Study on heat transfer, pressure drop and efficiency of ZnO/Oil nanofluid in a novel hexagonal tube

In this study, alternating hexagonal tube as a new form is introduced. The research method is experimental. Experiments were performed on 3 AH tubes in 600 to 1500 Re range. The base fluid was heat transfer oil and ZnO/oil nanofluids with volumetric concentrations of 1% and 2%. Experiments indicate reducing in segments' length lead to increasing heat transfer in AH tubes by a factor of 1.5, 1.8, and 1.9 compared to circular tubes. also Pressure drop increases by 1.07, 1.1 and 1.12 times. The use of nanoparticles and also increasing the concentration of them enhances heat transfer and pressure drop. The least segment's length with 2% particle concentration results in 1.25 and 2.21 times increase in pressure drop and heat transfer compared to the circular tube respectively. Performance Enhanced Ratio is used to investigate pressure drop and heat transfer simultaneously. Our results indicate that the efficiency of the alternating hexagonal tube is higher than the circular tube and enhaces with the increase in number of segments and nanoparticles concentration. The efficiency ratio of alternating hexagonal tubes to circular tube is 1.17, 1.3 and 1.5, respectively. The highest efficiency ratio of nanofluid is 1.77 times the base fluid in a circular tube. The result of this study is that the use of alternating hexagonal tube and nanoparticles improves performance.