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Effect of obstacles with different opening means on thermal stratification in hot water storage tanks
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为研究具有内置隔板的太阳能蓄热水箱隔板开孔尺寸及位置对其内部热分层效果的影响,对9种隔板开孔位置的太阳能蓄热水箱内温度场进行了数值分析,结果显示:在相同的流动参数及开孔面积条件下,隔板中心开1个圆孔的水箱热分层效果最好。对于多开孔的水箱,开孔位置对水箱内热分层影响不大,但对蓄热量影响显著。对于隔板中心开1个圆孔的水箱,在不同流动参数条件下,冷、热水出口温差随着冷水入口流速的增大呈先增后减的趋势,当冷水入口流速大于0.9 m/s时,减弱了热分层的稳定性。 相似文献
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热水蓄热技术是解决我国热电耦合问题,提高热电系统和电网消纳可再生能源能力的重要手段。通过数值模拟方法研究水箱内置隔板的直径、高度和厚度对热分层特性的影响,基于理查森数、分层数和火用效率等性能指标,得到不同隔板设计尺寸对温度分层的影响规律,并提出隔板的结构优化设计方法。结果表明:内置隔板对水箱内冷热水掺混程度的抑制作用和对水箱内温度分层的改善效果与流体的流动参数及温度密切相关,当隔板高度为19.275 m,直径为10 m,厚度为0.3 m时具有最佳的热分层特性。 相似文献
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高速旋转的汽轮机隔板密封内流体流动的模拟 总被引:1,自引:0,他引:1
采用数值求解粘性Navier-Stokes方程,研究考虑轴旋转效应的汽轮机高低齿迷宫式隔板密封内流体流动特性及其影响因素.采用有限体积方法离散控制方程,紊流模型采用标准κ-ε两方程模型进行求解.数值模拟了三种齿间距下不同压比时的高低齿迷宫式隔板密封内部的流场特性,并且计算了相应的无量纲流量系数.计算结果揭示了隔板密封内由于环形腔室和高低齿的作用导致密封内流体的动能有效地耗散为热能,起到了密封的作用.研究结果表明:在相同的几何结构下,压比的增加导致密封泄漏量的减小;在相同的压比条件下,密封的泄漏量随着齿间距的减小而减小.图6参4 相似文献
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采用数值求解三维粘性Reynolds-Averaged Navier-stokes(RANS)方程技术,研究汽轮机低压光轴迷宫式隔板密封内泄漏流动特性及其影响因素。采用有限体积方法离散控制方程,标准k-ε紊流模型封闭求解方程组,同时考虑轴的旋转效应。针对典型的光轴整体加工尖齿隔板密封,分别数值研究了相同的轴向距离和径向间隙下三种齿间距在不同压比下的泄漏流动特性,计算了相应的无量纲流量系数。计算结果显示出迷宫隔板密封与轴之间的环形腔室内三维涡流使泄漏流动的动能有效地耗散成热能,起到了密封的作用。研究结果表明在相同的几何尺寸下迷宫隔板密封的泄漏量随着压比的减小而增大,在相同的压比条件下,泄漏量随着密封齿间距的减小而减小。本文的研究工作对合理有效地设计迷宫式隔板密封提供一定的理论依据和技术支撑。 相似文献
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为了研究水轮发电机组下导轴承油雾成因和机理,设计了抑制油雾逸出的新型轴承结构。运用VOF两相流模型和SST k-ω湍流模型,基于有限差分法,从流场特性、温度特性和相分布等方面分析了轴承油雾形成的原因和流动特性。结果表明:下导轴承的油雾形成主要与轴承结构相关;轴领内外两侧空腔的巨大压力差为油雾的逸出提供了驱动力,下导轴承挡油管缺乏密封结构,巨大空腔为油雾提供了逸出通道,最终导致油箱油雾大量逸出;轴瓦与轴领的摩擦生热导致部分润滑油气化形成气态油雾,油雾从轴领与挡油管之间的空腔散发出去。 相似文献
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为得到单罐内熔融盐释热传热规律以提高换热量,分析无隔板下进上出、无隔板上进下出和有隔板上进下出3种不同取热条件下熔盐的释热实验规律。通过对单罐内熔盐温度分布、释热换热器出口温度、释热换热量、能量释放率及释热换热器的瞬时效率5个评价指标对单罐蓄热系统释热性能进行分析。结果表明,单罐系统内布置圆柱形隔板,且以释热介质从蓄热罐顶部流入底部流出的取热形式,熔盐温度出现微小分层,释热换热器出口温度及释热换热量均达到最高,盘管换热器的瞬时效率最高,取热时间最短。此研究结果可为熔盐单罐蓄热系统设计提供依据。 相似文献
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Thermal stress in the fabrication process of thermal barrier coating system (TBCs) has a significant effect on the quality of TBCs and the durability of gas turbine. In this work, a new analytical model was developed to calculate the thermal stress during the fabrication process of TBCs. Variations of the material properties with temperature of TBCs were well considered in the present model. Several spraying factors: such as pre-heating temperature, cold gas dynamic spraying (CGDS) method, thickness of top coating and thickness of substrate, which has significant effects on thermal stress generation, are also discussed in this work. 相似文献
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对污泥加热处置的干燥或干燥—焚烧、直接焚烧等技术进行了理论分析与计算,并与工程应用数据进行对比,结果表明,采用干燥或干燥—焚烧技术对污泥进行热处置,具有显著的节能和环保效益。 相似文献
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为了提高火电厂的发电热效率,降低冷端余热热污染,应对火电厂中的汽轮机乏汽热量进行回收利用.现在以N1030-26.25/600/600为例:对该机组热力循环系统进行改进,加入有机工质循环;利用其自身的热力特性,使有机工质吸收机组凝汽器中水蒸汽中的汽化潜热;成为有一定压力和温度的过热蒸汽,再进入低压缸做功.经过热经济性计算,结果显示:在THA、75% THA、50% THA工况下,采用甲苯、R365MFC、正戊烷3种有机工质,在机组总热耗、机组排汽温度与原机组相同的情况下,新系统的冷端热量减少,发电热效率得到了提高;采用新系统可以使机组热经济性提高;其中工质R365MFC环保性好,发电热效率高,排汽压力合适,为新系统最适合的有机工质. 相似文献
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More than £109 are spent annually in the world on thermal insulants, yet it is surprising how little attention is devoted to the selection of the most suitable insulant for the chosen purpose as an essential step in the design process. Too often the choice between insulants (for example, between X which possesses a very low thermal conductivity, Y which has a high strength and Z which is easily applied) is made on the basis of ill-informed opinion or limited experience. Thus details of the pertinent physical properties for commercially-available insulants have been gleaned and sifted, often from scattered and sometimes from esoteric sources of information, in order to facilitate the designer (whether he be an engineer or an architect) making the optimal choice. 相似文献
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A preliminary procedure has been developed for assessing the prospective performance of idealised sensible- and latent-heat storage systems. Design charts relating storage volume, thermal capacity, boundary insulant thickness and time constant are presented. 相似文献
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介绍了通过计算不舒适指标评价房间热性能的方法。基于人体热反应从热舒适角度来评价房间的热性能 ,得出人体热舒适对房间建筑参数的敏感程度。这些参数主要包括围护结构的物理性质 ,房间的位置、朝向及几何形状 相似文献
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采用扫描电子显微镜(SEM)、激光脉冲等方法研究了204NS和204NS-G粉末对等离子喷涂热障涂层组织结构及热导率的影响。结果表明:相比204NS-G粉末,204NS粉末制备的YSZ涂层具有较高的密度和较低的孔隙率。在1 000℃下,204NS粉末制备的YSZ涂层热导率为0.78 W/m·K,比204NS-G粉末制备的YSZ涂层热导率高约20%。 相似文献
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《Applied Thermal Engineering》2014,62(1):105-112
In addition to greenhouse gas emissions, coastal thermal power plants would gain further opposition due to their heat rejection distressing the local ecosystem. Therefore, these plants need to enhance their thermal efficiency while reducing their environmental offense. In this study, a hybrid plant based on the principle of Ocean Thermal Energy Conversion was coupled to a 740 MW coal-fired power plant project located at latitude 28°S where the surface to deepwater temperature difference would not suffice for regular OTEC plants. This paper presents the thermodynamical model to assess the overall efficiency gained by adopting an ammonia Rankine cycle plus a desalinating unit, heated by the power plant condenser discharge and refrigerated by cold deep seawater. The simulation allowed us to optimize a system that would finally enhance the plant power output by 25–37 MW, depending on the season, without added emissions while reducing dramatically the water temperature at discharge and also desalinating up to 5.8 million tons per year. The supplemental equipment was sized and the specific emissions reduction was estimated. We believe that this approach would improve the acceptability of thermal and nuclear power plant projects regardless of the plant location. 相似文献
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Ocean thermal energy conversion (OTEC) power plants require an ocean temperature difference sufficient to operate turbines as efficiently as possible. In 1975, Ocean Data Systems, Inc. (ODSI) assembled an ocean temperature data base for OTEC purposes for the National Science Foundation. From this data, summaries were prepared identifying seasonal OTEC thermal gradients for ocean areas surrounding the North American continent. Under the Energy Research and Development Administration program, ODSI updated the historical file and identified the thermal resource for many specific sites on a monthly basis. Now, the Department of Energy and ODSI have done a worldwide OTEC thermal resource study. Two charts of the world's oceans showing the gross resource available at depths of 500 and 1000 m have been produced (Figs. 1 and 2). 相似文献