Entropy Generation Incorporating γ-Nanofluids under the Influence of Nonlinear Radiation with Mixed Convection

Nanofluids offer the potential to improve heat transport performance. In light of this, the current exploration gives a numerical simulation of mixed convection flow (MCF) using an effective Prandtl model and comprising water- and ethylene-based γγ−Al2O3 particles over a stretched vertical sheet. The impacts of entropy along with non-linear radiation and viscous dissipation are analyzed. Experimentally based expressions of thermal conductivity as well as viscosity are utilized for γγ−Al2O3 nanoparticles. The governing boundary-layer equations are stimulated numerically utilizing bvp4c (boundary-value problem of fourth order). The outcomes involving flow parameter found for the temperature, velocity, heat transfer and drag force are conferred via graphs. It is determined from the obtained results that the temperature and velocity increase the function of the nanoparticle volume fraction for H2O\C2H6O2 based γγ−Al2O3 nanofluids. In addition, it is noted that the larger unsteady parameter results in a significant advancement in the heat transport and friction factor. Heat transfer performance in the fluid flow is also augmented with an upsurge in radiation.

Download Full-text

Effect of Nanofluid on Heat Transfer Enhancement for Mixed Convection Flow Over a Corrugated Surface

Journal of Non-Equilibrium Thermodynamics ◽

10.1515/jnet-2020-0008 ◽

2020 ◽

Vol 45 (4) ◽

pp. 373-383

Author(s):

Nepal Chandra Roy ◽

Sadia Siddiqa

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Nusselt Number ◽

Mixed Convection ◽

Local Nusselt Number ◽

Richardson Number ◽

Thermal Boundary Layer ◽

Volume Fraction ◽

Convection Flow ◽

Mixed Convection Flow

AbstractA mathematical model for mixed convection flow of a nanofluid along a vertical wavy surface has been studied. Numerical results reveal the effects of the volume fraction of nanoparticles, the axial distribution, the Richardson number, and the amplitude/wavelength ratio on the heat transfer of Al2O3-water nanofluid. By increasing the volume fraction of nanoparticles, the local Nusselt number and the thermal boundary layer increases significantly. In case of \mathrm{Ri}=1.0, the inclusion of 2 % and 5 % nanoparticles in the pure fluid augments the local Nusselt number, measured at the axial position 6.0, by 6.6 % and 16.3 % for a flat plate and by 5.9 % and 14.5 %, and 5.4 % and 13.3 % for the wavy surfaces with an amplitude/wavelength ratio of 0.1 and 0.2, respectively. However, when the Richardson number is increased, the local Nusselt number is found to increase but the thermal boundary layer decreases. For small values of the amplitude/wavelength ratio, the two harmonics pattern of the energy field cannot be detected by the local Nusselt number curve, however the isotherms clearly demonstrate this characteristic. The pressure leads to the first harmonic, and the buoyancy, diffusion, and inertia forces produce the second harmonic.

Download Full-text

Transient mixed convection flow of nanofluids in a vertical tube

International Journal of Numerical Methods for Heat &amp Fluid Flow ◽

10.1108/hff-01-2012-0017 ◽

2014 ◽

Vol 24 (2) ◽

pp. 376-389 ◽

Cited By ~ 2

Author(s):

Catalin Viorel Popa ◽

Cong Tam Nguyen ◽

Stéphane Fohanno ◽

Guillaume Polidori

Keyword(s):

Heat Transfer ◽

Mixed Convection ◽

Convective Heat Transfer ◽

Convective Heat ◽

Volume Fraction ◽

Convective Heat Transfer Coefficient ◽

Vertical Tube ◽

Navier Stokes ◽

Convection Flow ◽

Content Type

Purpose – In the present work, a theoretical model based on the full Navier-Stokes and energy equations for transient mixed convection in a vertical tube is extended to nanofluids with nanoparticle volume fraction up to 5 percent to ensure a Newtonian fluid behaviour. The paper aims to discuss these issues. Design/methodology/approach – The nanofluids considered, alumina/water and CuO/water, flow inside a vertical tube of circular cross-section, which is subjected to convective heat exchange at the outer surface. The transient regime is caused by a sudden change of nanofluid temperature at the tube inlet. The range of the Richardson number (1.6=Ri=2.5) investigated in this study corresponds to classic cases of mixed convection flow. Findings – Results have shown a significant reduction in the size of the recirculation zone near the wall when the particle volume fraction increases. This may be attributed to the viscosity increase with the volume fraction. Moreover, the flow structure clearly changes when the convective heat transfer coefficient is modified. A decrease of the wall temperature along the tube was found when increasing the convective heat transfer coefficient imposed at the tube external surface. Research limitations/implications – The problem formulation in 2D axisymmetric geometry includes the continuity, the Navier-Stokes and energy equations and is based on the stream function and vorticity; the numerical solution of equations is carried out using a finite difference method. Practical implications – From an economic point of view, this research paper is innovative in the sense that it considers nanofluids as a new and more efficient way to transfer heat. This paper could find applications for heat exchange purposes of compact systems with high thermal loads. Originality/value – Across the world, a still growing number of research teams are investigating nanofluids and their properties. Investigations concern several aspects such as the preparation of the nanofluids, as well as the applications of these nanofluids for convective heat transfer purposes. The dynamical study will consist in the instantaneous and spatial characterization of the dynamic flow field for different nanoparticle volume fractions.

Download Full-text

G-jitter fully developed heat transfer by mixed convection flow of nanofluid in a vertical channel

Malaysian Journal of Fundamental and Applied Sciences ◽

10.11113/mjfas.v13n3.647 ◽

2017 ◽

Vol 13 (3) ◽

Author(s):

Wan Nor Zaleha Amin ◽

Noraihan Afiqah Rawi ◽

Mohd Ariff Admon ◽

Sharidan Shafie

Keyword(s):

Heat Transfer ◽

Mixed Convection ◽

Base Fluid ◽

Volume Fraction ◽

Vertical Channel ◽

Convection Flow ◽

Physical Parameters ◽

Mixed Convection Flow ◽

Temperature Ratio ◽

Water Base

In this study, the effect of g-jitter fully developed heat transfer by mixed convection flow of nanofluid in a vertical channel is investigated. The nanoparticles of aluminum oxide and copper with water as a base fluid are used in this study. The equations corresponding to this study are solved analytically to find the exact solutions. The results of velocity and temperature profiles with the influence of physical parameters such as mixed convection, oscillation, temperature ratio and volume fraction of the nanoparticles are plotted and analyze in details. The behavior of steady state flow is also investigated. Results shown that as mixed convection, oscillation, and temperature ratio increased, the velocity profiles increased. The conductivity and viscosity of the nanofluid are also increased due to the increase of the volume fraction of nanoparticles in the water base fluid.

Download Full-text

Separation time analysis of transient magnetohydrodynamic mixed convection flow of nanofluid at lower stagnation point past a sphere

Malaysian Journal of Fundamental and Applied Sciences ◽

10.11113/mjfas.v13n3.637 ◽

2017 ◽

Vol 13 (3) ◽

Cited By ~ 1

Author(s):

Mohamad Alif Ismail ◽

Nurul Farahain Mohammad ◽

Sharidan Shafie

Keyword(s):

Boundary Layer ◽

Differential Equations ◽

Mixed Convection ◽

Stagnation Point ◽

Magnetic Particles ◽

Volume Fraction ◽

Convection Flow ◽

Mixed Convection Flow ◽

Boundary Layer Equations ◽

Keller Box Method

In this paper, the unsteady magnetohydrodynamics (MHD) mixed convection flow of nanofluid at lower stagnation point past a sphere is studied. Nanoparticles Cu and TiO2 with water as a base fluid are considered. The separation times of the flow as the boundary layer start to separate at the surface of the sphere are given attention. The governing boundary layer equations in the form of partial differential equations are transformed into nonlinear coupled ordinary differential equations and solved numerically using an implicit finite-difference scheme known as Keller-box method. Results of the separation times of boundary layer flow for viscous and nanofluid influenced by magnetic parameter and volume fraction are shown in tabular form and analysed. This study concluded that the separation times can be delayed by added more magnetic particles and small amount the volume fraction.

Download Full-text

Unsteady MHD Mixed Convection Flow of Non-Newtonian Casson Hybrid Nanofluid in the Stagnation Zone of Sphere Spinning Impulsively

Fluids ◽

10.3390/fluids6060197 ◽

2021 ◽

Vol 6 (6) ◽

pp. 197

Author(s):

Essam R. El-Zahar ◽

Abd El Nasser Mahdy ◽

Ahmed M. Rashad ◽

Wafaa Saad ◽

Laila F. Seddek

Keyword(s):

Heat Transfer ◽

Mixed Convection ◽

Volume Fraction ◽

Convection Flow ◽

Published Data ◽

Hybrid Nanofluid ◽

Shear Stresses ◽

Stagnation Zone ◽

Mixed Convection Flow ◽

Surface Shear

In the present analysis, an unsteady MHD mixed convection flow is scrutinized for a non-Newtonian Casson hybrid nanofluid in the stagnation zone of a rotating sphere, resulting from the impulsive motion of the angular velocity of the sphere and the velocity of the free stream. A set of linearized equations is derived from the governing ones, and these differential equations are solved numerically using the hybrid linearization–differential quadrature method. The surface shear stresses in the x- and y-directions and the surface heat transfer rate are improved due to the Casson βo, mixed convection α, rotation γ and magnetic field M parameters. In addition, as nanoparticles, the solid volume fraction (parameter ϕ) increases, and the surface shear stresses and the rate of heat transfer are raised. A comparison between earlier published data and the present numerical computations is presented for the limiting cases, which are noted to be in very good agreement.

Download Full-text