Graphene Oxide Nanofluids Research Articles

Quantitative analysis of cooling and lubricating effects of graphene oxide nanofluids in machining titanium alloy Ti6Al4V

Ti6Al4V is widely used in industry due to its outstanding mechanical properties. However, the severe abrasion and high temperature at tool/chip and tool/workpiece interfaces cause various types of tool wear in machining Ti6Al4V. To ensure high machining efficiency and high quality of machined surface, cooling fluid is often used to reduce the cutting temperature and friction. In this paper, the cooling and lubricating effects of coolant with graphene oxide nanosheet suspension were investigated experimentally and theoretically. Cutting experiments were conducted to compare the performance of conventional coolant with that of the coolant with graphene oxide nanosheets of different weight percentages (0.1% and 0.5%). Cutting force and temperature on the rake face were measured in each cutting pass. A theoretical model based on computational fluid dynamics (CFD) was developed to investigate the temperature distribution and cooling efficiency quantitatively. Friction force and coefficient of friction at tool/chip interface and tool/workpiece interface were calculated to analyse the lubrication effects of different types of coolant. The results showed that the performance of cooling and lubrication of the coolant became better with the addition of graphene oxide nanosheets. Results from the analysis of flank wear and crater wear and the morphological characteristics proved that there was a significant further reduction in cutting temperature and friction force when coolant with graphene oxide nanosheets was used.

Heat transport features of magnetic water–graphene oxide nanofluid flow with thermal radiation: Stability Test

This paper documents the incompressible hydro-magnetic flow and heat transfer analysis of water–Graphene oxide (GO) nanofluid. More exactly, the nanofluid flow occurs along a thin needle moving axially. Despite the fact that there seems to be various works on the subject in the existing literature, however, very few studies have been carried out to investigate the dual numerical solution for such flow. Consequently, the inspiration here is to look for dual numerical solutions for such a non-linear phenomenon along with the stability analysis of computed solutions. The governing coupled equations representing the mathematical formulation of the current physical problem were obtained from the equation of motion and the mass and the energy conservations by taking steady and incompressible flow. The numerical solution of governing set of simultaneous ordinary differential equations is computed with the assistance of Matlab solver bvp4c. This research aimed at revealing the conceivable impacts of existing fluid interaction parameters on non-dimensional velocity and temperature distributions. These computations exhibits that more than one solution is possible only in case of flow over shrinking needle for certain combinations of the parameters. The result shows that the skin friction coefficient increases in both solutions with higher nanoparticles volume fraction. Furthermore, an enhancement in local Nusselt number is noted as the thermal radiation parameter increases. • We simulate the fluid flow over a past a continuously moving thin needle immersed in a nanofluid. • Dual branch of solutions are possible for a certain range of parameter. • A stability analysis is carried out to examine which solution stable and physically realizable. • The bvp4c collocation formula is employed to get the solution for governing problem.

Effects of graphene oxide nanofluids on cutting temperature and force in machining Ti-6Al-4V

The significant amount of heat and friction generated in machining Ti-6Al-4V affects the cutting performance and results in serious problems such as severe tool wear and poor surface quality. Graphene oxide (GO) nanoparticles have excellent thermal conductivity and high lubrication capability and have emerged as a promising solution to the heat and tribology issues. As an additive material, GO nanoparticles mixed in base fluids may lead to significant increase in thermal conductivity and lubrication capability, which in turn, could result in smaller cutting forces and lower cutting temperature in the cutting zone. This paper presents new models of using GO nanofluids in turning processes which can accurately predict the change in cutting temperature and cutting forces. The cutting temperature model was created by considering the thermal conductivity and specific heat of the GO nanofluids along with their heat transfer coefficient and friction coefficient, whereas the cutting force model was developed by taking into account friction, tool geometry and the friction coefficient associated with the thermal properties of nanofluids.

Effect of V-shaped rib roughness on the performance of nanofluid-based direct absorption solar collectors

Solar heating systems, which used nanofluid-based direct absorption solar collectors, have been recently introduced as the more efficient solar thermal systems because of the volumetric absorption of solar radiation within the direct absorption solar collectors. In this paper, a new direct absorption solar collector is constructed with the V-shaped ribs on its bottom surface in order to study the outdoor thermal performance of the conventional and ribbed collector, experimentally. Using graphene oxide nanofluid as the working fluid, the energy and exergy efficiencies of the conventional and ribbed direct absorption solar collectors are obtained by varying the nanofluid volume fraction, flow rate and the rib geometry (forward and backward rib). Measuring the spectral transmittance of the nanofluid samples shows that the absorbed energy fraction (F) for collector channel depth of 1 cm is 50.9%, 59.82%, 64.5% and 65.3% for nanofluid samples of 125 ppm, 250 ppm, 500 ppm and 1000 ppm, respectively. In volumetric flow rate of 15 L h−1, the zero-loss efficiency for BR-DASC and FR-DASC is increased up to about 16.6% and 11.7%, compared to DASC. These values attain 21% and 13.4% when the volumetric flow rate increases from 15 to 45 L h−1. The optimum volume fraction of graphene oxide nanofluid is 500 ppm in conventional and forward-ribbed direct absorption solar collectors in terms of both energy and exergy efficiencies. The higher friction factors, as a result of ribs, lead to lower exergy efficiency of the ribbed direct absorption solar collector in comparison with the conventional one.

Supercooling and heterogeneous nucleation in acoustically levitated deionized water and graphene oxide nanofluids droplets

The supercooling and heterogeneous nucleation factors of deionized water and graphene oxide nanofluid were investigated in this study. Graphene oxide nanofluid (0.03 wt%) was prepared by adding graphene oxide nanosheets into deionized water. A large number of nucleation experiments have been performed to quantify the supercooling degree of acoustically levitated deionized water and graphene oxide nanofluid droplets. These deionized water droplets were supercooled at 2.5–15.6 K, whereas the supercooling degrees of graphene oxide nanofluid droplets varied from 2.6 K to 12.5 K. In addition, the heterogeneous nucleation was investigated by the statistical analysis based on the classical nucleation theory. Results demonstrated that the heterogeneous nucleation factor for graphene oxide nanofluid was less than that of deionized water, and the nucleation area for graphene oxide nanofluid was 4.44 times that of deionized water. Consequently, the nucleation rate of the graphene oxide nanofluid was increased and the supercooling degree was reduced.

Thermal Performance of the Graphene Oxide Nanofluids Flow in an Upright Channel Through a Permeable Medium

The three-dimensional flow of Water based Graphene Oxide (GO-W) and Ethylene Glycol based Graphene Oxide (GO-EG) nanofluids amongst the binary upright and parallel plates is considered. The unsteady movement of the nanofluid is associated with the porous medium and the uniform magnetic field is executed in the perpendicular direction of the flow field. The basic governing equations have been altered using the Von Karman transformation, including the natural convection in the downward direction. The solution for the modeled problem has been attained by means of optimal homotopy analysis method (OHAM). The influence of the physical parameters on the momentum boundary layer, pressure, and temperature fields is mainly focused. Moreover, the comparison of the GO-W and GO-EG nanofluids under the impact of physical constraints has been analyzed graphically and numerically. The imperative physical constraints of the drag force and heat transfer rate have been computed and discussed. The results have been validated using the error analysis and the obtained outcomes have been shown and discussed. The obtained results are compared with the numerical ND-Solve method. It is obtained that the increasing order of the iterations reduces the absolute error and the results go to the strong convergence. Moreover, the impact of the physical parameters is more precise in the GO-EG nanofluid due to its higher thermophysical properties.

The natural convective graphene oxide nanofluid flow in an upright squeezing channel

The 3-D flow of water based graphene oxide (GO-W) and ethylene glycol based graphene oxide (GO-EG) nanofluids amongst the binary upright and parallel plates is considered. The unsteady movement of the nanofluid is associated with the porous medium and the unbroken magnetic field is executed in the perpendicular track of the flow field. The basic governing equations have been altered using the Von Karman transformation, including the natural-convection in the downward direction. The solution for the modeled problem has been attained by means of optimal homotopy analysis method (OHAM). The influence of the physical parameters on the momentum boundary-layer, pressure and temperature fields is mainly focused. Moreover, the comparison of the GO-W and GO-EG nanofluids under the impact of physical constraints have been analyzed graphically and numerically. The imperative physical constraints of the drag force and heat transfer rate have been computed and conferred. The consequences have been validated using the error analysis and the obtained outcomes have been shown and discussed.

Evaporation behavior of PEGylated graphene oxide nanofluid droplets on heated substrate

In this study, the evaporation behavior of graphene nanofluid droplets deposited on sapphire substrate was investigated in the temperature range from ambient to 106 °C. The evaporation process and the thermal mapping on the air/liquid interface of the droplets were recorded by side-view CCD camera and top-view infrared camera respectively. Graphene oxide (GO, 0.25 mg/ml), PEGylated reduced graphene oxide (rGO-PEG, 0.25 and 0.8 mg/ml) nanofluids, and water were tested at ambient conditions. The PEGylation was proved to improve the nanoparticles dispersion and the evaporation performance. Preparation without PEG-functionalization, or with an increased nanoparticle concentration, decreases the evaporation rate due to the poor dispersion of graphene nanoparticles and large accumulation. Because of extremely high intrinsic thermal conductivity, the addition of graphene nanoparticles in water is assumed to significantly improve evaporation rate, which is in accordance with thermal performance of water and 0.25 mg/ml rGO-PEG nanofluid at ambient temperature. However, on heated substrates, the evaporation rate of water is dramatically higher than 0.25 mg/ml rGO-PEG nanofluid at high substrate temperature despite the exceptional thermal conductivity of graphene nanofluid. The convective flows induced by thermal Marangoni effect are responsible for the increased evaporation rate of water at high substrate temperature and the application of graphene nanofluid to enhance the heat transfer efficiency is more effective at low substrate temperature. The calculations of thermal Marangoni number show that thermal Marangoni effect is always more important on water droplet evaporation than that of rGO-PEG nanofluid.

Experimental study on heat transfer and pressure drop of in-house synthesized graphene oxide nanofluids

In this article, first, graphene oxide nanosheets were synthesized in-house according to the modified Hummers method, and these nanosheets were used to prepare graphene oxide nanofluids at two concentrations. Then the thermophysical properties of nanofluids were characterized using X-ray diffraction analysis, a scanning electron microscope, and UV–Vis spectrophotometry. The particle size distribution was investigated using dynamic light scattering. Then, a fundamental study was conducted on the thermal-hydraulic characteristics of graphene oxide nanofluids flowing through a straight copper tube. An experimental setup was developed to find the heat transfer characteristics and pressure drop of nanofluids in the test section consisting of a copper tube with constant heat flux. The flow regimes and associated pressure drop and heat transfer characteristics at varying flow rate were investigated at three different heat flux conditions of 7.4, 9.1, and 12.6 kW/m2. Due to the increase in viscosity, flowrate and Reynolds number decreased from 0.01 to 0.1 wt% of graphene oxide nanofluids at constant pump frequency. Experimental data obtained for water were validated with the findings from the literature, and the correlations were formulated for the Nusselt number and Reynolds number by considering the multiple regression analysis. The convective heat transfer coefficient for graphene oxide at 0.01 wt% was higher when compared to graphene oxide at 0.1 wt% and water. The variation of Nusselt number with the heat flux and velocity was insignificant.

Rheological Behavior of Water-Ethylene Glycol Based Graphene Oxide Nanofluids

Traditionally water-ethylene glycol mixture based nanofluids are used in cold regions as a coolant in the car radiators. In the present study, the rheological properties of water-ethylene glycol based graphene oxide nanofluid are studied using Non-Equilibrium Molecular Dynamics (NEMD) method at different temperatures, volume concentrations, and shear rates. NEMD simulations are performed with considering 75/25, 60/40, and 40/60 ratios of water/ethylene glycol as the base fluids at volume concentrations of 3%, 4%, and 5% graphene oxide nanosheets. The results, which demonstrated good agreement with experimental data, show that the viscosity and density of base fluids significantly decrease with temperature and increases with ethylene glycol volume fraction. Also, the viscosity and density of nanofluids depends directly on the volume concentrations of nanoparticles and decreases with increasing temperature. For example, at 289.85 K, the viscosity of water (75%)-ethylene glycol (25%) based nanofluids containing 3%, 4% and 5% volume concentrations of nanoparticles increased by 33%, 43%, and 56%, respectively. Similarly, the density of the same nanofluids increased by 1%, 1.7 %, and 2.2%, respectively. Moreover, the theoretical models confirm the obtained results. According to the shear rate analysis, the water-ethylene glycol based graphene oxide nanofluid behaves as a non-Newtonian fluid.

Influence of graphene oxide nanofluids and surfactant on thermal behaviour of the thermosyphon

The paper presents a thermal performance analysis of a thermosyphon filled with graphene oxide nanofluid. It focuses on factors influencing thermal resistance and geyser boiling processes, such as the presence of surfactant (here: sodium dodecyl sulphate), the time-related deterioration of nanoparticles, and working conditions. Results indicate that GO nanofluids improved heat transfer at low heat loads and that enhancements were limited to the evaporator section. Although thermal resistance of the device was similar for all tested working fluids at high evaporator temperatures, the time-dependent behaviour was different. Both water and GO nanofluid facilitated geyser boiling. Sodium dodecyl sulphate inhibited the phenomenon for pure water, but the same concentration of surfactant in the graphene oxide nanofluid did not show the same effect. SEM analysis showed that substantial amount of surfactant attached to the surface of graphene oxide flakes, which explains the previously described behaviour.

The experimental study to examine the stable dispersion of the graphene nanoparticles and to look at the GO–H2O nanofluid flow between two rotating disks

The nanofluid analysis has been carried out as a function of temperature and this idea is utilized to study the graphene oxide (GO) water-based nanofluid from both experimental and numerical perspectives. Various spectral investigations were used to endorse the successful synthesis of graphene oxide. The obtained GO exhibits large size platelet morphology with stable dispersion in water. The experimental procedure of the preparation of nanofluid and its outputs has been analyzed with numerical data. The obtained results from the Chebyshev spectral scheme were transformed into a mathematical model considering the 3D flow of the dispersed GO nanofluid between two parallel rotating disks using the governing Navier–Stokes equations and energy equation with the utilization of Von Karman similarity transformations. The obtained nonlinear differential equations have been examined through a recently fashionable analytic approximation method called the Optimal Homotopy Analysis Method (OHAM). Opposite and same direction rotational effects have been conferred on the flow characteristics. To analyze how the velocities, pressure and temperature fields are affected by various parameters, plots have been displayed. Convergence of the obtained results has been authenticated with residual errors physically and numerically. Moreover, the physical parameters impact, such as local Nusselt number and skin friction coefficients are obtained through numerical data and inspect.

Analytical and Numerical Investigations of Unsteady Graphene Oxide Nanofluid Flow Between Two Parallel Plates

In this research, different analytical methods were applied to characterize thermal behavior of unsteady graphene oxide–water nanofluid flow between two parallel moving plates. First of all, partial differential equations (PDEs) were transformed to a system of nonlinear ordinary differential equations (ODEs) using similarity solution. Then, collocation method (CM), least square method (LSM) and Galerkin method (GM) were used to solve the system of ODEs and determine velocity and temperature distribution functions. In addition, effects of moving parameter, concentration, Eckert and Prandtl numbers on nanofluid velocity and temperature profiles were examined. Next, using numerical solution of the obtained system of differential equations, the results obtained from the analytical solutions were validated with that of the numerical solution. The validation results indicated high and appropriate accuracy of the analytical solutions compared to the numerical one.

Experimental investigation on the competition between enhancement of electrical and thermal conductivities in water-based nanofluids

In this paper, experimental investigations on the thermal and electrical conductivities of three kinds of water based nanofluids are conducted. The experimental data are collected for Ag, SiC, and Graphene oxide (GO) nanofluids with respect to temperature and nanoparticle concentration. Results show that both the temperature and nanoparticle concentration have positive effect on the thermal and electrical conductivities of nanofluids. The effect of temperature and volume fraction of nanoparticles on the thermal conductivity of nanofluids is almost the same; however, the effect of nanoparticle concentration is much higher than the temperature for electrical conductivity. Furthermore, to better survey the benefit of nanofluids as coolant in electrically active heat transfer environments, the thermo-electrical conductivity (TEC) ratio was established based on the achieved experimental data and checked explicitly.

Heat transfer analysis of hydromagnetic water–graphene oxide nanofluid flow in the channel with asymmetric forced convection on walls

In this paper, heat transfer of hydromagnetic water–graphene oxide nanofluid flow in the channel with asymmetric forced convection on walls is analyzed. The basic partial differential equations include momentum and energy for this problem are reduced to the ordinary differential equations which are solved numerically by using finite element method (FEM) using FlexPDE software package. For validity, the results are compared with 4th order Runge–Kutta numerical solution. The effects of different physical parameters such as the nanoparticle volume fraction, the Magnet parameter, the Biot number and the Eckert number on the dimensionless velocity profile, the dimensionless temperature profile and the dimensionless gradient temperature profile are discussed. It was concluded that with increase in the nanoparticle volume fraction and Magnet parameter, the dimensionless velocity profiles of flow reduce. With rising of the Biot number, the dimensionless temperature decreases and dimensionless gradient temperature profile increases. Moreover, by increasing of the nanoparticle fraction volume, the dimensionless temperature profiles of flow is increased and the heat transfer coefficient enhanced. In addition, by increasing of the nanoparticle fraction volume, the convection on walls increases within the channel. Also, with increases of the Eckert number, the dimensionless temperature profile increases and the heat transfer rate on the channel walls is increased.

Localized solar heating via graphene oxide nanofluid for direct steam generation

In the present paper, the performance of the graphene oxide in the solar steam generation has experimentally been examined. For this purpose, a setup was built for measuring the evaporation rate, which consists of a solar simulator with a xenon lamp as a radiation source, a pyranometer for light intensity measuring, and a sensory system for measuring the temperature and the mass. Then, the nanofluid with three nanoparticle mass concentrations of 0.001, 0.002, and 0.004% was prepared and exposed to the light intensity of 3.5 Suns (3.5 kW m−2). Finally, the effects of the light intensity variations on the solar steam generation were studied at the steady and transition conditions. The results showed that the examined carbon nanostructure is efficiently capable of direct solar energy harvesting, such that a maximum total efficiency of 78.9% at 3.5 Suns can be obtained, while the corresponding value for the case of pure water is about 54%. Furthermore, it was found that increasing the light intensity from 1.5 to 3.5 Suns enhances the evaporation flux rate, yet, reduces the evaporation efficiency.

Heat Transfer Enhancement in Circular Tube Flow Using Graphene Oxide Nanofluid and Its Application to Multi-Heat Pipe

SummaryThe experimental study is performed to study convective heat transfer behavior of nanoparticles, i.e., graphene oxide (GO) flowing through a horizontal tube heated under constant heat flux condition. Its application to a multi-heat pipe cooling device in the condition of different filling ratio (40%, 60%, 80% and 100%) under constant heat flux conditions is experimentally investigated. It was found that (i) heat transfer enhancement is caused by suspending nanoparticles, so that maximum value of the Nusselt number is over twice than that of the pure working fluid, (ii) the thermal performance of heat pipe increases with increasing the concentration of GO nanoparticles in the base fluid, while the maximum heat transfer enhancement yields at 0.2% volume concentration, (iii) GO/water nanofluid shows lower thermal resistance compared to pure water, (iv) the optimal thermal resistance is obtained at 100% filling charge ratio with 0.2% volume concentration, and (v) heat transfer coefficient of the heat pipe significantly increases with an increase in heat flux and GO nanoparticles concentration.

Heat transfer analysis of radiator using graphene oxide nanofluids

As the technology is developing day by day, there is a requirement for enhancement in performance of automobile radiator to have a better performance of the IC Engine and fuel effectiveness. One of the major and recent approach to upgrade the performance of a radiator is that nanoparticles must be suspended in the general coolant (Ethylene Glycol – Water) which form nanofluids. Present work has been carried out by suspending graphene oxide nanoparticles in 50:50 Ethylene Glycol and RO-Water as base fluid. Experimentation is carried out by using three volume concentrations of the nanofluid (0.02%, 0.03% and 0.04%) and at different volumetric flow rates ranging from 3 to 6 LPM. Effect of volume concentration, inlet temperature and flow rate on Effectiveness, pressure drop and friction factor has been studied experimentally. Effectiveness versus NTU curves are plotted for further design calculations. The results show that the nanofluids will enhance the performance of an automobile radiator when compared with base fluid. Results also shows a maximum of 56.45% and 41.47% improvement in effectiveness for 0.03% volume concentration and 5 LPM flow rate at 40°C and 50°C inlet temperatures respectively.

Volumetric solar steam generation enhanced by reduced graphene oxide nanofluid

Solar steam generation is a highly efficient photo-thermal conversion method that has a wide range of applications in water purification, distillation, power plants, and seawater desalination. Low steam generation efficiency was obtained for solar steam generation using traditional working media. Therefore, reduced graphene oxide (rGO) nanofluids with good stability and light absorption capability were fabricated to achieve highly efficient volumetric solar steam generation in this work. The effects of rGO mass concentration and light intensity on solar steam generation enhancement were investigated experimentally. It was found that a hot area was formed at water–air interface due to the unique lamellar structure of rGO with good light absorption characteristic, and sunlight was absorbed by the hot area to generate steam locally, which reduced thermal loss and improved evaporation efficiency. The solar steam generation enhancement achieved by the rGO nanofluids reduced evaporation costs and expanded their applicability in seawater desalination, clean water production, sterilization of waste, etc.

Impact of Viscous Dissipation on Temperature Distribution of a Two-dimensional Unsteady Graphene Oxide Nanofluid Flow between Two Moving Parallel Plates Employing Akbari-Ganji Method

In the current study, an efficient, reliable and relatively novel analytical method is applied to describe the temperature behavior of an unsteady nanofluid flow containing water as the base fluid and graphene oxide particles as the nanoparticles between moving parallel plates. The first phase of this investigation involves turning the governing equations including partial differential equations (PDE) into ordinary differential equations (ODE) using similarity solution. Subsequently, a system of differential equations is solved applying Akbari-Ganji method (AGM) and reliable functions are obtained for temperature and velocity distributions. The effect of viscous dissipation in the derived equations is considered and comprehensively discussed. In order to examine the accuracy and precision of the current analytical results, the equations are also solved by using appropriate numerical solution. By comparing the results, a proper agreement with low error rate is observed between the analytical and numerical results. Finally, by definition of a viscous dissipation ratio parameter, the amount of heat due to shear stress is calculated for several nanoparticles and Eckert numbers. According to the results, viscous dissipation ratio of titanium oxide nanoparticles is greater than that of the other considered nanoparticles.