Etude numérique de la convection mixte lors de l'écoulement d'un nanofluide hybride (Ag-MgO/Eau) dans une cavité trapézoïdale ventilée soumise à l'action d'un champ magnétique

The goal of this numerical study, is to investigate the hydromagnetic mixed convection heat transfer flow inside a ventilated cavity, crossed by hybrid nanofluid. This latter is made of Ag and MgO nanoparticles (50:50 vol %) dispersed in water as base fluid. The enclosure is under the influence of a uniform and constant magnetic field, applied in a horizontal direction. In this work, the cavity is of right angled trapezoid shape, and is assumed to be of infinite length in the third direction imparting a two-dimensional character to the flow. The cavity is subjected to a laminar and steady jet of fresh hybrid nanofluid entering the enclosure through an opening placed on the lower corner of the bottom wall which is adiabatic, just like the vertical right wall. The fluid is evacuated through an opening representing the upper base of the cavity. The left wall is inclined, and is maintained at a constant and uniform hot temperature. It is assumed that the nanofluid is Newtonian, incompressible and substantially behaves as a single phase fluid. Moreover, the Boussinesq approximation is valid for buoyancy force. New correlations to predict the viscosity and thermal conductivity of Ag-MgO / water hybrid nanofluid are employed in the study. The dimensionless governing equations with the appropriate boundary conditions, are discretized by the finite volume method and solved numerically via the SIMPLER algorithm. All the simulations were performed for the case of pure mixed convection (Ri = 1), and are presented on the one hand, through hydrodynamic and thermal fields in the cavity as well as the velocity profiles. On the other hand, a special focus is granted to the heat transfer rate, through the evaluation of the average Nusselt number at the hot inclined wall. The study focuses on the determination of the conditions that provide the best thermal performance of the cavity. We investigate the effect of some parameters including the influence of the hybrid nanofluid jet intensity (Reynolds number), the magnetic field strength (Hartmann number) and nanoparticles volume fraction. The results indicate that the hybrid nanofluid flow is strongly affected by the increase in the intensity of the magnetic field. Globally, the augmentation of Reynolds and Hartmann numbers enhance the heat transfer rate. We also note that, the increase in nanoparticles concentrations promotes the heat transfer. However, the contribution of nanoparticles on the improvement of heat transfer has a significant impact at low values of the Reynolds number

Entropy generation due to the mixed convection flow of MWCNT−MgO/water hybrid nanofluid in a vented complex shape cavity

This paper reports a numerical study of mixed convection heat transfer with entropy generation in a vented complex shape cavity filled with MWCNT−MgO (15:85 vol %) /water hybrid nanofluid. A hot source is placed at the mid potion of the inclined plate of the enclosure, while the rest of the rigid walls are adiabatic. A thermo-dependent correlations proposed by [12] for the dynamic viscosity and the thermal conductivity, especially developed for the considered fluid, are used. After validation of the model, the analysis has been done for a Reynolds numbers ranging from 10 to 600 and total nanoparticles volume fraction ranging from 0.0 to 0.02 using the finite volume method. The predicted results of streamlines, isotherms, isentropic lines, average Nusselt number, average entropy generation and average Bejan number are the main focus of interest in the present paper

Entropy generation due to the mixed convection flow of MWCNT−MgO/water hybrid nanofluid in a vented complex shape cavity

This paper reports a numerical study of mixed convection heat transfer with entropy generation in a vented complex shape cavity filled with MWCNT−MgO (15:85 vol %) /water hybrid nanofluid. A hot source is placed at the mid potion of the inclined plate of the enclosure, while the rest of the rigid walls are adiabatic. A thermo-dependent correlations proposed by [12] for the dynamic viscosity and the thermal conductivity, especially developed for the considered fluid, are used. After validation of the model, the analysis has been done for a Reynolds numbers ranging from 10 to 600 and total nanoparticles volume fraction ranging from 0.0 to 0.02 using the finite volume method. The predicted results of streamlines, isotherms, isentropic lines, average Nusselt number, average entropy generation and average Bejan number are the main focus of interest in the present paper

Double-diffusive mixed convection of pseudoplastic fluids in an inclined square cavity partially heated

Mixed convection heat and mass transfer in an inclined square cavity partially heated is numerically studied in the present paper. The cavity is filled with a non-Newtonian pseudoplastic fluid. The governing equations are solved numerically using the finite volume method. The velocitypressure coupling is achieved using the SIMPLER algorithm. This study focuses on the effect of some parameters, namely, the Richardson number and the power law index, on the flow pattern as well as on heat and mass transfer rates. The results indicate that the increase of the Richardson number decreases both heat and mass transfer rates. However, the latter are improved with the increase of the power law index whatever the value of the Richardson number

Development and Validation of an Open-Source Finite-Volume Method Solver for Viscoplastic Flows

In the present paper, we discuss implementation details of a free and open-source numerical solver based on the finite volume method for numerical simulation of viscoplastic non-Newtonian fluids. In addition to the fact that they are involved in many industrial applications, both their physical properties and their rheological behavior make them challenging for numerical simulation. Viscoplastic fluids are known to behave as solid unless the shear stress reaches a critical level, known as yield-stress, beyond which they behave as liquid. In most cases, both yielded and unyielded regions coexist in the fluid domain. In mathematical model of viscoplastic fluid, the constitutive equation is a non-differentiable function. This is often overcome by using the approximate constitutive equation that has a regularized form, e.g. the Papanastasiou regularization model. Using the same approach, we assess the influence of regularization parameters on simulation convergence and results accuracy. In this study, we give implementation details of viscoplastic fluid models in freeCappuccino open-source Computational Fluid Dynamics code. Moreover, we perform validation on several well known benchmark cases and compare proposed approach with those existing in published literature. We also perform a parametric analysis and show the effect of Reynolds and Bingham numbers on the extent of the yielded regions. Conclusions of the study have relevance in practical application of computational fluid dynamics to viscoplastic fluids in particular and to non-Newtonian fluids in general. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Proceedings of the International Conference of Experimental and Numerical Investigations and New Technologies, CNNTech 2021 (Zlatibor, Serbia; June 29 - July 2, 2021

Heat transfer analysis of nanofluid flow through backward facing step

This paper presents the numerical predictions of hydrodynamic and thermal characteristics of nanofluid flow through backward facing step. The governing equations are solved through the finite volume method, as described by Patankar, by taking into account the associated boundary conditions. Empirical relations were used to give the effective dynamic viscosity and the thermal conductivity of the nanofluid. Effects of different key parameters such as Reynolds number, nanoparticle solid volume fraction and nanoparticle solid diameter on the heat transfer and fluid flow are investigated. The results are discussed in terms of the average Nusselt number and streamlines

Heat transfer analysis of nanofluid flow through backward facing step

This paper presents the numerical predictions of hydrodynamic and thermal characteristics of nanofluid flow through backward facing step. The governing equations are solved through the finite volume method, as described by Patankar, by taking into account the associated boundary conditions. Empirical relations were used to give the effective dynamic viscosity and the thermal conductivity of the nanofluid. Effects of different key parameters such as Reynolds number, nanoparticle solid volume fraction and nanoparticle solid diameter on the heat transfer and fluid flow are investigated. The results are discussed in terms of the average Nusselt number and streamlines

Heat transfer and fluid flow of Biodiesel at a backward-Facing step

You should Three-dimensional simulation of a biodiesel fluid flow within a rectangular duct over a backward-facing step is investigated in the present paper. The fluid, which obeys to the Newtonian rheological behavior, is obtained by transformation of Algerian waste cooking oil into a biodiesel. Flow through a rectangular channel subjected to a constant wall temperature or constant heat flux as boundary conditions. The partial differential equations governing fluid flow and heat transfer are solved by the Fluent CFD computational code based on the Finite Volume Method. The numerical experiments are carried out to examine the effect of the Reynolds number by fluid inlet velocity variation for the two boundary conditions. The results are analyzed through the distribution of the temperature and the velocity contours. The variation of the Reynolds number and boundary conditions affects greatly the heat transfer and the fluid flow, in particular near the step region

Heat transfer and fluid flow of Biodiesel at a backward-Facing step

You should Three-dimensional simulation of a biodiesel fluid flow within a rectangular duct over a backward-facing step is investigated in the present paper. The fluid, which obeys to the Newtonian rheological behavior, is obtained by transformation of Algerian waste cooking oil into a biodiesel. Flow through a rectangular channel subjected to a constant wall temperature or constant heat flux as boundary conditions. The partial differential equations governing fluid flow and heat transfer are solved by the Fluent CFD computational code based on the Finite Volume Method. The numerical experiments are carried out to examine the effect of the Reynolds number by fluid inlet velocity variation for the two boundary conditions. The results are analyzed through the distribution of the temperature and the velocity contours. The variation of the Reynolds number and boundary conditions affects greatly the heat transfer and the fluid flow, in particular near the step region