Critical Review of Dimple Profiles in Tubular Heat Exchangers: Focus on Thermal and Economic Aspects

Passive heat transfer enhancement techniques are gaining attention for their energy efficiency and environmental sustainability, as they eliminate the need for external power. Dimpled surfaces are often preferred as they offer heat transfer augmentation with relatively inferior pressure drop. This critical review examines the influence of various dimple configurations on the thermal-hydraulic performance of tubular heat exchangers. The methodology involves a comparative analysis by focusing on flow dynamics, energy efficiency, and economic analysis. Key findings reveal that dimple-induced mechanisms, such as flow separation, recirculation, vortex formation, and reattachment, significantly enhance convective heat transfer. Elliptical and teardrop dimples generate longitudinal vortices, whereas the inclined dimples promote multidirectional flow. Despite these benefits, dimpled tubes incur higher initial costs and pressure losses, emphasizing the importance of conducting an economic evaluation. This review highlights the limitations of existing literature, a research gap in correlating dimple geometry with a dual focus on thermal and economic aspects.