turbulence model and f is the correction factor selected from Schuh et al (1989).…”

Numerical Simulation of Particle Dispersion in the Wake of a Circular Cylinder

“…The first part consists of the nature of the solid surface impact and the material erosion. Considerable research has been done on the prediction of erosion of bluff body due to particle impacts (Ilias and Douglas 1989;Schuh et al 1989;Yao et al 2000;Fan et al 2002). The second part consists of the particle trajectories.…”