Abstract
• Both thermal-hydraulic and anti-fouling performance of double H-type finned tubes are investigated. • Grooves can create secondary saltation of fly ash particles and reduce the fouling. • LVGs can result in more particles colliding with fin surface and increase the fouling. • An advanced fin structure with three pairs of grooves and one pair of LVGs is recommended. Heat exchangers for residual heat recovery in coal-fired power plants face the issues of low heat transfer efficiency of flue gas side and the fly ash fouling. However, heat transfer enhancement structures always increase the fouling on the fin. Efficient methods are required to improve both heat transfer and anti-fouling performance of the heat exchanger. In present study, the thermal-hydraulic and anti-fouling performances of enhanced double H-type finned tubes are numerically investigated using the discrete phase model coupled with particle deposition and removal model. Five types of double H-type finned tubes with different layouts of grooves and longitudinal vortex generators (LVGs) are investigated to improve both thermal-hydraulic and anti-fouling performance of fin. The effects of particle diameter, flue gas velocity and layout of enhanced structures are discussed. It is found that the transverse vortex induced by grooves can lead to the secondary saltation of fly ash particles, which will significantly reduce particle deposition on fins. However, the longitudinal vortex generated by LVGs can result in the fly ash particles with saltation mode or suspension mode colliding with fin surface, which causes more particle deposition on fins. The recommended fin with three pairs of grooves and one pair of LVGs can enhance heat transfer by 12.92–16.63% with 21.75–30.72% flow resistance penalty and reduce the fouling rate by 2.4–23.7% for particle diameter under 20 μm. It can be considered as a promising heat transfer component for heat recovery in coal-fired power plants.
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