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Study on Variable Condition of Large Temperature Differential Heating System With Integrated Ejector Heat Pump

Kung Cheng Je Wu Li Hsueh Pao/Journal of engineering Thermophysics 2022年第4期43卷 863-869页

作者： Wang, Li-Yuan Liu, Ji-Ping Fu, Yue Liu, Ming Yan, Jun-Jie Key Laboratory of Heat Flow Science and Engineering of Ministry of Education Xi'an Jiaotong University Xi'an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

In the case of increasing urban heating demand, reducing the return water temperature of primary heating network can improve the heating capacity and utilize and recycle low-temperature waste heat resources. The ejector heat pump can use the high temperature heat source of the primary heat network to reduce the temperature of the return water, it has the advantages of simple structure, stable and reliable operation. In this paper, a model of ejector heat pump system is established to study the variable operating conditions of ejector heat pump system under central heating regulation. The results show that the ejector heat pump can effectively reduce the primary heat network return water temperature, and the primary network return water temperature can be reduced by 22 degree centigrade under the same primary network water supply temperature. With the increase of water supply temperature of primary network, the temperature of primary network return water, COP of the heat pump system and ejector ejection ratio increase gradually, the exergy efficiency decreases gradually. In the process of heating regulation, with the increases of outdoor temperature, the primary network return water temperature increases continuously, and the exergy efficiency decreases gradually;However, when the outdoor temperature is lower than the local design temperature, the ejector ejection ratio and the COP of the heat pump system decrease sharply. © 2022, Science Press. All right reserved.

关键词： Water temperature

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Changing Conditions and Thermodynamic Transient Characterization of Therminol VP-1 Oil-Water Heat Exchanger

Changing Conditions and Thermodynamic Transient Characteriza...

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power System and New Energy Technology Innovation Forum (NPSIF), Boao New power System International Forum -

作者： Shuai Dong An Zheng Peng Wang Chaoyang Wang HUANENG YIMIN COAL-POWER CO. LTD. Hulunbuir China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (数字)9798331504557

ISBN: (纸本)9798331504564

In this paper, the exergy efficiency of high-pressure heater feedwater in a coal-fired power generation thermal system heated with Therminol VP-1 as the thermal fluid is investigated, and the transient characteristics of the heat exchanger are analyzed after changes in heat transfer oil parameters. The results show that the exergy efficiency of Therminol VP-1 for heating feedwater tends to decrease as the unit load decreases. The exergy efficiency for heating high pressure heater feedwater was 80% to 90%, with a maximum of 90.3%. The time required to reach the new steady state after perturbation of the boundary parameters of the oil-water heat exchanger increased with the load rate, with a minimum of 200 s and a maximum of 500 s in the study range. the new steady state was reached more quickly with increasing load than with decreasing load.

关键词： Thermodynamics Technological innovation Oils Water heating power system stability Thermal analysis Steady-state Transient analysis Heat transfer Turbines

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Novel Matching Strategy for the Coupling of Heat Flux in Furnace Side and CO_(2)Temperature in Tube Side to Control the Cooling Wall Temperatures

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Journal of Thermal Science 2021年第4期30卷 1251-1267页

作者： LIU Chao MIAO Zheng XU Jinliang XU Zeyu LI Mingjia Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power UniversityBeijing 102206China Key Laboratory of Power Station Energy Transfer Conversion and System North China Electric Power UniversityMinistry of EducationBeijing 102206China Key Laboratory of Thermo-Fluid Science and Engineering of Ministry of Education School of Energy&Power EngineeringXi’an Jiaotong UniversityXi’an 710049China

Required by the supercritical carbon dioxide(s CO_(2))coal-fired power cycle,s CO_(2)entering a boiler has a high temperature and can cause overheating of *** eliminate the pressure drop penalty effect,the s CO_(2)boiler consists of several modules,each having different heat flux received from the furnace side(q)and different CO_(2)temperature in the cooling wall tube(T_f).We aim to search for the best matching strategy coupling furnace side and tube side to obtain the lowest temperature of *** theoretically analyzing the wall temperature influenced by q,T_f and a comprehensive thermal resistance C,two matching methods are introduced:the heat flux-temperature matching(HTM)which matches higher q with lower T_f,and the heat flux-heat flux matching(HHM)that matches higher q with higher allowable-heat-flux at the temperature limit of *** is a conventional method but HHM is newly proposed *** show that,if C is identical for different modules,the two methods coincide;otherwise,HHM is *** a s CO_(2)boiler driving 1000 MWe power plant,smaller cooling wall temperatures are obtained by HHM than *** on HHM,the mid-partition wall,heat transfer enhancement,and downward flow are comprehensively used,decreasing the wall temperature significantly.

关键词： sCO_(2)power cycle sCO_(2)modular boiler cooling wall temperature allowable heat flux matching strategy

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Experimental Study on the Propagation Mechanism of Acetylene-Air Detonation Waves in a Unilaterally Intermittently Constrained Channel

SSRN

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SSRN 2024年

作者： Gai, Jingchun Qiu, Hua Xiong, Cha Zhao, Minghao He, Xinlu Yang, Zhan Feng, Zhiyuan Cehn, Xitao Huang, Zuohua School of Power and Energy Northwestern Polytechnical University Xi’an710072 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

This study experimentally explores the propagation mechanisms of acetylene/air detonation waves within a channel intermittently constrained on one side, utilizing soot foil and high-speed schlieren photography to capture the cellular structure and shock-flame evolution. The experiments revealed that the detonation waves traverse the semi-enclosed channel with various discrete wall configurations on the side in four distinct propagation modes: (I) periodic detonation failure and re-initiation;(II) single extinction and re-initiation;(III) localized extinction and (IV) non-extinction. Mode I occurs exclusively when the open area ratio exceeds 0.85, while detonation tends to favour Mode II when the gaps between discrete walls exceed three times the cell size;otherwise, it tends towards Modes III and IV. The re-initiation mechanism of detonation involves curvature shocks inducing local explosions of reactive mixtures through multiple Mach reflections off the discrete walls. The self-sustained propagation mechanism of the detonation wave is maintained by the interaction of strong transverse shocks reflected from discrete walls with the inherent transverse waves within the detonation structure, sustaining the instability of the cellular detonation. © 2024, The Authors. All rights reserved.

关键词： Detonation

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A Preliminary Study on the Blistering Behavior of Dispersion Plate-Type Fuel Assembly

SSRN

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SSRN 2024年

作者： Yu, Songjiao Zhang, Kui Yang, Yiming Liu, Yumin Tian, Wenxi Qiu, Suizheng School of Nuclear Science and Technology Shanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China

The dispersion plate fuel assembly, owing to its favorable characteristics of low temperature gradient, high stability, and excellent thermal conductivity, has become a focal point in the research of novel high-performance fuel elements. However, the current literature lacks a comprehensive understanding of the fuel plate's performance, particularly with regard to the bubbling phenomenon in the fuel plate cladding. In this study, we have implemented a fission gas release model, building upon previous analyses of fuel plate performance under steady-state operation. By comparing our calculation results with the Forsberg-Massih model, we find a close correspondence in trends, thereby validating the accuracy of our computational approach. Furthermore, we utilize the upgraded FROBA-PLATEs code to predict the blistering behavior of fuel plates under specific quasi-steady-state conditions. Our results demonstrate that the occurrence position and threshold temperature of blistering in the fuel assembly can be precisely predicted using this approach. © 2024, The Authors. All rights reserved.

关键词： Fission products

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Low temperature overpressurization analysis for CPR1000

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International Journal of Advanced Nuclear Reactor Design and Technology 2021年 3卷 145-153页

作者： Liang, Yu Wang, Mingjun Li, Zhen Liao, Haoyu Zhang, Dalin Tian, Wenxi Qiu, Suizheng Su, G.H. School of Nuclear Science and Technology Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China Huaneng Shandong ShidaoBay Nuclear Power Plant China

An additional low temperature overpressure protection system which relies on the Pressurizer (PRZ) pressure relief valves has been put forward under the situation in which the Residual Heat Removal System (RHRS) is unavailable or isolated. Taking into account the risk of Reactor Pressure Vessel (RPV) brittle fracture and LOCA under cold overpressurization transients, it is urgent to strengthen the low temperature overpressure protection for in-service Pressurized Water Reactors (PWR) in China. In this paper, the simulation and analysis of two types of overpressure transients at low temperature during the shutdown process are carried out through the detailed Relap5 modeling of CPR1000. The results show that the place where the brittle fracture occurs firstly is the lower plenum. The sensitivities of the system temperature and the opening/closing time of the additional protection system's valve are analyzed. The system set point becomes more restrictive at lower coolant temperature. Additional threshold values of the PRZ pressure relief valve are given under different Effective Full power Years (EFPY). The set point should be less than 5.5 MPa in the case of 5 EFPY and less than 3.7 MPa at 10 *** results can be applied to engineering practice, which can effectively improve the safety of CPR1000. © 2021

关键词： Pressure relief valves

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Co-Optimization for Distributed Multi-Energy System Based on Multi-Objective Robust Stackelberg Game: Energy Management and Multi-Energy Pricing

SSRN

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SSRN 2024年

作者： Ren, Xiaoxiao Wang, Jinshi Yang, Sifan Zhao, Quanbin Jia, Yifan Ou, Kejie Hu, Guangtao Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China School of Energy Engineering Yulin University Yulin719000 China

To achieve low-carbon operation of distributed multi-energy system (DMES) and enhance its activity in the energy market, this paper proposes a novel multi-objective Stackelberg game model. The DMES operator (DMEO) acts as the leader, guiding users' behavior through DMES optimal scheduling and multi-energy pricing. The optimization objectives include maximizing DMEO revenues, minimizing DMES primary energy consumption and carbon emissions. The users act as followers, adjusting energy demand based on upper-level energy pricing with the objective of maximizing consumption surplus. To achieve the low-carbon and flexible operation of DMES, carbon trading and demand response mechanisms are introduced. The upper-level model is solved using the non-dominated sorting genetic algorithm III (NSGA-III), while the lower-level model is solved by the Gurobi solver. Furthermore, a robust optimization model with adjustable robust measure is established to mitigate the impact of renewable energy uncertainty. Finally, the validity of the proposed model is verified by a data center in Qinghai. Compared with traditional Stackelberg game model, the proposed model reduces DMEO revenue by 0.63% but decreases carbon emissions by 1.64% and energy consumption by 1.59%. Under this optimization framework, the energy efficiency and exergy efficiency of DMES are 0.798 and 0.535, and the share of renewable energy is 34.6%. Besides, increasing renewable energy uncertainty leads to lower DMEO revenue, higher carbon emissions and energy consumption, while significantly reducing energy efficiency and exergy efficiency. The proposed multi-objective Stackelberg game model may provide some references for multi-stage energy system optimization. © 2024, The Authors. All rights reserved.

关键词： Energy utilization

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Numerical Simulation Investigating the Influence of Varied Stack Parameters on the Energy Conversion in Thermoacoutic Engines

SSRN

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SSRN 2024年

作者： Yao, Chen Zhou, Yao Liu, Jiping Yan, Junjie MOE Key Laboratory of Thermal Fluid Science Engineering Xi’an Jiaotong Univeristy Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong Univeristy Xi’an710049 China

The stack is a crucial component of the thermoacoustic heat engine, influencing its capacity to generate stable pressure amplitude and enhance efficiency. Utilizing the discontinuous Galerkin (DG) method, fully compressible Navier-Stokes equations were solved to simulate the energy exchange between the stack and surrounding air under various conditions.(1) Simulations were conducted under different stack wall boundary conditions, including linear temperature distribution wall, isothermal wall, and adiabatic wall. The work performed by 1 kg of gas at a specific position during one cycle was defined as local energy density to analyse the effect of different stack spacing, stack length and stack thickness. (2) Too small a stack spacing causes the inability to generate pressure amplitude. Increasing the stack spacing continuously enhances the generated pressure amplitude, with the energy density distribution near the hot heat exchanger becoming more significant. As the stack spacing continues to increase, the energy density decreases at positions farther from the wall, leading to a reduction in pressure amplitude. The generated acoustic streaming intensity diminishes faster with the continuous increase in stack spacing. (3) A smaller stack length results in reduced viscous dissipation at the wall, leading to a larger generated pressure amplitude. However, shorter stack lengths cause increased gas oscillation displacement, resulting in lower energy density concentrate around the stack. This raises the load on the two heat exchangers, consequently reducing the overall efficiency. (4) The pressure amplitude decreases with the increase in stack thickness. The vortex intensity at the gap between the hot heat exchanger and the stack increases with the stack thickness, leading to higher viscous losses for the fluid passing through this region. Consequently, the performance of the thermoacoustic engine declines. These findings provide valuable guidance for the design of thermoa

关键词： Numerical methods

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Data-Driven Surrogate Model for the Dynamic Characteristics of Supercritical Units

Data-Driven Surrogate Model for the Dynamic Characteristics ...

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power System and New Energy Technology Innovation Forum (NPSIF), Boao New power System International Forum -

作者： Shuai Dong An Zheng Junyao Jiang Wei Gao Ming Liu HUANENG YIMIN COAL-POWER CO. LTD. Hulunbuir China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an China

ISBN: (数字)9798331504557

ISBN: (纸本)9798331504564

Coal-fired power generation units are characterized by large inertia, strong coupling, and high delay, making dynamic characteristic modeling inherently complex and computationally intensive. To address this, this paper utilizes GSE software to explore the dynamic characteristics of supercritical units. Data-driven approaches are then employed to develop surrogate model for these dynamics, comparing neural networks and support vector regression methods in the process. The study indicates that the surrogate model achieves a relative prediction error of less than 1% for live steam temperature, reheater steam outlet temperature, and power output. For live steam pressure and reheater steam outlet pressure, the model maintains a relative error within 10%.

关键词： Support vector machines Technological innovation Temperature Accuracy Computational modeling power system dynamics Neural networks Predictive models Vectors Load modeling

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Study on the Three-Dimensional flow Control of Two-Phase flow Around a Cylinder by an Attached Cylinder

SSRN

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SSRN 2023年

作者： Xia, Yizhan Hu, Yu Huang, Shengxian Wang, Ying Shanghai key laboratory of multiphase flow and heat transfer of power engineering School of Energy and Power Engineering University of Shanghai for Science and Technology Shanghai China

Enhancing the separation of flow, shedding of vortices, and sediment deposition around blunt bodies, particularly in cylindrical flows within the realm of ocean engineering, emerges as a pivotal safety factor. This study delves into the control of two-phase flow encircling a cylinder using an affixed cylinder under three-dimensional real ocean conditions. Employing the SST turbulence model, a two-dimensional incompressible RANS numerical simulation is performed. Initially, the influence of varying gap ratios between the auxiliary small cylinder and the main cylinder is scrutinized. Subsequently, the impact of attached small cylinders on the flow field surrounding the main cylinder is examined under different particle characteristics. Lastly, employing the UDF function, four small cylinders exhibiting distinct vibration modes are defined, and the numerical simulation investigates the effects of Grain flow on particle flow and distribution in the wake region of the main cylinder. © 2023, The Authors. All rights reserved.

关键词： Cylinders (shapes)

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