Aqueous Nanofluids Research Articles

Stability Study of Graphene Oxide Based Aqueous Nanofluids for Solar Absorption Application

Stability Study of Graphene Oxide Based Aqueous Nanofluids for Solar Absorption Application

Augmenting the double pipe heat exchanger efficiency using varied molar Ag ornamented graphene oxide (GO) nanoparticles aqueous hybrid nanofluids

The optimization of heat transfer in heat exchanging equipment is paramount for the efficient management of energy resources in both industrial and residential settings. In pursuit of this goal, this empirical study embarked on enhancing the heat transfer performance of a double pipe heat exchanger (DPHX) by introducing silver (Ag)-graphene oxide (GO) hybrid nanofluids into the annulus of the heat exchanger. To achieve this, three distinct molar concentrations of Ag ornamented GO hybrid nanoparticles were synthesized by blending GO nanoparticles with silver nitrate at molarities of 0.03 M, 0.06 M, and 0.09 M. These Ag-GO hybrid nanoparticles were then dispersed in the base fluid, resulting in the formation of three distinct hybrid nanofluids, each with a consistent weight percentage of 0.05 wt%. Thorough characterization and evaluation of thermophysical properties were performed on the resulting hybrid nanomaterials and nanofluids, respectively. Remarkably, the most significant enhancement in heat transfer coefficient, Nusselt number, and thermal performance index (62.9%, 33.55%, and 1.29, respectively) was observed with the 0.09 M Ag-GO hybrid nanofluid, operating at a Reynolds number of 1,451 and a flow rate of 47 g/s. These findings highlight the substantial improvement in thermophysical properties of the base fluid and the intensification of heat transfer in the DPHX with increasing Ag molarity over GO. In summary, this study emphasizes the vital importance of optimizing the molarity of the material, which also plays a significant role in nanoparticle synthesis to achieve the optimal amplification of heat transfer.

Enhanced photothermal conversion performance of MWCNT/SiC hybrid aqueous nanofluids in direct absorption solar collectors

Nanofluids containing light-absorbing nanoparticles are potential alternative working fluids in solar collectors. In this work, a novel hybrid aqueous nanofluid containing multi-walled carbon nanotubes (MWCNTs) and SiC nanoparticles is prepared to improve the photothermal conversion ability of working fluids. The hybrid nanofluid overcomes the disadvantages of one-component nanofluids and achieves good solar absorption on the merit of the complementary optical property of MWCNTs and SiC nanoparticles. The prepared nanofluids show excellent stability due to the hydroxyl functionalization of MWCNTs, and the thermal conductivity of hybrid nanofluids is also enhanced. A high photothermal conversion efficiency of 64.7 % is achieved by the hybrid nanofluid after 1-hour irradiation, which is significantly higher than that of the reported MWCNT-based aqueous nanofluids in the literature. Meanwhile, the mechanism of efficiency enhancement in MWCNT/SiC hybrid nanofluids is analyzed. This study promotes the application of MWCNT/SiC hybrid nanofluids as light-absorbing working fluids in solar collectors.

Analytical Investigation of Electroosmotically Regulated Peristaltic Propulsion of Cu-water Nanofluid Through a Microtube

The purpose of this investigation is to determine and analyze the fluid inertia of electroosmotic flow on the Cu-water nanofluids by peristaltic transport. Fluid flow properties and heat transfer characteristics are studied for aqueous ionic nanofluids through a vertical microtube of a constant radius. Streamlines are plotted for the governing fluid flow.

Effect of Different Preparation Parameters on the Stability and Thermal Conductivity of MWCNT-Based Nanofluid Used for Photovoltaic/Thermal Cooling

The thermal conductivity and stability of any nanofluid are essential thermophysical properties. These properties are affected by many parameters, such as the nanoparticles, the base fluid, the surfactant, and the sonication time used for mixing. In this study, multi-walled carbon nanotubes (MWCNTs) were selected as additive particles, and the remaining variables were tested to reach the most suitable nanofluid that can be used to cool photovoltaic/thermal (PVT) systems operating in the harsh summer conditions of the city of Baghdad. Among the tested base fluids, water was chosen, although ethylene glycol (EG), propylene glycol (PG), and heat transfer oil (HTO) were available. The novelty of the current study contains the optimization of nanofluid preparation time to improve MWCNTs’ PVT performance with different surfactants (CTAB, SDS, and SDBS) and base fluids (water, EG, PG, and oil). When 1% MWCNT mass fraction was added, the thermal conductivity (TC) of all tested fluids increased, and the water + nano-MWCNT advanced all TC (EG, PG, and oil) by 119.5%, 308%, and 210%, respectively. The aqueous nanofluids’ stability also exceeded the EG, PG, and oil at the mass fraction of 0.5% MWCNTs by 11.6%, 20.3%, and 16.66%, respectively. A nanofluid consisting of 0.5% MWCNTs, water (base fluid), and CTAB (surfactant) was selected with a sonication time of three and quarter hours, considering that these preparation conditions were practically the best. This fluid was circulated in an installed outdoor, weather-exposed PVT system. Experiments were carried out in the harsh weather conditions of Baghdad, Iraq, to test the effectiveness of the PVT system and the nanofluid. The nanofluid-cooled system achieved an electrical efficiency increase of 88.85% and 44% compared to standalone PV and water-cooled PVT systems, respectively. Additionally, its thermal efficiency was about 20% higher than that of a water-cooled PVT system. With the effect of the high temperature of the PV panel (at noon), the electrical efficiency of the systems was decreased, and the least affected was the nanofluid-cooled PVT system. The thermal efficiency of the nanofluid-cooled PVT system was also increased under these conditions. This success confirms that the prepared nanofluid cooling of the PVT system approach can be used in the severe weather of the city of Baghdad.

Electroosmotically augmented peristaltic flow of carbon nanotubes based nanofluid through asymmetrical channel

AbstractThe peristaltic flow of nanofluids is an emerging area of scientific research due to its vital industrial and medical applications. Herein, a model study is conducted to numerically investigate, the electroosmotically augmented peristaltic pumping of electrically conducting aqueous ionic nanofluid through an inclined asymmetric channel. The behavior of the model for various involved parameters is expressed through a set of graphs. The velocity profile gained a significant increment for Joule heating and electroosmotic velocity parameters. The velocity dropped for the Hartmann number, while a dual behavior is noted for the thermal Grashof number. However, the magnetic number enhances the temperature, while a lower temperature is perceived for the electroosmotic velocity and Debye length parameters. The streamline pattern for the fluid flow subject to multiple values of the electroosmotic velocity parameter can be seen to indicate that for negative values of the parameter, a larger number of streamlines are circulated compared to the case when the electric field is absent, that is, . However, in the case of an opposing electric field, that is, for the positive values of the parameter, the streamline bolus occurs across the centerline of the channel.

Squeezing flow of aqueous CNTs-Fe3O4 hybrid nanofluid through mass-based approach: Effect of heat source/sink, nanoparticle shape, and an oblique magnetic field

Here, the squeezing unsteady 2-dimensional incompressible hybrid nanofluid flow between two collateral sheets has been investigated numerically, considering the influences of magnetic field and the mutable thermal conductivity. The solid-particles are the magnetite (Fe3O4) and the carbon nanotubes (CNTs) inserted in the base liquid (water). To give a complete development investigation of the present problem, the influences of a heat source/sink have also been analyzed. The technique used is pursuant to the Tiwari-Das nanofluid method which nanoparticle weights are considered instead of the volumetric concentration of the solid-particles. At first, the controlling dimensional PDEs, including continuity, momentum conservation, and energy conservation, are changed to a non-dimensional ODEs system applying adequate similarity reduction. The Runge–Kutta–Fehlberg (RK4) approach and shooting procedure is utilized to solve nonlinear ODEs system numerically. The impression of the controlling parameters on the temperature and velocity of working fluid as well as the Nusselt number, and the skin friction has been studied and analyzed. The mass-based manner gives trustable results for the flow and heat transfer analysis in the presence heat generation source and also an oblique magnetic ground. The results demonstrate that the entity of temperature-dependent thermal conductivity and the oblique magnetic ground reduces heat transfer. Furthermore, the greatest temperature distribution was related to spherical solid-particles in the presence of a horizontal magnetic ground.

Entropy generation and exergy destruction in two types of wavy microchannels working with various aqueous nanofluids using a multi-phase mixture model

Entropy generation and exergy destruction in two types of wavy microchannels working with various aqueous nanofluids using a multi-phase mixture model

Aqueous hybrid nanofluids containing silver-reduced graphene oxide for improving thermo-physical properties

Aqueous hybrid nanofluids containing silver-reduced graphene oxide for improving thermo-physical properties

Radiative and exponentially space-based thermal generation effects on an inclined hydromagnetic aqueous nanofluid flow past thermal slippage saturated porous media

Advances in nanoscience and technology acquired the significance of the nanofluid in novel functional polymers like fibre insulation, geothermal system and chemical catalytic reactors. Inspired by the above applications, an innovative mathematical model is established for radiative nanoliquid flow and is engendered due to stretching sheet with inclined magnetic field which is immersed with nanoparticles. Joule dissipation and exponentially-based heat source/sink effects are employed in the present phenomenon under the heat constraints. The governing equations, which describe the flowing nanofluid, are transformed into invariant dimensionless equations with suitable similarity quantities. With the adoption of a shooting scheme with Runge–Kutta-45, the resultant equations are numerically simplified. The impact of several converted dimensionless elements on physically interesting values is depicted visually. The current analysis is validated through comparison with some selected related literature, which shows a positive correlation. The nanoparticle thermal conductivity is raised for an increased value of the thermal radiation, thermal viscosity and heat source to propel temperature profiles. The heat flux gradient significantly affects the heat propagation all over the flow regime.

INFLUENCE OF VARIOUS FACTORS ON THE HEAT TRANSFER CHARACTERISTICS OF MINIATURE TWO-PHASE THERMOSYPHONS WITH NANOFLUIDS

Currently, various types of nanofluids are of increasing interest as heat carriers for heat transfer in thermosiphons and other evaporative-condensation devices. This paper presents and analyzes experimental data on heat transfer characteristics (total thermal resistances, maximum transferable heat fluxes and equivalent thermal conductivity) of two-phase miniature thermosyphons with nanofluids. Geometric parameters of thermosiphons for all experimental samples were identical and were: total length 700 mm, inner diameter 5 mm. The length of the heating zone was changed stepwise from 45 mm to 200 mm. The length of the condensation zone was 200 mm for all investigated thermosyphons. The amount of coolant in the thermosiphons was the same, and its height in the heating zone before the start of the study was 88 mm. Distilled water and aqueous nanofluids with nanoparticles of carbon nanotubes, synthetic diamond, and carbon black were used as heat carriers. The main attention is paid to the study of the influence of the filling factor and the angle of inclination of the thermosyphon, the value of the transferred heat flux and the chemical nature of the coolant (nanofluid) on the heat transfer characteristics of thermosyphons. The strong influence of these factors on the efficiency of a miniature closed two-phase thermosyphon has been demonstrated. A more than twofold increase in the heat transfer characteristics of thermosyphons (the maximal transferred heat flux) was obtained with a sharp decrease in their thermal resistance. It is assumed that the significantly higher heat transfer capacity of such thermosiphons compared to those filled with water is explained not only by the higher thermal conductivity of the coolant, but also by the appearance of a peculiar porous structure that prevents the appearance of a vapor film and promotes the intensification of heat transfer processes during boiling. Bibl. 16, Fig. 10, Tab. 2.

Influence of thermal cycling on stability and thermal conductivity of nanofluid ice slurry

Nanofluid ice slurry has the advantages of large phase change latent heat, high energy storage density and cooling rate. In this article, a two-step approach was used to prepare water-based graphene oxide (GO), Al2O3, and GO-Al2O3 hybrid nanofluids. The effects of thermal cycling on the stability and thermal conductivity of nanofluid ice slurry were also investigated. Moreover, thermal conductivity model considering thermal cycling and mass fraction was proposed. Results show with the increase of the number of phase change cycles, the stability of nanofluids decreases gradually, and tends to be stable after 6 cycles. The lower the minimum temperature of the thermal cycling, the more serious the segregation of nanoparticles, the worse the stability of nanofluids after thermal cycling. In addition, multi-cycle of phase change has less influence on thermal conductivity of GO nanofluid than that of non-phase-change, although the influence is a little larger at the dilute concentration range. The thermal conductivity of GO-Al2O3 hybrid nanofluid ice slurry is between that of GO and Al2O3 aqueous single nanofluid after phase change thermal cycling. The influence of the phase change cycles on thermal conductivity decreases with the increase of concentration, however, the smaller the concentration, the larger the thermal conductivity reduction. The hybrid nanofluid ice slurry can ensure the dispersion stability and thermal conductivity of the fluid, and its comprehensive performance is better than that of nanofluid with one type of nanoparticle.

Heat Transfer Characteristics of Fullerene and Titania Nanotube Nanofluids under Agitated Quench Conditions.

Distilled water and aqueous fullerene nanofluids having concentrations of 0.02, 0.2, and 0.4 vol % and titania (titanium dioxide, TiO2) nanofluids of 0.0002, 0.002, and 0.02 vol % were analyzed for heat transfer characteristics. Quenching mediums were stirred at impeller speeds of 0, 500, 1,000, and 1,500 RPMs in a typical Tensi agitation system. During the quenching process, a metal probe made of ISO 9950 Inconel was used to record the temperature history. The inverse heat conduction method was used to calculate the spatial and temporal heat flux. The nanofluid rewetting properties were measured and matched to those of distilled water. The maximum mean heat flux was 3.26 MW/m2, and the quickest heat extraction was 0.2 vol % fullerene nanofluid, according to the results of the heat transfer investigation.

Anticorrosion and lubricating properties of an aqueous graphene-based nanofluid

Anticorrosion and lubricating properties of an aqueous graphene-based nanofluid

Particle size and temperature effects on thermal conductivity of aqueous Ag nanofluids: modelling and simulations using classical molecular dynamics

Particle size and temperature effects on thermal conductivity of aqueous Ag nanofluids: modelling and simulations using classical molecular dynamics

Insight into the investigation of Fe3O4/SiO2 nanoparticles suspended aqueous nanofluids in hybrid photovoltaic/thermal system

This experimental study aims to evaluate the energetic performance of a photovoltaic-thermal system with a serpentine tube collector. A photovoltaic-thermal unit with a serpentine tube collector is used to compare the unit's performance metrics to those of a PV panel without cooling. The considered heat transfer fluid is the hybrid nanofluid prepared using water and Fe3O4/SiO2 nanoparticles. Using irradiance data from an average day in Aligarh, India, the experiment is conducted in indoor environment in a solar simulator under regulated operating circumstances. Effects of mono and hybrid nanofluids are examined at 3% wt. concentration for varying flow rates (20, 30, 40 LPM). The experimentation analysis showed that the maximum drop in PV temperature at 20 LPM is 25 °C, 24 °C, and then 16 °C for Fe3O4/water, SiO2/water, and Fe3O4/SiO2 nanofluids-based PVT systems, respectively with a highest possible increase in electrical efficiency of 12.6 percent, 18.46 percent, and 24.34 percent, respectively, when compared to traditional PV systems. At a flow rate of 40 LPM, the best performance is obtained using a hybrid PVT method coupled with an aqueous Fe3O4/SiO2 nanofluid. Additionally, it is discovered that hybrid nano-fluid-based PVT systems exhibit 10.5% and 5% greater thermal efficiency than Fe3O4-Water and SiO2-Water PVT systems, respectively. The overall highest efficiency of 67% is achieved for hybrid nanofluid at a flow rate of 40LPM. The hybrid Fe3O4/SiO2 nanofluid is capable of serving as an acceptable cooling fluid for the PV/T collector, as evidenced by the PV/T system's notable improvement in thermal and electrical efficiency and prominent cooling impact. Keywords : Solar energy, Hybrid nano-fluid, Heat transfer, Electrical Power, Thermal Efficiency, PVT system. • The role of hybrid nanofluids for the performance of PVT systems was studied. • Hybrid nature of nanofluid make it more stable than mono-nanofluid. • Electrical and thermal efficiency were analysed at fixed concentration and varying flowrate. • Comparison of Fe 3 O 4 /SiO 2 nanofluid is carried out with individual mono-nanofluid.

Experimental Investigation on the Thermophysical and Rheological Behavior of Aqueous Dual Hybrid Nanofluid in Flat Plate Solar Collectors

This work investigates the thermal–physical and rheological properties of hexagonal boron nitride/carbon nanotubes (hBN/CNTs) applied to reinforce water-based working fluid in a flat plate solar collector (FPSC). The hybrid nanoadditives of hBN and the chemically functionalized CNTs (CF-CNTs) were suspended in distilled water (DW) with a nonionic surfactant. The hybridization ratio between CF-CNTs and hBN was optimized to be 40:60. The thermal efficiency tests on the solar collector were carried out using different volumetric flow rates (2, 3, and 4 L/min) under the ASHRAE-93-2010 standard. The morphological characteristics of the hybrid nanoadditives were evaluated using X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Different concentrations of hBN/CF-CNTs were added to the water-based working fluid to record the optimal wt.% for maximum enhancement in the FPSC’s efficiency. The results revealed that using only 0.1 wt.% of hBN/CF-CNTs with a flow rate of 4 L/min remarkably improved the collector efficiency by up to 87% when compared to the conventional working fluid used in FPSC.

Influences of Aqueous Nanofluid Emulsion on Diesel Engine Performance, Combustion, and Emission: IoT (Emission Monitoring System)

Pollution is the primary ecological threat to nature and it also raises the temperature of the Earth. The primary cause of air pollution is exhaust emissions from the combustion chamber. This study aims to focus on controlling emissions using an aqueous nanoemulsion method and to analyze positive vibrations for the reduction of pollutants in diesel engines. In this study 3% NWED (nano-based water emulsion diesel), 7% NWED, and 12% NWED emulsion blended diesel were mixed with Tween-20 as a solvent. In addition, this work was accomplished with a multiuser remote control system for the continuous monitoring of emissions with IoT technology applied to diesel engines. Experimental results have been measured with an IoT kit and five gas analyzers and reported that emission of oxides of nitrogen and hydrocarbons can be reduced by using a 7% NWED blend when compared with diesel. In addition, the experimental result also shows that the brake-specific fuel consumption is reduced with an improvement in thermal efficiency at 7% NWED when compared with other blends.

Improving the thermal characteristics of a cooling tower by replacing the operating fluid with functionalized and non-functionalized aqueous MWCNT nanofluids

In this study, the thermal properties of the operating fluid by replacing the fluid with better thermal properties and lower water loss in a cross-flow cooling tower (CFWCT) investigated. For this purpose, MWCNTs/H2O, MWCNTs-COOH/H2O, and MWCNTs-OH/H2O nanofluids were used instead of water, and the results were compared. The visual method and dynamic light scattering (DLS) were used to guarantee the stability of nanofluids and to determine the size distribution of the nanoparticles in the nanofluid. The influence of nanofluids concentration on cooling towers performance variables such as evaporation rate, performance characteristics, temperature drop, and tower efficiency were investigated. The results showed that the functionalized nanofluids with lower evaporation rates than water and the non-functionalized nanofluids with higher evaporation rates than water improved the thermal performance of CFWCT. For example, at a concentration of 0.1 wt% MWCNTs-COOH/H2O, MWCNTs-OH/H2O, and MWCNTs/H2O, the efficiency of the cooling tower was 46%, 45.3%, and 43.2%, and the performance characteristics were improved by 15.8%, 11.2%, and 6.1%, respectively, compared with water. Among the nanofluids, MWCNTs-COOH/H 2 O nanofluid had the best performance, in which the evaporation rate, performance characteristics, temperature drop, and efficiency were increased by about −4.3%, 15.8%, 15.9%, and 8.7%, respectively, compared to water.

Thermal and Rheological Characterization of Aqueous Nanofluids Based on Reduced Graphene Oxide (rGO) with Manganese Dioxide Nanocomposites (MnO2).

Nanofluids have become of interest in recent years thanks to their improved thermal properties, which make them especially interesting for microchannel heat sink applications. In this study, we prepared two aqueous nanofluids based on reduced graphene oxide (rGO) decorated with manganese dioxide (MnO) at a concentration of 0.1 wt.%. The difference between the two nanofluids was in the preparation of the reduced graphene oxide decorated with MnO. In the first case, the manganese salt was mixed with ascorbic acid before GO reduction with NaOH, and in the second case, the GO reduction with NaOH occurred under ascorbic acid. Ascorbic acid not only plays the role of a non-toxic and ecofriendly reducing agent but also acts as an important parameter to control the reaction kinetics. The structural, microstructural and spectral characterizations of the MnO/rGO nanocomposite were conducted via X-ray diffractometry (XRD), Raman spectroscopy, FT-IR, TEM, SEM and EDS analyses. Moreover, the synthesized MnO/rGO nanocomposites were utilized as nanofluids and their stability, thermal conductivity and rheological behaviors were studied. The thermal conductivity of the MnO/rGO and MnOAsA/rGO nanofluids was 17% and 14.8% higher than that of water for the average temperature range, respectively, but their viscosity remained statistically equal to that of water. Moreover, both nanofluids presented Newtonian behavior in the analyzed shear rate range. Therefore, both MnO/rGO and MnOAsA/rGO nanofluids are promising alternatives for use in applications with micro- and millichannel heat sinks.