Numerical investigation on direct contact condensation-induced water hammer in passive natural circulation system for offshore applications

Abstract

For the passive natural circulation systems (PNCSs) in offshore floating nuclear plants, the ocean environment is usually regarded as the final heat sink. Condensation-induced water hammer (CIWH) may occur as the saturated steam released into the ocean by natural circulation. This study aims to develop a CFD model to analysis the CIWH phenomenon induced by direct contact condensation (DCC) in the PNCSs. In the model framework, the two-phase interface is tracked explicitly by the volume of fluid method; the interface heat transfer is acquired by the hybrid Heat Transfer Coefficient model based on the Surface Renewal Theory; the condensation heat and mass transfer rate are obtained by user-defined functions (UDF). The condensation model is firstly validated with the PMK-2 experimental data, showing consistency with the measured temperature evolutions. Then, the model is applied to investigate the CIWH events in the horizontal pipe geometry of the passive natural circulation systems. The simulation results indicate that the reverse flow of subcooled water triggers the formation of the CIWH events, by increasing the condensation rate and forming the entrapped bubble. The reverse flow periodically occurs afterwards, inducing multiple CIWHs. The increase of inlet stream velocity lengthens the reverse flow period and the distance, thus strengthening the interfacial condensation and the pressure impulse of CIWH.

Keywords:

• Condensation-induced water hammer
• direct contact condensation
• offshore applications
• passive natural circulation systems
• reverse flow

Disclosure statement

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 article.

Additional information

Funding

This work was sponsored by the Oceanic Interdisciplinary Program of Shanghai Jiao Tong University (project number: SL2020ZD101), the National Natural Science Foundation of China (grant number 52001207), the LingChuang Research Project of China National Nuclear Corporation, the Young Talent Project of China National Nuclear Corporation and the Cultivation of Scientific Research Ability of Young Talents of Shanghai Jiao Tong University (Grant No. 19X100040072).