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
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 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
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 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
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
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
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
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 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
Experiments were carried out to investigate the boiling heat transfer characteristics of Al_2O_3-water nanofluids in swirl microchannels under terrestrial gravity and acceleration fields. A centrifuge with a two-meter...Experiments were carried out to investigate the boiling heat transfer characteristics of Al_2O_3-water nanofluids in swirl microchannels under terrestrial gravity and acceleration fields. A centrifuge with a two-meter long rotational arm was used to simulate the acceleration magnitude up to 9 g and three various acceleration directions. Three test sections with different geometric parameters were applied. The volume concentration of Al_2O_3 nanoparticles with an average diameter of 13 nm was varied from 0.07% to 0.1%. The mass flow rate and vapor quality were in ranges of 3–6 kg/h and 0.4–1.0%, respectively. The effects of the mass flow rate, microchannel aspect ratio,vapor quality, nanoparticle volume concentration, and acceleration direction and magnitude were analyzed in a systematic manner. Experimental results showed that the acceleration direction and magnitude had significant influences on the boiling heat transfer. The heat transfer under configuration C was found to be superior to that under configurations A and B. Moreover, the heat transfer coefficient increased with increases of the mass flow rate and the volume concentration and decreased with the aspect ratio.展开更多
This article concentrates on the steady magnetohydrodynamic （MHD） flow of viscous nanofluid. The flow is caused by a permeable exponentially stretching surface. An incompressible fluid fills the porous space. A comp...This article concentrates on the steady magnetohydrodynamic （MHD） flow of viscous nanofluid. The flow is caused by a permeable exponentially stretching surface. An incompressible fluid fills the porous space. A comparative study is made for the nanoparticles namely Copper （Cu）, Silver （Ag）, Alumina （A1203） and Titanium Oxide （TiO2）. Water is treated as a base fluid. Convective type boundary conditions are employed in modeling the heat transfer process. The non-linear partial differential equations governing the flow are reduced to an ordinary differential equation by similarity transformations. The obtained equations are then solved for the development of series solutions. Convergence of the obtained series solutions is explicitly discussed. The effects of different parameters on the velocity and temperature profiles are shown and analyzed through graphs.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
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
The buoyant Marangoni convection heat transfer in a differentially heated cavity is numerically studied. The cavity is filled with water-Ag, water-Cu, water-Al2O3, and water-TiO2 nanofiuids. The governing equations ar...The buoyant Marangoni convection heat transfer in a differentially heated cavity is numerically studied. The cavity is filled with water-Ag, water-Cu, water-Al2O3, and water-TiO2 nanofiuids. The governing equations are based on the equations involving the stream function, vorticity, and temperature. The dimensionless forms of the governing equations are solved by the finite difference （FD） scheme consisting of the alternating direction implicit （ADI） method and the tri-diagonal matrix algorithm （TDMA）. It is found that the increase in the nanoparticle concentration leads to the decrease in the flow rates in the secondary cells when the convective thermocapillary and the buoyancy force have similar strength. A critical Marangoni number exists, below which increasing the Marangoni number decreases the average Nusselt number, and above which increasing the Marangoni number increases the average Nusselt number. The nanoparticles play a crucial role in the critical Marangoni number.展开更多
This article addresses melting heat transfer in magnetohydrodynamics(MHD)nanofluid flows by a rotating disk. The analysis is performed in Cu-water and Ag-water nanofluids. Thermal radiation, viscous dissipation, and c...This article addresses melting heat transfer in magnetohydrodynamics(MHD)nanofluid flows by a rotating disk. The analysis is performed in Cu-water and Ag-water nanofluids. Thermal radiation, viscous dissipation, and chemical reactions impacts are added in the nanofluid model. Appropriate transformations lead to the nondimensionalized boundary layer equations. Series solutions for the resulting equations are computed.The role of pertinent parameters on the velocity, temperature, and concentration is analyzed in the outputs. It is revealed that the larger melting parameter enhances the velocity profile while the temperature profile decreases. The surface drag force and heat transfer rate are computed under the influence of pertinent parameters. Furthermore, the homogeneous reaction parameter serves to decrease the surface concentration.展开更多
In order to study the effects of nanoparticles on the CO_2 absorption in ammonia,nanofluids with different ammonia concentration and different nanoparticle solid loading were prepared by a two-step method.The nanoflui...In order to study the effects of nanoparticles on the CO_2 absorption in ammonia,nanofluids with different ammonia concentration and different nanoparticle solid loading were prepared by a two-step method.The nanofluids-enhanced gas absorption test devices were also established. The CO_2 absorption in TiO_2,CuO,SiO_2 nanofluids,which nanoparticles solid loading were 1. 0-8. 0 g/L,was tested respectively. In comparison with the blank absorption experiment,the effects of nanoparticle solid loading,nanoparticle types,ammonia concentration on the removal efficiency and removal rate were obtained. Experimental results show that adding nanoparticles can enhance the removal efficiency and removal rate,which increase first and then decrease with the increase of nanoparticle solid loading,and there exists an optimum solid loading of TiO_2 nanoparticles. The effect of SiO_2 nanofluid is inhibitory on the reaction. The enhancement factor of CuO nanofluid is always hovering around 1,which does not show the obvious enhancement or inhibition on the reaction. The optimum solid loading decreases gradually with the increase of ammonia concentration. In addition,according to the experimental results,the mechanism of enhanced absorption was analyzed theoretically.展开更多
Nanofluids because of their surface characteristics improve the oil production from reservoirs by enabling different enhanced recovery mechanisms such as wettability alteration,interfacial tension(IFT)reduction,oil vi...Nanofluids because of their surface characteristics improve the oil production from reservoirs by enabling different enhanced recovery mechanisms such as wettability alteration,interfacial tension(IFT)reduction,oil viscosity reduction,formation and stabilization of colloidal systems and the decrease in the asphaltene precipitation.To the best of the authors’ knowledge,the synthesis of a new nanocomposite has been studied in this paper for the first time.It consists of nanoparticles of both SiO2 and Fe3O4.Each nanoparticle has its individual surface property and has its distinct effect on the oil production of reservoirs.According to the previous studies,Fe3O4 has been used in the prevention or reduction of asphaltene precipitation and SiO2 has been considered for wettability alteration and/or reducing IFTs in enhanced oil recovery.According to the experimental results,the novel synthesized nanoparticles have increased the oil recovery by the synergistic effects of the formed particles markedly by activating the various mechanisms relative to the use of each of the nanoparticles in the micromodel individually.According to the results obtained for the use of this nanocomposite,understanding reservoir conditions plays an important role in the ultimate goal of enhancing oil recovery and the formation of stable emulsions plays an important role in oil recovery using this method.展开更多
Nanofluid flow occurs in extensive applications, and hence has received widespread attention. The transition of nanofluids from laminar to turbulent flow is an important issue because of the differences in pressure dr...Nanofluid flow occurs in extensive applications, and hence has received widespread attention. The transition of nanofluids from laminar to turbulent flow is an important issue because of the differences in pressure drop and heat transfer between laminar and turbulent flow. Nanofluids will become unstable when they depart from the thermal equilibrium or dynamic equilibrium state. This paper conducts a brief review of research on the flow instability of nanofluids, including hydrodynamic instability and thermal instability. Some open questions on the subject are also identified.展开更多
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.
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 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.
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.
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.
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the financial support from the Youth Talent Plan of Beijing of China (No. YETP 1087)
文摘Experiments were carried out to investigate the boiling heat transfer characteristics of Al_2O_3-water nanofluids in swirl microchannels under terrestrial gravity and acceleration fields. A centrifuge with a two-meter long rotational arm was used to simulate the acceleration magnitude up to 9 g and three various acceleration directions. Three test sections with different geometric parameters were applied. The volume concentration of Al_2O_3 nanoparticles with an average diameter of 13 nm was varied from 0.07% to 0.1%. The mass flow rate and vapor quality were in ranges of 3–6 kg/h and 0.4–1.0%, respectively. The effects of the mass flow rate, microchannel aspect ratio,vapor quality, nanoparticle volume concentration, and acceleration direction and magnitude were analyzed in a systematic manner. Experimental results showed that the acceleration direction and magnitude had significant influences on the boiling heat transfer. The heat transfer under configuration C was found to be superior to that under configurations A and B. Moreover, the heat transfer coefficient increased with increases of the mass flow rate and the volume concentration and decreased with the aspect ratio.
基金supported by the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, Saudi Arabia
文摘This article concentrates on the steady magnetohydrodynamic （MHD） flow of viscous nanofluid. The flow is caused by a permeable exponentially stretching surface. An incompressible fluid fills the porous space. A comparative study is made for the nanoparticles namely Copper （Cu）, Silver （Ag）, Alumina （A1203） and Titanium Oxide （TiO2）. Water is treated as a base fluid. Convective type boundary conditions are employed in modeling the heat transfer process. The non-linear partial differential equations governing the flow are reduced to an ordinary differential equation by similarity transformations. The obtained equations are then solved for the development of series solutions. Convergence of the obtained series solutions is explicitly discussed. The effects of different parameters on the velocity and temperature profiles are shown and analyzed through graphs.
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.
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 Fundamental Research Grant Scheme of the Ministry of Education of Malaysia(No.FRGS/1/2014/SG04/UKM/01/1)the Dana Impak Perdana of Universiti Kebangsaan Malaysia(No.DIP-2014-015)
文摘The buoyant Marangoni convection heat transfer in a differentially heated cavity is numerically studied. The cavity is filled with water-Ag, water-Cu, water-Al2O3, and water-TiO2 nanofiuids. The governing equations are based on the equations involving the stream function, vorticity, and temperature. The dimensionless forms of the governing equations are solved by the finite difference （FD） scheme consisting of the alternating direction implicit （ADI） method and the tri-diagonal matrix algorithm （TDMA）. It is found that the increase in the nanoparticle concentration leads to the decrease in the flow rates in the secondary cells when the convective thermocapillary and the buoyancy force have similar strength. A critical Marangoni number exists, below which increasing the Marangoni number decreases the average Nusselt number, and above which increasing the Marangoni number increases the average Nusselt number. The nanoparticles play a crucial role in the critical Marangoni number.
文摘This article addresses melting heat transfer in magnetohydrodynamics(MHD)nanofluid flows by a rotating disk. The analysis is performed in Cu-water and Ag-water nanofluids. Thermal radiation, viscous dissipation, and chemical reactions impacts are added in the nanofluid model. Appropriate transformations lead to the nondimensionalized boundary layer equations. Series solutions for the resulting equations are computed.The role of pertinent parameters on the velocity, temperature, and concentration is analyzed in the outputs. It is revealed that the larger melting parameter enhances the velocity profile while the temperature profile decreases. The surface drag force and heat transfer rate are computed under the influence of pertinent parameters. Furthermore, the homogeneous reaction parameter serves to decrease the surface concentration.
基金Sponsored by the Hebei Natural Science Foundation of Hebei Province of China(Grant No.B2014502056)
文摘In order to study the effects of nanoparticles on the CO_2 absorption in ammonia,nanofluids with different ammonia concentration and different nanoparticle solid loading were prepared by a two-step method.The nanofluids-enhanced gas absorption test devices were also established. The CO_2 absorption in TiO_2,CuO,SiO_2 nanofluids,which nanoparticles solid loading were 1. 0-8. 0 g/L,was tested respectively. In comparison with the blank absorption experiment,the effects of nanoparticle solid loading,nanoparticle types,ammonia concentration on the removal efficiency and removal rate were obtained. Experimental results show that adding nanoparticles can enhance the removal efficiency and removal rate,which increase first and then decrease with the increase of nanoparticle solid loading,and there exists an optimum solid loading of TiO_2 nanoparticles. The effect of SiO_2 nanofluid is inhibitory on the reaction. The enhancement factor of CuO nanofluid is always hovering around 1,which does not show the obvious enhancement or inhibition on the reaction. The optimum solid loading decreases gradually with the increase of ammonia concentration. In addition,according to the experimental results,the mechanism of enhanced absorption was analyzed theoretically.
文摘Nanofluids because of their surface characteristics improve the oil production from reservoirs by enabling different enhanced recovery mechanisms such as wettability alteration,interfacial tension(IFT)reduction,oil viscosity reduction,formation and stabilization of colloidal systems and the decrease in the asphaltene precipitation.To the best of the authors’ knowledge,the synthesis of a new nanocomposite has been studied in this paper for the first time.It consists of nanoparticles of both SiO2 and Fe3O4.Each nanoparticle has its individual surface property and has its distinct effect on the oil production of reservoirs.According to the previous studies,Fe3O4 has been used in the prevention or reduction of asphaltene precipitation and SiO2 has been considered for wettability alteration and/or reducing IFTs in enhanced oil recovery.According to the experimental results,the novel synthesized nanoparticles have increased the oil recovery by the synergistic effects of the formed particles markedly by activating the various mechanisms relative to the use of each of the nanoparticles in the micromodel individually.According to the results obtained for the use of this nanocomposite,understanding reservoir conditions plays an important role in the ultimate goal of enhancing oil recovery and the formation of stable emulsions plays an important role in oil recovery using this method.
基金Project supported by the National Natural Science Foundation of China(No.91852102)
文摘Nanofluid flow occurs in extensive applications, and hence has received widespread attention. The transition of nanofluids from laminar to turbulent flow is an important issue because of the differences in pressure drop and heat transfer between laminar and turbulent flow. Nanofluids will become unstable when they depart from the thermal equilibrium or dynamic equilibrium state. This paper conducts a brief review of research on the flow instability of nanofluids, including hydrodynamic instability and thermal instability. Some open questions on the subject are also identified.
