三重同心套管相变传热的数值模拟与实验研究

通过数值模拟与实验,研究了三重同心套管内的相变传热过程。相变材料填充在三重同心套管的夹层内,热流体和冷流体分别在套管外层和内层中流动。根据能量守衡,运用了一种简化数值模拟方法(称为温度热阻叠代法)计算分析了三重同心套管内凝固过程。搭建了实验台,实验验证了数值模拟结果,并得出冷流体的入口温度及流量对释热量的影响规律。     

高温熔融盐壳管式相变换热器的传热特性

建立了高温熔融盐壳管式相变换热器的同心套管模型.采用Fluent软件,分析了在考虑相变区域自然对流条件下,熔融盐流体与相变材料的物性参数、内管进口温度与进口流向等因素对液相率与熔化时间的影响,并在熔融盐传热-蓄热实验平台上进行了试验研究.发现:考虑相变区域自然对流时,总的熔化时间减少16.2%;模拟得到的壳侧相变材料温...     

相变蓄热水平套管内凝固过程的数值模拟

该文针对相变蓄热水平套管相变过程,考虑相变区内的自然对流效应,利用计算流体力学软件Fluent软件内的凝固/融化模型对套管内十八烷相变材料进行模拟,得到了不同时刻下套管内传热流体与相变材料耦合问题的温度场、流速场的变化规律.结论表明凝固过程开始阶段,对流换热对换热的影响十分强烈,不能忽略不计.研究结果对蓄热套管在工程实际中的应用具有一定的参考价值.     

蓄冷冰球中相变传热过程的数值分析

对蓄冷冰球中的相变传热进行分析,建立传热的数值方程.试验测量冰球中心的温度曲线,该曲线计算和试验结果的对比表明,文中的数值方法可以对冰球中的相变传热过程进行准确计算.计算结果亦反映出,直径100 mm冰球完全相变所需时间约为50 mm冰球的2.4倍.球壳和传热流体的对流传热系数较小时,增加对流传热系数对提高相变速率有显著影响.冰球相变所需时间和相变材料的初温呈线性关系,传热流体温度接近相变温度时,传热流体温度变化对相变时间有显著影响.计算结果可用于指导蓄冷冰球的传热参数设计.     

蓄冷平板二维凝固特性的焓式有限元法分析

为了研究一种相变材料的蓄冷特性,采用焓式有限元法对该材料的凝固特点进行了研究.获得了以该介质为蓄冷媒介的蓄冷平板在第一类边界条件下凝固时的相界面移动规律、板内温度分布及预测蓄冷时间等参数.数值模拟与实验结果吻合度较好,为板式蓄冷器的优化设计和该相变蓄冷材料的应用提供了一定的理论依据.     

三通道同心套管导热与对流耦合换热的数值模拟

采用整体求解法对常物性的冷、热流体在三通道同心套管中层流逆流流动时的导热与对流耦合传热问题，进行了数值模拟．结果表明，3个通道除各自的入口段局部努塞尔数Nu沿通道变化外，其后均为充分发展段，局部Nu保持不变，且通道内侧的换热比外侧好．固体与流体的导热系数之比λsf对耦合换热产生影响，耦合情况下的Nu比均匀热流边界条件下的Nu要小，随λsf的减小，固壁内的导热对Nu的影响加大．     

相变蓄热装置传热模型的建立

提出了一种采用新型相变材料的内通流体并联螺旋盘管相变蓄热装置,针对所设计相变蓄热式装置的传热特点,在对其传热过程进行合理简化的基础上,提出了相应的相变换热的二维非稳态焓法模型,并对传热基本控制方程进行了空间和时间上的离散化,从而提出了内通流体相变蓄热装置的数值模拟方法。     

夏热冬冷地区相变石膏板相变特性的模拟

基于焓法数值模型,利用Fluent软件模拟定形相变石膏板(PCP)在不同保温位置及不同相变温度时传热的热流密度及内表面温度情况,分析适用于夏热冬冷地区PCP的参数、不同相变温度与放置位置对外墙的隔热性能的影响。结果表明:相变材料最适宜的相变温度为27℃,在此相变温度下,同一时刻的内、外侧位置的内表面最大温差为0.9℃;相变温度为27℃的墙体比普通墙体约节能27.6%,此时相变材料潜热利用率为38.7%。     

含球形相变胶囊的混合储能水箱特性模拟研究

储能水箱是在太阳能光利用过程中的重要元件,是协调未来能源供需平衡,解决可再生能源空间不足的有效方法之一。本文是对含有相变胶囊的混合储能水箱特性进行模拟研究。采用RT35作为相变材料,水作为传热流体,创建了储能水箱的含相变胶囊的数值模型,模拟水箱内部的蓄热过程,探究水箱内热分层机理。水箱内部温度为278.15K,入口温度为353.15K,采用了理查德森数、平均蓄热率和平均蓄热密度作为储能水箱的储能评价指标,对不同的相变胶囊高度、不同的入口流速以及不同的相变胶囊尺寸进行了模拟实验。实验结果表明,随着相变胶囊距水箱底部的高度越高、相变胶囊直径越小,理查德森数越大,平均蓄热率和蓄热密度越大。入口流速越小,理查德森数越大,平均蓄热率和蓄热密度越小。相变蓄热胶囊内相变材料一半进行液化所需的时间与入口流速、相变胶囊尺寸成反比,与相变相变胶囊的距水箱底部的高度成正比。     

板式相变储换热器的储换热准则

为提高蓄冷系统的功效,建立了分析板式相变储换热器储、换热性能的理论模型,采用温度—相变界面迭代法分析了相变界面和流体温度随时间和位置的变化规律,讨论了当传热流体为气体时,在气体侧加肋片后的强化换热效果,得到了相变界面、蓄冷量和流体温度的量纲一的公式,它们不局限于某一种相变材料或工况,对板式相变储换热器的设计和性能优化具有普适的指导意义。     

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.     

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