Post-dryout heat transfer characteristics in horizontal mini-tubes and a prediction method for flow boiling of CO₂

The post-dryout heat transfer coefficients were analyzed by differentiating them into two regions, based on their observed trends. One is a transition region. The other is a fully dryout region. The effects of test conditions for heat flux and saturation temperature on the boundaries of the two regions were also investigated, and the existing models for post-dryout heat transfer coefficients were verified for both regions. To develop a prediction method for flow boiling of CO₂, we applied the critical liquid film model, to predict the point of dryout vapor quality. The Yun et al. model and the Groeneveld model are used to estimate the heat transfer coefficients prior to and subsequent to the point of dryout vapor quality, respectively. The former shows a mean deviation of 38%, and the latter gives 36.4% for the three different data sources.