Graphene Nanofluids Research Articles

Micro-Channel Oscillating Heat Pipe Energy Conversion Approach of Battery Heat Dissipation Improvement: A Review

The application of batteries has become more and more extensive, and the heat dissipation problem cannot be ignored. Oscillating Heat Pipe (OHP) is a good means of heat dissipation. In this paper, the methods to improve the energy conversion and flow thermal performance of micro-channel OHP are studied and summarized. The working principle, heat transfer mechanism, advantages and applications of PHP are also introduced in detail in this study. Proper adjustment of the micro-channel layout can increase the heat transfer limit of PHP by 44%. The thermal resistance of two-diameter channel PHP is 45% lower than that of conventional PHP. The thermal resistance of PHP under uneven heating can be reduced to 50% of the original. PHP pulse heating can alleviate the phenomenon of dryness. Different working fluids have different effects on PHP. The use of graphene nano-fluids as the work medium can reduce the thermal resistance of PHP by 83.6%. The work medium obtained by the mixture of different fluids has the potential to compensate for the defects while inheriting the advantages of a single fluid.

Investigation of thermal conductivity enhancement of water-based graphene and graphene/MXene nanofluids

New nanofluids based on graphene (GR) and GR/MXene were prepared to enhance the thermal conductivity. The thermal conductivity and viscosity of nanofluids at various temperatures in the 5–60 °C range were tested, and their stability was investigated by zeta potential and visual observation. The thermal performance of the nanofluids was evaluated through numerical simulation analysis. The results demonstrate that MXene can effectively improve the dispersion stability of GR nanofluids. The nanofluid with 2.0 wt% GR at 60 °C exhibited the maximum thermal conductivity enhancement (65.34%) but also the maximum viscosity increment (70.69%). With the addition of MXene, the high thermal conductivity of nanofluids was maintained while the viscosity significantly decreased. GR can greatly improve the heat transfer efficiency of nanofluids, and the temperature at the monitoring point resulted from 2.0 wt% GR decreased by 9.19 ℃ compared to water. The heat transfer efficiency of GR/MXene nanofluids was almost identical to that of GR nanofluids.

Investigation of the effect of graphene nanofluid on heat transfer and cooling capacity of refrigerants

Investigation of the effect of graphene nanofluid on heat transfer and cooling capacity of refrigerants

Enhancing the mechanical and functional performance of carbon fiber reinforced cement mortar by the inclusion of a cost-effective graphene nanofluid additive

In this study, a low-cost and industrially scalable graphene nanofluid additive (GNA) was incorporated into carbon fibre-reinforced cement mortar (CFRCM) to enhance its functionalities. The results indicated that the synergistic effect of the carbon fibres and the GNA significantly improved many properties of the cement mortar. For the CFRCM modified with GNA (G-CFRCM), the maximum increases in the flexural and compressive strengths, 101% and 126%, respectively, which were much greater than those of the control, 25% and 45%, respectively, and the maximum increases in the thermal and electrical conductivities of the G-CFRCM, 36% and 68%, respectively, were much greater than those of the control, 27% and 19%, respectively. In addition, a surprising increase in the service life of the corresponding cathodic protection system with the G-CFRCM, more than 200% compared to that of the control showed, that this novel composite material is ideally suited for applications in high-efficiency cathodic protection systems.

Enhancing Thermal Conductivity and Heat Transfer using Graphene Nanofluid

Due to their low density and inherent thermal conductivity in compared to metals or metal oxides, carbon nanostructures among other nanoparticles exhibit better thermal conductivity. The ability of graphene Nano fluids to transmit heat has been studied in this work through a review of the findings of several studies. The current techniques for making graphene nanofluids have been summarized, along with several characteristics including viscosity, concentration, particle size, and temperature that have an impact on thermal conductivity. The convective heat transfer capabilities of graphene nanofluids have also been subjected to a careful analysis. The study shown that employing graphene nanofluids as a working fluid through a tube channel can improve heat transfer with considerable results. There hasn't been any research on the effects of graphene Nano fluids on facing steps and corrugated surfaces, according to the literature.

Predicting and optimizing the heat transfer performance of radiator with functionalized graphene nanofluids

AbstractAccurately predicting the heat transfer characteristics of coolants used in thermal management of energy systems like heat exchangers, power electronics, and heating, ventilation, and air conditioning is indispensable in maintaining its operating conditions within safety limits. Apart from safety, factors such as power consumption and operating cost are the most important constraints to be considered in designing an energy‐efficient and cost‐effective cooling solution. In this study, the experimental data available from previous research on the use of functionalized graphene‐based nanofluids in compact heat exchangers such as the automotive radiator is used to optimize the heat transfer performance parameters like Nusselt number of the nanofluid, the friction factor, and effectiveness of the heat exchanger. A supervised machine learning technique like the artificial neural network is used to obtain the objective functions of the response variables in terms of input features such as Reynolds number, Prandtl number, the volume concentration of nanoparticles in the base fluid, number of transfer units, heat capacity, the density of nanofluid, pressure drop and velocity. On the current dataset, it is found that by using the Bayesian regularization training algorithm and tangent sigmoidal activation function in the neural network, the best accuracies in the prediction can be achieved. Well‐known nature‐inspired optimization algorithms like genetic algorithms and simulated annealing are used in optimizing the above‐mentioned response variables. Both algorithms converged to the same values of the objective functions. The optimum values of Nusselt number, effectiveness, and friction factor are 105.65, 0.506, and 0.0038, respectively, for the given composition of the nanofluid and radiator configuration.

The mechanism of oil viscosity reduction with the addition of graphene nanoparticles

• Oil viscosity was found to decrease when graphene nanoparticles were added. • The viscosity reduction mechanism of oil-based graphene nanofluids is due to the self-assembly of graphene nanoparticles. • Direct observation of self-assembling of graphene nanoparticles in a carrier fluid flow. Understanding the interaction mechanisms between graphene nanoparticles (GNPs) and oil molecules is crucial for successful oil recovery. Numerous studies have shown that nanofluids (NF), especially nanofluids from the graphene family (GNF), are suitable candidates for enhanced oil recovery in various reservoirs. Increased oil recovery from nanofluid injection is attributed to changes in wettability, decreases in interfacial tension and changes in viscosity. Therefore, knowing the mechanisms affecting GNF viscosity is an urgent task of modern science, both fundamental and applied. In this paper, we conducted a comprehensive study of the molecular interaction between GNPs and hydrocarbon molecules of oil in order to establish the mechanisms affecting the viscosity of nanofluids. This paper presents the results of a study of the rheological properties of oil with different content of graphene nanoparticles in it. At low concentrations of GNP a decrease in the dynamic viscosity of the base fluid by 10%-17% was observed. It is also shown that the viscosity is affected not only by the concentration, but also by the temperature. Thus, for the concentration of graphene nanoparticles wt = 0.5 × 10 −3 % and temperature T = 50 °C, a maximum viscosity reduction of 17% is observed. When the concentration of graphene nanoparticles increases from wt = 5 × 10 −3 % and more, the viscosity profile of GNF does not differ from that of most NF. The paper presents the methodology and describes the experimental setup to study the behavior of nanoparticles while moving in the flow of a carrier fluid. Based on this technique, including computer simulation and observation of self-assembly of GNP and hydrocarbon molecules, using a specially designed setup, a mechanism is proposed which explains the decrease in nanofluid viscosity at low concentrations of nanoparticles. The mechanism of GNF viscosity reduction, where the base fluid (BF) is oil, is related to the self-assembly of GNP in the carrier fluid flow. However, according to the results of experiments and analysis of the viscosity mechanism of GNF, the viscosity reduction for water based GNF, with increasing concentration of nanoparticles, is not possible. The findings of this study can help for better understand the rheological properties of GNF, which opens up new possibilities for the commercial use of NF in the petroleum and energy industries.

Surfactant assisted exfoliation of high purity graphene in aqueous solution as a nanofluid using kitchen blender: Influence on dispersion, thermal conductivity and rheological properties

In this work, graphene is exfoliated from graphite flakes in distilled water solution containing Tween 80 as surfactant and by using the mechanical exfoliation method through a kitchen blender. The blending time is an important parameter for the size reduction and concentration of graphene exfoliation in a nanofluid. Graphene obtained using a kitchen blender is of high purity having no basal plane defects, as depicted from Raman spectroscopic investigation. The viscosity of graphene nanofluid increases with blending time up to 7 h and thereafter the viscosity decreases. All graphene nanofluid samples prepared using different blending time shows shear thinning behavior by fitting the power law of non-linear viscoelastic measurement data. The linear viscoelastic region measured was in the strain range of 0.01–0.8%. Further, the frequency sweep measurement using a rheometer has indicated the gel-like behavior of graphene nanofluid in a certain frequency range and depends on the concentration of graphene. The use of two-dimensional nanosheets-based nanofluid has attracted the attention of researchers for improving pool boiling properties. Herein, the pool boiling of graphene nanofluid at 7 h of blending shows the 77.4% enhancement in critical heat flux (CHF). This work has established mechanical exfoliation as a process to synthesize the graphene nanofluid and can be used for heat transfer applications.

On the friction stir welding of alloy AA2014 under n-MQL cooling condition

Friction stir welding (FSW) of AA2014 alloy requires cooling to prevent the dissolution of precipitates. The sustainable minimum quantity lubrication technique with graphene nanofluid is employed in this study for cooling purposes. FSW was carried out at 1200 rpm and 72 mm/min. A tool with a square pin was used. The microstructural evolution of the FSW joint under uniaxial tensile load is explored in detail for the first-time using electron backscatter diffraction. The results show that the grains undergo discontinuous dynamic recrystallisation during FSW and continuous dynamic recrystallisation during tensile deformation. Pole figures reveal the shear texture formed by plastic deformation. Tensile deformation has reduced local grain misorientation remarkably and thereby the dislocation accumulation. A significant increase of 94.5% is observed in grain size. Tensile deformation transforms a significant number of sub-grains with low-angle grain boundaries into stable grains with high-angle grain boundaries. The stable recrystallized grains with HAGBs and subgrains with LAGBs significantly influence the mechanical properties of the weld.

Synthesis and characterization of green-functionalized graphene nanofluids as an enhanced working fluid in heat transfer applications

Energy crisis is one of the major concerns that requires significant attention around the world. An access to reliable, sustainable, and affordable energy will not be attractive if the safety of human and environmental is neglected. Hence, the advancement of energy harvesting method is expected not to be just efficient, but also clean, safe, and environmental-friendly. In this research work, synthesis, and characterization of a green-based functionalized graphene nanofluids is presented. Clove extract was prepared and functionalized on the graphene nanoplatelets (GNP) using apple cider vinegar, followed by dispersion in distilled water to produce clove with apple cider vinegar functionalized graphene (clove+ACV GNP) nanofluids at 0.1 wt.% concentration. Characterization of the clove+ACV GNP nanofluids was carried out using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) to examine the successfulness of the synthesis and functionalization, while the thermal conductivity was determined using KD2 Pro Thermal Properties Analyzer. The covalent bonds shown in the FTIR spectrum, and the morphological structure from the SEM images have indicated that the synthesis and functionalization of clove+ACV GNP have been successfully carried out. As for the thermal conductivity, 0.1 wt.% of clove+ACV GNP nanofluids have shown up to 24.4% enhancement when compared with distilled water, 3.9% enhancement when compared to clove-functionalized GNP at the same concentration, and up to 6.8% when compared with conventional GNP nanofluids. These findings have given a preliminary insight that this safe, non-toxic- clove+ACV functionalized graphene nanofluids is a promising alternative to the conventional, toxic- nanofluids as an enhanced and effective working fluid in heat transfer applications.

Analysis and prediction of uncertain responses using regression and fuzzy logic for friction stir welding of AA2014 under n-MQL

AA2014 is an Al-Cu alloy friction stir welded under different combinations of rotational speed (800, 1000 and 1200 rpm) and transverse speed (44, 60, 72 mm/min) under minimum quantity lubrication condition with graphene nanofluid as coolant. Design of experiments is performed using Taguchi L9 orthogonal array. Analysis of variance technique is adapted to find the most influencing input parameter (rotational speed, transverse speed) of each output response (ultimate tensile strength, % elongation, microhardness and grain size). Regression and fuzzy logic based models are developed to predict the output responses. The reliability of the predicted results is tested by calculating the correlation coefficient. The predicted results from regression and fuzzy logic are then compared with the experimental results. The results of trend analysis exhibit the substantial influence of both the input parameters on the output responses. The results from ANOVA reveals that the rotational speed highly influences ultimate tensile strength and grain size while transverse speed majorly influences microhardness. The error in prediction using fuzzy model is observed to be significantly limited with correlation coefficients in the range of 0.70–0.96. The developed models are observed to be highly efficient and therefore can be used for prediction in any uncertain engineering applications.

Reactive molecular dynamics simulation of thermo-physicochemical properties of non-covalent functionalized graphene nanofluids

In this paper, the effect of adding sodium dodecyl benzenesulfonate(SDBS), sodium dodecyl sulfate (SDS), and triton X-100 on the thermophysical properties and the stability of water/ethylene glycol- graphene (G)- nanofluids (NFs) was investigated. Final observations demonstrate that the viscosity of NFs with 0.036 wt% of surfactants in comparison with 0.013 wt% NFs improved by 6.29%, 79.36%, and 39.13% for triton X-100, SDS, and SDBS, respectively. In addition, by increasing the fraction of SDS surfactant from 0.036 to 0.051 wt% thermal conductivity was enhanced by 84%. It was found that the thermophysical properties of NFs were more affected than their stability by adding surfactants. The results of this study can be used to produce G-NFs with optimized thermophysical properties and stability by using suitable surfactants.

The investigation of heat transfer enhancement by using different mixture conditions of graphene nanofluids on a downward facing surface

Abstract In this study, graphene nanofluids were used to explore the effect of various concentrations on boiling heat transfer of downward-facing heating. Five concentrations of graphene nanofluids were prepared for pool boiling heat transfer experiments. The experimental results show that when the mass concentration is 10 mg/L, the maximum enhancement of the CHF is up to 76.1%. In order to explore the mechanism of graphene nanofluid enhancing boiling heat transfer, after the experiment, the wettability and roughness of the heating surface were measured and the heating surface was characterized by a scanning electron microscope (SEM) and electronic differential system (EDS). The results show that the wettability is enhanced and the surface roughness is reduced. In addition, boiling curves (the curves of heat flux with surface superheat) and the curves of heat transfer coefficient with heat flux at different concentrations have also been observed to further explore the mechanism of enhanced heat transfer.

Low-salinity nanofluid – A smart fluid enhanced oil recovery method

This paper proposes a novel Janus graphene nanofluid that enhances the low salinity water oil flooding performance. Two kinds of Janus hydroxylated graphene oxide (JHGO-1 and JHGO-2) were prepared by the high internal phase emulsion method. JHGO nanosheets were well dispersed in low salinity water, and their zeta potential was lower than −30 mV. Compared with JHGO-1, JHGO-2 has more excellent interfacial properties, remarkably reducing 73% of the oil-water interfacial tension and improving the interfacial viscoelastic modulus and shear viscosity. Furthermore, JHGO can form bubble film, interfacial film, and climbing film at the oil/water interface due to its amphiphilic nature, which endows it with intelligent oil-finding properties. JHGO nanofluid alters the rock surface into strong water-wet and changes the capillary force into the driving force of oil flooding. JHGO nanofluid can also rapidly peel crude oil from rock surfaces by reducing adhesion work and forming disjoining pressure. These excellent interfacial properties help low-salinity nanofluid to have a 15.4% enhanced oil recovery at the ultra-low concentration (50 mg/L). This smart fluid flooding lays the foundation for efficient oilfield development.

Numerical investigation of aqueous graphene nanofluid ice slurry passing through a horizontal circular pipe: Heat transfer and fluid flow characteristics

Ice slurry is an attractive phase-change cold storage medium that offers excellent thermal performance, thus rendering it a good prospect for applications in renewable energy storage, power peak-cutting, and valley filling. In this study, a computational fluid dynamic (CFD) numerical framework is employed based on the particle dynamics approach of an Euler-Euler two-fluid model coupling interphase transfer mechanisms. Thermal transport of a water-based graphene nanofluid ice slurry moving in the turbulent regime in a horizontal circular straight pipe is simulated and described. During the flow, the ice crystals tend to cluster on the top of the horizontal pipe, according to the findings, while uniformity of the crystal size distribution improves with an increase of velocity and the ice packing factor (IPF). Under the conditions of inlet IPF of 10% and heat flux q = 8000 (W m−2), the heat transfer coefficient on the heated section wall is increased by around 9% and 15%, respectively, as compared to pure water ice slurry and water. However, since the nanofluids have a higher viscosity than water, the pressure drop of nanofluid ice slurry is about 5% higher than that of pure water ice slurry in the same working environment.

Dynamics of ethylene glycol-based graphene and molybdenum disulfide hybrid nanofluid over a stretchable surface with slip conditions

In this research study, numerical and statistical explorations are accomplished to capture the flow features of the dynamics of ethylene glycol-based hybrid nanofluid flow over an exponentially stretchable sheet with velocity and thermal slip conditions. Physical insight of viscous dissipation, heat absorption and thermal radiation on the flow-field is scrutinized by dissolving the nanoparticles of molybdenum disulfide (MoS2) and graphene into ethylene glycol. The governing mathematical model is transformed into the system of similarity equations by utilizing the apt similarity variables. The numerical solution of resulting similarity equations with associated conditions are obtained employing three-stages Lobatto-IIIa-bvp4c-solver based on a finite difference scheme in MATLAB. The effects of emerging flow parameters on the flow-field are enumerated through various graphical and tabulated results. Additionally, to comprehend the connection between heat transport rate and emerging flow parameters, a quadratic regression approximation analysis on the numerical entities of local Nusselt numbers and skin friction coefficients is accomplished. The findings disclose that the suction and thermal radiation have an adverse influence on the skin friction coefficients and heat transport rate. Further, a slight augmentation in the thermal slip factor causes a considerable variation in the heat transport rate in comparison to the radiation effect.

Thermal performance and entropy generation for nanofluid jet injection on a ribbed microchannel with oscillating heat flux: Investigation of the first and second laws of thermodynamics

In current numerical study, forced flow and heat transfer of water/NDG (Nitrogen-doped graphene) nanofluid in nanoparticles mass fractions ( φ ) of 0, 2% and 4% at Reynolds numbers ( Re ) of 10, 50, 100 and 150 are simulated in steady states. Studied geometry is a two-dimensional microchannel under the influence of nanofluid jet injection. Temperature of inlet fluid equals with T c = 293 K and hot source of microchannel is under the influence of oscillating heat flux. Also, in this research, the effect of the variations of attack angle of triangular rib (15°, 30°, 45° and 60°) on laminar nanofluid flow behavior inside the studied rectangular geometry with the ratio of L / H = 28 and nanofluid jet injection is investigated. Obtained results indicate that the increase of Reynolds number, nanoparticles mass fraction and attack angle of rib leads to the increase of pressure drop. By increasing fluid viscosity, momentum depreciation of fluid in collusion with microchannel surfaces enhances. Also, the increase of attack angle of rib at higher Reynolds numbers has a great effect on this coefficient. At low Reynolds numbers, due to slow motion of fluid, variations of attack angle of rib, especially in angles of 30°, 45° and 60° are almost similar. By increasing fluid velocity, the effect of the variations of attack angle on pressure drop becomes significant and pressure drop figures act differently. In general, by using heat transfer enhancement methods in studied geometry, heat transfer increases almost 25 %.

Optical properties and photothermal conversion performances of graphene based nanofluids

• Single-layer graphene and GO nanofluids were designed for solar thermal application. • Uniform temperature distribution is achieved in nanofluids based on the RI-DASC mode. • The photothermal conversion efficiency of SLG is 49.13% at 100 ppm in the RI-DASC mode. • The photothermal conversion efficiency of GO reaches 46.26% at 100 ppm in the RI-DASC mode. Direct absorption solar collectors (DASC) are extremely attractive in solar energy utilization. In this paper, starting from these two aspects, graphene-based nanofluids, including single-layer graphene (SLG) and graphene oxide (GO), are prepared to enhance solar absorption and photothermal conversion performance. The influence of nanofluids' concentration and two different irradiation modes: traditional DASC and reverse radiation DASC (RI-DASC) on the photothermal conversion performance of graphene-based nanofluids has been studied. The addition of a small amount of SLG or GO significantly improves the photothermal conversion efficiency of base fluid, and it increases along with the increase of the concentration. Furthermore, the RI-DASC mode has a more uniform thermal field distribution and the higher photothermal conversion efficiency than the DASC mode. In DASC mode, the photothermal conversion efficiency of pure water is 17.00%. By changing the irradiation mode, the introduction of GO and SLG nanofluids (100 ppm) increased the photothermal conversion efficiency by about 172% and 189%, reaching 46.26% and 49.13%. According to the photothermal-thermoelectric conversion experiment, the positive correlation between the output power of the TE module and the heating state of the nanofluid makes it possible to adjust the nanofluid in real-time. This work presents a feasible way to enhance solar energy absorption and improve the photothermal conversion efficiency of nanofluids for DASC.

Thermal effectiveness of solar collector using Graphene nanostructures suspended in ethylene glycol–water mixtures

Flat plate solar collectors (FPSCs) are the most often used as solar collectors due to their easiness of installation and usage. The current research investigates the energy efficiency of FPSC using different mass concentration with varied base fluids containing Graphene nanofluids (T-Gr). Mass concentration of 0.1%-wt., 0.075%-wt., 0.050%-wt. and 0.025%-wt. were mixed with ethylene glycol (EG) and distilled water (DW) in different rations. The operating conditions were volumetric flowrate (1.5, 1 and 0.5) LPM 50 °C-input fluid temperature and 800 W/m2-global solar irradiation. Scanning electron microscope (SEM) and energy dispersive X-ray (EDX) were used to synthesize the thermally treated nanomaterial. The theoretical investigation indicated that using T-Gr nanosuspensions increased the FPSC efficiency in comparison with the host fluid for all examined mass concentrations and volumetric flowrates. In quantitative terms, the maximum thermal effectiveness improvement for the EG, (DW:70 + EG:30) and DW:EG (DW:50 + EG:50) and using flowrates of (1.5, 1 and 0.5) LPM were 12.54%, 12.46% and 12.48%. In addition, the research results pointed that the essential parameters (i.e., loss energy (FRUL)) and gain energy (FR (τα)) of the T-Gr nanofluids were increased significantly.

Performance of two-phase loop thermosiphon with graphene nanofluid

• Investigation of loop thermosiphon using inflated aluminium plate with nanofluid. • The best heat transfer performance occurs for the thermosphion with a 70% filling ratio. • At 90 W, thermal resistance reduced by 6% relative to the filling ratio of 30%. • Uniform heat source has a better heat transfer performance than non-uniform one. • Thermal resistance is reduced by 4% with increase of concentration from 0 to 0.5 wt%. In this research, thermal resistance of the modified inflated aluminium plate that features a closed thermosiphon under natural convection was tested. HFE-7000 dielectric fluid and graphene nanofluid were used as the working fluids for different filling ratios (30%, 50%, and 70%), graphene concentrations (0.3 wt%, 0.5 wt%, 1 wt%), and supplied powers (30 W, 60 W, 90 W). The effect of uniform and non-uniform heat source on the thermal resistance are examined and a separate flow visualization is also conducted to understand the boiling phenomenon. It is found that a 70% filling ratio offers the best heat transfer performance. At a supplied power of 90 W and filing ratio of 70%, the thermal resistance is reduced by around 4% relative to the filling ratio of 30% for the same supplied power of 90 W. In terms of input power, the decrease in thermal resistance was found as the power increases. The uniform heat source has a better heat transfer performance than the non-uniform one. From the visualization experiment, appreciable graphene was entrained from evaporator to condenser due to boiling especially at a higher concentration of 1%, causing the blockage and raising the thermal resistance. Therefore, the best concentration of graphene should be kept to below 0.5 wt% in which the size of the bubbles was sufficiently large enough to facilitate latent heat transfer effectively for supplied powers of 60 and 90 W.