Local convective heat transfer coefficient and friction factor of γ-Al2O3 /water nanofluid in a double tube heat exchanger

چكيده فارسي ندارد.

The local convective heat transfer coefficient measurement and thermal and flow characteristics of γ-Al2O3/water nanofluids, flowing through a double tube heat exchanger were experimentally investigated. The nearly spherical shaped γ-Al2O3 nanoparticles of an average size of 20 nm were dispersed in distilled water in a 0.05–0.15 vol%. Experiments were carried out at different Reynolds numbers ranging from 18,000 to 40,000, approximately, and various nanofluid inlet temperatures ranging from 45 °C to 65 °C. The results indicated that addition of very small amounts of nanoparticles to the base fluid augmented heat transfer moderately. There was no much effect on heat transfer enhancement with increasing the volume fraction of nanoparticles. The measurements also showed that the pressure drop of nanofluid was slightly higher than that of the base fluid and increased with increasing the volume concentration. Finally, in order to find the optimum condition of this nanofluid for practical applications, thermal performance factor was defined to consider increasing Nusselt ratio besides increasing friction ratio simultaneously. The results show that the maximum thermal performance factor of this nanofluid was 1.11, which was calculated for 0.15% nanoparticle volume fraction at Reynolds number 18,237.