Journal Of Thermal Analysis And Calorimetry (13886150)(1)
The effect of nanoparticles aggregation on the heat transfer coefficient in a heat dissipation process of a circular tube is evaluated through computational fluid dynamics (CFD) technique, and the simulation results are compared to experimental data. The experimental data of MgO/CuO/Al2O3 water-based nanofluids which were obtained in our previous study under turbulent flow regime and Reynolds numbers ranging from 11,000 to 47,000 are used to validate the CFD results. Two-phase mixture and k-ε RNG turbulence models are coupled with the population balance model (PBM) to consider the impact of nanoparticles aggregation in the flow domain using the commercial CFD software ANSYS Fluent 17.2. The particle size distribution (PSD) determined by conducting dynamic light scattering (DLS) analysis for nanoparticle concentrations of 0.02, 0.05, 0.07 and 0.09%v. is fed to solve the governing equations. The CFD model with aggregation results is in very good agreement with the experimental data, and the maximum relative absolute average deviation (RAAD) from the experiments is about 7.5%, while the CFD model without aggregation leads to less accurate results with maximum 17.56% deviation compared to experimental data. The consideration of the aggregation effect with accurate PSD data enhances the CFD simulation and makes its outcomes more reliable. © 2020, Akadémiai Kiadó, Budapest, Hungary.
Colloids and Surfaces A: Physicochemical and Engineering Aspects (09277757)
This study presents a novel and facile route to produce the methotrexate (MTX) loaded liposomal particles using the double flow focusing microfluidic (double-MHFF) device in a single step process. The double-MHFF design, due to the intensification of the mass diffusion by increasing the diffusion surface area of both phases can be a good candidate to produce the drug-loaded PEGylated liposomes. The physicochemical characteristics of the prepared MTX-liposome (MTX-L) and MTX-PEGylated liposome (MTX-PLL) such as particle size, polydispersity (PDI), and encapsulation efficiency are optimized by adjusting the operational and formulation parameters, like flow rate ratio (FRR), total flow rate (TFR), total lipid concentration and MTX concentration. Also, the release study is performed for MTX-L and MTX-PLL particles. The range of average size of the MTX-L and MTX-PLL nanoparticles are within 90–230 nm and 118–258 nm with PDI ≤ 0.32 and PDI ≤ 0.23, respectively. The double-MHFF device has the ability for achieving high encapsulation efficiency (≥ 60 %), especially for MTX-PLL. Also, the MTX-PLL nanoparticles have a sustained release and long-term fashion up to 72 h (≤ 48 %). This means that the high encapsulation efficiency and low release of MTX result from the production process. © 2021
Chemical Engineering and Technology (09307516)(12)
Methods of computational fluid dynamics and design of experiments are implemented in modeling the heat transfer of an Al2O3/water-ethylene glycol (EG) nanofluid as a coolant in a car radiator system. The main purpose of the study is to propose a model to predict the Nusselt number using the design of computer experiment. The response surface methodology is applied to investigate the effects of the flow rate, the nanoparticle concentration, the water/EG ratio, and the inlet temperature on Nu. Analysis of variance is performed to obtain a suitable correlation that could predict Nu, leading to the elimination of insignificant terms in the initial proposed quadric model and the attainment of a reduced model. Moreover, the reduced model is converted to a simpler linear model using Box-Cox transformation, which predicts Nu with an accuracy of ±20 %. © 2021 Wiley-VCH GmbH
Soft Matter (1744683X)(47)
The present study shows a facile route for producing doxorubicin (DOX)-loaded polycaprolactone (PCL) nanoparticles using a microfluidic device with a flow-focusing platform in a single step. Indeed, the evaluation of the performance of the flow-focusing microfluidic device for the preparation of DOX-loaded PCL (DOX/PCL) nanoparticles with a uniform size distribution and high encapsulation efficiency (EE) by applying the liquid non-solvent precipitation process is very important. Accordingly, the physicochemical characteristics of the DOX/PCL nanoparticles such as their mean size, polydispersity index (PDI), and EE were investigated by studying different parameters such as the flow rate ratio (FRR) and DOX concentration. Also, the release study was carried out at two pH of 5.5 and 7.4. The mean size of DOX/PCL nanoparticles achieved was in the range of 120-320 nm with a PDI ≤ 0.29 and EE between 48% and 87%. Moreover, the release profile of DOX/PCL nanoparticles was sustained for 10 days (≤66%) at pH 7.4. This means that the production process can result in a high EE and low release of the DOX drug. This journal is © The Royal Society of Chemistry.
Journal of Flow Chemistry (2062249X)(3)
This systematic investigation assessed the potential applications of microfluidic devices in producing a uniform size distribution of polycaprolactone (PCL) nanoparticles by applying the liquid non-solvent precipitation process. Five arrangements of microfluidic devices are fabricated with different designs. The effects of different operational and geometrical factors such as flow rate ratio (FRR), total flow rate (TFR), mixing channel width, mixing channel length, and confluence angles of the inlet channels are investigated on the size, polydispersity index (PDI), and the size distribution of PCL particles. Further, a study was performed to enhance the production throughput of PCL nanoparticles. The mean size of nanoparticles is precisely controlled within the range of 40–370 nm with PDI values of 0.2–0.37. According to the results, the optimal conditions for rapid production of nanoparticles with a size smaller than 200 nm and PDI ≤ 0.31 are obtained at FRR of 8, TFR of 70 ml h−1, channel width of 200 μm, channel length of 20 mm, and the confluence angle of 60o. Furthermore, the microfluidic device with a wider channel width of 600 μm provided a higher productivity rate of the PCL nanoparticles with a similar size and lower PDI than those obtained by other widths. © 2020, Akadémiai Kiadó.
Journal of Inorganic and Organometallic Polymers and Materials (15741443)(5)
Carbon nanofibers are synthesised via chemical vapour deposition of acetylene as carbon source through using water soluble catalysts. The new water soluble catalyst is prepared by supporting the copper on sodium chloride salt. Copper acetate and copper nitrate salts are used for preparing catalysts through impregnation method. The yield of carbon deposits using the catalyst prepared by copper acetate is almost twenty times higher than the one prepared by copper nitrate precursor. The X-ray diffraction pattern and field emission scanning electron microscopy (FESEM) images confirm the formation of CuO in the catalyst after calcination process. The growth time for carbon material is 15 min. The FESEM images show the growth of helical and straight carbon nanofibers on the catalysts with metal loading of 5 wt% at 600, 650 and 680 °C. The results showed that the morphology of the carbon deposited on the catalyst depends on both the amount of metal loaded on the catalyst and reaction temperature, while there is a significant interaction between them. However, fishbone carbon nanofibers with diameters less than 100 nm are deposited on the catalysts with metal loading of 1 wt% at 650 °C. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.
Chemical Engineering and Technology (09307516)(10)
Polycaprolactone nanoparticles (PCL NPs) were produced by a liquid nonsolvent nanoprecipitation process in a flow-focusing microfluidic device and optimized in terms of particle size, polydispersity index (PDI), and zeta potential ζ. The effects of flow rate ratio (FRR), total flow rate (TFR), the organic solvents tetrahydrofuran and dimethylformamide (DMF), the surfactants polyvinyl alcohol and Tween 80, and polymer molecular weight on the size, PDI, and ζ of PCL NPs were investigated. A stability study was performed to compare the effect of the surfactants on the characteristics of PCL NPs over 7 d. The smallest particles are produced at the highest FRR, TFR, and polymer molecular weight and lowest polymer concentration in DMF. The presence of both surfactants results in smaller NPs. © 2020 Wiley-VCH GmbH
Industrial and Engineering Chemistry Research (08885885)(51)
In the present study, a double flow-focusing platform is applied to evaluate the application of microfluidic devices for the synthesis of liposomes with a uniform size distribution. The size, polydispersity index (PDI), and size distribution of liposomes are measured by varying different factors such as flow rate ratio (FRR), total flow rate (TFR), total lipid concentration, lipid/cholesterol molar ratio, and various lipid formulations. A comparison is made between the performance of double flow-focusing and single flow-focusing devices. The liposomes in the size range of 50-200 nm are produced with low PDIs of 0.1-0.37. The results show that the smallest particles are synthesized at the highest FRR and TFR, the lowest total concentration, a lipid/cholesterol molar ratio of 60:40, and single-lipid formulation. Also, the double flow-focusing device has the ability to apply higher TFR values than the single flow-focusing device, which leads to a higher productivity rate and smaller liposomes. Copyright © 2019 American Chemical Society.
Journal of Petroleum Science and Engineering (09204105)
In this research, graphene oxide (GO) is used to prepare stable Pickering emulsions in chemical flooding for enhanced oil recovery (EOR). The effects of GO concentration (0–7 mg/mL), salinity of aqueous phase (0–10 wt%), and asphaltene concentration in organic phase (0–2 wt%) on the stability and morphology of the emulsions are examined. Moreover, the influence of these independent variables on the interfacial tension (IFT) between organic and aqueous phase is assessed through response surface methodology. The results show that the concentrations of GO and asphaltene have the most significant effect on the IFT; indeed, the IFT reduces with increasing both GO and asphaltene concentrations. Defining two quantitative indexes make it possible to compare the efficiency of emulsions formation (ESVI) and the stability of formed emulsions during time (ESTI) against creaming at different conditions. The maximum reported values for the ESTI and ESVI are 100% and 70%, respectively. In all conditions, the type of emulsions is oil-in-water (O/W) which is more suitable in EOR. However, water-in-oil emulsions (W/O) are observed at asphaltene concentrations higher than 1.5 wt%. For dominating this phenomenon, the water/oil ratio should be increased. At the presence of asphaltene and salinities higher than 1 wt%, some water-in-oil-in-water (W/O/W) multiple emulsion droplets are observed. The minimum of the reported average droplet size is 0.69 μm for GO concentration of 1 mg/mL and asphaltene concentration of 0.05 wt%. These results demonstrate the potential applications of graphene based functional materials for EOR. © 2019 Elsevier B.V.
Journal Of Thermal Analysis And Calorimetry (13886150)(1)
Nanofluids are obtained by suspending metallic or non-metallic nanoparticles in conventional base liquids and can be employed to increase heat transfer rate in various applications. In this study, the effects of adding three types of nanofluids on turbulent convective heat transfer at the entrance region of a constant wall heat flux tube were experimentally studied. The nanofluids were mixtures of aluminium oxide, copper oxide, and silicon carbide at various nanoparticle volume fractions ranging from 0.0002 to 0.002 in water. The convective heat transfer coefficient was measured at different Reynolds numbers of 10,000–50,000. At these concentrations and Reynolds numbers, a maximum of 11–18% of convection heat transfer coefficient was observed as compared to the base fluid, showing a 6–9% increase on average. In this study, it was observed that changes in the nanoparticle type had no considerable effect on heat transfer coefficient increase. According to the model proposed here, the dimensionless thickness of laminar sub-layer is specified as a functional equation of the volume fraction of nanoparticles for each material. © 2018, Akadémiai Kiadó, Budapest, Hungary.
Journal Of Heat And Mass Transfer Research (23833068)(2)
In this study, the thermal characteristics of turbulent nanofluid flow in a helical tube in the tube heat exchanger (HTTHE) were assessed numerically through computational fluid dynamics (CFD) simulation. The findings of both the turbulent models: realizable k-epsion (kε) and re-normalisation group (RNG) k-epsilon were compared. The temperature distribution contours show that realizable and RNG k-ε models, together with the swirl dominated flow are of more uniform temperature distributions. The proper prediction of two layer theory leads to having a uniform temperature distribution and proper dimensionless wall distance (Y+). The turbulent flow and heat transfer of two nanofluids (SiO2, Al2O3) and base fluid with respect to swirl dominated flow was simulated through the RNG model. The effects of the concentration of nanoparticles on heat transfer characteristics in HTTHE and two turbulent models were analyzed in a comprehensive manner. It is concluded that up to 1% concentration of SiO2 and 1% concentration of Al2O3, similar heat transfer characteristics are observed. Comparison between the CFD results with the predicted values for friction factor coefficient (f) and Nusselt number (Nu) calculated through experimental correlations indicate the maximum errors of 6.56% and 0.27%, respectively. © 2019 Published by Semnan University Press. All rights reserved.
Journal of Petroleum Science and Engineering (09204105)
In this study, the asphaltene particle aggregation process is studied and effects of asphaltene concentration, n-heptane to toluene volume ratio, type and concentration of asphaltene aggregation inhibitor are investigated on onset of precipitation and asphaltene particle size distribution (APSD). The measurement of APSD is performed through dynamic light scattering technique. The results show that the concentration of asphaltene doesn't have significant effect on the onset point; however, it leads to form bigger particles. An increase in n-heptane volume ratio leads to increases the asphaltene particles size where 5% of particles are bigger than 6 μm after 40 min. Dodecyl benzene sulfonic acid component displaces the onset point reasonably and causes 7% rise in the amount of required n-heptane. Dodecyl resorcinol has the best performance at concentration of 50 ppm as an asphaltene dispersant and causes required n-heptane volume increment of 2%. It reduces the asphaltene particles size significantly and delays the asphaltene particles agglomeration process of about 30 min. © 2018 Elsevier B.V.
Heat and Mass Transfer/Waerme- und Stoffuebertragung (09477411)(1)
Nanoparticles suspended in a base fluid yield increased thermal conductivity, which in turn increases convection heat transfer rate. Prediction of suitable relations for determination of thermal conductivity results in heightened accuracy in the calculation of convection heat transfer coefficient and reduced costs. In the majority of studies performed on the prediction of thermal conductivity, some relations and models were used in which the effect of aggregation of particles, especially at low concentrations was ignored. In this research, the thermal conductivity of the nanofluid is measured experimentally at low volumetric concentrations, within the range of 0.02–0.2% for the nanoparticles of Al2O3, MgO, CuO, and SiC in the base fluid of distilled water. The results obtained from the models are compared by the available models considering and neglecting the effect of aggregation of particles. Within the range of the applied concentrations, the relative absolute average deviation ratio of the thermal conductivity models without considering the aggregation effect in relation with the models considering the aggregate, is observed to be between 2 and 6 times. Therefore, it is recommended that even at low concentrations, the effect of aggregation should be considered in the prediction of thermal conductivity. © 2017, Springer-Verlag GmbH Germany.
Journal of the Taiwan Institute of Chemical Engineers (18761070)
This study mainly deals with the adsorption behavior of the graphene oxide (GO) onto sandstone which is an important factor for applying a material in chemical enhanced oil recovery methods. The combined effects of initial GO concentration, salinity and pH of the solution are assessed by adopting response surface methodology. The results show that the GO concentration has a stronger influence on the GO adsorption than those of the initial pH and salinity. The effect of pH on the GO adsorption becomes significant at high GO concentrations and low salinities. The Derjaguin–Landau–Verwey–Overbeek (DLVO) theory is applied to explain the observed trend of GO adsorption under various salinity and pH conditions. Reduction in the height of energy barrier and formation of a secondary minimum are responsible for increasing the GO adsorption at lower pH values and moderate salinities (1 wt.%). The contact angle measurement of the rock surface treated in GO solution at optimum conditions (GO concentration of 0.89 mg/mL, salinity of 5 wt.% and pH of 6.74) shows that the adsorbed GO can alter the wettability of sandstone from strongly oil wet (150°) to intermediate conditions (90°). © 2017 Taiwan Institute of Chemical Engineers
International Journal of Heat and Technology (03928764)(4)
The extent of increase in the convection heat transfer of MgO/water nanofluid was investigated at low concentrations within the range of 0.02 to 0.12 % vol, under turbulent flow and within the Reynolds number range of 11,000 to 49,000. It was found that at about 12 %, the heat transfer coefficient was increased compared with the base fluid, where on average, around 6 % increase was observed within the entire concentration range and the investigated Reynolds number. The aggregate effect of particles was examined in predicting the models for the determination of the physical properties of thermal conductivity and viscosity. It was observed that fractal models enjoy a greater accuracy when compared with other models. In addition, a model was proposed to predict the local heat transfer coefficient, in which the aggregate effect of nanoparticles was also investigated. It was observed that the relative average deviation of the proposed model is around 2.5 %, when compared with experimental values.
Chemical Product and Process Modeling (21946159)(1)
This study presents a numerical simulation through computational fluid dynamics on mixing and flow structures in convergent-divergent micromixer with a triangular obstacle. The main concept in this design is to enhance the interfacial area between the two fluids by creating a transverse flow and split, and recombination of fluids flow due to the presence of obstacles. The effect of triangular obstacle size, the number of units, changing the position of an obstacle in the mixing channel and operational parameter like the Reynolds number on the mixing efficiency and pressure drop are assessed. The results indicate that at inlet Reynolds numbers below 5, the molecular diffusion is the most important mechanism of mixing, and the mixing index is almost the same for all cases. By increasing the inlet Reynolds number above 5, mixing index increases dramatically, due to the secondary flows. Based on the simulation results, due to increasing the effect of dean and separation vortices as well as more recirculation of flow in the side branches and behind the triangular obstacle, the highest mixing index is obtained at the aspect ratio of 2 for the triangular obstacle and its position at the front of the mixing unit. Also the highest value of mixing index is obtained by six unit of mixing chamber. The effect of changing the position of the obstacle in the channel and changing the aspect ratio of the obstacle is evident in high Reynolds numbers. An increase in the Reynolds number in both cases (changing the aspect ratio and position of the obstacle) leads to pressure drop increases. © 2017 by De Gruyter.
Journal of Petroleum Science and Engineering (09204105)
The physico-chemical properties of asphaltene were studied at temperature range of 80–150 °C to optimize asphaltene aggregation and separation from crude oil in the thermal de-asphaltene process without adding n-alkane. The particle size obtained through dynamic light scattering (DLS) indicate that increasing temperature up to 120 °C led to an increase in the physical dimensions of the asphaltene particles, while a decrease in size is noticed at temperatures above 120 °C. The structural molecular parameter of asphaltene indicate that the maximum and minimum aromaticity of asphaltene aggregates occur at 80 and 120 °C, respectively. Increasing the size of the particles and decreasing the aromaticity, as well as raising the efficiency of asphaltene thermal isolation indicate a growth in asphaltene particles at a temperature rise from 80 to 120 °C. All the obtained data suggest an optimal temperature of 120 °C for the thermal de-asphalting of this test sample. The surface morphologies of asphaltene particles at this optimal temperature were assessed by scanning electron microscopy (SEM). © 2016 Elsevier B.V.
Chemical Engineering and Technology (09307516)(2)
A two-dimensional mathematical dynamics model is presented to predict coke formation due to thermal cracking inside the tubes of fired heaters on two types of petroleum fluid. The laminar and turbulent flows are analyzed for both petroleum fluids. The second-order k-ε standard model is adopted to make this mathematical model more accurate than previous models of coke formation. The radial and axial variations for temperature, velocity, and concentration due to the high temperature gradients inside the tubes are considered in the model equations. The finite volume method is the numerical model used to discretize the conservation equations. The proposed model is suitable to predict coke formation inside heater tubes since it indicates operational conditions where coke formation is minimized. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Petroleum Science and Technology (15322459)(7)
The oil content of petroleum wax is an important parameter for evaluating the quality of petroleum waxes. In order to characterize petroleum waxes, the relation between the oil content of waxes and their refractive index is investigated. Sixteen groups of waxes with different amounts of oil content are separated from a special raffinate using crystallization technique with MEK and toluene solvents. A direct measurement of the wax refractive index replaces the oil content evaluation method of petroleum wax. Refractive index is readily measured and is a good indicator of the oil content of petroleum waxes. The results show a linear relation between the oil content of the studied waxes and their refractive indexes. © 2014 Taylor and Francis Group, LLC.
Journal of Dispersion Science and Technology (01932691)(3)
The aggregation coupled sedimentation of asphaltene particles in toluene and heptanes mixture are investigated in the presence of two asphaltene inhibitors including, dodecyle resorcinol (DR) and hazelnut oil. An image processing technique is adopted in the three sections in a settling column setup. The aggregation and sedimentation phenomena are evaluated through a time-driven Monte Carlo (MC) model. The results are in good agreement with the obtained experimental results. The results indicate that in controlling asphaltene sedimentation DR is more effective. The results also revealed that the hazelnut oil has a capacity to inhibit asphaltene sedimentation at high concentration. © 2014 Copyright Taylor & Francis Group, LLC.
An experimental study is conducted to determine the wax deposition potential of three waxy crude oils during laminar flow in a pipeline system. The Taguchi experimental design approach is used to evaluate the influence of important operating factors such as inlet crude oil temperature, temperature difference between the oil and the pipe wall (ΔT), the flow rate of crude oil, wax content and time on wax deposition phenomena. It is found that the parameter ΔT and flow rate have maximum and minimum percentage of contribution on the amount of deposited wax, respectively. The results demonstrate that a waxy crude oil with higher wax content could lead the more deposited solid wax in transportation lines. The differential scanning calorimetry (DSC) analysis showed that wax appearance temperature (WAT) and solid content of the deposit were increased as deposition time increased. © 2012 Elsevier Ltd. All rights reserved.
Journal of Petroleum Science and Engineering (09204105)
In this article the factors affecting two heavy crude oil types in water emulsion viscosity through the Taguchi method are studied. The factors of oil concentration, emulsifier concentration and temperature have the greatest impact on the viscosity of emulsions of the two heavy oil types. With an increase in oil concentration and emulsifier concentration, the viscosity increases, while with an increase in temperature the viscosity decreases. A modified rheological equation is introduced for predicting the viscosity of oil in water emulsion based on the factors affecting viscosity. This equation is developed based on shear rate, oil concentration, emulsifier concentration and temperature. In comparison with the two existing rheological equations this developed equation fits better with viscosity of emulsions of both oil types experimental results. The coefficients of the modified equation give a better estimate of the effects of discussed factors. © 2013 Elsevier B.V.
Journal of Dispersion Science and Technology (15322351)(2)
In this article, the effects of various operating factors on the surface tension, viscosity, and stability of two heavy oil types in water emulsions for pipeline transportation are studied using the Taguchi experimental design approach. The surface tension of heavy crude oil-in-water emulsion is decreased by increasing the emulsifier concentration while the stability of emulsions is increased. The viscosity and stability are increased by an increase in oil content. An increase in the salinity and mixing speed leads to an increase in the stability of emulsion. © 2013 Copyright Taylor and Francis Group, LLC.
Journal of Dispersion Science and Technology (15322351)(4)
The kinetics of asphaltene flocculation are studied on two types of Iranian crude oil. Kinetic studies are conducted by applying near infrared spectrophotometry. The presence of inhibitors in the sample reduces the amount of light absorption of crude oil sample. The effect of these inhibitors according to the initial changes in the light absorption of crude oil samples is studied. The obtained results indicate that the asphaltenes are the highest stabilized in presence of the vegetable oil types (hazelnut and walnut) and chemical compound (4-dodecylresorcinol). © 2013 Copyright Taylor and Francis Group, LLC.
Journal of Dispersion Science and Technology (15322351)(4)
In this article, the aggregation and breakage processes are simulated through Monte Carlo method for asphaltene aggregates under shear-induced petroleum mixtures. The simulation results are verified by the aggregate size distributions of two types of asphaltenes having different fractal dimensions extracted from Iranian crude oil types. The obtained aggregate size distributions are affected by shear rate, toluene to heptane ratios and the oil type. The dynamic evolution of asphaltene aggregates shows an ascendant trend with time until they reach a maximum average diameter and then descent to a steady-state size. The asphaltene fractal dimension affects the aggregation process. © 2013 Copyright Taylor and Francis Group, LLC.
Journal of Dispersion Science and Technology (15322351)(8)
In this article, simultaneous occurrences of aggregation and sedimentation processes of asphaltene particles in toluene and n-heptane mixture are studied. Image processing technique is applied in a settling column setup to evaluate the size distribution evolution at three sections. Each section consists of three distinct zones that are introduced on the aggregate size evolution: the stable, ascending and the descending zones. The effect of the toluene to n-heptane volume ratio (T:H) and the structure of asphaltenes on the size distribution are investigated. The asphaltene aggregates with higher aromaticity factor have more tendencies to aggregate with one another. A time-driven Monte Carlo (MC) model is proposed to predict asphaltene aggregate size distribution during sedimentation in toluene and heptane media. The results of this model are in good agreement with experimental results. By increasing the aggregation probability, the fractal dimension becomes smaller in the simulated case studies. © 2013 Copyright Taylor and Francis Group, LLC.
Journal of Dispersion Science and Technology (15322351)(6)
The use of soluble amphiphiles oil types provide the most practical and economical solution for crude oil treatment in order to control the asphaltene precipitation phenomenon. In this article, the inhibition performance of a number of new chemical additives to asphaltene precipitation is examined on two types of Iranian crude oil. An automatic titration method is used in experimental evaluation. The vegetable oil types (hazelnut, wheat germ, and walnut), organic acids (oleic and linoleic) and chemical additives (4-dodecylresorcinol and benzyl alcohol) displayed the highest capacity to inhibit asphaltene precipitation. A remarkable onset displacement is displayed by dodecyl resorcinol. The results also revealed that the vegetable oil have high potential in delaying asphaltene precipitation. © 2012 Copyright Taylor and Francis Group, LLC.
Journal of Petroleum Science and Engineering (09204105)(3-4)
Asphaltene deposition in oil reservoirs during primary oil recovery and using the enhanced oil recovery methods are complicated and destructive problem with which most of the oil field in worlds has encountered. In this research, the examination of formation damage due to the asphaltene deposition, a four phase black oil model (oil, water, gas, and asphaltene) is developed in combination with proper thermodynamic and deposition models in cylindrical coordinates around a well in a reservoir. Subsequently, this model has been used for examining the effect of well production rate and the initial reservoir permeability on the asphaltene deposition behavior in a typical reservoir during primary production process. The results of model indicate that at a fixed permeability, with increase in the production rate, the amount of asphaltene deposits will increase. However, an increase in the reservoir permeability will decrease the deposition rate because of the existence of further channels for flow. © 2010 Elsevier B.V.
Energy and Fuels (15205029)(2)
new population balance model is developed to predict asphaltene fractal aggregates size distribution. Asphaltene aggregates fractal dimension is increased when shear is induced to them. Fractal dimension evolution is a dynamic process. This model predicts aggregate size distribution more accurately in comparison to a previously proposed model, which considered that aggregates have a constant fractal dimension. The fractal dimension increases from an initial value of 1.6 to final steady-state values. The final value depends upon the shear rate and is described by an exponential function. This function contains some constants that are calculated from experimental data. The asphaltene size distribution of Iranian crude oil asphaltene solutions in mixtures of toluene and n-heptane are predicted by the developed model accurately Copyright © 2010 American Chemical Society.
Energy and Fuels (08870624)(2)
In situ image analyzing measurements are applied in determining the evolution of crude oil asphaltene aggregate size distribution in toluene solutions. The experimental data are compared to the predictions of a population balance model. The effect of different asphaltenes nature on the fractal-like aggregate size is investigated as a function of shear rate and toluene to n-heptane volume ratio. Good agreement is found for the average size evolution of asphaltene aggregate size distribution, assuming a fractal approach for model discretization. Initially, the average-number asphaltene aggregate size increases with time and then beyond a maximum value decreases to an almost constant steady-state size. The aggregates fractal dimension value can strongly affect the evolution kinetics of aggregation. © 2009 American Chemical Society.
Energy and Fuels (08870624)(5)
A population balance model was developed to determine the evolution of crude oil asphaltene aggregate size distribution. The model predictions have good accuracy in comparison with experimental results that were obtained by the image processing method. The fractal nature of asphaltene aggregates was attended assuming fractal dimension equal 1.6. Effects of shear rate, solvent composition, and initial particle size were studied on the evolution of number average diameter. The average diameter of particles reaches a maximum value and then declines to a steady state size. Shear rate and initial average diameter affect the maximum diameter and its time, but initial size has no effect on the steady state size. The combination of the image processing method and fractal approach determines the asphaltene solid content of samples. Asphaltene was extracted from Iranian heavy crude petroleum using toluene and normal heptane. © 2008 American Chemical Society.
Energy Sources (00908312)(1-2)
The precipitation of waxy constituents in petroleum mixtures subjected to a cold environment gives rise to a variety of problems well-known in the petroleum industry. A revised multi-solid phase thermodynamic model for predicting wax precipitation in petroleum mixtures is presented in this article. The Peng-Robinson equation of state is used to evaluate the phase behavior of both liquid and vapor phases. The results predicted by this model agree with the experimental data of wax precipitating for several synthetic oils and crudes.
Energy Sources (00908312)(1-2)
One of the problems faced by the petroleum industry is the wax deposition in pipelines during transportation of waxy crude oil. Oil companies dealing with waxy crude often spend millions of dollars in remedial procedures. An ideal design should use an accurate mathematical model that would include all salient features of wax deposition and waxy crude transport to predict wax deposition during crude oil transportation. In this article, a comprehensive mathematical model, both in laminar and turbulent flow regimes, is developed. The model couples energy equation with deposition and removal kinetics model and thermodynamic model. The k - ε turbulent flow model and energy equation were used to predict velocity and temperature distributions in the turbulent flow regime. Molecular diffusion of wax, as a mechanism of deposition and sloughing effect due to the hydrodynamic forces of fluid on deposited wax, have been considered. Parametric studies on the variation of the amount of wax deposition were performed for a mixture of toluene and oil wax cut in an experimental setup. Overall predictive ability of the proposed model is excellent for the laminar flow. For the turbulent flow regime, no necessary complete experimental data for model were available. Consequently, qualitative results were presented and discussed.
A novel model for predicting wax deposition during turbulent and laminar flow of crude oil was developed. Experiments carried out using a mixture of toluene and an oil wax cut, in a laboratory flow loop, revealed model results on total mass of wax deposition showing a very conformity with experimental findings in the laminar flow regime. Molecular diffusion was the dominant mechanism during laminar flow. Sloughing effect was an important mechanism during wax deposition in the turbulent flow regime that should not be neglected. In the turbulent flow regime, there were critical flow rates for any system containing non-isothermal flow of waxy crude oil. These critical rates depended on the fluid (oil) characterization and pipeline characteristics, as well as operational conditions. Increasing flow rate beyond the critical flow rate decreased the amounts of wax deposit. These trends were similar to what were concluded in other experiments.
One of the problems faced by the petroleum industry is the wax deposition in pipelines during transportation of waxy crude oil. A comprehensive mathematical model for quantitative prediction of wax deposition for a multicomponent hydrocarbons mixture (oil) was developed. Deposition as a function of time was obtained as a solution of differential equations derived from the principles of mass and energy conservation, considering the thermodynamic of phase transition. Experiments were conducted using a mixture of toluene and an oil wax cut, in a laboratory flow loop. Model results on total mass of wax deposition showed conformity with experimental results in the laminar flow regime. These comparisons verified that molecular diffusion is the dominant mechanism during laminar flow.
