Correlations for prediction of the bubble departure radius on smooth flat surface during nucleate pool boiling

Based on a modified force balance model, new correlations were proposed for the prediction of vapor bubble departure radius in saturated and subcooled pool boiling under atmospheric pressure. To predict the departure radius, the wall temperature and contact angle are two important input parameters. Instead of the static contact angle, the present correlations use the dynamic advancing contact angle at root of the bubble base at the moment before bubble detachment (i.e., the maximum dynamic advancing contact angle) to calculate the bubble departure radius. The results show that for the bubble departure radius obtained in this study, the developed correlation can predict all the data points within a maximum error of 3.8% in both normal earth gravity and 0.01g_e reduced gravity. Moreover, for data sets in the literature including 1g saturated boiling, 1g subcooled boiling, saturated boiling in reduced gravity, and subcooled boiling in reduced gravity, it is also demonstrated that compared with the thirteen existing correlations, the proposed correlations exhibit a big improvement in predicting bubble departure radius.