Understanding of the fundamental mechanism of boiling from enhanced structures is currently incomplete. The main focus of the present study was to develop a semi-analytical model to predict the bubble departure diameter, frequency, and nucleation site density for a boiling enhancement structure. Existing models in literature were used as a framework to develop this. Salient feature of the model is the improvements on sub-models for bubble departure diameter, evaporation within the channels and convective heat transfer from the external surfaces of the enhanced structure. The model was used to calculate the total heat dissipated from the structures. Comparisons to experiments revealed that the bubble departure is predicted within +/-10%, frequency within +/-30% for all data points except a couple, nucleation site density within +/-40% and the heat flux within +/-50%. Sample calculations have been included to show its use in optimizing the geometrical parameters for maximizing heat transfer. (C) 2003 Elsevier Ltd. All rights reserved.