A Study on Mixed Convection Flow in a Lid-Driven Cavity Filled With Micropolar Nanofluid by Considering Brownian Motion

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Amin Hadizade ◽  
Amin Haghighi Poshtiri
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Physical Properties ◽  
Newtonian Fluid ◽  
Volume Fraction ◽  
Bottom Wall ◽  
Fluid Viscosity ◽  
Driven Cavity ◽  
Micropolar Nanofluid ◽  
Thermo Physical Properties

The mixed convective heat transfer of a micropolar nanofluid in a square lid-driven cavity has been numerically studied. The lid is thermally insulated, the side walls are kept cold, and the bottom wall is kept hot with sinusoidally thermal boundary condition. The governing equations were solved by finite volume method using the SIMPLE algorithm. The effect of Grashof number (102–105), the volume fraction of nanoparticles (0.0–0.1), and micropolarity (0.0–2.0) has been investigated on the heat transfer of Al2O3–water nanofluid. Also, the variable model was used to calculate fluid viscosity and thermal conductivity coefficient of the nanofluid. The results showed that an increase in Grashof amplifies the buoyancy force and enhances the Nusselt number. Also, an increase in vortex viscosity at low Grashof numbers strengthens the forced convection and increases the Nusselt number over the bottom wall. However, at Gr = 105, the increase in vortex viscosity up to K = 1.0 leads to a decrease in the amount of heat transfer, but its further increase entails the increase in heat transfer. Although the addition of nanoparticles to the fluid improves heat transfer rate, the extent of improvement at nonzero K values is lower than that in the Newtonian fluid. The comparison of the average Nusselt number computed on the hot wall under two different states of temperature-depended thermo-physical properties and constant thermo-physical properties reveals that their difference is more significant for the Newtonian fluid especially at higher volume fraction.

Effect of geometrical and temperature-dependence parameters on forced convection of a nanofluid in a micro-channel heat sink

2016 ◽  
Vol 13 (5) ◽  
pp. 399-406 ◽  
Author(s):  
Rabah Nebbati ◽  
Mahfoud Kadja
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Physical Properties ◽  
Forced Convection ◽  
Heat Sink ◽  
Volume Fraction ◽  
Micro Channel ◽  
Temperature Dependent ◽  
Content Type ◽  
Thermo Physical Properties

Purpose The purpose of this study is the numerical prediction of the thermal and hydraulic characteristics (Nusselt number and shear stress) of a forced convection laminar flow through a rectangular micro-channel heat sink, using constant and temperature-dependent thermo-physical properties. The effects of the solids volume fraction and the size of the micro-channel on heat transfer enhancement have also been investigated. Design/methodology/approach The authors use the flow of a water-Al2O3 nanofluid and a single-phase approach. The equations are solved using the commercial code Fluent Version 6.3. This code uses the finite volume approach to solve the equations subject to the boundary conditions, which govern three-dimensional conjugate convection-conduction heat transfer model. The physical domain was meshed using the code GAMBIT. The mesh used is non-uniform and was obtained by sweeping in the Z direction an X-Y surface meshed with QUAD/pave type cells. Findings The results clearly show that the inclusion of nanoparticles produces a considerable increase in the heat transfer. Also, the temperature-dependent models present higher values of local and average Nusselt number than in the case of constant thermo-physical properties, and an increase in the channel dimensions leads to an important increase in heat transfer. Consequently, we ensure a better cooling of the base of the micro-channel heat sink. Research limitations/implications Because of the settling of nanoparticles, the research results may not be generalized to high values of solids volume fraction. Therefore, researchers are encouraged to find other techniques of cooling when the heat loads exceed values that cannot be dissipated using nanonofluids. Practical implications The paper includes implications for the miniaturization of electronic devices such as in microprocessors or those used in robotics and automotive industries, where continually increasing power densities are requiring more innovative techniques of heat dissipation from a small area and small coolant requirements. Originality/value This paper shows the implementation of variable property nanofluid models in CFD commercial codes.

Heat Transfer and Crystallization Modeling during Compression Molding of Thermoplastic Composite Parts

2015 ◽  
Vol 651-653 ◽  
pp. 1507-1512 ◽  
Author(s):  
Jalal Faraj ◽  
Baptiste Pignon ◽  
Jean Luc Bailleul ◽  
Nicolas Boyard ◽  
Didier Delaunay ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Physical Properties ◽  
Volume Fraction ◽  
Thermoplastic Composite ◽  
Large Temperature ◽  
Process Conditions ◽  
Thermoplastic Resin ◽  
Whole Process ◽  
Low Viscosity ◽  
Thermo Physical Properties

We present in this paper, the coupling of heat transfer to the crystallization of composite in a closed mold. The composite is based on thermoplastic resin (low viscosity PA 66) with glass fiber (50% volume fraction). In order to realize this coupling, an accurate characterizationof thermo physical properties in process conditions, especially in the molten and solid state is needed. In addition, theidentification of the parameters of crystallization kinetics is required. Therefore, we present the methods that were used to study the thermo physical properties as the thermal conductivity, heat capacity and the specific volume. Moreover, the kinetic of crystallization was estimated over a large temperature range by using Flash DSC and classical DSC. In order to validate the measurements, the whole process was modeled by finite elements. The model includes the resolution of the strong coupling between the heat transfer and crystallization. Finally, the experimental and numerical results were compared.

scholarly journals Study of convection heat transfer enhancement inside lid driven cavity utilizing fins and nanofluid

2017 ◽  
Vol 21 (6 Part A) ◽  
pp. 2431-2442
Author(s):  
Arash Lavasani ◽  
Mousa Farhadi ◽  
Darzi Rabienataj
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Richardson Number ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Thermal Conductivity Ratio ◽  
Convection Flow ◽  
Driven Cavity ◽  
Ratio Change ◽  
Hot Surface

In the present study, the effect of suspension of nanoparticle on mixed convection flow is investigated numerically in lid driven cavity with fins on its hot surface. Study is carried out for Richardson numbers ranging from 0.1 to 10, fin(s) height ratio change from 0.05 to 0.15 and volume fraction of nanoparticles from 0 to 0.03, respectively. The thermal conductivity ratio (kfin/kf) is equal to 330 and Grashof number is assumed to be constant (104) so that the Richardson numbers changes with Reynolds number. Results show that the heat transfer enhances by using nanofluid for all studied Richardson numbers. Adding fins on hot wall has different effects on heat transfer depend to Richardson number and height of fins. Use of low height fin in flow with high Richardson number enhances the heat transfer rate while by increasing the height of fin the heat transfer reduces even lower than it for pure fluid. The overall enhancement in Nusselt number by adding 3% nanoparticles and 3 fins is 54% at Ri=10. They cause reduction of Nusselt Number by 25% at Ri=0.1. Higher fins decrease the heat transfer due to blocking fluid at corners of fins.

Numerical Study of Turbulent Convective in Upward Flows of Supercritical Water in the Triangular Lattice Fuel Rod Bundle

2014 ◽  
Author(s):  
Mohsen Modirshanechi ◽  
Kamel Hooman ◽  
Iman Ashtiani Abdi ◽  
Pourya Forooghi
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Turbulent Boundary Layer ◽  
Physical Properties ◽  
Supercritical Water ◽  
Triangular Lattice ◽  
Rod Bundles ◽  
Fuel Rod ◽  
Thermo Physical Properties

Convection heat transfer in upward flows of supercritical water in triangular tight fuel rod bundles is numerically investigated by using the commercial CFD code, ANSYS Fluent© 14.5. The fuel rod with an inner diameter of 7.6 mm and the pitch-to-diameter ratio (P/D) of 1.14 is studied for mass flux ranging between 550 and 1050 kg/m2s and heat flux of 560 kW/m2 at pressures of 25 MPa. V2F eddy viscosity turbulence model is used and, to isolate the effect of buoyancy, constant values are used for thermo-physical properties with Boussinesq approximation for the density variation with temperature in the momentum equations. The computed Nusselt number normalized by that of the same Reynolds number with no buoyancy against the buoyancy parameter proposed by Jackson and Hall’s criterion. Mentioned results are compared with V2F turbulence model whereas strong nonmonotonic variation of the thermo-physical properties as function of temperature have been applied to the commercial CFD code using user defined function (UDF) technique. A significant decrease in Nusselt number was observed in the range of 10-6<Grq/Reb3.425Prb0.8<5×10-6 before entering a serious heat transfer deterioration regime. Based on an analysis of the shear-stress distribution in the turbulent boundary layer and the significant variation of the specific heat across the turbulent boundary layer, it is found that the same mechanism that leads to impairment of turbulence production in concentric annular pipes is present in triangular lattice fuel rod bundles at supercritical pressure.

Heat transfer and second law analysis of ethylene glycol based ternary hybrid nanofluid under laminar flow

2021 ◽  
pp. 1-45
Author(s):  
Lingala Sundar ◽  
Kottutu V.V. Chandra Mouli ◽  
Zafar Said ◽  
Antonio C.M. Sousa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Laminar Flow ◽  
Ethylene Glycol ◽  
Physical Properties ◽  
Friction Factor ◽  
Base Fluid ◽  
Hybrid Nanofluid ◽  
Pumping Power ◽  
Thermo Physical Properties

Abstract Experiments were conducted to evaluate the thermal and frictional entropy generation and exergy efficiency of rGO-Fe3O4-TiO2 hybrid nanofluid in a circular tube under laminar flow. The ternary nanoparticles are synthesized using the sol-gel technique and characterized by XRD, SEM, and FTIR. The stable ethylene glycol based ternary hybrid nanofluid were prepared and thermo-physical properties, heat transfer, friction factor, and pumping power at various particle weight concentrations (0.05% to 0.2%) and Reynolds number (211 to 2200) were investigated. Enhancement in the thermal conductivity and viscosity of 10.6% and 108.3% at ψ = 0.2% and at 60°C over the base fluid were obtained. Similarly, Nusselt number is enhanced to 17.78%; heat transfer coefficient is enhanced to 24.76%; thermal entropy generation is reduced to 19.85%; exergy efficiency enhancement of 6.23% at ψ = 0.2% and at Re = 1548 is achieved. The pressure drop, pumping power, and friction factor is augmented to 13.65%, 11.33%, and 16% at ψ = 0.2% and at Re = 221.1 over the base fluid. The overall thermal performance of the system is enhanced to 14.32%. New equations are modeled to evaluate the thermo-physical properties, Nusselt number, and friction factor.

scholarly journals Numerical study of mixed convection heat transfer in lid-driven cavity utilizing nanofluid: Effect of type and model of nanofluid

2015 ◽  
Vol 19 (5) ◽  
pp. 1575-1590 ◽  
Author(s):  
Nader Pourmahmoud ◽  
Ashkan Ghafouri ◽  
Iraj Mirzaee
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Volume Fraction ◽  
Numerical Study ◽  
Published Data ◽  
Driven Cavity ◽  
Laminar Mixed Convection ◽  
Special Cases

Numerical investigation of the laminar mixed convection in two-dimensional lid driven cavity filled with water-Al2O3, water-Cu or water-TiO2 nanofluids is done in this work. In the present study, the top and bottom horizontal walls are thermally insulated while the vertical walls are kept at constant but different temperatures. The governing equations are given in term of the stream function-vorticity formulation in the non-dimensionalized form and then solved numerically by second-order central difference scheme. The thermal conductivity and effective viscosity of nanofluid have been calculated by Maxwell-Garnett and Brinkman models, respectively. An excellent agreement between the current work and previously published data on the basis of special cases are found. The governing parameters are Rayleigh number 103 ? Ra ? 106 and solid concentration 0 ? ? ?0.2 at constant Reynolds and Prandtl numbers. An increase in mean Nusselt number is found as the volume fraction of nanoparticles increases for the whole range of Rayleigh numbers. In addition, it is found that significant heat transfer enhancement can be obtained by increasing thermal conductivity coefficient of additive particles. At Ra=1.75?105, the Nusselt number increases by about 21% for TiO2-Water, and almost 25% for Al2O3-Water, and finally around 40% for Cu-Water nanofluid. Therefore, the highest values are obtained when using Cu nanoparticles. The result obtained using variable thermal conductivity and variable viscosity models are also compared to the results acquired by the Maxwell-Garnett and the Brinkman model.

Forced convection heat transfer of Ag–MgO/water micropolar hybrid nanofluid inside a stairway channel

2021 ◽  
pp. 2150147
Author(s):  
Hanif Heidari ◽  
Rasul Mohebbi ◽  
Amir Kazemi
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Forced Convection ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Hybrid Nanofluid ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Micropolar Nanofluid

In this paper, the forced convection heat transfer of Ag–MgO/water hybrid micropolar nanofluid in a channel is studied numerically which the top wall of channel is smooth and bottom of it is in stairway form. The lattice Boltzmann method (LBM) is used for solving the fluid flow and heat transfer equations. The effects of Reynolds numbers ([Formula: see text]–400), volume fraction of nanofluid ([Formula: see text], 0.01 and 0.02) and stairway aspect ratio ([Formula: see text], 0.2 and 0.3) on the velocity, temperature and local and average Nusselt number profiles are investigated. The results show that by incrementing the Reynolds number and solid volume fraction and decreasing the [Formula: see text]/[Formula: see text] simultaneously, the average Nusselt number increases.

Effect of Nanofluid on Heat Transfer Enhancement for Mixed Convection Flow Over a Corrugated Surface

2020 ◽  
Vol 45 (4) ◽  
pp. 373-383
Author(s):  
Nepal Chandra Roy ◽  
Sadia Siddiqa
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Local Nusselt Number ◽  
Richardson Number ◽  
Thermal Boundary Layer ◽  
Volume Fraction ◽  
Convection Flow ◽  
Mixed Convection Flow

AbstractA mathematical model for mixed convection flow of a nanofluid along a vertical wavy surface has been studied. Numerical results reveal the effects of the volume fraction of nanoparticles, the axial distribution, the Richardson number, and the amplitude/wavelength ratio on the heat transfer of Al2O3-water nanofluid. By increasing the volume fraction of nanoparticles, the local Nusselt number and the thermal boundary layer increases significantly. In case of \mathrm{Ri}=1.0, the inclusion of 2 % and 5 % nanoparticles in the pure fluid augments the local Nusselt number, measured at the axial position 6.0, by 6.6 % and 16.3 % for a flat plate and by 5.9 % and 14.5 %, and 5.4 % and 13.3 % for the wavy surfaces with an amplitude/wavelength ratio of 0.1 and 0.2, respectively. However, when the Richardson number is increased, the local Nusselt number is found to increase but the thermal boundary layer decreases. For small values of the amplitude/wavelength ratio, the two harmonics pattern of the energy field cannot be detected by the local Nusselt number curve, however the isotherms clearly demonstrate this characteristic. The pressure leads to the first harmonic, and the buoyancy, diffusion, and inertia forces produce the second harmonic.

Effects of uniform or non-uniform heating at bottom wall on MHD mixed convection in a porous cavity saturated by nanofluid

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Subramanian Muthukumar ◽  
Selvaraj Sureshkumar ◽  
Arthanari Malleswaran ◽  
Murugan Muthtamilselvan ◽  
Eswari Prem
Keyword(s):  
Magnetic Field ◽  
Heat Transfer ◽  
Transfer Rate ◽  
Hartmann Number ◽  
Volume Fraction ◽  
Solid Volume Fraction ◽  
Darcy Number ◽  
Bottom Wall ◽  
Uniform Heating ◽  
The Magnetic Field

Abstract A numerical investigation on the effects of uniform and non-uniform heating of bottom wall on mixed convective heat transfer in a square porous chamber filled with nanofluid in the appearance of magnetic field is carried out. Uniform or sinusoidal heat source is fixed at the bottom wall. The top wall moves in either positive or negative direction with a constant cold temperature. The vertical sidewalls are thermally insulated. The finite volume approach based on SIMPLE algorithm is followed for solving the governing equations. The different parameters connected with this study are Richardson number (0.01 ≤ Ri ≤ 100), Darcy number (10−4 ≤ Da ≤ 10−1), Hartmann number (0 ≤ Ha ≤ 70), and the solid volume fraction (0.00 ≤ χ ≤ 0.06). The results are presented graphically in the form of isotherms, streamlines, mid-plane velocities, and Nusselt numbers for the various combinations of the considered parameters. It is observed that the overall heat transfer rate is low at Ri = 100 in the positive direction of lid movement, whereas it is low at Ri = 1 in the negative direction. The average Nusselt number is lowered on growing Hartmann number for all considered moving directions of top wall with non-uniform heating. The low permeability, Da = 10−4 keeps the flow pattern same dominating the magnetic field, whereas magnetic field strongly affects the flow pattern dominating the high Darcy number Da = 10−1. The heat transfer rate increases on enhancing the solid volume fraction regardless of the magnetic field.

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