Turbulent Convective Heat Transfer and Pressure Drop of Graphene–Water Nanofluid Flowing Inside a Horizontal Circular Tube

Turbulent convective heat transfer of graphene–water nanofluids with various concentrations inside a uniformly heated circular tube is studied experimentally. For this purpose, experiments are conducted to measure thermal conductivity, viscosity, pressure drop, and heat transfer coefficient. Results show enhancement of thermal conductivity and moderate increment of viscosity with addition of low amounts of nanoparticles. Moreover, heat transfer coefficient shows relatively high augmentation, and pressure drop remains unchanged. The maximum enhancements are 10.30%, 4.95%, and 6.04% for thermal conductivity, viscosity, and heat transfer coefficient, respectively. UV–Vis spectroscopy results show that the nanofluids are highly stable.     

Effects of a Novel Organic Alkali on the Interfacial Tension and Emulsification Behaviors Between Crude Oil and Water

Experiments have been carried out to investigate the interfacial tension (IFT) and emulsification behaviors between Shengli crude oil and a novel organic alkali (OA). The dynamic IFT and minimum IFT are adopted to characterize the IFT behaviors; the microscopic method, Turbiscan stability index, separated water rate, and laser particle size analysis method are used to show the emulsification behaviors. The dynamic and minimum IFT both decrease continuously with the increase of OA concentration whether surfactant is added or not; because of the synergy of OA and surfactant, the minimum IFT will be reduced to the ultralow value. The synergy is also crucial for the crude oil emulsification. When OA and surfactant are used together, owing to the mosaic and cross-multiple adsorption of OA, surfactant and in situ soap at the interfacial film, the oil can be emulsified more easily, the quantity of emulsified droplets is higher, and the emulsion is more stable with OA concentration increases. The relationship of the minimum IFT and emulsification is investigated; it indicates that the emulsion stability improves, the degree of dispersed homogeneity of oil droplets increases, and the median diameter of emulsified oil droplets decreases with the decline of the minimum IFT.     

Pressure Drop and Performance Characteristics of Water-Based Al2O3 and CuO Nanofluids in a Triangular Duct

An experimental study is performed to determine the pressure drop and performance characteristics of Al₂O₃/water and CuO/water nanofluids in a triangular duct under constant heat flux where the flow is laminar. The effects of adding nanoparticles to the base fluid on the pressure drop and friction factor are investigated at different Reynolds numbers. The results show that at a specified Reynolds number, using the nanofluids can lead to an increase in the pressure drop by 35%. It is also found that with increases in the Reynolds number, the rate of increase in the friction factor with the volume fraction of nanoparticles is reduced. Finally, the performance characteristics of the two nanofluids are investigated using the data of pressure drop and convective heat transfer coefficient. The results show that the use of Al₂O₃/water nanofluid with volume fractions of 1.5% and 2% is not helpful in the triangular duct. It is also concluded that at the same volume fraction of nanoparticles, using Al₂O₃ nanoparticles is more beneficial than CuO nanoparticles based on the performance index.     

Salinity Selection for a Low Salinity Water-Low Salinity Surfactant Process

A laboratory selection of salinity for a low salinity water-low salinity surfactant (LS-LSS) process is presented in this paper with systematical investigation on surfactant phase behavior, interfacial tension (IFT), and dynamic retention in porous media with IOS2024 and isoamyl alcohol (IAA) as surfactant system. The results show that 0.4 wt% IOS2024 with 1 wt% IAA can provide ultra-low IFT of 10^?3 mN/m at around 3000–4000 mg/L total dissolved solids, but at that salinity range the surfactant retention is very high. The search for an optimum surfactant formulation has to consider solution properties and retention in addition to the low IFT. The salinity for a LS-LSS process should thus not be focused on either optimal salinity or ultra-low IFT, but instead the best choice could be a compromise between the properties in question. The three-phase region, where ultra-low IFT are found, is also associated with high retention values. However, we show that as salinity is increased from a two-phase region with oil solubilized in a water continuous microemulsion, there is a region close to the three-phase boundary which has potential. This region does not give ultra-low, but fairly low (10^?2 mN/m in this case) interfacial tensions, and also significantly lower retention.      

Synthesis of a New CO2 Philic Surfactant for Enhanced Oil Recovery Applications

The synthesis of CO₂ philic surfactant using maleic anhydride and 4-tert-butylbenzyl alcohol is reported. We reacted maleic anhydride with 4-tert-butylbenzyl alcohol to form bis(4-(tert-butyl)benzyl) fumarate and sulfonated the produced diester. The esterification reaction was optimized for a maximum yield of 98% of bis(4-(tert-butyl)benzyl) fumarate. First-order reaction kinetics with respect to acid was observed. The activation energy was found to be 55.62 kJ/mol. The sulfonated product of diester was obtained by the sulfonation reaction and the yield of 82% of surfactant was achieved. The in-house developed surfactant effectively lowered down the IFT between CO_2/brine to 4.2 mN/m. This surfactant is targeted for CO₂-EOR applications.     

Study of Bimodal Drop Size Distributions of Emulsion

In order to increase the present understanding of bimodal emulsion drop size distributions, systematic series of experiments have been carried out to investigate the effects of formulation variables on bimodal drop size distributions, and probability distribution functions were proposed to analyze the distribution. The results show that, the span of the drop size and Sauter mean diameter become larger when the dispersed phase volume fraction becomes higher and rotor speed becomes lower; the Frechet function represents the experimental data satisfactorily. The prediction model of Sauter mean diameter established by combining the prediction theory of the maximum stable drop diameter and experimental analysis results can fit the experimental data well.     

Foam Flooding with Ultra-Low Interfacial Tension to Enhance Heavy Oil Recovery

Severe viscous fingering during water flooding of heavy oil leaves a large amount of oil untouched in the reservoir. Improving sweep efficiency is vital for increasing heavy oil recovery. Previous researches have proved that foam flooding can increase the sweep efficiency and oil recovery. The polymers could make the foam more stable and have better plugging capacity, but the interfacial tension (IFT) of oil and water increase which could decrease the displacement efficiency of the heavy oil. In view of the deficiency of conventional foam flooding, it is necessary to research the ultra-low interfacial tension foam which could improve macro-swept volume and micro-displacement efficiency in heavy oil reservoir. In this paper a novel foam agent is developed by the combination of surfactant and additives to lower the IFT of oil and water. The operating parameters including foam injections modes and gas liquid ratio were investigated by core flooding experiments. Field test performance shows that oil production per day increased from 85.6 to 125.7 t, water cut declined from 92.1 to 83.6% after 3 months injection. This study provides a novel method to improve heavy oil recovery with an ultra-low interfacial tension foam flooding system.     

Novel Surfactant for the Reduction of CO2/Brine Interfacial Tension

The synthesis of novel CO₂ philic surfactant using maleic anhydride and dipropylene tertiary butyl alcohol is reported. The synthesis involved the esterification of maleic anhydride to produce bis(2-(2-(tert-butoxy)propoxy)propyl) maleate and subsequent sulfonation of the esterified product. Para toluene sulfonic acid was employed as catalyst for the esterification reaction. The esterification reaction was optimized for the maximum yield of 98% of bis(2-(2-(tert-butoxy)propoxy)propyl) maleate. The esterification reaction kinetics employing heterogeneous catalyst were also studied. Although this is a bimolecular reaction, a first order reaction kinetics with respect to acid has been observed. The activation energy was found to be 58.71 kJ/mol. The diester was followed by the sulfonation process and a yield of 85% of surfactant was achieved. The synthesized surfactant successfully lowered down the IFT between CO_2/brine to 1.93 mN/m. This surfactant has a great potential to be used for CO₂-EOR applications.     

Dilational Rheology at Air/Water Interface and Molecular Dynamics Simulation Research of Hydroxyl Sulfobetaine Surfactant

Hydroxyl sulfobetaines with hexadecyl-, octadecyl-hydrophobic chain and an industrial product hydroxyl sulfobetaine were synthesized from analytical-grade and industrial-grade tertiary amine, respectively. The dilational properties and surface tension of the three surfactants at the water-air interface were investigated by drop shape analysis and ring method. The influences of oscillating frequency and bulk concentration on dilational properties were explored. The experimental results show that the dilational module of octadecyl-hydroxyl sulfobetaine was higher than hexadecyl hydroxyl sulfobetaine and the dilational elastic component of the three surfactants were higher than dilational viscous component. Furthermore, the dilational elastic component of mixed surfactant system shows two maxima in a lower concentration than that of single surfactant system. As a result, the surface tension of mixed surfactant system reaches to minimum value in a lower concentration compared with single surfactant system. The simulation results show that the hydrophobic chains in the mixed betaine solution were more curled than in single-component betaine solution ascribed to stronger interaction among different hydrophobic chains, resulting to a more compact interfacial film.     

Interaction of Quercus Infectoria Natural Dye with Cationic and Anionic Surfactants: Adsorption/Micellization of Dye

The interaction of Indian natural dye, that is, Himalaya (Quercus infectoria) with cationic surfactant (cetyl trimethyl ammonium bromide) and anionic surfactant (sodium lauryl sulphate) has been studied. The spectrophotometric data showed an interaction between the natural dye and surfactants. Critical micelle concentration (CMC) of the surfactants, determined by measurement of specific conductance and surface tension methods, was found to be increase in case of anionic surfactant while that was found to decrease in case of cationic surfactant. Thermodynamic and surface parameters showed domination of micellization of dye in case of cetyl trimethyl ammonium bromide and domination of adsorption of dye in case of sodium lauryl sulphate.     

Synthesis and Interfacial Activity of Nonyl Phenol Polyoxyethylene Ether Carboxylate

In order to study the interfacial activity of the anionic-nonionic surfactant, five nonyl phenol polyoxyethylene ether carboxylates were synthesized and mass spectra were used to characterize their structures. The tensions of the anionic–nonionic surfactant aqueous solutions against crude oil were measured and the effects of the surfactant structure, concentration, and salinity on the interfacial activities were discussed. It was shown that nonyl phenol polyoxyethylene (6) ether carboxylate can produce ultralow interfacial tension when the concentrations are not lower than 0.10%, exhibiting a high interfacial activity and a good anti-dilution resistance. Moreover, it was proved that there exists synergism between NaCl and MgCl₂ (or CaCl₂), which is crucial to achieve the ultralow interfacial tension.     

Unique Micellization and CMC Aspects of Gemini Surfactant: An Overview

Critical micelle concentration (CMC) is an essential fundamental property of surfactant molecules, as the CMC value provides significant information regarding the surfactant for industrial use. The industrial efficacy of surfactant molecules totally depends on its CMC value. Without a complete perceptive approach of CMC, it is impractical to employ surfactant molecules efficiently. This article provides an elaborate discussion of dimeric gemini surfactant and pays particular attention to the aggregation behavior, that is, micelle formation, CMC, and thermodynamics of micellization. Micelles structures, packing parameters, and properties of the micelles are summarized. The principles and techniques involved in the determination of CMC are discussed. Thermodynamics of micellization of dimeric surfactants including free energy, enthalpy, and entropy is successively reviewed. Superiority of gemini surfactant in respect of their CMC values is interpreted.     

Determination of Required HLB of Capryol 90

The required hydrophilic-lipophilic balance (HLB) of an oily substance indicates the HLB of the surfactants required to prepare a stable emulsion using the oil. This study utilizes empirical method to calculate required HLB (RHLB) of Capryol 90 using surfactant blends (Span 20, Tween 20, vitamin E TPGS, Pluronic F68, Span 60, and Tween 80). The methods used were assessment of degree of creaming after centrifugation and after shelf storage for 28 days at room temperature, turbidimetric method, accelerated stability study, and droplet size analysis. The droplet size was found to be in the range of 15 to 2 µm and v/v% separation after centrifugation was found to be 0–82%. The RHLB for Capryol 90 was found to be 15. The effect of various surfactant blends was investigated. Results revealed that a blend of tocopherol polyethylene glycol succinate (TPGS) and Pluronic F68 gave the most stable emulsion for Capryol 90.     

Minimum Evaporation Model of Dermatological Delivery Systems. Lamellar Liquid Crystal Formulations Containing Brazilian Nut (Bertholletia excelsa HBK) Vegetable Oil and Guarana Glycolic Extract

Formulations with lyotropic liquid crystals were prepared from a Brazilian nut vegetable oil, guarana extract and combination of sorbitan monooleate (Span 80) and sorbitan monolaurate ethoxylate EO 20 (Tween 20) in the ratio 1:3 (surfactant component) and their physical–chemical aspects and rheological properties were determined. Compositions with liquid crystals were found in the pseudoternary diagram in a surfactant range of 70–90% and polarized light microscopy, small-angle x-ray scattering (SAXS) showed them to be lamellar. The preparations were furthermore characterized rheologically by shear stress shear rate sweeps finding plastic and pseudoplastic behavior without thixotropy. Electric conductivity and pH measurements demonstrated a potential for future application as dermatological delivery system of the active compounds in the Bertholletia excelsa and Paullinia cupana.      

Breakage and Coalescence Phenomena in Ultrasound Field for Liquid-Liquid Dispersion Systems

In this article, emulsification process of liquid-liquid systems was presented, where the emulsification was conducted using ultrasound energy. Mathematical model describing coalescence and droplet breakage phenomena in the ultrasound field based on the model of Laso, Steiner, and Hartland was proposed.