In this work, the auto-ignition experiments of nitromethane at the low to intermediate temperature, fuel concentration of 2%, pressure of 30 bar and different equivalence ratios have been investigated by using rapid c...
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The stability of small vacancy clusters including divacancy,trivacancy and tetravacancy has been studied in body-centered cubic high-entropy alloy Nb_(0.75)ZrTiV_(0.5) in structures of random solid solution and short-...
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The stability of small vacancy clusters including divacancy,trivacancy and tetravacancy has been studied in body-centered cubic high-entropy alloy Nb_(0.75)ZrTiV_(0.5) in structures of random solid solution and short-range order by first-principles calculations and molecular dynamics *** from conventional body-centered cubic metals,the tightly bound configurations have a lower structural stability and are not preferred energetically in the studied high-entropy *** of vacancy configurations leads to vacancy-atom exchanges that favor less compact *** formation energy of small vacancy clusters is much smaller than its constituent elements of Nb and V due to the large structural adjustment induced by severe local lattice *** difference in local lattice distortion and elemental arrangement in the vacancy neighborhood leads to significant site-to-site variation in vacancy cluster energy and *** formation energy has a strong correlation with the local energy state of the vacancy configuration and the extent of structural *** to random solid solution,the structure of short-range order has a higher stability for the most compact cluster configurations and tends to have higher vacancy cluster formation *** to classical molecular dynamics simulations of cluster diffusion at high temperature,the studied high-entropy alloy has a higher probability of cluster dissociation compared to Nb and *** unconventional energetics of small vacancy clusters is expected to have a profound impact on their generation,diffusion,dissociation,coalescence,as well as the defect microstructure evolution during irradiation.
The Ni-doped (CuIn)0.2Zn1.6S2 photocatalysts were prepared via a two-step ultrasonic-hydrothermal method under an environmental-friendly condition. XRD pattern profiles suggested that Ni2+ successfully doped into (CuI...
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The dynamic characteristics of molten droplets and hot particles at the very beginning of their fall into coolant pools are presented. The falling course of a single droplet or a single hot particle was recorded by a ...
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The dynamic characteristics of molten droplets and hot particles at the very beginning of their fall into coolant pools are presented. The falling course of a single droplet or a single hot particle was recorded by a highspeed camera and a curve of velocity vs. time was obtained. Emphasis was placed on the effects of the droplet's size and temperature, the coolant's temperature and properties, and the droplet's physical properties on the moving behavior. The results for the all cases showed that the velocity of a falling droplet/particle decreased rapidly but rebounded shortly, at the beginning of droplet/particle falling in the coolant. Following such a V-shaped evolution in velocity, the droplet/particle slows down gradually to a comparatively steady velocity. An increase in either coolant temperature or droplet temperature results in a larger velocity variation in the 'J-region', but a smaller deceleration when it moves out of the 'J-region'. The elevated volatility of a coolant leads to a steeper deceleration in the 'J-region' and beyond. The bigger size of a particle leads to a greater velocity variation in the 'J-region' and terminal velocity. A high melting point and thermal conductivity as well as lower heat capacity contribute to dramatic variation in the 'J-region' and low terminal velocity.
An experimental study on the natural convection heat transfer on a horizontal downward facing heated surface in a water gap was carried out under atmospheric pressure conditions. A total of 700 experimental data point...
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An experimental study on the natural convection heat transfer on a horizontal downward facing heated surface in a water gap was carried out under atmospheric pressure conditions. A total of 700 experimental data points were correlated using Rayleigh versus Nusselt number in various forms, based on different independent variables. The effects of different characteristic lengths and film temperatures were discussed. The results show that the buoyancy force acts as a resistance force for natural convecti on beat transfer ona downward facing horizontal heated surface in a confined space. For the estimation of the natural convection heat transfer under the present conditions, empirical correlations in which Nusselt number is expressed as a function of the Rayleigh number, or both Rayleigh and Prandtl numbers, may be used. When it is accurately predicted, the Nusselt number is expressed as a function of the Rayleigh and Prandtl numbers, as well as the gap width-to-heated surface diameter ratio; and uses the temperature difference between the heated surface and the ambient fluid in the definition of Rayleigh number. The characteristic length is the gap size and the film temperature is the average fluid temperature.
Rate coefficients of H-atom abstraction and addition reactions of 3-hexene by the hydroxyl radical (H) were determined using canonical variational transition-state theory, with potential energy surface evaluated at th...
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The limited availability of studies on the natural convection heat transfer characteristics of fluoride salt has hindered progress in the design of passive residual heat removal systems(PRHRS)for molten salt *** paper...
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The limited availability of studies on the natural convection heat transfer characteristics of fluoride salt has hindered progress in the design of passive residual heat removal systems(PRHRS)for molten salt *** paper presents results from a numerical investigation of natural convection heat transfer characteristics of fluoride salt and heat pipes in the drain tank of a *** results are compared with experimental data,demonstrating the accuracy of the calculation *** distribution of fluoride salt and heat transfer characteristics are obtained and *** radial temperature of liquid fluoride salt in the drain tank shows a uniform distribution,while temperatures increase with increase in axial height from the bottom to the top of the drain *** addition,natural convection intensity increases with increase in height of the heat pipes in the *** between heat pipes has no obvious effect on the natural convection heat transfer *** study will contribute to the design of passive heat removal systems for advanced nuclear reactors.
The corrugated packing is prone to break down easily, which can affect the tower efficiency substantially. It is the inner environment of the vacuum distillation tower including the temperature and chemical nature of ...
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The corrugated packing is prone to break down easily, which can affect the tower efficiency substantially. It is the inner environment of the vacuum distillation tower including the temperature and chemical nature of fluid that lead to the packing damage. The theoretical analysis indicates that it is the inner material flow of vacuum distillation tower that leads to the vibration of packing, which can affect the corrosion fatigue of packing significantly. Meanwhile, the modal shape and inherent frequency of packing under prestress can be obtained by means of mathematical analysis. Based on the two kinds of analysis, the flow induced vibration and corrosion fatigue are accountable for the failure of packing.
Structural integrity of steam generator should be maintained during operation, since it performs as the pressure boundary of primary side coolant. Localized thermal-hydraulic parameters of secondary side are essential...
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ISBN:
(纸本)9781632668264
Structural integrity of steam generator should be maintained during operation, since it performs as the pressure boundary of primary side coolant. Localized thermal-hydraulic parameters of secondary side are essential for the analysis of tube wastage, fatigue and failure. In this paper, a three-dimensional thermohydraulics analysis code, named STAF, is developed based on FLUENT. With STAF code, three-dimensional thermohydraulics of secondary side of AP1000 steam generator are generated. This code is developed based on the porous media theory. In this code, the drift flux two-phase model coupled with a simplified flow boiling model is utilized to present two-phase flow among the U-tube bundle. Downcomer, tube bundle, support plates and primary separators in steam generator are considered in STAF code. The calculated results are compared with a general steam generator thermohydraulic analysis code ATHOS, which is developed by the Westinghouse. The comparison indicates that STAF code performs well in evaluating thermal-hydraulic parameters in steam generator. The results show that the flow field varies significantly at different position in AP1000 steam generator. flow vapor quality at the inlet of primary separators varies significantly, which is a severe challenge to the capacity design of separators.
In this paper, a three-layer Back Propagation (BP) algorithm artificial neural network (ANN) for predicting critical heat flux (CHF) in saturated forced convective boiling on a heated surface with impinging jets was t...
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