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As a compound multi-phase dispersion system, nanofluids can enhance the energy transfer performance of solutions and are considered to be effective in promoting the formation of hydrates. Hence, in this study, a compound system of SiO2 nanofluid and sodium dodecyl sulfate (SDS) solution at 6 MPa and 275.15 K was used to study the effects of Cu and SiO2 nanofluids on CH4 hydrate formation at different concentrations, and the results were compared. The results showed that the Cu nanofluids promoted the formation of natural gas hydrates. At lower Cu nanofluid concentrations, the gas storage capacity of the hydrates increased with increasing Cu nanofluid concentration. At a concentration of 2200 ppm, the gas storage capacity reached 111.57 Vg/Vw. However, the SiO2 nanofluid only promoted the formation of hydrates at lower concentrations. The gas storage capacity reached 108.26 Vg/Vw at a concentration of 800 ppm. As the concentration of the SiO2 nanofluid increased, the gas storage capacity of the hydrates gradually decreased, and hydrate formation was eventually inhibited. Therefore, reasonable selection of the type and concentration of nanofluids is required to improve the gas storage capacity of hydrates. [ABSTRACT FROM AUTHOR]

Research shows that the viscosity greatly reduction of viscous crude oil can improve the exploitation and promote the fluidity. We studied the effects and the mechanism of viscosity reduction of viscous crude oil emulsion after introducing the ternary compound of sulfonate-straight chain alcohol-alkaline as the viscosity reducer. Results showed that the best emulsifying performance can be achieved using 5% 1-pentanol. 0.2% of Na2CO3 and DEA shows the strongest emulsification ability of the O/W emulsion. The use of AOS, straight chain alcohol and petroleum carboxylate resolves diffusion on the oil-water interface, which can form a dense surfactant of single molecular layer to reduce the interfacial tension and prevent the phase change of the emulsification. When the mass fraction of AOS, Na2CO3, DEA and 1-pentanol were 0.2%, 0.25%, 0.2% and 5% respectively, the viscous crude oil would achieve the best effect of viscosity reduction. [ABSTRACT FROM AUTHOR]

In order to investigate the effect of different nonionic surfactants on hydrate formation in oil-water emulsion systems, the hydrate formation experiments were carried out in a diesel water-in-oil emulsion system with a water cut of 40% using nonionic surfactants such as Span80, Tween80, Span20 and Tween20, respectively. The results show that under the experimental conditions of 275 K and 7 MPa, a certain concentration of nonionic surfactant can promote the growth of hydrates in diesel emulsion systems, shorten the hydration reaction time, and have a significant effect on the improvement of gas storage density. The combination of Span80 and Tween80 in a mass ratio of 1:1 was the most effective in promoting the formation of hydrate in the emulsion system. When the mass fraction was 0.5%, the hydration reaction time was the shortest and the hydrate gas storage density was the highest. Due to the addition of the nonionic surfactant, a stable interfacial film and interfacial charge are formed around the water droplets of the emulsion system, making it difficult for the droplets to approach and polymerize, which maintains the stability of the water-in-oil emulsion system and has great reference value for the study of hydrate storage and transportation. [ABSTRACT FROM AUTHOR]

Boundary element method (BEM) is introduced to calculate the heavy oil seepage in this paper. The pressure contours with different temperatures and arbitrary oil reservoir shapes are obtained by solving the variable coefficients Darcy’s equations. The numerical simulation results indicate that temperature has evident effect on pressure contours when the pressure is lower. Varieties of pressure contours with different boundary conditions coincide well with the heavy oil seepage law, which indicates the validity and accuracy of BEM in dealing with the irregular boundary problem. The numerical simulation results can provide theoretical basis for the heavy oil well pattern. [ABSTRACT FROM AUTHOR]

In recent years, gas–liquid membrane contactors have attracted increasing attention. A membrane contactor is a device that realizes gas–liquid or liquid–liquid mass transfer without being dispersed in another phase. The membrane gas absorption method combines the advantages of chemical absorption and membrane separation, in addition to exhibiting high selectivity, modularity, and compactness. This paper introduces the operating principle and wetting mechanism of hollow membrane contactors, shows the latest research progress of membrane contactors in gas separation, especially for the removal of carbon dioxide from gas mixtures by membrane contactors, and summarizes the main aspects of membrane materials, absorbents, and membrane contactor structures. Furthermore, recommendations are provided for the existing deficiencies or unsolved problems (such as membrane wetting), and the status and progress of membrane contactors are discussed. [ABSTRACT FROM AUTHOR]

It is great significant to explore the changes of compressor performance for hydrogen transportation. We found that a Gray-RBF neural network prediction model improved prediction accuracy. The prediction error of the model is 2.34 % by data verification. It was found that the hydrogen blending ratio was increased from 0 % to 30 %, the pipeline transmission power was reduced by 9.3 %. Simultaneously injecting hydrogen to natural gas causes the performance curve of the compressor to shift downwards. The pressure ratio decreases by 18.9 % and shaft power decreases by 28.6 % when the hydrogen blending ratio increases from 0 % to 30 %. The injection of hydrogen to natural gas causes the surge range of the compressor to increase, so the stable range to narrow. In general, this research may provide reference and guidance for the transportation research of hydrogen blended natural gas and compressor operation about gas industry. [Display omitted] • Creating a combination model improved the accuracy of performance prediction. • Injecting hydrogen into natural gas reduced the power of pipeline gas transmission. • Enlarging initial pressure caused the gas transmission power increase. • Injecting hydrogen into natural gas caused decreases of compressor performance curves. • Injecting hydrogen into natural gas increased the surge range of the compressor. [ABSTRACT FROM AUTHOR]

This paper designs and investigates a novel combined cooling, heating, and power (CCHP) system for effectively utilizing liquefied natural gas (LNG) cold energy and waste heat of exhaust gas based on thermodynamic, exergoeconomic and exergoenvironmental analysis. The effects of the mass flow rate of the ORC-I's working fluid, turbine 1 inlet temperature, compressor and pump outlet pressure and the turbines' isentropic efficiency on the system performance were investigated. In addition, the non-dominated sorting genetic algorithm II (NSGA-II) and the particle swarm optimization (PSO) were employed to optimize the CCHP system with multiple objectives, respectively, to find the optimal operating conditions of the system. The optimization results showed PSO was superior for the multi-objective optimization of this novel CCHP system compared to NSGA-II, showing the exergy efficiency, product unit cost and product unit environmental impact of 70.20%, 21.50 $/GJ and 57.91 mPts/GJ, respectively. • Proposed a novel combined cooling, heating and power system. • Evaluated the economic performance from exergoeconomic viewpoint. • Evaluated the environmental influence from exergoenvironmental viewpoint. • Performed multi-objective optimization of the proposed system using two algorithms. [ABSTRACT FROM AUTHOR]

The application of existing gas transmission pipelines to deliver hydrogen-blended natural gas is the most operable method among many delivery methods. Hydrogen-blended natural gas with different hydrogen-blending ratios after passing through the throttling element is not the same. Using FLUENT to analyze the temperature variation after the Joule–Thomson effect for 0%, 5%, 10%, 20%, and 30% hydrogen mixing ratios. Workbench is used to analyze the soil temperature field around the pipeline and the stress displacement of the buried pipeline in the permafrost zone under different hydrogen mixing ratios. The analysis revealed that as the hydrogen mixing ratio increases, the temperature of the same point gradually increases after the Joule–Thomson effect, the low-temperature area around the buried pipe is gradually replaced by the high-temperature area, and the stress of the buried straight pipe also gradually decreases; while the maximum stress of the pipe initially decreases and then increases, and the displacement has no obvious change. Buried pipelines, which are generally accepted worldwide as one of the many forms of natural gas transmission, pass through permafrost areas during their laying, thus triggering freeze-ups and posing a potential hazard to the safe transportation of natural gas. Most of the existing methods to solve the frozen rise of buried pipelines in the permafrost zone have problems of high energy consumption and construction difficulties. Therefore, this paper, combined with the current trend of vigorous development of hydrogen-blending natural gas projects around the world, proposes a method to alleviate the purpose of freeze-ups by inputting a reasonable hydrogen-blending ratio before the regulator through the negative Joule–Thomson effect of hydrogen and using the phenomenon of temperature rise along the pipeline after the hydrogen passes through the regulator to neutralize the temperature drop of pure natural gas. In this paper, we applied finite element analysis software to simulate the effect of five mixing ratios of hydrogen gas, such as 0%, 5%, 10%, 20%, and 30%, on buried pipelines and also selected 0%–5% as the best mixing ratio to relieve freezing under the working conditions of the simulation environment. The feasibility of delivering hydrogen-blended natural gas at appropriate blending ratios to mitigate freeze-ups in buried pipelines in permafrost areas is demonstrated. It provides a new method for freeze-rise mitigation measures at gas transmission sites. [ABSTRACT FROM AUTHOR]

The phase equilibrium conditions of methane hydrate, particularly the phase equilibrium pressure, are influenced by capillary pressure. In this study, the existing model for phase equilibrium pressure is enhanced, and a novel methane hydrate dissociation model is formulated by integrating it with the established hydrate dissociation model. A numerical simulation is conducted on experimental research, and the reliability of the model is validated through comparison with experimental data, yielding consistent results. The significance and necessity of considering capillary pressure between hydrate and water in the exploration of methane hydrate dissociation in micropores are elucidated. The proposed model is employed to further elucidate the evolution of various factors such as methane generation rate, phase distribution, temperature distribution, and phase equilibrium pressure distribution. The findings underscore the critical role of capillary pressure between hydrates and water, emphasizing its substantial impact on the accuracy of hydrate dissociation models. Specifically, the cumulative gas production and methane generation rate values obtained are relatively diminished when neglecting capillary pressure between hydrate and water. Capillary pressure, hydrate dissociation effects, and the coupled effect of interphase heat transfer collectively influence the distribution of phase equilibrium pressure, methane generation rate, phase distribution, temperature distribution, and phase equilibrium pressure distribution. Capillary pressure elevates the phase equilibrium pressure of hydrate, augments the driving force for hydrate dissociation, and accelerates the dissociation process. • Hydrate dissociation model is proposed based on an improved phase equilibrium model. • Significance and necessity of considering capillary pressure are elucidated. • Coupling effects of capillary pressure and hydrate dissociation are studied. • Capillary pressure raises hydrate phase equilibrium pressure and dissociation rate. [ABSTRACT FROM AUTHOR]

Although gas hydrate is an excellent clean fuel and energy storage form, its natural generation rate is very slow. The key to accelerate the industrialization is to find an appropriate promotion method. In this paper, Span80 and Tween80 were used to study the rapid formation technology of hydrate in diesel water-in-oil emulsion at 275.15 K and 7 MPa. Firstly, hydrate formation in different water cut systems was studied. Results show that hydrate with higher water cut has a faster formation rate and a higher gas storage density, and the system has the shortest induction time with a 40% water cut. The addition of PEG400 and SDS to the original emulsion system resulted in higher gas densities and denser hydrates. Moreover, the addition of emulsifier can reduce the interfacial energy and form a stable interface membrane. Gas storage density also reflects the same phenomenon. Finally, the double electron layer structure formed by different charged ions can also make the emulsion system more stable and promote hydrate formation. Hydrate can be rapidly formed in the diesel water-in-oil emulsion system, which has a great reference value for the future hydrate storage and transportation. [ABSTRACT FROM AUTHOR]

Management becomes more challenging as machinery becomes more widely used. From the health management history case records of mechanical devices, we can find that there are many health problems of the same type occurring repeatedly, but when similar problems occur again, solutions are not found in a short period. Case-based reasoning technology aimed at solving the above problems are widely used in equipment health management, but there are problems such as inadequate data utilization and failure to achieve the required accuracy and reliability. To uncover important information from historical failure case data and help reduce equipment downtime due to failure, this paper proposes a machinery equipment health management method based on improved intuitionistic fuzzy entropy and case reasoning technology. Firstly, the axiomatic definition of traditional intuitionistic fuzzy entropy is optimized and a new intuitionistic fuzzy entropy formula in the framework of case-based reasoning decision matrix is proposed. Secondly, the weight value of each attribute is obtained by combining the formula of the entropy weight method. Finally, the feature attribute weight values are fused into the case-based reasoning, and the historical cases that are most similar to the target cases are obtained by combining the existing case base. The effectiveness of the method was verified by comparing and analyzing the example calculation results with the traditional method. The method improves the management of machinery equipment operation and maintenance data. Furthermore, it helps enterprises to carry out the management and analysis of machinery equipment health problems. • This method applies the idle historical fault case data in the enterprise to play its maximum role. • Improved the axiomatic definition of intuitionistic fuzzy entropy. • Based on the improved definition, a new intuitionistic fuzzy entropy calculation formula is proposed. • Introduce weights into case reasoning technology for calculation. • The accuracy of the results of this method is significantly improved compared with other methods at this stage. [ABSTRACT FROM AUTHOR]

• Proposed a novel combined cooling, heating, and power system. • Applied exergoeconomic analysis to evaluate the economic performance. • Used multi-objective optimization to find the optimal working conditions. • Exhibited an exergy efficiency of 80.49% and a product unit cost of 48.04 $/GJ. With the increase of liquified natural gas trade, more and more attention has been paid to the liquified natural gas cold energy utilization. In order to better recover and utilize liquified natural gas cold energy, a novel combined cooling, heating and power system based on liquified natural gas cold energy utilization and exhaust gas waste heat recovery is proposed in this paper. The system consists of a three-stage organic Rankine cycle, a Kalina cycle and liquified natural gas direct expansion. To evaluate the performance of the combined cooling, heating and power system, a mathematical model was established, and through the thermodynamic analysis the net output power, thermal efficiency, and exergy efficiency of the system were 1257.708 kW, 43.43%, and 70.4%, respectively. The effects of the pump and compressor outlet pressure, n -hexane mass flow rate in the first Rankine cycle, turbine inlet temperature, and isentropic efficiency of the turbines on the system performance were analyzed. Moreover, exergoeconomic analysis is used to calculate the total product unit cost of the combined cooling, heating and power system, which was found to be 51.1 $/GJ. In addition, single- and multi-objective optimizations of the system were performed. The multi-objective optimization results show that the maximum exergy efficiency and minimum total product unit cost of this novel combined cooling, heating and power system were 80.49% and 48.04 $/GJ, respectively. This work shows a great potential in utilizing the liquified natural gas cold energy and waste heat of exhaust gas by a combined cooling, heating and power system. [ABSTRACT FROM AUTHOR]

After over 20 years of development in Daqingzijiang Oilfield, isolated sand bodies under the delta front and pro-delta in the Qingshankou Formation(qn)have become important oil and gas reservoir bodies. However, the cause for large amounts of isolated bar sand bodies in the lake-basin delta sediment system has not been reported in China. This article, through core observation, reveals plenty of evidence that there storm waves once existed. Combined with paleogeography and hydrodynamic force analysis, it describes the transformation effect of waves on delta sand bodies and on the formation mechanism of bar sand bodies. Based on a study on paleogeomorphology and the statistics of sand body distribution, we consider 'Storm waves conveying sand' and 'landform controlling sand' as the cause and distribution model of the delta's isolated bar sand body formation. We also think that the superposition of multiple bar sand bodies is the direct cause of the strong anisotropy in reservoirs and the complex relationship between oil and water in reservoirs. Most of these sand bodies have formed into lenticular lithologic hydrocarbon accumulations. On the basis of this integrated study on hydrocarbon accumulation, we set up an accumulation model of lenticular hydrocarbon accumulation involving the variables 'Surrounded by source rocks to generate hydrocarbon', 'Driven by pressure difference', 'Migration through multi pathways' and 'Accumulation by filtering water'. [ABSTRACT FROM AUTHOR]