Numerical evaluation of alternate tube configurations for particle deposition rate reduction in heat exchanger tube bundles

The potential of two passive techniques, namely elliptic-shaped tubes and asymmetric tube bundle arrangement, for deposition rate reduction in lignite-fired utility boiler heat exchangers is numerically studied through comparison with an in-line tube arrangement with circular tubes. The simulation is based on a two-dimensional calculation of the turbulent two-phase flow in heat exchanger tube bundles using a subgrid-scale model for the small-scale turbulent structures and a particle adhesion model for the particle-surface interaction. Large-scale motion is found to be an important mechanism for tube surface fouling. Of the three tube bundle arrangements that were studied, the in-line tube bundle with elliptic-shaped tubes shows the lowest fouling rates and pressure drop. Taking advantage of these, heat transfer rates might be increased by placing more rows in the same area. (C) 2001 Elsevier Science Inc. All rights reserved.