The Experts below are selected from a list of 12147 Experts worldwide ranked by ideXlab platform
B.h. Yan - One of the best experts on this subject based on the ideXlab platform.
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The experimental and theoretical analysis of a natural circulation system in Rolling Motion
Progress in Nuclear Energy, 2012Co-Authors: B.h. YanAbstract:Abstract The natural circulation in Rolling Motion is investigated experimentally. The RELAP5/MOD3.3 code is modified by adding a module calculating the effect of Rolling Motion and introducing new flow and heat transfer models. The thermal hydraulic code in Rolling Motion is developed to simulate the natural circulation in Rolling Motion. The experimental data are used to validate the theoretical models and calculation results. It is shown that the new flow and heat transfer models could correctly predict the frictional resistance and heat transfer coefficients in Rolling Motion. The thermal hydraulic code is used to simulate a natural circulation system in Rolling Motion. The calculation results are in agreement with experimental data. The relative discrepancies between calculation results and experimental data are less than 5%.
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CFD analysis of the effect of Rolling Motion on the flow distribution at the core inlet
Annals of Nuclear Energy, 2012Co-Authors: B.h. Yan, Ge ZhangAbstract:Abstract The flow distribution at the core inlet in Rolling Motion is investigated with software CFX12.0. The calculation results were in agreement with experimental data in steady state. As the increasing of Rolling amplitude and the decreasing of Rolling period, the effect of Rolling Motion on the flow distribution factor and the flowing behavior increases. In Rolling Motion, the variation of flow distribution factor is not regular. The Rolling Motion could decrease the minimum flow distribution factor. The effect of Rolling Motion on the coolant field and flow distribution diminishes with the Reynolds number increasing. The effect of Rolling Motion on the flow distribution in the case of single loop operation is more significant than that in the case of double loops operation.
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Theoretical analysis of the fluid mixing at the core inlet in Rolling Motion
Nuclear Engineering and Design, 2012Co-Authors: B.h. Yan, Ge ZhangAbstract:Abstract The fluid mixing at the reactor core in Rolling Motion and steady state is investigated numerically with CFX12.0. The CFD results are validated with experimental data in steady state. In Rolling Motion, the fluid mixing factor at the center of the core oscillates in a cosine function, but the variation of the fluid mixing factor surrounding the core is not regular. The variation amplitude of the fluid mixing factor next to the boundary line of fluid mixing is the most significant. The variation of fluid mixing factor increases with the increasing of additional force. The increasing of Reynolds number could depress the effect of Rolling Motion on the fluid mixing.
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Theoretical model of laminar flow in tubes in Rolling Motion
Applied Mathematical Modelling, 2012Co-Authors: B.h. YanAbstract:Abstract The theoretical model of laminar flow in tubes in Rolling Motion is established. The velocity and temperature correlations are derived, and the frictional resistance coefficient and Nusselt number are also obtained. The oscillation of parameters is induced by the tangential force due to Rolling Motion. The effect of centrifugal and Coriolis forces on the flow is negligible. The tangential force does not effect on the average parameters. The oscillating amplitude of Nusselt number increase with the Prandtl number increasing. Both the oscillating amplitudes of frictional resistance coefficient and Nusselt number increase with the Rolling frequency increasing.
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The modeling and validation of the flow and heat transfer models of pulsating flow in channels in Rolling Motion
Progress in Nuclear Energy, 2012Co-Authors: B.h. YanAbstract:Abstract The flow and heat transfer models of laminar flow and turbulent flow in Rolling Motion are established theoretically and modified with CFD results and experimental data. The correlations of frictional resistance coefficient and Nusselt number in pipes in Rolling Motion are obtained. The effect of Rolling Motion on the flow and heat transfer is mainly affected by the Reynolds number, angular acceleration and channel diameter. As the channel diameter is small, the effect of Rolling Motion on the flow and heat transfer is weak. The modified correlations of frictional resistance coefficient and Nusselt number in Rolling Motion could predict the flow and heat transfer in pipes in Rolling Motion correctly. The average discrepancy between theoretical correlations and experimental data is about 15%.
Yu Lei - One of the best experts on this subject based on the ideXlab platform.
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Development and Validation of Thermal Hydraulic Code in Rolling Motion
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2012Co-Authors: Yu LeiAbstract:The RELAP5/MOD3.3 code was modified by adding a module calculating the effect of Rolling Motion and introducing new flow and heat transfer models.The thermal hydraulic code in Rolling Motion was developed.The experimental data were used to validate the theoretical models and calculation results.It is shown that the new flow and heat transfer models can correctly calculate the frictional resistance and heat transfer coefficients in Rolling Motion.The developed thermal hydraulic code can be used to simulate the thermal hydraulic system in Rolling Motion.
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Effect of Rolling Motion on Flow in Tight Lattice
Nuclear Power Engineering, 2011Co-Authors: Yu LeiAbstract:The flow oscillation and large scale coherent structure in tight lattice in Rolling Motion is in-vestigated theoretically with URANS.The calculation results are consistent with the experimental data.The Rolling Motion may have effect on the flow oscillation and coherent structure.The oscillation period in Rolling Motion is about ten percent bigger than that in steady state.The coherent velocity in Rolling Motion is a little different from that in steady state.The minimum coherent streamwise velocity is at the channel center,while the maximum coherent streamwise velocity is at the transition region of the channel center and narrow gap.However,the effect of Rolling Motion on the flow and heat transfer characteristics in tight lattice is limited.
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Models of Frictional Resistance for Circular Tubes in Rolling Motion
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2011Co-Authors: Yu LeiAbstract:The forces affected on the laminar and turbulent flows in Rolling Motion were analyzed.The flowing models of laminar and turbulent flows were established on the basis of Navier-Stokes equation.The correlations of velocity and frictional resistance coefficient of laminar and turbulent flows in Rolling Motion were derived.The influence mechanism of Rolling Motion on the flowing characteristics of these flows was also investigated.The theoretical models were validated with experimental results.The theoretical results are consistent with experimental results.
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LES Research on Flowing Characteristics of Turbulent Flow in Rectangular Tubes in Rolling Motion
Nuclear Power Engineering, 2011Co-Authors: Yu LeiAbstract:The turbulent flow in rectangular tubes in Rolling Motion is investigated theoretically with FLUENT code and large eddy simulation.The effects of Rolling Motion and tube size on the flowing characteristics of turbulent flow are analyzed.The results show that if the rectangular tube is narrow,the effect of Rolling Motion on the turbulent flow can be depressed by the tube wall.If the Rolling amplitude is small,the effect of Rolling Motion on the turbulent flow is very limited.With the decrease of length-width ratio of the tube,the turbulent frictional resistance coefficient decreases.The frictional resistance coefficient is in a wave or slope shape.If the Rolling amplitude is big,the counter flow occurs first at the π/2 phase.With the decrease of Rolling period,the frictional resistance coefficient on the wall decreases first,and increases later.
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Flowing and Heat Transfer Characteristics of Turbulent Flow in Typical Rod Bundles at Rolling Motion
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2011Co-Authors: Yu LeiAbstract:The influence mechanism of Rolling Motion on the flowing and heat transfer characteristics of turbulent flow in typical four rod bundles was investigated with Fluent code.The flowing and heat transfer characteristics of turbulent flow in rod bundles can be affected by Rolling Motion.But the flowing similarity of turbulent flow in adiabatic and non-adiabatic can not be affected.If the Rolling period is small,the radial additional force can make the parameter profiles,the turbulent flowing and heat transfer change greatly.At Rolling Motion,as the pitch to diameter ratio decreases,especially if it is less than 1.1,the flowing and heat transfer of turbulent flow at Rolling Motion change significantly.The variation of pitch to diameter ratio can change the profiles of secondary flow and turbulent kinetic energy in cross-section greatly.
G H Su - One of the best experts on this subject based on the ideXlab platform.
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experimental and theoretical study on single phase natural circulation flow and heat transfer under Rolling Motion condition
Applied Thermal Engineering, 2009Co-Authors: G H SuAbstract:Experimental and theoretical studies of single-phase natural circulation flow and heat transfer under a Rolling Motion condition are performed. Experiments with and without Rolling Motions are conducted so the effects of Rolling Motion on natural circulation flow and heat transfer are obtained. The experimental results show the additional inertia caused by Rolling Motion easily causes the natural circulation flow to fluctuate. The average mass flow rate of natural circulation decreases with increases in Rolling amplitude and frequency. Rolling Motion enhances the heat transfer, and the heat transfer coefficient of natural circulation flow increases with the Rolling amplitude and frequency. An empirical equation for the heat transfer coefficient under Rolling Motion is achieved, and a mathematical model is also developed to calculate the natural circulation flow under a Rolling Motion condition. The calculated results agree well with experimental data. Effects of the Rolling Motion on natural circulation flow are analyzed using the model. The increase in the flow resistance coefficient is the main reason why the natural circulation capacity decreases under a Rolling Motion condition.
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heat transfer model of single phase natural circulation flow under a Rolling Motion condition
Nuclear Engineering and Design, 2009Co-Authors: G H Su, Tan Sichao, Gao PuzhenAbstract:Experimental studies on heat transfer characteristics for single-phase natural circulation flow under a Rolling Motion condition are performed. Experiments with and without Rolling Motions are conducted so that the effects of Rolling Motion on natural circulation heat transfer are obtained. The experimental results show Rolling Motion enhances the heat transfer. The heat transfer coefficient of natural circulation flow increases with the Rolling amplitude and frequency. A modified Reynolds number that considers the influence of the acceleration is employed to express the effect of heat capacity. Using experimental data, an empirical equation for the heat transfer coefficient under a Rolling Motion condition is obtained. The calculated results agree with the experimental data.
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experimental study on two phase flow instability of natural circulation under Rolling Motion condition
Annals of Nuclear Energy, 2009Co-Authors: G H SuAbstract:Two-phase flow instability of natural circulation under a Rolling Motion condition is experimentally studied. The experimental results show the Rolling Motion induces a fluid flow fluctuation. At the trough point of the flow fluctuation, Rolling Motion can cause the early occurrence of natural circulation two-phase flow instability, and this case is defined as trough-type flow oscillation. The system stability decreases with increasing Rolling amplitude and effect of Rolling frequency is nonlinear. The complex overlap effect of trough-type flow oscillation and density wave oscillation can enhance the system coolant fluctuation; this case is defined as complex flow oscillation. Complex flow oscillation may be divided into two types: regular and irregular complex flow oscillations. Irregular complex flow oscillation is a transition type from trough-type flow oscillation to regular complex flow oscillation. Under the same thermal hydraulic conditions, the marginal stability boundary (MSB) of regular complex flow oscillation is similar to that of density wave oscillation without Rolling Motion, and the influences of Rolling parameters on the MSB are slight.
Yan-hua Yang - One of the best experts on this subject based on the ideXlab platform.
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Theoretical models of turbulent flow in Rolling Motion
Progress in Nuclear Energy, 2010Co-Authors: B.h. Yan, Yan-hua YangAbstract:Abstract The flowing and heat transfer characteristics of turbulent flow in tubes and rectangular channels in Rolling Motion are investigated theoretically. The flowing and heat transfer models of turbulent flow in Rolling Motion are established. The correlations of frictional resistance coefficient and Nusselt number are derived. The results are also validated with experiments. The effects of several parameters on frictional resistance coefficient and Nusselt number are investigated. The oscillating amplitude of Nusselt number is in direct ratio with Prandtl number and Rolling frequency approximately. The more the flowing velocity is, the less the effect of Rolling Motion on the flow is. The variation of initial phase difference between Nusselt number and Rolling Motion with Rolling frequency is very limited.
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The Flowing and Heat Transfer Models of Turbulent Flow in Rolling Motion
18th International Conference on Nuclear Engineering: Volume 4 Parts A and B, 2010Co-Authors: B.h. Yan, Yan-hua Yang, Yanping HuangAbstract:The flowing and heat transfer characteristics of turbulent flow in tubes in Rolling Motion are investigated theoretically. The flowing and heat transfer models of turbulent flow in Rolling Motion are established. The correlations of frictional resistance coefficient and Nusselt number are derived. The results are also validated with experiments. The effects of several parameters on Nusselt number are investigated. The oscillating amplitude of Nusselt number is in direct ratio with Prandtl number and Rolling frequency approximately. The more the flowing velocity is, the less the effect of Rolling Motion on the flow is. The variation of initial phase difference between Nusselt number and Rolling Motion with Rolling frequency is very limited.Copyright © 2010 by ASME
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CFD Analysis of Turbulent Flow in Typical Rod Bundles in Rolling Motion
Applied Mechanics and Materials, 2010Co-Authors: Bing Yan, Yan-hua YangAbstract:The influence mechanism of Rolling Motion on the flowing and heat transfer characteristics of turbulent flow in typical four rod bundles is investigated with FLUENT code. The flowing and heat transfer characteristics of turbulent flow in rod bundles can be affected by Rolling Motion. But the flowing similarity of turbulent flow in adiabatic and non-adiabatic can not be affected. If the Rolling amplitude is big or if the Rolling period is small, the radial additional force can make the parameter profiles and the turbulent flowing and heat transfer change greatly. And the frictional resistance coefficient and heat transfer coefficient can not be solved by the correlations in steady state. In Rolling Motion, as the pitch to diameter ratio decrease, especially if it is less than 1.1, the flowing and heat transfer of turbulent flow in Rolling Motion change significantly.
Puzhen Gao - One of the best experts on this subject based on the ideXlab platform.
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Boiling heat transfer characteristics of pulsating flow in rectangular channel under Rolling Motion
Experimental Thermal and Fluid Science, 2016Co-Authors: Chong Chen, Puzhen Gao, Si-chao TanAbstract:Abstract Boiling heat transfer technology is widely used in the barge-mounted nuclear power plant and received increasing attention recently, because that the boiling flow behaviors under ship Motion conditions are very complicated and important. In order to study the boiling heat transfer characteristics of pulsating flow in a rectangular channel under Rolling Motion, a series of experiments were performed. The results demonstrate that the boiling heat transfer coefficient fluctuations have the same period with the Rolling Motion. The fluctuation intensity of the coefficient increases with the increase of Rolling amplitude and period. The time average boiling heat transfer coefficient of pulsating flow under Rolling Motion condition is equal to that in the steady state. Based on this phenomenon a new correlation for predicting the time average boiling heat transfer coefficient of rectangular channel under Rolling Motion and steady state was proposed, with a MAE of 15.1%, as well as 95.4% and 81.3% of the data points within ±30% and ±20% error bands, respectively. Furthermore, the predicted correlations that used to calculate the relative pulsation amplitude and instantaneous boiling heat transfer coefficients of pulsating flow were developed based on the heat transfer characteristics of pulsating flow under Rolling Motion conditions.
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visualization study of bubble behavior in a subcooled flow boiling channel under Rolling Motion
Annals of Nuclear Energy, 2015Co-Authors: Si-chao Tan, Puzhen GaoAbstract:Abstract Boiling heat transfer equipment in a vessel can be affected by the additional force which is generated by the Rolling, swing and heaving Motion of the vessel. Bubble behavior is very important for the research of boiling phenomenon. Bubble behavior under Rolling Motion condition is experimentally studied by using a high speed camera. The experiment is conducted in a subcooled flow boiling rectangular channel, and the cross section size of the channel is 2 mm × 40 mm. Two types of bubbles with large discrepancies in sliding and condensation behaviors can be observed in the captured images. The first type bubbles disappear quickly after generation and the slide distance is only a few times of bubble maximum diameter, while the second type bubbles can survive a longer time after leaving the nucleation site and slide for a long distance with the flowing fluid. Bubble characteristics under Rolling Motion are separately studied for different type bubbles based on the above reasons. The results show that the lifetime, maximum diameter, nucleation frequency and sliding velocity of the first type bubble are periodically fluctuated and the period is same with the Rolling Motion. The fluctuation intensity of the bubble lifetime and maximum diameter can be enhanced by the increase of the Rolling amplitude. The peak value of bubble lifetime, maximum diameter, and nucleation frequency appears when the Rolling platform plate rolls to the maximum positive angle, while opposite trend can be observed in the variation of bubble sliding velocity. In view of the characteristics of the second type bubbles, lifetime and maximum diameter are not measured. And the variation of nucleation frequency and sliding velocity of the second type bubbles under the effect of Rolling Motion is same with the first type bubbles. Furthermore, the effects of additional force, variation of local pressure and flow rate oscillation on bubble behavior are analyzed. The results indicate that the fluctuations of the bubble parameters can be generated by the variation of local pressure caused by Rolling Motion even no influential flow rate fluctuation occurs. The effect of the acceleration variation vertical to the heated surface on bubble behavior is unclear and need more researches in the future work.
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Experimental study on single-phase heat transfer of natural circulation in circular pipe under Rolling Motion condition
Nuclear Engineering and Design, 2014Co-Authors: Chang Wang, Hao Wang, Puzhen GaoAbstract:Abstract Experimental investigation of the single-phase natural circulation heat transfer characteristic in static and Rolling Motion conditions are conducted. The results show that Rolling Motion leads to the reduction of cycle-averaged flow rate compares to that in the static state with the same thermal–hydraulic parameters. And the flow rate changes cyclically with the same period of the Rolling Motion. In addition, the results also indicate that the flow pulsation enhances the cycle-averaged heat transfer characteristic. Furthermore, the relative pulsation amplitude of the Nusselt number increased linearly with the relative pulsation amplitude of Reynolds number. Based on the relationship between the cycle-averaged flow rate before and after Rolling Motion start, and the relationship between Rolling Motion parameters, the relative pulsation amplitude of Nusselt number and cycle-averaged Reynolds number, the instantaneous Nusselt number under Rolling Motion condition can be predicted using the thermal–hydraulic parameter in static condition.
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Experimental research of bubble number density and bubble size in narrow rectangular channel under Rolling Motion
Nuclear Engineering and Design, 2014Co-Authors: Si-chao Tan, Puzhen GaoAbstract:Abstract Bubble number density and bubble size are two important parameters in the research of subcooled flow boiling and the channel power of water-cooled nuclear reactor are greatly affected by the two parameters through the neutron feedback caused by the variation of local void fraction. By using the high speed camera in combination with the digital image processing technology, the bubble number density and bubble mean diameter in an up-flow narrow rectangular channel under Rolling Motion are experimentally researched. Experimental results indicate that the bubble number density and the bubble mean diameter under Rolling Motion periodically fluctuated with the same period as that of the Rolling Motion. The camera captured bubbles consisted of sliding bubbles coming from the upstream flow and nucleation bubbles emerging in the scope of the observing window. Variations of the bubble mean diameters under Rolling Motion are analyzed by the distribution of the bubble diameters. Both the diameters of sliding bubbles and nucleation bubbles periodically changed under the effect of the Rolling Motion, and the two kinds of bubble share the same variation trend. The fluctuation amplitude of the bubble number density and the bubble mean diameter is determined by the Rolling period and amplitude. The fluctuation amplitudes of the above two parameters are intensified by the Rolling amplitude, whereas the effect of the Rolling period is weak. At the same time, local pressure, wall temperature and local fluid velocity oscillated periodically in the Rolling Motion. Effect of the fluid velocity oscillation can be neglected due to its tiny fluctuation amplitude in this research. Variation of the effective wall superheat induced by the change of wall temperature and local pressure is the main reason accounting for the fluctuation of bubble parameters under Rolling Motion.
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Non-linear time series analysis on flow instability of natural circulation under Rolling Motion condition
Annals of Nuclear Energy, 2014Co-Authors: Wenchao Zhang, Si-chao Tan, Puzhen Gao, Zhanwei Wang, Liansheng Zhang, Hong ZhangAbstract:Abstract Non-linear characteristics of natural circulation flow instabilities under Rolling Motion conditions were studied by the method of non-linear time series analysis. Experimental flow time series of different dimensionless power and Rolling parameters were analyzed based on phase space reconstruction theory. Attractors which were reconstructed in phase space and the geometric invariants, including correlation dimension, Kolmogorov entropy and largest Lyapunov exponent, were determined. Non-linear characteristics of natural circulation flow instabilities under Rolling Motion conditions was studied based on the results of the geometric invariant analysis. The results indicated that the values of the geometric invariants first increase and then decrease as dimensionless power increases which indicated the non-linear characteristics of the system first enhance and then weaken. The irregular complex flow oscillation is typical chaotic oscillation because the value of geometric invariants is at maximum. The threshold of chaotic oscillation becomes larger as the Rolling frequency or Rolling amplitude becomes big. The main influencing factors that influence the non-linear characteristics of the natural circulation system under Rolling Motion are thermal driving force, flow resistance and the additional forces caused by Rolling Motion. The non-linear characteristics of the natural circulation system under Rolling Motion changes caused by the change of the feedback and coupling degree among these influencing factors when the dimensionless power or Rolling parameters changes.
