Gas Transport in Shale Nanopores with Miscible Zone

Based on the results of molecular dynamics simulation, in a gas-water miscible zone, the velocity profiles of the flowing water film do not increase monotonously but increase first and then decrease, which is due to the interaction between water and gas molecules. This exhibits a new physical mechanism. In this paper, we firstly propose a gas-water flow model that takes into account the new physical phenomena and describes the distribution of gas-water velocity in the whole pore more accurately. In this model, a decreasing factor for water film in the gas-water miscible zone is used to describe the decrease of water velocity in the gas-water miscible zone, which leads to the gas velocity decrease correspondingly. The new flow model considers the interaction among gas and water molecules in the miscible zone and can provide more accurate velocity profiles compared with the flow models not considering the miscible region. Comparison calculation shows that the previous model overestimates the flow velocity, and the overestimation increases with the decrease of the pore radius. Based on the new gas-water flow model, a new permeability correction factor is deduced to consider the interaction among gas and water molecules.

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Enhanced Mechanism of Water Evaporation Through Nanoporous Membrane

ASME 2021 Heat Transfer Summer Conference ◽

10.1115/ht2021-61719 ◽

2021 ◽

Author(s):

Runkeng Liu ◽

Zhenyu Liu

Keyword(s):

Water Film ◽

Dynamics Simulation ◽

Natural Phenomenon ◽

Water Evaporation ◽

Water Molecules ◽

Multilayer Graphene ◽

Evaporation Process ◽

Research Attention ◽

Nanoporous Membrane ◽

Film Evaporation

Abstract Evaporation through nanoporous membrane has attracted tremendous research attention as a ubiquitous natural phenomenon, which can be used in numerous applications. In this work, we explored the ultrathin water film evaporation process on nanoporous membrane based on non-equilibrium molecular dynamics simulation. A heat localization design of multilayer graphene coated at the bottom of membrane was implemented to reduce the heat loss along the non-evaporation direction. The underlying mechanism of water evaporation through nanoporous membrane was investigated after analysis of the average number of hydrogen bonds per water molecule, the temperature variation and the mean squared displacement of water molecular during the evaporation process. The results showed that the change of pore size will affect the water molecules structure. We also discussed the effect of heat localization design on ultrathin water film evaporation process. The result suggested that water molecules are more active and evaporation efficiency is improved correspondingly. This work reveals the feasibility of the novel nanoporous membrane structure design for enhancing heat and mass transfer, which can be adopted in efficient thermal management and low-cost approaches for water desalination.

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Understanding the Physical Phenomena of Pipeline Decompression

Volume 2: Integrity and Corrosion; Offshore Issues; Pipeline Automation and Measurement; Rotating Equipment ◽

10.1115/ipc2000-249 ◽

2000 ◽

Author(s):

X. L. Zhou ◽

R. G. Moore ◽

G. G. King

Keyword(s):

Heat Transfer ◽

Flow Model ◽

Fluid Phase ◽

Heat Transfer Fluid ◽

Complete Understanding ◽

Flow Models ◽

Complex Process ◽

Flow Phenomena ◽

Physical Phenomena ◽

Fluid Characteristics

Pipeline decompression is an important aspect of risk assessment during the design and operation of high-pressure gas transmission pipelines. As numerical simulation technology improves, more sophisticated multiphase decompression flow models are emerging. A complete understanding of physical phenomena occurring during rapid pipeline decompression is essential in developing an accurate, advanced and fundamentally sound multiphase flow model. Pipeline decompression is a complex process that involves many thermodynamic and hydrodynamic non-equilibrium phenomena that govern the characteristics of fluid flow in the pipe. It is affected by parameters such as pipeline geometry, heat transfer, fluid characteristics, and various interactions between them. In this paper, we describe and discuss the pipeline decompression process, critical flow phenomena, fluid phase behavior, thermodynamic and hydrodynamic non-equilibria, characteristics of fluid mechanics, heat transfer and pipeline mechanics. Hopefully, this will enhance understandings of the predictive capabilities and limitations of various types of pipeline decompression models currently used for this process.

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Molecular Simulation on Explosive Boiling of Water on a Hot Copper Plate

Volume 1: Heat Transfer in Energy Systems; Thermophysical Properties; Theory and Fundamental Research in Heat Transfer ◽

10.1115/ht2013-17001 ◽

2013 ◽

Cited By ~ 3

Author(s):

Yijin Mao ◽

Yuwen Zhang

Keyword(s):

Liquid Film ◽

Liquid Water ◽

Water Film ◽

Copper Plate ◽

Dynamics Simulation ◽

Bulk Liquid ◽

Water Molecules ◽

Confined Space ◽

Explosive Boiling ◽

Short Period

In this paper, molecular dynamics simulation is carried out to study the explosive boiling of liquid water film heated by a hot copper plate in a confined space. A more physically-sound thermostat is applied to control the temperature of the metal plate and then to heat water molecules that are placed in the elastic wall confined simulation domain. The results show that liquid water molecules close to the plate are instantly overheated and undergo an explosive phase transition. A huge pressure in the region between liquid film and hot copper plate formed at the beginning and leads to a low density vapor region by partially vaporizing water film. A non-vaporization molecular layer, with a constant density of 0.2 g/cm3, tightly attached to the surface of the plate is observed. The z-component of COM (center of mass) trajectory of the liquid film in the confined space is tracked and analyzed. The one-dimensional density profile indicates the water film have a piston-like motion after short period of explosive boiling. Temperatures at three corresponding regions, which are vapor, liquid, and vapor from the top plate surface, are also computed and analyzed along with the piston-like motion of the bulk liquid film.

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QM/MM Simulations of Organic Phosphorus Adsorption at the Diaspore-Water Interface

10.26434/chemrxiv.8075204 ◽

2019 ◽

Author(s):

Prasanth Babu Ganta ◽

Oliver Kühn ◽

Ashour Ahmed

Keyword(s):

Interaction Energy ◽

Dynamics Simulation ◽

Water Molecules ◽

Hydroxyl Groups ◽

Water Interface ◽

Mineral Surfaces ◽

Soil Mineral ◽

Phosphorus Adsorption ◽

Covalent Bonds ◽

Binding Mechanisms

The phosphorus (P) immobilization and thus its availability for plants are mainly affected by the strong interaction of phosphates with soil components especially soil mineral surfaces. Related reactions have been studied extensively via sorption experiments especially by carrying out adsorption of ortho-phosphate onto Fe-oxide surfaces. But a molecular-level understanding for the P-binding mechanisms at the mineral-water interface is still lacking, especially for forest eco-systems. Therefore, the current contribution provides an investigation of the molecular binding mechanisms for two abundant phosphates in forest soils, inositol hexaphosphate (IHP) and glycerolphosphate (GP), at the diaspore mineral surface. Here a hybrid electrostatic embedding quantum mechanics/molecular mechanics (QM/MM) based molecular dynamics simulation has been applied to explore the diaspore-IHP/GP-water interactions. The results provide evidence for the formation of different P-diaspore binding motifs involving monodentate (M) and bidentate (B) for GP and two (2M) as well as three (3M) monodentate for IHP. The interaction energy results indicated the abundance of the GP B motif compared to the M one. The IHP 3M motif has a higher total interaction energy compared to its 2M motif, but exhibits a lower interaction energy per bond. Compared to GP, IHP exhibited stronger interaction with the surface as well as with water. Water was found to play an important role in controlling these diaspore-IHP/GP-water interactions. The interfacial water molecules form moderately strong H-bonds (HBs) with GP and IHP as well as with the diaspore surface. For all the diaspore-IHP/GP-water complexes, the interaction of water with diaspore exceeds that with the studied phosphates. Furthermore, some water molecules form covalent bonds with diaspore Al atoms while others dissociate at the surface to protons and hydroxyl groups leading to proton transfer processes. Finally, the current results conﬁrm previous experimental conclusions indicating the importance of the number of phosphate groups, HBs, and proton transfers in controlling the P-binding at soil mineral surfaces.

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