The present research work explores the effects of suction/injection and viscous dissipation on entropy generation in the boundary layer flow of a hybrid nanofluid (Cu–Al2O3–H2O) over a nonlinear radially stretching porous disk. The energy dissipation function is added in the energy equation in order to incorporate the effects of viscous dissipation. The Tiwari and Das model is used in this work. The flow, heat transfer, and entropy generation analysis have been performed using a modified form of the Maxwell Garnett (MG) and Brinkman nanofluid model for effective thermal conductivity and dynamic viscosity, respectively. Suitable transformations are utilized to obtain a set of self-similar ordinary differential equations. Numerical solutions are obtained using shooting and bvp4c Matlab solver. The comparison of solutions shows excellent agreement. To examine the effects of principal flow parameters like suction/injection, the Eckert number, and solid volume fraction, different graphs are plotted and discussed. It is concluded that entropy generation inside the boundary layer of a hybrid nanofluid is high compared to a convectional nanofluid.

No abstract

The flow and heat transfer analysis in the conventional nanofluid A l 2 O 3 − H 2 O and hybrid nanofluid C u − A l 2 O 3 − H 2 O was carried out in the present study. The present work also focused on the comparative analysis of entropy generation in conventional and hybrid nanofluid flow. The flows of both types of nanofluid were assumed to be over a thin needle in the presence of thermal dissipation. The temperature at the surface of the thin needle and the fluid in the free stream region were supposed to be constant. Modified Maxwell Garnet (MMG) and the Brinkman model were utilized for effective thermal conductivity and dynamic viscosity. The numerical solutions of the self-similar equations were obtained by using the Runge-Kutta Fehlberg scheme (RKFS). The Matlab in-built solver bvp4c was also used to solve the nonlinear dimensionless system of differential equations. The present numerical results were compared to the existing limiting outcomes in the literature and were found to be in excellent agreement. The analysis demonstrated that the rate of entropy generation reduced with the decreasing velocity of the thin needle as compared to the free stream velocity. The hybrid nanofluid flow with less velocity was compared to the regular nanofluid under the same circumstances. Furthermore, the enhancement in the temperature profile of the hybrid nanofluid was high as compared to the regular nanofluid. The influences of relevant physical parameters on flow, temperature distribution, and entropy generation are depicted graphically and discussed herein.

The significance of an externally applied magnetic field and an imposed negative temperature gradient on the onset of natural convection in a thin horizontal layer of alumina-water nanofluid for various sizes of spherical alumina nanoparticles (e.g., 30 , 35 , 40 , 45) and volumetric fractions (e.g., 0.01, 0.02, 0.03, 0.04) is explored and analyzed numerically in this paper. The generalized Buongiorno's mathematical model with the simplified Maxwell's equations and the Oberbeck-Boussinesq approximation were adopted to simulate the two-phase transport phenomena, in which the Brownian motion and thermophoresis aspects are taken into account. Moreover, the rheological behavior of alumina-water nanofluid and related flow are assumed to be Newtonian, incompressible and laminar. Based on the linear stability theory, the perturbed partial differential equations (PDEs) of magnetohydrodynamic convective nanofluid flow are firstly simplified formally using the normal mode analysis technique and secondly converted to a generalized eigenvalue problem considering more realistic boundary conditions, in which the thermal Rayleigh number is the associated eigenvalue. Additionally, the resulting eigenvalue problem was solved numerically using powerful collocation methods, like Chebyshev-Gauss-Lobatto Spectral Method (CGLSM) and Generalized Differential Quadrature Method (GDQM). Furthermore, the thermo-magneto-hydrodynamic stability of the nanofluidic system and the critical size of convection cells are highlighted graphically in terms of the critical thermal Rayleigh and wave numbers, for various values of the magnetic Chandrasekhar number, the volumetric fraction and the diameter of alumina nanoparticles.

In this article, the peristaltic flow of blood-based nanofluid is examined numerically by employing the generalized differential quadrature method. The Casson constitutive model is adopted to depict the flow characteristics in a uniform wavy tube. Besides, the non-Newtonian nature and heat transfer feature of the nanofluidic medium are also scrutinized properly in the presence of platelet magnetite nanoparticles Fe 3 O 4 . After deriving the governing conservation equations, the resulting flow model is modeled successfully under the realistic assumptions of long wavelength and low Reynolds number. Also, the experimentally tested correlations related to the thermophysical properties of nanofluids are incorporated in the conservation equations to explore the effect of adding magnetite nanoparticles in the biofluidic medium. Mathematically, the obtained partial differential equations are transformed into the dimensionless form by utilizing feasible transformations. Furthermore, the impacts of sundry physical parameters on the trapping phenomena, pressure gradient, velocity, wall shear stress, and temperature are discussed thoroughly for the present MHD non-Newtonian nanofluid flow model via various displays.