高压气体在膜式螺旋管环形通道中的对流换热特性

在加压的条件下试验研究了膜式螺旋管环形通道内的对流换热特性,试验气体有单质气体He和N2,也有混合气体如He+N2,试验压力为0.5～3.5 MPa,给出了不同螺旋管结构、不同气体和压力下的对流换热系数,以及典型冲刷形式的对流换热关联式及其适用条件.试验研究表明,气体压力、气体组分、冲刷形式对换热系数均有影响,特别是气体压力的影响最为突出.由数据分析得出了膜式螺旋管环形通道的对流换热关联式,该关联式可以适用于各种气体成分.     

煤粉加压气化炉膜式螺旋管和蛇形管对流传热特性研究

对煤粉加压气化炉对流段的不同换热结构进行了换热特性的实验研究,其中换热结构包括膜式螺旋管环形通道换热器和膜式蛇形管平行通道换热器,实验气体为单质气体N2、He及其混合气,实验压力为0.5～3.5MPa.为此,针对不同冲刷形式、不同气体和压力提出了换热器换热系数及其扩展的计算方法,同时给出了典型冲刷形式的对流换热的关联式和适用条件.实验研究表明:冲刷形式对换热系数有很大影响,单通道和多通道换热系数与换热面积之间呈加权平均的关系;在相同换热条件下,膜式螺旋管环形通道换热器的换热系数高于膜式蛇形管平行通道换热器.     

蛇形管平行通道中高压气体的对流换热特性研究

在高温加压的条件下研究了膜式蛇形管平行通道换热器的对流换热特性,试验气体为N2,试验工质的压力为0.5～3MPa.提出了不同冲刷形式、不同压力下的具体换热系数计算方法,同时给出了典型冲刷形式的对流换热关联式及其适用条件.试验研究表明:冲刷形式对换热系数有很大影响;单通道与多通道的换热系数是面积加权平均的关系;在相同的换热条件下,膜式蛇形管平行通道换热器的换热系数高于蛇形管平行通道换热器;相同温度条件下随着压力的升高,换热系数升高,但升幅逐渐减小.     

换热器螺旋管冷凝换热的数值模拟与实验研究

为了研究换热器螺旋管的冷凝传热性能,对R22制冷剂使用VOF模型在螺旋直径为300mm、螺距为19.52mm、管道直径为9.52mm的换热器螺旋管进行了数值模拟,分析了换热器螺旋管的流场分布特性,研究了流体流速和饱和温度对螺旋管内换热性能的影响。通过实验研究了不同参数对螺旋管内换热性能的影响,对数值模拟的准确性进行验证。实验结果表明,在不同流体流速时冷凝换热系数的模拟数据与实验数据之间的相对误差为3%-11%,在不同饱和温度时冷凝换热系数的模拟数据与实验数据之间的相对误差为3%-8%,说明数值模拟方法和结果是合理的。该研究为螺旋管换热器的设计优化以及空调热水器一体机的节能损耗给予了一些参考。     

超临界压力下水在螺旋管内的混合对流换热

采用FLUENT 6．0 CFD商业软件，对螺旋管内超临界压力下水在发展段的层流混合对流换热特性进行了数值研究，细致地分析了螺旋管螺距、入口流动Grashof数和Dean数等对流动和换热的影响．研究结果表明，在超临界压力下，水物性参数的剧烈变化在垂直流动方向引起了很强的二次流动，同时由螺旋管引起的向心力也造成了很强的二次流，与相同尺寸直管道相比，螺旋管内二次流的存在大大强化了流动换热，但是也相应地增加了流动阻力，因此螺旋管入口De数越小，则二次流越大，摩擦阻力越小。同时，流动换热随质量流速的增加而增加。     

热声发动机非共振自循环换热环路实验研究

为考察非共振自循环换热环路的实际工作特性,将其与热声发动机相耦合,在不同工况下研究了两种厚度的单向阀片对其内部压力分布、换热特性、声功损耗及压比的影响。为减少该新换热环路的阻力损失和声功耗散,提出了一种新型的水冷换热器以取代其中的传统板式换热器。实验结果表明,当由0.1 mm厚的单向阀片所组成的换热环路内的工作气体平均压力为3.0 MPa、驱动频率为66 Hz时,若输入系统内的热量为1.5 kW,换热量为1.05 kW,其热量传输能力已经超过了传统热声换热器。     

高温气冷堆示范工程螺旋管式直流蒸汽发生器工程验证试验

研发一种新型蒸汽发生器必须进行一定规模的工程验证试验。清华大学核能与新能源技术研究院在其实验基地建设了高温气冷堆示范工程(HTR-PM)螺旋管式直流蒸汽发生器的工程验证试验回路(engineering test facility for steam generator, ETF-SG)。工程验证试验回路能够模拟HTR-PM运行参数,可对HTR-PM蒸汽发生器一个换热组件进行1∶1的工程验证试验。回路设计热功率10 MW,氦回路设计压力8 MPa,最高设计温度800℃,二回路设计压力18 MPa,最高设计温度600℃。在工程验证试验回路上针对高温气冷堆蒸汽发生器完成了几十项热工水力试验,对蒸汽发生器的温度均匀性、堵管后温度分布及其温度展平调节、热工水力瞬态特性、两相流不稳定性等进行了试验研究,验证了HTR-PM螺旋管式直流蒸汽发生器的热工水力和结构设计,并为其调试、运行、低功率及启停工况参数的确定提供了重要数据和参考。     

膜式空气弹簧刚度的试验分析

本文通过计算获得了膜式空气弹簧刚度的一般表达式,以试验手段对比分析膜式空气弹簧在不同条件下的刚度效应。通过五种空气弹簧在0.5MPa压力下垂直刚度特性曲线对比,得出膜式空气弹簧垂向刚度随着外直径的增加而增大。通过不同形状活塞底座的空气弹簧刚性试验,得出了正圆锥形活塞底座在受压时比倒圆锥形活塞底座的刚性好的结论。     

二氧化碳置换甲烷试验中渗透率变化研究

为研究煤层注CO2置换CH4过程中煤样对气体的吸附特性及渗透率变化特征,利用沁水盆地圆柱体原煤试样,在恒定体积应力(36 MPa)及不同注入压力(1~5 MPa)条件下,进行CO2置换CH4试验。结果表明:煤体对CO2的渗透率高于CH4气体;置换试验中,随注入压力的降低,煤体中CO2吸附相浓度逐渐升高,而CH4气体吸附相浓度呈相反变化趋势;在试验压降范围内,煤体对CO2、CH4气体的吸附量分别降低了48.73%、68.04%,煤体解吸CH4能力强于CO2气体。同时,在置换过程中,煤样置换渗透率受有效应力效应、基质收缩效应及滑脱效应等作用影响,其随注入压力的降低呈现先降低再增大的变化关系,且渗透率最低值出现在压力3.25 MPa时;在体积应力36 MPa条件下,注入压力下降后期渗透率相对于初期提高了17.03%。     

紧凑型滚压强化管管束内水和盐水的沸腾强化换热特性

对水平光滑和滚压强化两种传热管管束在不同压力条件下的窄小空间内沸腾强化换热进行了实验研究，确认了窄小空间能够有效强化沸腾换热特性，存在着一个换热强化效果最好的最佳管距．当管距很小时，光滑管几乎具有和强化管相同的换热特性．实验范围内盐水浓度对换热特性几乎无影响．实验证明，对紧凑满液型蒸发换热器，利用传热管管束狭窄空间内早期沸腾强化换热机理，可以将中小热流密度条件下的自然对流换热转化为旺盛核沸腾换热，其换热性能大大优于传统的降膜式蒸发换热器．     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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