Investigating the thermal-hydraulic enhancement and ash deposition characteristics of leeward-cut spiral finned tube heat exchangers

Abstract

The spiral finned tube (SFT) heat exchanger is a vital component in industrial boilers for energy utilization and recovery. To enhance its efficiency and reduce material usage, a leeward-cut spiral finned tube (LSFT) structure is proposed. In this study, LSFTs with different cutting angles are numerically simulated within the range of Re = 6800–10,850 using a CFD model, which is later validated using a self-developed experimental platform. The discrete phase model (DPM) coupled with the van Beek collision model is utilized to depict the ash deposition characteristics with different particle sizes on LSFTs. The results demonstrate that the LSFT outperforms SFT. The 60° cutting angle LSFT, for example, the Nu improves by 12% and the deposition density decreases 28.3% at Re = 9500 compared to SFT. The light gradient boosting machine (LightGBM) model and multi-objective particle swarm optimization (PSO) algorithm are adopted to optimize the design parameters including longitude and transversal tube pitch (sL, sT), fin high and pitch (Ph, Pf), cutting angle (θ). Compared with the original designed SFT, energy efficiency index JF increase by 15.1%–23.6% at various Re when using the optimized LSFT. Besides, the deposition density of particles in optimized LSFT decreases by 63.6%, while the overall weight lessens by 21%.