Effects of radiation and magnetic field on mixed convection stagnation-point flow over a cylinder in a porous medium under local thermal non-equilibrium

Alizadeh, Rasool; Karimi, Nader; Nourbakhsh, Amireh

doi:10.1007/s10973-019-08415-1

Cited by 43 publications

(29 citation statements)

References 47 publications

(81 reference statements)

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“…The latter implies that the velocity of the fluid and solid particles is the same without any slip velocity. Boussinesq approximation is used to calculate the fluid density as a function of temperature [26,27].…”

Section: Problem Configuration and Boundary Conditionsmentioning

confidence: 99%

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Analysis of unsteady mixed convection of Cu–water nanofluid in an oscillatory, lid-driven enclosure using lattice Boltzmann method

Ardalan

Alizadeh

Fattahi

et al. 2020

J Therm Anal Calorim

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The unsteady physics of laminar mixed convection in a lid-driven enclosure filled with Cu-water nanofluid is numerically investigated. The top wall moves with constant velocity or with a temporally sinusoidal function, while the other walls are fixed. The horizontal top and bottom walls are, respectively, held at the low and high temperatures, and the vertical walls are assumed to be adiabatic. The governing equations along with the boundary conditions are solved through D2Q9 fluid flow and D2Q5 thermal lattice Boltzmann network. The effects of Richardson number and volume fractions of nanoparticles on the fluid flow and heat transfer are investigated. For the first time in the literature, the current study considers the mechanical power required for moving the top wall of the enclosure under various conditions. This reveals that the power demand increases if the enclosure is filled with a nanofluid in comparison with that with a pure fluid. Keeping a constant heat transfer rate, the required power diminishes by implementing a temporally sinusoidal velocity on the top wall rather than a constant velocity. Reducing frequency of the wall oscillation leads to heat transfer enhancement. Similarly, dropping Richardson number and raising the volume fraction of the nanoparticles enhance the heat transfer rate. Through these analyses, the present study provides a physical insight into the less investigated problem of unsteady mixed convection in enclosures with oscillatory walls. Keywords Mixed convection • Cu-water nanofluid • Sinusoidal lid-driven enclosure • Unsteady heat transfer • Lattice Boltzmann method List of symbols AR Aspect ratio c p (J kg −1 K −1) Specific heat at constant pressure F Volumetric force f (x, t) Momentum distribution function G(x, t) Temperature distribution function Gr Grashof number g (m s −2) Gravitational acceleration H (m) Height h (W m −2 K −1) Heat convection coefficient k (W m −1 K −1) Thermal conductivity Nu Nusselt number p (Pa) Fluid pressure Pr Prandtl number Re Reynolds number Ri Richardson number T (K) Temperature t (s) Time u (m s −1) Velocity component along x v (m s −1) Velocity component along y * Nader Karimi

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Section: Problem Configuration and Boundary Conditionsmentioning

confidence: 99%

“…Four mesh sizes of 40 × 120, 50 × 150, 60 × 180 and 70 × 210 on the x-y domain were examined. The nondimensional temperature versus time at the midpoint of the (27) enclosure, located at x * = y * = 0.5 , is presented in Fig. 4 for various mesh sizes.…”

Section: Grid Independencymentioning

confidence: 99%

Analysis of unsteady mixed convection of Cu–water nanofluid in an oscillatory, lid-driven enclosure using lattice Boltzmann method

Ardalan

Alizadeh

Fattahi

et al. 2020

J Therm Anal Calorim

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“…To calculate the local rate of entropy generation the velocity, temperature and concentration equations are incorporated into the equations of volumetric local entropy generation given in Refs. [45,[49][50][51][52].…”

Section: Solutions Of Momentum Energy and Mass Transfer Equationsmentioning

confidence: 99%

Double-diffusive transport and thermodynamic analysis of a magnetic microreactor with non-Newtonian biofuel flow

Saeed

Karimi

Hunt

et al. 2019

J Therm Anal Calorim

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Magnetic microfuel-reforming is a promising method of biofuel processing in diesel engines. However, the complex interactions amongst the non-Newtonian biofuel flow, magnetic field and reactor have hindered understanding of their influences upon the transport phenomena in the system. To resolve this issue, the transport of heat and mass in a porous microreactor containing a Casson rheological fluid and subject to a magnetic field is investigated analytically. The system is assumed to host a homogenous and uniformly distributed endothermic/exothermic chemical reaction. Two-dimensional analytical solutions are developed for the temperature and concentration fields as well as the Nusselt number and local entropy generations, and the results are rigorously validated. It is demonstrated that changes in the non-Newtonian characteristics of the fluid and altering the magnetic and thermal radiation properties can lead to bifurcation of temperature gradient on the surface of the porous medium. The general behaviour of such bifurcation is dominated by the exothermicity (or endothermicity) of the chemical reaction in the fluid phase. It is also shown that variations in the Casson fluid parameter and changes in the intensity and incident angle of the magnetic field can modify the Nusselt number considerably. The extent of these modifications is found to be heavily dependent upon the wall thickness and diminishes as the walls become thicker. Further, the total entropy generation is shown to be highly sensitive to the wall thickness and increases by intensifying the magnetic field, provided that the microreactor walls are thin.

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“…In their study, the dual solutions are obtained only in opposing flow. Alizadeh et al [19] examined the impact of radiation and electromagnetic field in a mixed convection stagnation-point flow surrounding a cylinder. It is concluded that the radiative system produces a higher Nusselt number and less thermal irreversibilities.…”

Section: Introductionmentioning

confidence: 99%

Mixed Convection Flow of Powell–Eyring Nanofluid near a Stagnation Point along a Vertical Stretching Sheet

Halim

Noor

2021

Mathematics

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A stagnation-point flow of a Powell–Eyring nanofluid along a vertical stretching surface is examined. The buoyancy force effect due to mixed convection is taken into consideration along with the Brownian motion and thermophoresis effect. The flow is investigated under active and passive controls of nanoparticles at the surface. The associating partial differential equations are converted into a set of nonlinear, ordinary differential equations using similarity conversions. Then, the equations are reduced to first-order differential equations before further being solved using the shooting method and bvp4c function in MATLAB. All results are presented in graphical and tabular forms. The buoyancy parameter causes the skin friction coefficient to increase in opposing flows but to decrease in assisting flows. In the absence of buoyancy force, there is no difference in the magnitude of the skin friction coefficient between active and passive controls of the nanoparticles. Stagnation has a bigger influence under passive control in enhancing the heat transfer rate as compared to when the fluid is under active control. Assisting flows have better heat and mass transfer rates with a lower magnitude of skin friction coefficient as compared to opposing flows. In this case, the nanofluid parameters, the Brownian motion, and thermophoresis altogether reduce the overall heat transfer rates of the non-Newtonian nanofluid.

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Effects of radiation and magnetic field on mixed convection stagnation-point flow over a cylinder in a porous medium under local thermal non-equilibrium

Cited by 43 publications

References 47 publications

Analysis of unsteady mixed convection of Cu–water nanofluid in an oscillatory, lid-driven enclosure using lattice Boltzmann method

Analysis of unsteady mixed convection of Cu–water nanofluid in an oscillatory, lid-driven enclosure using lattice Boltzmann method

Double-diffusive transport and thermodynamic analysis of a magnetic microreactor with non-Newtonian biofuel flow

Mixed Convection Flow of Powell–Eyring Nanofluid near a Stagnation Point along a Vertical Stretching Sheet

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