Forced Convection Of Nanofluid Flow Research Articles

Study of Bejan number and entropy generation for mixed convection of nanofluid flow inside a chamber under an inclined magnetic field

Examination of the efficiency and losses in heat exchange devices is pivotal. Therefore, the entropy generation (EYG) and Bejan number (Be) of mixed convective heat transfer of nanofluid flow in a rectangular cavity (RCY) are evaluated in this study. Five baffles are placed at the lower hot wall of the RCY. The cold upper wall moves and causes forced convection flow of nanofluid. The magnetic field (MFD) at different angles affects the nanofluid when the Hartmann number (Ha) changes from 10 to 40. The length of stepped baffles is changed, and the values of frictional EYG, thermal EYG, and total EYG are estimated. The simulations are done using the LBM and an in-house code. The results demonstrate that the improvement in Ha decreases the amount of frictional EYG, thermal EYG, total EYG, and Be. The total EYG and Be also increase as the MFD angle is increased. The increment in the Richardson number (Ri) reduces the frictional EYG and total EYG (61.8 %) and increases the value of thermal EYG. Enhancing the length of the baffles intensifies the amount of Be and total EYG (3.4 %) and thermal EYG, but decreases the frictional EYG.

Analysis of forced convective nanofluid flow through a wavy channel with linearly varying amplitude at the entrance

PurposeThe purpose of this paper is to analyze the heat and momentum transfer for steady two-dimensional incompressible nanofluid flow through a wavy channel with linearly varying amplitude in the entrance region.Design/methodology/approachThe mass, momentum and energy conservation equations for laminar flow of Cu-water nanofluids are computationally solved using the finite element method. A parametric study is carried out by varying the dimensionless length of the channel section with varying amplitude (EL), Reynolds number (Re) and nanoparticle volume fraction (Φ) in the ranges 0 ≤ EL ≤ 25.5, 105 ≤ Re ≤ 900 and 0 ≤ Φ ≤ 0.04.FindingsA higher heat transfer rate is seen in the wavy channel compared to a plane channel beyond a critical value of Re (Recrit) whose value varies with EL; moreover, the overall heat transfer decreases with EL. The heat transfer rate increases with phi for all EL values investigated. The combined effects of the increase in the overall heat transfer and the associated pressure drop in the wavy channel compared to the parallel plate channel are presented as performance factor (PF) against EL. For the highest value of EL (= 25.5), PF monotonically decreases with Re. For smaller values of EL (= 5.5 and 11.5) and also for EL = 0, PF decreases with Re in the lower and the higher Re regimes, while it increases in the intermediate Re regime. In all cases, PF is higher for φ = 0.04 than for the base fluid. The sensitivity of the average Nusselt number to nanoparticle volume fraction follows a non-monotonic trend with the change in Re, φ and EL.Practical implicationsThis study finds relevance in several applications such as solar collectors, heat exchangers and heat sinks.Originality/valueTo the best of the authors’ knowledge, the analysis of forced convection flow of nanofluid through a wavy channel with linearly varying amplitude is reported for the first time in the literature.

Analysis of the forced convection of two-phase Ferro-nanofluid flow in a completely porous microchannel containing rotating cylinders

In the present work, the forced convection of nanofluid flow in a microchannel containing rotating cylinders is investigated in different geometries. The heat flux applied to the microchannel wall is 10,000 W m−2. The effects of Reynolds number, the volume fraction of nanoparticles, and the porosity percentage of the porous medium are investigated on the flow fields, temperature, and heat transfer rate. Reynolds number values vary from Re = 250–1000, non-dimensional rotational velocities 1 and 2, respectively, and volume fraction of nanoparticles 0–2%. The results show that increasing the velocity of rotating cylinders increases the heat transfer; also, increasing the Reynolds number and volume fraction of nanoparticles increases the heat transfer, pressure drop, and Cf,ave. By comparing the porosity percentages with each other, it is concluded that due to the greater contact of the nanofluid with the porous medium and the creation of higher velocity gradients, the porosity percentage is 45% and the values of are 90% higher than the porosity percentage. Comparing porosity percentages with each other, at porosity percentage 90% is greater than at porosity percentage 45%. On the other hand, increasing the Reynolds number reduces the entropy generation due to heat transfer and increases the entropy generation due to friction. Increasing the volume fraction of nanoparticles increases the entropy generations due to heat transfer and friction.

Two-phase analysis of heat transfer and entropy generation of water-based magnetite nanofluid flow in a circular microtube with twisted porous blocks under a uniform magnetic field

In the present numerical analysis, the forced convection of nanofluid flow is investigated in a microtube with twisted porous blocks while existing a uniform magnetic field based on the first and second laws of thermodynamics with various geometries. Using the finite volume technique and SIMPLE algorithm, the governing equations are discretized and solved. The governing equations are solved using a two-phase mixture model and second-order upwind technique. With the heat flux of 5000 W.m−2, the effects of Hartmann number, Reynolds number, the volume fraction of nanoparticles, as well as porosity percentage of twisted porous blocks are investigated on pressure drop, heat transfer rate, and flow fields. The values of the Hartmann and Reynolds numbers are different within the range of Ha = 0 to Ha = 20 and Re = 250 to Re = 1000, respectively, and the volume fraction of nanoparticles is different within φ = 0 to 2%. The findings indicate that placing the porous blocks in the microtube leads to protrusions in the local diagrams, moreover, by increasing the number of twisted porous block layers, the vertices value of these protrusions increments. By incrementing the Reynolds number, the pressure drop and convective heat transfer coefficient are increased, and the friction factor is decreased. Incrementing φ and the thermal conductivity of the fluid increase the heat transfer rate. Moreover, by increasing the Hartmann number, the local friction factor and the Nusselt number are increased. According to the results, by increasing the number of twisted porous block layers in the highest φ, the average pressure drop becomes 38.171 Pa. The performance evaluation criterion in Ha = 20 and microchannel with three twisted block layers possess the highest value of 1.717.

Numerical investigation of the effect of oscillating injection nanofluid flow on forced convection heat transfer enhancement over a backward-facing step

In this study, the effect of the oscillating injection flow on laminar forced convection of nanofluid flow over a 2D backward-facing step was numerically investigated. The effects of Reynolds number, Strouhal number, and momentum flux ratio in terms of injection velocity, and injection position on the fluid flow and heat transfer were studied. The comparison of the results of the oscillating injection with different cases (with and without constant injection) indicates that using oscillating injection flow generates periodic oscillation in the flow and heat transfer characteristics, which can lead to heat transfer enhancement. Furthermore, the time-spatial average Nusselt number based on the Strouhal number exhibited a resonant-type behavior, and the best effect of flow oscillation on the heat transfer rate was achieved at St = 0.1. The numerical results showed that the oscillating injection can provide a heat transfer enhancement of about 144% in Xj = H for Reynolds number of (Re = 100) and momentum flux ratio of (J = 4). Moreover, it was found that the maximum effectiveness parameter, as a sufficient and reliable criterion, at the Re = 100 is equal to $$\eta = 1.54$$ .

Two-phase forced convection of nanofluids flow in circular tubes using convergent and divergent conical rings inserts

Numerical investigations are conducted using finite volume method to study the thermal and hydraulic characteristics of turbulent forced convection of nanofluid flow in a circular tube equipped with conical ring inserts. Four nanofluids with different types of nanoparticles, Al2O3, CuO, SiO2, and ZnO with 1–4% volume fraction and particle diameters from 20 to 50 nm in base fluid (water) are tested. Two different approaches for simulating nanofluids viz., a single-phase and two-phase mixture are implemented. The effects of Reynolds number (2000–10,000) and conical rings type (convergent and divergent) are studied to test the heat transfer enhancement. The results revealed that the highest performance enhancement criteria based on the same pumping power is provided by the divergent ring inserts with 365%. Among the four tested nanofluids, those with SiO2 particles have achieved the highest heat transfer enhancement in terms of Nusselt number and the friction factor. The Nusselt number is enhanced with the increase of the particle volume fraction and Reynolds number, and with the decrease of nanoparticle diameter. It is found that the comparison of calculated results for different models with the experimental and numerical values shows that the two-phase mixture model is more precise than the single-phase model.

Impact of Brownian moment and thermophoresis on magnetohydrodynamic flow of magnetic nanofluid past an elongated sheet in the presence of thermal diffusion

Purpose The purpose of this paper is to report the impact of thermophoresis and Brownian moment on MHD two-dimensional forced convection flow of nanofluid past a permeable stretching sheet in the presence of thermal diffusion. Design/methodology/approach The flow governing PDEs are reduced to ODEs by utilizing pertinent transmutations and then resolved by employing a fourth-order Runge-Kutta-based shooting technique. The energy and diffusion equations are incorporated with Brownian motion, thermophoresis and Soret parameters. The velocity, thermal and concentration attributes along with skin friction factor, local Nusselt and Sherwood number are discussed under the influence of sundry pertinent parameters and presented with the assistance of graphical and tabular values. Findings The results infer that Sherwood number is accelerated by Soret parameter but it controls the thermal transport rate. And also, Brownian and thermophoresis play a vital role in enhancing heat conduction process. Originality/value Considering the industrial applications of flow of magnetic nanofluid over a stretching surface, this paper presents the solution of the flow problem considering thermophoresis, Brownian motion, magnetic field and thermal diffusion effects. In addition, the aim and objectives of this paper fills a gap in the industry.

RETRACTED: MHD forced convection flow of nanofluid in a porous cavity with hot elliptic obstacle by means of Lattice Boltzmann method

RETRACTED: MHD forced convection flow of nanofluid in a porous cavity with hot elliptic obstacle by means of Lattice Boltzmann method

Numerical simulation for aspects of homogeneous and heterogeneous reactions in forced convection flow of nanofluid

Abstract Mixed convection stagnation point flow of nanofluid by a vertical permeable circular cylinder has been addressed. Water is treated as ordinary liquid while nanoparticles include aluminium oxide, copper and titanium dioxide. Homogeneous-heterogeneous reactions are considered. The nonlinear higher order expressions are changed into first ordinary differential equations and then solved by built-in-Shooting method in mathematica. The results of velocity, temperature, concentration, skin friction and local Nusselt number are discussed. Our results demonstrate that surface drag force and heat transfer rate are enhanced linearly for higher estimation of curvature parameter. Further surface drag force decays for aluminium oxide and it enhances for copper nanoparticle. Heat transfer rate enhances with increasing all three types of nanoparticles. In addition, the lowest heat transfer rate is obtained in case of titanium dioxide when compared with copper and aluminium oxide.

Turbulent forced convection flow of nanofluids over triple forward facing step

PurposeThe purpose of this paper is to numerically study the phenomenon of separation and subsequent reattachment that happens due to a sudden contraction or expansion in flow geometry, in addition, to investigating the effect of nanoparticles suspended in water on heat transfer enhancement and fluid flow characteristics.Design/methodology/approachTurbulent forced convection flow over triple forward facing step (FFS) in a duct is numerically studied by using different types of nanofluids. Finite volume method is employed to carry out the numerical investigations. with nanoparticles volume fraction in the range of 1-4 per cent and nanoparticles diameter in the range 30-75 nm, suspended in water. Several parameters were studied, such as the geometrical specification (different step heights), boundary conditions (different Reynolds [Re] numbers), types of fluids (base fluid with different types of nanoparticles), nanoparticle concentration (different volume fractions) and nanoparticle size.FindingsThe numerical results indicate that the Nusselt number increases as the volume fraction increases, but it decreases as the diameter of the nanoparticles of nanofluids increases. The turbulent kinetic energy and its dissipation rate increase as Re number increases. The velocity magnitude increases as the density of nanofluids decreases. No significant effect of increasing the three steps heights on Nusselt along the heated wall, except in front of first step where increasing the first step height leads to an increase in the recirculation zone size adjacent to it.Research limitations/implicationsThe phenomenon of separation and subsequent reattachment happened due to a sudden contraction or expansion in flow geometry, such as forward facing and backward facing steps, respectively, can be recognized in many engineering applications where heat transfer enhancement is required. Some examples include cooling systems for electronic equipment, heat exchanger, diffusers and chemical process. Understanding the concept of these devices is very important from the engineering point of view.Originality/valueConvective heat transfer can be enhanced passively by changing flow geometry, boundary conditions, the traditional fluids or by enhancing thermal conductivity of the fluid. Great attention has been paid to increase the thermal conductivity of base fluid by suspending nano-, micro- or larger-sized particles in fluid. The products from suspending these particles in the base fluid are called nanofluids. Many studies have been conducted to investigate the heat transfer and fluid flow characteristics over FFS. This study is the first where nanofluids are employed as working fluids for flow over triple FFS.

Numerical Investigation on Conjugate Heat Transfer Performance of Microchannel Using Sphericity-Based Gold and Carbon Nanoparticles

ABSTRACTNumerical study has been carried out on the laminar forced convection flow of nanofluids in a wide rectangular microchannel. The flow and heat transfer characteristics of gold and of single-walled carbon (SWCNT) nanofluids are investigated in order to find an efficient and cost-effective heat transfer fluid. The effects of nanoparticle volume concentration and of spherical and cylindrical particulate sizes on the conjugate heat transfer performance of the microchannel are reported. The effective thermal conductivity of a nanofluid is evaluated on the basis of particle sphericity by considering the volume and surface area of the nanoparticles. The average convective heat transfer coefficient increases with increase in Reynolds number and volume concentration. Moreover, sphericity-based thermal conductivity evaluation showed that increasing the length of the SWCNT nanoparticle has significant effect on the heat transfer performance, concluding that axial heat conduction dominates the radial heat conduction within the nanoparticle. The carbon nanofluid is identified as an optimized heat transfer fluid with better heat transfer characteristics in comparison with the gold nanofluid. It also reduces the cost of the working fluid. The variations in the interface temperature between solid and fluid regions are reported for nanofluids with different concentrations at different Reynolds numbers. The diameter and length of the SWCNT nanoparticle show a significant effect on heat transfer characteristics.

Numerical Study Of Turbulent Thermal-Hydraulic Performance Of Al2o3-Water Nanofluid In Channel With Triangular Baffles

In this paper, turbulent forced convection of nanofluid flow in channel with isoscelestriangular baffles is numerically investigated over Reynolds number ranges of 5000-10000. One baffle mounted on the bottom wall of channel and another mounted on the top wall. Al2O3-water nanofluid with nanoparticles volume fraction of 4% and nanoparticles diameters of 25 nm is used. The governing continuity, momentum and energy equations as well as the low Reynolds number k-ε model of Launder and Sharma have been solved using finite volume method. The effect of baffle height, baffle distance as well as Reynolds number on the flow and thermal characteristics have been presented and discussed. It is found that the enhancement ratio of the average Nusselt number as well as the fraction factor increase with increasing in the baffles height. It is also found that the enhancement ratio of the average Nusselt number increases as the distance of top baffle decrease. Furthermore, the best thermal-hydraulic performance of channel with triangular baffles using nanofluid can be obtained at baffle height of 2.5 mm, distance of the top baffle of 40 mm and Reynolds number of 5000.

Numerical Study of Forced Convection of Nanofluid Flow Over a Backward Facing Step With a Corrugated Bottom Wall in the Presence of Different Shaped Obstacles

In this paper, a numerical study of laminar forced convection of nanofluid flow over a backward facing step with a corrugated bottom wall in the presence of different shaped obstacles placed behind the step was performed. The bottom corrugated wall of the channel downstream of the step is isothermally heated and the other walls of the channel and obstacle surface are assumed to be adiabatic. The governing equations are solved with a finite-element method. The influences of the Reynolds number (between 10 and 200), solid volume fraction of the nanoparticle (between 0 and 0.05), and obstacle type (circular, square, and diamond shaped) on fluid flow and heat transfer are numerically investigated. It is observed that among different obstacles, the diamond shaped obstacle provides better local heat transfer enhancement characteristic in the vicinity of the step compared to the circular or square obstacle at high Reynolds number. Heat transfer enhancement of 6.66% is achieved in terms of maximum values with a diamond shaped obstacle compared to the no-obstacle case of the corrugated channel. Adding an obstacle deteriorates heat transfer in terms of average values for the backward facing step geometry with a corrugated wall. When the solid volume fraction of nanoparticle is increased, maximum and average heat transfer rate increase. Heat transfer enhancements of 7.45%, 7.42%, 6.94%, and 6.64% are obtained for the average values for circle, diamond, square, and no-obstacle cases, respectively, when solid volume fraction of 0.05 is compared to pure fluid.

Numerical Investigation of Forced Convection Flow of Nanofluids in Rotating U-Shaped Smooth and Ribbed Channels

The impact of the nanoparticles and ribs on the thermal performance of the rotating U-type cooling channel are investigated for turbulent forced convection flow of nanofluids. The nanofluids are provided by the inclusion of the nanoparticles of TiO2 and Al2O3 in water as the base fluid, namely, water/Al2O3 and water/TiO2 nanofluids mixtures. The simulations are performed for three-dimensional turbulent flow and heat transfer using an RNG k-ϵ turbulence model for Reynolds number range of 5000 to 20,000. To show the effectiveness of the ribs and nanofluids, three criteria are employed: heat transfer enhancement, pressure drop or power consumed, and the thermal performance factor. It is found that the contribution of turbulence promotion in heat transfer enhancement of the ribbed channel is more effective than that of enlarging the heat surface area. The results show that using ribs at the lowest Reynolds number and utilizing nanofluids at the highest one provide high heat transfer rate and thermal performance. At the middle Reynolds numbers, the effects of these two methods on heat transfer enhancement are relatively close to each other. In this case, if the pumping power is the main concern, using nanofluids is recommended due to providing a smaller pressure drop penalty.

Influence of inclination angle of magnetic field on mixed convection of nanofluid flow over a backward facing step and entropy generation

In this paper, numerical study of laminar forced convection of nanofluid flow over a backward facing step for different inclination angles of magnetic field is performed. The bottom wall of the channel downstream of the step is isothermally heated and the other walls of the channel are assumed to be adiabatic. Finite element method was used to solve the governing equations. The influence of the Reynolds number (between 20 and 200), Hartmann number (between 0 and 50) and solid volume fraction of the nanoparticle (between 0 and 0.04) on the fluid flow and heat transfer are numerically investigated for different orientation angles of the magnetic field. It is observed the averaged heat transfer increases as the Reynolds number increases and this effect is more pronounced with higher values of inclination angle of the magnetic field. As the value of the Hartmann number decreases for horizontally aligned magnetic field and volume fraction of the nanoparticles increases averaged and local enhancement of heat transfer are observed. For the inclined and vertical magnetic field, suppression of the recirculation zone behind the step is observed as the value of Ha increases which results in heat transfer enhancement. The total entropy generation ratio increases with increasing values of Reynolds number, solid volume fraction of nanoparticles and decreasing values of Hartmann number for horizontally oriented magnetic field.

Experimental and numerical investigations of turbulent forced convection flow of nano-fluid in helical coiled tubes at constant surface temperature

In the present research, steady state turbulent forced convection developing flow of a CuO nano-fluid inside helically coiled tubes at constant wall surface temperature was investigated both numerically and experimentally. Both the pressure drop and convective heat transfer behaviors of the nano-fluid were investigated in detail and compared with the results for pure water. In the experimental section, a heat exchanger was designed to provide different helically coiled tubes with constant wall temperature. Based on the temperature and pressure drop measurement at the inlet and outlet of the pipes, the friction factor and Nusselt number were experimentally obtained for both water and the CuO nano-fluid flow. In the numerical part, the governing equations were solved by virtue of finite volume method in OpenFOAM. The buoyant_Boussinesq_SimpleFoam solver with the assumption of single-phase flow and constant effective thermo-physical properties, computed at mean bulk temperature, was employed. The numerical results respectively demonstrate a 6–7% and a 9–10% increase in the convective heat transfer and pressure drop of the applied CuO nano-fluid over pure water, whereas experimental results show a 16–17% increase in the heat transfer coefficient and a 14–16% increase in the pressure drop for different tube geometries and different Re numbers. Furthermore, the results show that both the pressure drop and heat transfer coefficient increase as the curvature ratio and Re number increase. Finally, using the numerical and the experimental results, correlations are proposed to model the friction factor coefficient and the Nusselt number.

Conjugate heat transfer analysis of micro-channel using novel hybrid nanofluids ([formula omitted

Laminar forced convection flow of nanofluids in a wide rectangular micro-channel has been numerically studied. The present study investigated the flow and heat transfer characteristics of Aluminium oxide (Al2O3), silver (Ag) and hybrid (Al2O3+Ag) nanofluids in a micro-channel. The conduction phenomena of the solid region show a significant effect on the heat transfer characteristics of nanofluid. Hence, the channel is considered with finite thickness on its bottom to accommodate heat source or electronic component and a uniform heat flux is applied to the three sides of the solid region. A two-dimensional conjugate heat transfer homogeneous phase model has been developed and results are reported for different Reynolds numbers. The governing equations are solved by Simplified Marker and Cell (SMAC) algorithm on non-staggered grid using finite volume method. The effects of Reynolds number, pure nanoparticles volume concentration, hybrid nanoparticles mixture volume concentrations and nanoparticles size on the flow and heat transfer characteristics are reported. The results show that the average convective heat transfer coefficient increases with increase in nanoparticles volume concentration and Reynolds number. The nanofluids obtained by dispersing nanoparticles such as Al2O3, Ag and hybrid (Al2O3+Ag) in the base fluid shows a significant enhancement of average convective heat transfer coefficient in comparison with pure water. It is also observed that 3 vol.% hybrid nanofluid (0.6 vol.% Al2O3+2.4 vol.% Ag) shows higher average convective heat transfer coefficient than that of pure water, pure oxide (Al2O3) and pure metallic (Ag) nanofluids. The study presents that hybrid nanofluids are the new class of working fluids with less volume concentration of metallic (Ag) nanoparticles. Moreover, use of hybrid nanofluids at high volume concentration reduces the cost of the working fluid and enhances the heat transfer characteristics in comparison with that of metallic nanofluids. The interface temperature between solid and fluid regions are reported for different nanofluids. The size of the nanoparticle shows significant effect on heat transfer characteristics. The present results are matching with the numerical and experimental results available in the literature.

Heat transfer and entropy generation of turbulent forced convection flow of nanofluids in a heated pipe

Eulerian–Eulerian multi-phase mixture model is applied to numerically analyse the turbulent flow and heat transfer behaviour of water based Al2O3 and TiO2 nanofluids in a pipe. The main goal of the present work is to investigate the effects of volume concentrations, Brownian motion and size diameter of nanoparticles on the flow and heat transfer. Analysis of entropy generation is presented in order to investigate the condition that optimises the thermal system. Results reveal that small diameter of nanoparticles with their Brownian motion has the highest heat transfer rate as well as thermal performance factor for χ=6%. Above all, the higher heat transfer rate is found while using the multi-phase model than the single-phase model (Saha and Paul [1]). Also, the optimal Reynolds number is found to be Re=60×103 for χ=6% and dp=10nm, which minimises the total entropy generation. Finally, it is showed that TiO2–water nanofluid is the most energy efficient coolant than Al2O3–water nanofluid, and some new correlations have been proposed for the calculation of average Nusselt number.

English

2 ABSTRACT: In the present paper, the problem of transient laminar forced convection flow of nanofluids in horizontal square duct has been thoroughly investigated using a single phase approach. The water is adopted as base fluid ,while the(Al2O3) and(CuO) are a solid nanoparticles. Computations are validated with experimental data available in the literature, good agreements are obtained. The results showed that Convective heat transfer coefficient for nanofluids is greater than that of the base liquid. Heat transfer enhancement increases with the particle volume concentration increase, but it is accompanied by increasing wall shear stress values. The isotherms are presented for various void fractions and Reynolds numbers. Also, the relation between the Nusselt number, and friction factor with Time are introduced for various Reynolds numbers and volume fraction of nanoparticles.

Comparison between single-phase and two-phases CFD modeling of laminar forced convection flow of nanofluids in a circular tube under constant heat flux

In this article, forced convection heat transfer with laminar and developed flow for water-Al2O3 nanofluid inside a circular tube under constant heat flux from the wall was numerically investigated using computational fluid dynamics method. Both single and two-phase models are accomplished for either constant or temperature dependent properties. For this study nanofluids with size particles equal to 100nm and particle concentrations of 1 and 4wt% were used. It is observed that the nanoparticles when dispersed in base fluid such as water enhance the convective heat transfer coefficient. The Nusselt number and heat transfer coefficient of nanofluids were obtained for different nanoparticle concentrations and various Reynolds numbers. Heat transfer was enhanced by increasing the concentration of nanoparticles in nanofluid and Reynolds number. Also, a correlation based on the dimensionless numbers was obtained for the prediction the Nusselt number. The modeling results showed that the predicted values were in very good agreement with reference experimental data.