An investigation on flashing instability induced water hammer in an open natural circulation system

Hou, Xiaofan; Sun, Zhongning; Su, Jian; Fan, Guangming

doi:10.1016/j.pnucene.2016.09.015

Cited by 32 publications

(6 citation statements)

References 19 publications

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“…Large system codes like RELAP5, Trac and CATHARE are used for the safety analysis of transients in NPP, and they model two-phase flow transients. Numerical simulations of CIWH are performed by using large system codes as ATHLET, WAHA3 [25], RELAP5 [20], Trac, CATHARE, in-house codes [26] and OpenFOAM, open source CFD software [21]. A type of the CIWH known as the water cannon phenomenon can occur during the discharge of steam into a large volume of cold water.…”

Section: Condensation Induced Water Hammermentioning

confidence: 99%

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Boiling and Condensation in Two-Phase System Transients with Water Hammer

Milivojevic,

Stevanovic,

M. Petrovic

et al. 2024

Advances in Boiling and Condensation

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Water hammer in two-phase systems, induced by direct steam condensation on subcooled water or by separation of subcooled water column, results in the most intensive pipeline pressure surges. Amplitudes of pressure spikes along the course of these dangerous transients strongly depend on the condensation and evaporation rates. The present paper provides a literature overview of thermal-hydraulic models for the prediction of water hammer phenomenon in two-phase systems, together with an original mechanistic approach for the prediction of phase transition rates, based on the shape and size of vapor-liquid interfacial area and the phase transition potential expressed through vapor and liquid phase temperature difference. Available water hammer experimental conditions were numerically simulated with the new modeling approach. Driving parameters of boiling and condensation rates at the steam-water interfaces are evaluated, and a good agreement is shown between numerical results and experimental data of bulk two-phase flow parameters during water hammer transients.

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Section: Condensation Induced Water Hammermentioning

confidence: 99%

“…Hou et al [26] experimentally and numerically investigated flashing instability induced water hammer (FIIWH), which belongs to the class of CIWH, and occurs in open natural circulation systems (NCS). The occurrence of FIIWH is more likely in NCS with long horizontal pipes.…”

Section: Condensation Induced Water Hammermentioning

confidence: 99%

Boiling and Condensation in Two-Phase System Transients with Water Hammer

Milivojevic,

Stevanovic,

M. Petrovic

et al. 2024

Advances in Boiling and Condensation

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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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“…Owing to the advantage of low costs and high reliability, passive cooling systems driven by natural circulation are being considered for various advanced light water reactor concepts. For example, the ESBWR of General Electric [8,9], the KERENA TM of Framatome [10], the AP1000 of Westinghouse [11], and the HPR1000 of China General Nuclear Power Group [12] all applied natural circulation for the heat removal from the core or containment. During such a circulation, warm water from the heat source flows up through a long adiabatic riser pipe, is cooled by a heat exchanger at the top of the circuit, and then returns to the heat source through the downcomer (see Figure 1).…”

Section: Introductionmentioning

confidence: 99%

CFD Modeling of Phase Change during the Flashing-Induced Instability in a Natural Circulation Circuit

Liao

Lucas

2023

Processes

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Flashing-induced instability (FII) has a significant impact on the safe operation of a natural circulation circuit, a phenomenon frequently encountered in the cooling systems of advanced light water reactors. While one-dimensional system codes are commonly used for the engineering design and safety analysis of FII, there is a strong academic interest in understanding the underlying physical mechanisms. To address this, high-resolution computational fluid dynamics (CFD) simulations serve as a valuable tool. However, the current state of CFD modeling for two-phase flows with phase change, which are particularly highly transient fluctuating flashing flows, is still in its early stages of development. In this study, we establish a CFD model that focuses on interphase heat transfer to analyze the phase change during FII. By incorporating experimental data from the literature, we investigate the transient flow field and thermodynamic behavior in the riser of the GENEVA test facility. The study provides valuable insights into the non-equilibrium and interfacial transfer phenomena during the phase change as well as the effect of high-frequency fluctuation. Additionally, we discuss in detail the challenges associated with FII modeling and the limitations of the current model. We also provide suggestions for potential improvements in future numerical studies. The results show that the thermal phase change and heat transfer coefficient model adopted for the simulation reasonably captures the evaporation and condensation process. However, it tends to under-predict the evaporation rate, which results in a larger pressure drop through the riser. The observation that the void fraction close to the wall is higher than that in the riser center evidences that the reliable modeling of bubble size distribution as well as the inclusion of non-drag forces are important for predicting the transverse void distribution. Furthermore, it reveals that both the temperature and pressure change in an FII, and their effects on phase change should be taken into account simultaneously.

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An investigation on flashing instability induced water hammer in an open natural circulation system

Cited by 32 publications

References 19 publications

Boiling and Condensation in Two-Phase System Transients with Water Hammer

Boiling and Condensation in Two-Phase System Transients with Water Hammer

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

CFD Modeling of Phase Change during the Flashing-Induced Instability in a Natural Circulation Circuit

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