Difference Analysis of Gas Molecules Diffusion Behavior in Natural Ester and Mineral Oil Based on Molecular Dynamic Simulation

Natural ester, as a new environmentally green insulating oil, has been widely used in transformer. In an oil-immersed transformer, the normal aging, thermal failure, and discharge failure could easily lead to the decomposition of the oil-paper insulation system and produce different kinds of gases. Studying gas dissolution in natural ester and mineral oil could provide assistance in applying criteria to make a diagnosis of different kinds of faults in the transformer. In this paper, the molecular dynamics method was used to investigate the diffusion behavior of seven fault characteristic gases (including H2, CO, CH4, C2H2, CO2, C2H4, C2H6) in natural ester and mineral oil. The simulation parameters of free volume, interaction energy, mean square displacement, and diffusion coefficient were compared between the natural ester and mineral oil. Meanwhile, the influence of temperature on the diffusion of gas molecules in two kinds of oils was also analyzed. Results showed that the free volume, the interaction energy, and the relative molecular mass of gas molecules were the factors influenced by the diffusion of gas molecules in natural ester and mineral oil. The order of the diffusion coefficients of gas molecules in natural ester was as follows: H2 > CH4 > CO > C2H2 > C2H4 > CO2 > C2H6 and that in mineral oil was as follows: H2 > CH4 > CO> C2H2 > C2 H4 > C2H6 > CO2. By comparing the diffusion behavior of gas molecules in natural ester and mineral oil, it was found that the smaller free volume and higher interaction energy of gas molecules in natural ester were the major reasons for the gas molecules to be more difficult to diffuse in natural ester. The rising temperature could enhance the free volume and reduce the interaction energy between gas molecules and oil. The diffusion coefficient of gas molecules increased exponentially with the follow of temperature. However, the temperature didn’t affect the ordering of diffusion coefficient, free volume, and interaction energy of gas molecules in natural ester and mineral oil.

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MOLECULAR DYNAMICS STUDY OF THE DISRUPTION OF H-BONDS BY WATER MOLECULES AND ITS DIFFUSION BEHAVIOR IN AMORPHOUS CELLULOSE

Modern Physics Letters B ◽

10.1142/s0217984912500881 ◽

2012 ◽

Vol 26 (14) ◽

pp. 1250088 ◽

Cited By ~ 12

Author(s):

RUIJIN LIAO ◽

MENGZHAO ZHU ◽

XIN ZHOU ◽

FUZHOU ZHANG ◽

JIAMING YAN ◽

...

Keyword(s):

Molecular Dynamics ◽

Hydrogen Bonding ◽

Diffusion Coefficient ◽

Hydrogen Bonds ◽

Water Molecule ◽

Free Volume ◽

Water Molecules ◽

Amorphous Cellulose ◽

Diffusion Behavior ◽

Bonding Structure

Hydrolysis is an important component of the aging of cellulose, and it severely affects the insulating performance of cellulosic materials. The diffusion behavior of water molecules in amorphous cellulose and their destructive effect on the hydrogen bonding structure of cellulose were investigated by molecular dynamics. The change in the hydrogen bonding structure indicates that water molecules have a considerable effect on the hydrogen bonding structure within cellulose: both intermolecular and intramolecular hydrogen bonds decreased with an increase in ingressive water molecules. Moreover, the stabilities of the cellulose molecules were disrupted when the number of intermolecular hydrogen bonds declined to a certain degree. Both the free volumes of amorphous cells and water molecule-cellulose interaction affect the diffusion of water molecules. The latter, especially the hydrogen bonding interaction between water molecules and cellulose, plays a predominant role in the diffusion behavior of water molecules in the models of which the free volume rarely varies. The diffusion coefficient of water molecules has an excellent correlation with water molecule-cellulose interaction and the average hydrogen bonds between each water molecule and cellulose; however, this relationship was not apparent between the diffusion coefficient and free volume.

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Molecular Dynamics Study of H2O Molecular Diffusion Behavior in PAM/PVA Polymer Blends

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1119.268 ◽

2015 ◽

Vol 1119 ◽

pp. 268-272

Author(s):

Qing Hua Wei ◽

Ya Nen Wang ◽

Ming Ming Yang ◽

Wei Hong Chai ◽

Ying Feng Zhang

Keyword(s):

Molecular Dynamics ◽

Diffusion Coefficient ◽

Polymer Blends ◽

Molecular Diffusion ◽

Theoretical Method ◽

Component Ratio ◽

Diffusion Behavior ◽

Method Of Molecular Dynamics ◽

Influence Of Temperature On ◽

Water Contents

The theoretical method of molecular dynamics was applied to study H2O molecular diffusion behavior in PAM/PVA Polymer blends, investigated the effects of component ratios, temperatures and water contents on diffusion coefficient. Results show that with the increase of PVA content in blend systems, the H2O molecule diffusion coefficient first increased and then decreased. This indicates there is an optimum component ratio to make the H2O molecule diffusion coefficient maximum. There is a certain influence of temperature on H2O molecular diffusion in PAM/PVA blend system, the higher the temperature, the bigger the H2O molecular diffusion coefficient. When the less H2O molecules contained in system, there is a less impact on the diffusion coefficient. As the number of H2O molecules reaches a certain amount, the effect on the diffusion coefficient is more obvious.

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Anomalous Diffusion with an Apparently Negative Diffusion Coefficient in a One-Dimensional Quantum Molecular Chain Model

Symmetry ◽

10.3390/sym13030506 ◽

2021 ◽

Vol 13 (3) ◽

pp. 506

Author(s):

Sho Nakade ◽

Kazuki Kanki ◽

Satoshi Tanaka ◽

Tomio Petrosky

Keyword(s):

Diffusion Coefficient ◽

Diffusion Constant ◽

Mean Square Displacement ◽

Second Law Of Thermodynamics ◽

Molecular Chain ◽

Chain Model ◽

Phase Mixing ◽

One Dimensional ◽

The One ◽

Negative Diffusion

An interesting anomaly in the diffusion process with an apparently negative diffusion coefficient defined through the mean-square displacement in a one-dimensional quantum molecular chain model is shown. Nevertheless, the system satisfies the H-theorem so that the second law of thermodynamics is satisfied. The reason why the “diffusion constant” becomes negative is due to the effect of the phase mixing process, which is a characteristic result of the one-dimensionality of the system. We illustrate the situation where this negative “diffusion constant” appears.

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Investigation of Survival/Hazard Rate of Natural Ester Treated with Al2O3 Nanoparticle for Power Transformer Liquid Dielectric

Energies ◽

10.3390/en14051510 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1510

Author(s):

Raymon Antony Raj ◽

Ravi Samikannu ◽

Abid Yahya ◽

Modisa Mosalaosi

Keyword(s):

Survival Rate ◽

Hazard Rate ◽

Power Transformer ◽

Mineral Oil ◽

Interpolation Polynomial ◽

Distribution Functions ◽

Flash Fire ◽

Predicted Values ◽

Natural Ester ◽

Electrical Apparatus

Increasing usage of petroleum-based insulating oils in electrical apparatus has led to increase in pollution and, at the same time, the oils adversely affect the life of electrical apparatus. This increases the demand of Mineral Oil (MO), which is on the verge of extinction and leads to conducting tests on natural esters. This work discusses dielectric endurance of Marula Oil (MRO), a natural ester modified using Conductive Nano Particle (CNP) to replace petroleum-based dielectric oils for power transformer applications. The Al2O3 is a CNP that has a melting point of 2072 °C and a low charge relaxation time that allows time to quench free electrons during electrical discharge. Al2O3 is blended with the MRO and Mineral Oil (MO) in different concentrations. The measured dielectric properties are transformed into mathematical equations using the Lagrange interpolation polynomial functions and compared with the predicted values either using Gaussian or Fourier distribution functions. Addition of Al2O3 indicates that 0.75 g/L in MRO has an 80% survival rate and 20% hazard rate compared to MO which has 50% survival rate and 50% hazard rate. Considering the measured or interpolated values and the predicted values, they are used to identify the MRO and MO’s optimum concentration produces better results. The test result confirms the enhancement of the breakdown voltage up to 64%, kinematic viscosity is lowered by up to 40% at 110 °C, and flash/fire points of MRO after Al2O3 treatment enhanced to 14% and 23%. Hence the endurance of Al2O3 in MRO proves to be effective against electrical, physical and thermal stress.

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Effect of thermal aging on the dielectric properties of mixture between mineral oil and natural ester

TENCON 2015 - 2015 IEEE Region 10 Conference ◽

10.1109/tencon.2015.7372866 ◽

2015 ◽

Cited By ~ 5

Author(s):

Suwarno ◽

Jusua Marbun

Keyword(s):

Dielectric Properties ◽

Thermal Aging ◽

Mineral Oil ◽

Natural Ester

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Influence of Hydrostatic Pressure and Cationic Type on the Diffusion Behavior of Chloride in Concrete

Materials ◽

10.3390/ma14112851 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2851

Author(s):

Huanqiang Liu ◽

Linhua Jiang

Keyword(s):

Diffusion Coefficient ◽

Hydrostatic Pressure ◽

Diffusion Model ◽

Coupling Effect ◽

Experimental Results ◽

Chloride Diffusion ◽

Concrete Durability ◽

Chloride Diffusion Coefficient ◽

Diffusion Behavior ◽

Diffusion Source

The durability of the concrete in underground and marine engineering is affected by the underground and ocean environment. Chloride diffusion coefficient under hydrostatic pressure is a key parameter of concrete durability design under corresponding conditions. Therefore, this paper studies the diffusion behavior of chloride in different diffusion source solutions by experiment and simulation. Based on the experimental results, this paper proposes a new chloride diffusion model under the coupling effect of diffusion and convection. The interaction of ions and compounds in the diffusion source solutions, concrete pore fluid, and concrete material are considered in the new chloride diffusion model. The experimental results show that chloride diffusion rate is significantly affected by hydrostatic pressure, which increases with the increase of hydrostatic pressure. The chloride diffusion coefficient shows a certain difference in difference diffusion source solutions. The chloride diffusion coefficient in divalent cationic diffusion source solutions is the largest, the chloride diffusion coefficient in the divalent and monovalent cationic compound ones is in the middle, and the chloride diffusion coefficient in the monovalent cationic ones is the smallest. There is a linear relationship between the chloride diffusion coefficient and the hydrostatic pressure whether in single or combined cationic diffusion source solutions.

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