We use non-equilibrium molecular dynamics simulations to calculate the self-diffusion coefficient, D, of a Lennard Jones fluid over a wide density and temperature range. The change in self-diffusion coefficient with t...
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We use non-equilibrium molecular dynamics simulations to calculate the self-diffusion coefficient, D, of a Lennard Jones fluid over a wide density and temperature range. The change in self-diffusion coefficient with temperature decreases by increasing density. For density ρ＊ = ρσ3 = 0.84 we observe a peak at the value of the self-diffusion coefficient and the critical temperature T＊ = kT/ε = 1.25. The value of the self-diffusion coefficient strongly depends on system size. The data of the self-diffusion coefficient are fitted to a simple analytic relation based on hydrodynamic arguments. This correction scales as N-α, where α is an adjustable parameter and N is the number of particles. It is observed that the values of a 〈 1 provide quite a good correction to the simulation data. The system size dependence is very strong for lower densities, but it is not as strong for higher densities. The self-diffusion coefficient calculated with non-equilibrium molecular dynamic simulations at different temperatures and densities is in good agreement with other calculations fronl the literature.
Boiling is a very complex and illusive process with very high efficiency of heat *** many sub-processes in boiling phenomenon,gravity can be involved and play much important *** reveal its influence,long-term,steady m...
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Boiling is a very complex and illusive process with very high efficiency of heat *** many sub-processes in boiling phenomenon,gravity can be involved and play much important *** reveal its influence,long-term,steady microgravity are ***,the opportunity is much ***,ground-based short-term microgravity experiment becomes an attractive alternative. Experiments of transient pool boiling of highly subcooled FC-72 on a smooth silicon chip with the dimensions of 10×10x0.5 mm3 were studied in short-term microgravity condition utilizing the drop tower *** heating currents were switched on near the release of the drop *** bubble behaviors and heat transfer of air-dissolved FC-72 on the silicon chip were obtained at the bulk
An empirical corrosion model for SS316L in simulated proton exchange membrane fuel cell (PEMFC) environments is developed based on systematic experimental data on the effects of various factors, such as acidity, fluor...
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The spray and combustion characteristics of biodiesel (BDF) and diesel fuels injected by a micro-hole nozzle of 0.08 mm diameter under increasing injection pressure up to ultra-high value of 300 MPa were investigated ...
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Thermal impact of the parallel laying of gas and oil pipelines remains unclear though that of two oil pipelines has been relatively well studied. A numerical simulation method combined by finite volume and finite diff...
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Thermal impact of the parallel laying of gas and oil pipelines remains unclear though that of two oil pipelines has been relatively well studied. A numerical simulation method combined by finite volume and finite difference was used to investigate the complex heat transfer in three typical parallel laying patterns between gas and oil pipelines: hot oil pipeline with cold gas pipeline;cold oil pipeline with hot gas pipeline and hot oil pipeline with hot gas pipeline. In terms of these three different parallel laying cases, the present paper analyzed characteristics of the maximum differential temperature range and thermal distribution of oil/gas temperatures at different intervals along pipelines relative to the single laying. The numerical simulation results can provide some guidelines for designs and safe operations of the parallel laying of oil/gas pipelines.
Metal hydride represents a promising candidate for hydrogen storage, because the technique is essentially safe, compact and flexible. However, the properties of the metal hydride tend to change in repeated hydriding/d...
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Metal hydride represents a promising candidate for hydrogen storage, because the technique is essentially safe, compact and flexible. However, the properties of the metal hydride tend to change in repeated hydriding/dehydriding cycles, which will inevitably affect the performance of corresponding hydrogen storage system. The effect is investigated in this paper by numerical simulation using a commercial package COMSOL MULTIPHYSICS 3.5a, and a typical material- LaNi5 is chosen for discussion. Through sensitivity analysis, the influences of variation in key properties over repeated cycles on the charging time of a tank-type storage system, are evaluated and some useful conclusions are drawn.
Ignition delay times of methane/hydrogen/oxygen/nitrogen mixtures with hydrogen amount-of-substance fractions ranging from 0–20% were measured in a shock tube *** ambient temperature varied from 1422 to 1877 K and th...
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Ignition delay times of methane/hydrogen/oxygen/nitrogen mixtures with hydrogen amount-of-substance fractions ranging from 0–20% were measured in a shock tube *** ambient temperature varied from 1422 to 1877 K and the pressure was maintained at 0.4 MPa behind the reflected shock *** experiments were conducted at an equivalence ratio of *** fuel mixtures were diluted with nitrogen gas so that the nitrogen amount-of-substance fraction was 95%.The experimental ignition delay time of the CH4/H2 mixture decreased as the hydrogen amount-of-substance fraction *** enhancement of ignition by hydrogen addition was weak when the ambient temperature was >1750 K,and strong when the temperature was <1725 *** ignition delay time of 20% H2/80% CH4 was only one-third that of 100% CH4 at 1500 K.A modified model based on GRI-Mech 3.0 was proposed and used to calculate the ignition delay times of test *** calculated results agreed with the experimental ignition delay *** sensitivity analysis showed that HO·+H2 →H·+H2O was the main reaction for the formation of the H· at 1400 *** the hydrogen amount-of-substance fraction increased,chain branching was enhanced through the reaction H·+O2→O·+HO·,and this reduced the ignition delay *** 1800 K,the methyl radical (H3C·) became the key species that influenced the ignition of the CH4/H2/O2/N2 mixtures,and sensitivity coefficients of the chain termination reaction 2H3C·(+M)→C2H6(+M),and chain propagation reaction HO2+H3C·→HO·+CH3O decreased,which reduced the influence of hydrogen addition on the ignition of the CH4/H2 mixtures.
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