Magnetohydrodynamic Mixed Convection Heat Transfer Research Articles

Entropy analysis and MHD mixed convection heat transfer of the magnetic nanofluid in an asymmetric T-shaped cavity using the lattice Boltzmann method

The magneto hydrodynamic (MHD) mixed convection of titanium oxide/water nanofluids (NFs) in a T-shaped two-dimensional cavity is studied numerically in this article. The upper wall of the cavity has a low temperature and the lower walls of the cavity have a high temperature. The cavity has an inclination angle of 45⁰ under the influence of a horizontal magnetic field (MFD) with Ha = 20. On the upper wall, the slip parameter is changed from 0 to 0.1. The values ​​of entropy generation (ETG), Bejan number (Be), and Nusselt number (Nu), as well as velocity and temperature contours, are presented for different slip parameters when Richardson number (Ri) changes in the range of 0.1 to 100. Lattice Boltzmann method (LBM) is used for simulations. The results demonstrate that an enhancement of the slip parameter causes a decrease in the ETG and a reduction in Nu slightly. ETG and Nu have a decreasing trend by changing Ri from 0.1 to 10; but, they are increased with a further increase of Ri to 100. With an increase in Ri, the local Nusselt number on the left side of the cold wall decreases.

Magnetohydrodynamic mixed convection and entropy generation analysis of Al2O3-water nanofluid past a confined circular cylinder

Numerical simulations are carried out for transient magnetohydrodynamic mixed convective heat transfer of alumina–water nanofluid flow past an isothermal circular cylinder confined in an electrically insulated rectangular duct in the presence of a uniform transverse magnetic field. A control volume method is used to solve the governing equations on a nonuniform Cartesian grid, and the cylinder is imposed using the immersed boundary method. Numerical experiments are performed for a Reynolds number based on the cylinder diameter of ReD=200, blockage ratio of BR=0.2, Richardson numbers of (Ri=−1;0;2), nanoparticle volume fractions of (φ=0.0;0.1;0.2), and Hartmann numbers in the range 0≤Ha≤13. In this work, mean and instantaneous flow and thermal distributions are analyzed graphically, and their corresponding sensitivity to the nanoparticle volume fraction has been determined. Numerical predictions demonstrate the impact of buoyancy and magnetic parameters regarding the spatial development and shedding characteristics of the near wake, and we explore their potential use to selectively excite or suppress vortex shedding, augmentation of heat transfer, and entropy generation minimization in nanofluid flow. The results reported herein indicate that depending on the parametric set, linear and nonlinear flow response to magnetic excitation is observed with bifurcations between different states. The outcome of the study shows that vortex shedding is completely suppressed when a critical value of the Hartmann number is reached, and that the threshold value of the Hartmann number strongly depends on the value of the buoyancy parameter and nanoparticle volume fraction. Based on the entropy distributions, we show that for all values of the nanoparticle volume fraction and in the range of buoyancy and magnetic parameters considered in this work, the entropy generation is dominated by irreversibilities due to heat transfer and the relative contributions of entropy generation due to fluid friction and magnetic effect are not preponderate.

Magneto-hydrodynamic mixed convective heat transfer in a nanofluid filled wavy conduit having rotating cylinders

Flow and thermal characteristics of mixed convection in a nanofluid filled wavy conduit was numerically investigated in this study. The conduit was considered to contain a pair of rotating cylinders. It was heated and cooled from its lower and upper wavy surface, respectively. The rotating cylinders were placed along the centerline of the wavy conduit. It was also permeated by an external magnetic field. Finite element method was implemented to simulate the conservation equations. Based on the current investigation, a new model was developed for improving thermal conductivity of nanofluids inside a wavy conduit. In addition, a detailed parametric study was presented to visualize the effects of governing parameters on the flow structure and temperature field in the conduit. The numerical results indicated that the physical parameters noticeably influenced both fluid flow in terms of streamlines, velocity profiles and temperature distributions in terms of isotherms, average Nusselt number. The rotating cylinders, wavy surfaces and the inclined magnetic field were found to have the most significant effect on the heat transfer mechanism. Maximum heat transfer occurred as the magnetic field was placed at an angle of 90o.

Heat Transfer Augmentation

This article presents a brief review of various methodologies applied for heat transfer enhancement in laminar flow convection regime. Experimental setup for laminar flow convection heat transfer enhancement using insertions has been explained along with the associated results. Nusselt’s number is found to be a key parameter for investigatigation in order to perceive the enhancement in heat transfer. Similarly, the magnetohydrodynamic mixed convection heat transfer enhancement technique has also been explored. The results of isotherms and fluid flow parameters are discussed which directly affect the heat transfer coefficient. This review article complements the literature in related field and thus will be helpful in order to carry out further experiments in heat transfer enhancement in future.

Heat Transfer Augmentation

This article presents a brief review of various methodologies applied for heat transfer enhancement in laminar flow convection regime. Experimental setup for laminar flow convection heat transfer enhancement using insertions has been explained along with the associated results. Nusselt’s number is found to be a key parameter for investigatigation in order to perceive the enhancement in heat transfer. Similarly, the magnetohydrodynamic mixed convection heat transfer enhancement technique has also been explored. The results of isotherms and fluid flow parameters are discussed which directly affect the heat transfer coefficient. This review article complements the literature in related field and thus will be helpful in order to carry out further experiments in heat transfer enhancement in future.

A Theoretical Study of Steady MHD mixed convection heat transfer flow for a horizontal circular cylinder embedded in a micropolar Casson fluid with thermal radiation

In this study, an investigation is carried out for laminar steady mixed 2D magnetohydrodynamic (MHD) flow of micropolar Casson fluid with thermal radiation over a horizontal circular cylinder with constant surface temperature. In the present study, an investigation is carried out on the effects of physical parameters on Casson fluid non dimensional numbers. The governing nonlinear partial differential equations and the controlling boundary conditions are derived for this case study. Furthermore, these equations are solved numerically using finite difference technique known as Keller Box Method (KBM). The effects of non-dimensional governing parameters, namely Casson parameter, mixed convection parameter, magnetic parameter, radiation parameter on the Nusselt number and local friction coefficient, as well as temperature, velocity and angular velocity are discussed and shown graphically. It is noticed that the local skin friction and the local Nasselt number has decrement behaviors when increasing the values the Casson parameter. But the opposite happens when the mixed convection parameter λ increase. It is found that the results in this study are in good agreement with previous studies. This proves that calculations using KBM method and the chosen step size are accurate enough for this type of problems.

Nanoparticle transport effect on magnetohydrodynamic mixed convection of electrically conductive nanofluids in micro-annuli with temperature-dependent thermophysical properties

This is a numerical investigation of nanoparticle transport effect on magnetohydrodynamic mixed convective heat transfer of electrically conductive nanofluids in micro-annuli with temperature-dependent thermophysical properties. The modified Buongiorno's non-homogeneous model is applied for the nanoparticle-fluid suspension to simulate the migration of nanoparticles into the base fluid, originating from the thermophoresis (nanoparticle migration because of temperature gradient) and Brownian motion (nanoparticle slip velocity because of concentration gradient). Due to surface roughness at the solid–fluid interface in micro-annuli, the wall surfaces are subjected to a linear slip condition to assess the non-equilibrium region near the interface. The fluid flow has been assumed to be fully developed, and the governing equations including continuity, momentum, energy, and nanoparticle transport equation are reduced to a system of ordinary differential equations, before they have been solved numerically. The results are presented with and without considering the dependency of thermophysical properties upon the temperature. It is indicated that ignoring the temperature dependency of thermophysical properties does not significantly affect the flow fields and heat transfer behavior of nanofluids, but it changes the relative magnitudes. Furthermore, in the presence of magnetic field, smaller nanoparticles are more appropriate than larger ones.

Nanoparticles migration effects on magnetohydrodynamic (MHD) laminar mixed convection of alumina/water nanofluid inside microchannels

This is a theoretical study on effects of nanoparticles migration on magnetohydrodynamic mixed convective heat transfer of alumina/water nanofluid inside a vertical microchannel. Walls are subjected to different heat fluxes; q''lw for the left wall and q''rw for the right wall, and nanoparticles are assumed to have a slip velocity relative to the base fluid, induced by Brownian diffusion and thermophoresis. Scale analysis of the governing equations indicates that buoyancy effects due to the temperature distribution is insignificant, however, the buoyancy effects due to concentration distribution of nanoparticles have vast effects on flow and heat transfer characteristics. Further, it is shown that nanoparticles eject themselves from the heated walls and accumulate in the core region, but they are more likely to accumulate near the wall with lower heat flux. Also, the non-uniform nanoparticle distribution causes velocities to move toward the wall with higher heat flux and enhances heat transfer rate there. Moreover, while the nanoparticle volume fraction is smaller than 0.1, the maximum increase in the values of heat transfer rate is 37% for small nanoparticles which drops to 14% for larger nanoparticles. Applying a magnetic field leads to 42% and 30% increase in the values of heat transfer rate for small and large nanoparticles respectively. Additionally, one-sided heating serves as another causing factor for increasing the heat transfer rate which boosts it up to 80% for large nanoparticles.

Effect of conditions of preparation of zinc oxide catalysts with and without added indium and gallium upon catalytic properties in homo-molecular isotopic oxygen exchange reaction

This is a numerical investigation of nanoparticle transport effect on magnetohydrodynamic mixed convective heat transfer of electrically conductive nanofluids in micro-annuli with temperature-dependent thermophysical properties. The modified Buongiorno's non-homogeneous model is applied for the nanoparticle-fluid suspension to simulate the migration of nanoparticles into the base fluid, originating from the thermophoresis (nanoparticle migration because of temperature gradient) and Brownian motion (nanoparticle slip velocity because of concentration gradient). Due to surface roughness at the solid–fluid interface in micro-annuli, the wall surfaces are subjected to a linear slip condition to assess the non-equilibrium region near the interface. The fluid flow has been assumed to be fully developed, and the governing equations including continuity, momentum, energy, and nanoparticle transport equation are reduced to a system of ordinary differential equations, before they have been solved numerically. The results are presented with and without considering the dependency of thermophysical properties upon the temperature. It is indicated that ignoring the temperature dependency of thermophysical properties does not significantly affect the flow fields and heat transfer behavior of nanofluids, but it changes the relative magnitudes. Furthermore, in the presence of magnetic field, smaller nanoparticles are more appropriate than larger ones.