共查询到15条相似文献,搜索用时 171 毫秒
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在可视化观察的基础上,实验研究了矩形通道高宽比对两相流动阻力和流型关系的影响。实验选择了3种通道尺寸的实验段,截面宽度相同,全部为43 mm,高度分别为1.41、3和10 mm,根据受限因子Co,前两个实验段属于窄通道,第3个属于常规通道。实验结果表明:高宽比不同时,随着气相流速的增加,通道内两相流动压降呈不同的变化趋势。对于10 mm通道,低气相流量时重位压降占主要成分,而对于1.41 mm和3 mm通道,摩擦压降占主要成分;随着气相流量的增大,总压降中摩擦压降的比例也增大;对于10 mm矩形通道,可利用压降变化规律确定搅混流的发生范围。 相似文献
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在中低压条件下,对矩形窄缝通道两相流动传热进行试验研究,分析两相流动传热的变化规律,拟合出饱和沸腾传热系数计算关系式,并采用简化的一维分析方法对两相压降进行分析计算。试验结果表明:在相同热平衡含汽率(x)情况下,两相流动压降随系统压力(p)的降低而增大,随系统流量的增大而增大的变化规律;p越低,两相流动压降随x的增加而增大越剧烈;流量越大,两相流动压降随x的增加而增大越剧烈。通过数据回归方法得到汽相湿周长比例因子F并拟合了计算关系式,其计算值与试验值符合得较好。矩形窄缝通道内饱和沸腾平均传热系数受p、质量流量及热流密度的影响较大。 相似文献
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常压下,以空气和水为工质,对宽高比不同的两个矩形通道内两相流动摩擦阻力特性进行了研究,并对常规通道和微小通道内两相压降的计算模型进行了验证和评价。结果表明:传统的常规通道经验关系式并不适用于窄矩形通道中的压降计算;基于微小通道的计算方法中,Lee-Lee模型与实验值符合程度较好,但在一定的参数范围内仍存在较大误差。提出基于Chen模型的Chisholm C系数方法的修正关系式,式中综合考虑了矩形通道宽高比、全液相雷诺数和L-M参数对Chisholm C系数的影响,修正关系式与实验值符合较好。 相似文献
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基于换热器小型化的研究背景,对水在矩形窄通道内流动沸腾阻力特性进行了实验研究与分析,并利用实验结果对常规通道和窄通道的两相摩擦压降计算的6种方法进行了评价。结果表明,应用于常规通道的关系式已不适于窄通道中流动沸腾压降的计算,而基于窄通道的Zhang-Mishima及Sun-Mishima关系式预测结果与实验值符合较好。实验结果和理论分析表明,利用分相流方法得到的分液相摩擦因子计算式中Chisholm系数C与Martinelli参数X存在指数关系,且随着质量流速的变化也有所不同,据此给出了新的分液相摩擦因子的计算方法,新方法具有更高的计算精度。 相似文献
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Tewfik Hamidouche Nouara Rassoul El-Khider Si-Ahmed Hakim El Hadjen Anis Bousbia-salah 《Progress in Nuclear Energy》2009,51(3):485-495
Establishment of safety margins and the corresponding operating condition limits will ensure achievement of a safe operation of nuclear installations. For this purpose, several critical phenomena have been analyzed theoretically and experimentally and a great number of models and correlations are made available. Among these critical issues the well-known flow instability has been intensively investigated by several authors especially for nuclear power plants' (NPPs) operating conditions. However, limited published work is available for research reactor operation conditions. In general, the Whittle and Forgan correlation is widely used to define the margin to static flow instabilities in narrow parallel heated channels for research reactors.In the framework of verification and assessment of the capabilities of the RELAP5/Mod 3 system code to determine the onset of flow instability in research reactor conditions, a simple model based on steady-state equations adjusted with drift-flux correlations has been developed. The program is used to draw the pressure drop characteristic curves and to establish the conditions of the Ledinegg instability in a uniformly heated channel subject to constant outlet pressure. The model is assessed by using experimental data from a thermal hydraulic test loop by Siman-Tov and numerical results from RELAP5/Mod 3. The model presents acceptable estimation of the target mass flow that would induce flow instability and the latter could be then used to establish a conservative margin to the Ledinegg instability. 相似文献
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An analytical model for predicting the onset of Ledinegg instability in vertical channel under both downflow and upflow conditions has been developed and evaluated. The model divides the flow field into two regions based upon the fluid temperature. The pressure drop is then found by solving an appropriate set of equations for each region. The theoretical results are compared to an existing set of experimental data covering a range of channel diameters and operating conditions. A very good agreement is obtained with the available experimental data from the literature for water systems. A parameter, the ratio between the surface heat flux and the heat flux required to achieve saturation at the channel exit for a given flow rate, is found to be a very accurate indicator of the minimum point velocity in the demand curve. 相似文献
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矩形通道几何尺寸偏差对热工水力特性的影响 总被引:3,自引:1,他引:2
与圆管和棒束几何通道相比,板型元件窄边的几何尺寸偏差对流道流通截面积影响较大。本文以某一尺寸为例,定量评估了矩形通道窄尺寸偏差对热工水力特性(流动压降和CHF)的影响。通道尺寸对压降的影响主要表现在当造成热通道含汽后,即使含汽量只有1%,从单相压降向两相压降变化造成的流量偏离仍可达11%。在单相区,窄边偏差0.1mm对流量的影响一般不超过4.0%。对CHF的影响则与所使用的公式有关,对于本文所选C 相似文献
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