In this paper, the problem of steady forced convection heat transfer and fluid flow characteristics of a hybrid nanofluid flowing through an isothermally heated horizontal tube considering various nanoparticle shapes has been investigated numerically. The three dimensionless cylindrical coordinate equations are discretized using the finite volume method and solved via a FORTRAN program. A numerical parametric investigation is carried out for a tube filled with regular water, (TiO 2 /water) nanofluid and (Ag-TiO 2 /water) hybrid nanofluid. Four different types of nanoparticle shapes are considered in this study, spherical, cylindrical, platelets and blades, with different volume fractions ranging from 0 to 8% using water as a base liquid. The influence of nanoparticle shape, nanoparticle concentration and Reynolds number on the local Nusselt number and the friction factor is essentially examined. The results showed that the friction factor of both nanofluid and hybrid nanofluid flow was increased as the nanoparticle volume fraction increased for all kinds of nanoparticle shapes, whereas it decreased as the Reynolds number increased. Nusselt number increased with increase in the nanoparticle concentration and Reynolds number. The highest heat transfer rate was acquired for the maximum nanoparticle volume concentration by using blade nanoparticle shape followed by platelet shape, cylindrical shape and lastly the sphere shape. It was found that the maximum values of the friction factor were registered for platelet-shape nanoparticles.
The heat transport and friction factor in a three‐dimensional horizontal concentric annular duct filled with nanofluids comprising clove‐treated multiwalled carbon nanotubes are investigated numerically in this paper. The cylinder's outer surface is thermally insulated, while uniform heat flux is imposed on the cylinder's inner surface. The problem is formulated in dimensionless cylindrical coordinates. The numerical solutions were obtained based on the finite volume technique with second‐order precision, and cover a range of the Reynolds number 1000 ≤ Re ≤ 2000 and nanoparticle weight fractions 0.075, 0.125, and 0.175 wt%. To describe the results for both heat exchange and fluid flow performance, the temperature profile, Nusselt number, heat transfer coefficient, and friction factor are represented. The findings state that heat transport increases as Reynolds is increased and nanoparticles are introduced. The friction factor was also observed to improve as the concentration of nanoparticles increased. In addition, two new Nusselt number and friction factor correlations were established.
This present study is intended for a CFD analysis of hydrodynamic and thermal characteristics of water-based fluid containing TiO2 or CuO nanoparticles flowing in laminar regime in a 3D uniformly heated horizontal annulus utilizing several. Four distinct models have been developed using various combinations (A, B, C and D) of the available theorical-based and experimental-based thermal conductivity and viscosity correlations. A CFD-Fortran code based on the finite volume technique was elaborated for the numerical solution of the mathematical model of the problem. The implications of Grashof number, volume fraction, and type of nanoparticle on isovelocity, isotherms, mean and wall temperatures, Nusselt number, heat transfer coefficient, pressure drop, and thermal performance evaluation criteria are explored using these different models. The results demonstrate that the Nusselt number and heat transfer coefficient of all developed models improve with the addition of nanoparticles. For 2% of nanoparticles’ concentration, the largest enhancement was reached for model D by about 23.5% with respect to the based liquid, while the smallest enhancement was obtained for model B by about 1.16%. The highest Performance Evaluation Criteria (PEC) are attained by employing model D by about 1.263, followed by model C by about 1.074.
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