Countercurrent Flooding in Pipes Containing Multiple Elbows and an Orifice.

Kawaji, Masahiro; Lotocki, A Paul; Krishnan, V.S.

doi:10.1299/jsmeb.36.397

Cited by 7 publications

(3 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In the case of analytical or semi-analytical works on the CCFL in a PWR hot leg using multiple elbows was found to be limited. For this purpose, Kawaji et al (1993) adopted a superposition principle whereby the piping system is represented as a combination of simple geometries (vertical, horizontal or inclined pipes). The most limiting gas velocities as each liquid flow rate are combined to obtain the predicted CCFL conditions over the entire range of the liquid flow rates.…”

Section: Review Of Models and Methods For Two-phase Flowmentioning

confidence: 99%

Thermal hydraulic considerations of nuclear reactor systems: Past, present and future challenges

Yeoh

2019

Exp. Comput. Multiph. Flow

View full text Add to dashboard Cite

Thermal hydraulic analysis of nuclear reactor core and its associated systems can be performed using analysis system, subchannel or computational fluid dynamics (CFD) codes to estimate the different thermal hydraulic safety margins. The safety margins and operating power limits under different conditions of the primary as well as secondary cooling system such as the system pressure, coolant inlet temperature, coolant flow rate, and thermal power and its distributions are considered as key parameters for thermal hydraulic analysis. Considering the complexity of rod bundle geometry, boiling heat transfer and different turbulent scales bring about the many challenges in performing the thermal hydraulic analysis to ensure the safe design and operation of nuclear reactor systems under normal and abnormal conditions. A comprehensive review is presented of past, present and future challenges in state-of-the-art thermal hydraulic analysis covering various aspects of experimental, analytical and computational approaches.

show abstract

Section: Review Of Models and Methods For Two-phase Flowmentioning

confidence: 99%

Thermal hydraulic considerations of nuclear reactor systems: Past, present and future challenges

Yeoh

2019

Exp. Comput. Multiph. Flow

View full text Add to dashboard Cite

show abstract

“…Some researchers also conducted countercurrent flow experiments in a channel with flow obstructions to evaluate the influence of the obstructions on CCFL [20][21][22][23][24]. Sun [20] carried out two-phase countercurrent flow experiments in a BWR bundle model.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

“…The results indicated that the obstruction advances the flooding phenomenon. Kawaji et al [23] experimentally investigated the countercurrent flooding in pipes containing multiple elbows and an orifice. They found that the orifice placed in the horizontal section generally lowered flooding gas velocities, with the greatest effect noted for the smallest orifice tested.…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

Countercurrent Flow Limitation in a Pipeline with an Orifice

Zhao

Wang

et al. 2022

Energies

View full text Add to dashboard Cite

Countercurrent flow limitation (CCFL) refers to an important class of gravity-induced hydrodynamic processes that impose a serious restriction on the operation of gas–liquid two-phase systems. In a nuclear power plant, CCFL may occur in the liquid level measurement system where an orifice is applied in the pipeline, which may introduce error into the level measurement system. CCFL can occur in horizontal, vertical, inclined, and even much more complicated geometric patterns, and the hot-leg channel flow passage has been widely investigated; however, a pipeline with variable cross-sections, including an orifice, has not yet been investigated. An experimental investigation has been conducted in order to identify the phenomenon, pattern, and mechanism of CCFL onset in this type of geometry. Both visual and quantified experiments were carried out. A high-speed camera was applied to capture the flow pattern. Visual experiments were implemented at atmospheric pressure, while quantified pressurizer experiments were implemented at higher pressures. It was determined that if the condensate drainage is low and the liquid level is also low, with a stable stratified flow upstream of the orifice, there is no oscillation of the differential pressure. However, at higher condensate drainage levels, when the liquid level increases, a stratified wavy flow occurs. One of these waves can suddenly rise upstream of the orifice to choke it, which subsequently gives rise to differential pressure across the orifice, with periodic variation. This pattern alternately features stratified flow, stratified wavy flow, and slug flow, which indicates the occurrence of CCFL. The CCFL occurring under these experimental conditions can be expressed as a Wallis type correlation, where the coefficients m and C are 0.682 and 0.601, respectively.

show abstract