水平旋转圆筒表面对流传热和传质实验

采用微热偶式测温和测湿技术,分别对大直径水平旋转圆筒表面对流传热和传质特性进行了对比实验研究.实验数据验证了在圆筒表面对流传热和传质之间存在着良好的可类比性,即旋转对圆筒表面对流传热边界层温度场分布和局部努塞尔数的影响规律与旋转对传质边界层浓度场分布和局部舍伍得数的影响规律相似,但顺向侧和逆向侧之间存在着明显的差异;旋转对圆筒表面平均传热努塞尔数数和平均传质舍伍得数的影响规律也相似,都存在临界雷诺数.当旋转雷诺数小于或等于临界雷诺数时,平均努塞尔数和平均舍伍得数随旋转雷诺数的变化基本保持不变;当旋转雷诺数大于临界雷诺数时,平均努塞尔数和平均舍伍得数随旋转雷诺数的增大而增大.实验中还发现,由于传热和传质的边界层条件不同,热质交换共存时的临界雷诺数小于纯对流传热时的临界雷诺数.     

旋转圆筒表面对流传质特性

为研究水平旋转圆筒多孔介质表面的传质特性，用微型热偶式干湿球温度计测量了圆筒表面边界层温度分布和浓度分布，确定了顺向侧和逆向侧的局部对流传质系数；用硅橡胶板量热计测定了圆筒表面的平均对流传质系数．结果表明，旋转对圆筒表面顺向侧对流传质的强化作用比逆向侧明显；在较低旋转雷诺数下，平均舍伍得数基本保持不变，在较高旋转雷诺数下，平均舍伍得数随旋转雷诺数的增大而增大；旋转圆筒表面的对流传质和传热特性之间具有类比性．在实验数据的基础上，归纳和整理出了反映水平圆筒在静止空气中旋转时表面对流传质特性的准则关联式及临界雷诺数的判别式．     

空气喷射对旋转圆筒表面传质特性的影响

通过对旋转雷诺数R,喷射雷诺数Rej,喷嘴宽度和圆筒直径比B／d,喷射距离与喷嘴宽度之比L／B等影响旋转圆筒表面传质特性参数的实验研究,发现：在空气喷射作用下,由旋转产生的第一临界点消失,只存在第二临界点;平均舍伍德数Sh与Rej,B／d和L／B之间的关联式为Sh=0．515Re^2/3（B／d）^0.3（L／B）^0.1;空气喷射对圆筒表面传质的强化作用大于旋转的作用．     

微小孔径旋转冲击射流换热特性的数值模拟

采用数值模拟方法模拟了旋转冲击射流的换热过程,分析了换热过程中喷射孔径、喷射间距、旋转角速度以及流场分布特性对冲击射流换热的表面传热系数与平均换热效果的影响.结果表明:相同雷诺数下,3 mm孔径射流的平均换热效果比6 mm孔径的强;大孔径射流时的平均传热系数受角速度的影响要比小孔径时大;角速度的增加使换热板上的最大换热系数减小且由驻点向外偏移;旋转使板上的换热更加均匀,表现为角速度越高,平均表面传热系数曲线越平坦.     

MPC轴流管壳式换热器的壳程局部传热性能

对一种具有并流多通道进出口结构(MPC)的轴流管壳式换热器的壳程局部传热性能进行实验研究,分别在有壳程进口段分布挡板与无分布挡板的情况下,探讨了进口段局部表面传质努塞尔数的分布、局部平均表面努塞尔数与管束位置及雷诺数的关系,分析了进口段和换热器整体的平均传质努塞尔数与雷诺数的变化关系,揭示了壳程进口段的局部表面努塞尔数的分布规律,并进行了机理分析.研究结果表明,分布挡板能够有效促进壳程流场的分布,提高换热器壳程的整体传热性能.     

水平旋转圆筒表面温度和浓度边界层的测量

用自制的微热偶式测温和测湿装置分别对大直径水平旋转圆筒表面温度边界层和浓度边界层进行了测量．实验表明,旋转对顺向侧和逆向侧的影响情况有所不同顺向侧边界层的温度梯度和浓度梯度随旋转雷诺数的增加一直增大,而逆向侧的温度梯度和浓度梯度随旋转雷诺数的增加先减小后增加用微热偶式测温装置测量边界层温度分布时,由辐射引起的温度测量误差不超过3%,用微热偶式测湿装置测量边界层浓度分布时,由辐射引起的湿球温度测量误差在3％～8％,且离圆筒越近测量误差越大。     

管式换热器传热系数的研究

研究影响传热系数的因素,包括换热器几何结构和列管换热器的不同管程流动分布的影响,以便在设计过程中合理调整结构参数,使换热器提高传热性能.通过对换热器结构、流动状态、管程流动分布变化的实验,处理并分析实验数据,得出在套管换热器内,插入强化丝不仅可以增加空气侧对流传热系数,而且对蒸汽侧对流传热系数也有提高作用,空气流速越快,效果越明显;列管换热器中,单管流动总传热系数最大,随着流通管数的增加,流速降低,传热系数降低.插入强化丝导致流动阻力增大、速率减小、边界层变厚、热阻增加、强化效果不理想.     

轴向浮力驱动下的旋转圆筒热对流稳定性

研究了热对流驱动下的同轴旋转圆筒的线性稳定性问题. 模拟内外圆筒温差引起的热浮力采用了Boussinesq假设, 双圆筒同向旋转, 其半径比为0.5, Prandtl数为0.709. 通过分析发现, 由于圆筒旋转离心失稳和热浮力剪切失稳两种机制的互相竞争, 临界失稳中性曲线发现间断现象, 失稳模态产生跳跃, 形成“孤岛”效应. 在研究稳定性问题的同时还对求解圆筒稳定性问题的数值方法进行了研究和探讨.     

轴向旋转通道内浮升力对湍流影响的直接模拟

采用直接数值模拟方法对绕截面中心轴旋转的方通道内的充分发展湍流进行了数值模拟,湍流雷诺数和普朗特数分别为400和0.71.为了分析浮升力对流体运动的影响,给出了不同格拉晓芙数Gr下的主流平均速度场、温度场、二次流、湍流强度、雷诺应力等湍流统计量的分布情况,并对旋转效应的稳定与否以及由此对湍流统计量的影响进行了分析.结果表明:旋转效应稳定的区域湍流受到抑制,旋转效应不稳定的区域湍流增强,随Gr的增加旋转效应稳定性变得更加复杂;浮升力对流场和温度场有明显的影响,随Gr的增加影响更加明显.     

低温海水外掠圆管混合对流传热规律实验

以自然海水为工质,对层流范围内低温海水的混合对流传热特性进行实验研究,研究换热特性与雷诺数、格拉晓夫数和管径的关系,并与经验公式进行对比;提出适用于层流范围内低温海水外掠圆管流动与换热系数的经验公式。结果表明,在实验范围内努赛尔数随着雷诺数和格拉晓夫数增大而增大,且雷诺数越小,格拉晓夫数对努赛尔数的影响越明显;努赛尔数随着立管直径增大逐渐减小,小管径有利于增强对流传热强度;自然对流的影响随着雷诺数增加而减小,随着格拉晓夫数增大而增大;立管直径越大,自然对流对于总换热量的影响越强,且雷诺数越小,管径变化对自然对流在总换热量中的影响越明显。     

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.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

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.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

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