Numerical simulation and experiment of gas-solid two phase flow and ash deposition on a novel heat transfer surface

Ash deposition on heat transfer surface is a serious problem which is crucial to the operation of the heat recovery steam generator (HRSG). Researches have been done to reduce the deposits and maintain heat transfer performance. In this paper, a novel rhombic heat transfer surface is studied by numerical simulation method. The characteristics of particle deposition and distribution of different diameters and velocities are analyzed based on the Fluent 15.0, extended by user-defined functions (UDFs). Comparison has been done between different tube arrangements of rhombic, aligned and staggered. The actual model is built and operated on a HRSG in a cement plant. Results show that the rhombic heat transfer surface is favorable for decreasing ash deposits. Particle diameter and gas velocity are the two dominant factors which influence the deposition ratio. Small particles have strong deposition propensity with high velocity and the decrease of velocity promotes the sticking of large particles. The deposits concentrate on the leeward side on the front surface because of eddy impaction, but in other regions, deposits on the windward are dominant. With such rhombic tube arrangement, ash deposition is alleviated greatly so that heat transfer has been enhanced to a large extent. (C) 2016 Published by Elsevier Ltd.