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SSRN 2022年

作者： Shakeel, Asim Chong, Daotong Wang, Jinshi State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi'An710049 China

Accurate load forecasting of district heating networks (DHN) is an essential guide to guaranteeing effective energy production, distribution, and rational utilization. Artificial neural networks have been extensively applied to heating energy prediction in DHN. An improved FB-Prophet model with additional positional encoding layers has been developed to forecast the DHN heat consumption. The accuracy of univariate and multivariate FB-prophet models is evaluated;this paper also investigates how training data affects the accuracy and robustness of improved FB-prophet model. Results revealed that the accuracy of the improved FB-Prophet model increases as the amount of training data increases;it is also observed that there exists a turning point after which robustness starts to decrease. To explore the performance of the improved FB-Prophet model in heating load forecasting tasks, another seven machine learning models, namely FB-Prophet, DeepVAR, long-short term memory (LSTM), extreme gradient boosting (XGBoost), multilayer perceptron (MLP), recurrent neural network (RNN), and support vector regression (SVR) are used for comparison. The historical heating load, outside temperature, relative humidity, speed of wind, direction of wind, and weather type (sunny, overcast, rainy) of a DHN in Serbia are utilized as the key parameters to extensively investigate the effectiveness of the improved FB-Prophet model. The prediction outcomes of all the models were analyzed thoroughly. The results indicated that the improved FB-Prophet model can generate the most precise and consistent predictions and it showed better results for sparse and noisy data of DHN. The prediction curve is fitted to the trend of hourly DHN consumption change, which can play an effective guiding function in the distribution of heat. © 2022, The Authors. All rights reserved.

关键词： Forecasting

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Comprehensive Performance Analysis of Steam and Flue Gas Stepwise/Staged Heating Molten Salt Thermal Storage Systems Coupled with Coal-Fired Power Plants

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SSRN 2024年

作者： Jing, Hao Wang, Dengliang Chen, Weixiong Zhao, Yongliang Wang, Chaoyang Zhang, Kezhen Yan, Junjie State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Xi’an710049 China Xi’an Thermal Power Research Institute Co. Ltd. Xi’an710054 China

The rapid development of renewable energy has put forward higher requirements for the flexibility and deep peak shaving ability of coal-fired power plants (CFPPs). Molten salt thermal energy storage (TES) is considered a potential solution. In this study, a CFPP coupled steam and flue gas stepwise/staged heating molten salt TES system is proposed. The proportion of steam thermal energy allocated to the molten salt and feed water is adjusted. The thermodynamic and economic performance of two configurations under different thermal load distribution ratios are compared and studied. The results show that with the increase of molten salt thermal load distribution ratio, the thermal storage capacity, denitrification efficiency, and charging exergy loss increase, while the equivalent round-trip efficiency, energy storage density, and discharging exergy loss decrease. When the molten salt thermal load distribution ratio is the same, the stepwise configuration has higher energy storage density and denitrification efficiency, lower charging exergy loss of TES, and better economic performance. The staged configuration has higher thermal storage capacity and lower exergy loss of CFPP. In general, the economic performance of the stepwise configuration is higher, while the staged configuration's thermodynamic performance is higher. © 2024, The Authors. All rights reserved.

关键词： Coal fired power plant

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Experimental Study on Non-Isothermal Mixing Characteristics of Water in T-Junction

Experimental Study on Non-Isothermal Mixing Characteristics ...

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China Instrument and Control Society (ACCIS), Academic Conference of

作者： Shuhan Liu Wencang Guo Xianliang Lei Zhaojun Yuan Shuqi Meng Desheng Jin State Key Laboratory of Multiphase Flow Engineering Xi'an Jiaotong University Xian China China Nuclear Power Technology Research Institute Co. Ltd. Shen Zhen Guangdong China

ISBN: (数字)9798350350326

ISBN: (纸本)9798350350333

T-junction is an essential component in piping system of various thermal systems. When hot and cold fluid mixing in the T-junction, several compound mechanisms (like turbulent mixing, turbulent penetration, fluid stratification) make the mixing characteristics more complex. To clearly reveal such mixing mechanism with non-isothermal fluids, an experimental study was conducted with Ultrasound Doppler Velocimetry (UDV) and fast-response thermocouples bundle. The results show that the local velocity uncertainty of the UDV is within 10%, the uncertainty of the thermocouple bundle is 0.5°C, and the response time is 66.7 ms. After verification, the mixing characteristics between the main and branch pipe under different momentum ratios and temperature differences were discussed. It is shown that as the momentum ratio decreases, the location of the most intense radial temperature fluctuations and velocity fluctuations shifts towards the lower wall. At the same time, the peak flow rate in the cross-section increases by 35.7% and the main branch fluid mixing is more homogeneous. As the temperature difference increases, the thermal stratification is more pronounced and the velocity fluctuation peak moves towards the upper wall of the pipe.

关键词： Temperature measurement Temperature distribution Fluctuations Fluids Uncertainty Measurement uncertainty Thermocouples Distance measurement Velocity measurement Voltage control

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A Gpu-Accelerated Multi-Resolution Lsmps Method for multiphase flows Simulation with Gas-Liquid Phase Transition

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SSRN 2024年

作者： Cao, Sheng Ren, Qianyong Wang, Wenpeng Zhang, Bin Shan, Jianqiang School of Nuclear Science and Technology Xi’an Jiaotong University Shaanxi Xi’an710049 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

The meshless Lagrangian method (particle method) demonstrates significant advantages in simulating multiphase flows with highly dynamic phase interfaces and has been widely applied in research areas such as ocean engineering, nuclear engineering, and aerospace engineering. The least squares moving particle semi-implicit (LSMPS) method theoretically attains high-order accuracy, significantly enhancing the precision and stability of simulations. However, compared to traditional Eulerian methods, its numerical discretization is more complex and computationally intensive, which limits its applicability in large-scale simulations. To mitigate these challenges, a multi-resolution particle model is implemented to reduce computational costs, and algorithmic improvements and optimizations enable GPU-based parallel processing, significantly boosting computational efficiency. Building on this foundation, a high-precision surface particle detection algorithm and a stable gas-liquid phase transition model are developed. The phase transition model integrates the volume change resulting from phase transition as a source term in the pressure Poisson equation. Benchmark tests of single bubble rising in liquid, Rayleigh-Taylor instability, and two-dimensional horizontal film boiling were conducted to validate the accuracy and efficiency of the GPU- accelerated multi-resolution LSMPS method for simulating multiphase flows, thereby promoting the application of the LSMPS method in both scientific research and practical engineering. © 2024, The Authors. All rights reserved.

关键词： Poisson equation

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A Novel Optimization Framework for Distributed Multi-Energy System Management and Multi-Energy Pricing Based on Stackelberg Game

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SSRN 2023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. © 2023, The Authors. All rights reserved.

关键词： Energy utilization

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Thermal Characteristics and Structural Parameters Optimization of Apg/Cu/Pcm Integrated Architecture

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SSRN 2024年

作者： Su, Lizheng Zhang, Tianning Li, Xiaoyang Li, Dong Jiang, Xinyu Xie, Zhongnan Xi'an Electronic Engineering Research Institute Xi’an710100 China State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi’an710049 China State Key Laboratory of Nonferrous Metals and Processes GRINM Group Co. Ltd. Beijing100088 China

The challenges faced by radar seeker primarily stem from inadequate heat dissipation in chips and excessive weight. To address these issues, this study introduces a novel integrated phase-change heat sink architecture, composed of a copper alloy matrix, annealed pyrolytic graphite (APG), and phase-change materials (PCMs) serving as heat conduction reinforcements. The numerical analysis of the heat dissipation performance of this architecture is conducted using Fluent software. The study evaluates the impact of APG anisotropy, APG/Cu interface thermal resistance, APG thickness, and surface area on the heat conduction efficiency. Results demonstrate that APG facilitates a uniform in-plane temperature distribution, allowing PCMs to absorb heat more evenly. Consequently, APG proves effective in enhancing heat dissipation and safeguarding chips from high temperatures. In comparison to a pure copper component, the APG/Cu/PCM structure reduces chip temperature by a substantial 56.27%. Furthermore, increasing the surface area of APG generally contributes to an enhanced heat transfer capability of entire architecture. The paper presents a quantitative relationship between APG surface area and optimal thickness. Importantly, APG satisfies the lightweight requirement, further emphasizing its suitability for addressing the thermal challenges in radar seeker structures. © 2024, The Authors. All rights reserved.

关键词： Phase change materials

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Uncertainty Analysis of FLiNaK Thermophysical Properties on Convective Heat Transfer Characteristics in Circular Tube

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SSRN 2024年

作者： Li, Haoyang Ding, Ming Guo, Zehua Heilongjiang Provincial Key Laboratory of Nuclear Power System & Equipment Harbin Engineering University Harbin150001 China State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi’an Jiaotong University Xi’an710049 China

Molten salts have attracted a spate of quantity of interest in energy and chemistry fields due to their large volumetric capacity, and thermodynamic stability at elevated temperatures. However, on account of immature technology and measurement methods, the physical properties of molten salts, such as dynamic viscosity, thermal conductivity, specific heat capacity and density, have large uncertainties, which will be transported with CFD simulation equations and experimental processes. While present investigations normally focus on thermal-hydraulic characteristics, disregarding the impact of uncertainty on reactor safety. Thus, this paper firstly performs a numerical simulation to investigate the thermal-hydraulic performance of FLiNaK (LiF-NaF-KF, 46.5–11.5–42 mol%) in a horizontal tube using a computational fluid dynamic (CFD) tool, STAR-CCM+, and validates the applicability of classic correlations for molten salt. Based on this, an uncertainty analysis methodology, polynomial chaos expansion (PCE) is carried out to analyze the uncertainty that contributes to the heat transfer characteristic. Three primary physical properties of molten salt are considered as the input parameter, tensor product quadrature nodes are employed in this work to calculate the representative sample points to alleviate the computational expense. The contributions of each parameter to heat transfer are also analyzed by the sobol composition method. Finally, deviations in the experimental post-processing (compared with classic correlations) caused by discrepancies in the selected properties from the actual properties due to uncertainty are also taken into account. The result shows the thermal-hydraulic performance can be nicely modeled and simulated results are in good agreement with widely used correlations. Meanwhile, the consequences of uncertainty analysis suggest that the polynomial chaos expansion methodology is robust and neoteric for molten salt analysis. © 2024, The Authors. All righ

关键词： Uncertainty analysis

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金属原子诱导的微环境调控在聚合氮化碳光催化析氢中的研究

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Science China Materials 2024年第6期67卷 1765-1779页

作者：赵大明杨雨骁 Vasileios Binas 沈少华 School of Advanced Energy Shenzhen Campus of Sun Yat-sen UniversityShenzhen 518107China International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049China Institute of Electronic Structure and Laser(IESL) Vasilika VoutonHeraklion GR-71110Greece Physical Chemistry Laboratory Chemistry DepartmentAristotle University of ThessalonikiThessaloniki 54124Greece

开发高效稳定的半导体光催化剂对光催化技术迈向实际应用至关重要.聚合物氮化碳(CN)因其优异的物理化学性质而被视为最具发展前景的制氢光催化剂之一.在过去几十年中,从热力学或动力学角度开发的一系列改性策略已经显著提升了CN的光催... 详细信息

开发高效稳定的半导体光催化剂对光催化技术迈向实际应用至关重要.聚合物氮化碳(CN)因其优异的物理化学性质而被视为最具发展前景的制氢光催化剂之一.在过去几十年中,从热力学或动力学角度开发的一系列改性策略已经显著提升了CN的光催化制氢性能.近期,金属原子修饰策略为CN改性提供了一条新途径,这种策略可以精确调控CN的微环境.本文全面回顾了金属原子修饰的CN光催化剂在光催化分解水制氢领域的最新研究进展,包括金属单原子修饰的CN、金属双原子修饰的CN、金属单原子与团簇共修饰的CN,重点阐述了金属原子对提升光催化性能的关键作用.此外,本文还全面总结了发展先进的金属原子修饰的CN光催化剂所面临的挑战与机遇.

关键词： metal atom polymeric carbon nitride hydrogen evolution photocatalysis solar energy conversion

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Exploring Comprehensive Properties of a Novel Shape-Stabilized Composite Phase Change Material Of Lauric Acid-Palmitic Acid- Tetradecyl Alcohol/Vitrified Beads for Thermal Energy Storage

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SSRN 2024年

作者： Yan, Qiuhui Jia, Mengyu Luo, Jieren Meng, Zeyu School of Building Services Science and Engineering Xi’an University of Architecture and Technology Xi’an710055 China State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong University Shaanxi Xi’an710049 China

Excellent thermal properties are the cornerstone of phase change materials (PCMs) employed for energy storage, and leakage prevention and sufficient strength are the key problems that must be solved in the practical application process of PCMs. Therefore, the advantages of ternary PCMs (Lauric Acid-Palmitic Acid-Tetradecyl Alcohol, LA-PA-TA) and adsorbent carriers (Vitrified Bead, VB) are integrated to obtain a novel LA-PA-TA/VB composite PCM which exhibits favorable phase change temperature (20.1°C-20.5°C) and excellent subcooling (0.4°C). Then, the novel LA-PA-TA/VB is encapsulated with five materials to form shape-stabilized PCMs to reduce leakage. The experiments show that a shape-stabilized LA-PA-TA/VB (SS-LA-PA-TA/VB) encapsulated with the real stone paint emulsion-cement powder presents the optimal packaging effect, namely superior stability and reliability with low mass loss ratio of only 2.67% after 50 times phase change cycles. Next, the SS-LA-PA-TA/VB of the optimal package is further made into thermal energy storage mortar (TESM) with different SS-LA-PA-TA/VB content. It is shown that the thermal properties of TESM increase and the mechanical properties decrease with LA-PA-TA/VB. However, even with the LA-PA-TA up to 30% (30TESM), the compressive strength, flexural strength, apparent density, water absorption, and softening coefficient of the TESM still meets the Chinese National Standard, and some microscopic mechanisms have been investigated. Lastly, temperature regular ability and heat insulation performance of 30TESM and reference mortar are compared by temperature probe embedded inside the mortar blocks and installed in experiential small room. The results present that internal temperature of the mortar blocks, backside and central temperature of small room are 5.4°C, 5.6°C and 2.1°C lower than that of the reference group, respectively. It is thus clear that the novel low cost TESM exhibits a good temperature damping effect and temperature control p

关键词： Phase change materials

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A Novel Demand Response-Based Distributed Multi-Energy System Optimal Operation Framework for Data Centers

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SSRN 2023年

作者： Ren, Xiaoxiao Wang, Jinshi Hu, Xiaoyang Sun, Zhiyong Zhao, Quanbin Chong, Daotong Xue, Kai 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 address the increasing energy demands in data centers, distributed multi-energy system (DMES) may provide an efficient solution to achieve clean and sustainable energy supply. The use of a DMES optimal scheduling approach with source-load interaction plays a crucial role in improving data center performance. In this study, A DMES coupled by photovoltaics, wind turbines, ground source heat pump, internal combustion engines, electric chillers, absorption chillers, and energy storage devices is proposed. Considering the flexibility of workload scheduling and the challenges of renewable energy consumption, an integrated demand response model is established that considers time-of-use pricing and renewable energy peak subsidies. Then, a clean and economical optimal operation model for DMES based on proposed demand response and carbon trading mechanisms is established. Finally, to enhance the robustness of scheduling, the impacts of uncertainties in renewable energy output and demand response on system operation are analyzed by combining the Monte Carlo method and the interval method. Case study results demonstrate that implementing the proposed demand response and carbon trading mechanism improves data center performance by reducing total costs by 1.85%, carbon emissions by 0.56%, electricity purchases by 2.93%, while increasing renewable energy utilization by 0.77%. Additionally, optimization considering multiple uncertainties, results in higher total costs and broader interval widths compared to single-factor uncertainty optimization, but reduces system operational risk. © 2023, The Authors. All rights reserved.

关键词： Energy utilization

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