Improvement of RELAP5 code for density wave instability analysis in parallel narrow rectangular channels

Lian, Qiang; Tian, Wenxi; Qiu, Suizheng; Su, G.H.

doi:10.1016/j.anucene.2018.08.049

Cited by 12 publications

(4 citation statements)

References 30 publications

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“…Instability Types in Natural Circulation Systems. Numerous experimental and theoretical studies have proved that flashing induced instability [20][21][22][23][24][25][26][27][28][29][30][31] and density-wave instability [32][33][34][35][36] usually occur in natural circulation systems.…”

Section: Density Wave Instability In Static Casementioning

confidence: 99%

Study on the Density Wave Instability in Natural Circulation System under Rolling Conditions

Gong

Zhang

Gui

et al. 2023

International Journal of Energy Research

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In the ocean environment, the thermal fluid system installed on the ship moves with the waves. This unsteady transient motion imposes additional body forces on the liquid. Thereby, the thermohydraulic properties of the thermal fluid system are changed, especially for natural circulation systems with a low driving force. Flow instability related to system security is a common two-phase flow system phenomenon. It is an essential subject in the study of thermal-hydraulic characteristics. In this paper, the density wave instability in a low-pressure natural circulation system with several parallel heating channels in the circumstances of rolling motion is studied by PNCMC (Program for Natural Circulation under Motion Condition). PNCMC is a newly developed program by adding extra body force induced by ship motions in two-phase’s momentum equations. The mechanism of rolling motion and its impact on flow oscillation and unstable boundary power are investigated. The supercooled boiling caused by the higher surface heat flux firstly promotes the occurrence of density wave oscillations between parallel heating channels. When enough steam enters the riser, the system density wave oscillation occurs under the gravity pressure drop-flow rate-vapor fraction feedback. A more complicated compound oscillation is created by superimposing the interchannel oscillation and the system density wave oscillation. If the rolling motion has little change to the natural circulation flow, when density wave instability arises, the flux oscillation rule and the instability boundary power are basically consistent with the vertical conditions. When the rolling angle is large, the fairly large amplitude flow oscillation generated by rolling will prevent density wave instability from occurring and force the flow oscillation to obey the law of rolling effects.

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Section: Density Wave Instability In Static Casementioning

confidence: 99%

Study on the Density Wave Instability in Natural Circulation System under Rolling Conditions

Gong

Zhang

Gui

et al. 2023

International Journal of Energy Research

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“…Due to the time lag of void propagation in the two-phase mixture, the inlet flow and outlet flow rates are not synchronous after the disturbance. It is widely accepted that the inlet resistance stabilizes the parallel-channel system, while the outlet resistance has the opposite function (Colombo et al, 2012;Xia et al, 2012;Lian et al, 2018). This is because the concentrated form pressure drop at the inlet is in-phase with the inlet flow rate, while the outlet form pressure drop is out-phase.…”

Section: Influence Of Resistancementioning

confidence: 99%

“…The capability of RELAP5 to predict the density wave instability in parallel channels is also ascertained by the comparison with experimental results (Ambrosini and Ferreri, 2006;Colombo et al, 2012). However, RELAP5 may not be suitable for the analysis of narrow rectangular channels (Lian et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…The results show that the joint influence of different factors of the water-cooled blanket requires further research. many parallel channels are simulated as one pipe with the same hydraulic diameter (Lian et al, 2018) to improve the calculation efficiency. In order to investigate the flow instability, the coolant channel in the system should be modeled independently.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Parametric study of density wave instability in parallel channels of a water-cooled blanket in a fusion reactor

Lian,

Liang,

Liao

et al. 2023

Front. Energy Res.

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In fusion reactors, many blanket concepts are designed with water as a coolant to transfer high-density heat from the fusion reaction out of the reactor core. The coolant temperature and pressure are maintained as the validated use in water-cooled fission reactors. However, the flow channel in a water-cooled blanket is independent of each other, and there is no flow mixing between coolant channels. Therefore, flow instability may occur in the independent parallel channels in a water-cooled blanket due to its unique structure and heat distribution, especially under the high heat flux caused by plasma rupture. In this study, the parametric analysis of density wave instability is performed using a thermal-hydraulic code developed for independent parallel channels based on the homogeneous model for the two-phase flow. The parallel-channel system in a water-cooled ceramic breeder (WCCB) blanket of the China Fusion Engineering Experimental Reactor (CFETR) is established for its first wall structure. A small disturbance is introduced into the system to determine if it is stable under different conditions. It is found that the channel number has no obvious influence on the prediction of the flow instability boundary. Therefore, the two-channel system is adopted to investigate the influence of different parameters, such as the pressure, resistance, flow rate, and inclination, on the flow instability boundary of the parallel-channel system in the CFETR WCCB blanket. The results show that flow instability occurs more easily in this study compared to the traditional instability analysis, especially under high-pressure conditions. In general, conditions of high pressure, large flow rate, and no inclination can stabilize the system, while the influence of resistance is quite different under different conditions of resistance and pressure. The research work indicates that more attention should be paid to the joint influence of different parameters for the water-cooled blanket during its design and operation.

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Research of two‐phase density wave instability in reactor core channels with rolling motion

et al. 2020

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Improvement of RELAP5 code for density wave instability analysis in parallel narrow rectangular channels

Cited by 12 publications

References 30 publications

Study on the Density Wave Instability in Natural Circulation System under Rolling Conditions

Study on the Density Wave Instability in Natural Circulation System under Rolling Conditions

Parametric study of density wave instability in parallel channels of a water-cooled blanket in a fusion reactor

Research of two‐phase density wave instability in reactor core channels with rolling motion

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