Statistical method for determining the onset of nucleate boiling under forced and natural convections in a rectangular channel

A statistical method based on temperature change with heat flux in a single-phase flow is proposed to determine the onset of nucleate boiling (ONB) incipience. Experiments under forced and natural convections were performed with different inlet temperatures. ONB wall temperatures determined by the proposed method were compared with that determined by the intersection method. The difference between ONB wall temperatures obtained by the proposed and intersection methods under forced convection was insignificant; however, the difference was significant under natural convection. In addition, ONB wall temperatures for forced and natural convections were compared for predictions by existing ONB correlations, namely, Bergles and Rohsenow (1964), Jens and Lottes (1951), and Thom et al. (1965). The results showed that the Jens-Lottes correlation overestimated the ONB incipience, whereas the Bergles-Rohsenow correlation underestimated the ONB incipience. However, the existing correlations are still applicable for predicting ONB wall temperatures at extremely low flow rates.