A Comprehensive Review of Twisted Tube Heat Exchangers: Enhancing Heat Transfer Efficiency with Lobed and Polygonal Designs

Heat exchangers are vital components of industrial thermal systems, requiring high heat transfer efficiency, compact geometry, and cost-effectiveness. Twisted tubes, as a passive heat transfer enhancement technique, offer a practical and economical solution due to their simple manufacturing and robust performance. These tubes induce secondary swirling flows that disrupt thermal and hydrodynamic boundary layers, thereby enhancing convective heat transfer. Notably, twisted tubes with lobed and polyhedral cross-sections generate stronger secondary vortices compared to elliptical or oval counterparts. This review comprehensively analyzes experimental and numerical studies on twisted tubes with lobed and polyhedral geometries, considering both straight and curved configurations. It also explores hybrid approaches that combine twisted tubes in conjunction with additional passive enhancement approaches including tape insert devices and nanofluid mixtures, as well as active enhancement mechanisms like magnetic field-assisted heat transfer. Furthermore, the review summarizes and correlates key geometric parameters with Nusselt numbers and friction factors, providing predictive insight regarding the thermal-hydraulic behavior of these systems. By integrating extensive experimental and computational findings, this review advances the understanding and optimization of high-performance heat exchanger designs.