A Modification of Departure from Nucleate Boiling Model Based on Mass, Energy, and Momentum Balance For Subcooled Flow Boiling in Vertical Tubes

Several analytical models for the departure from nucleate boiling (DNB) phenomenon have been developed during the last decade. Among these, Chang & Lee's model based on a bubble crowding mechanism is remarkable in the fundamental features characterized as the formulation of mass, energy, and momentum balance equation at thermal-hydraulic conditions leading to the DNB. However, Bricard and Souyri remarked that the assumption of stagnant bubbly layer at the DNB condition is questionable and the signs on the axial projections of the momentum fluxes at the core/bubbly layer interface in the momentum balance equations are erroneous. From this remark, Chang & Lee's model has been re-examined and modified by correcting the erroneous treatments in the momentum balance equations and removing the spurious assumptions. The revised model predicts well the extensive DNB data of water in uniformly heated tubes at low qualities and shows more accurate prediction compared with the original model.