Performance Enhancement of Solar Latent Heat Thermal Storage System with Particle Dispersion — an Exergy Approach     

Selvaraj Jegadheeswaran  Sanjay D. Pohekar  Tarik Kousksou 《洁净——土壤、空气、水》2011,39(10):964-971

Phase change material (PCM) employed latent heat thermal storage (LHTS) system has been showing good potential over the years for energy management, particularly in solar energy systems. However, enhancement in thermal conductivity of PCMs is emphasized as PCMs are known for their poor thermal conductivity. In this work, the thermal performance of a shell and tube LHTS module containing PCM‐metal particles composite is investigated while charging and is compared with that of pure PCM system. The effect of particle dispersion on latent heat capacity of pure PCM is also analyzed. Enthalpy based governing equations are solved numerically adopting FLUENT code. Exergy based performance evaluation is taken as a main aspect. The numerical results are presented for various operating conditions of heat transfer fluid (HTF) and indicate considerable performance improvement of the system when particles are dispersed.  相似文献   

Joint elastic‐electrical effective medium models of reservoir sandstones     

Angus I. Best  Lucy M. MacGregor  Jeremy Sothcott  Tim A. Minshull 《Geophysical Prospecting》2011,59(4):777-786

Improvements in the joint inversion of seismic and marine controlled source electromagnetic data sets will require better constrained models of the joint elastic‐electrical properties of reservoir rocks. Various effective medium models were compared to a novel laboratory data set of elastic velocity and electrical resistivity (obtained on 67 reservoir sandstone samples saturated with 35 g/l brine at a differential pressure of 8 MPa) with mixed results. Hence, we developed a new three‐phase effective medium model for sandstones with pore‐filling clay minerals based on the combined self‐consistent approximation and differential effective medium model. We found that using a critical porosity of 0.5 and an aspect ratio of 1 for all three components, the proposed model gave accurate model predictions of the observed magnitudes of P‐wave velocity and electrical resistivity and of the divergent trends of clean and clay‐rich sandstones at higher porosities. Using only a few well‐constrained input parameters, the new model offers a practical way to predict in situ porosity and clay content in brine saturated sandstones from co‐located P‐wave velocity and electrical resistivity data sets.  相似文献   

Abell 851: Are we looking at the beginning of a merging process?     

E. De Filippis  S. Schindler 《Astrophysics and Space Science》2003,285(1):167-171

We present an XMM observation of the moderately distant (z=0.41)galaxy cluster CL 0939+4713 (Abell 851), an exceptionally rich cluster. The formation and evolution of clusters depends sensitively on cosmological parameters like the mean matter density in the universe Ο_m. Therefore it is important to determine the dynamical state of clusters at different redshifts, i.e. at different evolutionary states. The X-ray morphology alone is not the best indicator of the dynamical state, but it should be complemented with all other information available, e.g. the temperature map or the galaxy distribution. The combination of all findings gives a detailed picture of the state of a cluster. This analysis, of this relatively distant cluster, can be used as a basis for comparisons at lower and higher redshifts. The capability of XMM to perform spatially resolved spectroscopy can be used also to determine the distribution of the metal abundances. Not only the overall value of metallicity but also its spatial distribution gives important indications on the metal enrichment processes. The X-ray image shows pronounced substructure. There are two main subclusters which have also some internal structure. This is an indication that the cluster is a dynamically young system. This conclusion is supported by the temperature distribution: a hot region is found between the two main subclusters indicating that the cluster is in the process of a major merger, in which the two subclusters will probably collide in a few hundreds of Myr. The intra-cluster gas of CL 0939+4713 shows variations of the metal abundances. The optically richer subcluster has a somewhat higher metallicity. This finding together with the absence of post-starburst galaxies in this region gives interesting hints on the metal enrichment processes favouring recent enrichment processes like ram-pressure stripping or tidal stripping. Throughout this paper we use H ₀ =50 km s^-1Mpc^-1 and q ₀ =0.5; all errors are 90% confidence levels. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

福建武夷山上西坑钼矿矿石学特征     

王翠芝 《地质与勘探》2013,49(1):39-49

福建武夷山上西坑钼矿为中温热液型钼矿.文章根据野外考察,在岩相学的基础上,进行了矿相学及辉钼矿矿石矿物学的系统研究,得出上西坑钼矿矿石自然类型主要为构造角砾岩型、石英脉型.矿石构造主要有角砾状构造、浸染状构造、细脉状构造.矿石结构以细-中细粒鳞片结构为主,局部呈现厚板状、带状分布;矿石矿物辉钼矿铅灰色,多色性明显,2H多型,矿物成分中杂质含量较低,Re含量为1.479 ～34.35μg/g,显示其矿源为壳幔混合源;Re作为伴生矿产,具一定的综合利用价值.  相似文献   

各向异性介质中大地电磁场的异常特征     

罗天涯  熊彬  李长伟  杨红  黄业中 《物探化探计算技术》2013,(6):645-650

给出各向异性介质二维地电断面大地电磁场的边值问题以及等价的变分问题。对计算区域采用矩形网格中进一步三角细化的剖分方式并在三角单元内进行线性插值,解出有限单元法数值解。通过典型模型的正演模拟,得到大地电磁测深曲线,并与前人的研究工作对比,验证了该方法的有效性。  相似文献   

河流水位差计设计及其应用的可行性研究          下载免费PDF全文

卢玉成 《水文》2013,33(6):29-34

水工建筑物或控制河段的上下游水位差是水流运动的决定性要素,是流量推算中的最重要因子。在平原水网区,水位差很小,人工观测精度对其影响十分突出,直接影响流量定线和流量推算的精度,不能满足社会对水资源精细配置的需求。为提高水位差的测量精度,设计了河流水位差计;付之应用,对水位差的测量,无需进行水尺零点高程校正,无需进行水位的对比观测,而且能在任意数量级内提高水位差精度(根据精度选择探头),所构成的误差只有很微小的仪器器差,可满足流量定线与精确推流的目的。该系统还可以同时测记水位。河流水位差计设计简洁,仪器生产难度小,附属设施施工方便,整体造价低廉,具有良好的开发应用前景。  相似文献   

基于均匀化理论的土石混合体应力应变关系     

周博  卢自立  汪华斌  李纪伟 《地质通报》2013,32(12):2001-2007

将土石混合体等效为理想的二元介质混合材料,假定块石元为理想的脆弹性材料,土体元为典型的弹塑性材料。选取邓肯-张模型定义土体的本构关系,引入块石元局部应变系数建立土石混合体代表单元体积平均应变与其中块石元、土体元微应变的桥联关系。通过均匀化理论对土石混合体代表单元的一般应力应变关系进行了详细探讨。选取广东省云罗高速高填路基土石混填料中的残积粉质粘土,通过室内常规三轴压缩实验对土体邓肯-张模型的参数进行标定,描绘出不同围压及不同含石率条件下土石混合料一般应力应变关系曲线图。结果表明,均匀化理论得到的函数关系式能够较好地反映土石混合体在不同条件下的一般应力应变关系。随着土石混合体含石率的提高其抗剪能力显著增加,但当含石率小于0.3时,块石元的增强效应并不明显。  相似文献   

Reflectivity template,a quantitative intercept-gradient AVO analysis to study gas hydrate resources – A case study of Iranian deep sea sediments     

《Marine and Petroleum Geology》2014

Presence of gas hydrate and free gas in Iranian part of Makran accretionary prism changes the elastic properties of unconsolidated sediments and produces sharp bottom simulating reflectors (BSRs) which are observed on the 2-D seismic data. Different methods have been applied to estimate the gas hydrate and free gas saturations in marine sediments based on seismic measurements. Most of these methods are based on relating the elastic properties to the hydrate and free gas saturations and remotely estimating their concentration. In this regard, using the effective medium theory (EMT) which was developed for different modes of hydrate distribution is more considered among other rock physics theories. The main concern about saturation estimations based on EMT is that the velocities of the hydrate-bearing sediments primarily depend on how they are distributed within the pore space. Therefore, understanding the modes of hydrate distribution (at least cementing or non-cementing modes) is necessary to decrease the estimation uncertainties.The first intention of paper is to investigate amplitude variation versus offset (AVO) analysis of BSR to determine the hydrate distribution modes. The results from the probable saturation revealed that if the hydrate cements the sediment grains, BSR would show the AVO class IV and if hydrate does not cement the sediment grains, then BSR would show either the AVO class II or class III depending on the free gas saturation just beneath the BSR. The second intention of paper is to introduce some templates called reflectivity templates (RTs) for quantitative study of hydrate resources. These templates are provided based on the EMT to quantify the hydrate and free gas near the BSR. Validation of this approach by synthetic data showed that a reliable quantification could be achieved by intercept-gradient RTs, only if these attributes are determined with a high accuracy and good assumptions are made about the mineralogical composition and porosity of the unconsolidated host sediments. The results of this approach applied to a 2-D marine pre-stack time migrated seismic line showed that less than 10% of the gas hydrate accumulated near to the BSR in anticlinal-ridge type structure of Iranian deep sea sediments. The free gas saturation near to the BSR by assuming a homogeneous distribution was less than 3% and by assuming patchy distribution was about 3–10%.  相似文献   

深埋海底隧洞内水压力下饱和土的动力特性          下载免费PDF全文

高华喜  闻敏杰 《海洋工程》2014,32(2):46-51

将衬砌分别视为多孔柔性材料和弹性介质,在频率域内研究内水压力作用下饱和分数导数黏弹性土-深埋圆形隧洞多孔柔性或弹性衬砌系统的耦合简谐振动。土体的宏观力学特性采用多孔介质理论来模拟。通过引入与土体体积分数相关的应力系数,利用衬砌和土体界面处位移连续,分别得到饱和黏弹性土和衬砌的位移、应力和孔隙水压力等的解析表达式。在此基础上,分析了多孔柔性衬砌和弹性衬砌结构的差异,并考察了应力系数、渗透系数、分数阶导数本构参数等对系统动力响应的影响,结果表明:多孔柔性衬砌材料条件下系统的动力响应明显大于弹性衬砌材料条件下系统的动力响应;随着分数导数阶数和材料参数比的增加,系统共振效应明显减弱;衬砌边界透水和不透水只是反映边界渗透性的两种极限状态。  相似文献   

基于改进BISQ机制的双相HTI介质波传播伪谱法模拟与特征分析   总被引：3，自引：3，他引：0       下载免费PDF全文

刘财  兰慧田  郭智奇  冯晅  鹿琪 《地球物理学报》2013,56(10):3461-3473

改进BISQ(Biot-Squirt)机制在不引入特征喷流长度的情况下,将含流体孔隙介质中Biot流动和喷射流动两种重要的力学机制有机地结合起来,且各相关参数具有明确物理意义和可实现性.本文将改进BISQ机制一维孔隙流体压力公式推广到三维具有水平对称轴横向各向同性介质(HTI介质)情况,结合裂缝各向异性理论,给出了基于改进BISQ机制的双相HTI介质模型及其二维三分量波传播方程,采用伪谱法求解该方程,进行了不同相界、不同频率以及双层地质结构情况下该类介质中波场的数值模拟与特征分析.数值模拟结果表明:伪谱法模拟精度高,压制网格频散效果好,可以得到高精度的波场快照和合成记录;基于改进BISQ机制的双相HTI介质模型兼具裂缝各向异性特征和孔隙弹性特征,其为从双相各向异性理论角度深入研究裂缝性储层的地震响应奠定了理论基础.  相似文献