The Experts below are selected from a list of 61131 Experts worldwide ranked by ideXlab platform
Philippe Coussot - One of the best experts on this subject based on the ideXlab platform.
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Yield Stress and Minimum Pressure for Simulating the Flow Restart of a Waxy Crude Oil Pipeline
Energy and Fuels, 2016Co-Authors: Rafael Mendes, Guillaume Vinay, Philippe CoussotAbstract:Waxy crude Oils are likely to develop a yield stress when cooled to a temperature below its wax appearance temperature. In a subsea pipeline, when the flow stops and the Oil cools down, a minimum differential pressure is required to restart the flow. In order to estimate that pressure, it is crucial knowing the yield stress distribution in the pipe at restart time. However, the yield stress of waxy crude Oils depends on the histories of shear and temperature experienced by the Oil. In this paper, we present the parameters that play a major role on the yield stress determination by measuring creep tests in different conditions. For the analyzed Oil Sample, final temperature and shear while cooling are the most important yield stress parameters. Based on those results, we introduce a correlation between the Oil cooling conditions and its yield stress at low temperature. Then, by calculating the Oil cooling history during steady-state flow and cool-down time at rest, it is possible to correlate those histories to the yield stress developed by the Oil. That is an essential information for calculating the minimum flow restart pressure. Here, 2D axisymmetric calculations were performed. Results for a given Oil Sample show that at restart time the Oil-gel is likely to break at the wall, concentrating shear at that region and forming a plug flow with unsheared material at the center of the pipe.
Nagi Nagarajan - One of the best experts on this subject based on the ideXlab platform.
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prediction of the wax content of the incipient wax Oil gel in a pipeline an application of the controlled stress rheometer
Journal of Rheology, 1999Co-Authors: Probjot Singh, Scott H Fogler, Nagi NagarajanAbstract:High molecular weight paraffins are known to form gels of complex morphology at low temperatures due to the low solubility of these compounds in aromatic or naphthene-base Oil solvents. The characteristics of these gels are strong functions of the shear and thermal histories of these Samples. A model system of wax and Oil was used to understand the gelation process of these mixtures. A significant depression in the gel point of a wax-Oil Sample was observed by either decreasing the cooling rate or increasing the steady shear stress. The wax-Oil Sample separates into two layers of different characteristics, a gel-like layer and a liquid-like layer, when sheared with a controlled-stress rheometer at high steady shear stresses and low cooling rates. The phase diagram of the model wax-Oil system, obtained using a controlled-stress rheometer, was verified by analyzing the wax content of the incipient gel deposits formed on the wall of a flow loop. Based on the rheological measurements, a law has been suggested for the prediction of the wax content of the gel deposit on the laboratory flow loop walls. The wax content of the incipient gel formed on the wall of a field subsea pipeline was predicted to be much higher than that for the flow loop at similar operating conditions. This variation in the gel deposit characteristics is due to the significant differences in the cooling histories in the two cases.
Rafael Mendes - One of the best experts on this subject based on the ideXlab platform.
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Yield Stress and Minimum Pressure for Simulating the Flow Restart of a Waxy Crude Oil Pipeline
Energy and Fuels, 2016Co-Authors: Rafael Mendes, Guillaume Vinay, Philippe CoussotAbstract:Waxy crude Oils are likely to develop a yield stress when cooled to a temperature below its wax appearance temperature. In a subsea pipeline, when the flow stops and the Oil cools down, a minimum differential pressure is required to restart the flow. In order to estimate that pressure, it is crucial knowing the yield stress distribution in the pipe at restart time. However, the yield stress of waxy crude Oils depends on the histories of shear and temperature experienced by the Oil. In this paper, we present the parameters that play a major role on the yield stress determination by measuring creep tests in different conditions. For the analyzed Oil Sample, final temperature and shear while cooling are the most important yield stress parameters. Based on those results, we introduce a correlation between the Oil cooling conditions and its yield stress at low temperature. Then, by calculating the Oil cooling history during steady-state flow and cool-down time at rest, it is possible to correlate those histories to the yield stress developed by the Oil. That is an essential information for calculating the minimum flow restart pressure. Here, 2D axisymmetric calculations were performed. Results for a given Oil Sample show that at restart time the Oil-gel is likely to break at the wall, concentrating shear at that region and forming a plug flow with unsheared material at the center of the pipe.
Reza Farhoosh - One of the best experts on this subject based on the ideXlab platform.
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The Effect of Operational Parameters of the Rancimat Method on the Determination of the Oxidative Stability Measures and Shelf-Life Prediction of Soybean Oil
Journal of the American Oil Chemists' Society, 2007Co-Authors: Reza FarhooshAbstract:Operational parameters of the Rancimat method, including Oil Sample size, airflow rate, and temperature, were evaluated to determine their effects on the oxidative stability index (OSI), temperature coefficient, Q _10 number, and shelf-life prediction for soybean Oil. Operational parameters of the Rancimat method had statistically significant effects ( P
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the effect of operational parameters of the rancimat method on the determination of the oxidative stability measures and shelf life prediction of soybean Oil
Journal of the American Oil Chemists' Society, 2007Co-Authors: Reza FarhooshAbstract:Operational parameters of the Rancimat method, including Oil Sample size, airflow rate, and temperature, were evaluated to determine their effects on the oxidative stability index (OSI), temperature coefficient, Q 10 number, and shelf-life prediction for soybean Oil. Operational parameters of the Rancimat method had statistically significant effects (P < 0.05) on the OSI. Whenever the Oil Sample size and airflow rate at a given temperature were such that the air-saturated condition could be established, the OSIs showed no statistically significant differences. As temperature increased, OSIs decreased, while their average coefficient of variation (CV) increased. In general, the conditions where the Sample was saturated with air and had a relatively lower CV were an Oil Sample size of 6 g at all temperatures and airflow rates, then 3-g Oil Sample size at low temperatures (100 and 110 °C) and low airflow rates (10 and 15 L h−1). The temperature coefficient and Q 10 number were found to be independent of the Oil Sample size and airflow rate, and their mean values for soybean Oil were calculated to be −3.12 × 10−2 °C−1 and 2.05, respectively. Oil Sample size and airflow rate showed a significant effect on shelf-life prediction for soybean Oil. Therefore, choosing the right levels of these operational parameters in the Rancimat method may produce the least possible difference between predictions from long-term storage studies and the OSI test.
Jing Liu - One of the best experts on this subject based on the ideXlab platform.
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Mechanism of Ultrasonic Physical-Chemical Viscosity Reduction for Different Heavy Oils.
ACS omega, 2021Co-Authors: Jing Liu, Fukang Yang, Junyong XiaAbstract:In this study, the mechanism of physical-chemical viscosity reduction of different heavy Oils under ultrasonic wave is explored. Experiments of viscosity reduction and viscosity recovery of different heavy Oils under ultrasonic excitation were carried out, and the optimal ultrasonic parameters, ultrasonic physical disturbance, and cavitation viscosity reduction extent of different Oil Samples were determined. Based on the element analysis methods, four-component analysis, gas chromatography analysis, and formation water pH value test, the micro-mechanism of the Oil chemical structure change and water Samples under ultrasonic wave was analyzed. The results show that the water content, temperature, and initial viscosity of heavy Oil are the key to reduce the viscosity of heavy Oil. The higher viscosity of the initial Oil Sample, the higher water content, and the temperature were needed. Compared with the lower viscosity Oil Sample, the higher viscosity Oil Sample has higher extent of cavitation viscosity reduction and lower extent of physical disturbance viscosity reduction under ultrasonic wave. After ultrasonic treatment, the contents of heteroatoms, resins, and asphaltenes in heavy Oil Samples with high viscosity decreased significantly, and the conversion extent of high carbon chain to low carbon chain was greater. In addition, the pH of water in heavy Oils decreased after ultrasonic treatment, and the pH of water in high viscosity heavy Oil decreased more significantly after ultrasonic treatment.
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Mechanism of Ultrasonic Physical–Chemical Viscosity Reduction for Different Heavy Oils
ACS omega, 2021Co-Authors: Jing Liu, Fukang Yang, Xia JunyongAbstract:In this study, the mechanism of physical-chemical viscosity reduction of different heavy Oils under ultrasonic wave is explored. Experiments of viscosity reduction and viscosity recovery of different heavy Oils under ultrasonic excitation were carried out, and the optimal ultrasonic parameters, ultrasonic physical disturbance, and cavitation viscosity reduction extent of different Oil Samples were determined. Based on the element analysis methods, four-component analysis, gas chromatography analysis, and formation water pH value test, the micro-mechanism of the Oil chemical structure change and water Samples under ultrasonic wave was analyzed. The results show that the water content, temperature, and initial viscosity of heavy Oil are the key to reduce the viscosity of heavy Oil. The higher viscosity of the initial Oil Sample, the higher water content, and the temperature were needed. Compared with the lower viscosity Oil Sample, the higher viscosity Oil Sample has higher extent of cavitation viscosity reduction and lower extent of physical disturbance viscosity reduction under ultrasonic wave. After ultrasonic treatment, the contents of heteroatoms, resins, and asphaltenes in heavy Oil Samples with high viscosity decreased significantly, and the conversion extent of high carbon chain to low carbon chain was greater. In addition, the pH of water in heavy Oils decreased after ultrasonic treatment, and the pH of water in high viscosity heavy Oil decreased more significantly after ultrasonic treatment.
