The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a n...The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a necessary step before their practical application.As these investigations are time and resource-consuming undertakings,an effective prediction model can significantly improve the efficiency of research operations.In this work,an Artificial Neural Network(ANN)model is developed to predict the thermal conductivity of metal oxide water-based nanofluid.For this,a comprehensive set of 691 data points was collected from the literature.This dataset is split into training(70%),validation(15%),and testing(15%)and used to train the ANN model.The developed model is a backpropagation artificial neural network with a 4–12–1 architecture.The performance of the developed model shows high accuracy with R values above 0.90 and rapid convergence.It shows that the developed ANN model accurately predicts the thermal conductivity of nanofluids.展开更多
This study numerically examines the heat and mass transfer characteristics of two ternary nanofluids via converging and diverg-ing channels.Furthermore,the study aims to assess two ternary nanofluids combinations to d...This study numerically examines the heat and mass transfer characteristics of two ternary nanofluids via converging and diverg-ing channels.Furthermore,the study aims to assess two ternary nanofluids combinations to determine which configuration can provide better heat and mass transfer and lower entropy production,while ensuring cost efficiency.This work bridges the gap be-tween academic research and industrial feasibility by incorporating cost analysis,entropy generation,and thermal efficiency.To compare the velocity,temperature,and concentration profiles,we examine two ternary nanofluids,i.e.,TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O and TiO_(2)+SiO_(2)+Cu/H_(2)O,while considering the shape of nanoparticles.The velocity slip and Soret/Dufour effects are taken into consideration.Furthermore,regression analysis for Nusselt and Sherwood numbers of the model is carried out.The Runge-Kutta fourth-order method with shooting technique is employed to acquire the numerical solution of the governed system of ordinary differential equations.The flow pattern attributes of ternary nanofluids are meticulously examined and simulated with the fluc-tuation of flow-dominating parameters.Additionally,the influence of these parameters is demonstrated in the flow,temperature,and concentration fields.For variation in Eckert and Dufour numbers,TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O has a higher temperature than TiO_(2)+SiO_(2)+Cu/H_(2)O.The results obtained indicate that the ternary nanofluid TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O has a higher heat transfer rate,lesser entropy generation,greater mass transfer rate,and lower cost than that of TiO_(2)+SiO_(2)+Cu/H_(2)O ternary nanofluid.展开更多
This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Div...This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Diverse volume fractions(1%, 2%, and 3%) of Al_(2)O_(3)-water nanofluids are meticulously prepared and analyzed. The essential physical properties of these nanofluids, critical for evaluating their thermal and flow characteristics, have been comprehensively assessed. From a quantitative perspective, numerical simulations are employed to predict the Nusselt number(Nu) and friction factor(f). The empirical findings reveal intriguing trends: the friction factor experiences an upward trend with diminishing velocity, attributed to heightened molecular cohesion. Conversely, the friction factor demonstrates a decline with diminishing volume fractions, a consequence of reduced particle size. Both the nanofluid's viscosity and heat transfer coefficient exhibit a rise in tandem with augmented volume flow rate and concentration gradient. Notably, the simulation results harmonize remarkably well with experimental data. Rigorous validation against prior studies underscores the robust consistency of these outcomes. In the pursuit of augmenting heat transfer, a volume fraction of 3% emerges as particularly influential, yielding an impressive 53.8% enhancement. Minor increments in the friction factor, while present, prove negligible and can be safely overlooked.展开更多
High-efficiency solar energy systems are characterized by their designs,which primarily rely on effective concentration and conversion methods of solar radiation.Evaluation of the performance enhancement of flat plate...High-efficiency solar energy systems are characterized by their designs,which primarily rely on effective concentration and conversion methods of solar radiation.Evaluation of the performance enhancement of flat plate solar collectors by integration with thermal energy storage could be achieved through simulation of proposed designs.The work aims to analyze a new solar collector integrated with a porous medium and shell and coiled tube heat exchanger.The heat transfer enhancement was investigated by varying the geometrical parameters in shell and helically coiled tubes operating with CuFe_(2)O_(4)/water with different volume fractions of 0.02%,0.05%,and 0.1 vol.%.This study presents an experimental and numerical investigation of the performance of the flat plate solar collector integrated with a helical coil heat exchanger using nanofluids.The solar collector has a dimension of 180 cm×80 cm and works with close-loop systems operated by the thermo siphon method.Two types of helical coil heat exchangers,Coil-A and Coil-B have been investigated.The diameter of the glass porous media was investigated at 2,5,and 10 mm.The results manifested that the enhancement in the Nusselt number of the nanofluid reached maximum values of 15%,18%,and 22%for nanofluid ferrofluid with volume concentrations of 0.02%,0.05%,and 0.1%,respectively,for Coil-A.The maximum values of Nusselt number enhancement were 14%,17%,and 20%for ferrofluid concentrations of 0.02%,0.05%,and 0.1 vol.%,respectively,for Coil-B.The results also elucidated that the nanofluid mass flow and heat transfer rates could be noticeably compared to water.Where the increase is 5%,10%,and 20%for each concentration and diameter of the porous media,it specifies the enormous ranges of operational and geometrical parameters.展开更多
The growth of computing power in data centers(DCs)leads to an increase in energy consumption and noise pollution of air cooling systems.Chip-level cooling with high-efficiency coolant is one of the promising methods t...The growth of computing power in data centers(DCs)leads to an increase in energy consumption and noise pollution of air cooling systems.Chip-level cooling with high-efficiency coolant is one of the promising methods to address the cooling challenge for high-power devices in DCs.Hybrid nanofluid(HNF)has the advantages of high thermal conductivity and good rheological properties.This study summarizes the numerical investigations of HNFs in mini/micro heat sinks,including the numerical methods,hydrothermal characteristics,and enhanced heat transfer technologies.The innovations of this paper include:(1)the characteristics,applicable conditions,and scenarios of each theoretical method and numerical method are clarified;(2)the molecular dynamics(MD)simulation can reveal the synergy effect,micro motion,and agglomeration morphology of different nanoparticles.Machine learning(ML)presents a feasiblemethod for parameter prediction,which provides the opportunity for the intelligent regulation of the thermal performance of HNFs;(3)the HNFs flowboiling and the synergy of passive and active technologies may further improve the overall efficiency of liquid cooling systems in DCs.This review provides valuable insights and references for exploring the multi-phase flow and heat transport mechanisms of HNFs,and promoting the practical application of HNFs in chip-level liquid cooling in DCs.展开更多
This study investigates laminar convection in three regimes(forced convection,mixed convection,and natural convection)of a bi-nanofluid(Cu-Al_(2)O_(3)-water)/mono-nanofluid(Al_(2)O_(3)-water)inside a square enclosure ...This study investigates laminar convection in three regimes(forced convection,mixed convection,and natural convection)of a bi-nanofluid(Cu-Al_(2)O_(3)-water)/mono-nanofluid(Al_(2)O_(3)-water)inside a square enclosure of sliding vertical walls which are kept at cold temperature and moving up,down,or in opposite directions.The enclosure bottom is heated partially by a central heat source of various sizes while the horizontal walls are considered adiabatic.The thermal conductivity and dynamic viscosity are dependent on temperature and nanoparticle size.The conservation equations are implemented in the solver ANSYS R2(2020).The numerical predictions are successfully validated by comparison with data from the literature.Numerical simulations are carried out for various volume fractions of solid mono/hybrid-nanoparticles(0≤ϕ≤5%),Richardson numbers(0.001≤Ri≤10),and hot source lengths((1/5)H≤ε≤(4/5)H).Isothermal lines,streamlines,and average Nusselt numbers are analyzed.The thermal performance of nanofluids is compared to that of the base heat transfer fluid(water).Outcomes illustrate the flow characteristics significantly affected by the convection regime,hot source size,sidewall motion,and concentration of solid nanoparticles.In the case of sidewalls moving downward,using hybrid nanofluid(Cu-Al_(2)O_(3)-water)shows the highest heat transfer rate in the enclosure at Ri=1,ε=(4/5)H and volume fraction ofφ=5%where a significant increment(25.14%)of Nusselt number is obtained.展开更多
The thermal nanofluids have garnered widespread attention for their use in multiple thermal systems,including heating processes,sustainable energy,and nuclear reactions.Research on nanofluids has revealed that the the...The thermal nanofluids have garnered widespread attention for their use in multiple thermal systems,including heating processes,sustainable energy,and nuclear reactions.Research on nanofluids has revealed that the thermal efficiencies of such materials are adversely affected by various thermal features.The purpose of the current work is to demonstrate the thermal analysis of Jeffrey nanofluids with the suspension of microorganisms in the presence of variable thermal sources.The variable effects of thermal conductivity,Brownian diffusivity,and motile density are utilized.The investigated model also reveals the contributions of radiation phenomena and chemical reactions.A porous,saturated,moving surface with a suction phenomenon promotes flow.The modeling of the problem is based on the implementation of the Cattaneo-Christov approach.The convective thermal constraints are used to promote the heat transfer features.A simplified form of the governing model is treated with the assistance of a shooting technique.The physical effects of different parameters for the problem are presented.The current problem justifies its applications in heat transfer,coating processes,heat exchangers,cooling systems in microelectronics,solar systems,chemical processes,etc.展开更多
The current work aims to numerically investigate the impact of using(50%ZnO and 50%Al_(2)O_(3))hybrid nanofluid(HNf)on the performance of convective heat transfer inside a horizontal wavy micro-channel.This issue repr...The current work aims to numerically investigate the impact of using(50%ZnO and 50%Al_(2)O_(3))hybrid nanofluid(HNf)on the performance of convective heat transfer inside a horizontal wavy micro-channel.This issue represents a novel approach that has not been extensively covered in previous research and provides more valuable insights into the performance of HNfs in complex flow geometries.The conjugate heat transfer approach is used to demonstrate the influence of adding hybrid nanoparticles(50%Al_(2)O_(3) and 50%ZnO)to pure water on the rate of heat transfer.The governing equations are numerically solved by using ANSYS FLUENT(2021 R2).The behaviors of convective heat transfer coefficient(HTC),Nusselt number(Nu)and pressure drop are presented under various volume concentrations of(1%,2%and 3%)and Reynolds numbers(Re=600,1200 and 1800).The numerical results are validated against the experimental one,where the validation test shows a good agreement between them.The findings display that the highest HTC enhancement is reached at 59.5%when using a volume concentration of 3%and Re=1800.TheNusselt number is increased with the rise in volume concentration of nanoparticles,where the value of the Nusselt number is improved by 42.25%at 3%volume concentration.The reduction in pressure is raised with an increase in volume concentration and Re.The results also show that the combination of dispersion characteristics,Brownian movement and nanoparticles leads to an improvement in the rate of heat transfer.It is concluded that Nu and the behavior of heat transfer are considerably enhanced when using a hybrid nanofluid inside a wavy micro-channel.展开更多
The use of nanofluids as heat transfer media represents an innovative strategy to enhance heat transfer performances.This study investigates experimentally the turbulent convective heat transfer characteristics of wat...The use of nanofluids as heat transfer media represents an innovative strategy to enhance heat transfer performances.This study investigates experimentally the turbulent convective heat transfer characteristics of waterbased nanofluids containing TiO_(2),CuO,and graphene nanoplatelet(GNP)nanoparticles as they flow through a copper tube.Both the dynamic viscosity and thermal conductivity of these nanofluids were modeled and experimentally measured across varying nanoparticle concentrations(0.01,0.02,and 0.03 vol.%)and temperatures(25℃,35℃,and 45℃).The findings indicate that the behavior of nanofluids depends on the parameter used for comparison with the base fluid.Notably,both the friction factor and heat transfer coefficient increase with higher nanoparticle volume concentrations at a constant Reynolds number.The results further reveal that the GNP/water nanofluid,with a volume concentration of 0.03%at 45℃,exhibit the highest Nusselt number,followed by the CuO/water and TiO_(2)/water nanofluids,with respective increases of 17.8%,11.09%,and 8.11%.展开更多
This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity a...This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity and thermal slip boundary conditions are also examined.The considered hybrid nano-fluid contains silver(Ag)and iron oxide(Fe_(3)O_(4))nanoparticles dispersed in the water to prepare the Ag-Fe_(3)O_(4)/water-based hybrid nanofluid.The requisite posited partial differential equations model is converted to ordinary differential equations using similarity transformations.For a numerical solution,the shooting method in Maple is employed.Moreover,the duality in solutions is achieved for both cases of the disk(stretching(λ>0)and shrinking(λ<0)).At the same time,a unique solution is observed for λ=0.No solution is found for them at λ<λ_(c),whereas the solutions are split at the λ=λ_(c).Besides,the value of the λ_(c) is dependent on the φ_(hnf).Meanwhile,the values of f″(0)and -θ′(0)intensified with increasing φ_(hnf).Stability analysis has been applied using bvp4c in MATLAB software due to a dual solution.Furthermore,analysis shows that the first solution is stable and feasible physically.For the slip parameters,an increase in the velocity slip parameter increases the velocity and shear stress profiles while increasing the temperature profile in the first solutions.While the rise in thermal slip parameter reduces the temperature profile nanoparticle volume fractions increase it.展开更多
This study explores free convective heat transfer in an electrically conducting nanofluid flow over a moving semi-infinite flat plate under the influence of an induced magnetic field and viscous dissipation.The veloci...This study explores free convective heat transfer in an electrically conducting nanofluid flow over a moving semi-infinite flat plate under the influence of an induced magnetic field and viscous dissipation.The velocity and magnetic field vectors are aligned at a distance from the plate.The Spectral Relaxation Method(SRM)is used to numerically solve the coupled nonlinear partial differential equations,analyzing the effects of the Eckert number on heat and mass transfer.Various nanofluids containing Cu,Ag,Al_(2)O_(3),and TiO_(2) nanoparticles are examined to assess how external magnetic fields influence fluid behavior.Key parameters,including the nanoparticle volume fraction ϕ,magnetic parameter M,magnetic Prandtl number Prm,and Eckert number Ec,are evaluated for their impact on velocity,induced magnetic field,and heat transfer.Results indicate that increasing the magnetic parameter reduces velocity and magnetic field components in alumina-water nanofluids,while a higher nanoparticle volume fraction enhances the thermal boundary layer.Greater viscous dissipation(Ec)increases temperature,and Al_(2)O_(3) nanofluids exhibit higher speeds than Cu,Ag,and TiO_(2) due to density differences.Silver-water nanofluids,with their higher density,move more slowly.The SRM results closely align with those from Maple,confirming the method’s accuracy.展开更多
Peristaltic transport of non-Newtonian nanofluids with double diffusion is essential to biological engineering,microfluidics,and manufacturing processes.The authors tackle the key problem of Sisko nanofluids under dou...Peristaltic transport of non-Newtonian nanofluids with double diffusion is essential to biological engineering,microfluidics,and manufacturing processes.The authors tackle the key problem of Sisko nanofluids under double diffusion convection with thermal radiations and electroosmotic effects.Thestudy proposes a solution approach by using Morlet-Wavelet Neural Networks that can effectively solve this complex problem by their superior ability in the capture of nonlinear dynamics.These convergence analyses were calculated across fifty independent runs.Theil’s Inequality Coefficient and theMean Squared Error values range from 10^(-7) to 10^(-5) and 10^(-7) to 10^(-10),respectively.These values showed the proposed method is scientifically reliable and fast converging.Studies reveal that the intensity of the magnetic field causes a reduction in the flow velocity profile in the center of the channel.It is also evaluated that thermal radiations enhance the energy of the system,which promotes thermally induced diffusion and particle flow.The physical applications of this work pertain to improving fluid flow and heat transfer in engineering structures like converters or cooling devices or magnetic fluids in electronics,energy,and biomedical applications,where optimal control of fluid behavior is of paramount importance.展开更多
To improve the efficiency of coal seam water injection,the influence of nanofluids on coal surface wettability was studied based on the nano drag reduction and injection enhancement technology in the field of tertiary...To improve the efficiency of coal seam water injection,the influence of nanofluids on coal surface wettability was studied based on the nano drag reduction and injection enhancement technology in the field of tertiary oil recovery.The composition optimization and performance evaluation of nanofluids with nano-silica and sodium lauryl sulfate as the main components were carried out,and the effects of the nanofluid with the optimal ratio on coal wettability were studied through spontaneous upward imbibition experiments.The results show that the composite nanofluid has a lower surface tension,and the lowest value of the interfacial tension is 15.79 m N/m.Therefore,the composite nanofluid can enhance the wettability of coal.However,its effects on coal samples with different metamorphic degrees is different,that is,low rank coal is the largest,middle rank coal is the second,and high rank coal is the least.In addition,a functional relationship between time and imbibition height is found for pulverized coal with different particle sizes.When the particle size of pulverized coal is 60–80 mesh,the wettability of nanofluid to coal is best.The findings in this paper provide a new perspective for improving the water injection efficiency for coal seams with low permeability.展开更多
In the present research,Tiwari and Das model are used for the impact of a magnetic field on non-Newtonian nanofluid flow in the presence of injection and suction.The PDEs are converted into ordinary differential equat...In the present research,Tiwari and Das model are used for the impact of a magnetic field on non-Newtonian nanofluid flow in the presence of injection and suction.The PDEs are converted into ordinary differential equations(ODEs)using the similarity method.The obtained ordinary differential equations are solved numerically using shooting method along with RK-4.Part of the present study uses nanoparticles(NPs)like TiO_(2) andAl_(2)O_(3) and sodium carboxymethyl cellulose(CMC/water)is considered as a base fluid(BF).This study is conducted to find the influence of nanoparticles,Prandtl number,and magnetic field on velocity and temperature profile,however,the Nusselt number and coefficient of skin friction parameters are also presented in detail with the variation of nanoparticles and parameters.The obtained results of the present study are presented usingMATLAB.In addition to these,some simulations of partial differential equations are also shown using software for graphing surface plots of velocity profile and streamlines along with surface plots and isothermal contours of the temperature profile.展开更多
A numerical analysis of the log-law behavior for the turbulent boundary layer of a wall-bounded flow is performed over a flat plate immersed in three nanofluids(Zn O-water,SiO_(2)-water,TiO_(2)-water).Numerical simula...A numerical analysis of the log-law behavior for the turbulent boundary layer of a wall-bounded flow is performed over a flat plate immersed in three nanofluids(Zn O-water,SiO_(2)-water,TiO_(2)-water).Numerical simulations using CFD code are employed to investigate the boundary layer and the hydrodynamic flow.To validate the current numerical model,measurement points from published works were used,and the compared results were in good compliance.Simulations were carried out for the velocity series of 0.04,0.4 and 4 m/s and nanoparticle concentrations0.1% and 5%.The influence of nanoparticles’ concentration on velocity,temperature profiles,wall shear stress,and turbulent intensity was investigated.The obtained results showed that the viscous sub-layer,the buffer layer,and the loglaw layer along the potential-flow layer could be analyzed based on their curving quality in the regions which have just a single wall distance.It was seen that the viscous sub-layer is the biggest area in comparison with other areas.Alternatively,the section where the temperature changes considerably correspond to the thermal boundary layer’s thickness goes a downward trend when the velocity decreases.The thermal boundary layer gets deep away from the leading edge.However,a rise in the volume fraction of nanoparticles indicated a minor impact on the shear stress developed in the wall.In all cases,the thickness of the boundary layer undergoes a downward trend as the velocity increases,whereas increasing the nanoparticle concentrations would enhance the thickness.More precisely,the log layer is closed with log law,and it is minimal between Y^(+)=50 and Y^(+)=95.The temperature for nanoparticle concentration φ=5%is higher than that for φ=0.1%,in boundary layers,for all studied nanofluids.However,it is established that the behavior is inverted from the value of Y^(+)=1 and the temperature for φ =0.1% is more important than the case of φ =5%.For turbulence intensity peak,this peak exists at Y^(+)=100 for v=4 m/s,Y^(+)=10 for v=0.4 m/s and Y^(+)=8 for v=0.04 m/s.展开更多
Thermo-hydraulic characteristics of TiO_2-water nanofluids in thin-wall stainless steel test tubes(corrugated tube and circular tube) filled with copper foam(40 PPI) are experimentally investigated and compared with t...Thermo-hydraulic characteristics of TiO_2-water nanofluids in thin-wall stainless steel test tubes(corrugated tube and circular tube) filled with copper foam(40 PPI) are experimentally investigated and compared with those in test tubes without copper foam. The effects of nanoparticle mass concentration on flow and heat transfer performances are investigated. In addition, the mutual restriction relationships between Reynolds number(Re), Nusselt number(Nu) and resistance coefficient(f) are discussed respectively. Also, the comprehensive coefficient of performance(CCP) between heat transfer and pressure drop is evaluated. The results show that core-enhancement region for heat transfer using experimental tubes filled with copper foam is notably different from that of tubes without copper foam. There is a corresponding Reynolds number(about Re = 2400) for the maximum CCP of each condition. And the heat transfer can be enhanced dramatically and sustained at 8000 ≤ Re ≤ 12000.展开更多
In order to investigate the mechanism of nanoparticles enhancing the heat and mass transfer of the ammonia-water absorption process,several types of binary nanofluids were prepared by mixing Al2O3 nanoparticles with p...In order to investigate the mechanism of nanoparticles enhancing the heat and mass transfer of the ammonia-water absorption process,several types of binary nanofluids were prepared by mixing Al2O3 nanoparticles with polyacrylic acid(PAA),TiO2 with polyethylene glycol(PEG 1000),and TiN,SiC,hydroxyapatite(noodle-like) with PEG 10000 to ammonia-water solution,respectively.The thermal conductivities were measured by using a KD2 Pro thermal properties analyzer.The influences of surfactant and ammonia on the dispersion stabilities of the binary nanofluids were investigated by the light absorbency ratio index methods.The results show that the type,content and size of nanoparticles,the temperature as well as the dispersion stability are the key parameters that affect the thermal conductivity of nanofluids.For the given nanoparticle material and the base fluid,the thermal conductivity ratio of the nanofluid to the ammonia-water liquid increases as the nanoparticle content and the temperature are increased,and the diameter of nanoparticle is decreased.Furthermore,the thermal conductivity ratio increases significantly by improving the stabilities of nanofluids,which is achieved by adding surfactants or performing the proper ammonia content in the fluid.展开更多
In this work, some thermodynamic properties of nanofluids such as Sb_2O_5;SnO_2/(EG + H_2O), ZnO/(EG + H_2O),Al_2O_3/(EG + H_2O), ZnO/(PEG + H_2O), ZnO/PEG, and TiO_2/EG were estimated from the extended Tao–Mason equ...In this work, some thermodynamic properties of nanofluids such as Sb_2O_5;SnO_2/(EG + H_2O), ZnO/(EG + H_2O),Al_2O_3/(EG + H_2O), ZnO/(PEG + H_2O), ZnO/PEG, and TiO_2/EG were estimated from the extended Tao–Mason equation of state, together with the Pak and Cho equation in various temperature, pressure, and volume fractions.The equations of state using minimum input data and density at room temperature as scaling constants, were developed to estimated densities of the above mentioned nanofluids. Furthermore, the artificial neural network plus principal component analysis(PCA) technique(with 20 neuron in hidden layer) was performed over the whole range of available conditions. The AADs of the calculated molar densities of all nanofluids using the EOS and ANN at various temperatures and volume fractions are 1.11% and 0.48%, respectively. In addition, the heat capacity and isentropic compressibility of the above mentioned nanofluids are predicted using obtained densities of EOS with the Pak and Cho equation.展开更多
We studied the relationship between corona structure and properties of solvent-free Fe3O4 nanofluids. We proposed a series of corona structures with different branched chains and synthesize different solvent-free nano...We studied the relationship between corona structure and properties of solvent-free Fe3O4 nanofluids. We proposed a series of corona structures with different branched chains and synthesize different solvent-free nanofluids in order to show the effect of corona structure on the phase behavior, dispersion, as well as rheology properties. Results demonstrate novel liquid-like behaviors without solvent at room temperature. Fe3O4 magnetic nanoparticles content is bigger than 8% and its size is about 23 nm. For the solvent-free nanofluids,the long chain corona has the internal plasticization, which can decrease the loss modulus of system, while the short chain of corona results in the high viscosity of nanofluids. Long alkyl chains of modifiers lead to lower viscosity and better flowability of nanofluids. The rheology and viscosity of the nanofluids are correlated to the microscopic structure of the corona, which provide an in-depth insight into the preparing nanofluids with promising applications based on their tunable and controllable physical properties.展开更多
Nanofluids or liquids with suspended nanoparticles are likely to be the future heat transfer media, as they exhibit higher thermal conductivity than those of liquids. It has been proposed that nanoparticles are apt to...Nanofluids or liquids with suspended nanoparticles are likely to be the future heat transfer media, as they exhibit higher thermal conductivity than those of liquids. It has been proposed that nanoparticles are apt to congregate and form clusters, and hence the interaction between nanoparticles becomes important. In this paper, by taking into account the interaction between nearest-neighbour inclusions, we adopt the multiple image method to investigate the effective thermal conductivity of nanofluids. Numerical results show that then the thermal conductivity ratio between the nanoparticles and fluids is large, and the two nanoparticles are close up and even touch, and the polnt-dipole theory such as Maxwell-Garnett theory becomes rough as many-body interactions are neglected. Our theoretical results on the effective thermal conductivity of CuO/water and Al2O3/water nanofluids are in good agreement with experimental data.展开更多
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(2021R1A6A1A10044950).
文摘The thermal conductivity of nanofluids is an important property that influences the heat transfer capabilities of nanofluids.Researchers rely on experimental investigations to explore nanofluid properties,as it is a necessary step before their practical application.As these investigations are time and resource-consuming undertakings,an effective prediction model can significantly improve the efficiency of research operations.In this work,an Artificial Neural Network(ANN)model is developed to predict the thermal conductivity of metal oxide water-based nanofluid.For this,a comprehensive set of 691 data points was collected from the literature.This dataset is split into training(70%),validation(15%),and testing(15%)and used to train the ANN model.The developed model is a backpropagation artificial neural network with a 4–12–1 architecture.The performance of the developed model shows high accuracy with R values above 0.90 and rapid convergence.It shows that the developed ANN model accurately predicts the thermal conductivity of nanofluids.
基金supported by DST-FIST(Government of India)(Grant No.SR/FIST/MS-1/2017/13)and Seed Money Project(Grant No.DoRDC/733).
文摘This study numerically examines the heat and mass transfer characteristics of two ternary nanofluids via converging and diverg-ing channels.Furthermore,the study aims to assess two ternary nanofluids combinations to determine which configuration can provide better heat and mass transfer and lower entropy production,while ensuring cost efficiency.This work bridges the gap be-tween academic research and industrial feasibility by incorporating cost analysis,entropy generation,and thermal efficiency.To compare the velocity,temperature,and concentration profiles,we examine two ternary nanofluids,i.e.,TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O and TiO_(2)+SiO_(2)+Cu/H_(2)O,while considering the shape of nanoparticles.The velocity slip and Soret/Dufour effects are taken into consideration.Furthermore,regression analysis for Nusselt and Sherwood numbers of the model is carried out.The Runge-Kutta fourth-order method with shooting technique is employed to acquire the numerical solution of the governed system of ordinary differential equations.The flow pattern attributes of ternary nanofluids are meticulously examined and simulated with the fluc-tuation of flow-dominating parameters.Additionally,the influence of these parameters is demonstrated in the flow,temperature,and concentration fields.For variation in Eckert and Dufour numbers,TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O has a higher temperature than TiO_(2)+SiO_(2)+Cu/H_(2)O.The results obtained indicate that the ternary nanofluid TiO_(2)+SiO_(2)+Al_(2)O_(3)/H_(2)O has a higher heat transfer rate,lesser entropy generation,greater mass transfer rate,and lower cost than that of TiO_(2)+SiO_(2)+Cu/H_(2)O ternary nanofluid.
文摘This study delves into both experimental and analytical examinations of heat exchange in a straight channel, where Al_(2)O_(3)-water nanofluids are utilized, spanning the Reynolds number spectrum from 100 to 1800. Diverse volume fractions(1%, 2%, and 3%) of Al_(2)O_(3)-water nanofluids are meticulously prepared and analyzed. The essential physical properties of these nanofluids, critical for evaluating their thermal and flow characteristics, have been comprehensively assessed. From a quantitative perspective, numerical simulations are employed to predict the Nusselt number(Nu) and friction factor(f). The empirical findings reveal intriguing trends: the friction factor experiences an upward trend with diminishing velocity, attributed to heightened molecular cohesion. Conversely, the friction factor demonstrates a decline with diminishing volume fractions, a consequence of reduced particle size. Both the nanofluid's viscosity and heat transfer coefficient exhibit a rise in tandem with augmented volume flow rate and concentration gradient. Notably, the simulation results harmonize remarkably well with experimental data. Rigorous validation against prior studies underscores the robust consistency of these outcomes. In the pursuit of augmenting heat transfer, a volume fraction of 3% emerges as particularly influential, yielding an impressive 53.8% enhancement. Minor increments in the friction factor, while present, prove negligible and can be safely overlooked.
文摘High-efficiency solar energy systems are characterized by their designs,which primarily rely on effective concentration and conversion methods of solar radiation.Evaluation of the performance enhancement of flat plate solar collectors by integration with thermal energy storage could be achieved through simulation of proposed designs.The work aims to analyze a new solar collector integrated with a porous medium and shell and coiled tube heat exchanger.The heat transfer enhancement was investigated by varying the geometrical parameters in shell and helically coiled tubes operating with CuFe_(2)O_(4)/water with different volume fractions of 0.02%,0.05%,and 0.1 vol.%.This study presents an experimental and numerical investigation of the performance of the flat plate solar collector integrated with a helical coil heat exchanger using nanofluids.The solar collector has a dimension of 180 cm×80 cm and works with close-loop systems operated by the thermo siphon method.Two types of helical coil heat exchangers,Coil-A and Coil-B have been investigated.The diameter of the glass porous media was investigated at 2,5,and 10 mm.The results manifested that the enhancement in the Nusselt number of the nanofluid reached maximum values of 15%,18%,and 22%for nanofluid ferrofluid with volume concentrations of 0.02%,0.05%,and 0.1%,respectively,for Coil-A.The maximum values of Nusselt number enhancement were 14%,17%,and 20%for ferrofluid concentrations of 0.02%,0.05%,and 0.1 vol.%,respectively,for Coil-B.The results also elucidated that the nanofluid mass flow and heat transfer rates could be noticeably compared to water.Where the increase is 5%,10%,and 20%for each concentration and diameter of the porous media,it specifies the enormous ranges of operational and geometrical parameters.
基金funded by the Science and Technology Project of Tianjin(No.24YDTPJC00680)the National Natural Science Foundation of China(No.52406191).
文摘The growth of computing power in data centers(DCs)leads to an increase in energy consumption and noise pollution of air cooling systems.Chip-level cooling with high-efficiency coolant is one of the promising methods to address the cooling challenge for high-power devices in DCs.Hybrid nanofluid(HNF)has the advantages of high thermal conductivity and good rheological properties.This study summarizes the numerical investigations of HNFs in mini/micro heat sinks,including the numerical methods,hydrothermal characteristics,and enhanced heat transfer technologies.The innovations of this paper include:(1)the characteristics,applicable conditions,and scenarios of each theoretical method and numerical method are clarified;(2)the molecular dynamics(MD)simulation can reveal the synergy effect,micro motion,and agglomeration morphology of different nanoparticles.Machine learning(ML)presents a feasiblemethod for parameter prediction,which provides the opportunity for the intelligent regulation of the thermal performance of HNFs;(3)the HNFs flowboiling and the synergy of passive and active technologies may further improve the overall efficiency of liquid cooling systems in DCs.This review provides valuable insights and references for exploring the multi-phase flow and heat transport mechanisms of HNFs,and promoting the practical application of HNFs in chip-level liquid cooling in DCs.
文摘This study investigates laminar convection in three regimes(forced convection,mixed convection,and natural convection)of a bi-nanofluid(Cu-Al_(2)O_(3)-water)/mono-nanofluid(Al_(2)O_(3)-water)inside a square enclosure of sliding vertical walls which are kept at cold temperature and moving up,down,or in opposite directions.The enclosure bottom is heated partially by a central heat source of various sizes while the horizontal walls are considered adiabatic.The thermal conductivity and dynamic viscosity are dependent on temperature and nanoparticle size.The conservation equations are implemented in the solver ANSYS R2(2020).The numerical predictions are successfully validated by comparison with data from the literature.Numerical simulations are carried out for various volume fractions of solid mono/hybrid-nanoparticles(0≤ϕ≤5%),Richardson numbers(0.001≤Ri≤10),and hot source lengths((1/5)H≤ε≤(4/5)H).Isothermal lines,streamlines,and average Nusselt numbers are analyzed.The thermal performance of nanofluids is compared to that of the base heat transfer fluid(water).Outcomes illustrate the flow characteristics significantly affected by the convection regime,hot source size,sidewall motion,and concentration of solid nanoparticles.In the case of sidewalls moving downward,using hybrid nanofluid(Cu-Al_(2)O_(3)-water)shows the highest heat transfer rate in the enclosure at Ri=1,ε=(4/5)H and volume fraction ofφ=5%where a significant increment(25.14%)of Nusselt number is obtained.
基金appreciation to King Saud University for funding this work through researchers supporting project(No.RSPD2025R1056).
文摘The thermal nanofluids have garnered widespread attention for their use in multiple thermal systems,including heating processes,sustainable energy,and nuclear reactions.Research on nanofluids has revealed that the thermal efficiencies of such materials are adversely affected by various thermal features.The purpose of the current work is to demonstrate the thermal analysis of Jeffrey nanofluids with the suspension of microorganisms in the presence of variable thermal sources.The variable effects of thermal conductivity,Brownian diffusivity,and motile density are utilized.The investigated model also reveals the contributions of radiation phenomena and chemical reactions.A porous,saturated,moving surface with a suction phenomenon promotes flow.The modeling of the problem is based on the implementation of the Cattaneo-Christov approach.The convective thermal constraints are used to promote the heat transfer features.A simplified form of the governing model is treated with the assistance of a shooting technique.The physical effects of different parameters for the problem are presented.The current problem justifies its applications in heat transfer,coating processes,heat exchangers,cooling systems in microelectronics,solar systems,chemical processes,etc.
文摘The current work aims to numerically investigate the impact of using(50%ZnO and 50%Al_(2)O_(3))hybrid nanofluid(HNf)on the performance of convective heat transfer inside a horizontal wavy micro-channel.This issue represents a novel approach that has not been extensively covered in previous research and provides more valuable insights into the performance of HNfs in complex flow geometries.The conjugate heat transfer approach is used to demonstrate the influence of adding hybrid nanoparticles(50%Al_(2)O_(3) and 50%ZnO)to pure water on the rate of heat transfer.The governing equations are numerically solved by using ANSYS FLUENT(2021 R2).The behaviors of convective heat transfer coefficient(HTC),Nusselt number(Nu)and pressure drop are presented under various volume concentrations of(1%,2%and 3%)and Reynolds numbers(Re=600,1200 and 1800).The numerical results are validated against the experimental one,where the validation test shows a good agreement between them.The findings display that the highest HTC enhancement is reached at 59.5%when using a volume concentration of 3%and Re=1800.TheNusselt number is increased with the rise in volume concentration of nanoparticles,where the value of the Nusselt number is improved by 42.25%at 3%volume concentration.The reduction in pressure is raised with an increase in volume concentration and Re.The results also show that the combination of dispersion characteristics,Brownian movement and nanoparticles leads to an improvement in the rate of heat transfer.It is concluded that Nu and the behavior of heat transfer are considerably enhanced when using a hybrid nanofluid inside a wavy micro-channel.
文摘The use of nanofluids as heat transfer media represents an innovative strategy to enhance heat transfer performances.This study investigates experimentally the turbulent convective heat transfer characteristics of waterbased nanofluids containing TiO_(2),CuO,and graphene nanoplatelet(GNP)nanoparticles as they flow through a copper tube.Both the dynamic viscosity and thermal conductivity of these nanofluids were modeled and experimentally measured across varying nanoparticle concentrations(0.01,0.02,and 0.03 vol.%)and temperatures(25℃,35℃,and 45℃).The findings indicate that the behavior of nanofluids depends on the parameter used for comparison with the base fluid.Notably,both the friction factor and heat transfer coefficient increase with higher nanoparticle volume concentrations at a constant Reynolds number.The results further reveal that the GNP/water nanofluid,with a volume concentration of 0.03%at 45℃,exhibit the highest Nusselt number,followed by the CuO/water and TiO_(2)/water nanofluids,with respective increases of 17.8%,11.09%,and 8.11%.
基金the Researchers Supporting Project number(RSPD2025R997),King Saud University,Riyadh,Saudi Arabia.
文摘This paper discusses the model of the boundary layer(BL)flow and the heat transfer characteristics of hybrid nanofluid(HNF)over shrinking/stretching disks.In addition,the thermal radiation and the impact of velocity and thermal slip boundary conditions are also examined.The considered hybrid nano-fluid contains silver(Ag)and iron oxide(Fe_(3)O_(4))nanoparticles dispersed in the water to prepare the Ag-Fe_(3)O_(4)/water-based hybrid nanofluid.The requisite posited partial differential equations model is converted to ordinary differential equations using similarity transformations.For a numerical solution,the shooting method in Maple is employed.Moreover,the duality in solutions is achieved for both cases of the disk(stretching(λ>0)and shrinking(λ<0)).At the same time,a unique solution is observed for λ=0.No solution is found for them at λ<λ_(c),whereas the solutions are split at the λ=λ_(c).Besides,the value of the λ_(c) is dependent on the φ_(hnf).Meanwhile,the values of f″(0)and -θ′(0)intensified with increasing φ_(hnf).Stability analysis has been applied using bvp4c in MATLAB software due to a dual solution.Furthermore,analysis shows that the first solution is stable and feasible physically.For the slip parameters,an increase in the velocity slip parameter increases the velocity and shear stress profiles while increasing the temperature profile in the first solutions.While the rise in thermal slip parameter reduces the temperature profile nanoparticle volume fractions increase it.
文摘This study explores free convective heat transfer in an electrically conducting nanofluid flow over a moving semi-infinite flat plate under the influence of an induced magnetic field and viscous dissipation.The velocity and magnetic field vectors are aligned at a distance from the plate.The Spectral Relaxation Method(SRM)is used to numerically solve the coupled nonlinear partial differential equations,analyzing the effects of the Eckert number on heat and mass transfer.Various nanofluids containing Cu,Ag,Al_(2)O_(3),and TiO_(2) nanoparticles are examined to assess how external magnetic fields influence fluid behavior.Key parameters,including the nanoparticle volume fraction ϕ,magnetic parameter M,magnetic Prandtl number Prm,and Eckert number Ec,are evaluated for their impact on velocity,induced magnetic field,and heat transfer.Results indicate that increasing the magnetic parameter reduces velocity and magnetic field components in alumina-water nanofluids,while a higher nanoparticle volume fraction enhances the thermal boundary layer.Greater viscous dissipation(Ec)increases temperature,and Al_(2)O_(3) nanofluids exhibit higher speeds than Cu,Ag,and TiO_(2) due to density differences.Silver-water nanofluids,with their higher density,move more slowly.The SRM results closely align with those from Maple,confirming the method’s accuracy.
文摘Peristaltic transport of non-Newtonian nanofluids with double diffusion is essential to biological engineering,microfluidics,and manufacturing processes.The authors tackle the key problem of Sisko nanofluids under double diffusion convection with thermal radiations and electroosmotic effects.Thestudy proposes a solution approach by using Morlet-Wavelet Neural Networks that can effectively solve this complex problem by their superior ability in the capture of nonlinear dynamics.These convergence analyses were calculated across fifty independent runs.Theil’s Inequality Coefficient and theMean Squared Error values range from 10^(-7) to 10^(-5) and 10^(-7) to 10^(-10),respectively.These values showed the proposed method is scientifically reliable and fast converging.Studies reveal that the intensity of the magnetic field causes a reduction in the flow velocity profile in the center of the channel.It is also evaluated that thermal radiations enhance the energy of the system,which promotes thermally induced diffusion and particle flow.The physical applications of this work pertain to improving fluid flow and heat transfer in engineering structures like converters or cooling devices or magnetic fluids in electronics,energy,and biomedical applications,where optimal control of fluid behavior is of paramount importance.
基金supported by the National Natural Science Foundation of China(Nos.51974176,51934004,52174194)the Shandong Province Natural Science Foundation of Outstanding Youth Fund(ZR2020JQ22)+1 种基金the Shandong Province Colleges and Universities Youth Innovation and Technology Support Program(2019KJH006)the Special funds for Taishan scholar project(TS20190935)。
文摘To improve the efficiency of coal seam water injection,the influence of nanofluids on coal surface wettability was studied based on the nano drag reduction and injection enhancement technology in the field of tertiary oil recovery.The composition optimization and performance evaluation of nanofluids with nano-silica and sodium lauryl sulfate as the main components were carried out,and the effects of the nanofluid with the optimal ratio on coal wettability were studied through spontaneous upward imbibition experiments.The results show that the composite nanofluid has a lower surface tension,and the lowest value of the interfacial tension is 15.79 m N/m.Therefore,the composite nanofluid can enhance the wettability of coal.However,its effects on coal samples with different metamorphic degrees is different,that is,low rank coal is the largest,middle rank coal is the second,and high rank coal is the least.In addition,a functional relationship between time and imbibition height is found for pulverized coal with different particle sizes.When the particle size of pulverized coal is 60–80 mesh,the wettability of nanofluid to coal is best.The findings in this paper provide a new perspective for improving the water injection efficiency for coal seams with low permeability.
基金The fifth author also thanks Prince Sultan University for funding this work through research-group number RG-DES2017-01-17.
文摘In the present research,Tiwari and Das model are used for the impact of a magnetic field on non-Newtonian nanofluid flow in the presence of injection and suction.The PDEs are converted into ordinary differential equations(ODEs)using the similarity method.The obtained ordinary differential equations are solved numerically using shooting method along with RK-4.Part of the present study uses nanoparticles(NPs)like TiO_(2) andAl_(2)O_(3) and sodium carboxymethyl cellulose(CMC/water)is considered as a base fluid(BF).This study is conducted to find the influence of nanoparticles,Prandtl number,and magnetic field on velocity and temperature profile,however,the Nusselt number and coefficient of skin friction parameters are also presented in detail with the variation of nanoparticles and parameters.The obtained results of the present study are presented usingMATLAB.In addition to these,some simulations of partial differential equations are also shown using software for graphing surface plots of velocity profile and streamlines along with surface plots and isothermal contours of the temperature profile.
基金support he received through General Research Project under the grant number (R.G.P.2/138/42)。
文摘A numerical analysis of the log-law behavior for the turbulent boundary layer of a wall-bounded flow is performed over a flat plate immersed in three nanofluids(Zn O-water,SiO_(2)-water,TiO_(2)-water).Numerical simulations using CFD code are employed to investigate the boundary layer and the hydrodynamic flow.To validate the current numerical model,measurement points from published works were used,and the compared results were in good compliance.Simulations were carried out for the velocity series of 0.04,0.4 and 4 m/s and nanoparticle concentrations0.1% and 5%.The influence of nanoparticles’ concentration on velocity,temperature profiles,wall shear stress,and turbulent intensity was investigated.The obtained results showed that the viscous sub-layer,the buffer layer,and the loglaw layer along the potential-flow layer could be analyzed based on their curving quality in the regions which have just a single wall distance.It was seen that the viscous sub-layer is the biggest area in comparison with other areas.Alternatively,the section where the temperature changes considerably correspond to the thermal boundary layer’s thickness goes a downward trend when the velocity decreases.The thermal boundary layer gets deep away from the leading edge.However,a rise in the volume fraction of nanoparticles indicated a minor impact on the shear stress developed in the wall.In all cases,the thickness of the boundary layer undergoes a downward trend as the velocity increases,whereas increasing the nanoparticle concentrations would enhance the thickness.More precisely,the log layer is closed with log law,and it is minimal between Y^(+)=50 and Y^(+)=95.The temperature for nanoparticle concentration φ=5%is higher than that for φ=0.1%,in boundary layers,for all studied nanofluids.However,it is established that the behavior is inverted from the value of Y^(+)=1 and the temperature for φ =0.1% is more important than the case of φ =5%.For turbulence intensity peak,this peak exists at Y^(+)=100 for v=4 m/s,Y^(+)=10 for v=0.4 m/s and Y^(+)=8 for v=0.04 m/s.
基金Supported by the National Natural Science Foundation of China(51606214)
文摘Thermo-hydraulic characteristics of TiO_2-water nanofluids in thin-wall stainless steel test tubes(corrugated tube and circular tube) filled with copper foam(40 PPI) are experimentally investigated and compared with those in test tubes without copper foam. The effects of nanoparticle mass concentration on flow and heat transfer performances are investigated. In addition, the mutual restriction relationships between Reynolds number(Re), Nusselt number(Nu) and resistance coefficient(f) are discussed respectively. Also, the comprehensive coefficient of performance(CCP) between heat transfer and pressure drop is evaluated. The results show that core-enhancement region for heat transfer using experimental tubes filled with copper foam is notably different from that of tubes without copper foam. There is a corresponding Reynolds number(about Re = 2400) for the maximum CCP of each condition. And the heat transfer can be enhanced dramatically and sustained at 8000 ≤ Re ≤ 12000.
基金Projects(51176029,50876020) supported by the National Natural Science Foundation of ChinaProject(2011BAJ03B00) supported by the 12th Five-Year National Science and Technology Support Key Program of China Project(ybjj1124) supported by the Foundation of Graduate School of Southeast University,China
文摘In order to investigate the mechanism of nanoparticles enhancing the heat and mass transfer of the ammonia-water absorption process,several types of binary nanofluids were prepared by mixing Al2O3 nanoparticles with polyacrylic acid(PAA),TiO2 with polyethylene glycol(PEG 1000),and TiN,SiC,hydroxyapatite(noodle-like) with PEG 10000 to ammonia-water solution,respectively.The thermal conductivities were measured by using a KD2 Pro thermal properties analyzer.The influences of surfactant and ammonia on the dispersion stabilities of the binary nanofluids were investigated by the light absorbency ratio index methods.The results show that the type,content and size of nanoparticles,the temperature as well as the dispersion stability are the key parameters that affect the thermal conductivity of nanofluids.For the given nanoparticle material and the base fluid,the thermal conductivity ratio of the nanofluid to the ammonia-water liquid increases as the nanoparticle content and the temperature are increased,and the diameter of nanoparticle is decreased.Furthermore,the thermal conductivity ratio increases significantly by improving the stabilities of nanofluids,which is achieved by adding surfactants or performing the proper ammonia content in the fluid.
文摘In this work, some thermodynamic properties of nanofluids such as Sb_2O_5;SnO_2/(EG + H_2O), ZnO/(EG + H_2O),Al_2O_3/(EG + H_2O), ZnO/(PEG + H_2O), ZnO/PEG, and TiO_2/EG were estimated from the extended Tao–Mason equation of state, together with the Pak and Cho equation in various temperature, pressure, and volume fractions.The equations of state using minimum input data and density at room temperature as scaling constants, were developed to estimated densities of the above mentioned nanofluids. Furthermore, the artificial neural network plus principal component analysis(PCA) technique(with 20 neuron in hidden layer) was performed over the whole range of available conditions. The AADs of the calculated molar densities of all nanofluids using the EOS and ANN at various temperatures and volume fractions are 1.11% and 0.48%, respectively. In addition, the heat capacity and isentropic compressibility of the above mentioned nanofluids are predicted using obtained densities of EOS with the Pak and Cho equation.
基金supported by National Natural Science Foundations(51073129 and50971104)Aeronautical Science Foundation of China(2010ZF53060)graduate starting seed fund of Northwestern Polytechnical University(Z2011012)
文摘We studied the relationship between corona structure and properties of solvent-free Fe3O4 nanofluids. We proposed a series of corona structures with different branched chains and synthesize different solvent-free nanofluids in order to show the effect of corona structure on the phase behavior, dispersion, as well as rheology properties. Results demonstrate novel liquid-like behaviors without solvent at room temperature. Fe3O4 magnetic nanoparticles content is bigger than 8% and its size is about 23 nm. For the solvent-free nanofluids,the long chain corona has the internal plasticization, which can decrease the loss modulus of system, while the short chain of corona results in the high viscosity of nanofluids. Long alkyl chains of modifiers lead to lower viscosity and better flowability of nanofluids. The rheology and viscosity of the nanofluids are correlated to the microscopic structure of the corona, which provide an in-depth insight into the preparing nanofluids with promising applications based on their tunable and controllable physical properties.
基金Project supported by the National Natural Science Foundation of China （Grant No 10204017） and the Natural Science of Jiangsu Province, China （Grant No BK2002038）.
文摘Nanofluids or liquids with suspended nanoparticles are likely to be the future heat transfer media, as they exhibit higher thermal conductivity than those of liquids. It has been proposed that nanoparticles are apt to congregate and form clusters, and hence the interaction between nanoparticles becomes important. In this paper, by taking into account the interaction between nearest-neighbour inclusions, we adopt the multiple image method to investigate the effective thermal conductivity of nanofluids. Numerical results show that then the thermal conductivity ratio between the nanoparticles and fluids is large, and the two nanoparticles are close up and even touch, and the polnt-dipole theory such as Maxwell-Garnett theory becomes rough as many-body interactions are neglected. Our theoretical results on the effective thermal conductivity of CuO/water and Al2O3/water nanofluids are in good agreement with experimental data.
