共查询到19条相似文献,搜索用时 156 毫秒
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本文利用快速关闭阀门法和电导探针法分别测量了卧式螺旋管内空气-水两相流的总平均截面含气率和平均截面含气率沿周向的分布,并以分相流动模型为基础,导出了平均截面含气率周向分布的计算公式。理论预测和实验结果符合较好。 相似文献
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采用高速摄像机对水力直径为1.15 mm的正三角形小通道内气液两相流流型进行实时拍摄和图像采集,提出一种利用数字图像处理技术检测小通道内气液两相弹状流体积含气率的方法。针对小通道内两相流型中气泡间相互无遮掩的优势,利用图像处理技术对各流型图像进行消噪、边缘提取、二值化、区域标记和填充等处理,根据提出的三维气相体积计算模型得到体积含气率。最后与漂移流模型计算结果进行比较,比较和实验结果都表明:对于弹状流,该方法得到的含气率与真实值的误差在±15%以内,具有较高的测量精度;并对实验数据进行回归分析得到了截面含气率公式,可用于微小通道内气液两相流参数的在线检测,为今后微小通道内的两相流动特性研究提供参考。 相似文献
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应用电导探针测量列管式余热锅炉中管束的截面含气率。实验段采用垂直布置的管壳式换热器模型,其圆形外壳内的管束由49根管子组成,并沿长度方向用3块折流板将管束分成4个冲刷流程。当水-空气两相流从实验段底部的侧面进入并斜向上冲管束时,测出了局部截面含气率的分布规律,通过分析得到了平均截面含气率的计算式。 相似文献
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气液两相流体在垂直上升矩形截面管道内横向冲刷水平布置的柱体时,一定条件下会在柱体后面产生旋涡交替脱落现象.利用管壁压差法来研究气液两相流横掠圆柱体和方柱体时的旋涡脱落特性,得到了涡街的脱落频率和斯特罗哈数的变化情况.实验中雷诺数的范围为0.9×10~4~2.3×10~4,截面含气率的范围为0~0.2.实验结果表明:在一定的含气率范围内,两种柱体涡街的脱落频率与斯特罗哈数都随着截面含气率的增大而增大;方柱体斯特罗哈数增大的梯度与雷诺数无关,圆柱体斯特罗哈数增大的梯度受雷诺数的影响. 相似文献
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This article is the second part of a two-part paper, dealing with an experimental study of convective condensation of R134a at a saturation temperature of 40 °C in an 8.38 mm inner diameter smooth tube in inclined orientations. The first part concentrates on the flow pattern and the heat transfer coefficients. This second part presents the pressures drops in the test condenser for different mass fluxes and different vapour qualities for the whole range of inclination angles (downwards and upwards). Pressures drops in a horizontal orientation were compared with correlations available in literature. In a vertical orientation, the experimental results were compared with pressure drop correlations associated with void fraction correlations available in literature. A good agreement was found for vertical upward flows but no correlation predicted correctly the measurements for downward flows. An apparent gravitational pressure drop and an apparent void fraction were defined in order to study the inclination effect on the flow. For upward flows, it seems as if the void fraction and the frictional pressure drop are independent of the inclination angle. Apparent void fractions were successfully compared with correlations in literature. This was not the case for downward flows. The experimental results for stratified downward flows were also successfully compared with the model of Taitel and Dukler. 相似文献
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An experimental study has been carried out to clarify the characteristics of the void fraction and the liquid film thickness of the air‐water two‐phase flow in vertical tubes of 25‐mm inside diameter with wire coils of varying wire diameter and pitch. The flow pattern in the experiment on the average void fraction and the local void fraction distribution in cross section was a bubble flow, and the liquid film thickness was in the region of semiannular and annular flows. It is clarified from these experiments that the average void fraction in tubes with wire coils is lower than that in a smooth tube and decreases with the wire diameter owing to the centrifugal force of the swirl flow which concentrates bubbles at the center of the tube, that the local liquid film thickness becomes more uniform with a decrease in the pitch of the wire coil, and that the liquid film becomes thicker after the passage through the wire coil with an increase in the wire diameter. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(8): 652–664, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10067 相似文献
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Hiroshi Goda Seungjin Kim Jennifer Uhle 《International Journal of Heat and Mass Transfer》2003,46(25):4835-4844
In view of the practical importance of the drift-flux model for two-phase flow analysis in general and in the analysis of nuclear-reactor transients and accidents in particular, the distribution parameter and the drift velocity have been studied for downward two-phase flows. The constitutive equation that specifies the distribution parameter in the downward flow has been derived by taking into account the effect of the downward mixture volumetric flux on the phase distribution. It was assumed that the constitutive equation for the drift velocity developed by Ishii for a vertical upward churn-turbulent flow determined the drift velocity for the downward flow over all of flow regimes. To evaluate the drift-flux model with newly developed constitutive equations, area-averaged void fraction measurement has been extensively performed by employing an impedance void meter for an adiabatic vertical co-current downward air-water two-phase flow in 25.4-mm and 50.8-mm inner diameter round tubes. The newly developed drift-flux model has been validated by 462 data sets obtained in the present study and literatures under various experimental conditions. These data sets cover extensive experimental conditions such as flow system (air-water and steam-water), channel diameter (16-102.3 mm), pressure (0.1-1.5 MPa), and mixture volumetric flux (−0.45 to −24.6 m/s). An excellent agreement has been obtained between the newly developed drift-flux model and the data within an average relative deviation of ±15.4%. 相似文献
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AcousticWavePredictioninFlowingSteam-WaterTwo-PhaseMixtureXuJinliang;ChenTingkuan(StateKeyLaboratoryofMultiphaseFlowinPowerEn... 相似文献
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David Albagli 《International Journal of Heat and Mass Transfer》2003,46(11):1993-2003
The characteristics of high speed bubbly flows through convergent-divergent nozzles are studied theoretically. A steady, one-dimensional flow is considered. The liquid phase is water, whereas the gaseous phase consists of a mixture of both non-condensable (air) and condensable (water vapor) components. The comprehensive physical model allows for momentum and thermal lags as well as mass transfer between the gaseous and liquid phases due to evaporation and condensation. The parametric analysis reveals that choked flow with supersonic speeds along the diverging section of the nozzle, similar to the behavior of a compressible gas flow, may be obtained under appropriate conditions. Effects of flow parameters such as wall friction, interphase heat transfer, initial bubble size and void fraction are demonstrated. 相似文献
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An experiment of upward gas–liquid two‐phase flow was conducted in an air–water isothermal system under atmospheric pressure. The differential pressure was measured at the fully developed section by using a variable reluctance type transducer to classify the flow patterns and their transitions. The flow behavior was observed with a high‐speed video camera. The probability density function (PDF) of the differential pressure signal was employed to identify the flow pattern. A simplified one‐dimensional flow model was proposed to clarify dominant factors affecting the formation and transitions of flow patterns. The model dealt with the gas‐component advection based on the spatiotemporal void fraction behaviors by considering the gas compressibility, the wake, and the liquid phase redistribution mechanism. The simulation results of the model indicated four kinds of the void wave patterns (ripple‐like, rectangular, distorted rectangular, and uniform wave patterns) depending on gas and liquid volumetric fluxes. These void wave patterns corresponded well to the experimentally observed flow patterns. The transitions among void wave patterns agree well with the Mishima–Ishii flow pattern map. The friction loss estimated by the present model coincides fairly well with Chisholm's empirical formula. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(7): 445–461, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20029 相似文献
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A.S. Dalkilic S. Laohalertdecha S. Wongwises 《International Communications in Heat and Mass Transfer》2009
In the present study, the void fraction and film thickness of pure R-134a flowing downwards in a vertical condenser tube are indirectly determined using relevant measured data together with an annular flow model and various void fraction models reported in the open literature. The vertical test section is a countercurrent flow double tube heat exchanger with refrigerant flowing down in the inner tube and cooling water flowing upward in the annulus. The inner tube is made from smooth copper tubing of 9.52 mm outer diameter with a length of 0.5 m. The experimental runs are carried out at average saturated condensing temperatures of 40 and 50 °C, and mass velocities are around 456 kg m− 2 s− 1, over the vapour quality range 0.82–0.93, while the heat fluxes are between 45.60 and 50.90 kW m− 2. Analysis based on simple void fraction models of the annular flow pattern are presented for forced convection condensation of pure R134a, taking into account the effect of the different saturation temperatures at high mass flux conditions. The comparisons of calculated film thickness show that the void fraction models of Spedding and Chen, and Chisholm and Armand are the most accurate ones with the experimental data due to their low deviation with Whalley's annular flow model over 35 void fraction models presented in this paper. 相似文献
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A special experimental loop is designed and constructed to study the characteristics of the void fraction of gas–liquid two-phase flow in vertically-downward pipes. The test section is made of transparent pipe with a length of 6 m and an internal diameter of 25 mm. The void fraction ranging from 0.1 to 0.98 widely is measured using quick-closing valve method. It is found that the range of the void fraction could be divided into three regions with different flow patterns and different relationships between the void fraction and the gas–liquid volumetric flow rate ratio. Moreover, 39 correlations for calculating the void fraction collected from present literature, are classified, and evaluated using the experimental data obtained in this study. The prediction of correlations in the literature needs to be improved when the void fraction is small. 相似文献