两相喷射器的压缩/喷射制冷系统性能分析

研究了两相喷射器中流体的流动过程,并应用质量守恒、动量守恒、能量守恒对两相喷射器建立了热力学模型,以R134a/R1234yf为工质,分析了喷射器结构参数以及工况参数对压缩/喷射制冷系统性能的影响。计算结果表明:喷射器存在最佳喷嘴出口面积和最佳喉部面积比使压缩/喷射制冷系统的性能最佳;性能系数(COP)随蒸发温度升高和冷凝温度降低而升高,而性能系数提高率(COPi)随着蒸发温度降低和冷凝温度升高而升高;相同工况下,以R134a为工质的系统性能系数、制冷量均高于R1234yf;当系统以R1234yf为工质,蒸发温度为5℃,冷凝温度为55℃时,压缩/喷射制冷系统的COP值较传统压缩制冷系统的COP值可提高26%。     

基于两相喷射器的压缩/喷射制冷系统性能分析

研究了两相喷射器中流体的流动过程,并应用质量守恒、动量守恒、能量守恒对两相喷射器建立了热力学模型,以R134a/ R1234yf为工质,分析了喷射器结构参数以及工况参数对压缩/喷射制冷系统性能的影响。计算结果表明：喷射器存在最佳喷嘴出口面积和最佳喉部面积比使压缩/喷射制冷系统的性能最佳;性能系数(COP)随蒸发温度升高和冷凝降低而升高,而性能系数提高率(COPi)随着蒸发温度降低和冷凝温度升高而升高;相同工况下,以R134a为工质的系统性能系数、制冷量均高于R1234yf;当系统以R1234yf为工质,蒸发温度为5℃,冷凝温度为55℃时,压缩/喷射制冷系统的COP值较传统压缩制冷系统的COP值可提高26%。     

船用喷射制冷-转轮除湿空调系统工质选择

为了给船用喷射制冷-转轮除湿空调选择合适的制冷剂,在考虑系统构架和工作条件对系统性能影响的基础上,分析了5种环保制冷工质(R134a,R245fa,R718,R717,R1234yf)的基本物性、引射系数、COP(coefficient of performance)和充注量,并进行了对比。结果认为没有任何一种制冷剂可以在各种场合都具备最佳的性能。但在船用喷射制冷-转轮除湿空调系统具备较高发生温度(≥150℃)和较低冷凝温度(≤40℃)时,R718具有较好的应用潜力;而当发生温度较低(90℃)时,R1234yf是一种较为理想的选择。     

以R1234yf为替代工质的喷射制冷循环特性

R134a作为喷射制冷循环的工质可获得较高循环性能,但因其具有较高全球变暖潜能值(global warming potential,GWP),所以将逐步被限制使用或被新型绿色环保制冷剂所替代。本文提出以低GWP值的R1234yf作为喷射制冷循环工质,建立了喷射制冷循环热力学数学模型。分析了以R1234yf、R134a和R600a为工质的喷射制冷循环喷射器的喷射因数、制冷量和性能因数随着蒸发温度、冷凝温度和发生器出口温度的变化关系。研究结果表明:相同的工况下,采用R1234yf为工质喷射制冷循环可获得最高喷射器喷射因数和最大制冷量,但以R1234yf为工质喷射制冷循环所获得性能因数(coefficient of performance,COP)较R134a低7.0%,比R600a高20.2%。综合评价认为:R1234yf为工质的喷射制冷循环性能优于R600a,且与采用R134a为工质的喷射制冷循环性能相当。     

低品位余热源新型双喷射式制冷系统研究

提出了用气-液喷射器代替机械泵,有效回收低品位余热能源的新型双喷射式制冷系统.该制冷循环本身不需要消耗电能.研究了气-液喷射器的运行特性和喷射系数与工作参数的关系,发现在一定范围内系统效率随工作压力提高而提高,然后下降.分析了双喷射式制冷系统COP与发生器温度、冷凝器温度的关系,模拟了不同余热温度条件下双喷射式制冷系统的运行性能,结果表明制冷剂R123制冷性能优于R134a.系统COP可达0.3.     

两相喷射器增压的二级压缩制冷系统性能分析

建立一维等面积两相喷射器热力学模型,改进传统的二级压缩系统,提出一种喷射器增压的二级压缩制冷系统.以R1234yf为制冷剂,采用能量分析模型,研究不同设计工况下喷射器的性能.结果表明:当蒸发温度升高时,系统的性能系数(COP)和喷射系数增大,喷射器升压比减小;当冷凝温度升高时,COP和喷射系数减小,喷射器升压比增大;当蒸发温度为0℃,冷凝温度为50℃时,COP随着中间温度的升高先增大后减小,且存在一个最优中间温度,系统性能提高率可达10%以上.     

低温级以CO2为工质的复叠式制冷循环热力学分析

传统的复叠式制冷循环通常采用的几种工质破坏臭氧层且温室效应较强，为此，对低温级以CO2为工质的复叠式制冷系统进行热力学理论分析，计算了不同蒸发温度下最佳COP及其对应的低温循环冷凝温度和流量比．通过对几种工质组合(R22-R12，R134a-CO2，NH3-CO2，R290-CO2，CO2-CO2，CO2-CO2加膨胀机)的比较，可发现自然工质的COP与传统工质的相当．综合考虑环境因素及设备的选择，自然工质系统值得推荐．     

典型气象日蓄热型太阳能喷射制冷系统性能分析

以太原地区的气象参数为背景,利用TRNSYS仿真软件,模拟计算以R141b为制冷剂的蓄热型太阳能喷射制冷系统在夏季典型日的性能,分析系统的喷射系数、制冷量、能效比(COP)随着太阳辐射照度的逐时变化,以及蒸发温度、冷凝温度、喷射器喉部面积比(r)对系统性能系数的影响.结果表明:系统的性能随太阳辐射照度增强而提高;蓄热装置的使用拓宽了系统高效运行的时间,更加有效地利用了太阳能;在系统运行时段,各性能系数逐时变化趋势一致,且随着蒸发温度的升高而增大,随着冷凝温度的升高而减小;同一工况下,r值越大喷射系数越大,     

基于一维模型的喷射制冷系统性能计算分析

对索科洛夫等人提出的一维喷射器模型进行了修正并与其他部件的控制方程相结合,建立了更为完善的喷射制冷系统的性能计算模型,提高了计算模拟的准确性。以R141b为制冷剂,对热力参数和喷射器喉部面积比变化时喷射制冷系统的性能进行了模拟计算。计算结果表明:蒸发温度越高,喷射制冷系统的喷射系数和性能系数(COP)越高;冷凝温度降低、发生温度升高均有利于喷射系数和COP的提高,但冷凝温度和发生温度存在一个最佳值;喉部面积比越大,最大临界喷射系数越大,但需要的发生温度也越高。因此,在喷射制冷系统的设计和运行中要选择合理的喷射器结构参数和运行参数,以提高喷射制冷系统的性能。     

带节能器的CO2跨临界循环制冷系统

为避免CO2跨临界循环运行因高低压差增大而导致压缩过程偏离等熵过程太远，减小CO2跨临界循环系统损失，提高系统性能并降低系统成本，采用带节能器的CO2跨临界制冷循环，对其热力学模型进行计算分析，并与基本带膨胀机循环进行对比．结果表明，不同于传统工质带节能器制冷循环的补气压力介于系统高压和低压之间，带节能器CO2跨临界制冷循环的补气压力应介于临界压力和低压之间；其制冷系数与膨胀机效率为0．6的系统性能相当；制冷性能随蒸发温度的升高而提升，随气体冷却器出口温度的升高而降低；相对补气压力对系统性能的影响较大，当相对补气压力为0．9～1．1时制冷性能较高，在较低蒸发温度下降低压缩机排气温度的优势明显．     

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.     

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

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