共查询到19条相似文献,搜索用时 62 毫秒
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《原子能科学技术》2015,(Z1)
在核电站安全壳和稳压器中存在膜状凝结现象。液膜的雷诺数关系式是膜状凝结传热计算的基础,有分别基于质量和能量的两种关系式形式,前人工作中未具体研究这两种关系式的差别。针对管外纯蒸汽自然对流膜状冷凝传热,本文通过求解液膜传热关系式和不同雷诺数关系式组成的联立方程,分别得到在光滑的和有波动的液膜层流区基于质量和能量关系的雷诺数表达式。分析表明:在光滑液膜层流区域,基于质量和能量关系得到的雷诺数具有等价性,计算得到的传热系数相等;在有波动液膜层流区域,基于质量关系得到的雷诺数Re_(mass)较能量关系得到的雷诺数Re_(energy)偏小,且计算得到的平均传热系数最大偏差可达30.3%。通过与实验数据比较,验证了基于Re_(energy)计算得到的平均传热系数在层流波动区域更加准确。 相似文献
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定位格架对再淹没传热的影响 总被引:1,自引:1,他引:0
采用21根束棒元件研究定位格架对再淹没传热的影响。测量了元件壁温、塌陷液位、液体夹带的瞬态变化过程,研究了流道外壳温度对再湿速度的影响。试验表明,再淹没过程中,定位格架下游的元件表面温度明显下降,骤冷前,定位格架下游的传热系数比上游高,特定工况下,可高出70%,定位格架对传热的影响程度随试验参数及距骤冷前沿位置的不同而不同;影响范围约为100至150mm。试验的参数范围为:入口欠热度为15~80℃;初始壁温400~610℃;入口淹没率15~60mm/s;加热功率0~0.25kW/m;系统压力为常压。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(12):545-553
An investigation was carried out with the object of determining the physical effects of separation and the associated reattachment and redevelopment, upon the heat transfer characteristics of turbulent flow in pipes and to compare the results of these flow conditions with the fully developed one-dimensional condition and with a recently developed numerical technique for the solution of recirculating flows. Separation of the flow was induced in a 4 ft length of 2 in. internal diameter nicrome tube of wall thickness 0.001 in. by means of a sudden enlargement of diameter at the entry of the tube. The tube was electrically heated by the passage of a current along its length. The first 25 in. of the tube was metered by thermocouples which gave the wall temperatures and from these the local heat transfer rates and Reynolds numbers up to 5×104 using air as the working fluid. 相似文献
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缩小比例的单项和整体性试验台架对研究和开发大型先进压水堆核电站及其分析验证程序都具有重要意义,而由缩比引入的相关现象的失真又直接影响了对台架的设计和试验结果的理解。本文以等效换热系数的形式对非能动安全壳冷却系统(PCS)壳内液膜冷凝在试验台架上的缩比失真进行分析,结合H2TS比例分析方法,系统评价了这种失真对模拟台架中壳内压力响应的作用。结果表明,台架缩比对壳内冷凝液膜换热的影响是保守的。 相似文献
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《Journal of Nuclear Science and Technology》2013,50(6):535-546
An experiment was performed in a wide range of core flooding rate to study the effect of liquid flow rate on the film boiling heat transfer during reflood using a 6 × 6 heater rod bundle with a full-height heated length. The flooding rate was in the range of 2–30cm/s. The obtained data were evaluated through assessment and improvement of Murao-Sugimoto heat transfer coefficient correlation, which predicted well the heat transfer coefficient under the core flooding rate up to 10 cm/s, but underestimated the heat transfer coefficient in the range of the flooding rate higher than 10 cm/s. An empirical correction factor for the Murao-Sugimoto correlation was proposed based on the present experimental data. The proposed correction factor was confirmed to be applicable to another large scale tests. 相似文献
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以水蒸气为工质,实验研究了水平管内纯蒸汽冷凝的局部换热特性。实验选取换热管内径为25 mm、换热管进口压力为0.15~0.4 MPa、局部蒸汽的Re=5756~92289,分析了蒸汽压力及流速、壁面过冷度对冷凝传热系数的影响,并将采用现有关系式计算的冷凝传热系数与实验结果进行了对比。结果表明:冷凝传热系数随壁面过冷度的增大而减小,随压力的升高和流速的增大而增大;采用现有关系式计算的冷凝传热系数与实验值的偏差较大,关系式有待进一步改进;在实验范围内,由拟合换热关系式计算所得冷凝传热系数与实验结果的相对偏差在15%左右。 相似文献
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为计算液态铅铋(LBE)在环管内不同加热环境下的湍流换热,基于开源计算流体力学程序OpenFOAM开发了四方程模型求解器4eqnFoam。将LBE在平板和圆管内的预测结果与直接数值模拟结果和实验结果进行对比,验证了求解器的有效性。基于该求解器,分别计算了LBE在外壁绝热内壁加热以及内外壁面等热流加热环管内不同雷诺数下的湍流换热量。结果表明:随着雷诺数的增加,两种加热条件下的无量纲温度脉动、雷诺热流、湍流热扩散作用增大,而平均湍流普朗特数减小;当雷诺数增加到一定程度时,平均湍流普朗特数变化不明显。基于4eqnFoam求解器,可为计算LBE热工水力现象提供更多参考。 相似文献