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Ren W.Y.,Xian University of Science and Technology | Yu G.J.,Xian University of Science and Technology | Bian J.W.,Xian University of Science and Technology | Tian W.X.,Xian University of Science and Technology | And 4 more authors.
International Topical Meeting on Nuclear Reactor Thermal Hydraulics 2015, NURETH 2015 | Year: 2015

Condensation of two-phase flow inside a tube within sub-cooled coolant injected show a complicated phenomenon which affects both the pressure drops from the upstream to downstream and the void fraction distribution in tube. This phenomenon always appears in the T-junction which kind of structure could be found in nuclear power plants design. The investigation about injection to two-phase flow in this structure can help us predict the hydrodynamic phenomenon of condensation heat transfer. Distribution of the fluid temperature and heat transfer coefficient (HTC) due to fluid-fluid mixing and steam condensation had been considered to be a significant process which is included in the pressurized thermal shock (PTS) research. Previous researches had built the integral effect test to analysis the effect of thermal mixing. However, the practical condensate process in T-junction injected is too hard to be predict accurately, which is contributed to the structure, the geometric dimension, the mass flow rate between the main and branch pipe, the flow patterns, the void fraction of two-phase flow, temperature of flow, pressure, etc. We analyzed the process of cooling water injecting from the branch pipe into a horizontal main pipe, and also focus on the phenomena of water injection in steam or different flow patterns. We had set some thermo couples inserting to the tube to keep observing the temperature field inside. The initial conditions of the experiment about the flow pattern before the injection includes stratified flow, wavy flow, annular flow and dispersed flow. We also took the heat dissipation between the test facility and surround into consideration. The experiment is a separate effect test program which based on the phenomena about condensation in T-junction with 45° incidence injection and progressed on ordinary pressure. Source

Meng Z.,Xian University of Science and Technology | Liu L.,State Nuclear Power Software Development Center | Liu L.,National Key Laboratory of Nuclear Power Software | Ding L.,Xian University of Science and Technology | And 6 more authors.
Experimental Thermal and Fluid Science | Year: 2015

For the previous experiments of entrainment at T-junction, the air-cold water two-phase flow is always selected as working medium, and the theoretical models of liquid entrainment are established mainly based on the experimental data of air-water entrainment through a small break. The saturated steam-water entrainment experiments are gravely insufficient, especially the steam-water experiments of entrainment through a large size branch are even fewer. Hence, a scale-down experiment of steam-water entrainment at T-junction has been conducted referring to liquid entrainment through ADS-4 (Fourth Stage Automatic Depressurization System) in AP1000 nuclear plant. The steam-water experimental results are comprehensively compared with the results of the previous similar air-water experiment: The visualization research shows that the same entrainment phenomena can be observed including intermittent flow entrainment, stratified flow entrainment and annular flow entrainment; The transition conditions between the two entrainment phenomena have a little difference but can be negligible; The comparison of experimental data of entrainment onset and stable entrainment indicates that the experimental data of steam-water and air-water have the same change tendency, and the air-water correlation can agree well with the steam-water data. Hence, we can make a conclusion that effect of different working mediums on liquid entrainment is negligible. In addition, based on the analysis of model formation, we suppose that effect of the system pressure on entrainment can be neglected under 0.22 MPa. © 2015 Elsevier Inc. Source

Meng Z.,Xian University of Science and Technology | Fu X.,State Nuclear Power Software Development Center | Fu X.,National Key Laboratory of Nuclear Power Software | Ding L.,Xian University of Science and Technology | And 6 more authors.
Experimental Thermal and Fluid Science | Year: 2014

An experimental and theoretical research has been performed for liquid entrainment at T-junction consisting of hot leg and ADS-4 pipe in view of the insufficiency of existing studies. Based on visualization research, three kinds of entrainment phenomena including intermittent entrainment, stratified entrainment and annular entrainment are clearly observed, and the feature of each flow regime is summarized and recorded by high-speed camera. Also, the flow pattern map is plotted from the experimental data to indicate the transition conditions of different flow regimes. For the purpose of modeling and expanding previous research, the influence of entrance length on entrainment is discussed on the basis of two different test sections. The effect of liquid flow on onset entrainment and stable entrainment is analyzed, and experiment results show that the effect of liquid flow on entrainment through ADS-4 pipe can be neglected. Also, onset entrainment model and branch quality model are established and accord with experimental data well. © 2014. Source

Meng Z.,Xian University of Science and Technology | Dong B.,State Nuclear Power Software Development Center | Dong B.,National Key Laboratory of Nuclear Power Software | Wang L.,Xian University of Science and Technology | And 6 more authors.
Annals of Nuclear Energy | Year: 2014

In this study, based on a T-junction that consists of Automatic Depressurization System Stage Four (ADS-4) and hot leg in an AP1000 plant, a small-scale experimental research on entrainment at a T-junction was performed. This study mainly focused on the effect of various factors on entrainment, such as the effect of branch size, branch shape and liquid crossflow. The flow pattern map was plotted from the experimental data, and the visualization research indicated that the entrainment phenomena through a large size branch were apparently different from that through a small branch. Three entrainment phenomena were observed in the studies, two entrainment mechanisms could be found in the stratified flow regime entrainment area, the existence of branch contributed to generating intermittent flow in the horizontal main pipe, and the backflow region was observable in the vicinity of a large size branch inlet. Also, experimental research showed that downstream of the branch of T-junction had an important effect on the onset entrainment, and liquid crossflow did not seem to affect the onset entrainment. © 2014 Elsevier Ltd. All rights reserved. Source

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