The Experts below are selected from a list of 15018 Experts worldwide ranked by ideXlab platform
Zhangxin Chen - One of the best experts on this subject based on the ideXlab platform.
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flow behavior of Gas confined in nanoporous shale at high pressure Real Gas Effect
Fuel, 2017Co-Authors: Zhangxin Chen, Kun Wang, Heng Wang, Shuhua Wang, Xiaohu DongAbstract:Abstract Understanding and controlling the Gas flow at the nanoscale has tremendous implications in the fields of separation science, catalytic reactions, and energy storage, conversion and extraction. However, the Gas flow behavior at the nanoscale is significantly different from that occurring at larger scales. In this work, we focus on a Real Gas Effect, stemming from a strong Gas intermolecular interaction force at high pressure and an un-negligible Gas molecule volume at the nanoscale, on Gas flow through nanoporous shale. An analytical and unified model is developed and validated with the published results of the Lattice-Boltzmann equation and experiments. This unified model covers all Gas flow mechanisms, including viscous flow, slip flow and transition flow, and captures the Real Gas Effect, which enhances flow capacity through nanoporous shale. This unified model is a ready-to-use tool for fast and accurately modeling Gas flow through nanopores, and provides a basic foundation for numerical simulation and production prediction in shale Gas reservoirs.
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a model for multiple transport mechanisms through nanopores of shale Gas reservoirs with Real Gas Effect adsorption mechanic coupling
International Journal of Heat and Mass Transfer, 2016Co-Authors: Zhangxin Chen, Chaohua Guo, Mingzhen WeiAbstract:Abstract Multiple transport mechanisms coexist in nanopores of shale Gas reservoirs with complex pore size distribution and different Gas-storage processes, including continuum flow, slip flow and transition flow of bulk Gas and surface diffusion for adsorbed Gas. The force between Gas molecules and the volume of the Gas molecules themselves cannot be negligible in shale Gas reservoirs with high pressure and nanoscale pores, influences Gas transport and must be taken into account as a Real Gas Effect. During depressurization development of shale Gas reservoirs, the adsorbed Gas desorption and a decrease in an adsorption layer influence Gas transport. Meanwhile, due to the stress dependence, decreases in intrinsic permeability, porosity and a pore diameter also influence Gas transport. In this work, a unified model for Gas transport in organic nanopores of shale Gas reservoirs is presented, accounting for the Effects of coupling the Real Gas Effect, stress dependence and an adsorption layer on Gas transport. This unified model is developed by coupling a bulk Gas transport model and an adsorbed Gas surface diffusion model. The bulk Gas transport model is validated with published molecular simulation data, and the adsorbed Gas surface diffusion model is validated with published experimental data. The results show that (1) in comparison with the previous models, the bulk Gas transport model developed on the basis of a weighted superposition of slip flow and Knudsen diffusion can more reasonably describe bulk Gas transport, (2) surface diffusion is an important transport mechanism, and its contribution cannot be negligible and even dominates in nanopores with less than 2 nm in diameter, and (3) the Effect of stress dependence on fluid flow in shale Gas reservoirs is significantly different from that in conventional Gas reservoirs, and is related to not only the shale matrix mechanical properties and the Effective stress but also the Gas transport mechanisms.
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Real Gas transport through nanopores of varying cross section type and shape in shale Gas reservoirs
Chemical Engineering Journal, 2015Co-Authors: Zhangxin ChenAbstract:Abstract A model for Real Gas transport in nanopores of shale Gas reservoirs (SGRs) was proposed on the basis of the weighted superposition of slip flow and Knudsen diffusion, where the ratios of the intermolecular collisions and the molecule–nanopore wall collisions to the total collisions are the weighted factors of slip flow and Knudsen diffusion, respectively. The present model takes account of slip Effect and Real Gas Effect, additionally, the Effects of cross-section type and its shape of nanopores on Gas transport are also considered in this paper. The present model is successfully validated against existing molecular simulation data collected from different sources in literature. The results show: (1) the present model is reasonable to describe all of the Gas transport mechanisms known, including continuum flow, slip flow and transition flow in nanopores of SGRs; (2) the cross-section type and shape of nanopores both affect Gas transport capacity: at the same cross-sectional area, Gas transport capacity of nanopores with a circular cross section is greater than that with a rectangular cross section, and Gas transport capacity of nanopores with a rectangular cross section decreases with an increasing aspect ratio; compared to the cross-section type, the Effect of the cross-section shape on Gas transport capacity is stronger; (3) a Real Gas Effect improves Gas transport capacity, which becomes more obvious with an increasing pressure and a decreasing pore size; (4) and compared to nanopores with a circular cross section, the Effect of Real Gas Effect on Gas transport capacity of nanopores with a rectangular cross section is stronger, and the Effect increases with an increasing aspect ratio. The proposed model can provide some theoretical support in numerical simulation of reservoir behavior in SGRs.
Daniel Favra - One of the best experts on this subject based on the ideXlab platform.
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the Effect of Real Gas on the properties of herringbone grooved journal bearings
Tribology International, 2010Co-Authors: Jurg Alexande Schiffma, Daniel FavraAbstract:Driven by applications using herringbone grooved bearings lubricated with a Gas operating under conditions where the perfect Gas assumption is not valid, the Real Gas Effect has been introduced into the existing narrow groove theory. The enhanced model has been linked to a rotordynamic code and to a multi-objective optimizer resulting in optimum bearing geometries that differ from the ones under the perfect Gas assumption. It is suggested that rotors on bearings that have been optimized under the perfect Gas assumption may get unstable if they are submitted to a lubricant that operates close to the saturation line.
Jianfei Zhang - One of the best experts on this subject based on the ideXlab platform.
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an analytical model for shale Gas transport in kerogen nanopores coupled with Real Gas Effect and surface diffusion
Fuel, 2017Co-Authors: Ying Yin, Jianfei ZhangAbstract:Abstract Understanding the behavior of shale Gas transport in kerogen is a key issue in predicting Gas production. The reservoir structure is characterized by widespread micro/nanoscale pores, various occurrence states, and typical high pressure. An analytical model is proposed to Effectively reveal the Gas transport behavior in kerogen nanopores. The model can fully consider the Real Gas Effect, Gas slippage, and surface diffusion derived from absorbed Gas. In particular, a method based on dense Gas theory with the Redlich–Kwong equation of state is used to acquire the viscosity of shale Gas under high pressure. The second-order slippage boundary condition coupled with surface diffusion is presented to describe the free Gas slippage, and Langmuir isotherm theory and Fick’s law are adopted to calculate the surface diffusion. The Real Gas Effect has a significant Effect on the physical properties of methane, Knudsen number, and the flow behaviors of free Gas and adsorbed Gas. The surface diffusion velocity can enhance the free Gas flow. The mass flow rate of total adsorbed Gas increases as pore size increases, and its major influence is obtained from the induced free Gas at the increased pore size. The slippage Effect is reduced as the pressure increases and the temperature decreases. The absorbed Gas comprises a substantial proportion of the total Gas produced when the pore size is less than 2 nm. The combined influences of slippage Effect and absorbed Gas cannot be ignored when the pore size is less than 10 nm. This work provides a comprehensive and theoretical guidance for the Effective development of shale Gas.
Xiaohu Dong - One of the best experts on this subject based on the ideXlab platform.
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flow behavior of Gas confined in nanoporous shale at high pressure Real Gas Effect
Fuel, 2017Co-Authors: Zhangxin Chen, Kun Wang, Heng Wang, Shuhua Wang, Xiaohu DongAbstract:Abstract Understanding and controlling the Gas flow at the nanoscale has tremendous implications in the fields of separation science, catalytic reactions, and energy storage, conversion and extraction. However, the Gas flow behavior at the nanoscale is significantly different from that occurring at larger scales. In this work, we focus on a Real Gas Effect, stemming from a strong Gas intermolecular interaction force at high pressure and an un-negligible Gas molecule volume at the nanoscale, on Gas flow through nanoporous shale. An analytical and unified model is developed and validated with the published results of the Lattice-Boltzmann equation and experiments. This unified model covers all Gas flow mechanisms, including viscous flow, slip flow and transition flow, and captures the Real Gas Effect, which enhances flow capacity through nanoporous shale. This unified model is a ready-to-use tool for fast and accurately modeling Gas flow through nanopores, and provides a basic foundation for numerical simulation and production prediction in shale Gas reservoirs.
Costante Mario Invernizzi - One of the best experts on this subject based on the ideXlab platform.
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the role of Real Gas brayton cycles for the use of liquid natural Gas physical exergy
Applied Thermal Engineering, 2011Co-Authors: G Angelino, Costante Mario InvernizziAbstract:Abstract When using the cooling capacity of LNG several thermodynamic schemes are proposable employing conventional and non conventional conversion cycles. All conventional systems make use of organic working fluids such as methane or propane in series of Rankine cycles used in a cascading mode. A simpler system is available, using a single cycle and a single fluid in a Brayton cycle. However ordinary Brayton cycles exhibit a modest efficiency. Resorting to Brayton cycles with strong Real Gas Effects (which is possible selecting the base parameters of pressure and temperature in the vicinity of the critical point) improves considerable cycle performance. Since the level of cold in a LNG flow is thermodynamically predetermined, working fluids must be selected with a critical point which fit the LNG thermal capacity, i.e. some 5–15 C higher than the usual LNG temperature which is around −160 °C. Nitrogen was found as the best fluid to exploit Real Gas Effects with efficiencies above 63% while perfect Gas cycles give efficiencies around 56%. However, in Real Gas cycles the cooling capacity of LNG is only partially exploited: a better exploitation is obtained from perfect Gas cycles or for more complex cascading Rankine cycle. Selecting working fluids with a higher critical temperature than nitrogen, as for example argon, the efficiency decreases to 58% respect to 63% for nitrogen, but the utilization of the cold of LNG improves from 0.30 MW/(kg/s) to 0.75 MW/(kg/s). Obviously as heat rejection temperature increases a larger fraction of cold in the LNG flow can be utilized. Combined cycles making use of a Gas turbine offer also a good performance. The merits of Real Gas Effect Brayton cycles also in this case remains evident. Finally, it is theoretically possible to use Real Gas Effect Brayton cycles at low temperatures, which are typical of waste heat (say 100–150 °C: in this case cycle efficiency remain good, but power obtainable from a unit flow of LNG is modest.
