CFD Analysis and Visualization of the Two Phase Flow in a Thermosyphon for a Passive Heat Removal System of a Nuclear Power Plant

A thermosyphon, wickless heat pipe, is a heat transfer device of high thermal conductance that functions passively on the principle of evaporation and condensation of a working fluid. The heat-pipe concept was first proposed by Gaugler in 1942. After its independent invention by Grover in the early 1960s, serious development progress was made, and the heat pipe concept was studied intensively for both space and terrestrial applications, because of its beneficial characteristics. Annamalai and Ramalingam developed a CFD modeling for wick part of heat pipe using commercial code, ANSYS CFX. Khurram Kafeel numerically studied thermal hydraulic characteristics of thermosyphon in both transient and steady state. Bandar Fadhl et al. built a CFD modeling for boiling and condensing of thermosyphon using VOF method of ANSYS Fluent. They made user defined function (UDF) to define source term based on Lee model. In this study, CFD model of 1m-thermosyphon has been studied using VOF model. Unlike formal studies, vacuum pressure condition was applied because thermosyphon with vacuum inner pressure is much generally used. Furthermore, to check out hydraulic characteristics of the model, transparent thermosyphon experiment also has been conducted. The main purpose of this research is the investigation of CFD model of thermosyphon. Simulations using VOF method were performed to analyze evaporating, condensing and two phase flow of a thermosyphon. The simulation results show that complex phenomena inside of thermosyphon can be modeled using VOF method. Flow visualizations of working fluid matched well with transparent heat pipe experiment