Modeling and simulation of onset of condensation-induced water hammer

doi:10.1016/j.pnucene.2020.103555

Progress in Nuclear Energy

Volume 130, December 2020, 103555

https://doi.org/10.1016/j.pnucene.2020.103555 Get rights and content

Highlights

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A condensation-induced water hammer in horizontal pipes was studied.
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A map for the onset of condensation-induced water hammer was developed.
•
Modified Jakob and Froude numbers were identified as key parameters.
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The semi-analytical model was developed to predict the onset of the water hammer.
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RELAP5 was used for simulating condensation-induced water hammer.

Abstract

In view of the importance of the condensation-induced water hammer in various engineering fields, this study performed an analytical modeling and numerical simulation to obtain the map of the onset of the condensation-induced water hammer. Two linear boundaries were experimentally observed for the transitions between no condensation-induced water hammer and non-periodic condensation-induced water hammer and between non-periodic condensation-induced water hammer and periodic condensation-induced water hammer. The analytical modeling based on the energy balance equation was conducted to derive the onset of the condensation-induced water hammer. The analytical model suggested that the map of the onset of the condensation-induced water hammer could be displayed by two essential non-dimensional parameters, such as modified Jakob number and Froude number. The model indicated that the slope of the boundary of the onset of the condensation-induced water hammer was the product of modified Stanton number, non-dimensional interfacial area concentration, and non-dimensional temperature difference. The model could predict the boundaries between no condensation-induced water hammer and non-periodic condensation-induced water hammer and between non-periodic condensation-induced water hammer and periodic condensation-induced water hammer satisfactorily. The one-dimensional nuclear thermal-hydraulic system analysis code, RELAP5, was used for simulating the onset of the condensation-induced water hammer. The obtained boundary corresponded to the experimentally obtained boundary between non-periodic condensation-induced water hammer and periodic condensation-induced water hammer.

Graphical abstract

Introduction

In the system where steam and subcooled water are mixed due to some cause, condensation-induced water hammer or bubble collapse water hammer may occur due to rapid steam condensation, and the condensation-induced water hammer may destroy the equipment. Examples are troubles due to (1) water hammer in the feed water line of the steam generator in Indian Point No. 2 PWR, and (2) water hammer at the 10″ and 12” headers of a steam supply system in a plant (Andrew et al., 1995).

The mechanism of the condensation-induced water hammer is summarized as follows. The first example is a counter-current flow of steam and subcooled water. Steam and subcooled water are stratified at the beginning. When the wave amplitude becomes high enough to form the steam cavity, bubble collapse water hammer occurs due to the rapid condensation of the steam cavity (Block et al., 1977; Rothe et al. 1977). The second example is a steam line in a long resting state where the drain water is accumulated. If steam is supplied into the steam line, stratified gas and liquid are formed. After a liquid slug or steam cavity is formed due to the gas-liquid interface fluctuation, a water hammer occurs due to the rapid condensation of the steam cavity. As such, the basic mechanism of the condensation-induced water hammer has been classified into four types (Yow et al. 1988): (1) steam-water counter flow in a horizontal pipe, (2) subcooled water with condensing steam in a vertical pipe, (3) pressurized water entering a vertical steam-filled pipe, and (4) hot water entering a lower pressure line. Wang et al., (2018) conducted an extensive literature review and summarized the current status of the condensation-induced water hammer in Table 1. In addition, Mazed et al. (Mazed et al. 2016, 2018) performed an experimental investigation of steam condensation in a water tank at sub-atmospheric pressure. They compared the condensation regime at sub-atmospheric and atmospheric pressure and analyzed the condensation efficiency and jet plume expansion at sub-atmospheric pressure. Lo Frano et al. (Lo Frano et al. 2017, 2018) experimentally obtained the condensation regime map. They analyzed the vibrations caused by the steam condensation when steam condensed in a water tank at sub-atmospheric pressure.

Wang et al., (2018) pointed out that most of the existing condensation-induced water hammer researches were focused on one condensation-induced water hammer event at each test condition. The obtained major finding was that the condensation-induced water hammer was highly stochastic. Due to the insufficient study of the continuous and multiple condensation-induced water hammer under low steam mass flux, Wang et al. performed the experimental research to elucidate the process of the continuous and multiple condensation-induced water hammer for steam-water direct contact condensation in a horizontal pipe with steam mass flux ranging 1.0–3.5 kg/(m²s). Their study identified the condensation-induced water hammer into three regimes: (1) no condensation-induced water hammer, (2) non-periodic condensation-induced water hammer, and (3) periodic condensation-induced water hammer.

In view of the importance of the map of the onset of condensation-induced water hammer, this generic study performs analytical modeling to predict the onset of the condensation-induced water hammer, and numerical simulation of the condensation-induced water hammer using RELAP5 mod 3.3 code.

Section snippets

Experimental system

Fig. 1(a) shows a schematic diagram of the experimental system (Wang et al., 2018). The experimental system mainly consisted of a steam generator, buffer tank, steam pipes, cylinder water tank, data acquisition system, and high-speed video camera. Steam supplied by the steam generator flowed through thermally-insulated pipes after being stabilized in the buffer tank. After passing a vertical pipe, the steam flowed into the horizontal pipe, where the steam directly contacted with water and

Applicability of existing model

Bjorge and Griffith (1984) performed the experiment of the condensation-induced water hammer using steam-water counter-current flows, shown in Fig. 5. The formation of a steam cavity can be viewed as the transition from the stratified flow to the slug flow. Bjorge and Griffith experimentally demonstrated that the transition criterion between stratified and slug flows, Eq. (1), proposed by Taitel and Dukler (1976), could be applicable to the prediction of the condensation-induced water hammer

RELAP5 node model and initial boundary conditions

The ability of a one-dimensional thermal-hydraulic simulation code in simulating condensation-induced water hammer is tested here. RELAP5 mod 3.3 is adopted in the simulation. Selected constitutive equations relevant to the water hammer simulation are listed in Table 3. The constitutive equations include the interfacial area concentration, and heat transfer coefficients for subcooled liquid, subcooled gas, superheated liquid, and superheated gas.

The test loop shown in Fig. 1 is modeled by

Modeling of onset of non-periodic condensation-induced water hammer

As can be seen in Fig. 8, two boundaries exist in the map of the onset of the condensation-induced water hammer. They are (1) the boundary between non-periodic and no condensation-induced water hammers and (2) the boundary between non-periodic and periodic condensation-induced water hammers.

As indicated by the dotted blue lines in Fig. 8, the boundary between no condensation-induced water hammer and non-periodic condensation-induced water hammer may be approximated by a linear function between

Conclusions

Due to the importance of the condensation-induced water hammer, extensive researches have been performed (Wang et al., 2018). This generic study has performed analytical modeling to predict the onset of the condensation-induced water hammer, and numerical simulation of the condensation-induced water hammer using RELAP5 mod 3.3 code. The major results are summarized as follows.

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An analytical model has been derived to predict the onset of the condensation-induced water hammer. The model

Credit author statement

Takashi Hibiki: Conceptualization, Methodology, Writing- Reviewing and Editing, Data Curation, Supervision. Somboon Rassame: Data Curation, Software, Visualization. Wenbing Liu: Writing- Reviewing and Editing. Lutao Wang: Writing- Reviewing and Editing. Quanbin Zhao: Writing- Reviewing and Editing. Daotong Chong: Conceptualization, Methodology, Writing- Reviewing and Editing. Junije Yan: Writing- Reviewing and Editing.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

A part of this work was supported by the National Natural Science Foundation of China (No. 51876168) and the Natural Science Foundation of Shaanxi Province (2018JC-005). Some of the authors (Liu, Wang, Zhao, Chong, and Yan) sincerely appreciate the supports.

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Citation Excerpt :
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Condensation-induced water hammers (CIWHs) can occur in pipelines when saturated steam comes into direct contact with subcooled water, causing severe damage to related equipment and personal safety. An experimental study of the occurrence and development of CIWHs in a horizontal pipe is carried out at the special test facility developed in Electrogorsk Research and Development Center for NPP Safety. Subcooled water is supplied into the horizontal pipe filled with steam as a result of which CIWH may occur. The test facility has two novel features: 1) a damper cap to stabilize the water flow at the inlet part of the horizontal pipe and 2) a discharge vessel with closed drainage (during the experiment). The first feature allows us to study the effect of the water flow contraction at the inlet section of the pipe on the CIWHs occurrence. The second feature makes it possible to study CIWHs in various hydrodynamic conditions during the experiment. Four stages of the process are identified: 1) initial flow of water through a steam filled pipe; 2) free falling discharge of water; 3) filling the horizontal pipe; 4) filling the upper part of the discharge vessel. The features of the arising CIWHs at each stage are described. The main parameters affecting the occurrence of CIWH are the temperature and flow rate of the supplied water. An increase in water subcooling contributes to the CIWH probability and an increase in CIWH pressure peaks. CFD calculations reveal that at high flow rates of supplied water (3–5 t/h), strong disturbances develop on the interfacial surface due to the new mechanism of steam–water interaction under these conditions, which can contribute to the occurrence of water hammers. On the plane of parameters “water subcooling - Froude number”, a map of CIWHs based on the present study and other works, as well as the theoretical boundary of the occurrence of CIWHs, has been built. Our results shown on this map are in full agreement with the results of other researchers. It is found that in experiments performed under the same conditions, significantly different magnitudes of water hammers can be obtained, which is associated with the stochastic nature of this phenomenon. It has been revealed that the maximum magnitudes of water hammers are achieved when the horizontal pipe is half filled with water, and the area of the interfacial surface on which steam condenses occurs is maximum.

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Modeling and simulation of onset of condensation-induced water hammer

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Experimental system

Applicability of existing model

RELAP5 node model and initial boundary conditions

Modeling of onset of non-periodic condensation-induced water hammer

Conclusions

Credit author statement

Declaration of competing interest

Acknowledgement

Nucl. Eng. Des.

Int. J. Heat Mass Tran.

Nucl. Eng. Des.

Nucl. Eng. Des.

Int. J. Multiphas. Flow

Fusion Eng. Des.

Fusion Eng. Des.

Nucl. Eng. Des.

Int. J. Multiphas. Flow

Exp. Therm. Fluid Sci.

Gas-liquid Two-phase Flow

Condensation induced water hammer in steam supply system

Multiple condensation induced water hammer events, experiments and theoretical investigations

Kerntechnik

Initiation of waterhammer in horizontal and nearly horizontal pipes containing steam and subcooled water

J. Heat Tran.

An Evaluation of PWR Steam Generator Water Hammer

KAIST-CIWH computer code and a guide chart to avoid condensation-induced water hammer in horizontal pipes -nuclear engineering and technology | korea science

Nuclear Engineering and Technology