Research PaperAnalysis on performance of nanofluid-cooled vortex-generator channels with variable longitudinal spacing among delta-winglets

•This is an experimental on Al2O3/water nanofluid flow in VG channels.•Effects of variable longitudinal spacing among delta-winglets are investigated.•The maximum overall hydrothermal performance factor is around 41%.•Using nanofluid can improve the overall hydrothermal performance factor by 54%.

The current article presents details of an experimental study to investigate the effect of variable longitudinal spacing among delta-winglets in vortex-generator (VG) channels. Four different classes of the VG channels are fabricated and tested in a wide range of the Reynolds number from 4000 to 10,000. Working fluids are selected to be water and Al2O3/water nanofluid (NF) containing low mass fractions (0.1% and 0.3%) of α-Al2O3 nanoparticles with the average size of 30 nm. In order to validate the current experiments, the preliminary results of a smooth channel using water are compared with some well-known correlations, and an acceptable compliance is obtained. The main results disclose a good improvement in the thermal performance of smooth channel by using the proposed arrangements of delta-winglets. It is found that the heat transfer coefficient is enhanced by 10-50% for water as working fluid. In addition, the NF flow improves the thermal performance by 8.5-17.6% with respect to water flow in expense of increasing the pressure drop by 5.4-9.3%. Finally, the maximum value for the overall hydrothermal performance factor of VG channels is around 1.41%. Furthermore, the use of NFs can improve the overall hydrothermal performance factor by 54%.

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