In this paper, a novel rectangular corrugated tube is proposed for the cooling application in supercritical water reactors (SCWRs), numerically. Standard k-epsilon turbulence model from ANSYS-FLUENT commercial softwar...
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In this paper, a novel rectangular corrugated tube is proposed for the cooling application in supercritical water reactors (SCWRs), numerically. Standard k-epsilon turbulence model from ANSYS-FLUENT commercial software is used for the simulation. Alumina-water is used as the nanofluid for the cooling in supercritical conditions and tried to find the optimized geometry to reach maximum heat transfer efficiency. Three geometry parameters are considered and by Central composite design (CCD) possible geometries (11 Cases) were designed and optimized by the Response Surface Method (RSM). As the main outcome, parameters a and c had more effects on the Nusselt number and nanoparticles with phi = 0.01 reported greatest Nusselt numbers. Also, by increasing the nanoparticles concentration from 0.01 to 0.04, the Nusselt number was decreased by 26.29% due to decreasing the heat capacity of SCW. (c) 2021 Elsevier Ltd. All rights reserved.
To gain a deeper understanding of the performance of V-Cone meter in low pressure wet gas measurement, the over-reading of the V-Cone meter was experimentally investigated in the present study. The equivalent diameter...
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To gain a deeper understanding of the performance of V-Cone meter in low pressure wet gas measurement, the over-reading of the V-Cone meter was experimentally investigated in the present study. The equivalent diameter ratio of the V-Cone meter is 0.55. The experimental fluids were air and tap water. The operating pressure and the gas volume fraction ranged from 0.1 MPa to 0.4 MPa and 97.52%-100%, respectively. The results showed that the existing V-Cone wet gas correlation, which was developed for the medium and high pressure wet gas cannot be well extended to the low pressure conditions. The Chisholm exponent monotonically decreased with the ratio of liquid-to-gas mass flow rate increasing, and was almost not affected by the gas to liquid density ratio and the gas densiometric Froude number in the present test ranges. A measurement correlation dedicated for the low pressure wet gas was developed. In the present cases, the relative deviation of the gas mass flow rate predicted by the new correlation was within +/- 4.0% and +/- 3.0% under the 95% and 90% confidence level, respectively;the average relative deviation was 0.046%. Our results provide insights into the measurement performance of V-Cone meter in low pressure wet gas and may help to develop a more comprehensive wet gas correlation.
Numerical simulations of a freely bubbling cylindrical fluidized bed are carried out using a coupled computational fluid dynamics and discrete element method (CFD-DEM) model and compared to recent experimental data. T...
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Numerical simulations of a freely bubbling cylindrical fluidized bed are carried out using a coupled computational fluid dynamics and discrete element method (CFD-DEM) model and compared to recent experimental data. The experiments were conducted using high-resolution and high-frequency magnetic resonance imaging providing high-fidelity data of the bubbling within a central 10 mm slice of the bed. Qualitatively, we find more regular (i.e., less chaotic) structures in the simulated beds than observed experimentally. Quantitatively, however, the bubble diameter and number of bubbles as a function of height within the bed is predicted well by the base model. Unfortunately, the regularity in the simulations manifests as a considerable discrepancy in the speed of the (dense) emulsion phase. The simulated velocity probability distribution functions show an accumulation of low-speed regions and deficiency of high-speed regions. A simple parametric study of the base model is also car-ried out considering many of the most common CFD-DEM modeling parameters. It is found that the fluid grid size, geometry resolution, transfer kernel and drag law did not have a significant effect on bubble or particle dynamics. (c) 2021 Elsevier B.V. All rights reserved.
Steam jet condensation through sonic nozzle in quiescent subcooled water pool is important for the safety of nuclear reactor system. In this study, the dynamic process of stable condensation jet steam plume is obtaine...
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ISBN:
(纸本)9780791859100
Steam jet condensation through sonic nozzle in quiescent subcooled water pool is important for the safety of nuclear reactor system. In this study, the dynamic process of stable condensation jet steam plume is obtained by numerical simulation method. The simulation results are in good agreement with the experimental results. The flow field results indicate that two typical fluctuation regimes exist in the dynamic process of steam plume. Simultaneous analysis of pressure and flow field indicates that two fluctuation regimes produce different pressure pulses. When the detachment phenomenon occurs during the fluctuation of the steam plume, a pressure pulse which value is clearly greater than 220 kPa is generated. When the plume sharply contracts without obvious detachment phenomenon during the fluctuation process, a pressure pulse which value is almost lower than 120 kPa is generated.
Topological physics has broadened its scope from the study of topological insulating phases to include nodal phases containing band structure singularities. The geometry of the corresponding quantum states is describe...
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Photothermal catalysis enhances energy conversion by coupling photoexcitation with thermal activation, yet challenges persist in spatiotemporal decoupling and multiscale transport mechanisms. This review focuses on th...
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Photothermal catalysis enhances energy conversion by coupling photoexcitation with thermal activation, yet challenges persist in spatiotemporal decoupling and multiscale transport mechanisms. This review focuses on the quantitative relationship between photothermal coupling mechanisms and energy/mass transfer across cross-scale catalytic systems (single atoms, sub-nanoclusters, and nanoparticles), systematically establishing “band structure regulation-local field engineering thermodynamic matching” cross-scale material design framework. Additionally, the mechanisms of cross-scale catalytic systems are comprehensively analyzed through multiscale characterization and theoretical modeling. In-situ synchrotron X-ray absorption spectroscopy paired with ultrafast spectroscopy exposes dynamic coordination restructuring of single atom active sites under photothermal coupling fields. Concurrently, density functional theory (DFT) integrated with finite element multi-physics simulations quantifies the relationship between cluster quantum size effects and photothermal conversion efficiency. Machine learning driven high throughput screening further advances cross-scale catalyst design principles for industrial applications such as methane reforming and water splitting. Central to this analysis are the electron-phonon coupling properties of atomic sites, quantum confinement-boosted hot carrier injection in sub-nanoclusters, and the cooperative interplay between nanoparticles plasmonic effects and macroscopic thermal gradients. This review elucidates synergistic photothermal catalysis mechanisms, establishes unified theoretical frameworks and scalable engineering strategies for efficient solar energy conversion, advancing practical implementation.
Carbon deposition is a thorny issue for the SOFC fueled by low carbon hydrocarbons such as biomass syngas. Moreover, long-term large temperature gradients would reduce SOFC durability. Regarding these two issues, a tw...
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The photo-thermal effects of laser on tissue is widely used in ophthalmology to treat retinal diseases. By adjusting the pulse duration from nano to tens of seconds, the multi-scale retinal lesion from micro to millim...
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Y Experimental investigation on vertical upward co-current air-water slug flow was carried out at atmospheric pressure, employing optical probes and high-speed photography. Experiments were performed with water superf...
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Y Experimental investigation on vertical upward co-current air-water slug flow was carried out at atmospheric pressure, employing optical probes and high-speed photography. Experiments were performed with water superficial velocity ranging from 0.089 to 1.52 m/s and gas superficial velocity ranging from 0.049 to 1.06 m/s in a polymethyl methacrylate tube of 15 mm inner diameter. Taking advantage of the time-domain characteristics of optical probes, slug flow has been disposed as a combination of Taylor bubbles and liquid slugs. Slug flow identification, characteristic parameters measurement and analysis were conducted in the present study. Firstly, combined with subjective observation, a developed methodology of flow pattern identification based on machine learning was proposed, with emphasis on slug flow. Results showed that the proposed method exhibited an outstanding advantage in the identification in the flow pattern transition region. More importantly, extensive data on local void fraction in liquid slugs (alpha(l, LS)) and in continuous slug units (alpha(l)), gas-phase velocity of Taylor bubble (U-TB) and liquid slug (U-LS), length of Taylor bubble (L-TB) and liquid slug (L-LS), were obtained. Through comprehensive analysis, it was found that turbulence intensity and flow pattern transitions were the dominant factors in affecting the characteristics of slug flow parameters. (C) 2021 Elsevier Ltd. All rights reserved.
Supercritical CO2 (S-CO2) power cycle has been widely applied in the field of nuclear energy, solar energy and waste heat recovery because of its high efficiency, compact structure and suitability for various heat sou...
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Supercritical CO2 (S-CO2) power cycle has been widely applied in the field of nuclear energy, solar energy and waste heat recovery because of its high efficiency, compact structure and suitability for various heat sources. Compressor and turbine are the key components of the S-CO2 power cycle which significantly affect the cycle performance. Therefore, it is of great necessity to carry out the cycle optimization design and key components performance analysis. In this paper, a novel system-component coupled optimization method of S-CO2 power cycle, which fully considers the performance of compressor, turbine and the S-CO2 power cycle performance, is proposed for improving the accuracy of optimization design results and guarantee a good match between the optimal thermodynamic parameters of S-CO2 power cycle and the performance of key components. The system-component coupled optimization method is implemented by genetic algorithm based on the one-dimensional model of the SCO2 centrifugal compressor and S-CO2 radial inflow turbine to obtain the accurate optimal cycle thermodynamic parameters and the key components design parameters. Using the obtained design parameters of S-CO2 centrifugal compressor and S-CO2 radial inflow turbine, three-dimensional modeling and CFD simulation of S-CO2 centrifugal compressor and S-CO2 radial inflow turbine are implemented. The results show that using system component coupled optimization method can evaluate the cycle performance more reasonably and accurately. The optimized cycle thermal efficiency and the cycle net power output are 19.47% and 987.3 kW, respectively. The optimized turbine efficiency and compressor efficiency are 82.57% and 81.25%, respectively. Unsteady CFD simulation results show that the turbine total-to-total efficiency obtained by steady computation is 0.83% higher than the unsteady time-averaged value obtained by unsteady computation. The relative errors of one-dimensional design results and three-dimensional simu
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