Experimental investigation of heat transfer, pressure drop, and efficiency of TiO2/Oil nanofluid in alternating flattened tubes

In this study, the analysis of experimental results is used to investigate heat transfer and pressure drop characteristics of Titanium Oxide nanoparticles in an Alternating Flattened Tube. The impact of nanoparticles has not been studied before on Alternating Flattened tubes heat transfer characteristics. Experiments were conducted on 3 different AF tubes with heat transfer oil as base fluid with TiO2 nanoparticles volumetric concentrations of 1% and 2% in 400 to1800 Re range. Our experiments show increasing in flattening leads to a heat transfer increase in AF tubes by a factor of 1.58, 2.08, and 2.21 compared to circular pipes. Pressure drop also increases by 1.08, 1.19 and 1.25 times. The addition of TiO2 nanoparticles enhances heat transfer and pressure drop as well. We also found higher nanoparticle concentration provides more improvement. The most flattened tube with 2% particle concentration shows 2.85 and 1.32 times increase in heat transfer and pressure drop compared to the circular tube respectively. An efficiency parameter is used to study heat transfer and pressure drop simultaneously. Our analysis shows that the efficiency of the alternating flattened tube is higher than the circular tube and increases with the increase in flattening and nanoparticles concentration. The efficiency of alternating flattened tubes reads 1.26, 1.62 and 1.76 times that of a circular tube. The efficiency of nanofluid with a volume concentration of 2% in alternating flattened tubes is 1.76, 2.01 and 2.15 times the base fluid in a circular tube. This experiment concludes the presence of nanoparticles improves overall heat exchange performance at the alternating flattened tubes.