低品位热驱动混合溶液除湿降温系统性能分析

对低品位热驱动混合溶液除湿降温系统的性能进行了模拟研究.基于混合溶液传质关联式,对混合溶液除湿、再生过程进行了数学建模,比较了不同浓度溶液除湿器和再生器出口空气含湿量的实验值与模型计算值,其误差均在10%之内,从而验证了模型的可靠性.模拟分析了混合溶液浓度对系统性能的影响,模拟结果表明:在设计工况下,使用48%混合溶液的系统送风参数为19℃,9. 7 g/kg,氯化钙和氯化锂的混合溶液的除湿能力与氯化锂溶液相当,而混合溶液成本则大大降低,成本最高可降低65. 7%;随着混合溶液浓度的增加,系统热力性能提高且输配能耗降低,但也会导致送风温度及含湿量偏高,因此为了满足送风及节能需求,需要合理地选择氯化钙和氯化锂的混合溶液浓度.     

(1.中国矿业大学 电力学院,江苏 徐州221116;2.中国矿业大学 化工学院,江苏 徐州221116)

为研究流体在石墨多孔介质中的流动规律,通过水的单相饱和渗流实验,揭示了水在不同孔隙率的石墨多孔介质中的非Darcy渗流规律.实验结果表明:流动偏离达西定律,呈现非线性,可以用一元二次方程的形式拟合,而且精度较高,相关系数达0.99以上;流体在渗流过程中存在最小启动压力梯度,其大小随孔隙率的增加而急剧减小,按其大小随孔隙率的变化将石墨多孔介质分为3类:"易渗类"孔隙率约>18%,"难渗类"孔隙率约<11%,"过渡类"孔隙率在两者之间;水在石墨渗流过程中雷诺数的计算结果也表明流动为非Darcy渗流,与实验现象相一致.     

大温差条件下多孔材料干燥过程数值模拟

基于热力学平衡假设并结合动态边界条件,对大温差下多孔保温材料中的水分迁移及三态相变过程进行数值模拟,并以海绵干燥过程为例给出了实验验证.在数学模型中考虑了由于温差引起的自然对流效应,分析了不同时刻海绵内部的温度、水蒸气浓度、液态水及冰体积分数的分布规律,讨论了材料主要物性参数对水分传递过程的影响.结果表明:数学模型能够实现对大温差下多孔介质中水分传递过程的准确预测;由物性参数分析的结果可知,相比于影响多孔保温材料水分传递的有效扩散系数和孔隙率两个关键物性参数而言,有效导热系数影响相对微弱.     

利用瞬态法提取岩样非Darcy流渗透特性

建立了一种测定岩样非Darcy流渗透特性试验系统的动力学模型.基于岩样两端孔隙压差的时间序列,利用差分计算或曲线拟合得到渗流速度及其变化率的时间序列.通过线性回归,得到岩样的Forchheimer非Darcy流渗透特性,即渗透率、非Darcy流β因子和加速度系数.试验结果表明,无论岩样处于峰前还是峰后应力状态,岩样中的渗流都不服从Darcy定律;当非Darcy流β因子为正时,非Darcy流的渗透率κ小于Darcy流的渗透率κD;渗透率(κ和κD)、非Darcy流β因子和加速度系数可近似表示为应变的幂指数函数;三种渗透特性中的每两种整体上存在幂指数关系;在加载的初始阶段,由于孔隙和微裂隙的压缩和闭合,渗透率随应变减小,而非Darcy流β因子和加速度系数随应变增大;随后,由于裂隙的扩展,岩样的渗透率迅速增大,而非Darcy流β因子和加速度系数迅速减小,并在峰值应力附近达各自的极值;由于围压的作用,峰后应力状态下岩样的渗透特性随应变的变化缓慢.图3,参18.     

考虑两相影响的PEMFC内部传递过程三维模拟

针对常规流场的质子交换膜燃料电池提出了三维非等温数学模型,在考虑水相变的情况下对电池内部传热传质和电化学反应进行了数值模拟,分析了多孔介质内水蒸气凝结和液态水分布对传递过程和电池性能的影响,并同单相模拟结果进行了对比.计算表明,水蒸气的凝结在降低多孔介质渗透性的同时,加强了反应气体向反应界面的传递;两种模型在高电流密度下阳极均缺水严重,需要更好的水管理;单相模型由于忽略了水蒸气的凝结,实际低估了电池的欧姆极化.     

多孔介质模型的三维重构方法

建立准确的多孔介质模型在微观渗流机理的研究中具有重要意义.为了更加方便准确地建立多孔介质模型,总结了多孔介质模型重构的物理实验方法和数值重构方法,通过重构方法的优缺点对比及适用性分析,优选出马尔可夫链-蒙特卡洛方法(MCMC).针对3种不同性质的多孔介质,采用MCMC方法分别对其进行了重构.结果表明,MCMC方法计算速度快,适用范围广泛,重构效果好.最后将MCMC方法扩展到三维空间,重构出三维多孔介质模型,为微观渗流机理的研究提供了一个模拟平台.     

多孔介质中浆液动界面扩散规律及工程应用研究

基于渗流连续性方程、Darcy定律、线性滤过定律及渗流压力降方程,建立了多孔介质中水泥浆三维动界面速度模型和压力模型,分析了渗滤效应下动界面的速度、压力降及压力变化规律;通过现场试验,研究了水泥浆三维动界面压力的特征规律,并将试验值与理论值进行了对比分析.结果表明,相同条件下,恒定压力的Darcy渗流速度是考虑渗滤效应浆液动界面速度的1.3~2.6倍;忽略和考虑渗滤效应时的浆液扩散距离相差约1倍;固定扩散距离处,水泥浆动界面速度随水泥浆区多孔介质渗透系数Kc的减小而降低;特定时间点时,浆液单位压力降ΔP'和动界面压力p均沿程减小;随着浆液由渗透扩散转变为滞留淤堵,动界面压力降p'呈先增后减、压力p呈先减后增趋势.     

低渗透多孔介质变渗透率数值模拟方法

 根据流体在低渗透多孔介质中的渗流特征,建立了低渗透多孔介质数学模型,通过引入无因次渗透率变化系数描述低速非达西渗流规律,并基于黑油模型数值模拟系统,开发了低渗透多孔介质变渗透率数值模拟软件。采用矿场实际数据,分别使用达西渗流、考虑启动压力梯度为常数的拟线性渗流和变渗透率渗流模型,对五点井网进行模拟计算,对比分析了不同渗流规律下的油井产油量、含水率、含油饱和度及不同时间的地层渗透率分布。结果表明,变渗透率渗流模型计算的油井产油量、含水率和含油饱和度分布介于达西渗流和拟启动压力梯度渗流模拟结果之间,油水井附近地层渗流能力强,远离主流线地层渗流能力弱;井距越小,地层渗流能力越强;流体在低渗透多孔介质的渗流过程中,达西渗流仅发生在井筒附近小面积区域内,地层大部分区域发生变渗透率渗流,且占据了地层渗流的主导地位,变渗透率数值模拟方法弥补了其他方法未考虑渗透率变化因素的不足,变渗透率数值模拟软件能够更准确地预测流体在低渗透多孔介质中的流动特征。     

水压致裂作用下岩体参数对裂纹扩展影响的数值模拟

应用真实破裂过程分析系统RFPA2D20-Flow,以赋予材料非均匀性为特点,采用有限元计算方法,创建渗流-应力-损伤耦合模型.模拟分析了不同层理角度及不同岩石强度的非均质层理岩体在孔隙水压力作用下的水压致裂过程,描述了这两种岩体参数对拉伸裂缝萌生及扩展的影响趋势.模拟分析结果表明,层理角度和岩石强度对水压致裂作用下层理岩体裂纹扩展模式及岩体稳定性的影响是不可忽略的;随着层理角度的增加,最大主应力及层理弱面分别对压裂裂纹的萌生和扩展起主要控制作用;在同一层理角度条件下,随着岩石强度的减小,层理岩体的稳定性降低,其破裂模式亦产生较大的变化.     

某突出矿煤岩非Darcy流渗流稳定性实验研究

为了获得煤岩非Darcy流渗透特性,利用MTS-02型岩石力学试验系统采用全程位移控制对煤与瓦斯突出矿煤样进行了全应力应变过程数控瞬态渗透法试验。计算出煤样破坏过程中不同应变下非Darcy流渗透率、非Darcy流β因子、加速度系数及渗流稳定性指数,并给出发生渗流失稳所需的压力梯度。研究表明:该突出矿煤样的渗流稳定性指数χ的负值较多出现在峰值应力后并且其发生渗流失稳所需的压力梯度较大。     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

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