Universal approach to predicting full-range post-dryout heat transfer under uniform and non-uniform axial heat fluxes

In the present study, based on three experiments including two uniform axial heat flux experiments (Becker and KIT) and one non-uniform axial heat flux experiment (BeckerII), an universal mechanistic model was developed for the full-range post-dryout heat transfer. The whole post-dryout heat transfer region consists of a developing region and a fully developed region. A determination equation for the length of the developing post-dryout region was proposed and verified to distinguish and quantify these two regions, which can be used to calculate the peak wall temperature position in most cases. The mechanistic model considers three-path heat transfer that involves heat transfer from heated wall to vapor, from vapor to droplets, and from direct contact between wall and droplets. The cross-section of the flow was separately considered in the modeling as a film region and a core region, which makes it possible to account for the impact of the droplets' concentration distribution over the cross-section on the interfacial heat transfer between vapor and droplets. Model assessments cover a broad range of flow conditions, around 25,000 data points, and multiple types of fluid. Results indicate that the proposed model could provide precise predictions for the full-range post-dryout heat transfer.