Analysis of metastable regimes in a parallel channel single phase natural circulation system with RELAP5/MOD3.2

An open natural circulation system applied to the passive containment cooling system is proposed for the large dry double-wall concrete containment after severe accidents. In order to investigate the operating behaviors of the open loop, a numerical code is developed to simulate the transient flow characteristics from the startup to the long-term operation. The results show that the open system may experience such four stages as startup process, quasi-steady single-phase flow, transition stage and quasi-steady two-phase flow. Flashing is the dominated factor in the last two flow phases. Additionally, the effects of some systematic parameters on the mass flow rate are analyzed in detail. Both increasing the condensation heat transfer coefficient and the containment temperature can enhance the flow effectively whichever stage the system operates in. But the the initial fluid temperature can only affect the duration of the single-phase flow but has little impact on the mass flow rate. Moreover, greater riser height can lead to bigger single-phase flow rate, but nearly has no influence on the long-term two-phase flow and the flashing region.

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Stability analysis of a parallel channel-loop system with single-phase natural circulation under asymmetric conditions

Annals of Nuclear Energy ◽

10.1016/j.anucene.2021.108552 ◽

2021 ◽

Vol 163 ◽

pp. 108552

Author(s):

Enping Zhu ◽

Ting Wang ◽

Pengcheng Zhao ◽

Shengwen Deng ◽

Shenquan Zeng ◽

...

Keyword(s):

Stability Analysis ◽

Single Phase ◽

Natural Circulation ◽

Loop System ◽

Parallel Channel

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Flow characteristics of single phase natural circulation in parallel channel.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.55.182 ◽

1989 ◽

Vol 55 (509) ◽

pp. 182-187

Author(s):

Hideki NARIAI ◽

Ataru ICHINOSE ◽

Isao KOMORlYA

Keyword(s):

Single Phase ◽

Natural Circulation ◽

Flow Characteristics ◽

Parallel Channel

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Experimental Study on the Natural Circulation System for Single-Phase Water

ASME 2015 Power Conference ◽

10.1115/power2015-49230 ◽

2015 ◽

Author(s):

Zesen Nie ◽

Qincheng Bi ◽

Di Wu ◽

Jiangbo Wu

Keyword(s):

Single Phase ◽

Natural Circulation ◽

Engineering Application ◽

Heating Power ◽

Circulation System ◽

Circulation Flow ◽

System Pressure ◽

Straight Line ◽

Phase Water ◽

Heat Exchange Efficiency

The investigation on a natural circulation system for single-phase water is of value for engineering application, which has been researched by various methods. In the present study, a natural circulation experiment for single-phase water in a rectangular loop was conducted, in which water was electrical heated in a tank at the bottom of the loop and cooled by pool boiling outside of the tube bundles at the top of the loop. The system pressure was 2–6 MPa and heating power was 10–30 kW. Results show that natural circulation flow increases with heating power as a straight line for the same pressure, while no obvious influence of pressure on circulation flow for the same heating power can be found. In addition, a contrast experiment was carried out with different system resistance for further study, and it was found that the system resistance could significantly decrease heat exchange efficiency of the natural circulation system, which mainly resulted from distinctly reductive circulation flow. Emphasis was also put on extending the correlation proposed by Vijayan to the present experiment.

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