Synthetic Oil Research Articles

Tribological behavior of DLC film models in base oils: Analysis of influence of sp3/sp2 ratio and hydrogen content

DLC coatings have been proven in formulated oils used in the automotive industry. The development of electric cars and its consequences on the future of the internal combustion engine makes it increasingly necessary that these coatings take their place in other applications where lubrication is generally of lower quality such as for example strips cold rolling where DLC shows significant potential both for production and finishing cold rolling. As a result, the interest of the behavior of these coatings in base oils takes on a new dimension. In this study, we explore the influence of the composition and the sp3/sp2 ratio on tribological behavior of DLC coatings in mineral and synthetic base oils. Hydrogenated DLC films deposited by conventional PECVD with various levels of hydrogen measured by Elastic Recoil Detection Analysis (ERDA) and non-hydrogenated DLC films deposited by PLD in the nanosecond mode (ns-PLD) and by cathodic arc evaporation, thus allowing to have different sp3/sp2 ratios confirmed by Multiwavelength Raman spectrometry, are tested and compared. The tests are performed on a ball-on-flat device with coated balls to better evaluate wear level. The behavior of highly hydrogenated DLC is of particular interest; with a very high level of durability in both base oils and friction level which comparatively varies between low and very low depending on the base oil.

The Enhancement of Oil Delivery and Bearing Performance via a Guiding-Structured Nozzle under Oil–Air Lubrication

The oil–air lubrication method is specifically employed for high or ultra-high-speed spindle rolling bearings. Under high-speed conditions, the air curtain formed inside the bearing cavity obstructs oil delivery, thereby limiting further increases in spindle rotation speed. To enhance oil delivery capability, a guiding-structured nozzle has been developed to concentrate the jet flow and improve penetration through the air curtain. Tests were conducted on an oil–air lubricated bearing test bench to investigate the impact of nozzle structures and oil types on torque and temperature rise. The results demonstrate that compared to conventional nozzles, the guiding-structured nozzle requires smaller optimal amounts of oil supply, indicating its superior ability to deliver oil. Further examination of oil jet patterns and droplet distributions confirms that the guiding-structured nozzle provides a more concentrated jet flow with uniform distribution and smaller droplet sizes in diameter. These characteristics contribute to highly efficient oil delivery. Additionally, synthetic oils reduce droplet size, torque, and temperature rise in mixed lubrication regimes due to their formation of an anti-friction absorption layer on rubbing surfaces.

A Novel Biosurfactant-Based Oil Spill Response Dispersant for Efficient Application under Temperate and Arctic Conditions.

Synthetic oil spill dispersants have become essential in offshore oil spill response strategies. However, their use raises significant concerns regarding toxicity to phyto- and zooplankton and other marine organisms, especially in isolated and vulnerable areas such as the Arctic and shorelines. Sustainable alternatives may be developed by replacing the major active components of commercial dispersants with their natural counterparts. During this study, interfacial properties of different types of glycolipid-based biosurfactants (rhamnolipids, mannosylerythritol lipids, and trehalose lipids) were explored in a crude oil-seawater system. The best-performing biosurfactant was further mixed with different nontoxic components of Corexit 9500A, and the interfacial properties of the most promising dispersant blend were further explored with various types of crude oils, weathered oil, bunker, and diesel fuel in natural seawater. Our findings indicate that the most efficient dispersant formulation was achieved when mannosylerythritol lipids (MELs) were mixed with Tween 80 (T). The MELs-T dispersant blend significantly reduced the interfacial tension (IFT) of various crude oils in seawater with results comparable to those obtained with Corexit 9500A. Importantly, no leaching or desorption of MELs-T components from the crude oil-water interface was observed. Furthermore, for weathered and more viscous asphaltenic bunker fuel oil, IFT results with the MELs-T dispersant blend surpassed those obtained with Corexit 9500A. This dispersant blend also demonstrated effectiveness at different dosages (dispersant-to-oil ratio (DOR)) and under various temperature conditions. The efficacy of the MELs-T dispersant was further confirmed by standard baffled flask tests (BFTs) and Mackay-Nadeau-Steelman (MNS) tests. Overall, our study provides promising data for the development of effective biobased dispersants, particularly in the context of petroleum exploitation in subsea resources and transportation in the Arctic.

Yield optimization of nonedible vegetable oil-based bio-lubricant using design of experiments

In recent years, there has been a focused effort to reduce the harmful effects of synthetic and mineral-based lubricants by emphasizing the use of biodegradable-based lubricants. These lubricants play a crucial role in minimizing friction, ensuring smooth operation of machines, and reducing the likelihood of frequent failures. With petroleum-based reserves depleting worldwide, prices are rising, and environmental damage is increasing. However, biolubricants derived from nonedible vegetable oils offer environmental benefits as they are nontoxic, emit minimal greenhouse gases, and are biodegradable. In this study, biolubricants are synthesized from jatropha and jojoba oil using sulphuric acid (H2SO4) and hydrochloric acid (HCl) as catalysts through the transesterification and epoxidation processes. The optimization of influencing parameters is achieved using Taguchi’s orthogonal array, a statistical methodology. By employing design of experiments (DOE), the number of experimental trials is minimized while providing comprehensive details on the impact of control factors such as molar ratio, catalyst concentrations, and temperature. The results obtained from DOE reveal that the best optimized yield for jatropha biolubricant with H2SO4 and HCl catalysts is achieved with a molar ratio of 0.5:1.5, a temperature of 70 °C, and a catalyst concentration of 1.2 ml. The experimental yield for jatropha biolubricant with H2SO4 and HCl catalysts was measured at 226 ml and 238 ml, respectively, while the model predicted yield was 221 ml and 231 ml, respectively. The experimental yield for jojoba biolubricant with H2SO4 and HCl catalysts was recorded at 232 ml and 248 ml respectively, whereas the model predicted yield was 226 ml and 245 ml, respectively. Based on the analysis of variance (ANOVA) results, it is evident that among the three control factors, the molar ratio significantly influences the yield of both jatropha and jojoba biolubricants, as indicated by a p-value of less than 5%. The percentage contribution of the molar ratio in jatropha biolubricant with H2SO4 and HCl catalysts is found to be 98.99% and 97.2%, respectively. Furthermore, the R2 value, which exceeds 90%, signifies a strong relationship between the independent and dependent variables. The deviation between the experimental and regression-predicted equations for the yield remains within 2.5% for all combinations of jatropha and jojoba biolubricants. In conclusion, the study successfully prepared biolubricants from jatropha and jojoba-based non-edible vegetable oils and determined the optimal conditions for their production.Graphical abstract

Synthesis and biodegradation testing of some synthetic oils based on ester

Synthetic ester oils are widely used in many applications due to their ideal cleaning properties, lubricating performance and assured polarity. The majority of esters oils are more biodegradable. than any other base stock. For instance, oil soluble polyalkyleneglycols (PAGs) or polyalphaolephins (PAOs), are only biodegradable in the lower viscosity grades. The goal of this study is to create some synthetic base oils by two major protocols; the first is esterifying valeric acid with various glycols (ethylene glycol, propylene glycol, butylene glycol and poly (ethylene glycol 400). The second involves esterification of propanoic acid, heptanoic acid, or octanoic acid with ethylene glycol. The reaction yield varies between 85 and 94%. The chemical composition of the prepared esters was examined using various spectroscopic methods (Fourier-transform infrared (FT-IR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. The thermal properties investigation by thermo gravimetric analysis (TGA) showed pronounced thermal stability of the prepared esters. The biodegradability was verified versus two bacterial isolates (B1, B2). The results showed that percentage of degradation of the lube oil was in the range of 34% to 84% after 3 days of incubation. Moreover, the rheological study revealed that the prepared esters exhibited Newtonian rheological behaviours. Viscosity examination displayed that the esters based on ethylene glycol, such as (A), had the highest VI: 179 values when compared to those based on higher glycols. Viscosity and viscosity index results showed slight increase as the number of carbon atoms in the acid chain increases. At last, most of the synthesized esters possessed pour points ≤ − 32 °C: ≤ − 40 except in case of using higher acids like heptanoic acid and octanoic acid in preparation the pour point increases to − 9 °C and − 15 °C.

Study on the intermediate products of Fischer Tropsch synthesis as a collector for coal flotation: Molecular dynamics and experimental studies

As a general coal flotation collector, diesel is often used in the industrial production process, and diesel is not renewable and belongs to the hazardous reagents, so there is an urgent need to find a new type of flotation collector to replace diesel. In this paper, three intermediate products produced by Fischer-Tropsch synthesis technology were used as collector. And five emulsifiers, Span80, Tween80, sodium dodecyl sulfate, betaine, and hexadecyl trimethyl ammonium bromide were used to emulsify 3# synthetic oils to produce emulsion with good stability. The flotation performance of three synthetic oil products as well as emulsified collectors were investigated, and the adsorption capacity of 2# and 3# synthetic oils on the coal surface was studied by molecular dynamics simulation. The results showed that the flotation results of synthetic oil were better than those of diesel, with collector 1# having the best flotation results. The oil in water (O/W) emulsion formulated with Tween80 had the best properties, and remained unstratified in half a month, and there were a large number of 0.1–1 μm oil droplet in the emulsion. Moreover, the emulsified collector of Tween80 with oil-water ratio of 4:6 showed excellent flotation performance, which was nearly 1.5 % higher than that of diesel. The molecular dynamics results are consistent with the synthetic oil flotation results at high concentration dosages, where 3# oil showed better adsorption behavior on the coal surface than 2# oil, but was slightly inferior to diesel adsorption. Therefore, the synthetic oil can be completely used as a substitute for diesel, and the emulsion with oil-water ratio of 4:6 formulated with Tween80 has excellent flotation performance and greatly saves the actual consumption of synthetic oil, which has very high economic and environmental value.

Enzymatic synthesis of TMP esters based on pelargonic acid from the cleavage of oleic acid: Evaluation of synthetic process, physicochemical properties and lubrication performance

Biolubricants produced by chemically modifying vegetable oils are promising to replace mineral-based lubricants. However, the performances of biolubricants synthesized through traditional chemical modification routes, such as transesterification/esterification, epoxidation with further ring opening, and estolide formation, cannot satisfy the demands of extreme conditions. Meanwhile, complicated multi-step reactions cause expensive costs, which hinders their large-scale application. In this study, pelargonic acid (PA) derived from the cleavage of oleic acid was esterified with trimethylolpropane (TMP) to produce branched-chain esters (tri-TMP esters) catalyzed by the lipase (Candida sp. 99–125), focusing on batch stability of the lipase, thermal-oxidation stability and lubrication performance of the product. The lipase maintained high activity for 4 continuous batches in 5 L enzyme reactor with the conversion of PA > 96% and the accumulation of tri-TMP esters > 84% in each batch. The obtained tri-TMP esters had a pour point of − 56 °C, a viscosity index of 137, and a flash point of 276 °C. Anti-oxidation stability test and thermogravimetric behaviors showed that the biolubricant had favorable thermal-oxidative stability. Friction tests verified that the product displayed excellent lubrication performance with a minimum coefficient of friction (COF) of 0.099 and an average wear spot diameter (WSD) of 221.5 µm. The green and high-selective synthetic pathway fills the defect of existing routes for the preparation of biolubricants from chemically modified vegetable oils.

Experimental investigation of the effects of oil asphaltene content on CO2 foam stability in the presence of nanoparticles and sodium dodecyl sulfate

Foam stability tests were performed using sodium dodecyl sulfate (SDS) surfactant and SiO2 nanoparticles as foaming system at different asphaltene concentrations, and the half-life of CO2 foam was measured. The mechanism of foam stability reduction in the presence of asphaltene was analyzed by scanning electron microscope (SEM), UV adsorption spectrophotometric concentration measurement and Zeta potential measurement. When the mass ratio of synthetic oil to foam-formation suspension was 1:9 and the asphaltene mass fraction increased from 0 to 15%, the half-life of SDS-stabilized foams decreased from 751 s to 239 s, and the half-life of SDS/silica-stabilized foams decreased from 912 s to 298 s. When the mass ratio of synthetic oil to foam-formation suspension was 2:8 and the asphaltene mass fraction increased from 0 to 15%, the half-life of SDS-stabilized foams decreased from 526 s to 171 s, and the half-life of SDS/silica-stabilized foams decreased from 660 s to 205 s. In addition, due to asphaltene-SDS/silica interaction in the aqueous phase, the absolute value of Zeta potential decreases, and the surface charges of particles reduce, leading to the reduction of repulsive forces between two interfaces of thin liquid film, which in turn, damages the foam stability.

Synthetic Ester-Based Oils and Their Application in Power Industry

Suitable (biodegradable) substitution of classic mineral petroleum-based oils used in power transformers is studied. Paper presents test results of six paper-oil insulation systems varying by different type of oil. Three common transformer oils and three new synthetic oils (never used in power transformers before) were selected for the purpose of experiment. The oils have been exposed to accelerated thermal aging (at the temperature of 90 °C) and their properties were measured in time intervals of 0, 50, 125, 225, 500, 1000 and 2000 hours.

Investigating Friction and Antiwear Characteristics of Organic and Synthetic Oils Using h-BN Nanoparticle Additives: A Tribological Study

Friction and wear are two major elements that influence the life of a variety of equipment. According to estimates, as much as 30% of the energy used is dissipated as friction. However, this figure can be reduced by developing materials that enhance surfaces and apply lubricants appropriately. This study aims to analyze the impact of hexagonal boron nitride (h-BN) nanoparticles on the rheological and antiwear characteristics of four distinct oil varieties, namely Society of Automotive Engineers SAE-20W50, soybean, Polyalphaolefin PAO-4, and olive oils. The results of the tribological tests demonstrated a noteworthy enhancement in antiwear characteristics with the addition of 0.2 wt.% of h-BN nanolubricant. Among all nanolubricants, the maximum reduction in coefficient of friction (COF) and wear scar diameter was observed at 0.2 wt.% of h-BN in SAE-20W50 oil. Compared to the base oils, the wear scar diameter decreased by 17.93%, 8.80%, 22.65%, and 24.04% for (soybean oil and 0.2 wt.% of h-BN), (SAE20W50 and 0.2 wt.% of h-BN), (PAO4 and 0.2 wt.% of h-BN), and (olive oil and 0.2 wt.% of h-BN), respectively. Rheological test results indicated that with the addition of h-BN nanoparticles, the viscosity of the base oils significantly increased. The maximum viscosity was observed at 40 °C for SAE20W50 base nanolubricants, according to the rheological measurements.

Investigations on Ways to Improve the Scuffing and Wear Behavior of Oil-Free Water-Based Lubricants for Gear Applications

Abstract Today, mineral or synthetic oils that are made out of fossil raw materials are the most common lubricants in gear drive applications. Most of them are nonbiodegradable and may pose a risk to the environment. An important step to minimize the risk and the ecological footprint is the use of biodegradable and eco-friendly lubricants. Former research shows the potential of water-based lubricants in gear applications. Therefore, an oil-free, water-based lubricant was developed for this study. The base lubricant contains plant-based thickeners to generate an appropriate viscosity for a sufficient lubricant film thickness in the tooth contact. In experimental investigations, the sliding wear and scuffing performance has been examined under variation of the added polymers and additives. The scuffing tests A/8.3/RT are performed according to DIN ISO 14635-1. The wear test procedure is based on DGMK 377-01. In both scuffing tests with the sample, the failure load stage = 8 was achieved. For case-carburized gears, a “medium” to “high” amount of wear can be detected. Additional tests with nitrided gears show a “low” amount of wear. This article aims to show the great potential of water-based oils for gear lubrication and suggests operating conditions for maximum wear and scuffing carrying capacity.

Effect of different base oils on the friction behaviour of polycrystalline diamond compact

AbstractThis study analysed and discussed the friction and wear properties, as well as the interface evolution behaviour of polycrystalline diamond compact (PDC) under various base oils, through conducting friction experiments on PDC/Si3N4 with different base oils. The friction and lubrication mechanism of PDC under different base oils were examined using scanning electron microscopy (SEM), x‐ray energy dispersive spectrometry (EDS), three‐dimensional white light interferometry, and Raman spectroscopy. The results of the study demonstrated that PDC exhibited the best friction and wear performance when lubricated with synthetic oil PAO, followed by castor oil. The inferior performance of paraffin oil can be attributed to its low viscosity, resulting in a lower presence of ions capable of passivating the carbon dangling bond. Consequently, paraffin oil displayed inadequate oxidation stability and increased susceptibility to oil film destruction, ultimately leading to suboptimal friction and wear characteristics. Overall, this study provides valuable insights for industrial applications, aiding in the selection of appropriate base oils as cutting fluids for PDC cutting tools and enhancing the friction and wear properties of PDC.

A numerical study on effect of intra and inter spaced winding configuration on performance of oil forced transformer cooling system

The present work aims at investigating, numerically, the heat transfer characteristics of transformer cooling system under forced circulation for three different winding configurations. The purpose of a transformer cooling system is to keep the hot spot temperature within the critical value for a long life of transformer, which increases with enhanced cooling of transformer windings. Thus, two different winding configurations are modeled by providing space within the windings (an intra-space model) and in between the windings (an inter-space model) to improve the fluid-solid interaction. A conventional winding, without spacing, is also modeled for comparative study. A 315 kVA, 3-phase core type transformer is taken as the base model from which the winding and core specifications are obtained analytically. Parameters chosen to measure the influence of winding configuration are local temperature distribution in the windings and core and maximum transformer temperature. Results are obtained for all three models with varying space for various cooling mediums like naphthenic oil, silicon oil, and synthetic ester oil at flow velocities ranging from 0.72 m/s to 2.16 m/s. It is observed that the gap between the windings, interspacing, decreases the secondary winding temperatures, while it increases the core and primary winding temperatures. However, the intra spacing configuration finds a drop in local temperatures at all locations of the transformer windings and core. The enhanced heat dissipation to the cooling agent, with intra spacing winding configuration, reduces the maximum transformer temperature. Contrasting to the above, the inter-space model has an adverse effect on maximum temperature at all widths of space considered. Quantitatively, the space within the transformer reduces the maximum temperature by 5% in comparison with the space between the windings. The increased velocity of the cooling medium, Naphthenic oil, from 0.72 m/s to 2.16 m/s reduces the maximum temperature by 4.5 units. The study made to know the role of cooling medium discloses that the synthetic ester oil shows better performance for reducing temperature values due to its highly viscous nature.

The influence of various grease compositions and silver nanoparticle additives on electrically induced rolling-element bearing damage

Leakage currents accelerate surface degradation of metal contacts via small scale arcing across lubricating films, but recent observations suggest that metallic nanoparticle additives in lubricants may be useful to improve contact performance. These findings prompted a study that examined electrically induced surface pitting of steel contacts in the presence of several lubricating greases including some containing nanometer-sized colloidal silver (Ag) particles. Reciprocating rolling sphere-on-disk experiments were conducted under electro-tribological loads employing polyurea greases derived from mineral and synthetic base oils with and without additives. Friction forces and electrical resistance were monitored continuously during the tests; surface changes were characterized by means of optical spectroscopy, stylus profilometry, and scanning electron microscopy (SEM) including compositional analysis using energy dispersive spectroscopy (EDS). The observations demonstrate that surface pitting induced by arcing occurs mainly at the points were the rolling motion changes direction and that eroded metal is deposited along the wear grove. Micron-sized pits are formed which contain carbon and oxygen indicating that arcing causes decomposition of the hydrocarbon lubricants. Numerous findings indicate a significant inhibition of pitting is induced by the Ag nanoparticles; some greases containing other additives exhibit a similar, although less pronounced, effect.

A comparative study of thermo‐physical properties of different nanofluids for effective heat transfer leading to Li‐ion battery pack cooling

AbstractThe rapid advancement in Lithium‐ion battery technology has significantly boosted the electric vehicle market worldwide. These batteries are highly sought after by automobile manufacturers and researchers due to their exceptional energy storage and power capabilities. However, efficient working temperatures ranges from 15°C to 35°C, making it essential to implement battery cooling and heating methods to maintain optimal performance. This study primarily focuses on battery cooling. The automotive manufactures have focused on ethylene glycol, water and synthetic oils as commonly used coolants for keeping the lithium‐ion battery pack within working temperature limits. However, these fluids have lower heat conduction, leading to reduced heat transfer rates and diminished cooling performance. To address this issue, nano‐enhanced fluids, which are engineered fluids containing suspended nanospheres, have been explored. The heat transfer properties of conventional coolants are increased using nano‐enhanced fluids, thereby improving heat conduction and promoting efficient heat transfer within the battery. The study compares the temperature‐related characteristic of different nano‐enhanced fluids, including oxides of copper (CuO), titanium (TiO2), aluminum (Al2O3), silicon (SiO2), and zinc (ZnO), when added to base fluids such as synthetic oils, water and ethylene glycol. The importance to capacity of specific heat, conductivity of fluid thermally, fluid resistance to flow and fluid volumetric mass which are affected by changes in temperature limits are stressed upon. Depending on the specific application and test conditions, the effectiveness of one nano‐enhanced fluid may outperform the others. In conclusion, the thermo physical properties of nanofluids play a critical role in maintaining the battery pack temperature within operating temperature limits. The selections of nanofluids for particular battery thermal management system depends upon its arrangement along the battery pack and cell geometry. The cooling performance using nanofluids as coolant is 10% to 15% higher than the conventional used fluids. This nano‐enhanced fluid show great promise in enhancing the cooling capabilities of battery cooling systems, contributing to improved Lithium‐ion battery performance in electric vehicles.

Visualization of CO2-oil vanishing interface to determine minimum miscibility pressure using microfluidics

The determination of the minimum miscibility pressure (MMP) assumes paramount significance in evaluating CO2 enhanced-oil recovery strategies. We created a microfluidic method for determining the MMP of CO2 and oil samples by integrating the direct observation of the vanishing interface and the analysis of fluorescence intensity exhibited by oil samples. A microfluidic chip is designed with closed-end microchannels to mimic the blind-end fractures which contributes to reveal the complete picture of residual oil mobilization during CO2 miscible flooding. The maximum deviation of 3.83 % and 5.47 % unequivocally attested to the accuracy of our method by comparing measured MMPs with those reported in the literature and theoretically calculated in this study. The effects of alkane types, temperature and oil compositions on MMP was investigated. The MMPs for binary synthetic oils (C8 + C14) increased non-linearly with contents of tetradecane and increased significantly at C14 > 75 vol%. MMPs of nine n-alkanes, seven binary synthetic oils, four ternary synthetic oils and kerosene were provided reliably as the unprecedented new data. Such unique advantages as in-situ visualization, chip pattern customizability, user-independence, and the clear criterion render this research highly valuable for determining the MMP as well as elucidating the microscopic mechanisms underlying residual oil mobilization.

“DEVELOPMENT AND CHARACTERIZATION OF SELF-MICROEMULSIFYING DRUG DELIVERY SYSTEM (SMEDDS) FOR BAUHINIA VARIEGATA LEAF EXTRACT”

This study aimed to formulate and characterize a Self-Microemulsifying Drug Delivery System (SMEDDS) for Bauhinia variegata leaves, a traditional medicinal plant renowned for its anti-tumor properties, in order to enhance the solubility and bioavailability of its bioactive compounds. Bauhinia variegate leaves were collected locally (Amity university ).The successful formulation and characterization of the SMEDDS for Bauhinia variegata not only contribute to advancing drug delivery technologies for traditional medicines but also pave the way for further research into practical applications in the pharmaceutical and herbal medicine industries. This study provides valuable insights for the development of innovative and effective delivery systems for bioactive compounds derived from traditional medicinal plants. Developing a self-microemulsifying drug delivery system (SMEDDS) for an ethanol extract from Bauhinia Variegate leaves involves creating a formulation that can spontaneously form a stable microemulsion when introduced to aqueous media, such as the gastrointestinal fluids. The use of a ternary phase diagram can help optimize the proportions of the key components in the formulation. SMEDDS are described as isotropic mixtures of herbal or synthetic oils, solid or liquid surfactants, or instead, one or greater hydrophilic solvents and co-solvents/surfactants that have a completely unique ability of forming satisfactory oil-in-water (o/w) microemulsions upon mild agitation followed by way of dilution in aqueous media, including GI fluids

An experimental study on pressure drop of air-oil flow in horizontal pipes using two synthetic oils

This study focuses on the frictional pressure drop in gas-liquid two-phase flow, characterized by nonlinear behavior under various flow conditions due to complex two-phase phenomena. The experimental investigation involves an air-oil mixture flowing through horizontal pipes with diameters of 20 mm and 40 mm, aiming to observe the flow patterns and quantify the pressure drop. Two oils with different thermophysical properties are used as the liquid phase. The operating temperature and pressure of the test pipes are controlled within the range of 24–44°C and 1–3 bar, respectively. Seven air-oil flow patterns are identified based on visualization results: stratified smooth, stratified wavy, annular, plug, slug, bubbly, and dispersed bubble flows. On analyzing 1043 data points from the experiment, this study explores the effects of total mass velocity, flow quality, pipe diameter, operating temperature, operating pressure, and oil type on the frictional pressure gradient. Particular attention is given to the variation of the frictional pressure gradient concerning operating pressure, and its relationship with total mass velocity, flow quality, and flow pattern is discussed. Additionally, the study examines predictions from 55 previous correlations against the current pressure drop data. The predictive capability of these correlations is evaluated for the entire dataset and its subsets, categorized by oil type, pipe diameter, operating pressure, flow condition, total mass velocity, flow quality, and flow pattern. Evaluation metrics include mean absolute errors and the proportions of data points within 30% and 50% of absolute error. In addition, average and standard deviation values are calculated for each dataset to provide a comprehensive assessment.

Контроль вмісту розчинених газів у свіжих та окиснених турбінних оливах

The article is a publication of scientific and methodical character. Gas chromatography methods were used to determine the content of dissolved diagnostic gases in mineral turbine oil «Agrinol Tp-46» and in synthetic fire-resistant turbine oils «Fyrquel®L», «Reolube®OMTI», «Reolube®46 RS». The following were studied: the solubility of these gases in mineral oil «Agrinol Tp-46» and in synthetic oil «Reolube®46 RS»; dependence of solubility values for diagnostic gas H2S on temperature in the system «mineral turbine oil – dissolved gas H2S»; distribution coefficients of dissolved gases in turbine oils in systems «turbine oil – dissolved gas – gaseous extractant»; dissolved gas content in «Reolube®46 RS» synthetic turbine oils by application method. This will make it possible to determine the content of dissolved gases in wet turbine oils for diagnostics of oil-filled equipment.

Techno-economic and environmental analysis of a hybrid PV/T solar system based on vegetable and synthetic oils coupled with TiO2 in Cameroon

To assess the production potential, economic profitability and ecobalance of the photovoltaic/thermal (PV/T) system in Cameroon, different configurations of HTF based on water, vegetable and synthetic oils, coupled with different forms of titanium dioxide (TiO2) are used. A numerical code is written in Matlab. The PV/T model connected in direct contact PV-absorber is validated and a multi-objective optimization of the system is performed. The hourly evolution of PV cell temperature for the six HTF configurations revealed a value below 36 °C with Coton/TiO2. The platelets-and spherical-shaped nanoparticles increase the convection transfer coefficient between the fluids and the tubes. TiO2 showed a higher thermal influence in vegetable and synthetic oils than in water at a volume concentration of 4 %. The cotton/TiO2 configuration showed a 12.08 % improvement in electrical efficiency over conventional PV systems with low exergy efficiency compared to water. Configurations with therminolVP-1/TiO2 are better, with the proposed energy cost reduced to 33 % of the price of electricity in Cameroon. The PV/T-Palm/TiO2 system showed an energy cost of $0.03 with a net present value of $568.45, an emission rate of 7.78 kg, a reversibility index of 1.95, an annual cost of $7.07 and a payback time of 5.97yr. This shows that PV/T systems based on vegetable oils are economical.