Analysis Of Mixed Convection Flow Research Articles

Effect of ferro nanofluids on mixed convection in an open cavity with phase change material

Numerical analysis of mixed convection flow in an open channel cavity was performed by placing PCM and using ferro nanofluids (water based Fe3O4 nanofluid) with different volume fractions (1.0%, 3.0% and 5.0%) as working fluids. The effect of different Richardson numbers under laminar flow conditions with constant Reynolds number was analyzed to reveal how the nanofluid volume fraction and PCM position in the cavity affect the flow and heat transfer characteristics. The main reason for considering the use of nanofluid as a working fluid with the PCM layer is the thermal control of the cavity. It has been determined that the use of ferro nanofluids has a positive effect on the thermal control of the flow by increasing the thermal energy storage capacity of the PCM. As the Ri number increased, the importance of mixed convection effects increased, and for the highest Ri number, natural convection played a dominant role, causing a 65.5% decrease in the heated wall dimensionless temperature. Since the heat flux applied for pure water at highest Ri number is one third of that applied for 5.0% nanofluid, the specified temperature increase is quite lower by comparing heat flux thanks to the nanofluid high convection capability. Different than pure water, in all PCM cases the rate of melting is higher for 5.0% ferro nanofluid due to the higher convective heat transfer. In the case of the PCM on the bottom wall, the highest thermal energy storage capacity was obtained for each working fluid and 50% more energy was stored compared to the right heated wall at the same Ri number. Moreover, the maximum average Nu number was determined for the bottom heated case and for the same Ri number at 5.0% ferro nanofluid which was obtained approximately twice as much as pure water when flow reached steady state.

Inclined surface mixed convection flow of viscous fluid with porous medium and Soret effects

Abstract The combined heat and mass transfer phenomenon is a significant aspect of engineering and industrial processes. This phenomenon finds applications in various areas such as air conditioning, cooling and heating control of electronic devices, reactors, chemical systems, and emission processes. This research model focuses on the analysis of mixed convection flow of a viscous fluid with heat and mass transfer on an inclined surface with porous medium characteristics. The study also considers external heat transfer effects, radiation, Soret influence, and chemical reactions. A perturbation solution is derived in closed form, and the impact of various parameters on the thermal behavior is investigated. A comparative analysis of the heating and cooling regimes in plate flow is conducted, revealing a reduction in velocity in the heated plate regime with changes in the permeability parameter and an increase in concentration phase due to the Soret number.

Analysis of mixed convection flow on Arrhenius-controlled heat generating/absorbing fluid in a super-hydrophobic microchannel: A semi-analytical approach

The theoretical analysis of steady mixed convection with Arrhenius-controlled heat flow for a viscous and an electrically-conducting fluid traveling across an isothermally heated vertical parallel plate in a slit micro-channel is investigated in this study. One wall had super-hydrophobic slip and a temperature spike, while the other did not. A semi-analytical technique (perturbation series) was employed to analyze the nonlinear and coupled leading equations. The results were carefully scrutinized, and the effects of the relevant and pertinent parameters were illustrated using various plots. It is concluded from this work that the actions of mixed convection and chemically reacting factors are noticed to substantially strengthen the fluid movement in the micro-channel for a constant pressure gradient. Additionally, the function of heat source parameter is depicted to raise the fluid flow while heat absorption parameter yields the reverse phenomenon. In the fields of engineering and medicine, it is essential to understand these fluids' characteristics. Owing to the lubrication of micro-channel boundary surfaces where conductivity and viscosity interact with thermos-physical behavior, the results of the present investigation can significantly enhance the functioning of micro-electro-mechanical systems (MEMS) and micro-devices relying on micro-fabrication processes.

Homotopy analysis of mixed convection flow of a magnetized viscoelastic nanofluid from a stretching surface in non-Darcy porous media with revised Fourier and Fickian approaches

This article addresses theoretically the mixed convection hydromagnetic flow of electrically conducting viscoelastic nanofluid from a vertical permeable stretching sheet in a non-Darcy porous medium with Cattaneo–Christov double-diffusion model to evaluate the heat transfer phenomena in steady boundary layer flow on a stretchable surface. In this regard, thermal and solutal hyperbolic wave relaxation effects are included for non-Fourier and non-Fickian models. Heat absorption is also included in the analysis. The Buongiorno two-component nanoscale model is adopted for simulating Brownian motion and thermophoretic body force effects. A non-Darcy drag force model is employed for the porous medium and the Reiner–Rivlin second-grade model for non-Newtonian characteristics. Via appropriate dimensionless similarity variables, the nonlinear dimensional partial differential conservation equations for momentum, energy and concentration with associated boundary conditions are rendered into a nonlinear dimensionless ordinary differential boundary value problem. The homotopy analysis method (HAM) is utilized to solve the boundary value problem and the impact of emerging parameters including thermal relaxation parameters, non-Newtonian material parameter, Darcy permeability parameter, porous inertial parameter and Hartmann magnetic number on the momentum, heat and mass transfer characteristics are visualized graphically and in tables. A 30th-order approximation for HAM is shown to produce sufficient accuracy for the velocity and temperature fields and a 40th-order estimates is adequate for the concentration field. It is observed that increasing the magnitude of thermal and solutal relaxation parameters has the opposite effect on the thermal and concentration distributions. The novelty of the work is the simultaneous inclusion of multiple effects (non-Fourier and non-Fickian thermal relaxation hyperbolic wave models, non-Darcy drag effects and heat generation/absorption) which are relevant to rheological nanomaterials processing and also the deployment of homotopy analysis as an alternative to conventional numerical methods such as finite differences, finite elements and MATLAB solvers. The study is relevant to the manufacture of electro-conductive polymers (ECPs) and smart (functional) magnetic nano-liquids.

Dual solutions and linear temporal stability analysis of mixed convection flow of non-Newtonian special third grade fluid with thermal radiation

The present study aims to investigate the steady mixed convection stagnation-point flow of a special third grade fluid over a vertical stretching/shrinking sheet with the inclusion of suction and thermal radiation effects. The governing momentum and energy equations are transformed into a system of ordinary differential equations (ODEs) using the Lie scaling group of transformations. The resulting system of highly nonlinear boundary value problems (BVPs) is solved numerically with the help of Matlab solver ‘bvp4c’. Dual similarity solutions are found for the opposing flow case within the range λc≤λ<0, where λ is the buoyancy parameter. Emphasis has been given to conducting a temporal stability analysis to determine the practically reliable solution. The analysis reveals that the primary (upper) solution branch is stable while the other solution branch is unstable. It has been observed that the range of dual solutions and the magnitude of the critical point increase with the increasing value of the suction parameter. The increment of the thermal radiation parameter enhances fluid temperature in the upper solution branch, whereas temperature diminishes far away from the sheet in the lower solution branch.

Magnetohydrodynamic mixed convection flow of liquid metals in a vertical channel: A stability analysis

The impact of applied magnetic field on liquid metal flows has good prospects for the industry. For a better understanding of flow dynamics, the stability analysis of liquid metal flows through a confined transverse magnetic field is of fundamental importance in designing advanced magnetohydrodynamic (MHD) devices for the next generation. In this paper, we report the linear stability analysis of mixed convection flow of electrically conducting liquid metals with low Prandtl number (Pr) in a vertical channel under a transverse magnetic field. The flow is described by quasi-static MHD approximation. The instability properties are examined numerically through a spectral collocation method. The influence of magnetic field on instability mechanism is examined for a good range of Pr. The results demonstrate that the growth of the infinitesimal disturbance decreases with increasing strength of the applied magnetic field due to the effective Lorentz force exerted on the flow, i.e., stability of the flow increases. In contrast, the stability of the basic flow decreases on increasing the value of Pr, except for a small range of Pr, where it increases. The kinetic energy balance shows that for very small values of Pr, the shear instability dominates the flow, whereas for relatively larger values of Pr, thermal-buoyant instability plays a significant role in the instability mechanism. The dissipation of energy in the kinetic energy balance occurs prominently due to the presence of the applied magnetic field. The secondary flow pattern shows that the applied magnetic field suppresses the disturbance in the vicinity of channel walls. In contrast, a decrease in thermal diffusivity provokes instability by inviting a strong disturbance cell in the middle portion of the channel. The energy dissipation in the kinetic energy balance occurs mainly due to the presence of the magnetic field.

OHAM analysis of Newtonian heating in mixed convective flow of CNTs over a stretched cylinder

This work reports mathematical modeling and analysis of mixed convection flow of nanofluids with stagnation point by a stretching cylinder. Carbon nanotubes are dispersed as nanomaterial in the baseliquid of water. Heat transfer characteristics are explored through Newtonian heating. Transformation method is employed in order to obtain ODEs. Furthermore series solutions are developed. Variations in flow, temperature, skin friction and local Nusselt number under influential variables have been plotted. It is elaborated that fluid velocity intensifies with rise in curvature parameter, conjugate parameter, mixed convection parameter, nanoparticle volume fraction and velocity ratio parameter. Similarly decay in temperature of the fluid is analyzed for higher velocity ratio parameter while it enhances with increment in nanoparticle volume fraction, mixed convection parameter, conjugate parameter and curvature parameter. Skin friction can be minimized via higher estimations of mixed convection parameter, velocity ratio parameter and nanoparticle volume fraction. Heat transfer rate or cooling process (Nusselt number) is regulated through higher conjugate and curvature parameters. During comparative analysis of SWCNTs with MWCNTs, better performance is shown by SWCNTs. Skin friction coefficient in limiting sense is also compared with previously published articles.

Finite element analysis of mixed convection flow in a trapezoidal cavity with non-uniform temperature

A two dimensional flow analysis in a cavity shaped isosceles trapezium is carried out. Non-parallel sides of a trapezium are adiabatic. A varying sinusoidal temperature is applied to the lower wall while the upper wall is at constant temperature. Upper wall of the cavity moves with a velocity η0 in the positive x-direction. Also, B0 is constant magnetic field of strength aligned in the same x-direction and Newtonian fluid is considered. The values of magnetic field parameter used are Ha=0,50, the Richardson number is Ri=0.1,1,10, Re=100 is Reynolds number used for the analysis, the amplitude of sinusoidal temperature is m=0.25,0.5,1. The impacts of different leading parameters are analyzed by plotting streamlines for flow fields and isotherm contours for temperature of the flow dynamics. The graphs that signify the variation of average Nusselt number and local Nusselt number are sketched for both lower and upper walls of the cavity. Result indicated that with constant temperature the top wall of the boundary layer thickness decreases as Richardson number Ri increases and for bottom wall with variable temperature. The Nusselt number gets higher with an increment in the amplitude of the oscillation of temperature function. Furthermore, the study revealed that the average Nusselt number gets reduced as the intensity of magnetic field is enhanced. The variation in transit of heat at the bottom wall is similar but the maximum value of heat transfer at the bottom wall shows a variation from 3.8 to 20 when Ha=0 and from 3 to 18 when Ha=50. The accuracy of the present numerical algorithms is also established.

Heat transfer analysis of mixed convection flow in a vertical microchannel with electrokinetic effect

In this article, the transient/steady mixed convective flow formation inside a vertical microchannel subjected to uneven wall zeta potentials in the presence of an electric body force is carried out theoretically. Employing the Navier–Stokes, Poisson–Boltzmann and energy equations, the velocity profile, electric potential and temperature distributions respectively governing flow formation and heat transfer in dimensional form are presented. Using appropriate dimensionless parameters, the corresponding dimensionless form of the governing equations are obtained. At the transient state, the Laplace transform technique is utilized while at the steady-state, direct integration as well as undetermined coefficients are employed to obtain solutions to governing equations. To justify solutions obtained, the steady state solution is found and compared with the implicit finite difference method at large time; this comparison gives an excellent agreement. Graphical simulations show that the skin-friction could have incurred an error of up to 19% if the buoyancy term in the momentum equation had been neglected. In addition, it is established that for a large electric double layer, the interval of no reverse flow at the microchannel walls is significantly extended.

Linear stability analysis of mixed convection flow in a horizontal channel filled with nanofluids

AbstractThe convective instability driven by buoyancy in the Poiseuille–Rayleigh–Bénard flow through two infinite parallel horizontal plates filled with nanofluids is investigated using linear stability analysis. We considered water‐based nanofluids with different volume fractions of aluminum () and silver () nanoparticles. A spectral collocation method founded on Chebyshev polynomials is implemented and the obtained algebraic eigenvalue problem is solved. In this study, we have numerically determined the critical Rayleigh number of the onset of longitudinal and transversal rolls and the results are represented in the form of marginal stability curves. Critical wave numbers that describe the size of convective cells in the flow are also presented, analyzed, and compared with those of the Poiseuille–Rayleigh–Bénard flow without nanoparticles. The effects of the type and nanoparticle volume fractions on the onset of both longitudinal and transversal rolls are investigated.

Analysis of mixed convection flow in an inclined lid-driven enclosure with Buongiorno’s nanofluid model

The laminar mixed convection flow in an inclined lid-driven cavity filled with a nanofluid is investigated in the presence of internal heat generation. The two sidewalls of the enclosure are sinusoidally heated while the top and bottom walls are insulted. The Buongiorno’s model that incorporates the effects of Brownian motion and thermophoresis is applied to describe the nanofluid behaviours. Parametrical studies are given on the regimes of the complex flow, temperature and concentration fields. The developed equations are nondimensionalized and then solved numerically by the newly developed wavelet-homotopy technique. Comparisons with previously studies in literature are presented and found to be in excellent agreement. The results of this work indicate that the Grashof number, the slipping parameters, the nanoparticles related parameters, the inclination, the boundary coefficients including amplitude ratios of temperature and concentration, as well as the phase deviation have significant effects on characteristics of the cavity flow.

Analysis of mixed convection flow of a nanofluid in a vertical channel with the Buongiorno mathematical model

The laminar, fully developed mixed convection flow between two paralleled vertical flat plates filled by a nanofluid is investigated. By means of a new set of similarity variables, the governing equations are reduced to a set of three coupled equations with an unknown constant. The exact solutions are obtained by means of the homotopy analysis method for both the buoyancy-assisted and the buoyancy-opposing cases and their accuracies are checked in detail. The effects of the Grashof number Gr and the Prandtl number Pr on the nanofluid flows are then investigated successively. We further consider the effects of the buoyancy ratio Nr, the Brownian motion parameter Nb, the thermophoresis parameter Nt on the pressure parameter σ and the Nusselt number Nu. It is found that the heat transfer characteristic can be improved significantly as the proper nanofluids are applied.

Transport at large downstream distances in mixed convection flow adjacent to a vertical uniform-heat-flux surface

A perturbation analysis of mixed convection flow over a vertical semi-infinite surface with uniform heat flux is presented. A matched asymptotic expansion technique is used to construct inner and outer expansions including, for the first time, both mixed convection and higher-order boundary layer effects. It is shown that these effects must be simultaneously included to obtain consistent higher-order approximations to mixed convection boundary layer flow at large downstream distances. Numerical calculations are presented for Pr = 0.733 and 6.7 which indicate the relative magnitudes of mixed convection and non-boundary layer effects. In addition, new experimental measurements of surface heat transfer rates and velocity and temperature profiles are presented for mixed convection flow adjacent to a vertical uniformheat-flux surface in air. The measured profiles are found to be in excellent agreement with those predicted by the analysis. The predicted variation of the Nusselt number is also seen to agree well with the values inferred from the measurements.