Papers by Keyword: Thermophoresis

Abstract: This article examines laminar mixed convection of a nanofluid within a square cavity that contains a vertical rectangular obstacle serving as a vortex promoter. Employing Buongiorno's theory, the dimensionless governing equations are numerically solved using the finite element method to analyze the distributions of velocity, temperature, nanoparticle concentration, and entropy generation. Attention is paid to the entropy generation. Results are presented and discussed, showing that increasing the Reynolds number generates a large vortex near the obstacle, which diminishes reverse flow, enhances heat conduction, and increases entropy generation. Moreover, thermophoresis drives tiny nanoparticles from hot to cold regions, affecting heat transfer. Indeed, nanoparticle concentration decreases with higher thermophoresis (N_T) and Brownian motion (N_B) constraints, as these parameters are inversely related to the concentration profile.

Abstract: This paper deals with natural thermal convection combined with the mass transfer of nanoparticles occurring in the boundary layers of a nanofluid subjected to magnetohydrodynamics. The wall consists of an inclined plate is considered according to a temperature as well as the volume fraction of the nanoparticles varying as the power of the axial coordinate. In addition, internal heat generation/absorption is taken into account in the mathematical formulation. The governing partial differential equations based on Buongiorno's approach are transformed into a set of ordinary differential equations. The two-level method of no-similarity equations is used to achieve higher accuracy. The whole calculation procedure is implemented using a limit value problem program written according to the Matlab computer language that applies the Lobbato IIIa finite difference method. The obtained results have revealed that small variations of the boundary conditions with the axial coordinate become very significant on the local Nusselt number and the local Sherwood number for nanoparticles. Moreover, a better heat transfer has been obtained with a larger S. However, a trade-off between desired heat transfer rate and level of reduced skin friction should be scheduled.

Abstract: This paper examined the thermophoresis effect and suction/injection process on steady MHD in a semi-infinite inclined porous plate. Chemical reaction, heat generation and thermal radiation are taking into account. The governing partial differential equations are transformed via similarity technique into a system of nonlinear ordinary differential similarity equations, which are solved numerically by applying the Lobbato IIIa-finite-difference method. Favorable comparisons with previously published work are performed. Numerical pertinent results for the velocity, temperature and concentration profiles as well as for the skin-friction coefficient, wall heat transfer and mass transfer rates are obtained and reported graphically for various parametric conditions to show interesting aspects of the solution. The main results are the dominant influence of suction/injection process to control the principal boundary layers and the role played by the combined chemical reaction, heat generation and thermal radiation on the changes in the quantities of interest.

Abstract: The onset of convection in a horizontal nanofluid layer of finite depth is a subject that can never be over-emphasized as it plays a significant role in controlling the transport phenomenon within a nanofluidic medium. This body of knowledge led to a doubtful report in 2014 by Nield and Kuznetsov concerning some obtained equations and established results. However, the accuracy of the thermal stability characteristics is strongly dependent on the used model as well as the employed methodological procedure. In this report, countable models are suggested as a better improvement of the aforementioned analysis. Either mathematical or technical point of view, it is worth concluding that the approximate analytical results elaborated by Nield and Kuznetsov can be improved properly by using the models presented herein.

Abstract: An analysis of nonlinear mixed convection transport of hydromagnetic Casson nanofluid over a nonlinear stretching sheet near a stagnation point is deliberated in this study. The flow is confined in a porous device in the presence of thermophoresis, Ohmic heating, non-uniform heat source with temperature-dependent thermal conductivity associated with haphazard motion of tiny particles. The transport equations are translated from nonlinear partial differential equations into ordinary ones via similarity transformation technique and subsequently tackled with shooting method coupled with Runge-Kutta Fehlberg algorithm. The significant contributions of the embedded parameters on the dimensionless quantities are graphically depicted and deliberated while the numerical results strongly agree with related published studies in the limiting conditions. It is found that a rise in the magnitude of Casson fluid parameter decelerates the fluid flow while enhancing the viscous drag and thermal profiles. The inclusion of the nonlinear convection term aids fluid flow whereas heat transfer reduces with growth in the thermophoresis and Brownian motion terms.

Abstract: In this paper, boundary layer flow of non-Newtonian Casson fluids past a semi-infinite porous plate in the presence of thermal radiation, viscous dissipation and heat generation is explored. Fluids of this type act as solid elastic and they are very important in food technology, biological science, etc. The flow took place over a semi-infinite vertical porous plate. The presence of viscous dissipation in the flow equations plays a significant role on flows having high viscosity such as polymers and oils. Thermal radiation and heat generation plays a decisive role in the design of many advanced energy conversion system which operates at higher temperature. Hence, the present study is useful in food processing industries and thermal engineering processes. The flows governing equations are numerically solved with spectral relaxation method (SRM). SRM is an iterative procedure that employs the Gauss-siedel type of relaxation approach to linearize and decoupled the system of coupled differential equations. The influence of controlling parameters on velocity, temperature and concentration profiles are plotted in graphs. Furthermore, numerical computations of the local skin friction, local Nusselt number and local sherwood number are presented in tabular form. Results revealed that the presence of the thermophoresis in the concentration equation has great influence on the velocity and concentration profiles because increasing the thermophoresis parameter intensifies the velocity and concentration profiles.

Abstract: Three-dimensional mixed convection flow, heat and mass transfer of Eyring-powell fluid over a convectively heated stretched sheet is inspected in this paper. The encouragement of Brownian motion, Thermophoresis and thermal radiations are accounted. Appropriate transformations are used to reduce the principal PDE’s into set of coupled highly non-linear ODE’s which are then solved numerically using RKF fourth-fifth order method. The consequence of several parameters on flow, heat and mass transfer characteristics are deliberated with the help of graphs and tables. It is observed that, the temperature and concentration profiles diminish for higher values mixed convection parameter.

Abstract: A study on the thermophoresis and Brownian moment effects on magnetohydrodynamic flow of dissipative Casson fluid over a stretching sheet is considered. The governing equations of the flow, heat and mass transfer is transformed to ordinary differential equations by using similarity transformation. Numerical solutions of these equations are obtained by using shooting technique. The influence of pertinent parameters on the velocity, temperature and concentration profiles along with friction factor, local Nusselt and Sherwood numbers are discussed and presented through graphs and tables. It is found that the heat and mass transfer rate is high in steady flow when compared to unsteady flow.

Abstract: This study covers a numerical investigation of gyrotactic microorganisms contained MHD flow over a vertical plate bearing thermal radiation, thermophoresis, Brownian motion, chemical reaction and inclined magnetic field effects. With the assistance of similarity transforms, the derived governed equations are transformed as set of ODEs and solved numerically by R-K and Newton’s methods. Graphs are exhibited and explained for various parameters of interest. For engineering interest, we mainly talked about the Skin friction coefficient, reduced Sherwood, Nusselt numbers and density of motile microorganisms. We noticed a rise in the heat transfer rate of motile microorganisms for rising values of the thermophoresis and Brownian motion parameters. Increasing values of the aligned angle hikes the drag force.

Abstract: Mathematical modeling to study the effect of nonlinear thermal radiation on Casson nanofluid flow between parallel plates is established. Second order velocity slip condition is implemented at the boundary of the lower plate. An appropriate transformation is applied to alter the PDEs into ODEs and then tackled numerically by employing RKF-45. The consequence of several prevailed parameters on the Casson nanoliquid velocity components, temperature and concentration fields are portrayed graphically and deliberated in detail. Velocity component decreases near the region of lower plate while it increases along the upper plate region for magnetic and slip parameter whereas opposite behavior is obtained for the Casson parameter for the same component.