Numerical Prediction of the Outcomes of Binary-Droplet Collision in Steam-Water Separator

A theoretical model is carried out to describe the regimes of binary-droplet collision in steam-water separator (SWS). Different from previous researches which seldom concerned the interaction between droplets moving in the SWS, this study indicates that droplet collision, especially the binary-droplet collision, is a key factor to influence the efficiency of SWS. Four regimes of binary-droplet collision including bounce, coalescence, reflexive separation and stretching separation are considered. A brief summary is showed how this theoretical model is established according to previous papers. Then we use this model to study the probability of the four regimes and the states of droplets (e. g., number, size and velocity) after binary-droplet collision. The results perform that, at low symmetric Webber number (Wes), coalescence is the dominate regime. While, with the increasing Wes, the probability of stretch separation goes up quickly. Otherwise, coalescence would not occur frequently at this time. The probability of reflexive separation always stays at a low level. In addition, bounce would not happen whatever the Wes is. From the calculation results of post-collision drops, binary-droplet combine as one drop in coalescence. In reflexive or stretch separation, the large drop and the small one would remain their velocities but their radii might decrease, for satellite droplets may be generated.