Numerical study on single-phase flow of natural circulation under ocean condition using coupled relap5 system code and fluent code

摘要

Natural circulation (NC) flow characteristic under ocean condition is important to the inherent safety of offshore (or floating) nuclear reactors, which is the subject of current study that being investigated by the coupling RELAP5 system code and FLUENT CFD software, in which the momentum equations of RELAP5 and FLUENT are modified to simulate the ocean condition, and the User Defined Function (UDF) of FLUENT is developed to couple the two different spatial- and time-scale software. Performance analysis of the coupling program and numerical method is conducted by comparison with experimental data about the same experimental system that is employed to the current modeling. The results under inclination condition indicate that the flow rate of the natural circulation has shown to differ even when the inclination angle is symmetric due to the density difference in the horizontal pipe. For the case of heaving condition, the flow rate has the same manner in terms of sinusoid as that of heaving motion, however, with a phase difference that is related to the fluid mass and the heaving period. For rolling condition, the behavior of the flow rate is more complex and exhibits two different forms in terms of double-trough wave and sine wave respectively attributing to the combined effect of gravitational driving pressure head (GDPH) and additional driving pressure head (ADPH). Besides, the impacts of motion parameters and thermal parameters on NC are also discussed.