Heat Transfer Of Nanofluid Flow Research Articles

Turbulent heat transfer and nanofluid flow in a protruded ribbed square passage

In this article, turbulent heat transfer of nanofluid flow in square passage with protruded rib shape is numerically and experimentally studied over Reynolds number ranges of 4000–18000. Different nanoparticles (Al2O3, CuO, and ZnO), with different concentration (φ) range of 1–4% and different nanoparticle diameter (dnp) range of 30–45nm are disperse in water (base fluid). Several parameters such as stream wise distance (Xs/dp) range of 1.4–2.6, span wise distance (Ys/dp) range of 1.4–2.6, ratio of protruded height to print diameter (ep/dp) range of 0.83–1.67 also studied to find the consequence on thermal and hydrodynamic characteristics. Simulations were carried out to obtain heat and fluid flow behaviour of smooth and ribbed square channel using commercial CFD software, ANSYS 15.0 (Fluent). Renormalization k-ε model was employed to assess the influence of protruded ribs on turbulent flow and velocity field. The outcome indicates that Al2O3 nanofluid has the highest value of average Nusselt number as compare to other nanofluids. The average Nusselt number increases as the concentration increases and it decreases as nanoparticle diameter increases. The thermal hydrodynamic performance parameter based on equal pumping power, average Nusselt number and average friction factor were found to be highest for Al2O3, φ=0.04, dnp=30nm, Xs/dp=1.8, Ys/dp=1.8 and ep/dp=1.0. The numerical data are compared with the corresponding experimental data. Comparison between CFD and experimental analysis results showed that good agreement as the data fell within ±7.0% error band.

Finite Element Analysis of Unsteady Natural Convective Heat Transfer and Fluid Flow of Nanofluids inside a Tilted Square Enclosure in the Presence of Oriented Magnetic Field

In this paper, the problem of unsteady natural convective heat transfer flow of nanofluids having various sizes of nanoparticles inside an inclined square enclosure in the presence of oriented magnetic field is investigated numerically. The Brownian motion of nanoparticles is taken into consideration in the thermal conductivity model construction. Two opposite walls of the enclosure are insulated and the other two walls are kept at different temperatures. Galerkin weighted residual finite element technique has been employed to solve the governing nonlinear dimensionless equations. In order to ensure the accuracy of the present numerical code, comparisons with previously published works are performed and excellent agreement is obtained. The effects of model parameters such as Rayleigh number, Hartmann number, nanoparticles volume fraction, inclination angle of magnetic field, inclination angle of the geometry, diameter and Brownian motion of the nanoparticles on the fluid flow and heat transfer are investigated. The results indicate that an increment in Rayleigh number and nanoparticle volume fraction increases the heat transfer rate in a significant way, whereas, an increment in Hartmann number decreases the overall heat transfer rate. It is also observed that the heat transfer enhancement strongly depends on the diameter of the nanoparticles as well as the types of the nanofluids. It is observed that the time taken to reach the steady state is controlled by the different model parameters and in particular, it is longer for low Rayleigh number and shorter for high Rayleigh number. A comparison between the two studies of with and without Brownian motion shows that when Brownian motion is considered, the solid volume fraction has more significant effects on the heat transfer rate at all Rayleigh numbers considered in the square cavity. Finally, the distribution of average heat transfer rate for different cavity inclination angle along with various model parameters has been found as almost parabolic shape.

Numerical Investigation Of Nanofluids Flow and Heat Transfer in 90 Elbow With square Cross-Section

In this article, forced convective heat transfer of nanofluid flow in a horizontal tube with a square cross-section and 90-degree elbow under heat flux was investigated in a numerical method. The homogeneous nanofluid of aluminum oxide and water (Al2O3) was used as the working fluid. For the numerical solution of continuity, momentum and energy equations, the finite volume method was used. In this study, the effect of Reynolds number and the solid volume fraction and the impact of the elbow on the flow field and the heat transfer rate and pressure drop was investigated. The results were presented in the form of flow and temperature contours and the Nusselt diagrams, which have a good relation with the experimental results, and showed that by increasing the solid volume fraction and Reynolds number, the heat transfer in the elbow increases. Also the concave surface from inside the tubes had a greater impact on heat transfer than the convex surface.

Numerical investigation of magnetic field effect on mixed convection heat transfer of nanofluid in a channel with sinusoidal walls

In this study, mixed convection heat transfer of nano-fluid flow in vertical channel with sinusoidal walls under magnetic field effect is investigated numerically. The heat transfer and hydrodynamic characteristics have been examined. This study has performed for 500≤Re≤1000, 5×104≤Gr≤1×106 , three amplitude sine wave (0.1, 0.2 and 0.3) and three values of Hartman numbers (0, 5 and 10). Water was utilized as the base fluid and Al2O3 is the considered nano-particle. Flow is assumed two dimensional, laminar, steady and incompressible. As well the thermo-physical properties of nano-fluid are considered constant. The Boussinesq approximation used for calculated the density variations. The average Nusslet number increases by increasing the Grashof number for nano-fluids with different volume fraction. The average Nusselt and Poiseuille number increase as Reynolds number increases. Also, the average Nusselt number and Poiseuille number increases by increasing the Hartman number.

The Effect of Reynolds Number on the Thermal and Hydrodynamic Characteristics of Turbulence Flow of the Nanofluid in the Heat Exchanger

Abstract. Reynolds number is one of the most important parameters in investigation of heat transfer in double tube heat exchangers. In this paper, the effect of this parameter has been investigated on the convective heat transfer coefficient and surface friction coefficient of the wall. Turbulent forced convection heat transfer of nanofluid flow of Al 2 O 3 /water in a double tube heat exchanger with rough tubes in the annular portion was numerically studied. The finite volume method and the second-order upstream difference scheme were used for the discretization of the governing equations. The volume fraction and mean diameter of nanoparticles were assumed to be 4% and 32 nm, respectively. After reviewing the results, it was observed that the convective heat transfer coefficient in the outer and inner walls of heat exchanger increases with the increase of the Reynolds number. The wall surface friction coefficient, which decreases by increasing Reynolds number, is another examined parameter.

Convective heat transfer of nanofluid flow through conduits with different cross-sectional shapes

This study investigates the laminar forced convective heat transfer of TiO2/water nanofluids through conduits with different cross sections, experimentally. The effects of different parameters, such as cross-sectional shape, Reynolds number, and concentration of nanoparticles, on the enhanced heat transfer are examined by designing and assembling an experimental apparatus. Results show that adding a small amount of nanoparticles to the base fluid improves heat transfer behavior in conduits. A conduit with a circular cross section performs better than conduits with square and triangular cross sections. However, conduits with square and triangular cross sections exhibit more relative enhancements than a conduit with a circular cross section.

Mixed Convective Heat and Mass Transfer Flow of Nanofluids in Concentric Annulus

This paper studies the non-Darcy natural convective heat transfer flow of nanofluid flow through a porous medium in a co-axial cylindrical duct where the boundaries are maintained at constant temperature and concentration. The flow in the porous material is given by a linear Brinkman-Forchheimer-extended Darcy equation. The Boussinesq approximation is invoked so that the effect of density variation is combined to the buoyancy forces. The equations of momentum, energy and diffusion are coupled and linear. Galerkin finite element analysis is employed with quadratic polynomial approximations. At different axial positions, analysis is conducted for the behaviour of velocity, temperature and concentration.

Application of different CFD multiphase models to investigate effects of baffles and nanoparticles on heat transfer enhancement

In this work, the effect of baffles in a pipe on heat transfer enhancement was studied using computational fluid dynamics (CFD) in the presence of Al2O3 nanoparticles which are dispersed into water. Fluid flow through the horizontal tube with uniform heat flux was simulated numerically and three dimensional governing partial differential equations were solved. To find an accurate model for CFD simulations, the results obtained by the single phase were compared with those obtained by three different multiphase models including Eulerian, mixture and volume of fluid (VOF) at Reynolds numbers in range of 600 to 3000, and two different nanoparticle concentrations (1% and 1.6%). It was found that multiphase models could better predict the heat transfer in nanofluids. The effect of baffles on heat transfer of nanofluid flow was also investigated through a baffled geometry. The numerical results show that at Reynolds numbers in the range of 600 to 2100, the heat transfer of nanofluid flowing in the geometry without baffle is greater than that of water flowing through a tube with baffle, whereas the difference between these effects (nanofluid and baffle) decreases with increasing the Reynolds number. At higher Reynolds numbers (2100–3000) the baffle has a greater effect on heat transfer enhancement than the nanofluid.

An investigation on the hydrodynamic and heat transfer of nanofluid flow, with non-Newtonian base fluid, in micromixers

Abstract In this study heat transfer and fluid flow of a non-Newtonian nanofluid in two dimensional parallel plate microchannel without and with micromixers have been investigated for nanoparticle volume fractions of ϕ = 0 , ϕ = 0.04 and nanofluid Reynolds numbers of Renf = 5, 20, 50. The nanofluid is composed of CuO nanoparticles and the non-Newtonian base fluid of 0.5 wt% aqueous solution of Carboxymethyl Cellulose (CMC). Two baffles on the bottom and top walls work as micromixer. A single-phase finite difference FORTRAN code using Projection method has been written to solve the governing equations with constant wall temperature boundary condition. A new correlation for thermal conductivity of this nanofluid has been introduced and also the effect of various parameters such as the baffles distance, height and order of arranging has been studied. Results show that the presence of baffles and also increasing the Re number and nanoparticle volume fraction increases the local and average heat transfer and friction coefficients of non-Newtonian nanofluid. Also, the effect of nanoparticle volume fraction on heat transfer coefficient is more than friction coefficient in most of the cases. It was found that the main mechanism of enhancing heat transfer or mixing is the recirculation zones that are created behind the baffles. The size of these zones increases with Re number and baffle height. The fluid pushing toward the wall by the opposed wall baffle and reattaching of separated flow are the locations of local maximum heat transfer and friction coefficients.

Nanofluid flow and heat transfer in an asymmetric porous channel with expanding or contracting wall

In this study, the least square method (LSM) and the Galerkin method (GM) are used to simulate flow and heat transfer of nanofluid flow between two parallel plates. One of the plates is externally heated, and the other plate, in which coolant fluid is injected through it, expands or contracts with time. The fluid in the channel is water containing different nanoparticles (Cu, Ag and Al2O3). The effective thermal conductivity and viscosity of the nanofluid are calculated by the Maxwell–Garnetts (MG) and Brinkman models, respectively. The effects of the nanoparticle volume fraction, Reynolds number, expansion ratio and power law index on flow and heat transfer are investigated. The results show that the Nusselt number increases with an increase of the nanoparticle volume fraction and Reynolds number. Also it can be found that in order to reach the maximum Nusselt number, copper should be used as a nanoparticle.

Flow and Heat Transfer Analysis of a Nanofluid along a Vertical Flat Plate in Presence of Thermal Radiation Using Similarity Transformation Method.

In the present work effects of viscous dissipation and thermal radiationon convective heat transfer in nanofluid flow over a stretching sheet under the influence of applied magnetic field was analyzed. Three types of nanofluids, namely Cu-water, Al2O3-water and TiO2-water were considered. A similarity transformation was used to obtain a system of non-linear ordinary differential equation which was then solved numerically using MATLAB bvp4c function. Numerical results were obtained for Local Nusselt number as well as velocity and temperature profiles for selected values of parameters such as nanoparticle volume fraction Φ, Eckert number EC, Magnetic parameter M and thermal radiation parameter NR for fixed value of Prandtl number Pr=6.2(corresponding to water).It was shown that the Cu-water nanofluid exhibits higher heat transfer rate as compared to Al2O3-water and TiO2-water.

Numerical solutions to heat transfer of nanofluid flow over stretching sheet subjected to variations of nanoparticle volume fraction and wall temperature

The numerical analysis of heat transfer of laminar nanofluid flow over a flat stretching sheet is presented. Two sets of boundary conditions (BCs) are analyzed, i.e., a constant (Case 1) and a linear streamwise variation of nanoparticle volume fraction and wall temperature (Case 2). The governing equations and BCs are reduced to a set of nonlinear ordinary differential equations (ODEs) and the corresponding BCs, respectively. The dependencies of solutions on Prandtl number Pr, Lewis number Le, Brownian motion number Nb, and thermophoresis number Nt are studied in detail. The results show that the reduced Nusselt number and the reduced Sherwood number increase for the BCs of Case 2 compared with Case 1. The increases of Nb, Nt, and Le numbers cause a decrease of the reduced Nusselt number, while the reduced Sherwood number increases with the increase of Nb and Le numbers. For low Prandtl numbers, an increase of Nt number can cause to decrease in the reduced Sherwood number, while it increases for high Prandtl numbers.

Convective Heat Transfer of Oil based Nanofluid Flow inside a Circular Tube

An experimental investigation was carried out to study convective heat transfer of nanofluid flow inside an inclined copper tube under uniform heat flux condition. Required data are acquired for laminar and hydrodynamically fully developed flow inside a round tube. The stable CuO-base oil nanofluid with different nanoparticle weight fractions of 0.5%, 1% and 2% was produced by means of ultrasonic device in two steps method. In this study, the effect of different parameters such as tube inclination, nanofluid weight fraction and Reynolds number on heat transfer coefficient was considered. Results show that the heat transfer coefficient of nanofluid with different weight fractions increases with the increasing Reynolds number inside horizontal and inclined round tubes. Also, nanofluid flow inside the inclined tube at 30 degrees exhibit the most heat transfer enhancement amongst other tube inclinations at same Reynolds number.

Combined Convection Heat Transfer of Nanofluids Flow over Forward Facing Step in a Channel Having a Blockage

Numerical simulations of two dimensional laminar combined convection flows using nanofluids over forward facing step with a blockage are analyzed. The continuity, momentum and energy equations are solved using finite volume method (FVM) and the SIMPLE algorithm scheme is applied to examine the effect of the blockage on the heat transfer characteristics. In this project, several parameters such as different types of nanofluids (Al2O3, SiO2, CuO and ZnO), different volume fraction in the range of 1% - 4%, different nanoparticles diameter in the range of 25nm-80nm were used. Effects of different shapes of blockage (Circular, Square and Triangular) were studied. The numerical results indicated that SiO2nanofluid has the highest Nusselt number. The Nusselt number increased as the volume fraction and Reynolds number increase, while it decreases as the nanoparticles diameter increases. Circular blockage produced higher results compared to triangular and square one.

Numerical analysis of laminar flow heat transfer of nanofluids in a flattened tube

In this work, a three-dimensional analysis is used to study the heat transfer performance of nanofluid flows through a flattened tube in a laminar flow regime and constant heat flux boundary condition. CuO nanoparticles dispersed in ethylene glycol with particle volume concentrations ranging between 0 and 4vol.% were used as working fluids for simulating the heat transfer of nanofluids. Effects of some important parameters such as nanoparticle volume concentration, particles Brownian motions, and Reynolds number on heat transfer coefficient have been determined and discussed in details. Results have shown that the heat transfer coefficient increases with increase in the volume concentration level of the nanoparticle, Brownian motion and the Reynolds number. Numerical results have been validated by comparison of simulations with those available in the literature.

Numerical study of hydrodynamic and heat transfer of nanofluid flow in microchannels containing micromixer

In this study heat transfer and fluid flow of Al2O3/water nanofluid in two dimensional parallel plate microchannel without and with micromixers have been investigated for nanoparticle volume fractions of ϕ=0,ϕ=4% and base fluid Reynolds numbers of Ref=5, 20, 50. One baffle on the bottom wall and another on the top wall work as a micromixer and heat transfer enhancement device. A single-phase finite difference FORTRAN code using Projection method has been written to solve governing equations with constant wall temperature boundary condition. The effect of various parameters such as nanoparticle volume fraction, base fluid Reynolds number, baffle distance, height and order of arrangement have been studied. Results showed that the presence of baffles and also increasing the Re number and nanoparticle volume fraction increase the local and averaged heat transfer and friction coefficients. Also, the effect of nanoparticle volume fraction on heat transfer coefficient is more than the friction coefficient in most of the cases. It was found that the main mechanism of enhancing heat transfer or mixing is the recirculation zones that are created behind the baffles. The size of these zones increases with Reynolds number and baffle height. The fluid pushing toward the wall by the opposed wall baffle and reattaching of separated flow are the locations of local maximum heat transfer and friction coefficients.

Heat transfer of Cu-water nanofluid flow between parallel plates

Heat transfer of a nanofluid flow which is squeezed between parallel plates is investigated analytically using homotopy perturbation method (HPM). Copper as nanoparticle with water as its base fluid has been considered. The effective thermal conductivity and viscosity of nanofluid are calculated by the Maxwell–Garnetts (MG) and Brinkman models, respectively. This investigation is compared with other numerical methods and they were found to be in excellent agreement. The effects of the squeeze number, the nanofluid volume fraction and Eckert number and δ on Nusselt number are investigated. The results show that Nusselt number has direct relationship with nanoparticle volume fraction, δ, the squeeze number and Eckert number when two plates are separated but it has reverse relationship with the squeeze number when two plates are squeezed.

Mixed Convective Heat Transfer Flow of Nanofluid past a Permeable Vertical Flat Plate with Magnetic Effects: A Finite Element Study

Steady, two dimensional mixed convection laminar boundary layer flow of incompressible nanofluid along a permeable vertical semi-infinite flat plate with magnetic field effects has been investigated numerically. The resulting govering equations (obtained from the boussinesq) with associated boundary conditions are solved, using a robust, extensively validated, Galerkin Finite Element Method for different types of spherical shaped metal oxide nanoparticles with two different ratios of the nanolayer thickness to the original particle radius (0.02 or 0.1). The effects of the parameters governing the problems are discussed and shown graphically. The present study is of immediate interest in next-generation solar film collectors, heat exchangers technology, material processing exploiting vertical surfaces and all those processes which are highly affected with heat transfer.

Turbulent Convective Heat Transfer of Nanofluids

In this paper, the convective heat transfer of nanofluid flow in a turbulent boundary layer of a flat plate is simulated numerically. Turbulent flow equations with RNG K-ε turbulence model are solved employing Fluent software. Furthermore, the effects of nanoparticle concentration on the heat transfer characteristics are studied. The results show that nanofluids enhance the heat transfer coefficient dramatically with little change in pressure drop.