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Numerical study on satellite droplet formation in laminar jet breakup for a liquid droplet radiator

ANNALS OF NUCLEAR ENERGY 2022年 174卷

作者： Zhu, Maoguo Zhao, Quanbin Chong, Daotong Chen, Weixiong Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Liquid Droplet Radiator is promising for the waste heat removal of space nuclear power systems, and droplet properties have an impact on its performance. Breakup behaviors of laminar liquid jets with continuous droplets formation were numerically studied. Results verified that satellite droplets formation would destroy uniform droplet streams. The effects of We, Oh, Ca, and k on laminar jet breakup behaviors were investigated. Increasing Oh shifted jet breakup pattern from downstream pinching to upstream pinching, and it reversed as We increased. The jet breakup was more delayed with Oh increased at low We and jet oscillation amplitude became larger with We increased. At low We, breakup length and breakup time decreased firstly and then increased with k increased, but increased with Ca increased. However, the influence of Ca became slight at high We. Moreover, quantitative criteria were proposed for accurately identifying three satellite droplet formation regimes. (C) 2022 Elsevier Ltd. All rights

关键词： Liquid droplet radiator Waste heat removal Numerical simulation Laminar jet breakup behavior Satellite droplet formation regime

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Coordinated control strategy assessment of a virtual power plant based on electric public transportation

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JOURNAL OF ENERGY STORAGE 2023年 59卷

作者： Tian, Zeyu Wang, Zhu Chong, Daotong Wang, Jinshi Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

With the rapid development of the public transportation industry in recent years, electric public transportation (EPT) with regular operating times and fixed load demands has considerable potential for energy storage. Aiming to solve the problem of insufficient large-scale energy storage and ensure renewable energy development, this study builds the dynamic simulation model of a virtual power plant (VPP) consisting of EPT groups, large-capacity public distributed generations (PDGs) containing a photovoltaic (PV) unit, and a coal-fired unit. Then, the coordinated control strategy, which includes the time-sharing plan part and execution part with multi-section, is proposed to make a trade-off between maximizing the utilization of EPT and ensuring the operational stability of VPP. The control strategy includes two modes (1) gaining benefits through electricity tariff differences and participation in the carbon trading market and (2) peak shaving the consumption of VPP using off-peak grid power. Moreover, the evaluation model related to the control performance and achievement of targets is established. The influence of the EPT number on benefits and peak shaving capability is compared. Results show that the optimal number of EPT for the system is the value at which the energy storage utilization is maximum at the specific period. The optimal daily benefit is 37,300-83,700 yuan, and the optimal daily discharge value is 117.77 MW.h when the maximum peak demand reduction is 38.31 MW. Overall, the proposed strategy makes full use of the energy storage potential of EPT groups, which provide technical support for maintaining grid security and achieving the dual-carbon target.

关键词： Electric public transportation Virtual power plant Dynamic simulation Coordinate control strategy

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Efficient and accurate computation scheme of p-T thermodynamic properties of water and steam

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JOURNAL OF THE TAIWAN INSTITUTE OF CHEMICAL ENGINEERS 2012年第6期43卷 845-851页

作者： Wang, Xiao-Dong An, Bin Duan, Yuan-Yuan Wang, Zhi-Xue Lee, Duu-Jong N China Elect Power Univ State Key Lab Alternate Elect Power Syst Renewabl Beijing 102206 Peoples R China N China Elect Power Univ Beijing Key Lab Multiphase Flow & Heat Transfer L Beijing 102206 Peoples R China Tsinghua Univ Minist Educ Key Lab Thermal Sci & Power Engn Beijing 100084 Peoples R China Natl Taiwan Univ Sci & Technol Coll Engn Dept Chem Engn Taipei 106 Taiwan Natl Taiwan Univ Dept Chem Engn Taipei 106 Taiwan

IAPWS-IF97 is widely applied to computations of thermodynamic property for water and steam;however, the proposed computation algorithm is not high efficient enough to complicated applications such as heat cycles optimization and as database for computational fluid dynamics software. This paper proposed a rapid and accurate computation scheme based on double-grid, bi-quadratic spline interpolation scheme for calculating thermodynamic properties of water and stream on p-T thermodynamic surface. The computational region proposed is valid at 273.16-1073.15 K and 0.001-100 MPa, covering IAPWS-IF97 regions 1-4. To resolve the discontinuity problem for thermodynamic properties and their derivatives in the vicinity of the saturated line and in the critical region, the division of computational region is divided in to thirty-two sub-regions with adopted equidistant grids in each sub-region. A boundary normalization approach is proposed to convert the sub-regions with saturated line or pseudo-critical temperature curve as boundary into rectangular computational region. Then the spline functions g(SPL)(p,T), rho(SPL)(p,T), s(SPL)(p,T) and h(SPL)(p,T) are determined based on data by IAPWS-95 formulation. All tested results revealed superior performance in both computation speed (10.8-642 times faster) and prediction consistency (1-2 orders better) for the present interpretation scheme than the IAPWS-IF97. (C) 2012 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

关键词： Water and steam p-T thermodynamic surface Thermodynamic properties Spline interpolation Rapid computation

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Entropy and exergy analysis of the steam jet condensation in crossflow of subcooled water

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ANNALS OF NUCLEAR ENERGY 2023年 180卷

作者： Xu, Qiang Liu, Qimeng Zhu, Yongshuai Luo, Xinyi Tao, Leqing Guo, Liejin Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The direct contact condensation of steam jet in the liquid is an irreversible process with inevitable energy loss. In this paper, interaction between the subcooled water and gas-liquid two-phase boundary, and influence of thermal hydraulic parameters on the change of entropy and exergy are studied. Because of the crossflow of subcooled water, two-phase heat transfer occurs mainly in four regions of the plume cross-section. With increasing temperature, the growth rate of subcooled water entropy flow increases significantly, and the change in the dissipation ratio and damping ratio of kinetic energy is smoother. With the increase of steam mass flux, the entropy flow of the subcooled water reaches a peak at the end of the plume and the peak continuously increases, and the dissipation ratio of kinetic energy and the subcooled water entropy flow fluctuate more violently. Most energy dissipation occurs between the location of maximum jet velocity and the tail of steam jet.

关键词： Direct contact condensation Jet in crossflow Two-phase flow Entropy analysis Exergy analysis

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Combustion Desorption for Carbon Capture by Waste Incineration

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INDUSTRIAL & engineering CHEMISTRY RESEARCH 2020年第44期59卷 19657-19667页

作者： Zhang, Jingfeng Zhang, Chen Yu, Yunsong Zhang, Zaoxiao Wang, Geoff Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian 710049 Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China Univ Queensland Sch Chem Engn St Lucia Qld 4072 Australia

Amine scrubbing is the benchmark technology for carbon capture. However, amine scrubbing requires elevated-temperature steam to promote CO2 desorption. In order to solve the problem of high energy consumption, a combustion desorption reaction system (CDRS) was proposed, which integrates an electrochemical process and waste incineration process. A CDRS model was developed. Experimental study and numerical simulations on the CDRS were conducted. The effects of the initial value of concentration, the position of the anode plate, the depth of the solution, and the size of the reactor on CDRS performance were studied. It is found that electron transfer occurs during the reaction and a voltage of 0.35 V is generated. In addition, it is shown that the maximum CO2 desorption temperature in the system is 88 degrees C, and its average value is around 63 degrees C. The energy consumption is determined as 1.4 GJ/t. The CDRS increases the CO2 desorption rate by 98% at 90 degrees C compared to the amine scrubbing technology.

关键词： Redox reactions Desorption Wastes Amines Energy

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Kramers' problem and the Knudsen minimum: A theoretical analysis using a linearized 26-moment approach

Kramers' problem and the Knudsen minimum: A theoretical anal...

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作者： Gu, Xiao-Jun Emerson, David R. Tang, Gui-Hua Computational Science and Engineering Department STFC Daresbury Laboratory Warrington WA4 4AD United Kingdom School of Energy and Power Engineering State Key Lab of Multiphase Flow Xi'An Jiaotong University Xi'an 710049 China

A set of linearized 26 moment equations, along with their wall boundary conditions, are derived and used to study low-speed gas flows dominated by Knudsen layers. Analytical solutions are obtained for Kramers' defect velocity and the velocity-slip coefficient. These results are compared to the numerical solution of the BGK kinetic equation. From the analysis, a new effective viscosity model for the Navier-Stokes equations is proposed. In addition, an analytical expression for the velocity field in planar pressure-driven Poiseuille flow is derived. The mass flow rate obtained from integrating the velocity profile shows good agreement with the results from the numerical solution of the linearized Boltzmann equation. These results are good for Knudsen numbers up to 3 and for a wide range of accommodation coefficients. The Knudsen minimum phenomenon is also well captured by the present linearized 26-moment equations. © 2009 Springer-Verlag.

关键词： Method of moments

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Thermodynamic analysis and optimization of Allam cycle with a reheating configuration

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ENERGY CONVERSION AND MANAGEMENT 2020年 224卷 113382-113382页

作者： Chan, Wen Lei, Xianliang Chang, Fucheng Li, Huixiong Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The Allam cycle is one of the most promising oxy-combustion systems and has attracted much attention from the energy industry. A novel layout of the Allam cycle, which combines a reheating configuration with the original Allam cycle, was proposed in the present study. The effects of key variables on the net cycle efficiency and net specific work of the new system were investigated. The Allam cycle with reheat was optimized to maximize the cycle efficiency and compared with other cycles. The results showed that the minimum cycle temperature and the outlet temperature of the second combustor have significant effects on the cycle performance, while the maximum cycle pressure has minimum effect on the cycle performance. The highest exergy destruction of the optimized cycle is contributed from the two combustors, which accounts for 25.42% of the total input exergy. The net efficiency of the optimized Allam cycle with reheat is up to 49.32%, a little higher than those of other oxy-combustion cycles and about 5 percentage points lower than that of the original Allam cycle. However, the net power output and net specific work are up to 904.6 MWe and 606.2 kJ/kg for this novel system, about 2.1 times and 2.2 times of those of the original Allam cycle, respectively.

关键词： Oxy-combustion Allam cycle Thermodynamics Optimization Carbon capture

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Flexibility and efficiency co-enhancement of thermal power plant by control strategy improvement considering time varying and detailed boiler heat storage characteristics

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ENERGY 2021年 232卷 121048-121048页

作者： Wang, Zhu Liu, Ming Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Shaanxi Peoples R China

Flexibility enhancement of coal-fired power plants is extremely urgent to accommodate high-penetrated renewable energy and maintain the stability of power grid. Cycling rate, an important aspect of operational flexibility of coal-fired power plants, is mainly dragged by the large boiler thermal inertia. The idea of this study is to enhance the flexibility of the power plant by clarifying and considering the time varying and detailed boiler heat storage characteristics. The dynamic simulation and control models of a double-reheat power plant are developed and validated. The time varying and detailed boiler heat storage characteristics are represented by the principal parameters obtained by using stepwise regression algorithm. The improved control strategy is proposed and its performances are examined. Results show that the improved control strategy can enhance load cycling rate from 9.9 MW min(-1) to 23.1 MW min(-1), and the accumulative standard coal consumption rate can be reduced by 0.47%. Moreover, the control parameters, including output power and steam temperature, can reach the target quickly and are accurately controlled. The improved control provides a detailed guidance for the trade-off between the flexibility and high-efficiency in power plants during load cycling processes. (C) 2021 Elsevier Ltd. All rights reserved.

关键词： Heat storage Stepwise regression Control optimization Double reheat Coal-fired power plant

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Numerical investigation of the transient performance of a reversible solid oxide cell during the mode switching process

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ENERGY CONVERSION AND MANAGEMENT 2022年 268卷

作者： Li, Bohan Wang, Chaoyang Liu, Ming Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Reversible solid oxide cells (RSOC) have attracted much attention due to their unrivaled efficiency. As one of the most promising energy storage and conversion technologies, the RSOC will have to switch frequently between fuel cell and electrolysis mode to follow the nature of intermittent renewable energy sources and meet time-varying electricity demand. In this paper, a 3D dynamic model of a single repeating unit was developed and validated. Based on this model, the interaction between the transient external electrical performance with the temporal-spatial evolution of the reactant and product concentrations was investigated during the RSOC switching from SOFC to SOEC. Once the mode switching occurs, the power density decreases to a lower value and then asymptotically recovers to a new quasi-steady state. The recovery time of the concentration field within porous electrodes determines the total transient time. In addition, detailed parametric studies for the key design and operational parameters are conducted to find out their impact on the power density overshoot (PDO) and relaxation time (tau(0)). The results suggest that shortening the cell length can effectively reduce PDO and tau(0). With the hydrogen molar fraction of the incoming fuel gas (x(H2)) equal to 0.2 and 0.8, respectively, the maximum values of PDO and tau(0) are attained. Compared with the maximum value, when adopting 0.4 <= x(H2) <= 0.6, the PDO and tau(0) can be reduced by 40 % and 25 %, respectively. Extending the mode switching time can effectively reduce PDO and tau(0). The power density drops directly into the quasi-steady state without oscillations when the switching time is more than 0.3 s, and the tau(0) is slightly shorter than the mode switching time.

关键词： Reversible solid oxide cell Mode switching power density overshoot Transient performance

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Numerical investigation on the radiation performance of a crisscross liquid droplet radiator in space under different operating conditions

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APPLIED THERMAL engineering 2023年第1期229卷

作者： Zhu, Maoguo Sha, Zhaoyang Zhao, Quanbin Chong, Daotong Chen, Weixiong Yan, Junjie Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

Crisscross liquid droplet radiator (LDR) is a promising solution for the heat dissipation of large-power spacecraft. In this study, a three-dimensional steady numerical simulation of the radiation performance of crisscross LDR in space under different operating conditions was conducted. Significantly, the radiation interaction between adjacent droplet planes was introduced into the radiation model to accurately compute the radiative heat transfer in the crisscross droplet sheet. Simulation results indicated the radiation performance of crisscross droplet sheets deteriorated with an increase in the nonuniformity of droplet plane arrangement and the radiation power of uniform crisscross LDR was 17.7% higher than that of the most nonuniform. Moreover, there existed a critical droplet sheet angle of 72 degrees where the pressure disturbance frequency almost did not influence the radiation performance of crisscross LDR. For a certain pressure disturbance frequency, decreasing the droplet sheet angle can expand the available operational pressure difference range. The radiation performance of hightemperature crisscross LDR was more sensitive to the variation of droplet sheet angle than that of the lowtemperature crisscross LDR. Furthermore, the optimal working medium collocation scheme and droplet sheet structure for liquid metal crisscross LDR were proposed. Given the lightweight and efficiency of liquid metal crisscross LDR, the collocation scheme of working medium including liquid tin and lithium can be adopted and the droplet sheet angle should be designed as 15 degrees. The present work can provide significant guidance for selecting suitable operating conditions for droplet generators to optimize the thermal design of a crisscross LDR.

关键词： Numerical simulation Crisscross LDR Radiation performance Operating condition Droplet sheet angle Liquid metal

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