Solid Volume Fraction Of Nanofluid Research Articles

Numerical investigation on turbulent flow, heat transfer, and entropy generation of water-based magnetic nanofluid flow in a tube with hemisphere porous under a uniform magnetic field

This paper numerically investigates the forced convection and entropy generation of Fe3O4 water nanofluid inside a cylindrical tube with porous hemisphere media. The flow regime is turbulent under a uniform magnetic field and constant heat flux, and to solve the equations, the finite volume method is applied. The combination of nanofluid, magnetic field and porous hemisphere media on the flow and heat transfer in a tube is the main novelty. The effects of different parameters such as Reynolds number (10,000 to 25,000), porosity (ε = 20%, 40%, and 80%.), the solid volume fraction of nanofluid (0.5 vol%, 1 vol%, and 2.5 vol%), friction factor and entropy generation of Ferro-nanofluid in the tube are investigated. The Nusselt number, entropy generation, and friction factor have been discussed and analyzed detailly. It is found that as the Reynolds number enhances, the effect of inertial forces becomes more dominant. Furthermore, by increasing the porosity to 0.8, the Nusselt number decreases to a minimum value. Heat transfer enhancement by increasing Hartmann's number is less effective than adding nanoparticles. A more significant Hartmann number and larger nanoparticle volume fraction lead to more extensive performance evaluation criteria. It is also found that adding a magnetic field increases the friction factor. Adding nanoparticles to the pure water decreases entropy generation by heat transfer per unit volume.

Hydro-thermal performance on the two phase nanofluid convection heat transfer using the LBM-FD method

This paper is dedicated to the investigation of nanofluid natural convection inside a 2D cavity with various kinds of cold walls. To consider the different nanoparticle distribution in the cavity, Buongiorno’s two-phase model is used. The equations are solved by the homemade hybrid Lattice Boltzmann-Finite Difference (LBM-FD) code. It found that although the nanoparticle concentration is almost uniform inside the cavity, the apparent difference can be observed around the walls and edges of the vortices. The nanoparticles have higher concentrations around the cold wall and the lower concentration adjacent to the hot wall. For all cases, the local and average Nusselt number increases by increasing the solid volume fraction of nanofluid. The configuration of cold walls affects the flow pattern and distribution of temperature significantly. By applying the combination of right-angle and inclined walls, the best heat transfer performance for the present system.

Numerical analysis on heat transfer enhancement of Al2O3 nanofluid in the flattened conically coiled tubes

AbstractEnhancement in the heat transfer of the working fluid flowing inside the tube is achieved by modification of tubes and changing the direction of fluid flow. For this purpose, the straight tube can be changed into a conical coil tube, thereby, heat transfer is increased due to the centrifugal effect caused by the curvature of the tube. Furthermore, the circular cross‐section of the tube is modified into an oblong shape for more heat transfer enhancement. In this study, the numerical heat transfer and pressure drop characteristics of Al2O3–water nanofluids in the flattened conically coiled tube are studied. The effect of the aspect ratio, cone angle, coil pitch, and solid volume fraction of nanofluids on heat transfer and pressure drop are examined. It is found that the heat transfer coefficient and pressure drop increase with the rise of aspect ratio, Reynolds number, and solid volume fraction of nanofluid, while it decreases with the increment of cone angles and coil pitches of conical coil tube. Furthermore, the effect of aspect ratio on the heat transfer enhancement factor, pressure drop ratio, and thermal performance index for Al2O3–water nanofluid are presented.

Dynamics of flow in trapezoidal enclosure having a heated inner circular cylinder containing Casson nanofluid

In this article, simulation of the two-dimensional flow of natural convective transport in the partially heated lid-driven trapezoidal cavity was presented with finite element method using software called COMSOL Multiphysics®. Inside the cavity a stationary circular cylinder with a high temperature has been placed. The enclosure was filled with Cu−H2O nanofluid. The flow is assumed to be two-dimensional and has been examined when the parallel sides of the cavity are adiabatic. The temperature on non-parallel sides is assumed to be cold. The top wall of the cavity moves with a velocity η0 in the positive x-direction, and the considered fluid is a non-Newtonian Casson nanofluid. Computation has been done for the Rayleigh numbers 104,105 and 106, the Casson fluid parameter 0.1,0.5, and 1, and the nanofluid solid volume fraction 0 and 0.15. Prandtl number is kept fixed at Pr=6.2 throughout the calculations. Isotherms and streamlines were sketched to visualize the distribution of temperature and flow field in the cavity. The impacts of governing parameters such as Casson parameter, solid volume fraction, Rayleigh number on heat transfer, and flow field were numerically computed and analyzed. Average Nusselt number also exhibited in a tabular and graphical form to signify the rate of heat transfer in the cavity. It was found that the centers of the two larger circulations were observed to migrate towards the top wall of the cavity as the Rayleigh number increased. Furthermore, heat transport was enhanced as the concentration of nanoparticles increased.

Nanofluid MHD combined convection in a porous chamber with various thermal sources

The impact of various sizes and positions of the heater in a nanofluid-saturated porous lid-driven chamber with a uniform Lorentz force is studied numerically. In this investigation, three different lengths of heater with higher temperature at six different locations along the left sidewall of the cavity are considered. Lower temperature is maintained at the right sidewall. Further, lower and moving upper horizontal walls and the rest of left wall are supposed to be thermally insulated. Based on the finite volume method, the system of nondimensional governing equations is solved by SIMPLE algorithm. The results conclude that the average Nusselt number is reduced with the enhancement of Richardson and Hartmann numbers. When the heater length is reduced from bottom to top, the heat transfer rate is increased for all the considered Richardson, Darcy and Hartmann numbers. In the lower permeability of the porous medium, the effect of solid volume fraction of nanofluid is more vulnerable. In the case of nanofluid, the steady state is reached quickly than the pure fluid.

Influence of the Lorentz force on the ventilation cavity having a centrally placed heated baffle filled with the Cu − Al2O3 − H2O hybrid nanofluid

The objective of this paper is to examine the natural convection of the ventilation cavity filled with the Cu − Al2O3 − H2O hybrid nanofluid influenced by the effects of the magnetic field. The vertical heated baffle is fixed at the center of the ventilation cavity. The cavity walls are insulted. The opening ports are positioned diagonally at the vertical walls. The finite difference method is employed to solve the governing Navier stokes equations numerically. The computations are done with the Rayleigh number (104 − 106), Reynolds number (20,200,400), Hartmann number (0,20,50), nanoparticle solid volume fraction (0.0,0.03,0.06) and the width of the openings (0.10,0.20,0.30). The computed results are explained in the form of streamlines, isotherms and Nusselt numbers. The results show that the augmentation percentage of the hybrid nanofluid solid volume fraction enhances the heat transfer rate inside the cavity. Although, its performance depends on the other parameters too.

Nanofluid natural convection in a corrugated solar power plant using the hybrid LBM-TVD method

In the present study, the Buongiorno’s two-phase method was implemented to investigate the nanofluid heat transfer in a triangle solar collector with corrugated bottom wall. A novel hybrid Lattice Boltzmann method (LBM) with using Total Variation Diminishing (TVD) method was developed. The effects of important physical parameters such as Rayleigh number, volume fraction of nanoparticle and different types of corrugated walls on the fluid flow pattern, nanoparticles distribution and temperature fields are studied in details. Three cases were considered for the numerical simulation. It was found that the Case 2 has the largest heat transfer rate. Based on the obtained results, the center region (inside the enclosure) has nearly uniform particle distribution. However, the region near cold and hot wall have higher and lower nanoparticle concentration, respectively. With increasing nanofluid concentration (φ) while it is smaller than a critical value, the heat transfer enhancement’s ratio increases. In addition, when solid volume fraction of nanofluid is larger than the critical value, the heat transfer efficiency will be decreased by increasing the φ.

RETRACTED: Free convection and entropy generation in a nanofluid-filled star-ellipse annulus using lattice Boltzmann method supported by immersed boundary method

Abstract In the present work, it is aimed to investigate the natural convection numerically. The nanofluid flow and heat transfer in a star-ellipse annulus are investigated. The lattice Boltzmann method is utilized to carry out the numerical simulations. In addition, the Immersed Boundary Method (IBM) is used to treat the Dirichlet and Neumann conditions. The annulus consists a star-shaped cylinder and ellipse cylinder and filled with Cu-water nanofluid. The second law analysis is used to provide local maps of fluid friction irreversibility and heat transfer irreversibility and volumetric entropy generation. The influences of some main parameters including Rayleigh number in a range of 103 to 106, solid volume fraction of nanofluid in range of 0 to 0.03 and eccentricity -0.4

Multiple-relaxation-time lattice Boltzmann model for simulation of free convection in axisymmetric nanofluid-filled annulus-experimental and numerical observations

Purpose The MRT lattice Boltzmann simulation of natural convection in a confined environment is carried out. The flow and heat transfer during natural convection in a symmetrical annulus are studied. Design/methodology/approach The cavity is filled with TiO2-water nanofluid, and the thermal conductivity and dynamic viscosity of nanofluid are measured experimentally. The experimental data are utilized in the numerical simulations. The nanofluids are prepared at four different nanoparticle concentrations φ = 0, 0.1, 0.3 and 0.5. It is notable that the radial coordinate is used into the temperature distribution function. As a result, only one source term is required for the present lattice Boltzmann model. On the other hand, the macro cylindrical energy equation is exactly recovered using Chapman–Enskog analysis. Findings Influence of some main parameters including Rayleigh number in range of 103 to 106, solid volume fraction of nanofluid in range of 0 to 0.5 and four different aspect ratios on the the nanofluid flow (i.e. streamlines), heat transfer (i.e. temperature distribution and average Nusselt number) and entropy generation (i.e. total entropy generation and Bejan number) are presented, quantitatively and graphically. It is found that adding TiO2 nanoparticles to the base fluid has considerable positive effect on the heat transfer performance and entropy generation. In addition, the configuration of the annulus can be good controlling parameter on the heat transfer rate during natural convection. Originality/value The originality of this work is using of a modern numerical method to simulate the free convection and conducting experimental observations to calculate the thermo-physical properties of nanofluid. In addition, the numerical and experimental works are combined to provide accurate results.

Numerical simulation of natural convection heat transfer of copper-water nanofluid in a vertical cylindrical annulus with heat sources

In this work, natural convection of Cu—water nanofluid in a vertical cylindrical annulus enclosure with two discrete heat sources of different lengths is numerically investigated using the finite volume method with SIMPLER algorithm. The adiabatic unheated portions and the discrete heat sources are mounted at the inner wall. The top and bottom walls are thermally isolated, while the outer wall is maintained at a lower temperature. The effects of nanofluid solid volume fraction on hydrodynamic and thermal characteristics such as average and local Nusselt numbers, streamlines, and isotherm patterns for the Rayleigh number ranges from 103 to 106 and solid volume fraction ranges from 0 to 0.1 are presented. The heat transfer and temperature of heaters depend on the Rayleigh number, the solid volume fraction of nanoparticles, and the length of heaters.

Impacts of magnetic field and non-homogeneous nanofluid model on convective heat transfer and entropy generation in a cavity with heated trapezoidal body

A numerical study is made on the entropy generation and magnetohydrodynamics natural convection of $$\hbox {Al}_{2}\hbox {O}_3$$ -water non-homogeneous nanofluid inside a square enclosure equipped with a heated trapezoidal body. The Galerkin weighted residual finite element method is applied to solve the dimensionless governing equations within the utilized computational domain along with the algorithm of Newton–Raphson iteration that is used for simplifying the nonlinear terms in the equations. The characteristics of fluid flow fields, temperature distributions and entropy generation are studied for an enormous range of the Rayleigh number $$(10^{3}\le Ra \le 10^{6})$$ , volume fraction of nanoparticles ( $$0\le \phi \le 0.04$$ ), Hartmann number $$(0\le Ha \le 50)$$ , thermal conductivity of the trapezoidal solid body ( $$k_{\mathrm{w}}=0.5$$ , 0.76, 1.95, 7 and 16) and the height of the trapezoidal solid body ( $$0.15 \le D \le 0.45$$ ). It is shown that the streamlines pattern is more sensitive to the increase in the Hartmann number in comparison with the augmentation of the volume fraction of nanoparticles. Also, for a more thermodynamically optimized system, the higher Hartmann number at a higher solid volume fraction of nanofluid is recommended as they show less entropy generation.

Examining of nanofluid natural convection heat transfer in a [formula omitted]-shaped enclosure including a rectangular hot obstacle using the lattice Boltzmann method

The present investigation is set to evaluate the nanofluid thermogravitational convection within a Γ-shaped enclosure that consists of a local heater by the lattice Boltzmann method (LBM). In this study the Rayleigh number (103–106), cavity’s aspect ratio (0.2–0.6), nanofluid solid volume fraction (0–0.05), height and location of the heater on the liquid circulation and heat transfer parameters examined with respect to the Γ-shaped enclosure. The study is innovated in nature as it combines the nanofluid and the hot obstacle within the same Γ-shaped enclosure. The results of the conducted analyses indicate that the mean Nusselt number would increase as the Rayleigh number and nanoparticles concentration increased. This resulted in a reduction in the enclosure aspect ratio and increment in the obstacle’s height. The thermal transmission rate is highly affected by the obstacle’s position. Also, it is found that, when the heater is situated on the left border, the mean Nusselt number would be maximized.

Lattice Boltzmann method for nanofluid flow and heat transfer in a curve-ended T-shaped heat exchanger

PurposeThe study aims to study the nanofluid flow and heat transfer in a T-shaped heat exchanger. For the numerical simulations, the lattice Boltzmann method is used.Design/methodology/approachThe end of each branch of the heat exchanger is considered a curve wall that requires special thermal and physical boundary conditions. To improve the thermal performance of the heat exchanger, the CuO–water nanofluid, which has better heat transfer performance with respect to pure water, is used. The dynamic viscosity of nanofluid is estimated by means of KKL model. Several active fins and solid bodies are implanted within the heat exchanger with different thermal arrangements.FindingsIn the present work, different approaches such as heatline visualization, local and total entropy generation analysis, local and total Nusselt variation are used to detect the impact of different considered parameters such as Rayleigh number (103< Ra < 106), solid volume fraction of nanofluid (φ= 0,0.01,0.02,0.03 and 0.04vol.per cent) and thermal arrangements of internal bodies (Case A, Case B, Case C and Case D) on the fluid flow and heat transfer performance.Originality/valueThe originality of this work is to analyze the two-dimensional natural convection and entropy generation using lattice Boltzmann method.

Entropy generation analysis of mixed convection with considering magnetohydrodynamic effects in an open C-shaped cavity

This paper studies the effect of a constant magnetic field on the mixed convection heat transfer and the entropy generation of CuO-water nanofluid in an open C-shaped cavity with a numerical method. The governing equations are presented by control volume method and they are solved simultaneously by the SIMPLE algorithm. This study examines the effect of the Hartman number, aspect ratio, Reynolds number, and Richardson number parameters for different solid volume fraction of nanoparticles. Also Nusselt number, entropy generation, thermal performance criteria and coefficient of performance is studied in this research. The calculated parameters are the Hartman number, aspect ratio, Reynolds number, Richardson number, nanofluid solid volume fraction, Nusselt number, and coefficient of performance. The results show that increasing the Hartmann number reduces the entropy generation. However, the thermal performance increases. Increasing the aspect ratio raises heat transfer and thermal performance. The effects of nanofluid solid volume fraction on mixed convection heat transfer and entropy generation are also investigated and discussed.

Hydrothermal investigation of a stratified system in enclosure with jagged surface for application in lead-acid batteries

PurposeThe purpose of this paper is to investigate the three-dimensional natural convection and entropy generation in a cuboid enclosure filled with two immiscible fluids of nanofluid and air.Design/methodology/approachOne surface of the enclosure is jagged and another one is smooth. The finite volume approach is applied for computation. There are two partially side heaters. Furthermore, the Navier–Stokes equations and entropy generation formulation are solved in the 3D form.FindingsThe effects of different governing parameters, such as the jagged surface (JR=0, 0.02, 0.04, 0.08, 0.12 and 0.16), Rayleigh number (103⩽Ra⩽106) and solid volume fraction of nanofluid (φ=1, 1.5, 2 vol%), on the fluid flow, temperature field, Nusselt number, volumetric entropy generation and Bejan number are presented, comprehensively. The results indicate that the average Nusselt number increases with the increase in the Rayleigh number and solid volume fraction of nanofluid. Moreover, the flow structure is significantly affected by the jagged surface.Originality/valueThe originality of this work is to analyze the natural-convection fluid flow and heat transfer under the influence of jagged surfaces of electrodes in high-current lead–acid batteries.

Numerical investigation of nanofluids heat transfer in a channel consisting of rectangular cavities by lattice Boltzmann method

In this study, lattice Boltzmann method (LBM) simulation is performed to investigate laminar forced convection of nanofluids in a horizontal parallel-plate channel with three rectangular cavities. Two cavities are considered as located on the top wall of the channel and one on the bottom wall. The effects of the Reynolds number (100–400), the cavity aspect ratio (AR = 0.25, 0.5), the various distances of the cavities from each other ([Formula: see text]) at different solid volume fractions of nanofluids ([Formula: see text]) on the velocity and the temperature profiles of the nanofluids are studied. In addition, the flow patterns, i.e. the deflection and re-circulation zone inside the cavities, and the local and averaged Nusselt numbers on the channel walls are calculated. The results obtained are used to ascertain the validity of the written numerical code, which points to the excellent agreement across the results. The results show that, as the solid volume fraction of nanofluids is enhanced, the transfer of heat to working fluids increases significantly. Further, the results show that the maximum value of the averaged Nusselt number in the channel is obtained at [Formula: see text] for AR = 0.5 and [Formula: see text] for AR = 0.25. The interval [0.1224, 0.1304] is the best position for the second cavity. It is concluded that the results of this paper are very useful for designing optimized heat exchangers.

Proposing a new experimental correlation for thermal conductivity of nanofluids containing of functionalized multiwalled carbon nanotubes suspended in a binary base fluid

In this study, thermal conductivity of the nanofluid obtained by suspension of functionalized multi-walled carbon nanotubes (FMWCNTs) was experimentally assessed in the base fluid of water (80%) and ethylene glycol (20%). The nanofluid was tested at solid volume fractions from 0.025% to 0.8% and temperatures from 25 °C to 50 °C. The results showed that thermal conductivity has a direct relationship with solid volume fraction and temperature of the nanofluid. In the best case, it enhanced by 27.3% compared to the base fluid. Experimental results showed a sharp increase in thermal conductivity of nanofluid at lower solid volume fractions compared to the base fluid. Also, results were compared with the results of mathematical models. Accordingly, based on the experimental data, a correlation is presented as a function of temperature and solid volume fraction of nanofluids. The results of this study were compared with other studies in which carbon nanotubes were used as nanoparticles and water, ethylene glycol or a mixture of water and ethylene glycol was used as the base fluid. Comparison results showed that the quality of the nanofluid, solid volume fractions and percent of water and ethylene glycol as the base fluid, noticeably affect the thermal conductivity of nanofluid.

Lattice Boltzmann simulation for hydrothermal analysis of free convection within dumbbell-shaped heat exchanger

The lattice Boltzmann simulation of nanofluid flow and heat transfer during natural convection within a dumbbell-shaped heat exchanger is carried out. The heat exchanger is filled with CuO–water. The KKL model is employed to predict the thermo-physical properties of nanofluid. In order to perform a comprehensive hydrothermal investigation, different post-processing approaches such as heatline visualization, total entropy generation, local entropy generation based on local fluid friction irreversibility and heat transfer irreversibility, average and local Nusselt variation are employed. In the present investigation, it is tried to present the impact of different influential parameters like Rayleigh number, solid volume fraction of nanofluid and thermal arrangement of internal fins-bodies on the fluid flow, heat transfer rate and entropy generation.

MHD flow with heat and mass transfer of Williamson nanofluid over stretching sheet through porous medium

Two-dimensional hydromagnetic flow of an incompressible Williamson nanofluid over a stretching sheet in a porous media is examined during this work. Convective heat and mass transfer in the presence of Dufour, Soret, radiation absorption, heat generation, viscous dissipation, chemical reaction, Brownain motion and thermophoresis effects are taken in consideration. The system of partial differential equations which describe the momentum, energy and nanofluid solid volume fraction equations of the fluid is transformed to an ordinary differential equations by using the suitable transformations. Then these equations have been solved numerically using Runge–Kutta method of order four with shooting technique. The effects of various physical parameters on dimensionless velocity, temperature, nanoparticle volume fraction, as well as the skin friction, local Nusselt and local Sherwood numbers are analyzed and presented graphically.

Volume of fluid model to simulate the nanofluid flow and entropy generation in a single slope solar still

This paper proposes volume of fluid (VOF) model to investigate the potential of Al2O3-water nanofluid to improve the productivity of a single slope solar still. Accordingly, VOF model is utilized to simulate the evaporation and condensation phenomena in the solar still. An entropy generation analysis is used to evaluate the system from the second law of thermodynamics viewpoint. The effects of solid volume fraction of nanofluid on the productivity and entropy generation in the solar still have been examined. The numerical results are compared with the experimental data available in the literature to benchmark the accuracy of VOF model. The numerical results showed that the productivity of solar still increases with an increase in the solid volume fraction of nanoparticles. The productivity increases about 25% as the solid volume fraction increases in the range of 0%–5%. There is about 18% enhancement in the average Nusselt number as the solid volume fraction increases in the range of 0%–5%. Moreover, the maximum values of viscous and thermal entropy generations are happened at the regions around the bottom and top surfaces of the solar still. Both types of entropy generation increase by increasing the solid volume fraction of nanoparticles. The viscous and thermal entropy generations increase about 95% and 25%, respectively as the solid volume fraction increases in the range of 0%–5%.