汽车尾气温差发电器换热通道强化换热性能的数值模拟

提出一种适合汽车尾气温差发电器的方型双面翅片换热通道结构,利用流体仿真软件FLUENT,在一定的尾气流速下,对该强化换热通道进行数值模拟.通过改变翅片结构特性尺寸(翅片长度l、间距d、高度h)进行仿真计算,得到不同翅片结构管道的壁面努塞尔数(Nu)、摩擦因子(f)以及综合换热效率(η),发现翅片换热通道的综合换热效率与翅片长度和高度成正比,与翅片间距成反比.综合考虑翅片结构特性尺寸的多因素影响,得到强化换热性能最优的翅片结构为l=400mm,d=20mm,h=50mm.     

空冷器球突翅片换热与不可逆性分析

数值模拟了球突翅片管外空气的流动和换热,并基于耗散概念对球突翅片换热的不可逆性进行了分析。结果表明:与平直翅片相比,直接空冷器单排管换热器采用球突翅片可使换热显著强化。当球突个数相同时,错排布置方式优于顺排;在Re=600～1 500的范围内,球突错排时,平均换热系数比平直翅片增加30%～55%,阻力系数增加50%～85%,同功耗强化换热指数PEC为1.14～1.27。球突翅片的等效热阻显著减小,其传热的不可逆性减弱,这正是球突翅片具有良好强化换热性能的物理机制。     

窗翅间距比和翅片厚度对斜针形百叶窗翅片式散热器换热性能的影响研究

对斜针形百叶窗翅片建立了三维数值计算模型,研究了斜针形翅片窗翅间距比和翅片厚度对散热器换热性能的影响。结果表明:斜针形翅片厚度越大,其传热系数和压降越大,并且窗翅间距比在0.9～1.1范围内呈现高效流动,研究结论对工程实际具有理论指导意义。     

翅片阵列对翼面的冲击换热影响数值模拟研究

曲面冲击换热在飞机机翼前缘防除冰上有着广泛应用.为了进一步提高翼型前缘防除冰性能，采用数值模拟依次探索了不同翅片阵列在平板和曲面上的冲击换热特性.平板模型的翅片阵列包含8片、12片直翅片以及12片弯翅片3种结构；曲面模型包括8片短翅片和8片长翅片两种阵列结构.仿真结果表明：在平板和翼型曲面上添加翅片阵列可以显著提高模型在不同雷诺数下的射流冲击换热性能；与无翅片相比，翼面上的换热效果整体提升高达4%～10%,其中在驻点位置处的强化换热效果最为明显.深入分析发现，引入的翅片阵列一方面增大了强化换热面积，同时也改变了冲击射流流动结构，从而增强了射流冲击换热的效果.     

斜针形百叶窗翅片数及窗翅角均匀性对换热性能影响研究

该文通过建立斜针形百叶窗翅片换向区两侧不同翅片数目及窗翅角均匀性三维数值计算模型,研究了换向区两侧不同翅片数目和窗翅角均匀性对散热器换热性能的影响。结果表明:换向区两侧翅片数目对散热器的换热及流阻性能影响较小;换向区角度均匀性变化对换热性能有一定的影响,jf~(1/3)最大相差9%。     

整体翅片切削—挤压成型技术

整体翅片切削 -挤压成型技术是利用切削 -挤压复合成型原理 ,使被加工工件表层金属经切削、展平、直立的连续变形直接转变成与母体连成一体的“整体翅片”,通过改变翅片的宏观和微观结构强化热传导的效果。主要特点 :1翅片热传导效率高 ,比滚轧翅片高 3 0 %,可节约铜材 3 0 %～ 5 0 %;2应用范围广 ,可在圆管、平面和薄壁件上制作精细翅片 ,翅片尺寸、形状、疏密度可任意调整 (目前可制出翅厚 0 .1 mm以上、翅高 0 .5～ 3 .5 mm的整体翅片 ) ,可在纯铜、铝及其合金以及碳钢、不锈钢等材料上形成翅片 ,扩大了翅片的使用范围 ;3通用性能好 ,可…     

整体翅片切削-挤压成型技术

整体翅片切削 -挤压成型技术是利用切削 -挤压复合成型原理 ,使被加工工件表层金属经切削、展平、直立的连续变形直接转变成与母体连成一体的“整体翅片”,通过改变翅片的宏观和微观结构强化热传导的效果。主要特点 :1翅片热传导效率高 ,比滚轧翅片高 3 0 % ,可节约铜材 3 0 %～ 5 0 % ;2应用范围广 ,可在圆管、平面和薄壁件上制作精细翅片 ,翅片尺寸、形状、疏密度可任意调整 (目前可制出翅厚 0 .1 mm以上、翅高 0 .5～ 3 .5 mm的整体翅片 ) ,可在纯铜、铝及其合金以及碳钢、不锈钢等材料上形成翅片 ,扩大了翅片的使用范围 ;3通用性能好 ,…     

翅片材料对扁管管翅式换热器耦合传热特性影响

为获得翅片材料对扁管管翅式换热器换热性能的影响,在耦合边界条件下对6种翅片材料对应的气—水换热器内层流流动与传热进行了数值分析.结果表明:翅片导热系数对翅片表面温度的不均匀性、空气通道内水平面上低温区长度以及空气通道内流场结构有不同程度的影响.管壁附近翅片表面局部Nu数几乎不受翅片材料影响,随着背离管壁的距离增大,小导热系数的翅片对前排管处表现出了较好的强化效果,不同管排对应位置上翅片表面局部Nu数的分布并不一致,小导热系数的翅片对板芯平均传热系数的影响较大导热系数翅片显著,而大导热系数的翅片对换热板芯平均传热系数的影响与空气流态关联性较大.     

齿型螺旋翅片管束传热及通风特性试验研究

对一种先进的强化换热元件──齿型螺旋翅片管束进行了传热及通风阻力特性试验研究，试验用直接法进行．得出受洁净气流冲刷时该管束传热特性关联式和通风阻力特性关联式，并将该种齿型螺旋翅片管束的性能与相同结构的整体型螺旋翅片管束进行了比较．     

整体翅片切削-挤压成型新技术及装备

该成果是针对机械制造业中各类翅片管的加工问题开发出的整体翅片加工技术。该技术利用切削 -挤压复合成型原理 ,使被加工工件表层金属经切削、展平、直立的连续变形直接转变成与母体连成一体的“整体翅片”。通过改变翅片的宏观和微观结构方式强化热传导的效果。成果的主要特点 :1翅片热传导效率高 ,比滚轧翅片高 3 0 % ,可节约铜材 3 0 %～ 50 %。 2应用范围广 ,可在圆管、平面和薄壁件上制作精细翅片 ,翅片尺寸、形状、疏密度可任意调整 (目前可制出翅厚 0 .1 mm以上、翅高 0 .5～ 3 .5mm的整体翅片 ) ;可在纯铜、铝及其合金以及碳钢、不…     

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.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

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     

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

正~~