Experimental investigation on transition boiling during reflooding in a narrow rectangular channel with high wall temperature

During LOCA (loss of coolant accident) of a nuclear reactor, the complex heat transfer during reflooding with high wall temperature of the fuel element is very important to nuclear safety. The transition boiling regime is a specific regime with a transition from film boiling to nucleate boiling during reflooding of the nuclear fuel element. In this study, a bottom reflooding experiment is carried out to investigate the transition boiling in a narrow rectangular channel and analyze the effects of working conditions including inlet subcooling, reflooding velocity, initial wall temperature, and system pressure in detail. It is found that the heat transfer coefficient during reflooding is a positive correlation to the inlet velocity, subcooling, and pressure, while inversely related to the initial wall temperature. In addition, according to the characteristics of the bottom reflooding of the narrow rectangular channel, a prediction model is proposed to predict the heat transfer coefficient during transition boiling during reflooding. By comparing the predicted results with the experimental data, the proposed model is in good agreement with the experimental result.