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Coupling effect between film boiling heat transfer and evaporation drag around a hot-particle in cold liquid 总被引:1,自引:0,他引:1
Extremely rapid evaporation could occur when high-temperature particles contact withlow-temperature liquid. This kind of phenomenon is associated with the engineering safety and the problems in high-transient multi-phase fluid and heat transfer. The aim of our study was to design and build an observable experiment facility. The first series of experiments were performed by pouring one or six high-temperature particles into a low saturated temperature liquid pool. The particle's falling-down speed was recorded by a high-speed camera, thus we can find the special resistant feature of the moving high-temperature particles, which is induced by the high-speed evaporation surrounding the particles. The study has experimentally verified the theory of evaporation drag model. 相似文献
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辐射换热是钍基先进CANDU型反应堆(TACR)压力管和排管间换热的主要途径.本文以灰体辐射模型和电网络分析方法为基础建立了TACR压力管和排管间辐射换热的计算模型,利用该模型计算了给定温度边界和热流密度边界的情况下,压力管和排管间的辐射换热能力.计算结果表明,该模型可以用于TACR压力管和排管间辐射换热能力的计算. 相似文献
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Present study investigates the effects of combined mixed convection and thermal radiation for laminar ascending flows. Finite
volume method is applied for solving mass, momentum and energy balance equations simultaneously and for radiation transfer
equation (RTE) discrete ordinate method is used. Temperature-dependent thermophisycal properties are considered for absorbing–emitting–scattering
medium (H2O and CO2 gases) when solving governing equations. Results are presented in terms of velocity and temperature fields, surface heat
flux and total Nusselt number. Results show that thermal radiation speeds the development of velocity and temperature fields,
delay reverse flow occurrence and enhances total Heat Transfer but decrease buoyancy effects. 相似文献
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核动力装置的非能动安全系统采用了大量的各类换热器。在自然循环条件下,换热器内的流动较弱,换热系数较低,处于层流状态。为了强化换热器的换热效果,提出了一种新型扭带——同轴交叉三扭带(CCTTT),并对换热管内插入不同扭率(2、3、4、∞)的CCTTT以强化水的换热效果进行了数值模拟研究。结果表明,在雷诺数Re=40~1200的范围内,CCTTT能有效强化换热器内流体的单相对流换热。随着扭率的减小,CCTTT的强化换热效果增强,评价准则数(PEC)增大。扭率为4.0的CCTTT的PEC是2.02,而扭率为2.0的CCTTT的PEC可达2.64。通过与其他工作介质比较发现,相同Re时,随着流动工质普朗特数的增大,CCTTT的PEC均增大。 相似文献
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The Prototype Fast Breeder Reactor (PFBR) is a 500 MWe sodium cooled pool type fast reactor being constructed at Kalpakkam, India. PFBR has all the reactor components immersed in the pool of sodium and the fission heat generated in the core, is removed by the sodium circulating in the pool. During normal operation this fission heat is transferred by primary sodium to secondary sodium, which in turn transfers the heat to water in the steam generator for producing steam. The removal of the decay heat generated in the reactor core after the reactor shutdown is also very important to maintain the structural integrity of reactor core components. PFBR employs two independent systems namely, Operational Grade Decay Heat Removal system (OGDHRS) and Safety Grade Decay Heat Removal System (SGDHRS) for decay heat removal. SGDHR system is a passive system working on natural convection to ensure the core coolability even under station blackout condition. It is very important to study the thermal hydraulic behavior of Safety Grade Decay Heat Removal system of PFBR to ensure its reliable operation. A scaled down model of the circuit, named SADHANA has been modeled, designed, constructed and commissioned for demonstration and evaluation of these systems. The facility has completed around 2000 h of high temperature operation. The performance of the experimental system is satisfactory and it meets all the design requirements. At 550 °C sodium pool temperature in test vessel the secondary sodium loop generated a sodium flow of 6.7 m3/h. These experiments have revealed the adequacy and capability of SGDHR system to remove the decay heat from the fast breeder reactor core after its shutdown. 相似文献
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利用三维流场计算程序PHOENICS 3 2研究了水平布置干式乏燃料贮存罐内的自然对流传热特性 ,将计算结果与文献的实验数据及计算结果进行了对比分析 ,符合较好。采用同样的布置方式及 2 0 0MW低温供热堆燃料组件的结构及余热功率参数 ,分别采用氮气及水作为工质进行了计算 ,以研究乏燃料贮存罐应用于低温供热堆的可能性。从计算结果中还发现水作为工质的换热效率比氮气高 相似文献
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大功率先进压水堆IVR有效性评价中熔池换热研究 总被引:2,自引:2,他引:0
熔融物堆内滞留-压力容器外部冷却(IVR-ERVC)是一种重要的核电厂严重事故缓解措施。当前针对IVR有效性评价的方法主要是基于集总参数模型对下封头熔池换热进行分析。在大功率先进压水堆熔池集总参数法计算中,堆芯重量变大、压力容器尺寸增加会导致熔池自然对流换热中的瑞利数Ra ′增大。通过使用集总参数分析程序,对比研究熔池氧化层各换热模型的适用范围,计算大功率先进压水堆高瑞利数条件下稳态熔池的自然对流换热,模拟两层稳态熔池模型中压力容器外壁面的热流密度分布,对其进行选定严重事故序列下的IVR-ERVC有效性评价,并对堆内构件设计提出建议。 相似文献
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建立了含内热源的多孔介质模型.该模型以水作为流动介质,流道内填满金属颗粒球,金属颗粒球呈正三角形排列.作为内热源的金属球内镶嵌电阻丝.在此模型的基础上,通过实验研究了流速、金属球壁面温度对含内热源多孔介质局部换热特性的影响规律.研究结果表明:压力对换热特性几乎没有影响;低热流密度下,表面热流密度对换热特性没有显著的影响;高热流密度时,换热系数随热流密度的增大而增加;冷却剂进口温度与换热系数成反比;球层区有入口效应存在,但是影响区域明显小于管内流体的流动区域;获得了幂指数形式的无量纲换热准则关联式,预测值与实验值误差在±10%以内. 相似文献
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对倾斜条件下圆管内强迫流动的传热特性进行实验研究及数值分析。实验结果表明,对于单相流动,在浮力的作用下圆管内的传热呈现非对称状态;圆管上侧传热减弱,壁温升高,而圆管下侧传热增强,壁温降低。数值模拟的结果也是如此。以此为基础,提出引入倾斜条件下传热的修正因子,可以较好地预测倾斜条件下单相对流传热的变化幅度。对两相流动中的汽泡进行受力分析,揭示倾斜条件对两相传热影响不大的原因。 相似文献
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为了深入认识超临界压力下不同流体传热中的共性反映出的传热机理及物性导致的特性差异,以水和氟利昂R134a为工质分别在SWAMUP回路和SMOTH回路上开展了竖直圆管内上升流传热试验。在正常传热、传热强化、小质量流速时浮升力导致传热恶化和大质量流速时加速效应导致传热恶化的工况中,氟利昂和水的换热系数(HTC)随无量纲温度表现出一致的变化规律。浮升力无量纲数πB增大,换热系数与经典关系式计算值之比减小;加速效应无量纲数πA较小时,换热系数比随πA的增大而增大,达到峰值后换热系数比随πA的增大而减小。πB对超临界水试验数据的相关性更佳,而πA对超临界氟利昂试验数据的相关性更好。无量纲数表征的超临界压力下传热规律的高度相似性初步验证了以模化流体氟利昂R134a研究超临界水传热特性是合理可行的。 相似文献
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为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现:从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。 相似文献