TiO2 Nanofluids Research Articles

Investigation of the synergistic effect of TiO2 nanofluid and biomaterials derived from three bacteria in various culture media: Implications for enhanced oil recovery

Recently, nanofluids and microorganisms -as environmentally friendly agents- have indicated superb potential in the enhanced oil recovery process. Herein, the interface properties of nanofluid and rock surfaces were surveyed by a synergistic combination of nano and biomaterials. The stability of the synthesized TiO2 nanofluid with the aid of steric and electrostatic methods (at 25 and 80 °C) was studied by sedimentation tests, particle size distribution, and zeta potential analysis. The growth rate of bioproducts from three bacteria (Acinetobacter, Bacillus, and Klebsiella) in different carbon sources was optimized. The high stability of nanofluid was achieved by the use of sodium dodecyl sulfate surfactant and pH = 8 for 30-day at temperatures of 25 °C and 80 °C as the base fluid. The optimal growth media for bacteria is a 3-day incubation at 37 °C in a shaking incubator with whey as the carbon source. Finally, the simultaneous use of nano (0.005 wt%) and biomaterials (0.01 wt%) showed the highest wettability alteration, transforming it from strongly oil-wet to water-wet at an optimal concentration of materials. Overall, the findings of this study can help to reduce environmental concerns and operating expenses.

Experimental studies of different operating parameters on the photovoltaic thermal system using a flattened geometrical structure.

The efficiency of the photovoltaic (PV) cell reduces with an increase in solar irradiation. The reduction in the efficiency of the photovoltaic (PV) cell can be attributed to the increase in cell temperature. A novel design of a thermal absorber fabricated by a flat spiral tube is used to remove heat and decrease the cell temperature, thus forming the photovoltaic thermal system (PVTS). Water and titanium oxide (TiO2) nanofluid (NF) with a concentration ratio of 0.1% are used as the working fluid in the PVTS. The study has been carried out for the mass flow rates (mf) of 0.05, 0.066, and 0.083kg/s. The reduction in the cell temperature is obtained to be 5.7 and 11.2°C due to the cooling effect of water and TiO2 NF, respectively. The percentage increase in electrical efficiency is 2.93 and 5.28% by cooling using water and TiO2 NF, respectively. The hourly variation of the performance of the PVTS shows that TiO2 NF at 0.083kg/s shows the highest photovoltaic thermal efficiency of 69.2% and thermal and electrical efficiency of 56.45 and 12.75%, respectively. The best coefficient of energy for TiO2 NF is 1.27 for a mf of 0.083kg/s.

Friction reduction of Al2O3, SiO2, and TiO2 nanoparticles added to non-Newtonian water based mud in a rotating medium

In drilling industry, energy consumption counts from 20 to 40 percent of total costs. Enhanced water-based mud (WBM) drilling fluids with nanoparticles can save energy in drilling processes. An in-house Taylor-Couette flow system (TCS) was developed at Australian University (AU) to study WBM enhanced by Al2O3, SiO2, and TiO2 nanoparticles. The TCS is really a practical tool to help well drillers with a rough idea of viscosity when nanoparticles are added. The TCS for sure cannot substitute advanced rheometry. The goal of the present experiment is to produce a rough estimate in field operation. Experimental results were examined with several rheology models in our previous publications. In the present work, the enhanced WBM of Al2O3, SiO2, and TiO2 nanofluids are compared with each other at very low volume fractions of 0.05%, 0.1%, 0.5% and 1% and at TCS rotational speeds of 200–1600 RPM. Results in form of consistency charts for shear stress and apparent viscosity are presented here. It is observed that both shear stress and apparent viscosity were reduced for all the nanofluids. Also results for Darcy friction factor were evaluated. It is observed that TiO2 nanofluid friction factor was significantly reduced by 42–76% at the volume fraction of 0.05%; Al2O3 by 36–50% at 0.1%; TiO2 by 40–53% at 0.5%; and Al2O3 by 23–50% at 1.0%; respectively. SiO2 nanofluid friction factor was lightly reduced by 30–45%. Enhancement of WBM with nanoparticles were significant at lower volume fractions and at lower TCS speeds.

Experimental study on synergistic enhancement of thermal performance of a closed two-phase thermosyphon by a TiO2 nanofluid doped with Al2O3

The heat transfer performance of two-phase closed thermosyphon solar collectors (TPCTs) can be improved by adding nanoparticles to the conventional working fluid, but it is necessary to ensure good rheological properties while improving the heat transfer performance. Therefore, spherical (TiO2) nanoparticles with good rheological properties and rod-shaped (Al2O3) nanoparticles with high thermal conductivity were mixed and applied to the TPCT. First, the effects of individual factors such as the concentration of nanoparticles and the operating parameters on the thermal performance of the TPCT were investigated and a regression analysis was performed. Then, the joint effect of inclination angle and filling ratio on the thermal performance of TPCT was further investigated by orthogonal experiment. The results show that doping TiO2 with Al2O3 can further improve the thermal performance of TPCT. For the volume concentration of 0.6% of nanoparticles, filling ratio of 50% and inclination angle of 80°, the best heat transfer performance of TPCT was achieved. Compared with the deionized water (DW), the thermal resistance of the single (TiO2–H2O) and hybrid (Al2O3+TiO2–H2O) nanofluid TPCT is reduced by 10.7% and 13.4%, the thermal efficiency is increased by 11.0% and 13.7%, and the equivalent heat transfer coefficient is increased by 16.2% and 18.7%, respectively.

Effect of Nanoparticle Size and Concentration on Pool Boiling Heat Transfer with TiO2 Nanofluids on Laser-Textured Copper Surfaces.

The enhancement of boiling heat transfer has been extensively shown to be achievable through surface texturing or fluid property modification, yet few studies have investigated the possibility of coupling both enhancement approaches. The present work focuses on exploring the possibility of concomitant enhancement of pool boiling heat transfer by using TiO2-water nanofluid in combination with laser-textured copper surfaces. Two mass concentrations of 0.001 wt.% and 0.1 wt.% are used, along with two nanoparticle sizes of 4–8 nm and 490 nm. Nanofluids are prepared using sonification and degassed distilled water, while the boiling experiments are performed at atmospheric pressure. The results demonstrate that the heat transfer coefficient (HTC) using nanofluids is deteriorated compared to using pure water on the reference and laser-textured surface. However, the critical heat flux (CHF) is significantly improved at 0.1 wt.% nanoparticle concentration. The buildup of a highly wettable TiO2 layer on the surface is identified as the main reason for the observed performance. Multiple subsequent boiling experiments using nanofluids on the same surface exhibited a notable shift in boiling curves and their instability at higher concentrations, which is attributable to growth of the nanoparticle layer on the surface. Overall, the combination of nanofluids boiling on a laser-textured surface proved to enhance the CHF after prolonged exposure to highly concentrated nanofluid, while the HTC was universally and significantly decreased in all cases.

A novel solar PV/T driven photocatalytic multifunctional system: Concept proposal and performance investigation

This article proposes a novel PV/T driven liquid-photocatalytic-purification multifunctional system that combines photocatalytic purification technology with PV/T technology. The experiments on the effects of concentration and depth of TiO2 nanofluids layer, and air bubble rate on the electrical, dissolving and photocatalytic oxidation of formaldehyde performance were conducted. Then the energy analysis on the proposed system in a typical day was investigated. The following results are obtained. (1) Both the concentration and depth of TiO2 nanofluids layer have very significant effect on the electrical performance. A certain amount of TiO2 nanoparticles in TiO2 nanofluids could improve the formaldehyde solubility in water. (2) The photocatalytic oxidation rate increases with the formaldehyde concentration of 0.01–0.15 mg/L (3) The photocatalytic process could be divided into three stages: accumulation area, rapid reaction area and complete reaction area. While the air bubbling can merge the accumulation area and rapid reaction area, and thus enhances the photocatalytic process. (4) In a typical day, the proposed system has the reduction of 22.9% and 17.0% in thermal efficiency and electrical efficiency compared with conventional PV/T water system, while it has an additional efficient sterilization time of 2.5 h.

Convective flow of a Williamson hybrid nanofluid in a porous medium through a cone and wedge with the effect of the shape of nanoparticles

AbstractThe performance of nanofluid in the heat transport phenomena showed satisfactory results, which have been considered by scientists and researchers. The dispersion of two nanoparticles to form a mixture which named as hybrid nanofluid. It has been proved experimentally that hybrid nanofluid has good thermal performance compared to unitary nanofluid. The present study inspected the convective flow of a Williamson hybrid nanofluid through a cone and wedge in a porous medium of different shapes of nanoparticles (cylindrical‐, spherical‐, blades‐, platelets‐, bricks‐) under the influence of a magnetic field. The partial differential equations were converted to an ordinary differential equation and the resulting equations were solved using the bvp4c MATLAB code. The effect of some important physical parameters on both the velocity and temperature profile was graphically plotted and the effect of the shape and size of nanoparticles was discussed, the numerical values of the friction coefficient and Nusselt number were obtained. As observed, the friction factor of Ag–TiO2–H2O hybrid nanofluid was more than that of TiO2–H2O nanofluid. A significant enhancement in bulk temperature is seen for the Ag–TiO2 hybrid and nanofluid formed by blade‐shaped nanoparticles followed by cylindrical, platelet, brick, and spherical nanoparticles. In addition, for a 5% volume fraction of using blade nanoparticles shape givean increase in skin friction factor about 4.8% compared tobrick hybrid nanoparticles. A comparative study of different forms for Ag‐TiO2was presented graphically.

Enhancing the Thermal Performance of Radiators using Nanofluids- A CFD Approach

In the present study, the thermal performance of a simple car radiator has been investigated for different conditions such as coolant type and coolant inlet velocity. Different types of nanofluids have been used as coolants such as Al2O3, CuO, and TiO2 nanofluids. The base fluids taken are water and 50-50 volume percentage of water and ethylene glycol (EG) mixture. The volume percentage of 1%, 2%, and 3% of nanoparticles has been used for all the cases. The lowest outlet temperature and highest heat transfer rate are found for Water-EG based nanofluids. The lowest coolant outlet temperature (355.91 K) is found for 3 vol% of Water-EG based TiO2 nanofluid and the highest heat transfer rate (67.87 W) is found for 3 vol% of Water-EG based CuO nanofluid. The highest outlet temperature and the lowest heat transfer rate are found to be 358.50 K and 51.73 W respectively for water-based CuO nanofluid. Nonetheless, the Water-EG based nanofluids showed better results than water-based nanofluids showing a low coolant outlet temperature and a high heat transfer rate.

Evaluation of three methods of static contact angle measurements for TiO2 nanofluid droplets during evaporation

This article discusses the evaluation of three methods of static contact angle measurements of de-ionized (DI) water and TiO2 nanofluid droplets with three concentrations (0.5%, 1%, and 5%) that evaporate on the substrate of three different temperatures. To compare the discussed approximation methods, the differences between the results of the mean contact angles were identified; the highest standard deviation was recorded for the Young–Laplace and circle methods, such as for the nanofluid TiO2–DI with 1% at 50 °C, it is 3.21°, while the lowest value was obtained for TiO2–DI with 5% at Tenv, SD = 0.04°, by comparing the contact angle results using the ellipse and circle methods. Research shows that circular shape approximation is not to be excluded for contact angle determination in the angular range of 0°–75°.

Energetic and Exergetic performances of a parabolic solar trough collector working with TiO2 & Al2O3 nanofluids for variable temperature applications

ABSTRACT Thermal efficiency of parabolic solar trough collectors (PTCs) can be enhanced by dispersing TiO2 nanoparticles into the conventionally used heat transfer fluids. In the present experimental work, a one-dimensional mathematical model is designed to study the outcome of TiO2 nanoparticles dispersed in the base fluid for variable temperatures PTCs. The major finding of this work is that the TiO2 nanofluid enhances the thermal efficiency of the PTC slightly. Elevated working temperatures are most appropriate for nanofluids using to generate highest gain of energy discharged. It is found that the Exergetic effectiveness enhancement is most important than energetic effectiveness. The maximum exergy efficiency is achieved by TiO2 based nanofluid and is about 8.09%. The highest relative gain of thermal energy discharged is found to be 9.66% higher than the water-based collector by using 0.3% of TiO2 in the base fluid.

Experimental Investigation of Mass Transfer Intensification for CO2 Capture by Environment-Friendly Water Based Nanofluid Solvents in a Rotating Packed Bed

In this research, two intensification approaches for CO2 capture via a rotating packed bed (RPB) and nanofluids were examined simultaneously to maximize the experimental mass transfer coefficient. The two intensification approaches were done by using water as a green, environmentally friendly absorption solvent and as the base fluid for preparing nanofluids and also by using centrifugal acceleration in an RPB. Physicosorption of CO2 in an RPB was carried out by applying Al2O3, TiO2, and SiO2 nanofluids to intensify the mass transfer in water, and the operation parameters such as the angular speed of the rotor, concentration and type of nanoparticles, gas and liquid flow rates, and CO2 concentration in mass transfer intensification were evaluated and several nanofluids were selected to survey investigate how they affect the mass transfer at low pressure. The results show that the Al2O3 nanofluid was more effective than other nanofluids and that the 40 nm nanofluid of this type was more efficient than the 20 nm size. Therefore, a correlation is proposed in this paper for liquid volumetric mass transfer coefficient prediction that includes the microconvection of nanoparticles and surface tension.

Bisurfactant‐functionalized TiO2 nanoparticles as additives of the lubricating oil

AbstractIn this work, TiO2 nanoparticles modified with octadecylamine and dodecyl mercaptan (DDM/ODA@PDA@TiO2 NPs) are uesd to improve the tribological properties of the white oil. The DDM/ODA@PDA@TiO2 NPs which are simply prepared by mussel inspired chemistry and the Michael addition reaction can be facilely dispersed in the white base oil. Tribological measurements showed that the dispersion of the white oil containing 3 wt% DDM/ODA@PDA@TiO2 NPs displays significant reductions in the friction coefficient and wear scar diameter at room temperature and 75°C. Further XPS investigation shows that the favourable tribological properties of DDM/ODA@PDA@TiO2 NPs are ascribed to the synergistic effect of tribofilm (Fe2O3, Fe3O4, FeS2, FeS and FeSO4) and TiO2 nanofluids.

Experimental investigation of erosion due to nanofluids

The demand for efficient and sustainable energy is continuously increasing. Among the many technologies with great potential within this field are nanofluids. Nevertheless, there is still a considerable lack of information regarding their erosive effects on systems materials. In this research, the tribological behaviour of aqueous 1.33 wt% TiO2 nanofluid was investigated when jet-impinged with an average velocity of 0.8 m/s at flat targets of various materials (plastic, copper, rubber). The target surfaces were analysed using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and X-ray diffraction (XRD). It was found that impinging TiO2 nanofluid caused erosion of 282 g/( yr.mm2) for copper and 212 g/( yr.mm2) for plastic. In addition, a deposition of nanoparticles was found for rubber at rate of 2.7 kg/(yr.mm2).

Surveying the hybrid of radiation and magnetic parameters on Maxwell liquid with TiO2 nanotube influence of different blades

AbstractIn this paper, the impacts of Maxwell nanoliquid transmission, rectangular with titanium oxide nanoparticles are explored over the triangular, chamfer blades. The innovation of this paper is the use of the number of chamfers, rectangular, and triangular blades at the top and bottom of a stretched plate to study physical nanofluid parameters such as temperature and the effects of magnetism. Also, by determining the appropriate height and length for the blades, we achieve the best optimization of temperature and velocity of nanofluid between the plate and the blades, which improves heat transfer and with a more and better effect of magnetic effects. The finite element method is utilized for the calculated differential equations. In this paper, by utilizing the reaction surface strategy, we optimized the titanium oxide nanofluid velocity and temperature, and magnetic parameter passing from the extending sheet. On average, the titanium oxide nanoparticle velocity around the two rectangular blades at the beginning of the sheet is 73.09% higher than triangular blades and 66.98% higher than chamfer blades. Based on the outcomes got from the titanium oxide nanofluid speed charts and the warm exchange cantors and magnetic impacts within the Design‐Expert computer program, the most excellent optimization occurred for TiO2 nanofluid speed and TiO2 nanofluid temperature and TiO2 magnetic parameter with u = 0.523, T = 3.25, and H = 2.671.

Manufacturing a TiO2-Based Semiconductor Film with Nanofluid Pool Boiling and Sintering Processes toward Solar-Cell Applications.

For the first time, nanofluid boiling was applied as a process for the creation of a semiconductor TiO2 nanoparticle film that can be deposited onto a conductive substrate (F-doped SnO2 glass: FTO). A steel-base device designed for pool boiling was used to deposit a TiO2-based nanofluid consisting of nanoparticles with an average size of about 20 nm. The boiling of the nanofluid directly on the FTO glass substrate allowed for the deposition of the nanoparticles onto the FTO surface. In principle, the surface responsible for transferring heat to the fluid can be covered with these nanoparticles when the nanofluid boils. Using the as-deposited films, crystal growth of the TiO2 nanoparticle was controlled by varying the strategies of the post-sintering profile. The maximum temperatures, periods, and ramping rates for the obtained samples were systematically changed. Scanning electron microscopy (SEM) revealed that a densely packed TiO2-nanoparticle layer was obtained for the as-deposited substrate via pool boiling. For the maximum temperature at 550 °C, the TiO2 grain sizes became larger (~50 nm) and more round-shaped TiO2 nanostructures were identified. Notably, we have demonstrated for the first time how the sintering of TiO2 nanoparticles proceeds for the nanoporous TiO2 films using high-resolution transmission electron microscopy (TEM) measurements. We found that the TiO2 nanoparticles fused with each other and crystal growth occurred through neighboring 2–4 nanoparticles for the 550 °C sample, which was proved by the TEM analysis that continuous lattice fringes corresponding to the (101) anatase phase were clearly observed through the entire area of some nanoparticles aligned horizontally. In addition, the loss of the TiO2 nanofluid (precursor solution) was completely avoided in our TiO2 deposition. Unlike the commonly used spin-coating method, nanofluid pool boiling would provide an alternative cost-effective approach to manufacture semiconductor layers for various applications, such as solar cells.

Heat Transfer Characteristics of Metallic Body during Quenching in Saturated Nanofluids

Heat transfer characteristics (HTCs) of a metallic rod during quenching were investigated in saturated water-based nanofluids and the results were compared to distilled water. In this study, a 50 mm length of cylindrical copper rod with a diameter of 15 mm was rapidly quenched at an initial temperature of 600 ℃ in saturated water-based nanofluids under atmospheric pressure. Three different types of nanoparticles (Al2O3, SiO2 and TiO2) were used to obtain water-based nanofluids with 0.001% particle volume fraction. In this experiment, heat transfer rates were evaluated using the cooling curves (temperature vs time) of the copper rod quenched in different quenching media. Results showed that the quenching heat transfer in nanofluids was stochastic during the first quenching, with SiO2 showing a deterioration in HTC, enhancement was observed in Al2O3 and TiO2 compared to distilled water in the present work. However, after successive quenching, from second to seventh, all nanofluids demonstrated enhancement in the cooling time, with quenching in TiO2 nanofluid showing the most significant enhancement compared to distilled water. Some deposition of nanoparticles on the surface of the rod was noticed, due to oxidation in distilled water quench, and mixed oxidation and nanoparticles deposition in the nanofluid quench. The present work suggested oxidation lead to deterioration of HTC, but a mixed effect of oxidation and nanoparticles deposition during the quenching process, altered the surface roughness of the rod surface and improved wettability. Hence, it was possible that the effect of surface structure vapour during film boiling influenced the dynamics of the bubbles in nucleate boiling and therefore enhanced the rapid cooling of the rod.

Flexible MXene-based Janus porous fibrous membranes for sustainable solar-driven desalination and emulsions separation

Sustainable solar energy driven seawater desalination technology is currently deemed as a promising pathway to overcome the shortage of freshwater resources, but solar water evaporation material suffers from serious salt-fouling, low freshwater yield, and poor long-term performance in seawater. Herein, a Janus photothermal porous fibrous membrane, composed of hydrophobic MXene/Poly(dimethylsiloxane) coatings and a hydrophilic polylactic acid/TiO2 nanofluids porous fibrous membrane, was prepared. During the solar-driven seawater desalination process, the hydrophilic fibrous membrane, functioned as salt-rejection barrier, induced by TiO2 nanofluids and transport seawater to the surface through its microporous channels; the MXene/PDMS coatings acted as a photothermal layer and generated localized heat at the water-vapor interface upon light irradiation. The solar-thermal test results show that, the Janus porous fibrous membrane displays stable solar-thermal conversion efficiency of 60%, freshwater yield of 1 kg m-2 h-1 and low ion concentration (≤1 ppm) under 1 sun irradiation in direct contact mode, which is superior to other literatures reported. With synergistic effect of TiO2 nanofluids and MXene, the Janus fibrous membrane exhibits a high salt rejection rate of 99.95%, and antibacterial activity as high as of 100%. Notably, benefiting from opposite wettability of Janus porous fibrous membrane, the as-prepared membranes also display excellent separation flux and high separation accuracy (>99.95%) in various surfactant-stabilized oil/water emulsions. It is anticipated that this versatility of Janus porous fibrous membrane has excellent photothermal conversion capability and separation properties, making it have great application potential in using sustainable solar energy to collect freshwater from seawater, medical service wastewater and other application in environmental protection.

Thermal behavior estimation of a solar wall operated by TiO2 nanofluids using several machine learning models

Thermal behavior estimation of a solar wall operated by TiO2 nanofluids using several machine learning models

Microchannel flow and heat transfer enhancement via ribs arrangements

Enhanced heat transfer rates in microchannel flow remain challenging in terms of channel design, proper selection of carrier fluid, and setting the appropriate flow conditions. Introducing extended surfaces, such as ribs, in microchannel design, and the use of nanofluids enable to enhance the thermal performance of the flow system. In the present study, heat transfer characteristics in a microchannel flow incorporating the ribs arrangements on the channel wall are considered and the influence of the ribs location and carrier fluid on the thermal performance of the channel is examined. Temperature and velocity variations in the channel are predicted numerically and the findings of the Nusselt number are compared with that obtained from the experiments. The location of ribs along the channel wall is altered and the resulting variation of the Nusselt number and pressure drop along the microchannel is assessed. Al2O3 and TiO2 nanofluids are incorporated as a working fluid and water are also considered for the comparison. Temperature parameters are introduced to scale the rise of the maximum fluid temperature and temperature difference across the channel length. It is found that locating the ribs in the close region of the channel exit improves the Nusselt number by 25% and increases the pressure drop along the microchannel by 10% as compared to those corresponding to no-ribs arrangements. In addition, nanofluids improve the heat transfer rates and slightly alter the pressure drop across the microchannel.

Heat transfer enhancement for nanofluid flows over a microscale backward-facing step

In this paper, we provide a numerical study of laminar flow in a micro-sized backward-facing step channel for water-based nanofluids containing Al2O3 and TiO2 nanoparticles and investigate the impact of the temperature differences between the inlet and the downward wall temperatures. The present work is the first study to introduce a temperature-dependent separation flow model. The velocity increases with increasing concentration of nanoparticles. However, when comparing Al2O3 and TiO2 nanofluids, Al2O3 has a velocity and shear stress higher than TiO2 for 0.04 volume fraction. Increasing the volume fraction of nanofluid led to an increase in the rate of heat transfer from the wall to the fluid, as the thermal properties improved as the volume ratio increased. The performance efficiency index (PEI) decreases as the volume fraction of the particle increases after a certain amount of nanoparticles. The simulation results of the nanofluid separation flow in the recirculation and reattachment shows that the velocity increases as the temperature difference increases, the size of the primary and secondary recirculation regions behind the step is significantly influenced with the temperature difference, a larger temperature difference means a larger recirculation zone.