A new CHF model for enhanced pool boiling heat transfer on surfaces with micro-scale roughness

A new CHF model was developed for saturated pool boiling on surfaces with micro-scale roughness, including micro-pillar, micro-ridge structures as well as random roughness made by emery paper or sandpapers. The model accounted for the effects of roughness-augmented wettability and capillary wicking on CHF enhancement. Geometric size parameters of well-defined micro structures were explicitly included in the correlation of present model, which was then extended to include randomly roughened surfaces based on the equivalent geometric sizes obtained from roughness parameter, Ra. The present model was evaluated by comparing with 104 CHF data in literatures with different working fluids, surface materials and surface morphologies. The results showed that present model could match most of the data within 25% and the overall mean absolute error was 13.7%. Particularly, the present model was capable of predicting the decrease trend of CHF with increase of roughness factor appeared in experimental studies and this trend was not reflected in previous models. The present study was expected to improve the understanding of CHF augmentation mechanism on micro-structured surfaces and to provide guidelines for optimal surface design.