# Showing papers on "Nanofluid published in 2021"

Journal ArticleDOI

TL;DR: In this paper, the effects of thermal radiation and surface roughness on the complex dynamics of water conveying alumina and copper oxide nanoparticles, in the case where the thermophysical properties of the resulting mixture vary meaningfully with the volume fraction of solid nanomaterials, as well as with the Brownian motion and thermophoresis microscopic phenomena.
Abstract: Sequel to the fact that hybrid nanofluidic systems (e.g. scalable micro-/nanofluidic device) exhibit greater thermal resistance with increasing nanoparticle concentration, little is known on the significance of thermal radiation, surface roughness and linear stability of water conveying alumina and copper oxide nanoparticles. This study presents the effects of thermal radiation and surface roughness on the complex dynamics of water conveying alumina and copper oxide nanoparticles, in the case where the thermophysical properties of the resulting mixture vary meaningfully with the volume fraction of solid nanomaterials, as well as with the Brownian motion and thermophoresis microscopic phenomena. Based on the linear stability theory and normal mode analysis method, the basic partial differential equations governing the transport phenomenon were non-dimensionalized to obtain the simplified stability equations. The optimum values of the critical thermal Rayleigh number depicting the onset of thermo-magneto-hydrodynamic instabilities were obtained using the power series method and the Chock–Schechter numerical integration. The increase in the strength of Lorentz forces, thermal radiation and surface roughness has a stronger stabilizing impact on the appearance of convection cells. On the contrary, the stability diminishes with the increasing values of the volumetric fraction and diameter of nanomaterials. The partial substitution of the alumina nanoparticles by the copper oxide nanomaterials in the mixture stabilizes importantly the hybrid nanofluidic medium.

135 citations

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TL;DR: In this paper, the authors present empirical and numerical analyses of thermal performance development in flat plate solar collectors (FPSCs) and provide a complete overview of the up-to-date developments, methods, critical economic factors, the significance of solar water heating, and the challenges faced by the implementations of such solar energy heating systems.
Abstract: The current review presents empirical and numerical analyses of thermal performance development in flat plate solar collectors (FPSCs). Generally, the productivity of photovoltaic (PV) modules diminishes with the increase of working temperature. Thus, many photovoltaic systems utilize various liquids to decreases the temperature of such modules. The operation of a PVT and thermal system employing nanofluids increases the electrical and the thermal energy. Thermal and electrical energies can be produced by a flat plate photovoltaic system, as shown by many papers. In the current review, two kinds of flat plate collectors are categorized and then discussed comprehensively (PVT and thermal systems). Utilizing nanofluids in such collectors provides a higher overall performance because of suspended nanoparticles’ greater thermal conductivity inside a base fluid. Studies illustrate employing 24% of alumina oxide, 12% of Multi-walled carbon nanotubes (MWCNT), 10% of copper oxide, and other types of nanofluids inside FPSCs. By studying the information resulted from numerical and empirical studies, it was observed that the increment in performances of around 29, 9, and 20–30% were obtained employing 0.2 wt% of alumina oxide, 0.05 wt% of copper oxide, and 1.0 wt% of MWCNT, respectively. Also, the heat transfer rates in plates are investigated with the change of other parameters. Therefore, some results and recommendations for future studies are expressed using nanofluids in the reviewed systems. The current review article provides a complete overview of the up-to-date developments, methods, critical economic factors, the significance of solar water heating, and the challenges faced by the implementations of such solar water heating systems, which could be beneficial for all stakeholders of solar energy.

135 citations

Journal ArticleDOI

TL;DR: In this paper, an adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) were used for predicting the relative viscosity and electrical conductivity of the two types of hybrid ferrofluids.
Abstract: Recently, the suspension of hybrid nanoparticles in conventional fluids has been investigated as a technique for improving the thermophysical properties of nanofluids. The dearth of documentation on the trio influence of volume concentration, base fluid, and temperature on the electrical conductivity and viscosity of hybrid alumina–ferrofluids [Al2O3–Fe2O3 (25:75 mass%)] has led to this study. The effective viscosity and electrical conductivity of the deionized water (DW)-based and ethylene glycol (EG)–DW-based (50:50 vol%) hybrid alumina–ferrofluids were measured at temperatures of 20–50 °C and volume concentrations of 0.05–0.75%. Based on the importance of soft computing methods to engineers, adaptive neuro-fuzzy inference system (ANFIS) and artificial neural network (ANN) were used for predicting the relative viscosity and electrical conductivity of the two types of hybrid ferrofluids. The measured data for viscosity and electrical conductivity were used in the modeling. Model performances were evaluated using the root mean squared error index. Viscosity was enhanced by 3.23–43.64% and 2.79–49.38%, while electrical conductivity was increased by 163.37–1692.16% and 717.14–7618.89% for the DW- and EG–DIW-based hybrid ferrofluids, respectively, compared with the respective base fluids. Increasing volume concentration augmented the viscosity and electrical conductivity of all the hybrid alumina–ferrofluids, whereas a rise in temperature enhanced their electrical conductivity and detracted the viscosity. DW-based hybrid alumina–ferrofluid was observed to have a lower viscosity and higher electrical conductivity than the EG–DW-based counterpart. The results showed that the optimum ANN and ANFIS models have a maximum error of less than 4.5% and 3.9% for relative viscosity and electrical conductivity, respectively, which were lower than those proposed using regression analysis. With the hybrid alumina–ferrofluids possessing a lower viscosity relative to single-particle ferrofluids, they are recommended for engineering application.

92 citations

Journal ArticleDOI
TL;DR: In this article, the effects of different shape factors have been investigated for a mixture of water and nanofluid with hybrid nanoparticles (MWCNT-Ag) over a vertical stretching cylinder, while a magnetic field has been applied to the system.
Abstract: In this study, flow of a mixture of water and ethylene glycol (50–50%) with hybrid nanoparticles (MWCNT–Ag) over a vertical stretching cylinder has been investigated. In this research, the fluid passes through a porous media, while a magnetic field has been applied to the system. Furthermore, the effects of thermal radiation, viscous dissipation, and natural convection have been studied. As a novelty, the effects of different shape factors have been investigated. In the first step, the governing equations are extracted from partial differential equations and then converted to ordinary differential equations (ODE) using the similarity solution. In the next step, the fifth-order Runge–Kutta method has been used to solve the related ODEs. The effects of parameters such as magnetic field, radiation parameter, porosity parameter, nanofluid volume fraction, and nanofluid shape factor on dimensionless velocity and temperature profile have been presented for single and hybrid nanofluid. The results showed that at $$\eta$$ = 2.5 for hybrid nanoparticles the shape factors lamina and spherical have the largest difference; lamina is smaller by 6%, also the results demonstrated that at $$\eta$$ = 2 with increasing Ha, the radial velocity reduced 9.68% for hybrid nanoparticles.

80 citations

Journal ArticleDOI
TL;DR: In this article, six-lobed absorber tube equipped with combined turbulators was investigated to enhance the productivity of solar unit, hybrid nanoparticles were added in to working fluid.

78 citations

Journal ArticleDOI

TL;DR: In this article, a mathematical analysis for three-dimensional Eyring-Powell nanofluid nonlinear thermal radiation with modified heat plus mass fluxes is investigated, and the slip condition is introduced to enhance the dynamical and physical study of structure.
Abstract: In this paper, a mathematical analysis for three-dimensional Eyring–Powell nanofluid nonlinear thermal radiation with modified heat plus mass fluxes is investigated. To enhance the dynamical and physical study of structure, the slip condition is introduced. A Riga plate is employed for avoiding boundary-layer separation to diminish the friction and pressure drag of submarines. To evaluate the heat transfer, the Cattaneo–Christov heat flux model is implemented via appropriate transformation. A comparison between bvp4c results and shooting technique is made. Graphical and numerical illustrations are presented for prominent parameters.

76 citations

Journal ArticleDOI
TL;DR: In this article, the irreversibility in convective nanofluid flow in the occurrence of a magnetic field (MHD) in a cavity with chamfers is calculated by numerical approach.
Abstract: The irreversibility in convective nanofluid flow in the occurrence of a magnetic field (MHD) in a cavity with chamfers is calculated by numerical approach. The nanofluid flow is considered under the impacts of magnetic field and thermal gradient. The continuity, motion and energy equations are solved by applying COMSOL Multiphysics computer package. The impacts of $$({\text{Ha}})$$ Hartmann number, $$(\gamma )$$ elevation of magnetic field, nanoparticle volume fraction, heat transmission and entropy analysis on the flow of nanofluid are discussed. Results reveal that, the impacts of volume fraction and the magnetic force on different irreversibility are significant. Moreover, results indicate the existence of a critical $$({\text{Ha}}_{{\text{c}}} )$$ Hartmann number this represents the frontier between the domains where the magnetic field dominates via its intrinsic effect and its extrinsic effect.

75 citations

Journal ArticleDOI
TL;DR: In this article, the effect of aluminum oxide suspended in water at concentration of 0.03% as nanomaterial for turbulent flow using multiple twisted tapes (TTn) in a solar flat plate collector was scrutinized.
Abstract: In the present examination, the effect of Aluminum oxide suspended in water at concentration of 0.03% as nanomaterial for turbulent flow using multiple twisted tapes (TTn) in a solar flat plate collector was scrutinized. Properties are estimated by utilizing previous correlations. Outputs are described for a different number of turbulator and Reynolds number (Re). The increase in Sgen,f (1604.672) is more significant for higher Re = 20,000. The highest Sgen,th (15,788.13) is observed for TTn = 1 and Re = 4000. The highest number of Be is 0.9987 when the TTn = 1 and Re = 4000. Both the Be number and the Фs shows the same trend for the reported results. The increase in the number of Re and TTn reduces the values of Be and Фs. Output results verify that the use of turbulators enhances the nanofluid flow resulting in enhanced heat transfer, which also provides higher flow disturbance. Therefore, it can be concluded that using twisted tapes and nanofluids can result in reduces exergy losses.

74 citations

Journal ArticleDOI

TL;DR: In this paper, three methods including MARS, artificial neural network (ANN) with Levenberg-Marquardt for training and GMDH are employed for thermal conductivity of the nanofluids containing ZnO particles.
Abstract: Nanofluids are attractive alternatives for the current heat transfer fluids due to their remarkably higher thermal conductivity which leads to the improved thermal performance. Nanofluids are applicable in porous media for improving their heat transfer. Proposing accurate models for forecasting this feature of nanofluids can facilitate and accelerate the design and modeling of nanofluids’ thermal mediums with porous structure. In the present study, three methods including MARS, artificial neural network (ANN) with Levenberg–Marquardt for training and GMDH are employed for thermal conductivity of the nanofluids containing ZnO particles. The confidence of the models is compared according to various criteria. It is observed that the most accurate model is obtained by using ANN with Levenberg–Marquardt followed by GMDH and MARS. R2 of the mentioned models are 0.9987, 0.9980 and 0.9879, respectively. Finally, sensitivity analysis is performed to find the importance of the input variables and it is concluded that the thermal conductivity of the base fluids has the highest importance followed by volume fraction of solid phase, size of particles and temperature.

69 citations

Journal ArticleDOI
TL;DR: In this paper, the effect of entropy generation through a non-linear radiative flow of viscous fluid of hybrid nanoparticles over a stretchable rotating disk was explored, where similarity transformations were utilized to reduce the governing problem into the nonlinear ordinary differential equations.
Abstract: This research article explores the effect of entropy generation through a non-linear radiative flow of viscous fluid of hybrid nanoparticles over a stretchable rotating disk. Mixed convection and slip conditions i-e velocities and thermal are examined. The examination is accomplished in aluminum oxide (Al2O3)-water and copper (Cu)-water nanofluids. Similarity transformations are utilized to reduce the governing problem into the nonlinear ordinary differential equations. Flow in the permeable medium is analyzed by assuming the Darcy-Forchheimer model. The impact of various parameters consisting of mixed convection parameter, porosity parameter, velocities as well as thermal slips parameters, stretching parameter, non-linear radiation parameter, and Reynolds number on radial velocity profile, tangential velocity profile and temperature profile are studied. Also, entropy generation and heat transfer rates have been analyzed in view of different parameters in the current study. The mathematical formulation is numerically solved by the bvp4c techniques

68 citations

Journal ArticleDOI
TL;DR: In this paper, communication, mathematical modeling and numerical simulation are presented for the steady, incompressible two-dimensional Darcy-Forchheimer nanofluid flow of viscous material towards a stretched surface.
Abstract: In this research, communication, mathematical modeling and numerical simulation are presented for the steady, incompressible two-dimensional Darcy-Forchheimer nanofluid flow of viscous material towards a stretched surface. The flow is generated due to stretching surface and saturated through Darcy-Forchheimer relation. The radiative heat flux and viscous dissipation effects are utilized in the modeling of energy expression. Second order slip and convective condition are imposed at the stretchable boundary for velocity and temperature respectively. A total entropy rate, which depends three different types of irreversibilities i.e., heat transfer, fluid friction and Darcy-Forchheimer relation or porosity are calculated via the second law of thermodynamics. Here Silicon dioxide and Molybdenum disulfide are considered as nanomaterials and water as base fluid. The boundary layer approximation concept is used to model the governing equations of momentum and temperature. Appropriate similarity transformations are used to alter the governing equations into ordinary ones and numerical results are obtained via Built-in-Shooting method. The obtained results are compared with existing work and noticed to be in excellent agreement. Behavior of pertinent flow parameters is discussed graphically on the velocity, temperature, Bejan number and entropy generation for both nanoparticles (Silicon dioxide, Molybdenum). Furthermore, the skin friction coefficient (surface drag force) and heat transfer rate (Nusselt number) are discussed in the presence of slip parameters and stratification parameter. It is noted from the obtained results that entropy generation rate enhances for higher Brinkman number and temperature decreases against higher values of stratification parameter.

Journal ArticleDOI

TL;DR: In this article, a time-dependent flow of magnetized rheological Carreau nanoliquid conveying microorganisms over a moving wedge with velocity slip and thermal radiation features is considered.
Abstract: This article addresses the time-dependent flow of magnetized rheological Carreau nanoliquid conveying microorganisms over a moving wedge with velocity slip and thermal radiation features. Carreau fluid is auspicious to depict several types of physical issues because this fluid model has the capability of revealing the rheology of multiple specific fluids such as fluids with brief-chain suspension particles, fluid crystals, detergents, and blood in animals and humans. The mathematical formulation is developed by combining the impact of infinite shear rate viscosity. The physical aspects for both static and moving are discussed in detail. At first, relevant similarity transformations are employed to obtain dimensionless form of equations, and then renovated equations have been solved numerically by employing bvp4c via MATLAB based on shooting technique. Both the numerical and graphical results against physical quantities, such as velocity temperature, nanoparticles concentration and density of gyrotactic microorganism, are observed under the influence of physical parameters.

Journal ArticleDOI

TL;DR: In this paper, the properties, preparation and stability of hybrid nanofluids (HNFs) are investigated, and some models and correlations for predicting HNFs properties are presented.
Abstract: These days, the importance of energy consumption has led scientists to optimize thermal devices. One of the solutions proposed for this purpose is using solid nanoparticles to amend the thermal properties of conventional fluids. Adding the nanoparticles into the foundation fluids results in an improvement in the fluid properties (thermal conductivity, viscosity, etc.). Nanofluid (NF) has been drawing attention in various engineering applications in the past decade due to its superior heat transfer characteristics than the conventional working fluid. In recent years, the researchers have focused on adding two or more nanoparticles into foundation fluids, known as hybrid nanoparticles. Hybrid nanofluids (HNFs) suggest a more appropriate heat transfer performance and thermophysical features than the conventional heat transfer fluids (ethylene glycol, water and oil) and even NFs with single nanoparticles. It was proven that HNF can be an alternative to the single NF, since it can provide more heat transfer enhancement, particularly in the context of the solar energy, electromechanical, HVAC, electromechanical and automobile. In the current research, the properties, preparation and stability of HNFs are investigated. Also, some models and correlations for predicting HNFs properties are presented.

Journal ArticleDOI
, Min Yang1, Yali Hou1, Li Runze3
TL;DR: In this article, a convective heat transfer coefficient model was established based on the theory of boiling heat transfer and conduction, and the numerical simulation of finite difference and temperature field in the grinding zone under different vortex tube cold air fractions was conducted.
Abstract: Under the threat of serious environmental pollution and resource waste, sustainable development and green manufacturing have gradually become a new development trend. A new environmentally sustainable approach, namely, cryogenic air nanofluid minimum quantity lubrication (CNMQL), is proposed considering the unfavorable lubricating characteristic of cryogenic air (CA) and the deficient cooling performance of minimum quantity lubrication (MQL). However, the heat transfer mechanism of vortex tube cold air fraction by CNMQL remains unclear. The cold air fraction of vortex tubes influences the boiling heat transfer state and cooling heat transfer performance of nanofluids during the grinding process. Thus, a convective heat transfer coefficient model was established based on the theory of boiling heat transfer and conduction, and the numerical simulation of finite difference and temperature field in the grinding zone under different vortex tube cold air fractions was conducted. Simulation results demonstrated that the highest temperature initially declines and then rises with increasing cold air fraction. Afterward, this temperature reaches the lowest peak (192.7 °C) when the cold air fraction is 0.35. Experimental verification was conducted with Ti–6Al–4V to verify the convective heat transfer coefficient model. The results concluded that the low specific grinding energy (66.03 J/mm3), high viscosity (267.8 cP), and large contact angle (54.01°) of nanofluids were obtained when the cold air fraction was 0.35. Meanwhile, the lowest temperature of the grinding zone was obtained (183.9 °C). Furthermore, the experimental results were consistent with the theoretical analysis, thereby verifying the reliability of the simulation model.

Journal ArticleDOI
TL;DR: In this article, the activation energy on a Riga plate was studied and the governing equations were formulated including activation energy and viscous dissipation effects, and numerical results were obtained through the use of shooting method and are depicted graphically.
Abstract: This article deals with a study of Arrhenius activation energy on thermo-bioconvection nanofluid propagates through a Riga plate. The Riga plate is filled with nanofluid and microorganisms suspended in the base fluid. The fluid is electrically conducting with a varying, parallel Lorentz force, which changes exponentially along the vertical direction, due to the lower electrical conductivity of the base fluid and the arrangements of the electric and magnetic fields at the lower plate. We consider only the electromagnetic body force over a Riga plate. The governing equations are formulated including the activation energy and viscous dissipation effects. Numerical results are obtained through the use of shooting method and are depicted graphically. It is noticed from the results that the magnetic field and the bioconvection Rayleigh number weaken the velocity profile. The bioconvection Schmidt and the Peclet number decrease the microorganism profile. The concentration profile is enhanced due to the increment in activation energy and the Brownian motion tends to increase the temperature profile. The latter is suppressed by an increment of the Prandtl number.

Journal ArticleDOI

TL;DR: A review of the progress made in the area of nanofluids preparation and applications in various heat transfer devices such as solar collectors, heat exchangers, refrigeration systems, radiators, thermal storage systems and electronic cooling is presented in this paper.
Abstract: The field of nanofluids has received interesting attention since the concept of dispersing nanoscaled particles into a fluid was first introduced in the later part of the twentieth century This is evident from the increased number of studies related to nanofluids published annually The increasing attention on nanofluids is primarily due to their enhanced thermophysical properties and their ability to be incorporated into a wide range of thermal applications ranging from enhancing the effectiveness of heat exchangers used in industries to solar energy harvesting for renewable energy production Owing to the increasing number of studies relating to nanofluids, there is a need for a holistic review of the progress and steps taken in 2019 concerning their application in heat transfer devices This review takes a retrospective look at the year 2019 by reviewing the progress made in the area of nanofluids preparation and the applications of nanofluids in various heat transfer devices such as solar collectors, heat exchangers, refrigeration systems, radiators, thermal storage systems and electronic cooling This review aims to update readers on recent progress while also highlighting the challenges and future of nanofluids as the next-generation heat transfer fluids Finally, a conclusion on the merits and demerits of nanofluids is presented along with recommendations for future studies that would mobilise the rapid commercialisation of nanofluids

Journal ArticleDOI
TL;DR: In this paper, the effects of the radiation parameter, porosity, and the magnetic parameter have been analyzed on temperature distribution and fluid flow streamlines and also, on the local and average Nusselt numbers.
Abstract: Investigation of fluid behavior in a cavity enclosure has been a significant issue from the past in the field of fluid mechanics. In the present study, hydrothermal evaluation of hybrid nanofluid with a water–ethylene glycol (50–50%) as the base fluid which contains MoS2–TiO2 hybrid nanoparticles, in an octagon with an elliptical cavity in the middle of it, has been performed. In this problem, the effects of the radiation parameter, porosity, and the magnetic parameter have been analyzed on temperature distribution and fluid flow streamlines and also, on the local and average Nusselt numbers. The governing equations have been solved by the finite element method (FEM). As a novelty, the Taguchi method has been utilized for test design. Further, the response surface method (RSM) has been applied to achieving the optimum value of the involved parameters. The obtained results illustrate that with an augment in the Rayleigh number from 10 to 100, the average Nusselt number will improve by about 61.82%. Additionally, regarding the correlation, it is indeed transparent that the Rayleigh number has the most colossal contribution comparing other factors on the achieved equation, by about 61.88%.

Journal ArticleDOI
Man-Wen Tian, Cong Qi4
TL;DR: In this paper, the effects of fin's length and different types of heat sinks with various lengths on the entropy generation rate (EGR) and Nusselt number (Nu) were investigated at different Richardson numbers (Ri) considering slip and non-slip conditions.
Abstract: The mixed convection heat transfer (MCHT) as a combination of forced and natural convection is studied in this paper. A rectangular enclosure with heatsink is considered that is filled with a hybrid nanofluids (HNFs). The assumed magnetic field (MF) applied the Lorentz force to the enclosure with heatsink. For the enclosure with heatsink, the boundary conditions are assumed as moving upper wall and lower wall with high temperature; Other both walls are well insulated to avoid heat transfer (HT) from them. There was a heat sink on the lower wall with the same temperature of the wall. The Flow could slip over the moving wall, and the non-slip boundary condition is violated on this wall. The governing equations of fluid flow and boundary conditions are discretized using the control volume formulation of the finite difference method and SIMPLE algorithm is used to solve the coupled equations. The effects of fin's length and different types of heat sinks with various lengths on the entropy generation rate (EGR) and Nusselt number (Nu) are investigated at different Richardson numbers (Ri) considering slip and non-slip conditions. The results showed that the HT and EGR increase by increasing the height of the fins. When the length of the heatsink blades was 1, it had the lowest manufacturing cost and at the same time the highest heat transfer per unit blade length, and economically, it was the most economical mode of the heatsink among the various models. The Nu and EGR are decreased using the slip boundary condition. Based on the results, The Nu per length reaches the maximum value for the lowest length of fin.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the magnetic force and nonlinear thermal radiation on hybrid bio-nanofluid flow in a peristaltic channel under the influence of an applied magnetic field with high and low Reynolds number.
Abstract: This work investigates the magnetic force and nonlinear thermal radiation on hybrid bio-nanofluid flow in a peristaltic channel under the influence of an applied magnetic field with high and low Reynolds number. Gold and copper nanoparticles are taken into account. Momentum, Maxwell, and heat with nonlinear thermal radiation and heat source think equations are considered in the dimensionless form without any approximation as a system of nonlinear partial differential equations. The expressions of velocity, induced magnetic field components, magnetic pressure, stream function, magnetic force, joule heating, shear stress, and Nusselt number have been obtained using the Adomian decomposition method. Influences of miscellaneous physical and biomedical parameters including moderate Reynolds, magnetic Reynolds, hybrid nanofluid volume fraction, Hartmann, dimensionless wavenumber, electric field stress, nonlinear thermal radiation, and internal heat generation absorption parameters on velocity, induced magnetic field components, magnetic pressure, normal component of the pressure gradient, heat distribution shear stress on the walls and Nusselt number are plotted and examined. During the investigation, it is found that the gold nanofluid has the highest velocity compared with hybrid, copper, and base fluid, while the hybrid nanofluid has a high magnetic force. The nonlinear thermal radiation is rising the heat distribution for hybrid nanofluid

Journal ArticleDOI

TL;DR: In this paper, the importance of different forces in nanofluid flows that exist in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, Van der Waals, electrostatic double layer forces are considered.
Abstract: The efficient exploitation of solar irradiation is one of the most encouraging ways of handling numerous environmental concerns. Solar collectors are suitable devices that capture solar irradiation and convert it into thermal energy and electricity. In the last years, the nanofluids used in solar thermal systems have been studied as a useful technique for enhancing the solar collectors’ performance and establishing them as viable and highly efficient systems. The present review paper aims to summarize and discuss the most important numerical and experimental studies in nanofluid-based solar systems for application at low and medium temperature levels, while the emphasis on the fundamental physical phenomena that occur. In the first part, numerous numerical models and the principal physical phenomena affecting the heat transfer rate in the nanofluid have been analyzed. More specifically, the importance of different forces in nanofluid flows that exist in particulate flows such as drag, lift (Magnus and Saffman), Brownian, thermophoretic, Van der Waals, electrostatic double-layer forces are considered. Moreover, an overview of the thermophysical properties, physical models, heat transfer models, and evaluation criteria of nanofluids are included in this work. In the second part, which is the main part of this work, a comprehensive review is performed to gather and discuss the new advantages in the nanofluid-based solar collectors that operate at low and medium temperatures. More specifically, the examined solar systems are the flat plate collectors, the evacuated tube collectors, the direct absorption collectors, and the thermal photovoltaic systems, while the investigated applications are space-heating, space-cooling, household hot water production, desalination, industrial activities, and power generation. The aforementioned collectors and applications are the most usual in the real systems, indicating the importance of the present work. Moreover, the emphasis is given in the thermal, exergy, economic, and environmental evaluation of the studied systems, as well as in the discussion of the possible limitations of the use of nanofluids like the lack of long-term stability, the agglomeration of nanoparticles, and the increased pumping work due to the increased pressure drop. Finally, it is found that the nanofluid utilization usually enhances the collector efficiency up to 5%, while higher enhancements can be found in thermal photovoltaics. Moreover, it is concluded that there is a need to emphasize issues such as stability and the use of eco-friendly solar systems. Lastly, the field's future trends are highlighted, and a clear image of the present situation and the next steps in the field are given.

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TL;DR: In this article, carbon nanotubes suspended magnetohydrodynamics micropolar dusty nanofluid impinging on a permeable extending sheet placed in a porous regime is taken into account.
Abstract: The current paper on carbon nanotubes suspended magnetohydrodynamics micropolar dusty nanofluid impinging on a permeable extending sheet placed in a porous regime The Darcy–Forchheimer scheme with heat source/sink and thermal radiation is taken into account The shooting method is instrumental for obtaining numerical solutions of the transformed-converted system of nonlinear equations The prescribed surface temperature (PST) and prescribed heat flux (PHF) boundary conditions are used The impact of governing parameters on velocity, temperature, skin friction coefficient, Nusselt number, entropy generation rate and Bejan number are incorporated The significant outcomes of the current investigation are that increment in the suction parameter decline the flow velocity and temperature (for both PST and PHF cases) while the injection uplift them An enhancement in magnetic strength, the skin friction and heat transfer rate show the opposite trend for both SWCNT and MWCNT Bejan number is increasing with the increase in nanoparticle volume fraction $$\phi$$ for both SWCNT and MWCNT

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TL;DR: In this article, a dimensionless model for peristaltic transport of MHD hybrid nanofluids (TiO2-Cu/H2O) in an asymmetric channel is presented.
Abstract: Slippage impacton peristaltic transport of MHD hybrid nanofluids (TiO2–Cu/H2O) in an asymmetric channel is addressed. Impact of viscous dissipation and Hall current are analyzed in the modeling as well. Constitutive expressions for viscoelastic Jeffery fluid are employed. The mathematical expressions of the problem are transformed into a set of ordinary differential equations by employing appropriate quantities. Well-known long wavelength assumption is invoked. The obtained dimensionless model is then numerically solved with the help of Adams–Bashforth method. The effects of sundry parameters on flow distributions are demonstrated via plots.

Journal ArticleDOI
, Min Yang1, Yali Hou1, Li Runze4
TL;DR: In this article, the authors used the heat transfer model and finite difference model to verify the feasibility of Nanofluid minimum quantity lubrication (NMQL) conditions in grinding cemented carbide.
Abstract: Nanofluid minimum quantity lubrication (NMQL) has better stability, higher thermal conductivity, and excellent lubrication performance compared with traditional flood lubrication. The heat transfer model and finite difference model were established to verify the feasibility of NMQL conditions in grinding cemented carbide. Based on them, the grinding temperature of cemented carbide is calculated numerically. Results show that the grinding zone temperatures of flood grinding and NMQL are lower, 85.9 °C and 143.2 °C, respectively. Surface grinding experiments of cemented carbide YG8 under different working conditions are carried out. Dry grinding (227.2 °C) is used as the control group. Grinding zone temperatures of flood grinding, minimum quantity lubrication, and NMQL decrease by 64.2%, 39.5%, and 20.4%, respectively. The error is 6.3% between theoretical calculation temperature and experimental measurement temperature. Based on machining process parameters (specific grinding force, force ratio) and experimental results (microstructure of grinding wheel, workpiece, and grinding debris), the effects of different working conditions on wheel wear are studied. NMQL achieves the highest G ratio of 6.45, the smallest specific grinding force, and the smallest Fn/Ft ratio of 2.84, which further proves that NMQL is suitable for grinding cemented carbide.

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TL;DR: In this paper, the impact of Cattaneo-Christov model and convective boundary on second-grade nanofluid flow alongside a Riga pattern is investigated.
Abstract: Present communication aims to determine the impact of Cattaneo–Christov model and convective boundary on second-grade nanofluid flow alongside a Riga pattern. Zero mass flux is accounted at the solid surface of Riga pattern such that the fraction of nanoparticles maintains itself on strong retardation. The impact of Lorentz forces generated by Riga pate is also an important aspect of the study. The governing nonlinear problem is converted into ordinary problems via suitably adjusted transformations. Spectral local linearization method has been incorporated to find the solutions of the nonlinear problems. Variation in horizontal movement of the nanofluid, thermal distribution and concentration distribution of the nanoparticles has been noted for various fluid parameters. The results are plotted graphically. Outcomes indicate that the horizontal movement gains enhancement for elevated values of modified Hartman factor. Thermal state of the nanofluid and concentration of nanoparticles receive reduction for incremental values of relaxation time parameters. Numerical results for skin friction and heat flux have been reported in tabular form. The CPU run time and residual error are obtained to check the efficiency of the method used for finding the solution.

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TL;DR: In this paper, a least square support vector machine (LS-SVM) was used to predict the convection heat transfer coefficient of nanofluids through circular pipes as an accurate alternative way and draw a clear path for future researches.
Abstract: Convection is one of the main heat transfer mechanisms in both high to low temperature media. The accurate convection heat transfer coefficient (HTC) value is required for exact prediction of heat transfer. As convection HTC depends on many variables including fluid properties, flow hydrodynamics, surface geometry and operating and boundary conditions, among others, its accurate estimation is often too hard. Homogeneous dispersion of nanoparticles in a base fluid (nanofluids) that found high popularities during the past two decades has also increased the level of this complexity. Therefore, this study aims to show the application of least-square support vector machines (LS-SVM) for prediction of convection heat transfer coefficient of nanofluids through circular pipes as an accurate alternative way and draw a clear path for future researches in the field.,The proposed LS-SVM model is developed using a relatively huge databank, including 253 experimental data sets. The predictive performance of this intelligent approach is validated using both experimental data and empirical correlations in the literature.,The results show that the LS-SVM paradigm with a radial basis kernel outperforms all other considered approaches. It presents an absolute average relative deviation of 2.47% and the regression coefficient (R2) of 0.99935 for the estimation of the experimental databank. The proposed smart paradigm expedites the procedure of estimation of convection HTC of nanofluid flow inside circular pipes.,Therefore, the focus of the current study is concentrated on the estimation of convection HTC of nanofluid flow through circular pipes using the LS-SVM. Indeed, this estimation is done using operating conditions and some simply measured characteristics of nanoparticle, base fluid and nanofluid.

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TL;DR: The heat transfer and pressure drop performance of magnetic nanofluids (MNFs) under different alternating magnetic fields were investigated experimentally as discussed by the authors, and the results showed that the effect of alternating magnetic field on local heat transfer coefficient is better than that of unidirectional and non-magnetic fields along flow direction.
Abstract: The heat transfer and pressure drop performance of magnetic nanofluids (MNFs) under different alternating magnetic fields were investigated experimentally. The results showed that the effect of alternating magnetic field on local heat transfer coefficient is better than that of unidirectional and non-magnetic fields along flow direction. The local heat transfer coefficient in the rear of the flow channel has a greater promoting capacity than that in the front. The heat transfer performance is higher at a lower Reynolds number (Re), but worse at a higher Re. Heat transfer coefficient always increases with the increase of volume fraction with or without alternating magnetic fields. When the volume fraction is among 1 vol%-3 vol%, the greater the alternating frequency is, the better the heat transfer performance will be. When the volume fraction is greater than 3 vol%, increasing the frequency of alternating magnetic field has little effect on heat transfer performance. For magnetic nanofluids with different volume fractions and different magnetic fields, they also show quadratic variation rules. The larger the volume fraction and magnetic field frequency are, the greater the pressure drop will be. The improvement of the overall heat transfer performance increases first and then decreases when the alternating frequencies and Reynolds numbers increase. The reasons for the improvement of the heat transfer are the movement and accumulation of magnetic nanoparticles at the thermal boundary layer, and the eddy action of MNFs.

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TL;DR: In this paper, numerical simulations were adopted to explore the heat transfer and flow characteristics of magnetic nanofluids under different magnetic field intensities, volume fractions, and magnetic field directions, and they found that the effect of heat transfer enhancement was small under a weak magnetic field, but it increased considerably under a strong magnetic field.
Abstract: Numerical simulations were adopted to explore the heat transfer and flow characteristics of magnetic nanofluids under different magnetic field intensities, volume fractions, and magnetic field directions. Due to these parameters have a significant effect on thermal hydraulic performance and the mechanism of this enhancement are not yet clear, a turbulent model of Re-normalization group (RNG) k-e is used to analyze the variation of thermal boundary layer and particle motion. The obtained results found that the effect of heat transfer enhancement was small under a weak magnetic field, but it increased considerably under a strong magnetic field. Besides, the convection heat transfer coefficient initially increased and then decreased with an increase of volume fractions of magnetic nanoparticles. Moreover, the directions of the magnetic field have a significant effect on convective heat transfer coefficient, which results in 8% increase when the direction is perpendicular to direction of flow.

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TL;DR: In this article, the authors examined the deposition of thermophoretic particles in the flow of hybrid nanofluid suspended by ferrite nanoparticles past an expansion/contraction moving disk with rotation.
Abstract: The research on flow of fluids fuelled by rotating disk motion has been increasing, due to the development of machine technology. Inspired by this development, we examined the deposition of thermophoretic particles in the flow of hybrid nanofluid suspended by ferrite nanoparticles past an expansion/contraction moving disk with rotation. Estimated PDE's are converted to ODEs with consideration of the corresponding similarity transformations. The obtained nondimensional expressions are solved by a numerical process known as the Runge-Kutta Fehlberg fourth - fifth order (RKF-45 method) by adopting shooting technique. Behavioural studies of velocity, concentration and thermal profiles of various parameter values are assessed using graphs. Physical concern parameters such as, velocity of thermophoretic particle deposition and velocity of thermophoretic are also analyzed graphically. The result reveals that, speed of the disk movement in the upward direction escalates the tangential as well as radial velocity gradients and rise in values of thermophoretic coefficient and thermophoretic parameter declines the rate of mass transfer.

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TL;DR: In this paper, two distinct nanoparticles are immerged in micropolar fluid to interrogate the feature of heat and mass transfer, and non-dimensional similarity transformation is utilized to transform the partial differential equations into nonlinear ordinary differential equations, and resulting coupled equations are solved numerically using bvp4c from MATLAB.
Abstract: Cattaneo–Christov with variable thermal relaxation time and entropy generation is the main concern of this study. The micropolar fluid with absorption of heat in the existence of mixed convection and partial slip is scrutinized. Two distinct nanoparticles, i.e., single-wall carbon nanotube and multi-wall carbon nanotube, are immerged in micropolar fluid to interrogate the feature of heat and mass transfer. The non-dimensional similarity transformation is utilized to transform the partial differential equations into nonlinear ordinary differential equations, and resulting coupled equations are solved numerically using bvp4c from MATLAB. The present results show the fabulous agreement with previous published results. The temperature field diminishes with larger thermal relaxation time parameter. Entropy generation profile is an increasing function of Brinkmann number, while Bejan number is a diminishing function. Further the solid volume fraction diminishes the velocity profile and enhances the temperature distribution and entropy generation.

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TL;DR: In this paper, the authors focused on the hydrothermal features of both hybrid and usual nanofluid flow over a slippery permeable bent structure, where Ferrous and graphene nanoparticles along with the host fluid water were taken to simulate the flow.
Abstract: The present investigation concentrates on the hydrothermal features of both hybrid nanofluid and usual nanofluid flow over a slippery permeable bent structure. The surface has also been considered to be coiled inside the circular section of radius R. Ferrous and graphene nanoparticles along with the host fluid water are taken to simulate the flow. The existence of heat sink/source and thermal radiation are incorporated within the system. Resulting equations are translated into its non-dimensional form using similarity renovation and solved by the RK-4 method. The consequence of pertinent factors on the flow profile is explored through graphs and tables. Streamlines and isotherms for both hybrid nanofluid and usual nanofluid are depicted to show the hydrothermal variations. The result communicates that temperature is reduced for curvature factor, whereas velocity is found to be accelerated. Heat transfer is intensified for thermal Biot number, and the rate of increment is higher for hybrid nanosuspension. Velocity and temperature are intensified for enhanced nanoparticle concentration. The heat transport process is decreased for the heat source parameter, but the reduction rate is comparatively slower for hybrid nanofluid.