Abstract
This paper presents the numerical study of thermal performance factor of Al2O3-Cu/water hybrid nanofluid in circular and non-circular ducts (square and rectangular). Turbulent regime is studied with the Reynolds number ranges from 10000 to 100000. The heat transfer performance and flow behaviour of hybrid nanofluid are investigated, considering the nanofluid volume concentration between 0.1 and 2%. The thermal performance factor of hybrid nanofluid is evaluated in terms of performance evaluation criteria (PEC). This present numerical results are successfully validated with the data from the literature. The results indicate that the heat transfer coefficient and Nusselt number of Al2O3-Cu/water hybrid nanofluid are higher than those of Al2O3/water nanofluid and pure water. However, this heat transfer enhancement is achieved at the expense of an increased pressure drop. The heat transfer coefficient of 2% hybrid nanofluid is approximately 58.6% larger than the value of pure water at the Reynolds number of 10000. For the same concentration and Reynolds number, the pressure drop of hybrid nanofluid is 4.79 times higher than the pressure drop of water. The heat transfer performance is the best in the circular pipe compared to the non-circular ducts, but its pressure drop increment is also the largest. The hybrid nanofluid helps to improve the problem of low heat transfer characteristic in the non-circular ducts. In overall, the hybrid nanofluid flow in circular and non-circular ducts are reported to possess better thermal performance factor than that of water. The maximum attainable PEC is obtained by 2% hybrid nanofluid in the square duct at the Reynolds Number of 60000. This study can help to determine which geometry is efficient for the heat transfer application of hybrid nanofluid.
Highlights
The development of industrial activities in the past few decades has created a substantial demand of energy sources
Extensive efforts are made for heat transfer enhancement purposes, but the performance is limited by the poor thermal conductivity of conventional heat transfer fluids, such as water, oil and ethylene glycol [1]
Al2O3-Cu/water hybrid nanofluid obtained by Suresh et al [28], which was applicable for the concentration range from 0-2%
Summary
The development of industrial activities in the past few decades has created a substantial demand of energy sources. It was revealed that the heat transfer enhancement of A l2O3-CNT hybrid nanofluid was the greatest, followed by A l2O3-Cu/water and A l2O3/water nanofluids They remarked an average increment of Nusselt number from 13.66 to 26.62% when the nanoparticle loading of Al2O3-CNT/water nanofluid was increased from 0.1 to 0.3 vol.%. In terms of flow behaviour, the mono nanofluid and hybrid nanofluid could increase the friction factor and pressure drop of the host fluid. Huminic and Huminic [22] conducted numerical study on the laminar heat transfer and flow behaviour of graphene oxide (GO)–cobalt oxide (Co3O4)/water hybrid nanofluid in ducts with different cross-section (circular, flat and elliptical ducts). According to the review above, there is limited information on the comparison of the thermal performance factor of hybrid nanofluid in plain ducts with different crosssection (circular, square and rectangular ducts) It is the aim of this study to address this research gap.
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