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diffusivity 3

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Richards’ equation 1

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ash layer 1

carbon dioxide 1

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free volume 1

fujita model 1

hydraulic diffusivity 1

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Solubility and diffusivity of CO

Guilan Chen, Xingfu Song, Shuying Sun, Yanxia Xu, Jianguo Yu

Frontiers of Chemical Science and Engineering 2016, Volume 10, Issue 4, Pages 480-489 doi: 10.1007/s11705-016-1603-1

Abstract: In this study, the solubility and diffusivity of CO in -butanol+ N235 system were measured and reportedThe diffusivity of CO increases firstly and then decreases with the increase in the mass fraction of

Keywords： carbon dioxide N235 solubility diffusivity coupled process

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Effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke

Yiqun HUANG, Yiran LI, Man ZHANG, Boyu DENG, Hao KONG, Junfeng WANG, Junfu LYU, Hairui YANG, Lingmei WANG

Frontiers in Energy 2021, Volume 15, Issue 2, Pages 320-327 doi: 10.1007/s11708-020-0674-3

Abstract: Thus, effective diffusivity of oxygen in the ash layer was a crucial parameter worthy of careful investigationIn this paper, the effective diffusivity of oxygen in the ash layer of Huadian oil shale semicoke wasThe experimental results showed that higher temperature would lead to a higher effective diffusivityEspecially, the effective diffusivity along the direction perpendicular to bedding planes was much lowerIn addition, an effective diffusivity model was developed, which could be used to describe the mass transfer

Keywords： oil shale semicoke diffusivity pore structure ash layer

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Molecular dynamics simulation of diffusivity

LIU Juanfang, ZENG Danling, LI Qin, GAO Hong

Frontiers in Energy 2008, Volume 2, Issue 3, Pages 359-362 doi: 10.1007/s11708-008-0039-9

Abstract: Equilibrium molecular dynamics simulation was performed on water to calculate its diffusivity by adopting

Keywords： diffusivity Equilibrium molecular influence potential

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Stable expression and control parameters in the numerical simulation of unsaturated flow

Zhiyuan ZHANG; Xu LI; Yongkang WU; Xiaokang LI

Frontiers of Structural and Civil Engineering 2022, Volume 16, Issue 12, Pages 1501-1514 doi: 10.1007/s11709-022-0893-2

Abstract: The Richards’ equation describes the flow phenomenon in unsaturated porous media and is essential to hydrology and environmental science. This study evaluated the numerical stability of two different forms of the Richards’ equation. Sensitivity analyses were performed to investigate the control parameters of the equation. The results show that the h-form Richards’ equation has better applicability for calculating variable saturation flows than the θ-form Richards’ equation. For the h-form Richards’ equation, the hydraulic conductivity of the soil in the low-suction range and the specific moisture capacity in the high-suction range primarily influenced the solution. In addition, sensitivity analyses indicated that the saturated hydraulic conductivity, initial condition, and air-entry pressure have a higher sensitivity to the simulation results than the saturated water content, rainfall intensity, and decline rate of hydraulic conductivity. Moreover, their correctness needs to be guaranteed first in numerical simulations. The research findings can provide a helpful reference for improving the reliability of numerical simulations of unsaturated flows.

Keywords： Richards’ equation sensitivity analysis unsaturated soil hydraulic diffusivity seepage simulation

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Molecular dynamics study of water diffusion in an amphiphilic block copolymer with large difference in the blocks’ glass transition temperatures

Yang Zhou, Phillip Choi

Frontiers of Chemical Science and Engineering 2017, Volume 11, Issue 3, Pages 440-447 doi: 10.1007/s11705-017-1626-2

Abstract: Isothermal-isobaric molecular dynamics simulation was used to study the diffusion mechanism of water in polyurethane- -poly( -isopropyl acrylamide) (PU- -PNIPAm) with a hydrophobic PU/hydrophilic PNIPAm mass ratio of 1.4 to 1 at 298 K and 450 K. Here, the experimental glass transition temperature ( ) of PU is 243 K while that of PNIPAm is 383 K. Different amounts of water up to 15 wt-% were added to PU- -PNIPAm. We were able to reproduce the specific volumes and glass transition temperatures (250 K and 390 K) of PU- -PNIPAm. The computed self-diffusion coefficient of water increased exponentially with increasing water concentration at both temperatures (i.e., following the free volume model of Fujita). It suggested that water diffusion in PU- -PNIPAm depends only on its fractional free volume despite the free volume inhomogeneity. It is noted that at 298 K, PU is rubbery while PNIPAm is glassy. Regardless of temperature, radial distribution functions showed that water formed clusters with sizes in the range of 0.2–0.4 nm in PU- -PNIPAm. At low water concentrations, more clusters were found in the PU domain but at high water concentrations, more in the PNIPAm domain. It is believed that water molecules diffuse as clusters rather than as individual molecules.

Keywords： molecular dynamics simulation amphiphilic block copolymer free volume water diffusivity fujita model