Experimental study on the ash deposition and heat transfer characteristics of a heat pipe air preheater

Abstract

In this paper, a scaled-down air preheater for a heat pipe is prepared and a visualization experiment system for ash deposition is established. The local and global characteristics of ash deposition and the heat transfer performance of the air preheater are investigated, and the effects of parameters including the gas velocity and the ash concentration are discussed. Experimental results show that a loose ash deposition is formed on the fin of the heat pipe with test time. The ash deposition mass has a maximum at Row #2 and a secondary peak at Row #6 due to the enhanced flow disturbance. With increasing gas velocity, the mass of ash deposition on the windward side gradually decreases, but there is a mass peak on the leeward side. The effect of gas velocity on the mass of ash deposition in the heat pipe fins is severe on the windward side. When the gas velocity reaches or exceeds 10 m/s, the ash deposition mass on the fin is mainly concentrated on the leeward side (>80.1%). Furthermore, as the gas velocity increases or the ash concentration decreases, the total ash deposition mass in the preheater decreases, and the overall heat transfer coefficient increases. The descending range of the heat transfer coefficient over the test time decreases from 10.0% to 4.3% as the gas velocity increases from 6 m/s to 12 m/s and increases from 3.2% to 7.8% as the ash concentration increases from 23 g/m3 to 38 g/m3.