Influence of parameters and optimization on flow heat transfer and particle deposition in twisted elliptical tubes

Twisted elliptical tubes (TETs) are promising for heat exchanger applications due to their enhanced heat transfer capability, but the deposition characteristics of particles within their structure remain unclear. This study numerically investigated the effects of flattening ratio (1.2–3.0), pitch (200–800 mm ), and flow velocity (0.5–1.3 m/s ) on flow, heat transfer, and particle deposition patterns using the discrete phase model (DPM) in Fluent and a deposition criterion based on the Johnson-Kendall-Roberts (JKR) theory. The model was verified by experimental data, with a Nu deviation of less than 17% and a friction factor deviation of less than 14%. The results show that a higher flatness can enhance the convective mixing of hot and cold fluids, with the Nu increased by 15% - 40%, but it also increases the flow resistance; a smaller pitch can enhance secondary flow, reducing the deposition amount by up to 30%. The deposition rate showed a non-monotonic dependence on flattening ratio, with FR =2.0 yielding the lowest fouling tendency. A multi-objective optimization using an improved particle swarm algorithm identified the optimal parameters ( FR =2.25, P =250 mm , v =1.28 m/s ), achieving balanced performance with Nu =185.3, f =0.064, and Dep =0.294. These findings provide quantitative guidance for designing efficient, anti-fouling heat exchangers in particle-laden fluid systems.