Abstract
In this study, forced convection of nanofluid flow in various channel geometries with a hydraulic diameter of 16 mm and length of 1.5 m under laminar flow condition has been investigated numerically. Constant heat flux of 6 kW/m2 has been applied on to the surfaces of the channels. Fe3O4/water nanofluid has been used in the analyses to enhance the convective heat transfer of the base fluid. Analyses have been performed for Reynolds numbers between 500≤Re≤2000, and for volume concentrations of nanoparticles between 1% and 5% in cylindrical, square, rectangle, and triangle cross-sectioned channel geometries. The finite volume discretization method has been used to solve the governing equations. The effects of some parameters; Reynolds number, nanoparticle volume fractions, channel geometries on the average Nusselt number, Darcy friction factor and entropy generation have been investigated in detail. The results indicate that nanofluid offers further convective heat transfer enhancement according to base fluid and cylindrical cross-sectioned channel gives the best heat transfer performance among other cross-sectioned channel geometries. Using water as a working fluid, cylindrical cross-sectioned channel geometry gives the highest heat transfer rate among other channel geometries, whereas triangle one gives the lowest. Cylindrical cross-sectioned channel geometry offers up to 77.6% enhancement compared to triangle cross-sectioned channel geometry for the same hydraulic diameter and same heat flux. However, triangle cross-sectioned channel geometry has highest convective heat transfer increment ratio (4.12%) for changing working fluid as water to nanofluid. Also, some new Nu correlations based on the channel geometries and nanoparticle volume fractions were proposed in the present study.
Highlights
Higher heat transfer rates are targeted in modern industrial applications nowadays
Cylindrical cross-sectioned channel geometry offers up to 77.6% convective heat transfer enhancement compared to triangle cross-sectioned channel geometry
Square cross-sectioned channel geometry up to 36.4%, and rectangular cross-sectioned channel geometry up to 40.1% enhancement compared to triangle cross-sectioned channel geometry for the same hydraulic diameter and same heat flux
Summary
Higher heat transfer rates are targeted in modern industrial applications nowadays. Enhancement of the heat transfer characteristics of working fluids has become an important research topic. Minea [6] studied the numerically to investigate the nanoparticle concentration effect on forced convection heat transfer in a tube She used the single-phase model on the solution of Al2O3-water nanofluid flow for both laminar and turbulent regime. Ting et al [8] investigated the convection heat transfer and flow characteristics of water-based Al2O3 nanofluids with different volumetric nanoparticle concentrations (0.1–2.0 vol.%) under the constant wall temperature boundary condition. Davarnejad et al [17] numerically investigated the heat transfer characteristics of Al2O3/water nanofluid in a circular tube under constant heat flux and showed that the convective heat transfer coefficient increases by increasing velocity and decreasing particle diameter. Kaya et al [21], have studied TiO2/water nanofluid with different volumetric nanoparticle concentrations (ranging from 1.0 vol.%-4.0 vol.%) in a semi-circular cross-sectioned microchannel under steady-state laminar flow condition. An enhancement in the average Nusselt number can reach up to 10% along with increasing the volumetric nanoparticle concentration of TiO2/water nanofluid
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