Experimental Analysis of Unsteady Drag Forces During Pool Boiling

Abstract Understanding two-phase flow is key to the safety and efficiency analyses of light water nuclear reactors (LWRs). The bubble departure diameter highly influences the prediction of the heat flux of the system. By using high-speed photography, this work seeks to conduct a quantitative examination of individual forces contained in a force-balance approach for bubble departure diameter prediction. A comparison of different models to estimate the growth force can provide further insight into the force-balance approach. Computation of an experimental growth force had an average magnitude of ≈10−6 N. However, when using the Rayleigh–Plesset and added mass models with the radius functions used by Klausner et al. (1993) and Sugrue and Buongiorno (2016), the average magnitude for the growth force was higher at ≈10−3 N, while at the same time the profile shape of these modeled growth forces differed from that of the experimental growth force. In comparison, when using the growth force models with the experimental radius, the profiles of these forces were similar to the experimental growth force profile shape, but the average magnitudes were ≈10−4 N and ≈10−5 N, respectively. It was found that when the radius takes the form of a square root minus a linear function, the profile of the growth force using the models is closer to the experimental force profile. The analysis performed in this work can contribute to a better bubble departure diameter prediction, further enhancing pool boiling analyses with applications in LWR operation.