Heat Transfer Enhancement in Curved Geometries

Curved flow passages introduce centrifugal forces that drive secondary vortices and disturb thermal boundary layers, leading to significant improvements in convective heat transfer compared with straight channels. These enhancements arise from mechanisms such as Dean vortices, swirl generation and repeated redirection of flow, which improve the alignment of velocity and temperature gradients in accordance with the field synergy principle. A variety of passive strategies have been explored, including non-circular cross-sections, periodic convergent–divergent profiles, helical corrugations, multi-rib embeds and surface turbulators. While heat transfer coefficients can be increased by up to twofold or more, these interventions often incur higher friction factors and pressure drops; thus, performance evaluation criteria (PEC) are employed to balance thermal gains against pumping power penalties. Applications span refrigeration, chemical processing, renewable energy systems and compact electronic cooling, where compactness and energy efficiency are paramount. Current research emphasises optimisation of curvature, pitch and cross-sectional shape, as well as integration with advanced working fluids such as nanofluids, to achieve maximal thermal performance with minimal irreversibility.

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Heat Transfer Enhancement in Curved Geometries publication trend

The graph below shows the total number of articles in heat transfer enhancement in curved geometries across all publications each year (not limited to Nature Index journals).

Technical terms

Dean number: Dimensionless parameter quantifying the ratio of centrifugal to viscous forces in curved channels, indicative of secondary vortex intensity.

Nusselt number: Dimensionless measure of convective heat transfer relative to conductive transfer across a fluid layer.

Friction factor: Dimensionless coefficient representing pressure loss due to shear stress in pipe or channel flow.

Performance evaluation criteria (PEC): Ratio of heat transfer enhancement to increase in friction factor, used to assess overall efficacy of enhancement techniques.

Field synergy principle: Concept that heat transfer is maximised when velocity and temperature gradient vectors are closely aligned, enhancing convective mixing.

References

1. Heat transfer enhancement of tubes in various shapes potentially applied to CO2 heat exchangers in refrigeration systems: Review and assessment. International Journal of Thermofluids (2023).
2. Geometrical and coil revolution effects on the performance enhancement of a helical heat exchanger using nanofluids. Case Studies in Thermal Engineering (2022).
3. Energy, exergy, economy analysis and geometry optimization of spiral coil heat exchangers. Case Studies in Thermal Engineering (2023).