Mixed convectional and chemical reactive flow of nanofluid with slanted MHD on moving permeable stretching/shrinking sheet through nonlinear radiation,energy omission

Hybrid nanofluids are remarkable functioning liquids that are intended to reduce the energy loss while maximizing the heat transmission.In the involvement of suction and nonlinear thermal radiation effects,this study attempted to explore the energy transmission features of the inclined magnetohydrodynamic(MHD)stagnation flow of CNTs-hybrid nanofluid across the nonlinear permeable stretching or shrinking sheet.This work also included some noteworthy features like chemical reactions,variable molecular diffusivity,quadratic convection,viscous dissipation,velocity slip and heat omission assessment.Employing appropriate similarity components,the model equations were modified to ODEs and computed by using the HAM technique.The impact of various relevant flow characteristics on movement,heat and concentration profiles was investigated and plotted on a graph.Considering various model factors,the significance of drag friction,heat and mass transfer rate were also computed in tabular and graphical form.This leads to the conclusion that such factors have a considerable impact on the dynamics of fluid as well as other engineering measurements of interest.Furthermore,viscous forces are dominated by increasing the values ofλ_(p),δ_(m)andδ_(q),and as a result,F(ξ)accelerates while the opposite trend is observed for M andφ.The drag friction is boosted by the augmentation M,λ_(p)andφ,but the rate of heat transfer declined.According to our findings,hybrid nanoliquid effects dominate that of ordinary nanofluid in terms of F(ξ),Θ(ξ)andφ(ξ)profiles.The HAM and the numerical technique(shooting method)were found to be in good agreement.

Influence of various shapes of nanoparticles on unsteady stagnation-point flow of Cu-H_(2)O nanofluid on a flat surface in a porous medium:A stability analysis

The nanofluid and porous medium together are able to fulfill the requirement of high cooling rate in many engineering problems.So,here the impact of various shapes of nanoparticles on unsteady stagnation-point flow of Cu-H_(2)O nanofluid on a flat surface in a porous medium is examined.Moreover,the thermal radiation and viscous dissipation effects are considered.The problem governing partial differential equations are converted into self-similar coupled ordinary differential equations and those are numerically solved by the shooting method.The computed results can reveal many vital findings of practical importance.Firstly,dual solutions exist for decelerating unsteady flow and for accelerating unsteady and steady flows,the solution is unique.The presence of nanoparticles affects the existence of dual solution in decelerating unsteady flow only when the medium of the flow is a porous medium.But different shapes of nanoparticles are not disturbing the dual solution existence range,though it has a considerable impact on thermal conductivity of the mixture.Different shapes of nanoparticles act differently to enhance the heat transfer characteristics of the base fluid,i.e.,the water here.On the other hand,the existence range of dual solutions becomes wider for a larger permeability parameter related to the porous medium.Regarding the cooling rate of the heated surface,it rises with the permeability parameter,shape factor(related to various shapes of Cu-nanoparticles),and radiation parameter.The surface drag force becomes stronger with the permeability parameter.Also,with growing values of nanoparticle volume fraction,the boundary layer thickness(BLT)increases and the thermal BLT becomes thicker with larger values of shape factor.For decelerating unsteady flow,the nanofluid velocity rises with permeability parameter in the case of upper branch solution and an opposite trend for the lower branch is witnessed.The thermal BLT is thicker with radiation parameter.Due to the existence of dual solutions,a linear stability analysis is made and it is concluded that the upper branch and unique solutions are stable solutions.

SiO_(2)-H_(2)O纳米流体强化煤尘润湿性的微观机理研究

煤尘污染是世界煤炭行业亟需解决的难题之一,探索绿色高效的新型煤尘润湿剂对于该领域来说具有潜在的应用价值。以Wender模型为研究对象,借助Materials Studio分子模拟软件与物理实验探究了SiO_(2)-H_(2)O纳米流体对煤尘润湿性的影响机制。研究表明:SiO_(2)纳米颗粒(NPs)的反应活性较高,其表面羟基容易与煤分子和水分子形成氢键,从而影响煤尘的润湿特性。NPs与煤分子的相互作用能力较强,其吸附在煤尘表面后能吸附更多的水分子。当体系中NPs的吸附数量为0~5时,随NPs数量的增加,吸附体系中煤和NPs、NPs和水之间的相互作用能以及固-液分子间氢键的数量呈增大的趋势。煤和NPs中氢、氧原子之间的g(r)曲线值最大,峰值较高,而煤和水中氢、氧原子之间的g(r)曲线与之相反。随着NPs吸附数量的增加,水分子均方位移与扩散系数呈增大的趋势,加速了对煤尘的润湿。与水相比,纳米流体具有较低的表面张力,当颗粒浓度为2.0%(质量)时,改性煤尘接触角下降率达到了52.85%~61.51%,同时纳米流体处理后的煤尘表面NPs吸附集聚现象明显。本研究分子模拟结果与实验结果相互验证,阐明了NPs强化煤尘润湿性的微观机理,获得了NPs对煤尘润湿性的影响规律,揭示了NPs在煤尘表面的吸附特征,为SiO_(2)-H_(2)O纳米流体强化煤尘润湿性奠定了理论基础。

Experimental investigation into Fe3O4/SiO2 nanoparticle performance and comparison with other nanofluids in enhanced oil recovery

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.

Natural convection of an alumina-water nanofluid inside an inclined wavy-walled cavity with a non-uniform heating using Tiwari and Das' nanofluid model

The present study is devoted to numerical analysis of natural convective heat transfer and fluid flow of alumina-water nanofluid in an inclined wavy-walled cavity under the effect of non-uniform heating. A single-phase nanofluid model with experimental correlations for the nanofluid viscosity and thermal conductivity has been included in the mathematical model. The considered governing equations formulated in dimensionless stream function, vorticity, and temperature have been solved by the finite difference method. The cavity inclination angle and irregular walls(wavy and undulation numbers)are very good control parameters for the heat transfer and fluid flow. Nowadays, optimal parameters are necessary for the heat transfer enhancement in different practical applications. The effects of the involved parameters on the streamlines and isotherms as well as on the average Nusselt number and nanofluid flow rate have been analyzed. It has been found that the heat transfer rate and fluid flow rate are non-monotonic functions of the cavity inclination angle and undulation number.

Temporal Stability Analysis of Magnetized Hybrid Nanofluid Propagating through an Unsteady Shrinking Sheet: Partial Slip Conditions

The unsteady magnetohydrodynamic(MHD)flow on a horizontal preamble surface with hybrid nanoparticles in the presence of the first order velocity and thermal slip conditions are investigated.Alumina(Al_(2)O_(3))and copper(Cu)are considered as hybrid nanoparticles that have been dispersed in water in order to make hybrid nanofluid(Cu-Al_(2)O_(3)/water).The system of similarity equations is derived from the system of partial differential equations(PDEs)by using variables of similarity,and their solutions are gotten with shooting method in the Maple software.In certain ranges of unsteadiness and magnetic parameters,the presence of dual solutions can be found.Further,it is examined that layer separation is deferred due to the effect of the hybrid nanoparticles.Moreover,the capacity of the thermal enhancement of Cu-Al_(2)O_(3)/water hybrid nanofluid is higher as compared to Al_(2)O_(3)/water based nanofluid and enhancements inCu are caused to rise the fluid temperature in both solutions.In the last,solutions stability analyzes were also carried out and the first solution was found to be stable.

Water Based Nanofluids: A Computational Study on Temperature Distribution in a Pipe Flow

Fluid containing nanometer-sized particles (i.e. nanoparticles) is known as nanofluid. Three different nanofluids flowing in a pipe with heat source at the inlet and sink in the walls are studied. The base fluid is water. 20 nm size nanoparticle Al2O3 is mixed with base fluid with volume concentrations of 0.1%, 0.2% and 0.5%. Simulation is done using ANSYS Workbench 17.1. The result shows correlation between concentration of nanoparticle and temperature gradient at the outlet of the pipe.

Investigation of Nanofluids as Potential Cutting Fluids in Gear Hobbing Processes of AISI 4118 Steel

The present work focuses on the performance of nanofluids called CN46-NanoAl2O3.80 formulated by using dispersions of nano aluminum oxide （Al2O3） in the ISO VG46 industrial oil on machining performance during gear hobbing of AISI 4118 steel. In machining gears, hobbing is one of the most important processes, especially to produce various gear shapes for adapting to diverse applications. However, the demand for high quality brings attention to product quality, particularly the roughness of the machined gear surface because of its effect on product appearance, function, and reliability. For additional improvement, applying nanofluids may produce superior product quality, as the rolling action of billions of nanoparticle units in the tool chip interface can significantly decrease the friction led to reduce the cutting forces. In addition, the characteristics of heat transfer of nanoparticles can contribute to reduce tool wear. In this experimental study, the performance of nanolubricant compared with the case of using ordinary cutting-fluid systems in the existing production line is investigated. The experimental results reveal that the tool life of the hob is significantly enhanced of 55.2%, gear surface roughness is smaller （27.3%）, and gear accuracy is significantly increased by using the nanofluid. This result, therefore, shows a promising solution to achieve the engineering-economy effectiveness in gear machining.

Research on Applying Nano Cutting Oils in Spur Gear Hobbing Process

Nanolubricant mixing the normal lubricant with nanoparticles, gradually becomes a new trend study for metal cutting enhancement. An addition of the nanoparticles improves lubricating properties and convective heat transfer coefficient (cooling properties) of nanolubricants. In the present work, nanolubricant is formulated by using dispersions of 0.3% Al2O3 nanoparticles in normal industrial oil VG46 for enhancement of gear machining performance of SCM420 steel. Comparative study of flank wear, crater wear and gear profile error in gear hobbing with normal oils in the existing production line as well as nanolubricant is studied. This study clearly reveals that tool wear, and gear profile error are reduced by the use of nanolubricant compared to that of normal oils. The paper results not only contribute the deeper understanding of the novel performance of nanoparticles in conventional cutting fluids, but also show a very promising solution to achieve the engineering economy effectiveness in gear machining.

匀强电场下TiO_(2)-H_(2)O纳米流体沉积及传热特性研究

为探究匀强电场下纳米流体在换热表面上的沉积特性,以两步法制备的TiO_(2)-H_(2)O纳米流体为研究对象,依托环形可视化在线监测实验台,通过改变匀强电场强度探究电场强度对TiO_(2)-H_(2)O纳米流体在换热表面上的沉积与传热特性。结果表明:电场的施加对TiO_(2)-H_(2)O纳米流体在换热表面沉积影响显著。其污垢热阻渐近值随着电场强度的加强先减小后增大,当电场强度E=30 kV·m^(-1)时对应的污垢热阻渐近值最低,抑垢率为32.13%。电场的施加还可以有效地延长清洁状态时长,在这一过程中,纳米颗粒不会沉积在换热表面导致传热性能的降低。此外,电场的施加还可以有效延长总传热系数的下降时间,当电场强度在30 kV·m^(-1)时,纳米流体中颗粒沉积对传热系数的影响最小,为33.2%。

铜-水基纳米流体环路热管太阳能热水系统的实验研究

采用“二步法”制备了铜水基纳米流体,并对纳米流体进行了透射电镜分析。对不同质量浓度下(0.1%、0.15%、0.2%)铜水基纳米流体的环路热管太阳能热水系统进行了实验研究,分析了环路热管太阳能热水系统中的水箱水温变化、瞬时光热效率,并与去离子水系统进行了对比分析。实验结果表明,纳米铜颗粒的加入增加了液体的导热系数,铜水基纳米流体更适合作为太阳能重力环路热管热水系统的相变传热工质,且存在一个最佳的纳米流体工质质量浓度(最佳质量浓度为0.15%),可使得环路热管热水系统的传热性能最佳。

Transport of Cu-H2O nanofluid through a channel with wavy walls under velocity slip and connective boundary conditions

Present study examines the mixed convective peristaltic transport of Cu-H2O nanofluid with velocity slip and convective boundary conditions. Analysis is performed using the two-phase model of the nanofluid. Viscous dissipation and heat generation/absorption effects are also taken into account. Problem is formulated using the long wavelength and low Reynolds number approach. Numerical solutions for the pressure rise per wavelength, pressure gradient, axial velocity, temperature and heat transfer rate at the boundaxy are obtained and studied through graphs. Results show that the area of peristaltic pumping decreases with an increase in the nanoparticles volume fraction. Increase in the velocity slip parameter shows an increase of the pressure gradient in the occluded part of the channel. Further, addition of copper nanoparticles reduces both the axial velocity and temperature of the base fluid. Temperature of the nanofluid also decreases sufficiently for an increase in the value of Blot number.

MWCNTs/SWCNTs Nanofluid Thin Film Flow over a Nonlinear Extending Disc: OHAM Solution

The aim of this research is the improvement towards the consumption of energy in the field of engineering and industry. The efforts have been paid to the enhancement of heat transmission and cooling process through a nanofluid coating of a nonlinear stretching disc. The combination of Water(H2 O) and multiple walled carbon nanotubes(MWCNT)/single walled carbon nanotubes(SWCNT) have been used as a nanofluid. The spreading of a thin nano-layer with variable thickness over a nonlinear and radially stretching surface has been considered. The estimated results of the problem have been accomplished using the Optimal Homotopy Analysis Method(OHAM). The residual errors of the OHAM method have been shown physically and numerically. The important physical parameters of skin friction and Nusselt number have been calculated and discussed. The other embedding parameters like generalized magnetic parameter, Prantl number, nanofluid volume fraction and Eckert number have been intended and discussed. The obtained results have been compared with the Numerical(ND-Solve) method for both sorts of CNTs. The closed agreement of both methods has been achieved.