Three-dimensional multiphase CFD modeling of thermal–hydraulic characteristics of nanofluid flow in helical microchannels

Forced convection heat transfer of two different types of water-based nanofluids (Al₂O₃, TiO₂) was investigated numerically. In this numerical investigation, mixture two-phase model was considered and the governing equations were discretized based on the finite element method. The developed model agrees well with the experimental data for the two straight and helical microchannel tubes. The presented model covers the helical microchannel with different axial pitches and curvature ratios. The obtained results showed that geometrical parameters (curvature ratio and axial pitch) with a combination of nanofluid types and concentration have impressive effects on thermal performance and pressure drop. The results revealed that the Nu number was about 14% higher compared to pure water for the helical-containing Al₂O₃ nanofluids. Moreover, addition of both nanoparticles had negligible effect on friction factor in helical microchannel. The optimum operating conditions which are most economical from an industrial point of view were evaluated using the effectiveness parameter (η). Graphical abstract:

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