The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Suizheng Qiu - One of the best experts on this subject based on the ideXlab platform.
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theoretical investigation of two phase Flow Instability between parallel channels of natural circulation in rolling motion
Nuclear Engineering and Design, 2019Co-Authors: Xiaoyan Wang, Ronghua Chen, Wenxi Tian, Siyang Huang, Dalin Zhang, Suizheng QiuAbstract:Abstract In present work, the two-phase Flow Instability between rectangular parallel channels of natural circulation under static and rolling conditions was coupled studied theoretically. Models including two-phase Flow Instability, natural circulation system components, and the additional force were established in combination based on the homogenous model. A computational program was written in FORTRAN language which was solved by Gear multi-value method by using control volume integrating method. The program was validated with experiments, and the results matched well with the experiment data. The marginal stability boundary (MSB) maps under different parameters were obtained by using nondimensional numbers Nsub and Npch. The influence of different kinds of pressure drop, inlet subcooling temperature of heating channels, system pressure, valve resistance, venturi Flowmeters resistance, structure height, rolling condition, and the interaction effect of natural circulation and two-phase Flow Instability between rectangular parallel channels were analyzed. The results show that with the increase in system pressure and venturi Flowmeters resistance, the system stability of natural circulation is enhanced. The influence of inlet subcooling temperature is nonlinear. The increase in valve resistance leads to the Instability of system. The increase in structure height does not change system stability significantly. The rise in rolling angle and period both reduce the system stability.
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Effect of Rolling Motion on Flow Instability of Parallel Rectangular Channels of Natural Circulation
Volume 5: Advanced Reactors and Fusion Technologies; Codes Standards Licensing and Regulatory Issues, 2018Co-Authors: Xiaoyan Wang, Wenxi Tian, Siyang Huang, Lie Chen, Suizheng QiuAbstract:In order to study the effect of rolling motion on Flow Instability of parallel rectangular channels of natural circulation, the natural circulation reactor simulation system is used for physical prototype. And theory analysis model of parallel rectangular channels of natural circulation system under rolling motion is established and coded by Fortran. The results of the program are verified to the experiments, and the results are in good agreement. The Flow Instability boundaries of different pressure under static and rolling motion are calculated respectively. The results show that: 1) under static condition, with the increase of the pressure, the Instability boundary line changes, and the system becomes more stable; 2) under rolling conditions, the heating power of Instability boundary decreases comparing to the stable conditions. The Instability occurs earlier; 3) the stability of the system decreases with the increasing of rolling amplitude and frequency.Copyright © 2018 by ASME
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Research on two-phase Flow Instability in parallel rectangular channels
Annals of Nuclear Energy, 2014Co-Authors: Libo Qian, Shuhua Ding, Suizheng QiuAbstract:Abstract In the present work, a theoretical model for Density Wave Oscillations Flow Instability in parallel rectangular channels is built with a lumped mathematical model based on homogenous hypothesis. The parallel channel comprises the entrance section, heating section and riser section and the model consists of the boiling channel model, pressure drop model, parallel channel model and constructive model, while subcooled boiling effect is neglected and the final nonlinear ordinary differential equations are solved by Gear method. The model is validated with experimental data of a single channel with constant pressure drop and that of a twin-channel Flow Instability experiment. Then the Flow Instability in twin rectangular channel system is studied under different conditions. The effects of pressure, P , inlet throttling coefficient, k in and exit throttling coefficient, k out are examined through the parameter plane of the subcooling number, N sub and phase change number, N pch and the frequency of the oscillations, f . Finally, the effects of asymmetric heating and throttling on Flow Instability are also analyzed.
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Theoretical study on the Flow Instability of supercritical water in the parallel channels
Progress in Nuclear Energy, 2013Co-Authors: Jian Feng, Wenxi Tian, Hao Zhao, Suizheng QiuAbstract:Abstract Super Critical Water (SCW) will experience considerable changes on the thermal and transport properties such as density, enthalpy, specific heat and thermal conductivity at normal operating condition. The Flow Instability in the parallel channels with SCW was studied in this paper. Mathematical and physical models were established to simulate the Flow and the heat transfer characteristics of supercritical water with semi-implicit scheme and staggered mesh scheme. The Flow Instability of SCW was analyzed using the tiny perturbation method. Pseudo-subcooling number ( N SPC ) and pseudo-phase change number ( N TPC ) which can be used to distinguish the system Instability were derived based on the property of SCW. The marginal stability boundary (MSB) was then obtained by using the N SPC and N TPC . The effects of different parameters, such as mass Flow rate, heat flux, inlet temperature and system pressure, on the Flow Instability boundary were also investigated. When increasing the mass Flow rate and the system pressure, decreasing the heat flux, the Flow stability in the parallel channels increases. The effect of inlet temperature in the low pseudo-subcooling number region is different from that in high pseudo-subcooling number region.
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Theoretical Study on the Flow Instability of Supercritical Water in the Parallel Channels
Volume 5: Fusion Engineering; Student Paper Competition; Design Basis and Beyond Design Basis Events; Simple and Combined Cycles, 2012Co-Authors: Jian Feng, Wenxi Tian, Suizheng QiuAbstract:For the Flow of the supercritical water (SCW), the fierce variation of density and specific volume possibly cause Flow Instability. Based on the structure of parallel channels, mathematical and physical models were established to simulate the Flow and heat transfer characteristics of the supercritical water in the parallel channels with semi-implicit scheme and staggered mesh scheme. Flow Instability of super-critical water was obtained by using the little perturbation method. Pseudo-subcooling number (NSUB) and pseudo-phase change number (NPCH) are defined based on the property of SCW. The marginal stability boundary (MSB) is obtained with using the NSUB and NPCH. The effects of mass Flow rate, inlet temperature and system pressure on the Flow Instability boundary were also investigated. When increasing the mass Flows and system pressure, decreasing the heat flux, the stability in the parallel channels increases. The effect of inlet temperature in the low pseudo-subcooling number region is different from that in high pseudo-subcooling number region.Copyright © 2012 by ASME
Wenxi Tian - One of the best experts on this subject based on the ideXlab platform.
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theoretical investigation of two phase Flow Instability between parallel channels of natural circulation in rolling motion
Nuclear Engineering and Design, 2019Co-Authors: Xiaoyan Wang, Ronghua Chen, Wenxi Tian, Siyang Huang, Dalin Zhang, Suizheng QiuAbstract:Abstract In present work, the two-phase Flow Instability between rectangular parallel channels of natural circulation under static and rolling conditions was coupled studied theoretically. Models including two-phase Flow Instability, natural circulation system components, and the additional force were established in combination based on the homogenous model. A computational program was written in FORTRAN language which was solved by Gear multi-value method by using control volume integrating method. The program was validated with experiments, and the results matched well with the experiment data. The marginal stability boundary (MSB) maps under different parameters were obtained by using nondimensional numbers Nsub and Npch. The influence of different kinds of pressure drop, inlet subcooling temperature of heating channels, system pressure, valve resistance, venturi Flowmeters resistance, structure height, rolling condition, and the interaction effect of natural circulation and two-phase Flow Instability between rectangular parallel channels were analyzed. The results show that with the increase in system pressure and venturi Flowmeters resistance, the system stability of natural circulation is enhanced. The influence of inlet subcooling temperature is nonlinear. The increase in valve resistance leads to the Instability of system. The increase in structure height does not change system stability significantly. The rise in rolling angle and period both reduce the system stability.
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Study on safety boundary of Flow Instability and CHF for parallel channels in motion
Nuclear Engineering and Design, 2018Co-Authors: Wenxi Tian, Mengmeng Xi, Ronghua Chen, Guanghui SuAbstract:Abstract The safety boundary of Flow Instability and critical heat flux(CHF) for parallel channels was theoretically investigated in static and motion. For Flow Instability, a parallel-channel Instability mechanistic model was adopted. For CHF, the liquid sublayer dryout mechanism model was used. Also, a unified form of additional forces caused by motion was derived for both Flow Instability and CHF model. An in-house code was developed combining the Flow Instability model and the CHF model in motion. The safety boundary of twin rectangular parallel channels with length of 40 mm, width of 2 mm and height of 1 m was calculated in static, inclination, heaving, pitching and rolling motions. The results show that the safety boundary consists of CHF lines and Instability boundary. The heating power of the parallel channels is limited by Flow Instability or CHF depending on the mass flux. All the motions have little influence on the Instability boundary. The effects of longitudinal inclination, heaving and pitching motions on the safety boundary are no more than 1%. However, the CHF is obviously reduced in transverse inclination due to Flow maldistribution and in rolling motion due to pulsating Flow.
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Effect of Rolling Motion on Flow Instability of Parallel Rectangular Channels of Natural Circulation
Volume 5: Advanced Reactors and Fusion Technologies; Codes Standards Licensing and Regulatory Issues, 2018Co-Authors: Xiaoyan Wang, Wenxi Tian, Siyang Huang, Lie Chen, Suizheng QiuAbstract:In order to study the effect of rolling motion on Flow Instability of parallel rectangular channels of natural circulation, the natural circulation reactor simulation system is used for physical prototype. And theory analysis model of parallel rectangular channels of natural circulation system under rolling motion is established and coded by Fortran. The results of the program are verified to the experiments, and the results are in good agreement. The Flow Instability boundaries of different pressure under static and rolling motion are calculated respectively. The results show that: 1) under static condition, with the increase of the pressure, the Instability boundary line changes, and the system becomes more stable; 2) under rolling conditions, the heating power of Instability boundary decreases comparing to the stable conditions. The Instability occurs earlier; 3) the stability of the system decreases with the increasing of rolling amplitude and frequency.Copyright © 2018 by ASME
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Theoretical study on the Flow Instability of supercritical water in the parallel channels
Progress in Nuclear Energy, 2013Co-Authors: Jian Feng, Wenxi Tian, Hao Zhao, Suizheng QiuAbstract:Abstract Super Critical Water (SCW) will experience considerable changes on the thermal and transport properties such as density, enthalpy, specific heat and thermal conductivity at normal operating condition. The Flow Instability in the parallel channels with SCW was studied in this paper. Mathematical and physical models were established to simulate the Flow and the heat transfer characteristics of supercritical water with semi-implicit scheme and staggered mesh scheme. The Flow Instability of SCW was analyzed using the tiny perturbation method. Pseudo-subcooling number ( N SPC ) and pseudo-phase change number ( N TPC ) which can be used to distinguish the system Instability were derived based on the property of SCW. The marginal stability boundary (MSB) was then obtained by using the N SPC and N TPC . The effects of different parameters, such as mass Flow rate, heat flux, inlet temperature and system pressure, on the Flow Instability boundary were also investigated. When increasing the mass Flow rate and the system pressure, decreasing the heat flux, the Flow stability in the parallel channels increases. The effect of inlet temperature in the low pseudo-subcooling number region is different from that in high pseudo-subcooling number region.
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Flow Instability analysis of supercritical water-cooled reactor CSR1000 based on frequency domain
Annals of Nuclear Energy, 2012Co-Authors: Xiaoyan Tian, Wenxi Tian, Guanghui SuAbstract:Abstract Flow Instability was studied for supercritical water-cooled reactor CSR1000 based on frequency domain method in this paper. A code named FREDO-CSR1000 (Frequency Domain Analysis of CSR1000) has been developed. The analysis of Flow Instability for CSR1000 both in average channel and hot channel within rated power and Flow has been performed with the FREDO-CSR1000 code. The key parameters including decay ratio, the maximum cladding surface temperature and the proper orifice pressure drop coefficient were obtained as well. The calculation results indicated that the decay ratio of the first Flow path varies with power and Flow monotonically. However, the decay ratio of the second Flow path ascends first and then descends, the trend of which is fluctuant because of the simultaneous influence of a multitude of variables. Besides, it is found that the location where the Flow Instability happened is directly determined by the point at which the pseudo-critical temperature reached. Moreover, the neutral stability boundary for hot channel of CSR1000 was obtained so that the threshold of Flow Instability can be predicted.
James J. Feng - One of the best experts on this subject based on the ideXlab platform.
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A novel low inertia shear Flow Instability triggered by a chemical reaction
Physics of Fluids, 2007Co-Authors: Teodor Burghelea, Kerstin Wielage-burchard, Ian Frigaard, D. Mark Martinez, James J. FengAbstract:We present an experimental investigation of a novel low Reynolds number shear Flow Instability triggered by a chemical reaction. An acid-base reaction taking place at the interface between a Newtonian fluid and carbopol-940 solution leads to a strong viscosity stratification, which locally destabilizes the Flow. Our experimental observations are made in the context of a miscible displacement Flow, for which the Flow Instability promotes local mixing and subsequently improves the displacement efficiency. The experimental study is complemented by a simplified normal mode analysis to shed light on the origin of the Instability.
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A novel shear Flow Instability triggered by a chemical reaction in the absence of inertia
arXiv: Fluid Dynamics, 2006Co-Authors: Teodor Burghelea, Kerstin Wielage-burchard, Ian Frigaard, D. Mark Martinez, James J. FengAbstract:We present an experimental investigation of a novel low Reynolds number shear Flow Instability triggered by a chemical reaction. An acid-base reaction taking place at the interface between a Newtonian fluid and Carbopol-940 solution leads to a strong viscosity stratification, which locally destabilizes the Flow. Our experimental observations are made in the context of a miscible displacement Flow, for which the Flow Instability promotes local mixing and subsequently improves the displacement efficiency. The experimental study is complemented by a simplified normal mode analysis to shed light on the origin of the Instability
Teodor Burghelea - One of the best experts on this subject based on the ideXlab platform.
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A novel low inertia shear Flow Instability triggered by a chemical reaction
Physics of Fluids, 2007Co-Authors: Teodor Burghelea, Kerstin Wielage-burchard, Ian Frigaard, D. Mark Martinez, James J. FengAbstract:We present an experimental investigation of a novel low Reynolds number shear Flow Instability triggered by a chemical reaction. An acid-base reaction taking place at the interface between a Newtonian fluid and carbopol-940 solution leads to a strong viscosity stratification, which locally destabilizes the Flow. Our experimental observations are made in the context of a miscible displacement Flow, for which the Flow Instability promotes local mixing and subsequently improves the displacement efficiency. The experimental study is complemented by a simplified normal mode analysis to shed light on the origin of the Instability.
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A novel shear Flow Instability triggered by a chemical reaction in the absence of inertia
arXiv: Fluid Dynamics, 2006Co-Authors: Teodor Burghelea, Kerstin Wielage-burchard, Ian Frigaard, D. Mark Martinez, James J. FengAbstract:We present an experimental investigation of a novel low Reynolds number shear Flow Instability triggered by a chemical reaction. An acid-base reaction taking place at the interface between a Newtonian fluid and Carbopol-940 solution leads to a strong viscosity stratification, which locally destabilizes the Flow. Our experimental observations are made in the context of a miscible displacement Flow, for which the Flow Instability promotes local mixing and subsequently improves the displacement efficiency. The experimental study is complemented by a simplified normal mode analysis to shed light on the origin of the Instability
Guanghui Su - One of the best experts on this subject based on the ideXlab platform.
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Study on safety boundary of Flow Instability and CHF for parallel channels in motion
Nuclear Engineering and Design, 2018Co-Authors: Wenxi Tian, Mengmeng Xi, Ronghua Chen, Guanghui SuAbstract:Abstract The safety boundary of Flow Instability and critical heat flux(CHF) for parallel channels was theoretically investigated in static and motion. For Flow Instability, a parallel-channel Instability mechanistic model was adopted. For CHF, the liquid sublayer dryout mechanism model was used. Also, a unified form of additional forces caused by motion was derived for both Flow Instability and CHF model. An in-house code was developed combining the Flow Instability model and the CHF model in motion. The safety boundary of twin rectangular parallel channels with length of 40 mm, width of 2 mm and height of 1 m was calculated in static, inclination, heaving, pitching and rolling motions. The results show that the safety boundary consists of CHF lines and Instability boundary. The heating power of the parallel channels is limited by Flow Instability or CHF depending on the mass flux. All the motions have little influence on the Instability boundary. The effects of longitudinal inclination, heaving and pitching motions on the safety boundary are no more than 1%. However, the CHF is obviously reduced in transverse inclination due to Flow maldistribution and in rolling motion due to pulsating Flow.
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Flow Instability analysis of supercritical water-cooled reactor CSR1000 based on frequency domain
Annals of Nuclear Energy, 2012Co-Authors: Xiaoyan Tian, Wenxi Tian, Guanghui SuAbstract:Abstract Flow Instability was studied for supercritical water-cooled reactor CSR1000 based on frequency domain method in this paper. A code named FREDO-CSR1000 (Frequency Domain Analysis of CSR1000) has been developed. The analysis of Flow Instability for CSR1000 both in average channel and hot channel within rated power and Flow has been performed with the FREDO-CSR1000 code. The key parameters including decay ratio, the maximum cladding surface temperature and the proper orifice pressure drop coefficient were obtained as well. The calculation results indicated that the decay ratio of the first Flow path varies with power and Flow monotonically. However, the decay ratio of the second Flow path ascends first and then descends, the trend of which is fluctuant because of the simultaneous influence of a multitude of variables. Besides, it is found that the location where the Flow Instability happened is directly determined by the point at which the pseudo-critical temperature reached. Moreover, the neutral stability boundary for hot channel of CSR1000 was obtained so that the threshold of Flow Instability can be predicted.