scholarly journals Numerical Study of Free Convection inside the Differentially Heated Cavity incorporating Variable Property Al2O3-H2O Nanofluid

2021 ◽  
Author(s):  
Bishwajit Sharma ◽  
◽  
Md. Feroz Alam ◽  
Mayur Krishna Bora ◽  
Rabindra Nath Barman ◽  
...  
Keyword(s):  
Free Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Particle Diameter ◽  
Nano Particle ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Percentage Concentration ◽  
Prandtl Numbers ◽  
Dependent Viscosity

This paper investigates free convection in a partially heated square cavity filled with alumina-water nanofluid. The investigation is carried out at the three-volume fraction of nanoparticles (0, 0.03, 0.05), two Prandtl numbers (2.66, 6), and constant Grashof number (105) with three shapes of insulating obstacles (Square, Circular, and Rectangular). The results show that the nanofluid volume fraction and Prandtl number significantly enhance the heat transfer. The user-defined function (UDF) is developed and computed to investigate the effect of nanoparticle diameter and its temperature-dependent viscosity on convection. The average Nusselt number (Nu) increased with the temperature-dependent viscosity model and by increasing the percentage concentration of the nanoparticles. For all obstacle shapes, the thermal performance improved with increase in the nano-particle diameter.

scholarly journals Effects of Second-Order Slip Flow and Variable Viscosity on Natural Convection Flow of CNTs − Fe 3 O 4 /Water Hybrid Nanofluids due to Stretching Surface

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Ayele Tulu ◽  
Wubshet Ibrahim
Keyword(s):  
Volume Fraction ◽  
Local Heat Transfer ◽  
Velocity Slip ◽  
Local Heat ◽  
Second Order ◽  
Hybrid Nanoparticles ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Hybrid Nanofluids ◽  
Dependent Viscosity

This study deals with natural convection unsteady flow of CNTs − Fe 3 O 4 /water hybrid nanofluids due to stretching surface embedded in a porous medium. Both hybrid nanoparticles of SWCNTs − Fe 3 O 4 and MWCNTs − Fe 3 O 4 are used with water as base fluid. Effects of hybrid nanoparticles volume friction, second-order velocity slip condition, and temperature-dependent viscosity are investigated. The governing problem of flow is solved numerically employing spectral quasilinearization method (SQLM). The results are presented and discussed via embedded parameters using graphs and tables. The results disclose that the thermal conductivity of CNTs − Fe 3 O 4 / H 2 O hybrid nanofluids is higher than that of CNTs − H 2 O nanofluids with higher value of hybrid nanoparticle volume fraction. Also, the results show that momentum boundary layer reduces while the thermal boundary layer gros with higher values of temperature-dependent viscosity and second-order velocity slip parameters. The skin friction coefficient improves, and the local heat transfer rate decreases with higher values of nanoparticle volume fraction, temperature-dependent viscosity, and second-order velocity slip parameters. Furthermore, more skin friction coefficients and lower local heat transfer rate are reported in the CNTs − Fe 3 O 4 / H 2 O hybrid nanofluid than in the CNTs − H 2 O nanofluid. Thus, the obtained results are promising for the application of hybrid nanofluids in the nanotechnology and biomedicine sectors.

scholarly journals Numerical Study for the Effects of Temperature Dependent Viscosity Flow of Non-Newtonian Fluid with Double Stratification

2020 ◽  
Vol 10 (2) ◽  
pp. 708 ◽  
Author(s):  
Hafiz Abdul Wahab ◽  
Hussan Zeb ◽  
Saira Bhatti ◽  
Muhammad Gulistan ◽  
Seifedine Kadry ◽  
...  
Keyword(s):  
Newtonian Fluid ◽  
Numerical Study ◽  
Mathematical Formulation ◽  
Nano Particles ◽  
Physical Parameters ◽  
Concentration Profiles ◽  
Temperature Dependent ◽  
Double Stratification ◽  
Temperature Dependent Viscosity ◽  
Dependent Viscosity

The main aim of the current study is to determine the effects of the temperature dependent viscosity and thermal conductivity on magnetohydrodynamics (MHD) flow of a non-Newtonian fluid over a nonlinear stretching sheet. The viscosity of the fluid depends on stratifications. Moreover, Powell–Eyring fluid is electrically conducted subject to a non-uniform applied magnetic field. Assume a small magnetic reynolds number and boundary layer approximation are applied in the mathematical formulation. Zero nano-particles mass flux condition to the sheet is considered. The governing model is transformed into the system of nonlinear Ordinary Differential Equation (ODE) system by using suitable transformations so-called similarity transformation. In order to calculate the solution of the problem, we use the higher order convergence method, so-called shooting method followed by Runge-Kutta Fehlberg (RK45) method. The impacts of different physical parameters on velocity, temperature and concentration profiles are analyzed and discussed. The parameters of engineering interest, i.e., skin fraction, Nusselt and Sherwood numbers are studied numerically as well. We concluded that the velocity profile decreases by increasing the values of S t , H and M. Also, we have analyzed the variation of temperature and concentration profiles for different physical parameters.

Crosswise stream of methanol–iron oxide (CH3OH–Fe3O4) with temperature-dependent viscosity and suction/injection effects

2019 ◽  
Vol 233 (5) ◽  
pp. 1013-1023 ◽  
Author(s):  
Rabil Tabassum ◽  
R Mehmood
Keyword(s):  
Heat Transfer ◽  
Volume Fraction ◽  
Treatment Plant ◽  
Exponential Model ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Coating Materials ◽  
Similarity Transformations ◽  
Dependent Viscosity ◽  
Energy Equations

Manufacturing of modern coating materials doped with magnetic nanoparticles has arisen as an exciting new area of materials processing fluid dynamics. Methanol is primarily used in chemical manufacturing, specialized vehicles fuel, energy carrier, as an antifreeze in pipelines, in wastewater treatment plant, and many more. In this article, a mathematical model is therefore developed to study crosswise flow of methanol-based ferromagnetic fluid through a permeable medium with suction/injection effects. Temperature-dependent viscosity is taken with Reynolds exponential model. The Tiwari–Das and Maxwell–Garnett nanofluid models are used, which alters the electrical conductivity, density, and thermal conductivity properties with nanoparticle volume fraction. The two-dimensional mass, momentum, and energy equations are normalized into nonlinear system comprising ordinary differential equations via appropriate similarity transformations. The solution of the emerging physical problem is attained by shooting scheme in MATLAB symbolic software. Validation of the results is presented through comparison with previously reported literature in the limiting sense. The influence of pertinent parameters on the flow and heat transfer characteristics is revealed through graphs. It is found that velocity profiles are suppressed with greater magnetic parameter and porosity parameters but temperature profile is enhanced. Velocity and temperature profiles for injection case are higher when compared with the suction phenomenon. Shear stress at the wall is decreased with volume fraction. Heat transfer gradient at the wall is significantly enhanced with volume fraction.

Buoyancy-driven convection in cylindrical geometries

1969 ◽  
Vol 36 (2) ◽  
pp. 239-258 ◽  
Author(s):  
S. F. Liang ◽  
A. Vidal ◽  
Andreas Acrivos
Keyword(s):  
Numerical Solutions ◽  
Perturbation Expansion ◽  
Boussinesq Equations ◽  
Temperature Dependent ◽  
Temperature Dependent Viscosity ◽  
Cylindrical Cell ◽  
Prandtl Numbers ◽  
Buoyancy Driven Convection ◽  
Dependent Viscosity ◽  
Rayleigh Numbers

Numerical solutions to the Boussinesq equations containing a temperature-dependent viscosity are presented for the case of axisymmetric buoyancy-driven convective flow in a cylindrical cell. Two solutions, one with upflow and the other with downflow at the centre of the cell, were found for each set of boundary conditions that were considered. The existence of these two steady-state régimes was verified experimentally for the case of a cylindrical cell having rigid insulating lateral boundaries and isothermal top and bottom planes.Using a perturbation expansion it is also shown that only one of these solutions remains stable in the subcritical régime. This, however, seems to be confined to a very narrow range of Rayleigh numbers, beyond which, according to all the evidence presently at hand, both solutions are equally stable for those values of the Rayleigh and Prandtl numbers for which axisymmetric motions occur.Finally, certain fundamental differences between the problem considered here and that of thermal convection in a layer of infinite horizontal extent are briefly discussed.

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