During the implementation of underground H 2 storage (UHS), geological CO 2 sequestration (GCS), and CO 2 -enhanced oil recovery (CO 2 -EOR) measures in shale reservoirs, kerogen will interact with typical shale fluid...
During the implementation of underground H 2 storage (UHS), geological CO 2 sequestration (GCS), and CO 2 -enhanced oil recovery (CO 2 -EOR) measures in shale reservoirs, kerogen will interact with typical shale fluids (H 2 , CO 2 , shale oil and gas). These interactions will thereby affect the implementation effects of the above industrial measures. Kerogen at various maturity degrees exhibits complex interactions with shale fluids due to its different molecular structures, which are shaped by factors such as reservoir type, maturation time, and geological environment. Despite this complexity, the types of elements (C, H, O, N, and S) and chemical groups that constitute kerogen molecules are limited. In this study, we utilized molecular dynamic (MD) simulations to reveal the interaction mechanism between a single kerogen molecule and typical shale fluid (H 2 , CH 4 , Neopentane, and CO 2 ) from the perspective of component elements and chemical groups. In addition, we developed an interaction energy fitting formula to quantify these interactions without relying on MD simulations, thereby facilitating the rapid assessment of the difficulty in separating shale fluids from shale organic matter. Lastly, we proposed two simplification strategies to reduce the experimental procedures involved in constructing kerogen molecules, while allowing for a certain degree of evaluation of the interaction between kerogen and shale fluids.
This article presents a theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor. Through numerically solving the one-dimensional steady-state single...
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This article presents a theoretical investigation on the steady-state natural circulation characteristics of a new type of pressurized water reactor. Through numerically solving the one-dimensional steady-state single-phase conservative equations for the primary circuit and the steady-state two-phase drift-flux conservative equations for the secondary side of the steam generator, the natural circulation characteristics were studied. On the basis of the preliminary calculation analysis, it was found that natural circulation mass flow rate was proportional to the exponential function of the power and that the value of the exponent is related to the operating conditions of the secondary side of the steam generator. The higher the outlet pressure of the secondary side of the steam generator, the higher the primary natural circulation mass flow rate. The larger height difference between the core center and the steam generator center is favorable for the heat removal capacity of the natural circulation.
A two-way coupling three-dimensional Vortex-In-Cell (VIC) method is developed for the simulation of gas-solid turbulent flow. The evolution of vortex elements and the motion of solid particles are tracked in the Lagra...
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A two-way coupling three-dimensional Vortex-In-Cell (VIC) method is developed for the simulation of gas-solid turbulent flow. The evolution of vortex elements and the motion of solid particles are tracked in the Lagrangian frame, while the flow field is solved by the vorticity Poisson equation on the Eulerian grid. Two-way coupling is implemented by introducing a vorticity source term induced by the motion of particle. This method is applied to simulate the particulate jet generated by solid particles falling from a circular orifice into unbounded quiescent air. The simulation results agree well with the experiment conducted by Ogata, which confirmed the validation of this method. The simulation results demonstrate that the air velocity radial distribution due to the particulate jet satisfies Gaussian distribution. The particle flow rate has little influence on the spread of particles, while velocity of particles increases with increasing the particle flow rate.
The pressure drop characteristic of wet air with ash particles in a horizontal tube bundle heat exchanger was studied experimentally. The variations with time, effects of water vapor mass fractions and mainstream velo...
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The pressure drop characteristic of wet air with ash particles in a horizontal tube bundle heat exchanger was studied experimentally. The variations with time, effects of water vapor mass fractions and mainstream velocities on pressure drop characteristic were presented. Experimentally results showed that with the increase in the time, the pressure drop coefficient firstly increased then became stable. In the case of wet air with ash particles, the pressure drop coefficient increased with the increase of the water mass fraction and decreased with the increase of the mainstream velocity. Compared with wet air without ash particles, the pressure drop coefficients were higher in the presence of ash particles, due to ash deposition.
The wind velocity plays a crucial role in the operation characteristic of indirect cooling tower. In this paper a 2×330MW vertical arrangement indirect air-cooled system was taken as research object, and numerica...
The wind velocity plays a crucial role in the operation characteristic of indirect cooling tower. In this paper a 2×330MW vertical arrangement indirect air-cooled system was taken as research object, and numerical simulation method was used to analyze the relative influence of the wind speed, ranging from 4m/s to 18m/s, on the outlet water temperature of cooling tower, the outlet air temperature of radiator, the facing wind speed of the fan segment and on the outlet air speed of the cooling tower. The result shows that the impact of the natural wind speed on the cooling tower efficiency varies greatly and this impact increases as the wind speed increases.
Increasing attention is paid on wet gas flow measurement with V-Cone meter in the production of natural gas. Annular-mist flow is a common flow regime in the wet gas flow metering. Knowledge of the annular-mist flow s...
Increasing attention is paid on wet gas flow measurement with V-Cone meter in the production of natural gas. Annular-mist flow is a common flow regime in the wet gas flow metering. Knowledge of the annular-mist flow such as the distributions of the pressure, the droplet and the liquid film in the V-Cone meter is critical to improve the wet gas measurement model. In this paper, a numerical method based on a three-fluid closure model of film, droplet and gas was developed to simulate the annular-mist wet gas flow in the V-Cone meter. The method agreed well with the existing correlation and the relative error of simulation data is less than ±2.5%. The distributions of the droplet, liquid film and static pressure in a V-cone meter and the results on different flow conditions were simulated with the present method. The simulations showed that under the adjustment of the V-Cone element, the droplets moved in a straight path close to the wall after the throat section and a liquid jet was formed. It continues through the diffuser and reattaches to the wall. Some droplets will re-coalescence in the downstream of the V-Cone. It was found that little droplet was entrained in the back of the V-Cone, which was benefit for obtaining the low pressure. The results of the liquid film distribution showed that the liquid film thickness on the pipe wall and the cone body was affected by both the geometry of the V-Cone and the area and strength of the low pressure domain. The pressure in the low pressure domain decreased with the liquid and gas velocity increasing, and the gas-to-liquid viscosity ratio had little effects on the pressure distribution. The downstream low pressure port justifiably locates at six or more pipe diameters downstream of the cone back face for the present V-Cone meter.
Although rapid load variation of coal-fired power plants has become a prior objective for improving the operational flexibility, it will cause a lifetime reduction of heaters due to alternating stresses during transie...
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Although rapid load variation of coal-fired power plants has become a prior objective for improving the operational flexibility, it will cause a lifetime reduction of heaters due to alternating stresses during transient processes. In the paper, among four flexible regulating measures, the dynamic characteristics of thermal parameters were obtained by GSE software, and thermo-mechanical stresses of 1# high-pressure (HP) heater were calculated by Finite Element Analysis, then the fatigue lifetimes of 1# HP heater were estimated and compared. It turns out that the most stressed position is at water chamber baffle, the allowable numbers of cycles at four measures are 5913-9419, and fatigue damage ratios for per cycle are 0.0106-0.0169%. The study can provide a detailed reference for operators to ensure the operational security of coal-fired power plants within flexibility frameworks.
Chaotic characteristics of direct contact condensation(DCC) for steam jet in subcooled water in a rectangular channel were analyzed at subcooled water temperature of 30 ℃. The steam mass flux and Reynolds number of s...
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Chaotic characteristics of direct contact condensation(DCC) for steam jet in subcooled water in a rectangular channel were analyzed at subcooled water temperature of 30 ℃. The steam mass flux and Reynolds number of subcooled water were in the range of 250-600kg/(m 2 s) and 78,000-172,000 respectively. Three different flow patterns, bubble flow, oscillation jet and stable jet, were observed. Correlation dimension( D 2 ) changes with flow patterns. For bubble flow, oscillation jet and stable jet, the corresponding correlation dimension values increase and are in the ranges of 9.68~10.30, 10.03~11.17 and 11.10~12.62, respectively. Different flow patterns have different Hurst exponent( H ). From the range of correlation dimensions and Hurst exponents, the flow pattern of steam jet can be recognized without looking the picture of steam plume. This result is very important for flow pattern recognition without the observation windows.
In present experiment, the vapor mixture with different velocities (2m⋅s−1, 4m⋅s−1) and different ethanol mass fraction (0.5%, 1%, 2%, 5%, 10%, 20%, 50%) flew through vertical micro-tube and condensed on the outer tub...
In present experiment, the vapor mixture with different velocities (2m⋅s−1, 4m⋅s−1) and different ethanol mass fraction (0.5%, 1%, 2%, 5%, 10%, 20%, 50%) flew through vertical micro-tube and condensed on the outer tube surface at pressure 31.16kPa, 47.36kPa. The condensation modes were observed by CCD camera, and the characteristics of the heat transfer coefficients versus the vapor-to-surface temperature differences for different experimental conditions were obtained. The condensation heat transfer coefficients of vapor mixture decrease with the vapor concentration increasing. The maximum peak value of heat transfer coefficients, up to 39 kW⋅m−2⋅K1, which was about 3-4 times greater than that of steam, appeared when the ethanol mass fraction was 2%. A heat transfer coefficient correlation including the effects of all the tested parameters is proposed by using the multiple linear least squares method based on the experimental data. The calculated values agreed well with the experimental data and the deviations between them were from −20% to 20%.
The reasons of frequent tube burst of the high temperature reheater in a supercritical 600 MW unit were systematically investigated via the examination of macroscopic inspection, chemical composition, mechanical prope...
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