Oil Nanofluid Research Articles

Microstructure and Mechanical Properties of CK35 Steel by Using Nano Fluid (Water/TiO2) and Oil (SAE 10W40/TiO2) as Quenching Media

Four different quenching media (water, oil(SAE 10W40), Water/TiO2 nanofluid and oil(SAE 10W40/TiO2) nanofluid were used to compare the influence of quenching media on the mechanical properties and microstructure of CK35 steel. The results have proved that the microstructure for nanofluid (water base) quenching and tempering sample is the combination of tempered martensite and retained austenite with best mechanical properties and for water quenching and tempering specimen is mostly tempered martensite. While for Nanofluid (oil base) quenching and tempering specimen the microstructure is the heterogeneous mixture of ferrite and perlite with formation of Fe3C during the quenching, while for oil quenching and tempering specimen is an equi-axed arrangement of ferrite grains with grainy spheroidized spots of cementite at the ferrite grains and along the grain boundaries.

Experimental study of carbon nano tube/oil nanofluid in dish concentrator using a cylindrical cavity receiver: Outdoor tests

The application of nanofluids is accounted as an effective way for improving the thermal performance of solar systems. In the current study, MWCNT/thermal oil nanofluid was experimentally tested as a solar heat transfer fluid. A dish collector, using a wounded cylindrical cavity receiver, was considered as the solar system. The main aim of this work was the experimental investigation of the cylindrical cavity’s performance, using MWCNT/thermal oil nanofluid. Two experimental models were suggested for the prediction of the cavity’s thermal efficiency, by considering MWCNT/thermal oil nanofluid and pure thermal oil in the steady-state period. It was indicated that the heat loss coefficient of the cylindrical cavity receiver decreased by the application of nanofluid. The results revealed the average thermal efficiencies of 63.9% and 56.44% for MWCNT/thermal oil nanofluid and pure thermal oil, respectively. The thermal efficiency was changed form 60.04% to 64.76%, by using the nanofluid, in the steady-state period. Also, it was observed that the thermal performance of the cavity receiver was improved by 13.12%, by using MWCNT/thermal oil nanofluid. Based on the obtained results, the application of MWCNT/oil nanofluid is recommended in the solar dish concentrators with cavity receiver.

Comparative thermal performance analysis of water, engine coolant oil and MWCNT-W nanofluid in a radiator

Comparative thermal performance analysis of water, engine coolant oil and MWCNT-W nanofluid in a radiator

Morphology and thermophysical properties of non-aqueous titania nanofluids

This work deals with the experimental investigation on thermophysical properties of TiO2-nanofluids and characterization of morphology and structure of TiO2 nanoparticles. Non-aqueous liquids like silicone oil and ethylene glycol are used as base fluids to prepare the nanofluids. Thermophysical properties including viscosity and thermal conductivity of these nanofluids are measured at different concentrations and temperatures. Results showed that silicone oil-based TiO2 nanofluid is Newtonian and the viscosity of this nanofluid increases with the loading of nanoparticles but it decreases nonlinearly with increasing temperature. Existing viscosity models are found unable to predict the viscosity of nanofluids. Although the effective thermal conductivities of both the silicone oil and ethylene glycol-based nanofluids increased with the TiO2 concentration, their enhanced thermal conductivity was found to decrease with increasing temperature.

Investigation on enhancing breakdown voltages of transformer oil nanofluids using multi‐nanoparticles technique

This study presents particularly an innovative technique to enhance charging dynamics in transformer's oil using multi-nanoparticles (NPs). A charging dynamic process in power transformer oils is the main way to slow down the streamer propagation and upping dielectric strength. In addition, transformer oil's based suspension multi-NPs (dielectric, conductive, and semi-conductive) have substantial levels of deposited electrons higher than suspension traditional nanofluids. An experimental work has been done to verify the importance of using multi-NPs for slowing down positive streamer propagation in transformer oils against using individual NP techniques or traditional transformer oils.

Breakdown strength of transformer oil filled with carbon nanotubes under various gap distances

A new class of colloidal insulating transformer oil is formulated by dispersing CNT nanomaterials with mineral oil in purpose to enhance the breakdown strength performance of existing transformer oil. This paper represents the experimental studied dealing with the influence of CNT nanomaterials mix with transformer mineral oil in term of AC breakdown voltage at various gap distances. The concentrations of CNT nanomaterials were measured in range 0.01g/L to 0.2g/L. The impact of three gap distances (1.5mm, 2.5mm and 3.5mm) for mushroom-mushroom electrode configuration is studied in order to observe and compare the trend between conventional mineral oil and CNT nanofluids. To employ CNTs as effective reinforcement in mineral oil, proper dispersion methods need to be applied.

A new turbine model for enhancing convective heat transfer in the presence of low volume concentration of Ag-Oil Nanofluids

This study aims to experimentally investigate and introduce a new model for enhancing convective heat transfer in the presence of Ag/ oil nanofluid. An annular tube was designed with a turbine element attached to the inner tube. The inner tube was a bearing shaft which could rotate with the rotation of turbine element. As the previous works by authors, the setup was conducted with a fully developed laminar flow regime with the Reynolds numbers less than 160. The outer surface of the annular tube was heated by an element with constant heat flux of 204 W. Ag/ oil nanofluid was used in different volume concentrations of 0.011%, 0.044% and 0.171%. The new model could enhance the convective heat transfer coefficient up to 54% (compared to the simple annular tube in the case of base fluid) for the best studied case (nanofluid with the volume concentration of 0.171%) while the friction factor remained low. The new model can be applied for related applications regarding Ag/ oil nanofluid as a new step in enhancing the convective heat transfer coefficient.

Mitigating the impact of aging byproducts in transformer oil using TiO<inf>2</inf> nanofillers

After several operating years of power transformers, the oil is aged resulting in deterioration in oil properties. This deterioration is attributed to the effect of aging byproducts represented by acidity and moisture content. From this view point, this study aims to mitigate the impact of aging byproducts and enhance the aged oil properties with the aid of nanofillers to be reused in the transformer. To simulate actual operating period of the transformer, accelerated aging test is carried out in the laboratory. This test mainly depends on heating the oil in an oven at 120 °C for different number of days. Through these conditions, one day in the oven is considered to simulate one year in the field. Aged oil-based nanofluids are obtained through direct mixing and dispersion of nanoparticles with the aged oil. Titanium oxide is selected as the filled nanoparticles through this study. After the preparation, the samples of aged oil and aged oil-based nanofluids are tested. Different concentrations of nanoparticles are considered. The breakdown voltage (BDV) for the prepared nanofluids is measured and compared to that of pure aged oil. Also, dielectric constant, dielectric dissipation factor (DDF) and conductivity have been measured. Nanofluids exhibited significant enhancement regarding BDV. Also, DDF and conductivity enhanced to some extent. With the aid of acidity, moisture content and particle size measurements, the physical mechanisms behind the obtained enhancement have been discussed considering the effect of aging, the role of nanofiller and the effect of weight fraction. It is found that nanoparticles alleviate the effect of moisture through adsorbing moisture species and forming hydroxyl groups around the surface of nanoparticles.

Investigation of rheological behavior of hybrid oil based nanolubricant-coolant applied in car engines and cooling equipments

In this study the rheological behavior of MWCNT-MgO (10–90%) hybrid nanofluids in the base fluid, SAE40 engine oil, investigated experimentally. For this purpose, the nanofluid has been prepared by two-step procedure and viscosity data is measured by viscometer Cap 2000+. The plotted graphs of viscosity versus shear rate and curve fitting of shear stress – shear rate curve show that nanofluid has non-Newtonian behavior and an increase in temperature increasing this behavior. However, the base fluid has Newtonian behavior completely. A comparative study of nanofluid of this study and other nanofluids with the same base fluid shows very different values for viscosity of nanofluids. This applied comparison shows that nanofluids with very different features can be produced using a base fluid. Which can be applied in different areas of lubrication and heat transfer. Comparison of experimental data with proposed theoretical models shows the difference between predicted results and measured values. So at the end of the study, a relation is proposed to estimate the values of viscosity of oil nanofluids.

Al/ oil nanofluids inside annular tube: an experimental study on convective heat transfer and pressure drop

In this work, an experimental study on nanofluid preparation stability, thermo-physical properties, heat transfer performance and friction factor of Al/ Oil nanofluids has been carried out. Electrical Explosion Wire (E.E.W) which is one of the most reliable one-step techniques for nanofluids preparation has been used. An annular tube has been considered as the test section in which the outer tube was subject to a uniform heat flux boundary condition of about 204 W. The utilized nanofluids were prepared in three different volume concentrations of 0.011%, 0.044% and 0.171%. A wide range of parameters such as Reynolds number Prandtl number, viscosity, thermal conductivity, density, specific heat, convective heat transfer coefficient, Nusselt number and the friction factor have been studied. The experiment was conducted in relatively low Reynolds numbers of less than 160 and within a hydrodynamically fully-developed regime. According to the results, thermal conductivity, density and viscosity increased depending on the volume concentrations and working temperatures while the specific heat declined. More importantly, it was observed that convective heat transfer coefficient and Nusselt number enhanced by 28.6% and 16.4%, respectively, for the highest volume concentration. Finally, the friction factor (which plays an important role in the pumping power) was found to be increased around 18% in the volume fraction of 0.171%.

Mixed convection heat transfer and pressure drop characteristics of the copper oxide-heat transfer oil (CuO-HTO) nanofluid in vertical tube

In this paper, the mixed natural-forced convection is experimentally investigated for the heat transfer oil-copper oxide (HTO-CuO) nanofluid flow upward in a vertical tube. The flow regime is laminar and the temperature of the tube surface is constant. The effect of the nanoparticles concentration on the heat transfer rate and the pressure drop is studied as Richardson number varies between 0.1 and 0.7. It is observed that the mixed convection heat transfer rate increases with both the nanoparticles concentration and Richardson number. New correlations are proposed to predict the Nusselt number of the nanofluid flow with the reasonable accuracy. As the heat transfer enhancement methods usually accompany with increment in the pressure drop, the figure of merit is evaluated experimentally. As such the maximum figure of merit of 1.31 is achieved using the 1.5% concentration of the nanoparticles in Richardson number of 0.7. This study provides a platform to design next generation of low flow rate nanofluid-based heat exchangers and may improve the accuracy of predicting the mixed convection characteristics of nanofluid flows.

Effect of carbon nanotube concentration on cooling behaviors of oil-based nanofluids during the immersion quenching

Oil-based nanofluids including 0.75%—1.75% (mass fraction) carbon nanotubes (CNTs) without any surfactants have been synthesized by a two-step process. The probes machined from 45# steel with 22mm diameter and 50mm length are quenched in the as-synthesized CNT nanofluids for testing the cooling behaviors of the nanofluids. The laser diffraction particle size analyzer, scanning electronic microscope (SEM), X-ray diffractometer and transmission electron microscope (TEM) are used to characterize the quality and distribution of CNTs in the nanofluids. The wettability and viscosity of 30# oil and oil-based CNT nanofluids are measured by a goniometer at 15 ◦C and a rotational type viscometer at 40 ◦C, respectively. The results show that the cooling efficiency of the oil-based CNT nanofluids is better than that of 30# oil. Moreover, the cooling rate of the naonofluids increases with the further increase of the CNT concentration. When the mass fraction of CNTs increases to 1.75%, the cooling rate of the naonofluids reaches a maximum at 760 ◦C and it is increased by 77.8% as compared to that of base oil. The improved cooling rate of oil by CNTs is mainly due to the uniform distribution and excellent thermal conductivity of CNTs.

Fractal Analysis of Positive Streamer Patterns in Transformer Oil-Based TiO2Nanofluid

In this paper, prebreakdown streamers in transformer oil and transformer oil-based TiO2 nanofluid were observed by the schlieren method under positive lightning impulse voltage. Streamers in the nanofluid have numerous branches with much shorter length, whereas in the pure oil, they exhibit only certain filaments with longer length. The discrepancy in positive streamer pattern of both oils is further investigated under a range of applied voltages. The complexity of streamer patterns was quantitatively described using the fractal analysis method. Results indicate that the fractal dimension of streamer patterns shows different changing tendencies in both oils, and it keeps higher value in the nanofluid than that in pure oil during the whole propagation process, well corresponding with streamer propagating structures. Moreover, a new parameter, the ratio of fractal dimension to propagation length (D/L), is introduced to classify the complex streamer patterns for the first time. Three propagation zones in both nanofluid and pure oil are clearly categorized by the value of D/L, providing a quantitative way to distinguish the streamer patterns.

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.

Performance improvement of eco-friendly MQL technique by using hybrid nanofluid and ultrasonic-assisted grinding

MQL technique has many technological and economic advantages in grinding operation. It can improve grinding performance in terms of surface integrity, grinding forces and G-ratio. On the other hand, MQL is eco-friendly technique because of its small consumption of cutting fluid. Despite these advantages, MQL technique has a serious thermal problem in grinding operations due to a small amount of cooling. Nanofluids can increase heat transfer from workpiece/wheel interface due to its high thermal conductivity. On the other hand, ultrasonic machining can decrease heat generation due to its reciprocating mechanism and reduction of time and length of contact between grain and workpiece. So, it is anticipated that simultaneous utilization of these techniques can reduce thermal damages. In this research MWCNT, Al2O3 and hybrid MWCNT/Al2O3 nanofluid oil mists have been utilized in ultrasonic assisted grinding. MWCNT has high thermal conductivity and Al2O3 has good lubrication effect. Output parameters were maximum temperature, grinding forces and friction coefficient. The results revealed that combination of MQL and UAG decrease of maximum grinding temperature up to 56.3% in comparison to dry grinding (from 254 to 111 °C). Moreover, tangential and normal grinding forces and friction coefficient have been reduced up to 61.5, 47.1, and 27.3%, respectively. Moreover, shiny surface without any thermal damages and burning obtained in comparison to dark and burned surface in dry grinding.

Characteristics of Mineral Oil-based Nanofluids for Power Transformer Application

Trends in the field of nanomaterial-based transformer oil show most of the conducted works have focused only on the transformer oil-based nanofluids but limited studies on the stability of transformer oil-based nanofluids. Since mineral oil-based nanofluids still can produce the sedimentation, thus the cold-atmospheric pressure plasma method is proposed to functionally modify the Silicon Dioxide (SiO<sub>2</sub>) nanofiller in order to enhance the electrical properties of the mineral oil-based nanofluids. The AC breakdown strength oil samples before and after modification were measured. It was found that the plasma treated nanofluids have higher AC breakdown voltage compared to pure oil and untreated nanofluids. Also, Fourier Transform Infrared (FTIR) Spectroscopy has been used in this study to analyse the physical changes of oil samples. It is envisaged that the added silica nanofiller has significant effect on electrical properties of the transformer oil-based nanofluids which would enable to the development of an improved class of liquid dielectric for the application of power transformer.

Thermodynamic analysis of a solar dish receiver using different nanofluids

Nanofluid application as the working fluid is proposed as a way for improving the solar system performance. In this study, a dish concentrator with a cylindrical cavity receiver was numerically modeled. Four different nanofluids including Al2O3/thermal oil, Cu/thermal oil, SiO2/thermal oil, and TiO2/thermal oil, were investigated as the working fluid of the solar system. The effects of the nanoparticles concentration in the range of 0–5% on the first and second law of the thermodynamic were considered in this study. The results indicated that the thermal efficiency decreased with increasing nanoparticle volume concentration. Also, the calculated results showed that the obtained exergy and efficiency of exergy improved by increasing the nanofluid concentrations. And it can be concluded from results that the entropy generation reduced with increasing nanofluid concentrations. The Bejan number increased with enhancing the nanoparticles volume fraction. In general Cu/thermal oil nanofluid has best exergy manner among the investigated nanofluid in the cylindrical cavity receiver.

Mixed convection heat transfer: an experimental study on Cu/heat transfer oil nanofluids inside annular tube

The heat transfer and flow characteristics of Cu–heat transfer oil nanofluid during mixed convection through horizontal annular tubes under uniform heat flux as boundary condition are investigated experimentally. Data were acquired at low Reynolds number ranged from about 26 to 252. The applied nanofluid prepared by Electrical Explosion of Wire technique with no nanoparticles agglomeration during nanofluid preparation process and experiments. Pure heat transfer oil and nanofluids with nanoparticles weight concentrations of 0.12, 0.36 and 0.72% were used as the working fluids. Based on these results, Effects of nanoparticles concentration, heat flux and free convection on the thermal field development are studied under buoyancy assisted flow condition for Grashof number, Richardson number between 2820 and 12,686, and 0.1–10, respectively. Results show that Nusselt number increases with an increase of nanoparticles weight concentrations from 0 to 0.72% under certain Richardson numbers.

Measurement and Prediction of Thermal Conductivity of Nanofluids Containing TiO₂ Nanoparticles.

In this paper, experimental results on thermal conductivity of TiO₂-Water, TiO₂-Ethylene Glycol and TiO₂-Engine Oil nanofluids in concentration range between 0.25 to 2 volume percent and temperature range of 10–70 °C is presented. Results show that thermal conductivity of nanofluids increases with increasing concentration and lower enhancement is observed with temperature as compared with concentration. Maximum enhancements are 9.3%, 15% and 8.9% for 2% volume of TiO₂ nanoparticles at 70 °C for TiO₂-Water, TiO₂-Ethylene Glycol and TiO₂-Engine Oil nanofluids respectively. 4-input and 1-output Artificial Neural Network (ANN) approach is used to predict thermal conductivity of nanofluids. Experimental results obtained were compared with some theoretical models and ANN approach. It is observed that ANN approach gives better predictions and is in good agreement with experimental results.

Thermal Performance and Viscosity of Biologically Produced Silver/Coconut Oil Nanofluids

Thermal Performance and Viscosity of Biologically Produced Silver/Coconut Oil Nanofluids