Heat transfer improvement and fouling analysis of flue gas driven molten-salt-heat-exchanger with inclined tube and staggered H-type fins

To increase the grid's renewable energy consumption, a thermal energy storage/release system is integrated into conventional coal-fired power units to achieve thermoelectric decoupling and enhance operational flexibility. The key innovation is a flue gas energy storage system with a flue gas driven molten-salt-heat-exchanger (MSHE) as the core component. This study proposes an inclined tube structure with a self-extraction function for the MSHE to improve molten salt operation safety. A three-dimensional model of flue gas flowing across a 10-row H-fin inclined tube is established to analyze flow and heat transfer characteristics, yielding velocity profiles, temperature distributions, fin-tube temperature differences, and heat transfer coefficients. Three tube configurations are compared, revealing that non-uniform longitudinal spacing induces oscillatory heat transfer coefficients across tube rows while maintaining equivalent performance to uniform spacing configurations. Based on the non-uniform longitudinal spacing configuration, an innovative staggered fin arrangement is proposed, achieving an 18 % higher downstream fin-tube temperature difference and improved heat transfer. Additionally, ash particle entrainment analysis shows that the staggered arrangement reduces backflow ash particle concentrations by regulating the flow field at the H-type fin gaps, minimizing ash deposition risks. These findings offer valuable guidance for optimizing and applying the novel flue gas-driven MSHE.