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High Voltage 2024年第1期9卷 217-229页

作者： Lijing Zhang Yingting Luo Gehao Sheng Zizhan Ni Xiuchen Jiang department of electrical engineering Shanghai Jiao Tong UniversityShanghaiChina electric power Research Institute of Guangdong power Grid Corporation GuangzhouChina

Accurate assessment of hot-spot temperature is essential for the safe operation of power *** dynamic thermal models cannot estimate hot-spot temperature accurately since some input parameters are roughly determined by transformer capacity and cooling mode while ignoring the effect of winding structure,tank dimensions,and material physical *** improve the accuracy of temperature assessment,empirical parameters of the IEC thermal model including thermal constants,winding and oil exponents are optimised with the help of numerical simulation in this *** on energy conservation and heat transfer theory,a computational fluid dynamic(CFD)model of a transformer in oil natural air natural(ONAN)cooling mode is *** CFD model simulates the entity's structure,sizes,and multi-stage heat dissipation processes realistically,so it can more precisely calculate the dynamic hot-spot *** to the simulated temperature curves at different operating conditions,the thermal constants and oil exponent are estimated using non-linear regression,and the winding exponent is optimised using linear regression.A case study is conducted on an ONAN *** shows the improved IEC model with optimised parameters can more accurately evaluate hot-spot temperature,and the absolute error is decreased by 2.4 K(38.7%)compared with traditional thermal models.

关键词： temperature properties. thermal

Numerical Investigation on Characteristics of Supercritical CO_(2)Heat Transfer in Vertical Circular Tubes with Circumferentially Half-Side Heating

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Journal of thermal Science 2024年第5期33卷 1744-1756页

作者： ZHANG Yan ZHANG Xinyi YAN Chenshuai WU Wenhua GAO Erman School of Energy and power engineering Northeast Electric Power UniversityJilin 132012China

The design of heat exchangers in the advanced supercritical power conversion system cannot be separated from the study of heat transfer ***-side heating mode is often encountered for solar receiver and supercritical ***,the characteristics of supercritical CO_(2)(sCO_(2))convection heat transfer in vertical tubes with circumferentially half-side heating was numerically investigated through the SST k-ωturbulent model which matches well with the experimental ***,heat transfer between sCO_(2)upflow and downflow was *** to film boiling heat transfer at subcritical pressure,numerical results were processed according to the supercritical pseudo-phase transition hypothesis,with liquid-like phase in the tube core region and vapor-like film in the region near the heated tube *** structure of two layers was demarcated by pseudo-critical temperature T_(pc).Therefore,sCO_(2)heat transfer was assessed according to double thermal resistances caused by vapor-like film near the wall and core liquid-like *** findings suggest that wall temperature for upflow is higher than that for downflow,which is attributed to larger thermal resistance in the fluid domain for upflow than that for *** difference guarantees the excellent heat transfer performance for downflow than *** is also further concluded that the formation of vapor-like film near the wall due to pseudo-phase transition plays a key role in dominating wall temperature and inducing heat transfer deterioration in half-side heating *** present contribution is significant to the design of supercritical heat exchanger under half-side heating mode.

关键词： supercritical CO_(2) pseudo-phase transition half-side heating thermal resistance flow direction

Stall Evolution Mechanism of a Centrifugal Compressor with a Wide-Long Vaneless Diffuser

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Journal of thermal Science 2024年第3期33卷 899-913页

作者： ZHANG Lei KANG Jiacheng LANG Jinhua AN Guangyao ZHANG Qian WANG Longyao WANG Qifang department of power engineering North China Electric Power UniversityBaoding071003China Hebei Key Laboratory of Low Carbon and High Efficiency power Generation Technology North China Electric Power UniversityBaoding071003China

The rotating stall mechanism is of high importance for the stability of centrifugal compressors and thermal power *** majority of research concerning this topic has concentrated on the initial stall ***,the evolution of stall cells in wide-long diffusers has not been comprehensively *** this paper,the causes of rotating stall in the wide-long diffuser and the three-dimensional evolution mechanism of stall cells during the stall process were thoroughly *** the stall induction phase,an annulus vortex structure was found in the reverse-flow zone near the hub side of the diffuser outlet,which was the initial form of stall *** whole evolution process of stall cells was divided into three phases as the flow rate *** the initial stall phase,the dynamic equilibrium was built under effects of the impeller wake and the adverse pressure *** a result,the number of stall cells was kept at seven and the size of stall cells remained *** the transition phase,the flow in the diffuser became *** cells extended to the impeller outlet,and the effect of the wake flow was strengthened *** cells started integrating and separating *** a result,the number and propagation speed of stall cells varied periodically at a constant mass flow *** the deep stall phase,the size of stall cells remained unchanged,and the number of stall cells kept at *** study has important practical guidance and engineering value for the high-efficiency design and safe operation of centrifugal compressors.

关键词： centrifugal compressor wide-long vaneless diffuser stall evolution mechanism wake flow

A Detailed thermal Resistance Network Analysis of FCBGA Package

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Journal of thermal Science 2024年第1期33卷 18-28页

作者： DANG Hao LU Yang DU Yanzheng ZHANG Xiu ZHANG Qian MA Weigang ZHANG Xing Key Laboratory for thermal Science and power engineering of Ministry of Education Department of Engineering MechanicsTsinghua UniversityBeijing 100084China Zhongxing Telecom Equipment Corporation Shanghai 201203China

Using thermal models to describe the heat dissipation process of FCBGA is a significant topic in the field of ***,the thermal resistance model considering the structure of each part of the chip is still ambiguous and rare,but it is quite desirable in *** this work,we propose a detailed thermal resistance network model,and describe it by using thermal conduction resistance and thermal spreading *** a striking FCBGA case,we calculated the thermal resistance of each part of the structure according to the temperature field simulated by *** thermal resistance network can be used to predict the temperatures in the chip under different *** example,when the power changes by 40%,the relative error of junction temperature prediction is only 0.24%.The function of the detailed thermal resistance network in evaluating the optimization space and determining the optimization direction is *** work illustrates a potential thermal resistance analysis method for electronic devices such as FCBGA.

关键词： FCBGA package thermal resistance network thermal spreading resistance junction temperature

Using CONTAM to design ventilation strategy of negative pressure isolation ward considering different height of door gaps

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Energy and Built Environment 2024年第1期5卷 32-45页

作者： Mingyao Ma Changsheng Cao Yukun Xu Zhijian Liu Lingjie Zeng Chengquan Zhang Jun Gao School of Mechanical engineering Tongji UniversityShanghai 200092China department of power engineering North China Electric Power UniversityBaodingHebei 071003China College of Civil engineering Tongji UniversityShanghai 200092China

Infectious disease departments in hospitals require pressure gradient to create unidirectional airflow to prevent the spread of contaminants,typically by creating active air infiltration through the difference between supply and exhaust air *** door gap is the channel of air flow between rooms,so its height has an important influence on the pressure difference and infiltration air volume of the *** is still a lack of research on setting reasonable ventilation strategies according to the different heights of door gaps at different positions in the *** this study,model of a set of isolation wards was established and analyzed using the multi-zone simulation software CONTAM,and the ventilation strategies with different heights of door gaps were applied to the actual infection diseases *** results show that in a building with ventilation system divided by functional area,the difference in the height of the door gaps requires different active infiltration air *** fluctuations in the medical and patient corridors are greater than in other *** significance of this study is to understand the active infiltration of air to guide the design and operation of ventilation systems in infectious disease hospitals or building remodeled to isolate close contacts of COVID-19 *** is also instructive for the design of pressure gradients in clean workshops,biological laboratories,and other similar buildings.

关键词： Door gap height Active infiltration Pressure gradient Multizone model CONTAM Control strategy

Low-Carbon Dispatching for Virtual power Plant with Aggregated Distributed Energy Storage Considering Spatiotemporal Distribution of Cleanness Value

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Journal of Modern power Systems and Clean Energy 2024年第2期12卷 346-358页

作者： Hongchao Gao Tai Jin Guanxiong Wang Qixin Chen Chongqing Kang Jingkai Zhu State Key Laboratory of power System Operation and Control Department of Electrical EngineeringTsinghua UniversityBeijing 100084China Sichuan Energy Internet Research Institute Tsinghua university Chengdu 200016China power Dispatching and Control Center of shanghai Municipal electric power Company Shanghai 200122China IEEE

The scale of distributed energy resources is increasing,but imperfect business models and value transmission mechanisms lead to low utilization ratio and poor *** address this issue,the concept of cleanness value of distributed energy storage(DES)is proposed,and the spatiotemporal distribution mechanism is discussed from the perspectives of electrical energy and *** on this,an evaluation system for the environmental benefits of DES is constructed to balance the interests between the aggregator and the power system ***,an optimal low-carbon dispatching for a virtual power plant(VPP)with aggregated DES is constructed,where-in energy value and cleanness value are both *** achieve the goal,a green attribute labeling method is used to establish a correlation constraint between the nodal carbon potential of the distribution network(DN)and DES behavior,but as a cost,it brings multiple nonlinear ***,a solution method based on the convex envelope(CE)linear re-construction method is proposed for the multivariate nonlinear programming problem,thereby improving solution efficiency and ***,the simulation verification based on the IEEE 33-bus DN is *** simulation results show that the multidimensional value recognition of DES motivates the willingness of resource users to ***,resolving the impact of DES on the nodal carbon potential can effectively alleviate overcompensation of the cleanness value.

关键词： Distributed energy storage virtual power plant(VPP) spatiotemporal distribution low-carbon dispatching

Design and performance investigation of modified dual reflector parabolic trough collector with double planar mirrors

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Science China(Technological Sciences) 2024年第3期67卷 902-918页

作者： LI Peijing LIU TaiXiu QIN YuanLong LI JiChao LIU QiBin School of Energy Powerand Mechanical EngineeringNorth China Electric Power University Beijing 226China Institute of engineering Thermophysics Chinese Academy of SciencesBeijing 100190China university of Chinese Academy of Sciences Beijing 100049China department of thermal Science and Energy engineering University of Science and Technology of ChinaHefei 230027China

In a typical parabolic trough collector(PTC), sunlight is concentrated at the bottom of the absorber tube. This concentrated solar flux leads to uneven heat distribution, resulting in high local temperatures and significant thermal stress on the absorber *** limitations have restricted the application of PTCs in solar thermochemistry and other fields and have impacted their safe operation. In this study, a new PTC with dual planar mirrors(DPMS) is proposed to homogenize the circumferential solar flux distribution of the absorber tube. A design method and single-objective optimization of the new PTC with a DPMS are proposed,and an uncertainty analysis of the operational and structural parameters is performed. A coupled light-heat-structure numerical model was developed to study the heat transfer performance and structural mechanical properties. The thermodynamic properties of the PTC with DPMS under different boundary conditions were analyzed. The results show that the circumferential temperature difference of the new PTC is within 2.6 K, and the circumferential thermal deformation is within 0.9 mm under typical working conditions(the inlet velocity of the heat transfer fluid is 3 m/s, inlet temperature is 573.15 K, and the direct normal irradiance is 1000 W/m^(2)). Compared with conventional PTCs, the circumferential temperature difference is reduced by 74%–90%, and the maximum thermal deformation along the y-axis is reduced by more than 95% under all working conditions(1–5 m/s, 373.5–675.15 K, 200–1000 W/m^(2)). The new PTC maintains the uniformity of the circumferential solar flux distribution for different operating parameters(sun incident angle of 0°–3°) and installation errors(±3 mm), is suitable for solar energy applications in various fields, and has the potential for large-scale applications.

关键词： solar thermal energy parabolic trough collector secondary reflector solar flux distribution optical optimization

New Hybrid CHP System Integrating Solar Energy and Exhaust Heat Thermochemical Synergistic Conversion with Dual-Source Energy Storage

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Journal of thermal Science 2024年第3期33卷 970-984页

作者： QIN Yuanlong LIU Taixiu LI Peijing ZHAO Kai JIAO Fan PEI Gang LIU Qibin department of thermal Science and Energy engineering University of Science and Technology of ChinaHefei230027China Institute of engineering Thermophysics Chinese Academy of SciencesBeijing100190China university of Chinese Academy of Sciences Beijing100049China School of Energy Power and Mechanical EngineeringNorth China Electric Power UniversityBeijing102206China

For the efficient use of solar and fuels and to improve the supply-demand matching performance in combined heat and power(CHP)systems,this paper proposes a hybrid solar/methanol energy system integrating solar/exhaust thermochemical and thermal energy *** proposed system includes parabolic trough solar collectors(PTSC),a thermochemical reactor,an internal combustion engine(ICE),and hybrid storage of thermal and chemical energy,which uses solar energy and methanol fuel as input and outputs power and *** methanol thermochemical decomposition reaction,mid-and-low temperature solar heat and exhaust heat are upgraded to chemical energy for efficient power *** thermal energy storage(TES)stores surplus thermal energy,acting as a backup source to produce heat without emitting CO_(2).Due to the energy storage,time-varying solar energy can be used steadily and efficiently;considerable supply-demand mismatches can be avoided,and the operational flexibility is *** the design condition,the overall energy efficiency,exergy efficiency,and net solar-to-electric efficiency achieve 72.09%,37.65%,and 24.63%,*** fuel saving rate(FSR)and the CO_(2) emission reduction(ER_(CO_(2)))achieve 32.97%and 25.33%,*** research findings provide a promising approach for the efficient and flexible use of solar energy and fuels for combined heat and power.

关键词： hybrid energy system solar thermochemical exhaust heat energy storage operational flexibility

Energy Management of Price-maker Community Energy Storage by Stochastic Dynamic Programming

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CSEE Journal of power and Energy Systems 2024年第2期10卷 492-503页

作者： Lirong Deng Xuan Zhang Tianshu Yang Hongbin Sun Yang Fu Qinglai Guo Shmuel S.Oren department of electrical engineering Shanghai University of Electric PowerShanghai 200000China Tsinghua-Berkeley Shenzhen Institute Tsinghua UniversityShenzhen 518055China department of Industrial engineering and Operations Research University of California BerkeleyBerkeleyCAUSA Risk Analytics and Optimization Chair EPFLSwitzerlandand also with Power Systems LaboratoryETH Zurich8092 ZurichSwitzerland State Key Laboratory of power Systems Department of Electrical EngineeringTsinghua UniversityBeijing 100084China

In this paper,we propose an analytical stochastic dynamic programming(SDP)algorithm to address the optimal management problem of price-maker community energy *** a price-maker,energy storage smooths price differences,thus decreasing energy arbitrage ***,this price-smoothing effect can result in significant external welfare changes by reduc-ing consumer costs and producer revenues,which is not negligible for the community with energy storage *** such,we formulate community storage management as an SDP that aims to maximize both energy arbitrage and community *** incorporate market interaction into the SDP format,we propose a framework that derives partial but sufficient market information to approximate impact of storage operations on market *** we present an analytical SDP algorithm that does not require state *** from computational efficiency,another advantage of the analytical algorithm is to guide energy storage to charge/discharge by directly comparing its current marginal value with expected future marginal *** studies indicate community-owned energy storage that maximizes both arbitrage and welfare value gains more benefits than storage that maximizes only *** proposed algorithm ensures optimality and largely reduces the computational complexity of the standard *** Terms-Analytical stochastic dynamic programming,energy management,energy storage,price-maker,social welfare.

关键词： Analytical stochastic dynamic programming energy management energy storage price-maker social welfare

Modification of streamer-to-leader transition model based on radial thermal expansion in the sphere-plane gap discharge at high altitude

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Plasma Science and Technology 2024年第1期26卷 42-49页

作者：耿江海林果王平丁玉剑丁杨俞华 department of electric power engineering North China Electric Power UniversityBaoding 071003People’s Republic of China China electric power Research Institute Beijing 100192People’s Republic of China Xinjiang electric power Company Research Institute Urumchi 830000People’s Republic of China Shanxi electric power Company Research Institute Taiyuan 030001People’s Republic of China

Historically,streamer-to-leader transition studies mainly focused on the rod-plane gap and low altitude analysis,with limited attention paid to the sphere-plane gap at high altitude *** this work,sphere-plane gap discharge tests were carried out under the gap distance of 5 m at the Qinghai Ultra High Voltage(UHV)test base at an altitude of 2200 *** experiments measured the physical parameters such as the discharge current,electric field intensity and instantaneous optical *** duration of the dark period and the critical charge of streamer-toleader transition were obtained at high *** on radial thermal expansion of the streamer stem,we established a modified streamer-to-leader transition model of the sphere-plane gap discharge at high altitude,and calculated the stem temperature,stem radii and the duration of streamer-to-leader *** with the measured duration of sphere-plane electrode discharge at an altitude of 2200 m,the error rate of the modified model was 0.94%,while the classical model was 6.97%,demonstrating the effectiveness of the modified *** the comparisons and analysis,several suggestions are proposed to improve the numerical model for further quantitative investigations of the leader inception.

关键词： streamer-to-leader transition model high altitude streamer stem convective diffusion radial thermal expansion