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Numerical Analysis on Charging Performance of the Macro-Encapsulating Combined Sensible-Latent Heat Storage System with Structural Parameters

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Journal of Thermal Science 2024年第3期33卷 1026-1036页

作者： WANG Wei PAN Zhenfei WANG Jingfu wu yuting MA Chongfang Key Laboratory of Enhanced Heat Transfer and Energy Conservation Ministry of EducationCollege of Energy and Power EngineeringBeijing University of TechnologyBeijing100124China Key Laboratory of Heat Transfer and Energy Conversion Beijing MunicipalityCollege of Energy and Power EngineeringBeijing University of TechnologyBeijing100124China

For combined sensible-latent heat storage system(CSLHS)(termed as the hybrid configuration),macro encapsulation can effectively solve the leakage problem of PCMs.However,due to the poor thermal conductivity of PCMs,the charging performance of the hybrid configuration slightly increases compared to the solid structure(with only sensible materials).Meanwhile,the natural convection in the PCMs zone could improve the charging performance.So,how to improve natural convection intensity is a key issue for the CSLHS by macro encapsulating.It is found that adding fins can significantly enhance natural convection and accelerate the melting of PCM.In this paper,we proposed the hybrid configuration with fins built-in by macro encapsulation,and analyzed its charging performance with different fin structural parameters in the PCM zone by CFD simulation.In the case,the sensible heat storage material is high-temperature concrete and the PCM is a low-melting-point mixed molten salt.We analyzed the effects of fin number,fin length and fin thickness on the charging performance of the hybrid configuration respectively.From the result,the charging performance increases with the fin number,but the increase rate gradually decreases.When the fin number is 6,the charging performance increases by 20.18%compared to the situation without fin.The charging performance increases gradually with the fin length.Compared with the hybrid configuration without fin,for each 10 mm increase in fin length,its charging performances increase by 4.09%,5.26%,7.02%,8.77%,11.70%,and 15.79%,respectively.Different from number and length of fins,the effect of thickness on the charging performance is very small.When the fin thickness increased from 1 mm to 4 mm,the charging performance only increased by 2.3%.It indicates that the main reason for the improving the charging performance is to increase the natural convection intensity by dividing the PCM zone through fins.These results show that the charging performance of the CSLHS with macro encapsulation can be im

关键词： macro-encapsulation hybrid configuration natural convection structural parameter charging performance

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Structural Optimization of the Inlet Header of Supercritical Carbon Dioxide Printed Circuit Board Heat Exchanger

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Journal of Thermal Science 2024年第4期33卷 1458-1467页

作者： WANG Yanquan LU Yuanwei WANG Yuanyuan HAN Xinlong wu yuting GAO Qi MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of Technology

Supercritical carbon dioxide printed circuit board heat exchangers are expected to be applied in third-generation solar thermal power generation.However,the uniformity of supercritical carbon dioxide entering the heat exchanger has a significant impact on the overall performance of the heat exchanger.In order to improve the uniformity of flow distribution in the inlet header,this article studies and optimizes the inlet header of a printed circuit board heat exchanger through numerical simulation.The results indicate that when supercritical carbon dioxide flows through the header cavity,eddy currents will be generated,which will increase the uneven distribution of flow rate,while reducing the generation of eddy currents will improve the uniform distribution of flow rate.When the dimensionless factor of the inlet header is 6,the hyperbolic configuration is the optimal structure.We also reduced the eddy current region by adding transition segments,and the results showed that the structure was the best when the dilation angle was 10°,which reduced the non-uniformity by 21% compared to the hyperbolic configuration,providing guidance for engineering practice.

关键词： third-generation solar thermal power generation inlet header PCHE numerical simulation

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Numerical Study on Heat Transfer and Frictional Resistance of Two Types of Molten Salts in Straight Channels and Supercritical Carbon Dioxide in Airfoil Channels

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Journal of Thermal Science 2024年第4期33卷 1443-1457页

作者： WANG Yanquan LU Yuanwei GAO Qi LI Feng MA Yancheng WANG Yuanyuan wu yuting MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of Technology

Molten salt and supercritical carbon dioxide（sCO2） are considered to be one of the most promising combined heat transfer refrigerants for third-generation solar thermal power generation.To evaluate the potential of chloride salts and carbonates in third-generation solar thermal power generation,this paper uses molten salts and sCO2as the working media of printed circuit board heat exchangers（PCHE）,and uses numerical simulation to study the heat transfer and friction of PCHE channels with different molten salts and sCO2,and establishes predictive correlations respectively.A local heat transfer and friction study was conducted on the sCO2side of the airfoil channel,and it was found that the inlet mass flow rate has a significant impact on it,while the inlet temperature has a relatively small impact.A comprehensive comparison was made between the heat transfer and friction of two molten salts,and the comprehensive performance of chloride salts was 70%-80% higher than that of carbonates.The results indicate that the potential of chloride salts in third-generation solar thermal power generation is much greater than that of carbonates.

关键词： third generation solar thermal power generation sCO 2 PCHE molten salt

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Fabricating a smart clothing system based on strain-sensing yarn and novel stitching technology for health monitoring

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Science China(Technological Sciences) 2024年第2期67卷 587-596页

作者： TANG Jian wu yuting MA ShiDong ZHANG YuMin XU RuoJie YAN Tao PAN ZhiJuan College of Textile and Clothing Engineering Soochow UniversitySuzhou 215123China National Engineering Laboratory for Modern Silk Suzhou 215123China

Various yarn-shaped flexible strain sensors have recently been developed.However,research is lacking on additive manufacturing for smart clothing for integrating yarn sensors with commercial garments.Herein,a strain-sensing yarn is sewn into a piece of fabric through a novel stitching technique,and the influence of the stitching method and needle pitch on the sensing performance is investigated using finite element analysis(FEA).The sensing performance could be improved when the sensing yarn is self-locked in the fabric at the needle eyes,and the needle pitch was reduced to 0.5 cm,which is attributed to the enhanced stress and strain concentration.Meanwhile,the composite sensing fabric featured outstanding performance,including a low detection limit(0.1%),rapid response(280 ms),excellent durability(10000 cycles),and high stability(negligible drift and frequency independence).In addition,the remarkable wear resistance,washability,and anti-interference to ambient humidity and perspiration were obtained.Therein,the optimal stitch trace lengths of sensing yarn for detecting elbow motion,breathing,and heartbeats are discussed.Finally,a smart clothing system composed of smart clothing,data acquisition unit,and mobile APP was developed to simultaneously detect human movement and physiological signals.This work provides a reference to produce intelligent garments based on yarn sensors for health monitoring.

关键词： strain-sensing yarn composite sensing fabric smart clothing system stitching technology health monitoring

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A Matching Algorithm with Reinforcement Learning and Decoupling Strategy for Order Dispatching in On-Demand Food Delivery

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Tsinghua Science and Technology 2024年第2期29卷 386-399页

作者： Jingfang Chen Ling Wang Zixiao Pan yuting wu Jie Zheng Xuetao Ding Department of Automation Tsinghua UniversityBeijing 100084China Department of Delivery Technology MeituanBeijing 100102China

The on-demand food delivery(OFD)service has gained rapid development in the past decades but meanwhile encounters challenges for further improving operation quality.The order dispatching problem is one of the most concerning issues for the OFD platforms,which refer to dynamically dispatching a large number of orders to riders reasonably in very limited decision time.To solve such a challenging combinatorial optimization problem,an effective matching algorithm is proposed by fusing the reinforcement learning technique and the optimization method.First,to deal with the large-scale complexity,a decoupling method is designed by reducing the matching space between new orders and riders.Second,to overcome the high dynamism and satisfy the stringent requirements on decision time,a reinforcement learning based dispatching heuristic is presented.To be specific,a sequence-to-sequence neural network is constructed based on the problem characteristic to generate an order priority sequence.Besides,a training approach is specially designed to improve learning performance.Furthermore,a greedy heuristic is employed to effectively dispatch new orders according to the order priority sequence.On real-world datasets,numerical experiments are conducted to validate the effectiveness of the proposed algorithm.Statistical results show that the proposed algorithm can effectively solve the problem by improving delivery efficiency and maintaining customer satisfaction.

关键词： order dispatching on-demand delivery reinforcement learning decoupling strategy sequence-to-sequence neural network

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A Parametric Study on the Effect of Mixing Chamber for Expansion Work Recovery CO_(2) Ejector

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Journal of Thermal Science 2022年第6期31卷 1914-1927页

作者： FENG Xu ZHANG Zhenying wu yuting TIAN Dingzhu Key Laboratory of Enhanced Heat Transfer and Energy Conservation Ministry of Education and Key Laboratory of Heat Transfer and Energy ConversionBeijing MunicipalityCollege of Environmental and Energy EngineeringBeijing University of TechnologyBeijing 100124China School of Architecture and Civil Engineering North China University of Science and TechnologyTangshan 063210China

A numerical study of supercritical CO_(2) two-phase flow in the ejector was carried out by computational fluid dynamics(CFD) methods. Through the comparison of simulation results and available experimental data in the literature, the accuracy of the three-dimensional CFD model was verified. A comparison of the effects of four turbulence models on the simulation calculation results was also presented. The distributions of pressure, velocity, two-phase volume fraction, shock wave and exergy flux inside the ejector were analyzed. The effects of the mixing section geometry on the performance of the ejector were obtained. Then, the entrained performance of the ejector was investigated by changing the area ratio between the constant-area mixing chamber and the outlet of the motive nozzle(AR) and the ratio between the length and the diameter of the constant-area mixing chamber(LDR). Finally, the optimum AR and LDR were determined to be 8.3 and 8.1, respectively based on the maximum entrained ratio and the minimum exergy destruction. Through optimizing the mixing chamber geometry, the minimum total exergy destruction and the maximum mass entrainment ratio(MER) of the ejector can attain 0.33 J/(kg·K) and 0.698, respectively.

关键词： CO_(2)ejector mixing chamber CFD AR LDR

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Oncogenic β-catenin-driven liver cancer is susceptible to methotrexate-mediated disruption of nucleotide synthesis

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Chinese Medical Journal 2024年第2期137卷 181-189页

作者： Fangming Liu yuting wu Baohui Zhang Shuhui Yang Kezhuo Shang Jie Li Pengju Zhang Weiwei Deng Linlin Chen Liang Zheng Xiaochen Gai Hongbing Zhang Department of Physiology State Key Laboratory of Common Mechanism Research for Major DiseasesHaihe Laboratory of Cell EcosystemInstitute of Basic Medical Sciences and School of Basic MedicineChinese Academy of Medical Sciences and Peking Union Medical CollegeBeijing 100005China Department of Physiology Institute of Basic Medical Sciences and School of Basic MedicineGraduate School of Peking Union Medical CollegeChinese Academy of Medical SciencesBeijing100005China Department of Physiology School of Life ScienceChina Medical UniversityShenyangLiaoning 110122China School of Life Sciences Westlake UniversityHangzhouZhejiang 310024China Key Laboratory of Pediatric Hematology and Oncology Ministry of HealthInstitute of Pediatric Translational MedicineShanghai Children’s Medical CenterShanghai Jiao Tong School of MedicineShanghai 200127China

Background:Liver cancer is largely resistant to chemotherapy.This study aimed to identify the effective chemotherapeutics forβ-catenin-activated liver cancer which is caused by gain-of-function mutation of catenin beta 1(CTNNB1),the most frequently altered proto-oncogene in hepatic neoplasms.Methods:Constitutiveβ-catenin-activated mouse embryonic fibroblasts(MEFs)were established by deleting exon 3(β-catenin^(Δ(ex3)/+)),the most common mutation site in CTNNB1 gene.A screening of 12 widely used chemotherapy drugs was conducted for the ones that selectively inhibitedβ-catenin^(Δ(ex3)/+)but not for wild-type MEFs.Untargeted metabolomics was carried out to examine the alterations of metabolites in nucleotide synthesis.The efficacy and selectivity of methotrexate(MTX)onβ-catenin-activated human liver cancer cells were determined in vitro.Immuno-deficient nude mice subcutaneously inoculated withβ-catenin wild-type or mutant liver cancer cells and hepatitis B virus(HBV);β-catenin^(lox(ex3)/+)mice were used,respectively,to evaluate the efficacy of MTX in the treatment ofβ-catenin mutant liver cancer.Results:MTX was identified and validated as a preferential agent against the proliferation and tumor formation ofβ-catenin-activated cells.Boosted nucleotide synthesis was the major metabolic aberration inβ-catenin-active cells,and this alteration was also the target of MTX.Moreover,MTX abrogated hepatocarcinogenesis of HBV;β-catenin^(lox(ex3)/+)mice,which stimulated concurrent Ctnnb1-activated mutation and HBV infection in liver cancer.Conclusion:MTX is a promising chemotherapeutic agent forβ-catenin hyperactive liver cancer.Since repurposing MTX has the advantages of lower risk,shorter timelines,and less investment in drug discovery and development,a clinical trial is warranted to test its efficacy in the treatment ofβ-catenin mutant liver cancer.

关键词： Liver cancer β-catenin Methotrexate Nucleotide synthesis Chemotherapy

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Flow Characteristics of a Refrigerant-Oil Mixture in a Vapor Compression Heat Pump Heat Exchanger for Space Applications

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Journal of Thermal Science 2022年第2期31卷 407-416页

作者： MA Rui YE Yilin MA Xudong wu yuting YAN Suying WANG Feng College of Energy and Power Engineering Inner Mongolia University of TechnologyHohhot 010051China Key Laboratory of Wind and Solar Energy Utilization Mechanism and Optimization in Inner Mongolia Inner Mongolia University of TechnologyHohhot 010051China Key Laboratory of Enhanced Heat Transfer and Energy Conservation Ministry of EducationBeijing 100124China

The vapor compression heat pump is considered as the best option for aerospace thermal control system.The heat exchanger in vapor compression heat pump is a component that is greatly influenced by the cosmic environment.Lubricating oil enters heat pump system with a refrigerant under microgravity,and the entrance of the lubricant increases the complexity of the flow.In this work,FLUENT software was used to study the flow and lubricant deposition of a two-phase mixture of lubricant POE RL 68H and refrigerant R134a in a heat exchanger without the consideration of phase-change heat transfer.The functional relationships between the oil film thickness and the proportion of lubricating oil,the gravitational acceleration,the inlet flow velocity,and the placement directions of the two phases of oil in the heat exchanger were established.The results demonstrate that with the increase of the gravitational acceleration and the lubricating oil content,the thickness of the oil film will exhibit an S-type change in line with the Boltzmann function,and the amount of lubricating oil deposition will increase.With the increase of the flow velocity,the thickness of the oil film will exhibit an exponential decline.

关键词： heat exchanger two-phase flow microgravity numerical simulation vapor compression heat pump

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Numerical Simulation of Charging Performance of Combined Sensible-Latent Heat Storage System with a Macro-Encapsulation Method

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Journal of Thermal Science 2023年第6期32卷 2008-2017页

作者： WANG Wei PAN Zhenfei LEI Biao wu yuting WANG Jingfu MA Chongfang Key Laboratory of Enhanced Heat Transfer and Energy Conservation Ministry of EducationCollege of Energy and Power EngineeringBeijing University of TechnologyBeijing100124China Key Laboratory of Heat Transfer and Energy Conversion Beijing MunicipalityCollege of Energy and Power EngineeringBeijing University of TechnologyBeijing100124China

In recent years,heat storage system combining sensible and latent heat materials has received more and more attentions.In this paper,we proposed the hybrid configuration with a macro-encapsulation,and analyzed its charging performance with different influencing factors by CFD simulation.In the case,the sensible heat storage materials are magnesia brick or HT concrete and the phase change materials(PCMs)are mixed molten salts.Firstly,we analyzed the heat transfer characteristics of the hybrid configuration in charging process.Then,we analyzed the effect of heating power on charging performance.The maximum temperature of the heating surface shall not exceed 500℃as the constraint condition,the heat storage capacity increases at first and then decreases with the heating power.Then,we compared the charging performance of different solid structure and the hybrid configurations.Whether magnesia brick or HT concrete,the charging performance of the solid structure is better than that of the hybrid configuration,because the thermal conductivity of the molten salt is significantly lower than that of the two sensible heat storage materials.Then,we compared the charging performance of different molten salts.The hybrid configuration with lower melting point molten salt has better performance because of more intensity natural convection.Finally,we analyzed the charging performance of the hybrid configuration used the composite phase change material(CPCM)with high thermal conductivity and specific heat.From the result,the charging performance increases by 22.5%compared with the solid structure.These results indicate that the hybrid configuration with the macro-encapsulation method is a potential form of thermal energy storage,but it needs to be further optimized.

关键词： thermal energy storage hybrid configuration natural convection thermophysical property charging performance

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Flexible Operation Mode of Coal-fired Power Unit Coupling with Heat Storage of Extracted Reheat Steam

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Journal of Thermal Science 2022年第2期31卷 436-447页

作者： WEI Haijiao LU Yuanwei YANG Yanchun ZHANG Cancan wu yuting LI Weidong ZHAO Dongming MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionFaculty of Environment and LifeBeijing University of TechnologyBeijing 100124China China Huaneng Group Clean Energy Research Institute Co.Ltd Beijing 102209China

In order to provide more grid space for the renewable energy power,the traditional coal-fired power unit should be operated flexibility,especially achieved the deep peak shaving capacity.In this paper,a new scheme using the reheat steam extraction is proposed to further reduce the load far below 50%rated power.Two flexible operation modes of increasing power output mode and reducing fuel mode are proposed in heat discharging process.A 600 MW coal-fired power unit with 50%rated power is chosen as the research model.The results show that the power output is decreased from 300.03 MW to 210.07 MW when the extracted reheat steam flow rate is 270.70 t·h^(-1),which increases the deep peak shaving capacity by 15%rated power.The deep peak shaving time and the thermal efficiency are 7.63 h·d^(-1)and 36.91%respectively for the increasing power output mode,and they are 7.24 h·d^(-1)and 36.58%respectively for the reducing fuel mode.The increasing power output mode has the advantages of higher deep peak shaving time and the thermal efficiency,which is recommended as the preferred scheme for the flexible operation of the coal-fired power unit.

关键词： coal-fired power unit flexible operation deep peak shaving extracted reheat steam heat storage

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