Preparation Of Nanofluids Research Articles

Characterization of thermal and electrical properties of hybrid nanofluids prepared with multi-walled carbon nanotubes and Fe2O3 nanoparticles

The thermal and electrical features of fluids are the most important parameters for designing suitable nanofluids to be used as coolants in automotive systems, transportation, power plants, industrial facilities, as well as oil, gas, petrochemical and electronic industries. This research aims at the thermal, electrical and physical properties of hybrid nanofluids that consist of multi-walled carbon nanotube (MWCNT) and Fe2O3 nanoparticles in ethylene glycol/water as base fluid. The conditions for nanofluid preparation were optimized through the response surface methodology. EG, MWCNT, Fe2O3 nanoparticles proportion and solution pH were chosen as parameters of effect on Thermal conductivity. The experimental data point out that Thermal conductivity would increase proportional to increase the amount of nanoparticle, but it would decrease in alkaline environments. Also, highest electrical conductivity (545 [μS/cm]) was observed at 0.69 [%w.v] of MWCNT and 1.67 [% w.v] of Fe2O3 nanoparticles dispersed in a 44:56 ethylene glycol-water mixture, as compared to other base fluids. The synergetic effect of both nanoparticles added to the base fluid on the thermos-electrical property was confirmed by the measurement of thermal and electrical conductivities and electrochemical impedance spectroscopy (EIS).

Efficient Stabilization of Mono and Hybrid Nanofluids

Currently; the transfer of new technologies makes it necessary to also control heat transfer in different industrial processes—both in practical and research—applications. Not so long ago water and ethylene glycol were the most frequently used media in heat transfer. However, due to their relatively low thermal conductivity, they cannot provide the fast and effective heat transfer necessary in modern equipment. To improve the heat transfer rate different additives to the base liquid are sought, e.g., nanoadditives that create mono and hybrid nanofluids with very high thermal conductivity. The number of scientific studies and publications concerning hybrid nanofluids is growing, although they still represent a small percentage of all papers on nanofluids (in 2013 it was only 0.6%, and in 2017—ca. 3%). The most important point of this paper is to discuss different ways of stabilizing nanofluids, which seems to be one of the most challenging tasks in nanofluid treatment. Other future challenges concerning mono and hybrid nanofluids are also thoroughly discussed. Moreover, a quality assessment of nanofluid preparation is also presented. Thermal conductivity models are specified as well and new representative mono and hybrid nanofluids are proposed.

Experimental investigation of rheological properties and thermal conductivity of SiO2\u2013P25 TiO2 hybrid nanofluids

Over many years, great efforts have been made to develop new fluids for heat transfer applications. In this paper, the thermal conductivity (TC) and viscosity of SiO2–P25 TiO2 (SiO2–P25) hybrid nanofluids were investigated for different nanoparticle volume concentrations (0.5, 1.0 and 1.5 vol%) at five various temperatures (20, 30, 40, 50 and 60 °C). The mixture ratio (SiO2:P25) in all prepared hybrid nanofluids was 1:1. Besides, pure SiO2, P25 nanofluids were prepared with the same concentrations for comparison with the hybrid nanofluids. The base fluid used for the preparation of nanofluids was a mixture of deionized water and ethylene glycol at a ratio of 5:1. Before preparing the nanofluids, the nanoparticles were analyzed with energy-dispersive X-ray analysis, scanning electron microscope, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The zeta potentials of the prepared nanofluids except SiO2 nanofluids were above 30 mV. These nanofluids were visually observed for stability in many days. The TC enhancement of the hybrid nanofluid was higher than the pure nanofluid. In particular, with 1.0 vol% concentration, the maximum enhancement of SiO2, P25 and SiO2–P25 nanofluids were 7.5%, 9.9% and 10.5%, respectively. The rheology of the nanofluids was Newtonian. The viscosity increment of SiO2, P25 and hybrid nanofluids were 19%, 32% and 24% with 0.5 vol% concentration. A new correlation was developed for the TC and dynamic viscosity of SiO2–P25 hybrid nanofluid.

A review on the properties, preparation, models and stability of hybrid nanofluids to optimize energy consumption

These days, the importance of energy consumption has led scientists to optimize thermal devices. One of the solutions proposed for this purpose is using solid nanoparticles to amend the thermal properties of conventional fluids. Adding the nanoparticles into the foundation fluids results in an improvement in the fluid properties (thermal conductivity, viscosity, etc.). Nanofluid (NF) has been drawing attention in various engineering applications in the past decade due to its superior heat transfer characteristics than the conventional working fluid. In recent years, the researchers have focused on adding two or more nanoparticles into foundation fluids, known as hybrid nanoparticles. Hybrid nanofluids (HNFs) suggest a more appropriate heat transfer performance and thermophysical features than the conventional heat transfer fluids (ethylene glycol, water and oil) and even NFs with single nanoparticles. It was proven that HNF can be an alternative to the single NF, since it can provide more heat transfer enhancement, particularly in the context of the solar energy, electromechanical, HVAC, electromechanical and automobile. In the current research, the properties, preparation and stability of HNFs are investigated. Also, some models and correlations for predicting HNFs properties are presented.

Correction to: Review on the recent progress in the preparation and stability of graphene-based nanofluids

Numerous researches to prepare and stabilize graphene-based nanofluids have been developed.

Hybrid Nanocellulose-Copper (II) Oxide as Engine Oil Additives for Tribological Behavior Improvement

Friction and wear are the main factors in the failure of the piston in automobile engines. The objective of this work was to improve the tribological behaviour and lubricant properties using hybrid Cellulose Nanocrystal (CNC) and Copper (II) oxide nanoparticles blended with SAE 40 as a base fluid. The two-step method was used in the hybrid nanofluid preparation. Three different concentrations were prepared in a range of 0.1% to 0.5%. Kinematic viscosity and viscosity index were also identified. The friction and wear behavior were evaluated using a tribometer based on ASTM G181. The CNC-CuO nano lubricant shows a significant improvement in term of viscosity index by 44.3–47.12% while for friction, the coefficient of friction (COF) decreases by 1.5%, respectively, during high and low-speed loads (boundary regime), and 30.95% during a high-speed, and low load (mixed regime). The wear morphologies results also show that a smoother surface was obtained after using CNC-CuO nano lubricant compared to SAE 40.

Few-Layer Graphene-Based Nanofluids with Enhanced Thermal Conductivity.

High-quality graphene is an especially promising carbon nanomaterial for developing nanofluids for enhancing heat transfer in fluid circulation systems. We report a complete study on few layer graphene (FLG) based nanofluids, including FLG synthesis, FLG-based nanofluid preparation, and their thermal conductivity. The FLG sample is synthesized by an original mechanical exfoliation method. The morphological and structural characterization are investigated by both scanning and transmission electron microscopy and Raman spectroscopy. The chosen two-step method involves the use of thee nonionic surfactants (Triton X-100, Pluronic® P123, and Gum Arabic), a commercial mixture of water and propylene glycol and a mass content in FLG from 0.05 to 0.5%. The thermal conductivity measurements of the three FLG-based nanofluid series are carried out in the temperature range 283.15–323.15 K by the transient hot-wire method. From a modeling analysis of the nanofluid thermal conductivity behavior, it is finally shown that synergetic effects of FLG nanosheet size and thermal resistance at the FLG interface both have significant impact on the evidenced thermal conductivity enhancement.

Thermal Conductivity Enhancement via Synthesis Produces a New Hybrid Mixture Composed of Copper Oxide and Multi-walled Carbon Nanotube Dispersed in Water: Experimental Characterization and Artificial Neural Network Modeling

Nanofluid is a solid–fluid mixture. By using one solid nanoparticle or one fluid, mono-nanofluid (MN) forms, and by using two solid nanoparticles (NPs) or two fluids, hybrid-nanofluid (HN) forms. For this study, for MN, copper oxide (CuO) and for HN, two solids, which are CuO and multi-walled carbon nanotube (MWCNT) were dispersed in base fluid which is water. After nanofluid preparation, thermal conductivity was measured, and the achievements were numerically modeled. After that, XRD–EDX were performed for the phase-structural analysis. Then, FESEM was examined for NPs-microstructural study. Thermal conductivity (TC) of MN and HN were investigated at 0.2 % to 1.0 % volume fractions (Vf) in 25 °C to 50 °C temperature (T) ranges. Thermal conductivity enhancements of 19.16 % and 37.05 % were seen at the utmost Vf and T for mono-nanofluid and hybrid-nanofluid, respectively. New correlations have been presented with R2 = 0.9, and also Artificial Neural Network (ANN) has been done with R2 = 0.999. For the presented correlation, 0.86 %, and 0.51 % deviations, and for the trained model, 0.41 % and 0.51 % deviations were estimated for mono-nanofluid and hybrid-nanofluid, respectively. As a final result, by adding MWCNT to CuO–H2O mixture, thermal conductivity is raised by 17.89 %, and the hybrid-nanofluid has acceptable heat-transfer capability.

Effect of Ball Milling and Oxidation on Dispersibility and Dispersion Stability of Multiwalled Carbon Nanotubes in High Viscous Heat Exchange Fluids

AbstractMultiwalled carbon nanotubes (MWCNTs) tend to agglomerate resulting in poor dispersion in most of the common solvents due to possessing long tubular structure, high Vander Waal force of attractions and poor interfacial interactions with the surrounding matrix. To improve the dispersion stability, MWCNT, were subjected to ball milling with 300 rpm for 1 h to reduce the length of the MWCNT to improve the functional groups to the MWCNT wall during chemical functionalization. MWCNTs were subjected to thermal oxidation in air at different temperatures before acid treatment to remove the amorphous carbon from MWCNT. Morphology studies of MWCNTs nanofluids were carried out by using a SEM and TEM methods to characterize the surface deformity of MWCNT structure and extent of defect formation, respectively. FT IR and XRD methods were used for the identification of different functional groups and crystalline nature of pristine, ball milled and oxidized MWCNT, respectively. Raman spectroscopy was applied to measure the relative intensities (ID/IG) to estimate the defect ratios. Preparation of nanofluid by dispersing high defect ratio MWCNTs with a concentration of 100 ppm in the base fluid by the ultra‐sonication method. Nanofluids dispersion stability and cycle stability were studied by using UV‐Visible spectroscopy and MWCNTs treated with combined ball milling and oxidation method have exhibited high stability and high dispersibility.

Effect of ZrO2 Nanoparticle Deposited Layer on Pool Boiling Heat Transfer Enhancement

Nanofluid preparation and its deposition on metallic surfaces are in wide practice due to their enhancement capability in the pool boiling heat transfer. The effect of zirconia nanoparticles coated layer on pool boiling heat transfer has been investigated with de-ionized water. The turbidity, viscosity and stability test are conducted, and confirmed a better dispersion of nanoparticles. The synthesized zirconia nanofluid is deposited by nanofluid boiling nanoparticle technique at different concentrations on three copper samples. The conventional characterization techniques confirm the better structural behavior of the coating. The obtained results of non-coated copper sample fits well with Rohsenow correlation, which signifies the reliability and stability of the obtained results. Experimental results shows that sample with 200 nm coating thickness and 227 nm surface roughness improved the heat transfer coefficient by 31.52% compared to non-coated copper sample. The bubble behavior of the same has the highest velocity and lower bubble diameter compared to other at 785 kW/m2 of heat flux. Hence by this experimentation, it is found that the effect of surface characteristics of the zirconia coated layer on the copper surface enhances the pool boiling heat transfer coefficient at the maximum coating thickness and surface roughness by the considered coating technique.

The preparation and spontaneous imbibition of carbon-based nanofluid for enhanced oil recovery in tight reservoirs

In this work, carbon-based nanofluid was prepared composed of hydrophilic carbon nanoparticles (CNPs) and Tween-80 to enhance oil recovery through spontaneous imbibition in tight reservoirs. The CNPs were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), 1HNMR, interfacial tension and wettability measurements. The particle size of CNPs was <10 nm and CNPs nanofluid showed excellent stability at high temperature and high salinity. CNPs nanofluid exhibited a stronger ability to reduce interfacial tension and change wettability than brine. The 1HNMR imaging showed that CNPs had seeped into the core. The spontaneous imbibition tests showed that the spontaneous imbibition oil recovery of CNPs nanofluid can reach 24%, compared with 11% oil recovery of NaCl solution. CNPs nanofluid can efficiently enhance oil recovery, which was ralated to capillary force and structural disjoining pressure. CNPs nanofluid has great potential for enhancing oil recovery, especially in tight reservoirs.

Preparation and characterisations of magnetic nanofluid of zinc ferrite for hyperthermia

Zinc ferrite (ZnFe2O4) nanoparticles were synthesised by using solution gelation and the self-combustion technique. The resulting zinc ferrite nanoparticles were structurally analysed by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometry for structural, morphological and magnetic properties, respectively. The XRD pattern shows that the prepared sample has a spinel monophasic cubic structure, and the broadening of X-ray peaks indicates the nanocrystalline size of the particles to be on the order of 13 nm. FE-SEM analysis shows spherical-type grains and confirms the nanocrystalline nature with an average grain size of 24 nm. The energy-dispersive X-ray analysis spectrum indicates the purity of the sample and the presence of the desired ions in good proportions. The magnetisation–field strength (M–H) hysteresis loop shows enhanced magnetisation with the superparamagnetic nature of zinc ferrite nanoparticles compared with previous literature reports. The saturation magnetisation value (M s) was estimated to be 23·25 emu/g. The obtained nanoparticles of zinc ferrite were used to prepare nanofluids with water as a base fluid (2 mg/ml concentration). Magnetic hyperthermia studies were carried out using an induction heating system. The induction heating results show that a small amount (2 mg/ml) of zinc ferrite nanoparticles can achieve a 42°C temperature for 258 s at 4·0 kA/m.

Experimental measurements of thermal conductivity of engine oil-based hybrid and mono nanofluids with tungsten oxide (WO3) and MWCNTs inclusions

In this study, an experimental analysis was used to measure the thermal conductivity (knf) of WO3-MWCNTs/Engine Oil hybrid nanofluids, and a new significance was established. The preparation of nanofluid with a two-step method was achieved through the suspension of WO3 nanoparticles and MWCNTs in engine oil using ultrasonic waves. The diameter of the WO3 nanoparticles is in the range of 23 to 65 nm and the diameter of the MWCNTs in the range of 20 to 30 nm. According to the results, the knf grows as the temperature and volume fraction of nanoparticles (φ) go up. Of course, the φ has a more significant influence on the knf, compared to temperature. Also, the maximum amount of knf of hybrid nanofluid was at T = 60 °C and ϕ = 0.6%, which increased by 19.85% compared to the base fluid. At last, two mathematical models for assessing knf were introduced.

Effect of base fluids on thermo‐physical properties of SiO2 nanofluids and development of new correlations

The enhanced thermal properties are the prominent objective behind the usage of nanofluids. Hence, it is necessary to study the base/nanofluid physical properties at various conditions. This article projects the experimental results of thermal conductivity and viscosity of two different nanofluids. The ratio was considered as 60:40 and 40:40 by volume in water and ethylene glycol, respectively. The preparation of nanofluids was started by scattering SiO2 nanoparticles in EG and “water” (W) blended in “60:40” (60EGW) and “40:60” (40EGW) ratio by volume. The regression analysis was conducted with available data, and correlations were formulated for thermal properties. The nanofluids were used in evaluating “viscosity” and “thermal conductivity” experimentally. From the results, the SiO2 particles have achieved an enhancement of 34% and 32% in thermal conductivity with the two base fluids. Similarly, an enhancement of 102% and 62% was reported in viscosity. Hence, it can be observed that SiO2 nanofluids in 40EGW nanofluid are better heat transfer fluids when compared with SiO2 in 60EGW nanofluid.

Experimental investigation on the effectiveness of MHTHS using different metal oxide-based nanofluids

In recent times, the mini heat sink is suggested for cooling the miniature components employed in several engineering applications. In the present work, the thermal performance of the mini hexagonal tube heat sink (MHTHS) was investigated experimentally. Nanofluids and deionized water (DIW) were made to flow through the hexagonal tube side and mini-passage side, respectively. For the preparation of different nanofluids of 0.01 volume fraction, DIW was considered to be a base fluid; Al2O3, CuO, and SiO2 nanoparticles were reckoned to be the supporting materials. Experiments were run under two different conditions in order to ascertain the enhanced thermal performance of the MHTHS. They are as follows: (1) keeping the flow rate of hot DIW constant at 30 L h−1 in the mini-passage side, the flow rates of nanofluids in the hexagonal tube were varied such as 15, 20, 25, 30, 35, 40, 45, and 50 L h−1; (2) keeping the flow rate of nanofluids constant at 30 L h−1 in the hexagonal tube side, the flow rates of hot DIW in the mini-passage side were varied such as 15, 20, 25, 30, 35, 40, 45, and 50 L h−1. From the experimental results, it divulges that the heat transfer coefficient and effectiveness were found to be higher for Al2O3–DIW nanofluid, while comparing other nanofluids. A further improvement in the thermal performance of MHTHS could be achieved at higher volume flow rates of nanofluids in the hexagonal tube side and constant volume flow rate of hot DIW in the mini-passage side.

Nanofluid flow driven by thermal and magnetic forces – Experimental and numerical studies

Since the nineties, when first nanofluid preparation was reported, the nanofluids are attracting more and more attention. It is mainly due to their potential in the heat transport processes. Introduction of nanofluids in a strong magnetic field, as it is done in this studies, has the same aim – heat transfer enhancement. Additional goal of presented research is connected with a deep understanding of a weakly magnetic nanoparticles behaviour in a fluid, influenced by magnetic environment. Due to the nanofluids opaqueness, it is not possible to use the optical experimental methods for investigations of transport phenomena, especially momentum transport and connected with it flow structure. Therefore, the numerical studies were conducted to get an information about the forces and their mutual interaction, influencing transport processes occurring in the system, which was differentially heated and filled with silver nanofluid under operation of the strong magnetic field (up to 10 (T)). The results of numerical analysis were compared with experimental ones related to the heat transfer processes and average value of the Nusselt number. Very good agreement between the results was obtained.

Thermal performance enhancement studies using graphite nanofluid for heat transfer applications

AbstractEnhanced boiling heat transfer using nanofluids is highly relevant due to its potential applications in thermal management of systems producing large heat fluxes. However, the sedimentation of nanoparticles limits their application in heat transfer systems. So, the preparation of a stable nanofluid remains a big research challenge. The stability issues arise due to the large difference in the density of nanoparticle and the base fluid. Graphite nanoparticle is selected in this study, as it has 4.5 times lower density than copper and comparable thermal conductivity. An experimental study is conducted to evaluate the suitability of graphite nanofluid in mesh wick heat pipes, which are devices that utilize boiling and condensation principles to transfer high heat fluxes. Thermal transport properties and boiling heat transfer characteristics showed enhancement and the effect of nanofluid on the device level thermal performance is thoroughly assessed. Experimental results are compared with the published literature. A reduction in thermal resistance by 32.5% and an improvement in the heat transfer coefficient by 48.02% in comparison with base fluid clearly indicate the superiority of the graphite nanofluid for heat transfer applications.

Experimental Analysis of H2O–LiBr Absorption Refrigeration System Using Al2O3 Nanoparticles

The objective of this paper is to study the effect of nanoparticles on Coefficient of Performance (COP) and thermal load of main components (generator, condenser, evaporator and absorber) of absorption refrigeration system using H2O–LiBr. Al2O3 nanoparticles have been added into the H2O–LiBr solution to make the binary nanofluid, and Polyvinyl Alcohol (PVA) has been used as a stabilizer. Experimentation part involves the preparation of nanofluid and tests on H2O–LiBr and H2O–LiBr with 0.05% Al2O3. The effect of nanoparticles on COP and thermal load of components has been studied by varying the operating temperatures (generator, condenser and absorber temperature) and volume fraction of nanoparticles. The results show that COP and thermal loads of system with nanoparticles at different operating temperatures are following the same trend as base fluid system. The COP of system with nanoparticles at each operating temperature is higher than base fluid system. The heat supplied to generator with nanoparticles is less than without nanoparticles while heat rejected in condenser and absorber with nanoparticles is higher than without nanoparticles at each operating temperature. The heat exchanged in evaporator with nanoparticles is also higher than that without nanoparticles at each operating temperature. We also obtained maximum COP with 0.2% volume fraction of nanoparticles.

Investigation of the effects of base fluid type of the nanofluid on heat pipe performance

Most recently, an ascending tendency in nanoparticles containing working fluid utilization has been observed in such thermal systems as double pipe heat exchangers and thermosiphons in so far as its advantages upon the performance of such systems. In order to investigate how the type of the base fluid affects the nanofluid’s properties used for thermal applications, an experimental test rig was setup and two different nanofluid each of which involves different base fluid, but same nanoparticles and surface active agent were tested. During the nanofluid preparation process, bauxite nanoparticles as nanoparticle material and sodium dodecyl benzene sulfonate as surface active agents were used in volume fractions of 2% and 0.5%, respectively. As the base fluid type, ethylene glycol and deionized water were utilized. The tests were conducted under diverse working conditions and vacuum pressure. Distribution of temperature ahead the heat pipe wall, efficiency and heat pipe’s thermal resistance was experimentally investigated. It was observed from the experiments that each nanofluid improved the heat pipe performance significantly; however, deionized water/bauxite nanofluid gave the best results in terms of heat pipe’s thermal performance. For each nanofluid, the maximum increment in efficiency was observed under 200 W heating power and 10 g/s cooling water mass flow rate conditions, and improvement rates were 29.5% and 13.3% for ethylene glycol-based and deionized water-based nanofluids, respectively. At least 20% of decline in thermal resistance of the heat pipe was also recorded, when nanofluid was employed as working fluid.

Improving stability and thermal properties of TiO2-based nanofluids for concentrating solar energy using two methods of preparation

Nanofluids are considered a promising alternative to the classic fluids used in heat transfer processes. One interesting application of nanofluids is their use as a heat transfer fluid in thermosolar plants, such as those using concentrating solar power (CSP) technology. Therefore, this study presents the preparation of nanofluids based on TiO2 nanoparticles and the most common thermal oil used in CSP plants. The nanofluids were prepared using a one-step method by means of the solvothermal synthesis of TiO2 and also using a two-step method by means of ultrasonic waves and stabilizing the nanoparticles using 1-octadecanethiol as a surfactant. The stability of the nanofluids was analysed using UV–Vis spectroscopy, particle size and ζ potential measurements. The formation of TiO2 nanoparticles in the one-step method was detected using X-ray diffraction, Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Thermophysical properties were also measured obtaining an atypical improvement of isobaric specific heat of up to 25.4% for the nanofluids prepared by the two-step method. For the nanofluids prepared by the two-step and one-step methods, thermal conductivity increased by up to 52.7% and 31.4% at higher temperatures, respectively. Finally, enhancements of up to 35.4% of the heat transfer coefficient were estimated, which means these nanofluids are suitable for being used as heat transfer fluids in CSP plants.