Titania Nanofluids Research Articles

Turbulent flow analysis of a flattened tube in- plane curved solar collector using Titanium oxide nanofluid

The present study deals with the experimental investigation on the performance of a solar water heater consisting of a flattened tube absorber with a spiral configuration. The analysis is carried out by using water and Titanium oxide nanofluid of 0.1% concentration as the working fluid adopting forced circulation for various flow rates of 0.05 kg/s, 0.066 kg/s, 0.083 kg/s. The effect of mass flow rate on the flatness of the tube and spiral configuration of the absorber is investigated. The outlet fluid temperature, instantaneous efficiency, Reynolds number, Nusselt number, and heat transfer coefficient, friction factor, and Dean number are the parameters considered in this analysis. The results show that there is a significant increase in heat transfer coefficient of 22% for TiO2 (φ = 0.1) nanofluid compared to water. The results indicate that the instantaneous efficiency increases by 7.5% for TiO2 nanofluid. The highest outlet temperature of 67 °C was obtained for a mass flow rate of 0.066 kg/s. The removal energy parameter FRUL increases by 20% and the absorbed energy parameter FR(τα) increases by 5% for TiO2 nanofluid comparing with water. The values of the Nusselt number, friction factor and dean number obtained experimentally are compared with numerical correlation and the deviation is found to be within ±3% to ±8%. The Dean number is calculated for different curvature ratio of κ1 = 0.141, κ2 = 0.070 and κ3 = 0.047.Increase dean number of 18% with increase in curvature ratio is found.

Analysis of porous filled heat exchangers for electronic cooling

An innovative porous filled heat exchanger is modeled to investigate the cooling effectiveness and temperature distribution at its base subject to a high heat flux. The effects of different nanofluid coolants (5% titanium dioxide (TiO2) in water, 1% alumina in water, 0.03% multi walled carbon nanotubes (MWCNT) in water, and 1% diamond in 40:60 ethylene glycol/water), different porous materials (copper and annealed pyrolytic graphite (APG)), and porosity values are investigated. The coolant enters from an inlet channel normal to the base, moves through the porous medium, and leaves the heat exchanger through two opposite exit channels parallel to the base. The effects of the inclination angle of the foam filled channel, inlet velocity value, and heat flux value are also studied. In addition, the effect of the inlet cross section is investigated by studying two different designs. One of the designs has a rectangular cross sectional inlet channel (extended all along the transverse direction) and the other design has a square one. The results indicate the importance of the utilization of a high conductive porous material. Utilization of APG porous matrix improves the cooling effectiveness at the base of the heat exchanger, for all studied coolants of pure water and water based nanofluids. The results also show that utilizing titanium dioxide nanofluids (TiO2) as coolant for both copper and APG porous matrices at low and high porosity structures, and for both square and rectangular inlet cross sections improves the cooling efficiency and temperature uniformity over the base. Investigation of the effect of inlet channel geometry, i.e., square and rectangular, indicates that employing a square cross section inlet channel would result in lower temperature values along the streamwise direction while higher temperature values are observed far from the center in transverse direction.

Thermal conductivity optimization and entropy generation analysis of titanium dioxide nanofluid in evacuated tube solar collector

Titanium dioxide (TiO2) nanofluid is produced by dispersing a small amount of TiO2 nanoparticles in distilled water. The high thermal conductivity of the TiO2 nanofluid can improve the performance of evacuated tube solar thermal collector (ETSC). The main objectives of this study are to evaluate the thermal efficiency and perform entropy analysis of an ETSC in which TiO2 nanofluid is used as the working fluid. Response surface methodology is used to determine the optimum thermal conductivity of the TiO2 nanofluid. The following factors are varied for the optimization process: (1) volumetric concentration of nanoparticles, (2) amount of surfactant, and (3) sonication time. The optimum factors are as follows: (1) volumetric concentration of TiO2 nanoparticles: 0.50 vol%, (2) surfactant-to-nanoparticle ratio: 1:1, and (3) sonication time: 10.0 min. Excessive amounts of polyvinylpyrrolidone (PVP) surfactant significantly reduce the thermal conductivity of the TiO2 nanofluid. The thermal conductivity of the TiO2 nanofluid increases by 7.28% when it is prepared under optimum conditions. The TiO2 nanofluid with the optimum thermal conductivity is used as the working fluid in the ETSC. It is found that thermal efficiency of the ETSC increases with an increase in the mass flow rate of water and TiO2 nanofluid. The results show that the entropy generation decreases by 1.23% whereas the thermal efficiency increases by 16.5% when the optimum TiO2 nanofluid is used in the ETSC compared with those for distilled water at a mass flow rate of 0.033 kg/s. The heat transfer capability increases by using TiO2 nanofluid with high thermal conductivity as well as high mass flow rate. In conclusion, the performance of the ETSC can be enhanced by using stable nanofluid as the heat transfer fluid because of its high thermal conductivity.

Thermal diffusivity control in titanium dioxide nanofluid through phase tuning

The potential of TiO2 is greatly understood in diversified fields of science and technology. With the advent of nanotechnology, the study of nanofluids has gained significant attention. The physical properties of a fluid can considerably be varied with nanoparticle incorporation. The present work describes methods for controlling the thermal diffusivity of TiO2 nanofluid. The thermal diffusivity of the nanofluid is measured by single beam thermal lens technique. TiO2 nanoparticles synthesized by sol–gel method with different amount of oxalic acid and the sample calcined at different temperatures are analyzed by x-ray diffraction (XRD) technique. The field emission scanning electron microscopic (FESEM) image and XRD analysis confirmed the particle formed to be nano in size. The transformation of phase from anatase to rutile with temperature and the amount of oxalic acid is studied from the XRD pattern. The thermal lens study of the samples reveals that the thermal diffusivity increases with temperature and amount of oxalic acid. The study also suggests the possibility of controlling the thermal diffusivity of TiO2 nanofluid through phase tuning.

Mixed convection of silver and titanium dioxide nanofluids along inclined stretching sheet in presence of MHD with heat generation and suction effect

Mixed convection of silver and titanium dioxide nanofluids along inclined stretching sheet in presence of MHD with heat generation and suction effect

Performance enhancement of a renewable thermal energy collector using metallic oxide nanofluids

A renewable thermal energy collection device was built and metallic oxide nanofluids namely cerium oxide, aluminium oxide and titanium oxide in base fluid water were used. At 3 vol% and a flow of four litres per minute, the renewable energy collector efficiency was computed and compared with the values obtained using water as the working fluid. It was observed that by using Ceria, Alumina and Titania nanofluids, collector efficiencies of 60%, 58% and 56% were achieved respectively. When compared with the values obtained by using water, the efficiency enhancement was 27% for Ceria, 25% for Alumina and 23% for Titania nanofluids.

Pressure drop characteristics and efficiency enhancement by using TiO<sub align="right">2-H<sub align="right">2O nanofluid in a sustainable solar thermal energy collector

Titania nanofluid is procured and six different volumes fractions are prepared and homogenised. The nanofluid is subjected to experimental study in a built sustainable solar thermal energy collector model. Theoretical models for the calculation of pressure drop are used and the values are compared with results obtained using experimental setup. The experimental values obtained are on the higher side. At a volume fraction of 3% of the titania nanofluid, the collector exhibited thermal efficiency of 56% with a pressure drop of 16 mm of water column. This is compared with values using water with 28% thermal efficiency at a pressure drop of 4.5 mm of water column. Finally, a model is developed to predict the pressure drop and thermal efficiency by using TiO2-H2O nanofluid in a solar thermal energy collector.

Pressure drop characteristics and efficiency enhancement by using TiO<sub align="right">2-H<sub align="right">2O nanofluid in a sustainable solar thermal energy collector

Titania nanofluid is procured and six different volumes fractions are prepared and homogenised. The nanofluid is subjected to experimental study in a built sustainable solar thermal energy collector model. Theoretical models for the calculation of pressure drop are used and the values are compared with results obtained using experimental setup. The experimental values obtained are on the higher side. At a volume fraction of 3% of the titania nanofluid, the collector exhibited thermal efficiency of 56% with a pressure drop of 16 mm of water column. This is compared with values using water with 28% thermal efficiency at a pressure drop of 4.5 mm of water column. Finally, a model is developed to predict the pressure drop and thermal efficiency by using TiO2-H2O nanofluid in a solar thermal energy collector.

Performance study of conical strip inserts in tube heat exchanger using water based titanium oxide nanofluid

The objective of the study is to observe the Nusselt number and friction factor behavior in a tube heat exchanger fitted with staggered and non-staggered conical strip inserts using water based titanium oxide nanofluid under laminar flow conditions. Water based titanium oxide nanofluid was prepared using a two-step method with a volume concentration of 0.1% and 0.5%. The tube inserts used were staggered and non-staggered conical strips having three different twist ratios of 2, 3, and 5. The experimental results indicated that the Nusselt number increased in the presence of water based titanium oxide nanofluid compared to the base fluid. Nusselt number further increased enormously with the use of conical strip inserts than a tube with no inserts. It was observed that the strip geometry and the nanofluid had a major effect on the thermal performance of the circular tube heat exchanger. It was found that with the staggered conical strip having a twist ratio of Y = 3 and 0.5% volume concentration of nanofluid provided the highest heat transfer. Correlations have been derived using regression analysis.

Production improvement in gas condensate reservoirs by wettability alteration, using superamphiphobic titanium oxide nanofluid

Many gas condensate reservoirs suffer a loss in productivity owing to accumulation of liquid in near-wellbore region. Wettability alteration of reservoir rock from liquid-wetting to gas-wetting appears to be a promising technique for elimination of the condensate blockage. In this paper, we report use of a superamphiphobic nanofluid containing TiO2 nanoparticles and low surface energy materials as polytetrafluoroethylene and trichloro(1H,1H,2H,2H-perfluorooctyl)silane to change the wettability of the carbonate reservoir rock to ultra gas-wetting. The utilization of nanofluid in the wettability alteration of carbonate rocks to gas-wetting in core scale has not been reported already and is still an ongoing issue. Contact angle measurements was conducted to investigate the wettability of carbonate core plugs in presence of nanofluid. It was found that the novel formulated nanofluid used in this work can remarkably change the wettability of the rock from both strongly water- and oil-wetting to highly gas-wetting condition. The adsorption of nanoparticles on the rock and formation of nano/submicron surface roughness was verified by Scanning Electron Microscope (SEM) and Stylus Profilometer (SP) analyses. Using free imbibition test, we showed that the nanofluid can imbibe interestingly into the core sample, resulting in notable ultimate gas-condensate liquid recovery. Moreover, we studied the effect of nanofluid on relative permeability and recovery performance of gas/water and gas/oil systems for a carbonate core. The result of coreflooding tests demonstrates that the relative permeability of both gas and liquid phase increased significantly as well as the liquid phase recovery enhanced greatly after the wettability alteration to gas-wetting.

An experimental investigation on heat transfer enhancement in the laminar flow of water/TiO2 nanofluid through a tube heat exchanger fitted with modified butterfly inserts

Nanofluids are advanced heat transfer fluids that exhibit thermal properties superior than that of the conventional fluids such as water, oil etc. This paper reports the experimental study on convective heat transfer characteristics of water based titanium dioxide nanofluids in fully developed flow through a uniformly heated pipe heat exchanger fitted with modified butterfly inserts. Nanofluids are prepared by dispersing TiO2 nanoparticles of average particle size 29 nm in deionized water. The heat transfer experiments are performed in laminar regime using nanofluids prepared with 0.1% and 0.3% volume fractions of TiO2 nanoparticles. The thermal performance characteristics of conventional butterfly inserts and modified butterfly inserts are also compared using TiO2 nanofluid. The inserts with different pitches 6 cm, 9 cm and 12 cm are tested to determine the effect of pitch distance of inserts in the heat transfer and friction. The experimental results showed that the modification made in the butterfly inserts were able to produce higher heat transfer than conventional butterfly inserts.

Noise and vibration analysis for automotive radiator cooling fan

This paper aims to analyse the noise and vibration of the automotive radiator specifically focused on its cooling fan for different fan conditions and different coolants used namely Ethylene Glycol (EG) water-based and Titanium Oxide (TiO2) nanofluid. Noise source identification is carried out by utilizing the sound intensity mapping method while an accelerometer is used to measure the vibration results. Both of these experiments are conducted when the fan was both in static and working conditions. The maximum cooling fan speed for the working fan detected by a tachometer for EG water-based is 1990 rpm while TiO2 nanofluid is 2030 rpm. The difference in speed is due to the different physical properties such viscosity of each coolant has where TiO2 nanofluid has lower viscosity than EG water-based. The maximum sound power level produced by EG water-based is 53.73 dB while TiO2 nanofluid is 101.94 dB. Meanwhile, the vibration frequencies of EG water-based are higher than TiO2 nanofluid. The noise level increases with the cooling fan speed but decreases with the vibration frequency. Apart from studying the noise and vibration of the automotive radiator, this research also analysed the potential application using nanofluid due to its great properties according to its major use in the heat transfer enhancement. As a conclusion, nanofluid as a radiator coolant could improve heat transfer rate, and could also reduce the presence of vibration in the automotive cooling system.

Experimental analysis of energy and friction factor for titanium dioxide nanofluid in a water block heat sink

Heat dissipation is a critical issue in modern electronic components, due to the technological advances that have reduced their size and caused their heat flux to rise. Different types of heat sinks are promising for cooling of such electronics and nanofluid can enhance the cooling performances. In this present work, a titanium dioxide (TiO2/water) nanofluid (with a volume fraction of 0.1%) is prepared by dispersing nanoparticles in distilled water. The nanofluid is then passed through the heat sink at various flow rates (1.00, 1.25, and 1.50L/min). The interface temperature of the water block was reduced up to 6.40°C by using the nanofluid, as compared to water. Due to the decline of interface temperature the heat transfer coefficient was improved by 20.82% compared to water. The maximum energy efficiency found 77.56% for nanofluid. Therefore, the titanium dioxide nanofluid is a superior coolant than pure water. Moreover, the heat transfer effectiveness and energy effectiveness were found highest at the minimum flow rate of 1.00L/min.

Experimental investigation on the influence of titanium dioxide nanofluid on emission pattern of biodiesel in a diesel engine

The present study investigates the effect of the TiO2 nanofluid on the formation of hydrocarbon, carbon-monoxide, nitrogen oxide and smoke emission from a neat mustard oil methyl ester fueled diesel engine. TiO2 nano particle with an average size of 50 nm was synthesized by sol-gel route. The synthesized particles are dispersed with mustard oil methyl ester at various concentrations (100 and 200 ppm) by the means of a mechanical homogenizer and an ultrasonicator. Experiments were conducted in a four-stroke, single-cylinder, diesel-engine, fuelled with diesel, neat mustard oil methyl ester and nanofluid incorporated methyl ester. From the obtained results, it can be recognized that methyl ester from mustard oil is potential candidate as an alternative fuel in existing diesel engine. Further, it is also observed that TiO2 nanofluid associated to mustard oil methyl ester reduced various emissions over neat mustard oil methyl ester.

Investigation on Stability and Optical Properties of Titanium Dioxide and Aluminum Oxide Water-Based Nanofluids

Water is regarded as a poor absorber of solar energy. This affects the efficiency of solar thermal systems. The addition of nanoparticles to heat transfer fluids used in solar thermal systems can enhance their optical properties. These new-generation heat transfer fluids are known as nanofluids. The present study investigates the stability and optical properties of three nanofluids, including aluminum oxide (13 nm and <50 nm) and titanium dioxide (21 nm) nanofluids. The stability of the nanofluids was observed through a photo-capturing method and zeta potential measurements. Ultraviolet–visible (UV–Vis) spectrophotometer was used to measure the absorbance and transmittance of the prepared nanofluids. The effect of factors such as type of particle, type of surfactant, and pH of the solution on the optical properties of the nanofluids was also investigated. We found that the titanium dioxide nanofluid had better optical properties but lower stability compared to aluminum oxide nanofluids.

Experimental Assessment of Saturation Behavior of Boiling Nanofluids: Pressure and Temperature

The need to dissipate heat fluxes more than those commonly handled by boiling flows is forcing designers to consider boiling nanofluids flows as cooling option. In modeling boiling flows in cooling applications, the dependency of temperature and pressure is of great importance. In the present study, pressure–temperature variations at saturation conditions are empirically measured for different types of water-based nanofluids with variable volume fractions. Titanium oxide, silver, gold and nickle nanoparticles are studied. Results show that, except for titanium oxide and gold nanofluids, nanoparticles do not influence saturation conditions of the pure water significantly. Two individual correlations are proposed in this study to simulate the saturation pressure–temperature behavior of gold and titanium oxide water-based nanofluids in different volume fractions.

Experimental investigation of thermal properties of cutting fluid using soluble oil-based TiO2 nanofluid

In this study, soluble oil-based titanium dioxide was employed as a drilling fluid to enhance the performance of drilling process in terms of smoothness. The results of drilling process in the presence of titanium dioxide as an additive were compared with the dry condition and once applying pure drilling fluid. Further, forced convective heat transfer coefficient of the soluble oil-based titanium dioxide nanofluid flowing through a horizontal circular tube was also investigated experimentally under constant wall heat flux boundary condition. To this end, soluble oil-based titanium dioxide nanofluids were prepared at the weight concentrations of 0.3, 0.6 and 1%. To have a proper colloidal stability, gum Arabic (GA) was used as a surfactant with 1:1 weight ratio of GA and titanium dioxide. The results showed that the addition of titanium dioxide nanoparticles to the soluble oil decreased significantly the surface roughness of work-piece as well as the drilling temperature as compared to the pure soluble oil and dry condition. Moreover, as the concentration of titanium dioxide increased, the convective heat transfer coefficient increased significantly, and it was further improved by increasing Reynolds number. Note that increasing the concentration of nanoparticle into the base fluid was more effective than that of improving Reynolds number in the range studied herein.

Investigating the collector efficiency of silver nanofluids based direct absorption solar collectors

A one-dimensional transient heat transfer analysis was carried out to analyze the effects of the Nanoparticle (NP) volume fraction, collector height, irradiation time, solar flux, and NP material on the collector efficiency. The numerical results were compared with the experimental results obtained by silver nanofluids to validate the model, and good agreement was obtained. The numerical results show that the collector efficiency increases as the collector height and NP volume fraction increase and then reaches a maximum value. An optimum collector height (∼10mm) and particle concentration (∼0.03%) achieving a collector efficiency of 90% of the maximum efficiency can be obtained under the conditions used in the simulation. However, the collector efficiency decreases as the irradiation time increases owing to the increased heat loss. A high solar flux is desirable to maintain a high efficiency over a wide temperature range, which is beneficial for subsequent energy utilization. The modeling results also show silver and gold nanofluids obtain higher photothermal conversion efficiencies than the titanium dioxide nanofluid because their absorption spectra are similar to the solar radiation spectrum.

Nanofluid Heat Transfer in Laminar Pipe Flow With Twisted Tape

ABSTRACTA comparative study with respect to the scaling of heat transfer of Newtonian titania nanofluid with concentrations of 5.0 vol.% and 10.0 vol.% is undertaken. For that purpose, experiments in circular flow pipe with inserted twisted tape having a pitch to diameter ratio of nearly 6 under constant heat flux are carried out in a Reynolds number range from 300 to 1300. The experimental data are ordered according to three different scaling approaches based on Reynolds number, on Reynolds and Prandtl numbers, and based on Reynolds and Prandtl numbers and nanoparticle concentration. It is found that, despite its relevance with respect to the flow dynamics, the first scaling is not sufficient to capture the heat transfer features properly. While the second approach is already based on the necessary and sufficient similarity numbers, the third approach does not provide deeper insight into the flow physics. It is concluded that description of laminar nanofluid pipe flow with inserted twisted tape based on a combination of Reynolds and Prandtl numbers is sufficient because two-phase flow effects like Brownian and thermophoretic diffusion are of minor importance. This finding is in agreement with most recent experimental results for the entrance region of laminar flow in empty pipes.

Rheological behavior of starch–poly(vinyl alcohol)–TiO2 nanofluids and their main and interactive effects

ABSTRACTIn this study, an investigation of the rheological behavior of starch/poly(vinyl alcohol) (PVA)/titanium oxide (TiO2) nanofluids was performed. It revealed that the rheological behavior of starch suspensions displays a particular change due to the presence of PVA and TiO2. All examined fluids demonstrated non‐Newtonian behavior and followed the Power law model. The main and interacting effects of starch, PVA, and TiO2 nanoparticles concentrations were studied using the analysis of variance. The results indicated that the flow behavior index (n), as well as the consistency index (K) of suspensions, is influenced by the PVA and TiO2 contents. The flow behavior index (n) decreased and consistency index (K) increased by an increase in PVA concentration. A reverse trend is observed by the addition of TiO2 nanoparticles to starch and PVA blend suspensions. The difference in rheological behaviors was ascribed to the presence of binary and triplet interactions between starch, PVA, and TiO2 nanoparticles. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44062.