Experiments were conducted to investigate the characteristics of the flow boiling critical heat flux (CHF) and transition boiling for liquid flowing through a heated surface with longitudinal microchannels machined into the surface. A physical model of the capillary flow and rewetting in the microchannels on the heated surface was proposed to describe theoretically the CHF enhancement mechanism and transition boiling. The numerical predictions from the proposed model are in quite good agreement with the experimental measurements. These prove that the microchan-nel structure can evidently increase the CHF of a heated plate and augment the transition boiling heat transfer. Experiments were conducted to investigate the characteristics of the flow boiling critical heat flux (CHF) and transition boiling for liquid flowing through a heated surface with longitudinal microchannels machined into the surface. A physical model of the capillary flow and rewetting in the microchannels on the heated surface was proposed to describe theoretically the CHF enhancement mechanism and transition boiling. The numerical predictions from the proposed model are in quite good agreement with the experimental measurements. These prove that the microchan-nel structure can evidently increase the CHF of a heated plate and augment the transition boiling heat transfer.