Two-color laser induced fluorescence (LIF) technique is applied to investigate the temperature distribution in rod bundles with spacer grid in this paper. In order to evaluate the characteristic, dye spectrum was anal...
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In the nuclear power station, the steam-water separator is a crucial appliance, a sequence of droplet lifecycle phenomena take place, including the droplet formation, droplet motion in the steam space, the mutual coll...
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In the nuclear power station, the steam-water separator is a crucial appliance, a sequence of droplet lifecycle phenomena take place, including the droplet formation, droplet motion in the steam space, the mutual collisions between droplets, droplet extinction and the phase transformation. Together with the entraining steam, the droplets experiencing above complex processes consist a typical sparse two-phase flow, which can be well investigated by the Euler-Lagrange approach in terms of numerical simulations. With the Euler-Lagrange method, the microscopic behavior of the droplets and the steam-water separating mechanism are promising to be captured. When applying the Euler-Lagrange approach to simulate the droplets motion in the fluid field, one should first obtain the fluid parameters surrounding the droplets by the interpolation method, which may significantly influence the efficiency and precision of subsequent simulation results. In the present work, we examined the performance of four different interpolation schemes in the simulation of the droplet-steam flow inside the steam-water separator, including the k-d tree and the brute force search algorithm, the nearest point and 4-point interpolation method, and the boundary layer meshes refinement and total mesh refinement method. The computational efficiency and precision of the four methods were studied in comparison. The nearest point interpolation scheme takes less computing time, whereas with lower accuracy. Therefore, the sufficiently fine meshes are necessary to improve the calculation accuracy, which in turn lead to the reduced computational efficiency. The accuracy of the four-points interpolation scheme is remarkably higher than that of the nearest point interpolation scheme at the cost of much more (more than 2 folds) CPU time. To make a trade-off between the efficiency and precision, a high efficiency and precision interpolation method is put forward by combining the nearest point interpolation scheme
Flywheel, as a kinetic energy storage and conversion device, has promising applications due to its high efficiency, no pollution and long lifetime. In particular, with a three-layer structure packed with heavy metal a...
Flywheel, as a kinetic energy storage and conversion device, has promising applications due to its high efficiency, no pollution and long lifetime. In particular, with a three-layer structure packed with heavy metal alloy middle layer, a flywheel can achieve both a large rotational inertia and a high energy density. To guarantee structural strength safety of this type of multi-ring packed flywheel operating at high temperature, structural and thermal stress analysis for a flywheel with a tungsten alloy layer sandwiched between two stainless steel layers is carried out using finite element method (FEM). Based on plane stress assumption, flywheel stress characteristic along radius under assembly force, centrifugal force and thermal loading is demonstrated. The results show that, the rise of temperature causes inconsistent thermal expansion between neighbouring layers and results in a large thermal stress. Particularly, a high circumferential tensile stress occurs in the middle layer. It is also found that, the segments of the middle tungsten alloy layer can efficiently relieve the inconsistent thermal expansion and lower the thermal stress. Moreover, the number of segments significantly influences the efficiency of thermal stress releasing and the reserved gap between adjacent segments significantly improves the contact pressure between inner hub and tungsten alloy layer. This work may provide reference for structural design of the multi-ring packed flywheels under thermal loading.
To study the development mechanisms and flow structure characteristics of the free surface vortices and get a better understanding of the vortices phenomena. Two-phase, three dimensions, transient CFD simulations of f...
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The transient performance of the Secondary Passive Residual Heat Removal system (SPRHR) for a small modular PWR was studied, the study focused on the thermal hydraulic characteristics at different initial water invent...
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In order to quickly calculate the flow characteristics in the simulated two-dimensional Rayleigh-Bénard convection model, a reduced-order extrapolation difference model for solving two-dimensional Rayleigh-Bé...
In order to quickly calculate the flow characteristics in the simulated two-dimensional Rayleigh-Bénard convection model, a reduced-order extrapolation difference model for solving two-dimensional Rayleigh-Bénard is established based on the Proper Orthogonal Decomposition (POD) method. Firstly, the classical difference format is used to calculate the flow field on the initial time span, the sample data is to construct the POD basis, and the truncation error generated in the process of constructing the POD base is analysed. Then, the two-dimensional reduced-order extrapolation Rayleigh-Bénard model is constructed by combining the SVD and POD methods. By numerical examples, the classical difference model and the reduced-order extrapolation model are numerically simulated under the given initial boundary value. The reliability and effective of the reduced-order method are verified by comparing the flow field temperature cloud maps in the two calculation stages.
During the operation of the Pressurized Water reactor recirculation steam generator, sludge particles from the feed water system and secondary system, mainly corrosion products, converge in the secondary side of steam...
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ISBN:
(纸本)9784890471676
During the operation of the Pressurized Water reactor recirculation steam generator, sludge particles from the feed water system and secondary system, mainly corrosion products, converge in the secondary side of steam generator. Since the saturated steam exiting the steam generator carries almost no sludge, the corrosion products' concentration increases with time. Although a part of the sludge can be removed by the blowdown system, the rest will either suspend in the water or deposit as a result of gravity, boiling or turbulence. Some sludge particles deposited on the surfaces of heat transfer tubes, tube sheet, and tube supporting plates or in the gaps around will cause a variety of problems, such as accelerating component device corrosion. The sludge collector is a passive device located in the upper internals of a PWR U-tube natural recirculation steam generator. It is able to trap and collect the sludge particles suspending in the secondary side fluid, which helps in reducing the amount of sludge available to settle on the tube bundle area. In this paper, the flow conditions and the sludge particle tracks around the sludge collector in a typical U-tube recirculation steam generator are studied by using a Computational Fluid Dynamics method. For the simulation method, a k-e model is selected as the turbulent model, and the two-way coupling Lagrangian Particle Tracking scheme is employed to account for the momentum transfer effects between the continuous phase of fluid and the discrete phase of particles. The forces acting on the sludge particles in this paper include the drag force, buoyancy force, and other additional forces such as added mass force and pressure gradient force. And the number of the representative particles captured by the sludge collector is also studied, while the mass flow rate entering the sludge collector is always paid more attention. The simulation results have successfully captured the flow patterns and the tracks of the representative
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