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Theoretical and Experimental Analysis of Heat Transfer and Condensation in Micro-Ribbed Tubes

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Fluid Dynamics & Materials Processing 2023年第6期19卷 1411-1424页

作者： Daoming Shen Jinhong Xia chao gui Songtao Xue Xinxiang University Xinxiang453000China Department of Architecture Tohoku Institute of TechnologySendai982-8577Japan

The thermal transmission coefficient for a micro-ribbed tube has been determined using theoretical relationships and the outcomes of such calculations have been compared with experiments conducted using a R1234yf refrigerant undergoing condensation.In particular four theoretical single-phase flow and three multi-phase flow models have been used in this regard.The experimental results show that:the Oliver et al.criterion equation overestimates the experimental results as its accuracy is significantly affected by the specific conditions realized inside micro-fin tubes;the Miyara et al.criterion equation prediction error is less than 15%;the Cavallini et al.approach gives the highest prediction accuracy;the Goto et al.model overestimates the test data.Such results are critically discussed and some indications for the improvement of such models are provided.

关键词： Micro-ribbed tube flow condensation thermal transmission coefficient dimensionless criterion equation

Application of different molecular sieves in photothermal catalysis of Jatropha oil

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International Journal of Agricultural and Biological Engineering 2023年第5期16卷 204-212页

作者： Yijie Yang Longlong Ma Lumin Sun Xinghua Zhang chao gui Yubao Chen School of Energy and Environmental Science Yunnan Normal UniversityKunming 6500500China School of Energy and Environment Southeast UniversityNanjing 210096China School of Environmental Science and Engineering Tan Kah Kee CollegeXiamen UniversityZhangzhou 363105FujianChina

The preparation of green and economical bio-aviation fuel is a priority for the sustainable development industry.In this study,Jatropha oil was used as a raw material to catalyze the conversion of raw material to aviation kerosene fraction by photothermal coupling under the conditions of light and low temperature.The correlations among conversion rate,target alkane selectivity,composition distribution,and catalyst microstructure were investigated by X-ray diffraction(XRD),high-resolution transmission electron microscopy(HRTEM),nitrogen(N2)adsorption and desorption,X-ray fluorescence(XRF),ammoniatemperature programmed desorption(NH3-TPD),ultraviolet-visible spectrophotometry(UV-Vis),and other characterization.The correlation between conversion and target alkane selectivity and composition distribution and catalyst microstructure was investigated,and different modification methods and different molecular sieve materials were selected.The results showed that the molecular sieves modified with the solid dispersion method could retain the structural stability of titanium dioxide(TiO2)and molecular sieves to a great extent while slightly enhancing the pore capacity and pore size of the catalyst to make it easier to adsorb reactants;the introduction of active metal platinum(Pt)could reduce the forbidden bandwidth of the catalyst,increase the weak acid amount of the catalyst,improve the adsorption capacity of hydrogen(H2),and thus improve the catalytic ability,resulting in a suitable catalyst for this study:P-21.The photothermal catalytic reaction of Jatropha oil using P-21 catalyst obtained 97.21%conversion and 74.99%selectivity of the target alkanes under the optimal process parameters.The results of this study provide effective catalyst parameters for research in the field of clean energy.

关键词： Jatropha oil applications of molecular sievers photothermal catalysis biofuel

Experimental Analysis of the Performances of Unit Refrigeration Systems Based on Parallel Compressors with Consideration of the Volumetric and Isentropic Efficiency

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Fluid Dynamics & Materials Processing 2020年第3期16卷 489-500页

作者： Daoming Shen chao gui Jinhong Xia Songtao Xue College of Civil Engineering and Architecture Xinxiang UniversityXinxiang453000China Research Institute of Structural Engineering and Disaster Reduction Tongji UniversityShanghai20092China Department of Architecture Tohoku Institute of TechnologySendai982-8577Japan

The performances of a refrigeration unit relying on compressors working in parallel have been investigated considering the influence of the compressor volumetric efficiency and isentropic efficiency on the compression ratio.Moreover,the following influential factors have been taken into account:evaporation temperature,condensation temperature and compressor suction-exhaust pressure ratio for different opening conditions of the compressor.The following quantities have been selected as the unit performance measurement indicators:refrigeration capacity,energy efficiency ratio(COP),compressor power consumption,and refrigerant flow rate.The experimental results indicate that the system refrigeration capacity and COP decrease with a decrease in evaporation temperature,increase of condensation temperature,and increase in pressure ratio.The refrigerant flow rate increases with the increase in evaporation temperature,decrease in condensing temperature and increase in pressure ratio.The compressor power consumption increases with the increase in condensing temperature and increase in pressure ratio,but is not significantly affected by the evaporation temperature.

关键词： Parallel compressor unit evaporation temperature condensation temperature pressure ratio refrigeration capacity energy efficiency ratio(COP)

PASS: a simple, efficient parallelism-aware solid state drive I/O scheduler

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Journal of Zhejiang University-Science C(Computers and Electronics) 2014年第5期15卷 321-336页

作者： Hong-yan LI Nai-xue XIONG Ping HUANG chao gui Wuhan National Laboratory for Optoelectronics School of Computer Science and TechnologyHuazhong University of Science and Technology School of Information Management Hubei University of Economics School of Computer Science Colorado Technical University Colorado Spring

Emerging non-volatile memory technologies,especially flash-based solid state drives(SSDs),have increasingly been adopted in the storage stack.They provide numerous advantages over traditional mechanically rotating hard disk drives(HDDs)and have a tendency to replace HDDs.Due to the long existence of HDDs as primary building blocks for storage systems,however,much of the system software has been specially designed for HDD and may not be optimal for non-volatile memory media.Therefore,in order to realistically leverage its superior raw performance to the maximum,the existing upper layer software has to be re-evaluated or re-designed.To this end,in this paper,we propose PASS,an optimized I/O scheduler at the Linux block layer to accommodate the changing trend of underlying storage devices toward flash-based SSDs.PASS takes the rich internal parallelism in SSDs into account when dispatching requests to the device driver in order to achieve high performance.Specifically,it partitions the logical storage space into fixed-size regions(preferably the component package sizes)as scheduling units.These scheduling units are serviced in a round-robin manner and for every chance that the chosen dispatching unit issues only a batch of either read or write requests to suppress the excessive mutual interference.Additionally,the requests are sorted according to their visiting addresses while waiting in the dispatching queues to exploit high sequential performance of SSD.The experimental results with a variety of workloads have shown that PASS outperforms the four Linux off-the-shelf I/O schedulers by a degree of 3%up to41%,while at the same time it improves the lifetime significantly,due to reducing the internal write amplification.

关键词： Solid state drive(SSD) I/O scheduler Parallelism

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三摆臂式扰流片矢量气动力数值仿真研究

科学技术与工程 2024年第4期24卷 1488-1495页

作者：杨海涛廖贵超习敏帅超中国船舶集团有限公司第710研究所宜昌443003

为适应智能可控弹药发动机喷口愈来愈小的发展趋势,针对三摆臂式扰流片矢量控制形式开展了气动力数值仿真。研究三摆臂式扰流片推力和侧向力调节能力。结果表明:推力随着主推角的增加而降低,最大推力损失仅与主推角有关;当主推角大于36... 详细信息

为适应智能可控弹药发动机喷口愈来愈小的发展趋势,针对三摆臂式扰流片矢量控制形式开展了气动力数值仿真。研究三摆臂式扰流片推力和侧向力调节能力。结果表明:推力随着主推角的增加而降低,最大推力损失仅与主推角有关;当主推角大于36°,扰流片间的气动干扰增强;侧向力随着侧向角和入口压力的增加而增大;当3个扰流片均位于发动机尾流中,前后方向和左右方向侧向力调节干扰小,且侧向力调节对推力影响小。

关键词：固体火箭发动机扰流片数值仿真推力矢量控制

8位不同取代基氟硼染料纳米颗粒的制备与性质研究

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安徽化工 2024年第2期50卷 97-100,105页

作者：刘世博旷桂超中南大学粉末冶金研究院湖南长沙410083

合成了三种8位分别为四苯乙烯基、蒽甲基和二溴苯甲基的氟硼染料(BDP)衍生物BDP-Ar,BDP-En及BDP-Br,采用核磁共振、紫外光谱和荧光光谱对三种氟硼染料的结构以及光物理性质进行了表征。通过添加表面活性剂磷脂-甲氧基聚乙二醇(DSPE-PEG2... 详细信息

合成了三种8位分别为四苯乙烯基、蒽甲基和二溴苯甲基的氟硼染料(BDP)衍生物BDP-Ar,BDP-En及BDP-Br,采用核磁共振、紫外光谱和荧光光谱对三种氟硼染料的结构以及光物理性质进行了表征。通过添加表面活性剂磷脂-甲氧基聚乙二醇(DSPE-PEG2000),包覆制备了三种氟硼染料纳米颗粒,并采用动态光散射和透射电镜测定了氟硼染料纳米颗粒的粒径大小、分散程度以及颗粒形貌。

关键词：荧光染料氟硼染料纳米颗粒

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考虑热作用的复合织构滑动轴承润滑性能

轴承 2024年第5期 71-77页

作者：王长清陈立杉姜景明桂超孟凡明中国航发哈尔滨东安发动机有限公司哈尔滨150060 重庆大学机械传动国家重点实验室重庆400044 中国船舶集团有限公司第七〇五研究所西安710077 上海宇航系统工程研究所上海201109

为揭示热作用对复合织构滑动轴承润滑性能的影响规律,建立考虑润滑剂热作用影响的复合织构滑动轴承润滑性能求解模型,分析织构位置、转速及长径比对复合织构滑动轴承润滑性能的影响,并将其与单层织构轴承和无织构轴承进行对比。结果表明... 详细信息

为揭示热作用对复合织构滑动轴承润滑性能的影响规律,建立考虑润滑剂热作用影响的复合织构滑动轴承润滑性能求解模型,分析织构位置、转速及长径比对复合织构滑动轴承润滑性能的影响,并将其与单层织构轴承和无织构轴承进行对比。结果表明:1)无论是否考虑热作用,织构位置在轴承压力上升区时,复合织构轴承的承载力最大,摩擦系数最小;随转速的增加,轴承承载力与摩擦力增大,且复合织构轴承承载力最大,摩擦力最小;随长径比的增大,轴承承载力增大但摩擦系数减小,复合织构轴承承载力最大,摩擦系数最小。2)考虑热作用后,相同工况参数下,轴承承载力、摩擦力和摩擦系数相较于不考虑热作用的更低,但复合织构轴承的承载力总是高于单层织构轴承与无织构轴承,且摩擦力与摩擦系数最低。

关键词：滑动轴承热作用表面织构润滑性能质量守恒

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Three dimensional phase-field simulation for non-isothermal binary alloy solidification: Comparison with LKT theory

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China Foundry 2023年第6期20卷 545-552页

作者： Jun Wu Ting-yi Liu gui-chao Hu Rong Ma Xiao-peng Zhang Yu-fei Li chao Luo Institute of Materials China Academy of Engineering PhysicsJiangyou 621907SichuanChina

Using the advanced algorithm combining parallel computing,adaptive mesh re-griding and multigrid methods,quantitative 3D phase-field simulations of non-isothermal solidification of binary alloy were carried out.The 3D phase-field simulation results were compared with the analytical LKT(Lipton,Kurz and Trivedi)theory.For comparison,the simulation and analytical results for 2D cases were also given.The 3D phase-field simulation results support the transport portion of the LKT theory.However,the tip radius and tip velocity predicted by the simulations are not in good agreement with the LKT theory over the whole range of undercooling.The stability parameter calculated from phase-field simulations varies significantly with the Peclet number,indicating that the stability criterion,which assumes that the stability parameter is constant,is invalid.

关键词： 3D phase-field non-isothermal solidification free dendritic growth

Sliding Window Network Coding for Free Viewpoint Multimedia Streaming in MANETs

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国际计算机前沿大会会议论文集 2016年第2期 53-55页

作者： chao gui Chengli Huang Baolin Sun Xiaoyan Zhu School of Information and Engineering Hubei University of EconomicsWuhan 430205China Computer Engineering Department Guangdong Youth Vocational CollegeGuangzhou 510507China School of Mathematics and Computer Science Jianghan UniversityWuhan 430056China

Network coding(NC)can prove to be particularly useful in multimedia streaming applications,where it could help to increase the network throughput and data persistence in Mobile Ad hoc NETwork(MANET).Slidingwindow Network Coding is a variation of NC that is an addition to multimedia streaming and improves the data delay on MANETs.In this paper,we propose a Sliding Window Network Coding for free Viewpoint Multimedia streaming in MANETs(SWNC-VM).SWNC-VM preserves the degree distribution of the encoded packets through the recombination at the nodes.SWNC-VM enables to control the decoding complexity of each sliding-window independently from the packets received and recover the original data.The performance of the SWNCVM is studied using NS2 and evaluated in terms of the encoding overhead,decoding delay,packet loss probability and throughput when a packet is transmitted.The simulations result shows that the SWNC-VM with our proposition can significantly improve the network throughput and encoding efficiency.

关键词： MANET Network coding Free viewpoint multimedia Encoding efficiency