The effect of the radial heat loss, upper reservoir temperature, and corrugated wall channel on the flooding critical heat flux

This study measured the flooding critical heat flux (flooding CHF) for two vertical annular channels with different channel gaps. The experiments were conducted at atmospheric pressure and with no flow. The effects of the upper reservoir temperature within 30–80 °C and radial heat loss have been studied. It was found that the upper reservoir temperature has a small effect on the flooding CHF values, and it varied in the range of up to 10% compared to the saturated conditions. On the other hand, a significant effect of the radial heat loss was observed on the measured flooding CHF values (up to 100%). The flooding CHF experimental results were compared with numerous empirical correlations from the literature, some initially based on air-water counter-current flow experiments (flooding experiments with no heating). It was found that based on the onset flooding velocity experiments, the flooding CHF results can be successfully predicted. The effect of the wall corrugation on the flooding CHF was also examined in the simple air-water counter-current flow setup. This study shows that the air flooding velocity in a corrugated channel is higher than in a smooth channel with the same cross-section geometry and dimensions. Therefore, using a smooth channel flooding CHF value for a corrugated one guarantees a conservative result.